Motores Aeronauticos Diesel

8/12/2019 Motores Aeronauticos Diesel

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Chapter 1Development of the Diesel Aircraft Engine

Most people in the United States who are interested in aviation associate the gasoline engine with the airplane as its powerplant. True, the gasoline engine has made flight possible and it has been developed to a fine art. Progress does not stand

still, however, and now the Diesel or compression ignition engine has become a challenger of the gasoline engine foraviation.

Today, the Diesel provides the motive power for fast streamlined trains and swift motorships as well as for powerfultrucks, busses and tractors. Its use in warships and tanks is growing rapidly and it is being adopted for mechanizedtransport. Adoption of the Diesel for aviation has been relatively slow because of the difficulty in reducing its weightsufficiently for use in the air. Now this problem has been solved and we are on the threshold of a new era in aviation inwhich the Diesel will play an important part.

Dr. Rudolf Diesel

By common usage, the word Diesel has become synonymous forcompression ignition engine and few people remember its inventor or the

difficulties he encountered in its development. More than forty years haveelapsed since the first industrial engine operating on this principle was built.It is nearly fifty years since the first patent was issued to Dr. Rudolf Dieselfor his invention of an internal combustion engine with compressionignition.

Dr. Diesel, like many inventors, had quite an adventurous career (Fig. 1).He was born in Paris of German parents on March 18, 1858, and when hewas only twelve years old, his family had to flee from the city during theFranco-Prussian War. His parents settled in England and young Diesel wassent to relatives in Augsburg to receive a German education. There hecompleted his schooling and entered the Technical Institute at Munich to

study engineering. His mechanical talents developed rapidly and he becameparticularly interested in thermodynamics, which study helped form thebasis of his career.

While Diesel was studying at Munich, his teacher, Dr. Linde-the discovererof liquid air-happened to mention one day that in a steam engine only 6 to 10 per cent of the heat produced wastransformed into energy. This statement made in 1878 so impressed Diesel that from then on, the idea of a newpower-saving engine remained uppermost in his mind. During the years which followed, Diesel was employed by SulzerBrothers in Switzerland and later he became assistant professor at the Technical Institute at Munich. In 1889, he joinedDr, Linde in Paris as manager of his refrigeration plant and it was there that be began to make plans for the developmentof his engine.

Development of the Diesel Principle

Recalling his school days, Dr. Diesel remembered a "fire tube" with which he had experimented and in which combustiblematerials could be made to ignite by compressing air to a high temperature. This apparatus was like a bicycle pump buthad a glass cylinder so that the effect of sharply pushing in thepiston could be seen. This method of igniting fuel by compressingair to a high temperature was what Dr. Diesel wanted and headopted the principle in his new engine. Virtually, the cylinder ofhis engine became a pneumatic fire tube with the pistoncompressing the air to ignite the fuel.

Abundance of coal in Germany and the idea of utilizing coal dust

for fuel undoubtedly influenced Dr. Diesel when he applied for apatent. The first one issued to him, Patent No. 67,207 datedFebruary 28, 1892, specified an engine with compression ignition


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The First Practical Heat Engines

After three years' work, in 1896 Dr. Diesel completed his first engine design to use coal dust for fuel and air compressed tohigh pressure and temperature to ignite it. This engine exploded and nearly killed him but he persevered and built anotherengine using petroleum for fuel. -His second engine built in 1897 was successful and justified his theories. It was of theslow-speed, type with a single vertical cylinder which developed 25 h.p. at 170 r.p.m. (Fig. 2). Subsequent tests showedthat it had a thermal efficiency of 35 per cent compared with 12 per cent for the steam engine of that time 2

The First American Diesel

At the Machinery Exposition held in Munich in 1898, three engines built to Dr. Diesel's designs by Krupp, M.A.N. andDeutz constituted the biggest attraction. So much interest was aroused that by 1901licenses had been granted in manycountries and twenty-seven firms were building Diesel engines. Well-known firms such as Sulzer in Switzerland andNobel in Russia began to build them on a large scale. In the United States, the first Diesel was built by the firm of Busch-Sulzer in St. Louis in 1898.

During the next fifteen years, Dr. Diesel received many invitations to visit other countries where he was honored and fetedand addressed engineering conventions. In 1912, his visit to the United States was in the nature of a triumphal tour. At thistime the marine Diesel. was fast being adopted for submarines and other naval vessels. After his return to Germany, Dr.Diesel was called to England to consult with the British Admiralty about the use of his engine in submarines. Travelingfrom Antwerp to Harwich on the night of September 29, 1913, he mysteriously disappeared from the ship, as did all of hisimportant documents. Thus passed Dr. Diesel, the inventor of countless engines which bear his name.

Developments in Germany

Development of lightweight Diesels for aviation from heavy industrial and marine engines of this type was started inGermany in 1910. It was not until 1930, however, that the Diesel aircraft engine became really practical. Dr. Hugo Junkersinitiated this development and before be died in 1935, be bad the satisfaction of seeing his Diesels successful in the air.

Dr. Hugo Junkers

Dr. Junkers' career is interesting in that like Dr. Diesel, be was deeply interested in thermodynamics which proved to be ofgreat benefit to him in his work. He was born in 1859 and when he was twenty-nine years old, he began experimentingwith gas engines at Dessau. There he began manufacturing heating devices and in 1897, he was appointed to the Chair ofThermal Studies at Achen Technical Academy.

At Dessau and Achen Dr. Junkers' thoughts began to turn to aviation and on February 1, 1910, be was granted Patent No.253,788 for an "all wing" airplane, This invention consisted of a single hollow metal wing which housed within itsframework not only the engines and their fuel tanks, but also the passengers and crew. The engines, even at that earlydate, were shown as being of the opposed-piston type. This thick section all-metal cantilever wing which at first wasridiculed and rejected as impractical has now, thirty years later, became the accepted pattern for high-speed airplanes anda successful all-wing" airplane has been built and flown.

Dr. Junkers' activities were not confined solely to his all-metal airplane. He was also interested in means of propulsion andsubsequent to 1910, his time was divided between experiments with his airplane and work on a Diesel engine to propel it.He chose an opposed-piston engine design as he had achieved considerable success with this type of power plant in theindustrial field. He also chose two-cycle operation for his engine with piston-controlled ports instead of valves andcompressed air for scavenging the cylinders.

The First Junkers Diesels

The first two Junkers Diesels built for aviation were the four-cylinder MO-3 completed in 1913 and the six-cylinderMO-8 completed in 1914. The next experimental engine was the six-cylinder FO-2 built in 1916 which was rated at 500h.p. at 2,400 r.p.m. A 1,000 h.p. Diesel was also designed at that time which showed the extraordinary progressiveness ofDr. Junkers.' All of these engines ran on fuel oil injected under pressure and were equipped with spark ignition.

Post World War I Development

Development after World War I was slow due to the restrictions


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was placed in regular service on the airlines of Deutsche Lufthansa.4 Subsequently, the engine became known as the Jumo204 and its output was increased to 770 h.p. at 1,800 r.p.m. In 1935, its manufacture was discontinued in favor of theJumo 205 of similar construction but of considerably smaller size. Now the Jumo, 205 has been developed to the pointwhere it has an output of 700 h.p. at 2,500 r.p.m. and 880 h.p. at 3,000 r.p.m.(Fig. 4). When equipped with anexhaust-driven super-charger it is known as the Jumo 207 and has a rating of 1,000 h.p. at 3,000 r.p.m. A slightly largerDiesel-the Jumo 206-has a rating of 1,200 h.p. and is now reportedly used in military planes. All of these engines have sixvertical -water-cooled cylinders with two pistons in each cylinder and two crankshafts. Their specific weights range from

2.1 lb. per h.p. for the earlier models to 1.4 lb. per h.p. for the latest engines.Another Diesel aircraft engine which has been developed inGermany is the B.M.W.-Lanova 114 V-4 Diesel built by B.M.W.Flugmotorenbau. G.m.b.H. (Fig. 5). Dr. Schwager has beenresponsible for much of the work on this nine-cylinder radial whichis moderately supercharged and rated at 650 h.p. at 2,200 r.p.m.This engine, like the radial gasoline engines manufactured by thefirm, functions on the four-cycle principle. It is unique in thatalthough it isliquid-cooled, it is a self-contained unit with smallradiators mounted

between its cylinderswhere they do notincrease the frontal area.This arrangement makesit interchangeable withair-cooled B.M.W.gasoline engines whichare used for both civiland military purposes inGermany.

In addition to in-line Diesels for high-performance airplanes and radial Diesels for replacement units, there is still a third

type which is manufactured in Germany. This is the Mercedes-Benz DB 602 Diesel built by Daimler-Benz A.G. for use inairships (Fig. 6). Sixteen individual water-cooled cylinders are used on this four-cycle engine which has a maximumpower output of 1,320 h.p. at 1,650 r.p.m. and a specific weight of 3.3 lb. per h.p. Dr. Berger, chief engineer of the firm,designed this powerful Diesel which is unsupercharged. Four of them were used on the Zeppelin LZ-129, theHindenburg,and four more of them were installed on the Zeppelin LZ-130, the Graf Zeppelin.

Developments in the United States

The first public showing of the Junkers FO-3 Diesel aircraft engine inGermany in 1926 created such world-wide interest that it was not longbefore experimental work of this nature was under way in the UnitedStates. Here most of our Diesel aircraft engine designers concentrated

on four-cycle, air-cooled radials based upon gasoline aircraft engineswith which they were familiar. This has worked out all right forlow-powered and medium-powered engines, but for larger powerplants two-cycle, liquid-cooled Diesels are needed. The GodfreyManufacturing Corp. has done extensive single-cylinder experimentalwork with the last-mentioned type of engine and has prepared designsfor a large Diesel aircraft engine embodying two-cycle operation.

The Packard Diesel

In the United States, the first Diesel aircraft engine to appear was thePackard. Work on this nine-cylinder, air-cooled radial was started in1928 under the direction of Capt. Lionel Woolson, chief aeronautical

engineer of the Packard Motor Car Co., and Professor HermanDohner, a German engineer. Captain Woolson was considered one ofthe foremost engineers of his day and designed the 600 h p and 800


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with six airplanes in the show equipped with it as well as several others on the flying field. Among the latter was atri-motored 11-passenger Ford 11-A airliner which was equipped with three Packard Diesels and could cruise at a fuelcost of three cents a mile.

Hardly had the Packard Diesel been launched on its career than tragedy overtook its forty-two year old inventor. On April24, 1930, Captain Woolson and his two companions took off from Detroit for New York in a Verville Air-Coach

equipped with one of the Diesels. Lost in a storm, they crashed near Attica, New York, and all were killed.

Following the death of Captain Woolson, the inventive genius and driving force behind aircraft engine production in thePackard factory came to a standstill. Production of the Diesels in their specially built and equipped factory wasdiscontinued. Despite this change in policy, Packard Diesels continued to be used for a time and on May 28, 1931, WalterE. Lees and Frederick A. Bossy established the world's nonrefueling duration record with one of them in a Bellanca

Pacemaker at Jacksonville, Florida. They took off with a load of 481 gallons of fuel oil and remained in the air for 84

hours and 32 minutes. This still constitutes the world's record for both Diesel-engined and gasoline-engined airplanes.

As an indication of the high esteem in which the Packard Diesel washeld it should be mentioned that the Collier Trophyfor the most important contribution to aviation during 1931 was awarded to the Packard Motor Car Company for its workwith this type of engine.

The Guiberson Contributions

About the time that the Packard Diesel passed into oblivion, anotherDiesel aircraft engine of similar design appeared to take its place.This newcomer was a product of the Guiberson Diesel EngineCompany of Dallas, Texas, a firm which had had considerableexperience in the industrial Diesel field. Work on the firstGuiberson Diesel aircraft engine was started in 1930 to the designsof F. A. Thaheld, a young Austrian engineer. Early in 1931, aftermore than 800 hours on the test stand, the nine-cylinder, air-cooledGuiberson A-980 Diesel was ready to take to the air. For the testflights, the services of Col. Arthur G. Goebel, famous for his

transpacific flight between San Francisco and Honolulu, weresecured. The Diesel was installed in his Waco biplane and on a testflight he covered the 960 miles from Dallas to Detroit on 96 gallonsof furnace oil. The cost of this fuel, at seven cents a gallon, was only$6.72 or less than one cent a mile. Most of the return trip was madein a downpour of rain which did not affect the engine as it had noelectrical ignition system.

Later in the same year Colonel Goebel reached an altitude of 21,686ft. with this unsupercharged Diesel and flight tests proved that it bada better performance than contemporary gasoline engines of thesame power. In November, 1931, the Guiberson A-980 passed its

government tests and was awarded A.T.C. No. 79 with a ratedpower output of 185 h.p. at 1,925 r.p.m. (The engine used is shown in Fig. 8.)

Despite the gloom which settled over the youthful Diesel aircraft engine industry after the Packard Diesel was abandoned,development of the Guiberson Diesel proceeded and was kept alive by the persevering efforts of S. A. Guiberson, Jr.Next, a slightly larger Diesel known as the Guiberson A-918 model was constructed under the supervision of C. C.Spangenberger, chief engineer of the firm. In 1934, the United States Navy showed considerable interest in the engine andtwo of the A-918 Diesels were delivered to the Bureau of Aeronautics for test These engines were rated at 253 h.p. at

2,100 r.p.m. and after improvements hadbeen made, two more of them wereordered.

A later Guiberson. Diesel is the A-1020model which is similar to itspredecessors but has up-to-date valving


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Diesel field, in their factory located in Illinois. Still larger and more powerful Guiberson Diesels are projected forairplanes and tanks with power outputs up to 1,000h.p. made possible by supercharging.

Other American Developments

Successful development of Diesel aircraft engines in the United States has been limited to Packard and Guiberson Dieselsas these are the only engines which have been flown. Other Diesels have been built and bench-tested but for one reasonand another, they have been abandoned. Mention should be made of the 75 h.p., two-cylinder, water-cooled Attenduairship engine built for a Navy airship in 1925 which weighed 6.5 lb. per h.p.; the 400 h.p., seven-cylinder aviation Dieselwith radial, air-cooled cylinders which was completed in 1932 and weighed 3.5 lb. per h.p.; and the 1,200 h.p.,twelve-cylinder Deschamps engine which was built in 1934 and weighed 2.0 lb. per h.p. The Deschamps V 3050 Dieselwith its two banks of inverted liquid-cooled cylinders and low frontal area was a promising engine but financialdifficulties have prevented its further development and flight testing

DEVELOPMENTS IN GREAT BRITAIN

In 1927, a year after the first public showing of the Junkers FO-3 Diesel in Germany, the Bristol Aeroplane Co., Ltd.,

began work on a Diesel or compression-ignition (C.I.) engine as it is called in England. Financial aid was given by theBritish Air Ministry and the work was carried out under the direction of Dr. Roy Fedden, chief engineer of the enginedivision of the Bristol firm. Several years were devoted to research and after bench tests totaling more than 1,500 hourshad been completed with single-cylinder Diesels it was decided that the results warranted the building of a fullsizedengine.

The Bristol Diesels

The Bristol Phoenix, as this nine-cylinder, air-cooled Diesel was called,resembled the contemporary Bristol Jupiter VIII F gasoline engine to a greatextent (Fig. 10). It was of the same size and displacement and with its ratingof 430 h.p. at 2,000 r.p.m., it bad practically the same power output. Its first

flights were made in 1933 when it was installed in a Westland Wapitiobservation plane and took part in the annual Royal Air Force Display atHendon. After a supercharger of moderate capacity had been added, thePhoenix was flown in the same airplane to an altitude of 27,453 ft. on May 11,1934,by H. J. Penrose. This flight was made under the official observation ofthe Royal Aero Club and established the world's altitude record forDiesel-engined airplanes.

Subsequently, interesting comparisons were obtained by flying the WestlandWapiti with the Phoenix Diesel and the Jupiter VIII F gasoline engine. It wasfound that the Diesel-engined plane had the better performance as its rate ofclimb was increased by 15per cent and its speed at altitude was increased by

4per cent (Fig. 11). Its fuel consumption was also reduced by as much as 35per cent. These improvements were due tothe better power output characteristics of the Diesel at altitude (Fig. 12). Recently, further work has been done on theBristol Phoenix and its crankshaft speed and supercharger impeller speed have been increased so that it is now rated at635 h.p. at 2,100 r.p.m.


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The Beardmore Diesels

Concurrent with the Bristol development, the firm of William Beardmore & Co., Ltd., designed an airship Diesel for theBritish Air Ministry which passed its tests in 1930. The Beardmore Tornado, as this engine was called, was of heavierconstruction than an airplane engine and with its eight-in-line, steam-cooled cylinders had a weight of 7.8 lb. per h.p. Fiveof these Diesels rated at 585 h.p. at 900 r.p.m. were installed on H. M. Airship R-101 which was destroyed in a stormwhile flying in India. Beardmore also designed an interesting airplane Diesel with horizontallyopposed cylinders forsubmerged installation inside the wing. This twelve-cylinder, watercooled engine was intended to develop 500 h.p. at1,750 r.p.m. but it was never completed.

The Napier Experiments

Realizing the difficulties to be overcome in the development of a successfulDiesel aircraft engine, the British Air Ministry then decided to investigatethe Junkers Diesel which had established an excellent reputation for itself in

Germany. In 1935, after exhaustive tests of one of these engines by the airministry, the -firm of D. Napier & Sons, Ltd., acquired a license to build theJunkers Jumo 4 and Jumo 5 in England. Several Napier Culverins with anoutput of 720 h.p. at 1,700 r.p.m. corresponding to the Jumo 4 were built andsome of them were flight-tested in a Blackburn flying boat (Fig. 13).Nothing came of this project, however, and the Napier Cutlass of 535 h.p.corresponding to the Jumo 5 was never placed in production.

Other British Developments

In addition to aiding in the development of these engines, the British AirMinistry also played a part in the conversion of two RollsRoyce Condor gasoline engines to Diesel operation. The Royal

Aircraft Establishment and Ricardo also aided in this conversion but the best that they could obtain from -thesetwelve-cylinder, water-cooled engines was an output of 480 h.p. at 1,900 r.p.m. One of these converted engines weighing2.9 lb. per h.p. was flown in a HawkerHorsley torpedo bomber in 1933.


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Developments in France and Other Countries

In 1931 Coatalen left the Sunbeam firm and returned to his native country. There he continued his Diesel research on asix-cylinder Panhard while engaging in the manufacture of Lockheed hydraulic brakes. The Coatalen 12 Vrs 2 Dieselaircraft engine which he subsequently built was constructed in the remarkably short time of six months. It was exhibitedin the Paris Aero Show in 1936. On the test bed, this twelve-cylinder water-cooled engine developed 600 h.p. at 2,200r.p.m. and weighed 2.0 lb. per h.p. Coatalen later planned a two-cycle Diesel of approximately the same size as his

four-cycle Diesel which he hoped would develop 1,000 h.p.

The Clerget Diesels

Pierre Clerget has built more four-cycle Diesel aircraft engines than anyone in France and a number of them have beentest-flown. As long ago as 1930, he exhibited a nine-cylinder, air-cooled radial Diesel known as his 9-A model with arating of 100 h.p. at 1,800 r.p.m. Since then, several models have been built and for a time the firm of Hispano-Suizacarried on this development work. Later, the French Air Ministry took over all Clerget developments and assisted him inbuilding larger fourteen-cylinder Diesels. One of these engines,, known as the Clerget 14 F-01 and rated at 940 h.p. at2,400 r.p.m. was test-flown to an altitude of 25,114 ft. in a Potez 25 observation plane in 1937 (Fig. 14). The pilot on thisoccasion was M. Detre and the Right was certified by the Aero Club of France.

The latest Clerget development was a large sixteen-cylinder,watercooled Diesel known as the 16-H model which wasbench-tested in 1939. This engine was designed to develop morethan 2,000 h.p. and it weighed 1.9 lb. per h.p. Fourexhaust-driven (turbo) superchargers were installed on it with theobject of maintaining its rated power output to an altitude ofapproximately 20,000 ft. It was exhibited at the Paris Aero Showin 1938 with the designation "Type Transatlantique."

Another French Diesel, the Salmson SH 18 built underSzydlowski license, is interesting in that it is a water-cooledradial with its eighteen cylinders arranged in tandem pairs around

the crankcase. Rated at 600 h.p. at 1,700 r.p.m.

and designed tooperate on the two-cycle principle, the SH 18 weighs 1.9 lb. perh.p. This engine was exhibited at the Paris Aero Show in 1934 buit has yet to prove itself in the air.

The C.L.M. Diesels

Not wanting to lag behind Great Britain in Diesel development,France also acquired a license to build the Junkers Jumo 5 Dieselin 1935. This license was taken out by the firm of CompagnieLilloise de Moteurs S.A., more commonly known as C.L.M.Several engines known as the Lille 6 AS model were constructedwith a rating of 600 h.p. at 2,200 r.p.m. Some flight testing was

done with them in a Bernard 82 long-range monoplane with a view to attempting to establish a long distance record. Atthe present time the firm of C.L.M ' is showing little activity with Diesels of this type for aviation but is building them asrailcar engines with power outputs of 150, 250 and 500 h.p.

The Jalbert-Loire Diesels

Jalbert-Loire Diesel aircraft engines built by Ateliers' et Chantiers de la Loire S.A., near Paris, have also receivedencouragement from the French Air Ministry and three different sizes of engines have been constructed. These comprise afourcylinder 160 h.p. engine and a six-cylinder 235 h.p. engine with inverted in-line cylinders, and a sixteen-cylinderengine known as the 16-H model which has its cylinders in H-formation and develops 600 h.p. at 2,400 r.p.m. All of theseengines are water-cooled and the largest one weighs 2.0 lb. per h.p.

Other French Developments

France certainly has not lacked for Diesel aircraft engine projects. Other engines worthy of mention are the nine-cylinder


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results in small training planes with many hundreds of hours of flying to itscredit. Dr. Ostroil and his follow engineers were responsible for the ZOD260-B Diesel which weighed 2.3 lb. per h.p.

Italy is the only remaining country in which results of Diesel developmentshave been made public. This work is not of recent origin, however, as itwas in 1930 that the Fiat ANA Diesel was built and flown. This engine had

six in-line, water-cooled cylinders and was rated at 220 h.p. at 1,700 r.p.m.and weighed 4.0 lb. per h.p. A still earlier Diesel of Italian origin, theGaruff a, was exhibited at the Paris Aero Show in 1921. Considering thetremendous advantages to be derived from Diesel aircraft engines with theirlow fuel consumption, it is strange that more progress has -not been madewith them in Italy where aircraft engine fuel is at a premium.

Japan has shown great interest in Diesel aircraft engines which issignificant inasmuch as the firm of Mitsubishi has a license to build Junkersengines and airplanes. It is possible that arrangements have been made for the Junkers Jumo 205 Diesel to bemanufactured in Japan as a number of -these engines have been used there for experimental purposes and have beenreportedly installed in bombers used against the United States.

The U.S.S.R. is also alert to the possibilities of the Diesel for longrange flight operations and undoubtedly work onDiesels proceeded there, probably under the guidance of German engineers before Germany's attack on Russia in thesecond World War.


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Chapter 2How the Diesel Aircraft Engine Functions

People who are familiarwith the functioning of a gasoline aircraft engine need not have any difficulty in understanding

how a high speed Diesel aircraft engine works. In size and outward appearance the two types of engines are similar as

they both are internal combustion engines in which the fuel is burned inside the cylinder. Parts of the engines such as thecrankcase, the cylinders, the crankshaft and the connecting rods are of the same design. The chief difference between the

two types of engines is in the method used for admitting the air and the fuel into the engine cylinders and the method used

for igniting the fuel. This difference in construction is necessitated by the use of nonexplosive fuel oil in the Diesel.

Feeding Fuel

Close examination reveals that the Diesel has no carburetor in which the air and the fuel can mix before being admitted to

the cylinder. In the Diesel, the air containing the oxygen required for combustion is admitted through the inlet valve into

the cylinder on the suction stroke of the piston. When the piston reaches the bottom of this stroke, the inlet valve closes

and the air contained in the cylinder is compressed to a high pressure. The fuel, which consists of No. 2 furnace oil or its

equivalent, is compressed to a still higher pressure in a small plunger-type injection pump and is forced through an

injector into the engine cylinder. In this respect, the Diesel is similar to some of the latest gasoline aircraft engines which

are equipped with direct fuel injection instead of a carburetor.

Igniting the Fuel

The method used to ignite the fuel charge in a Diesel is entirely different from that used in a gasoline engine. The Diesel

has no magnetos, spark plugs or high-tension wires as it uses air heated by compression to a high temperature to ignite its

fuel. In order to compress the air charge to this high temperature, the compression ratio in the cylinder of a Diesel is

considerably higher than in a gasoline engine. Compression ratios in Diesel aircraft engines range from 14:1 to 17:1 which

is sufficient to raise the temperature of the air charge to "red" heat or approximately 1,000 degrees Fahrenheit. When the

fuel is injected in the form of a fine spray, it ignites readily and the gases of combustion expand as in a gasoline engine

forcing the piston outward on its expansion or power stroke.

The ignition of the fuel charge in a Diesel by highly heated air is somewhat slower than the ignition of the combustible

mixture in a gasoline engine by means of an electric spark. Higher peak pressures are encountered in the cylinder of a

Diesel, however, due to the smaller size of its combustion chamber which results in more rapid pressure rise when the fuel

ignites. For a time this rapid pressure rise necessitated heavier cylinder construction and made the Diesel too heavy for

aviation. Now methods have been devised whereby the duration of the ignition delay period is reduced and this tends to

cut down the rate of pressure rise.

Four-Cycle Diesels

In a Diesel aircraft engine operatingon the four-cycle principle, thesequence of events is similar to thatin a four-cycle gasoline aircraftengine:1. Suction stroke-intake of air chargethrough inlet valve.2. Compression stroke-compressionof air charge to a high temperatureand injection of fuel charge justbefore top dead center.3. Expansion stroke-ignition andcombustion of fuel and expansion ofgases transmitting power to thecrankshaft,4. Exhaust stroke-evacuation ofburnt gases through exhaust valve.

These events can be seen in Fig.16.


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The Combustion Chamber

The design of the combustion chamber

in a Diesel aircraft engine is very

important and various kinds of open

chambers, turbulence chambers and

pre-combustion chambers can be used.

The turbulence chamber used in

conjunction with the Lanovacombustion system is particularly

interesting as it is used extensively in

high-speed four-cycle automotive and

marine Diesels and also is suitable for

Diesel aircraft engines. The

combustion chamber is in the form of

a horizontal figure 8 with the inlet

valve and the exhaust valve in the

centers of the two lobes. The injector

is on one side of the narrow portion of

the chamber and injects a portion of

the fuel charge into an energy cell opposite to it. The gas blast produced by the energy cell creates strong rotationalturbulence in the two lobes of the chamber mixing the air charge with the remainder of the incoming fuel charge (Fig. 18).

Referring back to the diagram in Fig. 16, it is seen that in a four-cycle engine

the piston is productive during only one stroke out of four, or once during

two complete revolutions of the crankshaft. It has to be driven by the

crankshaft during the remainder of the period. From the viewpoint of

efficiency, a better arrangement is to have the piston productive during one

stroke out of two, or once during one complete revolution of the crankshaft.

This last-mentioned arrangement is obtainable in a two-cycle engine.

Two-Cycle Diesels

In an engine functioning on the two-cycle principle, events happen twice asfast as in a four-cycle engine. Each up stroke of the piston is a compression

stroke and each down stroke is an expansion stroke.

Exhaust or evacuation of the burnt gases and suction or intake of the new air

charge have to take place during the brief interval when the piston is near

bottom dead center. This kind of engine requires special valving so that the

burnt gases can be evacuated rapidly and a new air charge admitted before

the valves close and compression begins.

Small gasoline engines used in motorboats and motorcycles run quite well on

the two-cycle principle. These engines are constructed so that the

gasoline-and-air mixture is compressed in the crankcase to a pressure slightly above atmospheric. A deflector on top ofthe piston permits a new charge to be admitted into the cylinder through a transfer passage immediately after the exhaust

port has been uncovered by the piston. Considerable pollution of the incoming charge naturally occurs and the engine

does not function with very high efficiency. Obviously, such an arrangement is impracticable for a large multi-cylinder

gasoline aircraft engine in which high specific power output and low specific fuel consumption are of paramount

importance.

In a Diesel aircraft engine operatingon the two-cycle principle, thefollowing events take place:1. Compression stroke-intake of aircharge, compression of air charge to

a high temperature and injection offuel charge just before top deadcenter.


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The Diesel, whether it be small or large,

functions with high efficiency on the

two-cycle principle. Only air is contained

in the cylinder prior to the injection of fuel

near top dead center and this air can be

compressed slightly by external means

before it is admitted into the cylinder. A

blower or supercharger is used on atwo-cycle Diesel aircraft engine to provide

the preliminary air pressure. The volume of

the-air forced in during each intake period

is in excess of the cylinder displacement so

that sufficient air is available for

scavenging as well as for charging the

cylinder.

While it might appear that a two-cycle

Diesel will develop twice as much power as

a four-cycle Diesel because it has twice as

many power strokes, such is not the case. Difficulty in evacuating the exhaust gases from a two-cycle Diesel necessitatesopening the exhaust valve or port sooner and more of the power generated during the expansion stroke is lost. This power

loss is not excessive and is only approximately 10 per cent more than in a four-cycle engine. A two-cycle Diesel therefore

develops approximately 80 per cent more power than a four-cycle Diesel of the same displacement.

The two-cycle Diesel aircraft engine offers an attractive

solution of the need for a high-powered, high-efficiency power

plant for aviation. Its torque is considerably smoother than that

of a four-cycle engine due to the more frequent but less violent

power impulses transmitted to the crankshaft. Due to the more

frequent generation of beat in its cylinders, the two-cycle

Diesel aircraft engine usually is water-cooled or liquid-cooled

(Fig. 20). Provided good combustion is obtained by impartingrotational swirl to the air charge so that it mixes with the fuel

rapidly, the Diesel has a higher thermal efficiency than a

gasoline aircraft engine. The fuel consumption of the Diesel is

appreciably less than that of the gasoline engine as more of the

heat units in its fuel are converted into mechanical energy.

The Fuel Injection SystemThe choice of a fuel injection system for a Diesel aircraft

engine depends to a great extent upon the cycle upon which the

engine functions, the arrangement of the engine cylinders and

the injection equipment which is available on the market. The

Bosch fuel injection system which has been used on a numberof Diesel aircraft engines is typical of a high-pressure solid

injection system in which the fuel is sprayed

into the engine cylinders in the form of

minute solid particles. The equipment

required for each cylinder of the engine

consists of an injection pump, an injector

and a length of high-pressure tubing.

Bosch injection pumps are manufactured in

both the individual type containing one or

two pump units in one housing, and in the

multi-unit type containing several pumpunits in one housing. On the Zbrojovka ZOD

260-B Diesel aircraft engine, nine individual


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injection pumps each containing four pump units can be mounted on brackets at the rear of the crankcase (Fig. 23).

Sixteen individual injection pumps could also be used on the last-mentioned type of Diesel aircraft engine.

Bosch injection pumps are of the

constant-stroke plunger type. The length of

the plunger stroke is constant at all times and

is not varied to control the size of the fuel

charge. Control of the quantity of fuelinjected into the engine cylinder is obtained

by turning the plunger slightly in the barrel

of the pump so as to vary the moment of

pressure release in the pressure chamber.

The plunger is cam-actuated by a cam ring

or camshaft inside the engine in the case of

an individual pump, or by a small camshaft

inside the pump housing itself in the case of

a multi-unit pump.

How the Injection Pump Functions

The functioning of a Bosch injection pumpunit is the same whether it is contained in an

individual housing or in a multiple housing

(Fig. 24). The fuel enters a sump in the

upper part of the housing and on the down

stroke of the plunger it rushes into the barrel

as soon as the top of the plunger comes below the two radially-opposed ports in the barrel. During the first part of the up

stroke of the plunger, excess fuel in the barrel is displaced back into the sump through the ports until the latter are

completely covered by the rising plunger. Then the fuel contained in the pressure chamber above the plunger is

compressed highly and the spring-loaded non-return delivery valve is lifted off its seat so that the fuel can be forced

through the highpressure or discharge tubing into the injector. Finally the fuel opens the spring-loaded non-return valve in


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In the Bosch injection pump, terminationof fuel delivery controls the pump output and the quantity of fuel delivered by

the plunger on each stroke. For maximum fuel delivery, the plunger is turned slightly in the barrel by means of a toothed

control rod so that the helix does not uncover the by-pass port until very late in the stroke. For zero delivery, the plunger

is turned until the helix communicates with the by-pass port during all positions of plunger stroke and the fuel is not

compressed sufficiently in the pressure chamber to open the discharge valve. The plunger and its barrel are carefully

lapped and matched in pairs so that they are a very close fit.

In addition to controlling the quantity of fuel injected into the cylinders of a Diesel aircraft engine it is also necessary tocontrol the timing of the commencement of fuel injection which corresponds roughly to the moment of firing in a gasoline

aircraft engine. In the case of individual injection pumps actuated by a cam ring or a camshaft means are devised by the

engine manufacturer for varying the timing of the cams. When a multi-unit injection pump containing its own camshaft is

used the timing of the camshaft can be varied by interposing a special device with sliding helical splines between the

camshaft and the drive shaft from the engine.

A single-unit injection pump of suitable capacity is sufficient for each cylinder of a Diesel aircraft engine. It is sometimes

found desirable, however, to use two pump units in one housing or two individual single-unit pumps together with two or

more injectors for each cylinder in order to improve the injection characteristics. In the latter case, each pump unit is

designed to have sufficient capacity to supply the cylinder under full load. Single-unit and two-unit (duplex) injection

pumps are flange-mounted on the crankcase of the engine where they can be actuated conveniently by a cam ring or

camshaft. The cam profile has to be designed with great care in order to attain the best injection characteristics and engineperformance.

On four-cycle Diesel aircraft engines the injection pumps are driven at one-half crankshaft speed while on two-cycle

engines they are driven at crankshaft speed. Operating speeds as high as 3,000 r.p.m. are now permissible for the latest

types of injection pumps. The manufacturers of Bosch injection equipment recommend that the maximum injection

pressure should not exceed 3,500 lb. per sq. in. to insure long life of the actuating and moving parts. They also

recommend that the high pressure tubings connecting the injection pumps and the injectors should be of the same length

so that each cylinder of the engine will develop approximately the same power.

The Injectors

Bosch injectors comprise two main parts-the nozzle body and the nozzle valve. These two parts are carefully lapped and

matched in pairs and are contained in a nozzle holder made of steel or duralumin. The injector is of the closed type with aspring-loaded nozzle valve which seats in an orifice in the bottom of the nozzle body. The movement of the nozzle valve

is controlled hydraulically by the pressure of the fuel against its tapered end when the fuel is admitted through the

discharge tubing from the injection pump.

Two basic types of nozzles are used in Bosch injectors. These are the hole-type nozzle which is suitable for Diesel aircraft

engines having open combustion chambers and the pintle nozzle which is suitable for engines constructed with

high-turbulence combustion chambers or pre-combustion chambers. (See Fig. 24.)

The hole-type nozzle injects the fuel in one or more sprays according to the number of holes in the nozzle body. The

shape and penetration of the sprays depend upon the diameter and length of the holes. The holes are arranged

symmetrically at suitable angles in the bulbous end of the nozzle body so that the sprays will penetrate in the desired

directions.

The pintle-type nozzle has a nozzle valve with a short pin or pintle on its tip which protrudes through the circular orifice

in the bottom of the nozzle body. The pintle is appreciably smaller in diameter than the orifice and when the nozzle valve

lifts from its seat the fuel strikes the pintle with considerable force as it emerges and produces a hollow cone-shaped spray

by refraction. The shape and penetration of the spray depend upon the diameter and length of the orifice and the clearance

space between the orifice and the pintle.

There is also a throttling nozzle which is a variety of the pintle nozzle with a longer pintle in the shape of an inverted

cone. It is designed to control the rate of fuel injection so that only a small quantity of fuel is sprayed into the engine

cylinder at the beginning of the injection period. The main fuel charge is injected when the lift of the nozzle valve is

increased by the pressure of the initial fuel charge as it emerges. This type of nozzle prevents excessive accumulation of

fuel in the combustion chamber prior to ignition and helps to reduce the rate of pressure rise in the engine cylinder.

The High-Pressure Tubing


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The fuel filtering system is considerably more elaborate on a Diesel aircraft engine than on a gasoline aircraft engine

equipped with a carburetor. The fuel oil has to be filtered very carefully before it enters the injection pumps and injectors

so that it will not contain impurities in suspension which might score the closely fitted plungers and barrels, and nozzle

valves and nozzle bodies of these precision instruments. On most Diesel aircraft engines a fuel filtering system comprising

a first-stage filter of the metal-disc type followed by a final stage filter of the paper-element type in a sealed case is

sufficient for the purpose (Fig. 25).

A supercharger of the centrifugal type is highly desirable for a four-cycle

Diesel aircraft engine and an absolute necessity for one functioning on the

two-cycle principle. The supercharger may be of the gear-driven, single-speed

type which absorbs from 10 per cent to 15 per cent of the power output of the

engine for its drive, or it may have two speeds or two stages and absorb still

more power from the engine. An exhaust-driven supercharger is more

advantageous as it absorbs practically no power and has an output equivalent

to that of a two speed gear driven supercharger. The exhaust-driven

supercharger is particularly, adaptable to the Diesel as the exhaust gases

emerge from the latter at a lower temperature than from a gasoline engine and

consequently the turbine wheel and its blades are not subjected to unduly high

temperatures and stresses.

Starting a Diesel aircraft engine does not present any difficulty despite its high

compression. A hand and electric inertia starter such as the Eclipse or a

cartridge starter such as the Breeze (Coffman) can be installed as on a gasoline

aircraft engine but it may have to be the next size larger for a Diesel engine. A

compressed air starting system also can be used with a distributor driven from

the engine and air injection valves in one bank or row of cylinders.


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CHAPTER 3

The Guiberson Diesel

The Guiberson A-1020 Diesel aircraft engine represents the most advanced type of four-cycle Diesel which has been

produced in the United States. It is a nine-cylinder air-cooled radial which can hardly be distinguished from an up-to-dategasoline aircraft engine. Ten years I research work and many hundreds of thousands of dollars have been spent in thedevelopment of Guiberson Diesel aircraft engines. The A-1020 model is not supercharged but it performs well at highaltitudes (Fig. 26).

The Crankcase

The crankcase of the engine is made of aluminum alloy and consistsof a front section and a rear section held together with nine throughbolts. The nose section is integral with the front section as thepropeller drive is direct and there is no necessity for a gear housing.The rear section contains the valve tappet guides and the mountingsfor the nine individual fuel injection pumps. An accessory section

made of aluminum alloy is attached to the crankcase by the ninethrough bolts and nine additional studs and nuts (Fig. 27). Provisionis made for attaching the various accessories by means of studsscrewed into the accessory section. Drives are contained in thissection to operate them.

The Cylinders

The cylinder barrels are machined from steel forgings and areprovided with shallow cooling fins. The cylinder heads are made ofaluminum alloy with deep cooling fins around the combustionchambers and the exhaust valve rocker arm boxes and exhaustoutlets. The heads are screwed and shrunk onto the barrels and each

cylinder is attached to the power section of the crankcase by meansof a flange and twelve studs and nuts.

The Crankshaft

The crankshaft is of the single-throw type, made in two pieces and machined from solid steel forgings. It is supported inroller bearings of large diameter in the front and rear sections of the crankcase and in a ball thrust bearing in the nosewhich absorbs the propeller thrust and axial loads. The crankshaft is bored for lightness and drilled for forced-feedlubrication. A vibration damper in the form of a spring-loaded counter-balance weight is attached to the rear cheek of thecrankshaft.

The Connecting Rods

The master connecting rod is machined from an I-section steel forging and has a steel-backed lead-bronze bushing in its

big-end. The eight articulated or link rods are of the same construction and are fitted with bronze bushings in theirbig-ends. The link rods are machined all over and have bronze bushings in their small-ends. This construction is shown inthe longitudinal section view of the engine.

The Pistons

The pistons are machined from heat-treated aluminum alloy castings. The top surface of the piston is concave so that itforms a semispherical combustion chamber in conjunction with the concave interior of the cylinder head. Each piston isfitted with three compression rings and one oil ring above the piston pin and one oil scraper ring below it. The piston pinis of the floating type with aluminum alloy plugs at each end to prevent it from scoring the cylinder wall.


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The Valves

The valving consists of an inlet valve and an exhaust valve of the poppet type operating in valve seats of aluminumbronze and Silcrome steel respectively shrunk in the cylinder head. The valves are actuated by means of rocker armsenclosed in oil-tight boxes and enclosed push rods and roller tappets. The push rods are made of steel tubing and are fittedwith hardened and ground ball ends. The rocker arms are mounted on ball bearings and have adjustable sockets for thepush rod ends.


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The Cams

The cam ring which actuates the valve tappets is machined from asteel forging and has four lobes. It is supported on a duro bronzebushing on the rear end of the crankshaft and is driven by means oan intermediate gear wheel which rotates it in the oppositedirection to the crankshaft at one-eighth engine speed. Afour-lobed cam ring for actuating the injection pumps is attached

to the valve cam ring by bolts and nuts with slots for adjustment.

The Fuel Pumps

The nine individual Guiberson fuel injection pumps used on theengine are flange-mounted around the rear section of the crankcasewhere they connect with fuel supply passages drilled in thecastings. Tapered roller actuating arms are provided between thestems of the plungers of the injection pumps and their cam ring.The actuating arms are mounted eccentrically on a control platewhich can be rotated slightly so as to vary the amount of plungerlift and the commencement of injection (Fig. 29). The injectionpumps are connected with the injectors in the cylinder heads by

equal lengths of high-pressure seamless steel tubing. The injectorsare mounted so that their axes are at an angle of 30 degrees fromthe vertical axes of the cylinders.

The Lubrication System

The lubrication system functions on the dry sump principle as in agasoline aircraft engine. Lubricating oil is delivered underpressure through the hollow crankshaft to the main bearings andthe cam rings. The cylinder walls, the crankshaft thrust bearings,the piston pins and the injection pump tappets are lubricated bysplash. The oil sump is in the form of a separate unit locatedbetween the two bottom cylinders of the engine.

The Accessories

The accessory section which is attached to the rear section of thecrankcase contains drives and mountings for the variousaccessories. These accessories comprise one pressure-feed andtwo scavenge pumps of the rotary-gear type, a pressure reliefvalve and a Cuno metal-disc filter for the lubrication system; aPesco rotary-vane transfer pump and a Purolator metal-disc filterfor the fuel system; a cartridge starter contacting the end of thecrankshaft for starting the engine; and an Eclipse electric

generator for charging the batteries in the airplane.

FUEL INJECTION SYSTEMThe fuel injection system used on the Guiberson A-1020 Diesel aircraft engine differs considerably from the Boschinjection system described in a previous section. Although the Guiberson injection pump is also of the plunger type, thelength of the stroke of its plunger is variable and not constant as in the Bosch. Control of the output of the pump isobtained by varying the quantity of fuel admitted into the pressure chamber. The design of the pump is such that constantoutput at any particular throttle setting is maintained without recourse to a governor or other mechanism.


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The output of the injection pump at any particular throttle setting is maintained constant by the compensating action of theplunger. If the engine speed decreases, the pump plunger uncovers the inlet port or portion thereof longer and a largerquantity of fuel is admitted increasing the engine speed to normal. If the engine speed increases unduly above normal, thiscompensating action is reversed.

The injectors used on the engine are operated hydraulically by the pressure of the fuel and are of the closed type. Thespring loaded nozzle valve in the injector is opened by the differential action of the fuel against its tapered end. The fuel is

sprayed through a multi-hole nozzle having three small holes direct into the combustion chamber in the engine cylinder.The fan-shaped spray of finely atomized fuel created mixes quite well with the air charge.

The use of individual fuel injection pumps on the Guiberson A-1020 Diesel aircraft engine is in line with similarinstallations of fuel injection equipment on radial Diesels such as the Clerget 14 F-01, the Salmson SH 18 and the ZOD260-B. It is advantageous on a radial engine because the high-pressure lines connecting the pumps and the injectors can berelatively short, thereby eliminating any possibility of fuel surge between the injection periods. The additional driverequired for individual injection pumps consists of another cam ring which can be attached to the cam ring actuating thevalve tappets. The injection pumps can be mounted with their bodies extending into the cam ring housing so that they arelubricated automatically by the oil spray from the crankcase.

BENCH AND FLIGHT TESTS

After the first Guiberson A-1020 Diesel aircraft engine bad been completed it was submitted to numerous bench tests atthe factory before it was installed in an airplane. The manufacturer I s tests consisted of 50 hours at full throttle in runs of 5hours' duration, and 50 hours at 75 per cent throttle also in 5-hour periods. The Government tests to which it wassubmitted consisted of 50 hours at full throttle in periods of 5 hours each conducted under the strict supervision of theCivil Aeronautics Authority (Fig. 32).

The C.A.A. bench tests were completedsatisfactorily in January, 1940. Themaximum power output of the enginewas held to 310 h.p. which it developedat a crankshaft speed of 2,150 r.p.m. Themaximum I power output curve waspractically a straight line peaking at 325

h.p. at 2,275 r.p.m. after which it fell offrapidly. The fuel consumption at fullload at 2,150 r.p.m. was found to be0.42 lb. per h.p. per hour and at cruisingspeed the consumption was 0.37 lb. perh.p. per hour. The lubricating oiconsumption at full load was 0.008 lbper h.p. per hour, equivalent to 2.47 lbor 0.33 gallons per hour (Fig. 33).

The Actual Flight Test

For the 10 hours' flight tests which are

also a prerequisite for governmentapproval the engine was installed in a4-place StinsonReliant monoplanewhich previously had been powered

with a supercharged Wright Whirlwind R 760 E2 gasoline aircraft engine rated at 320 h.p. at 2,200 r.p.m. As the twoengines were of approximately the same diameter the same cowling was used for the Diesel installation. With outpropeller and fuel it was found that the Diesel installation was only 6 lb. heavier than that of the gasoline engineinstallation. The engine itself weighed 650 lb., or 2.1 lb. per h.p. No difficulty was encountered in mounting the engineand it was found that the Diesel started readily or.) ordinary furnace oil at the first impulse of the starter.


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The official flight tests for the C.A.A. were completed satisfactorily and on one of the flights an altitude of 18,300 ft. wasattained with the airplane still climbing at the rate of 500 ft. per min. This altitude compares very favorably with theceiling of 14,500 ft. guaranteed for the gasoline-engined Stinson and indicates that a ceiling of at least 20,000 ft. could beattained by the Diesel-engined Stinson without supercharging. A.T.C. No. 220 was issued for the Guiberson A-1020Diesel aircraft engine in April, 1940, giving it a continuous rating of 310 h.p. at 2,150 r.p.m. at sea-level.

With regard to the excellent performance of an unsupercharged Diesel at

high altitudes, it should be mentioned that this type of engine can runwith excess air at sea-level and low altitudes as it is not fuel sensitive andits air-to-fuel ratio is comparatively flexible. The Guiberson A-1020Diesel runs with 18 per cent excess air at sea-level withoutsupercharging, with its valve timing arranged so that the volume of aircompressed in each cylinder is equivalent to 118 per cent of thecylinder's displacement. At high altitudes it does not experience the sameair shortage and lack of oxygen for combustion as does a gasolineengine.

The results obtained with the Guiberson A-1020 Diesel aircraft engine atrelatively high altitudes without the use of a supercharger compare very

favorably with those obtained with a gasoline aircraft engine equippedwith a supercharger of medium output. It is also found that when agear-driven supercharger is fitted to a Diesel the latter has a performancesuperior to that of a gasoline engine equipped with the same type ofsupercharger.

The superior performance of a supercharged Diesel aircraft engine wasdemonstrated by M. Clerget a short time ago. He conducted a series ofcomparative flight tests with his Clerget 14 F-01 Diesel equipped with agear-driven Gnome-Rhone 1-speed supercharger and then substituted agasoline aircraft engine of approximately the same power output and

equipped with a similar supercharger in the airplane. He used the same propeller on the two engines so as to ensure

accurate results.

It was found that while the two engines ran at the same crankshaft speed and developed the same power output atsea-level and up to their rated altitude of 7,800 ft., above this altitude there was a marked difference in their crankshaftspeeds and corresponding power outputs. In the case of the Diesel its crankshaft speed increased from 1,745 r.p.m. at analtitude of 7,800 ft. to as much as 1,880 r.p.m. at an altitude of 25,000 ft. without changing the throttle setting. In the caseof the gasoline aircraft engine its crankshaft speed decreased from 1,745 r.p.m. at 7,800 ft. to 1,650 r.p.m. at 25,000 ft.accompanied by a considerable loss in power output.

FLIGHTS WITH THE ENGINEAfter the Guiberson A-1020 Diesel had received its A.T.C., the Diesel-engined Stinson was flown from the factory toWashington, D. C., to demonstrate it before high-ranking Army, Navy, and civil aviation officials. The flight of 1,500

miles from Dallas, via Birmingham and Charleston, was completed in 10 hours and 35 minutes flying time at an averagespeed of 142 m.p.h. An altitude of approximately 3,000 ft. was maintained with the engine cruising at 220 h.p. at 1,800r.p.m. Regular Texaco Diesel Chief fuel oil costing 6 cents a gallon such as is used in Caterpillar tractors was consumed atthe rate of 11 1/2 gallons an hour or 0.37 lb. per h.p. per hour and its total cost was only $6.90. Lubricating oil to theextent of 3 gallons at $1.40 a gallon added $4.20 to the expenditure, making a total cost of $11.10 for fuel and oil for theentire journey. The fuel cost of less than 12 cent a mile is an unheard-of figure for flight operations in this country.


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After creating a very favorable impression at Washington the Stinson was flown to New York where the public had anopportunity of seeing it at Roosevelt Field (Fig. 34). The engine installation was found ' to be perfectly normal and onecould not tell that a Diesel was hidden underneath the regular cowling on the airplane. Demonstrations showed that theengine started quickly with a cartridge starter and that it idled quietly and evenly without vibration. When the throttle waspushed open the engine accelerated just like a gasoline engine and at cruising speed there was no evidence of smokyexhaust.

The return flight to the Guiberson factory at Dallas

was made by way of Chicago and at the latter city theDiesel-engined Stinson also received much favorablecomment. It was obvious to those who saw theairplane and its engine that flying would beappreciably safer when Diesels and theirnon-explosive fuel were available for private airplanesas well as for commercial and military aircraft. Amongthose who welcomed the Stinson at Chicago wereofficials of the Buda Company, an outstanding firm inthe Diesel industry which has arranged to manufactureGuiberson Diesels in its extensive factory at Harvey,near Chicago, anticipating a considerable demand for

these engines and possibly other models for the UnitedStates government.

FUTURE POSSIBILITIESThe arrangements which have been made between theGuiberson Diesel Engine Company and the BudaCompany are that the-latter will manufactureGuiberson air-cooled radial Diesels for use in both

airplanes and tanks. The tank engine is known as the T-1020 model and is identical in size and design with the A-1020aircraft engine. For cooling purposes the T-1020 engine is equipped with a large fan in front of its cylinders which isgear-driven from an extension of its crankshaft. .So great has been the demand for these tank engines for the United StatesArmy that special air-conditioned buildings have been built at the Buda factory in which the engines are manufactured by

the latest flowline production methods. These buildings are unique and anticipate air-raid "blackouts" in that they areconstructed without windows and are equipped with fluorescent lighting.

As most of the parts of the A-1020 and T-1020 Diesels are identical the production of the engines is of a very flexiblenature. If there is an urgent demand for aircraft engines few changes are required in the machine shop or the productionline to divert tank engine parts for this purpose. Not only does this arrangement facilitate production but it also helps toreduce production costs. Present-day low production cost of gasoline engines was not obtained until the engines could beproduced in considerable quantities. The same thing applies to the Diesel aircraft engine-its production costs can only bereduced to those of the gasoline engine by increasing its production volume, and selling considerable quantities ofengines.

As for the future of the Guiberson A-1020 Diesel, it should find a ready market for small airplanes such as the popular

StinsonReliant. Other models also are contemplated for future development. For instance, by reducing the number ofcylinders from nine to seven an engine with a power output of approximately 240 h.p. could be obtained. Furtherreduction in the number of cylinders to five would give an engine of approximately 170 h.p. It is also possible to increasethe power output of the A-1020 without adding to the number of its cylinders by equipping it with a gear-drivensupercharger. In this way its power could be boosted to approximately 400 h.p.

Motores Aeronauticos Diesel

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