Japanese jet engines

PM 18

November 1945.

NAVY DEPARTMENT

BUREAU OF AERONAUTICS

WASHINGTON

POWER PLANT MEMORANDUM NO. 18

JAPANESE POWER PLANTS FOR JET PROPULSION

Prepared by: R. M. SALTER, JR, Lieutenant, USNR.

Approved by: S.B. SPANGLER, Captain, USN

A. Introduction.

1. The purpose of this report is to present preliminary data on Japanese jet engines in general and Japanese turbo-jets in particular.

Information received to date reveals a rather meager embarkation by the Japanese into the field of jet propulsion. Apparently the Air Ministry was reluctant to allocate any of the reciprocating power plant facilities for a jet program, relying instead on Navy Yards and the Air Technical Arsenal. The Navy Yards, needless to say, were unfamiliar with problems involved in building aircraft power plants and in working with light metals. Three Ne-20 turbo jet units produced at the Yokosuka Navy Yard were tested at Hadano by the jet engine laboratory of the Air Technical Arsenal and found to be poor in quality.

Although the Japanese had a few original turbo jet designs these were cancelled in favor of four engines based upon the German BMW 003.

German designs also were used in the Japanese liquid, fuel rocket engine. The KR 10 is apparently a Japanese built Walther R 211 unit.

Other types of jet power plants tried were an intermittent jet engine and a Campini type engine.

B. History.

1. Turbo-jets. Japanese jet development began in 1942. Initial work was done by the First Air Technical Arsenal and employed centrifugal compressors. The first of these was undesignated but served as a prototype for the TR 10. The TR 10 produced 770 lbs. thrust and was to be used in the twin-engined "anti invasion" bomber Kikka. The TR 12 was the next of the series and represented an improved TR 10 with four axial compressor stages added; thus following a compressor development pattern similar to German Heinkel Hirth engines. The TR712 was considered to be too heavy. The TR 12B followed with a weight of 770 lbs. This latter engine was abandoned in March 1945 in favor of the Ne-20. It was found that the TR 12B lagged considerably behind the development of the Kikka airframe. About 40 of these engines were fabricated.(Figure 15).

The TR 30 was an enlarged TR 12B and two TR 30's were to be installed in Keiun, a reconnaissance plane. The TR¬30 was also abandoned in favor of the Ne-20 in December 1944. (Figures 10 and 11).

In May 1944 photographs of the BMW 003 arrived by submarine. A companion sub containing production drawings was sunk enroute. From the 003 photo prints evolved four engines, the Ne-20 by the Air Technical Arsenal, the Ne 130 by Ishikawajima, the Ne 230 by Hitachi and the Ne 330 by Mitsubishi.

The Ne-20 is about a three quarter sized 003 and was ready for production in the summer of 1945. (Figures 1 7). It was flight tested successfully in Kikka in August 1945. The Ne-20 was also destined for the Oka 43 (Baka). (Figures 8 and 9). Nine engines were built by the Air Technical Arsenal and 12 by the Yokosuka Navy Yard. This latter agency was to be the manufacturer of the Ne-20. To date only two Ne-20's have been recovered.

Of the three reciprocating engine manufacturers experimenting in turbojets, Ishikawajima probably was in a better position than Hitachi or Mitsubishi due to the latters' production commitments for conventional engines. In addition to the Ne 130, Ishikawajima also designed the Ne 140 and the GTPR. The Ne 140 was a larger engine than the Ne 130 and served as a prototype for it. The Ne 130 compares more closely in performance to the BMW 003 than any other Japanese turbo jet. The Army was interested in the Ne 130 for use in Koryu. The GTPR (Gas Turbine Propeller Rocket) was an ambitious propeller gas turbine design originally involving a 19 stage axial flow compressor, four combustion chambers and a three stage turbine. (Figures 12 14). A later GTPR design was promulgated with a 12 stage axial compressor with a 4:1 pressure ratio, 5 stage turbine and an annular combustion chamber of the BMW type employing 12 burners. The engine rpm was to be 5000 and the propeller rpm 1500. The prop reduction was to be of the double helical spur type. The length was estimated at 18 ft, diameter 31.5 inches and weight 5500 lbs. Estimated sea level power was 3500 bhp delivered to the propeller and 1500 equivalent jet thrust bhp at 373 mph. Operating temperatures were expected to be 1290 F. combustion chamber and 840 F. tail pipe. The GTPR was destined for a large low speed, low altitude airplane. Research on the GTPR was terminated in August 1944 probably since it was a rather long range project, although some component testing was done.

The Ne 130, Ne 230 and Ne 330 were in approximately the same state of development at the war's end. One model of the Ne 130 was produced but was destroyed on bench test. The Ne 230 was also completed and was under test by the Navy at Takahagi. The Ne 330 was almost completed but work was terminated due to air raid damage. The best of the three above engines was to be used in Keiun.

2. Campini type engines. Early Japanese jet propulsion efforts were directed along the lines of the Campini system. Documents recovered in 1942 show that this type of engine was being investigated at that time.

As a stop gap between the Oka 11 (Baka with solid propellant rockets) and the Oka 43 for the Ne-20, the Oka 22 with the TSU 11 Campini type engine was developed by the Air Technical Arsenal. (Figures 16 and 17). The TSU 11 is a Hatsukaze 11 four cylinder inverted in line air cooled engine driving a single stage axial compressor. The Hatsukaze is rated at 150 bhp at 3000 rpm. The compressor is geared up 3:1 and rotates at 9000 rpm. The compressor wheel is 21.3 inches in diameter with an effective blade height of 3.8 inches. Four fuel burners are located aft of the compressor to provide afterburning. Three TSU 11 engines were built.

Flight tests were made in 1944 using the TSU 11 as a booster for Frances. One successful flight of an Oka 22 was made in July 1945, the Oka 22 being launched from a Frances.

Hitachi began manufacturing of the the TSU 11 in June 1945 and was also experimenting with a similar type of power plant. This latter was designated the M.T.P.R. and consisted of a combination propeller reciprocating Atsuta engine and turbo jet. Part of the reciprocating engine power was transmitted to the compressor of the turbo jet. This project was abandoned in August 1944 in favor of the Ne 230.

3. Miscellaneous engines. The Air Technical Arsenal tried various other types of jet engines. These were the KR 10 (TOKU RO2) bi fuel rocket, the Ka 10 intermittent jet, and a Pescara type free piston compressor design study. The KR 10 is apparently a copy of the German Walther R 211 rocket engine used in the ME 163. (Figures 18 and 19). The KR 10 is installed in the Shusui which is very similar to the ME 163. (Figure 20). German sources state that complete ME 163 plans were turned over to the Japanese about a year before their surrender. The Japanese experienced the same difficulties in producing “T Stoff" (hydrogen peroxide) and "C Stoff" (hydrazine methanol¬-catalyst) fuels as did the Germans. The engines were put into production in July 1945. Shusui made one flight in July 1945 but crashed due to probable fuel feed failure.

The KR 10 develops 3300 lbs. thrust for 4 minutes and weighs 375 lbs. A description of this engine will not be made here due to the similarity of KR 10 to the German engine.

The KA 10 intermittent jet is also borrowed from the German designs, namely the Argus As 0014 "V 1" engine. '(Figure 21). The only departure in design from the As 0014 is the expansion chamber aft of the valve matrix. 288 fuel nozzles are used in this matrix. 990 lbs. thrust were obtained on the test stand with a 2.6 lbs/hr lb.thrust specific fuel consumption. The KA 10 was to be used in the Baika aircraft.

No information is available on the free piston compressor system other than it was destined for a large aircraft and the project was abandoned in August 1944.

C. Summary.

Table I shows a tabulation of the various jet engines tried by the Japanese. It should be noted that information on these engines is derived from Japanese Naval sources. However, interrogation of German personnel revealed that of the Japanese technical officers sent to Germany, only those of the Navy were interested in jet development work. The Army group wanted production drawings solely. This same policy was reflected in Japanese conventional engines Army engine research was on the whole poorer than that by the Navy.

Figures 1 to 21 show photographs of jet power plants taken in Japan. The Navy Department is arranging for test of one of the two Ne-20 turbojets recovered. This engine appears to be the most promising of those developed by the Japs.

It is believed that gasoline and pine root distillate were used as fuel for turbo jets. Germany had to resort to 50/50 diesel fuel and kerosene due to gasoline shortages and resultant specific fuel consumptions were higher.

Electric furnace alloy steels with no Nickel were being developed by the Air Technical Arsenal for turbines. These were specified to have a creep limit of 20 Kg/sq. mm at 600 C. The steel developed was a Mn Cr V alloy (1 309) with .22% C, 16% Mn, 11% Cr and .7% V. A nitrogenized alloy of .15% C, 14% Mn, 11% Cr, .7% V and .15% N was anticipated to up the temperature limit above to 650 C. A flux coated welding rod using 1 309 was developed for welding of blades and disks.

The Japanese jet program can well be summarized by the expression "too little, too late".

1—The KR-10 was a clone design based on the Walther HWK 109-509 bi-propellant rocket engine which powered the Me-163B “Komet” fighter.

2—The “Campini” type jet engine is odd enough(in 2008) to require a brief explanation. The basic design consisted of a piston engine driving a compressor. Fuel was injected into the air stream coming from the compressor to provide more heat and jet thrust. Sometimes the piston engine also drove a propeller, but sometimes not. There was no exhaust turbine nor any potential for turbine blade failures, a problem which plagued early turbojet designs. The most famous airplane powered by this type of engine was the two-seat experimental Italian aircraft, the Caproni-Campini N-1, which first flew in 1940. A hand-built biplane with a similar engine design had flown(after a fashion, it then crashed) in 1910, product of a Romanian designer, pilot and engineer living in Paris, Henri Coanda. Engines of this type are today often referred to as a “motorjet” or “thermojet” engine. The fundamental problem of the type, as I understand it(I’m not an aeronautical or aerodynamic engineer) is that the competing turbojets were not encumbered by a whole piston engine, but instead relied on a light and compact arrangement of turbine and compressor disks. If you could get them to run reliably at the temperatures involved, turbojets were a fundamentally better bet, as the Japanese discovered for themselves. The Soviets also built some planes with this type of powerplant, an example being the prototype Mikoyan I-250/N.

Yokosuka=First Naval Air Technical Arsenal at Yokosuka; they handled a wide range of technical, test flight and design tasks for the Imperial Navy. Among other things, they designed the D4Y1-4 “Judy” dive bombers which were manufactured by Aichi Ltd in Southern Japan as well as the land-based P1Y1 “Frances” twin-engined bomber.

Ishikawa=Ishikawajima-Harima

Status, e=experimental, s=series(built in modest numbers), p=projected(but not built)

Arrangement: reading from left to right(the purported direction of the airflow), p=propeller, r=radial(centrifugal) compressor, a=axial compressor or turbine(some with number of stages), Oc=annular combustion chamber

Pulse=Pulsejet or Lorin Duct, similar in layout to the Argus 014 which powered the V-1 “Buzz-Bomb” cruise missile. It was cheap to manufacture and simple, but it had major problems with flexibility, noise and vibration. When Messerschmidt tried to air launch an Me-328 prototype with two pulsejets, once they were started the harrowing vibration from two such engines tore the little plane apart. After building some V-1(or FZG-76) prototypes with a seat for a pilot and manual controls as part of the V-1 development program, the German Air Force went on to build manned versions of the V-1 as the “Reichenberg” manned bomb. If they had been used operationally, they would have worked a lot like the Ohka (or the American flying bombs of “Project Aphrodite”), but Hitler quashed the project.