The Nakajima Homare (誉, "praise") was a Japanese aircraft engine manufactured during World War II.
It was an air-cooled radial engine in the 2000-HP class, and was used widely by both the Imperial Japanese Army and the Imperial Japanese Navy. "Homare" was the navy designation; the army called it the Ha-45 (ハ45) and the manufacturer's designation was NK9.
Development of the 18-cylinder twin-row Homare started in 1940, and certification was completed in 1941. It succeeded Nakajima's previous 14-cylinder Sakae (Ha-25) engine, with its forward nine cylinders staggered from the rear nine for efficient cooling.
The design was exceptionally compact, with an external diameter of 118cm, a mere 3cm larger than the Sakae. With a bore and stroke of 130mm x 150mm, it was classified as a short-stroke engine. It was designed to output around 1800hp, or 100hp per cylinder. However, the tight design of the engine made it difficult to maintain quality in manufacturing, and unreliability in the field was a significant problem; actual output was in the range of 1300hp, far below the designed capability. Still, it became the predominant powerplant of Japanese military aircraft in the latter part of the war. A total of 8,747 were produced.
Specifications
- Type: Air-cooled twin-row 18-cylinder
- Output: 1,990HP at altitude
- Water-methanol fuel injection
- Displacement: 35,800cc
- Diameter: 1,180mm
- Weight: 830kg
