Bristol Perseus

The Perseus was a nine cylinder single-row radial aircraft engine produced by the Bristol Engine Company starting in 1932. It was the first sleeve valve engine to see significant use.

Design and development

In late 1925 and early 1926, the RAE published a series of papers by Harry Ricardo on the sleeve valve principle. The main advantages over the traditional poppet valves was better volumetric efficiency, and the ability to operate at higher rotational speeds. This allowed a smaller engine to produce the same power as a larger one, leading to better fuel efficiency and compact design, particularly in multi-row radial engines.

Roy Fedden, Bristol's primary engine designer, became interested in the concept and by 1927 he had constructed a working two cylinder V as a testbed, with the idea of developing it into a V-12. However several problems cropped up on the design, notably that the sleeves tended to burst during the power stroke and strip their driving gears. This led to a long series of tests and materials changes and upgrades that required six years and an estimated 2 million pounds to cure, but by 1933 the problems had been worked out.

The result was a Bristol Mercury-sized engine adapted to the sleeve system, the Perseus, and its smaller cousin, the Bristol Aquila. The first production versions of the Perseus were rated at 580 horsepower 433 kW), the same as the same-year model Mercury, which shows that the sleeve system was being underutilized. However this was quickly uprated as improvements were introduced, and by 1936 the Perseus was delivering 810 hp (604 kW), eventually topping out at 930 hp (690 kW) in 1939. This far outperformed even the most-developed versions of the Mercury.

The Perseus saw limited use in the civilian field, notably on the Short Empire flying-boats, but was more common in the then-expanding military field where it was found on the Westland Lysander, Vickers Vildebeest, Blackburn Botha, Skua and Roc bombers.

The main contribution of the Perseus is that its mechanicals were used as the basic piston and cylinder for the "twinned" versions, the tremendously successful Hercules and Centaurus. It was in these designs that the advantages of the sleeve valve were finally put to good use, and by war's end the Centarus was one of the most powerful engines in the world.

Specifications (Perseus XII)

pistonspecs

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type=Nine-cylinder single-row supercharged air-cooled radial engine
bore=5.75 in (146 mm)
stroke=6.5 in (165 mm)
displacement=1,519 in³ (24.9 L)
length=53.03 in (1,347 mm)
diameter=51.97 in (1,320 mm)
width=
height=
weight=1,025 lb (465 kg)
valvetrain=Sleeve valve
supercharger=Single-speed centrifugal type supercharger
fuelsystem=Claudel-Hobson carburetor
fueltype=87 octane rating gasoline
oilsystem=
coolingsystem=Air-cooled
power=
* 819 hp (611 kW) at 2,650 rpm for takeoff
* 893 hp (666 kW) at 2,750 rpm at 6,500 ft (1,980 m)
specpower=0.59 hp/in³ (26.75 kW/l)
compression=
fuelcon=
specfuelcon=0.43 lb/(hp•h) (261 g/(kW•h))
oilcon=0.28 oz/(hp•h) (11 g/(kW•h))
power/weight=0.87 hp/lb (1.43 kW/kg)
reduction_gear=0.5:1 turning a de Havilland variable pitch propeller

Applications

;GBR:
*Blackburn Botha
*Blackburn Roc
*Blackburn Skua
*de Havilland Flamingo
*Short Empire
*Vickers Vildebeest Mk.IV
*Westland Lysander Mk.II

References