Rolls royce crecy

Sir Henry Tysard, chairman of the Aeronautics Research Committee (ARC), who foresaw the need for such a power plant in connection with the growth of German air power back in 1935, was the author of the idea of ​​a powerful “sprinter” engine for fighter jets. It can be assumed that it was under the influence of Tizard, who was his friend, Harry Ricardo and began the development of the motor, which later became Crecy ^[3] . This idea was first discussed at a meeting of the subcommittee on engines in December 1935:

Preliminary experience was accumulated in 1927-30. during the operation of two Kestrel engines, converted, according to the contract with the Ministry of Aviation , for further research into two-stroke with gas distribution . Both engines were first converted to diesel engines , which led to a decrease in power and an increase in the number of mechanical breakdowns, although one of them was then successfully used by captain George Aiston to set the world wind speed record for the Wind Speed car. The second engine was subsequently redesigned into gasoline with direct injection, which gave a noticeable increase in power compared to the serial Kestrel ^[4] .

Design development began in 1937 according to the project of engineer Harry Wood using a single-cylinder test rig designed by Ricardo. Although the diesel engine was originally conceived, by the time the Rolls-Royce and the Ricardo company began working on the project, the Ministry of Aviation decided to return to the traditional spark ignition, however, leaving direct fuel injection.

Crecy's chief designer was Eddie Gass, who led the Harry Wood development team. The first full-size engine was assembled in 1941.

Technical Description

The cylinder diameter was 129.5 mm, the piston stroke was 165.1 mm, the compression ratio was 7: 1, and the engine weight was 862 kg ^[5] . The ignition timing (30 °) and boost pressure (100 kPa) were typical at that time. At bench tests, the engine developed a power of 1400 hp, but there were problems with vibration, as well as cooling of cylinders and liners ^[6] . According to developers, an exceptionally powerful engine exhaust at maximum speed could provide a 30% increase in thrust developed by the propeller . High engine power was of interest in itself, but an additional exhaust thrust could make it a useful intermediate solution between conventional reciprocating engines like Merlin and those expected in the future. The serial numbers of the motors were even, since the company traditionally assigned even numbers to right-hand rotation engines.

Sleeve gas distribution

Sliding open liners did not fit tightly to the cylinder heads, leaving slots at the top of the cylinder at the end of the cylinder liner for exhaust gas to exit. The windows in the sleeve therefore served only to let in a fresh charge of the mixture. The stroke of the sleeve was 30% of the piston stroke (49.5 mm) ahead of 15 ° ^[5] . Thus, the Crecy gas distribution mechanism was structurally similar to the mechanism with slewing sleeves developed by Roy Fedden and first successfully applied in 1932 on the Bristol Perseus motor, but had a different operating principle ^[7] .

Supercharging and turbine

Unlike most two-stroke engines, boost was used to a greater extent to increase the charge of the mixture than to increase the pressure in the crankcase . This made it possible to use a circulating lubrication system instead of the usual one for two-stroke flowing motors. The distribution of the mixture was layered : fuel was injected into the onion-shaped expansion of the combustion chamber , where the rich mixture was ignited by twin candles . By changing the ratio of the working mixture in the range 1:15 - 1:23, it was possible to control the engine power in the range of 60-100%. The concentration of the rich mixture near the candles reduced the detonation , which made it possible to increase the compression or boost pressure. At idle, a supercharger throttle was also used. An innovative vortex throttling system provided a change in the effective angle of attack of the compressor blades in the range of 30-60 ° ^{[ check translation ! ]} . This made it possible to reduce the power taken by the supercharger in the throttling mode and, consequently, the fuel consumption in the cruising mode.

In later tests, the engine was equipped with a power turbine , which was a half-sized turbine of the Power Jets W.1 engine designed by Frank Whittle , the first British turbojet to fly into the air. Unlike a conventional turbocharger , the turbine gave power to the auxiliary drive shaft, turning the engine into a turbocharged one . It was supposed to reduce fuel consumption in this way and make the engine suitable for installation on transport aircraft. Increased efficiency was confirmed during testing, but serious problems were revealed - shaft failure and severe overheating ^[8] .

Bench tests

Project Closure

The progress of jet engines has led to the need for motors like the Crecy to disappear. As a result of this work on the project were discontinued in December 1945. Only 6 full-size engines and another 8 experimental 2-cylinder sections were built. Crecy 10 developed a power of 1798 hp on December 21, 1944, and after installing a power turbine, this figure increased to 2500 hp. ^[9] Subsequent experiments on the Ricardo E65 single-cylinder experimental unit showed the possibility of reaching 5000 hp. in terms of a 12-cylinder engine ^[10] . By June 1945, the total operating time of full-sized motors during the tests was 1060 hours, and two-cylinder sections - 8600 hours ^[11] . The fate of the engines built remains unknown.

Hawker Henley

For flight tests of the engine, it was supposed to use Hawker Henley with serial number L3385 , which was delivered for rework at Hacknall airbase on March 28, 1943. The aircraft stood there without an engine until September 11, 1945, after which it was scrapped ^[12] .

Supermarine Spitfire

Two years earlier (in the summer of 1941) Spitfire Mk II was delivered to Hucknall with the number P7674 , on which they installed the Crecy model for making drawings of the hood and propeller group. Also, the delivery of the first Spitfire Mk III samples without engines for installing Crecy ready for flights was agreed in early 1942, but it did not take place, since the production of this modification did not go beyond the prototype. A comparative assessment of the Spitfire options with Crecy and Griffon 61 is dedicated to the report of the Royal Aviation Center No. E3932 for March 1942. It concluded that the power of the Crecy is excessively large for the Spitfire airframe, but its deformed version will give the fighter significant advantages over the Griffin ^[13] .

Main characteristics

• Type: piston / turbocharged two-stroke V-type 12-cylinder liquid-cooled engine
• Bore: 129.5 mm
• Piston stroke: 165.1 mm
• Engine displacement: 26 l
• Dry weight: 862 kg

Features of functioning

• Valves: Sleeve Timing
• Compressor : monitoring station with a variable angle of attack of the blades, the maximum boost pressure of 165 kPa
• Turbocharging : no turbocharger, installed power turbine with power transfer to the auxiliary shaft
• Fuel system: with direct fuel injection, two CAV injection pumps (one per unit)
• Fuel Type: 100 octane gasoline
• Lubrication system: circulating (dry sump), with gear pump
• Cooling system: liquid

Performance

• Output Power: 2729 HP (2035 kW)
• Power density : 105 hp / l (78.3 kW / l)
• Compression ratio : 7: 1
• Specific power by weight: 3.17 hp / kg (2.36 kW / kg)