From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Describing the Ljungstrom direct gasoline injection system for aviation engines.
| Identifier | ExFiles\Box 178\2\ img031 | |
| Date | 14th February 1940 guessed | |
| Memorandum Concerning Gasoline injection for aviation Engines Considerable interest has been aroused about direct injection of gasoline into the cylinders of aviation engines, thereby eliminating the carburettor, and the present type of fuel pump. The advantages are well known, of which the elimination of troubles with freezing at high altitudes is the most outstanding. Increase in power and efficiency is also claimed. In the Ljungstrom gasoline injection system, the amount of air to the cylinders is controlled in the usual manner by restricting the intake to the supercharger, by means of the air control valve as shown on the drawing No. 2-01-26. Thus maintaining control of power and speed. The control of the fuel injection is entirely automatic and is a matter of keeping the air-fuel weight ratio constant under all conditions. The fuel injection pump, drawing No. 2-1-25, is driven by the engine at half speed. A single cam is employed, which has been given a shape such as to facilitate constant injection over the total air intake period, thus giving a homogenous mixture in the entire cylinder charge. The injection nozzle, producing a flat fan shaped spray sheet approximately 1/32 inch thick, is located immediately under the intake valves so that all the air entering the cylinder must pass thru the spray. The stroke of the injector is constant, as the cam operating same is constant, but the useful stroke is variable and is accomplished by adjusting the plunger up or down regardless of cam motion. This adjustment is made by means of an oil pressure operated servomotor in which the pilot valve is subjected to the pressure in the supercharger diffuser, as well as the velocity in the control valve venturi. By this means the the mixture in the cylinder will be kept constant regardless of the altitude under all conditions of load and speed. The fuel injection pressure is below 100 pounds per square inch when used for Diesel injection. A primary fuel pump delivers the fuel to the plungers at a pressure of around 7 pounds per sq. inch. For calibration of the injectors so that all cylinders receive an equal amount of fuel, an adjustment is provided which is locked in place after the adjustment is accomplished. The air control valve shown on drawing No. 2-01-26 is a floating valve which is balanced perfectly in all positions and is practically frictionless, as no loaded bearings are employed, thus making the movements of the valve practically effortless. Venturi action in the air intake of the valve has been made use of in the servomotor together with the static pressure in the diffuser of the supercharger for the control of the injector. The equipment consists of the injector with primary fuel pump included, the servomotor which controls the injector and which receives oil under pressure for its operation from the engine lubrication system. The oil returned from the servomotor enters the injector housing for the lubrication of all parts of same, and is then returned to the engine crank case. Further parts of the equip- | ||