Fuel Injection in Oil Engines in Relation to Combustion

Abstract

The object of the paper, which deals with the jerk pump injection system, is to show the relationship between the design of fuel injection equipment and the design of the engine on which it is used. First the nozzle is considered as an orifice, in its relation to the combustion chamber, and an account is given of the features of hole type and pintle type nozzles. The action of the differential needle valve is then discussed, and particular reference is made to the design features necessary to ensure quick action of the valve, with good “chattering”. The author then considers the design of “restricting” or “delay” type nozzles, and a description is given of the delivery valve of the pump. The need for “unloading” of the delivery pipe is discussed, together with various types of delivery valve and their action. The delivery pipe itself is treated with reference to ( a) determination of size of pipe; ( b) pipe surges and their effects; ( c) methods of dealing with surges. In addition the action of a pump plunger and barrel of the ported type is considered in relation to its effect on pump output at varying speeds, also the combined effect of pump plunger and delivery valve. The author sets out the points to be considered in the selection of fuel injection equipment for a given engine. Basing his analysis on existing designs, he puts forward a classification of combustion chambers from the viewpoint of fuel injection. He shows that orifice diameter in hole type nozzles depends on the penetration required, and that the total orifice area is also dependent on the piston displacement per unit of time. The selection of a suitable pump to feed the nozzle is discussed, and the author arrives at specific ratios for assessing pump action in relation to the engine and the nozzle. Finally, consideration is given to the limiting capacity of an atomizer of given size, and to the release pressure in an atomizer and the maximum pressure of injection.