Two novel diesel injection systems have been tested in prototype form. Both are intended to overcome particular deficiencies of conventional equipment which are especially pronounced in small high-speed engines.
The ‘Fuel Hammer’ system for direct-injection engines has three main objectives: avoidance of the need for high-pressure pumping elements, separation of the pumping and control functions, and elimination of high impulsive torques in the pump drive.
These objectives were achieved by utilising the phenomenon usually called ‘water hammer’. Sufficiently high injection pressures were generated by rapidly halting a moving column of fuel. A continuously-operating pump thus generated injection pressures ten times higher than its delivery pressure. Injection data are given for a range of conditions.
The ‘Rapid Spill’ system is primarily intended for small high speed direct-injection engines whose performance is very dependent on the mean injection pressure attainable. A pressure-intensifier in the injector substantially increased the mean injection pressure. A very rapid end of injection was obtained by spilling at the injector rather than the pump. Reductions in injection period of up to 30% were achieved with no changes to pump or nozzle.
The features of both systems are discussed in the context of the injection system characteristics ideally required by modern diesels.