This paper describes the principles, effects and the potentials of impulse charging systems applied to SI and Diesel engines. In general, impulse charging is realized by closing the inlet port upstream of the inlet valve during the intake stroke with an additional switching device. The piston, moving towards bottom dead center, generates a vacuum inside the combustion chamber and inlet port. By opening the switching device abruptly, the sub-atmospheric pressure level induces an enhanced volumetric efficiency due to the significantly increased gas dynamic effects in the intake manifold.
One major advantage of impulse charging in comparison to the well known supercharging techniques lies in the dynamic behavior. The charging effect can be realized within one engine cycle. Furthermore, impulse charging provides high low-end torque, a nearly constant torque over a wide engine speed range with charging rates from 20% to 30%.
The requirements to realize an impulse charging device are high cross sections with minimized flow resistance, extremely fast opening and closing of the switching device, air tightness, and a good timing variability. Measurements performed on a SI engine equipped with an electromagnetic impulse charging device show indicated mean effective pressures higher than 1.4 MPa in an extended engine speed range with the charging effect being realized after one engine cycle.
Additional potentials with impulse charging can be expected by combining this technique with other supercharging systems especially a turbocharger and by using the impulse charger to control flow conditions and exhaust gas recirculation at part load.