Experimental Investigation of the Pilot Injection Effects on Single Cylinder Engine Performance

Report, 1998

A new concept for diesel combustion has been investigated by means of AVL single cylinder engine tests and combustion observations in order to reduce the NOx emission at constant BSFC. The concept is based on pilot injection. In this method, some part of fuel is injected at an early stage, short prior the main injection. It is well known that pilot injection is effective to shorten ignition delay of the main injection. Especially, when the main injection is considerably retarded, pilot injection suppresses the increase in NOx emissions due to the long ignition delay. Engine tests were carried out using a AVL single cylinder research engine at Chalmers University of Technology, Department of Thermo and Fluid Dynamics, equipped with C3EUI and 24 CU ECU via a PC. The pilot injection strategy was to inject a small amount of fuel short prior main injection, such as to be indicated by the needle lift and heat release curve. The experimental results showed that, the trade-off relation of BSFC against NOx emissions with the pilot injection concept is better than those of a conventional injection. The concept of pilot injection seems to interesting for further investigations in connection with compression ignition of lean pre-mixture with multiple injections.