TRANSFERRING THE VIRTUES OF DIVIDED COMBUSTION CHAMBER TO DIRECT INJECTION CHAMBER - A WAY FOR IMPROVING DIESEL ENGINE EFFICIENCY

摘要

It is well known and appreciated the performance of diesel engine with prechamber system, which provides combustion with very low emissions and a major reduction in particulates and noise. On the other hand, diesel engine with direct injection system operates with a large quantity of excess air, providing a good fuel efficiency and low exhaust smoke numbers. In order to improve the performances of a DI diesel engine, the authors decided to induce a controlled turbulence in the narrower combustion chamber recess in the piston. Considering the holes permitting communication between prechamber and main combustion chamber, the authors provides the piston of the DI diesel engine with several holes, allowing the air to improve tumble motion in addition to swirl. The motion of the air gets new virtues, its new trajectory being characterized as a partially lop-sided evolute and determine the rise of turbulence, which in turn leads to improvements of self-ignition and fuel combustion due to the use of this favorable air motion in addition to the energy generated by injection. The authors made the holes in the combustion chamber recess in the piston in ceramic material, providing the head of the piston with high thermal resistance. The researches were made on a DI diesel engine fitted on an off-road motorcar. The tests made with the engine emphasized a reduction in particulates and noise, and also a small improvement of power and torque at low loads. These improvements offer to the engine manufacturer the possibility to satisfy the requirements of emissions limits.