Abstract
The rapid diesel engine for motor-car needs an increased dynamics for self-ignition and combustion. A new possibility for achieving this is represented by the transfer of the virtues of the prechamber to the combustion chamber made in the piston head for direct injection. This objective is realised by changing the air and flow motion during combustion stage, through the holes with tangential jets or alveolus with a profile which intensifies the tumble and swirl motions, in optimum limits.
Turbulence intensifies due to the orifices made in the ceramic ring, increasing the diffusion coefficient. This coefficient is directly determined by the piston speed, which is very important for diesel engine because when the speed increases the time for blending decreases, and this tendency is compensated by the increase of the diffusion speed of fuel vapors and made possible blending in a relative short time. The convective heat transfer inside combustion chamber has a turbulent behavior. By increasing the turbulence the heat losses increase, the ignition is hard to develop and the efficiency decrease. The thermal insulation of combustion chamber reduces the heat transfer to the exterior and cancels these difficulties.
The transfer of divided combustion chamber virtues to combustion chamber inside piston head of DI engine could be a direction for a structural change of blending and combustion principles of diesel engine. Changing the elements that increase turbulence intensity speed increase, constructive modification of intake system, modification of combustion chamber architecture etc. it could be obtained flame propagation speed increase and combustion length reduction, therefore combustion efficiency increase, with all the benefits concerning power, fuel saving and pollution reduction for diesel engine.