Diesel Injector Fuel Injector 0445110466 0445110717 0445110794 Bosch for Jianghuai Auto

Large Eddy Simulation of diesel injector opening with a two phase cavitation model （part 1）

Abstract.

In the current paper, indicative results of the flow simulation during the opening phase of a Diesel injector are presented. In order to capture the complex flow field and cavitation structures forming in the injector, Large Eddy Simulation has been employed, whereas compressibility of the liquid was included. For taking into account cavitation effects, a two phase homogenous mixture model was employed.

The mass transfer rate of the mixture model was adjusted to limit as much as possible the occurrence of negative pressures. During the simulation, pressure peaks have been found in areas of vapour collapse, with magnitude beyond 4000bar, which is higher that the yield stress of common materials. The locations of such pressure peaks corresponds well with the actual erosion location as found from X ray scans.

1. Introduction

Diesel injection systems play a fundamental role in internal combustion engines since they affect the formation of the fuel spray, atomization and combustion, the formed emissions and the engine efficiency. The jet velocities formed are of the order of 500m/s, with upstream pressures around 2000bar. Current trends show injection pressures to even rise to 3000bar, in order to meet the future EU legislations in emissions. However, higher pressure levels causes very high velocities through the tight passages in the Diesel injector and strong accelerations in sharp direction changes (corners, fillets etc.), which lead to local static pressure dropping below the saturation pressure and causing cavitation.

Furthermore, cavitation may lead to cavitation erosion damage and serious degradation of the injector performance, even catastrophic injector failure, which could damage the engine, if the injector tip breaks off. There have been many efforts for the prediction of the Diesel injector erosion, see e.g. the work of Koukouvinis et al. [1].