Study of GDI Injector in constant volume chamber by optical measurements and CFD-Simulation

Better performance and the regulatory requirements concerning the combustion emissions have caused downsized GDI engine and consideration on strategies for improving in-cylinder mixture preparation. The sprays characteristics of the fuel injectors of GDI engines have been widely investigated by researchers. The interest in studying the characteristics of the spray is due to a strong relationship with the subsequent combustion reaction and thus with the engine thermal efficiency. This paper analyzes the mixture formation of the spray employing an experimental laser apparatus that was used to measure the spray penetration in a constant volume chamber (CVC) and simulations performed by the fast response CFD CONVERGE software. The fuel injector used in the tests was a six-hole direct injection injector with iso-octane fuel. The measurements were taken 100 mm downstream from the injector tip along the axis with 20 MPa injection pressure. During experiments, it was observed that spray development is not symmetrical with the vertical axis, and with decreasing chamber pressure, it develops faster. Moreover, the average of spray development velocities in simulations is in good agreement with experimental results.