Modification of an Experimental Model GDI Tumbling Flow by Direct Injection

Internal flow have a great contribution to the performance of internal combustion engines. A study of the modification of a model GDI tumbling flow is proposed in this paper. The first part gives an overview of the current works concerning in-cylinder flow. Our experiment generates and compress a tumbling vortex during one cycle. The experiment will be described as well as injection calibration. Indeed, It is not possible to use an industrial spray injector in our experiment since velocities in our chamber are lower than in cylinders. Furthermore, our flow is non reactive, the only vaporization would be due to the compression. We decide to use a gas injector. A non dimensional parameter comparing the angular momentum brought by the spray to the initial angular momentum of the tumble structure will be derived in the paper. This non dimensional parameter is useful to define and to analyse our model experiments while being sure to be relevant as engine situation is concerned. According to this parameter, further conditions of injection (angle) will be discussed.

PIV measurements of the tumble show that the structure is affected by the injection. The latter modifies the location of the rotation centre. Tumble behaviour during compression is not the same than without injection. Flow turns out to be three dimensional thus modifying breakdown proprieties. Tumble ability to participate to stratification will be discussed.