Correlating gasoline spray propagation in Constant Volume Chamber and optically accessible engines

Abstract

In DISI engines spray distribution and atomization directly influence mixture formation, quality of combustion and resulting emissions. Constant volume chambers (CVC) are commonly used to characterize spray distribution of gasoline injectors. The CVCs provide good optical access but the flow condition in the engine can't be reproduced.
Therefore it is required to investigate if the spray propagation in DI-engines and CVCs is comparable. Three gasoline injectors with multihole and twinjet atomization were studied in an optically accessible engine and CVC. The operating point in the engine was 1200 rpm and 2.0 bar BMEP. For different flow conditions the inlet valve lift was set to 1.2 mm and 9 mm. The new measurement method Laser lightsheet scanning (LSS) was used for the spray propagation recordings in the engine.
In the CVC the shadowgraphy method was used. Temperature and pressure correlated to the engine conditions during injection. Tumble flow and turbulence which occurs in the DI-engine could not be considered in a standard CVC. Penetration depth and significant changes in the spray shape served as comparison parameters between the two testing conditions.
At operation points with high valve lift and low charge movement in the engine the spray distribution was not influenced seriously. So the results between chamber and DI-engine are well comparable.
For low valve lift the exceeding tumble flow leads to high turbulence in the engine. Therefore the measurements in the engine show significantly different results compared to the chamber regarding penetration depth and spray shape. It is also shown that a higher charge motion enables better and quicker mixture formation, higher burning stability and reduced burn duration
To reproduce the tumble flow in a CVC a flow channel which can be attached to the chamber is in development.