内燃机近火化塞区域的PIV,高速PLIF 以及化学发光成像研究

Measurements of the local flow and mixture condition near the spark plug of internal combustion engines are important to characterize their influence on ignition and combustion performance. This is especially true for direct-injection engines where limited time is available for mixture formation and optimum stratification of the fuel/air mixture to achieve best performance. Transient processes need to be visualized in an optically challenging environment. The application of digital Particle Image Velocimetry (PIV) for flow field measurements along with crank angle-resolved planar laser induced fluorescence (PLIF) and chemiluminescence imaging is discussed in the context of investigations of a highly stratified sprayguided direct-injection engine. Flow fields were captured in a firing optical single-cylinder engine to study the interaction of the fast spray and the underlying in-cylinder tumble flow. The impingement of the fuel spray on the spark plug electrodes and subsequent dispersion of the fuel cloud was filmed at a rate of 12kHz with a new PLIF technique using a diode-pumped Nd:YAG laser. Subsequent flame development and combustion progress could be followed via high-speed imaging of OH* chemiluminescence. This approach was also combined with double-pulse PLIF imaging of fuel distributions.