Experimental Study Of In-Cylinder Fuel Distribution In HCCI Gasoline Engine With Different Injection And Valve Strategies

Homogenous charge compression ignition is a new type of combustion that canprovide both high efficiency and low emission (NOX and PM) for the internalcombustion engine. But lack of direct combustion control methods limits theapplication of HCCI. Fuel stratification has the potential to control the HCCIcombustion through affecting the in-cylinder components. This research focuses onthe application of in-cylinder fuel stratification in the control of HCCI, laserdiagnostic as the main research tool, the experimental research are carried out to studythe effect of injection and valve strategies on in-cylinder fuel distribution andcombustion process of HCCI.The optical engine measurement platform is set up based on a production engine.Using the laser induced fluorescence technology, combined with particle imagevelocimetry and chemiluminescence, the experimental research are carried out tostudy the effect of injection and valve strategies on in-cylinder fuel distribution,simultaneously analyze the effect of in-cylinder flow field on the location of rich zoneand the effect of valve strategies on location of auto ignition area.The results of in-cylinder fuel distribution at the end of compression stroke withdifferent injection strategies indicate: the delay of injection timing can make the fuelstratification obvious, the cyclic variation increases simultaneously. Using the strategyof late injection at the end of compression stroke, the experimental results show thatthe cyclic variation of indicated mean effective pressure increases when the injectiontiming is delayed, but with the optimized cyclic variation of the fuel concentration ofrich zone, which can lower the cyclic variation of combustion with late injectiontiming.A comparative study of different valve strategies (negative valve overlap,exhaust gas re-breathing and positive valve overlap) is carried out and analyzed forthe in-cylinder fuel distribution and auto ignition process. Combined with differentinjection strategies, three valve strategies have different impacts on the control of fuelstratification. Using the port fuel injection, three valve strategies form thehomogeneous mixture, but can still control the ignition timing with different exhaustgas course. Negative valve overlap strategy forms strongest fuel stratification withGDI injection.