Mixture Quality Evaluation for Transient Mode Gasoline Engine Calibration Available to Purchase

Gasoline engines have perfect emissions quality in stationary part load operation — how to ensure such ideal operation also at engine start, at tip-in tip-out, and at full load conditions? Key to the solution of these issues is the optimum use of components for mixture formation, combustion and exhaust gas aftertreatment with the focus on actuator calibration yielding reliable and low emissions combustion under transient operating conditions. Conventional testing of actuator parameter settings for such transients is evaluated with engine out emissions measurements. Any emissions peaks are well understood to be the result of some specific cycles which suffer from inadequate mixture formation due to limitations of fuel injection, evaporation or air supply. Consequently, improvements are achieved with adaptation of actuator parameters such as fuel injection timing, multiple injections or throttle and boost pressure settings in part load operation. With in-cylinder events being the root cause for emissions related issues, there is demand for diagnostic techniques capable of identifying emissions relevant in-cylinder processes for individual cylinders and on a cycle by cycle basis. This demand is met with the measurement of in-cylinder pressure together with flame radiation intensity. As cylinder pressure signals are evaluated for combustion stability, the simultaneously recorded flame signals provide information on mixture preparation quality. Well premixed charge results in flame radiation signals which are typical for homogeneous turbulent flames. Insufficiently evaporated and partially mixed fuel, especially at engine start, yields flame signals typical for diffusion flames. This simple relation between flame signals and soot formation events provides the basis for measurement techniques enabling mixture formation evaluation for individual cylinders and individual cycles. The application of such in-cylinder pressure and flame measurement techniques to PFI and GDI engines is presented with examples for engine cold start testing. The technique is further applied in the calibration of engine tip-in transients.