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Advanced combustion systems that simultaneously address PM and NOx while retaining the high efficiency of modern diesel engines, are being developed around the globe. One of the most difficult problems in the area of advanced combustion technology development is the control of combustion initiation and retaining power density. During the past several years, significant progress has been accomplished in reducing emissions of NOx and PM through strategies such as LTC/HCCI/PCCI/PPCI and other advanced combustion processes; however control of ignition and improving power density has suffered to some degree - advanced combustion engines tend to be limited to the 10 bar BMEP range and under. Experimental investigations have been carried out on a light-duty DI multi-cylinder diesel automotive engine. The engine is operated in low temperature combustion (LTC) mode using 93 RON (Research Octane Number) and 74 RON fuel.

A simulation tool has been developed for predicting steering effort of a vehicle during steering power-assist system failure. The vehicle system is modeled with the inclusion of a system-level vehicle model and a steering system model that are linked together through the steering moment at the kingpin and front road wheel angle. A driver model has also been designed to provide closed-loop steering angular input to make the car follow a certain target path. The simulation model is correlated well with actual vehicle tests under various steering input and lateral acceleration conditions. Also illustrated are some examples of comparison between measured and simulated sensitivity study for selected factors.

The simulation model developed and validated by the authors [1] for vehicle chassis transmissibility of steering shimmy and brake judder is used to analyze the transmissibility mechanism and quantify the relative importance of system factors, through modal analysis around equilibrium point and a virtual DOE (design of experiment) process. Contributing chassis vibration modes are discovered, relative importance of chassis factors is efficiently determined, and potential areas for improving chassis shimmy/judder sensitivity are identified. The DOE results are further confirmed by the comparison of simulated and on-road measured shimmy/judder change with the specification change of key factors. Also presented is some successful application of the simulation technology and analysis results to vehicle development.