| description abstract | In this study, the impacts of transient time, intake air temperature, coolant temperature, and piecewise transient strategies on energy and exergy terms during typical transient process of automotive diesel engine were researched based on experiment and numerical means. The results show that first, distortion of energy and exergy is relatively significant during shorter transient time. Fuel incomplete combustion is the root of energy and exergy distortion during transient process. Second, low intake air temperature is helpful to restrain work distortion and enhance efficiency during transient process, and comprehensive effects of local equivalence ratio (ER) and local in-cylinder temperature make in-cylinder exergy destruction (IED) little change at different intake air temperature. Third, enhancing the heat insulation characteristics of heat transfer boundary during transient process can effectively improve efficiency, while weaken the distortion degree of work. Tiny differences of local ER and local in-cylinder temperature at different coolant temperature result in the little change of IED during transient process. Fourth, the influences of different piecewise transient elements on efficiency are from strong to weak: first stage transient time > stagnation time > second stage transient time. Longer first-stage transient time and stagnation time are helpful to reduce energy and exergy distortion degree. Finally, there are some similarities on IED production mechanism between transient and steady-state process, moreover, the adjustment routes of boundary parameters to realize high efficiency during transient process: longer transient time coupling stagnation time, lower intake air temperature, and higher coolant temperature. | |
