Authors: Yasser M. Yacoub, Reda M. Bata, Donald W. Lyons
Addresses: Department of Mechanical and Aerospace Engineering, West Virginia University, USA. ' Department of Mechanical and Aerospace Engineering, West Virginia University, USA. ' Department of Mechanical and Aerospace Engineering, West Virginia University, USA
Abstract: An appropriate chassis dynamometer simulation of an actual vehicle road load is essential if a realistic emissions assessment is to be obtained. This requires a full understanding of the effects of actual road load parameters and the factors associated with their determination, as well as an accurate model to predict the dynamometer dissipated power at each vehicle speed of the testing cycle. In this study, details of the model which predicts the performance of an emissions testing facility are described. The model, based on a combination of fundamental energy balance relations and calibration data, includes predictions of the dissipated energy of the system|s main components. This energy is mainly attributed to friction rubbing between mating parts and pumping losses. A quadratic least square fit for dissipated torque measured at different steady-speed calibration tests is provided, and the physical meaning of each term is discussed. Employing the lumped thermal capacitance method, the subsystems| temperature profiles are predicted. The developed model is made to simulate the dynamometer|s performance during selected driving test cycles. Cycles are categorised as either being actual or synthesised after an evaluation of their events. A scale of fourteen parameters has been used to characterise each of the selected test cycles. Results of the simulation are pesented, which include the total energy consumed, flywheel wall shear losses, power absorber blower pumping work, the rubbing losses of the dynamometer main components, and predictions of the temperature history for each subsystem. The effect of the tested vehicle weight on the dynamometer|s performance is also investigated.
Keywords: chassis dynamometer; model development; modelling; dissipated power simulation; road load; emissions testing; driving test cycles; vehicle loading.
International Journal of Computer Applications in Technology, 1996 Vol.9 No.2/3, pp.76 - 94
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