An appropriate chassis dynamometer simulation of an actual vehicle road load is essential if a realistic emissions essessment 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 categorized as either being actual or synthesized after an evaluation of their events. A scale of fourteen parameters has been used to characterize each of the selected test cycles. Results of the simulation are presented, 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 increased vehicle weight has negligible effect on the calculated differential temperatures. On the other hand, the power absorber calculated temperature increased linearly, due to the increase in the power absorbed by the power absorber unit to simulate the road load for the tested vehicle. Thus it is concluded that for vehicle weights below 50000 lb, the differentials would be the most critical among the different dynamometer components; as the vehicle weight increases above 50000 lb, the power absorber unit has to be watched carefully.


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    Title :

    A simulation model of a chassis dynamometer: model development and cycles application


    Additional title:

    Simulationsmodell eines Kfz-Chassis-Dynamometers: Modellentwicklung und Zyklenapplikation


    Contributors:
    Yacoub, Y.M. (author) / Bata, R.M. (author) / Lyons, D.W. (author)


    Publication date :

    1996


    Size :

    18 Seiten, 22 Bilder, 2 Tabellen, 16 Quellen



    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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