This article describes measurements and calculations of friction losses in the crank train of an IVECO heavy duty truck engine. The main objectives were to quantify the effect on friction of variation in lubricant viscosity and to demonstrate the ability of CAE tools to predict friction at contacts in the crank train. Results of various measurements of friction are described. Cycle-averaged whole engine friction was derived from measurements of cylinder pressure and brake torque. In addition a motored friction teardown test was performed to separate the losses from different engine systems. Commercially available analysis tools were used to calculate friction at contacts in the crank train under the same conditions as the tests and this article describes key assumptions and input data and presents calculated results compared with measured data. The following conclusions can be drawn: Measured whole engine friction data obtained under fired conditions indicated the expected trends in terms of variation with load, speed and oil viscosity but the inherent inaccuracy of the method dictates caution when interpreting the results. Measured data from the motored teardown test indicated the contribution of the crank train to the total friction under motored conditions and also quantified the potential reduction in crank train friction due to the low viscosity lubricant. Analysis was used to quantify friction at each piston ring, piston skirt, each main bearing, big end bearing and small end bearing and their variation with load, speed and oil viscosity. Total calculated crank train friction was lower than the measured data obtained from the motored tear-down test but some known sources of loss were not included in the calculations so this was expected. However the total calculated crank train friction showed a greater response to the oil viscosity than the measurement (i.e. the gap between measurements and calculations was greater with the low viscosity oil). CAE models were also used to calculate total crank train friction loss under fired engine conditions (minimum load and full load) and the results were compared with measured data for whole engine friction (measured motored data for those systems not expected to be sensitive to engine load were used in the comparison). This work showed reasonable level of agreement.
Calculation of crank train friction in a heavy duty truck engine and comparison with measured data
2013
17 Seiten, 22 Bilder, 3 Tabellen, 20 Quellen
Article (Journal)
English
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