Analytical study on the influence of valve pumping work on engine efficiency

Driving cycles like WLTP and the consideration of real driving emissions increase the relevance of load-dependent process losses for the prediction of engine efficiency based on engine process simulation. The contribution of valve pumping work to the total gas exchange losses of an internal combustion engine is usually neglected during engine conception. However, its share of the total gas exchange power losses increases with engine load. Within this paper, the variation of load, engine speed and valve timings on valve pumping work is investigated on a theoretical basis using 1D-CFD-simulation for a three-cylinder turbo-charged gasoline engine. Further, the influence of the valve lift curve design on valve pumping work is evaluated. The consideration of valve pumping work can increase the accuracy of the engine efficiency prognosis based on engine process simulations. A comparison with results from the literature points out that 3D-CFD-based evaluations of the valve gas forces can provide even more accurate results than the conventional calculation approach which is presented within scope of this publication. Hence, future works on this subject might include the improvement of the standard calculation approach on an either physical or empirical basis considering valve and seat ring design details as parameters.