Validation of a New TVD Scheme Against Measured Pressure Waves in the Inlet and Exhaust System of a Single Cylinder Engine

Abstract

Recently a new TVD scheme was presented by the authors and a comparison was made with other algorithms for two engine related test cases (the shock tube and the tapered pipe). It was shown that the new scheme combines high accuracy with exact conservation of the mass flow, even in tapered pipes. In this paper the pressure waves in the inlet and exhaust system of a single cylinder engine are measured and compared to calculations with the new algorithm. The comparison is made under motoring and firing conditions of the engine with two different external mixture formation systems (different fuels: gasoline and methane). Modifications on intake and exhaust pipe configuration clearly show their influence on the pressure wave development. The importance of the loss coefficients for the flow through the inlet and exhaust valves (mass flow coefficient) is demonstrated. A test rig has been built to obtain these coefficients under steady-state conditions as a function of valve lift and mass flow rate. It is shown that for this engine configuration the measured steady-state loss coefficients are not reliable at low valve lifts. This can be explained by the influence of the Reynolds number and the appearance of a transition zone. For all mentioned comparisons the agreement is excellent. The next phase will be to evaluate the code for multi-cylinder engines under atmospheric and turbo-charged conditions. [S0742-4795(00)00204-0]