Engine model for mapping BSFC contours

Abstract

Engine manufacturers plot contours of constant BSFC (Brake Specific Fuel Consumption) on torque-speed maps to show those torque-speed combinations at which the engine will operate most efficiently. Conventionally, torque, speed and fuel consumption must be measured at hundreds of points on the map to permit accurate drawing of contours. Both the data taking and the plotting of the contours are very time consuming. Thermal and mechanical efficiencies of an engine were considered in developing a mathematical model that relates torque, speed and fuel consumption. The model can be calibrated to a specific diesel engine by using 40 to 50 experimental obervations of torque, speed and fuel consumption for the engine. Typically, the model can predict fuel consumption to within 1% at most points on the torque-speed map and maximum errors are less than 5%.The model has been extended and programmed to automatically plot contours of constant BSFC and also contours of constant engine power on a torque-speed map.