Development of a Method of Calculation of Energy Balance in Exhaust Systems in Terms of Energy Recovery

Energy balance of an engine is a distribution of heat supplied to the engine among the effective work and individual losses. The division of the total loss into constituent losses allows determining the influence of individual factors on the operation of engines under different conditions. The external energy balance of a combustion engine is mainly performed under laboratory conditions on engine dynamometers. In this method, a variety of parameters is measured, based on which individual energy losses are calculated such as fuel consumption, temperatures of the intake air and the exhaust gas, mass flow of the intake air and exhaust gas, inlet and outlet temperature of the coolant, mass flow of the coolant, engine speed and load. In order to determine the energy loss in the exhaust system, a new research method was proposed that, beside the measurement of the fundamental thermodynamic quantities, assumes utilization of modern measurement equipment such as portable measurement systems (PEMS) and engine dynamometers capable of reproducing actual driving cycles. The paper also presents the main assumptions of this method and the results of tests performed under actual operating conditions. The tests were carried out according to the RDE (Real Driving Emission) routines on PC (Passenger Cars), LDV (Light Duty Vehicles) and HDV (Heavy Duty Vehicles) vehicle categories fitted with spark ignition and diesel engines. Based on the above, the amount of exhaust gas energy in individual portions of the exhaust system was determined. Based on the obtained results, the potential for the application of energy recovery based on thermoelectric modules was presented. The areas of application of ATEG (Automotive Thermoelectric Generator) were specified. Simulation tests were carried out using tools based on CFD numerical fluid mechanics for heat exchangers of the proprietary ATEG generators.