A raise of efficiency is the strongest selling point concerning the total cost of ownership (TCO), especially for commercial vehicles (CV). Accompanied by legislations, with contradictive development demands, satisfying solutions have to be found. The analysis of energy losses in modern engines shows three influencing parameters. Wall heat transfer (WHT) losses are awarded with the highest optimization potential.
Critical for the occurrence of these losses is the WHT, which can be described by representing coefficients. To reduce WHT accompanying losses a decrease of energy transfer between combustion gas and combustion chamber wall is necessary. A measurement of heat fluxes is necessary to determine the WHT relations of the combustion chamber in an engine. As this has not been done for a Heavy-Duty (HD) engine, with peak pressures up to 250 bar, an increased in-cylinder turbulence and high exhaust gas recirculation (EGR)-rates before, it is presented in the following.
Different methods to determine wall heat flux, as well as data transfer variants for data measured at the piston, are presented and compared. The non-integer system identification method (NISI) and the data transfer with a specially manufactured printed circuit board (PCB) therefore represent explicit novelties for the usage in an internal combustion engine.
Finally the application chosen for the measurements to determine heat fluxes is described in greater detail. The assembly method, the positioning of the thermocouples at the engine parts and the considerations behind it are shown as well. The applied evaluation process, including a Fourier transformation and the method for a holistic determination of the WHT relations of a HD engine are presented. [1, 2]