Possibilities of Wall Heat Transfer Measurements at a Supercharged Euro IV Heavy-Duty Diesel Engine with High EGR-Rates, an In-cylinder Peak Pressure of 250 bar and an Injection Pressure up to 2500 bar 2019-24-0171
A raise of efficiency is, especially for CV, the strongest selling point concerning the TCO. 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. The losses resulting from taking real gas properties and non-ideal combustion into account have only a limited potential for gains, wall heat losses are currently believed to have the highest optimization potential.
Critical for the occurrence of these losses is the wall heat transfer, which can be described by 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 needed to determine the WHT relations at the combustion chamber of an engine. Methods to reduce the WHT can be developed and their effectiveness can be evaluated. As this is not done before for a heavy-duty engine, with peak pressures up to 250 bar, an increased in-cylinder turbulence and high EGR-rates is presented the following.
The different methods to determine wall heat flux are presented and compared. These are the direct measurement with heat flux probes, the determination of surface temperatures with thermocouples and the usage of the non-integer system identification method. Afterwards the transfer of data measured at the moving piston, e.g. the transfer by telemetry or the support with a linkage system, is presented.
Finally the application of surface thermocouples, data transfer via linkage system and the surface temperature method 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. The applied evaluation process, including a Fourier transformation and the method for a holistic determination of the WHT relations of a heavy-duty engine are presented.
Christian Hennes, Jürgen Lehmann, Thomas Koch
Daimler AG, KIT Karlsruhe Institute Of Technology
14th International Conference on Engines & Vehicles