Browse Publications Technical Papers 2018-01-1782
2018-09-10

Experimental Investigation of Flame-Wall-Impingement and Near-Wall Combustion on the Piston Temperature of a Diesel Engine Using Instantaneous Surface Temperature Measurements 2018-01-1782

The heat transfer process in a reciprocating engine is dominated by forced convection, which is drastically affected by mean flow, turbulence, flame propagation and its impingement on the combustion chamber walls. All these effects contribute to a transient heat flux, resulting in a fast-changing temporal and spatial temperature distribution at the surface of the combustion chamber walls.
To quantify these changes in combustion chamber surface temperature, surface temperature measurements on the piston of a single cylinder diesel engine were taken. Therefore, thirteen fast-response thermocouples were installed in the piston surface. A wireless microwave telemetry system was used for data transmission out of the moving piston.
A wide range of parameter studies were performed to determine the varying influences on the surface temperature of the piston. For instance, at later injection timings a shift of the peak temperature towards later crank angles with an immediately decreasing surface temperature increase can be measured. Higher engine speeds increase the mean piston temperature, while the local surface temperature increase during combustion decreases. At higher intake pressures and therefore higher gas densities, the flame-wall interaction is extenuated and temporally retarded.
The obtained data can be used to validate numerical simulation models that consider non-stationary surface temperatures, leading to an improved prediction accuracy of wall heat losses. In addition, understanding the measured results can provide a deeper insight into internal heat transfer processes. Thus, using both simulation models and measured results, ways to reduce wall heat losses can be evaluated.

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