Demonstrating the Use of Thin Film Gauges for Heat Flux Measurements in ICEs: Measurements on an Inlet Valve in Motored Operation

To optimize internal combustion engines (ICEs), a good understanding of engine operation is essential. The heat transfer from the working gases to the combustion chamber walls plays an important role, not only for the performance, but also for the emissions of the engine. Besides, thermal management of ICEs is becoming more and more important as an additional tool for optimizing efficiency and emission aftertreatment. In contrast little is known about the convective heat transfer inside the combustion chamber due to the complexity of the working processes. Heat transfer measurements inside the combustion chamber pose a challenge in instrumentation due to the harsh environment. Additionally, the heat loss in a spark ignition (SI) engine shows a high temporal and spatial variation. This poses certain requirements on the heat flux sensor.

In this paper we examine the heat transfer in a production SI ICE through the use of Thin Film Gauge (TFG) heat flux sensors. An inlet valve has been equipped with 7 TFG sensors in a row. In literature only measurements on the piston, cylinder liner or cylinder head could be found. First, the construction of the heat flux sensor will be discussed. Second, the heat flux measurement technique and the implementation of the TFG sensors are discussed. The choice for Thin Film sensors is highlighted. Only compression operation (motored) measurements are currently considered and compared to literature. The effect of a variation in manifold air pressure on the heat flux is analysed.