Knowledge of the air flow through and within the engine compartments of passenger cars has become more and more important in recent times. Flow visualization has been conducted, but, on the whole, there is a lack of real flow data. Experimental investigations by conventional probes have been, up to now, impossible, due to the highly turbulent and often unsteady nature of the flows resulting from the complexity of the engine compartment geometry.
The availability of reliable flow data, would help in solving some critical temperature problems.
Furthermore, experimental data could be used as a basis for a numerical approach by CFD codes which could probably help in analysing engine compartment flow in the future.
In order to better understand this flow, the Technical Development Center of General Motors Europe has recently carried out an experimental test program, aimed at collecting data on the engine compartment air flow of an Opel Vectra in the Pininfarina wind tunnel. A new two-component fiber-link Laser Velocimeter, with which it is possible to measure local velocities, was used.
This paper reports a description of this instrumentation, of the safety precautions that have to be taken when using this technology, as well as some of the results collected during these preliminary investigations.