Search Results

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures. Several stabilization techniques were studied to increase the compressor operating range without sacrificing the compressor efficiency. The paper presents an experimental study of one of these techniques, the axial variable inlet guide vanes (VIGV). Test rigs were put up to conduct two different experiments. The first was to study the effect of pre- rotation generated by VIGVs on the overall compressor performance and the second to determine the pressure loss through the VIGVs and to analyze the flow downstream the VIGV system using LDA (laser Doppler Anemometry) measurement.

In automotive applications, the filling and emptying of internal combustion engine are sometimes analyzed from the frequency spectrum of manifolds. However, this is always established with the assumption of small disturbances which is not realistic in engine ducting, where large pressure fluctuations may arise. For this reason, this paper presents a comparison between the frequency spectrum obtained with the assumption of small disturbances and spectra obtained with a shock test bench. Results of this study show that differences exist. These conclusions are validated by the use of a one-dimensional code which gives the possibility to determine the different parameters which have an influence on the results.

One of the main advantage of a hybrid thermal-electric vehicle is that the internal combustion engine (ICE) can be shut down when not needed anymore (Stop&Start system, propulsion with full-electric mode), thus reducing fuel consumption. But this use of the ICE impacts its thermal behavior because of a lack of heat source and thermal losses. Furthermore, the ICE is sometimes used with higher load in order to charge the batteries that increases the total heating power produced by the combustion. Therefore, the simulation of hybrid vehicles becomes really interesting to evaluate the effect of different control strategies (energy repartition between the engine and the electric motor) on the fuel consumption. However, in most of actual hybrid vehicles simulation tools, for calculation speed reasons, the thermal phenomena are either not taken into account, or their calculation is not based on physical equations (empirical formulas). Their predictive capability is then limited.

Usually, the simulation of a turbocharger included in a diesel engine model relies typically on the assumption of adiabaticity for the compressor. However experiments on a turbocharger test bench show that the heat transfers from the turbine to the compressor have a major influence on the compressor performances. So the manufacturers maps must be modified or used with a new method taking into account heat transfers. The methods proposed are a simple way to take into account heat transfers when the performance maps are used. They give results in relative good agreement with experimental measures in comparison to their easiness of use.