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Estimation of Engine Gas Temperatures During Pressure Transients

Coming stringent regulatory emissions requirements with Real Driving Emissions testing amplifies the need for efficient engine control at all driving scenarios. This thesis has investigated the air-flow transients that appears when changing the throttle position very fast, such as at a stop sign. Available information about the intake manifold temperature is today mainly sensor-based or zero-dimensional. Since the temperature of the air affects the fuel controller(s) and is believed to be able to help the knock-controller as well, a more detailed description of the temperature is warranted. Three different one-dimensional interpretations of the intake manifold has been modeled and one of them is implemented in a full air-path simulation - from the throttle to the exhaust. The best suited simulation model is validated against measurement data and compared to the well know adiabatic control volume model, which is zero-dimensional. The effect on the temperature contributed by the VVT, turbo, throttle-settings and engine speed was tested in a test cell. The results shows that the computational efficiency varies between the different one-dimensional intake manifold models and that one-dimensional accuracy comes at a great cost of computational power. The testing and validation showed that the pressure difference and throttle ramping time had a big impact and that the positive transients are more predictable with current models, compared to the negative transients.

Marcus Wallson


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