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
2018
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