1988-09-01

The Computer Simulation Of A Diesel Engine For Governor Development 885103

The introduction of electronically controlled fuel injection equipment for diesel engines has generated a need for a tool to develop electronic governor control algorithms.
It is possible to execute such development by building a flexible control system and experimenting with the control variables on an actual engine, but this is a time consuming and expensive process and the need has arisen for a computer simulation of an engine to expedite such work.
Many engine simulations written for such purposes rely on the concept of a fluctuating, but continuous, energy input to an engine which in turn accelerates after a fixed time delay representative of the combustion process and the variable leverage of the connecting rod and crank system. Such a simulation neglects the aliasing errors that can arise if governor actuating frequencies coincide with or exceed fuel injection frequencies, in which case the continuous mode of simulation becomes invalid.
The simulation described takes into account the pulsed nature of fuel injection equipment and engine operation by simulating the thermodynamic cycle, using Wiebe functions. The fuel injection equipment is simulated by a look-up table of fuelling and timing of injection against speed and governor control parameter. The engine inertia and damping is dealt with by traditional techniques and the proposed governor algorithm is separately programmed in.
The paper shows, by comparison with experiment, that the simulation gives results which overcome aliasing problems and enable a realistic assessment of a governor algorithm to be made.

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