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Typical fuel metering systems for small gas turbine engines consist of a metering valve and a bypass valve which is maintaining a constant differential pressure across the metering valve orifice. The metering valve is operated by the compressor pressure signal and the bypass valve acts automatically. It is proposed to bring both the metering and the bypass valves under the control of two digital linear actuators. The first one would move the metering plunger according to the compressor pressure and the second would move the bypass plunger in such a way, that the differential pressure across the metering orifice would be maintained constant only during steady state engine operation. During the engine transient processes, however, it would be increased or decreased as required, to speed up the change in the nozzle flow rate and consequently the engine dynamic response.

To increase the operational range of the vehicle equipped with direct injection gas supply and to eliminate the problems associated with the cryogenic pumps, a composite high pressure vessel is proposed for use as a thermocontrolled tank in vehicles. The test results showed that the liquefied natural gas can be brought from atmospheric pressure to the high pressure required for direct injection in a reasonable time period. Based on these results a mathematical model for the heat transfer to the natural gas was developed and simulated. Three different aspects of gas storage, namely, the initial operational temperature, the gas to vessel mass ratio and the gas weight to vessel volume ratio have been investigated and formulated as objectives for optimization. Due to the presence of different conflicting objectives, the problem was formulated as a nonlinear multi objective optimization problem and then solved.

Optimization of diesel injection system using computer aided design involves complex high speed, high pressure hydraulic transient process calculation. To find the fuel discharge characteristic from injector, the fuel pumping process is first computed based on the design parameters of the injection pump. Then, knowing the forward propagating pressure wave, the dynamic response of the injector is calculated resulting in the fuel discharge process. However, if the forward pressure wave could be precisely measured instead of being calculated, and then substituted into the computer program the total calculation procedure would be substantially reduced. In this paper, a computer controlled data acquisition system with high sampling rate was used to record the fuel pumping process in a specially made long pipe to avoid distortion by the reflected pressure wave. This method is convenient, quite accurate and can save the time of computer simulation.