| Summary: | 碩士 === 中華大學 === 機械與航太工程研究所 === 90 === ABSTRACT
In this stady, a micro gas turbine engine is used to formulate its dynamic response transfer function and compare with its test data to understand the development of a engine management system. The steady-state
performance of the engine is studied first. The results show that the servo command to the output of fuel flow rate and engine thrust has a linear relationship between 10000rpm and 120000rpm. The design point of the engine has a compression ratio of 2.35 with a efficiency of 0.54. Second the dynamic response of the engine is examined through the Bode plot. The transfer function that best fit the test data is a first order system for rotational speed and engine thrust, a second order system for exhaust gas temperature. The rotational speed and engine thrust increas monotonically but the exhaust gas temperature shows an overshoot and a undershoot for a step change. The response of rotational speed and engine thrust are almost identical. The fitted transfer functions of the above three quantities are compared with several sets of test data and show a good agreement. Finally, several operating parameters are used to study the deviation of the engine response for a step change. Changing the fuel from 50% gasoline and 50% kerosene to pure gasoline,the rotational speed show a delay at the beginning of jump,but catches up the original system for remaining part of the jump . This could be due to the mixing rate of the pure gasoline at the early stage of fuel jump. Using 100% of kerosene, the response is slower compared to the original output. This may be due to the fuel vaporization rate is low. The inlet temperature increases from 300C to 500C the response is faster slightly. This may be due to a higher of chemical reaction rate. Changing the fuel flow pressure level from 6 kg/cm to 7 kg/cm ,the response of the step change is faster significantly. When the servo actuator changed to a slow one, the step change is delayed at the beginning of the jump. Further study of the shape of combustion chember fuel spray, and rotor inertia is necessary to understand more of the engine response.
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