| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 87 === ABSTRACT
Subject：Investigation on the Discharge Coefficient in the Penetrations of Gas-Turbine Engine Combustors.
Student：Yen-Liang Lu
Advisor：Wei-Hsiang Lai
Unlike the conventional engines, the discharge coefficient of the micro gas-turbine engine combustor based on its size, pressure drop, duct geometry and flow condition is different from that of the large scale gas-turbine. As mentioned in many literatures, the hole pressure drop coefficient, also known as pressure parameter K, across the entry hole dominates the discharge characteristics of the large scale gas-turbine engine combustor. The major facility in this study is made to simulate the annulus channel and liner of engine combustor. In this acrylic model, there is a test section that is exchangeable the test hole with different length-to-diameter (L/D). It includes some measuring point to take the pressure data, such as the dynamic pressure at upstream and downstream of hole are interesting to calculate the hole pressure-drop coefficient (K). The air flow rates for air supply and discharging air may be obtained by different flow meters, so that the hole bleed ratio may be calculated. The discharge coefficient (Cd) is also determined by pressure data and air flow rate.
Results show that a critical point that is a local maximum of the discharge coefficient is found in this study of the experiment model, which approach an unique number (Cd=0.51) with the increasing of the pressure parameter as across this point. Another phenomenon is observed that the curve of the hole bleed ratio at the specific pressure parameter (about K=9) has an inversion point. An important conclusion in this research is based on the parameter of hole length-to-diameter (L/D) that is a dominant factor to affect the air entry situation. In this study, the pressure parameter K is a constant with increasing air flow rate when L/D=1, and the discharge coefficient is almost a constant. The experical formula KA = constant (about KA=145 in this model) is found by this research, where A is hole area. The K is decreased with increasing air flow rate when L/D>1 and K is increased with increasing air flow rate when L/D<1.
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