الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
Gas turbine has many applications for Example, aircraft, industrial applications, power generation, and M-1 tank. There is a small tip clearance between engine rotor and its casing. The tip clearance must allow free rotation and thermal expansion during operation. This clearance causes a leakage flow that escapes from the pressure side (high pressure) into the suction side (low pressure) of the blades over the blade tip. The gas accelerates as it passes through the tip clearance and results in an increase in a thermal load on the blade tip.
The present study aims to developing a simulation numerical model to predict the effect of blade tip injection on the heat transfer performance and flow field characteristics in a gas turbine engine. The main investigated design and operating parameters are tip clearance gap, inlet air temperature, and blowing ratio of injected coolant air.
In the present study, an experimental set-up was installed with a turbine cascade of five blades to validate the numerical model. Temperature and static pressure distributions over both blade pressure and suction sides were measured. Flow field before, inside, and after the blades cascade also was measured. The coolant air is injected from eleven holes with three mm diameter arranged perpendicular along the blade camber line. It is difficult to measure the flow behavior in the zone of tip clearance; therefore, the numerical model supplies a realistic prediction of the flow field inside this zone. The three dimensional flow is examined for the gas turbine linear cascade with/without tip injection. The numerical model gives three-dimensional turbulent flow behavior by solving Reynolds averaged Navier Stokes equations and the energy equation using FLUENT 6.3.26 software. The Shear Stress Transport (SST) k- model was employed to represent turbulent flow. The operating and boundary conditions supplied to the program were taken from the experimental measurements.
The obtained results illustrates the importance of blade tip injection to decrease the heat transfer over the blade surface and the tip leakage losses. The obtained results also showed that in the case without coolant injection secondary flow generated by the flow deflection and the tip leakage flow increases heat transfer coefficient on the blade suction surface. While, injection of coolant flow reduces the heat transfer coefficient over blade surface for all blowing ratios and all tip clearance height.
The obtained results related to the flow behavior through the blade cascade indicated that, the static pressure distribution on the blade pressure surface relatively identical in the cases with and without injection for all tip clearance and all blowing ratio, while suction surface is a slight affected by the tip leakage flow near the blade tip. In addition, changing the inlet air temperature has a slight effect on the heat transfer coefficient over the blade surface and the total losses through the blade cascade.