writeUP - Abstract Turbines are an essential aid to the...

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Abstract Turbines are an essential aid to the development of torque and shaft power resulting from momentum exchange between the working fluid and the turbine blades. Significant pressure drops between the turbine inlet and exit are needed in order to reach high velocities and exchange useful amounts of momentum. Pressure can be from a tank of compressed gas, or obtained by heating gas to expand it. The turbine which was used in this lab is called the Hilton Experimental Turbine F800. It is classified as a simple, single stage, axial flow, impulse turbine. Simple means that there are no complications such as velocity compounding. Single stage simply means that the fluid expansion happens in one stator and its rotor. Axial flow means that there are minimal radial components of velocity, and impulse means that the pressure drop happens in the stator. The objective of the experiment is to characterize the performance of the turbine by means of comparing its efficiency with the “ideal” isentropic efficiency, and estimate the rpms that give the greatest power for each inlet pressure. Results indicate that the greatest power in the form of shaft work was obtained from operating the turbine at higher inlet pressures and at lower speeds meaning the brake band is in use. Introduction This laboratory was designed to introduce students to an actual turbine system by having them characterize the performance of a Hilton Experimental Turbine F800. An important concept involved with analyzing the performance of turbines is the First Law of Thermodynamics which is the law of energy conservation. It simply states that the energy change in the system during a process is equal to the difference of energy entering
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and exiting the system. Figure 1 is an example of the conservation of energy across a turbines inlet and exit. Figure 1: First Law of Thermodynamics across inlet and exit of a turbine P 1 and p 2 are pressure at the inlet and exit respectively, h 1 and h 2 are specific enthalpy, v 1 and v 2 are velocity, q is specific heat transfer, and w is shaft work. The equation for energy conservation across a turbine with steady flow conditions is as follows. w v v h h q + - + - = 2 2 1 2 2 1 2 This can actually be reduced because the heat transfer and velocity effects are neglected. The resulting equation is what was used in the lab and is as follows. ) ( 2 1 h h W - = Since there is some enthalpy change across the inlet and exit of the turbine, there will be some temperature change associated. Since air is the working fluid, the air standard assumptions can be applied. Enthalpy change can be estimated by ) ( ) ( 1 2 1 2 T T C h h p - = - C p is the specific heat capacity of air in kJ/kg*K. T 1 and T 2 are the inlet and outlet temperature respectively. The shaft work that is output from the turbine can easily be
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This note was uploaded on 06/15/2009 for the course MAE 3183 taught by Professor Staff during the Spring '08 term at UT Arlington.

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writeUP - Abstract Turbines are an essential aid to the...

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