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q7p_sol

# q7p_sol - Unified Engineering Propulsion Quiz Spring 2004...

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Unified Engineering Propulsion Quiz NAME: SOLUTIONS ___ Spring 2004 Unified Propulsion Quiz May 7, 2004 Closed Book – no notes other than the equation sheet provided with the exam Calculators allowed. Put your name on each page of the exam. Read all questions carefully. Do all work for each problem on the pages provided. Show intermediate results. Explain your work --- don’t just write equations. Partial credit will be given (unless otherwise noted), but only when the intermediate results and explanations are clear. Please be neat. It will be easier to identify correct or partially correct responses when the response is neat. Show appropriate units with your final answers. Box your final answers. Exam Scoring #1 (15%) #2 (25%) #3 (15%) #4 (20%) #5 (25%) Total 1

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Unified Engineering Propulsion Quiz NAME: SOLUTIONS ___ Spring 2004 Below is a photograph of the Joint Strike Fighter (JSF). A lift fan (directly behind the cockpit) is driven by a shaft from the main engine to provide vertical take-off and landing capability. The exhaust nozzle on the main engine can also swivel 90 degrees to point directly down. The inlet for the main engine is split, with half the flow coming in either side of the cockpit, flowing through a y-shaped duct (with the shaft running through it) that wraps around the lift fan and meets in the center of the aircraft. There are also two small roll-control jets that exit the main engine aft of the compressor. U.S. Air Force photo 1. (15 points, partial credit given, L.O. C & D) What are the principal figures of merit for an engine of this type and why? When answering this question be sure to describe how these figures of merit are related to overall vehicle performance. The principal figures of merit for gas turbine engine performance are max-thrust, overall propulsive efficiency, impact on vehicle weight and impact on vehicle drag. These parameters directly impact mission performance for example: h L d Ê 1 W ˆ Range = h overall D l n W initial and for maneuvering: T V - D V = W dh g W final dt + dt Ë Á 2 g V 2 ¯ ˜ For this vehicle, the engine configuration alone suggests that maneuvering, especially vertical take-off and landing, is of great importance to the mission. Therefore an additional figure of merit would be the capability to reconfigure or vector the thrust. In addition to the performance figures of merit, it is important to add cost (acquisition cost and non-fuel operating costs).
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