BAYLOR UNIVERSITY DEPARTMENT OF ENGINEERING. EGR 4347 Analysis and Design of Propulsion Systems Fall 2002 ASSIGNMENT GUIDELINES

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1 BAYLOR UNIVERSITY DEPARTMENT OF ENGINEERING EGR 4347 Analysis and Design of Propulsion Systems Fall 2002 Design Project I Dr Van Treuren 100 points ASSIGNMENT GUIDELINES For this assignment, you may work with the following persons, in addition to your professor in this course: your assigned partner or group. For this assignment, you may use the following materials produced by other students: No student materials produced outside your group. Each team member is responsible for the content and quality of the entire assignment submitted. Your grade on this assignment will be based on your professor s assessment of your original effort.

2 INTRODUCTION: You are a propulsion engineer with the task of determining a suitable engine cycle for NASA's High Altitude Long Endurance (HALE) Unmanned Aerial Vehicle (UAV). Future assignments will depend heavily upon your group's effort in completing this task. Currently, the program is in the early Conceptual Design Phase, where engineers, logisticians and technical support personnel are conducting design, analysis and integration studies on all aircraft subsystems. Description of Mission: The aircraft s primary mission is high altitude survelance. As such it will be required to loiter at high altitudes (65,000 ft or highter) for up to 24 hours on station. The mission is illustrated below (assume standard day): M= 0.8; alt = ft 3 4 M = 0.5, alt = ft M= 0.8; alt = ft 5 6 0, Sea Level Sea Level 0-1: Warmup/Taxi Assume fuel expended is 0.08% of: beginning aircraft gross weight. 1-2: Takeoff Assume fuel expended is 1% of: Initial Aircraft Gross Weight (IAGW) at the beginning of the takeoff roll. 2-3: Climb Assume fuel expended is 6% of: IAGW at the beginning of the climb. 3-4: High Cruise Out Aircraft cruises in level, unaccelerated flight for a duration of 120 minutes. Assume the fuel loss occurs instantaneously at the end of this mission leg. 4-5: Loiter This mission leg involves flying near endurance airspeed for 20 hours at an altitude of 65,000 ft or higher. The aircraft must provide a stable platform for sensors to gather information over specific areas. 5-6: High Cruise Back Aircraft cruises in level, unaccelerated flight for a duration of 120 minutes. Assume the fuel loss occurs instantaneously at the end of this mission leg. 6-7: Descent Assume fuel expended is 0.01% of: IAGW at the beginning of the descent. 7-8: Landing/Taxi Assume the fuel expended is 0.05% of: IAGW at the beginning of the landing approach. The aircraft must have 300 to 310 lb of usable fuel remaining after engine shutdown. Description of Aircraft: NASA Dryden Flight Research Center is working with Gneral Atomics Aeronautical Systems, Inc. to develop a new version of its HALE research aircraft. Currently, work is being done on Predator B to equip it with a turboprop to fly at altitudes up to 60,000 ft. This capability is required to do both scientific experiments at high altitude and also to perform reconnaissance missions. The Altair is a variant of the Predator B 1

3 airframe with a longer wingspan (22 feet longer) and larger payload. Currently, a turboprop is planned for this aircraft however, the purpose of this study is to determine the feasibility of using a turbofan engine for its propulsion system. The following information on the Altair airframe is provided for your calculations. C D0 = S to = 4000 ft K 1 = S W = 225 ft 2 C Lmax = 1.4 Dry aircraft weight = 3250 lbf Payload = 750 lbf Usable fuel (JP-8) = 3000 lbf Computer Graphic of Altair (NASA) Description of Engine: A separate exhaust turbofan has been selected as the engine of choice. However, the gas turbine design variables (π c, π f, α) have not been specified. Also, the number of engines is left to the designer. 2

4 OBJECTIVE: To adequately define the engine design variables, you must first determine requirements for uninstalled thrust (F) and uninstalled specific fuel consumption (S) for the mission. This requires a complete mission analysis. To relate these quantities to their installed counterparts, T and TSFC, you will use the installation loss coefficient φ. You will assume φ = 0.17 at takeoff 0.02 at high cruise out 0.10 during loiter 0.03 at high cruise back Procedure: The basic algorithm for this analysis is given below. Start Select Average S Aircraft Velocity Warmup/Taxi High Cruise Out C L C D F T Takeoff Loiter Climb High Cruise Back Landing/Taxi Final Fuel Remaining within limits? No Yes Notes: 1. means execute the dashed-boxed routine and return. End 1

5 **IMPORTANT TIP** Your program should give you the ability to manually insert different values of S for each cruise leg and the combat leg. This capability will be required for the subsequent final engine design phase. A sample spreadsheet output is given at the end of this handout if you wish to verify your calculations. Note that the example is for a completely different aircraft! ASSIGNMENT: Your design group must accomplish the following: 1. Using a spreadsheet (preferred) or other software of your choice, execute the mission analysis algorithm to determine the uninstalled thrust requirements for the takeoff, high cruise out, loiter and high cruise back portions of the mission, as well as the required average S. This information will be used in subsequent phases of the engine design process. An Excel template labeled DP1temp.xls is available in the profdata EGR 4347 folder. 2. Submit a typewritten report of the work involved in performing your mission analysis. This should include discussions of: a. current technology medium/high bypass turbofan engines (i.e., provide typical values for thrust, specific fuel consumption, engine diameter, π c, π c, α). b. the purpose of doing a mission analysis. c. the complete mission description. d. full and complete discussions of the equations used in your spreadsheet and their corresponding assumptions. e. the average S needed for the mission. What drives the selection of average S? f. the effect of installation losses on engine thrust and specific fuel consumption. Include in the report a copy of your spreadsheet cell listing or program code, along with the spreadsheet/program output with F (takeoff, high cruise out, loiter and high cruise back), average S and fuel remaining clearly indicated. 3. Answer the following question: In designing an engine, a "design point" must be specified. It is usually a flight condition (altitude & Mach number) where the engine has been designed to operate "best". The selection of a design point is critical to overall engine/aircraft performance and is based on many factors such as: a. time spent at a particular flight condition b. best loiter (edurance) speed c. engine operating limits (i.e. rotational speeds, temperatures,...) d. "critical" mission leg etc... Given this information, what would you expect the engine design point to be for the HALE UAV? Justify your answer. Important Equations: T = F Dadd = F ( 1 - ϕ ) page 21 in Elements of Gas Turbine Propulsion S = TSFC ( 1 - ϕ) page 21 in Elements of Gas Turbine Propulsion For straight and level, unaccelerated flight: L = W = C L (0.5) ρ V 2 S W pages in Elements of Gas Turbine Propulsion D = T = C D (0.5) ρ V 2 S W pages in Elements of Gas Turbine Propulsion C D = C D0 + K 1 C L 2 pages in Elements of Gas Turbine Propulsion 2