Conceptual Design Requirements of a Newly Developed UAV as a ...

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Flight Endurance ( hrs ) 15 14.5 14 13.5 13 12.5 12 11.5 11 10.5 10 Propulsion system The objective of the project requires a reliable and efficient propulsion system specifically during cruise condition (180 - 220 km/hr) with a ceiling of 18,000 ft. In addition, the UAV has to be practical and easy to maintain. Type of System 10 8 6 4 2 1 Payload Mass ( kg ) Figure 10: Effect of Payload Mass on Flight Endurance, Fixed Fuel mass of 23 kg. For the UAV application similar to present UAV category, propulsion systems are usually limited to either turbojet or propeller driven by an IC engine. Propeller UAV are more popular due to lower cost and higher efficiency at relatively low speeds (Ma
Engine Requirements The engine has to be able to operate in the local environment. So the basic requirements are: Cruise - Power to meet takeoff at 9,000 ft altitude (Abha-Saudi Arabia) - Low fuel consumption to meet endurance requirements - Tolerate high temperature and dusty environment - Tolerate long periods of flights >20 hrs. - Tolerate high g forces during catapult launch. At level flight with a speed of V, the required propulsion power can be calculated as: Power P ⎛ D ⎞ = m g ⎜ ⎟ V (4) ⎝ L ⎠ For cruise at 18,000 ft and 220 km/hr, with gross weight of 65 kg and minimum L/D of 11, the required propulsion power will be Powerp = 3.54 kW ( 4.74 hp ). Typically, IC engines lose about 7% of output power per 3000 ft altitude. Taking this into consideration and assuming that the engine will operate at 67% of rated power during cruise, also assuming propeller efficiency of 60%, the required engine shaft power at standard atmospheric conditions should be about 20 hp, to meet the cruise condition. The extra 33% of engine power is for maneuver and climb requirement. High altitude takeoff For takeoff at 9,000 ft the power available will be 79% of the rated engine power. To maintain a reasonable weight to power ratio of less than 5.2 kg/hp, the engine rated shaft power should be > 15.82 hp. This is even less than the engine power requirement for cruise condition. Propeller Efficiency Based on endurance calculations, the required TSFC < 0.06 kg/N.hr. Most UAV engine suppliers claim specific fuel consumption (SFC) for their product as less than 0.33 kg/hp.hr. Diesel engines recently developed for aviation application can reach SFC as low as 0.19 13 . The TSFC is affected by both SFC and propeller efficiency (ηp) : V TSFC = 0. 00134 SFC (5) η 13 SSAS UAV Scientific Meeting & Exhibition, Jeddah, Saudi Arabia (June 6, 2006) Paper No. SSAS-2006-051 P
Page 1 and 2: Conceptual Design Requirements of a
Page 3 and 4: sensors and integration methodologi
Page 5 and 6: A. Aerodynamics and Structure Based
Page 7 and 8: Fuel Tanks Propulsio n Cruise perfo
Page 9 and 10: Figure 6: Typical Engines TSFC (12)
Page 11: Flight Endurance ( hrs ) Flight End
Page 15 and 16: For the present project the propell

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