theory of aerospace propulsion 航空推进理论.pdf

CHAPTER Idealized Flow Machines 1 CHAPTER OUTLINE 1.1 Conservation Equations 1 1.1.1 Conservation of mass 2 1.1.2 Conservation of momentum 3 1.1.3 Conservation of energy 3 1.2 Flow Machines with No Heat Addition: The Propeller 3 1.2.1 Zero heat addition with V V 3 e 0 1.2.2 Zero heat addition with V V 4 e 0 1.2.3 Zero heat addition with P ¼ constant 04 1.2.4 Propulsive efficiency4 1.3 Flow Machines with P [ 0 and Q [ Constant: The Turbojet, Ramjet, and Scramjet5 1.3.1 Heat addition, Q 0 5 1.3.2 Constant heat addition, Q ¼ constant 0 7 1.3.3 Overall efficiency8 1.3.4 Fuel efficiency8 1.4 Flow Machines with P [ 0, Q [ Constant, and A0 [ 0: The Rocket 11 1.5 The Special Case of Combined Heat and Power: The Turbofan 12 1.5.1 Very small bypass ratio, b 1, the turbojet15 1.5.2 Very large bypass ratio, b [ 1, the turboprop 15 1.5.3 Finite b, the turbofan16 1.6 Force Field for Air-Breathing Engines 16 1.7 Conditions for Maximum Thrust 22 1.8 Example: Jet and Rocket Engine Performance 25 1.8.1 Jet engine performance25 1.8.2 Rocket engine performance 26 1.9 Nomenclature 27 1.9.1 Subscripts 28 1.10 Exercises 29 Reference 34 1.1 CONSERVATION EQUATIONS A flow machine is one that ingests a stream of fluid, processes it internally in some fashion, and then ejects the processed fluid back into the ambient surroundings. An idealization of such a generalize