北京理工大学课件ppt飞行器系统概论08-Chapter4-S.ppt

4 Flight vehicle propulsion system ;Types of engines Basic concepts and principles Performance parameters liquid rocket engine solid rocket engine combination engines special engines Engine application;4.1 Types of engine system;Aviation and space engines -- development history piston engines (活塞） jet engines （喷气） ramjet （冲压）;4.1.1 Piston engines ;Complex construction Small power, 70~2000kW Used for low speed flight, helicopters and light low speed airplanes;;The power produced by a piston engine is converted into thrust by the propeller. Propeller is composed of two or more blades attached to a central shaft（轴）. Blades, really just small wings;Propeller;Piston don’t produce aerodynamic, by using propeller to produce lift.;turbojet（涡喷） turbofan（涡扇） turboprop（涡轮螺旋桨）;With air-breathing channel, ( front, two sides, wing root) compressor, combustion chamber, turbine, and nozzle. incendiary agent (fuel) oxygen ;1) Turbojet engines;Two types: axis-flow type  centrifugal type;Thrust for turbojet ;2) Turbofan engines;4.1.3 Ram engines;4.2 Basic concepts and principles;Combustion chamber;Pressure distribution： Internal pressure External (atmospheric) distribution;?Thrust Thrust of rocket engine is: momentum thrust pressure difference thrust Attention: No effect from the speed of a rocket, only by altitude.;Jet engines P is affected not only by flight speed, but also by flight altitude. V – aircraft speed – air flow quantity per second;4.3 Main performance parameters;★ Vacuum thrust（真空推力）; P = cppcAt Where, pc – combustion pressure At – nozzle throat area cp =f ( Ae /At , pe /pc, k) area ratio（面积比） -- Ae /At pressure ratio（压强比） -- pe /pc k – ratio of specific heat ( const pressure等压