航空发动机的种类与结构

Engine Requirements
• Compactness • To effect proper streamlining and balancing of an aircraft, the shape and size of the engine must be compact. • In a single engine aircraft, the shape and size of the engine will affect the view of the pilot.
Types Of Heat Engines
• Ramjet
Means of compression: Ram compression Engine working fluid: Fuel/air mixture Propulsive working fluid: Fuel/air mixture
Types Of Heat Engines
燃气涡轮发动机
应用最广。包括涡轮喷气发动机、涡轮风扇发动机、涡轮螺旋桨发动机和涡轮轴 发动机，都具有压气机、燃烧室和燃气涡轮。涡轮螺旋桨发动机主要用于时速小于 800千米的飞机；涡轮轴发动机主要用作直升机的动力；涡轮风扇发动机主要用于速 度更高的飞机；涡轮喷气发动机主要用于超声速飞机。
冲压发动机
冲压发动机特点是无压气机和燃气涡轮，进入燃烧室的空气利用高速飞行时的冲 压作用增压。它构造简单、推力大，特别适用于高速高空飞行。由于不能自行起动和 低速下性能欠佳，限制了应用范围，仅用在导弹和空中发射的靶弹上。
V-type Engines
• Cylinders are arranged in two in-line banks generally set 30-60° apart. • Even number of cylinders and are liquid or air cooled.
Radial Engines
Turboprop Engine
• For cruising speeds from 180 to 350 MPH the turboprop engine performs better. • Develops more power per pound then reciprocating. • Operate most economically at high altitudes.
• Consists of a row, or rows, of cylinders arranged radially about a center crankcase. • The number of cylinders composing a row may be either three, five, seven, or nine.
Turbojet/Turbofan Engines
• Intended to cruise from high subsonic speeds up to Mach 2.0. • Operates most efficiently at high altitudes. • Less instrumentation and controls required.
Types Of Heat Engines
• Turbojet
• Means of compression: Turbine-driven compressor • Engine working fluid: Fuel/air mixture • Propulsive wor源自文库ing fluid: Fuel/air mixture
Types Of Heat Engines
• Reciprocating
• Means of compression: Reciprocating action of pistons • Engine working fluid: Fuel/air mixture • Propulsive working fluid: Ambient air
Radial Engines
• Proven to be very rugged and dependable. • High horsepower.
Rotary-Radial
• Used during World War I by all of the warring nations. • Cylinders mounted radially around a small crankcase and rotate with the propeller.
Engine Requirements
• Powerplant Selection
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Reciprocating Engine
• For aircraft whose cruising speeds will not exceed 250 MPH the reciprocating engine is the usual choice. • Chosen for its excellent efficiency. • Turbocharged or supercharged for high altitude use. -- Turbo-use exhaust -- Super-use accessory drive
航空发动机的种类与结构
Aircraft Engine Types And Construction
三大种类
活塞式 燃气涡轮式 冲压式
活塞式航空发动机
早期在飞机或直升机上应用的航空发动机，用于带动螺旋桨或旋翼。大型活塞航 空发动机的功率可达 500千瓦。后来为功率大、高速性能好的燃气涡轮发动机所取代。 但小功率的活塞式航空发动机仍广泛地用于轻型飞机、直升机及超轻型飞机。
Types Of Reciprocating Engines
In-Line Engines
• Generally has even number of cylinders. • Liquid or air cooled. • Has only one crankshaft.
In-Line Engines
Engine Requirements
• Durability and Reliability • Durability is the amount of engine life obtained while maintaining the desired reliability. • Reliability and durability are built into the engine by the manufacture.
• Pulse-Jet • Means of compression: Compression due to combustion • Engine working Fluid: Fuel/air mixture • Propulsive working Fluid: Fuel/air mixture
• Continued reliability is determined by the maintenance, overhaul, and operating personnel
Engine Requirements
• Operating Flexibility • The ability of an engine to run smoothly and give desired performance at all speeds from idling to full-power. • The engine must also function efficiently through all variations in atmospheric conditions.
Types Of Heat Engines
• Turboprop
• Means of compression: Turbine-driven compressor • Engine working fluid: Fuel/air mixture • Propulsive working fluid: Ambient Air
Rotary-Radial
• Torque and gyro effect made aircraft difficult to control. • Problems with carburetion, lubrication, and exhaust.
Opposed Or O-type Engines
Engine Requirements
Engine Requirements
• Efficiency • Power and Weight: If the specific weight of an engine is decreased, the performance of the aircraft will increase. • Reciprocating engines produce approximately 1 HP for each pound of weight.
• Small Frontal area, better adapted to streamlining. • When mounted inverted, it offers the added advantages of a shorter landing gear. • High weight to horsepower ratio.
Types Of Heat Engines
• Rocket • Means of compression: Compression due to combustion • Engine working fluid: Oxidizer/fuel mixture • Propulsive working fluid: Oxidizer/fuel mixture
The Heat Engine
• Converts chemical energy (fuel) into heat energy. • Heat energy is then converted into mechanical energy. • The heat energy is released at a point in the cycle where the pressure is high, relative to atmospheric.
• Two banks of cylinders opposite each other with crankshaft in the center. • Liquid or air cooled, air cooled version used predominantly in aviation.
The Heat Engine
• Divided into groups or types depending upon: • The working fluid used. • The means of compression. • The Propulsive working fluid.
Types Of Heat Engines
Engine Requirements
• Fuel Economy • The basic parameter for describing the fuel economy of aircraft engines is specific fuel consumption. • Specific fuel consumption for reciprocating engines is the fuel flow (lbs/hr) divided by brake horsepower.