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Lesson 2: Aircraft Engine Types And Construction. 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. The Heat Engine.
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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.
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 • Turbojet • Means of compression: Turbine-driven compressor • Engine working fluid: Fuel/air mixture • Propulsive working fluid: Fuel/air mixture
Types Of Heat Engines • Turboprop • Means of compression: Turbine-driven compressor • Engine working fluid: Fuel/air mixture • Propulsive working fluid: Ambient Air
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 • Pulse-Jet • Means of compression: Compression due to combustion • Engine working Fluid: Fuel/air mixture • Propulsive working Fluid: Fuel/air mixture
Types Of Heat Engines • Rocket • Means of compression: Compression due to combustion • Engine working fluid: Oxidizer/fuel mixture • Propulsive working fluid: Oxidizer/fuel mixture
Types Of Heat Engines • Reciprocating • Means of compression: Reciprocating action of pistons • Engine working fluid: Fuel/air mixture • Propulsive working fluid: Ambient air
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.
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.
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. • 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.
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.
Engine Requirements • Powerplant Selection ?
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
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.
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.
In-Line Engines • Generally has even number of cylinders. • Liquid or air cooled. • Has only one crankshaft.
In-Line Engines • 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.
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 • 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.
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.
Rotary-Radial • Torque and gyro effect made aircraft difficult to control. • Problems with carburetion, lubrication, and exhaust.
Opposed Or O-type Engines • Two banks of cylinders opposite each other with crankshaft in the center. • Liquid or air cooled, air cooled version used predominantly in aviation.
Opposed Or O-type Engines • Has low weight-to-horsepower ratio. • Its narrow silhouette makes it ideal for installation on wings. • Little vibration.