AERONAUTICAL ENGINEERING SHIBIN MOHAMED Asst. Professor Dept. of Mechanical Engineering Al Ameen Engineering College Al- Ameen Engg. College 1
Aerodynamics-Basics These fundamental basics first must be acknowledged: The word comes from two Greek words: aerios, concerning the air, and dynamis, which means force. Aerodynamics is the study of forces and the resulting motion of objects through the air. Air is a fluid. It can be compressed & expanded. The atmosphere is composed of 78% nitrogen 21% oxygen 1% other gasses Al- Ameen Engg. College 2
Aerodynamics-Basics Newton s Laws of motion: Law 1 A body at rest will remain at rest. A body in motion will remain in motion Law 2 F=ma Force is equal to mass times acceleration. Law 3 For every action there is an equal and opposite reaction. Bernoulli s principle of Pressure: An increase in the speed of movement or flow will cause a decrease in the fluid s pressure. - Example: the Venturi tube Al- Ameen Engg. College 3
Al- Ameen Engg. College 4 FORCES ACTING ON AN AIRCRAFT
FORCES ACTING ON AN AIRCRAFT The Four Forces in flight The four forces acting on an aircraft are: Weight Acts straight down through the centre of gravity. Lift Is produced by the wings and acts upwards through the centre of pressure, Thrust Is provided by the engine through the propeller. Drag Is the resistance to motion experienced by all bodies within the atmosphere. Al- Ameen Engg. College 5
An Airplane shibin87@gmail.com flies by using an engine to produce power, called THRUST To overcome natural air resistance, called DRAG... S=Wing Surface Area To go through the air so that its wings can generate an upward force, called LIFT To counteract the effect of gravity, called Al- Ameen WEIGHT. Engg. College 6
Angle of Attack shibin87@gmail.com Angle between wing chord line and relative wind. The angle of attack at which airplane stalls does not change. AIRFOIL Al- Ameen Engg. College 7
Airfoils - Nomenclature shibin87@gmail.com Low p High p Chord line - straight line connecting the leading and trailing edges of an airfoil Camber line locus of all points equidistant from top and bottom of airfoil Camber distance between chord line and camber line Thickness maximum distance between top and bottom surfaces of wing Leading Edge Trailing Edge Wingspan (b) Al- Ameen Engg. College 8 Aspect Ratio (AR = b 2 /S)
THEORY OF LIFT Al- Ameen Engg. College 9
Stability & Control The 3 axes of motion. shibin87@gmail.com PITCH ELEVATOR CONTROL ROLL AILERON CONTROL YAW Al- Ameen Engg. College 10 RUDDER CONTROL
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TYPES OF AIRCRAFT ENGINES Ramjet Turbojet Turbofan Turboprop Turbo shaft Al- Ameen Engg. College 12
Ramjet It has no moving parts. Its compression ratio depends forward speed. on It has no static thrust guided-missile systems, Space vehicles use this type of jet Al- Ameen Engg. College 13
GAS TURBINE ENGINE The most practical form of jet engine in use today. The standard on nearly all transport and military aircraft. Types of gas turbine engines: 1- Turbojet. 2- Turboprop. 3- Turboshaft. 4- Turbofan. Al- Ameen Engg. College 14
TURBOJET ENGINES Straight forward operating principle. Air enters through the air intake, compressed by the compressor, fuel is added and burned in the combustion chamber, heat causes the compressed air to expand rearward, passes through the turbine and spins it, which drives the compressor, and the air then exit the engine at a much higher velocity than the incoming air. The difference between the entering air and the exiting gases that produces the thrust. EPR is the ratio of the turbine discharge pressure to engine inlet air pressure.( EPR probes) Al- Ameen Engg. College 15
TURBOJET ENGINES Al- Ameen Engg. College 16
TURBOJET ENGINES Al- Ameen Engg. College 17
TURBOPROP ENGINES Turboprop engine is a gas turbine engine that delivers power to a propeller. Power produced by a turboprop is delivered to a reduction gear system that spins a propeller. Used in business and commuter type aircraft because of the combination of jet power and propeller efficiency at speeds between 300 and 400 mph. Provide the best specific fuel consumption of any gas turbine engine. Al- Ameen Engg. College 18
TURBOPROP ENGINES Al- Ameen Engg. College 19
TURBOSHAFT ENGINES Turboshaft engine is a gas turbine engine that delivers power to a shaft that can drive something else. Most of the energy produced by the expanding gases is used to drive a turbine. Helicopters, auxiliary power units, electric generators, and surface transportation systems use turboshaft engines. Turboshaft engine power is measured in shaft horsepower. Al- Ameen Engg. College 20
TURBOSHAFT ENGINES Al- Ameen Engg. College 21
TURBOFAN ENGINES Consist of a multi-bladed ducted propeller driven by a gas turbine engine. Provide a compromise between the best features of the turbojet and the turboprop. Have turbojet-type cruise speed capability, yet retain some of the short-field takeoff capability of a turboprop. Al- Ameen Engg. College 22
TURBOFAN ENGINES Al- Ameen Engg. College 23
TURBOFAN ENGINES Forward-fan engines have the fan mounted in the front of the compressor. Aft-fan mounted engines have the fan mounted to the turbine section. Inlet air is divided into two separate streams.( engine core air, bypass air). Al- Ameen Engg. College 24
TURBOFAN ENGINES Thrust ratio, bypass ratio, and fan pressure ratio are the terms you should be familiar with. Thrust ratio is the comparison of the thrust produced by the fan to the thrust produced by the engine core exhaust. Bypass ratio is the ratio of incoming air to that bypasses the core to the amount of air that passes through the engine core. Fan pressure ratio is the ratio of air pressure leaving the fan to the air pressure entering the fan. Al- Ameen Engg. College 25
TURBOFAN ENGINES Turbofan engines are divided into three classification based on bypass ratio: 1- low bypass (1:1). 2- medium bypass (2:1 or 3:1). 3- high bypass (4:1 or greater). Low bypass engine, bypass air could be ducted directly overboard through a short fan duct or in a ducted fan where the bypass air is ducted along the entire length of the engine. Full fan ducts reduce aerodynamic drag and noise emissions. Both use a converging discharge nozzle that increases velocity and produce thrust. Al- Ameen Engg. College 26
TURBOFAN ENGINES Al- Ameen Engg. College 27
TURBOFAN ENGINES Al- Ameen Engg. College 28
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