AERODYNAMICS

[Aircraft Propulsion]

Thrust (T) = Mass x Velocity (MV)

Aircraft thrust:

Propeller engines move large mass of air at low velocity. Jet engines move small mass of gas at high velocity.

[Piston Engine]

Only type of aircraft engine during 1903-1940s. Very efficient for low speed flight. Lower load capacity compared to similar sized jet powered aircraft. Consumes less fuel, thus cheaper and much more economic than jets. Propellers are not used on high speed aircraft.

Piston engine: Energy is produced by burning a mixure of air and fuel. An aircraft engine is designed with weigth as a primary consideration. The piston aircraft engine demands high power for very long tiimes compared to car engines. An aircraft engine has at least two sets for every parts, including ignition system (spark plugs and magnetos) and fuel pumps compared to car engine. An aircraft engine has no need for air-cooling the engine.

Propeller: A type of fan which transmits power by converting rotational motion into thrust for moving the aircraft forward. Propeller blades have an aerofoil shape and are attached to a central hub which is mounted onto propeller shaft driven by the piston engine.

Example:

Piper PA-28-140 Cherokee: Started production in 1961, still in production. Top speed 125 kts, cruise speed 117 kts (220 km/h), gross weight 890 kg, empty weight = 540 kg, range 457 nm (850 km), rate of climb 250 m/min., ceiling 4.6 km, crew 1, passengers 3, used products average price $36,000

Engine: Lycoming O-320-E3D, 4 cylinder, 150 hp @ 2700 rpm, bore 130 mm, stroke = 98 mm, displacement = 1300 cc x 4 = 5200 cc, compression ratio 7:1, dry weight 125 kg, oil apacity 7.6 L, fuel capacity 36 gal (160 L) (standard), 50 gal (227 L) (reserve), fuel aviation grade 80/87 minimum octane, electric starter, 60-A alternator, dual magnetos, vacuum pump driver, electric fuel pump, float carburetor.

Propeller: Sensenich M74DM fixed-pitch aluminum alloy, diameter 190 cm, pitch 147 cm

Elecrtrical system: 14-V 60-A alternator, 12-V battery, voltage regulator, overvoltage relay, master switch relay

Vacuum system: For operating the air driven directional and attitude gyros. Engine-driven vacuum pump, vacuum regulator (used to protect the gyros, the valve is set at normal vacuum 5 inches of mercury for suffcient vacuum to operate all the gyros), filter, plumbing.

Instrument panel: Air speed, attitude gyro, vertical speed, altimeter, transponder, magnetic compass, marker beacon, omni & glide slope indicator, UHF transceiver, ADF receiver, autopilot, tachometer (engine rpm)

[Gas-Turbine Engine]

[Jet Engine = Gas-Turbine Engine]

History:

The first turbo jet engine was designed by Sir Frank Whittle in 1930. The first jet aircraft Heinkel He 178 was developed in England and Germany in 1939. The first figher aircraft Messerschmitt Me 262 went into service in the German Luftwaffe in 1943.

German V-1 bomb: 1st pulse jet engine used for military purpose

Bell P-59: 1st American jet aircraft

MiG-15: 1st Soviet jet aircraft

Introduction:

- Also called the gas turbine engine.

- Various types have been developed; turbo-jet, turbo-prop, turbo-shaft, turbo-fan, ramjet, scramjet.

- More fuel comsumption with more thrust.

- Jet aircraft speeds are far greater than propeller aircrafts.

- Greater weight capacity

- Very noisy

- Applications: civillian and military aircrafts, industrial power generation

Construction:

1 = air intake, 2 = low-pressure compression, 3 = high-pressure compression, 4 = combustion, 5 = exhaust, 6 = hot section, 7 = turbines, low and high pressure, 8 = combustion chambers, 9 = cold section, 10 = air inlet

Air intake (inlet): designed for minimum drag.

Compressor: Fans with many blades. Air temperature and pressure increased.

Burner: Fuel is sprayed to the compressed air. The mixure of air and fuel is burned generating high-engergy gas with high pressure and high temperature.

Turbine: Turbines use some of the heated gas energy to turn the compressor connected to the same shaft.

Nozzle: Makes the heated gas exits out of the engine at very high speeds resulting in thrust.

Types of Jet Engines:

Turbo-jet: SR-71 Blackbird

Turbo-fan: Commercial airliner. Most modern airliners use turbofan engines because of they can produce high thrust, lower fuel consumption and low engine-noise.

Turb-prop: Short-distance aircraft for better fuel economy. The propeller converts the power developed by the engine into thrust as effciently as possible under all operating conditions. Piltus PC-12, Hercules-1 C130

Turbo-shaft: Lynx helicopter

Ramjet: Used in rockets

Engine Materials:

Ni-based sueralloy turbine blades:

For additional study, see

http://en.wikipedia.org/wiki/Components_of_jet_engines#Turbines