POWERPLANT INTRO TO TURBINES PP2 Spokane Community Community College College

Bell XP-59 The first American jet-powered aircraft (1942)

TYPES OF JET PROPULSION Rocket Ramjet Pulsejet Gas Turbine Engines Turbojet Turboprop Turboshaft Turbofan Unducted Fan

ROCKET

Nonairbreathing engine carries its fuel carries oxygen to burn fuel TWO ROCKET TYPES Solid-propellant rockets solid fuel mixed with an oxidizer fuel formed in shapes to promote burning requires an ignitor common uses- military weapons, additional trust for takeoff Liquid –fuel rockets liquid fuel liquid oxidizer carried in two separate tanks when mixed tremendous heat and thrust generated

ROCKET

RAMJET

Air-breathing engines No moving parts Once air enters the engine fuel is injected then fuel is ignited Must be moving forward BEFORE in can create thrust Other names for Ramjet athodyd aero-thermodynamic-duct

RAMJET

PULSEJET

Ramjet with spring loaded shutters added shutters are spring loaded open close when combustion chamber air pressure increase Pulsejets can produce thrust before being accelerated Pulsejet engines are used on

PULSEJET

GAS TURBINE ENGINES Most practical form of jet engine used today Standard for transport category business military aircraft

TYPES OF GAS TURBINE ENGINES  Turbo-jet Engines  Turbo-propeller Engines (turbo-prop)  Turboshaft Engines  Turbofan Engines  Unducted Fan Engines

TURBOJET ENGINES

Basic Operating Principles  Air enters through inlet duct  Air proceeds to compressor section  Once compressed air flows to combustor section  Fuel is added and ignited  Heat expands air and forces it rearward  Air then passes through a set of turbine wheels  Turbine wheels drive compressor section via shaft  Expanding air turns turbines, in turn (pun) driving compressor section  Air then exits the engine at much higher velocity than the incoming air  This pressure difference creates thrust  Engine Pressure Ratio (EPR) indicates amount of thrust produced  EPR is the ratio of the turbine discharge pressure to the engine inlet pressure  Turbojets used on fast, high altitude aircraft  Output is measured in pounds of thrust (40,000 lbs. thrust)

TURBOJET ENGINES

TURBO-PROPELLER

TURBOPROP ENGINE A gas turbine engine that delivers power to a propeller = Turboprop Similar to a turbojet but drive a propeller Reduction gearing is necessary Used extensively in business and commuter type aircraft Performance tops out around 300 to 400 miles per hour Turbprops have the best specific fuel consumption of any gas turbine engine (SFC = # of pounds of fuel burned per hour to produce one horsepower) Output is measured in shaft horsepower or estimated shaft horsepower (shp) or (eshp).

TURBO-PROPELLER

TURBOSHAFT ENGINES

A gas turbine engine delivers power to drive a shaft = Turboshaft Most energy produced is used to drive a turbine rather than producing thrust Commonly used on Helicopters and Auxiliary Power Units (APU’s) Industrial uses include driving electrical generators and ground transportation Output is measured in shaft horsepower or estimated shaft horsepower

TURBOSHAFT ENGINES

TURBOFANS

A multi-bladed ducted propeller driven by a gas turbine engine Compromise best attributes of the turboprop and the turbojet Turbofans have turbojet cruise speeds and short-field takeoff of a turboprop Extremely common on modern airliners Fan can be mounted on the front of the engine (forward-fan) or on the back of the engine (aft-fan) Two streams of air 1st goes through engine core 2 nd stream coaxially bypasses the engine core

TURBOFANS

Three terms: thrust ratio, bypass ratio, fan pressure ratio. Thrust Ratio: the thrust produced by the fan compared to the thrust produced by the engine core exhaust Bypass Ratio: the amount of incoming air that bypasses the core compared to the amount of air that passes through the core of the engine. low bypass (1:1) medium bypass (2:1 or 3:1) high bypass (4:1 or greater) Fan pressure ratio: air pressure leaving the fan compared to the air pressure entering the fan low bypass engine typical fan pressure ratio is 1.5:1 high bypass engine typical fan pressure ratio 7:1

UNDUCTED FAN ENGINES

Ultra high bypass propfan (UHB) and unducted fan engines (UDF) Use titanium, lightweight stainless steel, and composites Achieve bypass ratios of 30:1 15% greater fuel economy Composite propeller blades feet long are designed for safe operation at high speeds Similar propfans have been enclosed in inlets, allowing for forward speeds of 0.9 MACH these engines are called ducted ultra high bypass engines

UNDUCTED FAN ENGINES