JET PROPULSION Part 4 Types of Jet Engines

Engine Types Turbo Jet Turbo Fan - Bypass Engines Turbo Prop Avon, Olympus 593 Turbo Fan - Bypass Engines SMALL BYPASS Spey, BR700 MEDIUM BYPASS Pegasus, BR715, V2500 LARGE BYPASS RB211, Trent Series Turbo Prop PROPELLER Dart, Tyne, BR715TP Turbo Shaft HELICOPTER Lycoming T55, Gem RN SHIPS Marine Spey POWER GENERATION Industrial Spey & Trent

Turbo Jet Rolls Royce Avon This is called: - COMPRESSOR SURGE At low rpm the rear of the compressor cannot get rid of all the air from the front of the compressor This can result in the rear end of compressor ‘choking’ So air blasts forwards 17 Stage Compressor driven by a 3 stage turbine Flame almost goes out - no power – no thrust. This is called: - COMPRESSOR SURGE With RPM (i.e. Thrust) changes, the airflow velocity does not change in proportion to engine RPM

Turbo Jet Rolls Royce Avon BUT air dumped sideways out of the engine Rear end of compressor ‘unchoked’ Air dumped overboard Rearward movement of air restored Power restored BUT air dumped sideways out of the engine produces no thrust. So a more efficient system was required

‘Excess’ air is dumped overboard through a valve Turbo Jet Rolls Royce Avon ‘Excess’ air is dumped overboard through a valve ‘Bleed’ valve

High Pressure Compressor Low Pressure Compressor Turbo Jet The Olympus 593 The Two Shaft Layout Single Shaft Layout driven by High Pressure Compressor High Pressure Turbine driven by Low Pressure Compressor Low Pressure Turbine

Turbo Jet The Olympus 593 The Two Shaft Layout Allows front end of compressor to slow down – move less air and Allows rear end of compressor to speed up – move more air Compressor surges lessened No wasted energy/thrust

Turbo Jet The turbojet is the simplest and earliest form of gas turbine. Used principally in high speed aircraft where its relatively low frontal area and high jet velocity are advantages. Examples are the Concorde supersonic transport and a variety of military aircraft including the Dominie/HS125.

Turbo Fan Low Bypass Engine Rolls Royce Spey Adour BR710 Series Part of the air is compressed fully and passes into the combustion chamber, while the remainder is compressed to a lesser extent and ducted around the hot section.

Turbo Fan Medium Bypass Engine Pegasus Two shaft layout with Contra-rotating shafts It has low pressure and high pressure AXIAL Flow Compressors Core flow to ‘Hot’ (rear) Nozzles Bypass flow to ‘Cold’ (front) Nozzles

Turbo Fan High Bypass Engine RB211 Series (Trent) Three shaft layout – all rotate same direction LP(Fan) Intermediate and HP AXIAL Flow Compressors In service with RAF – Wide-body Tristar Tanker/Transport Boeing 747 and later series, Airbus A330 and larger a/c

Turbo Fan High Bypass Engine RB211 Series (Trent)

Turbo Fan Turbofan engines are loosely categorised by the size of the bypass compared to the core flow. (The amount of air entering the core engine compared to the bypass duct) which is called the Bypass Ratio. The low bypass ratio is approximately 1:1. Half the air goes through the core or hot section, the other half goes through the bypass. Medium bypass engines have a 5:1 ratio, while high bypass have a ratio of 10:1 or more.

Turbo Fan The turbofan (bypass) reduces overall jet velocity, giving better propulsive efficiency at lower speeds, lower noise levels and improved specific fuel consumption, features which make the turbofan ideal for both civil and military aircraft. Examples are the Boeing 747 and 757, the Jaguar and Hawk, and the Tornado. The Harrier has a variation of the turbofan.

Turbo Prop Rolls Royce Dart Dart RDa6 = 2 stage turbine Dart RDa7 = 3 stage turbine Turbine drives 2 stage CENTRIFUGAL Compressor and Propeller Reduction Gearbox Prop Shaft Over 70 Marks of Engine – different power levels – 15 different aircraft Fokker F27, Fairchild F27, Briguet Alize, (and P51 Mustang and Dakota!)

Turbo Prop Tyne C160 Transall, Shorts Belfast, Brequet Atlantic, Avro Lincoln, Canadair CL44, Vickers Vanguard, Aeritalia 222. Reduction Gearbox 9 Stage HP Compressor 1 Stage HP Turbine 6 Stage LP Compressor 3 Stage LP Turbine Prop Shaft (via Reduction Gearbox)

Turbo Prop RR Allison T56-A-15 Tyne C160 Transall, Shorts Belfast, Brequet Atlantic, Avro Lincoln, Canadair CL44, Vickers Vanguard, Aeritalia 222. Reduction Gearbox 9 Stage HP Compressor 1 Stage HP Turbine 6 Stage LP Compressor 3 Stage LP Turbine Prop Shaft (via Reduction Gearbox)

Turbo Prop RR Allison T56-A-15 C130 Hercules Reduction Gearbox Thrust Strut Turbine drives compressor and propeller Output Shaft 4 Stage Turbine Air Intake 14 Stage HP Compressor

Turbo Prop The turboprop is basically a turbojet with an extra turbine designed to absorb the energy remaining in the gas stream after sufficient has been removed to drive the compressor. The turboprop is a very efficient power unit for relative low speed, low altitude aircraft. Examples are the 748 and F27, and the Transall C-160 and Atlantic.

Turbo Shaft Lycoming T55-GA-714 Boeing CH47 Chinook Front Rotor Transmission Rear Rotor Transmission Combining Transmission Turboshaft with Free Power Turbine

Turbo Shaft The turboshaft is virtually a turboprop without a propeller. The power turbine absorbs as much of the remaining gas energy as possible and the residual thrust is very low. The main use of the turboshaft is the helicopter and industrial and marine application, including power and pumping stations, hovercraft and ships. Examples are the Lynx, Chinook and the Sea King.

Which of these is a turbo jet engine? Check Understanding Which of these is a turbo jet engine? Tyne Spey Pegasus Olympus

Check Understanding Which of the following features makes the turbofan ideal for both civil and military aircraft? The turbine absorbs as much of the gas energy as possible Lower noise levels and improved specific fuel consumption Very efficient power unit for relative low speed, low altitude It is ideal for high-speed, high-altitude aircraft

Which of these is a turbo fan engine? Check Understanding Which of these is a turbo fan engine? Tyne Pegasus Dart Gem

Check Understanding Which application or type of operation best suits the turbojet engine? In low speed aircraft operating at high altitudes In high speed aircraft where low frontal area is an advantage In low speed aircraft operating at low altitudes In helicopters

Which of these is a turbo prop engine? Check Understanding Which of these is a turbo prop engine? RB 211 Dart Spey Avon

Check Understanding Which of these statements applies to a turboprop engine? It has one less turbine compared to a turbojet It has an extra turbine compared to a turbojet It is ideal for high-speed, high-altitude aircraft It has a very high residual thrust

Which of these is a turbo shaft engine? Check Understanding Which of these is a turbo shaft engine? Tyne Lycoming RB 211 Trent

JET PROPULSION End of Presentation