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JET ENGINE MECHANICAL ARRANGEMENT. More generally known as ‘GAS TURBINE’ Engine. THE WORKING PARTS OF A JET ENGINE. Rolls-Royce AVON – Canberra – 1950’s technology. JET ENGINE MECHANICAL ARRANGEMENT.
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JET ENGINE MECHANICAL ARRANGEMENT More generally known as ‘GAS TURBINE’ Engine THE WORKING PARTS OF A JET ENGINE
Rolls-Royce AVON – Canberra – 1950’s technology JET ENGINE MECHANICAL ARRANGEMENT
Fuel, Oil, and Hydraulic Pumps, Electrical Generators, RPM Governor. Rolls-Royce AVON - (Graphic Representation) Compressor Handling Bleed Valve Front Engine Mount Rear Compressor Case Combustion Chambers (Cans) Intake Anti-Icing Tube Jet Pipe (Exhaust) Front Compressor Casing Accessory Gearbox Oil Tank Turbine Section Rear Engine Mount JET ENGINE MECHANICAL ARRANGEMENT
Turbo-jet = no Bypass Duct JET ENGINE MECHANICAL ARRANGEMENT
FRONT BULLET AND SUPPORT VANES SUPPORT BEARINGS REAR CONE AND SUPPORT VANES NOZZLE GUIDE VANES (NGV’S) STATOR VANES COMPRESSOR OUTER CASINGS COMBUSTION OUTER CASINGS COMBUSTION INNER CASING COMBUSTION FLAME TUBE Engine Casings – Static Assembly JET ENGINE MECHANICAL ARRANGEMENT
Compressor Blades Turbine Blades Shaft Assembly Rotating Assembly JET ENGINE MECHANICAL ARRANGEMENT
Above ambient Ambient temp 450 Deg C 2,500 Deg C 1,000 Deg C The shaded area is called the ‘GAS PATH’. These sections expand first Problem! Temperature changes cause the shaft and casings to expand and contract But by different amounts! This could put tremendous unwanted forces on the casings and shaft leading to failures (We’ll look at what happens to the air passing through the GAS PATH in Gas Turbine Operation.) Solution? Its all in the bearings! JET ENGINE MECHANICAL ARRANGEMENT
Front Bearing Chamber Centre Bearing Chamber Rear Bearing Chamber Roller Bearing Ball Bearing (Location Bearing) Roller Bearing Bearing Chambers JET ENGINE MECHANICAL ARRANGEMENT
Ball Bearings Provide Positive Axial Location Hot section Casing Shaft Front Bearing Chamber Centre Bearing Chamber Rear Bearing Chamber Casing Representation of jet engine bearing layout JET ENGINE MECHANICAL ARRANGEMENT
Casing Then, with ‘heat soak’ the shaft expands Casing Shaft and Casing have no differential movement at this point Representation of jet engine layout The casing expands first - pushing the rear outer bearing with it The same happens at the front with pressured air and heat sink from the combustor heating the hardware The engine is actually designed to dimensions based on normal operating temperatures Shaft JET ENGINE MECHANICAL ARRANGEMENT
JET ENGINE COMBUSTOR OPERATION WHERE THE POWER IS PRODUCED
THE COMBUSTION PROCESS IN A PISTON ENGINE: - FUEL IS MIXED WITH AIR BEFORE ENTERING THE CYLINDERS THE FUEL/AIR MIXTURE IS THEN COMPRESSED THEN IT IS IGNITED BY A SPARK ONCE FOR TWO REVS OF THE ENGINE (IN THE 4 STROKE CYCLE) IN A JET ENGINE: - AIR IS COMPRESSED AND FORCED INTO THE COMBUSTOR FIRST THEN THE FUEL IS SPRAYED IN UNDER PRESSURE IT IS THEN IGNITED BY A SPARK (BUT ONLY ONCE FOR STARTING) COMBUSTION IS THEN CONTINUOUS WHILST THE ENGINE IS RUNNING THE SAME AS A PLUMBERS BLOW TORCH! JET ENGINE – Combustion Process
We’re going to look in detail at what happens here But first we’ll look at the layout of the combustion system JET ENGINE – Combustor Layout
ENGINE STRUCTURE AND SHAFTS EACH CAN HAS A FUEL SPRAY NOZZLE (FSN) OUTER CASING INNER CASING COMBUSTOR LAYOUT – (ALSO HISTORICAL DEVELOPMENT) INDIVIDUAL COMBUSTORS – ‘CANS’ 1st JET ENGINES WHITTLE ETC FLAME CONTAINED WITHIN THIS TUBE ‘FLAME-TUBE’ JET ENGINE – Combustor Layout
IGNITERS COMBUSTOR LAYOUT – (ALSO HISTORICAL DEVELOPMENT) CANS CONNECTED TOGETHER TO EQUALISE PRESSURES AND TO SPREAD THE FLAME ON START UP TYPICAL OF DART SERIES TURBO PROPS JET ENGINE – Combustor Layout
INDIVIDUAL CANS WITH INTER-CONNECTORS ANNULAR OUTER CASING IGNITERS COMBUSTOR LAYOUT ‘CAN-ANNULAR’ LAYOUT ALSO FORMS THE ENGINE STRUCTURE TYPICAL OF SPEY &TAY BYPASS ENGINES JET ENGINE – Combustor Layout
ANNULAR OUTER CASING ANNULAR INNER CASING COMBUSTOR LAYOUT ANNULAR LAYOUT GIVES EVEN TEMPERATURE FACE TO TURBINE BLADES THE LAYOUT OF CHOICE FOR MODERN BYPASS ENGINES ALLOWS MORE FSN’S TO BE FITTED JET ENGINE – Combustor Layout
THE CROSS SECTION OF ALL THESE LAYOUTS IS VIRTUALLY IDENTICAL AND THEREFORE SO IS THE AIRFLOW! JET ENGINE – Combustor Layout
Outer Combustion Casing 82% Cooling Flow Inner Flame Tube 1st Stage NGV’s 18% Vortex Flow Recirculating Vortex Fuel Feed JET ENGINE – Combustion Process