Description
Object description
A technical film which illustrates how the initial jet engine design is being continuously developed, particularly in relation to the intake and output nozzles. Early jet engines had only a single turbine stage but modern jet engines have at least four additional stages to maximise the efficiency of the original design. Much of this work is undertaken at the National Gas Turbine Establishment, Pyestock, and a variety of developments are illustrated in this film.
Content description
Film opens on a dull rainy day in London, as a man walks up and enters the Science Museum in South Kensington. He inspects exhibits of aeronautical engines on display: Liquid cooled from 1908 to 1912, V8 type from 1910 to 1917, H type from 1934 to 1944 and gas turbines from 1941 to 1960, where he pauses and looks upward to see prototype jet aircraft the Gloster E28/39 serial number W4041 designed by Frank Whittle, suspended from the ceiling.
Content description
Archive footage is shown of W4041 as the aircraft taxis out and takes off. The advantage of the jet engine is its simplicity and although there are complications due to the gas turbine, the basic design remains the same in 1966, but much research into the shape and sizes of the intake and output nozzles has been necessary. A diagrammatic explanation of a basic jet engine is given, noting that it is the difference in pressure and velocity between the nozzles that propels the aircraft, with a thermal efficiency of 55%, well beyond that of a reciprocating engine. For supersonic aircraft the design of the intake and output nozzles is both very different and critical. The key is the expansion of the air process as it moves through the engine. The National Gas Turbine Establishment at Pyestock has long been working on the design of the nozzles in addition to the gas turbine. The research workshops at Pyestock are seen, where three full size models of the air intake for the Concorde engine are under test in a 500 mph wind tunnel. An equal amount of work is spent on the exhaust system. The swivelling nozzles, both large and small, of a Harrier VTOL aircraft are seen being tested, a particular problem with the large nozzles when they are not horizontal is the hot exhaust gases can be taken in again by the input nozzle resulting in a sudden loss of power. Bird strike is another problem, a bird can be like a cannon ball to a fast moving aircraft. A large air gun is seen firing bodies similar to birds into the turbine blades to test their resilience.
Content description
A series of diagrams is used to illustrate the problems associated with engines for high speed flight. Because of their size and complexity turbine engines are tested in large wind tunnels, and the engine turbine run on a test bed, but the test of the engine as a whole must be conducted in simulated flight. Four test beds are available at Pyestock where a generating room supplies the tunnels with high speed air. A 70 ton machine which varies the input nozzle parameters of a running engine is seen, the huge volume of exhaust gases is feed away by pumps to vertical cooling towers.
Content description
Aerial views of the site at Pyestock. The work at Pyestock ranges from basic research on the design of new engines right through to the final flight clearance for use on an aircraft. Modern jet engines have five stages: intake/diffuser, turbine, reheater, thrust reversal, and propelling nozzle. The original jet engine had just one stage, the turbine, and nearly all development work has been on the four additional stages. The principal of the Ramjet with no turbine is noted. After-burners are used to increase thrust for short periods, whilst the thrust reversal aids the deceleration of an aircraft on landing. The propelling nozzle also requires variable geometry to accommodate the change in volume of gas associated with high and low engine speeds. To minimise engine noise, air bled from the inlet nozzle bye-passes the turbine and exhausts around the propelling hot gases. The bigger and slower an engine, the greater the thrust. Film cuts to the VC10 engine nacelles housing four bipass engines with a higher efficiency and consequent less noise. A further development of this principle is the Fan jet engine and the resultant gain in thrust and reduction in noise are substantial.
Content description
The film ends with footage of a Victor bomber taking off assisted by the afterburners.
Physical description
16mm