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In fixed-wing aircraft driven by one or more jet engines, certain aspects of performance such as thrust relate directly to the safe operation of the aircraft whereas other aspects of the engine operation such as noise and engine emissions impact the environment. The thrust, noise and emission elements of the operation of a jet engine are of vital importance in the takeoff phase of operation of the aircraft. The thrust and fuel consumption elements, and their variation with altitude, are of vital importance in the climb and cruise phases of operation of the aircraft. The behaviour of a jet engine and its effect both on the aircraft and the environment is categorised into different engineering areas or disciplines. For example the emissions come under a group called combustion, the origin of vibrations transmitted to the airframe come under an area called rotor dynamics. So what is performance? When the airframe sees fuel disappearing from its tanks and feels a thrust. The understanding of how a particular fuel flow produces a definite amount of thrust at a particular point in the flight envelope is called jet engine performance. Performance is the subject of a specialised discipline within aero engine design and development teams as is the understanding of noise and emissions by their respective specialists in other groups. The fundamental performance task for a single shaft turbojet is to match the operation of the compressor, turbine and propelling nozzle. For example, the way the compressor operates is determined by the flow resistances behind it, which occur in the combustor, turbine, tailpipe and propelling nozzle.〔"Jet Propulsion for Aerospace Applications" Second edition,Hesse and Mumford, Pitman Publishing Corporation 1964, p172〕 Matching may be defined as designing, sizing, and manipulating the operating characteristics〔"Method for Determining Component Matching and Operating Characteristics for Turbojet Engines" David G. Evans, Lewis Research Center〕 of the compressor, turbine and propelling nozzle. Three fundamental observations are built upon〔"Method for Determining Component Matching and Operating Characteristics for Turbojet Engines" David G. Evans, Lewis Research Center. Table 1 "Development of Matching Parameters"〕 as outlined below to develop the required understanding to match the components efficiently. The flow through the compressor is the same as that through the turbine. The speeds are the same. The power produced by the turbine equals that absorbed by the compressor. In addition, the flow resistance seen by the compressor is determined by the two restrictors downstream, namely the turbine nozzle area and the propelling nozzle exit area. The above three ties between the compressor and turbine are adjusted and refined to account for the flows and powers not being equal due to, for example, compressor flow and electric and hydraulic power〔"Method for Determining Component Matching and Operating Characteristics for Turbojet Engines" David G. Evans, Lewis Research Center. Table 1 "Development of Matching Parameters"〕 being diverted to the airframe. Thus the performance is understood and defined by using the practical engineering application of thermodynamics and aerodynamics.〔"Gas Turbine Aero-Thermodynamics" Sir Frank Whittle ISBN 978-0-08-026718-0〕 This article covers a wide scope of the discipline of jet engine performance. ==Navigating this article== Specific values of thrust and fuel consumption are promised to a prospective aircraft customer and these are derived using procedures detailed in section "Design point performance equations" and "Simple off-design calculation". An explanation for "off-design" is given in "General". An aircraft receives pneumatic, electric and hydraulic power in return for some of the fuel it supplies. This is mentioned in "Installation Effects". These effects define the difference between the performance of an uninstalled engine (as measured on a test bed) and one installed on an aircraft. When air is taken from the compressor and used to cool the turbine it has an adverse effect on the amount of fuel required to give the required thrust. This is covered in "Cooling Bleeds". The effect of fundamental design changes to the engine, such as increased pressure ratio and turbine inlet temperature, is covered in "Cycle improvements'. Ways to increase the pressure ratio are also covered. The effects of over-fuelling and under-fuelling which occur with changes in thrust demand are covered in "Transient model". There is an explanation of the Husk plot which is a concise way of summarising the performance of the engine. The thrust available is restricted by the turbine temperature limit at high ambient temperatures as explained in the "Rated performance" sections. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Jet engine performance」の詳細全文を読む スポンサード リンク
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