6.2: The jet engine

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截屏2022-01-20 下午9.21.36.png
Figure 6.2: Jet engine: Core elements and station numbers. Adapted from: © Jeff Dahl / Wikimedia Commons / CC-BY-SA-3.0.

Even though there are various types of jet engines (also referred to as gas turbine engines) as it is to be studied in Section 6.3, all of them share the same core elements, i.e., inlet, compressor, burner, turbine, and nozzle. Figure 6.2 illustrates schematically a jet engine with its core elements and the canonical engine station numbers, which are typically used to notate the airflow characteristics (\(T, p, \rho\), etc.) through the different components. In this Figure, the station 0 represent the free-stream air flow; 1 represents the entrance of the inlet; 2 and 3 represent the entrance and exit of the compressor, respectively; 4 and 5 represent the entrance and exit of the turbine, respectively; 6 and 7 represent the entrance and exit of the after-burner¹ (in case there is one, which is not generally the case), respectively; and finally 8 represents the exit of nozzle.

Roughly speaking, the inlet brings free-stream air into the engine; the compressor increases its pressure; in the burner fuel is injected and combined with high-pressure air, and finally burned; the resulting high-temperature exhaust gas goes into the power turbine generating mechanical work to move the compressor and producing thrust when passed through a nozzle (due to action-reaction Newton’s principle). Details of these engine core components are given in the sequel.

1. Notice that in the figure there is not after-burner, but however the station numbers 6 and 7 have been added for the sake of generalizing.