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【范围】
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1.1 Method:
A general method for the preliminary design of a single, straight-sided, low subsonic ejector is
presented. The method is based on the information presented in References 1, 2, 3, and 4, and
utilizes analytical and empirical data for the sizing of the ejector mixing duct diameter and flow
length. The low subsonic restriction applies because compressibility effects were not included in the
development of the basic design equations. The equations are restricted to applications where
Mach numbers within the ejector primary or secondary flow paths are equal to or less than 0.3.
1.2 Procedure:
A recommended step-by-step procedure is shown.
1.3 Equations:
The equations used in the procedure, as well as their derivations, are given.
1.4 Sample Calculation:
A sample calculation is presented to illustrate the use of the basic method.
1.5 Purpose:
In typical helicopter gas turbine engine installations, the engine is enclosed within a nacelle. Within
the nacelle, heat is rejected from the engine skin and from other sources such as the engine oil
cooler, generator, and airframe accessories. Therefore, it becomes necessary to provide a flow of
ventilating air through the nacelle to maintain the ambient temperature surrounding the engine at an
acceptable level.
One possible means of providing this ventilating air is to utilize the kinetic energy of the engine
exhaust gas in an ejector to induce an airflow through the enclosure. This device is also commonly
called an eductor, an aspirator, or a jet pump.
A straightforward method of defining the ejector geometry to provide the required cooling flow for a
given application is needed.strRefField
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