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Stage Loading is a measure of the load on a
turbomachinery Turbomachinery, in mechanical engineering, describes machines that transfer energy between a rotor and a fluid, including both turbines and compressors. While a turbine transfers energy from a fluid to a rotor, a compressor transfers energy fr ...
stage, be it a part of a
compressor A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can transp ...
, fan or
turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...
. The parameter, which is non-dimensional, is defined as: L = \frac where:
Imperial Units The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed thro ...
(SI Units) g acceleration of gravity ft/s/s (1.0) J mechanical equivalent of heat ft.lb/(s.hp) (1.0) H change in specific enthalpy over stage hp.s/lb (KW.s/Kg) U peripheral blade speed ft/s (m/s) Average stage loading has a very similar definition, where the number of stages, n, within the compressor, fan or turbine is used to provide an average value: L = \frac{nU^2} In this case the change in
enthalpy Enthalpy , a property of a thermodynamic system, is the sum of the system's internal energy and the product of its pressure and volume. It is a state function used in many measurements in chemical, biological, and physical systems at a constant p ...
is across the whole unit, not just a stage. Similarly, the blade speed used is a mean for the whole device. The above equation shows that if blade speed cannot be increased for, say, mechanical or
aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
reasons, the number of stages has to be increased to get the average stage loading back to an acceptable level, to obtain a satisfactory level of efficiency. The ideal average stage loading for a turbine is about 1.8. Turbomachinery