Roots blower performance

Abstract Analytical expressions describing the characteristic performance curves of the Roots blower have been developed in the following work. These are especially useful in simulating Roots blower performance on the digital computer, as well as showing quantitatively the interplay between the parameters affecting performance. The analysis rests largely in the accurate relation obtained, in terms of blower dimensions, for variations in leakage flow due to changes in speed and pressure ratio respectively. It differs in this respect from previous work where leakage flow has been defined in terms of experimentally determined leakage coefficients, rather than in terms of blower dimensions. To account for effects on leakage flow of rotor and casing thermal expansion a number of assumptions have been made. The latter are shown to be most satisfactory for the blower considered. The work is simplified by showing that performance may be predicted independently of cyclic pressure fluctuations within the receiver, and by utilizing empirical relations for the friction and heat transfer characteristics.