Rotor Profiles Synthesis for Lobe Pumps With Given Flow Rate Functions

Abstract

In this paper we present a complete synthesis procedure for lobe pumps with required flow rate functions. A dimensionless flow rate expression, called the “specific flow rate,” is used for our pump synthesis. This specific flow rate depends only on the pitch and deviation functions of the pump rotor, and it is independent of the individual pump size, neither pumping frequency. Another important design parameter used is the “lobe noncircularity,” which is defined as the ratio of the lobe length to the rotor center distance. It is found that the lobe noncircularity is linearly dependent on the ratio of maximum to minimum flow rate regardless of the type of flow rate function. As a result, our synthesis procedure can be simplified as (1) select a type of desirable flow rate function, (2) from the flow rate function derive the corresponding deviation function, (3) based on the deviation function generate the desired rotor profile, and (4) calculate the real pump size. Another advantage is that by using this method wide classes of lobe pumps can be designed. A detailed design example is presented for illustration. In addition, new lobe profiles are invented based on some typical flow rate functions.