Computational analysis of centrifugal compressor surge control using air injection

A Navier-Stokes solver for simulating unsteady viscous fluid flow in turbom achinery components has been developed and used to study fluid dynamic phen omena that lead to instabilities in centrifugal compressors. These studies indicate that large flow incidence angles, at reduced from rates, can cause boundary-layer separation near the blade leading edge. High-pressure jets upstream of the compressor face are studied as a means of controlling compr essor instabilities. Steady jets are found to alter the leading-edge flow p attern and effectively suppress compressor instabilities. It is also observ ed that yawed jets are more effective than parallel jets and that an optimu m yaw angle exists for each compression system. Pulsed jets can yield addit ional performance enhancements and lead to a reduction in external air requ irements for operating the jets. Jets pulsed at higher frequencies perform better than low-frequency jets.