On a newly built turbocharger test rig with auto-control equipment

a study of surge margin improvement and its effect on performance was carried out with a newly developed centrifugal compressor with pressure ratio of 4.5∶1.0

from which the following conclusions were made. The baffler

a kind of casing

has surge margin improvement when the pressure ratio is 3.5 and above

with surge mass flow being decreased by up to 6.4% and stable flow range improved by 2 percent. The positive vane

another kind of casing

also has the function of surge margin improvement

especially when the pressure ratio is between 2.0 and 4.5

the surge mass flow can be decreased by 3.0% to 6.6%

but it reduces the efficiency by up to 3 percent. Reduction of the compressor volute A/Ras a similar way to decrease the surge mass flow when the pressure ratio is 4.5 and below

particularly when the pressure ratio is between 1.5 and 3.5 and A/R is decreased by 17%

the surge flow falls down by more than 10%. Reduction of the TRIM value of impeller can improve the surge margin and reduce the surge flow when the pressure ratio is 2.5 and plus

the higher the rotation speed

the greater the reduction of the surge flow; the decrease in flow can reach by up to 12% and the improvement of stable flow range by up to 4% when the TRIM changes from 52 to 48.