Evaluation of effect of inlet distortion on aerodynamic performance of helium gas compressor for Gas Turbine High Temperature Reactor (GTHTR300) (Contract research)

Takada, Shoji; Takizuka, Takakazu; Yan, X.; Kurokochi, Naohiro; Kunitomi, Kazuhiko 

Because the main pipe is connected perpendicular to the flow direction inside the distributing header in the inlet casing of the helium gas compressor design of GTHTR300, the main flow flowing into the header tends to separate from the header wall and to cause reverse flow, which increases flow resistance in the header. This phenomenon increases the total pressure loss in the header and inlet distortion, which is considered to deteriorate the aerodynamic performance of the compressor. Tests were carried out to evaluate the effects of inlet distortion on aerodynamic performance of compressor by using a 1/3-scale helium gas compressor model by varying a level of inlet distortion. Flow was injected from the wall of header to adjust circumferential velocities uniform before and after the inverse flow region to dissipate the separation and inverse flow. At the rated flow point, inlet distortion was reduced 2-3 % by injection, which resulted in increasing adiabatic efficiency of blade section around 0.5 %. At the same time, pressure loss of the inlet casing was reduced around 3-5%, which is equivalent to adiabatic efficiency improvement around 0.8%. Surge flow rate was lowered from 10.0 kg/s to 9.6 kg/s. By setting orifice at the inlet of inlet casing and increasing inlet distortion 4% higher, the adiabatic efficiency of blade section became 1 % higher. A new correlation between inlet distortion and adiabatic efficiency of blade section at the rated flow rate was derived based on compressor-in-parallel model and fitted to the test results. Overall adiabatic efficiency of full scale compressor was predicted 90.2% based on the test results of efficiency and Reynolds number correlation, which was close to 89.7% that was predicted by test calibrated design and CFD codes, which satisfied the design value 89.0 % of the compressor for GTHTR300.