Tham khảo tài liệu 'gas turbine engineering handbook 2 episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Axial-Flow Compressors 285 where p medium density V velocity D impeller diameter p viscosity N speed Using this assumption one can apply this flow visualization method to any working medium. One designed apparatus consists of two large tanks on two different levels. The lower tank is constructed entirely out of plexiglass and receives a constant flow from the upper tank. The flow entering the lower tank comes through a large rectangular opening which houses a number of screens so that no turbulence is created by water entering the lower tank. The center of the lower tank can be fitted with various boxes for the various flow visualization problems to be studied. This modular design enables a rapid interchanging of models and work on more than one concept at a time. To study the effect of laminar flow the blades were slotted as shown in Figure 7-9. For the blade treatment cascade rig experiment a plexiglass cascade was designed and built. Figure 7-10 shows the cascade. This cascade Figure 7-9. Perspective of compressor blade with treatment. 286 Gas Turbine Engineering Handbook FPO Figure 7-10. Cascade model in axial-flow test tank. was then placed in the bottom tank and maintained at a constant head. Figure 7-11 shows the entire setup and Figure 7-12 shows the cascade flow. Note the large extent of the laminar-flow regions on the treated center blades as compared to the untreated blades. The same water tunnel was used for tests to study the effect of casing treatment in axial-flow compressors fn this study the same Reynolds number and specific speeds were maintained as those experienced in an actual axial-flow compressor. fn an actual compressor the blade and the passage are rotating with respect to the stationary shroud ft would be difficult for a stationary observer to obtain data on the rotating blade passage. However if that observer were rotating with the blade passage data would be easier to acquire. This was accomplished by holding the blade passage stationary
