نیشاموبروت سرد هژورپ
Detailed Flow Study of Mach Number 1.6 High Transonic Flow With a Shock Wave in a Pressure Ratio 11 Centrifugal Compressor Impeller
Requirements for aeronautical gas turbine engines for helicopters include small size, low weight, high output, and low fuel consumption. In order to achieve these requirements, development work has been carried out on high efficiency and high pressure ratio compressors. As a result, we have developed a single stage centrifugal compressor with a pressure ratio of 11 for a 1000 shp class gas turbine. The centrifugal compressor is a high transonic compressor with an inlet Mach number of about 1.6.
In high inlet Mach number compressors, the flow distortion due to the shock wave and the shock boundary layer interaction must have a large effect on the flow in the inducer. In order to ensure the reliability of aerodynamic design technology, the actual supersonic flow phenomena with a shock wave must be ascertained using measurement and Computational Fluid Dynamics (CFD). In This research, students must present the CFD results of the high transonic flow at the impeller inlet, with respect to the high transonic flow velocity distribution, pressure distribution, and shock boundary layer interaction at the inducer. The impeller inlet tangential velocity is about 460 m/s and the relative Mach number reaches about 1.6. Using a LDV, about 500 m/s relative velocity was measured preceding a steep deceleration of velocity.
Fig. 1: High transonic impeller
Figures 2 and Table 1 show the compressor characteristics, and compressor and impeller specifications respectively. The tangential velocity of the impeller outlet is about 680 m/s, the inlet tangential velocity is about 460 m/s, nand the machine Mach number reaches about 1.35. The blade tip clearance is about 0.2 mm. The impeller outlet absolute velocity is supersonic, and the Mach number is about 1.2. A radial channel diffuser is attached. A passage downstream of the diffuser is configured in the axial direction, with an axial vane diffuser. Regarding the compressor characteristics, the pressure ratio is 11 at a mass flow rate of 3.3 kg/s. The point just below the choke flow rate is the point of maximum efficiency. Both impeller efficiency and diffuser pressure recovery reach their maximum at this point.
Fig. 2: Compressor characteristics: (a) pressure ratio, (b) efficiency
