Design of an Inducer Pump with High Suction Performance and Backflow Control

The design of inducers is critical to achieving high suction performance in industrial pumps and rocket engine turbopumps. However, the conventional design approach, based on blade angles, often causes unstable pump operation. Instabilities such as strong inlet backflow and rotating cavitation in inducers may cause mechanical failures in pumps and the entire pumping system.

TURBOdesign1 has been successfully applied to the design of inducers and validated by experiments. By optimizing blade loading, the suction performance can be improved over the operating range. The low pressure area was reduced as shown in Figures1 and 2.

It was also confirmed that the inlet backflow can be controlled by optimizing the blade loading at the leading edge.

Fig.1: Conventional (Helical Type)

Fig.2: TURBOdesign1

TURBOdesign1 was also applied in the design of the main impeller of an inducer pump, see Figure 3.

Experimental validation confirmed that employing aft-loading at the shroud was effective in achieving high suction performance. In addition, consideration of the pre-swirl created by the inducer is important in improving the suction performance of the main impeller. See Figure 4.

The design of a highly loaded, rocket engine, turbo pump inducer, was carried out using TURBOdesign1 (Figure 5). The conventional helical type inducer has a strong inlet backflow even at the design point, the presence of which is confirmed by the photograph in Figure 6. This inlet backflow at the design point was eliminated by optimizing the blade loading distribution using TURBOdesign1, see Figure 7. The meridional geometry was also re-designed to achieve high loading. Figures 8 and 10 show the streamlines at design point, the elimination of the inlet backflow can be clearly seen.

Fig.3

Fig.4

Fig.5

Fig.6: Conventional

Fig.7: TURBOdesign1

The elimination of inlet backflow is important for assuring mechanical reliability, and avoiding deterioration of the “thermodynamic effects” on suppressing cavitation of liquid hydrogen. Figures 9 and 11 show the FFT analysis results of measured pressure fluctuation at the design point, and a cavitation number of σ = 0.04. In the case of the inducer designed by TURBOdesign1, pressure oscillation was maintained at a very low level and no evidence of rotating cavitation was observed.

Fig.8: Conventional

Fig.9: Conventional

Fig.10: TURBOdesign1

Fig.11: TURBOdesign1

References:

• Ashihara, K. and Goto, A., 1999, Improvements of Pump Suction Performance using 3-D Inverse Design Method, ASME FEDSM99-6846
• Ashihara, K. and Goto, A., 2002, Effects of Blade Loading on Pump Inducer Performance and Flow Fields, ASME FEDSM 2002
• Ashihara, K., Goto, A., Kamijo, K., Yamada, H., Hashimoto, and T., Uchiumi, M., 2001, Study on Turbopump Inducers Designed by 3-D Inverse Design Method, AFI-2001, Zao, Japan.