• International Journal of Fluid Machinery and Systems
• /
• v.4 no.1
• /
• pp.25-32
• /
• 2011

The objective of present work is to use numerical simulation to investigate the complex three-dimensional and secondary flow structures developed at the inlet and impeller in a centrifugal pump at design and off-design points. The pump impeller is shrouded with 6 backward swept blades and with a specific speed of 0.8574. The characteristic of the pump is measured experimentally with straight and curved intake sections. Numerical computation is carried out to investigate the pump inlet flow structures and subsequently the flow field within the centrifugal pump. The numerical results showed that strong interaction between the impeller eye and intake section. Secondary flow structure occurs upstream at the pump inlet has great influence on the pump performance and flow structure within the impeller.

• International Journal of Fluid Machinery and Systems
• /
• v.4 no.1
• /
• pp.209-216
• /
• 2011

The flow upstream of a centrifugal pump impeller has been investigated by both experimental test and numerical simulation. For experimental study, the flow field at four sections in the pump suction is measured by using PIV method. For calculation, the three dimensional turbulent flow for the full flow passage of the pump is simulated based on RANS equations combined with RNG k-$\varepsilon$ turbulence model. From those results, it is noted that at both design lo ad and quarter load condition, the pre-swirl flow whose direction is the same as the impeller rotation exists at all four sections in suction pipe of the pump, and at each section, the pre-swirl velocity becomes obviously larger at higher rotational speed. It is also indicated that at quarter load condition, the low pressure region at suction surface of the vane is large because of the unfavorable flow upstream of the pump impeller.

• International Journal of Fluid Machinery and Systems
• /
• v.4 no.1
• /
• pp.191-198
• /
• 2011

Based on the consideration that the cavitation would affect the operation stability of miniature pumps, the 3-D turbulent cavitating flow in a test pump was simulated by using a mixed cavitation model and k-${\omega}$ SST turbulence model. In order to investigate the influence of inlet geometry parameters on the cavitation performance of the miniature pump, two more impellers are designed for comparison. Based on the results, the following conclusions are drawn: 1) Cavitation performance of the double suction shaft-less miniature pump having different impeller is equivalent to the centrifugal pump having ordinary size, though the flow passage at impeller inlet is small; 2) The miniature pump having radial impeller can produce much higher pump head, but lower cavitation performance than that having the impeller based on the conventional design method; 3) It is believed that by applying the double suction design, the miniature pump achieved relatively uniform flow pattern upstream the impeller inlet, which is favorable for improving cavitation performance.

• International Journal of Fluid Machinery and Systems
• /
• v.3 no.1
• /
• pp.50-57
• /
• 2010

The attachment of inducer in front of main impeller is a powerful method to improve cavitation performance. Cavitation surge oscillation, however, often occurs at partial flow rate and extremely low suction pressure. As the cavitation surge oscillation with low frequency of about 10 Hz occurs in a close relation between the inlet backflow cavitation and the growth of blade cavity into the throat section of blade passage, one method of installing an axi-asymmetrical plate upstream of inducer has been proposed to suppress the oscillation. The inlet flow distortion due to the axi-asymmetrical plate makes different elongations of cavities on all blades, which prevent the flow from becoming simultaneously unstable at all throat sections. In the present study, changes of the suppression effects with the axial distance between the inducer inlet and the plate and the changes with the blockage ratios of plate area to the cross-sectional area of inducer inlet are investigated for helical inducers with tip blade angles of $8^{\circ}$ and $14^{\circ}$. Then a conceivable application will be proposed to suppress the cavitation surge oscillation by installing axi-asymmetrical inlet plate.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.2
• /
• pp.30-35
• /
• 2010

Pressure characteristics according to the duct shapes of turbo blowers connected in serial have been performed to reduce pressure loss in the piping system. To analyze three-dimensional flow field in the turbo blower system, general analysis code, CFX, is introduced in the present work. SST turbulence model is applied to estimate the eddy viscosity. Throughout the numerical simulation for the turbo blower system having a various shape of a inlet guide, optimal inlet guide can be selected. It is found that the pressure loss in the piping system having the optimal inlet guide can be reduced by minimizing the inflow distortion at the upstream of the impeller. Detailed flow analysis of the blower system serially connected is also performed and analyzed.

• International Journal of Fluid Machinery and Systems
• /
• v.3 no.2
• /
• pp.129-136
• /
• 2010

The attachment of inducer upstream of main impeller is an effective method to improve the suction performance of turbopump. However, various types of cavitation instabilities are known to occur even at the designed flow rate as well as in the partial flow rate region. The cavitation surge occurring at partial flow rates is known to be strongly associated with the inlet back flow. In the present study, in order to understand the detailed structure of internal flow of inducer, we firstly carried out the experimental and numerical studies of non-cavitating flow, focusing on the flow field near the inlet throat section and inside the blade passage of a two bladed inducer at a partial flow rate. The steady flow simulation with cavitation model was also made to investigate the difference of flow field between in the cavitating and no-cavitating conditions.