Reynolds Number Effect on Regenerative Pump Performance in Low Reynolds Number Range (original) (raw)
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Experimental and CFD Analysis of Regenerative Pump
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Numerical Study of Unsteady Flow Characteristics in Regenerative Pump
JES. Journal of Engineering Sciences
Regenerative pumps are turbomachines that achieve lower mass fluxes but higher-pressure differences than comparable pumps at the same circumferential velocity. The construction of these machines is very simple and inexpensive. On the other hand their efficiency does not exceed 45 % and they are noisy. To improve efficiency and reduce noise generation, a detailed knowledge of the unsteady flow in the machine is essential. In this work, we present unsteady flow characteristics of a typical regenerative pump based on numerical results obtained by using CFX-Tascflow code. The numerical results show highly unsteady pressure fluctuations around the stripper near both inlet and outlet ports. The lower pressure predicted near the inlet port indicates that the machine is prone to suffer cavitation problems. The amplitude of pressure fluctuation near the inlet is much higher than the outlet.
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The effect of inlet and outlet blade angles on a micro regenerative pump head was examined in experiments. The pump head was little increased by changing the blade angles compared with the original pump with the inlet and outlet blade angles of 0 degree. The effect of the axial clearance between the impeller and the casing on the pump head was also examined. The head was increased largely by decreasing the axial clearance. The computation of the internal flow was performed to clarify the cause of the increase of the pump head due to the decrease of the clearance. The local flow rate in the casing decreased as the leakage flow rate through the axial clearance decreased due to the decrease of the clearance. It was found that the larger head in the smaller clearance was just caused by the smaller local flow rate in the casing. In the case of the smaller clearance, the smaller local flow rate caused the smaller circumferential velocity near the front and rear sides of the impeller. This caused the increase of the angular momentum in the casing and the head.
Design optimisation of a regenerative pump using numerical and experimental techniques
International Journal of Numerical Methods for Heat & Fluid Flow, 2011
Regenerative pumps are the subject of increased interest in industry as these pumps are low cost, low specific speed, compact and able to deliver high heads with stable performance characteristics. The complex flow-field within the pump represents a considerable challenge to detailed mathematical modelling. This paper outlines the use of a commercial CFD code to simulate the flow-field within the regenerative pump and compare the CFD results with new experimental data. A novel rapid manufacturing process is used to consider the effect of impeller geometry changes on the pump efficiency. The CFD results demonstrate that it is possible to represent the helical flow field for the pump which has only been witnessed in experimental flow visualisation until now. The CFD performance results also demonstrate reasonable agreement with the experimental tests. The ability to use CFD modelling in conjunction with rapid manufacturing techniques has meant that more complex impeller geometry configurations can now be assessed with better understanding of the flow-field and resulting efficiency.
Literature Review on Different Factor's That Affecting Jet Pump Performance
The objective of this work is to study experimentally the characteristics of jet pump at various perimeter. Pressure head, Suction head, discharge head, density of fluid, and the ratio of nozzle to throat distance to nozzle diameter etc. are recorded. The effect of each parameter on the jet pump performance is studied, in order to have a better understanding about the behavior of such pump under various conditions & it also helpful to find out the highest efficiency of jet pump at such perimeter. Jet pump is a machine to convert kinetic energy of water into pressure energy. The jet pump is simple in structure and its work without any moving part. That's why it's reliable in performance and provide good sealing to pump. Jet pump has less efficient than any other conventional pump. The efficiency of jet pump has directly affect by the following perimeter. Such as Pressure head, Suction head, discharge head, density of fluid, and the ratio of nozzle to throat distance to nozzle diameter etc. In our study we are designed, developed and tested simple geometry jet pump. The experiments show that we should be careful in increasing the suction head, delivery head and efficiency of jet pump. As well as stability of jet pump must be considered between the suction head and the driving fluid mass flow rate.
A Comparative Study of Impeller Modification Techniques on the Performance of the Pump as a Turbine
International Journal of Rotating Machinery, 2022
The extensive use of the pump as a turbine (PAT) for micro-hydropower applications has a significant value from economic and technical viewpoints. However, the unavailability of the characteristics curve and relatively lower efficiency are the two basic limitations when considering pumps for power-generating applications. In this paper, the performance of the PAT is analyzed using the computational fluid dynamics (CFD) software called Ansys CFX in conjunction with standard k-ε. Then, experiments were done to verify the results of the simulation. Measurement inaccuracy effects are also taken into account. The initial performance of the PAT is refined by controlling basic design parameters (i.e., increasing the number of impeller blades, decreasing blade thickness, blade tip rounding, and adjusting blade inlet angle). Additionally, a new modification method known as blade grooving is also introduced in this research. Finally, all listed modification techniques are applied simultaneously to achieve maximum performance. The output of the study confirms that the adopted modification techniques have a positive effect on performance improvement. When the number of impellers is increased, the power output is enhanced by 5.72%, and blade grooving provides the most efficiency improvement, i.e., 7.00%. But decreasing blade thickness has no remarkable impact on the performance; the power output and efficiency are improved by 1.24% and 2.60%, respectively. The maximum performance improvement was achieved when the modification techniques are applied simultaneously with 10.56 and 10.20 percent of power and efficiency increments, respectively. From the entire study, it can be concluded that the chosen design parameters have an important effect on stabilizing the internal flow, decreasing the required head, decreasing the hydraulic loss in the impeller, and increasing the overall performance. The study also helps to figure out which modification technique is the most practical.
Effect of Impeller Size on the Performance of a Single Blade Pump
MATEC Web of Conferences
Changing the impeller diameter is a frequently used method for adjusting pump performance parameters. In the case of conventional multi-blade impellers, this is done by reducing the diameter on the machine tool to the prescribed shape. The other dimensions of the pump (diffuser, inlet) remain unchanged. This method is called trimming. The article deals with the diameter reduction and subsequent modification of the performance parameters of a single blade pump. These pumps are characterized by certain specific features. First of all, it is an unsymmetrical impeller that must be both statically and dynamically balanced. This plays an essential role in the whole modification process. Research results obtained on a pump with an impeller diameter of 138 mm are presented. The change in diameter was monitored on a total of 3 impellers. Experiments were carried out in the laboratory of hydraulic machinery. The results were verified by CFD calculations. Research background: The article conce...
IOP Conference Series: Earth and Environmental Science, 2022
A mixed-flow pump has a characteristic in which the pressure (P) decreases as the flow rate (Q) increases on the performance curve. Hence, the Q-P curve generally has a negative slope, which has been understood as an ideal and stable case. However, a complex recirculating flow may occur due to the increase in incidence angle at the low flow rates compared to the design flow rate. This phenomenon accompanies noise and vibration along with the deterioration of performance and causes a positive slope in the form of a saddle on the performance curve. In this study, the effect of the impeller inlet (eye) diameter of a mixed-flow pump on the saddle characteristics was confirmed through numerical simulation. The focus was on the internal flow field and performance of a pump, which could be solved with the steady-state analysis. Here, the impeller inlet diameter was adjusted with the leading edge (LE) vertex on the shroud line of the meridional plane. The blade angle was adjusted accordingly to maintain the previously optimized degree of the incidence angle. From this novel design method, the saddle characteristics were significantly improved. The performance in the saddle range was directly related to the recirculating flow near the shroud. The numerical results were validated with the experimental tests.