Characteristics Of Centrifugal Pump Research Articles

Investigations on the influence of tandem blades on inner flow and performance characteristics of centrifugal pump

Although significant advances have been made in tandem-blade technology for axial and centrifugal compressors, little attention has been paid to its application in centrifugal pumps. In this study, we propose a new tandem-blade design method for improving inner flow characteristics and overall performance of a centrifugal pump. With the SST k − ω turbulence model, three-dimensional turbulent flow fields in the centrifugal pump with tandem blades are simulated and analyzed. The effects of tandem blades on the inner flow and performance characteristics of the centrifugal pump are investigated. The predicted velocity and pressure distributions and flow behavior of the tandem-blade impeller are compared with those of a conventional single row blade impeller. It is indicated that the centrifugal tandem-blade impeller exhibits a significant advantage in terms of the uniformity of the impeller discharge flow. The tandem blades improve the jet-wake structure and uniformity of velocity and pressure distributions at the impeller outlet, and thus reduce the pressure fluctuation and hydraulic loss. Moreover, the hump phenomenon is eliminated or alleviated under low flow rate conditions, and the tandem-blade impeller has better hydraulic performance within a wider operating range as well as high reliability. This study provides a basis for the further development of the centrifugal pump with tandem blades.

Resource Efficiency Compromise for Centrifugal Pump

AnnotationThe main characteristics of centrifugal pumps, like many other mechanisms, include resource and efficiency. Often these are two competing parameters - while increasing the first, we sacrifice the second. This is because with an increase in the rotational speed of the pump rotor, the life of the bearings drops rapidly, and the efficiency, on the contrary, increases. There is a need to find a compromise solution, when at the selected value of one parameter the second is maximum.

Study on Unstable Characteristics of Centrifugal Pump under Different Cavitation Stages

In order to reveal the regularity of unsteady flow of centrifugal pump under different cavitation stages, a visual closed test-bed is built to collect signals such as the distribution of cavitation bubbles at the impeller inlet and external characteristics, etc. in the process of cavitation of centrifugal pumps. Combined with the shape and distribution of bubbles captured by high-speed photography, the cavitation stage of the centrifugal pump is divided. In addition, the variation of vorticity distribution, pressure pulsation and radial force of centrifugal pump under different cavitation stages are studied using the standard k-e turbulence model and the Kunz cavitation model. Main contributions are as follows: The cavitation bubbles can absorb the energy of vortex core to a certain extent and increase the volume of vortex core. Cavitation bubbles can also block the flow-path and induce the distortion of the internal flow field, resulting in unstable pressure waves that cause a significant increase in pressure pulsation rate. Besides, with the development of cavitation, the radial force on the impeller tends to remain invariable first and then decrease, and trajectory of the radial force changes from closed to open.

MATHEMATICAL MODELING OF THE CHARACTERISTICS OF OIL PUMPS, TAKING INTO ACCOUNT THE VISCOSITY OF THE TRANSPORTED OIL

For solving a range of assignments concerning design and operation of main oil pipelines it is necessary to possess appropriate mathematical models of centrifugal pump characteristics as the pumps appear to be the main equipment of pumping stations. Known analytical dependences describe only operating envelope of the pumps and thus can`t be applied for low flowrate regimes being inherent to the Ukrainian oil transmission system. In addition, these mathematical models do not take into account the effect of the viscosity of the transported oil on the pressure and energy characteristics of oil pumps. The work features the improved the method of mathematical modeling of the hydrodynamic characteristics of centrifugal pumps of main oil pipelines for the full range of working feeds, taking into account the effect of the viscosity of the pumped oil. It is also given a consideration to mathematical models of oil pumps characteristics, coefficients of which are found by the coordinates of two or three points of corresponding charts, and polynomial models, the coefficients of which are determined by the least squares method by a set of passport or experimental data. Adequate mathematical models for pressure characteristics and efficiency coefficient of oil pumps are proposed that are suitable for creation of computational algorithms for determining the throughput and energy efficiency of operation of main oil pipelines. It has been proved that for oil pumps that are operated under different combining schemes with significant reduction of theirs operation flowrate the advantage should be given to the mathematical models of the characteristics obtained by the method of least squares. In this case, polynomial models of the third degree provide the necessary accuracy of the calculations. The method of introducing a control unit for the influence of the transported oil viscosity on the characteristics of the pumps is proposed under determining the capability and energy efficiency of operation of main oil pipelines

Study on solid–liquid two-phase flow characteristics of centrifugal pump impeller with non-smooth surface

In order to improve the working performance of the solid–liquid two-phase flow in centrifugal pump, the current study attempted to probe into the influence of the solid-phase particle concentration on the characteristics of centrifugal pump and the drag reduction characteristics of impeller on non-smooth surface. Based on the principle of bionics and with MP80-160 single-stage single-suction centrifugal pump as a model, the current study adopted Eulerian model to carry out numerical simulation by building the pit-type non-smooth surface on the impeller blades. The results show that the higher concentration of solid-phase particles leads to the more centrifugal pump hydraulic head and decreasing efficiency. The pit type in the layout of the non-smooth surface area shows a better drag reduction effect. Shear stress of wall inside the pit is much less than that on the smooth surface, which can effectively improve the working performance of the solid–liquid two-phase flow in centrifugal pump.

Non-inertial stopping characteristics of a prototype pump

The characteristics of centrifugal pump in non-inertial stopping period have not been studied better by far. In this article, the variation characteristics of transient performance of a prototype p...

Experimental and Numerical Studies on Flow Characteristics of Centrifugal Pump under Air-water Inflow

Experimental and Numerical Studies on Flow Characteristics of Centrifugal Pump under Air-water Inflow

Wall roughness influence on the NPSH characteristics of centrifugal pumps

Pumps are very important and very widespread energetic machines. They are used in all branches of industry. Pumps are also a major consumer of electricity and therefore their development is even more important. From theoretical through experimental development in the last decades, a quantity of research has focused on numerical analysis. These are used to optimize all kinds of characteristics, from energy and cavitation, to dynamic characteristics. At the beginning of Computational Fluid Dynamics (CFD) analyses were related to the physical model (potential flow, Euler equation, Navier-Stokes equations). Subsequently, a lot of research was carried out in the field of various turbulent models. With the launch of high performance multi-processor computers, more and more time-dependent problems have been analysed. All the above mentioned research was carried out with numerical calculations on smooth surfaces. The fact is that in reality there is always some roughness on wet surfaces, depending on the material, the technology of production of certain parts of machines and finishing surface treatment. In the article, we give preliminary results of numerical analyses of centrifugal pumps, where the roughness of the walls was taken into account. The analyses were completed for different types of pumps, with different roughnesses and for different characteristics. First he effect of the roughness on the efficiency is shown, further the cavitation characteristics were analysed. The basic idea for research comes from the fact that there are still many cases where the matching of the results of the measurements and the results of numerical analyses are not perfect. One of the possible reasons can be the roughness of the walls.

Assessment of acoustic and pulsation characteristics of centrifugal pumps

Numerical investigations of unsteady viscous flow in centrifugal pumps were conducted in this paper. Verification of numerical approach was done. Hydraulic components of the pump were modernized with the purpose to improve their acoustic characteristics. Modernization was held on the base of isotropic turbulence noise measuring techniques. Results were confirmed by experiment. Pressure pulsations were studied in a flow between rotating impeller and stator for initial and improved flowing parts. As a result of numerical research, various impellers with different blade outlet angles were designed. During optimization, the optimal blade outlet angle was found, which provides increased vibroacoustic characteristics while maintaining a high level of efficiency.

Pressure fluctuation characteristics of centrifugal pump at low flow rate

The current investigation is aimed to simulate the unsteady internal flows in a centrifugal pump impeller with seven twisted blades by using a three-dimensional Navier-Stokes equations with Scale-adaptive simulation (SAS) turbulence model. A detailed analysis of the results at design flow rate Q0 and low flow rate 0.5Q0 and 0.3Q0, is presented. Unsteady flow analyses in centrifugal pump are focused mainly on the volute. The calculation results of pump head and efficiency at different flow rate conditions is in good agreement with the experimental data. Nine monitor points are positioned in the volute. The frequency of pressure fluctuations on all monitor points are analyzed and discussed. Under different flow rate conditions, the dominant frequency of pressure fluctuation in volute are the blade pass frequency and its integer multiples, the blade pass frequency always played the dominant role, and the largest pressure fluctuation maximum amplitude occurs near the volute tongue zone. With the flow rate decrease, the intensity of pressure fluctuation gets stronger, especially in spiral zone is the most obvious and the amplitude value of pressure fluctuation is the most dramatically increased. The maximum amplitude of pressure fluctuation in spiral zone is about 2∼3 times of design flow rate. Moreover, the streamline distribution in pump flow passage at flow rate Q0, 0.5Q0 and 0.3Q0 is analyzed. The results demonstrate that with the flow rate decrease, the vortex in the impeller flow passage is generating, developing and even blocking the whole impeller flow passage, which is disturbs the internal flow field and induces the strong pressure fluctuations in volute spiral zone. This research provided a reference for expanding the operation range of centrifugal pump and optimization design of volute in centrifugal pump.

The effect of impeller cut on the performance of middle specific speed centrifugal pump

For researching the influence of impeller cut ways and methods on the external characteristics of centrifugal pump, the flow in IS125-100-216 pump was simulated by using FLUENT software after impeller cut, and the external characteristics were also predicted. The predicted external characteristics show that the head reducing value after cutting impeller is significantly greater than that after cutting blade in the same cut value. When the cut angle is in the range of 0° to 10°, the efficiency in the forward skew cut is higher than that in the straight cut and the backward skew cut. The shaft power in the impeller cut is obviously lower than that in blade cut. When the cut angle is in the range of −10° to 10°, the shaft power in the skew cut is lower than that in the straight cut. The results of the inner flow analysis indicate that in the same cut value the forward skew cut significantly weakens the vortex phenomenon in the straight cut with the increase of the cut angle. No matter the straight cut or the skew cut is conducted, the effect of blade cut is better than that of impeller cut in the same cut value.

Investigation on centrifugal pump performance degradation under air-water inlet two-phase flow conditions

In order to study the flow characteristics of centrifugal pumps when transporting the gas-liquid mixture, water and air were chosen as the working medium. Both numerical simulation and experimental tests were conducted on a centrifugal pump under different conditions of inlet air volume fraction (IAVF). The calculation used URANS k-epsilon turbulence model combined with the Euler-Euler inhomogeneous two-phase model. The air distribution and velocity streamline inside the impeller were obtained to discuss the flow characteristics of the pump. The results show that air concentration is high at the inlet pressure side of the blade, where the vortex will exist, indicating that the gas concentration have a great relationship with the vortex aggregation in the impeller passages. In the experimental works, pump performances were measured at different IAVF and compared with numerical results. Contributions to the centrifugal pump performance degradations were analyzed under different air-water inlet flow condition such as IAVF, bubble size, inlet pressure. Results show that pump performance degradation is more pronounced for low flow rates compared to high flow rates. Finally, pressure pulsation and vibration experiments of the pump model under different IAVF were also conducted. Inlet and outlet transient pressure signals under four IAVF were investigated and pressure pulsation frequency of the monitors is near the blade passing frequency at different IAVF, and when IAVF increased, the lower frequency signal is more and more obvious. Vibration signals at five measuring points were also obtained under different IAVF for various flow rates.

Rotating Corrected-Based Cavitation Model for a Centrifugal Pump

Cavitation has bothered the hydraulic machinery for centuries, especially in pumps. It is essential to establish a solid way to predict the unsteady cavitation evolution with considerable accuracy. A novel cavitation model was proposed, considering the rotating motion characteristic of centrifugal pump. Comparisons were made with three other cavitation models and validated by experiments. Considerable agreements can be noticed between simulations and tests. All cavitation models employed have similar performance on predicting the pump head drop curve with proper empirical coefficients, and also the unsteady cavitation evolution was well solved. The proposed rotating corrected-based cavitation model (rotating based Zwart-Gerber-Belamri (RZGB)) obtained identical triangle cavity structure with the experiment visualizations, while the others also got triangle structure but with opposite direction. The maximum flow velocity in the impeller passage appears near the shroud, contributing to the typical triangle cavity structure. A preprocessed method for instant rotating images was carried out for evaluating the erosion risk area in centrifugal pump, based on the standard deviation of gray level. The results imply that the unsteady rear part of the attached cavity is vulnerable to be damaged, where the re-entrant flow was noticed. This work presented a suitable cavitation model and reliable numerical simulation approach for predicting cavitating flows in centrifugal pump.

Research on cavitation acoustic characteristics of centrifugal pump based on fluid-acoustic field coupling method

In order to study the change rules of interior acoustic field with the development of cavitation, this article presented a method that through comparing the experiment results with numerical simula...

Internal unsteady flow characteristics of centrifugal pump based on entropy generation rate and vibration energy

The transient fluid exciting force induced by unsteady flow in the centrifugal pump is the only exciting force that cannot be effectively eliminated. In order to explore the vibration problem caused by unsteady flow in the centrifugal pump, the steady and unsteady numerical calculations of the internal flow in a centrifugal pump with low specific speed were carried out under different flow rate conditions. With volute circumferential pressure pulsation test, the accuracy of numerical calculations was verified. At the same time, the vibration acceleration sensors were arranged in different positions of the pump body to complete the vibration characteristics experiment under different working conditions. Based on the numerical results, the amount and location of the internal flow loss of the centrifugal pump were predicted by the entropy generation rate method. According to the results of the vibration test, the vibration energy distribution of the centrifugal pump under different working conditions was obtained. In combination with the entropy generation rate and vibration energy distribution, the change rules of flow loss and the vibration energy with the flow condition of the pump were analyzed. By using the frequency-domain analysis method, the pressure pulsation, the unsteady radial fluid exciting force fluctuation and the vibration acceleration were compared and analyzed to study the change rules of the pressure pulsation, the unsteady fluid exciting force and the vibration characteristics with the flow rate. The results show that the internal flow loss is mainly concentrated in the impeller runner near the volute tongue under low flow condition and the internal flow loss under large flow rate condition is mainly concentrated in the volute channel near the pump outlet. The vibration induced by the unsteady flow in the centrifugal pump is mainly low-frequency vibration, which is very sensitive to the change of the flow rate. The vibration energy in the middle- and high-frequency ranges is almost not affected by the working condition. The internal flow loss and the low-frequency vibration energy change with the flow condition, showing similar change rules.

Experimental Investigation of Vibration Characteristics in a Centrifugal Pump with Vaned Diffuser

In order to investigate the vibration characteristics of centrifugal pump, a centrifugal pump with vaned diffuser whose specific speed is 190 was chosen for this research. Both the experiments of energy performance and vibration characteristics of the pump were performed. The results indicate that when flow rate of the pump is 270 m3/h, the head is 15.03 m and the efficiency is 71.47%. The maximum efficiency is 71.71% when the flow rate of the pump is 233 m3/h and the head is 16.92 m. And a wide frequency band of vibration appears at 600 Hz at outlet flange of the pump. The vibration intensity at the outlet flange is largest. The vibration intensities at both sides of bearing casing are slighter than those at outlet flange and larger than those at motor base. The vibration intensity at the motor base is larger than that at pump base, and the vibration intensity at the pump body is the lowest. The vibration intensity of monitoring point M4 in the X direction under 0.8Qd is 1.27 mm/s, which is the maximum under three flow rates.

Experimental research on hydraulic characteristic of centrifugal pump in plateau

Experimental research on hydraulic characteristic of centrifugal pump in plateau

The influence of micro grooves on the parameters of the centrifugal pump impeller

Obtained efficiency of centrifugal pumps with low specific speed is not high. In order to reduce hydraulic losses, a modified impeller channel with micro grooves was designed and patented. The article focuses on the impact of microgeometry on the efficiency of centrifugal pumps with extremely low specific speed (nq < 8). The results of experiments carried out on a test rig were presented. The characteristics of centrifugal pumps with a smooth impeller and one with micro blades/micro grooves were compared. To identify the flow phenomena, preliminary CFD calculations were performed. The obtained distribution of pressure and velocity fields on specific control panels were compared.

Investigation on Reverse Characteristics of Centrifugal Pump In Turbine Mode: A Comparative Study By An Experimentation And Simulation

In the biotic world for human life next to basic needs, water plays a vital role for human survival and sustainability. Water is available in plenty, in our earth which covers 70 percent of the surface area. In that, nearly 98 percent of water in ocean, seas and rivers only. Less than 2 percent of water is used for all sort of human needs. Many rivers originated from the mountains crosses various types of terrains and finally reaching the sea. Between the start and end, the water stream possesses huge level of potential and kinetic energy. Many of our power engineers was not attracted towards these natural penstock in form of water streams which can be able to operate mini and micro hydro power plants. In north and north-eastern areas of India, particularly in Himalayan range more than 6000 water streams are available, where large scale of hydro power project are not feasible. But the mini and micro level hydro power plants are possible. The success of any project is incorporated with the cost, in the way the hydraulic turbine cost also too high. In this perception this research paper an ordinary centrifugal pump was modified into the hydraulic turbine. This Pump-as-turbine (PAT) was studied experimentally and the numerical model was simulated and compared. The efficacy of PAT was 33.52% with the head and discharge of 40 m and 45.40 Kg/s respectively. For the same head the PAT numerical model predicts the efficacy of 44.87%.

Investigation on the influence of jetting equipment on the characteristics of centrifugal pump

To reduce radial noises from the motor of centrifugal pumps, this study designed a water cooling system called jetting equipment to replace traditional fan cooling systems in pump motors. By measuring radiated noises, head, efficiency, and cavitation performance, the research compared the differences among experimental results of the original pump unit, the one with a normal design jetting pipe and another one with a larger jetting pipe. Results show that the radiated sound pressure level of the model pump was significantly reduced by 8.3 dB after integrating the jetting pipe. With a normal jetting pipe, no significant changes were observed in the head, efficiency, and shaft power curves, and cavitation performance improved under small flow rate. However, the performance with the larger jetting pipe worsened, except the hump phenomenon of the model pump under a small flow rate was enhanced. Computational fluid dynamics method was used to calculate the internal flow of three model pumps in order to investigate the jetting flow effect. A comparison among the flow fields at the inlet of the three types of pumps indicated that high-pressure water injection can effectively control inlet recirculation and improve velocity distribution in the inlet flow field with decreased recirculation vortex strength and recirculation onset critical flow rate.