Pressure Pulsation Intensity Research Articles

Research on the Internal Flow Characteristics of an Electric Coolant Pump

Abstract To investigate the internal flow characteristics of an automotive electronic coolant pump, numerical simulations were performed utilizing the ANSYS CFX commercial software suite. The study delved into the velocity distribution, pressure pulsation intensity characteristics, and entropy generation of the electronic coolant pump under varying operational conditions. The findings revealed that with an increase in the flow rate, the coolant flow velocity within the pump also escalated. Concurrently, the separation flow at the trailing edge of the blade diminished, while the flow velocity at the trailing edge of the pressure surface escalated. Notably, the impeller and volute emerged as the primary sites generating pressure pulsations, with pressure pulsation intensity within the pump surpassing that of the design condition in off-design scenarios. Furthermore, entropy generation predominantly manifested at the impeller, volute, and front pump chamber locations, with the impeller exhibiting minimal total entropy generation under design conditions. These insights serve as crucial reference points for optimizing the design of automotive electronic coolant pumps.

Analysis of pressure pulsation in a multi-stage double suction centrifugal pump

Abstract Pressure pulsation is a common phenomenon, which results from different causes. The intenser pressure pulsation occurs in the pump, the severer the damage to the pump. In the paper, with the assistance of detached eddy simulation method, the characteristic of pressure pulsation in the multi-stage double suction centrifugal pump is studied to understanding the internal flow circumstance. The results reveal that the pressure pulsation intensity reaches the maximum at blade trailing edge, which propagates to the tongue region of forward flow channel and double-volute under the low rates. Furthermore, it can be concluded that the pressure pulsation of region with obvious rotor–stator interaction between rotating impeller and stationary volute is generally larger at low flow rates. The pressure pulsation near the suction side of blade trailing edge shows the feature of broadband frequency and with increasing flow rate the bandwidth of broadband decreases drops rapidly except BP1. Due to the influence of the number of impeller blades, the dominant frequency of monitoring points in the inter-stage flow channel and the volute is basically located at a frequency that is twice the blade frequency. Meanwhile, because of the symmetry of the geometric structure of the reverse flow channel, the pressure pulsation curve changes of its internal monitoring points are similar under the same flow rate.

Hydraulic performance improvement of a two-way pumping station through bell mouth shape design

A two-way pumping station is a specialized device that facilitates bidirectional water pumping and drainage. The pressure pulsation characteristics of two-way pumping stations have emerged as a prominent research focus in the field of hydraulic engineering. In this work, with the aim of systematically proposing optimization measures to ensure operational stability, a transient numerical simulation is conducted to elucidate the influence mechanism of the suspension height of the bell mouth (SHb) on the internal flow field and pressure pulsation of a two-way pumping station. High-precision experiments are performed to compare time-frequency domain characteristics under different SHb using a continuous wavelet transform (CWT). The findings indicate that an appropriate reduction in SHb effectively reduces unstable flow and pressure pulsation within the inlet conduit, consequently reducing the pressure pulsation of the impeller. With a reduction in SHb, the influx of low-velocity backflow into the bell mouth is prevented and the generation and propagation of suction vortices are suppressed. However, the reduction amplifies the flow impact between the mainstream flow and the bell mouth wall. The spatial distribution of the pressure pulsation is also examined, and it is found that a reduction in SHb increases the pressure pulsation intensity on the side facing the incoming flow and on the rear side, while the mainstream area tends to exhibit stability. In terms of time-frequency domain characteristics, a reasonable reduction in SHb leads to improved circumferential uniformity of the impeller inflow and the effective suppression of low-frequency disturbances.

Effect of Cavitator and Nozzle Parameters on the Efficiency job of the impulse Jet Generator

Studies of fluid jet flows in the presence of a ventilated cavity with a negative cavitation number, carried out at the Institute of Mechanics of Moscow State University, showed that under certain conditions, self-cavitational oscillations with a high intensity of pressure pulsations occur in such a hydraulic system. It was shown that it is possible in principle to use the self-oscillation regime to create periodic impulsed jets during outflow from a converging nozzle into the atmosphere. The influence of the parameters of the cavitator and the outlet nozzle on the intensity of the impact of the outflowing liquid on the screen located perpendicular to the outflow direction is studied. It is shown that an increase in the length of the nozzle can significantly increase the efficiency of the generator, and a smooth narrowing of the channel in front of the cavitator can increase the operating range of the generator in the direction of larger gas blows. It is shown that there is a scale effect - with increasing head pressure, the relative intensity of self-oscillations decreases, but tends to reach a horizontal asymptote.

Analysis of the performance and pressure pulsation in a high-speed centrifugal pump with different hub-cutting angles

In this study, the hub cutting of the impeller was presented to suppress the rotor–stator interference between the blade and volute tongue in a high-speed centrifugal pump with double volutes. The flow fields in the centrifugal pumps with four hub-cutting angles 0, 15∘, 30∘ and 45∘ were numerically simulated to investigate the influence on the internal flow and pressure pulsation using SST [Formula: see text] turbulent model. The predicted results of numerical simulation were in good agreement with the experimental ones. The results show that the relative velocity streamline distribution is more uniform and smoother in hub-cutting impeller compared with that in the original one. Also, the head and efficiency of the pumps with hub-cutting impeller are higher than that of the prototype pump, with the maximum increase of 1.97% of the head for the hub-cutting angle 45∘ under the design flow rate. The pressure pulsation intensity at volute 1 and the unsteady radial force of the hub-cutting pumps are smaller than that of the prototype pump due to the flow improvement. In addition, the maximum and average values of the unsteady radial force decrease with the increase of the cutting angle.

Design techniques for improving energy performance and S-shaped characteristics of a pump-turbine with splitter blades

The development of high-head pumped-storage projects presents various opportunities and challenges. One challenge is the operational stability of pumped-storage power plants, which is closely associated with the characteristics of pump-turbines. In this study, the design and experimental verification of the hydraulic performance of a pump-turbine runner with splitter blades are investigated. The effects of several main parameters on the performance curve and S-shaped characteristics of pump-turbines in turbine mode are examined via numerical simulation. Subsequently, model tests are conducted to validate the improvements in the performance curve, including a comparison of the S-shaped characteristic curve at a constant guide vane opening and under the same initial conditions. An emergency load rejection test based on the same guide vane closing scheme is performed to verify improvements in transient pressure in the spiral case, draft tube, and rotational speed. The results confirm the enhancement in the S-shaped characteristics and transient global parameters of the splitter blade design. Furthermore, a reduction in pressure pulsation intensity in the vaneless space during off-design conditions is confirmed.

Prediction of Aircraft Surface Noise in Supersonic Cruise State

The aerodynamic noise of an aircraft leads to vibration fatigue damage to structures. Herein, a prediction method for aircraft surface noise under the comprehensive effect of mixed acoustic sources during flight, primarily surface aerodynamic, air intake, and tail nozzle jet noises, was studied. In the supersonic cruising state, the internal and external flow fields of the aircraft were solved using the Reynolds-averaged Navier–Stokes equations to obtain the statistical average solution of the initial turbulence. The non-linear disturbance equation was used to obtain the surface acoustic load of the aircraft. The calculation results revealed that the main source of aircraft surface noise is aerodynamic noise. The sound pressure level on the fuselage increases gradually from front to rear along the aircraft, and the OASPL at the air intake and tail nozzle is relatively large. The jet noise has little effect on the sound pressure level at the front of the fuselage and only contributes to the OASPL at the tail nozzle of the fuselage. The intensity of pressure pulsations from the engine exhaust in the tail section is 93.3% of the total intensity of pressure pulsations.

Circumferential groove on flow field and pressure fluctuation intensity of a semi-open centrifugal pump under design condition

The tip leakage flow (TLF) generated by the tip clearance has adverse effect on the performance of the impeller and increases pressure fluctuation. To suppress the effect of TLF on the instable flow in a semi-open centrifugal pump, the circumferential groove method is proposed in this paper. The effect of the circumferential groove on the internal flow and pressure fluctuation under the design condition is studied by combining numerical simulation with experiment. The results show that the head and efficiency were reduced by 1.1% and 1.0%, respectively. However, the circumferential groove provided a circumferential channel for leading edge overflow. The fluid in the groove formed a jet near the low-pressure region, which can effectively disperse the low-energy fluid of the blade inlet. The initial position and trajectory of the tip leakage vortex (TLV) move downstream, which decreases the relative flow angle and low-velocity region. The flow field in the blade tip region was improved remarkably. The low-frequency pressure fluctuation in the pressure surface and tip clearance of the blade inlet was suppressed by the circumferential groove, and pressure pulsation intensity decreased by 50% and 66%, respectively.

Numerical Analysis of Flow Characteristics in Impeller-Guide Vane Hydraulic Coupling Zone of an Axial-Flow Pump as Turbine Device

An axial-flow pump as a turbine (PAT), as compared to the conventional Francis turbine, has the advantages of not being restricted by the terrain and having lower cost to reverse the pump as a turbine for power generation. When an axial-flow pump is reversed as a turbine, the internal flow pattern is more complicated than when in the pump mode, which can cause instability in the whole system and result in degradation of the hydraulic performance and structural vibration. The impeller and guide vane are the core of the axial-flow PAT unit. This research compares the experimental and numerical simulation results in order to verify the energy performance and pressure pulsation signal of the axial-flow PAT. The unsteady flow regime, fluid force, and pressure pulsation characteristics of the impeller-guide vane hydraulic coupling zone are analyzed in detail. The findings demonstrate that both the dominant frequency of the fluid force pulsation signal and the flow field pressure pulsation signal appear at 3 times of the rotation frequency. The blade passing frequency (BPF) of the impeller is the dominant frequency, and other frequency components are also dominated by the harmonic frequency of the BPF. The impeller and guide vane are primarily subject to radial fluid force. Under partial working conditions, the pressure pulsation intensity in the flow field greatly increases, and the pressure pulsation amplitude at the guide vane outlet and impeller outlet appears to be more sensitive to the flow rate change.

Pressure pulsation reduction in the draft tube of pump turbine in turbine mode based on optimization design of runner blade trailing edge profile

Reversible pump turbine plays an important role in pumped storage technology. Its pressure pulsation performance also directly affects the stability and efficiency of unit operation. In this paper, under the conditions of multiple guide vane openings and multiple heads for a pump-turbine unit, based on the reasonable runner blade geometric deconstruction, a parameter control method of runner blade trailing edge is proposed. The Genetic Algorithm combined with Fuzzy Logic (GA-FL) is used as the optimization strategy. After optimization iteration, the optimized runner blade trailing edge shape corresponding to minimum value of pressure pulsation intensity is obtained. In addition, numerical simulation calculation and test verification are carried out for the initial and optimized units, the results are all in good agreement. The results show that the unit efficiency is slightly improved and the relative pressure pulsation intensity in draft tube is significantly reduced. Especially in the case of small guide vane opening, the pressure pulsation performance of optimized unit meets the actual engineering standards.

Experimental investigation on the effect of axial gap on performance and unsteady pressure pulsations of low head axial flow hydraulic turbine

The stable operation of axial flow turbines (AFTs) in the energy conversion process directly affects their safety and performance. Because of its unstable pressure features, a dynamic analysis of its internal flow characteristics is required. To analyze, evaluate, and compare the pressure variation within the turbine under the base gap (Ƣ = 0.05D) and different axial gaps (Ƣ) of 0.09D, 0.14D, and 0.18D, a reliable measurement approach is required. Pressure sensors were installed on the flow domain of the AFT to measure dynamic pressure pulsation under various Ƣ and running flow conditions. Based on the experimental result, a 28% and 2.8% increase in turbine efficiency was recorded when the Ƣ was increased from 0.05D to 0.09D at 0.8Qd (design flow rate) and 1.0Qd, respectively.Further analysis of the frequency spectra reveals different unsteadiness in the flow structures due to changes in Ƣ which resulted in various excitation signals. A decrease in the Ƣ leads to an increase in pressure pulsation intensity. Consequently, AFT with Ƣ of 0.09D was recommended since it provides maximum efficiency with fewer pulses compared with Ƣ = 0.05D, where the vibrations are at peak value. The findings above will aid in the optimum use of energy resources since energy generated from AFT is clean and free of pollution and can lead to a sustainable energy generation process.

Investigation of Transient Characteristics of a Vertical Axial-Flow Pump with Non-Uniform Suction Flow

The aim of this paper is to study the influence of non-uniform suction flow on the transient characteristics of a vertical axial-flow pump device. The unsteady calculation is employed to forecast the unstable flow structure with three inlet deflection angles α, and the calculation accuracy under uniform inlet flow is verified by the external characteristic test. The results depict that a promotion in the α will increase the head and shaft power and thus improve the stress and fatigue failure risk of the impeller. At the impeller inlet, the pressure pulsation intensity (PPI) with α = 40° is lower than that with α = 0° caused by a decline in the axial velocity. The dominant frequency of the unsteady pressure signal is the blade-passing frequency (BPF), and the dominant frequency amplitude rises with the increase in α due to the improvement of the pre-rotation impact intensity. At the guide vanes inlet, the dominant frequency of the unsteady pressure signal at the guide vane inlet is also the blade-passing frequency. An improvement in α magnifies the angle between the trailing edge jet of the impeller and the leading edge of the guide vanes under 0.8Qdes and 1.0Qdes, while it diminishes the angle under 1.2Qdes. Thus, the PPI and dominant frequency amplitude with α = 40° are higher than that with α = 0° under 0.8Qdes and 1.0Qdes, but these are lower than that with α = 0° under 1.2Qdes.

Analysis of Transient Characteristics of Submersible Tubular Pump During Runaway Transition

In order to study the transient characteristics of the submersible tubular pump in the process of power failure, the 6DOF model was used to carry out three unsteady numerical values for the whole flow channel of the pump. The results show that the calculation results of the 6DOF model based on the fourth-order multi-point Adams–Moulton formula are in better agreement with the experimental results than the first-order format to predict the impeller motion. When the unit is powered off, the speed and flow of the pump device decrease rapidly with time. At the maximum head 3.41 m, when the unit enters the runaway condition, the speed is about −1.88 times the initial speed and the flow rate is about −1.98 times the initial flow. The axial force and radial force of the impeller increase alternately, and compared with the normal operating condition, the radial force is significantly increased. In the process of the pump device changing from forward flow to reverse flow, the internal flow state of the pump device is relatively chaotic, and there are a large number of vortices in the flow channel, which is easy to cause structural vibration. Before reaching the runaway state, a large number of vortices also appear inside the impeller and guide vane, causing flow blockage, especially when the flow rate is zero. At the same time, the reverse flow impact causes the local pressure on the blade surface to increase, which threatens the stability of the blade structure. The pressure at the impeller inlet, impeller outlet, and guide vane outlet monitoring points is the largest near zero flow, and the smallest during runaway. The main frequency of the pressure pulsation in the pump device is the blade pass frequency (fBRF) and its harmonics (2fBRF, 3fBRF, 5fBRF, etc.), and the pressure pulsation intensity increases with the increase of the impeller speed. The results of this study provide a theoretical reference for the operation of the submersible tubular pump to ensure the safety and stability of the pumping station.

Influence of Fluid Food Viscosity on Internal Flow Characteristics of Conveying Pump.

A fluid food conveying pump is used to convey edible or nutritional fluids and semi-fluids (containing suspended soft and hard particles and with different viscosities), such as water, glycerin, yogurt, and juice concentrate. Since different fluid food have different viscosities, the internal flow characteristics and conveying performance of food conveying pump are greatly affected by viscosity. To obtain the influence law of fluid food viscosity on the internal flow characteristics of the pump, the internal flow characteristics of food conveying pump when conveying food of 4 different viscosities (water, glycerin, 67.2 °Bx wild jujube juice, and 71.0 °Bx haw juice) were compared and observed in this study. The results showed that, with the increase in food viscosity, the overall flow loss in the pump, the entropy generation, and the proportion of total entropy generation in the pump chamber increase, but the conveying performance of the food conveying pump gets worse; however, the pressure pulsation intensity caused by static and dynamic interferences decreases with the increase in viscosity.

Pressure Distribution on the Inner Wall of the Volute Casing of a Centrifugal Pump

In order to grasp the distribution characteristics of the pressure field on the inner wall of the volute casing of an atypical open impeller centrifugal pump, the instantaneous pressure at different operating conditions was experimentally measured under four operating rotational speeds to obtain the distribution characteristics of the average static pressure field in the volute casing of this pump model. The pressure pulsation amplitude and pressure pulsation intensity were also analyzed at different rotational speed cases, and the standard deviation analysis was performed. The results showed that the instantaneous pressure pulsation on the inner wall of the volute casing strongly fluctuates during the pump operating, and the closer to the volute casing outlet, the more intense the pressure pulsation was. After increasing the pump shaft speed, the fluctuation amplitude gradually decreased. The pressure pulsation on the wall of tip clearance is more intense than that on the inner wall of the volute shell. The intensity of the pressure pulsation on the wall of tip clearance decreases with the increase of the rotational speed, and the higher the speed, the less intense the pressure pulsation.

Numerical study on hydrodynamic characteristics of a centrifugal pump influenced by impeller-eccentric effect

In this paper, the effect of impeller eccentricity caused by parallel misalignment of the coupling is considered, and the impact of the impeller eccentricity on the hydrodynamic characteristics of a centrifugal pump is numerically investigated. The finite volume method is adopted to simulate the dynamic process. The results show that the eccentric impeller will deteriorate the hydraulic performance of the pump, nonetheless the influence is limited. However, it significantly affects the amplitude of the flow-induced force at shaft frequency, and the amplitude is proportional to the eccentricity ratio to some extent. The influence of impeller eccentricity on pressure pulsation can be evaluated by the shaft orbit. The crest factor of the impeller trajectory is positively correlated with the pressure pulsation intensity. The minimum value of the impeller trajectory hasa negativerelationshipwith the average radial force of the impeller. The clocking position of the eccentric impeller primarily affects the phase relationship between the shaft frequency and the blade passing frequency. A function is proposed to characterize the fluctuating pressure distribution with a spatially periodic pattern around the volute under eccentric conditions. This research can provide an essential reference for fault diagnosis and vibration control of the centrifugal pump.

Experimental investigation on characteristics of venturi cavitating flow and Rhodamine B degradation in methanol solution

Hydrodynamic cavitation (HC) commonly occurs within industrial pipelines and its unsteady flow characteristics are of great significance for energy conservation and efficiency improvement. This study investigates the effects of methanol concentration (0–20 wt%) on the cavitating flow characteristics and the degradation of Rhodamine B (RhB) under operating conditions of a 0.7 MPa pressure drop, temperature of 30 °C, 200 passes through a venturi reactor, and an initial RhB concentration of 40 μmol/L. The transient cavitation behavior was monitored using a high-speed camera. The cavitation images show that the presence of methanol generates more stable bubbles, which results in less violent bubble collapse. The pressure pulsation and vibration induced by cavitation flow were synchronously measured using high-frequency pressure and acceleration sensors. The spectral analyses of the pressure pulsation indicate that methanol has no effect on the dominant frequency (∼5.5 Hz) at different positions, and the amplitude initially increases with increasing methanol concentration and then stabilizes. The pressure pulsation intensity increases due to the increased vapor pressure of the solution. The vibration spectral analyses show that methanol has little effect on the peak frequencies, which occur near 4.0 kHz and 14.3 kHz of the low and high-frequency bands, respectively, whereas the peak amplitude decreases with increasing methanol concentration. The per-pass degradation model of RhB in methanol solution considering pyrolysis of methanol was verified for the first time and show to adequately describe the experimental data. The degradation percentage and per-pass degradation factor decrease with increasing methanol concentration. The reduced surface tension of the solution prolongs the bubble lifespan and prevents bubble coalescence, thus weakening the vibration and degradation performance. The results provide important insight for cavitation applications and degradation modeling of mixed solutions.

Experimental Study on the Effect of Gas Volume Fraction on the Cavitation Performance of a Low-Specific-Speed Centrifugal Pump

In order to study the cavitation performance of centrifugal pumps with low specific speeds under the condition of gas–liquid two-phase flow, a cavitation test rig for pumping gas–liquid two-phase flow was set up. The cavitation performance of the pump with a specific speed of 32 was studied. The variation of the head, pressure pulsation intensity, and vibration intensity with the cavitation allowance NPSHa (Net Positive Suction Head available) of the centrifugal pump were obtained at different inlet gas volume fraction (IGVF) conditions of 0, 1%, 2%, and 3%. The results show that the cavitation performance of a low-specific-speed centrifugal pump can be improved obviously in a certain liquid flow range when the IGVF is 1%, especially at a low liquid flow rate. When cavitation did not occur or the degree of cavitation was low, a lower IGVF can reduce pressure pulsation intensity at the pump outlet and the vibration intensity at the pump inlet under design flow rate and high flow rate conditions. Additionally, all performances of the low-specific-speed pump are more sensitive to gas when the liquid flow rate is low. The results can provide a reference for improving the cavitation performance of low-specific-speed pumps for transporting gas–liquid two-phase flow and single-phase liquids.

Prediction of the Influence of Runner Tip Clearance on the Performance of Tubular Turbine

Tubular turbine is a type of turbine with low-head. Due to the fact that the runner of a tubular turbine is of axial-flow type, there will be a certain width of blade tip between the blade and the chamber. In order to explore the influence of tip clearance width on the flow inside the turbine, taking the model tubular turbine as the research object, six different tip clearance widths were compared and analyzed. The research shows that the increase in blade tip clearance width affects the performance of the turbine, reduces the minimum pressure at blade tip and causes cavitation in advance. Larger tip clearance width significantly increases pressure pulsation intensity inside the turbine, especially in the vaneless region between the runner and guide vane and the area of the runner tip. However, the increase in tip clearance width can greatly reduce the axial force for about 100 N and radial excitation force for about 50% of rotating parts. Therefore, during the design and processing of tubular turbines, the blade tip clearance width should be carefully selected to ensure safe and stable operation of the unit.

Dynamic Pressure Test and Analysis of Marine Ballasted Centrifugal Pump under Rapid Changing Conditions

Ship ballast pumps have stringent requirements for their transient characteristics. Here, the pneumatic control valve and programmable logic controller (PLC) are applied to realize the rapid reduction in flow rate for ballast pumps, and the dynamic pressure of steady and transient conditions and inner flow for the ballast pump are tested and analyzed. The results show that the dynamic pressure of each study scheme has cyclical increasing trends, however, the larger the amplitude of the flow rate reduction is, the greater the pressure increasing rate of the two measuring points. While the flow rate decreases to 0.4× Qd and 0.2× Qd, the rate of pressure increase is first fast and then slow. The dynamic pressure pulsation intensity is higher than the corresponding steady-state conditions after the transient conditions. With the increase in flow rate reduction, the characteristic frequencies of the dynamic pressure are 1APF (axial passing frequency) and 1BPF (blade passing frequency) and their harmonic frequency. The rapid decrease in flow rate causes the separation vortex in the impeller channel to be generated in advance, and the scale increases, which reduces the pulsation intensity of the pump outlet to prevent an increase in the level of broadband pulsation between 2APF and 1BPF.