Volute Tongue Research Articles

A flow field study of the interaction between a centrifugal compressor impeller and two different volutes

The interaction between an impeller with one large and one small overhung volute was investigated by both computational fluid dynamics simulation and experimental methods. The large volute was mainly generated by increasing the small volute axial length. The computational model, with k—∊ turbulence model and wall function, has been used to predict the internal flow of both volutes. The effect of volute tongue on the flow in the impeller was analysed at off-design conditions. The flow structure in the volutes was also investigated in detail. The performance test of the two configurations was carried out in the aero test facility at Solar Turbines Inc. A good agreement between experimental data and numerical simulation results was found on both the whole compressor stage performance and the impeller performance. The largest deviation is close to 10 per cent for the compressor stage performance prediction at high mass flowrate only.

Numerical analysis of the unsteady flow in the near-tongue region in a volute-type centrifugal pump for different operating points

An investigation is presented on the unsteady flow behaviour near the tongue region of a single-suction volute-type centrifugal pump with a specific speed of 0.47. For this study, the flow through the test pump, which was available at laboratory, was simulated by means of a commercial CFD software that solved the Navier–Stokes equations for three-dimensional unsteady flow (3D-URANS). A sensitivity analysis of the numerical model was performed in order to impose appropriate parameters regarding grid size, time step size and turbulence model. The predictions of the numerical model were contrasted with experimental results of both global (flow-head curve and static pressure distribution at volute front side) and unsteady variables (unsteady pressure distribution at the volute front side filtered at the blade-passing frequency). Once validated, the model was used to study the flow pulsations associated to the interaction between the impeller blades and the volute tongue as a function of the flow rate, for several flow rates ranging from 20% to 160% of the nominal flow rate. The study allowed relating the blade passage with the pulsations of pressure and tangential and radial velocity at a number of reference locations in the near-tongue region. The numerical model was also used to evaluate the evolution of the leakage flow between the impeller–tongue gap and of the flow exiting the impeller through some specific angular intervals, during one single-blade passage.

Relationship between volute pressure fluctuation pattern and tonal noise generation in a squirrel-cage fan

In this work, the pressure fluctuation pattern in the volute of a squirrel-cage fan is analyzed. Also studied is how this pattern is modified when a slight geometry change is introduced in the volute tongue. The study has been carried out on a commercial machine, used in automotive air conditioning units. A three-dimensional and unsteady numerical simulation of the flow in the complete machine has been carried out using the commercial code FLUENT. In this way, the pressure fluctuations in some locations near the volute wall have been obtained. The results of this numerical simulation have been compared to the sound pressure level spectra radiated by the fan, measured in a ducted test installation at the laboratory. The tendencies of the sound pressure levels measured at the blade passing frequency show a good correlation with the amplitudes of pressure fluctuations obtained numerically near the volute wall.

Experimental study on the noise reduction of an industrial forward-curved blades centrifugal fan

Many previous researches have concentrated on the noise of backward-curved (BC) blades and forward-curved (FC) multi-blade centrifugal fans. In this paper, an experimental study has been carried out to study the noise reduction of an industrial FC blades centrifugal fan. First of all, the performance and noise characteristics of the FC centrifugal fan were tested to compare the similarities and differences from those of BC blades and FC multi-blade centrifugal fans. And then, some different volute geometric configurations were carried out in order to study the effects of inclined volute tongue, impeller blade-tongue clearance, hub-volute clearance and their coupling effect to the performance and noise of the FC blades centrifugal fan. The aim of many different experimental tests is to validate whether the effects of different modifications to fan performance and noise are additive and to find a good impeller-volute matching to reduce the centrifugal fan noise without reducing performance. The experimental results show that a good coupled modification not only could reduce the fan noise but also could advance the fan performance and extend the operating range.

Performances and acoustic noise of micro multi-blade fan

In this paper, the performances and the acoustic noise of the traditional type micro multi-blade fan were investigated experimentally and numerically, to optimize the specifications of the fan for the resident circumstances. The acoustic noise level decreases but the efficiency deteriorates slightly with the increase of the blade number of the impeller. Besides, the acoustic noise decreases with the increase of the distance between the impeller outlet and the volute tongue, in accompanying with the increase of the input and the deterioration of the fan efficiency.

Noise Prediction of a Centrifugal Fan: Numerical Results and Experimental Validation

Centrifugal fans are widely used in several applications, and in some cases, the noise generated by these machines has become a serious problem. The centrifugal fan noise is frequently dominated by tones at the blade passing frequency as a consequence of the strong interaction between the flow discharged from the impeller and the volute tongue. In this study, a previously published aeroacoustic prediction methodology (Cho, Y., and Moon, Y.J., 2003, “Discrete Noise Prediction of Variable Pitch Cross-Flow Fans by Unsteady Navier-Stokes Computations,” ASME J. Fluids Eng., 125, pp. 543–550) has been extended to three-dimensional turbulent flow in order to predict the noise generated by a centrifugal fan. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. The unsteady forces applied by the fan blades to the fluid are obtained from the data provided by the simulation. The Ffowcs Williams and Hawkings model extension of Lighthill’s analogy has been used to predict the aerodynamic noise generated by the centrifugal fan from these unsteady forces. Also, the noise generated by the fan has been measured experimentally, and the experimental results have been compared to the numerical results in order to validate the aerodynamic noise prediction methodology. Reasonable agreement has been found between the numerical and the experimental results.

Green Pump Development Based on the Analysis of Unsteady Flow

Centrifugal pump is a kind of important industrial installation for fluid delivery. The research on the unsteady flow in centrifugal pump is very meaningful to reducing vibration. Particle image velocimetry (PIV) system and test pump designed for PIV measurement were introduced. The experimental scheme and the methods of numerical simulation were discussed. PIV technique was used to measure the unsteady velocity field near the volute tongue under the mode of external synchronization. The unsteady pressure field was simulated by using Sliding Mesh (SM) model provided by Fluent. The results show that the velocity and pressure fluctuate periodically with the rotation of impeller. Partial fluid flows back to the impeller passage and the velocity in the inlet of diffusion tube decreases significantly due to shunt effect of the volute tongue. On the section VIII, the magnitude and fluctuation range of velocity show a decreasing trend in radial direction. The fluctuation of circumferential velocity is related to the position of high-speed flow in impeller passage, and the fluctuation of radial velocity is influenced by blade interference and Coriolis force. The static pressure increases and the dynamic pressure decreases in the radial direction of volute. The velocity and the pressure on the section VIII and the outlet total pressure fluctuate intensively when the blade tail end passes the section VIII and the volute tongue. The vibration of pump can be reduced by increasing the volute tongue mounting angle and decreasing the blade outlet mounting angle properly.

A simple acoustic model to characterize the internal sound field in centrifugal pumps originated by blade‐tongue interaction

Conventional centrifugal pumps with volute casing generate fluid‐dynamic noise particularly at the so‐called blade‐passing frequency, due to the interaction of the flow exiting the pump impeller with the volute tongue. The amplitude of the sound generated is very dependent on the pump operating point. Following previous studies by the authors, a methodology has been applied to quantify the generation of tonal noise for a given centrifugal pump, previously tested in laboratory. The procedure is based on a simple acoustic model for the pump, in which one or several ideal point sources are located at some arbitrary position in the volute. These ideal sources are assumed to radiate plane sound waves along the volute, which was considered to be composed by a succession of slices, each of them equivalent to a linear three‐port acoustic system with sound transmission and reflexion coefficients according to the corresponding port areas. A series of tests was conducted to check the assumptions of the acoustic model, by applying external acoustic loads onto the pump outlet duct and measuring the noise reflected. The resulting reflection coefficient was in good agreement with the predictions of the acoustic model.

Computation of aerodynamic noise of centrifugal fan using large eddy simulation approach, acoustic analogy, and vortex sound theory

Large eddy simulation is applied to solve the unsteady three-dimensional viscous flow in the whole impeller-volute configuration of a centrifugal fan. The results of the simulation are used to predict the impeller-volute interaction and to obtain the unsteady pressure, velocity, and vorticity fluctuations in the impeller and volute casing. The simulation at the design point is carried out with the wall-adapting local eddy-viscosity subgrid-scale model and a sliding mesh technique is applied to consider the impeller-volute interaction. The results show that a strongly unsteady flow field occurs in the impeller and volute casing of the fan, and the flow is characterized with obvious pressure and vorticity fluctuations, especially at the tongue and at the blade wake region. The large pressure fluctuation at the tongue and the large fluctuation of the blade wake vorticity appear as the blade wake is passing the tongue. Acoustic analogy and vortex sound theory are used to compute the radiated dipole and quadrupole sound fields, which are in good agreement with the experiment. The sound results show that the vortex sound theory is convenient for the broadband noise computation, and the dipole sound is much higher than the quadrupole sound. The dipoles, distributed over the volute tongue surface, are the dominant sound source of the fan.

Effects of Tongue Position and Base Circle Diameter on the Performance of a Centrifugal Blood Pump

This article presents numerical investigations of the effect of radial gap and volute tongue position on the circumferential pressure distribution and the magnitude of resulting imbalanced radial force. A series of volute models was designed using the constant mean velocity method. The results indicate that a radial clearance of 10% is a good practical value that gives a relatively high head across the pump for a small radial force. The results show that the tongue position at 30 degrees gives the lowest radial force and pressure head. The tongue position at 15 degrees appears to give the best compromise results producing a generated head only 5% less than the maximum value while the radial force is about 22% less than the maximum force.

Influence of Impeller Geometry on the Unsteady Flow in a Centrifugal Fan: Numerical and Experimental Analyses

The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental studies have been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these impellers. The effects on the unsteady flow behavior related to irregular blade spacing, blade count and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using computational fluid dynamics (CFD) tools based on the unsteady Reynolds averaged Navier Stokes (URANS) approach. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H). The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 (1997) standard. In addition to this, pressure microphones have been flush mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL) measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found.

Reduction of the aerodynamic tonal noise of a forward-curved centrifugal fan by modification of the volute tongue geometry

In this work, an experimental study about the influence of some geometric features on the aeroacoustic behaviour of a squirrel-cage fan, used in automotive air conditioning units, has been carried out. The study focused on the effect of both the shape and the position of the volute tongue on the noise generated by the fan. Different geometric configurations were tested in order to compare the results. First of all, the performance curves were measured in a standardized test facility. Then, the acoustic behaviour of the fan was characterized by means of acoustic pressure measurements near the fan inlet. The comparison of the test results indicated a great dependence of both the shape and the position of the volute tongue and the noise generation. In particular, some geometric configurations of the volute tongue were able to reduce the fan noise generation without reducing the fan operating range.

Numerical calculation of centrifugal fan noise

A numerical study on the aerodynamic noise generation of an industrial centrifugal fan with forward swept blades is carried out. Three-dimensional numerical simulations of the complete unsteady flowfield in the whole impeller — volute configuration are performed to obtain the aerodynamic sound sources. Then, aerodynamic sound is calculated using the Lowson equation and compared with the measurements. Moreover, the fan is modified for noise reduction by increasing the distance between the impeller tip and the volute tongue and sloping the volute tongue. The sound levels of the modified fan are lower than those of the original one over almost the entire range of frequencies analysed. The blade passing frequency level of the modified fan is decreased by about 15 dB at the design point. The method described and applied in this work provides a good qualitative prediction of the noise generation when designing a new fan, thus facilitating the choice of the lowest noise fan from several feasible alternatives.

Three-dimensional quasi-unsteady flow simulation in a centrifugal pump: Comparison with experimental results

This work aims at assessing the velocity field, pressure, and radial thrust distribution inside a centrifugal pump (ENSIVAL-MORET MP 250.200.400 pump, diameter = 408 mm, five blades, specific speed = 32) at various flowrates. A three-dimensional flow simulation is first presented for the isolated impeller. A three-dimensional quasi-unsteady flow simulation of the impeller—volute assembly is then performed for several impeller blades and volute tongue relative positions. The computed pressure fields enable to evaluate the radial thrust on the pump shaft and to study its variations with the flowrates. The computed pressure fluctuations match the measures obtained from 10 unsteady pressure sensors placed on the impeller shroud and volute, so that the validity of the computed radial thrust is acknowledged.

Experimental determination of the tonal noise sources in a centrifugal fan

In this work, an experimental study about the aerodynamic tonal noise sources in a centrifugal fan with backward-curved blades has been carried out. Acoustic pressure measurements at the fan exit duct and pressure fluctuation measurements on the volute surface have been made for different flow rates. A correlation study of both pressure signals has been made in order to explain some of the features of the aerodynamic tonal noise generation. A strong source of noise caused by the interaction between the fluctuating flow leaving the impeller and the volute tongue is appreciated. The unsteady forces exerted on the fan blades constitute another noise generation mechanism, which affects the whole extension of the impeller, thus transmitting pressure fluctuations to the entire volute casing. The relative importance of this mechanism compared to the impeller–tongue interaction depends on the flow rate.

볼류트 형상이 원심 펌프의 성능에 미치는 영향에 대한 수치 해석적 연구

In this study, the effects of volute area distribution on the performance of a centrifugal pump were numerically studied using a commercial CFD code. To reduce the shutoff head, maintaining head and efficiency at a design flow rate, the flat head-capacity characteristic curves in which the head varies only slightly with capacity from shutoff to design capacity are frequently required. In order to control the shutoff head of a pump, several volute cross-sectional area distributions were proposed as a main parameter with the same impeller geometry. The calculation results show that the slope of the performance characteristic curve of the centrifugal pump can be controlled by modifying the area distribution from volute tongue to volute outlet with fixed volute outlet area and also varied volute outlet area.

Numerical Calculation of Pressure Fluctuations in the Volute of a Centrifugal Fan

In this work, a numerical model has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been compared to experimental results obtained in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been obtained, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. A good agreement has been found between the numerical and the experimental results.

Numerical Modelization of the Flow in Centrifugal Pump: VoluteInfluence in Velocity and Pressure Fields

A 3D‐CFD simulation of the impeller and volute of a centrifugal pump has been performed using CFX codes. The pump has a specific speed of 32 (metric units) and an outside impeller diameter of 400 mm. First, a 3D flow simulation for the impeller with a structured grid is presented. A sensitivity analysis regarding grid quality and turbulence models were also performed. The final impeller model obtained was used for a 3D quasi‐unsteady flow simulation of the impeller‐volute stage. A procedure for designing the volute, the nonstructured grid generation in the volute, and the interface flow passage between the impeller and volute are discussed. This flow simulation was carried out for several impeller blades and volute tongue relative positions. As a result, velocity and pressure field were calculated for different flow rates, allowing to obtain the radial thrust on the pump shaft.

Development and Design of a Centrifugal Compressor Volute

The volute is one of the key components of a centrifugal compressor. The design of the volute not only impacts the compressor efficiency but also influences the operating range. The detailed flow simulation presented here helps to better understand the volute flow mechanisms and provide design guidance in volute design to meet performance goals. In this study, the viscous Navier‐Stokes equations are used to simulate the flow inside the vaneless diffuser and volute. The detailed flow structures for different volute tongue geometries are studied in detail. The numerical calculations are compared with experimental data and good agreement is found. The results also suggest direction for further investigations in volute design.

A numerical study of flow-induced noise in a two-dimensional centrifugal pump. Part II. Hydroacoustics

This paper is concerned with determination of the acoustic pressure field in a centrifugal pump. The main noise-generating mechanism is assumed to be the unsteady impeller blade surface forces, which reach a maximum when the flow channel between two consecutive blades is shut off by the volute tongue. The acoustic sources are moving (rotating) dipoles. The strengths of these dipoles are estimated by using the discrete vortex method described in Part I of this two-part study, but may be determined by any other (appropriate) flow analysis method. The solution to the inhomogeneous wave equation which describes the generation and propagation of pressure waves is expressed in the frequency domain, by making use of Fourier transform. The dipole-type boundary term, which accounts for the scattering from the volute, is discretized by employing the boundary element method. The emphasis is on a two-dimensional procedure, but extension to three dimensions is also discussed. The method is applied to the flat ‘two-dimensional’ laboratory centrifugal pump considered in Part I. The frequency-domain solution is particularly useful for this kind of problem, as the interest typically is in the dominating frequency components only, which are the blade passage frequency f blade and its higher harmonics, 2 f blade, 3 f blade, etc. The numerical results are compared with available experimental results, by which they are well supported. The frequency-domain solution is also found to be very useful in connection with minimization of the flow-noise by design optimization.