Amplitude Of Pressure Fluctuations Research Articles

Study on the Spatio-temporal Evolutionary Properties of Gas-liquid Two-phase Flow in Centrifugal Pump as Turbine (PAT)

With the increasing complexity of the industrial production process, the transmission medium of the hydraulic turbine is no longer satisfied, and the gas-liquid two-phase mixed medium has to be considered. The presence of gas in the transmission medium will alters the internal flow structure of the hydraulic turbine and affect its operational stability. Therefore, for the purpose of clarifying the influence of inlet gas content on the internal flow of PAT, the unsteady flow of the PAT is simulated in this paper using numerical simulation. Based on the numerical simulation results, the influence of inlet gas content on the internal flow characteristics, characteristics of pressure fluctuation in impeller and volute, and vortex evolution of flow field are analyzed. The accumulation of gas phase leads to the emergence of vortices, and regions with low pressure values appear at the vortex generation. The major factor of the periodic variation of pressure fluctuation between volute and cut-water is the dynamic and static interference of impeller. The increase of gas content causes more flow disorder in the cut-water region and the volute contraction section. Since the gas in the flow channel is predominantly on the suction side of blades, the flow field on the suction side is more complex than that on the pressure side, and the amplitude of pressure fluctuation increases appropriately. The vortex structure is mainly distributed on balance hole, inlet area of impeller and suction side of blade. As the blade rotates, there are new shedding and growth of vortices, and finally attached to the volute wall. Increasing gas content enhances the influence of blade rotation on the vortex evolution characteristics in the volute and impeller.

Investigation of the transient characteristics of the Francis turbine during runaway process

Transient hydraulic phenomena, including flow separation, vortex structure and high amplitude pressure fluctuation, occur in the turbine during runaway process, significantly affecting the safe and stable operation. To clarify the unsteady flow characteristics in the runaway process, this paper focus on a low head model Francis turbine, examining the transient flow dynamics from rated speed to runaway speed. Numerical simulations show good agreement with experimental test results for the runaway speed and discharge. Results identify that two typical cavitation vortex structures within the runner: A cloud cavitation vortex near the hub on the pressure side and a columnar cavitation vortex on the suction side. Further analysis reveals that the pressure fluctuation induced by the former are low-frequency (0.08fn and harmonics), whereas those induced by the latter are high-frequency (1.16fn and harmonics). Entropy production analysis in homogeneous flow indicates that energy dissipation mainly occurs in the runner and draft tube during the runaway process. Turbulent entropy production within the turbine comprises a significant portion of the total entropy production. Additionally, areas around the recirculation zone exhibit considerable high entropy production, indicating that the energy of the fluid is dissipated by cavitation vortex structures generated in these areas. Additionally, the analysis indicates that the entropy production rate correlates with vapor generation, underscoring the cavitation vortex as the primary cause of energy dissipation. This investigation can provide valuable insights into the energy dissipation mechanisms during the runaway process.

Study on power losses and pressure fluctuations of diffuser mixed flow pump as turbine on different power generation speeds based on energy power models

Variable speed regulation represents an effective means to ensure the efficient operation of the diffuser mixed flow pump as turbine (DMFPAT). This paper employed computational fluid dynamics-based energy power models and high-frequency water pressure fluctuation tests to investigate the power losses and pressure fluctuations of DMFPAT under different power generation speeds. Analysis of power losses reveals that internal power losses in DMFPAT predominantly originate from the turbulent dissipation power (PEPD′) in the entropy production and the turbulent kinetic energy production power (PEBL3) in the energy balance equation, indicating that fully developed turbulence significantly contributes to substantial power losses in DMFPAT. A strong correlation exists between power generation speed and power losses, and decreasing rotational speed results in gradual reduction of power losses in DMFPAT. Additionally, a comprehensive analysis of the pressure fluctuation signals of DMFPAT under variable speed mode was conducted, revealing that the main frequency at each monitoring point is the rotational frequency and its harmonics. As speed decreases, the pressure fluctuation amplitude diminishes. The research presented demonstrates that adjusting the speed not only markedly reduces power losses but also eliminates adverse pressure fluctuations, thereby providing a theoretical basis for the efficient, stable and safe operation of DMFPAT.

Dynamics and experimental study of a novel proportional directional valve with displacement feedback groove controlled by high-speed switching valves

The intelligence of hydraulic roof support is an important guarantee for unmanned fully mechanized coal mining face. The water-based medium proportional directional valve is the main factor that restricts the intelligent realization of support system. The support control valve needs to meet the 2/3 (two-position three-way) structure, taking into account both manual and electro-hydraulic control functions. The current water-based proportional valve does not satisfy the structural or functional demands of the support system. In this paper, a novel 2/3 water-based proportional directional valve is presented based on the displacement-flow feedback principle, which has two control modes: manual on-off control and electro-hydraulic proportional control. The proportional valve comprises two main valve spools and two pilot valves. The pilot valve is composed of a 2/3 on-off valve with manual operation capability and a high-speed switching valve group controlled by PWM (Pulse Width Modulation). The mathematical model of the proportional valve is established, and the experimental system is built to verify the characteristics of proportional valve. The proportional valve can meet the special functional requirements of the support. In the proportional control mode, the adjustment of spool displacement is regulated through the modulation of PWM duty ratio, resulting in effective control performance of the proportional valve. Furthermore, the discontinuous flow of the high-speed switching valve causes the pressure fluctuation of the pilot hydraulic bridge. Increasing the carrier frequency of PWM can reduce the amplitude of control chamber pressure and spool displacement fluctuation. The findings of the study can offer valuable insights for the continued advancement and enhancement of water-based proportional valves used in hydraulic roof support systems.

A new strategy for reducing pressure fluctuation of Francis turbine by bionic modification of local components

Long term operation of hydroelectric units in low load conditions can induce large-scale blade vortices, swirling vortex ropes in the draft tube, and low-frequency high amplitude pressure fluctuation. These phenomena will cause adverse consequences such as excessive vibration of the unit and blade breakage of the runner. Taking inspiration from the protuberances of the leading edge of a humped whale flipper, the present study firstly proposes bionic modifications of guide vanes and draft tube to suppress high-amplitude pressure fluctuations for Francis turbine. Numerical simulations of transient flow characteristics of the prototype unit (PU), the bionic guide vane unit (BG), and the bionic draft tube unit (BDG) under two low load conditions are conducted. Results indicated that the bionic draft tube has a good effect on suppressing pressure fluctuations in the vaneless area and draft tube. Under the Q/QBEF = 0.41 working condition, BDG causes the main frequency amplitude of pressure fluctuation at the center point of the draft tube inlet to change from 8000.2 Pa to 390.9 Pa, a decrease of 95.11 %. Under the Q/QBEF = 0.57 working condition, BDG causes the maximum decrease rate of the main frequency amplitude in the draft tube to be 60.5 %. The reducing effect in BDG of monitoring points in the guide vane area has reached over 43 %. Under low load conditions, the vortices near the wall in the draft tube of BDG are intercepted by bionic structures, reducing the vortex scale and helping to prevent the generation of large swirling vortex ropes. The bionic guide vanes have a significant control effect on pressure pulsation in the the guide vane and vaneless regions, although perform poorly in the draft tube.

Using bionic tubercles to control swirling flow instabilities of a hydraulic turbine during the load rejection process

With the development of renewable energy sources, operations of hydroelectric units under off-designed conditions and frequently transition processes have gradually become normalized, which is accompanied by threats from swirling vortex ropes, high amplitude pressure fluctuations, and strong hydraulic vibrations. This study introduces bionic tubercles into the Francis turbine's draft tube and guide vane design to suppress pressure fluctuation and stabilize swirling vortex rope during the load rejection process. Results reveal that the bionic Francis turbine (BFT) reaches its maximum speed of 686.4 rpm at 3.804s, marking a 6.08 % reduction from the prototype Francis turbine's maximum speed during load rejection. Moreover, it significantly diminishes the principal frequency amplitude of low-frequency pressure fluctuations caused by swirling flow instability from the draft tube cone, achieving a reduction by one to two magnitude orders. It is interesting that the scale of the circumferential vortex in the vaneless region and blade vortices within the runner channels is verified to decrease. More importantly, it is attributed that the bionic tubercles effectively disrupt and disintegrate the walled circumferential vortex structures in the draft tube.

Numerical Prediction of Pressure Oscillation in a Centrifugal Pump at Shut-off conditions

In order to investigate the pressure fluctuation characteristics of centrifugal pumps under shut-off conditions, a numerical calculation was carried out using Fluent software based on the RNG k-ε turbulence model. The pressure fluctuation characteristics within the volute and impeller flow fields of the centrifugal pump under shut-off conditions were analyzed, and the shut-off head was predicted. The results show that the monitoring points within the volute flow passage exhibit obvious periodic patterns, and their peak pressure fluctuations occur at frequencies that are multiples of the vane passing frequency. Additionally, the closer the monitoring point is to the volute tongue, the greater the amplitude of pressure fluctuation. Furthermore, for monitoring points located on the centerline of the impeller flow passage, the closer they are to the impeller exit, the greater the amplitude of pressure fluctuation.

Research on the internal flow characteristics of centrifugal pump based on streamlined anti-guide vane

Abstract Anti-guide vane is part of the radial guide vane in multi-stage centrifugal pump, and the hydraulic loss of anti-guide vane is the dominant factor affecting the performance of radial guide vane. In this paper, the radial guide vane is chosen as the research object, an optimization scheme of streamlined anti-guide vane is proposed based on the arc-shaped anti-guide vane with inlet angle α=25°. The simulation calculation of multi-stage centrifugal pump is drawn using the SST k-ω turbulence model. and the influence of the streamlined anti-guide vane on the hydraulic performance is studied. The result shows that: Under various flow conditions, the head of the multistage centrifugal pump with streamlined anti-guide vanes is higher than that of the prototype. When the flow rate is 1.3Q, the head is increased by 7.2%. and the efficiency is increased by 2.3%. The amplitude of pressure fluctuation of the streamlined anti-guide vane is significantly decreased at each monitoring point compared to the prototype, indicating that the streamlined anti-guide vane weakens the influence of the pressure fluctuation. Furthermore, the streamlined anti-guide vane enhances the pre-swirl of the inlet fluid to the secondary impeller, reduces the impact loss, and improves the pressurization capacity of the secondary impeller.

Numerical Study on Pressure Fluctuation in Electric Coolant Pump

Abstract Adjusting the flow rate of an electronic coolant pump (ECP) over a wide range can cause significant internal pressure fluctuations, leading to vibration and noise. This study uses numerical simulation to compare pressure fluctuations at the backflow orifice and within the impeller of an ECP at various flow rates. The backflow creates periodic disturbances in the impeller inlet region. As the flow rate increases, the axial influence range of the backflow on the impeller inlet decreases, reducing the amplitude of pressure fluctuations by up to 7.9%. The characteristic frequencies of pressure fluctuations at the backflow orifice include the blade passing frequency and its first harmonic. Within the impeller, the pressure fluctuation amplitude increases with both flow direction and flow rate, with characteristic frequencies encompassing the rotational frequency, BPF, and its first harmonic. At low flow rates, the overall variation of pressure fluctuations inside the impeller shows an opposite trend compared to design and high flow rates. The impact of the rotational frequency on pressure fluctuations inside the impeller is significantly smaller at the design flow rate than at other flow rates. This study offers insights that can help optimize ECP design and enhance their operational performance.

Study on the influence of guide vane opening on pressure pulsation of pump-turbine under zero flow pump condition

Abstract Reversible pump-turbine is the key equipment of energy conversion in large pumped storage power station, and it is the core of stable operation of power station. Under the pump condition, the internal pressure pulsation law of the pump-turbine has an important influence on the stable operation of the pump. In order to study the pressure pulsation characteristics of pump-turbine in pump mode under zero flow condition, this study carried out unsteady numerical simulation on three kinds of guide vane openings, and analyzed the amplitude frequency characteristics of pressure pulsation in turbine under different head and the influence of internal flow characteristics on pressure pulsation. The research shows that in the pump mode, when the guide vane opening of the turbine increases, the influence of the blade frequency and the shaft frequency on the vaneless area increases, resulting in the maximum pressure fluctuation amplitude in the vaneless area under the pump condition, especially when GVO = 19 °. At the same time, due to the influence of dynamic and static interference, the larger turbulent kinetic energy appears in the vaneless area and the connection between the guide vane flow channel and the runner flow channel, resulting in an increase in hydraulic loss. Both the experimental and simulation results show that the guide vane opening of 19 ° should be avoided to reduce the hydraulic loss in the vaneless area when the turbine is operated under the zero flow pump condition.

Identification of the vortex in the main flow passage of a multiphase pump and the relationship with pressure fluctuation

AbstractThis article investigates the evolution of vortex structures in the impeller channel of a multiphase pump. By capturing the vortices in the impeller channel using the vorticity and Q‐criterion, the generation location of the vortex structures is analyzed, and the pressure fluctuations induced by vortices in the main flow passage of the impeller are studied in terms of their time‐ and frequency‐domain characteristics. The relationship between the vorticity and the amplitude of pressure fluctuations at the main frequency of the impeller is further investigated. This study develops a method of identifying vortices in the impeller channel of the multiphase pump, and reveals the intrinsic connection between the vortices and pressure fluctuations in the main flow passage. These findings offer some suggestions for eliminating the influence of vortices and enhancing the pressurizing capabilities of multiphase pumps.

The Influence of Pre-Lift Gate Opening on the Internal and External Flow Characteristics During the Startup Process of an Axial Flow Pump

This paper focuses on a vertical axial flow pump and employs a 1D-3D coupling method to investigate the effects of different gate pre-opening angles on the internal and external flow characteristics of the axial flow pump during startup. Through comparative analysis, the following conclusions are drawn: In the study, a fully open gate is defined as 1, while a fully closed gate is defined as 0. When starting the axial flow pump with different valve pre-opening degrees, backflow occurs within the first 20 s of startup, and the backflow rate inside the pump gradually increases with the increase in the valve pre-opening degree. At a valve pre-opening degree of 0.6, the maximum backflow rate inside the pump reaches 5.89% of the rated flow rate. When starting the pump with the valve fully open, the maximum backflow rate reaches 10.98% of the rated flow rate, and the efficiency is affected by the backflow rate. The valve pre-opening degree has little impact on the axial force acting on the impeller during startup. When starting with a valve pre-opening degree of 0.6, the internal pressure difference in the pump is minimized. Within the first 20 s of startup, the internal pressure difference in the impeller is 28.96% higher and the flow velocity is 14.62% higher with valve pre-opening degrees of 0.8 and 1.0 compared to a 0.6 degree opening. During the initial stage of pump startup, with valve pre-opening degrees of 0.8 and 1.0, the pressure fluctuation amplitude inside the pump is minimal, with maximum relative amplitudes of only 0.621 and 0.525, which are 41.00% and 28.51% lower than the maximum amplitudes at 0 and 0.2 degrees, respectively. In summary, the peak pressure inside the pump is minimized when the valve pre-opening degree is around 0.8, while the pressure difference and flow velocity are relatively lower at a pre-opening degree of 0.6. It is recommended to start the pump with a valve pre-opening degree of around 0.6 to 0.8.

Determining the mechanism for generating cavitation pressure fluctuations in throttle devices at high-head throttling of liquid

The object of this study is the process of generating cavitation pressure fluctuations behind the throttle device at high-head throttling of liquid. This paper addressed the problem of calculating the amplitude of cavitation pressure fluctuations at high-pressure liquid throttling. It was established that cavitation pressure fluctuations are a consequence of collisions of discrete masses of a transiting liquid jet in the region of pressure recovery. The range of cavitation pressure fluctuations reaches the pressure values at the inlet to the throttle device. The frequency band of cavitation pressure fluctuations is in the range from 1.5 to 20 kHz and higher. At high-head throttling of the liquid, caverns attached to the surface of the throttle channel, moving caverns and small bubbles in the transit flow are formed. Moving caverns compress the transit flow and divide it into separate fluid blocks. In the region of pressure restoration, the moving caverns are slammed shut and discrete fluid blocks collide. This causes high-frequency pressure fluctuations. Special feature of the results is the possibility of estimating the range of cavitation pressure fluctuations depending on the pressure drop on the throttle device. When the back pressure on the throttle device increases, the amplitude of cavitation pressure fluctuations decreases, and the frequency band shifts to the high-frequency region. The results make it possible to calculate the range of cavitation oscillations, to predict the development of cavitation erosion of materials depending on the parameters of throttling of the working fluid. The results of the work are used to design devices for cleaning products from contamination, for determining the volume content of water in aviation fuel, for intensification of technological processes in the chemical and food industries.

Intermittency transition to azimuthal instability in a turbulent annular combustor

We experimentally study the transition from a state of combustion noise to azimuthal thermoacoustic instability in a laboratory-scale turbulent annular combustor. This combustor has sixteen swirl-stabilized burners to facilitate continuous and spatially distributed combustion along the annular region. Our approach involves simultaneous measurement of CH* chemiluminescence emission of the flame using two high-speed cameras and the acoustic pressure fluctuations using eight piezoelectric pressure transducers mounted on the backplane of combustor. We observe that the transition from combustion noise to azimuthal instability occurs through mode shifting, where the system switches from a longitudinal mode to an azimuthal mode as the equivalence ratio is decreased. Throughout this progression, the combustor exhibits various dynamical behaviors, including intermittency, dual-mode instability, standing azimuthal instability, and beating azimuthal instability. These dynamical states are determined from the acquired pressure signals by decomposing the acoustic pressure fluctuations into clockwise (CW) and counterclockwise (CCW) waves, enabling a reconstruction of the amplitude of acoustic pressure fluctuations, nature angle, (anti-)nodal line location, and spin ratio. The global heat release response is then examined during various dynamical states, contrasting their behavior at different non-dimensional time steps by phase-averaging the fluctuations of the heat release rate over the acoustic pressure cycle. Distinctive flame behaviors were observed based on the direction of pressure wave propagation, showcasing characteristic CCW spinning, standing, and CW spinning heat release patterns. Moreover, our examination of relative phase distributions during various dynamical states, computed by analyzing the phase of heat release rate fluctuations across all burners with respect to one burner, reveals the emergence of diverse patterns in the interaction of neighboring flames influenced by acoustic field.

Two-phase flow instabilities during microgravity flow boiling onboard the International Space Station

This study is an elaboration on flow instabilities observed during flow boiling experiments conducted onboard the International Space Station (ISS) as part of the Flow Boiling and Condensation Experiment (FBCE). During highly subcooled flow boiling, liquid backflow into the channel that rapidly condenses vapor within the channel was observed. Experiments were conducted with an enhanced sampling frequency of 30 Hz and an extended image sequence recording duration of at least 4 seconds at 500 frames per second to further investigate the instability. Identical experiments were performed both in microgravity onboard the International Space Station (ISS) and in Earth gravity during vertical upflow. Instabilities in microgravity are more severe than those in Earth gravity and, at their most severe, propagate to the channel's upstream region. Instabilities are observed within the channel when the intensity, I, which is dependent on inlet pressure fluctuations and mass velocity, exceeds 1.8 × 105 W/m2. Parametric trends of the frequency and amplitude of inlet pressure fluctuations during instability are examined, which reveal instabilities are most severe at low flow rates, high inlet subcoolings, and high heat fluxes. Various stability maps proposed in the literature are evaluated against the present database, and instabilities only manifest for subcooling numbers greater than 14. A subset of the database containing the Onset of Flow Instability (OFI) point is extracted to first evaluate correlations available in the literature and then develop a new correlation. The new correlation is applicable in both microgravity and Earth gravity conditions and predicts the database with a Mean Absolute Error (MAE) of 1.3%.

Dynamical states associated with the shift in whistling frequency in aeroacoustic system

Self-sustained aeroacoustic oscillations arising from the interactions between the hydrodynamic and acoustic fields are perceived as a whistle. Such whistling can lead to large amplitude acoustic oscillations that have disastrous consequences for engineering systems such as large segmented solid rocket motors and large gas pipelines. The whistling corresponds to the state of limit cycle oscillations (LCO) in dynamical systems theory. An aeroacoustic system exhibits different dynamical states when the bulk flow velocity is varied as a control parameter. Understanding the dynamical states and the transitions between them, as the control parameter is varied, is crucial in designing control strategies for such aeroacoustic oscillations. Previous studies have shown that as the control parameter varies, in an aeroacoustic system that has a flow through orifices, the whistling frequency shifts. We show that such a change in frequency occurs via three different scenarios— (1) direct transition between the two LCOs as an abrupt transition, (2) via a state of intermittency, and (3) via a state of aperiodicity. In the current aeroacoustic system, the abrupt transition between the LCOs is manifested as a bursting behaviour where the amplitude of the acoustic pressure fluctuations abruptly switches between the high and low-amplitude LCOs. Further, we show that the dynamical state and the transition between them during the frequency shift have a correlation with the magnitude of the frequency shift. Using recurrence theory we show that there is a change in the dynamical state of the system during the frequency shift. Further, we use synchronisation theory to investigate the coupled behaviour of the velocity (u′) and the acoustic pressure (p′) fluctuations during the different dynamical states. Our findings imply that u′ and p′ exhibit phase synchronisation (PS) during the state of LCO, corresponding to whistling. In contrast, u′ and p′ are desynchronised during the state of aperiodicity, corresponding to stable operation. Furthermore, the bursts of periodic oscillations during intermittency correspond to the phase-synchronised epochs of periodic u′ and p′, and the aperiodic epochs correspond to the desynchronised aperiodic u′ and p′.

Numerical investigation of the vorticity transportation and energy dissipation in a variable speed pump-turbine

Variable speed technology is utilized in pump turbines to enhance their operational efficiency and stability. The unsteady internal flows of a variable speed pump turbine operating at different rotation speeds are numerically investigated with SST k-ω turbulence model. Firstly, the ideal rotating speed is selected for each output. Amongst three researched output levels, the lowest entropy production consistently occurs at minimum rotation speed,1350 rpm. Under similar outputs, higher rotation speeds result in higher entropy production. Difference between various rotation speed is up to 40 %. Secondly, Liutex method is used to structure the vortex while vorticity transport equation is applied to analyze its evolution. Results show that variable speed operation can effectively reduce pressure fluctuation amplitude with approximately 20 %–40 % amplitude drop. Subsequently, the relationship between vortex rope and entropy production in the draft tube is deeply explored as it reveals that entropy production in the draft tube correlates with vortex rope evolution. Moreover, direct dissipation's entropy production and turbulence dissipation's entropy production are two primary components leading to irreversible energy loss. It is clearly revealed that the entropy production reduces with rotation speed. The relationship between entropy production and vortex rope in the draft tube is confirmed.

Effect of branch-like structures created by vortex generators on cavitation dynamics at high angle of attack

When hydraulic machines operate away from their design condition, the angle between the inflow and the blade's leading edge increases significantly, causing severe cavitation. To address this, this investigation focuses on cavitation flow around hydrofoil with a high incidence angle. The effects of the vortex generators (VGs) on cavitation evolution, pressure fluctuations, and flow-induced noise were discussed. Experiments and simulations were jointly employed in this work. The results indicate that under current conditions, cavitation initiates upstream of the VGs, closer to the leading edge. The branch-like vortex cavitation induced by the VGs enhances the stability of the shedding cavities in the midstream of the hydrofoil, leading to a 15.24% reduction in the primary frequency of cavitation shedding. With the addition of the VGs, the amplitude of pressure fluctuations on the hydrofoil surface is reduced. Also, the acoustic power drops over the entire spectrum, especially in the high-frequency range. The sound pressure corresponding to the main frequency of cavitation noise is reduced by 7 dB.

Numerical simulation on unsteady cavitating flows in a rotational hydrodynamic cavitation reactor

Abstract The RNG k-ε turbulence model and mass transport cavitation model Zwart-Gerber-Belamri are used to simulate unsteady cavitating flows in a rotational hydrodynamic cavitation reactor (RHCR). The RHCR is mainly composed of rotor and stator. Unsteady cavitation flow field analyses in RHCR are focused mainly near the rotor surface. The numerical simulation results are in good agreement with the experimental data. The frequency of pressure fluctuations and streamline distribution are discussed by setting 10 monitoring points near the rotor surface. The numerical simulation results shows that the main frequency of pressure fluctuation inside RHCR is 24f r and 72f r; the maximum amplitude of pressure fluctuations appears near the inlet, and its value about 3 times than the minimum. Moreover, the streamline distribution analyses demonstrate that the vortex appears near the rotor surface, and is generating, growth and disappearing with time. The shape, vortex center and intensity of the vortex near the inlet change drastically with time. This research provided a reference for the optimization design of RHCR.

Study on the volute optimization and mechanism of vortex loss reduction for a centrifugal fan

Abstract In order to reduce the flow loss in the volute and improve the efficiency of the centrifugal fan further, a new type volute with a diffusion profile was designed and optimized. The effects of diffusion angles were clarified by using numerical simulations and the method of design of experiment. The mechanism of vortex loss reduction of the diffusion-type volute was revealed. The results show that diffusion-type volute can reduce the flow loss in the volute by 30.8% compared with the original volute, and increase the efficiency of the fan by 2.24%. Parametric studies show that the diffusion angle of front disc has a great influence on the efficiency of the fan, and the effect of diffusion angle of rear disc is relatively less. Mechanism analysis shows that the diffusion-type volute can greatly reduce the vortex strength in the volute, especially eliminate the high-intensity vortex near the volute tongue. As a result, the volute loss is remarkably reduced. In addition, the diffusion-type volute can effectively reduce the amplitude of pressure fluctuation in terms of shaft frequency, characteristic frequency and broadband signals in the volute.