Fan Efficiency Research Articles

SolidWorks Flow Simulation: Selecting the optimal mesh for conducting CFD analysis on a centrifugal fan

The accuracy of mesh use determines the suitability of simulation results with experimental test results, therefore it is necessary to study the type and number of mesh used for flow simulation. This study aims to investigate the type of mesh and the number of cells that are appropriately used in the simulation of centrifugal fans using the Solidworks Flow Simulation module. The research was conducted by comparing the simulation results with the experimental results on centrifugal fans that have been carried out by previous studies. In this research, the type of mesh used is global mesh. The parameter of determining the number of cells is done by varying the mesh level because the mesh level affects the number of cells. In this simulation study, the boundary condition is set to one flow volume of 5 m3/h and a rotation speed of 92.362 rad/s. In this study, the total pressure and efficiency of the centrifugal fan are the things that are seen from the comparison of flow simulation with the experiment. Based on the simulation results that have been carried out, mesh levels 1 to 4 show results that differ significantly from the experimental results. At machine levels 5 to 7, the results are close to the experimental results, but the closest total pressure and efficiency values are at mesh level 5. The results of this study can be a reference for research that simulates centrifugal fans.

Numerical study on the indoor flow field and ventilation performance in the power room of a hybrid locomotive that passes through a tunnel

Under the background of energy saving, emission reduction, and green transportation, the electrification construction of railway lines is difficult owing to long cycles and high costs. Hybrid locomotives have emerged as fuel locomotives that can run on electrified lines and that achieve energy saving, emission reduction, and railway emergency on non-electrified lines. Train power equipment is highly integrated in the locomotive power room, which leads to the ventilation and heat dissipation performance of indoor high-heat equipment becoming one of the main factors that affect the safe operation of trains. This study focuses on the flow field and ventilation of locomotive power rooms in railway vehicle/tunnel systems and explores the variation of the ventilation flow rate and flow field in a power room when trains pass through a tunnel at different speeds. Based on the unsteady Reynold-averaged Navier–Stokes (RANS) equations and shear-stress transformation (SST) k-ω turbulence model, the relative motion between a train and a tunnel is simulated by sliding mesh, and the related algorithm settings are verified through experiments. The results show that: train speed is linearly related to the air inlet flow rate, and trains have a critical speed, which affects the original indoor air-cooling circulation system. This critical speed is reduced by the tunnel environment; The propagation and superposition of the pressure wave in a tunnel have no evident effect on the flow rate of the power room vent; Train speed is negatively correlated with the fan efficiency; thus, it deteriorates the fan efficiency in the tunnel environment; The symmetrical distribution of ventilation openings in a power room can effectively balance the fresh-air flow, but it is not conducive to cooling equipment located near the locomotive. These conclusions can contribute to improving future designs of the ventilation systems of hybrid electric locomotive power rooms.

Influence of the Spatial Position of the Semi-open Impeller on the Internal Flow Field in Centrifugal Fans

This paper takes as its background the study of centrifugal fans in powered air-purifying respirators. To improve the efficiency of the centrifugal fan and the uniformity of the internal flow field, a steady-state simulation based on the realizable k-ε turbulence model, using the “frozen rotor method”, was carried out to analyze the effect of the spatial position of the impeller in the centrifugal fan on the internal flow field by matching the impeller to the worm gear. The results show that varying the eccentric angle, eccentric distance, and longitudinal depth of the semi-open impeller in the volute affects the internal flow field of the centrifugal fan to varying degrees. The concentric arrangement was not found to be optimal, and when the impeller rotates slightly further away from the worm tongue, the flow field inside the centrifugal fan is more uniform and the phenomena such as “wake-jet” and boundary layer separation are significantly reduced. In addition, it was found that the pressure distribution at the inlet is approximately the same as the pressure distribution in the flow field.

Modeling the Impacts of Filter Fouling on Energy Consumption

The use of higher efficiency particulate air filters in central heating, ventilating, and air-conditioning (HVAC) systems to improve indoor air quality (IAQ) in homes is continuing to increase. However, as filters are loaded with collected particulate matter and dust, the pressure drop will increase and lead to a variety of direct and indirect energy impacts. The magnitude of energy impacts on fouled, or dirty, filters is not yet known. Therefore, this paper explores the energy impacts of fouled filters on new energy-efficiency homes in multiple climates around the United States by performing whole building energy simulations using BEopt and EnergyPlus. Relevant inputs include filter pressure drop, total pressure drop, HVAC airflow rate, fan efficiency, heating and cooling nominal capacity, and rated airflow rate. The results indicate that annual energy consumption generally increases for permanent split capacitor (PSC) and electronically commutated motor (ECM) fans as the filter gets loaded or dirty over time, although the energy impacts are smaller for ECMs.

Aerodynamic Performance Optimization of Centrifugal Fan Blade for Air System of Self-Propelled Cotton-Picking Machine

To enhance the working efficiency and aerodynamic performance of the centrifugal fan in the air system of a cotton picker, a new type of centrifugal fan blade was designed by extracting the mid-arc section from the prototype blade and integrating an airfoil, which was transplanted and coupled to the mid-arc section. The design aimed to improve the airflow characteristics and performance of the centrifugal fan. By combining experimental data from centrifugal fans used in existing cotton-picker air systems and employing computational fluid dynamics (CFD) methods, the internal flow field structure of the centrifugal fan was simulated. This study focused on investigating the aerodynamic performance of the new centrifugal fan blade and its impact on improving the internal flow patterns within the centrifugal fan. The results of the flow field visualization analysis indicate that the new blade design exhibits excellent aerodynamic performance, improving the flow distribution within the centrifugal fan. It enhances the uniformity of the outlet airflow, reduces the occurrence of localized “jet-wake” phenomena at the impeller’s outlet, suppresses the generation and development of vortices in the flow channel, and reduces local energy losses within the impeller. These improvements contribute to an increase in the fan’s efficiency. Under rated operating conditions, the efficiency of the prototype fan was measured at 60.3%, while the optimized fan achieved an efficiency of 64.8%. This signifies a significant improvement in the efficiency of the centrifugal fan.

Loose Belt Fault Detection and Virtual Flow Meter Development Using Identified Data-driven Energy Model for Fan Systems

An energy model that correlates fan airflow, head, speed, and system power input is essential to detect device faults and optimize control strategies in fan systems. Since the application of variable-frequency drives (VFDs) makes the motor-efficiency data published by manufacturers inapplicable for VFD–motor–fan systems, the fan efficiency and drive (belt–motor–VFD) efficiency must be identified for each individual system to obtain accurate energy models. The objectives of this paper are to identify an energy model of existing VFD–motor–fan systems using available experimental data and demonstrate its applications in loose belt fault detection and virtual airflow meter development for optimal control. First, an approach is developed to identify the fan head, fan efficiency, and drive-efficiency curves using available fan head, speed, and system power input as well as temporarily measured airflow rate without measuring shaft power. Then, the energy model is identified for an existing VFD–motor–fan system. Finally, the identified model is applied to detect the slipped belt faults and develop the virtual airflow meter. The experiment results reveal that the developed approach can effectively obtain the energy model of VFD–motor–fan systems and the model can be applied to effectively detect slipped belt faults and accurately calculate the fan airflow rate.

Аналіз впливу похибок вимірювання на абсолютні похибки експериментального визначення ККД вентилятора

The subject of research in this article is the experimental determination of the characteristics of fans of turbofan engines with a high and ultra-high bypass ratio. Increasing the efficiency of fans of engines of the specified class requires solving many complex interrelated problems, one of which is the determination of characteristics based on test results. The goal is to substantiate the need to use a method based on the determination of torque and the formation of requirements for the accuracy of its measurement. Tasks: clarification of previously obtained relationships between measurement errors and accuracy of determination of efficiency and air flow, formation of universal dependencies that allow analysis of absolute errors of determination of efficiency of any fan or compressor based on known measurement errors, analysis of the accuracy of alternative methods of organization of measurements and calculations the specified parameters, a comparative study of the specified methods and the formation of recommendations for their practical use on the example of the characteristics of a real fan. The following results have been obtained: the formulas that relate the absolute errors of calculating the efficiency and air flow with the absolute errors of the measured parameters (mathematical models of errors) have been clarified, as well as the requirements for the accuracy of the torque measurement necessary to determine the efficiency with the specified accuracy have been specified. The scientific and practical novelty of the results obtained is as follows: the mathematical models of errors in determining the efficiency and air flow in the fan have been clarified, which connect the errors of the calculation results with the errors of the measured parameters, because of the use of these models, experimental methods of determining the characteristics of compressors and fans have been developed; for the first time, the distribution of errors in the entire area of determining the characteristics of a specific fan was analyzed in detail. It is shown that the errors in determining the efficiency of the fan depend significantly on the degree of pressure increase and air flow. At small values of these parameters, the errors increase significantly. In the area of low engine operating modes (close to the area of the low air consumption), the errors in determining the efficiency based on the processing of the measurement results are so large that a reliable determination of the efficiency becomes practically impossible without the involvement of additional information, which can be used as the calculated characteristics of the fan, and as well as the mathematical model of the engine and the results of measuring parameters of the work process in other nodes, except for the fan itself.

Enhancement of Power-Quality in a BLDC Ceiling-Fan Powered by Unity-Power-Factor Zeta Converter

This paper presents a permanent magnet brushless direct current motor (PMBLDCM) ceiling-fan (CF) that operates on AC mains with a unity power factor (UPF). An AC-DC power-factor-corrected converter (PFCC) performs in discontinuous-conduction mode (DCM) to facilitate various merits such as an inherent UPF, reduced passive components size, stable operation, and required voltage control. The PMBLDCM ceiling fan speed is controlled by a smooth change in converter voltage output, and it helps to operate a voltage source inverter (VSI) at a fundamental frequency with low switching losses. This control maximizes efficiency of a ceiling fan. The THD (Total Harmonics Distortion) of a supply-current is reduced with a wide range of speed control and supply voltage fluctuations. A prototype of it is developed to validate the design and control. Its performance is compared with a conventional PMBLDCM ceiling fan. Test results are shown to verify the design of PFCC. The power quality indices (PQI) at input supply are meeting the IEC61000-3-2 standard.

Coupling effect of vehicle wake and jet flow on the dispersion characteristics and dilution efficiency of pollutants in urban highway tunnels

The pollutants emitted by traveling vehicles are prone to accumulation inside urban highway tunnels, which poses a serious threat to the driving safety and health of passengers. This study employed the dynamic mesh method to simulate a traveling vehicle and investigated the coupling effect of vehicle wake and jet flow on the dispersion characteristics of pollutants in urban highway tunnels. To ensure the accuracy of the numerical simulation results, the turbulence model (realizable k–ε model) and dynamic mesh model were validated through field tests. The results revealed that jet flow can disrupt the large-scale longitudinal vortices pattern in the wake region, whereas vehicle wake can simultaneously weaken the entrainment strength of jet flow. The jet flow was found to be decisive in the space with a height greater than 4 m, whereas the vehicle wake intensity was considerably stronger at the bottom space of the tunnel, leading to the accumulation of pollutants in the passenger breathing zone. To evaluate the effect of jet fans on pollutants in the breathing zone, an innovative dilution efficiency was proposed. The dilution efficiency can be significantly affected by the intensity of vehicle wake and turbulence. Moreover, the dilution efficiency of alternative jet fans was better than that of traditional jet fans.

An Investigation on Optimized Performance of Voluteless Centrifugal Fans by a Class and Shape Transformation Function

Class and shape transformation functions are proposed to carry out the parametric design of the blade profiles because fan efficiency is closely related to the shape of blade profiles. An optimization with the objectives of fan efficiency and static pressure based on the Kriging models was established, and numerical simulation data were applied to construct the Kriging models. The dissipation function was used to analyze the fan energy loss. The prediction results show that the maximum accuracy error between the Kriging model and the experimental data is approximately 0.81%. Compared with the prototype fan, the optimized fan was able to ameliorate the distribution of the flow field pressure and velocity; the outlet static pressure increased by 9.03%, and the efficiency increased by 2.35%. The dissipation function is advantageous because it can intuitively indicate the location and amount of energy loss in the fan, while effectively obtaining the total energy loss as well. The situation of energy loss was mutually validated with the density of the static pressure contours and the streamline distribution. The flow fields at the leading edge of the optimized fans were improved by analysis of the dissipation function, and the leading edges of the three impellers selected from the Pareto front were narrower and flatter than those of the prototype fan.

Energy Efficiency Research In Fans and Experimental Investigation of the Effect of Motor Frequency

Fans are widely used in the industry, and they have a potential in energy efficiency studies. The aim of this paper is to introduce the fan systems and the energy efficiency studies on fan systems. The parameters like flow rate, active power, fluid power and pressure difference were explained and used in the investigations together with the experimental data obtained in the energy audits. The effects of air temperature, velocity, and frequency parameters on fan efficiency were studied. The results showed that the temperature increment negatively affects the fan efficiency, and 1 m/s increase in the air velocity reduces the system efficiency by % 1,088. Finally, according to achievements of this paper, reducing the frequency with Variable Speed Drive means less fan power and Variable Speed Drive provides energy-savings but not energy efficiency.

공기청정기와 기류 제어용 FAN의 운전조건에 따른 교실 내 공기질 변화에 대한 해석적 연구

This study investigated the influence of the operating conditions on an air purifier and extra FAN efficiency in reducing particulate matter in a classrooms. Computational fluid dynamics (CFD) simulation considering three locations of Air purifiers and operating conditions of four FANs was conducted to evaluate the optimal operating condition. In this study, the Clean Air Delivery Rate (CADR) of Air purifier was 2.4 m3/min (161.4 CMH) and 4.8 m3/min(322.8 CMH). Assuming the indoor particulate concentration is 150 μg/m3, the performance of reducing particle concentration varies by a maximum of 31.2% depending on the position of the air purifier and the operating condition of the FAN. When the CADR of the air purifier is low, particulate matter reduction performance can be improved by a FAN. When using the FAN, make sure that it does not interfere with the airflow of the air purifier.

Effect of inlet Mach number on performance and flow structure of an axial supersonic through-flow fan cascade

Ensuring the high efficiency and stable operation of a supersonic through-flow fan (STFF) in a wide range of inlet Mach numbers is of vital importance. The influence of inlet Mach number (M) ranging from 0.3 to 2.36 on the aerodynamic performance and flow structure in the STFF cascade is studied. The results indicate that at design incidence, the transonic inflow condition has a greater loss, a lower static pressure ratio, and a larger flow turning than the non-transonic inflow condition. The evolution of shock structure with the increasing inlet Mach number is as follows: shock-free → passage quasi-normal shock → leading edge (LE) local normal shock + λ shock → LE normal shock + trailing edge (TE) fishtail shock → LE bow shock + TE fishtail shock + multiple reflected oblique shocks → multiple oblique shocks. Under subsonic inflow conditions, the blade loss is dominated by boundary layer friction loss and wake loss. Under transonic inflow conditions, when the inlet Mach number rises from 0.66 to 0.86, the rear branch of passage λ shock impinges on the thickened separation region of the adjacent blade. This increases the loss. When the inlet Mach number rises to 1.06, the λ shock evolves into fishtail shocks, and the LE shock becomes stronger, reducing shock loss and separation loss significantly. As the inlet Mach number goes up to 1.26, the LE normal shock evolves into a bow shock, inducing a sharp reduction in LE shock loss. Under the supersonic inflow conditions, when the inlet Mach number rises from 1.96 to 2.36, the loss variation is mainly stemmed from LE bluntness loss, accounting for 66% of overall loss change.

Comprehensive analysis of model parameter uncertainty influence on evaluation of HVAC operation to mitigate indoor virus: A case study for an office building in a cold and dry climate

Simulation-based studies of HVAC operation to mitigate indoor virus have been conducted to understand tradeoffs between indoor air quality (IAQ) and energy consumption. However, the influence of model parameter uncertainty in these studies has not been systematically quantified, which is critical when providing guidance to building operators. To address this gap, we identify 20 model parameters for a typical medium office building system in a cold and dry climate that can influence IAQ and energy consumption for indoor virus scenarios. Next, the distributions of the parameter values are estimated from literature and a set of simulation samples for three representative days is generated that simultaneously sample all of the parameters from their distributions. Two HVAC virus mitigation strategies are studied: increased filtration using MERV 13 filters and increased ventilation, via supply of 100% outdoor air into buildings. The model parameter uncertainty leads to significant variability in the results, particularly for the IAQ because of the highly uncertain virus generation rate. Use of 100% outdoor air can be beneficial for some uncertain scenarios on the hot day, but shows less IAQ improvement and/or significant energy increases on the other days. The virus removal efficiency and pressure drop of the HVAC filter, fan efficiency, and internal heat gain are the most important parameters to determining the tradeoffs of the two strategies. The results demonstrate how this model parameter uncertainty analysis methodology can provide practical guidance to building operators.

Effect of Solidity and Aspect Ratio on the Aerodynamic Performance of Axial-Flow Fans With 0.2 Hub-to-Tip Ratio

AbstractAspect ratio and solidity play complementary roles in the aerodynamic design of axial fan rotor blades. Few studies have experimented the effect of the aspect ratio of rotor blades on the performance of low-speed axial fans or its interaction with blade solidity in terms of fan aerodynamic performance. This study examined the selection of the solidity and blade aspect ratio in the preliminary design of low-pressure industrial fans with minimized hub-to-tip ratios. The aim of this study was to make available to the fan community experimental data that allow the determination of the optimal aspect ratio for practical applications as a function of the blade solidity. Various aspects of the performance of 16 prototypes of a 315-mm-diameter propeller fan were compared. The industrial fan prototypes all had a hub-to-tip ratio of 0.2 and were derived from four baseline designs conceived to ideally achieve the same best efficiency operation with different values of the aspect ratio. In addition, the prototypes’ assemblies were conceived to allow operation with different blade counts, i.e., with different rotor solidities at a fixed blade aspect ratio. The aerodynamic performance of the fans, measured in accordance with the ISO-5801 standard, was evaluated to assess the sensitivity and trends of the fan pressure and efficiency with respect to the blade aspect ratio and solidity at fixed tip clearance. The measured effects of the aspect ratio and solidity are discussed on the basis of data available in the literature. The results of the experimental analysis were used to formulate general guidelines for the preliminary design of propeller fans with minimized hub-to-tip ratios.

Development and Application of a Mathematical Simulation Model to Evaluate Environmental Performance of Greenhouses Using Physical and Climatic Indicators

This study was conducted to determine and apply a mathematical model to simulate the environmental and climatic parameters to evaluate the performance of different greenhouses in three areas within the Khartoum North – Sudan (Date Palm Technology Company., Abu Halima Center and Khartoum University). The assessment method depends on development of a computer simulation model to generate from house physical characteristics and climate data ten environmental performance evaluation indicators (Relative moisture efficiency; Cooling effectiveness, Moisture saturation efficiency; Water consumption rate; House overall efficiency; House ventilation rate, Optimum internal temperature and internal relative humidity).The result of application of the evaluation model for nine greenhouses in three different locations in Khartoum North reveals that there is no significant differences (P = 0.05) in evaluation indicators between the three studied areas. The study concluded that additional work is needed to upgrade the mode of running greenhouse crop cultivation system with regards to: using sustainable and energy efficient cooling and ventilation technologies, adopting new techniques to conserve water and its efficient utilization, introducing properly adapted materials for high temperatures and strong solar radiation, and accessibility of technologies such as automation systems. In the current system moisture use efficiency in particular found to be lower than expected and measures to improvement are critically needed. With respect to the system efficiency and utility of fan and pad greenhouse the effectiveness of cooling system is function of internal environmental parameter (temperature and relative humidity with negative relation). The evaluation model shows that cooling efficiency tends to go up in the areas with low relative humidity.

Forced Convection during Cooling of Power Supply Box using Pulsation Flow with Piezoelectric Fan

AbstractForced convection flow of air through power supply box with piezoelectric fan of nine identical electrical devices has been numerically investigated. This work simulates a practical situation in which periodic temperature is generated in an electrical device as a result of its periodic input voltage. The finite volume method has been adopted to solve the governing equations. The effects of important parameters such as pulsation flow frequencies and temperature modulation frequency on heat transfer rates were investigated in details for Re = 500 corresponding to velocity of 0.39 m/s. The piezoelectric vibration amplitude is fixed at 0.2 and frequencies are varied in the range of [0–3] corresponding to [0–287] Hz. We have found that the time averaged Nusselt number for each electrical device depends on the pulsation frequency and heat modulation, and it is always larger than that in the steady‐state case. The results show that there exists a short band of frequencies which the enhancement of heat transfer of all electrical devices is higher than 55% compared with that of steady state. In addition, the heat transfer is maximum when heated pulsation frequency in the device is set as St = 3.0 corresponding to frequency of 58.5 Hz of input voltage. The combined pulsation flow by piezoelectric fan and heated pulsation by input voltage show vigorous heat transfer through electrical devices blocks and the heat transfer enhancement was observed in relatively narrow bands of frequencies. The efficiency of piezoelectric fan is expressed by the maximum temperature of the ninth electrical device which not exceed 80°C for time‐averaged velocity of 0.556 m/s and vibration frequency of 34.75 Hz of piezoelectric fan. The pressure drop and power pumping of piezoelectric fan are obtained for different Reynolds numbers. We found that the power loss was 4.6 times higher than for the piezoelectric fan at Re = 500. Good agreement between our numerical simulations of piezoelectric fan and experimental results available from the literature is obtained. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Acoustic preliminary design of a low-noise fan stage considering a variable-area nozzle and variable-pitch rotor blades

A low-noise low-pressure ultra-high-bypass-ratio fan stage to be implemented in the next generation of aircraft engines is described and evaluated acoustically with semi-empirical and analytical methods suited for preliminary design. As expected, good reduction potentials are observed for the jet noise and fan tonal noise components when the UHBR design is compared to current fans in service. However, concerns are identified for fan broadband noise, which are attributed to the off-design operation of the UHBR fan too close from its stability limit. By unloading the fan and thus reducing the size of the rotor wakes, the variable-area nozzle provides a substantial fan broadband noise reduction with a nozzle opened by around 15% from its design value. Alternatively, with the variable-pitch fan, closing the rotor blades by roughly 5° turns out to be an even more effective method to reduce fan noise, as the unloading mechanism is combined with a stronger tilting of the rotor wakes and a lower intra-stage flow Mach number. Opening the nozzle or closing the blades beyond the setting that provides the best fan efficiency is not recommended as the acoustic benefit progressively vanishes, whereas technical feasibility becomes more challenging. Finally, the presence of one of these systems may allow for the design of a low-solidity rotor, with a smaller contribution from the rotor wakes and thus a weaker fan noise emission.

Аналіз точності експериментального визначення ККД вентилятора з використанням вимірювачів крутильного моменту

The subject of research in this article is the processes of experimental determination of the characteristics of fans of turbojet bypass engines with a high and ultra-high bypass ratio. The goal is to substantiate the need to use a method based on the determination of torque, and the formation of requirements for the accuracy of its measurement. Tasks: determination of the relationship between measurement errors and the accuracy of determining the efficiency and air flow, analysis of the accuracy of alternative methods for organizing measurements and calculating the indicated parameters, comparative study of these methods, and the formation of recommendations for their practical use. For this, analytical methods of error analysis based on the methods of analysis of random variables are used. The following results were obtained: formulas that relate the errors in the calculation of efficiency and consumption with errors in the measured parameters (mathematical models of errors), and determine requirements to the torque measurement precision, which must determine the efficiency with a specified precision. The scientific and practical novelty of the results obtained is as follows: mathematical models of errors in determining the efficiency and flow in the fan have been formed, which relate the errors in the results of calculations with the errors in the measured parameters; because of the use of these models, experimental methods for determining the characteristics of compressors and fans have been developed; for the first time, an analytical expression was obtained that determines the requirements for the measurement error of torque to experimentally determine the efficiency of fans. It is shown that to determine the efficiency with an accuracy of 0.5 %, the accuracy of torque measurement even in the absence of other measurement errors cannot be worse than 0.5 %, and taking into account the perspective of measuring temperatures and pressures with relative standard deviations σδp = 0.02 % and σδT = 0.25 %, the standard deviation of the torque measurement error should not be more than 0.24 %.

Flow Capacity Optimization of a Squirrel Cage Fan with a New Rounded Rectangle Volute under Size Limitation

Squirrel cage fans (SCFs) are widely used in a variety of household appliances. Due to the restriction on installation size, the design of high-efficiency SCFs with high flow capacities is an important topic. In this study, we proposed a novel rounded rectangle volute profile (RRVP) for the design of compact high-flow SCFs. At first, we used computational fluid dynamics (CFD) to simulate the aerodynamic performances of three SCFs having the same impeller but different volutes, which were the common logarithmic-spiral volute profile, the cutting volute profile, and the RRVP volute at the maximum flow rate working condition. The CFD simulations indicate that the fan with RRVP volute has the highest flow rate at the maximum flow rate working condition. Then, we proposed a parameterization method for the RRVP with 16 control variables. The multiobjective evolutionary algorithm based on decomposition (MOEA/D) and Kriging model was used to optimize the aerodynamic shape of the compact SCF with an RRVP volute. Twenty-three control variables were used in the multiobjective optimization process, including the optimization of the blade angles and the impeller position. Optimization results show that the maximum volumetric flow rate of the optimal SCF with an RRVP volute increases from 147.1 cubic feet per minute (CFM) to 191.1 CFM, and the fan efficiency also increases from 32.21% to 33.5%, compared with the original SCF with the common logarithmic-spiral volute. Two main factors were found to increase the flow capacity and efficiency of the optimal SCF under strict size constrains. First, the RRVP became smooth and large, which reduced the flow loss and increased the flow cross-section; second, the eccentrically mounted impeller of the optimal fan enlarged the flow section near the outlet of the volute.