Blade Installation Angle Research Articles

Kriging surrogate model for optimizing outlet temperature distribution in low-emission combustors without dilution holes

Designing advanced combustors that operate at high temperatures and produce little pollution, especially in the absence of primary and dilution holes, is a difficult task that may bring significant challenges. In this regard, this paper introduces a Kriging surrogate model approach to optimize the outlet temperature distribution of the combustor to achieve such advanced low-pollution combustors. Building upon previous research, this study explores the effects of the swirler blade installation angle on the outlet temperature distribution of the combustor without primary or dilution holes. Traditional methods, such as the control variable method using computational fluid dynamics (CFD) for numerical simulation, are limited in application due to the complex coupling of flow, heat transfer, mass transfer, and combustion processes. In contrast, surrogate models, especially the Kriging model, offer a rapid and efficient alternative to extensive CFD simulations that provide accurate predictions and error estimates for the solution of the problem. In summary, this paper details the process of generating sample points through three-dimensional numerical simulations, develops a Kriging surrogate model through Latin hypercube sampling, and optimizes the model to identify the most uniform outlet temperature distribution achievable by adjusting the installation angle of the swirl blade. The optimal design parameters, which are quickly obtained through the Kriging model, showed a significant reduction in the overall temperature distribution function and the radial temperature distribution function by 21% and 27.14%, respectively.

CFD analysis and optimization of axial flow fans

The axial fan plays a vital role in the safe production of the mine, and in this paper, a mine axial flow ventilator is designed through numerical simulation to meet the demand of air exchange inside and outside of the mine, so as to maintain the oxygen supply of the mine and discharge the harmful gases. Finite element analysis of four structural factors of axial fan blade installation angle, number of blades, deflector plate, rotational speed, drawing fan wind pressure and rotational speed cloud diagram, calculation of axial power, by analyzing the distribution of the cloud diagram to design the shape of the fan blade, and derive the change rule of the wind pressure when changing the structure of the fan. By using gradient descent method to control the percentage of imported mass flow rate, the P-Q performance curve of the fan is obtained, which optimizes its aerodynamic performance, improves efficiency, and extends its service life.

Experimental study of the influence factors of the droplet size of rotary nozzles during manned helicopter spraying operations

The droplet size significantly affects the performance of aerial spraying operations. Thus, it is crucial to develop rotary nozzles for helicopter spraying operations and analyze the influence of droplet size. We conducted a calibration test of the nozzle rotation speed to analyze the effects of air velocity, blade installation angle, hub diameter, and blade length on the rotation speed. The results showed that the rotation speed increased with an increase in air velocity and nozzle diameter and decreased with an increase in the blade angle. The rotation speed of three types of rotary nozzles was measured in the range of 576–15 358 r/min. A high-speed wind tunnel test was conducted to determine the droplet size of the rotary nozzles at different rotation speeds, spray flow rates, and hub mesh numbers. The influence degree of the three factors on the droplet size was rotation speed > spray flow rate > mesh number. The multiple linear regression equation of the volume median diameter (VMD) of the droplet size was obtained. The droplet size obtained from wind tunnel and flight tests at 5000 and 7000 r/min was compared. The droplet size was in the range of 148.56–259.39 μm and was slightly larger under wind tunnel conditions than during the flight test. The relative width of the droplet spectrum was small for both test methods, indicating that the droplet size distribution of the three rotary nozzles was uniform. Finally, the spray nozzles were used for insect control in forest areas and achieved a control efficiency of 94.6. This study provides a reference for optimizing the operating parameters of spraying nozzles and improving the performance of helicopter-based low-volume spraying operations.

Vibration characteristics and strength analysis of two-stage variable-pitch axial-flow fan based on fluid-solid coupling method

The adjustment of the rotor blade installation angle of the two-stage variable-pitch axial-flow fan affects the surface pressure characteristics, which in turn affects the vibration characteristics of the rotor blade. In this paper, the finite element model of two-stage variable-pitch axial-flow fan is first established, and then the modal analysis of blades with aerodynamic and centrifugal loads is presented. The resonance of the blade is analyzed based on the pressure pulsation frequency domain characteristics. Finally, the equivalent stress distribution under variable blade installation angles is explored. Simulation results regarding the natural frequency show that the installation angle of the moving blade has a minimal impact on the natural frequency. In contrast, the centrifugal force load significantly affects the natural frequency of the moving blade. To ensure safety, we maintain a frequency margin of over 24 % to avoid the risk of resonance. Strength analysis results indicate that the maximum equivalent stress on the first-stage and second-stage rotor blades decreases by 43.14 MPa and 45.28 MPa, respectively. This reduction is attributed to a certain centrifugal load and a slight offset in aerodynamic loading. This research can provide guidance for the vibration control and safety research of two-stage variable-pitch axial-flow fan.

Optimization of a Multiphase Mixed Flow Field in Backfill Slurry Preparation Based on Multiphase Flow Interaction.

The paper analyzes the dynamic behavior during the preparation of cemented backfill slurry by combining the structural performance analysis of the double-shaft mixer and the Euler multiphase flow field computational fluid dynamics model. Considering the interaction between phases and gas phase disturbances, the transient kinetic parameters and the interaction between gas and liquid phases were introduced. According to the modified lift model, the user-defined function of the net lateral lift coefficient and the turbulence energy equation was adjusted. Taking the parameters of flow field velocity, gas phase mixing, uniformity, and turbulent energy dissipation as the evaluation indexes of the mixing effect, the double-shaft mixer at a rotation velocity of 45 rpm and with a blade installation angle of 25° is the optimal design in this study. Experimental tests were carried out and confirmed that the refined two-fluid model of interphase interaction can provide a basis for the performance evaluation of material mixing equipment.

Effects of the swirler on the performance of an advanced vortex combustor

Trapped vortex combustors have garnered significant interest due to the cavity vortex's insensitivity to flow disturbances. Swirling combustion is also highly desirable due to its excellent mixing performance. This study explores the potential of combining vortex combustors with swirling combustion under reacting conditions. Steady-state Reynolds-averaged Navier–Stokes equations are solved through three-dimensional numerical simulations. The results demonstrate a significant improvement in combustion efficiency, from 55% in original vortex combustor to over 99% in swirling vortex combustor, and fuel–air mixing effectiveness. The spatial spiraled vortex structure forms in the cavity and behind the blunt body when the swirler is used. The position of the blunt body influences the shape of the cavity vortex, with a round vortex structure forming when the cavity length to the total combustion chamber length ratio is around 0.2. When the radius of the blunt body to the radius of the combustion chamber, varying from 0.2 to 0.7, is 0.6, two main recirculation zones can be created in the model. Increasing the swirling number results in a larger recirculation zone in the cavity, with an elongated recirculation area appearing behind the blunt body at a blade installation angle of 60°, corresponding to the swirling number is 1.251. However, an excessively high swirling number leads to uneven pressure distribution in the outlet. These findings provide novel insights for advanced vortex combustor research and optimization.

Development and Performance Test of a Simulation-Based Tractor-Attachable Wind-Blast-Type Onion Stem Cutting Machine

Stem cutting process of many steps in onion farming involves the least supply of machines. Machines developed in foreign countries are not suitable owing to the geographic characteristics of Korea; it is necessary to develop customized machines. Therefore, in this study, a tractor-attachable blast-type onion stem cutting machine was developed to address these issues. To determine the installation angle of a detachable blade with a 300-mm length, 115-mm width, 5-mm thickness, and a cutting angle of 45° at the tip, we compared the simulation results with the analysis results obtained by fabricating a simple experimental device. Despite small differences in values, the R2 between the two results was found to be 0.99; if using a regression equation, they could be adequate for use in estimation. Moreover, by measuring the motor power consumption, wind speed, and high-speed camera shooting, the stem was raised, regardless of its water content, when the installation angle was greater than 30°. Motor power consumption could also be reduced when the installation angle was 30° rather than 40°. Therefore, the optimal cutter blade installation angle for the tractor-attachable blast-type onion stem cutting machine was confirmed to be 30°. The developed machine was tested at various rotating speeds. The best performance was obtained when the test was repeated thrice at a driving speed of 0.4 m/s. The remaining onion stem length averaged 9.98 cm, the standard deviation was 4.72 cm and the stem cutting rate was 96.8%.

Optimization and validation of blade parameters for inter-row weeding wheel in paddy fields.

The performance of existing rice-paddy weeding machines is not optimal. In this study, the influence of the installation angle of the weeding-wheel blade on cutting resistance and soil-slippage ability was analyzed. The optimal blade angle of the weeding wheel (i.e., the angle at which the resistance to the weeding wheel is minimal and the disturbance speed of the soil maximal) was shown to be< 20°; numerical simulation showed the actual optimal value to be 0°. Different weeding depths (30, 40, and 50 mm), rotation speed of weeding wheel (120, 180, and 240 r/min), and weeder forward speeds (0.3, 0.6, and 0.9 m/s) were used as test factors, and the rates of seedling injury and weeding were used as performance-evaluation criteria to optimize the machine in a secondary orthogonal-rotation combination test. Field experiments showed that the weeding wheel can exhibit optimal working performance under the operating conditions of weeding depth of 39 mm, rotation speed of 175 r/min, and forward speed of 0.6 m/s. The seedling injury and weeding rates were 4.4% and 88.2%, respectively, which were consistent with the numerically predicted results and met the agronomic requirements. This study provides a technical reference for the improvement of paddy-field weeding components.

Numerical simulation of aerodynamic noise for the two-stage adjustable-blade axial-flow fan

In this paper, a three-dimensional calculation model of a two-stage adjustable-blade axial-flow fan is established and verified by grid independence and numerical accuracy. The pressure distribution and sound power-level distribution characteristics of the blade surface are explored with variable blade installation angles. Based on the Q-criterion, the study reveals the spatial distribution of the channel and trailing-edge shedding and channel vortexes in the flow field. Then, the evolution laws of the fan's aerodynamic noise sound pressure level are also investigated, and its frequency domain characteristics with variable blade installation angles are obtained. The results show that when the rotor blade installation angle is −5°, the front-guide vane matches the installation angle of the first-stage impeller. The upper limit of sound power level is the smallest with variable blade installation angles, which is 123.56 dB. Meanwhile, the number and size of vortex structures in the front-guide vane area are the smallest, and the turbulent flow in the flow field is moderate. As the moving blade installation angle is deflected from −10° to 10°, the total sound pressure level of aerodynamic noise at each component of the fan first decreases and then increases. The minimum value is 121.40 and 128.40 dB at the inlet and outlet when the blade installation angle is −5°. In addition, the number of eddies periodically shed in the fan flow field is the least. This research can supply technical support for the noise reduction of the two-stage adjustable blade axial fan.

Liquid-vapor two-phase flow in centrifugal pump: Cavitation, mass transfer, and impeller structure optimization

Computational fluid dynamics (CFD) has been widely used to model the internal flow field of centrifugal pumps to analyze cavitation phenomena. However, accurate determination of cavitation in pumps remains a challenge. In this study, liquid-vapor two-phase flow in centrifugal pump at different conditions and impeller structural parameters were studied numerically and experimentally. Cavitation multiphase unsteady model was proposed to simulate the flow field in the centrifugal pump by CFD method, and an experimental platform was set up to obtain cavitation performance results. The simulation data were validated with experiment and good consistency was achieved. This study investigated the mass transfer and cavitation behavior of centrifugal pumps under various conditions and customizes a simulation process to obtain the optimal combination of impeller blade number, blade wrap angle, and blade installation angle, which was expected to provide helpful insights into the structural optimization design of centrifugal pumps with good cavitation resistance.

Mechanical property analysis of shaft tubular pump rotor with different blade angle based on fluid-structure interaction

Abstract Shaft tubular pump is widely used in large and medium-sized pumping stations with ultra-low head. But occasionally the blade cracks or even breaks, which seriously restricts the safe and stable operation of the pump station. In order to obtain the mechanical properties of the pump rotor with different blade installation angles, the fluid-structure interaction numerical simulation method is applied to analyze the structure of the pump rotor. Based on the SST k-ω model and the structured grid of the whole flow field, the three-dimensional numerical simulation of the internal flow field of the pump device is carried out by using CFX, and the reliability of the simulation is verified by model test. Then, the static analysis and modal analysis of the pump rotor structure under different working conditions are carried out by using Workbench. From the results, it can be found that the axial force increases with the increase of blade installation angle at a same flow rate. And at a same flow rate, the maximum deformation and equivalent stress increases with the increase of the blade installation angle. Finally, the change of the blade installation angle mainly affects the third and sixth order frequency which are only showed as blade vibration. Therefore, all of these results indicate that the blade installation angle has obvious influence on the mechanical property of the rotor of shaft tubular pump.

PARAMETER OPTIMIZATION OF WHOLE-STRAW RETURNING DEVICE BASED ON THE BP NEURAL NETWORK

To solve the poor fitting degree of errors in multiobjective parameter optimization and low accuracy, a multiobjective optimization method based on a BP neural network was proposed. By taking the 1ZT-210 type whole-straw returning device as the research object, a BP neural network model on power consumption, straw returning rate and the influencing factors was obtained. By optimizing the model by the proposed method, the optimal parameter combination of the test factors was as follows: the advancing speed of the device was 0.65 km/h, the blade roll rotating speed was 210 rpm, the blade installation angle was 55o, the minimum power consumption was 9.82 kW and the maximum straw returning rate was 93.23%. Under such test conditions, the minimum power consumption was 10.75 kW, and the straw returning rate was 92.46%, which were all better than those obtained by the regression analysis method. Finally, a verification test was conducted on the results of BP neural network optimization. The power consumption of the test was 10.04 kW, the absolute error was 0.22 kW and the relative error was 2.24%. For a straw returning rate of 93.11%, the absolute error was -0.12% and the relative error was 0.13%. The test results indicated that the optimization method was feasible.

Optimization of the Stirring Blade Structure of the Pumping Unit Based on the Improvement of Concrete Suction Efficiency

In this paper, a discrete element method (DEM) is used to simulate the suction process of fresh concrete in the pumping system, and the influence of the stirring blade on the suction is explored. The Hertz‐Mindlin with JKR Cohesion contact model is used to establish the DEM model of fresh concrete, and the suction work is realized by an API function of DEM, and the movement of particles in the suction cylinder can be completed smoothly. The changes of the concrete flow field during the suction process are further studied, and the influence mechanism of the stirring blade on the suction process is explained. A numerical simulation scheme is designed to explore the influence of the rotation speed, installation angle, and edges distance of the stirring blade on the suction efficiency and the stirring resistance torque, and the structure of the stirring blade is optimized according to the influence law. The simulation results show that the stirring resistance torque of the optimized stirring blade is reduced without the suction efficiency of the pumping system reduced, and the stirring energy consumption of the pump suction is reduced.

Optimal design of radial inflow turbine for ocean thermal energy conversion based on the installation angle of nozzle blade

Ocean Thermal Energy Conversion (OTEC), as a new type of renewable energy, has huge development potential. Turbine is the most critical component in the ocean thermal energy conversion system, which directly determines the performance and energy conversion efficiency of the system. Therefore, the optimal design of turbines is very important to improve the efficiency of ocean thermal energy conversion. Based on the full consideration of the small temperature difference application characteristics of ocean thermal energy conversion and the special thermophysical properties of organic working fluids, this paper designs an ammonia working centripetal turbine with a power of 100 kW for OTEC applications, and then analyzes the effect of different geometric parameters on turbine performance. At the same time, the key parameters of the turbine are optimized based on full three-dimensional CFD numerical simulation analysis. It's shown that the nozzle blade installation angle has a very important impact on the performance of the turbine. Through optimization, when the nozzle blade installation angle reaches 30.5°, the efficiency is 91.77%, which is 6.25% points higher than the design value. The internal flow field performance is the best without obvious shock wave and reverse vortex phenomenon, which further improves the efficiency of the turbine and improves the internal flow.

Research on aerodynamic performance and noise reduction of high-voltage fans on fuel cell vehicles

Due to the much higher cooling requirements of fuel cell vehicles, 350-Volt high-voltage fans are adopted instead of traditional 12-volt cooling fans, generating more aerodynamic noise. This paper is aimed at studying the aeroacoustic optimization methods of high-voltage fans on fuel cell vehicles on the basis of ensuring aerodynamic performance. The flow field and sound field characteristics of a high-voltage fan assembly are solved and analyzed by numerical simulation methods. The fan outer ring structure, blade installation angle, and circumferential blade spacing are adjusted to optimize the fan performance. Then, a bench test is conducted to verify the optimization results of the high-voltage fans. Under the premise of ensuring the same aerodynamic performance, the optimized fans can achieve a noise reduction of 1–1.5 dB at each speed. In order to enhance the optimization effect, an optimal design strategy of the surrounding layout parameters of a dual fan system is developed. Four key positional parameters between fans and surrounding components are selected, the flow rate and the sound pressure level of the entire fan system are used as evaluation indexes. According to the response surface method, a Box-Behnken test is designed and the quadratic regression agent model is adopted to construct relationships between fan performances and boundary parameters. A comprehensive evaluation function of fan performance is proposed and solved to obtain the optimal layout strategy of the dual fan system. The flow rate of the optimized fan system receives an increase of 12.8%, and the noise index shifts down by 0.98 dB. The proposed methods can provide reference significance for the design and optimization of high-voltage fans with low noise and high aerodynamic performance.

Effect of the rotor blade installation angle on the structure-borne noise generated by adjustable-blade axial-flow fans

The effect of rotor blade installation angle on the structure-borne noise of adjustable-blade axial-flow fans is analyzed based on the fluid–solid coupling method. The co-simulation environment ANSYS Workbench is adopted to perform one-way fluid–solid coupling analysis. Following this, the properties of the flow field and noise field with different installation angles are simulated. The flow field simulation results reported significant vorticity near the rotor and stator, and a larger installation angle may cause higher pressure fluctuation. The sound field results showed that the frequency spectrum characteristics for the sound pressure level and the sound power level are almost the same while the installation angle changes from −8° to 8°, and the peaks of frequency spectrum occur at the blade passing frequency and its harmonics. The total sound pressure level (TSPL) and the total sound power level (TPWL) all show increasing trends ranging from −8° to +8°. The maxima of TSPL and TPWL reach 134.1 and 176 dB, while their minima reach 123.1 and 163 dB, respectively. Thus, reduction of the installation angle can reduce the structure-borne noise. Besides, the structure-borne noise generated by adjustable-blade axial-flow fans is low-frequency noise, which lies in the range of 0–500 Hz.

Aerodynamic design and acoustic effect study of key geometric parameters of a sirocco fan

A sirocco fan (forward-curved centrifugal fan), including impeller blades and volute, is designed, and the empirical value ranges of several significant design parameters are discussed and summarized fromthe perspective of both aerodynamics and practical structure. Unsteady-flow numerical simulation and radiated sound-field calculation by indirect boundary element method are combined to evaluate its aerodynamic and acoustic performances. Both the discrete noise source from the rotating impeller and broadband noise source from the volute are considered. Obvious flow separation occurs in the flow passage of impeller blades due to large angle of attack, and the tongue region is the major noise source area due to the small impeller-tongue gap. Therefore, parametric studies for blade installation angle and impeller-tongue gap are performed. Analyses of flow- and sound-field indicate that appropriate reduction of blade geometry incidence angle weakens the flow separation, thereby improving both the aerodynamic and acoustic performances, and reasonable increase of the impeller-tongue gap has a remarkable noise reduction effect for the major noise source area near the volute tongue. The optimized sirocco fan meets the requirement of the industrial project, i.e., the far-field A-weighted sound power level lower than 64.0 dB(A), and achieves larger volume flow rate and total pressure rise. The results also imply that fast steady-flow numerical simulation result is indicative of the acoustic performance to some extent if the acoustic evaluation is urgent. Furthermore, optimization of the key structural parameters in the stage of design is preferable in practical engineering, instead of taking follow-up noise reduction measures.

A machine-learning approach to predicting the energy conversion performance of centrifugal pump impeller influenced by blade profile

Centrifugal pump is a kind of energy conversion machine for fluid delivering. It transfers the mechanical energy of impeller to the potential and kinetic energy of fluid. As a key factor in influencing the energy conversion performance of centrifugal pump, blade profile design is crucial. Traditional design concepts have ideal assumptions. To have a better design guidance, machine-learning based on neural network is used in this study. A typical centrifugal pump with simplified blade profile is numerically studied with experimental validation for a better discussion. Statistical results show that, for the high dimensional nonlinear relationship between blade angle and performance of centrifugal pump, neural network can adapt to this complex correlation better. The blade installation angle at leading-edge ( βLE′) and trailing-edge ( βTE′) and the wrap angle (Δ θ′) has significant correlation with the performance including pump head H, pump efficiency η, impeller head Himp, impeller efficiency ηimp and volute loss Δ Hvol. The influence level of blade angle follows the high-to-low order of Δ θ′, βLE′ and βTE′. Determination of blade profile can be done for improving the energy conversion efficiency. Optimal blade profiles have higher βLE′ and Δ θ′ with better flow-control ability. Compared with the blade parameters of the initial pump, the blade profile with the best centrifugal pump efficiency is the best βLE′ increased by 1.926°, Δ θ′ increased by 9.858°, Optimization of impeller efficiency βLE′ increased by 1.855°, Δ θ′ increased by 9.421°. Computational fluid dynamics indicate the elimination of vortex in impeller after optimal selection. Then, βTE′ and Δ θ′ are found influential in aggravating the circumferential flow component in this special circular-volute with generating higher loss. βTE′ has a positive correlation with impeller head which suits traditional theory. In general, the machine-learning using neural network is effective in determining blade profiles for enhancing the performance of centrifugal pump.

Energy harvesting efficiency analysis of counter-rotating horizontal-axis tidal turbines

ABSTRACT In this paper, a new design scheme for counter-rotating horizontal-axis tidal turbines (CRHATTs) is introduced using blade element momentum (BEM) theory. The coordinated working performance between rotor and generator of the CRHATT are analysed by experimental and CFD methods. The effects of the key parameters on the energy harvesting efficiency of the CRHATT are studied in detail. The study indicates the existence of the optimal rotor solidity (σ) combination and blade installation angle (γ) combination for dual rotors to reduce the power coefficient (C p ) deviation of the dual rotors. The distance between dual rotors (L) is suggested to be set as about 0.225D, which can maximise the C p of the CRHATT. Finally, the hydrodynamic performance of the flow field is carried out to verify the reliability of the CRHATT design. The results presented in this paper may serve as a reference in the design of CRHATTs in practical engineering.

Multiobjective Hydraulic Design and Performance Analysis of a Vortex Pump Based on Orthogonal Tests

We design optimization on the overall blade structure of a vortex pump conducted by using the orthogonal test method to clarify the matching relationship of impeller and casing structures and then improve the hydraulic performance of the vortex pump. Based on two different impeller structures of forward-deflecting (denoted as R1 − F2) and backward-deflecting (denoted as F1 − R2), key parameters describing the impeller structure are calculated through optimization for the objective function of hydraulic efficiency by means of orthogonal tests and computational fluid dynamic simulations. Optimization computations show that the forward-deflecting blade impeller is superior to the backward-deflecting one. Model test of the optimized vortex pump is carried out calculating the error from the comparison of pump efficiencies calculated by model test and numerical simulation is calculated to be less than 6%. The experimental verification shows that the flow simulation has some errors. The weight of structure parameters such as the blade installation angle (α), the blade deflecting angle (β), the position of blade deflecting point (L), the radius (r) of smoothing arc at the deflecting point, the wedge type (W) of blade, to the lift head, the flow rate, and the efficiency of the pump is investigated, through multiparameter optimizations. Visualization observation of flows in the model pump consisted of a back-placed impeller and a front vaneless chamber is further performed. The characteristic of vortex formation predicted by flow simulation agrees with the result of visualization observation. The above results demonstrate that the optimum impeller type of vortex pump is forward-deflecting blade impeller. The optimum combination of the key structure parameters is that the deflection angle of the blade inlet (α) equals 30°, the position of blade deflecting point lM = 2/3 L, the chamfering radius (r) at the deflecting point r = 3 mm, and the best wedge type is axial deflecting blade.