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Copyright of Nonferrous Metals (Extractive Metallurgy) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

When using Monte Carlo simulation involving repeated finite element analysis (FEA) to perform fatigue reliability evaluation for an impeller, a variety of uncertainties should be considered to ensure the comprehensiveness of fatigue predictions. These uncertainties include the aleatory uncertainty from the geometric, material and load condition, and epistemic uncertainty from the parameters of the physics‐of‐failure (PoF) model to yield fatigue prediction. However, the latter uncertainty is often ignored in fatigue reliability analysis. And the reliability assessment will become computationally unaffordable and inefficient when there are many random variables involved, as an enormous amount of FEAs are demanded. To address this problem, a Whale Optimization Algorithm‐extreme gradient boosting (WOA‐XGBoost) surrogate model is developed, based on relatively few FEA results obtained using a Latin hypercube sampling (LHS). Its strengths lie in the interpretability of the design variables and effective determination of fine‐tuned hyperparameters. A case study on an impeller is conducted considering uncertainties from 11 input variables, where an efficient XGBoost model with an R2 greater than 0.93 on test set is established using 400 samples from practical FEAs. In addition, the importance analysis indicates that elasticity modulus and density play the greatest impact on the maximum strain, showing a combined importance of 82.3%. Furthermore, the reliability assessment results under fatigue parameter derived from the Median method tend to be more conservative compared to those obtained from the Seeger method. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Considering the real stress and deformation state of impeller during the operation of centrifugal pump, the fluid-structure coupling numerical simulation of impeller of centrifugal pump model was carried out based on the software platform of Ansys Workbench and the computational fluid dynamics analysis software CFX. The strength of impeller of centrifugal pump under the combined action of centrifugal force and CFD pressure load was calculated. The position of the maximum stress on the impeller under the action of cyclic alternating stress during rotation is determined. Finally, nCode Designlife software was used to predict the fatigue life of the impeller. The results show that the maximum stress is located at the interface between the blade outlet edge and the cover plate, and the cyclic cyclic stress is the main cause of the fatigue damage of the impeller. The impeller meets the design of infinite life fatigue strength, and the impeller has no risk of fatigue failure. [ABSTRACT FROM AUTHOR]

A significant part of the compressor fleet in Russia consists of foreign-made centrifugal and screw compressors, which, with operating time and depreciation, require repair according to regulations or modernization due to changed technological operating conditions. The supply of spare parts needed for repairs has become more complicated due to the rise in cost or lack of logistics. This leads to the problem of maintaining the compressor equipment in working order or its downtime. The manufacture of spare parts is problematic due to the lack of design documentation from operating organizations. The offer of reverse engineering services for spare parts and compressor assemblies by specialists of JSC «NIIturbocompressor n. a. V. B. Shnepp» makes it possible to improve and solve the problem of maintaining the effective condition of foreign equipment. At the same time, the article describes the problems that arise during reverse engineering of rotors of centrifugal and screw compressors, the spatial profile of impellers and fluid film bearings. The main points contributing to the successful completion of reverse engineering tasks are indicated, the accuracy of 3D scanning is determined, and methods for setting nominal dimensions and deviation tolerances are presented.

The paper presents an analysis of semi-open centrifugal impellers of a three-stage multi-shaft compressor. A 3D-scanning of the geometry of the impellers is carried out, a CFD calculation is carried out at the design operating mode of the compressor, and the results obtained are analyzed. Problems have been identified with the second stage impeller. Next, the geometry of all three impellers is optimized using Ansys CFX software, an improvement in efficiency and an improvement in the flow pattern are obtained.

To explore the structural dynamic characteristics of the impeller and shaft system of the axial flow pump as turbine, the variation law of impeller transient equivalent stress, deformation, and the impeller and shaft system mode are analyzed by the transient fluid-structure interaction method. Findings indicate that the equivalent stress is centralized at the blade root around the hub and tends to decrease as it moves towards the shroud. The maximum equivalent stress at 1.0Qbep and 1.1Qbep is 1.26 times and 2.0 times higher than that at 0.8Qbep. Blade deformation is significantly influenced by flow rate. The maximum deformation of the blade at 1.0Qbep and 1.1Qbep is 1.6 times and 3.6 times higher than that at 0.8Qbep. The impeller and shaft system with prestress in dry mode has an average natural frequency of the first 10 orders that is 16.7 Hz higher than without prestress. However, with the fluid adding mass and flow damping, the average natural frequency of the first 10 orders of the impeller and shaft system in wet mode is reduced by 278.08 Hz compared with dry mode. In fact, the impeller and shaft system of the axial flow pump as turbine is not prone to vibration.

With the urgent need of energy saving and consumption reduction in today's world, the topic of increasing the energy conversion efficiency of ventilation fans has been attracted a lot of attentions, it has become a key issue in the field of ventilation. The understanding on the evolution mechanism of irreversible energy loss in impeller is the premise and basis for realizing the efficient energy conversion of ventilation fans. At present, the irreversible energy loss mechanism in impeller is still lack of research. Therefore, the internal flow field of the contra-rotating axial fan at different flowrates is obtained by numerical simulation and experimental methods. A theoretical model of irreversible energy loss in impeller of ventilation fans is established based on entropy production theory, and the relationship between the irreversible energy loss in impeller and the flow field parameters is clarified. A quantitative analysis is conducted on different types of energy loss in impeller, and the spatial evolution law and causes of energy loss are clarified by combining with the flow characteristics in impeller. The results show that the entropy production method is reliable in calculating the irreversible energy loss in impeller. Direct viscous dissipation loss and wall friction loss are important components of energy loss, while turbulent dissipation is the main cause of energy loss, accounting for 60% to 80% of the total energy loss. For the front impeller, the energy loss caused by turbulent dissipation reaches the minimum at 1.0 QBEP, while the energy loss of the rear impeller increases with the decrease of flowrate. The energy loss is mainly concentrated in the region of Span=0.6−1.0, reaching 70% of the total energy loss at optimal flow condition. The spiral vortex caused by blade tip leakage flow and overflow of blade leading edge, backflow in impeller, flow separation at blade pressure and suction surface, and blade trailing edge wake will cause energy loss. The high energy loss region caused by flow separation and wake is relatively small, and the energy loss is relatively limited. However, the vortex and backflow significantly affect the flow in impeller, ultimately leading to a significant energy loss in the region near the blade tip. The research results can provide a reference for the evaluation of irreversible energy loss of ventilation fans.

Abstract Multi-grain hole-forming sowing and uniform hole spacing are important agronomic requirements for precise hole-direct seeding of rice.This paper designs a kind of impeller type seed guiding device. The main structural parameters of the impeller seed guide device were analyzed by constructing the kinematics model of the rice seed in the impeller seed guide process. The experiment analysis were carried out with the long-grain rice variety Chuangliangyou 4418 as the seeding object. The optimal structural parameter combination of seeding-guiding device was determined as inner impeller radius 56 mm, blade offset angle 11° and seeding angle 36°. On this basis, the seeding performance test of different seed guiding devices of internal suction seed-metering device was carried out by using rice seeds with different external dimensions. The test results show that the impeller has better cavitation and hole spacing uniformity than the seed guide tube. The average hole diameter is not higher than 21.7 mm, the qualified rate of hole diameter is not lower than 96.1%, and the coefficient of variation of hole spacing is not higher than 10.1%. Compared with the seed guide tube, which is increased by 32%, 16% and 34% respectively, and the average hole distance is about 200 mm in theory.

In this paper, the cyclic elastic–plastic behaviors of the centrifugal steam compressor impeller (CSCI) structure under practical operating conditions are discussed employing the linear matching method (LMM). The three‐stage strategy of the LMM is employed to determine the shakedown and ratchet boundaries by conducting a series of iterative direct steady cyclic analysis, and based on this, the load regions corresponding to different types of damage behavior that may occur during the operation are identified. Computational results reveal slight contraction in the structural response diagram when considering actual material constitutive relationships, compared to ideal elastic–plastic models. Meanwhile, by integrating the unified ratchet and fatigue program with fatigue experimental data, a series of constant low‐cycle fatigue life curves has been presented for different service conditions. Furthermore, a comparison with detailed step‐by‐step inelastic analyses confirms the applicability and great efficiency of the LMM in practical engineering problems. Highlights: The cyclic elastic‐plastic behavior of impeller were investigated using the three‐stage procedure.The effect of temperature‐dependent and strain hardening on structural response of impeller were evaluated.The constant low‐cycle life fatigue curves of the impeller structure were generated.The applicability and great efficiency of linear matching method have been confirmed. [ABSTRACT FROM AUTHOR]

To explore the structural dynamic characteristics of the impeller and shaft system of the axial flow pump as turbine, the variation law of impeller transient equivalent stress, deformation, and the impeller and shaft system mode are analyzed by the transient fluid-structure interaction method. Findings indicate that the equivalent stress is centralized at the blade root around the hub and tends to decrease as it moves towards the shroud. The maximum equivalent stress at 1.0 Q bep and 1.1 Q bep is 1.26 times and 2.0 times higher than that at 0.8 Q bep. Blade deformation is significantly influenced by flow rate. The maximum deformation of the blade at 1.0 Q bep and 1.1 Q bep is 1.6 times and 3.6 times higher than that at 0.8 Q bep. The impeller and shaft system with prestress in dry mode has an average natural frequency of the first 10 orders that is 16.7 Hz higher than without prestress. However, with the fluid adding mass and flow damping, the average natural frequency of the first 10 orders of the impeller and shaft system in wet mode is reduced by 278.08 Hz compared with dry mode. In fact, the impeller and shaft system of the axial flow pump as turbine is not prone to vibration. [ABSTRACT FROM AUTHOR]

Stall, a complex flow phenomenon in centrifugal pump, plays a crucial role in pump safety and stability under part-load conditions. In this paper, a verified numerical simulation method is employed to analyze the three-dimensional flow field under the stall inception conditions. The results reveal the initial stall vortex occurs near the Q=0.7Qd condition in the prototype impeller. Based on stall formation mechanism, the high-velocity fluid near the blade pressure side is sucked into suction side of next impeller channel by setting a groove near the blade leading edge. This jet flow can prevent the narrow vortices near the impeller shroud from moving towards the blade suction side, thereby suppressing the formation of stall vortex. By comparing the effects of different groove locations, directions, and sizes on stall vortex control, the optimal groove width is determined to be approximately 1mm. Compared with the prototype impeller, the grooved impeller can completely eliminate the stall vortex and significantly reduce pressure pulsation under part-load conditions. Moreover, the head of grooved impeller is increased by nearly 15% under Q=0.6Qd condition, and the potential suppression mechanism is also explained. Based on the stall formation mechanism, this paper puts forward an effective stall control method, which delays the stall inception significantly. [ABSTRACT FROM AUTHOR]

Understanding the flow instabilities encountered by the turbocharger compressor is an important step toward improving its overall design for performance and efficiency. While an experimental study using Particle Image Velocimetry was previously conducted to examine the flow field at the inlet of the turbocharger compressor, the present work complements that effort by analyzing the flow structures leading to stall instability within the same impeller. Experimentally validated three-dimensional computational fluid dynamics predictions are carried out at three discrete mass flow rates, including 77 g/s (stable, maximum flow condition), 57 g/s (near peak efficiency), and 30 g/s (with strong reverse flow from the impeller) at a fixed rotational speed of 80,000 rpm. Large stationary stall cells were observed deep within the impeller at 30 g/s, occupying a significant portion of the blade passage near the shroud between the suction surface of the main blades and the pressure surface of the splitter blades. These stall cells are mainly created when a substantial portion of the inlet core flow is unable to follow the impeller's axial to radial bend against the adverse pressure gradient and becomes entrained by the reverse flow and the tip leakage flow, giving rise to a region of low-momentum fluid in its wake. This phenomenon was observed to a lesser extent at 57 g/s and was completely absent at 77 g/s. On the other hand, the inducer rotating stall was found to be most dominant at 57 g/s. The entrainment of the tip leakage flow by the core flow moving into the impeller, leading to the generation of an unstable, wavy shear layer at the inducer plane, was instrumental in the generation of rotating stall. The present analyses provide a detailed characterization of both stationary and rotating stall cells and demonstrate the physics behind their formation, as well as their effect on compressor efficiency. The study also characterizes the entropy generation within the impeller under different operating conditions. While at 77 g/s, the entropy generation is mostly concentrated near the shroud of the impeller with the core flow being almost isentropic, at 30 g/s, there is a significant increase in the area within the blade passage that shows elevated entropy production. The tip leakage flow, its interaction with the blades and the core forward flow, and the reverse flow within the impeller are found to be the major sources of irreversibilities. [ABSTRACT FROM AUTHOR]

Taking compressor impeller with pressure ratio less than 3 as research object, a prediction method of residual life of compressor impeller was proposed. Considering the action of "inertial" load centrifugal force, finite element method (FEM) technology and sub-model technology were used to comprehensively analyze the mechanical quantities, such as blade stress, and the hot spot stress location of compressor impeller was determined. Crack orientation was determined according to maximum principal stress criterion. The linear elastic fracture mechanics (LEFM) based on FEM and Forman-Newman-de Koning (FNK) model were used to investigate the whole process of crack growth, including stable growth and instability growth stages. The crack growth law and residual life of impeller at different rotate speeds were given. The results show that with the increase of rotate speed, the stress intensity factor (SIF) of initial crack front increases in a quadratic power law, the critical length decreases linearly, and the residual life decreases nonlinearly. The crack grows along the height of blade and then fractures after a deflection of about 90 degrees to the outer edge of blade. The obvious deflection of crack is the sign of crack transition from stable growth stage to instability growth stage. The life of crack in the instability growth stage can be neglected compared with that in the stable growth stage. The analysis method proposed in this article can provide a basis for the damage tolerance evaluation of compressor impeller, and can also provide a reference for maintenance work. [ABSTRACT FROM AUTHOR]

As a high-performance workpiece, an impeller must ensure both dimensional accuracy and aerodynamic performance. A five-axis machine tool has various geometric errors, which seriously influence the impeller processing quality, hence it is crucial to identify the key error items and compensate them. In this study a joint sensitivity analysis method for the key geometric errors of a five-axis machine tool is proposed that focuses on the aerodynamic performance of an impeller. First, a volumetric error model and an aerodynamic performance model were built, representing the relationships between the tool center point volumetric errors and each of the geometric errors and the impeller aerodynamic performance. Then, the improved Sobol method was implemented to compute the total sensitivity index of each variable in the two models, from which two sensitivity distribution matrices were obtained. Finally, a joint sensitivity analysis was performed on these two matrices to identify the key geometric errors. Experiments were executed to ascertain the impact of compensation strategies on the impeller aerodynamic performance. The results showed that after compensating for the key errors, the total pressure ratio and isentropic efficiency loss rate of the impeller are reduced by 72.2% and 55.8% under the design parameters. The significant improvement in the aerodynamic performance of the impeller demonstrates the accuracy of key geometric error identification.

Stall, a complex flow phenomenon in centrifugal pump, plays a crucial role in pump safety and stability under part-load conditions. In this paper, a verified numerical simulation method is employed to analyze the three-dimensional flow field under the stall inception conditions. The results reveal the initial stall vortex occurs near the Q=0.7Qd condition in the prototype impeller. Based on stall formation mechanism, the high-velocity fluid near the blade pressure side is sucked into suction side of next impeller channel by setting a groove near the blade leading edge. This jet flow can prevent the narrow vortices near the impeller shroud from moving towards the blade suction side, thereby suppressing the formation of stall vortex. By comparing the effects of different groove locations, directions, and sizes on stall vortex control, the optimal groove width is determined to be approximately 1mm. Compared with the prototype impeller, the grooved impeller can completely eliminate the stall vortex and significantly reduce pressure pulsation under part-load conditions. Moreover, the head of grooved impeller is increased by nearly 15% under Q=0.6Qd condition, and the potential suppression mechanism is also explained. Based on the stall formation mechanism, this paper puts forward an effective stall control method, which delays the stall inception significantly.

With the development of modern fluid machinery, the energy density of pumps is gradually being improved, and at the same time, higher demands are being placed on the cavitation performance, hence the introduction of the inducer and centrifugal impeller to form a dynamic–dynamic series structure. However, there are strict constraints on the axial size of pumps in fields such as firefighting and aerospace. The traditional empirical formula no longer satisfies the need to fit the axial dimensions between the induced wheel and the impeller at high velocities. Therefore, based on the wave-piercing theory, the drag reduction coefficient is introduced to explore the optimal axial fit size from the perspective of energy characteristics. This paper focuses on the influence of the inducer's wake on the energy characteristics of downstream impellers, and conducts the following research: by adjusting the axial matching dimensions between the upstream inducer and the centrifugal impeller in the initial model, ten sets of axial distance models with matching dimensions of KD are designed, and the drag reduction coefficient is embedded to determine the optimal axial distance. The results show that the optimal axial distance is 0.2D, which is far lower than the axial distance value of 0.42D obtained from the traditional empirical formula for axial matching dimensions. Meanwhile, this paper uses tangential velocity, the inlet flow angle of the impeller, entropy production theory, and other indicators to analyze the internal energy loss of the high-speed vehicular fire pumps one by one. All of them confirm that the impeller in the high-speed vehicular fire pump has the lowest energy loss and optimal performance at an axial distance of 0.2D. Specifically, at this axial distance, the head can reach 259 m, and the hydraulic efficiency is as high as 83.62%. Thus, the feasibility of determining the axial placement of the impeller using the drag coefficient is validated. This research provides new insights into determining the axial coordination dimensions between the inducer and the impeller. [ABSTRACT FROM AUTHOR]

The large CSD mud pump impeller is seriously worn in medium-coarse sand conveying, resulting in a decrease in the performance of the mud pump and an increase in fuel consumption. According to the current status of determining the timing of impeller replacement through the vibration of mud pump during construction, this paper analyzes the efficiency change characteristics of mud pump in different wear stages, compares the cost input, capacity improvement and overall economic benefits of pump impeller replacement under different cumulative conveying volumes, and provides guidance for optimizing mud pump impeller replacement strategies. The results indicate that when the impeller is replaced at 2millionm3 compared with 3 million m³ for a 10 million m³ project, 80.1 tons of fuel can be saved, and when the cumulative conveying volume is 2.5million m³, it is recommended to replace the impeller after reaching3 million m³ or scrapping. The replacement strategy of the impeller of the mud pump can significantly reduce construction costs, and achieve energy conservation and emission reduction. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the influence of various parts of the structure of a wet dust removal fan for mining (including the number of driving impeller blades, the airfoil of the driving impeller blades, the number of driven impeller blades, the rear guide vane, the swirl guide vane, and the length of the outlet section) on dust removal performance, a wet dust removal fan for mining was modeled according to different structural parameters. The internal flow field and dust removal of the fan were then numerically simulated using the Computational Fluid Dynamics (CFD) method. The results show that after the airflow passes through the swirl guide vane of the dust removal fan, there is an obvious swirl flow in the exit section of the dust removal fan. Under the action of centrifugal force, a large amount of dust is collected on the side wall of the exit section. With the increase in the number of driving impeller blades, the total pressure efficiency, static pressure efficiency, and dust removal efficiency of the dust removal fan decrease. When the driving impeller blade adopts the C-4 airfoil, the total pressure efficiency and static pressure efficiency of the dust removal fan are higher but the dust removal efficiency is lower than that of the same thickness circular plate airfoil. With the increase in the number of driven impeller blades, the power of the driving impeller shaft of the dust removal fan gradually increases; the total pressure and static pressure values first increase and then decrease; and the driven impeller speed, total pressure efficiency, static pressure efficiency, and dust removal efficiency gradually decrease. Adding the rear guide vane structure can improve the total pressure efficiency and static pressure efficiency of the dust removal fan but will reduce the dust removal efficiency of the dust removal fan. The increase in the swirl guide vane structure will reduce the total pressure efficiency and static pressure efficiency of the dust removal fan but the dust removal efficiency will be significantly improved. The extension of the outlet section of the dust removal fan will reduce the total pressure efficiency and static pressure efficiency of the dust removal fan, but the dust removal efficiency will increase. In this paper, by changing the structural parameters of the dust removal fan and establishing different models for numerical simulation and analysis, the influence law of the structural parameters of the dust removal fan on the dust removal performance is obtained, providing a way to improve the performance of the dust removal fan. [ABSTRACT FROM AUTHOR]

Ventilation, carried out using centrifugal fans, is essential for obtaining good quality ambient air. Its role is to satisfy hygiene and comfort needs. It aims in particular to provide fresh air, in order to allow the proper functioning of the various devices, to evacuate air polluted by various pollutants and to combat humidity and condensation. In this context, the objective of this work is to study the internal flow of humid air for different concentrations in a fan rotor using the ANSYS-CFX software, based on the finite volume method. Flow turbulence is taken into account using the k-Ε model. The scientific contribution in this field consists of showing that the concentration of humid air has a considerable effect on the properties of the flow such as: pressure, shear stresses and flow speed which is in agreement with the results of experimental studies. This study can be used to locate the area's most exposed to this change in flow properties and which will result in premature damage to the blades by erosion and a reduction in fan efficiency. It will therefore be possible to take preventive measures to minimize the harmful effects of humidity concentration on centrifugal fans. [ABSTRACT FROM AUTHOR]

Centrifugal pumps are used extensively in various everyday applications. The occurrence of corrosion phenomena during operation often leads to the failure of a pump's operating components, such as the impeller. The present research study examines the utilization of composite materials for fabricating centrifugal pump components using additive manufacturing as an effort to fabricate corrosion resistant parts. To achieve the latter two nanocomposite materials, carbon fiber reinforced polyamide and carbon fiber reinforced polyphenylene sulfide were compared with two metal alloys, cast iron and brass, which are currently used in pump impeller manufacturing. The mechanical properties of the materials are extracted by performing a series of experiments, such as uniaxial tensile tests, nanoindentation and scanning electron microscope (SEM) examination of the specimen's fracture area. Then, computational fluid dynamics (CFD) analysis is performed using various impeller designs to determine the fluid pressure exerted on the impeller's geometry during its operation. Finally, the maximum power rating of an impeller that can be made from such composites will be determined using a static finite element model (FEM). The FEM static model is developed by integrating the data collected from the experiments with the results obtained from the CFD analysis. The current research work shows that nanocomposites can potentially be used for developing impellers with rated power of up to 9.41 kW. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A design for a turbine pre-swirl system with impeller cavity is proposed to improve the quality of cooling air supplied to the turbine blades of an aeroengine. Impeller cavity is analyzed in order to increase the system pressure ratio with a low system power consumption at the system outlet. Theoretical and numerical investigation are used to investigate the flow characteristics in an impeller cavity pre-swirl system. The conclusions in this study indicate that the impeller structure can increases the pressure ratio by changing the power consumption and distribution of the absolute velocity in the impeller cavity and system outlet. To obtain high pressure ratio and low power consumption, the impeller should have a structure with a high outlet installation radius and low outlet angle. The highest increase in the pressure ratio compared with the empty cavity pre-swirl system is 6.4% and the corresponding increase in the power consumption is 2620 W. [ABSTRACT FROM AUTHOR]

The jet pump is one of the most popular types of fluid machinery in agriculture, industry and environmental engineering and many other fields. However, its internal flow structure is complex, showing obvious unsteady characteristics. The effect of throat diameter size on jet pump performance and energy property was investigated in this study based on numerical calculation and test verification, in order to improve the performance and internal flow field stability of jet pump. Five models with different throat diameters were obtained by adjusting the assembly structure and simulated by the computational fluid dynamics software to solve the Navier–Stokes equations for three-dimensional steady flow. The accuracy of numerical methods was verified by comparison with the experimental results. The compact jet pump performance under different throat diameters was then compared and analysed. The backflow at effuser outlet of different throat diameters causes the changes of vortex structure inside the injector rear chamber. The vortex diffuses downstream to the impeller inlet, making the flow structure of the impeller inlet show obvious circumferential inhomogeneity. This forms different vortex structures at different impeller flow channels, changing the distribution of entropy production within the impeller, ultimately leading to a decrease of pump efficiency. Therefore, this study found that selecting a reasonable throat diameter of the injector can improve the performance of the jet pump impeller, and thus improve the overall efficiency of the system. For the research object in this paper, the recommended range of throat diameter of injector is 16 mm–17 mm. This finding could provide useful insights for the improvement of the hydraulic performance and operational stability of compact jet pumps.

Accurate prediction of burst speed and critical location of a rotating disk is a great concern for turbomachinery designers and enables the reduction of test numbers required to show rotor integrity during turbo-engine certification. Existing burst methodologies mainly focused on axial disks with well-defined bore, web, and rim regions and mostly depended on correction factors that require previous test data of rotors with similar sizes and features. Furthermore, variation of radial and hoop stresses in a radial disk is less predictable than in axial disks due to the asymmetric nature of impellers, which results in uneven distribution of centrifugal and bending loads. This paper aims to explain the experimental and numerical effort dedicated to building an accurate burst methodology for impellers. Elastoplastic finite element analyses are performed by incorporating geometric and material nonlinearities. Analysis results allowed the prediction of failure locations and observation of redistribution of stresses due to material plasticity as rotor speed increases. An extensive test campaign is carried out to validate the numerical analysis. Critical strain criteria that correspond to the plastic strain of true ultimate tensile strength (UTS), are used to determine burst speeds before tests. Experimental results are compared with Robinson's average hoop stress criteria, Hallinan's criteria, and critical strain criteria to show the strong and weak sides of these methodologies for an impeller application. The numerical burst speeds and crack initiation locations associated with critical strain criteria are found to be in good agreement with the spin test results. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas & Oil is the property of Editorial Department of Natural Gas & Oil and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the flow instabilities encountered by the turbocharger compressor is an important step toward improving its overall design for performance and efficiency. While an experimental study using Particle Image Velocimetry was previously conducted to examine the flow field at the inlet of the turbocharger compressor, the present work complements that effort by analyzing the flow structures leading to stall instability within the same impeller. Experimentally validated three-dimensional computational fluid dynamics predictions are carried out at three discrete mass flow rates, including 77 g/s (stable, maximum flow condition), 57 g/s (near peak efficiency), and 30 g/s (with strong reverse flow from the impeller) at a fixed rotational speed of 80,000 rpm. Large stationary stall cells were observed deep within the impeller at 30 g/s, occupying a significant portion of the blade passage near the shroud between the suction surface of the main blades and the pressure surface of the splitter blades. These stall cells are mainly created when a substantial portion of the inlet core flow is unable to follow the impeller’s axial to radial bend against the adverse pressure gradient and becomes entrained by the reverse flow and the tip leakage flow, giving rise to a region of low-momentum fluid in its wake. This phenomenon was observed to a lesser extent at 57 g/s and was completely absent at 77 g/s. On the other hand, the inducer rotating stall was found to be most dominant at 57 g/s. The entrainment of the tip leakage flow by the core flow moving into the impeller, leading to the generation of an unstable, wavy shear layer at the inducer plane, was instrumental in the generation of rotating stall. The present analyses provide a detailed characterization of both stationary and rotating stall cells and demonstrate the physics behind their formation, as well as their effect on compressor efficiency. The study also characterizes the entropy generation within the impeller under different operating conditions. While at 77 g/s, the entropy generation is mostly concentrated near the shroud of the impeller with the core flow being almost isentropic, at 30 g/s, there is a significant increase in the area within the blade passage that shows elevated entropy production. The tip leakage flow, its interaction with the blades and the core forward flow, and the reverse flow within the impeller are found to be the major sources of irreversibilities.

【Background and Objective】 Fatigue fracture has become a major cause of failure in centrifugal pump impellers due to their operation at high speeds. Excessive speed leads to various prestresses, resulting in severe vibrations, resonance, and ultimately fatigue fracture of the impeller. This study aims to investigate the influence of different curvature radii of the front and rear covers on the natural frequency of high-speed centrifugal pump impellers. The findings provide a scientific basis for the optimal design of the impellers. 【Method】 The numerical simulation method is employed to determine the natural frequencies of the first six orders of the impeller. Modal analysis is then performed on impellers with varying curvature radii of the front and rear cover plates. A comparison chart of the modal frequencies of the first six orders is generated. 【Result】 The natural frequency of the impeller increases with an increase in the radius of curvature of the front cover. Specifically, when the radius increases from 10 mm to 14 mm, the natural frequency of the fourth order experiences the most significant change, increasing by 10%. On the other hand, increasing the radius of curvature of the rear cover has minimal effect on the impeller’s natural frequency, with a decrease of only 0.18% observed when the radius increases from 20 mm to 30 mm. 【Conclusion】 Increasing the radius of curvature of the front cover of the impeller can effectively raise the modal frequency of the centrifugal pump impeller and improve its dynamic characteristics.

The article presents a digital model for calculating the change in the angles of incidence of compressor rotor wheel blades that characterize tightness. The input parameters for the model are the geometric deviations of the disc slots and blades of the set. The calculation is based on the modeling of joints using the finite element method. To automate the modeling, a parametric design model of the blade created in the CAD module of the NX program is used; a calculation automation program created in the MATLAB environment and an algorithm for converting deformations at points obtained in finite element method into angles. The initial data and the resulting parameter values are stored in spreadsheets. Experimental studies have been carried out, including measurements of the disk and blades of the impeller, their assembly and measurement of interference. A Gaussian filter was applied to process the results of angle measurements. The tightness of the set under consideration was calculated using the developed model. The results showed that the limiting simulation error amounts to 16% of the value of experimental data; the index of correlation between the simulated and experimental data was 0.71.

Sustainable precision manufacturing requires a transformation from resource-based to intelligence-based reduction strategies for thermal errors. Current approaches such as machine cooling and air-conditioning of shop floors are highly energy intensive. Therefore, this paper presents and evaluates a comprehensive thermal error compensation strategy for 5-axis machine tools considering thermal errors of linear and rotary axes, as well as a wide variety of thermal load cases. The method encompasses an automatic characterization of the thermal behaviour of 5-axis machine tools as well as an automated setup and adaption of the data-driven compensation models to realize high robustness to changing thermal boundary conditions. The applied on-machine measurement cycle identifies 15 axis-specific thermal errors using a touch trigger probe and a precision sphere. To demonstrate the universal application and long-term robustness of the presented compensation strategy, it is evaluated on two different 5-axis machine tools using long-term experiments between 700 h and 900 h. The peak-to-peak values of the volumetric thermal errors at the considered working space positions are reduced from 76 µm to 20 µm and from 84 µm to 33 µm, respectively. This corresponds to a reduction of 74% and 61%. The corresponding root mean squared errors are reduced by 84% and 65%. Finally, the effectiveness of thermally compensated 5-axis machine tools is analysed during simultaneous 5-axis milling by manufacturing two uncompensated and two compensated impellers. The self-learning thermal error compensation reduces the maximum root mean squared error of the impeller blades up to 73% from 32 µm to 9 µm for temperature variations of about 10 °C. Thus, thermally compensated 5-axis machine tools increase the process capability in fluctuating ambient temperatures. Consequently, the self-learning thermal error compensation enables a significant increase in accuracy without requiring prior knowledge of the thermal machine tool behaviour. This provides a significant step towards more sustainable precision manufacturing. [Display omitted] • Comprehensive thermal error compensation strategy for 5-axis machine tools considering 15 linear and rotary axis errors. • Automated thermal characterization of machine tools using on-machine measurements and self-learning thermal error compensation. • Reduction of the RMSEs during long-term experiments of up to 900 h by 65% and 84% at two different machine tools. • Evaluation of thermally compensated 5-axis machine tools with impeller machining tests. • Reduction of the thermal errors during simultaneous 5-axis milling operations by up to 73% from 31.6 µm to 8.7 µm. [ABSTRACT FROM AUTHOR]

This research is addressed to investigate the characteristics of a centrifugal pump. In this work, the experiments were carried out with variations in impeller speed and at several valve openings. The measurement results show that head have the same tendency for all variations of inlet valve opening. Meanwhile for discharge and break horse power have almost the same values at low speed for both theoretical and measurement; however at higher speed there is a significant difference. Large inlet valve openings produce large discharges as well as break horse power and motor horse power. Meanwhile for the head, the inlet valve opening has no crucial effect because it produces almost the same value. [ABSTRACT FROM AUTHOR]