Centrifugal Compressor Impeller Research Articles

On the elastic–plastic behaviors of centrifugal steam compressor impeller under cyclic thermomechanical loading

AbstractIn 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.

Comparative Life Cycle Assessment of a centrifugal compressor impeller: Hybrid technology production versus welding production

Sustainable development is one of the main objectives in the turbomachinery sector to achieve the climate neutrality targets set by 2050 protocols. The manufacturing industry consumes an average of 23% of global energy, significantly contributing to the generation of greenhouse gases and other pollutants. Therefore, it is crucial to research technological solutions aimed at reducing consumption for the benefit of the environmental sustainability of the products manufactured. This study presents a comparative environmental impact assessment using the Life Cycle Assessment (LCA) methodology to evaluate the sustainability of two technological alternatives used to produce centrifugal impellers in the industrial sector. The first process analyzed deals with making an impeller by welding the shroud to the impeller body. The second process involves producing the component from a semi-finished product, machined through milling and Electrical Discharge Machining (hybrid solution). The study has been conducted at Nuovo Pignone company. It is based on primary inventory data collected through specific measurement campaigns and modeled using the environmental database Ecoinvent v3.9. The results were produced using the ILCD Midpoint method, and four different impact categories were investigated: Climate Change, Human Toxicity, Cancer Effects, and Freshwater Ecotoxicity. The results demonstrate that the solution produced through hybrid manufacturing is generally less impactful compared to the welded one. The insight implemented in the work is functional in drafting suggestions for manufacturers and customers to reduce the environmental burdens of the examined product.

Study on Flow Field Analysis and Structure Optimization in Impeller of Single-Stage Centrifugal Compressor

Fluent's built-in Latin hypercube sampling is used to generate a sample space, a total of 32 design points, a high-precision calculation model needs to be generated by CFD, the design parameters and their value ranges are determined, the response surface is used to establish a surrogate model, and the particle swarm optimization algorithm is used to obtain the optimal design parameters of the impeller with the pressure ratio and efficiency of the single-stage centrifugal compressor as the optimization goal, so as to achieve better performance of the impeller of the single-stage centrifugal compressor.

Dynamic mode characteristics of flow instabilities in a centrifugal compressor impeller

Centrifugal compressors are key parts of medium and small aircraft engines, the flow instabilities of centrifugal compressors have become the bottleneck of the developments of engines. It is vital to investigate the dynamic mode characteristics of flow instabilities in centrifugal compressors for solving the issues. In this study, unsteady full annular simulations of the centrifugal compressor flow are firstly implemented. It is found that the flow instability of the compressor primarily arises in the impeller. To capture the dominant transient modes in process of flow instabilities and accurately describe their temporal evolutions, a modified dynamic mode decomposition method (DMD-TC) is adopted to analyze the dynamic mode characteristics, which was proposed in our previous study. The results show that perturbations in the impeller can be mainly classified into three categories: impeller-diffuser interactions, self-excited perturbations, and vortex-induced perturbations. In detail, the modes induced by the impeller-diffuser interactions and self-excited perturbations are intrinsic modes, and they reflect the inherent flow unsteadiness in the impeller. On the one hand, the vortex-induced perturbations couple with the self-excited ones, which affect the spatial structures of modes induced by self-excited perturbations. The coupling effects enhance with the reduced mass flow rate, and the “resonance” effect might be excited. As a result, the mode of 4 RF (rotor frequency) grows during rotating stall process (RSP), which is a typical characteristic of rotating stall in the impeller. On the other hand, the vortex-induced perturbations emerge as different characteristic modes, due to the variant vortex structures with the mass flow rate. During the RSP, the growth of low-frequency characteristic modes is another typical feature of rotating stall in the impeller.

IMPROVING CHARACTERISTICS OF THE IMPELLER OF A HIGH-PRESSURE CENTRIFUGAL COMPRESSOR BY DESIGNING WITH THE HELP OF CAD

High-pressure compressors are among the most common pneumatic machines in industry and transport. Classical methods of designing such machines are based on flow modeling methods in two-dimensional and one-dimensional settings. The specified design methods lead to the creation of sufficiently perfect constructions, but their characteristics can still be improved. To simulate the flow in a high-pressure compressor, it becomes relevant to study the possibilities of optimizing the design using the Ansys Vista CAD system, which can significantly increase the efficiency of the compressor. The goal of the work is to improve the characteristics of the high-pressure centrifugal compressor impeller by designing with the help of CAD. The study was carried out on the basis of the design of the flow part of the impeller of a high-pressure centrifugal compressor using the Ansys VistaCCD automated design system based on the operation parameters of a mass-produced compressor. It was found that the efficiency maxima location of the designed and serial compressor impellers are approximately the same, while the polytropic efficiency of the designed impeller is 6 % more. At the same time, the ratio of total pressures decreases by 18 %. On the other hand, the high-efficiency zone of the impeller is significantly expanded for the designed impeller. This range has increased more than three times. At the same time, in the zone of optimal efficiency, the power consumed for the designed impeller decreases by 20 % to 240 kW. The designed impeller has a more perfect distribution of pressures for the splitter with approximately the same characteristics for the main blades of the impellers. Analyzing the velocity vectors and distributions, it can be derived that the serial compressor has two separation zones: in the blade bending region and at the outlet, unlike the designed one.

Numerical investigation of the self-induced unsteadiness phenomenon in the impeller of a high-loading centrifugal compressor

Unsteady flow phenomena are common in turbomachinery and have serious impacts on its stable operation. This paper reports a self-induced unsteady phenomenon inside a centrifugal impeller due to strong secondary flow that has not been previously reported. A high-loading centrifugal impeller is selected as the research object, an accurate three-dimensional model is established, and exhaustive numerical simulations are performed based on unsteady compressible Navier–Stokes equations. The unsteady performance of the compressor is measured in detail during the experiment, and the experimental results are compared with the numerical simulation results to verify the reliability of the numerical simulation method. The results of the unsteady pressure signal show the existence of unsteady phenomenon when the operating point is far away from the choke boundary. The power spectrum results of the unsteady pressure distribution at the impeller blade tip are analyzed, and two different modes of this unsteady phenomenon are confirmed. Higher-order frequency characteristics are not observed near the stall boundary. The detailed analysis of the flow field inside the impeller clarifies that the instability of the interface formed between the secondary flow and the main flow induces this unsteady phenomenon. This unsteady pressure disturbance propagates inside the blade passage through pressure waves, which contributes to the instability of the interface and the existence of this self-induced unsteady phenomenon.

Effect of Stage Loading and Tip Clearance on Tip Clearance Flows in a Centrifugal Compressor

The present paper reports measurement of periodic static pressures on the casing over the impeller of a low speed centrifugal compressor at different stage loadings and tip clearances. The periodic pressure data is acquired employing the technique called PLEAT. Experiments are carried out in a low speed centrifugal compressor with unshrouded impeller. Twelve holes are provided on the casing in which adapters are attached. A fast response pressure transducer, Kulite XCS-062 5pisd is inserted in the adapters. The pressure transducer measures pressure in terms of voltage. The voltage output is very low. The output voltage is amplified and converted to digital values for further processing of data. Sample results are presented and interpreted. From the measured static pressure, tip clearance flows can be easily identified. Effect of tip clearance and stage loading on tip clearance flows is highlighted.

Investigating the effects of shroud and blade thickness profiles on aeromechanical behavior and fatigue-life of 17-4PH impellers

In the present study, effects of blade and shroud thickness profiles on the stress distribution and fatigue life of centrifugal compressor impellers are investigated. Impeller geometry is generated based on an available data of a single-stage centrifugal compressor and is simulated in actual operating conditions. Pressure distribution on the impeller blades is obtained using Computational Fluid Dynamics (CFD) simulation which is then incorporated into Finite Element (FE) structural analysis. Equivalent stress and total deformation contours on the impeller are employed to pinpoint critical areas and maximum stress values. Simulations are performed for multiple cases with various shroud and blade thickness values to capture the role of these important parameters in aeromechanical behavior of the structure. Furthermore, fatigue stress amplitude limit and fatigue-life are evaluated based on the results of the FE analyses. It will be demonstrated that semi-open configuration is the most desirable design from mechanical stress and fatigue-life viewpoints. For shrouded impellers, it is shown that the mechanical stress increases and fatigue life decreases with increasing the blade thickness while for the shroud thickness, there exist an optimal point with minimum stress level and maximum fatigue life. The methodology and results of this paper can be employed for other impellers with different geometries and operating conditions to find the optimal design points from the structural mechanics perspective.

Collaborative Robust Design Optimization of Blade Geometry and Manufacturing Tolerance for a Transonic Centrifugal Impeller

Abstract Turbomachinery components are inevitably subjected to various sources of manufacturing errors. The resultant variations in blade geometry eventually lead to performance degradation. This is especially true for transonic centrifugal compressor impellers where the complex interaction between the geometric variations and shock waves may amplify such degradation. However, relevant studies on uncertainty quantification or robust design optimization of centrifugal impellers are quite rare. The mechanisms of how the realistic manufacturing errors influence the impeller aerodynamic performance are not clear. In addition, most existing studies have considered a fixed level of manufacturing tolerance applied to the impeller blade surface, which neglects the combined effect of blade geometry and manufacturing tolerance on impeller performance. In this study, a collaborative robust design optimization was performed for a transonic centrifugal impeller considering realistic manufacturing errors. The realistic manufacturing error field was first modeled based on the measurements of 92 centrifugal impellers. With a combination of computational fluid dynamics simulation and the non-intrusive polynomial chaos method, the influence of manufacturing errors on impeller performance and flow field variations was quantified. To save computational costs for the uncertainty quantification, a dual dimensionality reduction method was proposed to reduce the dimensionality of uncertainties. Finally, blade angles and the manufacturing tolerance of the impeller were collaboratively optimized to enhance the impeller performance robustness against manufacturing errors. The results show that the impeller aerodynamic performance exhibited a downward trend in the presence of manufacturing errors. The flow mechanisms responsible for this trend were mainly associated with increased intensity of the shock waves near the inducer blade tip. Such shock waves were significantly alleviated by reducing impeller inlet blade angles without the loss of pressure rise capability. Consequently, the impeller performance robustness against manufacturing errors was enhanced with the standard deviation of polytropic efficiency being reduced by 35% at a lower anticipated manufacturing cost due to increased tolerance allowance.

Integrated Approach for Geometric and Kinematic Design of Centrifugal Compressor Impellers

Integrated Approach for Geometric and Kinematic Design of Centrifugal Compressor Impellers

A novel method for work capacity calculation of centrifugal compressor impellers in energy storage systems

As the basis for centrifugal compressor design, the traditional one-dimensional scheme assumes that there is no flow prewhirl at the impeller inlet (i.e., C1u=0) when inlet guide vanes (IGVs) are absent. However, various experiments have proved that a natural prewhirl does exist at the impeller inlet even there is no IGV. In this study, a novel method is proposed to calculate the Euler work of impellers considering the natural prewhirl, and firstly applied to centrifugal compressors without IGVs. Stodola’s approach dealing with the slip velocity at the impeller outlet is adopted to the flow at the impeller inlet. A new formula for the Euler work calculation is deduced to evaluate the effect of natural prewhirl on centrifugal impellers. Then, this method is applied in two different model stages of industrial centrifugal compressors to verify against the experimental and numerical data. The results indicate that, compared to the traditional scheme assuming C1u=0, the novel method with modified formula considering the influence of C1u≠ 0 is more feasible for high-speed centrifugal compressors. With the aid of the novel calculation method proposed in this paper, the one-dimensional design accuracies of centrifugal compressor stages are improved by 7% compared with the traditional method.

Optimizing the performance of a single-shaft micro gas turbine engine by modifying its centrifugal compressor design

The purpose of this paper is optimizing the performance parameters of a single-shaft micro gas turbine with a power of about 150 kW at the design point by modifying its centrifugal compressor geometry. According to the physics of this problem, a hybrid optimization approach (including modern and numerical optimizers) was employed. The optimization was based on the numerical simulation of each geometry using a three-dimensional Reynolds Averaged Navier-Stokes solver. The geometric parameters of the centrifugal compressor impeller constituted the design variables and the Latin hypercube was employed for sampling. To reduce the cost of the numerical calculation, the neural network was chosen for approximate modeling of the design space. The physics of the optimization problem ahead was identified and a state-of-the-art optimization process was presented accordingly. Furthermore, a detailed discussion was conducted on the design space transparency, convergence criteria, and optimum design selection, the disadvantages of current optimization processes and the advantages of the present one were explained. NASA CC3 compressor was scaled down for the baseline engine, which is a 150 kW single-shaft gas turbine. This engine was optimized using the proposed optimization process and a significant improvement was achieved, where efficiency increased by 13.93% and power by 11.07%, and the specific fuel consumption decreased by 12.15%. Furthermore, despite the constant impeller tip diameter and rotational speed, in the optimum compressor, the mass flow increased by 2.22% and the pressure ratio by 29.62% compared to the baseline compressor, while the isentropic efficiency not only did not decrease but also increased slightly (0.2%). However, the operating range decreased by 12.64%.

Deep transfer residual variational autoencoder with multi-sensors fusion for tool condition monitoring in impeller machining

The data-driven deep learning models show incomparable superiority in tool wear monitoring. However, facing the monitoring environment of real-time changes in tool model, workpiece size, and cutting parameters in the machining of centrifugal compressor impeller, the flexibility of the model between different tools is rarely considered. In this manuscript, a novel deep transfer learning model based on residual variation autoencoder (Tresvae) with multi-sensors fusion signals is proposed. The sound pressure signals, acceleration signals, and spindle motor current signals are collected and confused into images as monitoring samples. Moreover, the residual network is used to optimize the encoding part of the variational autoencoder network while the decoding part remain unchanged. Then the parameter transfer strategy is adopted to realize the model transfer diagnosis between different tools. Experiments show that the proposed model achieves superior identification results than other methods on the same types and different types tools monitoring in impeller machining. Among them, the maximum recognition accuracy of the same type of tools is 97.25%, and that of different types of tools is 92%.

A Methodology and Information System for Computing and Optimization of Impellers and Vanned Diffusers Geometry Parameters

Abstract The study aims to develop an information-computing complex for computer design of a centrifugal compressor with parallel calculation of stages and optimization of the geometric parameters of the impellers and the diffusers. The paper presents a universal methodology and computerized information system of the main geometry parameter determination and optimization of the centrifugal compressor impellers and vanned diffusers. Optimization of cross-sectional areas of the input and output channels of the impeller and diffuser blade channels is held using a gradient descent method by gas flowrate quadratic integral deviation criteria. The information-computing complex is built on the algorithm proposed by the authors and implemented as a computer program with a human-machine interface. Calculation data are written in the form of numerical arrays with the possibility of interpolating data and obtaining graphical dependencies.

Performance improvement of centrifugal compressors for automotive turbochargers using adjoint method

Abstract A sensitivity calculation using adjoint method has a feature of low calculation cost because sensitivity information of all computational grid points can be calculated by only one numerical simulation. From this feature, it has been utilized as a calculation method of sensitivity information for a gradient-based optimization and this optimization procedure with adjoint method can be one of suitable ways for centrifugal compressor impeller which has a lot of design parameters such as meridional shape, blade angle and thickness. During the gradient-based optimization, mesh morphing, which moves the computational grid directly based on sensitivity information, is generally used for shape deformation. However, the mesh morphing is difficult to implement due to shape constraints which is particularly required for rotating blades, such as minimum blade thickness and rotationally axisymmetric shape. In this study, in order to avoid these problems, sensitivity information of each grid point was converted into that of conventional design parameters, and optimization was carried out. In order to verify the effectiveness of this method, two different optimizations were carried out for centrifugal compressor impeller. In the single-point optimization which focuses on efficiency improvement, maximum efficiency was increased by 3.5% compared to a baseline impeller. While, multi-points optimization which considers balance between flow capacity and efficiency showed that the maximum efficiency was improved by 0.6% compared to the baseline impeller while maintaining the same flow capacity.

Design of a high-performance centrifugal compressor impeller and an investigation on the linear effects of the hub

The performance of the turbocharger can be improved by optimizing the structural parameters of the compressor impeller. In this work, the existing centrifugal compressor impeller was taken as the case study, and the line shape of the hub was modified in order to study the influence of the line curvature of the hub on the compressor performance. Furthermore, the Navier–Strokes flow equation and the fourth-order Runge–Kutta method were used with Numeca software in order to solve the steady-state RANS equation, and the RANS equation is the averaging of unsteady N-S equations on time to solve the engineeringly required averaging. The numerical simulations and the performance predictions were made for each case, and then, the experiments were carried out to verify the accuracy of the aerodynamic performance that was obtained from the numerical simulations. The research results showed that within the design value range, the curvature of the impeller hub profile increased when the flow range and surge margin of the compressor impeller increased. Moreover, the pressure ratio, efficiency, and post-compression temperature increased when the relative Mach number at the inlet of the impeller decreased, the shock wave intensity that was generated by the gas in the flow channel decreased, and the velocity loss decreased. The obtained influence of the compressor impeller hub linearity on the compressor performance provides an opportunity to further improve the performance of the centrifugal compressor.

DESIGN OF CENTRIFUGAL COMPRESSOR IMPELLER FOR OPTIMAL EFFICIENCY

This research present a case steady namely design of centrifugal air compressor impeller for power station. This compressor is a dynamic compress which depends on a rotating impeller to compress the air. Impeller is the most important part of the centrifugal compressor components. Detail design calculation of centrifugal compressor impeller is described in this research. This study contains a complete set of detail drawing for blade profile of impeller. It can be used at sites which flow rate is 0.1275 m3 /s and 45561 rpm. The required data are collected from Ywama Power Station which is located in Yangon. For the given capacity, the inlet and outlet diameter are 0.054 m and 0.17 m and the number of blade is 19. Keywords: centrifugal compressor, impeller, velocity, diameter, width.

Design of compressor impeller under high Reynolds number conditions

PurposeA parametric method for designing the hub, casing and blades of the miniature centrifugal compressor impeller was developed. The relationship model of the size, aerodynamic and performance parameters of the centrifugal impeller was established. Based on the selected design parameters, the miniature centrifugal-type impeller was designed, and the work efficiency was calculated.Design/methodology/approachIn this study, a micro-centrifugal compressor impeller with a diameter of less than 25 mm was designed. A parametric design method was developed, and the functional relationship between the geometric and gas fluidity parameters was established.FindingsThe results of this study showed that the performance parameters of the designed micro-centrifugal impeller satisfied the design requirements. The proposed method is useful as a reference for designing and analysing compressor impellers under high Reynolds number conditions.Originality/valueA parametric design method was developed, and the functional relationship between the geometric and gas fluidity parameters was established. Under the Reynolds number conditions, the flow characteristics of the gas in the compressor were analysed; the shear-stress transport turbulence equation was solved using the finite volume method. In addition, the effects of the Reynolds number on the velocity, pressure, mass flow and efficiency of the micro-scale centrifugal compressor were evaluated. The results showed that the performance parameters of the designed micro-centrifugal impeller satisfied the design requirements. The proposed method is useful as a reference for designing and analysing compressor impellers under high Reynolds number conditions.

遠心圧縮機インペラに発生する衝撃波形成角度の計測

In a compressor, shock waves are generated when the impeller blade velocity reaches supersonic speed relative to the air drawn in from the air inlet. The shock interacts with the tip-leakage vortex and the boundary layer on the impeller blade surface. The interaction causes the pressure rise and the reverse flow. Thus, it is important to predict the formation of shock on the blades in compressor design. This study focused on a position of the shock in a centrifugal compressor. In general, simultaneous measurement by multiple pressure sensors is necessary to measure the angle of the shock formed near the leading edge of the impeller blade. In this study, a pressure history was measured at a single point near the leading edge of the blade using a semiconductor pressure transducer. The semiconductor pressure transducer has a diaphragm onto which a semiconductor strain gauge is glued. The pressure acting on the diaphragm is proportional to the strain at the center of the diaphragm. The direction of maximum principal strain of the diaphragm corresponds to the shock direction or its perpendicular direction. The strains in three different directions on the diaphragm were obtained and the direction of maximum principal strain was calculated using Rosette analysis. As a result, the angle of formation of the shock wave generated in the centrifugal compressor impeller was estimated.

Flow Simulation And Performance Analysis Of Centrifugal Compressor Using Cfd_Tool

This paper is concerned the flow simulation and performance analysis of the Centrifugal Compressor Using CFD – Tool. The complex internal flow of centrifugal compressor can be well analyzed, and the unique design system needs to be developed. It should be early to use the interface and also flexible for input and output. A 3-D flow simulation of turbulent – fluid flow is presented to visualize the flow pattern in-terms of velocity, streamline and pressure distribution on the blade surface are graphically interpreted. The standard K- e turbulence model and the simple model algorithm were chosen for turbulence model and pressure distribution well determined. The simulation was steady Heat transfer and moving reference frame was used to consider the impeller interaction under high resolution. Furthermore, A computational Fluid Dynamics (CFD) 3-D simulation is done to analyze the impeller head and efficiency required of centrifugal compressor. The impeller is rotated for a constant revolution and mass flow rate, in this study initially the geometry of centrifugal compressor impeller is created by an ANSYS Vista CCD, and the Blade modeller done by Bladegen, Finally, CFD analysis was performed in ANSYS CFX using the ANSYS Turbo grid meshing tool. According to the analysis, as the number of impeller blades increases, so does the value of the head and power imparted, as well as the impeller’s efficiency.