Centrifugal Compressor Impeller Research Articles

Про вплив форми меридіонального контуру на енергетичні характеристики відцентрового колеса компресора

This work is concerned with the development of approaches to the optimal aerodynamic design of centrifugal compressor wheels, which is due to the use of centrifugal stages in compressors of modern aircraft gas turbine engines and power plants. The aim of this work is a computational study of the effect of the meridional contour shape of a centrifugal compressor wheel on its power characteristics. The basic method is a numerical simulation of 3D turbulent gas flows in centrifugal wheels on the basis of the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. The computational study features: varying the shape of the hub and tip part of the meridional contour over a wide range, formulating quality criteria as the mean integral values of the wheel power characteristics over the operating range of the air flow rate through the wheel, and a systematic scan of the independent variable range at points that form a uniformly distributed sequence. As a result of multiparameter calculations, it was shown that in the case of a flow without separation in the blade channels of a wheel with a given starting shape of the meridional contour, varying that shape has an insignificant effect on the wheel power characteristics. It is pointed out that in similar cases it seems to be advisable to aerodynamically improve centrifugal wheels by varying the shape of their blades in the circumferential direction rather than in the meridional plane. This conclusion was made using rather a “coarse” computational grid, which, however, retains the sensitivity of the computed results to a variation in the centrifugal wheel geometry. On the whole, this work clarifies ways of further aerodynamic improvement of centrifugal compressor impellers in cases where the starting centrifugal wheel is a well-designed wheel with a flow without separation in the blade channels. The results obtained may be used in the aerodynamic optimization of centrifugal stages of aircraft gas turbine engines.

Study of the structure and mechanical properties of engineering products made of austenitic-martensitic steel, using the metal magnetic memory technique

Spontaneous phase transformation in local areas of the austenitic microstructure to martensite with the release of carbides may appear during the manufacturing or operation of engineering products made of two-phase austenitic-martensitic steel grades. When inspecting the quality of products made of these steels, the problem of detecting the local zones of the martensitic phase and carbide precipitation in the product metal arises. The article presents the results of an inspection by means of the metal magnetic memory (MMM) technique of centrifugal compressor impellers made of austenitic-martensitic steel 07Cr16Ni6. It was demonstrated that in the areas of stray field indications detected by means of the MMM technique, strength properties deteriorate, the metal structure degrades with abrupt changing of the metal phase composition and a carbide network formation, unacceptable δ-ferrite, was detected in the structure, and micro- and macro-cracks were found.

Numerical investigation of aerodynamic load on the impellers of centrifugal compressor with leakage flow

Numerical investigation of aerodynamic load on the impellers of centrifugal compressor with leakage flow

Microstructural and Very High Cycle Fatigue (VHCF) Behavior of Ti6Al4V-A Comparative Study.

In this study, an investigation is carried out to evaluate and compare the material and physical properties of Grade 5 Titanium alloy (Ti6Al4V G5) samples of three different impeller manufacturers. The study aims to identify the efficient impeller core material from different Ti6Al4V G5 manufacturers. Ultrasonic fatigue test for Ti6Al4V samples of 100 horsepower (hp) centrifugal compressor impeller parts is performed before and after heat treatment. The effect of microstructure on Very High Cycle Fatigue (VHCF) behavior of Ti6Al4V is also analyzed and discussed in detail. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) observation are carried out to investigate the microstructure of different Ti6Al4V material samples. The dynamic elastic properties are measured by the Impulse Excitation Technique (IET) at room temperature. The fracture behavior of the tensile specimens is analyzed by SEM. Post-heat-treatment analysis of Ti6Al4V is also carried out and presented which affects the grain size of the material sample and thus considerable effect in the mechanical properties. Chemical composition investigation of Ti6Al4V using SEM and Energy Dispersive X-ray Spectroscopy (EDS) also included in this study.

Performance improvement of a transonic centrifugal compressor impeller with splitter blade by three-dimensional optimization

This paper presents a procedure for three-dimensional optimization of a transonic centrifugal compressor impeller with splitter blades by integrating 3D blade parameterization method, a genetic algorithm (GA), an artificial neural network, and a CFD solver. Because computational fluid dynamics (CFD) is a time-consuming method, an artificial neural network is coupled with GA to evaluate the objective function. SRV2-O, a typical high-pressure ratio centrifugal impeller, is selected as the test case. A good understanding of flow characteristics in the passage of SRV2-O is obtained using 3D Reynolds Averaged Navier-Stokes solver. Twenty-eight design variables defining the impeller blade angle distribution are used to parametrize the blade geometry. Isentropic efficiency of the impeller is selected as the objective function while the total pressure ratio and mass flow rate are defined as constraints. The optimization results indicate that the performance of the optimum geometry is improved in comparison with the original impeller at both design and off-design conditions. The isentropic efficiency is increased by 0.97% at the design point, and total pressure ratio and mass flow rate are increased by 0.74%, 0.65%, respectively.

Uncertainty quantification based optimization of centrifugal compressor impeller for aerodynamic robustness under stochastic operational conditions

Centrifugal compressor impeller operates at stochastic boundary conditions. The operational uncertainties cause performance deviation from design value and consequently affect the reliability of the compressor. Considering the stochastic operational uncertainties in the early design stage, this paper presents an uncertainty quantification based optimization of centrifugal compressor impeller with splitter blades for aerodynamic robustness. The nonlinear response relation between the design variables, the aerodynamic boundary uncertainties and the impeller performance is modelled by a combination of the Latin Hypercube Sampling, the three dimensional CFD, the Kriging surrogate model and the Non-intrusive Probability Collocation method. A sensitivity analysis with single and multiple random geometry variations is carried out to identify the most sensitive parameters. The effects of rotor speed uncertainty on pressure ratio and efficiency are quantified. A case study is conducted to search for optimal impellers with higher performance and lower sensitivity to boundary uncertainty using NSGA-II. The optimization is verified by the Monte Carlo method. The results demonstrate that the aerodynamic robustness of the compress impeller with splitter blades is enhanced by the proposed approach, which provides references for compressors, turbines and other turbo machinery.

Experience in using anisotropic properties of composites in engineering the compressor impeller of a small-size gas turbine engine

The use of composite materials in modern aircraft and rocket engines is one of the most promising areas. Low density and high strength characteristics of composite materials are crucial when choosing a material for small-sized compressors. The main ability to bear the load of the composite material is provided by the reinforcing fibers of the filler. The greater the percentage of filler fibers has a particular orientation, the higher the strength and rigidity of the product in this direction. If the part is loaded with forces applied primarily in one or two directions, it makes sense to create a material with anisotropy of properties that will exactly match the applied loads. For example, the disk and blades of a centrifugal compressor operate under the action of centrifugal force and gas pressure. In this case, to manufacture a centrifugal compressor impeller from composite materials, it is only necessary to redistribute the fibers in the part space in such a way as to create an optimal anisotropy of properties. This article describes the procedure for selecting the optimal orientation of reinforcing fibers in the impeller of a centrifugal compressor of a small gas turbine engine.

НАПОРНАЯ ХАРАКТЕРИСТИКА ЦЕНТРОБЕЖНОГО КОМПРЕССОРА МАЛОРАЗМЕРНОГО ТУРБОРЕАКТИВНОГО ДВИГАТЕЛЯ НА ОСНОВЕ ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

Shown the possibility of using the standard ANSYS CFX hydrodynamic software package for calculating the gasdynamic characteristics of the centrifugal compressor impeller of micro turbojet engines with different options for profiling blades which based on physical and numerical modeling. Presented a methodology for designing the impeller of a centrifugal compressor based on solving the inverse problem of gas dynamics. As a result of a numerical study, the head coefficient of various forms of the impeller was obtained and presented the dependences of the head coefficient and efficiency on the blade back sweep angle 2 β . b The article discusses the effect of the blade back sweep angle 2 β b on the compressor efficiency and the head characteristic for three different values of the blade back sweep angle 2 β b for example, the impeller with the back sweep angle  2 β b and with the radial blades  2 β 90 b and with blades bent forward  2 β b The centrifugal compressor was designed using Vista CCD programs in one-dimensional computing and Fluid flow CFX in three-dimensional computing. For blade profiling, the BladeGend program was used with different profiling options in order to improve compressor efficiency. The computational grid and the construction of a structured hexahedral mesh for the impeller was carried out in Ansys Turbogrid and the SST model of turbulence was selected in the calculation, which, with sufficient grinding of the mesh at the walls, adequately simulates separated flows at the channel walls, as well as the flow in the flow core. When constructing a grid along the walls between the channel blades, the parameter y + was controlled, which should not exceed 2. It is permissible to use a coarser grid in the flow core compared to the grid near the walls. The design grid of the impeller consists of 350000 elements.

Decreasing the Mass of Turbomachinery Subansamblies Using Advanced Polymer Composites

The extension of use of light advanced polymer composites from structural parts of an aircraft to all kinds of components of the engine is presently very limited by the knowledge of both technological development process and materials behaviour during service. The paper comes to meet an area of interest for many researchers and large integrators and manufacturers, by presenting the first steps made into the manufacturing of a carbon fiber reinforced composite blades for a centrifugal compressor impeller. An existing metallic reference impeller was redesigned, air flow studies were achieved to establish new design performances, precursors (type, volume fraction, architecture, distribution) were defined for the CFRP (Carbon Fiber Reinforced Polymer), stress analyses were performed on proposed structural materials configurations. Furthermore, the paper award an important section to manufacturing process stages, the manufacturing technology used and first developed trials. It was concluded that an entire impeller CFRP (Carbon Fiber Reinforced Polymer) manufacturing can and shall be the next step of the study, using autoclave technology.

Experimental Investigation for Enhanced Control of Rotating Unsteady Flow Instabilities in an Unshrouded Centrifugal Compressor Impeller

Abstract Unshrouded industrial centrifugal compressor impellers operate at high rotational speeds and volume flow rates. Under such conditions, impeller blade excitation is dominated by high frequency interaction with stationary parts, i.e., vaned diffusers or inlet guide vanes. In a previous study conducted on two full compression units of the original equipment manufacturer (OEM), the authors identified, characterized, and quantified resonant blade vibration caused by the interaction of the impeller blades with rotating stall cells during severe off-design conditions. This caused significant dynamic stress in the blades. In a follow-up study, this phenomenon was reproduced successfully experimentally under representative off-design conditions in a downscaled test rig and numerically with unsteady computational fluid dynamics (CFD) and structural mechanical finite element method (FEM) analysis. The gained knowledge was translated into a new diffuser design philosophy, based on sectorwise circumferential variation of the leading edge angle. This paper presents the patented philosophy, which is experimentally verified on the same test rig configuration in terms of flow path geometry and measurement equipment that was used in the mentioned prior study to assess resonant blade interaction. The results confirm the design aims: rotating stall onset was delayed without affecting the aerodynamic performance of the stage. Resonant blade interaction with rotating stall observed in the baseline diffuser could not be avoided with the two new diffuser designs. However, with the two new diffusers, the induced mechanical stresses in the impeller and the excitability were reduced by up to 12%.

Numerical Analysis of Flow through High Pressure Ratio Centrifugal Compressor Impeller and Effect of Varying Diffuser Exit Width on Performance

Numerical Analysis of Flow through High Pressure Ratio Centrifugal Compressor Impeller and Effect of Varying Diffuser Exit Width on Performance

Damage mechanism and evaluation model of compressor impeller remanufacturing blanks: A review

The theoretical and technological achievements in the damage mechanism and evaluation model obtained through the national basic research program “Key Fundamental Scientific Problems on Mechanical Equipment Remanufacturing” are reviewed in this work. Large centrifugal compressor impeller blanks were used as the study object. The materials of the blanks were FV520B and KMN. The mechanism and evaluation model of ultra-high cycle fatigue, erosion wear, and corrosion damage were studied via theoretical calculation, finite element simulation, and experimentation. For ultra-high cycle fatigue damage, the characteristics of ultra-high cycle fatigue of the impeller material were clarified, and prediction models of ultra-high cycle fatigue strength were established. A residual life evaluation technique based on the “β-HV-N” (where β was the nonlinear parameter, HV was the Vickers hardness, and N was the fatigue life) double criterion method was proposed. For erosion wear, the flow field of gas-solid two-phase flow inside the impeller was simulated, and the erosion wear law was clarified. Two models for erosion rate and erosion depth calculation were established. For corrosion damage, the electrochemical and stress corrosion behaviors of the impeller material and welded joints in H2S/CO2 environment were investigated. KISCC (critical stress intensity factor) and da/dt (crack growth rate, where a is the total crack length and t is time) varied with H2S concentration and temperature, and their variation laws were revealed. Through this research, the key scientific problems of the damage behavior and mechanism of remanufacturing objects in the multistrength field and cross-scale were solved. The findings provide theoretical and evaluation model support for the analysis and evaluation of large centrifugal compressor impellers before remanufacturing.

A model order reduction technique for systems with nonlinear frequency dependent damping

Frequency domain solution of systems with frequency dependent damping is a computationally expensive endeavour especially when dealing with large order three-dimensional systems. A moment-matching based reduced order model is proposed in this work which is capable of handling nonlinear frequency dependent damping in second-order systems. In the proposed approach, local linear systems with frequency independent matrices are derived from the original system, and using the principles of the Rational Krylov approach, orthogonal basis vectors are computed from these local systems through the second-order Arnoldi procedure. The system is then projected on to the basis set to obtain a numerically efficient reduced order model, accurate in the entire frequency domain of interest. The proposed approach is also shown to be more accurate than the popular modal projection based multi-model approach of the same order. The proposed tool is applied to the problem of determining the frequency response of an idealised centrifugal compressor impeller with non-viscous (frequency dependent) damping.

Aerodynamic and Structural Characteristics of a Centrifugal Compressor Impeller

The present study focuses on the aerodynamic performance and structural analysis of the centrifugal compressor impeller. The performance characteristics of the impeller are analyzed with and without splitter blades by varying the total number of main and splitter blades. The operating conditions of the compressor under centrifugal force and pressure load from the aerodynamic analysis are applied to the impeller blade and hub to perform the one-way Fluid–Structure Interaction (FSI). For the stress assessment, maximum equivalent von Mises stresses in the impeller blades are compared with the maximum allowable stress of the impeller material. The effects of varying the pressure field on the deformation and stress of the impeller are also calculated. The aerodynamic and structural performance of the centrifugal compressor at 73,000 rpm are investigated in terms of the efficiency, pressure ratio, equivalent von Mises stress, and total deformation of the impeller.

Centrifugal Compressor Performance Improvement through Multi Splitter Impeller

Abstract In the paper, a back swept impeller of centrifugal compressor is experimentally studied and numerically validated and modified to increase its pressure ratio and improve efficiency, as well as to analyse the effect of splitter blade location between two main blades. The back swept multi splitter blade impeller was designed with a big splitter positioned close to the main blade suction surface and a smaller splitter close to the pressure surface. Adding this multi splitter improves the overall performance of the modified impeller due to less intensive flow separation and smaller pressure loss. In particular, the total pressure ratio was observed to increase from 4.1 to 4.4, with one percent increase in efficiency.

Prediction of service life of large centrifugal compressor remanufactured impeller based on clustering rough set and fuzzy Bandelet neural network

In order to predict the service life of large centrifugal compressor impeller correctly, the rough set and fuzzy Bandelet neural network are combined to construct the novel prediction model which can give full play to theirs advantages. The attribute reduction algorithm based rough set and clustering method is firstly designed to optimize the inputting variables of fuzzy Bandelet neural network. And then the prediction model based on fuzzy Bandelet neural network is proposed, the Bandelet function is used as the excitation function of hidden layer and is combined with fuzzy theory to improve the prediction effectiveness of the prediction model. The training algorithm of fuzzy Bandelet neural network is designed based on improved genetic algorithm, the improved genetic algorithm introduces the adaptive differential evolution method into the traditional genetic algorithm, which can effectively optimize the parameters of fuzzy Bandelet neural network. Finally, the original 30 input variables of fuzzy Bandelet neural network are reduced to 9 input nodes based on rough set using 500 remanufacturing impellers as research objects. The service life of remanufacturing impeller is predicted based on three prediction models, and simulation results show that the fuzzy Bandelet neural network optimized by improved genetic algorithm has highest prediction precision and efficiency, which can correctly predict the service life of remanufacturing impeller.

Multi Field Coupling Stress Calculation and Analysis of CentrifugalCompressor Impeller Under Different Atmospheric Conditions

To improve the power density, air pressurization systems are widely used in vehicle internal combustion engines, hybrid engines and fuel cell engines. Centrifugal compressor is the core component of air pressurization system. It’s aerodynamic and reliability performance is the key to the whole system design. The atmospheric environment has great influence on the performance and reliability of the centrifugal compressor. When the atmospheric environment changes, unexpected failures may happen to the compressor impeller, affecting the reliability of vehicle engine. Aiming at a centrifugal compressor impeller of turbocharger for diesel engine, the multi field coupling stress under different atmospheric conditions is studied, and the key influencing factors of impeller stress are analyzed. Based on experimental tests, the working conditions of the centrifugal compressor for turbocharged diesel engine operating as external characteristics are obtained. By establishing a numerical calculation model of multi field coupling stress, and applying BKIN model to the material, the variation law of impeller stress with atmospheric environment is analyzed in the range of elastic-plastic mechanics. The results show that the centrifugal stress is always the major component of the coupling stress and the high coupling stress region of the investigated impeller appears in the shaft hole near the rear face. The results could provide reliability design strategies for solving the problem of impeller strength under different atmospheric conditions and for structural optimization.

Numerical and Experimental Fluid–Structure Interaction-Study to Determine Mechanical Stresses Induced by Rotating Stall in Unshrouded Centrifugal Compressor Impellers

Unshrouded industrial centrifugal compressor impellers operate at high rotational speeds and volume flow rates. Under such conditions, the main impeller blade excitation is dominated by high frequency interaction with stationary parts, i.e., vaned diffusers or inlet guide vanes (IGVs). However, at severe part load operating conditions, sub-synchronous rotating flow phenomena (rotating stall) can occur and cause resonant blade vibration with significant dynamic (von-Mises) stress in the impeller blades. To ensure high aerodynamic performance and mechanical integrity, part load conditions must be taken into account in the aeromechanical design process via computational fluid dynamics (CFD) and finite element method (FEM) analyzes anchored by experimental verification. The experimental description and quantification of unsteady interaction between rotating stall cells and an unshrouded centrifugal compression stage in two different full scale compression units by Jenny and Bidaut (“Experimental Determination of Mechanical Stress Induced by Rotating Stall in Unshrouded Impellers of Centrifugal Compressors”, ASME J. Turbomach. 2016; 139(3):031011-031011-10) were reproduced in a scaled model test facility to enhance the understanding of the fluid–structure interaction (FSI) mechanisms and to improve design guide lines. Measurements with strain gauges and time-resolved pressure transducers on the stationary and rotating parts at different positions identified similar rotating stall patterns and induced stress levels. Rotating stall cell induced resonant blade vibration was discovered for severe off-design operating conditions and the measured induced dynamic von-Mises stress peaked at 15% of the mechanical endurance limit of the impeller material. Unsteady full annulus CFD simulations predicted the same rotating stall pressure fluctuations as the measurements. The unsteady Reynold's Averaged Navier-Stokes simulations were then used in FEM FSI analyses to predict the stress induced by rotating stall and assess the aerodynamic damping of the corresponding impeller vibration mode shape. Excellent agreement with the measurements was obtained for the stall cell pressure amplitudes at various locations. The relative difference between measured and mean predicted stress from fluid–structure interaction was 17% when resonant blade vibration occurred. The computed aerodynamic damping was 27% higher compared to the measurement.

Fatigue failure analysis of semi-open impeller with mistuning considered

Abstract High fatigue failure of blades, resulting from excessive vibration stress caused by wake excitation, is the main reason for failures of centrifugal compressor impeller such as fracture. However, a problem usually neglected is the mistuning phenomenon induced by random deviation in processing or operation. Inevitably, it will cause vibration localization and even greatly promote fatigue failure, and that's why some blades of semi-open impeller are primary to fracture first. The present paper aims at this problem based on numerical and experimental methods to conduct research on dynamic characteristic and fatigue failure of fractured blades of a realistic semi-open impeller. A finite element reduced order model (ROM) and vibration frequency response measurement system are established to support dynamic response analysis of impeller. Notably, attention is paid to the effect of mistuning on vibration stress local amplitude amplification and fatigue number in various conditions. In addition, in view of the deterioration of harsh environment for mistuning magnitude, a further analysis of fatigue life impacted by mistuning level is performed. Results demonstrate that the mistuning also results in blade failure because the increased vibration stress greatly contributes to the reduction of failure period. The present methodology and results are applicable to estimate operation security in some cases.

Effect of double splitter blades position in a centrifugal compressor impeller

This paper reveals a novel design of centrifugal compressor impeller with multisplitter blades for performance improvement. In order to investigate the effects of the location of the splitter between two main blades, two sample impellers were designed, keeping all flow conditions and impeller definitions same as the experimentally validated impeller: (1) with big splitter close to suction surface of main blade and smaller splitter close to pressure surface; (2) with small splitter close to suction surface of main blade and big splitter close to pressure surface. Flow field in both the impellers is analyzed and compared with the original experimentally validated impeller. Total pressure ratio is increased with improved efficiency in multisplitter blade impellers with the addition of pair of big and small splitters blades. It was identified that small splitter close to the suction surface of the main blade and big splitter close to the pressure surface has more uniform flow, reduced separation, and better efficiency than the placement of big splitter close to the suction surface.