The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed（SPS） casing treatment when fan/compressor suffers from a radial total pressure inlet distortion.Experimental res...The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed（SPS） casing treatment when fan/compressor suffers from a radial total pressure inlet distortion.Experimental researches are conducted on a low-speed compressor with and without SPS casing treatment under radial distorted inlet flow of different levels as well as uniform inlet flow.The distorted flow fields of different levels are generated by annular distortion flow generators of different heights.The characteristic curves under these conditions are measured and analyzed.The results show that the radial inlet distortion could cause a stall margin loss from 2%to30%under different distorted levels.The SPS casing treatment could remedy this stall margin loss under small distortion level and only partly make up the stall margin loss caused by distortion in large level without leading to perceptible additional efficiency loss and obvious change of characteristic curves.The pre-stall behavior of the compressor is investigated to reveal the mechanism of this stall margin improvement ability of the SPS casing treatment.The results do show that this casing treatment delays the occurrence of rotating stall by weakening the pressure perturbations and suppressing the nonlinear amplification of the stall precursor waves in the compression system.展开更多
A research on the heat transfer performance of kerosene flowing in a vertical upward tube at supercritical pressure is presented.In the experiments,insights are offered on the effects of the factors such as mass flux,...A research on the heat transfer performance of kerosene flowing in a vertical upward tube at supercritical pressure is presented.In the experiments,insights are offered on the effects of the factors such as mass flux,heat flux,and pressure.It is found that increasing mass flux reduces the wall temperature and separates the experimental section into three different parts,while increasing working pressure deteriorates heat transfer.The extended corresponding-state principle can be used for evaluating density and transport properties of kerosene,including its viscosity and thermal conductivity,at different temperatures and pressures under supercritical conditions.For getting the heat capacity,a Soave–Redlich–Kwong(SRK)equation of state is used.The correlation for predicting heat transfer of kerosene at supercritical pressure is established and shows good agreement with the experimental data.展开更多
Inspection techniques for aero-engine blades are a hot topic in industry. Since these blades have a sculptured surface and a small datum, measurement results may deviate from an actual position. There are few proper a...Inspection techniques for aero-engine blades are a hot topic in industry. Since these blades have a sculptured surface and a small datum, measurement results may deviate from an actual position. There are few proper approaches compensating for non-uniform distribution errors that are within specified tolerance ranges. This study aimed to develop a meshing structure measuring approach for the distortion of blades via non-contact optical 3D scanning. A rough measurement and a registration procedure are initially adopted to rectify the coordinate system of a blade, which avoids the initial coordinate system errors caused by the small datum. A measurement path with meshing structure is then unfolded on the blade surface. For non-uniform distribution errors, the meshing structure measurement is more visual and clear than the traditional constant height curves method. All measuring points take only 7 min to complete, and the distribution of error is directly and accurately presented by the meshing structure. This study provides a basis for future research on distortion control and error compensation.展开更多
A triple swirler combustor is considered to be a promising solution for future high temperature rise combustors. The present paper aims to study dilution holes including primary dilution holes and secondary dilution h...A triple swirler combustor is considered to be a promising solution for future high temperature rise combustors. The present paper aims to study dilution holes including primary dilution holes and secondary dilution holes on the performance of a triple swirler combustor. Experimental investigations are conducted at different inlet airflow velocities（40–70 m/s） and combustor overall fuel–air ratio with fixed inlet airflow temperature（473 K） and atmospheric pressure. The experimental results show that the ignition is very difficult with specific performance of high ignition fuel–air ratio when the primary dilution holes are located 0.6H（where H is the liner dome height）downstream the dome, while the other four cases have almost the same ignition performance. The position of primary dilution holes has an effect on lean blowout stability and has a large influence on combustion efficiency. The combustion efficiency is the highest when the primary dilution holes are placed 0.9H downstream the dome among the five different locations.For the secondary dilution holes, the pattern factor of Design A is better than that of Design B.展开更多
The fatigue lives of materials and structures at different strain levels show het- eroscedasticity. In addition when the number of test specimens is insufficient, the fatigue strength coefficient and fatigue ductility...The fatigue lives of materials and structures at different strain levels show het- eroscedasticity. In addition when the number of test specimens is insufficient, the fatigue strength coefficient and fatigue ductility coefficient of the fitting parameters in the total strain life equa- tion may not have definite physical significance. In this work, a maximum likelihood method for estimating probabilistic strain amplitude fatigue life curves is presented based on the fatigue lives at different strain levels. The proposed method is based on the general basic assumption that the logarithm of fatigue life at an arbitrary strain level is normally distributed. The rela- tionship among the parameters of total strain life equation, monotonic ultimate tensile stress and percentage reduction of area is adopted. The presented approach is finally illustrated by two applications. It is shown that probabilistic strain amplitude-fatigue life curves can be eas- ily estimated based on the maximum likelihood method. The results show that fatigue lives at different strain levels have heteroscedasticity and the values of fatigue strength coefficient and fatigue ductility coefficient obtained by the proposed method are close to those of the true tensile fracture stress and true tensile fracture strain.展开更多
The liquid droplet evaporation character is important for not only combustion chamber design process but also high-accuracy spray combustion simulation. In this paper, the suspended droplets＇ evaporation character wa...The liquid droplet evaporation character is important for not only combustion chamber design process but also high-accuracy spray combustion simulation. In this paper, the suspended droplets＇ evaporation character was measured in a quiescent high-temperature environment by micro high-speed camera system. The gasoline and kerosene experimental results are consistent with the reference data. Methanol, common kerosene and aviation kerosene droplet evaporation characteristics, as well as their evaporation rate changing with temperature, were obtained. The evaporation rate experimental data were compared with the prediction result of Ranz-Marshall boiling temperature model（RMB）, Ranz-Marshall low-temperature model（RML）, drift flux model（DFM）, mass analogy model（MAM）, and stagnant film model（SFM）. The disparity between the experimental data and the model prediction results was mainly caused by the neglect of the natural convection effect, which was never introduced into the droplet evaporation concept. A new droplet evaporation model with consideration of natural convection buoyancy force effect was proposed in this paper. Under the experimental conditions in this paper, the calculation results of the new droplet evaporation model were agreed with the experimental data for kerosene, methanol and other fuels, with less than 20% relative deviations. The relative deviations between the new evaporation model predictions for kerosene and the experimental data from the references were within 10%.展开更多
To shed light on the subgrid-seale （SGS） modeling methodology of nonlinear systems such as the Navier-Stokes turbulence, we define the concepts of assumption and restriction in the modeling procedure, which are show...To shed light on the subgrid-seale （SGS） modeling methodology of nonlinear systems such as the Navier-Stokes turbulence, we define the concepts of assumption and restriction in the modeling procedure, which are shown by generalized derivation of three general mathematical constraints for different combinations of restrictions. These constraints are verified numerically in a one-dimensional nonlinear advection equation. This study is expected to inspire future research on the SGS modeling methodology of nonlinear systems.展开更多
The smoothed particle hydrodynamics（SPH） method is usually expected to be an efficient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the probl...The smoothed particle hydrodynamics（SPH） method is usually expected to be an efficient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by introducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square（LS） and Moving-Least-Square（MLS） methods. Then detailed analysis in spectral space is presented for people to better understand this method. Finally we show three test examples to verify the method behavior.展开更多
Closure models started from Chou＇s work have been developed for more than 70 years, aiming at providing analytical tools to describe turbulent flows in the spectral space. In this study, a preliminary attempt is pres...Closure models started from Chou＇s work have been developed for more than 70 years, aiming at providing analytical tools to describe turbulent flows in the spectral space. In this study, a preliminary attempt is presented to introduce a closure model in the physical space, using the velocity structure functions as key parameters. The present closure model appears to qualitatively reproduce the asymptotic scaling behav- iors at small and large scales, despite some inappropriate behaviors such as oscillations. Therefore, further improvements of the present model are expected to provide appropriate descriptions of turbulent flows in the physical space.展开更多
The closure of a turbulence field is a longstanding fundamental problem, while most closure models are introduced in spectral space. Inspired by Chou＇s quasi-normal closure method in spectral space, we propose an ana...The closure of a turbulence field is a longstanding fundamental problem, while most closure models are introduced in spectral space. Inspired by Chou＇s quasi-normal closure method in spectral space, we propose an analytical closure model for isotropic turbulence based on the extended scale similarity theory of the velocity structure function in physical space. The assumptions and certain approximations are justified with direct numerical simulation. The asymptotic scaling properties are reproduced by this new closure method, in comparison to the classical Batchelor model.展开更多
The current paper presents experimental and computational results to assess the effectiveness of non-axisymmetric endwall contouring in a compressor linear cascade. The endwaU was designed by an endwall design optimi-...The current paper presents experimental and computational results to assess the effectiveness of non-axisymmetric endwall contouring in a compressor linear cascade. The endwaU was designed by an endwall design optimi- zation platform at 0° incidence （design condition）. The optimization method is based on a genetic algorithm. The design objective was to minimize the total pressure losses. The experiments were carried out in a compressor cascade at a low-speed test facility with a Mach number of 0.15. Four nominal inlet flow angles were chosen to test the performance of non-axisymmetric Contoured Endwall （CEW）. A five-hole pressure probe with a head diameter of 2 mm was used to traverse the downstream flow fields of the flat-endwall （FEW） and CEW cascades. Both the measured and predicted results indicated that the implementation of CEW results in smaller comer stall, and reduction of total pressure losses. The CEW gets 15.6% total pressure loss coefficient reduction at design condition, and 22.6% at off-design condition （＋7° incidence）. And the mechanism of the improvement of CEW based on both measured and calculated results is that the adverse pressure gradient （APG） has been reduced through the groove configuration near the leading edge （LE） of the suction surface （SS）.展开更多
The 2D incompressible Navier-Stokes equations arc solved based on the finite Flexible structure;Airfoil;Lock-in phenomenon;Lift coefficient;volume method and dynamic mesh technique is used to carry out partial fluid s...The 2D incompressible Navier-Stokes equations arc solved based on the finite Flexible structure;Airfoil;Lock-in phenomenon;Lift coefficient;volume method and dynamic mesh technique is used to carry out partial fluid structure interaction.The local flexible structure(hereinafter termed as flexible structure)vibrates in a single mode located on the upper surface of the airfoil.The Influence of vibration frequency and amplitude are examined and the corresponding fluid flow characteristics are investigated Computational fluid dynamics(CFD)which add complexity to the inherent problem in unsteady flow.The study is conducted for flow over NACA0012 airfoil at 600≤Re≤3000 at a low angle of attack.Vibration of flexible structure induces a secondary vortex which modifies the pressure distribution and lift performance of the airfoil.At some moderate vibration amplitude,frequency synchronization frequency of rigid airfoil.Evolution and shedding of vortices corresponding to the deformation of flexible structure depends on the Reynolds number.In the case of Re≤1000,the deformation of flexible structure is considered in-phase with the vortex shedding i.e.,increasing maximum lift is linked with the positive deformation of flexible structure.At Re=1500 a phase shift of about 1/π exists while they are out-of-phase at Re>1500.Moreover,the oscillation amplitude of lift coefficient increases with increasing vibration amplitude for Re£1500 while it decreases with increasing vibration amplitude for Re>1500.As a result of frequency lock-in,the average lift coefficient is increased with increasing vibration amplitude for all investigated Reynolds numbers(Re).The maximum increase in the average liftcoefficient is 19.72% within the range of investigated parameters.展开更多
基金supported by National Natural Science Foundation of China(51236001 and 51576008)National Basic Research Program of China(2012CB720201)+1 种基金Aeronautical Science Foundation of China(2014ZB51018)Fundamental Research Funds for the Central Universities
文摘The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed（SPS） casing treatment when fan/compressor suffers from a radial total pressure inlet distortion.Experimental researches are conducted on a low-speed compressor with and without SPS casing treatment under radial distorted inlet flow of different levels as well as uniform inlet flow.The distorted flow fields of different levels are generated by annular distortion flow generators of different heights.The characteristic curves under these conditions are measured and analyzed.The results show that the radial inlet distortion could cause a stall margin loss from 2%to30%under different distorted levels.The SPS casing treatment could remedy this stall margin loss under small distortion level and only partly make up the stall margin loss caused by distortion in large level without leading to perceptible additional efficiency loss and obvious change of characteristic curves.The pre-stall behavior of the compressor is investigated to reveal the mechanism of this stall margin improvement ability of the SPS casing treatment.The results do show that this casing treatment delays the occurrence of rotating stall by weakening the pressure perturbations and suppressing the nonlinear amplification of the stall precursor waves in the compression system.
基金Supported by the National Science Foundation of Zhejiang Province(Z13E060001)the National Natural Science Foundation of China(52176091)+1 种基金the National Science Foundation of Shandong Province(ZR2012EEQ017)the PhD Program Foundation of Ministry of Education of China(20120101110102)
文摘A research on the heat transfer performance of kerosene flowing in a vertical upward tube at supercritical pressure is presented.In the experiments,insights are offered on the effects of the factors such as mass flux,heat flux,and pressure.It is found that increasing mass flux reduces the wall temperature and separates the experimental section into three different parts,while increasing working pressure deteriorates heat transfer.The extended corresponding-state principle can be used for evaluating density and transport properties of kerosene,including its viscosity and thermal conductivity,at different temperatures and pressures under supercritical conditions.For getting the heat capacity,a Soave–Redlich–Kwong(SRK)equation of state is used.The correlation for predicting heat transfer of kerosene at supercritical pressure is established and shows good agreement with the experimental data.
基金supported by a grant from the National Science and Technology Major Projects of China (No. 2013ZX04001051)
文摘Inspection techniques for aero-engine blades are a hot topic in industry. Since these blades have a sculptured surface and a small datum, measurement results may deviate from an actual position. There are few proper approaches compensating for non-uniform distribution errors that are within specified tolerance ranges. This study aimed to develop a meshing structure measuring approach for the distortion of blades via non-contact optical 3D scanning. A rough measurement and a registration procedure are initially adopted to rectify the coordinate system of a blade, which avoids the initial coordinate system errors caused by the small datum. A measurement path with meshing structure is then unfolded on the blade surface. For non-uniform distribution errors, the meshing structure measurement is more visual and clear than the traditional constant height curves method. All measuring points take only 7 min to complete, and the distribution of error is directly and accurately presented by the meshing structure. This study provides a basis for future research on distortion control and error compensation.
基金supported by Funding for Outstanding Doctoral Dissertation in NUAA (No. BCXJ 14-01)Funding of Jiangsu Innovation Program for Graduate Education (No. CXLX12_0169)
文摘A triple swirler combustor is considered to be a promising solution for future high temperature rise combustors. The present paper aims to study dilution holes including primary dilution holes and secondary dilution holes on the performance of a triple swirler combustor. Experimental investigations are conducted at different inlet airflow velocities（40–70 m/s） and combustor overall fuel–air ratio with fixed inlet airflow temperature（473 K） and atmospheric pressure. The experimental results show that the ignition is very difficult with specific performance of high ignition fuel–air ratio when the primary dilution holes are located 0.6H（where H is the liner dome height）downstream the dome, while the other four cases have almost the same ignition performance. The position of primary dilution holes has an effect on lean blowout stability and has a large influence on combustion efficiency. The combustion efficiency is the highest when the primary dilution holes are placed 0.9H downstream the dome among the five different locations.For the secondary dilution holes, the pattern factor of Design A is better than that of Design B.
基金supported by the National Natural Science Foundation of China(No.51475022)
文摘The fatigue lives of materials and structures at different strain levels show het- eroscedasticity. In addition when the number of test specimens is insufficient, the fatigue strength coefficient and fatigue ductility coefficient of the fitting parameters in the total strain life equa- tion may not have definite physical significance. In this work, a maximum likelihood method for estimating probabilistic strain amplitude fatigue life curves is presented based on the fatigue lives at different strain levels. The proposed method is based on the general basic assumption that the logarithm of fatigue life at an arbitrary strain level is normally distributed. The rela- tionship among the parameters of total strain life equation, monotonic ultimate tensile stress and percentage reduction of area is adopted. The presented approach is finally illustrated by two applications. It is shown that probabilistic strain amplitude-fatigue life curves can be eas- ily estimated based on the maximum likelihood method. The results show that fatigue lives at different strain levels have heteroscedasticity and the values of fatigue strength coefficient and fatigue ductility coefficient obtained by the proposed method are close to those of the true tensile fracture stress and true tensile fracture strain.
基金supported by the National Natural Science Foundation of China (No. 51106006)
文摘The liquid droplet evaporation character is important for not only combustion chamber design process but also high-accuracy spray combustion simulation. In this paper, the suspended droplets＇ evaporation character was measured in a quiescent high-temperature environment by micro high-speed camera system. The gasoline and kerosene experimental results are consistent with the reference data. Methanol, common kerosene and aviation kerosene droplet evaporation characteristics, as well as their evaporation rate changing with temperature, were obtained. The evaporation rate experimental data were compared with the prediction result of Ranz-Marshall boiling temperature model（RMB）, Ranz-Marshall low-temperature model（RML）, drift flux model（DFM）, mass analogy model（MAM）, and stagnant film model（SFM）. The disparity between the experimental data and the model prediction results was mainly caused by the neglect of the natural convection effect, which was never introduced into the droplet evaporation concept. A new droplet evaporation model with consideration of natural convection buoyancy force effect was proposed in this paper. Under the experimental conditions in this paper, the calculation results of the new droplet evaporation model were agreed with the experimental data for kerosene, methanol and other fuels, with less than 20% relative deviations. The relative deviations between the new evaporation model predictions for kerosene and the experimental data from the references were within 10%.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11572025,11202013 and 51420105008
文摘To shed light on the subgrid-seale （SGS） modeling methodology of nonlinear systems such as the Navier-Stokes turbulence, we define the concepts of assumption and restriction in the modeling procedure, which are shown by generalized derivation of three general mathematical constraints for different combinations of restrictions. These constraints are verified numerically in a one-dimensional nonlinear advection equation. This study is expected to inspire future research on the SGS modeling methodology of nonlinear systems.
基金funding from the European Community’s Seventh Framework Program (FP7/2007-2013) under grant agreement 225967 ‘‘Next Mu SE”supported by the National Natural Science Foundation of China (Nos. 11202013, 11572025 and 51420105008)
文摘The smoothed particle hydrodynamics（SPH） method is usually expected to be an efficient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by introducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square（LS） and Moving-Least-Square（MLS） methods. Then detailed analysis in spectral space is presented for people to better understand this method. Finally we show three test examples to verify the method behavior.
基金supported by the National Natural Science Foundation of China(Nos.11572025,11202013,and 51420105008)
文摘Closure models started from Chou＇s work have been developed for more than 70 years, aiming at providing analytical tools to describe turbulent flows in the spectral space. In this study, a preliminary attempt is presented to introduce a closure model in the physical space, using the velocity structure functions as key parameters. The present closure model appears to qualitatively reproduce the asymptotic scaling behav- iors at small and large scales, despite some inappropriate behaviors such as oscillations. Therefore, further improvements of the present model are expected to provide appropriate descriptions of turbulent flows in the physical space.
文摘The closure of a turbulence field is a longstanding fundamental problem, while most closure models are introduced in spectral space. Inspired by Chou＇s quasi-normal closure method in spectral space, we propose an analytical closure model for isotropic turbulence based on the extended scale similarity theory of the velocity structure function in physical space. The assumptions and certain approximations are justified with direct numerical simulation. The asymptotic scaling properties are reproduced by this new closure method, in comparison to the classical Batchelor model.
基金supported by National Natural Science Foundation of China(51236001)National Basic Research Program of China(2012CB720201)Beijing Natural Science Foundation(No.3151002)
文摘The current paper presents experimental and computational results to assess the effectiveness of non-axisymmetric endwall contouring in a compressor linear cascade. The endwaU was designed by an endwall design optimi- zation platform at 0° incidence （design condition）. The optimization method is based on a genetic algorithm. The design objective was to minimize the total pressure losses. The experiments were carried out in a compressor cascade at a low-speed test facility with a Mach number of 0.15. Four nominal inlet flow angles were chosen to test the performance of non-axisymmetric Contoured Endwall （CEW）. A five-hole pressure probe with a head diameter of 2 mm was used to traverse the downstream flow fields of the flat-endwall （FEW） and CEW cascades. Both the measured and predicted results indicated that the implementation of CEW results in smaller comer stall, and reduction of total pressure losses. The CEW gets 15.6% total pressure loss coefficient reduction at design condition, and 22.6% at off-design condition （＋7° incidence）. And the mechanism of the improvement of CEW based on both measured and calculated results is that the adverse pressure gradient （APG） has been reduced through the groove configuration near the leading edge （LE） of the suction surface （SS）.
基金This work is supported by National Science Foundation of Zhejiang Province(LZ13E060001)National Natural Science Foundation of China(51210011)Zhejiang Provincial Public Projects(analysis and test)of Zhejiang Province(2015C37027).
文摘The 2D incompressible Navier-Stokes equations arc solved based on the finite Flexible structure;Airfoil;Lock-in phenomenon;Lift coefficient;volume method and dynamic mesh technique is used to carry out partial fluid structure interaction.The local flexible structure(hereinafter termed as flexible structure)vibrates in a single mode located on the upper surface of the airfoil.The Influence of vibration frequency and amplitude are examined and the corresponding fluid flow characteristics are investigated Computational fluid dynamics(CFD)which add complexity to the inherent problem in unsteady flow.The study is conducted for flow over NACA0012 airfoil at 600≤Re≤3000 at a low angle of attack.Vibration of flexible structure induces a secondary vortex which modifies the pressure distribution and lift performance of the airfoil.At some moderate vibration amplitude,frequency synchronization frequency of rigid airfoil.Evolution and shedding of vortices corresponding to the deformation of flexible structure depends on the Reynolds number.In the case of Re≤1000,the deformation of flexible structure is considered in-phase with the vortex shedding i.e.,increasing maximum lift is linked with the positive deformation of flexible structure.At Re=1500 a phase shift of about 1/π exists while they are out-of-phase at Re>1500.Moreover,the oscillation amplitude of lift coefficient increases with increasing vibration amplitude for Re£1500 while it decreases with increasing vibration amplitude for Re>1500.As a result of frequency lock-in,the average lift coefficient is increased with increasing vibration amplitude for all investigated Reynolds numbers(Re).The maximum increase in the average liftcoefficient is 19.72% within the range of investigated parameters.
