The low diffusion （LD） particle method, proposed by Burt and Boyd, is modified for the near-continuum two-phase flow simulations. The LD method has the advantages of easily coupling with the direct simulation Monte ...The low diffusion （LD） particle method, proposed by Burt and Boyd, is modified for the near-continuum two-phase flow simulations. The LD method has the advantages of easily coupling with the direct simulation Monte Carlo （DSMC） method for multi-scale flow simulations and dramatically reducing the numerical diffusion error and statistical scatter of the equilibrium particle methods. Liquidor solid-phase particles are introduced in the LD method. Their velocity and temperature updating are respectively, calculated from the motion equation and the temperature equation according to the local gas properties. Coupling effects from condensed phase to gas phase are modeled as momentum and energy sources, which are respectively, equal to the negative values of the total momentum and energy increase in liquid or solid phase. The modified method is compared with theoretical results for unsteady flows, and good agreements are obtained to indicate the reliability of the one-way gas-to-particle coupling models. Hybrid LD-DSMC algorithm is implemented and performed for nozzle discharging gas-liquid flow to show the prospect of the LD-DSMC scheme for multi-scale two-phase flow simulations.展开更多
Degenerative disc disease is the most common cause of low back pain. Intervertebral disc abnormalities are commonly evaluated by magnetic resonance imaging (MRI), and Pfirrmann’s system involves the use of T2-weighte...Degenerative disc disease is the most common cause of low back pain. Intervertebral disc abnormalities are commonly evaluated by magnetic resonance imaging (MRI), and Pfirrmann’s system involves the use of T2-weighted images (T2WI) to classify disc degeneration. However, as this classification is based on visual evaluation, it is not possible to quantify degeneration using this method. The present study was performed to establish an MRI-based intervertebral disc classification system using diffusional kurtosis imaging (DKI), to quantify intervertebral disc water content according to the Pfirrmann classification. Sagittal mean diffusional kurtosis (MK) mapping was performed for the L3/4, L4/5, and L5/S1 intervertebral discs in 32 patients (15 female, 17 male;age range, 24 - 82 years;mean age, 57.7 years). The degree of disc degeneration was assessed in the midsagittal section on T2WI according to the Pfirrmann classification (grade I - V). The relationships between MK values, which are correlated with intervertebral disc composition changes, and grade of degeneration determined using the Pfirrmann classification were analyzed. The MK values tended to decrease with increasing grade of degeneration, and differed significantly between grades I and IV, but not between grade IV and V (P < 0.05, Mann-Whitney U test). DKI is an effective means of detecting the early stages of disc degeneration. Therefore, DKI may be a useful diagnostic tool for quantitative assessment of intervertebral disc degeneration.展开更多
Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal a...Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal anodes severely hinder its application.In this work,the porous Cu skeleton modified with Cu_(6)Sn_(5)layer is prepared via dealloying brass foil following a facile electroless process.The porous Cu skeleton with large specific surface area and high electronic conductivity effectively reduces the local current density.The Cu_(6)Sn_(5)can react with lithium during the discharge process to form lithiophilic Li_(7)Sn_(2)in situ to promote Li-ions transport and reduce the nucleation energy barrier of lithium to guide the uniform lithium deposition.Therefore,more than 300 cycles at 1 mA cm^(−2)are achieved in the half-cell with an average Coulombic efficiency of 97.5%.The symmetric cell shows a superior cycle life of more than 1000 h at 1 mA cm^(−2)with a small average hysteresis voltage of 16 mV.When coupled with LiFePO_(4)cathode,the full cell also maintains excellent cycling and rate performance.展开更多
In this paper, we discussed population model of two competing populations with non-linear double diffusion and variable density which described by nonlinear system of competing individuals. We identify new properties,...In this paper, we discussed population model of two competing populations with non-linear double diffusion and variable density which described by nonlinear system of competing individuals. We identify new properties, such as finite speed of propagation, and localization of the outbreaks in a specific area.展开更多
Centrifugal compressors for the fuel cell vehicles often operate near the surge line compared with the turbocharger compressors.Low solidity and half vaned diffusers are recognized as good ways to improve the stabilit...Centrifugal compressors for the fuel cell vehicles often operate near the surge line compared with the turbocharger compressors.Low solidity and half vaned diffusers are recognized as good ways to improve the stability of the centrifugal compressor.The presented work investigated four diffuser configurations (i.e.,the vaneless diffuser (VLD),full-height low solidity vaned diffuser (LSVD),hub-side half vaned diffuser (HVD) and shroud-side half vaned diffuser (SVD)) through steady-state and unsteady numerical simulations.The results show that the best performance is achieved by the LSVD,HVD and SVD at the design,surge and choke conditions.The flow rate at the surge operating point of the HVD has decreased by 15.53% compared with the LSVD,and 9.21% compared with the VLD.At near surge operating point,a longitudinal suction side passage vortex is formed on the hub of the LSVD and rotates as circumferential stall cells.A hairpin vortex is formed along the leading edge and is dragged by the main flow along the suction side as a local vortex shedding.The mechanism of the stability improvement by half vaned diffusers is that the tip leakage vortex migrates from the clearance side to the vane mounting side and replenishes the low-momentum zone on the mounting side.The best position where the half vaned diffuser should be mounted is based on the impeller outlet flow conditions,namely,the location of the wake region,where the meridional velocity and relative stagnation pressure is low.展开更多
This paper deals with the effect of the blade tip-groove of the low solidity cascade diffuser (LSD) on the blowercharacteristic and the noise generated by the LSD. The small grooves were set up at the root and/or tip ...This paper deals with the effect of the blade tip-groove of the low solidity cascade diffuser (LSD) on the blowercharacteristic and the noise generated by the LSD. The small grooves were set up at the root and/or tip near theleading edge of the LSD blade. In order to clarify the mechanism of noise increase due to LSD and also to reducethe noise, the relationships between the noise increase based on the LSD, the LSD performance and the secondaryflow formed additionally by the tip-groove were investigated experimentally as well as numerically, especiallyanalyzing flow behaviors in the LSD in view points of flow separation on the suction surface of the LSD bladeand the secondary flow on the side walls. By reducing the stagnation region smaller near the root and/or tip of theLSD blade leading edge, the secondary flow behavior changes remarkably around the LSD blade, as a result, thenoise level and the blower characteristics vary. It can be concluded that, by means of a small tip-groove locatedonly at the shroud side near the LSD blade leading edge, the noise generated by the LSD can be reduced withoutdeteriorations of the LSD performance and the blower characteristics as well.展开更多
A numerical procedure for hydrodynamic redesign of the conventional vaned diffuser into the low solidity vaned diffuser by means of a real-coded genetic algorithm with Boltzmann, Tournament and Roulette Wheel selectio...A numerical procedure for hydrodynamic redesign of the conventional vaned diffuser into the low solidity vaned diffuser by means of a real-coded genetic algorithm with Boltzmann, Tournament and Roulette Wheel selection is presented. In the first part, an investigation on the relative efficiency of the different real-coded genetic algorithm is carried out on a typical mathematical test function. The real-coded genetic algorithm with Boltzmann selection shows the best optimization performance compared to the Tournament and Roulette Wheel selection. In the second part, an approach to redesign the vaned diffuser profile is introduced. Goal of the optimum design is to search the highest static pressure recovery coefficient and low solidity vaned diffuser. The result of the low solidity vaned diffuser optimum design confirms that the efficiency and optimization performance of the real-coded Boltzmann selection genetic algorithm outperforms the other selection methods. A comparison between the designed low solidity vaned diffuser and original vaned diffuser shows that the diffuser pump with the redesigned low solidity vaned diffuser has the higher static pressure recovery and improved total hydrodynamic performance. In addition, the smaller outlet diameter of designed vaned diffuser tends to a more compact size of diffuser pump compared to the original diffuser pump. The obtained results also demonstrate the real-coded Boltzmann selection genetic algorithm is a promising optimization algorithm for centrifugal pumps design.展开更多
This paper presents a hydrodynamic redesign of the conventional vaneddiffuser into the low solidity varied diffuser for the maximum static pressure recovery in acentrifugal pump. A Bezier curve representation for prof...This paper presents a hydrodynamic redesign of the conventional vaneddiffuser into the low solidity varied diffuser for the maximum static pressure recovery in acentrifugal pump. A Bezier curve representation for profile description was coupled with ablade-to-blade flow calculation and a real-coded genetic algorithm. A low solidity vaned diffuser of0.89 in solidity was obtained through the present optimum design. Numerical analysis andexperimental test were made to evaluate the hydrodynamic performance of the centrifugal pump withthe designed low solidity vaned diffuser and original vaned diffuser. The obtained resultsdemonstrate that the centrifugal pump with the optimized vaned diffuser has compact size comparedwith the original one while the performance requirements have been met.展开更多
According to the previous experimental works on the low solidity circular cascade diffuser (LSD), a pressure recovery of a centrifugal blower was improved by the LSD significantly in a wide range of flow rate, and the...According to the previous experimental works on the low solidity circular cascade diffuser (LSD), a pressure recovery of a centrifugal blower was improved by the LSD significantly in a wide range of flow rate, and the pres-sure recovery was improved further by the LSD with a tandem cascade in comparison with the LSD with a sin-gle-row cascade. In the present study, the flow behavior in the LSD with the tandem cascade has been analyzed numerically by using the commercial CFD code of ANSYS-CFX12. It was shown clearly that the higher pressure recovery was achieved by applying the LSD with the tandem cascade, and the high pressure recovery is based on the high pressure rise in the vaneless space upstream of the LSD and the high blade loading of the front blade of the LSD. The high pressure recovery in the LSD could be achieved by controlling the flow separation on the suc-tion surface of the front blade and also on that of the rear blade due to formation of the favorable secondary flow and due to increase in mass flow passing through the slit section between the front and rear blades.展开更多
High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating...High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating the efficiency at design flow rate. A numerical simulation is very effective in design procedure, however, cost of the numerical simulation is generally high during the practical design process, and it is difficult to confn＇m the optimal design which is combined with many parameters. A multi-objective optimization technique is the idea that has been proposed for solving the problem in practical design process. In this study, a Low Solidity circular cascade Diffuser （LSD） in a centrifugal blower is successfully designed by means of multi-objective optimization technique. An optimization code with a meta-model assisted evolutionary algorithm is used with a commercial CFD code ANSYS-CFX. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified by overall performance test. The detailed flow in the diffuser is also confirmed by means of a Particle Image Velocimeter. Secondary flow is clearly captured by PIV and it spreads to the whole area of LSD blade pitch. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect.展开更多
A three-dimensional blade of a low solidity circular cascade diffuser in centrifugal blowers is designed by means of a multi-point optimization technique. The optimization aims at improving static pressure coefficient...A three-dimensional blade of a low solidity circular cascade diffuser in centrifugal blowers is designed by means of a multi-point optimization technique. The optimization aims at improving static pressure coefficient at a design point and at a small flow rate condition. Moreover, a clear definition of secondary flow expressed by positive radial velocity at hub side is taken into consideration in constraints. The number of design parameters for three-dimensional blade reaches to 10 in this study, such as a radial gap, a radial chord length and mean camber angle distribution of the LSD blade with five control points, control point between hub and shroud with two design freedom. Optimization results show clear Pareto front and selected optimum design shows good improvement of pressure rise in diffuser at small flow rate conditions. It is found that three-dimensional blade has advantage to stabilize the secondary flow effect with improving pressure recovery of the low solidity circular cascade diffuser.展开更多
The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a...The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a back- ward curved impeller of 500 turn tip diameter and 24.5 mm width and its design flow coefficient is Фd=0.0535. Three different low solidity diffuser vane shapes namely uncarnbered aerofoil, constant thickness flat plate and circular arc cambered constant thickness plate were chosen as the variants for diffuser vane shape and all the three shapes have the same thickness to chord ratio （t/c=0.1）. Flow coefficient, polytropic efficiency, total head coeffi- cient, power coefficient and static pressure recovery coefficient were chosen as the parameters for evaluating the effect of diffuser vane shape on the stage performance. The results show that there is reasonable improvement in stage efficiency and total head coefficient with the use of the chosen diffuser vane shapes as compared to conven- tional vaneless diffuser. It is also noticed that the aero foil shaped LSD has shown better performance when com- pared to flat plate and circular arc profiles. The aerofoil vane shape of the diffuser blade is seen to be tolerant over a considerable range of incidence.展开更多
文摘The low diffusion （LD） particle method, proposed by Burt and Boyd, is modified for the near-continuum two-phase flow simulations. The LD method has the advantages of easily coupling with the direct simulation Monte Carlo （DSMC） method for multi-scale flow simulations and dramatically reducing the numerical diffusion error and statistical scatter of the equilibrium particle methods. Liquidor solid-phase particles are introduced in the LD method. Their velocity and temperature updating are respectively, calculated from the motion equation and the temperature equation according to the local gas properties. Coupling effects from condensed phase to gas phase are modeled as momentum and energy sources, which are respectively, equal to the negative values of the total momentum and energy increase in liquid or solid phase. The modified method is compared with theoretical results for unsteady flows, and good agreements are obtained to indicate the reliability of the one-way gas-to-particle coupling models. Hybrid LD-DSMC algorithm is implemented and performed for nozzle discharging gas-liquid flow to show the prospect of the LD-DSMC scheme for multi-scale two-phase flow simulations.
文摘Degenerative disc disease is the most common cause of low back pain. Intervertebral disc abnormalities are commonly evaluated by magnetic resonance imaging (MRI), and Pfirrmann’s system involves the use of T2-weighted images (T2WI) to classify disc degeneration. However, as this classification is based on visual evaluation, it is not possible to quantify degeneration using this method. The present study was performed to establish an MRI-based intervertebral disc classification system using diffusional kurtosis imaging (DKI), to quantify intervertebral disc water content according to the Pfirrmann classification. Sagittal mean diffusional kurtosis (MK) mapping was performed for the L3/4, L4/5, and L5/S1 intervertebral discs in 32 patients (15 female, 17 male;age range, 24 - 82 years;mean age, 57.7 years). The degree of disc degeneration was assessed in the midsagittal section on T2WI according to the Pfirrmann classification (grade I - V). The relationships between MK values, which are correlated with intervertebral disc composition changes, and grade of degeneration determined using the Pfirrmann classification were analyzed. The MK values tended to decrease with increasing grade of degeneration, and differed significantly between grades I and IV, but not between grade IV and V (P < 0.05, Mann-Whitney U test). DKI is an effective means of detecting the early stages of disc degeneration. Therefore, DKI may be a useful diagnostic tool for quantitative assessment of intervertebral disc degeneration.
基金supported by the National Natural Science Foundation of China(52072173)the Jiangsu Province Outstanding Youth Fund(BK20200016)the International Cooperation of Jiangsu Province(SBZ2022000084)
文摘Lithium metal batteries are emerging as a strong candidate in the future energy storage market due to its extremely high energy density.However,the uncontrollable lithium dendrites and volume change of lithium metal anodes severely hinder its application.In this work,the porous Cu skeleton modified with Cu_(6)Sn_(5)layer is prepared via dealloying brass foil following a facile electroless process.The porous Cu skeleton with large specific surface area and high electronic conductivity effectively reduces the local current density.The Cu_(6)Sn_(5)can react with lithium during the discharge process to form lithiophilic Li_(7)Sn_(2)in situ to promote Li-ions transport and reduce the nucleation energy barrier of lithium to guide the uniform lithium deposition.Therefore,more than 300 cycles at 1 mA cm^(−2)are achieved in the half-cell with an average Coulombic efficiency of 97.5%.The symmetric cell shows a superior cycle life of more than 1000 h at 1 mA cm^(−2)with a small average hysteresis voltage of 16 mV.When coupled with LiFePO_(4)cathode,the full cell also maintains excellent cycling and rate performance.
文摘In this paper, we discussed population model of two competing populations with non-linear double diffusion and variable density which described by nonlinear system of competing individuals. We identify new properties, such as finite speed of propagation, and localization of the outbreaks in a specific area.
基金The research is supported by National Natural Science Foundation of China(51875410).
文摘Centrifugal compressors for the fuel cell vehicles often operate near the surge line compared with the turbocharger compressors.Low solidity and half vaned diffusers are recognized as good ways to improve the stability of the centrifugal compressor.The presented work investigated four diffuser configurations (i.e.,the vaneless diffuser (VLD),full-height low solidity vaned diffuser (LSVD),hub-side half vaned diffuser (HVD) and shroud-side half vaned diffuser (SVD)) through steady-state and unsteady numerical simulations.The results show that the best performance is achieved by the LSVD,HVD and SVD at the design,surge and choke conditions.The flow rate at the surge operating point of the HVD has decreased by 15.53% compared with the LSVD,and 9.21% compared with the VLD.At near surge operating point,a longitudinal suction side passage vortex is formed on the hub of the LSVD and rotates as circumferential stall cells.A hairpin vortex is formed along the leading edge and is dragged by the main flow along the suction side as a local vortex shedding.The mechanism of the stability improvement by half vaned diffusers is that the tip leakage vortex migrates from the clearance side to the vane mounting side and replenishes the low-momentum zone on the mounting side.The best position where the half vaned diffuser should be mounted is based on the impeller outlet flow conditions,namely,the location of the wake region,where the meridional velocity and relative stagnation pressure is low.
文摘This paper deals with the effect of the blade tip-groove of the low solidity cascade diffuser (LSD) on the blowercharacteristic and the noise generated by the LSD. The small grooves were set up at the root and/or tip near theleading edge of the LSD blade. In order to clarify the mechanism of noise increase due to LSD and also to reducethe noise, the relationships between the noise increase based on the LSD, the LSD performance and the secondaryflow formed additionally by the tip-groove were investigated experimentally as well as numerically, especiallyanalyzing flow behaviors in the LSD in view points of flow separation on the suction surface of the LSD bladeand the secondary flow on the side walls. By reducing the stagnation region smaller near the root and/or tip of theLSD blade leading edge, the secondary flow behavior changes remarkably around the LSD blade, as a result, thenoise level and the blower characteristics vary. It can be concluded that, by means of a small tip-groove locatedonly at the shroud side near the LSD blade leading edge, the noise generated by the LSD can be reduced withoutdeteriorations of the LSD performance and the blower characteristics as well.
文摘A numerical procedure for hydrodynamic redesign of the conventional vaned diffuser into the low solidity vaned diffuser by means of a real-coded genetic algorithm with Boltzmann, Tournament and Roulette Wheel selection is presented. In the first part, an investigation on the relative efficiency of the different real-coded genetic algorithm is carried out on a typical mathematical test function. The real-coded genetic algorithm with Boltzmann selection shows the best optimization performance compared to the Tournament and Roulette Wheel selection. In the second part, an approach to redesign the vaned diffuser profile is introduced. Goal of the optimum design is to search the highest static pressure recovery coefficient and low solidity vaned diffuser. The result of the low solidity vaned diffuser optimum design confirms that the efficiency and optimization performance of the real-coded Boltzmann selection genetic algorithm outperforms the other selection methods. A comparison between the designed low solidity vaned diffuser and original vaned diffuser shows that the diffuser pump with the redesigned low solidity vaned diffuser has the higher static pressure recovery and improved total hydrodynamic performance. In addition, the smaller outlet diameter of designed vaned diffuser tends to a more compact size of diffuser pump compared to the original diffuser pump. The obtained results also demonstrate the real-coded Boltzmann selection genetic algorithm is a promising optimization algorithm for centrifugal pumps design.
文摘This paper presents a hydrodynamic redesign of the conventional vaneddiffuser into the low solidity varied diffuser for the maximum static pressure recovery in acentrifugal pump. A Bezier curve representation for profile description was coupled with ablade-to-blade flow calculation and a real-coded genetic algorithm. A low solidity vaned diffuser of0.89 in solidity was obtained through the present optimum design. Numerical analysis andexperimental test were made to evaluate the hydrodynamic performance of the centrifugal pump withthe designed low solidity vaned diffuser and original vaned diffuser. The obtained resultsdemonstrate that the centrifugal pump with the optimized vaned diffuser has compact size comparedwith the original one while the performance requirements have been met.
文摘According to the previous experimental works on the low solidity circular cascade diffuser (LSD), a pressure recovery of a centrifugal blower was improved by the LSD significantly in a wide range of flow rate, and the pres-sure recovery was improved further by the LSD with a tandem cascade in comparison with the LSD with a sin-gle-row cascade. In the present study, the flow behavior in the LSD with the tandem cascade has been analyzed numerically by using the commercial CFD code of ANSYS-CFX12. It was shown clearly that the higher pressure recovery was achieved by applying the LSD with the tandem cascade, and the high pressure recovery is based on the high pressure rise in the vaneless space upstream of the LSD and the high blade loading of the front blade of the LSD. The high pressure recovery in the LSD could be achieved by controlling the flow separation on the suc-tion surface of the front blade and also on that of the rear blade due to formation of the favorable secondary flow and due to increase in mass flow passing through the slit section between the front and rear blades.
基金financially supported by Japan Society for the Promotion of Science(JSPS) program of"Strategic young researcher overseas visits program for accelerating brain circulation"
文摘High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating the efficiency at design flow rate. A numerical simulation is very effective in design procedure, however, cost of the numerical simulation is generally high during the practical design process, and it is difficult to confn＇m the optimal design which is combined with many parameters. A multi-objective optimization technique is the idea that has been proposed for solving the problem in practical design process. In this study, a Low Solidity circular cascade Diffuser （LSD） in a centrifugal blower is successfully designed by means of multi-objective optimization technique. An optimization code with a meta-model assisted evolutionary algorithm is used with a commercial CFD code ANSYS-CFX. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified by overall performance test. The detailed flow in the diffuser is also confirmed by means of a Particle Image Velocimeter. Secondary flow is clearly captured by PIV and it spreads to the whole area of LSD blade pitch. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect.
基金financially supported by Harada memorial foundation and Japan Science and Technology Agency
文摘A three-dimensional blade of a low solidity circular cascade diffuser in centrifugal blowers is designed by means of a multi-point optimization technique. The optimization aims at improving static pressure coefficient at a design point and at a small flow rate condition. Moreover, a clear definition of secondary flow expressed by positive radial velocity at hub side is taken into consideration in constraints. The number of design parameters for three-dimensional blade reaches to 10 in this study, such as a radial gap, a radial chord length and mean camber angle distribution of the LSD blade with five control points, control point between hub and shroud with two design freedom. Optimization results show clear Pareto front and selected optimum design shows good improvement of pressure rise in diffuser at small flow rate conditions. It is found that three-dimensional blade has advantage to stabilize the secondary flow effect with improving pressure recovery of the low solidity circular cascade diffuser.
文摘The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a back- ward curved impeller of 500 turn tip diameter and 24.5 mm width and its design flow coefficient is Фd=0.0535. Three different low solidity diffuser vane shapes namely uncarnbered aerofoil, constant thickness flat plate and circular arc cambered constant thickness plate were chosen as the variants for diffuser vane shape and all the three shapes have the same thickness to chord ratio （t/c=0.1）. Flow coefficient, polytropic efficiency, total head coeffi- cient, power coefficient and static pressure recovery coefficient were chosen as the parameters for evaluating the effect of diffuser vane shape on the stage performance. The results show that there is reasonable improvement in stage efficiency and total head coefficient with the use of the chosen diffuser vane shapes as compared to conven- tional vaneless diffuser. It is also noticed that the aero foil shaped LSD has shown better performance when com- pared to flat plate and circular arc profiles. The aerofoil vane shape of the diffuser blade is seen to be tolerant over a considerable range of incidence.
