The Experimental Study of Matching Between Centrifugal Compressor Impeller and Diffuser

1999 ◽  
Vol 121 (1) ◽  
pp. 113-118 ◽  
Author(s):  
H. Tamaki ◽  
H. Nakao ◽  
M. Saito
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Design Flow ◽  
Negative Slope ◽  
Compressor Stage ◽  
Rate Analysis ◽  
System Pressure ◽  
Compressor Impeller

The centrifugal compressor for a marine use turbocharger with its design pressure ratio of 3.2 was tested with a vaneless diffuser and various vaned diffusers. Vaned diffusers were chosen to cover impeller operating range as broad as possible. The analysis of the static pressure ratio in the impeller and the diffusing system, consisting of the diffuser and scroll, showed that there were four possible combinations of characteristics of impeller pressure ratio and diffusing system pressure ratio, The flow rate, QP, where the impeller achieved maximum static pressure ratio, was surge flow rate of the centrifugal compressor determined by the critical flow rate. In order to operate the compressor at a rate lower than QP, the diffusing system, whose pressure recovery factor was steep negative slope near QP, was needed. When the diffuser throat area was less than a certain value, the compressor efficiency deteriorated; however, the compressor stage pressure ratio was almost constant. In this study, by reducing the diffuser throat area, the compressor could be operated at a flow rate less than 40 percent of its design flow rate. Analysis of the pressure ratio in the impeller and diffusing systems at design and off-design speeds showed that the irregularities in surge line occurred when the component that controlled the negative slope on the compressor stage pressure ratio changed.

scholarly journals The Experimental Study of Matching Between Centrifugal Compressor Impeller and Diffuser

1997 ◽  
Author(s):  
Hideaki Tamaki ◽  
Hidefumi Nakao ◽  
Masayasu Saito
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Design Flow ◽  
Negative Slope ◽  
Compressor Stage ◽  
Rate Analysis ◽  
System Pressure ◽  
Compressor Impeller

The centrifugal compressor for a marine use turbocharger with its design pressure ratio of 3.2 was tested with a vaneless diffuser and various vaned diffusers. Vaned diffusers were chosen to cover impeller operating range as broad as possible. The analysis of the static pressure ratio in the impeller and the diffusing system — consists of the diffuser and scroll — showed that there were four possible combinations of characteristics of impeller pressure ratio and that of diffusing system pressure ratio. The flow rate, QP, where the impeller achieved maximum static pressure ratio was the critical flow rate determined surge flow rate of the centrifugal compressor. In order to operate the compressor less than QP, the diffusing system whose pressure recovery factor was steep negative slope near QP was needed. Using the diffuser throat area less than a certain value, the compressor efficiency deteriorated, however the compressor stage pressure ratio was almost constant. In this study, the compressor by reducing the diffuser throat area could be operated at the flow rate less than 40% of its design flow rate. Analysis of the pressure ratio in the impeller and diffusing systems at design and off design speeds showed that the irregularities in surge line occurred when the component which controlled the negative slope on the compressor stage pressure ratio changed.

Effect of Recirculation Device With Counter Swirl Vane on Performance of High Pressure Ratio Centrifugal Compressor

2011 ◽  
Author(s):  
Hideaki Tamaki
Keyword(s):  
High Pressure ◽  
Mach Number ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Negative Slope ◽  
Tip Leakage Flow ◽  
Recirculation Flow ◽  
Operating Range ◽  
High Pressure Ratio

Centrifugal compressors used for turbochargers need to achieve a wide operating range. The author has developed a high pressure ratio centrifugal compressor with pressure ratio 5.7 for a marine use turbocharger. In order to enhance operating range, two different types of recirculation devices were applied. One is a conventional recirculation device. The other is a new one. The conventional recirculation device consists of an upstream slot, bleed slot and the annular cavity which connects both slots. The new recirculation device has vanes installed in the cavity. These vanes were designed to provide recirculation flow with negative preswirl at the impeller inlet, a swirl counterwise to the impeller rotational direction. The benefits of the application of both of the recirculation devices were ensured. The new device in particular, shifted surge line to a lower flow rate compared to the conventional device. This paper discusses how the new recirculation device affects the flow field in the above transonic centrifugal compressor by using steady 3-D calculations. Since the conventional recirculation device injects the flow with positive preswirl at the impeller inlet, the major difference between the conventional and new recirculation device is the direction of preswirl that the recirculation flow brings to the impeller inlet. This study focuses on two effects which preswirl of the recirculation flow will generate. (1) Additional work transfer from impeller to fluid. (2) Increase or decrease of relative Mach number. Negative preswirl increases work transfer from the impeller to fluid as the flow rate reduces. It increases negative slope on pressure ratio characteristics. Hence the recirculation flow with negative preswirl will contribute to stability of the compressor. Negative preswirl also increases the relative Mach number at the impeller inlet. It moves shock downstream compared to the conventional recirculation device. It leads to the suppression of the extension of blockage due to the interaction of shock with tip leakage flow.

Some Studies on Low Solidity Vaned Diffusers of a Centrifugal Compressor Stage

2005 ◽  
Author(s):  
T. Ch. Siva Reddy ◽  
G. V. Ramana Murty ◽  
Prasad Mukkavilli ◽  
D. N. Reddy
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Pressure Recovery ◽  
Compressor Stage ◽  
Recovery Coefficient ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Centrifugal Compressor Stage ◽  
Pressure Recovery Coefficient

Numerical simulation of impeller and low solidity vaned diffuser (LSD) of a centrifugal compressor stage is performed individually using CFX- BladeGen and BladeGenPlus codes. The tip mach number for the chosen study was 0.35. The same configuration was used for experimental investigation for a comparative study. The LSD vane is formed using standard NACA profile with marginal modification at trailing edge. The performance parameters obtained form numerical studies at the exit of impeller and the diffuser have been compared with the corresponding experimental data. These parameters are pressure ratio, polytropic efficiency and flow angle at the impeller exit where as the parameters those have been compared at the exit of diffuser are the static pressure recovery coefficient and the exit flow angle. In addition, the numerical prediction of the blade loading in terms of blade surface pressure distribution on LSD vane has been compared with the corresponding experimental results. Static pressure recovery coefficient and flow angle at diffuser exit is seen to match closely at higher flows. The difference at lower flows could be due to the effect of interaction between impeller and diffuser combinations, as the numerical analysis was done separately for impeller and diffuser and the effect of impeller diffuser interaction was not considered.

Investigation of Self-Recycling-Casing-Treatment (SRCT) Influence on Stability of High Pressure Ratio Centrifugal Compressor With a Volute

2011 ◽  
Author(s):  
Mingyang Yang ◽  
Ricardo Martinez-Botas ◽  
Yangjun Zhang ◽  
Xinqian Zheng ◽  
Takahiro Bamba ◽  
...  
Keyword(s):  
High Pressure ◽  
Numerical Method ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Flow Distortion ◽  
Casing Treatment ◽  
High Pressure Ratio ◽  
The Stability

Large feasible operation range is a challenge for high pressure ratio centrifugal compressor of turbocharger in vehicle engine. Self-Recycling-Casing-Treatment (SRCT) is a widely used flow control method to enlarge the range for this kind of compressor. This paper investigates the influence of symmetrical/asymmetrical SRCT (ASRCT) on the stability of a high pressure ratio centrifugal compressor by experimental testing and numerical simulation. Firstly, the performance of the compressor with/without SRCT is tested is measured investigate the influence of flow distortion on the stability of compressor as well as the numerical method validation. Then detailed flow field investigation is conducted by experimental measurement and the numerical method to unveil the reasons for stability enhancement by symmetrical/asymmetrical SRCT. Results show that static pressure distortion at impeller outlet caused by the volute can make passages be confronted with flow distortion less stable than others because of their larger positive slope of T-S pressure ratio performance at small flow rate. SRCT can depress the flow distortion and reduce the slope by non-uniform recycling flow rate at impeller inlet. Moreover, ASRCT can redistribute the recycling flow in circumferential direction according to the asymmetric geometries. When the largest recycling flow rate is imposed on the passage near the distorted static pressure, the slope will be the most effectively reduced. Therefore, the stability is effectively enhanced by the optimized recycling flow device.

scholarly journals Numerical and Experimental Studies of Single and Tandem Low-Solidity Cascade Diffusers in a Centrifugal Compressor

1993 ◽  
Author(s):  
Hideomi Harada ◽  
Masanori Goto
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Flow Analysis ◽  
Experimental Studies ◽  
Pressure Recovery ◽  
Compressor Stage ◽  
Analysis Method ◽  
Vaneless Diffuser ◽  
Low Solidity Cascade Diffuser

In order to experimentally determine the performance characteristics of low-solidity cascade diffusers, three kinds of diffusers, a vaneless diffuser, a single and a tandem low-solidity cascade diffuser were attached to a medium specific speed centrifugal compressor stage and tested on a closed-loop test stand. The three-dimensional incompressible viscous flow analysis method, which had recently been established in our laboratory, was used to calculate the internal flow conditions inside of these diffusers. Both the single and tandem low-solidity cascade diffusers performed better than the vaneless diffuser. In particular, the tandem low-solidity cascade diffuser showed an increase in static pressure recovery coefficient of greater than 15% at the design point, and an increase greater than 40% at the lower flow rate, as compared with the pressure recovery of a vaneless diffuser. The total-to-static overall compressor stage efficiency was improved by 4% to 10% from 100% to 70% flow rate by using the tandem diffuser. The measured blade to blade static pressure distribution inside the low-solidity cascade diffusers was compared with the numerical results obtained via 3D viscous incompressible flow analysis, and the authors found that the static pressure recovery was qualitatively well predicted by this flow analysis method.

Experimental Study of Pinch in Vaneless Diffuser of Centrifugal Compressor

2009 ◽  
Author(s):  
Teemu Turunen-Saaresti ◽  
Aki-Pekka Gro¨nman ◽  
Ahti Jaatinen
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Moderate Amount ◽  
Flow Angle ◽  
Isentropic Efficiency

A centrifugal compressor is often equipped with a vaneless diffuser because the operation range of a vaneless diffuser is wider than the operation range of vaned diffuser, and the geometry of the vaneless diffuser is simple and inexpensive. The flow field after the centrifugal compressor rotor is highly complicated and the velocity is high. A moderate amount of this velocity should be recovered to the static pressure. It is important to study the flow field in the vaneless diffuser in order to achieve guidelines for design and an optimal performance. In this article, the experimental study of the pinch in the vaneless diffuser is conducted. Five different diffuser heights were used, b/b2 = 1, b/b2 = 0.903, b/b2 = 0.854, b/b2 = 0.806 and b/b2 = 0.903 (shroud). In three of the cases, the pinch was made to both walls of the diffuser, hub and shroud, and in one case, the pinch was made to the shroud wall. The total and the static pressure, the total temperature and the flow angle were measured at the diffuser inlet and outlet by using a cobra-probe, kiel-probes and flush-mounted pressure taps. In addition, the static pressure in the diffuser was measured at three different radius ratios. The overall performance, the mass flow, the pressure ratio and the isentropic efficiency of the compressor stage were also monitored. Detailed flow field measurements were carried out at the design rotational speed and at the three different mass flows (close to the surge, design and close to the choke). The isentropic efficiency and the pressure ratio of the compressor stage was increased with the pinched diffuser. The efficiency of the rotor and the diffuser was increased, whereas the efficiency of the volute/exit cone was decreased. The pinch made to the shroud wall was the most effective. The pinch made the flow angle more radial and increased the velocity at the shroud where the secondary flow (passage wake) from the rotor is present.

The Analysis of Aerodynamic Load for High Speed Centrifugal Compressor Blade

2013 ◽  
Vol 675 ◽  
pp. 103-106
Author(s):  
Gui Hua Zhu ◽  
Tuan Hui Qiu ◽  
Min Xie
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Fluid Model ◽  
Pressure Ratio ◽  
Design Flow ◽  
Aerodynamic Load ◽  
Impeller Blade ◽  
Rate Condition ◽  
Rotating Speed

With the ANSYS Workbench software,the 3D fluid model of the impeller for the centrifugal compressor is set up,whose design flow is 3.2kg/s,rotating speed is 32473r/min,pressure ratio is 3.8,and then with the method of CFD,the k-ε two equations model is selected as the turbulence model,in the condition of design speed,the fluid region of the impeller is simulated under eight different flow rate,the aerodynamic load of the impeller blade and its distribution is acquired under different flow rate,the results showed that the location of the largest aerodynamic load is in the blade that near the outlet of impeller,under the design flow rate condition,the largest aerodynamic load is 0.1969MPa,the aerodynamic load increases with the flow rate decreases.

CFD Analysis of a Centrifugal Compressor Impeller and Volute

1999 ◽  
Author(s):  
Harri Pitkänen ◽  
Hannu Esa ◽  
Petri Sallinen ◽  
Jaakko Larjola
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Prediction Method ◽  
Navier Stokes ◽  
Recovery Coefficient ◽  
Compressor Impeller ◽  
Compressor Performance ◽  
Pressure Recovery Coefficient

In this study, centrifugal compressor performance was predicted using CFD. Three-dimensional time-averaged impeller and volute simulations were performed using a Navier–Stokes code. The presented performance prediction method has been divided into three phases. Firstly, the impeller was calculated with a vaneless diffuser. That gives inlet boundary conditions for the volute analysis and the pressure ratio at the diffuser exit. Next, the volute analysis was performed and a static pressure recovery coefficient obtained. Finally, that result was combined with the pressure ratio prediction from the impeller analysis, and the overall compressor performance thus obtained.

Numerical study on the Effect of Interaction Vaned Diffuser with Impeller on the Performance of a Modified Centrifugal Compressor

2013 ◽  
Vol 30 (2) ◽  
pp. 113-121 ◽  
Author(s):  
L. H. Jawad ◽  
S. Abdullah ◽  
R. Zulkifli ◽  
W. M. F. W. Mahmood
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Internal Flow ◽  
Compressor Stage ◽  
Vaned Diffuser ◽  
Centrifugal Compressor Stage ◽  
Compressor Impeller ◽  
Inlet Conditions

ABSTRACTThis paper is a numerical simulation that was made in the three-dimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an auto-motive turbo charger. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between compressor impeller and vaned diffuser, influencing significantly surge and the efficiency of centrifugal compressor stages. In addition, a modified compressor impeller, coupled with vane and vaneless diffuser, has been found to have similar internal flow patterns for both the vaneless and vaned diffuser design. The vaned diffuser effect has been paid particular attention in terms of better analysis where the diffuser was designed for high sub-sonic inlet conditions. Another aim of this research was to study and simulate the effect of vaned diffuser on the performance of a centrifugal compressor. The simulation was undertaken by using a commercial software, the so-called ANSYS CFX, to predict numerically the performance in terms of pressure ratio, poly tropic efficiency and mass flow rate for the centrifugal compressor stage. The results were generated from CFD and were analyzed for better understanding of the fluid flow through centrifugal compressor stage. Conclusively, it was observed that the effect of the vaned diffuser is to convert the kinetic energy into a high static pressure after analyzing the results of the simulation.

Experimental and Numerical Investigations on a High Pressure Ratio Centrifugal Compressor

2005 ◽  
Author(s):  
Jae Ho Choi ◽  
Ok Suck Sung ◽  
Seung-Bae Chen ◽  
Jin Shik Lim
Keyword(s):  
Centrifugal Compressor ◽  
Performance Test ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Design Flow ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Compressor Stage

An aerodynamic design, flow analysis and performance test of a pressure ratio 4:1 centrifugal compressor are presented in this paper. The compressor is made up of a centrifugal impeller, a two-stage diffuser consisted of radial and axial types. The impeller has a 45 degree backswept angle and the design running tip clearance is 5% of impeller exit height. Two types of diffusers are designed for this compressor. Three-dimensional numerical analysis is performed to analyze the flows in the impeller, diffuser and deswirler considering the impeller tip clearance. A test module and rig facilities for the compressor stage performance test are designed and fabricated. The overall compressor stage performances as well as the static pressure fields on the impeller and diffuser are measured. Two diffusers of wedge and airfoil types are tested with an impeller. The calculation and test results show the airfoil diffuser has the better aerodynamic characteristics than those of wedge diffuser in the studied models.

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