scholarly journals Experimental and Numerical Analysis of the Impeller Backside Cavity in a Centrifugal Compressor for CAES

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 420
Author(s):  
Zhihua Lin ◽  
Zhitao Zuo ◽  
Wei Li ◽  
Jianting Sun ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Internal Flow ◽  
Axial Thrust ◽  
Rotating Speed ◽  
Aerodynamic Performances ◽  
Shaft Power ◽  
Aerodynamic Parameters ◽  
Coupling Characteristics

Relying on a closed test rig of a high-power intercooling centrifugal compressor for compressed air energy storage (CAES), this study measured the static pressure and static temperature at different radii on the static wall of the impeller backside cavity (IBC) under variable rotating speeds. Simultaneously, the coupled computations of all mainstream domains with IBC or not were used for comparative analysis of the aerodynamic performances of the compressor and the internal flow field in IBC. The results show that IBC has a significant impact on coupling characteristics including pressure ratio, efficiency, torque, shaft power, and axial thrust of the centrifugal compressor. The gradients of radial static pressure and static temperature in IBC both increase with the decrease of mainstream flow or the increase of rotating speed, whose distributions are different under variable rotating speeds due to the change of the aerodynamic parameters of mainstream.

Flow Field Structures of the Impeller Backside Cavity and Its Influences on the Centrifugal Compressor

2009 ◽  
Author(s):  
Zhigang Sun ◽  
Chunqing Tan ◽  
Dongyang Zhang
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Leakage Flow ◽  
Coupled Flow ◽  
Axial Thrust ◽  
Aerodynamic Performances ◽  
Shaft Power

The impeller backside cavity is one of the unique features of the centrifugal compressors, it can affect the aerodynamic performances of a centrifugal compressor in many ways. This paper presents the researches on the coupled flow fields between a centrifugal compressor main flow passage and its impeller backside cavity. The flow field structures and features of the impeller backside cavity are presented for different leakage flow patterns, and its influences on the flow field details, axial thrust, shaft power, pressure ratio and efficiency of the centrifugal compressor have been studied. Some general conclusions are drawn for different centrifugal compressor operating conditions and impeller backside cavity leakage flow patterns.

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.

Investigation of Stall Process in a Centrifugal Compressor With a Volute Under Transonic Conditions

2019 ◽  
Author(s):  
Ce Yang ◽  
Wenli Wang ◽  
Hanzhi Zhang ◽  
Yanzhao Li ◽  
Ding Tong ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Cell Formation ◽  
Internal Flow ◽  
Growth Zone ◽  
Asymmetric Structure ◽  
Stall Inception ◽  
Stall Cells ◽  
Inlet Conditions

Abstract In a centrifugal compressor with a volute, the internal flow field is circumferentially nonuniform owing to the asymmetric structure of the volute. Currently, the mechanisms by which the volute influences the stall inception circumferential position and the stall process in a transonic centrifugal compressor are not clear. In this study, the stall process in the centrifugal compressor with a volute is investigated under transonic inlet conditions. Obtained by experimental and simulation results, the static pressure distributions around the casing wall are compared with each other. Thereafter, an unsteady simulation is conducted on the stall process under transonic inlet conditions. By analyzing the stall cell evolution pattern at the impeller inlet, the stall process can be divided into three stages: stall onset, stall development, and stall maturation. The spike-type stall inceptions occur twice at the tip in the circumferential 135° position of the impeller inlet. This circumferential position is also the affected position of the high static pressure region induced by the volute tongue. Because of the circumferentially nonuniform flow field, there is a stall cell decay zone and a stall cell formation/growth zone at the impeller inlet. For the compressor under study, the approximate circumferential range of 135° to 270° is the decay zone, and the circumferential range of 270° to 360° is the formation/growth zone. The stall inception cannot occur in the decay zone. However, the stall cells can pass through the decay zone when the stall cell size is large enough. The first stall inception cannot propagate circumferentially, while the second one can. The propagation speed of stall cells in the circumferential direction is at approximately 70% of the rotational speed of impeller.

Effects of Scalloped Centrifugal Impellers on Aerodynamic and Rotordynamic Performance Using CFD Techniques

2000 ◽  
Author(s):  
J. Jeffrey Moore
Keyword(s):  
Flow Field ◽  
Static Pressure ◽  
Rotating Stall ◽  
Thermodynamic Efficiency ◽  
Moderate Increase ◽  
Primary Flow ◽  
Axial Thrust ◽  
Flow Angle ◽  
Baseline Case ◽  
Shaft Power

Abstract Impeller scallops are intentional cuts in the hub and shroud surfaces at the exit of centrifugal impellers that are intended to prevent high cycle fatigue in these areas. The goal of this analysis is to determine what effect the scallops have on aerodynamic performance, rotordynamic stability, rotating stall criteria, axial thrust, and mechanical shaft power. Furthermore, this study improves the understanding of the interaction with the secondary passage and determines the effect on the flow field entering the diffuser. A 3D viscous CFD model is generated of a single blade passage that couples the primary flow passage with the secondary shroud passage. This approach captures the complex interaction that occurs at the impeller exit due to the presence of the scallops. The predictions show a small penalty in thermodynamic efficiency with the presence of the scallops compared to a baseline case. The results also show a moderate increase in shaft horsepower calculated by integrating static pressure and shear stress acting on the impeller and shroud surfaces. Circumferential swirl in the shroud passage shows only modest increases with the addition of the scallops. Therefore, rotordynamic performance is not significantly affected nor is axial thrust acting on the impeller. The predictions demonstrate the effect the scallops have on the flow field entering the diffuser including variations in flow angle at the impeller exit.

Aerodynamic analysis of nonuniform trailing edge blowing

2018 ◽  
Vol 91 (1) ◽  
pp. 134-144
Author(s):  
Dong Liang ◽  
Wenjie Wang ◽  
Peter J. Thomas
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Base Flow ◽  
Trailing Edge ◽  
Axial Thrust ◽  
Content Type ◽  
Low Speed ◽  
Rotor Stator Interaction ◽  
Aerodynamic Parameters ◽  
Total Pressure Ratio

Purpose Numerical and experimental results for different oncoming base-flow conditions indicate that nonuniform trailing edge blowing (NTEB) can expand the performance range of compressors and reduce the thrust on the rotor, while the efficiency of the compressor can be improved by more than 2 per cent. Design/methodology/approach Relevant aerodynamic parameters, such as total pressure, ratio of efficiency and axial thrust, are calculated and analyzed under conditions with and without NTEB. Measurements are performed downstream of two adjacent stator blades, at seven equidistantly spaced reference locations. The experimental measurement of the interstage flow field used a dynamic four-hole probe with phase lock technique. Findings An axial low-speed single-stage compressor was established with flow field measurement system and nonuniform blowing system. NTEB was studied by means of numerical simulations and experiments, and it is found that the efficiency of the tested compressor can be improved by more than 2 per cent. Originality/value Unlike most of the previous research studies which mainly focused on the rotor/stator interaction and trailing edge uniform blowing, the research results summarized in the current paper on the stator/rotor interaction used inlet guide vanes for steady and unsteady calculations. An active control of the interstage flow field in a low-speed compressor was used to widen the working range and improve the performance of the compressor.

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.

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.

Stability Improvement of a Turbocharger Centrifugal Compressor by a Nonaxisymmetric Vaned Diffuser

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Xinqian Zheng ◽  
Zhenzhong Sun ◽  
Tomoki Kawakubo ◽  
Hideaki Tamaki
Keyword(s):  
Flow Field ◽  
Flow Control ◽  
Centrifugal Compressor ◽  
Flow Separation ◽  
Static Pressure ◽  
Control Method ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Vaned Diffuser ◽  
Positive Effects

The nonuniformity of the flow field induced by a nonaxisymmetric volute significantly degrades the stability of a turbocharger centrifugal compressor. In this paper, a nonaxisymmetric vaned diffuser is investigated as a nonaxisymmetric flow control method using both three-dimensional computational fluid dynamics (CFD) and experiment. The numerical study first focuses on the relationship between the flow field and the static pressure distortion, and the steady CFD results indicate that the positive static pressure gradient in the rotating direction facilitates flow separation in the vaned diffuser and induces a nonuniform flow field. A nonaxisymmetric flow control method with variable stagger and solidity of the vaned diffuser is developed to suppress the flow separation, and the guideline of the method suggests narrowing flow passages where the flow separates or closing diffuser vanes upstream of flow separations. Steady CFD also presents the flow field of the investigated turbocharger centrifugal compressor with volute, and flow separation is found in the flow passages near the volute tongue. Under the guidance of the nonaxisymmetric flow control method, several nonaxisymmetric vaned diffusers are designed to make the flow field uniform, which are believed to be beneficial for compressor stability. Finally, an experiment is carried out to validate the positive effects of the nonaxisymmetric vaned diffuser for stability improvement. The test data show that Non-AxisVD (with a nonaxisymmetric vaned diffuser) extends the stable flow range (SFR) of the compressor by 26% compared with the AxisVD (with an axisymmetric vaned diffuser), at the cost of acceptable decreases in the maximum total pressure ratio and peak efficiency.

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