scholarly journals Investigation of Suction Flow Control on Centrifugal Compressor with Vaned Diffuser

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 583
Author(s):  
Suleyman Emre Ak ◽  
Sertac Cadirci

In this study, the effect of suction flow control on a centrifugal compressor at operation and stall flow rates was investigated using computational fluid dynamics (CFD). The compressor geometry was reconstructed from available open source profile data and the CFD analyses have been performed on this geometry using the appropriate mesh. To validate the CFD results, the compressor performance line was acquired and compared with the experimental results obtained at the design rotational speed. Then, suction flow control was employed at various suction slot positions with different suction flow rates to improve the performance of the compressor at operation and stall flow rates. As a result of the suction flow control trials, 0.85% increase in pressure ratio and 0.8% increase in adiabatic efficiency were achieved while the compressor was running at operation flow rate. The performance improvements corresponding to the stall flow rate of the compressor were 2.5% increase in pressure ratio and 2% increase in adiabatic efficiency.

1995 ◽  
Vol 117 (4) ◽  
pp. 602-608 ◽  
Author(s):  
A. Pinarbasi ◽  
M. W. Johnson

Detailed measurements have been taken of the three-dimensional velocity field within the vaneless diffuser of a backswept low speed centrifugal compressor using hot-wire anemometry. A 16 percent below and an 11 percent above design flow rate were used in the present study. Results at both flow rates show how the blade wake mixes out more rapidly than the passage wake. Strong secondary flows inherited from the impeller at the higher flow rate delay the mixing out of the circumferential velocity variations, but at both flow rates these circumferential variations are negligible at the last measurement station. The measured tangential/radial flow angle is used to recommend optimum values for the vaneless space and vane angle for design of a vaned diffuser.


Author(s):  
Mingyang Yang ◽  
Ricardo Martinez-Botas ◽  
Yangjun Zhang

The operating range of a centrifugal compressor, determined by surge and choke flow rate, is a key issue for turbocharging since a vehicle internal combustion engine (ICE) is usually operated across a wide range. In this paper a new flow control method is developed and validated numerically, in which an array of circumferentially distributed holes is designed in the inner wall of the inlet duct of a high pressure ratio centrifugal compressor of a turbocharger. Firstly the numerical method is validated by experimental results of the original turbocharging centrifugal compressor with a pressure ratio of 4. Next the validated method is used to investigate the new flow control method and its effect on the compressor’s performance. Results show that the method can enhance the compressor stability and widen the operating range effectively at all investigated speeds. At meantime, the choke flow reduces slightly. The flow details in the compressor are further analysed according to the CFD results. It is found that the flow near the blade tip at inlet is pre-swirled by the method as the conventional IGV does while the flow in the middle span or near the hub remains in an axial direction. As a result, the stability of the compressor is enhanced by the pre-swirl effect at the tip while minimally sacrificing the choke flow rate, thus the map is extended effectively by the flow control method.


Author(s):  
Hong-Won Kim ◽  
Jong-Il Park ◽  
Seung-Hyup Ryu ◽  
Seong-Wook Choi ◽  
Sang-Hak Ghal

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. Effective pressure recovery downstream of an impeller is very important to realize a centrifugal compressor with high efficiency and high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on modified NACA airfoil and second is channel diffuser and third is conformal transformation of NACA 65 airfoil. A mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. In this study, the off-design behavior of three different types of diffusers, given by mean-line prediction, was investigated using CFD results and selected the NACA 65 diffuser geometry which satisfy wider operating range and higher pressure recovery than the others. The numerical results were compared with experimental data for validation.


2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Xinqian Zheng ◽  
Zhenzhong Sun ◽  
Tomoki Kawakubo ◽  
Hideaki Tamaki

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.


2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Xinqian Zheng ◽  
Yangjun Zhang ◽  
Mingyang Yang ◽  
Takahiro Bamba ◽  
Hideaki Tamaki

This is part II of a two-part paper involving the development of an asymmetrical flow control method to widen the operating range of a turbocharger centrifugal compressor with high-pressure ratio. A nonaxisymmetrical self-recirculation casing treatment (SRCT) as an instance of asymmetrical flow control method is presented. Experimental and numerical methods were used to investigate the impact of nonaxisymmetrical SRCT on the surge point of the centrifugal compressor. First, the influence of the geometry of a symmetric SRCT on the compressor performance was studied by means of numerical simulation. The key parameter of the SRCT was found to be the distance from the main blade leading edge to the rear groove (Sr). Next, several arrangements of a nonaxisymmetrical SRCT were designed, based on flow analysis presented in part I. Then, a series of experiments were carried out to analyze the influence of nonaxisymmetrical SRCT on the compressor performance. Results show that the nonaxisymmetrical SRCT has a certain influence on the performance and has a larger potential for stability improvement than the traditional symmetric SRCT. For the investigated SRCT, the surge flow rate of the compressor with the nonaxisymmetrical SRCTs is about 10% lower than that of the compressor with symmetric SRCT. The largest surge margin (smallest surge flow rate) can be obtained when the phase of the largest Sr is coincident with the phase of the minimum static pressure in the vicinity of the leading edge of the splitter blades.


Author(s):  
Manabu Yagi ◽  
Tadaharu Kishibe ◽  
Takanori Shibata ◽  
Hideo Nishida ◽  
Hiromi Kobayashi

The improvement of efficiency and operating range by optimizing blade-loading distribution of three-dimensional (3D) centrifugal compressor impellers is investigated using computational fluid dynamics (CFD) analyses and performance tests. The design points of suction flow coefficients investigated in the present study were 0.05 and 0.073. Two design approaches for 3D impeller were employed: a conventional method and a newly developed one. In order to achieve higher efficiency and wider operating range, the blade loading and relative velocity distribution were optimized in the new design procedure. In addition, to clarify the performance improvement of 3D impellers against current two-dimensional (2D) ones, both performance characteristics were compared. The test results showed the efficiencies of the newly designed 3D impellers were increased by about 0.5–1.5% in comparison with those of the conventional impellers, while the operating ranges of both were almost the same. Further, the efficiencies of the newly designed 3D impellers increased by about 3% in comparison with those of the 2D impellers at both design points. At the same time, the operating ranges of the former impellers were about 2.1–2.8 times as wide as those of the latter.


Author(s):  
Bing Qiao ◽  
Yaping Ju ◽  
Chuhua Zhang

Abstract Negative flow from the outlet through the volute, diffuser, and impeller to the inlet of the centrifugal compressor can occur continuously as a result of system accidents. A physical comprehension of negative flow dynamics is crucial in evaluating the compressor characteristics under abnormal working conditions, and is also important in exploring the compressor aerodynamics over the entire flow range. However, limited research on the negative flow dynamics in centrifugal compressors, particularly with the consideration of vaned diffusers and volutes, can be found. This study aims to determine the compressor characteristics, including the negative flow rates of a centrifugal compressor, and to clarify the negative flow mechanism under the interaction of the volute, diffuser, and impeller. The last stage of a four-stage centrifugal compressor, including an internal volute, a vaned diffuser, and a closed impeller was simulated under both positive and negative flow conditions using a computational fluid dynamics (CFD) model. The results show that the pressure ratio-negative flow characteristic is almost matched with a parabolic curve. At negative flow rates, the backflow generated on the hub and shroud sides in the impeller expands upstream and causes flow separation in the diffuser. The negative flow enters the impeller at a large incidence angle and results in jet wall impingement on the pressure surface, flow spillage over the trailing edge, and flow separation near the suction surface. The impeller partially acts as a turbine impeller and performs negative work on the fluid. This work is of scientific significance to enrich the compressor aerodynamics in accident scenarios and of engineering value to improve the advanced design of compressor protection systems.


Author(s):  
Hong-Won Kim ◽  
Jong-II Park ◽  
Seung-Hyup Ryu ◽  
Seong-Wook Choi ◽  
Sang-Hak Ghal

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage; for energy efficiency, it is important to recover as much of this as possible. This is the function of the diffuser, which follows the impeller. Effective pressure recovery downstream of an impeller is very important in order to realize a centrifugal compressor with a high efficiency and a high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step in order to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances change as the vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and compared with its results. The first vaned diffuser type is based on a modified NACA airfoil, the second is a channel diffuser, and the third is a conformal transformation of NACA 65-(4A10)06 airfoil. A mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. Computational fluid dynamic (CFD) analyses and a detailed interior flow pattern study have been done. In this study, the off-design behavior of three different types of diffusers, given by the mean-line prediction, was investigated using CFD results and the NACA 65 diffuser geometry, which satisfies a wider operating range and has a higher pressure recovery than the others, was selected. The numerical results were compared with experimental data for validation and showed good agreement.


2014 ◽  
Vol 663 ◽  
pp. 347-353
Author(s):  
Layth H. Jawad ◽  
Shahrir Abdullah ◽  
Zulkifli R. ◽  
Wan Mohd Faizal Wan Mahmood

A numerical study that was made in a three-dimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an automotive turbo charger. In order to study the influence of vaned diffuser meridional outlet section with a different width ratio of the modified centrifugal compressor. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between the compressor impeller along the vaned diffuser. The aerodynamic characteristics were compared under different meridional width ratio. In addition, the velocity vectors in diffuser flow passages, and the secondary flow in cross-section near the outlet of diffuser were analysed in detail under different meridional width ratio. 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 using commercial software so-called ANSYS CFX, to predict numerically the performance charachteristics. The results were generated from CFD and were analysed for better understanding of the fluid flow through centrifugal compressor stage and as a result of the minimum width ratio the flow in diffuser passage tends to be uniformity. Moreover, the backflow and vortex near the pressure surface disappear, and the vortex and detachment near the suction surface decrease. Conclusively, it was observed that the efficiency was increased and both the total pressure ratio and static pressure for minimum width ratio are increased.


Author(s):  
Qiangqiang Huang ◽  
Xinqian Zheng ◽  
Aolin Wang

Air often flows into compressors with inlet prewhirl, because it will obtain a circumferential component of velocity via inlet distortion or swirl generators such as inlet guide vanes. A lot of research has shown that inlet prewhirl does influence the characteristics of components, but the change of the matching relation between the components caused by inlet prewhirl is still unclear. This paper investigates the influence of inlet prewhirl on the matching of the impeller and the diffuser and proposes a flow control method to cure mismatching. The approach combines steady three-dimensional Reynolds-averaged Navier-Stokes (RANS) simulations with theoretical analysis and modeling. The result shows that a compressor whose impeller and diffuser match well at zero prewhirl will go to mismatching at non-zero prewhirl. The diffuser throat gets too large to match the impeller at positive prewhirl and gets too small for matching at negative prewhirl. The choking mass flow of the impeller is more sensitive to inlet prewhirl than that of the diffuser, which is the main reason for the mismatching. To cure the mismatching via adjusting the diffuser vanes stagger angle, a one-dimensional method based on incidence matching has been proposed to yield a control schedule for adjusting the diffuser. The optimal stagger angle predicted by analytical method has good agreement with that predicted by computational fluid dynamics (CFD). The compressor is able to operate efficiently in a much broader flow range with the control schedule. The flow range, where the efficiency is above 80%, of the datum compressor and the compressor only employing inlet prewhirl and no control are just 25.3% and 31.8%, respectively. For the compressor following the control schedule, the flow range is improved up to 46.5%. This paper also provides the perspective of components matching to think about inlet distortion.


Sign in / Sign up

Export Citation Format

Share Document