Stability Improvement of Turbocharger Centrifugal Compressor by Asymmetric Vaneless Diffuser Treatment

2013 ◽  
Author(s):  
Xinqian Zheng ◽  
Yun Lin ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Hideaki Tamaki ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Design Principle ◽  
Static Pressure ◽  
Vaneless Diffuser ◽  
Asymmetric Flow ◽  
Flow Asymmetry ◽  
Negative Effect ◽  
Width Distribution ◽  
The Stability ◽  
Stable Flow

The asymmetric flow field induced by the volute has considerable influence on the performance of a turbocharger centrifugal compressor, especially through its effect on the stability. In this paper, a novel asymmetric vaneless diffuser treatment with a circumferentially non-axisymmetric diffuser width distribution was firstly developed to enhance the stability of a centrifugal compressor for turbocharger. Design principle of the asymmetric diffuser was proposed based on the asymmetric flow in the compressor. The objective of the asymmetric vaneless diffuser design is to alleviate the flow asymmetry in the diffuser, which requires that the phase of the maximal diffuser width is coincident with the phase of the minimum static pressure in the diffuser. The results of the numerical simulation showed that the designed asymmetric diffuser was able to decrease the magnitude of the pressure distortion induced by the volute and therefore alleviated the negative effect of the volute on compressor stability. Experimental results showed that the designed asymmetric diffuser extended the stable flow range by 28.3% at designed speed compared to the prototype with symmetric diffuser.

CFD Studies on the Performance of a Centrifugal Compressor With Single Wall Rotating Vaneless Diffusers at the Wall Extension Ratios of 1.1 and 1.15

2017 ◽  
Author(s):  
Srinivasa Rao Konakala ◽  
Mukka Govardhan
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Static Pressure ◽  
Substantial Improvement ◽  
Significant Loss ◽  
Vaneless Diffuser ◽  
Shear Forces ◽  
Overall Performance ◽  
Vaneless Diffusers ◽  
And Performance

Efficiency of the centrifugal compressor is affected by non-uniform flow at the exit of the impeller and the losses in the diffuser. This causes a significant loss of total pressure and drop in the performance of a centrifugal compressor. By rotating some portion of stationary vaneless diffuser walls with the speed of the impeller, the shear forces between the flow and diffuser walls are greatly reduced. Thereby improvement in the operating range and performance is achieved. This paper presents CFD studies on the effect of different single wall rotations i.e. hub rotation and shroud rotation of the vaneless diffusers on the overall performance at 10% and 15% extension of impeller walls. It is observed that the performance characteristics of compressors with all RVD models offer higher static pressure recovery and also higher rate of diffusion compared to the base compressor with SVD. It is clear that as extended radius increases from 10% to 15%, substantial improvement of efficiency and reduction of losses are observed for both type of models. Out of two single wall rotation models, SRVD model is able to better mix the jet-wake type of impeller exit flows and minimizes the losses therein and improve the performance of the centrifugal compressor.

Non-Axisymmetric Flow Structure in Vaneless Diffuser of Centrifugal Compressor for Turbochargers

2012 ◽  
Author(s):  
Chuanjie Lan ◽  
Xinqian Zheng ◽  
Hideaki Tamaki
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Internal Combustion Engines ◽  
Combustion Engines ◽  
Vaneless Diffuser ◽  
Asymmetric Flow ◽  
Oil Flow ◽  
Flow Visualizations

Turbocharger technology is widely used in internal combustion engines. With the downsizing of internal combustion engines and the introduction of strict emission regulations, there is urgent demand for turbochargers featuring centrifugal compressors with a wide flow range. The flow in a centrifugal compressor of a turbocharger is non-axisymmetric due to the inherent asymmetry of the discharge volute. The asymmetric flow field inside the diffuser has great influence on the performance of centrifugal compressor. In order to develop a flow control method that facilitates a wider flow range of turbocharger compressors, further understanding of the asymmetric flow structure is very important. The main subject of this study is to reveal the asymmetrical characteristics of the flow field in the vaneless diffuser of a centrifugal compressor followed by a volute. Oil flow visualizations and numerical simulations were used. The results of the numerical simulations are consistent with that of the oil flow visualizations near choke and at designed flow rate. The results show that a “dual-zone mode” asymmetric flow structure exists near the shroud of the vaneless diffuser at near choke condition. A bifurcation point at the volute tongue that divides the flow and creates two distinct flow patterns was found. The asymmetry of the flow structure near the hub was much less significant than that near the shroud. At the design flow rate, asymmetric flow patterns are found neither near shroud nor near hub. At near surge condition, the pattern of the oil flow traces near the shroud is very different from those near choke.

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 Study on Two Types of Stall Patterns in a Centrifugal Compressor with a Wide Vaneless Diffuser

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1251
Author(s):  
Qian Zhang ◽  
Liang Zhang ◽  
Qiuhong Huo ◽  
Lei Zhang
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Propagation Speed ◽  
Radius Ratio ◽  
Vaneless Diffuser ◽  
Vaneless Diffusers ◽  
Stall Cells ◽  
The Stability ◽  
The One

Two types of stall patterns in the centrifugal compressor with a wide vaneless diffuser were numerically studied in this paper. We carried out kinds of three-dimensional numerical simulations of the instability process in wide vaneless diffusers with different radius ratios. The results show that there are two kinds of stall patterns in wide vaneless diffusers with different radius ratios. For a short diffuser with a radius ratio of 1.5, the speed of the propagation of stalled cells is relatively high, and the propagation speed and frequency of stall cells do not change with the decrease in the flow rate. For a long diffuser with a radius ratio of 1.8, the propagation velocity of stall cells is smaller to the one in the short diffuser, and increases with the decrease in flow rate. For wide vaneless diffusers with different radius ratios, the main factor causing stall is the outlet reflux. Reducing the radius ratio of the wide vaneless diffuser has an important influence on the stability of the centrifugal compressor.

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.

scholarly journals Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetric Flow Control—Part I: Non-Axisymmetrical Flow in Centrifugal Compressor

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Mingyang Yang ◽  
Xinqian Zheng ◽  
Yangjun Zhang ◽  
Takahiro Bamba ◽  
Hideaki Tamaki ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Shift ◽  
Flow Control ◽  
Centrifugal Compressor ◽  
Rotational Speed ◽  
Static Pressure ◽  
Control Method ◽  
Pressure Ratio ◽  
Asymmetric Flow ◽  
High Pressure Ratio

This is Part I of a two-part paper documenting the development of a novel asymmetric flow control method to improve the stability of a high-pressure-ratio turbocharger centrifugal compressor. Part I focuses on the nonaxisymmetrical flow in a centrifugal compressor induced by the nonaxisymmetrical geometry of the volute while Part II describes the development of an asymmetric flow control method to avoid the stall on the basis of the characteristic of nonaxisymmetrical flow. To understand the asymmetries, experimental measurements and corresponding numerical simulation were carried out. The static pressure was measured by probes at different circumferential and stream-wise positions to gain insights about the asymmetries. The experimental results show that there is an evident nonaxisymmetrical flow pattern throughout the compressor due to the asymmetric geometry of the overhung volute. The static pressure field in the diffuser is distorted at approximately 90 deg in the rotational direction of the volute tongue throughout the diffuser. The magnitude of this distortion slightly varies with the rotational speed. The magnitude of the static pressure distortion in the impeller is a function of the rotational speed. There is a significant phase shift between the static pressure distributions at the leading edge of the splitter blades and the impeller outlet. The numerical steady state simulation neglects the aforementioned unsteady effects found in the experiments and cannot predict the phase shift, however, a detailed asymmetric flow field structure is obviously obtained.

scholarly journals The Centrifugal Compressor Inducer

1998 ◽  
Author(s):  
C. Rodgers
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
The State ◽  
Design Flow ◽  
Pressure Recovery ◽  
Centrifugal Compressors ◽  
High Static Pressure ◽  
Stable Flow ◽  
State Of Art

The function of the centrifugal compressor inducer is to provide wide flow margins from the design flow to the stall and choke flow limits, together with high static pressure recovery. At transonic conditions the inducer becomes the critical to impeller performance in that shock losses and blockage growth diminish stable flow range and may trigger near vertical stage characteristics. The paper covers the various types of inlet configurations upstream of the inducer, followed by a review of the state-of-art inducer design for centrifugal compressors, culminating with some research developments in transonic inducer blading characteristics.

Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetric Flow Control: Part I—Non-Axisymmetric Flow in Centrifugal Compressor

2010 ◽  
Author(s):  
Mingyang Yang ◽  
Xinqian Zheng ◽  
Yangjun Zhang ◽  
Takahiro Bamba ◽  
Hideaki Tamaki ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Shift ◽  
Flow Control ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Control Method ◽  
Pressure Ratio ◽  
Axisymmetric Flow ◽  
Asymmetric Flow ◽  
High Pressure Ratio

This is the Part I of a two-part paper documenting the development of a novel asymmetric flow control method to improve the stability of a high-pressure-ratio turbocharger centrifugal compressor. Part I focuses on the non-axisymmetric flow in a centrifugal compressor induced by the non-axisymmetric geometry of the volute while Part II describes the development of asymmetric flow control method to avoid the stall on the basis of the characteristic of non-axisymmetric flow. To understand the asymmetries, experimental measurements and corresponding numerical simulation were carried out. The static pressure was measured by probes at different circumferential and stream-wise positions to gain insights about the asymmetries. The experiment results show that there is an evident non-axisymmetric flow pattern throughout the compressor due to the asymmetric geometry of overhung volute. The static pressure field in the diffuser is distorted at approximately 90° in rotational direction of the volute tongue throughout the diffuser. The magnitude of this distortion varies slightly with the rotational speeds. The magnitude of the static pressure distortion in the impeller is a function of the rotational speed. There is a significant phase shift between the static pressure distributions at the leading edge of the splitter blades and the impeller outlet. The numerical steady state simulation neglects the mentioned unsteady effects found in the experiments and can not predict the phase shift, but a detailed asymmetric flow field structure are obviously obtained.

Experimental analysis of the influence of outlet network volume and inlet guide vane positioning on surge behavior in a single-stage low-speed centrifugal compressor

2017 ◽  
Vol 232 (4) ◽  
pp. 350-363 ◽  
Author(s):  
Kirill Kabalyk ◽  
Michal Jasek ◽  
Grzegorz Liskiewicz ◽  
Longin Horodko
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Guide Vane ◽  
Single Stage ◽  
Low Flow ◽  
Inlet Guide Vane ◽  
Vaneless Diffuser ◽  
Time Resolved ◽  
Low Speed ◽  
Deep Well

The paper focuses on experimental investigation of the influence of outlet network volume and type on the course of surge in a single-stage low-speed centrifugal compressor. The test rig design is based on a 330 mm impeller (tip Mach number of 0.33) coupled with a vaneless diffuser and a scroll. During the measurements, the rig has been successively connected to a four meter long pipe and to an 11.8 m deep well. Time-averaged probing of pressures and temperatures has served to obtain the performance maps with both networks at three different positions of inlet guide vanes. Time-resolved measurements of static pressure were done in three chosen locations of the rig and enabled to trace the formation of flow instabilities at low flow rates. The analysis of received dataset revealed a reasonable impact of network design on the inception moment, quantitative and qualitative traits of deep surge. The most significant changes concerned the frequencies of the first surge harmonics and the nature of the process. “Pipeline-surge” reminded more of a standing wave whereas “plenum-surge”—of a periodic process similar to the ones reported in the referenced studies.

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