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.

Inlet Duct Treatment for Stability Improvement on a High Pressure Ratio Centrifugal Compressor

2013 ◽  
Author(s):  
Mingyang Yang ◽  
Ricardo Martinez-Botas ◽  
Yangjun Zhang
Keyword(s):  
High Pressure ◽  
Flow Control ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Control Method ◽  
Pressure Ratio ◽  
Operating Range ◽  
High Pressure Ratio ◽  
Wide Range ◽  
Inlet Duct

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.

Effect of Recirculation Device on Performance of High Pressure Ratio Centrifugal Compressor

2010 ◽  
Author(s):  
Hideaki Tamaki
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Operating Range ◽  
High Pressure Ratio

Centrifugal compressors used for turbochargers need to achieve a wide operating range. A recirculation device, which consists of a bleed slot, an upstream slot and an annular cavity connecting both slots, is often applied to them. The author developed a high pressure ratio centrifugal compressor with pressure ratio 5.7 for a marine use turbocharger. In order to enhance operating range, a recirculation device was applied, the benefits of its application ensuring. This paper discusses how the recirculation device affects the flow field in the above transonic centrifugal compressor by using steady 3D calculations. It is reported that the interaction between shock and tip leakage vortex is one of the primary causes of stall inception in the impeller. Analysis of shock and tip leakage flow behavior leads to an understanding of the basic mechanism of the enhancement of operating range by the recirculation device. Hence this study focuses on the effect of the recirculation devices on the shock and tip leakage flow. Steady 3D calculations were performed and the effect of the recirculation device was clarified. The bleed slot of the recirculation device works in a similar way to circumferential grooves applied to axial compressors. It reduces the blade loading in the impeller tip region. And hence the velocity of tip leakage flow exiting the bleed slot becomes lower compared with that without the recirculation device. The flow through the bleed slot impinges on the tip leakage flow originated upstream and blocks the extension of the tip leakage flow. It also deflects the trajectory of the tip leakage vortex. In addition to these effects, the bleed slot removes the fluid near the casing. The shock moves downstream due to the reduction of the blockage. All these effects induced by the recirculation device are considered to lead to the suppression of the extension of blockage and to contribute to the enhancement of the compressor operating range.

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

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Hideaki Tamaki
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Recirculation Flow ◽  
New Device ◽  
Operating Range ◽  
High Pressure Ratio ◽  
Swirl Vane ◽  
Rotational Direction ◽  
Wide Operating

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.

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.

Experimental Investigation of High Pressure Ratio Centrifugal Compressor With Axisymmetric and Nonaxisymmetric Recirculation Device

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Hideaki Tamaki ◽  
Xinqian Zheng ◽  
Yangjun Zhang
Keyword(s):  
High Pressure ◽  
Pressure Drop ◽  
Flow Rate ◽  
Average Distance ◽  
Pressure Ratio ◽  
Low Flow ◽  
Blade Loading ◽  
Recirculation Flow ◽  
High Pressure Ratio ◽  
Compressor Efficiency

Centrifugal compressors used for turbochargers are required to have a wide operating range. A recirculation device, which consists of a bleed slot, an upstream slot, and an annular cavity connecting both slots, is often used with them. It improves the incidence angle of the impeller leading edge, i.e., the blade loading of the inducer, at low flow rates due to the recirculation flow supplied to the compressor inlet. However, the compressor efficiency drops when there is a recirculation flow from the bleed slot to the upstream slot. A one dimensional analysis in the first section of this paper showed that the reduction in the compressor efficiency can be lowered by decreasing the pressure drop or reducing the recirculation flow rate within the recirculation device. This study examined the possibility of improvement in the compressor efficiency by the use of a recirculation device with an asymmetric bleed slot. An impeller of a turbocharger compressor is normally contained in a volute. Since the geometry of the volute is not axisymmetric, the impeller is surrounded by an asymmetric flow field. Hence each impeller passage, which is formed by two adjacent full blades, is operated at a different operating point. This means that some of the passages need the improvement in the blade loading by the recirculation device but others do not. There is a possibility that this is realized by a recirculation device with an asymmetrically distributed bleed slot, called a nonaxisymmetric recirculation device in this paper. If the asymmetric bleed slot shortens the average distance between the bleed slot and upstream slot or reduces the area of the bleed slot, it can reduce the pressure drop or recirculation flow rate within the recirculation deviceand, hence, can improve the compressor efficiency. This study discusses the characteristics of high pressure ratio compressors for turbochargers without the recirculation device and those with the recirculation device with an axisymmetric bleed slot. Furthermore, the effects of nonaxisymmetric recirculation devices on the compressor characteristics are experimentally investigated. Two types of nonaxisymmetric recirculation devices were tested. One had the bleed slot of a sine wave pattern. The other had the bleed slot partially channeled in the circumferential direction. There were appropriate positions relative to the volute for both nonaxisymmetric recirculation devices. The compressor efficiency with nonaxisymmetric recirculation devices was higher than that with axisymmetric recirculation devices and the surge lines of the compressor with nonaxisymmetric recirculation devices were located at a flow rate lower than or equal to those with the axisymmetric recirculation devices.

scholarly journals Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetrical Flow Control—Part II: Nonaxisymmetrical Self-Recirculation Casing Treatment

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Xinqian Zheng ◽  
Yangjun Zhang ◽  
Mingyang Yang ◽  
Takahiro Bamba ◽  
Hideaki Tamaki
Keyword(s):  
High Pressure ◽  
Flow Control ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Control Method ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Casing Treatment ◽  
High Pressure Ratio ◽  
Compressor Performance

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.

A Comparison of the Predicted and Measured Performance of High Pressure Ratio Centrifugal Compressor Diffusers

1972 ◽  
Author(s):  
D. P. Kenny
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Mach Number ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Layer Growth ◽  
High Pressure Ratio ◽  
Wall Boundary Layer ◽  
Exit Mach Number ◽  
Boundary Layer Growth

A novel analysis of the hub and shroud wall boundary layer growth through the diffusing system of a centrifugal compressor is proposed to model the physical processes. It is shown that the diffuser throat blockage and total pressure loss characteristics can be accurately predicted for a 6:1 PR stage. The static pressure effectiveness and stalling limit are successfully predicted qualitatively, but are underestimated and overestimated by 14 and 12 percent respectively. It is argued that diffuser performance is largely controlled by the combined effect of the boundary layer conditions on the hub and shroud walls at impeller exit and the diffusion required to the diffuser throat. For this reason, it is contended that, for best performance at high pressure ratio (≃ 12:1), impeller exit Mach number must be minimized by employing zero to negative prewhirl at impeller entry which in turn maximizes impeller entry shroud relative Mach number. Performance maps are presented for a single-stage centrifugal compressor based on this premise with specific speed = 90. At 15, 12 and 101 PR, 72, 75 and 76.8 percent efficiency, respectively, were attached at 2.6 lb/sec.

Experimental Investigation of High Pressure Ratio Centrifugal Compressor With Axisymmetric and Non-Axisymmetric Recirculation Device

2012 ◽  
Author(s):  
Hideaki Tamaki ◽  
Xinqian Zheng ◽  
Yangjun Zhang
Keyword(s):  
High Pressure ◽  
Pressure Drop ◽  
Flow Rate ◽  
Average Distance ◽  
Pressure Ratio ◽  
Low Flow ◽  
Blade Loading ◽  
Recirculation Flow ◽  
High Pressure Ratio ◽  
Compressor Efficiency

Centrifugal compressors used for turbochargers are required to have a wide operating range. A recirculation device, which consists of a bleed slot, an upstream slot and an annular cavity connecting both slots, is often used with them. It improves the incidence angle of the impeller leading edge, i.e. the blade loading of the inducer, at low flow rates due to the recirculation flow supplied to the compressor inlet. However the compressor efficiency drops when there is a recirculation flow from the bleed slot to the upstream slot. A one dimensional analysis in the first section of this paper showed that the reduction in the compressor efficiency can be lowered by decreasing the pressure drop or reducing the recirculation flow rate within the recirculation device. This study examined the possibility of improvement in the compressor efficiency by the use of a recirculation device with an asymmetric bleed slot. An impeller of a turbocharger compressor is normally contained in a volute. Since the geometry of the volute is not axisymmetric, the impeller is surrounded by an asymmetric flow field. Hence each impeller passage, which is formed by two adjacent full blades, is operated at a different operating point. This means that some of passages need the improvement in the blade loading by the recirculation device but others do not. There is a possibility that this is realized by a recirculation device with an asymmetrically-distributed bleed slot, called a non-axisymmetric recirculation device in this paper. If the asymmetric bleed slot shortens the average distance between the bleed slot and upstream slot or reduces the area of the bleed slot, it can reduce the pressure drop or recirculation flow rate within the recirculation device, and hence can improve the compressor efficiency. This study discusses the characteristics of high pressure ratio compressors for turbochargers without the recirculation device and those with the recirculation device with an axisymmetric bleed slot. Further, the effects of non-axisymmetric recirculation devices on the compressor characteristics are experimentally investigated. Two types of non-axisymmetric recirculation devices were tested. One had the bleed slot of a sine wave pattern. The other had the bleed slot partially channeled in the circumferential direction. There were appropriate positions relative to the volute for both non-axisymmetric recirculation devices. The compressor efficiency with non-axisymmetric recirculation devices was higher than that with axisymmetric recirculation devices, and the surge lines of the compressor with non-axisymmetric recirculation devices were located at flow rate lower than or equal to those with the axisymmetric recirculation devices.

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