scholarly journals Stall Margin Improvement in a Centrifugal Compressor through Inducer Casing Treatment

2016 ◽  
Vol 2016 ◽  
pp. 1-19
Author(s):  
V. V. N. K. Satish Koyyalamudi ◽  
Quamber H. Nagpurwala
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Treatment Technique ◽  
Centrifugal Compressors ◽  
Stall Margin ◽  
Casing Treatment ◽  
Operating Range ◽  
Stable Operating ◽  
Stall Margin Improvement

The increasing trend of high stage pressure ratio with increased aerodynamic loading has led to reduction in stable operating range of centrifugal compressors with stall and surge initiating at relatively higher mass flow rates. The casing treatment technique of stall control is found to be effective in axial compressors, but very limited research work is published on the application of this technique in centrifugal compressors. Present research was aimed to investigate the effect of casing treatment on the performance and stall margin of a high speed, 4 : 1 pressure ratio centrifugal compressor through numerical simulations using ANSYS CFX software. Three casing treatment configurations were developed and incorporated in the shroud over the inducer of the impeller. The predicted performance of baseline compressor (without casing treatment) was in good agreement with published experimental data. The compressor with different inducer casing treatment geometries showed varying levels of stall margin improvement, up to a maximum of 18%. While the peak efficiency of the compressor with casing treatment dropped by 0.8%–1% compared to the baseline compressor, the choke mass flow rate was improved by 9.5%, thus enhancing the total stable operating range. The inlet configuration of the casing treatment was found to play an important role in stall margin improvement.

An Investigation of Centrifugal Compressor Stability Enhancement Using a Novel Vaned Diffuser Recirculation Technique

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Lee Galloway ◽  
Daniel Rusch ◽  
Stephen Spence ◽  
Klemens Vogel ◽  
René Hunziker ◽  
...  
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Vaned Diffuser ◽  
Casing Treatment ◽  
Operating Range ◽  
Stable Operating ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Casing Treatments

The main centrifugal compressor performance criteria are pressure ratio, efficiency, and wide flow range. The relative importance of these criteria, and therefore the optimum design balance, varies between different applications. Vaned diffusers are generally used for high-performance applications as they can achieve higher efficiencies and pressure ratios, but have a reduced operating range, in comparison to vaneless diffusers. Many impeller-based casing treatments have been developed to enlarge the operating range of centrifugal compressors over the last decades but there is much less information available in open literature for diffuser focused methods, and they are not widely adopted in commercial compressor stages. The development of aerodynamic instabilities at low mass flow rate operating conditions can lead to the onset of rotating stall or surge, limiting the stable operating range of the centrifugal compressor stage. More understanding of these aerodynamic instabilities has been established in recent years. Based on this additional knowledge, new casing treatments can be developed to prevent or suppress the development of these instabilities, thus increasing the compressor stability at low mass flow rates. This paper presents a novel vaned diffuser casing treatment that successfully increased the stable operating range at low mass flow rates and high pressure ratios. Detailed experimental measurements from a high pressure ratio turbocharger compressor stage combined with complementary CFD simulations were used to examine the effect of the new diffuser casing treatment on the compressor flow field and led to the improvement in overall compressor stability. A detailed description of how the new casing treatment operates is presented within the paper.

scholarly journals Axial Flow Compressor Stability Enhancement: Circumferential T-Shape Grooves Performance Investigation

Aerospace ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 12
Author(s):  
Marco Porro ◽  
Richard Jefferson-Loveday ◽  
Ernesto Benini
Keyword(s):  
Vortex Breakdown ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Suction Side ◽  
Treatment Technique ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stall Margin Improvement

This work focuses its attention on possibilities to enhance the stability of an axial compressor using a casing treatment technique. Circumferential grooves machined into the case are considered and their performances evaluated using three-dimensional steady state computational simulations. The effects of rectangular and new T-shape grooves on NASA Rotor 37 performances are investigated, resolving in detail the flow field near the blade tip in order to understand the stall inception delay mechanism produced by the casing treatment. First, a validation of the computational model was carried out analysing a smooth wall case without grooves. The comparisons of the total pressure ratio, total temperature ratio and adiabatic efficiency profiles with experimental data highlighted the accuracy and validity of the model. Then, the results for a rectangular groove chosen as the baseline case demonstrated that the groove interacts with the tip leakage flow, weakening the vortex breakdown and reducing the separation at the blade suction side. These effects delay stall inception, improving compressor stability. New T-shape grooves were designed keeping the volume as a constant parameter and their performances were evaluated in terms of stall margin improvement and efficiency variation. All the configurations showed a common efficiency loss near the peak condition and some of them revealed a stall margin improvement with respect to the baseline. Due to their reduced depth, these new configurations are interesting because they enable the use of a thinner light-weight compressor case as is desirable in aerospace applications.

Casing Treatment of Centrifugal Compressors

2015 ◽  
Author(s):  
Jisha Noushad ◽  
Anand Babu Dhamarla ◽  
Pavan Kumar
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Reverse Flow ◽  
Pressure Fluctuations ◽  
Centrifugal Compressors ◽  
Flow Rates ◽  
Casing Treatment ◽  
Operating Range ◽  
Mass Flow Rates ◽  
Ported Shroud

The operating range of any compressor is controlled by Surge and Choke. Surge occurs at lower mass flow rates with large pressure fluctuations and flow reversals, while choke occurs at higher mass flow rates when the flow rate reaches the limit which compressor can discharge. Ported shroud is a cost effective casing treatment that can greatly improve operating range of centrifugal compressors. By removing the stagnant and reverse flow from shroud wall boundary-layer region and recirculating it to impeller inlet, it has been demonstrated that larger range of operability can be achieved without much loss on compressor efficiency. This paper demonstrates the improvement of a centrifugal compressor operational range with ported shroud configuration. A series of CFD simulations were carried out with open source centrifugal compressor geometry (NASA HPCC 4:1) to create performance characteristics/speed-lines. The CFD methodology and practices were validated by comparing the results with the experimental data. Performance evaluation of ported shroud configuration is done with respect to solid shroud. Ported shroud compressor is proven to give higher choke mass flow and also a better surge margin compared to the Solid shroud model. The phenomena of in-flowing and out-flowing port have also been demonstrated. Emphasis was given to understand how ported shroud helps to achieve a better performance. A design optimization study has also been carried out in order to establish the optimum ported shroud configuration. Design parameter such as port location has been selected and the effect of this parameter on the performance of the compressor is studied using CFD. Optimum port geometry was proposed.

Numerical Investigation of an Asymmetric Double Suction Centrifugal Compressor With Different Backswept Angle Matching for a Wide Operating Range

2017 ◽  
Author(s):  
Hanzhi Zhang ◽  
Dazhong Lao ◽  
Longyu Wei ◽  
Ce Yang ◽  
Mingxu Qi
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Flow Distribution ◽  
Operating Mode ◽  
Mode Transition ◽  
Distribution Characteristics ◽  
Operating Range ◽  
Stable Operating ◽  
Angle Difference ◽  
Matching Models

The work presented here investigates the characteristics of the different impeller backswept angle matchings for a wide stable operating range in an asymmetric double suction centrifugal compressor. The numerical simulation was employed to investigate the influence of different backswept angle matchings on the stable operating range. The aim is to propose a proper change of the backswept angle matching between two impeller sides to improve the impeller power capability and mass flow distribution, furthermore, to delay the operating mode transition and widen the stable operating range of the compressor. Firstly, the method to determine the optimum backswept angle matching obtained by the theory calculation. Then, three matching models were proposed and analyzed in detail. In three matching models, the backswept angle differences between the front and rear impeller side are 0°, 10° and 20°, respectively. The analysis mainly focused on the influence of the different backswept angle matchings on the compressor flow field characteristics and the mass flow distribution characteristics. The results show that the change of the impeller backswept angle matching can improve the mass flow distribution characteristics for two impeller sides and further reduce the stall mass flow rate of the double suction compressor. The model that the backswept angle difference is 10° can delay the operating mode transition and reduce the stall mass flow of the double suction compressor. The model that the backswept angle difference is 20° can also reduce the stall mass flow and finally enable the front impeller into the stall condition. Therefore, the proper change of the backswept angle matching can achieve the purpose of reducing the stall mass flow and widening the operating range for the double suction centrifugal compressor.

Investigation of an Asymmetric Double Entry Centrifugal Compressor With Different Radial Impellers Matching for a Wide Operating Range

2015 ◽  
Author(s):  
Lei Jing ◽  
Ce Yang ◽  
Wangxia Wu ◽  
Shan Chen
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Mode Conversion ◽  
Critical Mass ◽  
Operating Mode ◽  
Operating Characteristics ◽  
Operating Range ◽  
Stable Operating ◽  
Parallel Mode ◽  
Power Capability

The work presented here investigates the impeller matching characteristics and widens the stable operating range of front and rear impellers for an asymmetric entry double sided centrifugal compressor. A numerical approach is employed to analyze the operating characteristics of front and rear impellers, and a strategy to widen the stable operating range of double sided compressor is presented. Firstly, the performance curves of a double sided centrifugal compressor are obtained by simulating the operation of the whole-stage compressor. The result shows that the compressor operating mode switches from parallel mode to single impeller mode automatically with the decrease of the mass flow. Thus, the stable operating range of the compressor is limited. Second, the simulation of a simplified double sided compressor is conducted to reveal the mechanism of the compressor operating mode conversion. It is found that the essential reason for the conversion of the compressor operating mode is the total pressure difference between the front and rear impeller inlets. A proper increase of the rear impeller radii is helpful for improving the impeller power capability, which enables the front and rear impeller to obtain a superior matching relationship in a wider operating range and widens the stable operating range of the compressor. Furthermore, by analyzing the respective performance characteristic curves in various calculation cases, there is a critical mass flow value between the front and rear impellers for compressors with the same flow capability. When one side impeller mass flow is below the critical value, with further decrease of the flow, the pressure ratio characteristic curve of this side rises and enters the stall zone gradually. Thus, the operating mode is converted from parallel mode to single mode. This result further explains the mechanism for extending the stable operating range of a double sided compressor in a wider scope.

Stability Enhancement by Casing Grooves: The Importance of Stall Inception Mechanism and Solidity

2010 ◽  
Author(s):  
Tim Houghton ◽  
Ivor Day
Keyword(s):  
Companion Paper ◽  
Rotor Blades ◽  
Stall Inception ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stable Operating ◽  
Before And After ◽  
Stall Margin Improvement ◽  
Prediction Techniques ◽  
Stability Enhancement

This paper concerns the optimisation of casing grooves and the important influence of stall inception mechanism on groove performance. Installing casing grooves is a well known technique for improving the stable operating range of a compressor, but the wide-spread use of grooves is restricted by the loss of efficiency and flow capacity. In this paper, laboratory tests are used to examine the conditions under which casing treatment can be used to greatest effect. The use of a single casing groove was investigated in a recently published companion paper. The current work extends this to multiple-groove treatments and considers their performance in relation to stall inception mechanisms. Here it is shown that the stall margin gain from multiple grooves is less than the sum of the gains if the grooves were used individually. By contrast, the loss of efficiency is additive as the number of grooves increases. It is then shown that casing grooves give the greatest stall margin improvement when used in a compressor which exhibits spike-type stall inception, while modal activity before stall can dramatically reduce the effectiveness of the grooves. This finding highlights the importance of being able to predict the stall inception mechanism which might occur in a given compressor before and after grooves are added. Some published prediction techniques are therefore examined, but found wanting. Lastly, it is shown that casing grooves can, in some cases, be used to remove rotor blades and produce a more efficient, stable and light-weight rotor.

Mechanism investigation of enhancing the stability of an axial flow rotor by blade angle slots

2019 ◽  
Vol 233 (13) ◽  
pp. 4750-4764 ◽  
Author(s):  
Haoguang Zhang ◽  
Wenhao Liu ◽  
Enhao Wang ◽  
Yanhui Wu ◽  
Weidong Yao
Keyword(s):  
Axial Flow ◽  
Maximum Efficiency ◽  
Smooth Wall ◽  
Blade Angle ◽  
Stall Margin ◽  
Casing Treatment ◽  
Flow Losses ◽  
Stable Operating ◽  
Stall Margin Improvement ◽  
The Stability

This paper seeks to reveal the mechanisms of enhancing the stability of a subsonic axial flow rotor by applying blade angle slots casing treatment (BSCT). When blade angle slots are applied, there is about 9% stall margin improvement for the experiment and about 8% stall margin improvement for the calculation, but the decrease in the rotor maximum efficiency is about 11% for the experiment and the calculation. The compared results between smooth wall and blade angle slots indicate that the backflow in the rotor top passage is weakened by the injected and sucked flows formed inside the slots of BSCT. Moreover, the injected flows inside the slots interfere with the flows in the rotor passage upstream, and this interference leads to large flow losses. Therefore, the rotor efficiency for blade angle slots is much lower than that for smooth wall. To confirm that the structural optimization of blade angle slots can effectively improve the compressor stability with small efficiency losses, optimized blade angle slots casing treatment (BSCT1) was designed according to the past experience of slot casing treatment. The calculated result shows that the optimized blade angle slots generate about 59% stall margin improvement, and the compressor maximum efficiency with the optimized blade angle slots is about 0.05% more than that for smooth wall. The flow field analyses show that the strong sucked flows formed inside the slots for BSCT1 can prevent the backflow, which exists in the rotor top passage for BSCT, from appearing. In addition, the level of interference of the flows in the rotor passage upstream for BSCT1 is much lower than that for BSCT, and the corresponding losses with BSCT1 become lower. Therefore, the rotor with BSCT1 has a larger stable operating range and better efficiencies than that with BSCT.

Characterizing Flow Effects of Ported Shroud Casing Treatment on Centrifugal Compressor Performance

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
George A. Christou ◽  
Choon S. Tan ◽  
Borislav T. Sirakov ◽  
Vai-Man Lei ◽  
Giuseppe Alescio
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Path ◽  
Main Flow ◽  
Tip Leakage Flow ◽  
Casing Treatment ◽  
Compressor Performance ◽  
Flow Effects ◽  
Ported Shroud

This paper presents an investigation of the effects of ported shroud (PS) self-recirculating casing treatment used in turbocharger centrifugal compressors for increasing the operable range. The investigation consists of computing three-dimensional flow in a representative centrifugal compressor with and without PS at various levels of approximations in flow physics and geometrical configuration; this provides an enabler for establishing the causal link between PS flow effects and compressor performance changes. It is shown that the main flow path perceives the PS flow as a combination of flow actuations that include injection and removal of mass flow and injection of axial momentum and tangential momentum. A computational model in which the presence of the PS is replaced by imposed boundary conditions (BCs) that reflect the individual flow actuations has thus been formulated and implemented. The removal of a fraction of the inducer mass flow has been determined to be the dominant flow actuation in setting the performance of PS compressors. Mass flow removal reduces the flow blockage associated with the impeller tip leakage flow and increases the diffusion in the main flow path. Adding swirl to the injected flow in the direction opposite to the wheel rotation results in an increase of the stagnation pressure ratio and a decrease of the efficiency. The loss generation in the flow path has been defined to rationalize efficiency changes associated with PS compressor operation.

Stability Enhancement by Casing Grooves: The Importance of Stall Inception Mechanism and Solidity

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Tim Houghton ◽  
Ivor Day
Keyword(s):  
Companion Paper ◽  
Rotor Blades ◽  
Stall Inception ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stable Operating ◽  
Before And After ◽  
Stall Margin Improvement ◽  
Prediction Techniques ◽  
Stability Enhancement

This paper concerns the optimization of casing grooves and the important influence of stall inception mechanism on groove performance. Installing casing grooves is a well known technique for improving the stable operating range of a compressor, but the wide-spread use of grooves is restricted by the loss of efficiency and flow capacity. In this paper, laboratory tests are used to examine the conditions under which casing treatment can be used to greatest effect. The use of a single casing groove was investigated in a recently published companion paper. The current work extends this to multiple-groove treatments and considers their performance in relation to stall inception mechanisms. Here it is shown that the stall margin gain from multiple grooves is less than the sum of the gains if the grooves were used individually. By contrast, the loss of efficiency is additive as the number of grooves increases. It is then shown that casing grooves give the greatest stall margin improvement when used in a compressor, that exhibits spike-type stall inception, while modal activity before stall can dramatically reduce the effectiveness of the grooves. This finding highlights the importance of being able to predict which stall inception mechanism might occur in a given compressor before and after grooves are added. Some published prediction techniques are therefore examined, but found wanting. Lastly, it is shown that casing grooves can, in some cases, be used to remove rotor blades and produce a more efficient, stable, and light-weight rotor.

Computational Analysis of Recess Vane Geometry Modification in the Casing Treatment Approach to Enhance Stall Margin in Axial Flow Fans

2013 ◽  
Author(s):  
Kiran Yelmar ◽  
K. Viswanath
Keyword(s):  
Treatment Approach ◽  
Great Influence ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Pressure Rise ◽  
Axial Flow Fan ◽  
Stall Margin ◽  
Casing Treatment ◽  
Operating Range ◽  
Stall Margin Improvement

Stall margin improvement, though finite, has great influence on performance of a compressor and fan. Modification to the geometry of the recess and the recess vane used in the recess vane casing treatment approach would increase the operating range of an axial flow fan by removing the whirl component of circulatory flow near the blade tip. The present paper investigates the combined effect of variation of recess height and amount of blade chord exposure on flow characteristics and stall margin in low speed axial flow fan. Numerical simulations and modeling was performed using CFX 13.0 and ICEMCFD. The simulated pressure rise, work input and efficiency characteristics agreed well with the experimental data of a low sped fan obtained from the literature. The range of the flow rates which correspond to the stall free operating range of the untreated fan is compared with the same for the different modifications carried out to the geometry. The sensitivity of the operating range to the modifications is analyzed and the effect of recess vane geometry parameters on stall margin improvement is evaluated. Simulations suggest that within the ranges of parameters investigated stall margin improvement increases with both blade chord exposure and height.

Sign in / Sign up

Export Citation Format

Share Document