A Study on the Influence of Hole’s Diameter With Holed Casing Treatment

2011 ◽  
Author(s):  
Wei Xu ◽  
Tong Wang ◽  
Chuangang Gu ◽  
Liang Ding
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Results ◽  
Radial Position ◽  
Bypass Flow ◽  
Stall Margin ◽  
Casing Treatment ◽  
Velocity Magnitude ◽  
Adaptive Effect ◽  
New Type ◽  
Self Adaptive

The holed casing treatment is a new type of casing treatment with self-adaptability for centrifugal compressor with unshrouded impellers. It is demonstrated experimentally and numerically that both of the stall margin and the choked margin of the compressor can be expanded by the treatment. Numerical results indicate that there is a reinjected flow in the holes when the compressor works at low flowrate conditions and a bypass flow at high flowrate conditions. Hole’s diameter is an important parameter for the holed casing treatment. Five cases of different diameter (1.0mm, 1.5mm, 2.0mm, 2.5mm and 3.0mm) were carried out to reveal its influence. Both the stall margin and efficiency are improving with increasing of the hole’s diameter in the cases of diameter below than 2.5mm. At diameter of 2.5mm, the stall margin increment and the efficiency of the compressor are the highest among all 5 cases. However, in the case of 3.0mm, the stable working range enhancing as well as the efficiency is weakened because the velocity magnitude of the reinjected flow decreases. Therefore a key principle of choosing the diameter and the radial position of the hole is presented in the paper to get the best self-adaptive effect: enhancing stable running range as much as possible and keeping higher efficiency.

A New Type of Self-Adaptive Casing Treatment for a Centrifugal Compressor

2010 ◽  
Author(s):  
Tong Wang ◽  
Wei Xu ◽  
Chuangang Gu ◽  
Jun Xiao
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Centrifugal Impeller ◽  
Stable Operation ◽  
Stable Range ◽  
Stall Margin ◽  
Casing Treatment ◽  
Surge Margin ◽  
New Type ◽  
Self Adaptive

Enhancing compressor stall and surge margin is very important for the development of turbo compressors. Casing treatment is an effective method to expand the stall margin and thus the stable operation range but it generally comes with a drop in efficiency. A new type of casing treatment with self-adaptivity for an unshrouded centrifugal impeller is presented in this paper. The idea of the self-adaptive casing treatment is to automatically control the bleeding flow rate through a set of round holes on the stationary shroud casing. When stall is approached, the casing treatment system will redirect the low-momentum fluid to improve the flow in the impeller and to extend its stable range. However, the system will not bleed or bleed a little flow when the operating point is far from the stall point. This decreases the bleeding-recirculation loss and increases the efficiency compared to bleed-slot casing treatment used before. The experimental results show that the centrifugal compressor with the new casing treatment can extend stable range by about 20% while the efficiency over the whole operating range increases by 0.2 to 1.5%. The theoretical results using CFD analyses agree with the experimental ones in the tendency for both pressure ratio and efficiency. Moreover some possible reasons for further enhancing the stable range are suggested in the paper. Based on our experiences, there should be existed a proper combination of impeller rotating speed, position and numbers of bleed port and other parameters that will maximize both surge margin range and efficiency.

Numerical Investigation of a Centrifugal Compressor With Holed Casing Treatment

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Wei Xu ◽  
Tong Wang ◽  
Chuangang Gu ◽  
Liang Ding
Keyword(s):  
Flow Rate ◽  
Centrifugal Compressor ◽  
High Flow ◽  
Hole Diameter ◽  
Low Flow ◽  
Bypass Flow ◽  
Stall Margin ◽  
Casing Treatment ◽  
New Type ◽  
Different Diameters

The holed casing treatment is a new type of casing treatment that has self-adaptability for a centrifugal compressor with unshrouded impeller. It was demonstrated experimentally and numerically that both the stall margin and the choked margin of the compressor were able to be expanded by the treatment. Numerical results indicate that there is reinjected flow in the holes when the compressor works at low flow rate conditions, and bypass flow at high flow rate conditions. The key principles for choosing the diameter and the radial position of the hole are presented in this paper. The hole’s diameter is an important parameter for the holed casing treatment. Five numerical cases with different diameters (1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm and 3.0 mm) were carried out to compare the results. The reinjected flow enters into the impeller passage periodically and it tends to increase when the hole diameter gets larger. In the case of 2.5 mm, both the stall margin increment and the efficiency of the compressor were the highest among the five cases. Unsteady simulations suggest that the reinjected flow is not only periodic in time but also periodic in circumferential direction. This is the reason why only 2% of the flow amounts would get 20% of the working range expansion.

Unsteady Simulation and Analysis on Centrifugal Impeller With Self-Adaptive Casing Treatment

2013 ◽  
Author(s):  
Tong Wang ◽  
Wei Wang ◽  
Chuangang Gu
Keyword(s):  
Boundary Condition ◽  
Back Pressure ◽  
The Self ◽  
Centrifugal Impeller ◽  
Bypass Flow ◽  
Unstable Flow ◽  
Recirculation Flow ◽  
Casing Treatment ◽  
Pressure Boundary Condition ◽  
Self Adaptive

A self-adaptive casing treatment for unshrouded centrifugal compressor was proposed in our previous studies. It is a kind of passive control techniques. The experimental results proved that the stable working range of the compressor was extended greatly with the technique. As for the stability mechanism, there is no convinced explanation. Many researchers believe that the unsteady flow could be one of the key points. In the paper, steady and unsteady numerical simulations were carried out to get the performances of the centrifugal impeller by ANSYS CFX software. The numerical method was validated by comparing with the experimental results. It was found that there were two types of flow pattern in the bleeding-recirculation passages by the numerical simulation with the self-adaptive casing treatment. One was the recirculation flow at the smaller flowrate working conditions and the other was bypass flow at the larger flowrate working conditions. The pressure at the bleeding ports was more than that at the recirculation port at the smaller flowrate. It would result in the recirculation flow in the bleeding-recirculation passages. Otherwise, it would result in the bypass flow in the bleeding-recirculation passages. The numerical results of each bleeding-recirculation passage provided the variation of mass flowrate in it with the pressure difference. The relation of the pressure drop coefficient and Reynolds number based on the bleeding hole was fitted. It was different for the recirculation flow and bypass flow. It is helpful to decide the position of the bleeding ports during the centrifugal compressor design process. Moreover, an unsteady numerical simulation method with the increasing back pressure boundary condition was proposed to investigate the unsteady process approaching to the numerical stall point or unstable flow. The dynamic pressure data in impeller and diffuser were recorded. The amplitudes of the data were picked up to compare the time dependent process. The dynamic pressure at the inlet of diffuser fluctuated more strongly than those at the other positions while the back pressure was increased to the numerical stall point. The experimental data provided the similar phenomena. It suggested that the unstable flow tendency could be caught up by the unsteady simulation process with the increasing back pressure boundary condition. Furthermore, the time dependent flow fields at the blade tip region were compared on the conditions with and without the self-adaptive casing treatment. The effect of the self-adaptive casing treatment was proved by unsteady numerical method with the increasing back pressure boundary condition. The stability mechanism of the self-adaptive casing treatment was explained to some extent.

Numerical Investigation of Different Casing Treatments on Performance of a High Speed Centrifugal Compressor Stage

2011 ◽  
Author(s):  
Yan Ma ◽  
Guang Xi ◽  
Guangkuan Wu
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Compressor ◽  
High Speed ◽  
The Other ◽  
Compressor Stage ◽  
Stall Margin ◽  
Casing Treatment ◽  
Centrifugal Compressor Stage ◽  
And Performance ◽  
Casing Treatments

In this paper, two different casing treatment devices—one adopting inlet recirculation at the shroud side of the impeller inlet and the other adopting circumferential casing grooves at the shroud side of the vaneless space, are designed for a high speed centrifugal compressor stage. The effects of different casing treatments to the flow range and performance of the centrifugal compressor stage are studied numerically. The results indicate that traditional inlet recirculation at impeller inlet does not extend the stall margin of the stage and the performance deteriorates due to the adding of the extra device. The study also shows that, when the location of the bleed slot moves downstream, the performance of the stage deteriorates due to the longer flow path. Moreover, the 2mm depth circumferential casing grooves extend the stall margin by about 12.05%. By contrast, the 6mm depth and 10mm depth grooves extend the stall margin by 3% and 2.4% respectively.

Numerical Investigation of a Centrifugal Compressor With a Single Circumferential Groove in Different Types of Diffusers

2017 ◽  
Author(s):  
Xuefei Chen ◽  
Zijian Ai ◽  
Yunfeng Ji ◽  
Guoliang Qin
Keyword(s):  
Centrifugal Compressor ◽  
Stable Operation ◽  
Stable Range ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Effective Measure ◽  
Stall Margin ◽  
Casing Treatment ◽  
Circumferential Groove ◽  
Different Types

Enhancing compressor stall and surge has a great importance for the development of turbo compressors. The application of casing treatment is an effective measure to expand the stall margin and stable operation range. Numerical investigations were conducted to predict the performance of a low flow rate centrifugal compressor with circumferential groove casing treatment in diffuser. Numerical cases with different radial location, radial width and axial depth of a circumferential single groove in different types of diffusers (vaned diffuser, half-vaned diffuser, vaneless diffuser) were carried out to compare the results. The computational fluid dynamics analyses results show that the centrifugal compressor with circumferential groove in vaned diffuser can extend stable range by about 9.1% while the efficiency over the whole operating range decreases by 0.2 to 1.7%; the results with half-vaned diffuser and vaneless diffuser can improve stable range less and the efficiency decreases more. Efforts were made to study blade level flow mechanisms to determine how the circumferential groove impacts the compressor’s stall margin and performance. The flow structures in the passage, the tip gap, and the grooves as well as their mutual interactions were plotted and analyzed. The flow transport across the tip gap in the smooth wall and the circumferential grooves were compared.

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.

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.

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