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Junqiang Zhu - One of the best experts on this subject based on the ideXlab platform.

  • Effects of low Reynolds number on flow stability of a transonic Compressor
    Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering, 2014
    Co-Authors: Shengfeng Zhao, Junqiang Zhu, Yang Chengwu
    Abstract:

    As the aircraft cruising at high altitude over 20,000 m with subsonic speed, the Reynolds number in terms of the Compressor blade becomes very low and the Compressor performance decreases dramatically due to separation of boundary layer and secondary-flow. The main objective in this paper is to understand the physical mechanism by which Reynolds number affects the Compressor stable range. In this paper, a series of steady and unsteady numerical simulations were carried out for a transonic Compressor Rotor under several conditions, which corresponded to the operations at sea level, and at high altitude. Detailed analyses of the flow visualization have exposed the different flow topologies of the complicated secondary flow. It was found that the transonic axial-flow Compressor Rotor used in current investigation was prone to tip stall behavior, and the complex flow mechanisms which occur near the blade tip are found to be the key factors for the limited flow stability both under high Reynolds number and low...

  • numerical investigation of the unsteady tip leakage flow and rotating stall inception in a transonic Compressor
    Journal of Thermal Science, 2010
    Co-Authors: Yanfeng Zhang, Wuli Chu, Junqiang Zhu
    Abstract:

    It is well known that tip leakage flow has a strong effect on the Compressor performance and stability. This paper reports on a numerical investigation of detailed flow structures in an isolated transonic Compressor Rotor-NASA Rotor 37 at near stall and stalled conditions aimed at improving understanding of changes in 3D tip leakage flow structures with rotating stall inception. Steady and unsteady 3D Navier-Stokes analyses were conducted to investigate flow structures in the same Rotor. For steady analysis, the predicted results agree well with the experimental data for the estimation of Compressor Rotor global performance. For unsteady flow analysis, the unsteady flow nature caused by the breakdown of the tip leakage vortex in blade tip region in the transonic Compressor Rotor at near stall condition has been captured with a single blade passage. On the other hand, the time-accurate unsteady computations of multi-blade passage at near stall condition indicate that the unsteady breakdown of the tip leakage vortex triggered the short length-scale — spike type rotating stall inception at blade tip region. It was the forward spillage of the tip leakage flow at blade leading edge resulting in the spike stall inception. As the mass flow ratio is decreased, the rotating stall cell was further developed in the blade passage.

  • numerical investigation of a high subsonic axial flow Compressor Rotor with non axisymmetric hub endwall
    Journal of Thermal Science, 2010
    Co-Authors: Junqiang Zhu
    Abstract:

    The major source of loss in modern Compressors is the secondary loss. Non-axisymmetric endwall profile contouring is now a well established design methodology in axial flow turbines. However, flow development in axial Compressors is differ from turbines, the effects of non-axisymmetric endwall to axial Compressors requires flow analysis in detail. This paper presents both experimental and numerical data to deal with the application of a non-axisymmetric hub endwall in a high-subsonic axial-flow Compressor. The aims of the experiment here were to make sure the numerically obtained flow fields is the physical mechanism responsible for the improvement in efficiency, due to the non-axisymmetric hub endwall. The computational results were first compared with available measured data of axisymmetric hub endwall. The results agreed well with the experimental data for estimation of the global performance. The coupled flow of the Compressor Rotor with non-axisymmetric hub endwall was simulated by a state-of-the-art multi-block flow solver. The non-axisymmetric hub endwall was designed for a subsonic Compressor Rotor with the help of sine and cosine functions. This type of non-axisymmetric hub endwall was found to have a significant improvement in efficiency of 0.45% approximately and a slightly increase for the total pressure ratio. The fundamental mechanisms of non-axisymmetric hub endwall and their effects on the subsonic axial-flow Compressor endwall flow field were analyzed in detail. It is concluded that the non-axisymmetric endwall profiling, though not optimum, can mitigate the secondary flow in the vicinity of the hub endwall, resulting in the improvement of aerodynamic performance of the Compressor Rotor.

  • Numerical Investigations of the Coupled Flow Through a Subsonic Compressor Rotor and Axial Skewed Slot
    Journal of Turbomachinery, 2009
    Co-Authors: Wuli Chu, Junqiang Zhu, Yangfeng Zhang
    Abstract:

    In order to advance the understanding of the fundamental mechanisms of axial skewed slot casing treatment and their effects on the subsonic axial-flow Compressor flow field, the coupled unsteady flow through a subsonic Compressor Rotor and the axial skewed slot was simulated with a state-of-the-art multiblock flow solver. The computational results were first compared with available measured data, that showed the numerical procedure calculates the overall effect of the axial skewed slot correctly. Then, the numerically obtained flow fields were interrogated to identify the physical mechanism responsible for improvement in stall margin of a modern subsonic axial-flow Compressor Rotor due to the discrete skewed slots. It was found that the axial skewed slot casing treatment can in-crease the stall margin of subsonic Compressor by repositioning of the tip clearance flow trajectory further toward the trailing of the blade passage and retarding the movement of the incoming/tip clearance flow interface toward the Rotor leading edge plane.

  • Experimental and Numerical Investigation of a Subsonic Compressor With Bend Skewed Slot Casing Treatment
    Volume 6: Turbomachinery Parts A and B, 2006
    Co-Authors: Wuli Chu, Junqiang Zhu
    Abstract:

    Based on the test results of discrete axial and blade angle slot casing treatment, a new type of casing treatment was designed for a subsonic axial flow Compressor Rotor by optimising various geometry parameters. To obtain a wide operating range and to minimize penalties in terms of isentropic efficiency, seven Compressor configurations incorporating casing treatments of 0%, 16.6%, 33.3%, 50%, 66.6%, 83.3% and 100% Rotor exposure were experimentally investigated. The results showed that significant improvements in stall margin are possible in all exposures and insignificant isentropic efficiency sacrifices are recorded in some exposures. Nearly 21.43% stall margin improvement in terms of the corrected mass flow rate was achieved with 33.3% Rotor blade tip axial chord exposure. The Compressor build with 16.6% Rotor exposure was the best configuration in terms of maximum isentropic efficiency gain. The second issue of the paper was to offer a contribution to the understanding of the physical mechanism by which bend skewed slot casing treatment improve stall margin under subsonic conditions. By applying a concept similar to “Domain Scaling” approach (as often used in multistage turbomachinery Flow-fields) to the interface between the Rotor blade passage and end-wall treatments, a time-dependent 3-dimentional numerical simulation was performed for the subsonic axial-flow Compressor Rotor with bend skewed slot casing treatment. The numerical results agreed well with experimental results. Detailed analyses of the coupled flow through bend skewed slot casing treatment and Rotor blade passage under subsonic conditions led to some preliminary conclusions as to the flow physics involved in the stall margin improvements afforded by the use of bend skewed slot casing treatment.© 2006 ASME

Jiawei Chen - One of the best experts on this subject based on the ideXlab platform.

  • The impact of various forward sweep angles on the performance of an ultra-high-load low-reaction transonic Compressor Rotor
    Applied Thermal Engineering, 2019
    Co-Authors: Shijun Sun, Songtao Wang, Shaowen Chen, Chuansijia Tao, Le Cai, Jiawei Chen
    Abstract:

    Abstract The impacts of different forward sweep angles (FSAs) at a constant sweep height on the performance and flow field have been investigated by numerical simulation in a newly designed low-reaction ultra-high-load Compressor Rotor. The main intent is to reveal the underlying physical mechanism of forward sweep blading on the change in performance. The results show that as FSA increases, stall margin presents an increasing upward trend with a maximum enhancement of 27.8%. While total pressure ratio and efficiency increase first and then drop with a maximum improvement (0.40% and 0.19%, respectively, at peak efficiency point) at an FSA of 10 deg. Not all of the schemes can improve efficiency. When FSA exceeds 20 deg, there appears to be a noticeable deficit in peak efficiency for a forward sweep Rotor comparing with the unswept Rotor. As FSA increases, the passage shock becomes more and more oblique to the incoming flow. The size of the high loss region and tip leakage vortex decrease gradually. The radial vortex on suction surface shrinks at peak efficiency condition but enlarges near stall condition, and tip leakage flow/main flow interface increasingly moves forward.

Shijun Sun - One of the best experts on this subject based on the ideXlab platform.

  • the influence of diversified forward sweep heights on operating range and performance of an ultra high load low reaction transonic Compressor Rotor
    Energy, 2020
    Co-Authors: Shijun Sun, Songtao Wang, Shaowen Chen
    Abstract:

    Abstract To provide a guideline for the optimal selection of forward sweep height (FSH) in terms of operating range and performance, numerical simulations are utilized to investigate the effects of different FSHs on a new-type low-reaction ultra-high-load Compressor Rotor. The results illustrate that it is an effective measure to amplify stall margin improvement (SMI) by adequately increasing FSH (no more than 50% span). Nonetheless, when FSH exceeds 50% span, there appears a drop in SMI. Both total pressure ratio (TPR) and peak efficiency (PE) demonstrate a continual downward trend with increasing FSH. It is noteworthy that compared with the unswept Rotor, forward sweep enhances stall margin in all Rotors but reduces PE and the corresponding TPR when FSH is more than 50% span. There exists an optimal FSH (50% span) that could maximize SMI (15.12%) and simultaneously achieve a negligible performance change at PE condition. A deep insight into the flow field reveals that as FSH increases, the shock gradually migrates downstream and the separation bubble on suction side shrinks at PE point and shortens in streamwise direction near stall. If FSH continually increases above 50% span, SMI brought by the change in shock structure and tip leakage flow will drop.

  • The impact of various forward sweep angles on the performance of an ultra-high-load low-reaction transonic Compressor Rotor
    Applied Thermal Engineering, 2019
    Co-Authors: Shijun Sun, Songtao Wang, Shaowen Chen, Chuansijia Tao, Le Cai, Jiawei Chen
    Abstract:

    Abstract The impacts of different forward sweep angles (FSAs) at a constant sweep height on the performance and flow field have been investigated by numerical simulation in a newly designed low-reaction ultra-high-load Compressor Rotor. The main intent is to reveal the underlying physical mechanism of forward sweep blading on the change in performance. The results show that as FSA increases, stall margin presents an increasing upward trend with a maximum enhancement of 27.8%. While total pressure ratio and efficiency increase first and then drop with a maximum improvement (0.40% and 0.19%, respectively, at peak efficiency point) at an FSA of 10 deg. Not all of the schemes can improve efficiency. When FSA exceeds 20 deg, there appears to be a noticeable deficit in peak efficiency for a forward sweep Rotor comparing with the unswept Rotor. As FSA increases, the passage shock becomes more and more oblique to the incoming flow. The size of the high loss region and tip leakage vortex decrease gradually. The radial vortex on suction surface shrinks at peak efficiency condition but enlarges near stall condition, and tip leakage flow/main flow interface increasingly moves forward.

Wuli Chu - One of the best experts on this subject based on the ideXlab platform.

  • flow mechanism of affecting an axial flow Compressor performance and stability with cross blade slot casing treatments
    Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2019
    Co-Authors: Haoguang Zhang, Wuli Chu, Xudong Zhang, Haiyang Kuang
    Abstract:

    The objective of this study is to evaluate the effect of cross-blade slot casing treatment on the stability and performance of an axial flow Compressor Rotor. The experimental and unsteady calculat...

  • numerical investigation of the unsteady tip leakage flow and rotating stall inception in a transonic Compressor
    Journal of Thermal Science, 2010
    Co-Authors: Yanfeng Zhang, Wuli Chu, Junqiang Zhu
    Abstract:

    It is well known that tip leakage flow has a strong effect on the Compressor performance and stability. This paper reports on a numerical investigation of detailed flow structures in an isolated transonic Compressor Rotor-NASA Rotor 37 at near stall and stalled conditions aimed at improving understanding of changes in 3D tip leakage flow structures with rotating stall inception. Steady and unsteady 3D Navier-Stokes analyses were conducted to investigate flow structures in the same Rotor. For steady analysis, the predicted results agree well with the experimental data for the estimation of Compressor Rotor global performance. For unsteady flow analysis, the unsteady flow nature caused by the breakdown of the tip leakage vortex in blade tip region in the transonic Compressor Rotor at near stall condition has been captured with a single blade passage. On the other hand, the time-accurate unsteady computations of multi-blade passage at near stall condition indicate that the unsteady breakdown of the tip leakage vortex triggered the short length-scale — spike type rotating stall inception at blade tip region. It was the forward spillage of the tip leakage flow at blade leading edge resulting in the spike stall inception. As the mass flow ratio is decreased, the rotating stall cell was further developed in the blade passage.

  • Numerical Investigations of the Coupled Flow Through a Subsonic Compressor Rotor and Axial Skewed Slot
    Journal of Turbomachinery, 2009
    Co-Authors: Wuli Chu, Junqiang Zhu, Yangfeng Zhang
    Abstract:

    In order to advance the understanding of the fundamental mechanisms of axial skewed slot casing treatment and their effects on the subsonic axial-flow Compressor flow field, the coupled unsteady flow through a subsonic Compressor Rotor and the axial skewed slot was simulated with a state-of-the-art multiblock flow solver. The computational results were first compared with available measured data, that showed the numerical procedure calculates the overall effect of the axial skewed slot correctly. Then, the numerically obtained flow fields were interrogated to identify the physical mechanism responsible for improvement in stall margin of a modern subsonic axial-flow Compressor Rotor due to the discrete skewed slots. It was found that the axial skewed slot casing treatment can in-crease the stall margin of subsonic Compressor by repositioning of the tip clearance flow trajectory further toward the trailing of the blade passage and retarding the movement of the incoming/tip clearance flow interface toward the Rotor leading edge plane.

  • Experimental and Numerical Investigation of a Subsonic Compressor With Bend Skewed Slot Casing Treatment
    Volume 6: Turbomachinery Parts A and B, 2006
    Co-Authors: Wuli Chu, Junqiang Zhu
    Abstract:

    Based on the test results of discrete axial and blade angle slot casing treatment, a new type of casing treatment was designed for a subsonic axial flow Compressor Rotor by optimising various geometry parameters. To obtain a wide operating range and to minimize penalties in terms of isentropic efficiency, seven Compressor configurations incorporating casing treatments of 0%, 16.6%, 33.3%, 50%, 66.6%, 83.3% and 100% Rotor exposure were experimentally investigated. The results showed that significant improvements in stall margin are possible in all exposures and insignificant isentropic efficiency sacrifices are recorded in some exposures. Nearly 21.43% stall margin improvement in terms of the corrected mass flow rate was achieved with 33.3% Rotor blade tip axial chord exposure. The Compressor build with 16.6% Rotor exposure was the best configuration in terms of maximum isentropic efficiency gain. The second issue of the paper was to offer a contribution to the understanding of the physical mechanism by which bend skewed slot casing treatment improve stall margin under subsonic conditions. By applying a concept similar to “Domain Scaling” approach (as often used in multistage turbomachinery Flow-fields) to the interface between the Rotor blade passage and end-wall treatments, a time-dependent 3-dimentional numerical simulation was performed for the subsonic axial-flow Compressor Rotor with bend skewed slot casing treatment. The numerical results agreed well with experimental results. Detailed analyses of the coupled flow through bend skewed slot casing treatment and Rotor blade passage under subsonic conditions led to some preliminary conclusions as to the flow physics involved in the stall margin improvements afforded by the use of bend skewed slot casing treatment.© 2006 ASME

  • Numerical and Experimental Investigations of Steady Micro-Tip Injection on a Subsonic Axial-Flow Compressor Rotor
    Hindawi Limited, 2006
    Co-Authors: Wuli Chu, Junqiang Zhu, Zhiting Tong
    Abstract:

    Steady tip injection has been demonstrated to be an effective means of extending the stable operating range of a tip-critical Compressor. This study presents a state-of-the-art design for the tip injection through the casing with flush-mounted inclined holes and the effectiveness of steady micro-air injection to enhance stability in a subsonic axial-flow Compressor Rotor using an external-air supply. For the tested Rotor, experimental results demonstrate that at 53% design speed, the stalling mass flow can be reduced by 7.69% using an injected mass flow equivalent to 0.064% of the annulus flow. Time-dependent CFD simulations were conducted to identify the physical mechanic that accounts for the beneficial effects of the steady micro-air injection on the performance and stability of the Compressor. Detailed analyses of the flow visualization at the tip have exposed the different tip flow topologies between the cases without tip injection and with tip injection. It was found that the primary stall margin enhancement afforded by the steady micro-air injection is a result of the tip-clearance flow manipulation. The repositioning of the tip-clearance vortex further towards the trailing edge of the blade passage and delaying the movement of incoming/tip-clearance flow interface to the leading edge plane are the physical mechanisms responsible for extending the Compressor stall margin

Shaowen Chen - One of the best experts on this subject based on the ideXlab platform.

  • the influence of diversified forward sweep heights on operating range and performance of an ultra high load low reaction transonic Compressor Rotor
    Energy, 2020
    Co-Authors: Shijun Sun, Songtao Wang, Shaowen Chen
    Abstract:

    Abstract To provide a guideline for the optimal selection of forward sweep height (FSH) in terms of operating range and performance, numerical simulations are utilized to investigate the effects of different FSHs on a new-type low-reaction ultra-high-load Compressor Rotor. The results illustrate that it is an effective measure to amplify stall margin improvement (SMI) by adequately increasing FSH (no more than 50% span). Nonetheless, when FSH exceeds 50% span, there appears a drop in SMI. Both total pressure ratio (TPR) and peak efficiency (PE) demonstrate a continual downward trend with increasing FSH. It is noteworthy that compared with the unswept Rotor, forward sweep enhances stall margin in all Rotors but reduces PE and the corresponding TPR when FSH is more than 50% span. There exists an optimal FSH (50% span) that could maximize SMI (15.12%) and simultaneously achieve a negligible performance change at PE condition. A deep insight into the flow field reveals that as FSH increases, the shock gradually migrates downstream and the separation bubble on suction side shrinks at PE point and shortens in streamwise direction near stall. If FSH continually increases above 50% span, SMI brought by the change in shock structure and tip leakage flow will drop.

  • The impact of various forward sweep angles on the performance of an ultra-high-load low-reaction transonic Compressor Rotor
    Applied Thermal Engineering, 2019
    Co-Authors: Shijun Sun, Songtao Wang, Shaowen Chen, Chuansijia Tao, Le Cai, Jiawei Chen
    Abstract:

    Abstract The impacts of different forward sweep angles (FSAs) at a constant sweep height on the performance and flow field have been investigated by numerical simulation in a newly designed low-reaction ultra-high-load Compressor Rotor. The main intent is to reveal the underlying physical mechanism of forward sweep blading on the change in performance. The results show that as FSA increases, stall margin presents an increasing upward trend with a maximum enhancement of 27.8%. While total pressure ratio and efficiency increase first and then drop with a maximum improvement (0.40% and 0.19%, respectively, at peak efficiency point) at an FSA of 10 deg. Not all of the schemes can improve efficiency. When FSA exceeds 20 deg, there appears to be a noticeable deficit in peak efficiency for a forward sweep Rotor comparing with the unswept Rotor. As FSA increases, the passage shock becomes more and more oblique to the incoming flow. The size of the high loss region and tip leakage vortex decrease gradually. The radial vortex on suction surface shrinks at peak efficiency condition but enlarges near stall condition, and tip leakage flow/main flow interface increasingly moves forward.