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Qingjun Zhao
Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China

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Journal article
Published: 05 July 2021 in Chinese Journal of Aeronautics
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Flow separation due to shock wave/boundary layer interaction is dominated in blade passage with supersonic relative incoming flow, which always accompanies aerodynamic performance penalties. A loss reduction method for smearing the passage shock foot via Shock Control Bump (SCB) located on transonic compressor rotor blade suction side is implemented to shrink the region of boundary layer separation. The curved windward section of SCB with constant adverse pressure gradient is constructed ahead of passage shock-impingement point at design rotor speed of Rotor 37 to get the improved model. Numerical investigations on both two models have been conducted employing Reynolds-Averaged Navier-Stokes (RANS) method to reveal flow physics of SCB. Comparisons and analyses on simulation results have also been carried out, showing that passage shock foot of baseline is replaced with a family of compression waves and a weaker shock foot for moderate adverse pressure gradient as well as suppression of boundary layer separations and secondary flow of low-momentum fluid within boundary layer. It is found that adiabatic efficiency and total pressure ratio of improved blade exceeds those of baseline at 95%-100% design rotor speed, and then slightly worsens with decrease of rotatory speed till both equal below 60% rated speed. The investigated conclusion implies a potential promise for future practical applications of SCB in both transonic and supersonic compressors.

ACS Style

Yongzhen Liu; Wei Zhao; Qingjun Zhao; Qiang Zhou; Jianzhong Xu. Passage shock wave/boundary layer interaction control for transonic compressors using bumps. Chinese Journal of Aeronautics 2021, 1 .

AMA Style

Yongzhen Liu, Wei Zhao, Qingjun Zhao, Qiang Zhou, Jianzhong Xu. Passage shock wave/boundary layer interaction control for transonic compressors using bumps. Chinese Journal of Aeronautics. 2021; ():1.

Chicago/Turabian Style

Yongzhen Liu; Wei Zhao; Qingjun Zhao; Qiang Zhou; Jianzhong Xu. 2021. "Passage shock wave/boundary layer interaction control for transonic compressors using bumps." Chinese Journal of Aeronautics , no. : 1.

Research article
Published: 21 May 2021 in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
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The sealing of the rotor-rotor gap and rotor disk cooling are vital to the safe operation of the vaneless counter-rotating turbine(VCRT). In order to quantifies the influence of the wheel-space cavity flow on the VCRT aerodynamic performance, and to improve turbine efficiency of the VCRT at certain rim seal ejection rates, numerical studies which considered the effects of rotor-rotor rim seal flow ejection are carried out in this paper. The three dimensional unsteady computational fluid dynamic analysis of a VCRT at the engine conditions are performed, and the seal flow ejected downstream of the high pressure rotor row at six sealing flow rate are modeled. The interaction among the high pressure rotor trailing shock wave, the downstream secondary flow and the seal flow has been studied and quantitatively characterized as a function of the purge ejection rate. Numerical results show that seal flow- mainstream flow interaction is entirely dominated by the high pressure rotor trailing edge shock at the hub, low pressure hub passage vortex and the mixing of the sealing flow from wheelspace and mainstream. When the mass flow rate of the coolant is smaller than some threshold value, the shock loss of the high pressure rotor and hub secondary flow loss of the low pressure rotor are decreased with the increasing of the coolant mass flow rate. It causes that the VCRT efficiency is gradually increased. On condition that the amount of the seal flows is beyond the threshold value, the key roles in modification of the VCRT performance are changed. The increment of the hub secondary flow loss and the mixing loss are gradually larger than the decrement of the shock loss. As a result, the turbine efficiency gradually decreases.

ACS Style

Xiuming Sui; Wei Zhao; Xiaorong Xiang; Te Pi; Qingjun Zhao. Investigation of the flowfield on a vaneless counter-rotating turbine with seal cavity flow ejection. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2021, 1 .

AMA Style

Xiuming Sui, Wei Zhao, Xiaorong Xiang, Te Pi, Qingjun Zhao. Investigation of the flowfield on a vaneless counter-rotating turbine with seal cavity flow ejection. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy. 2021; ():1.

Chicago/Turabian Style

Xiuming Sui; Wei Zhao; Xiaorong Xiang; Te Pi; Qingjun Zhao. 2021. "Investigation of the flowfield on a vaneless counter-rotating turbine with seal cavity flow ejection." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy , no. : 1.

Journal article
Published: 19 May 2021 in Mechanical Systems and Signal Processing
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Rotor blades, being the key part for power and energy conversion, are essential to the safety of turbomachinery. Monitoring the running state of rotor blades is significantly important to ensure the safety of blade operation. The blade tip-timing (BTT) technology has many advantages of non-intrusive measurement being a popular monitor method. The accuracy of vibration data obtained by BTT method is critical to evaluate the running state of blade. However, the blade vibration displacement obtained by the traditional BTT (T-BTT) method and its extended methods still faces the calculation errors caused by unstable rotation speed. To improve the calculation accuracy of blade vibration displacement and minimize the calculation errors caused by unstable rotation speed, the error correction BTT (EC-BTT) method is proposed. In this method, the calculation errors caused by unstable rotation speed are analyzed, and then the calculation errors are eliminated by the derived formula to obtain more accurate vibration displacement data. The EC-BTT method is proved to be feasible and effective by simulation models and a large-scale industry axial fan. The results indicate that the EC-BTT method can eliminate the calculation errors of vibration displacement caused by sudden change and fluctuating speed. The method also can be used in T-BTT and its extended methods.

ACS Style

Sanqun Ren; Xiaorong Xiang; Wei Zhao; Qingjun Zhao; Chen Wang; Qiangren Xu. An error correction blade tip-timing method to improve the measured accuracy of blade vibration displacement during unstable rotation speed. Mechanical Systems and Signal Processing 2021, 162, 108030 .

AMA Style

Sanqun Ren, Xiaorong Xiang, Wei Zhao, Qingjun Zhao, Chen Wang, Qiangren Xu. An error correction blade tip-timing method to improve the measured accuracy of blade vibration displacement during unstable rotation speed. Mechanical Systems and Signal Processing. 2021; 162 ():108030.

Chicago/Turabian Style

Sanqun Ren; Xiaorong Xiang; Wei Zhao; Qingjun Zhao; Chen Wang; Qiangren Xu. 2021. "An error correction blade tip-timing method to improve the measured accuracy of blade vibration displacement during unstable rotation speed." Mechanical Systems and Signal Processing 162, no. : 108030.

Research article
Published: 13 May 2021 in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
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The tip winglet is employed to improve the flow stability of NASA Rotor 37. Two suction-side winglets with the maximum width of 0.25 and 0.5 times of the width of local blade tip section and two pressure-side winglets with the maximum width of 0.5 and 0.9 times of the width of local blade tip section are designed and evaluated by numerical analysis of 3-D flowfield. The results show a rough leakage channel with two static pressure peaks over blade tip is formed due to the existing of pressure side winglet, and it benefits to reduce the effective through-flow area and massflow rate of leakage flow. The blocking effect on leakage flow weakens in new rotor with suction side winglet and it brings out the dramatical increase of leakage massflow rate and additional losses in tip region of rotor. With the comprehensive effects produced by tip winglet on leakage flow, the low-velocity region concerned on the interaction of leakage flow with passage shock has been reduced obviously in rotor with pressure side winglet and it leads to an over 11% increase of stall margin of transonic rotor with no penalty of efficiency. On the contrary, the suction side winglet contributes to a significant deterioration of tip flow characteristics of rotor with full expanded leakage flow and a smaller stall margin with over 17% decrease.

ACS Style

Qingjun Zhao; Weiwei Cui; Wei Zhao; Xiaorong Xiang; Jianzhong Xu. Investigation on the effects of winglet geometry in a high loading compressor rotor. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2021, 1 .

AMA Style

Qingjun Zhao, Weiwei Cui, Wei Zhao, Xiaorong Xiang, Jianzhong Xu. Investigation on the effects of winglet geometry in a high loading compressor rotor. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy. 2021; ():1.

Chicago/Turabian Style

Qingjun Zhao; Weiwei Cui; Wei Zhao; Xiaorong Xiang; Jianzhong Xu. 2021. "Investigation on the effects of winglet geometry in a high loading compressor rotor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy , no. : 1.

Research article
Published: 15 April 2021 in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
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The interactions of tip leakage flow with mainstream and shock wave result in larger aerodynamic losses and blockage in high loading compressors and tend to be one of the triggers for flow instability. In order to attenuate the influence of leakage flow and improve the stall margin of highly loaded compressor, the new rotors surrounded by tip winglet are investigated by a numerical method. The tip winglet is designed by extending the flat blade tip section in outer 1.5% span of rotor blade. As the angle between the leakage flow and main flow decreases due to winglet, the losses and flow blockage have been weakened near stall condition, and the stall margin of new rotor with pressure-side winglet has an increase of over 10%. The migration and accumulation of low-energy fluids near the corner of casing endwall are affected significantly by tip winglet. As a result, the pressure-side winglet causes an increase of static pressure near the casing corner of pressure surface. Although the driving pressure difference near the leading edge of blade has increased slightly in the tip region, the strength and massflow rate of leakage flow appear to be decreased. As the leakage flow weakens in the new rotor with pressure-side winglet, its interaction with mainstream and shock has been suppressed obviously, and the delay of rotating stall occurs as well. Moreover, the flowfields of the new rotor with pressure-side winglet have been simulated at 40%, 60%, and 80% design speed. It is shown that the flow blockage and losses in the tip region have also reduced near stall point, and an improvement of overall performance is present in the new rotor with pressure-side winglet. All the changes of tip flow structure caused by winglet benefit to an increase of aerodynamic performance of new rotor at full rotational speed range.

ACS Style

Qingjun Zhao; Weiwei Cui; Xiaorong Xiang; Qiangren Xu; Jianzhong Xu. Numerical investigation of blade tip winglet on flow structure in a high loading transonic rotor. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 2021, 1 .

AMA Style

Qingjun Zhao, Weiwei Cui, Xiaorong Xiang, Qiangren Xu, Jianzhong Xu. Numerical investigation of blade tip winglet on flow structure in a high loading transonic rotor. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering. 2021; ():1.

Chicago/Turabian Style

Qingjun Zhao; Weiwei Cui; Xiaorong Xiang; Qiangren Xu; Jianzhong Xu. 2021. "Numerical investigation of blade tip winglet on flow structure in a high loading transonic rotor." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering , no. : 1.

Journal article
Published: 27 January 2021 in Aerospace Science and Technology
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Lean Blow-Off (LBO) is of great significance for propulsion systems, and developing an efficient LBO prediction method can technically support combustor design. In this paper, a hybrid LBO prediction method combining Damköhler (Da) model and numerical simulation is proposed. The time scales of Damköhler number are defined based on Reaction Zone (RZ) which is obtained from the simulated flow field. RZ is divided into a number of blocks, and each block is modeled as a Perfectly Stirred Reactor (PSR). Two kinds of Damköhler numbers are calculated. Local Da (Dal) number is calculated specific to each reactor in RZ, and Dal field is generated to analyze the local flow and chemical characteristics within RZ under different operating conditions. The Dal fields under different LBO conditions show that reactions concentrate near the outlet of the swirl-cup where the flows out of the swirl-cup and the backflows caused by recirculation collide. Global Da number (Dag) is calculated based on the entire flow and chemical characteristics of RZ, and acts as an indicator of LBO. Theoretically, LBO occurs when Dag is smaller than 1. In the current study, though the inlet temperature (T3), inlet pressure (P3), and inlet mass-flow rate (ma) are varied, the Dag under LBO conditions maintains at about 1, and it is about 11 under design condition, which proves that LBO limits can be accurately predicted under wide operating conditions by the method proposed in this paper.

ACS Style

Zhonghao Wang; Bin Hu; Aibing Fang; Qingjun Zhao; Xing Chen. Analyzing lean blow-off limits of gas turbine combustors based on local and global Damköhler number of reaction zone. Aerospace Science and Technology 2021, 111, 106532 .

AMA Style

Zhonghao Wang, Bin Hu, Aibing Fang, Qingjun Zhao, Xing Chen. Analyzing lean blow-off limits of gas turbine combustors based on local and global Damköhler number of reaction zone. Aerospace Science and Technology. 2021; 111 ():106532.

Chicago/Turabian Style

Zhonghao Wang; Bin Hu; Aibing Fang; Qingjun Zhao; Xing Chen. 2021. "Analyzing lean blow-off limits of gas turbine combustors based on local and global Damköhler number of reaction zone." Aerospace Science and Technology 111, no. : 106532.

Journal article
Published: 19 October 2020 in Aerospace Science and Technology
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The precessing vortex core (PVC) and symmetric coherent structures in partly confined swirling flows of gas turbine combustors are investigated numerically. The computational combustor features a sidewall in the circumferential direction, and the ratio between the sidewall length (L) and dome height (H) is specified as 0, 0.27, 0.68, and 1 to construct various confinements. Then a large eddy simulation is performed under the isothermal condition to investigate the effect of different L/H values on dominant coherent structures in combustors. The time-averaged flowfields exhibit different shapes of the inner recirculation zone (IRZ) with increasing L/H. Proper orthogonal decomposition is used to extract coherent structures from the turbulence; the single helical structure referred to as the PVC, and the symmetric vortices that shed and are amplified in the shear layer, are found to dominate the evolution of the flow in all cases. Relevant phase-averaged velocity fields show that the PVC synchronizes with the IRZ rotating around the centerline of the combustor while the symmetric coherent structure causes the deformation of the IRZ. By examining the azimuthal wave related to the PVC, it is shown that the PVC is suppressed in the partly confined swirling flow, and its strength is enhanced as L/H increases. Changes in shear layer thickness are suggested as being responsible for the suppression of the PVC under the partly confined condition.

ACS Style

Junhua Zhang; Bin Hu; Aibing Fang; Zhonghao Wang; Qingjun Zhao. Analysis of coherent structures in partly confined swirling flows. Aerospace Science and Technology 2020, 107, 106280 .

AMA Style

Junhua Zhang, Bin Hu, Aibing Fang, Zhonghao Wang, Qingjun Zhao. Analysis of coherent structures in partly confined swirling flows. Aerospace Science and Technology. 2020; 107 ():106280.

Chicago/Turabian Style

Junhua Zhang; Bin Hu; Aibing Fang; Zhonghao Wang; Qingjun Zhao. 2020. "Analysis of coherent structures in partly confined swirling flows." Aerospace Science and Technology 107, no. : 106280.

Research article
Published: 27 August 2020 in International Journal of Engine Research
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Variable geometry orifice located upstream of a centrifugal impeller has been proposed to improve compressor low-end performance, by reducing compressor inlet flow area. The inlet flow area reduction is achieved by actuating the orifice flow area. The effects of the flow area reduction on compressor performance and the physical mechanisms controlling performance were investigated in the current work using numerical simulations and physical experiments. At the investigated compressor speed, with reduced inlet flow area, compressor efficiency at high flow rates is decreased by 2.01 percentage points based on the numerical predictions and by 6.47 percentage points based on the physical data. At low flow rate, however, compressor efficiency can be improved by 2.26 percentage points based on the numerical predictions and by 2.88 percentage points based on the physical data. Besides the efficiency, the inlet flow area reduction shifts the compressor stability limit toward the lower flow rate by 9.09% based on the numerical results and 41.13% based on the physical experiment and improves the compressor peak pressure ratio by 0.55% based on both the numerical and experimental data. At the flow rates lower than the peak efficiency point, it is beneficial to actuate the orifice to improve the compressor low-end performance. At flow rates higher than the peak efficiency point, it is necessary to deactivate the orifice to avoid the inlet flow area reduction that induces flow loss and degrades compressor performance.

ACS Style

Ben Zhao; Qingjun Zhao; Wei Zhao; Xiaorong Xiang; Xiaoyong Zhou. Numerical and experimental investigation of turbocharger compressor low-end performance improvement using a variable geometry inlet orifice. International Journal of Engine Research 2020, 1 .

AMA Style

Ben Zhao, Qingjun Zhao, Wei Zhao, Xiaorong Xiang, Xiaoyong Zhou. Numerical and experimental investigation of turbocharger compressor low-end performance improvement using a variable geometry inlet orifice. International Journal of Engine Research. 2020; ():1.

Chicago/Turabian Style

Ben Zhao; Qingjun Zhao; Wei Zhao; Xiaorong Xiang; Xiaoyong Zhou. 2020. "Numerical and experimental investigation of turbocharger compressor low-end performance improvement using a variable geometry inlet orifice." International Journal of Engine Research , no. : 1.

Research article
Published: 18 August 2020 in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
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In order to develop a tip clearance control system for an uncooled vaneless counter-rotating turbine, tip clearance variation of its high pressure rotor blade at off-design conditions is analyzed. Aero-thermal interaction simulation is performed to predict the temperature and deformation of the solid blade. At operating conditions with rotating speeds greater than 60% design value and expansion ratios greater than 85% design value, the blade tip clearance height at leading edge remains unchanged when the expansion ratio decreases, meanwhile that at trailing edge decreased obviously. However, the tip clearance height variations at the leading edge and trailing edge are almost the same in a conventional subsonic turbine at such conditions. The cause is that the flow in the high-pressure rotor is choked at these conditions. The choked flow results in that the fluid and solid blade temperatures upstream of the throat are not affected by the back pressure and only those downstream of the throat increases with the back pressure. Consequently, the blade height at leading edge keeps constant, and that at trailing edge varies because of thermal expansion. To avoid the rubbing of the blade and case, the blade height at trailing edge is diminished by 30%. As a result, the blade tip clearance height at low speed operating conditions increases in axial direction. Such a design leads to a stronger tip leakage flow. More flow losses might be generated. Therefore, a casing cooling method is proposed to control the blade tip clearance height at leading edge and trailing edge respectively. The deformations of the casing with different mass flow rate of cooling air at design and off-design conditions are calculated. It shows that the blade tip clearance heights at leading edge and at trailing edge of the rotor can be well controlled with appropriate amount of cooling air.

ACS Style

Wei Zhao; Xiuming Sui; Kai Zhang; Zeming Wei; Qingjun Zhao. Investigation on tip clearance control for the high-pressure rotor of an uncooled vaneless counter-rotating turbine. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 2020, 235, 566 -577.

AMA Style

Wei Zhao, Xiuming Sui, Kai Zhang, Zeming Wei, Qingjun Zhao. Investigation on tip clearance control for the high-pressure rotor of an uncooled vaneless counter-rotating turbine. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering. 2020; 235 (5):566-577.

Chicago/Turabian Style

Wei Zhao; Xiuming Sui; Kai Zhang; Zeming Wei; Qingjun Zhao. 2020. "Investigation on tip clearance control for the high-pressure rotor of an uncooled vaneless counter-rotating turbine." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 235, no. 5: 566-577.

Research article
Published: 01 August 2020 in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
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The flow in centrifugal compressors is viscous and unsteady. Flow separation off the blades challenges the accuracy of simulations. A viscous body force model is expected to speed up numerical convergence and reduce the computational costs of unsteady simulations. In this paper, both stability and accuracy of the viscous body force model are investigated based on the case of a low-speed centrifugal compressor. First, two formulations of the viscous body forces are obtained from the expression of the viscous flux. Then, the numerical stability of two body force models is found to be related to drag coefficient and flow angle. For large negative drag coefficients, the viscous body forces would lead to divergences. Since unsteady Reynolds-averaged Navier–Stokes simulations show that two formulas have considerable accuracy, stability is considered as the main factor for modeling. With the findings, a hybrid viscous body force method is proposed. To assess the applicability of the hybrid model, two test cases are compared against the results obtained by unsteady Reynolds-averaged Navier–Stokes simulations. The first case is the capability evaluation of unsteady characteristics capture for low-speed centrifugal compressors. The simulation results show that the hybrid viscous body force model can capture main unsteady viscous characters, including wake vortexes and tip leakage flow. The other is the case in which the inlet total pressure is disturbed. It is found that fluctuations of pressure, temperature, and velocity predicted by the viscous body force method are close to unsteady Reynolds-averaged Navier–Stokes results. In addition, the time-accurate overall performance of the compressor with disturbance is also predicted satisfactorily. With the advantage in lowering computer resource requirement, the viscous body force model is a promising method for long length scale unsteady cases.

ACS Style

Zhiyuan Liu; Qingjun Zhao; Xiaorong Xiang; Wei Zhao; Xiaoyong Zhou. A hybrid viscous body force model for low-speed centrifugal compressors. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2020, 235, 335 -350.

AMA Style

Zhiyuan Liu, Qingjun Zhao, Xiaorong Xiang, Wei Zhao, Xiaoyong Zhou. A hybrid viscous body force model for low-speed centrifugal compressors. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy. 2020; 235 (3):335-350.

Chicago/Turabian Style

Zhiyuan Liu; Qingjun Zhao; Xiaorong Xiang; Wei Zhao; Xiaoyong Zhou. 2020. "A hybrid viscous body force model for low-speed centrifugal compressors." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 235, no. 3: 335-350.

Research article
Published: 20 June 2020 in Chinese Journal of Aeronautics
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The modal vibration of the rotor is the main cause of excessive vibration of the aero-engine overall structure. To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control, the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method. A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper. The transmission, conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape, the conical whirling modal shape and the translational modal shape are analyzed, respectively. The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy, the kinetic energy and the energy dissipated by the damping of the structure. The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different. Especially for the first-order bending modal shape, the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft, resulting in large deformation at this part. To attenuate this harmful vibration, the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow. This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.

ACS Style

Yingqun Ma; Qingjun Zhao; Wei Zhao; Binbin Liu; Long Hao. Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics: Theoretical and numerical analysis and application. Chinese Journal of Aeronautics 2020, 33, 3288 -3305.

AMA Style

Yingqun Ma, Qingjun Zhao, Wei Zhao, Binbin Liu, Long Hao. Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics: Theoretical and numerical analysis and application. Chinese Journal of Aeronautics. 2020; 33 (12):3288-3305.

Chicago/Turabian Style

Yingqun Ma; Qingjun Zhao; Wei Zhao; Binbin Liu; Long Hao. 2020. "Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics: Theoretical and numerical analysis and application." Chinese Journal of Aeronautics 33, no. 12: 3288-3305.

Journal article
Published: 29 April 2020 in Journal of Engineering for Gas Turbines and Power
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The aero-engine casing is a key component for carrying loads. With the purpose of improving the thrust-weight ratio of the aero-engine, the casing is required to be designed to be as thin as possible. Therefore, the vibration of aero-engine's rotor, support, and casing will be easily coupled causing the whole engine's vibration to be more serious. Considering the structural vibration propagation is essentially the vibration energy transmission, the structural intensity (SI) method is popular and widely used to investigate the transmission phenomena of vibration energy in vibrating structures. This method combines forces with velocities to quantify the vibrational energy flow (VEF) transmitted in the structures by its directions and magnitude. Therefore, the SI fields are quantified by the developed computation system which combines the finite element design language and the in-house code. And a model of dual-rotor–support–casing coupling system subjected to the unbalanced forces of the rotors is established in this paper. The scalar and vector diagrams of instantaneous SI fields are visualized to show the main vibration energy transmission paths among these three parts. Moreover, the relationship between the SI and the mechanical energy is derived from the kinetic equation. According to this relationship, the phenomenon that the vibration energy and the strain energy are always converted to each other in the middle part of the rotor shaft with the first-order bending mode is discussed, which reveals the cause of the first-order bending mode of the rotor from a microscopic point of view.

ACS Style

Yingqun Ma; Qingjun Zhao; Kai Zhang; Meng Xu; Wei Zhao. Analysis of Instantaneous Vibrational Energy Flow for an Aero-Engine Dual-Rotor–Support–Casing Coupling System. Journal of Engineering for Gas Turbines and Power 2020, 142, 1 .

AMA Style

Yingqun Ma, Qingjun Zhao, Kai Zhang, Meng Xu, Wei Zhao. Analysis of Instantaneous Vibrational Energy Flow for an Aero-Engine Dual-Rotor–Support–Casing Coupling System. Journal of Engineering for Gas Turbines and Power. 2020; 142 (5):1.

Chicago/Turabian Style

Yingqun Ma; Qingjun Zhao; Kai Zhang; Meng Xu; Wei Zhao. 2020. "Analysis of Instantaneous Vibrational Energy Flow for an Aero-Engine Dual-Rotor–Support–Casing Coupling System." Journal of Engineering for Gas Turbines and Power 142, no. 5: 1.

Research article
Published: 21 April 2020 in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
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A hybrid lean blow-off prediction method based on Damköhler ( Da) number was proposed in the authors’ previous study. However, the uniform model for fuel drop size distribution cannot fully reflect the actual atomization quality under lean blow-off conditions, which has negative effects on prediction accuracy. In the current study, atomization experiments are conducted under different fuel supply pressure. The atomization quality is described by Rosin–Rammler model and is integrated into numerical simulation. The calculation method of chemical time scale ( τc) is improved by accurately differentiating the inlet and outlet surface of reaction zone. After the improvement, the Da number under lean blow-off conditions mainly lies between 0.3 and 0.8, while under the designing condition, the Da number is about 20. Compared with the former method, the optimized method in the present article can distinguish stable combustion states markedly from lean blow-off states. Through the introduction of detailed atomization information and the improvement of time scale calculation, lean blow-off prediction accuracy in the present work is efficiently improved, which can provide powerful technical support for engineering applications.

ACS Style

Zhonghao Wang; Bin Hu; Aibing Fang; Aiming Deng; Junhua Zhang; Qingjun Zhao. Predicting lean blow-off limit of gas turbine combustors based on Damköhler number and detailed atomization information. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2020, 235, 262 -278.

AMA Style

Zhonghao Wang, Bin Hu, Aibing Fang, Aiming Deng, Junhua Zhang, Qingjun Zhao. Predicting lean blow-off limit of gas turbine combustors based on Damköhler number and detailed atomization information. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy. 2020; 235 (2):262-278.

Chicago/Turabian Style

Zhonghao Wang; Bin Hu; Aibing Fang; Aiming Deng; Junhua Zhang; Qingjun Zhao. 2020. "Predicting lean blow-off limit of gas turbine combustors based on Damköhler number and detailed atomization information." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 235, no. 2: 262-278.

Journal article
Published: 20 February 2020 in Journal of Heat Transfer
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To estimate the thermal properties from transient data, a model is needed to produce numerical values with sufficient precision. Iterative regression or other estimation procedures must be applied to evaluate the model again and again. From this perspective, infinite or semi-infinite heat conduction problems are a challenge. Since the analytical solution usually contains improper integrals that need to be computed numerically, computer-evaluation speed is a serious issue. To improve the computation speed with precision maintained, an analytical method has been applied to three-dimensional (3D) cylindrical geometries. In this method, the numerical evaluation time is improved by replacing the integral-containing solution by a suitable finite body series solution. The precision of the series solution may be controlled to a high level and the required computer time may be minimized by a suitable choice of the extent of the finite body. The practical applications for 3D geometries include the line-source method for obtaining thermal properties, the estimation of thermal properties by the laser-flash method, and the estimation of aquifer properties or petroleum-field properties from well-test measurements. This paper is an extension of earlier works on one-dimensional (1D) and two-dimensional (2D) cylindrical geometries. In this paper, the computer-evaluation time for the finite geometry 3D solutions is shown to be hundreds of times faster than the infinite or semi-infinite solution with the precision maintained.

ACS Style

Te Pi; Kevin D. Cole; Qingjun Zhao; Wei Zhao. Investigation of Numerical Evaluation Improvement for Three-Dimensional Infinite Cylindrical Heat Conduction Problems. Journal of Heat Transfer 2020, 142, 1 .

AMA Style

Te Pi, Kevin D. Cole, Qingjun Zhao, Wei Zhao. Investigation of Numerical Evaluation Improvement for Three-Dimensional Infinite Cylindrical Heat Conduction Problems. Journal of Heat Transfer. 2020; 142 (4):1.

Chicago/Turabian Style

Te Pi; Kevin D. Cole; Qingjun Zhao; Wei Zhao. 2020. "Investigation of Numerical Evaluation Improvement for Three-Dimensional Infinite Cylindrical Heat Conduction Problems." Journal of Heat Transfer 142, no. 4: 1.

Review article
Published: 06 January 2019 in Chinese Journal of Aeronautics
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Lean Blow-Off (LBO) prediction is important to propulsion system design. In this paper, a hybrid method combining numerical simulation and Da (Damköhler) model is proposed based on bluffbody stabilized flames. In the simulated reacting flow, Practical Reaction Zone (PRZ) is built based on OH radical concentration, and it is considered to be the critical zone that controls LBO. Da number is obtained based on the volume-averaged parameters of PRZ. The flow time scale (τf) indicates the residence time of the fresh mixture flowing through the PRZ. It is obtained based on the characteristic length and volume-averaged axial velocity of the PRZ. The chemical time scale (τc) indicates the shortest time needed to trigger the reaction of the mixture. It is obtained by commercial software CHEMKIN through monitoring the transient variation of the reactor temperature. The result shows that the average Da number under different LBO conditions is 1.135(the Da number under each LBO condition ranges from 0.673 to 1.351). This indicates that the flow time scale and chemical time scale are comparable. The combustion is in a critical state where LBO is easy to occur. With the increase of the fuel mass flow rate (the global fuel/air ratio increases from 0.004761 to 0.01095), τf increases from 0.001268 s to 0.007249 s, and τc decreases from 0.00124 s to 0.00089 s. Accordingly, Da number increases from 1.023 to 8.145, which shows that the combustion becomes more stable. The above results show that the method proposed in the present study can properly predict the LBO limits of combustors, which provides important technical supports for combustor design and optimization.

ACS Style

Zhonghao Wang; Bin Hu; Aiming Deng; Junhua Zhang; Qingjun Zhao. Predicting lean blow-off of bluffbody stabilized flames based on Damköhler number. Chinese Journal of Aeronautics 2019, 32, 308 -323.

AMA Style

Zhonghao Wang, Bin Hu, Aiming Deng, Junhua Zhang, Qingjun Zhao. Predicting lean blow-off of bluffbody stabilized flames based on Damköhler number. Chinese Journal of Aeronautics. 2019; 32 (2):308-323.

Chicago/Turabian Style

Zhonghao Wang; Bin Hu; Aiming Deng; Junhua Zhang; Qingjun Zhao. 2019. "Predicting lean blow-off of bluffbody stabilized flames based on Damköhler number." Chinese Journal of Aeronautics 32, no. 2: 308-323.

Research article
Published: 11 July 2018 in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
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The impact of circumferential casing grooves on rotating instability is first assessed for both design and part speed operations in a transonic axial compressor, with the purpose of developing the next generation casing treatments for vibration control. Multi-passage time-resolved computations are performed to capture the origination and propagation behavior of the instability for cases with and without casing grooves. Probed pressure signals in different passages show a nonsynchronous fluctuation of tip flow. It proves tip leakage vortex and its self-excited oscillation is responsible for this type of inconsistence, regardless of the compressor operation speed. Although flow separation on blade suction surface and the consequent shedding vortex contributes to another origin of instability, the resulted flow appears to be consistent. Casing grooves are able to enhance the synchronization by greatly suppressing both tip leakage vortex oscillations and the intermittently shedding separation vortex, especially in the front part of blade passage. Both types of instability are constrained in several separated axial scope by casing grooves, which essentially increase the damping of flow oscillations. Thus, further improvement of casing treatment design can be expected if the axial transport of the instability in the tip region is restrained more efficiently, for both extending stall margin and enhancing aerodynamic stability.

ACS Style

Shubo Ye; Qingjun Zhao; Xiaoyong Zhou; Guang Xi; Jianzhong Xu. The impact of circumferential casing grooves on rotating instability in a transonic axial compressor. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 2018, 233, 2868 -2893.

AMA Style

Shubo Ye, Qingjun Zhao, Xiaoyong Zhou, Guang Xi, Jianzhong Xu. The impact of circumferential casing grooves on rotating instability in a transonic axial compressor. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering. 2018; 233 (8):2868-2893.

Chicago/Turabian Style

Shubo Ye; Qingjun Zhao; Xiaoyong Zhou; Guang Xi; Jianzhong Xu. 2018. "The impact of circumferential casing grooves on rotating instability in a transonic axial compressor." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 8: 2868-2893.

Journal article
Published: 01 July 2018 in Energy
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A novel Pre-cooled and Fuel-rich Pre-burned Mixed-flow Turbofan (PFPMT) cycle is presented for reusable high speed vehicles based on practical technologies to reduce the travelling time of long distance flights. The motivation and the working principle of the PFPMT are explained in detail. A performance simulation model for the PFPMT cycle is established with the assumption of equilibrium fuel rich gas as the working fluid in the gas generator. Then parametric cycle studies are performed with the variation of bypass ratio, fuel/air ratio, core compressor pressure ratio and bypass fan pressure ratio at the flight Mach number of 0 and 5 respectively. The interrelationships between cycle parameters and their effects on cycle performance are discussed. Based on the parametric analysis, cycle parameters for a practical PFPMT engine are suggested for the flight speeds of Mach 0, 3 and 5 respectively. The predicted engine performance shows that the PFPMT concept exhibits a competitive specific impulse with respect to an ATR GG engine and an enhanced thrust to weight ratio with respect to an ATREX engine, and might be a promising propulsion system for high speed air-breathing flying vehicles.

ACS Style

Wei Zhao; Chen Huang; Qingjun Zhao; Yingqun Ma; Jianzhong Xu. Performance analysis of a pre-cooled and fuel-rich pre-burned mixed-flow turbofan cycle for high speed vehicles. Energy 2018, 154, 96 -109.

AMA Style

Wei Zhao, Chen Huang, Qingjun Zhao, Yingqun Ma, Jianzhong Xu. Performance analysis of a pre-cooled and fuel-rich pre-burned mixed-flow turbofan cycle for high speed vehicles. Energy. 2018; 154 ():96-109.

Chicago/Turabian Style

Wei Zhao; Chen Huang; Qingjun Zhao; Yingqun Ma; Jianzhong Xu. 2018. "Performance analysis of a pre-cooled and fuel-rich pre-burned mixed-flow turbofan cycle for high speed vehicles." Energy 154, no. : 96-109.

Journal article
Published: 10 April 2018 in Applied Sciences
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The compressor is a key component in the supercritical carbon dioxide (SCO2) Brayton cycle. In this paper, the authors designed a series of supercritical CO2 compressors with different parameters. These compressors are designed for 100 MWe, 10 MWe and 1 MWe scale power systems, respectively. For the 100 MWe SCO2 Brayton cycle, an axial compressor has been designed by the Smith chart to test whether an axial compressor is suitable for the SCO2 Brayton cycle. Using a specific speed and a specific diameter, the remaining two compressors were designed as centrifugal compressors with different pressure ratios to examine whether models used for air in the past are applicable to SCO2. All compressors were generated and analyzed with internal MATLAB programs coupled with the NIST REFPROP database. Finally, the design results are all checked by numerical simulations due to the lack of reliable experimental data. Research has found that in order to meet the de Haller stall criterion, axial compressors require a considerable number of stages, which introduces many additional problems. Thus, a centrifugal compressor is more suitable for the SCO2 Brayton cycle, even for a 100 MWe scale system. For the performance prediction model of a centrifugal compressor, the stall predictions are compared with steady numerical calculation, which indicates that past stall criteria may also be suitable for SCO2 compressors, but more validations are needed. However, the accuracy of original loss models is found to be inadequate, particularly for lower flow and higher pressure ratio cases. Deviations may be attributed to the underestimation of clearance loss according to the result of steady simulation. A modified model is adopted which can improve the precision to a certain extent, but more general and reasonable loss models are needed to improve design accuracy in the future.

ACS Style

Zhiyuan Liu; Weiwei Luo; Qingjun Zhao; Wei Zhao; Jianzhong Xu. Preliminary Design and Model Assessment of a Supercritical CO2 Compressor. Applied Sciences 2018, 8, 595 .

AMA Style

Zhiyuan Liu, Weiwei Luo, Qingjun Zhao, Wei Zhao, Jianzhong Xu. Preliminary Design and Model Assessment of a Supercritical CO2 Compressor. Applied Sciences. 2018; 8 (4):595.

Chicago/Turabian Style

Zhiyuan Liu; Weiwei Luo; Qingjun Zhao; Wei Zhao; Jianzhong Xu. 2018. "Preliminary Design and Model Assessment of a Supercritical CO2 Compressor." Applied Sciences 8, no. 4: 595.

Conference paper
Published: 17 January 2018 in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
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The evolution mechanism of the boundary layer and coherent structures in a low-pressure turbine blade is discussed. Five different incidence angles over the T106A blade for a Mach number Ma = 0.404 and Reynolds number Re = 0.6 × 105 (based on the axial chord and outlet velocity) are performed using large eddy simulation method. The calculation results at +7.8 incidence angle are agreed well with the experimental and direct numerical simulation data. The influence of the incidence angle on the flow field is mainly shown at the front of the suction side and pressure side. As the incidence angle changes from positive to negative, the separation bubble near the leading edge disappears and the blade loading decreases gradually. When the incidence angle reduces to −5°, separation bubble appears near the leading edge of the pressure side. At the case of incidence angle equaling −10°, the length of time-averaged separation bubble on the pressure side grows to 39% axial chord and the evolution process of the coherent structures is extremely complex. The spanwise vortexes roll up near the leading edge and gradually evolve into streamwise vortexes. High-energy fluid in the main flow was driven to near-wall zone by the rotating effect of streamwise vortexes, which increases the fluid momentum inside the boundary layer. The streamwise vortexes are stretched by the strong acceleration of the flow until they transport to the trailing edge.

ACS Style

Yunfei Wang; Xiuming Sui; Kai Zhang; Xiaorong Xiang; Qingjun Zhao. Effects of incidence angle on a low-pressure turbine blade boundary layer evolution through large eddy simulation. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2018, 232, 722 -734.

AMA Style

Yunfei Wang, Xiuming Sui, Kai Zhang, Xiaorong Xiang, Qingjun Zhao. Effects of incidence angle on a low-pressure turbine blade boundary layer evolution through large eddy simulation. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy. 2018; 232 (6):722-734.

Chicago/Turabian Style

Yunfei Wang; Xiuming Sui; Kai Zhang; Xiaorong Xiang; Qingjun Zhao. 2018. "Effects of incidence angle on a low-pressure turbine blade boundary layer evolution through large eddy simulation." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 6: 722-734.

Research article
Published: 19 October 2017 in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
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An improved compressible model for estimating tip clearance loss in transonic compressors is presented with the emphasis on the effects of blade tip loading distribution and double leakage flow. Tip clearance flow is treated as three parts along the chord and the progressive relations from upstream to downstream part is revealed to be responsible for the formation of tip clearance flow. Control volume method is applied to simplify the mixing process and calculate the mixed-out loss for the three parts, separately. Computational study shows that mass flow of the incoming flow entering the control volume is consistent with that passing through an equivalent area of about half of tip leakage vortex region. The new model reveals that the second part of tip clearance flow has a larger mixed-out loss capacity than the two other parts. This difference is attributed to two factors: larger injection flow angle and more enrolled incoming flow, and both factors tend to increase the mixed-out loss. The success of the model implies that blade design or flow control strategies turning the tip clearance/main flow interface’s arrival onto blade tip pressure side downstream and the shock’s impingement point onto blade tip suction side upstream may be beneficial in desensitizing compressor performance to tip clearance size, without trading off pressure rise.

ACS Style

Shubo Ye; Qingjun Zhao; Weiwei Cui; Guang Xi; Jianzhong Xu. An improved model for tip clearance loss in transonic axial compressors. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2017, 232, 295 -314.

AMA Style

Shubo Ye, Qingjun Zhao, Weiwei Cui, Guang Xi, Jianzhong Xu. An improved model for tip clearance loss in transonic axial compressors. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy. 2017; 232 (4):295-314.

Chicago/Turabian Style

Shubo Ye; Qingjun Zhao; Weiwei Cui; Guang Xi; Jianzhong Xu. 2017. "An improved model for tip clearance loss in transonic axial compressors." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 4: 295-314.