Hu H.,Beihang University |
Wang Q.,Beihang University |
Wang Q.,Collaborative Innovation Center for Advanced Aerospace Engine
Journal of Heat Transfer | Year: 2017
The multiscale multigroup full-spectrum k-distribution (MSMGFSK) model was improved to adapt to radiation heat transfer calculations of combustion gas flow field with large temperature and pressure gradient. The improvements in calculation accuracy resulting from new sorting strategy of the spectral absorption coefficients were validated using a series of semi-1D problem in which strong temperature, pressure, and mole fraction inhomogeneities were present. A simpler method to attain compatibility between the MSMGFSK model and the gray-wall radiation emission has been established and validated. Finally, estimates are given for the calculation of wall radiation heat transfer characteristics and thermal emission imaging of the exhaust system of the parallel turbine-based combined cycle (TBCC) engine, using finite volume method (FVM) and ray trace method (RT), respectively. © 2017 by ASME.
Tu Z.,Nanjing University of Aeronautics and Astronautics |
Mao J.,Nanjing University of Aeronautics and Astronautics |
Mao J.,Collaborative Innovation Center for Advanced Aerospace Engine |
Han X.,Nanjing University of Aeronautics and Astronautics
Applied Thermal Engineering | Year: 2017
Numerical study was performed to investigate the film cooling performance for a flat plate with anisotropic thermal conductivity where the plate had a single row of round holes. The cooling effectiveness and temperature distribution were analyzed and compared between the results of isotropic and anisotropic plates. The effects of two angles on the cooling effectiveness were studied, i.e. the axial angle α (0°, 30°, 35°, 60° and 90°) and the spanwise angle β (0°, 30°, 60° and 90°), with regards to the inclined angle between the main thermal conductivity in the plate and the mainstream flow direction. The results obtained showed that the anisotropy of the thermal conductivity and the inclined angles affected the cooling effectiveness in a complex way. The highest average cooling effectiveness could be achieved with a specific α or β, depending on the downstream region of the film cooling hole being considered. With the blowing ratio Br = 0.5, the highest cooling effectiveness averaged over the 0–5D and 0–20D downstream regions (with D the diameter of the film cooling hole) could be obtained with an angle of around 35° and 90° for α, respectively. It was found that the uniformity of the cooling effect was improved with a larger β. Moreover, the effects of α and β on the average cooling effectiveness were found to be similar with different Br. However, the uniformity was affected by α and β non-monotonically in different cases of Br. This work demonstrates that proper inclined angle can lead to better film cooling performance. © 2016 Elsevier Ltd
Zhou Y.,Beihang University |
Wang Q.,Beihang University |
Wang Q.,Collaborative Innovation Center for Advanced Aerospace Engine |
Li T.,Beihang University |
Li T.,Collaborative Innovation Center for Advanced Aerospace Engine
Chinese Journal of Aeronautics | Year: 2017
A multi-scale narrow band correlated-k distribution (MSNBCK) model is developed to simulate infrared radiation (IR) from an exhaust system of a typical aircraft engine. In this model, an approximate approach instead of statistically uncorrelated assumption is used to treat overlapping bands in gas mixture. It significantly reduces the requirement for computing power through converting the exponential increase of computing power consumption with the increase of participating gas species to linear increase. Besides, MSNBCK model has a great advantage compared with conventional methods which can estimate each species' contribution to the total gas mixture radiation intensity. Line by line (LBL) results, experimental data and other results in the references are used to evaluate this new model, which demonstrates its advantage in terms of accuracy and computing efficiency. By coupling this model and finite volume method (FVM) into radiative transfer equation (RTE), a comparative study is conducted to simulate IR signature from the exhaust system. The results indicate that wall's IR emission should be considered in both 3-5. μm and 8-14. μm bands while gases' IR emission plays an important role only in 3-5. μm band. For plume IR radiation, carbon dioxide's emission is much more significant than that of water vapor in both 3-5. μm and 8-14. μm bands. Especially in 3-5. μm band, the water vapor's IR signal can even be neglected compared with that of carbon dioxide. © 2017 Chinese Society of Aeronautics and Astronautics.
Liu F.,Northwestern Polytechnical University |
Yan H.,Northwestern Polytechnical University |
Yan H.,Collaborative Innovation Center for Advanced Aerospace Engine |
Xu J.,Northwestern Polytechnical University
30th Congress of the International Council of the Aeronautical Sciences, ICAS 2016 | Year: 2016
The mechanism of oblique shock wave control by surface arc discharge plasma is explored through a combined numerical and experimental study. The experiments are conducted in a Mach 2.5 supersonic tunnel with static pressure of 0.3bar and temperature of 130K. An oblique shock is formed by a compression ramp with the angle of 7° mounted on the lower wall of the wind tunnel. Six electrodes are arranged equally spaced in the spanwise direction and upstream of the oblique shock. Two types of discharge are observed. One is generated between the two adjacent electrodes, forming a transversal arc. While the other one is formed between the electrode and the compression ramp due to high power input, thus a streamwise arc is observed. It is found that the streamwise arc is relatively stable compared to the transversal one, therefore is chosen in this study. The experimental results show that the presence of the stable arc discharge effectively reduces the oblique shock strength, leading to the increase of shock angle which is measured by Schlieren technique. A three-dimensional numerical simulation is performed and the surface arc discharge plasma is modeled as an equivalent heating source based on the thermal effect of plasma. Results show that the surface pressure increases in front of the oblique shock and decreases behind the shock, which is in good agreement with the experimental measurement. This validates the assumption of the arc discharge plasma model, and further confirms the predominant role of the thermal effect of plasma played in the shock manipulation.
Zhang K.,Beihang University |
Zhou Z.,Beihang University |
Zhou Z.,Collaborative Innovation Center for Advanced Aerospace Engine |
Ma L.,Beihang University
Measurement Science and Technology | Year: 2017
Laser ultrasonics has been investigated for inspecting the quality of a nuclear radiation protection structure. A possibility is proposed to improve the signal to noise ratio (SNR) of a laser ultrasonic inspection system. Then, a nuclear radiation protection structure composed of an AISI 1045 steel sheet connected with a lead alloy sheet by using an epoxy resin adhesive was manufactured with simulated defects. A non-contact laser ultrasonic inspection system, where the measured signals were filtered using a wavelet threshold de-noising method, was established to conduct a series of experiments. The proposed signal processing method can significantly improve the SNR of measured laser ultrasound signals on a rough solid surface. Compared with the SNR of original ultrasonic signals measured in transmission and reflection, the SNR of processed transmitted and reflected signals is improved by 13.8 and 16.6 dB, respectively. Moreover, laser ultrasonic C-scans based on the transmission and pulse-echo method can detect the simulated de-bonding defects, and the relative deviation between the measured sizes and design values is below 9%. Therefore, the laser ultrasonic method combined with effective signal processing can achieve the quantitative characterization of de-bonding defects in nuclear radiation protection structures. © 2016 IOP Publishing Ltd.
Fana H.,Beihang University |
Fana H.,University of British Columbia |
Gao J.,Collaborative Innovation Center for Advanced Aerospace Engine
53rd AIAA Aerospace Sciences Meeting | Year: 2015
In this study, the spectral difference (SD) method has been extended to deal with the Reynolds-Averaged Navier- Stokes (RANS) equations coupled with the Spalart-Allmaras (SA) and k ω turbulence models. The description of limiting or stabilization techniques adopted in order to prevent the simulation from blowing up are given in this paper. The reliability, robustness and accuracy of the implementation have been assessed by computing several validation cases: the flow over flat plate(Re = 5×106), the flow past a backward-facing step (Re = 37400) and the flow around NACA0012 airfoil at different angles of attack (α = 0°; 10°). Finally the developed SD solver is applied to simulate the tone noise generated by subsonic cavity flow at moderate Reynolds number. © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Li L.,Beihang University |
Li L.,Collaborative Innovation Center for Advanced Aerospace Engine |
Xue Z.,Beihang University |
Li C.,Beihang University |
Li C.,Collaborative Innovation Center for Advanced Aerospace Engine
Materials and Design | Year: 2016
The Pin-Force Model (PFM) and the Enhanced Pin-Force Model (EPFM) for analyzing the mechanical behavior of a composite beam with active materials are widely used because of simplicity and adaptability. However, the PFM and the EPFM overestimated the deformation of composite beams under a small thickness ratio of substrate and actuator. In this paper, the reasons for the above phenomenon are analyzed first. Then a revised model named Modified Pin Force Model (MPFM) is proposed, which involves the factors neglected in previous models. The detailed derivation and description of the models for both unimorph and bimorph bonding forms are given. The bending curvature of a composite beam predicted by the MPFM is compared with that obtained by both the Euler-Bernoulli beam model and finite element analysis. The result shows a good consistency even in the small thickness ratio. Experiments based on MFC materials were performed to validate the MPFM. The results demonstrate that the proposed model can well predict the bending deformation of a composite beam with mounted actuators in the small thickness ratio, which extends the application range of pin-force models. © 2016 Elsevier Ltd.
Lu Z.L.,Xi'an Jiaotong University |
Lu Z.L.,Collaborative Innovation Center for Advanced Aerospace Engine |
Cao J.W.,Xi'an Jiaotong University |
Cao J.W.,Collaborative Innovation Center for Advanced Aerospace Engine |
And 4 more authors.
Journal of Alloys and Compounds | Year: 2015
TiAl intermetallic and SiC ceramic are two kinds of important high-temperature structural material, but it is difficult to fabricate complex high-performance composites of them by traditional methods. In the paper, it is a pioneer study to prepare their composites so as to fabricate turbine blade by the hybrid technology of Stereolithography and gelcasting. Impregnation and pyrolysis behaviors of polycarbosilane were explored for SiC ceramic preparation, and the microstructure evolution and mechanical properties of TiAl-based composites were mainly analyzed. The results showed that adding trace amount of nickel and aluminum could remarkably promote the sintering of gelcasting TiAl intermetallic samples, the micropores inside TiAl samples were connected after debinding, and the metallurgical structures were all intermetallic. After the porous TiAl samples impregnated with polycarbosilane were then pyrolyzed three times, the final metallurgical structures were TiAl-based composites of TiAl, NiAl, SiC, TiC and Ti3SiC2. Ti3SiC2 was the interface layer formed between TiAl intermetallic and SiC ceramic, and their high-temperature bending strength was between 82 MPa and 90 MPa at 1100 °C. Therefore, it was a promising method for the fabrication of complex high-performance TiAl-based parts such as turbine blade. © 2015 Published by Elsevier B.V. All rights reserved.
Wu B.,Nanjing University of Aeronautics and Astronautics |
Huang J.-Q.,Nanjing University of Aeronautics and Astronautics |
Huang J.-Q.,Collaborative Innovation Center for Advanced Aerospace Engine
Hangkong Dongli Xuebao/Journal of Aerospace Power | Year: 2016
The parameter range of aeroengine in full flight envelope is so wide that a single controller is difficult to ensure the performance. To avoid this problem, a switched polytopic linear parameter varying (LPV) approach was proposed for the turbofan engine intermediate state control. The full envelope was firstly divided into several locally overlapped sub-regions according to the inlet conditions. The state reset method and the polytopic gain scheduling technique were used to derive the robust stability conditions of this switched LPV system, which was depicted as linear matrix inequality (LMI). Then, the resulting Lyapunov matrices were used to design a family of single LPV controllers which can be applied in the sub-region control combined with the scheduling strategy based on geometric position; Hysteresis switching strategy based on the overlapped sub-regions was used for switching, meanwhile the stability of this closed-loop switching system was also proved. Simulation results with a turbofan engine model show that the steady state error is less than 0.1 percent, and the maximum overshoot is less than 0.5 percent. © 2016, Editorial Department of Journal of Aerospace Power. All right reserved.
Lin K.,Northwestern Polytechnical University |
Yan H.,Collaborative Innovation Center for Advanced Aerospace Engine
Procedia Engineering | Year: 2015
The plasma actuator can make difference in changing the vortex characteristics in supersonic shear layer, leading to mixing enhancement and noise reduction in the supersonic shear layer. Large Eddy Simulation is performed to investigate the effect of plasma actuator on supersonic shear layer, in which the plasma actuator is simplified as heat source. A Mach 1.3 supersonic flow over a backward-facing step with a groove placed upstream of the step is simulated first. Then the plasma actuators are placed inside the groove, and the effect of the plasma actuator is studied. Results show that the cases with heat sources have larger growth of shear layer and area-Averaged vorticity compared with the baseline case, and increasing the amplitude of the actuation is a more efficient way for mixing enhancement. © 2015 The Authors.