Abstract:In order to attenuate interference with the hypersonic vehicle head shocks and flank front shocks, a simulation model on plasma high-energy synthetic jet shock-shock interference control is established. The flow field characteristics of the shock-shock interference control of plasma high-energy synthetic jet waves are analyzed, the effect of plasma high-energy synthetic jet for shock-shock interference control is explored, and the parameters of the control effect are studied for the installation position and the energy size of the actuator. The results show that the bow shock generated by the high plasma energy synthetic jet enables the head shock to lift a certain angle, reducing head shock to flank leading shock disturbance, and control the effect of heat flow and pressure in the shock-shock interference area. With increase of exit distance, the control effect of heat flow and pressure increases first and then decreases. Within a certain range, the higher the energy applies, the better the control effect.

Abstract:The use of ammonia and the solution of its combustion challenges in a two-carbon context have received attention from domestic and foreign scholars. To address the problem of improving ammonia combustion, this study developed a two-dimensional fluid dynamics-zero-dimensional reaction dynamics-combustion dynamics idea to analyze the cracking and combustion characteristics of ammonia under gliding arc plasma conditions. A two-dimensional fluid calculation model considering electromagnetism was developed using COMSOL calculation software to study the evolution of gliding arc in the reactor; A zero-dimensional gliding arc model applicable to ammonia was developed to study the evolution of temperature and components in the three stages of total-ionization,transition and non-equilibrium in the gliding arc; A combustion model was developed using CHEMKIN calculation software to evaluate the effect of plasma on the combustion characteristics of NH3/air mixture, and in addition the addition of CH4 to the mixture was also investigated. The results show that plasma can promote the cracking of ammonia, reduce the ignition delay time of ammonia, and increase its laminar burning velocity, but the overall combustion effect decreases after replacing NH3 with CH4 in the mixture under partial plasma conditions.

Abstract:Being simple in structure and rapid in response, plasma flow control technology is under interesting review by scholars. In order to reduce the turbulent frictional drag of the aircraft, a new turbulent drag reduction method based on grid-type plasma actuator is proposed. The discharge characteristics and induced jet characteristics are researched, and the parameters of actuator to reduce the turbulent friction drag of NACA0012 airfoil are obtained in the wind tunnel. The results show that under static conditions, the jet velocity induced by grid-type actuator is proportional to the duty cycle, and increases first and then decreases with the increase of pulse frequency. The maximum instantaneous velocity of induced jet is 1.75 m/s. When the inflow velocity is 15 m/s, the actuation makes the turbulent friction drag of the airfoil reduce by 3.5 %. The jet induced by the grid-type actuator makes the near-wall fluid lift and the near-wall vortex structure destroy, and further inhibit the generation of turbulence to achieve friction drag reduction.

Abstract:The influence of relevant geometric parameters on the flow characteristics and aerodynamic characteristics of the plasma jet airfoil is studied by wind tunnel experiments and numerical simulation methods, and the flow control mechanism is described. Slots at different heights are designed, and flow rate and jet velocity at the outlet of the slot under plasma excitation are studied. The slot of 4 mm being selected as an optimal parameter,and a plasma co-flow jet airfoil is designed by taking NACA0025 as a referenced airfoil. The lift or drag characteristics of the plasma co-flow jet airfoil are studied by numerical simulation. The results show that Re being equal to 68 000,  Up-p being equal to 13 kV, and f being equal to 8 kHz, the stall angle of attack increases from 8°to 14°, and the maximum lift coefficient is increased by 181% compared with the reference airfoil. The drag of the plasma jet airfoil decreases continuously with the increase of the angle of attack. Prior to an angle of attack of 10o, the drag is greater than the reference airfoil, and then smaller than the reference airfoil. The lift-drag ratio result shows the same variation characteristics as the drag and is better than the reference airfoil beyond the angle of attack of 10o because the trailing edge slot generates a positive drag at a small angle of attack, and the local drag becomes negative as the angle of attack increases. In contrast to the only leading edge blowing, the co-flow jet can increase the stall angle of attack from 12° to 16° because the co-flow jet airfoil can inject momentum locally through the blowing effect on the leading edge, and the suction effect on the trailing edge can reduce the low energy separation area to increase circulation.

Abstract:Aimed at the problems that aero-engine combustors need urgently to widen stability and prevent flameout under conditions of fast fuel reduction to verify the effect of plasma-assisted combustion (PAC) technology in widening the dynamic limit and other aspects, a swirl experimental platform is established with single dome under conditions of fast fuel reduction, and the dynamic characteristics study is conducted based on gliding arc plasma. Through collecting OH* chemical luminescence signals in the combustion process of fast fuel reduction, the combustion chamber flameout evolution process is analyzed, and then the influence of gliding arc plasma excitation on flameout characteristics is studied at different fuel reduction rates and flows in comparison. The results show that the lean blowout limit under dynamic fuel reduction is significantly smaller than that under quasi-steady conditions, and the lean blowout limit becomes narrower with the increase of dynamic fuel reduction and inlet airflow. After the application of PAC, the assisted combustion effect is significant, and the lean blowout fuel-air ratio of the fast fuel reduction condition is significantly reduced, especially under larger fuel reduction rate and inlet airflow can still maintain stable combustion. The limit widening is the largest at inlet airflow of 15 m3/h and fuel reduction rate of 009/s, widening from 0064 to 0052, and the widening degree reaches 23%.

Abstract:Flow separation in nacelle intakes occurred in a state of side wind operation, can lead engine intake to distort, even engine to wheeze. Plasma flow control technology has its own unique development advantages in the field of improving the flow field characteristics, and its main difficulty is whether the plasma actuation can effectively coupling with the flow field to achieve the flow control objective, and high-pressure pulse plasma technology with its relatively low power consumption, continuous disturbance of the flow field and other advantages in the control of wing/wing flow separation with remarkable results being achieved, and there is great potential in the control of nacelle flow separation. First, the baseline aerodynamic law of nacelle inlet under the influence of side wind is investigated, and the degree of total pressure distortion is analyzed quantitatively, determining the plasma actutaion working condition, and then the flow control effect of Nanoseconds Dielectric Barrier Discharge (NS-DBD) is verified and the influence law of actutaion parameters is studied under different actutaion frequency and voltage conditions with 120° circumferential actutaion layout. The results show that NS-DBD actutaion being exerted, the total pressure is low in loss coefficient, the flow separation is small in range, and the total pressure distortion basically disappears. With the increase of the actutaion frequency, the total pressure distortion shows a trend of decreasing first and increasing afterwards. There is an inherent optimal coupling frequency in the actutaion process, and the total pressure distortion improved is the best in the optimal coupling frequency. Under conditions of the incoming at flow velocity of 25 m/s and the incoming at flow declination angle of 10°, the NS-DBD is exerted on the flow control condition. Under condition of 25 m/s incoming at flow velocity and 10° incoming at flow deflection angle, the average total pressure loss coefficient is reduced by 26.09% and the aberration index is reduced by 31.48% by applying NS-DBD actutaion. An upper threshold being 10 kV for the actutaion voltage and a lower threshold being 8 kV by changing the actutaion voltage to change the actutaion energy injection, the improvement of the separation flow field improvement effect is not obvious, lowering the actutaion voltage to the voltage threshold as much as possible, achieving separated flow field control, helping reduce energy consumption, improve lifetime, and promote the wider application of plasma flow control technology.

Abstract:In recent years, numerous international scholars are paying a good deal attention to what is going on in plasma ignition and assisted combustion area. The traditional spark discharge reactor is designed based on repetitive experiment. But the heating effect is unable to cope with bad environment gradually, and the bad environment restricts the safe working boundary of the combustion chamber along with the increase of height, the decrease of pressure, and the increase of flow velocity in the combustion chamber. In order to maintain the spark discharge, the optimization of power supply is needed. The plasma discharge reaction is under more rationally and efficiently control to generate the required active particles and energy. The effect of discharge frequency and electron density growth method on spark discharge is analyzed by using two-dimensional model, zero-dimensional model and deep learning model. The results show that the growth rate of voltage amplitude becomes a negative linearity related to the growth rate of initial electron density by building neural network model. The slow-fast and segmented growth in electron density is more energy-saving in air discharge system, and the number of O atoms and O (1D) particles produced by the segmented growth of electron density is higher and more favorable for ignition. In consideration of the energy consumption and the particles of assisted combustion, the voltage waveform corresponding to the segmented growth of electron density is the best one in choices for spark discharge.

Abstract:In order to improve the stall characteristics of the non-slender delta wing at high angles of attack and explore the influence of the leading-edge shape on the flow control effect, wind tunnel experiments on the flow control of the non-slender delta wings are carried out based on alternating current dielectric barrier discharge (AC-DBD) plasma actuation. In view of three delta wing models with radius of curvature at leading-edge being different, the influence of actuation parameters on the flow control effect is studied. The results show that the lift coefficient of delta wing with sharp leading-edge shape is slightly higher than that of other two kinds of delta wings with blunt leading-edge shapes at small angle of attack. The maximum lift coefficient of delta wing with circular leading edge is the highest. The leading-edge actuation directed towards the wing's upper surface is the best control effect on the lift coefficient before the stall angle of attack, whereas the leading\|edge actuation directed towards the wing’s lower surface is the best control effect after the stall angle of attack. The round-shape leading edge delta wing is the best control effect. The lift under condition of the same actuation voltage (12 kV) for the sharp, round and elliptical leading edge delta wings can be increased by 3.6%, 5.9% and 4.2% respectively at the post-stall stage. The optimal dimensionless pulsed actuation frequency is f+=1to2, and the optimal duty cycle is 5%. The higher the voltage amplitude, the better the control effect. The analysis shows that main mechanism of AC-DBD actuation control of non-slender delta wings is its unsteady disturbance to the shear layer rather than the effect of body force. The distribution of leading\|edge kinetic energy affects the formation of induced stream-wise vortices, and the difference of leading-edge shapes makes a different effect of flow control for no-slender delta wings eventually achieve.

Abstract:An efficient blind-polarized direction-of-arrival (DOA) estimation method of conical conformal arrays is proposed with an idea of covariance matrix splitting of snapshot data being introduced into the direction finding of conical conformal array antennas. In this method, the subspace estimation is in the process of real-valued, and the ‘mirror blur’ problem caused by the splitting of the covariance matrix is solved by sub-array division. Simultaneously, the theoretical performance circle is analyzed, the improvement of algorithm complexity is discussed, and the algorithm complexity is effectively reduced on the premise of ensuring the accuracy of DOA estimation. The simulation experiments show that when the signal-to-noise ratio is 10 dB, the estimation accuracy of the proposed algorithm is basically the same as that of the existing blind polarization complex\|valued algorithm, the computation amount makes up 60%~70% of the existing complex-valued algorithm, and the algorithm is valid.

Abstract:Being characterized by high resolution and high frame rate imaging, Video Synthetic Aperture Radar (ViSAR) can continuously obtain the approximate video information showed interest in targets in the area on the ground, laying a foundation for the rapid development of target recognition and tracking technology based on SAR images. In order to meet the increasingly complex application requirements, the multi-target tracking technology has gradually developed and matured. Aimed at the problems that the state of each moving target in the process of multi-target tracking has space-time variability, and the number of targets has randomness, a multi-target tracking algorithm is established based on the Random Finite Set (RFS). On this basis, the Probability Hypothesis Density (PHD) algorithm under the Bayesian framework is discussed, and the Gaussian Mixture Probability Hypothesis Density (GM-PHD) filtering algorithm is studied and implemented under condition of the Gaussian mixture model, and then the RFS-based multi-target tracking algorithm is further implemented. The results show that the algorithm is valid under condition of the complex environment background.

Abstract:Software defined network (SDN) being enabled to decouple the control plane and the data plane by adopting a logically centralized approach to realize the network management, andutilizing the advantages of SDN, it is possible to build the ability of the centralized platforms controlling and unified network resources scheduling. To construct an aviation information network (AIN)of the SDN paradigm, the controller placement is put in the first place. In combination with the characteristics of aviation scenarios, this paper proposes a controller deployment strategy including network division and regional deployment. Firstly, the network is rapidly divided according to the key performance indicators of the network, and then the controller is deployed on the platform with the maximum reliability. The experimental result shows that the proposed algorithm has low computational complexity, and can effectively improve the network performance in terms of average requirement delay, load balance index, controller deployment cost and reliability, and is suitable for addressing the controller deployment issue in AIN scenario.

Abstract:Compressed sensing algorithm can be utilized for solving the problems of dynamic spectrum detection at the airport terminal area, and determining on the precision and the efficiency of signal recovery. Based on sparsity adaptive matching pursuit (SAMP) signal reconstruction algorithm, this paper introduces generalized Jaccard coefficient, t-average correlation coefficient and variable step size idea, and proposes a JTVS-SAMP algorithm. The generalized Jaccard coefficient in the atomic screening part of the algorithm can reduce the accuracy degradation caused by atomic confusion, the t-average correlation coefficient can avoid calculating the rip coefficient of the measurement matrix, and reducing the complexity of the algorithm. And the large step iteration in the variable step idea and the small step approach step enable the efficiency and accuracy of the algorithm to be greatly improved. Taking the 1-D Gaussian random sparse signal as the measurement signal for simulation, the measured signal after energy detection in the airport terminal area can be effectively simulated . Through the simulation, the performance of JTVS-SAMP is better than that of the traditional compressed sensing algorithm in the algorithm reconstruction success rate under different measurement numbers and sparsity. Compared with the SAMP algorithm, JTVS-SAMP performs significantly in the reconstruction error and algorithm time.

Abstract:Modern warfare requires efficient integration of multi-source heterogeneous equipment data. To solve the problem of inconsistent equipment names of data from different sources, the aggregation model and aggregation process of equipment data are studied and designed. Based on the comprehensive analysis of existing algorithms and the characteristics of equipment data, a new similarity algorithm is provided for the model, the algorithm combines Jaro-Winkler and the longest common subsequence to improve the matching accuracy. Finally, experiments show that the algorithm has high adaptability and robustness compared with the traditional similarity algorithm, and can provide effective support for equipment data aggregation.

Abstract:In order to improve the defect of insufficient data utilization in BN structure learning under small data sets，meanwhile，to improve the optimization efficiency of the Bayesian structure learning algorithm，the improved Bayesian network based on improved ant lion optimization structure learning algorithm (ISB-ALO) is proposed.Firstly，the network is Initially constructed through mutual information constraint，and the ant lion algorithm is initialized.Secondly，in order to effectively use the small data set，the matrix elements in the iteration are converted with improved sigmoid function.To further improve the search efficiency of ant lion algorithm，replace individual ants with the migration，variation and clearing operator in the biogeographic algorithm；Finally，combining update mechanism according to ant lion algorithm looking for the optimal solution.The experimental results show that the ISB-ALO has high optimization efficiency and fast convergence speed,which can jump out of the local optima and have higher accuracy.