Transactions of Nanjing University of Aeronautics & Astronautics
Volume 0,Issue 1,2023 Table of Contents
2023(1):1-12.
DOI: 10.16356/j.1005-1120.2023.01.001
Abstract:
The aim of this work is to develop a new calculation program to study the stagnation pressure effect of the combustion chamber on the design of the supersonic two-dimensional plug nozzle giving a uniform and parallel flow at the exit section. The model is based on the use of the real gas（RG） approach. The co-volume and the intermolecular interaction effect are taken into account by the use of the Berthelot state equation. The molecular vibration effect is taken into account in our model to evaluate the behavior of the gas at high temperature. The stagnation pressure and the stagnation temperature are important parameters in our model. At the lip， the temperature and the density are given by the resolution of a two nonlinear algebraic equations， which are formulated by an integration of four complex functions. The resolution is made by a new， robust and a fast algorithm. The other parameters are determined by analytical relations. The flow expansion in the nozzle is of the Prandtl Meyer type. The nozzle contour determination is made by discretizing the expansion zone at the nozzle lip by several points. The Mach number， flow deviation， pressure， temperature and density parameters are determined after inversion of the two-variable Prandtl Meyer function. The integration of the functions presented in the calculation is made by the Gauss Legendre quadrature of order 30. The validation of the results is controlled numerically by the convergence of calculated critical sections ratio to that obtained by the theory， because the flow at the throat and the exit section is unidirectional. In this case， the nozzle contour and the flow parameters， like the mass of the nozzle， the length and the thrust coefficient converge automatically to the exact solution. Our new RG model is considered as a generalization to the two perfect gas （PG） and high temperature（HT） models. The two latter can make the design for low stagnation pressure， and do not give any information on the variation of the stagnation pressure. So if the latter is high， it is necessary to correct the results given by the PG and HT models by considering our developed RG model. The plug nozzle has better performances and design parameters compared to other existing nozzles like the minimum length nozzle（MLN）. The mass， the length and the thrust coefficient of our plug nozzle for the PG and HT models are corrected by the use of our developed RG model. The application is made for air.
The aim of this work is to develop a new calculation program to study the stagnation pressure effect of the combustion chamber on the design of the supersonic two-dimensional plug nozzle giving a uniform and parallel flow at the exit section. The model is based on the use of the real gas（RG） approach. The co-volume and the intermolecular interaction effect are taken into account by the use of the Berthelot state equation. The molecular vibration effect is taken into account in our model to evaluate the behavior of the gas at high temperature. The stagnation pressure and the stagnation temperature are important parameters in our model. At the lip， the temperature and the density are given by the resolution of a two nonlinear algebraic equations， which are formulated by an integration of four complex functions. The resolution is made by a new， robust and a fast algorithm. The other parameters are determined by analytical relations. The flow expansion in the nozzle is of the Prandtl Meyer type. The nozzle contour determination is made by discretizing the expansion zone at the nozzle lip by several points. The Mach number， flow deviation， pressure， temperature and density parameters are determined after inversion of the two-variable Prandtl Meyer function. The integration of the functions presented in the calculation is made by the Gauss Legendre quadrature of order 30. The validation of the results is controlled numerically by the convergence of calculated critical sections ratio to that obtained by the theory， because the flow at the throat and the exit section is unidirectional. In this case， the nozzle contour and the flow parameters， like the mass of the nozzle， the length and the thrust coefficient converge automatically to the exact solution. Our new RG model is considered as a generalization to the two perfect gas （PG） and high temperature（HT） models. The two latter can make the design for low stagnation pressure， and do not give any information on the variation of the stagnation pressure. So if the latter is high， it is necessary to correct the results given by the PG and HT models by considering our developed RG model. The plug nozzle has better performances and design parameters compared to other existing nozzles like the minimum length nozzle（MLN）. The mass， the length and the thrust coefficient of our plug nozzle for the PG and HT models are corrected by the use of our developed RG model. The application is made for air.
2023(1):13-24.
DOI: 10.16356/j.1005-1120.2023.01.002
Abstract:
A convergent-divergent serpentine shock vector controlling nozzle can significantly reduce the infrared and electromagnetic radiation intensity of the engine tail， and realize the thrust vector control in the pitch direction of supersonic aircraft， which greatly enhances the stealth and maneuverability of the aircraft. As the nozzle with a rectangular outlet needs to be integrated with the rear fuselage， one side wall is usually extended as an aft deck， so that the deflection rule of the tail jet is different from that under the symmetrical nozzle outlet. In this paper， numerical simulation is used to compare the flow characteristics of serpentine shock vector controlling nozzle with and without an aft deck， and then the influences of the aft deck length and angle on the performance of serpentine shock vector controlling nozzle with an aft deck are studied respectively. The results show that under certain working conditions， the oblique shock wave induced by secondary flow injection from the upper wall will be reflected from the aft deck， which is not conducive to the generation of downward thrust vector angle. When there is no open separation of the aft deck surface， the outflow from the lower wall will flow along the aft deck surface， so the increase of the length or angle of the aft deck will deflect the jet velocity axis downward.
A convergent-divergent serpentine shock vector controlling nozzle can significantly reduce the infrared and electromagnetic radiation intensity of the engine tail， and realize the thrust vector control in the pitch direction of supersonic aircraft， which greatly enhances the stealth and maneuverability of the aircraft. As the nozzle with a rectangular outlet needs to be integrated with the rear fuselage， one side wall is usually extended as an aft deck， so that the deflection rule of the tail jet is different from that under the symmetrical nozzle outlet. In this paper， numerical simulation is used to compare the flow characteristics of serpentine shock vector controlling nozzle with and without an aft deck， and then the influences of the aft deck length and angle on the performance of serpentine shock vector controlling nozzle with an aft deck are studied respectively. The results show that under certain working conditions， the oblique shock wave induced by secondary flow injection from the upper wall will be reflected from the aft deck， which is not conducive to the generation of downward thrust vector angle. When there is no open separation of the aft deck surface， the outflow from the lower wall will flow along the aft deck surface， so the increase of the length or angle of the aft deck will deflect the jet velocity axis downward.
2023(1):25-36.
DOI: 10.16356/j.1005-1120.2023.01.003
Abstract:
Aiming at the difficulty of air-sea joint operation in complex multi-equipment combat with high uncertainty， a new intelligent decision-making method for air-sea joint operation based on deep reinforcement learning is proposed. To uniformly represent the input and output of complex networks and their corresponding relations， various networks are utilized， e.g.， perceptron， deep long-short term memory network and actor critical structure. Aiming at the instability of policy network learning process and the defects of the proximal policy optimization（PPO） algorithm， an improved proximate policy optimization algorithm is proposed. To enhance the variability of opponent’s strategy in the process of policy network self-learning， a baseline policy model selection method based on model performance and model diversity is proposed. The experiments demonstrate that the proposed method is effective and stable in air-sea joint operation decision. In the 4th Wargaming Competition hosted by Chinese Institute of Command and Control， the winning rate in more than 100 rounds against regular decision-making algorithm and human confrontation was 97%， which was about 20% higher than that of regular decision-making algorithms.
Aiming at the difficulty of air-sea joint operation in complex multi-equipment combat with high uncertainty， a new intelligent decision-making method for air-sea joint operation based on deep reinforcement learning is proposed. To uniformly represent the input and output of complex networks and their corresponding relations， various networks are utilized， e.g.， perceptron， deep long-short term memory network and actor critical structure. Aiming at the instability of policy network learning process and the defects of the proximal policy optimization（PPO） algorithm， an improved proximate policy optimization algorithm is proposed. To enhance the variability of opponent’s strategy in the process of policy network self-learning， a baseline policy model selection method based on model performance and model diversity is proposed. The experiments demonstrate that the proposed method is effective and stable in air-sea joint operation decision. In the 4th Wargaming Competition hosted by Chinese Institute of Command and Control， the winning rate in more than 100 rounds against regular decision-making algorithm and human confrontation was 97%， which was about 20% higher than that of regular decision-making algorithms.
2023(1):37-46.
DOI: 10.16356/j.1005-1120.2023.01.004
Abstract:
Semitransparent media widely exist in industrial and chemical equipment， and their heat radiative properties usually play a vital role in studying the heat transfer process in the media. In the paper， an improved stochastic particle swarm optimization （ISPSO） is proposed to determine heat radiative property parameters of semitransparent media， i.e. absorption coefficient， scattering coefficient and asymmetry factor， from the angular light-scattering measurement signals. The results show that compared with the stochastic particle swarm optimization （SPSO） algorithm， the ISPSO algorithm can avoid the phenomenon of local optima and low convergence accuracy， and reasonable retrieval results can be obtained even with 5% random measurement errors. Moreover， the robustness of the inverse results is satisfactory when there are only two parameters needed to be studied. The inverse accuracy will be decreased when more parameters needed to be retrieved. However， the results are still acceptable even with 5% random measurement errors， when the absorption coefficient， scattering coefficient and asymmetry factor are retrieved simultaneously. All the results confirm that the proposed technique is an effective and reliable technique in estimating multiple radiative property parameters in semitransparent media simultaneously.
Semitransparent media widely exist in industrial and chemical equipment， and their heat radiative properties usually play a vital role in studying the heat transfer process in the media. In the paper， an improved stochastic particle swarm optimization （ISPSO） is proposed to determine heat radiative property parameters of semitransparent media， i.e. absorption coefficient， scattering coefficient and asymmetry factor， from the angular light-scattering measurement signals. The results show that compared with the stochastic particle swarm optimization （SPSO） algorithm， the ISPSO algorithm can avoid the phenomenon of local optima and low convergence accuracy， and reasonable retrieval results can be obtained even with 5% random measurement errors. Moreover， the robustness of the inverse results is satisfactory when there are only two parameters needed to be studied. The inverse accuracy will be decreased when more parameters needed to be retrieved. However， the results are still acceptable even with 5% random measurement errors， when the absorption coefficient， scattering coefficient and asymmetry factor are retrieved simultaneously. All the results confirm that the proposed technique is an effective and reliable technique in estimating multiple radiative property parameters in semitransparent media simultaneously.
2023(1):47-59.
DOI: 10.16356/j.1005-1120.2023.01.005
Abstract:
This study takes an aviation electric fuel pump with an external gear pump directly driven by a six-phase permanent magnet synchronous motor as an object. Its fuel flow control system is studied in this paper， and a preview controller design approach based on adaptive sliding mode feedback linearization is proposed. Firstly， the mathematical model of six-phase permanent magnet synchronous motor and external gear pump is established. Secondly， the nonlinear model of the electric fuel pump is processed using the feedback linearization method， which is helpful for the following preview controller design. Then， the linearization errors caused by the model uncertainty are eliminated using an adaptive sliding mode control method， which can separate the uncertainty brought on by modeling error and load disturbance and prevent chattering brought on by high switching gain. At the same time， it does not require accurate uncertainty boundary information， which improves control performance. Finally， the linearization model created by the feedback linearization method is used to construct the preview controller， which will reduce the time the control system takes to respond to a fuel command. The simulation results demonstrate that the proposed control method has a less response time， strong robustness， and excellent chattering suppression ability.
This study takes an aviation electric fuel pump with an external gear pump directly driven by a six-phase permanent magnet synchronous motor as an object. Its fuel flow control system is studied in this paper， and a preview controller design approach based on adaptive sliding mode feedback linearization is proposed. Firstly， the mathematical model of six-phase permanent magnet synchronous motor and external gear pump is established. Secondly， the nonlinear model of the electric fuel pump is processed using the feedback linearization method， which is helpful for the following preview controller design. Then， the linearization errors caused by the model uncertainty are eliminated using an adaptive sliding mode control method， which can separate the uncertainty brought on by modeling error and load disturbance and prevent chattering brought on by high switching gain. At the same time， it does not require accurate uncertainty boundary information， which improves control performance. Finally， the linearization model created by the feedback linearization method is used to construct the preview controller， which will reduce the time the control system takes to respond to a fuel command. The simulation results demonstrate that the proposed control method has a less response time， strong robustness， and excellent chattering suppression ability.
6 Design and Verification of Free Space Optical Communication Relay Between Ground and Tethered Ball
2023(1):60-70.
DOI: 10.16356/j.1005-1120.2023.01.006
Abstract:
There are currently some deficiencies with microwave mobile relay networks， such as short relay distance， sluggish data transfer rate， high power consumption， and limited operating frequency. This paper builds a relay system using laser communication technology to complete real-time forwarding of infrared high-definition data within a distance of more than 20 km from the tethered aerostat and the ground base station. This experiment’s success serves as a technical reference for the use of laser communication technology as an airborne communication relay station. A scanning acquisition scheme and attitude stability compensation scheme based on probability statistics are proposed to address the uncertain initial pointing angle and the external conditions of the rapid change of platform attitude. To avoid the complex integral calculation， this paper proposes a method based on the fourth-order Runge-Kutta to improve the algorithm’s accuracy while ensuring the function’s realization. The feedforward speed is introduced into the speed loop of the closed-loop tracking system based on the spatial position of the target and the change in its own attitude， which effectively improves the system’s tracking stability. We plan to conduct experiments on relaying laser links in air-to-air networks in the future.
There are currently some deficiencies with microwave mobile relay networks， such as short relay distance， sluggish data transfer rate， high power consumption， and limited operating frequency. This paper builds a relay system using laser communication technology to complete real-time forwarding of infrared high-definition data within a distance of more than 20 km from the tethered aerostat and the ground base station. This experiment’s success serves as a technical reference for the use of laser communication technology as an airborne communication relay station. A scanning acquisition scheme and attitude stability compensation scheme based on probability statistics are proposed to address the uncertain initial pointing angle and the external conditions of the rapid change of platform attitude. To avoid the complex integral calculation， this paper proposes a method based on the fourth-order Runge-Kutta to improve the algorithm’s accuracy while ensuring the function’s realization. The feedforward speed is introduced into the speed loop of the closed-loop tracking system based on the spatial position of the target and the change in its own attitude， which effectively improves the system’s tracking stability. We plan to conduct experiments on relaying laser links in air-to-air networks in the future.
2023(1):71-79.
DOI: 10.16356/j.1005-1120.2023.01.007
Abstract:
The number of harmonics generated by power electronics in power systems is increasing， and the harmonic problem is a significant concern. In this paper， we propose an improved coprime sampling （CS） scheme for harmonic and interharmonic frequency estimation. The proposed scheme uses sparse sampling to reduce the sampling rate significantly and combines it with modern spectral estimation algorithms. Then， the segmented coprime sampling （SCS） method replaces the traditional CS， effectively reducing the sampling rate and the hardware system’s workload. In addition， the root-multiple signal classification （root-MUSIC） algorithm returns the commonly used MUSIC algorithm， which guarantees estimation accuracy and significantly reduces computational complexity. The simulation results show that the proposed scheme outperforms the traditional uniform sampling （US） method in estimation accuracy.
The number of harmonics generated by power electronics in power systems is increasing， and the harmonic problem is a significant concern. In this paper， we propose an improved coprime sampling （CS） scheme for harmonic and interharmonic frequency estimation. The proposed scheme uses sparse sampling to reduce the sampling rate significantly and combines it with modern spectral estimation algorithms. Then， the segmented coprime sampling （SCS） method replaces the traditional CS， effectively reducing the sampling rate and the hardware system’s workload. In addition， the root-multiple signal classification （root-MUSIC） algorithm returns the commonly used MUSIC algorithm， which guarantees estimation accuracy and significantly reduces computational complexity. The simulation results show that the proposed scheme outperforms the traditional uniform sampling （US） method in estimation accuracy.
2023(1):80-97.
DOI: 10.16356/j.1005-1120.2023.01.008
Abstract:
A new configuration of support structure for modular space deployable antenna is proposed， and its mechanical characteristics are studied to meet the urgent needs of large-scale， high-precision， and high-rigidity development of space deployable antenna. On the basis of the basic theory of mechanism， the overall scheme design and detailed design of support structure are developed， and a 3-D model of modular deployable antenna consisting of 19 hexagonal prism modules is established. In accordance with strut stability theory， a static analysis model of support structure is established， and the value range of pretightening force in cables is obtained. A dynamic analysis model of the antenna structure is established， and the modal analysis is conducted. The natural frequency influencing factors and sensitivity analysis are performed. A principle prototype of support structure is developed， and the deployment function test and verification are conducted. Results show that the pretightening cables have a great influence on the structural stiffness， and the structural stiffness is increased by about 2.01 times after the pretightening cables are deployed. The natural frequency is sensitive to the material density and elastic modulus of members and the size parameters of chord beams and diagonal beams. The developed principle prototype in this paper is deployed smoothly and gently， verifying the feasibility of the structural design. Research results provide theoretical reference and technical support for the basic research and engineering application of modular deployable antenna.
A new configuration of support structure for modular space deployable antenna is proposed， and its mechanical characteristics are studied to meet the urgent needs of large-scale， high-precision， and high-rigidity development of space deployable antenna. On the basis of the basic theory of mechanism， the overall scheme design and detailed design of support structure are developed， and a 3-D model of modular deployable antenna consisting of 19 hexagonal prism modules is established. In accordance with strut stability theory， a static analysis model of support structure is established， and the value range of pretightening force in cables is obtained. A dynamic analysis model of the antenna structure is established， and the modal analysis is conducted. The natural frequency influencing factors and sensitivity analysis are performed. A principle prototype of support structure is developed， and the deployment function test and verification are conducted. Results show that the pretightening cables have a great influence on the structural stiffness， and the structural stiffness is increased by about 2.01 times after the pretightening cables are deployed. The natural frequency is sensitive to the material density and elastic modulus of members and the size parameters of chord beams and diagonal beams. The developed principle prototype in this paper is deployed smoothly and gently， verifying the feasibility of the structural design. Research results provide theoretical reference and technical support for the basic research and engineering application of modular deployable antenna.
2023(1):98-105.
DOI: 10.16356/j.1005-1120.2023.01.009
Abstract:
High entropy alloy （HEA） particles are dispersed into 2024 aluminum alloy matrix by multi-pass friction stir processing （FSP） process to prepare HEA/Al composites. The effects of FSP passes on the macro morphology， microstructure and mechanical properties of the composites are studied. The microstructure observation shows that increasing FSP passes contributes to the uniform distribution of high entropy alloy particles and grain refinement. The test results of mechanical properties show that with the increase of FSP passes， the microhardness value of FSPed composites is significantly improved， the distribution is more uniform， and the strength and plasticity are also improved. The microhardness， strength and plasticity of five-pass FSPed composites reach 138 HV， 597 MPa and 5.1%， respectively.
High entropy alloy （HEA） particles are dispersed into 2024 aluminum alloy matrix by multi-pass friction stir processing （FSP） process to prepare HEA/Al composites. The effects of FSP passes on the macro morphology， microstructure and mechanical properties of the composites are studied. The microstructure observation shows that increasing FSP passes contributes to the uniform distribution of high entropy alloy particles and grain refinement. The test results of mechanical properties show that with the increase of FSP passes， the microhardness value of FSPed composites is significantly improved， the distribution is more uniform， and the strength and plasticity are also improved. The microhardness， strength and plasticity of five-pass FSPed composites reach 138 HV， 597 MPa and 5.1%， respectively.
2023(1):106-114.
DOI: 10.16356/j.1005-1120.2023.01.010
Abstract:
The cloud manufacturing required by an increasingly dynamic competitive industrial environment results in the formation of “digital twin enterprises”. In order to investigate the digital twin enterprise with an architecture-driven modeling approach， this paper first introduces the essential elements of the digital twin enterprise architecture. These elements are converged by the multi-agent technology to form digital resources that can be dynamically connected to the cloud manufacturing platform. Then， by combining the digital twin technology， the general activities of enterprises are further refined to form the main operation flow of the architecture. Finally， as the digital twin technology is the core supporting technology for cloud manufacturing， this paper conducts a detailed analysis of the process of digital twin enterprises participating in cloud manufacturing. Through the application of digital twin technology， enterprises can reasonably control their production resources， and the internal production data flow can be further utilized to optimize the production process. Meanwhile， the manufacturing resources of enterprises can be accessed to the networked manufacturing platform in real time， and personalized orders can be obtained and further exploited according to the enterprise’s real status. The digitalization degree of enterprises has been greatly improved by constructing the multi-agent operation framework and optimizing the process of enterprises participating in networked production activities.
The cloud manufacturing required by an increasingly dynamic competitive industrial environment results in the formation of “digital twin enterprises”. In order to investigate the digital twin enterprise with an architecture-driven modeling approach， this paper first introduces the essential elements of the digital twin enterprise architecture. These elements are converged by the multi-agent technology to form digital resources that can be dynamically connected to the cloud manufacturing platform. Then， by combining the digital twin technology， the general activities of enterprises are further refined to form the main operation flow of the architecture. Finally， as the digital twin technology is the core supporting technology for cloud manufacturing， this paper conducts a detailed analysis of the process of digital twin enterprises participating in cloud manufacturing. Through the application of digital twin technology， enterprises can reasonably control their production resources， and the internal production data flow can be further utilized to optimize the production process. Meanwhile， the manufacturing resources of enterprises can be accessed to the networked manufacturing platform in real time， and personalized orders can be obtained and further exploited according to the enterprise’s real status. The digitalization degree of enterprises has been greatly improved by constructing the multi-agent operation framework and optimizing the process of enterprises participating in networked production activities.
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