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The paper presents a numerical investigation on the clocking effect in a three-stage axial low pressure turbine. Equal pitch configuration was applied to reduce computation cost. The flow field was solved by commercial unsteady CF...
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The paper presents a numerical investigation on the clocking effect in a three-stage axial low pressure turbine. Equal pitch configuration was applied to reduce computation cost. The flow field was solved by commercial unsteady CFD solver. The performance for different clocking configurations is compared; the result indicates that the key of the clocking effect on overall efficiency is the loss variation of the downstream row in the clocking pair. For such row the loss-minimum clocking configuration at specified spanwise section is where the wake fragment enters the passage near the leading edge, especially from the suction side. The loss-minimum clocking configuration of entire span is identical to that of the spanwise section where the wake fragment strength reaches maximum. The entropy generation rate in the passage of the downstream clocking row is compared and analyzed. The result shows that the wake fragment decreases the time-averaged loss generated near its avenue. When the wake fragment enters the passage from the suction side of the leading edge, its avenue is more close to the high loss region, resulting in lower overall loss of the passage. A neighboring wake fragment avenue at suction side brings the risk of larger separation, but the impact on performance is not dominant in the studied model. The interaction of stator clocking and rotor clocking in the same stage is also studied. The effect of rotor clocking is shown to be slightly affected by the clocking of upstream stator, but the row-by-row clocking still yields a full clocking configuration with high efficiency.
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With the growth of air transport demand and the substantial increase of air transport volume, the airport flight schedule is becoming more and more intensive, even hard to find for a moment. As a result, some aircraft can not land...
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With the growth of air transport demand and the substantial increase of air transport volume, the airport flight schedule is becoming more and more intensive, even hard to find for a moment. As a result, some aircraft can not land or take off at the expected time. This paper studies the aircraft arrival scheduling problem in airports with multi-runways within the terminal area. It is different from the previous studies, according to the terminal area air traffic control operation rules, and this paper takes minimizing the total flight delay as the goal, considers the constraints of arrival point, flight schedule adjustment range, take-off interval and runway occupation time, establishes the flight schedule optimization model, and uses permutation coding method to solve the model using genetic algorithm. The results show that the proposed method can reduce the delay by 31.03% and improve the flight punctuality rate.
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Quadrotors are currently of widespread use in many commercial and military applications, thus, any development aiming at increasing their flight performance is of considerable relevance. Both the model structure and main dynamical...
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Quadrotors are currently of widespread use in many commercial and military applications, thus, any development aiming at increasing their flight performance is of considerable relevance. Both the model structure and main dynamical parameters of a quadrotor during forward flight are different from those present when hovering. This results in a poor performance of any controller designed for hovering equilibrium, when applied to forward flight scenarios. Aiming at this problem, we propose a design methodology for a quadrotor attitude controller and throttle acceleration autopilot, based on forward modeling. Firstly, the forward dynamics is modeled via system identification and designed experiment. Then, utilizing the linearization results, a frequency domain analysis method is investigated for tuning the parameters of attitude cascade PID controller of quadrotor. The three-layer structure requires it to be designed separately, where the inner loop solves the stability problem and the outer one improves the response performance. And this work regards crossover frequency and phase margin as indicators. Next, a novel closed-loop throttle autopilot with acceleration feedback is constructed to control the vertical movement fast and accurately. The control command in throttle channel is given from the relationship between equilibrium throttle and vertical acceleration, which will be processed by a PI correction and a first-order low-pass filter. Finally, the numerical simulations and comparisons are carried out to demonstrate the strong stability and transient behavior of the proposed scheme in different working regimes.
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Advances in reusable and hypersonic technology have accelerated the historic integration of transatmospheric ve-hicles, blurring the line between spacecraft and aeronautical vehicles. At the same time, MEA/AEA concept is widely us...
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Advances in reusable and hypersonic technology have accelerated the historic integration of transatmospheric ve-hicles, blurring the line between spacecraft and aeronautical vehicles. At the same time, MEA/AEA concept is widely used in the design of advanced aircraft developing towards electrification and intelligence, causing a lot of heat generated by Airborne electronic equipment, of which the cooling demand increases with the replacement of electronic equipment which causes the on-board electronic equipment will generate a lot of heat, and its complexity and energy requirements will increase with the replacement of electronic equipment. Therefore, the heat dissipation of the aircraft is not optimistic. As a power energy source, fuel stored in the fuel tanks around the fuselage and wings is also one of the important heat sinks of the aircraft. The heat transfer analysis of the fuel tanks is particularly necessary for the integrated thermal management of the aircraft. By computational fluid dynamics and numerical heat transfer method, the simulation calculation and analysis of external flow field and aerodynamic heating of different task profile provide the detailed outer boundary conditions for the next long endurance fuel temperature simulation and lays a foundation for the analysis and calculation of integrated fuel thermal management.
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Modern advanced aeroengine has a wide range of work envelope. To solve the problem of supersonic aero-engine multivariable and robust control, this paper analyzes Active Disturbance Rejection Control (ADRC) controller in accelerat...
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Modern advanced aeroengine has a wide range of work envelope. To solve the problem of supersonic aero-engine multivariable and robust control, this paper analyzes Active Disturbance Rejection Control (ADRC) controller in acceleration and deceleration process and switching afterburner state under three typical working conditions, the settling time and overshoot of ADRC control are comprehensively analyzed under the full flight envelope, the influence of the disturbance of the fan/compressor guide vane angle and the inlet ramp angle is also analyzed. The results show that the ADRC controller can realize the "zero error" following control of Nh and NPC under three typical working conditions, non-controlled parameters work in the normal range, while the NPC control loop fluctuates greatly and jumps violently under the switching afterburner state. ADRC controller can achieve stable control in the whole envelope. The response speed of NPR control loop is slightly faster than that of Nh control loop, but the overshoot is larger at high altitude, while the overshoot of Nh control loop is very small. ADRC controller can resist small disturbance of fan/compressor guide vane angle and inlet ramp angle under switching afterburner state and has good robust performance.
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Probe-and-drogue aerial refueling is a widely used military technique for transferring fuel between aircrafts. A dynamic model for the study of the hose-and-drogue system requires three essential elements, which are the dynamics o...
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Probe-and-drogue aerial refueling is a widely used military technique for transferring fuel between aircrafts. A dynamic model for the study of the hose-and-drogue system requires three essential elements, which are the dynamics of the bodies, the external loads and the constraints on the bodies. However, in the most advanced models, either the reel behavior is absent or the interactions between the reel and the hose are ignored. In this paper a model is presented that fully reflects the dynamic behaviors of the hose-drogue system in a multi-body dynamic approach. In the model, the hose is represented by a series of discrete links, while the reel and drogue are represented by mass points connected to the hose. The interaction between the reel and the discrete links of the hose are treated as variable constraints to accurately reflect the hose-drogue system before and during the hose-probe contact. A numerical method based on Newton-Raphson iteration is proposed to solve the multi-body dynamic system with variable constraints. A demonstrative simulation reveals the performance of the method. In the simulation result, the take-up behavior of the hose is observed, which validates the model.
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Aircraft manufacturing companies have long production cycles and complex product structures. The assembly process involves a variety of parts and components. There are many types of materials and high requirements for complete set...
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Aircraft manufacturing companies have long production cycles and complex product structures. The assembly process involves a variety of parts and components. There are many types of materials and high requirements for complete sets. The delayed delivery of a certain material will produce a domino effect, which will cause the delivery time of the final parts to be delayed by multiples. In order to reduce the influence of operation delay on the scheduling scheme, this paper studies the robust scheduling operation time difference relaxation. Considering the effect of delay, the robust indexes are selected, and a robust scheduling model with uncertain delays in a single operation is constructed. Then, a robust scheduling method based on operation interval relaxation is proposed, the priority order of operation time difference relaxation is analyzed, and the position and size of the operation time difference relaxation is obtained. Finally, some experiments demonstrated the effectiveness of the operation time difference relaxation method.
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The proportion of high-performance composite materials used in the aerospace industry has increased significantly. In the field of aircraft assembly, although there has been in-depth research on the assembly process simulation of ...
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The proportion of high-performance composite materials used in the aerospace industry has increased significantly. In the field of aircraft assembly, although there has been in-depth research on the assembly process simulation of traditional metal winglet parts, there are relatively few research cases on the assembly process simulation of composite winglet parts. In this paper, the production line is first investigated in the trial production stage of a typical composite small wing surface component. Draw a process flow chart, including the preceding process, process time and key resources. Then calculate the logistics path of the entire production line, and get the basic principles of the typical digital factory layout. Then build a 3D model of the digital factory based on CATIA. Finally, a process simulation model is established based on MATLAB to calculate the typical part capacity, resource utilization, resource waiting rate and the waiting rate of each process under different production resource constraints. This model provides decision-making reference for plant equipment layout and capacity analysis of product batch production investment.
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In this paper, the flight dynamic model of Vertical Take-Off and Landing (VTOL) aircraft which equips a propeller-wing-flap system that produces slipstream is established. The complete aircraft is modeled by combining experimental...
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In this paper, the flight dynamic model of Vertical Take-Off and Landing (VTOL) aircraft which equips a propeller-wing-flap system that produces slipstream is established. The complete aircraft is modeled by combining experimental results, theoretical calculation, and empirical data. Firstly, the propeller deflected slipstream effects and the parameters of ducted fan are obtained by bench test. The DATCOM are used for generating the aerodynamic coefficients. Then, the 6-DoF nonlinear flight dynamic model in both hover and forward flight conditions are deducted by employing the assumption of linear superposition. The gyro effect and gravity are considered. Finally, specific trim conditions in hovering, transitional and level flight states are determined, and dynamic characteristics at trim are studied by both full model simulation and linear system analysis obtained through small-perturbation theory. It is found that the aircraft is critically stable in hovering condition. The damping ratio of short-period mode is relatively small, and the phugoid mode divergence in the transition state. The aircraft is less well damped in the level flight condition. The built model accurately reflects the dynamic characteristics of the VTOL aircraft and provides help for the design of the flight control system afterward.
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Aircraft assembly, as the main component of aircraft manufacturing, bears the capacity of 40%-50% of the whole machine manufacturing. Among them, aircraft unit assembly is a powerful guarantee of aircraft quality, flight safety, c...
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Aircraft assembly, as the main component of aircraft manufacturing, bears the capacity of 40%-50% of the whole machine manufacturing. Among them, aircraft unit assembly is a powerful guarantee of aircraft quality, flight safety, cost and delivery cycle. The main characteristics of unit assembly are large size of parts, easy deformation of sheet metal parts or composite parts, complex assembly process, etc., which will produce assembly clearance or interference and other out-of-tolerance problems, especially in the unit joint area. In order to solve the above problems, SACC optimizes the unit assembly docking process of the mid fuselage in certain large airliner. This paper first introduces the status of the gap or interference in aircraft assembly, and investigates the main technical reasons and strategies. Secondly, combining with the situation of assembly in mid fuselage, from the aspects of assembly datum, unit precision and process allowance optimization and using the assembly tolerance analysis and the method for theoretical calculation of dimension chain, SACC finally realizes the breakthrough in mid fuselage assembly problems and efficiency. A solid foundation has been laid for improvement of customer satisfaction and meeting the delivery orders.
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