Zhou

Power Characteristics of Photovoltaic Modules of Solar-Powered Airplanes Including Thermal Effects

A power characteristic model of photovoltaic (PV) modules on the wing of solar-powered airplanes operated from sea level to the stratosphere is established. Because the efficiency of PV modules is a function of surface temperature, the proposed model includes thermodynamic effects. Firstly, the real-time power characteristics are analyzed at the altitudes of 10 km and 30 km and during the summer and winter solstice. Then, further investigations are conducted to research the daily averaged power per unit area from 0 km to 35 km throughout a whole year. The results show that the low atmosphere temperature is favorable condition for PV modules to obtain high absorption efficiency, and total solar radiation increases with the altitude increasing. However, the thinness of atmosphere density at high altitudes leads the deduction of Reynolds number, resulting in less heat carried away and the efficiency deterioration of PV modules. The maximum power collected occurs around 11 km. The research work shows that it is necessary to take into consideration the thermal effects on the efficiency of PV modules at high altitudes.

Numerical Investigations of Synthetic Jet Control for TAU0015 Airfoil

The aerodynamic performance of TAU0015 airfoil was investigated with synthetic jet control method. The simplified mathematical model of the active flow control was established with unsteady velocity boundary condition at the specific location of airfoil surface. The aerodynamic performance was simulated with synthetic jet and the efficiency of jet momentum coefficient was conducted. The result shows that the flow control model could perform the minor jet flow characteristics and higher jet momentum coefficient result better control efficiency.

Delayed Detached-Eddy Simulation and Application of a Coflow Jet Airfoil at High Angle of Attack

A DDES (Delayed Detached-Eddy Simulation) method is presented and applied to simulation and design of a CFJ (Coflow Jet) airfoil at high angle of attack. The method is based on average vorticity, and is used to predict a number of test cases, including a circular cylinder flow, vortex design and simulation of the CFJ airfoil. The results demonstrate that the DDES method is efficient for CFJ airfoil flow. It provides reference to flow control and aircraft design.

Analysis on Flight Dynamics of Solar UAV with Multiple Propulsion Systems

High Altitude Long Endurance (HALE) Solar UAV is integrated with a series of motor-propeller propulsion systems along the large aspect-ratio wing. These systems have an obvious effect on the flight dynamics of the UAV. This paper established a model for the interaction between distributed propulsion systems and the flight dynamics of the airplane, it was used to improve the computation of the UAV’s flight quality, results with and without the modified model were compared. It was found that the large aspect-ratio wing integrated with distributed propulsion systems can change its stability significantly. According to the result, parameters of the propulsion systems are adjusted to optimize the flight quality and system efficiency.

Analysis on the Power Characteristics of Lift-Fan VTOL

Based on the propeller momentum theory, this paper obtained the momentum model for internal flow of lift fan system. It analyzed the influence of its conceptual parameters on power characteristics of lift-fan VTOL to analyze the trend changes of the total power required with the increase of freestream velocity. The results can be used for selecting parameters at the preliminary phase of designing lift-fan VTOL and determining the design parameters of lift-fan VTOL.

Distributed Modeling and Control of Large-Scale Highly Flexible Solar-Powered UAV

The modeling, stability, and control characteristics of a large scale highly flexible solar-powered UAV with distributed all-span multielevons were presented. A geometrically nonlinear intrinsic beam model was introduced to establish the structural/flight dynamics coupled equation of motion (EOM); based on it, the explicit decoupled linear flight dynamics and structural dynamics EOM were derived through mean axis theory. Undeformed, deformed, and flexible models were compared through trimming and modal analysis. Since the deformation of wing has increased the UAV’s moment of inertia about the pitch axis, the frequency of short period mode has obviously decreased for the deformed model. The serious coupling between short period mode and 1st bending mode also significantly influences the roots of short period mode of flexible model. So flexible model was the only one which is able to accurately estimate the flight dynamics behaviors and was selected as the later control model. Forty distributed elevons and LQG/LTR controller were employed to control the attitude and suppress the aeroelastic deformation of the UAV simultaneously. The dynamics performance, robustness, and simulation results show that they were suitable for large scale highly flexible solar-powered UAV.

Mixed Integer Linear Programming for UAV Trajectory Planning Problem

This paper describes a method for vehicles flying Trajectory Planning Problem in 3D environments. These requirements lead to non-convex constraints and difficult optimizations. It is shown that this problem can be rewritten as a linear program with mixed integer linear constraints that account for the collision avoidance used in model predictive control, running in real-time to incorporate feedback and compensate for uncertainty. An example is worked out in a real-time scheme, solved on-line to compensate for the effect of uncertainty as the maneuver progresses. In particular, we compare receding horizon control with arrival time approaches.

Research on Longitudinal Static Stability for VFSW Tailless Configuration UAV

The Variable Forward-Swept Wing (VFSW) Tailless configuration UAV can well satisfy multipurpose demands. However, this kind of unconventional morphing aircraft lacks tail, which brings great challenge to stability analysis. The connatural aero-elasticity divergence and the strong aerodynamic coupling as well as many uncertain factors in mechanical environment, give the VFSW Tailless configuration UAV complicated dynamic characteristics. During the process of transformation, the variation of dynamic shape will inevitably lead to the variation about aerodynamic center and barycentre positions of airplane, then make the angle of attack static stability margin variable, and directly influence stability of aircraft. On the basis of introduction of the VFSW Tailless configuration UAV, according to its geometric shape, positions of aerodynamic center and barycentre, in different states with different forward-swept angle, were calculated, so as to obtain variation curve of longitudinal static stability margin, which provided preferences for dynamics analysis, position of barycentre adjustment and design of flight control system (FCS).

Parallelized Aeroelastic Investigation Based on Delaunay Graph Mapping

In this paper, an effective and well robust dynamic grid deformation method based on Delaunay graph mapping is developed to solve the deformation of the 3-D hybrid multiblocks grids which is combined by near-wall viscosity grids and unstructured grids. Further more, the static aeroelastics problems of the standard model M6 elastic wing is investigated altogether by coupled with structure dynamic equation. The comparison, analysis and investigation were done as well. The CFD grids domain is subdivided into subdomains for parallel computation. And the program is carried out by MPI parallel computation standards.

The Analysis of Motion Characteristics of Variable Forward-Swept Wing Mechanism with a Double Slideways

Based on the variable forward-swept wing configuration, this paper utilized a variable forward-swept wing mechanism with a double slideways, which make it possible for the aircraft to switch among orthogonal wing, forward-swept wing and delta wing freely. The general configuration of the variable forward-swept wing mechanism with a double slideways was elucidated by means of a three-dimensional model plot and then the mathematic simulation model was also established. The motion characteristics of linear motion were simulated, analyzed and optimized. The results indicated that the variable forward-swept wing mechanism with a double slideways can meet the aerodynamic requirements better. Moreover, there exists great linear relationship between the position of nut and the wing forward-swept angle. Therefore, this mechanism may serve as a useful reference when developing a morphing aircraft.