一般均衡模型下的税负归宿研究

税负归宿问题因其复杂的传导机制影响着人们对最终税收负担的判断，在局部均衡分析失效的情况下，一般均衡模型是研究税负归宿的更佳方案。基于经典的Harberger模型，运用线性化和逼近技术，讨论了一般均衡框架下的数量求解算法，得到了特定部门资本和劳动用量以及资本价格的微分值，并以此分析了局部要素税的税负归宿以及最终的税收负担。     

Artificial equilibrium points and bi-impulsive maneuvers to observe 243 Ida

In the restricted three-body problem, the traditional Lagrange points L₁ and L₂ are the only equilibrium points near the asteroid 243 Ida. The thrust generated by a solar sail over a spacecraft enables the existence of new artificial equilibrium points, which depend on the position of the spacecraft with respect to the asteroid and the attitude of the solar sail. Such equilibrium points generate new spots to observe the body from above or below the plane of motion. Such points are very good observational locations due to their stationary condition. This work provides a preliminary analysis to observe Ida through the use of artificial equilibrium points as spots combined with transfer maneuvers between them. Such combination can be used to observe the asteroid from more different points of view in comparison to fixed ones. The analyses are made for a spacecraft equipped with a solar sail and capable of performing bi-impulsive maneuvers. The solar radiation pressure is used both to maintain the equilibrium condition and to reduce the costs of the transfers and/or to create transfers with longer duration. This is a new aspect of the present research, because it combines the continuous thrust with initial and final small impulses, which are feasible for most of the spacecraft, because the magnitudes of the impulses are very low. These combined maneuvers may reduce the transfer times of the maneuvers in most of the cases, compared with the maneuvers based only on continuous thrust. Several options involved in these transfers are shown, like to minimize the fuel spent ($\mathrm{\Delta }\mathit{v}$) as a function of the transfer time or to extend the duration of the travel between the points. Extended transfer times can be useful when observations are required during the transfers.     

硝酸与固体燃料燃烧性能计算研究

建立了固液火箭发动机燃烧性能计算模型,采用一维化学平衡(ODE)方法对以硝酸为氧化剂的固液火箭发动机燃烧性能进行了初步探讨。计算表明,固液火箭发动机的比冲、特征速度和燃烧温度以及燃烧产物组分等与氧化剂和燃料的配比有密切关系,氧化剂与燃料质量配比在3.75附近时,固液火箭发动机内部的温度较高,燃烧产物组分以及特征速度达到最佳状态,比冲最高。     

状态方程对煤油液滴高压蒸发计算的影响

分别基于RK、SRK和PR等不同真实流体状态方程(EoS)建立了包含亚临界和超临界两种不同机制的瞬态液滴高压蒸发模型。针对我国新一代高压补燃液氧/煤油发动机,对煤油液滴在高压N 2 环境下的蒸发过程进行数值研究,重点分析了不同状态方程对N 2 -C 12 H 26 二元系统高压气液相平衡,及进一步对煤油液滴高压蒸发计算的影响。结果表明：对液滴蒸发速率影响最大的参数是液滴表面蒸气质量分数,而对该参数影响最大的则是所选取的状态方程。基于SRK和PR EoSs的高压气液相平衡及液滴高压蒸发计算结果均与试验数据符合较好,可正确描述液滴高压蒸发特性;而基于RK EoS的相平衡计算结果显著高估液滴表面蒸气质量分数和环境气体溶解度,并低估临界混合温度和偏摩尔相变热,进而在亚临界蒸发状态下高估蒸发速率,在超临界蒸发状态下低估蒸发速率。另外,基于RK EoS的计算中液滴发生跨临界转变所需的环境温度显著低于基于SRK和PR EoSs的。     

基于轨迹在线规划与跟踪律在线计算的自适应再入制导方法

针对高超声速飞行器非标称再入飞行任务的高精度自主制导问题,研究了一种基于轨迹在线规划与跟踪律在线计算的全自主自适应制导方法.该方法基于拟平衡滑翔条件与高精度的规划模型在线生成满足多路径约束的参考轨迹,在跟踪参考轨迹时引入符号函数法在线计算线性二次调节器的反馈增益矩阵,以获得高精度的自适应跟踪律.最后通过远程、近程两种工...     

基于燃烧室多反应器模型的民用涡扇发动机排放预测

选用燃油JetA为航空燃料,建立了简化火焰锋面模型、燃烧化学平衡模型、燃烧动力学模型、燃油雾化模型、燃油蒸发模型及污染排放生成模型.采用基于燃烧室多反应器模型对发动机在不同工作状态下的排放产物NOx、未燃碳氢化合物(unburned hydrocarbons,UHC)和CO进行了计算.结果表明:燃烧室内火焰温度越高,NOx排放量越大.在发动机工作在低转速工况下时,燃油液滴的雾化直径大,造成CO与UHC排放量增加.基于燃烧室多反应器模型计算通用性强、速度快,适合与发动机性能程序相结合,在发动机设计阶段对发动机不同工作状态下的排放产物含量进行预测计算.     

Approximate Nonlinear Modeling of Aircraft Engine Surge Margin Based on Equilibrium Manifold Expansion

Stable operation of aircraft engine compressions is constrained by rotating surge. In this paper, an approximate nonlinear surge margin model of aircraft engine compression system by using equilibrium manifold is presented. Firstly, this paper gives an overview of the current state of modeling aerodynamic flow instabilities in engine compressors. Secondly, the expansion form of equilibrium manifold is introduced, and the choosing scheduling variable method is discussed. Then, this paper also gives the identification procedure of modeling the approximate nonlinear model. Finally, the modeling and simulations with high pressure (HP) compressor surge margin of the aircraft engine show that this real-time model has the same accuracy with the thermodynamic model, but has simpler structure and shorter computation time.     

斜切径向旋流燃烧室主燃区光学测量与特性分析

针对斜切径向旋流环形燃烧室模型,采用可调谐二极管激光吸收光谱(TDLAS)、相干反斯托克斯喇曼光谱(CARS)光学测量手段,在模化状态(Case 2)下,对燃烧室主燃区进行温度测量,分别得到了主燃区内12个点的温度和沿两条路径的积分温度.使用Fluent 12.0对Case 2进行数值模拟,分别使用两种非预混燃烧模型:平衡化学反应模型(EM)和稳态层流小火焰(SLF)模型.通过将两种不同燃烧模型的计算结果与TDLAS,CARS试验测量数据作对比验证,发现EM计算得到的温度更高,并与试验测量温度更符合,其中与CARS测量的误差小于6%.在试验验证的基础上,完成燃烧室在冷流状态(Case 1)下的计算,分析主燃区的气流组织和主燃孔射流对回流区的影响;利用EM计算分析燃烧室主燃区在全压状态(Case 3)下燃料分布、温度场、组分分布和性能参数,如燃烧室的燃烧效率为0.97、出口温度分布系数为0.312等,较为全面反映了燃烧室内气流流动换热和燃烧现象.      

符合适航认证要求的燃油温度计算方法

基于适航认证需要,以某型飞机中央翼油箱隔舱在规定工况下实测的燃油温度变化曲线为输入条件,借助于MATLAB多项式分段拟合功能,获取了各个阶段燃油温度变化规律的高阶函数表达式;采用Monte Carlo评估模型中规定的指数衰减方程来表征燃油温度变化规律,其中环境总温(TAT)由评估模型中所指定方法获取,平衡温差和时间常数...     

平衡气体效应对飞行器动态特性的影响研究

通过数值求解N-S方程,模拟升力体外形的强迫振动过程,研究了平衡气体效应对带翼飞行器俯仰阻尼导数的影响。分别在完全气体和平衡气体假定条件下,给出了h=30km,Ma∞=8,α=0°,10°,20°,30°时的俯仰阻尼导数变化的定量分析结果。