氢氧末级长时间滑行贮箱压力控制及关键技术分析

为通过弹道优化设计提升火箭发射圆轨道卫星的运载能力,同时提高火箭对不同发射任务的适应性,需要火箭末级具备长时间在轨滑行能力。对氢氧末级火箭而言,延长在轨滑行时间需要解决的一个重要问题是液氢贮箱压力、推进剂温度的预示和控制。结合微重力下贮箱内低温推进剂力热耦合运动特征,给出了低温火箭在轨滑行过程中贮箱压力控制的设计流程和计算方法,并通过计算分析获得了整个滑行阶段液氢蒸发量、补压气瓶需求量等关键设计参数,为工程研制提供参考。     

Dynamics modeling and pressure control of composites tape winding system based on LQSMC

Pressure fluctuations during the composite fiber winding process seriously affect the product's compactness strength, fatigue resistance, stress uniformity, and resin content. The accuracy of pressure control systems is affected by nonlinear disturbances, such as friction, parameter perturbation, and measurement noise. A robust control algorithm based on linear quadratic optimal control and sliding mode control (LQSMC) is proposed to overcome these problems. The method is based on the system state space expression and linear quadratic optimal control. The state space model of the system is improved by using a Kalman filter and control input for state estimation, and a new sliding surface equation is defined. The ameliorated control algorithm exhibits good performance and can effectively suppress sliding mode control (SMC) chattering. Simulation and experimental results show that LQSMC offers high control precision, much stronger anti-interference, and robustness, which can effectively improve the positioning and tracking accuracy of a pressure control system compared with linear quadratic optimal control (LQC). The winding pressure control precision is improved by 45% to 50%. The results show that the porosity of composite fiber tape winding products decreased thanks to our method.     

氧换热器在两相流条件下的压力脉动机理分析

氢氧液体火箭发动机氧换热器在研制过程中出现了压力脉动现象，影响了换热器的正常工作。以该型换热器为研究对象，将换热器分为燃气侧、汇总管、圆管等结构，进行了CFD仿真计算，与试验结果对比，修正了传热相关参数，建立了换热器理论计算模型用于参数计算；利用非线性方法分析试验数据，确定了该换热器为混沌系统；利用两相流分析与电路类比两种方法分别针对换热器进行了建模与计算，均捕捉到了相变下换热器内的压力脉动。结果表明：通过CFD仿真及试验修正后的参数用于计算换热器的稳态参数，具有较好的一致性；换热器出现压力脉动时，具有一定非线性特征，且压力脉动越大，非线性程度越高；该换热器出现压力脉动的原因为氧工况接近两相区，相变使得介质密度发生剧变。根据分析结果提出了提高换热器设计压力的改进措施，通过试验得到了有效验证。     

Thermal stability improvement of sprayable fast-responding pressure-sensitive paint for measurement above 100 °C

The thermal stability of sprayable fast-responding Pressure-Sensitive Paint (fast PSP) was investigated to explore the possibility for application in turbomachinery and hypersonic research with temperature above 100 °C. The first part of the study focused on a widely-used Polymer Ceramic PSP (PC-PSP). The effects of thermal degradation on its key sensing properties, including luminescent intensity, pressure sensitivity and response time, were examined for a temperature range from 60 to 100 °C. Severe degradation in intensity and pressure sensitivity was found as temperature reached 70 °C or higher, which would cause failure of PSP application in these conditions. Subsequently, a fast-responding Mesoporous-Particle PSP (MP-PSP) was developed which did not show degradation effects until 140 °C. The greatly improved thermal stability of MP-PSP was attributed to: selection of polymer with higher glass transition temperature (polystyrene) to delay the saturation effect of oxygen quenching as temperature increased; porous and hollow structure of particles for luminophore deposition that minimizes polymer–luminophore interaction. This new paint formulation has significantly raised the upper temperature limit of fast PSP and offers more opportunities for applications in harsh environment.     

Pressure distribution guided supercritical wing optimization

Pressure distribution is important information for engineers during an aerodynamic design process. Pressure Distribution Oriented (PDO) optimization design has been proposed to introduce pressure distribution manipulation into traditional performance dominated optimization. In previous PDO approaches, constraints or manual manipulation have been used to obtain a desirable pressure distribution. In the present paper, a new Pressure Distribution Guided (PDG) method is developed to enable better pressure distribution manipulation while maintaining optimization efficiency. Based on the RBF-Assisted Differential Evolution (RADE) algorithm, a surrogate model is built for target pressure distribution features. By introducing individuals suggested by sub-optimization on the surrogate model into the population, the direction of optimal searching can be guided. Pressure distribution expectation and aerodynamic performance improvement can be achieved at the same time. The improvements of the PDG method are illustrated by comparing its design results and efficiency on airfoil optimization test cases with those obtained using other methods. Then the PDG method is applied on a dual-aisle airplane’s inner-board wing design. A total drag reduction of 8 drag counts is achieved.     

Effect of an end plate on surface pressure distributions of two swept wings

A series of wind tunnel tests was conducted to examine how an end plate affects the pressure distributions of two wings with leading edge(LE) sweep angles of 23° and 40°. All the experiments were carried out at a midchord Reynolds number of 8×10~5, covering an angle of attack(AOA) range from -2° to 14°. Static pressure distribution measurements were acquired over the upper surfaces of the wings along three chordwise rows and one spanwise direction at the wing quarter-chord line. The results of the tests confirm that at a particular AOA, increasing the sweep angle causes a noticeable decrease in the upper-surface suction pressure. Furthermore, as the sweep angle increases, the development of a laminar separation bubble near the LEs of the wings takes place at higher AOAs. On the other hand, spanwise pressure measurements show that increasing the wing sweep angle results in forming a stronger vortex on the quarter-chord line which has lower sensitivity to AOA variation and remains substantially attached to the wing surface for higher AOAs than that can be achieved in the case of a lower sweep angle. In addition, data obtained indicate that installing an end plate further reinforces the spanwise flow over the wing surface, thus affecting the pressure distribution.     

Change rules of a stratospheric airship's envelope shape during ascent process

Stratospheric airship is a special near-space air vehicle, and has more advantages than other air vehicles, such as long endurance, strong survival ability, excellent resolution, low cost, and so on, which make it an ideal stratospheric platform. It is of great significance to choose a rea-sonable and effective way to launch a stratospheric airship to the space for both academic research and engineering applications. In this paper, the non-forming launch way is studied and the method of differential pressure gradient is used to study the change rules of the airship's envelope shape dur-ing the ascent process. Numerical simulation results show that the head of the envelope will main-tain the inflatable shape and the envelope under the zero-pressure level will be compressed into a wide range of wrinkles during the ascent process. The airship's envelope will expand with the ascent of the airship and the position of the zero-pressure level will move downward constantly. At the same time, the envelope will gradually form a certain degree of stiffness under the action of the inner and external differential pressure. The experimental results agree well with the analytical results, which shows that the non-forming launch way is effective and reliable, and the analytical method has exactness and feasibility.     

压力传感器单电源调理电路技术研究

对单电源供电的压力传感器调试中出现零位输出较大且存在相应死区的问题，进行了理论分析，找出了问题原因，采取了有效的解决措施，为传感器产品化和产业化奠定了基础。     

两种紊流模型在通流计算中的应用研究

为验证紊流模型在基于周向平均Navier-Stokes方程的通流计算中的适用性，本文给出了周向平均形式的Spalart-Allmaras紊流模型，并选择Baldwin-Lomax模型作为对比。通过两个经典简单算例以及两个典型叶轮机械算例对采用了上述两种紊流模型的通流模型进行验证与对比。两个经典简单算例结果表明，上述两种紊流模型在无叶片的通流模型中均能够准确预测附面层发展，捕获激波，预测分离流动。两个典型叶轮机械算例结果表明两种紊流模型对轴流式叶轮机械的子午流面气动布局以及总体气动性能具备一定的的预测能力。在单转子算例中，S-A模型的计算结果略优于B-L模型的计算结果；在双级高压涡轮算例中两种紊流模型对总体性能参数以及气流角的计算结果相差不大，且S-A模型计算的马赫数比B-L模型的偏小。     

热力学排气系统对液氮贮箱控压特性的影响分析

为研究热力学排气系统(TVS)对低温推进剂贮箱控压特性的影响，搭建了液氮热力学排气技术控压试验平台，开展了混合模式和并行模式下的低温贮箱控压试验，研究了不同控压区间气枕压力及液相温度的变化规律，对并行模式过程中节流特性以及节流制冷量的输入对液相温度变化的影响进行了分析。试验结果表明，在混合模式中由于外部漏热和气枕压力的影响，液相温度呈波浪式上升趋势;在并行模式中，在节流制冷量输入和外部漏热的共同作用下，液相温度停止上升转而下降；在两种模式运行中，液相温度在较高的控压区间比较低的区间变化率大；理论模型能够较好反映试验测试结果，模拟分析得到的液相温度变化率与试验结果基本一致。