转静干涉对叶片非定常表面压力的影响

为了研究转静干涉对叶片表面压力的影响,通过数值模拟的方法,计算了一级低速轴流压气机流场,得到了充分收敛的周期性非定常流场解。在此基础上分析了叶片表面压力及气动力的变化规律,并通过改变背压,研究了流量对叶片表面压力和气动力的影响。最后在低速轴流压气机实验器上进行了实验验证,结果表明计算和实验的结果吻合得较好。     

椭圆形扰流柱冷却通道流动与换热数值研究

采用数值计算方法对涡轮叶片椭圆形扰流柱排冷却通道的流动和换热进行了研究,得到了排列间距、迎角、椭圆长短轴之比等因素对冷却通道流动和换热性能的影响.在相同截面积和排列方式条件下,椭圆形扰流柱迎角为0°时,分析结果表明,椭圆形扰流柱冷却通道压力损失系数约为圆形扰流柱通道的51.7%,平均努塞尔数约为圆形扰流柱通道的83.75%;长短轴比为5/1.8时,压力损失系数仅为圆形扰流柱通道的(长短轴比等于3/3)28.1%～35.5%,平均努塞尔数为圆形扰流柱通道的71.1%～75.06%.      

风力机翼型动态测压试验技术研究

结合国家高技术研究发展计划课题＂风力机先进翼型族的设计与试验研究＂,针对动态试验设备研制、数据采集和处理方法,在西北工业大学1.6m×3.0m低速翼型风洞（NF-3风洞）开展了风力机翼型动态测压试验技术的研究。采用S809风力机翼型模型,在雷诺数0.75×106和1.4×106、迎角-2°～＋18°条件下,通过改变模型3个平均迎角、3个振荡频率和2个振幅角等状态,进行了动态测压试验,并与静态测压及国外试验结果进行了对比。结果表明：NF-3风洞研制的试验设备,采用的数据采集和处理方法能够应用于风力机翼型的动态测压试验,并可推广应用于其他的翼型动态测压试验研究。     

两级超声速引射器流动机理研究

超声速引射器在航天发动机、化学激光器等的地面试验所需压力恢复系统中有着重要的应用,采用超-超引射方式是优化压力恢复系统的性能和实现设备小型化的途径之一。为探索适用于超-超引射器的设计准则,对一种两级超声速引射器的超-超引射流动现象开展了研究,试验发现该构型引射器在特定压力匹配范围内即可实现一、二级主流间的超-超引射又可以实现主流对二次流的超-超引射,结合数值仿真对流场结构和参数的分析表明超-超引射的形成机制可归结为压力匹配问题,通过提高来流总压与混合室匹配静压的压比可建立超-超引射;混合室匹配静压由引射气流主导;提高二次流总压或降低主流压力均可提高二次流马赫数,该规律对建立超-超引射、提高引射效率有指导意义。      

涡脱位置及温度对涡声效应压力振荡影响

为探索涡-声效应对固体火箭发动机中压力振荡特性的影响,基于VKI (Von Karman Institute for Fluid Dynamics)发动机,通过改变挡板位置与燃气温度,对旋涡脱落引起的压力振荡进行了大涡模拟数值研究.耦合分析表明:挡板位于速度波腹附近,压力振荡最为严重;旋涡能量在输运过程中易于被湍流耗散,靠近喷管的二阶速度波腹处旋涡脱落压力振幅明显高于其它位置.解耦分析表明:温度对旋涡脱落频率影响不大,当旋涡脱落频率与声振频率分离后,压力振幅显著下降.     

俯仰振荡翼型推阻力转变滞后机制数值研究

扑翼产生的反卡门涡街被认为是一种推力型尾迹,但已有研究指出,随着斯特劳哈尔数(St)增大,低雷诺数下俯仰振荡翼型的净推力产生明显滞后于反卡门涡街的出现.为探究该现象背后的物理机制,对NACA0012翼型在雷诺数1000条件下作简谐俯仰运动的流场进行了数值模拟.采用翼型表面积分方法和基于有限控制体的气动力估计方法分别研究...     

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.     

Response of the mesopause temperatures to solar activity over Yakutia in 1999–2013

OH(6-2) rotational temperature trends and solar cycle effects are studied. Observations were carried out at the Maimaga station (63.04°N, 129.51°E) for the period August 1999 to March 2013. Measurements were conducted with an infrared spectrograph. Temperatures were determined from intensity ratios in the P branch of the OH band. The monthly average residuals of temperature after the subtraction of the mean seasonal variation were used for a search for the solar component of temperature response. The dependence of temperatures on solar activity has been investigated using the Ottawa 10.7 cm flux as a proxy. A linear regression fitting on residual temperatures yields a solar cycle coefficient of 4.24 ± 1.39 K/100 solar flux units (SFU). The cross-correlation analyses showed that changes of the residual temperature follow changes of solar activity with a quasi-two year delay (25 months). The temperature response at the delay of 25 months reaches 7 K/100 SFU. The possible reason of the observed delay can be an influence of quasi-biennial oscillations (QBO) of the atmosphere on the relation of temperature and solar activity. The value of the temperature trend after the subtraction of seasonal and solar components is not statistically significant.     

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.