Design and application of an air-cooled probe for total pressure measurement at combustor outlet

An air-cooled probe was designed for measurement of total pressure at combustor outlet; its cooling scheme combined the film cooling and convection cooling. With the aid of CFD technique, cooling effectiveness of the coolant jets at various blow ratios was compared; suitable blow ratios and configuration of film holes were chosen accordingly. The overall cooling performance of the probe was evaluated via CFD technique, the design was improved according to the simulation result, and the cooling effect of the leading edge was obviously strengthened by increasing the local coolant mass flow rate. The results of wind tunnel test indicated that, between Mach numbers 0.2 and 0.4, the probe achieved a high accuracy at various attack angles. The probe was utilized in an annular combustor rig test, the highest temperature reached 1760K and total pressure reaches 1036kPa. The result of rig test demonstrates that the coolant film distribution consistent appropriately with the CFD results.      

磨牙修复体数控加工刀轨生成算法的实现

磨牙修复体CAD模型通常以STL格式存储.本文给出了基于STL格式新的拓扑结构,提出了基于顶点的实体等距算法,实现了磨牙修复体粗/精加工刀轨的快速生成.仿真加工结果表明,本文所提算法稳定性好,计算速度快,加工精度高.     

型腔尖角的轨迹优化

在铣削型腔尖角加工过程中,当环切法加工的行间距离比较大时,型腔尖角处将会出现加工残余.由于刀具与工件的接触线增加,使得尖角处铣削力增大.因此,采用了双圆弧过渡来处理型腔中的尖角,该方法能保证以尽可能大的行距走刀,缩短了加工时问,提高了加工效率,同时还可以清除尖角处的残余留量.尖角处刀具轨迹进行合理优化后,刀具沿着改进的轨迹快速运行,满足了高速铣削型腔的加工要求.最后,实验验证了该方法的有效性.     

新型AlTiN涂层钻头高效干式钻削40Cr的开发与试验

针对40cr的高效干钻削,开发了含铝质量百分比分别为40%和55%的AlTiN涂层钻头.通过刀具耐用度、加工表面质量、刀具磨损、切削变形等方面的研究,分析了不同含铝量的涂层对干钻削加工的影响.试验结果表明,AlTiN涂层钻头适合高效干钻削,并能保持良好的加工表面质量,特别是含铝量为55%的涂层,其耐用度在90 m/min的切削速度下是含铝40%涂层的1.3倍.试验还揭示了这两种涂层干钻削的磨损机理:两种AlTiN涂层都出现了氧化磨损,高含铝量的涂层在切削温度下易形成致密的氧化膜,使刀具抗高温性增加并减少涂层剥落,最终以涂层塌陷形式失效;低含铝量涂层刀具以涂层剥落、微崩刃形式失效.同时高含铝量涂层改善了加工过程中的润滑条件.     

A novel environmental control system based on membrane dehumidification

This paper conducts a simulation study of a novel aircraft environmental control system based on membrane dehumidification(MD-ECS),and compares the system with the up-to-date four-wheel high pressure de-water system(4WHPDW-ECS).Mathematical models for the two systems are established,and a system simulation using a numerical technique is performed to analyze and compare the cooling performance of the two systems.Simulation results show that the cooling capacity of MD-ECS is much higher than that of 4WHPDW-ECS under the same working conditions,indicating that the novel system is theoretically feasible and promising.The effects of the sweep ratio of the membrane dehumidifier on the dehumidification and cooling performance of the system is also investigated.     

细长体大攻角非对称流场控制

为了研究细长体大攻角非对称流态的机理以及开发新的控制技术进行了风洞实验.实验中观察到了侧向力的双稳态状态,并且它的正负指向很容易被来流中或者模型头部的微小扰动切换.连续改变滚转角时出现了迟滞回线.模型上游的扰动棒能改变侧向力的方向,当扰动棒移走后仍然可以保持该方向.根据以上观察,在模型头部安装了微型摆振片,该摆振片可以处在不同的周向位置.当摆振片静止时,迟滞回线消失,侧向力的方向不随紊流随机切换.截面侧向力的动态测量结果表明,当摆振片低频摆振时,侧向力可以跟随节奏变动.随着频率的增加,侧向力逐渐减少.当摆振频率进一步增加时,侧向力减少到零.如果摆振时,改变摆振片的平衡位置,则侧向力可以成比例的变化.根据上述实验实施,探讨了非对称现象的机理.     

A GPA diagnostic system foraeroengine applications

In this research, a GPA(Gas Path Analysis) diagnostic system enhanced with GPA Index is described for gas path sensor and component fault diagnosis.A method of measurement correction is used in order that the measurement data obtained at un-standard ambient and operating conditions can be used for diagnostic analysis.The developed diagnostic system has been implemented into a Cranfield University gas turbine performance and diagnostic analysis software PYTHIA for gas turbine performance degradation analysis.The developed method and software have been applied to a model aero gas turbine engine to test the effectiveness of the system.The analysis shows that the developed diagnostic system can diagnose degraded sensor and components effectively using performance deviation measured at un-standard ambient and operational conditions.Theoretically, the idea of the diagnostic approach can be applied to different gas turbine engines.      

Improved uncertainty propagation method of dynamic model for Mars entry spacecraft

In order to research the uncertainty propagation laws of Mars entry dynamic equations for the Mars entry phase,an improved method was presented for analyzing the effect of the initial state uncertainties and uncertainty factor on the system state in the state trajectories.When applying the method to the entry phase of one of the NASA Mars exploration missions,the simulation results agreed well with the Monte Carlo method,especially the flight path angle simulation at least reaching 92%.It is found that the improved method can not only predict the uncertainty propagation laws with high accuracy of at least 92%in flight path angle simulation and large application scope from-0.1degree to 0.1degree,compared with local linearization method,but also save several hours relative to Monte Carlo method.     

Experiments of flow and heat transfer performances for air-cooling laminated turbine vane

Flow resistance and heat transfer coefficients of typical double wall laminated film cooling configuration within a turbine vane were experimentally studied.The specimen was in large scale,and made of transparent organic glass.Laminated configuration consisted of double wall laminates,pin-fins,staggered arrays of impingement and film holes.The number ratio of impingement holes,pin-fins and film holes was2∶1∶1.Five experiment vanes were installed in static cascade,and experiments were carried out under constant heat flux.Re of internal cooling air in the experiment was from 104 to 2×105,and Re of external fluid was from 105 to 3×105.The experiment results show that flow resistances of front channel and back channel of the vane are in the same level,and both of them decrease as Re of cooling air increases.Nuof front channel is slightly higher than that of back channel.Both of them increase as Re of cooling air increases.And experiment results were obtained from experiment vanes were compared with that obtained from laminated flat plates,and the tendency of the results agrees well.     

Effect of the Interplanetary Electric Field on the Magnetopause From Global MHD Simulations

The north-south component B_z of the Interplanetary Magnetic Field (IMF) and solar wind dynamic pressure P_d are generally treated as the two main factors in the solar wind that determine the geometry of the magnetosphere. By using the 3D global MHD simulations, we investigate the effect of the Interplanetary Electric Field (IEF) on the size and shape of magnetopause quantitatively. Our numerical experiments confirm that the geometry of the magnetopause are mainly determined by P_dB_z, as expected. However, the dawn-dusk IEFs have great impact on the magnetopause erosion because of the magnetic reconnection, thus affecting the size and shape of the magnetopause. Higher solar wind speed with the same B_z will lead to bigger dawn-dusk IEFs, which means the higher reconnection rate, and then results in more magnetic flux removal from the dayside. Consequently, the dayside magnetopause moves inward and flank magnetopause moves outward.