Solution of idle LBO problem for high FAR aero combustor

The paper sheds light on the idle lean blow off(LBO)problem for high fuel air ratio(FAR)com⁃bustor,which is impossible to be addressed with traditional aero combustor design.A significant improvement in aero combustor design is required to resolve the idle LBO issue.The authors detailed a practical and efficient solu⁃tion,which not only solved the idle LBO issue but also defined the aero-thermal design for high-FAR combustor.The design will usher in a new era of aero combustor.

Parameters Sensitivity Characteristics of Highly Integrated Valve-Controlled Cylinder Force Control System

Nowadays, a highly integrated valve?controlled cylinder(HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high?performance robot control, the hydraulic force system still has problems, such as strong nonlinearity, and time?varying parameters. This makes HIVC force control very diffcult and complex. How to improve the control performance of the HIVC force control system and find the influence rule of the system parameters on the control performance is very significant. Firstly, the mathematical model of HIVC force control system is established. Then the mathematical expression for parameter sensitivity matrix is obtained by applying matrix sensitivity analysis(PSM). Then, aimed at the sinusoidal response under(three factors and three levels) working conditions, the simulation and the experiment are conducted. While the error between the simulation and experiment can’t be avoided. Therefore, combined with the range analysis, the error in the two performance indexes of sinusoidal response under the whole working condition is analyzed. Besides, the sensitivity variation pattern for each system parameter under the whole working condition is figured out. Then the two sensitivity indexes for the three system parameters, which are supply pressure, proportional gain and initial displacement of piston, are proved experimentally. The proposed method significantly reveals the sensitivity characteristics of HIVC force control system, which can make the contribution to improve the control performance.

Unsteady Numerical Simulation of Flow around 2-D Circular Cylinder for High Reynolds Numbers

In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×104〈Re〈1.54×106. The calculations were performed by means of solving the 2-D Unsteady Reynolds-Averaged Navier-Stokes （URANS） equations with a k-ε turbulence model. The calculated results, produced flow structure drag and lift coefficients, as well as Strouhal numbers. The findings were in good agreement with previous published data, which also supplied us with a good understanding of the flow across cylinders of different high Reynolds numbers. Meanwhile, an effective measure was presented to control the lift force on a cylinder, which points the way to decrease the vortex induced vibration of marine structure in future.

Control of mean and fluctuating forces on a circular cylinder at high Reynolds numbers

A narrow strip is used to control mean and fluctuating forces on a circular cylinder at Reynolds numbers from 2.0 ×10^4 to 1.0 ×^ 10^5. The axes of the strip and cylinder are parallel. The control parameters are strip width ratio and strip position characterized by angle of attack and distance from the cylinder. Wind tunnel tests show that the vortex shedding from both sides of the cylinder can be suppressed, and mean drag and fluctuating lift on the cylinder can be reduced if the strip is installed in an effective zone downstream of the cylinder. A phenomenon of mono-side vortex shedding is found. The strip-induced local changes of velocity profiles in the near wake of the cylinder are measured, and the relation between base suction and peak value in the power spectrum of fluctuating lift is studied. The control mechanism is then discussed from different points of view.

Transportation-cyber-physical-systems-oriented engine cylinder pressure estimation using high gain observer

In transportation cyber-physical-systems （T-CPS）, vehicle-to-vehicle （V2V） communications play an important role in the coordination between individual vehicles as well as between vehicles and the roadside infrastructures, and engine cylinder pressure is significant for engine diagnosis on-line and torque control within the information exchange process under V2V communications. However, the parametric uncertainties caused from measurement noise in T-CPS lead to the dynamic performance deterioration of the engine cylinder pressure estimation. Considering the high accuracy requirement under V2V communications, a high gain observer based on the engine dynamic model is designed to improve the accuracy of pressure estimation. Then, the analyses about convergence, converge speed and stability of the corresponding error model are conducted using the Laplace and Lyapunov method. Finally, results from combination of Simulink with GT- Power based numerical experiments and comparisons demonstrate the effectiveness of the proposed approach with respect to robustness and accuracy.

Grain boundary effects on spall behavior of high purity copper cylinder under sweeping detonation

A series of sweeping detonation experiments were conducted to study the grain boundary effects during the primary spallation of high-purity copper cylinder.The free surface velocity profile of the shocked samples was measured by Doppler pins systems.The soft-recovered samples were characterized by optical and electron backscatter diffraction microscopy,and the effects of microstructures like grain boundaries,and crystal orientation on spall behavior were investigated.The results indicated that the critical stress of deformation twinning in cylindrical copper increased.The nucleation sites of spallation damage were determined by the joint influence of the grain orientation(Taylor factor)and the angle between grain boundaries and radial impact-stress direction.Voids were prone to nucleating at the grain boundaries perpendicular to the radial impact-stress direction.Nevertheless,the number of voids nucleated at boundaries was relatively different from the results obtained from the plate impact experiment and plate sweeping detonation experiment,which is a result of the curvature that existed in the cylindrical copper and the obliquity of the impact-stress direction during sweeping detonation loading.

Safety estimation of high-pressure hydraulic cylinder using FSI method

Hydraulic cylinder is a primary component of the hydraulic valve systems.The numerical study of hydraulic cylinder to evaluate the stress analysis,the life assessment and the performance of operation characteristics in hydraulic cylinder were described.The calculation of safety factor,fatigue life,piston chamber pressure,rod chamber pressure and the change of velocity of piston with flow time after the beginning of hydraulic cylinder were incorporated.Numerical analysis was performed using the commercial CFD code,ANSYS with unsteady,dynamic mesh model,two-way FSI(fluid-structure interaction)method and k-εturbulent model.The internal pressure in hydraulic cylinder through stress analysis show higher than those of the yield strength.

NUMERICAL SIMULATION OF UNSTEADY FLOW AROUND A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS

A Lagrangian-Eulerian hybrid scheme to solve unsteady N-S equation in two-dimensional incompressible fluid at high Reynolds numbers is presented in this paper. A random walk is imposed to simulate the viscous diffusion, the vortex-in-cell method is used to obtain the convection velocity, and nascent vortices are created on a cylinder to satisfy the zero-slip condition. The impulsively started flow around a circular cylinder and the separation induced by a pair of incident vortices symmetrically approaching a circular cylinder have been successfully simulated by the hybrid scheme. The impulsively started flow from rest has been computed at Reynolds numbers 3000 and 9500. Comparisons are made with those results of finite-difference method, vortex method and flow visualization. Agreement is good. The particular attention has been paid to the evolutions of flow pattern. A topological analysis has been proposed in the region of the near wake. The bulge, isolated secondary vortex, a pair of secondary vortices, ' forewake phenomenon and other patterns are simulated numerically. The separation induced by a pair of incident vortices approaching a circular cylinder has been investigated by using the same scheme. The rebounding phenomenon of the incident vortex is observed and is attributed to the effect of the secondary vortex. In particular, we have found that a tertiary vortex can be formed near the surface; this phenomenon has been verified by flow visualization reported recently.

Numerical Simulation of High-Speed Water Entry of Cone-Cylinder

Numerical method by solving Reynolds-averaged Navier-Stokes equations is presented to solve the vertical high-speed water entry problem of a cone-cylinder. The results of the trajectory and cavity shape agree well with the results obtained by the analytical model from literatures. The velocity of the projectile decays rapidly during the penetration,which is about 90% losing in 80D penetration depth. Pressure distributions are also discussed and the results show that the largest pressure appears on the tip of the cone and the lowest pressure occurs inside the cavity and causes vapor generation. For inside the cavity,there is always a supplement of air from outside before the splash closed,after that,the cavity is mainly filled with vapor.

Friction Wearing Properties Research of High-silicon Aluminium Alloy Cylinder Sleeve

With tank special purpose lubricating oil,100N,200N and 800N loading force and different loading times,spray-formed high-silicon aluminium alloy and military superpower engine steel cylinder sleeve materials were used for comparative friction test and friction pair comparision test under simulated engine work condition.The results showed that,compared with steel cylinder sleeve materials,high-silicon aluminium alloy showed more excellent wearing resistance.The friction mechanism analysis of high-silicon aluminium alloy indicated that high-hardness particles in soft parent metal had determinative function,including wearing resistance and supporting ability when wearing happened.Dents on soft parent metal surface produced by friction could store oil and were helpful for lubrication.The friction trace analysis showed that,high-hardness particles in high-silicon aluminium alloy could produce friction trace on 42MnCr52 steel surface,which proved friction function of high-hardness particles in high-silicon aluminium alloy.

Piston-Cylinder高温高压实验装置及在壳幔动力学研究中的应用

介绍了目前在国际壳幔作用及动力学研究中普遍使用的Piston-Cylinder高温高压实验技术的主要工作原理、结构、样品装置设计及主要技术指标。通过分析Piston-Cylinder高温高压实验技术在大洋和大陆板块俯冲深部过程的流体活动、基性岩石部分熔融作用、岩浆活动机制及约束条件等壳幔相互作用研究中的应用实例,认为引进该项实验技术对于我国科技工作者开展高温高压条件下壳幔动力学研究以及缩短我国实验岩石学技术手段与国际间的差距具有重要意义。

Fully Nonlinear Simulations of Wave Resonance by An Array of Cylinders in Vertical Motions

The finite element method （FEM） is employed to analyze the resonant oscillations of the liquid confined within multiple or an array of floating bodies with fully nonlinear boundary conditions on the free surface and the body surface in two dimensions. The velocity potentials at each time step are obtained through the FEM with 8-node quadratic shape functions. The finite element linear system is solved by the conjugate gradient （CG） method with a symmetric successive overelaxlation （SSOR） preconditioner. The waves at the open boundary are absorbed by the combination of the damping zone method and the Sommerfeld-Orlanski equation. Numerical examples are given by an array of floating wedge- shaped cylinders and rectangular cylinders. Results are provided for heave motions including wave elevations, profiles and hydrodynamic forces. Comparisons are made in several cases with the results obtained from the second order solution in the time domain. It is found that the wave amplitude in the middle region of the array is larger than those in other places, and the hydrodynamic force on a cylinder increases with the cylinder closing to the middle of the array.

Large eddy simulation of a vortex ring impinging on a three-dimensional circular cylinder

Abstract A vortex ring impacting a three-dimensional circular cylinder is studied using large eddy simulation （LES） for a Reynolds number Re = 4 × 10^4 based on the initial translation speed and diameter of the vortex ring. We have investigated the evolution of vortical structures and identified three typical evolution phases. When the primary vortex closely approaches to the cylinder, a secondary vortex is generated and its segment parts move inward to the primary vortex ring. Then two large-scale loop-like vortices are formed to evolve in opposite directions. Thirdly, the two loop-like vortices collide with each other to form complicated small-scale vortical structures. Moreover, a series of hair-pin vortices are generated due to the stretching and deformation of the tertiary vortex. The trajectories of vortical structures and the relevant evolution speeds are analyzed. The total kinetic energy and enstrophy are investigated to reveal their properties relevant to the three evolution phases.

A UTD SOLUTION FOR THE RADIATED FIELD FROM MONOPOLE ON A CONDUCTING CYLINDER SURFACE WITH A DIELECTRIC COATING

A can0nical problem is investigated for high frequency electromagnetic radiation from amonopo1e on a conducting cylinder with c0ating-At first, the exact solution of this problem is given interms of Dyadic Green's function method. Then, using Watson transformation and high frequency asymptotic approximate technique to the exact soluton, a UTD soultion is obtained. The radiation field excitedby a monopole is expressed in terms of the compound Fock' S functions (CFF), which reduce to the geomertrical optics result in the deep lit region and the creeping waves in the shadow region.

基于ENVI/IDL的高分遥感数据自动预处理及植被提取方法:以湖南林业为例

随着我国高分对地观测系统的逐步完善,面向林业领域的国产高分遥感数据的应用需求也越来越大.本文提出一种基于ENVI/IDL的高分光学遥感数据自动预处理及植被提取方法,通过快速大气校正(QUAC)、RPC正射校正、GS图像融合和图像配准等步骤,实现高分数据自动预处理,一定程度上解决了林业应用中前期预处理耗时长及过程繁琐的问题.通过进一步提取植被覆盖区域,可为湖南省林业调查人员提供高质量卫星遥感影像.在湖南省郴州市和常德市的高分二号遥感数据上进行的实验验证结果表明,所提方法进行高分遥感数据的自动预处理以及植被提取时性能较好,且处理时长稳定,可以满足实际需求.

Research on testing method of resin sand high temperature compressive strength

High temperature compressive strength is one of the most important performances of resin sand; its value directly concerns the quality of castings. In order to seek the best testing method of resin sand high temperature compressive strength, a self-developed instrument was used to carry out experiments, and the sample shape and size were designed and studied. The results show that a hollow cylinder sample can reflect the strength difference of different resin sands better than a solid cylinder sample, and its data is stable. The experiments selected φ20/5×30 mm as the size of the hollow cylinder samples. The high temperature compressive strengths of phenol-formaldehyde resin coated sand, furan resin self-setting sand, and TEA resin sand were each tested. For the resin sand used for cast steel and cast iron, 1,000 ℃ was selected as the test temperature; for the resin sand used for cast non-ferrous alloy, 800 ℃ was selected as the test temperature; and for all the resin sand samples, 1 min was selected as the holding time. This testing method can truthfully reflect the high temperature performance of three kinds of resin sand; it is reproducible, and the variation coefficients of test values are under 10%.

Numerical simulation and experimental verification of a novel double-layered split die for high-pressure apparatus used for synthesizing superhard materials

Based on the principles of massive support and lateral support, a novel double-layered split die(DLSD) for high-pressure apparatus was designed to achieve a higher pressure-bearing capacity and larger sample cavity. The stress distributions of the DLSDs with different numbers of divided blocks were investigated by the finite element method and compared with the stress distributions of the conventional belt-type die(BTD). The results show that the cylinders and first-layer supporting rings of the DLSDs have dramatically smaller stresses than those of the BTD. In addition, increasing the number of divided blocks from 4 to 10 gradually increases the stress of the cylinder but has minimal influence on the stress of the supporting rings. The pressure-bearing capacities of the DLSDs with different numbers of divided blocks, especially with fewer blocks, are all remarkably higher than the pressure-bearing capacity of the BTD. The contrast experiments were also carried out to verify the simulated results. It is concluded that the pressure-bearing capacities of the DLSDs with 4 and 8 divided blocks are 1.58 and 1.45 times greater than that of the BTD. This work is rewarding for the commercial synthesis of high-quality, large-sized superhard materials using a double-layered split high-pressure die.

Z-High连轧机窜辊缸底座优化的研究及应用

针对RAP线Z-High连轧机原设计的本身缺陷而造成五个机架出现窜辊缸底座螺丝断裂、影响设备稳定运行、轧制功能精度严重不足、引发大量不合卷及长时间故障停车的问题。通过对机架窜辊缸底座结构进行优化改进,利用在线加工技术,对薄弱部位进行优化处理,彻底解决了螺丝断裂的问题,极大地保证了机组的稳定运行。

高性能液压缸数智化设计与制造平台的构建与应用

高性能液压缸的生产工艺柔性大,加工周期长,其生产属于典型的非标、单件小批量离散型制造模式,在设计和生产中难以优化和控制。针对液压缸生产企业在使用数字化设计和流程管控软件时软件集成度低和耦合度高的问题,设计了一种高性能液压缸数智化设计与制造平台。通过可重构中间件技术,该平台集成了AutoCAD、SolidWorks等软件接口,并在融合神经网络算法和多目标优化技术的同时,构建了图库、工时预测、柔性工艺规划等数字化设计和生产管控模块。该数智化设计与制造平台可以实现设计与制造过程的全生命周期管控,为制造企业实现数智化转型提供有力支撑。

地铁气体灭火系统气瓶微变形监测技术研究

市场上使用的部分消防气瓶已远超年限,存在潜在的安全隐患,容易发生气瓶爆炸事故。因此,为保障消防气瓶安全,研究开发了以检测消防气瓶微变形为基础的安全监测技术,采取在气瓶表面缠绕线型传感器的方法检测变形。通过气瓶爆破试验,验证了该技术可有效探测高压气瓶的微变形,并利用以太网将信息传输至大数据平台集中管理,实现主动监管功能。