XM908P智能仪表在超速机温度控制中的应用

XM908P智能仪表是一种新兴的技术产品。它不仅具有传统的温度检测功能,同时还具有多输出、专家PID自整定以及对温度控制具有可编程等多种功能。该仪表通过外部按钮或PLC输出接点可实现对仪表的控制、串行通信和报警等功能。通过XM908P智能仪表在超速机温度控制中的应用,简要介绍了该仪表的使用方法及参数设定。实验证明:XM908P智能仪表配合各类传感器、变送器等。

通用型机械强度超速试验机

本文介绍了一种新型机械强度超速试验机的设计方案,其中采用了挤压油膜阻尼器、柔性轴等技术,以期减小超速试验时过临界转速所引起的振动,是一次有益的探索。

用超速CT机检测99例无症状香港中国人降低钙指数

回顾分析Ｍａｔｉｌｄａ医院超速ＣＴ室筛选首批病人中９９例中国人资料，很明显从通常采用１３０－１００Ｈｏｕｎｓｆｉｅｌｄ单位作为检出冠状血管钙化的基数应用至中国人身上其阈值数目需要降低，同时，我们也发现如果病人年龄按每１０年范围分组（２１－３０，３０－４０，４１－５０，５１－６０）而计算其超速ＣＴ的钙化指数会较随机男女一起按平均计算更易区分其差异．进一步分析显示，男性中年时候超速ＣＴ指数已达最高值，而女性则晚１０年方达最高值，因此，为了更易探测冠脉循环内钙化倾向应作出超速ＣＴ检出钙化的指数数目．这些实践经验对动脉粥样硬化过程的预测或预防有实际意义．

TRANSONIC DRAG REDUCTION ON SUPERCRITICAL WING SECTION USING SHOCK CONTROL BUMPS

Two-dimensional and three-dimensional shock control contour bumps are designed for a supercritical wing section with the aim of transonic wave drag reduction. The supercritical airfoil （NASA SC （02）-0714） is selected considering the fact that most modern jet transport aircrafts that operate in the transonic flow regime （cruise at transonic speeds） employ supercritical airfoil sections. Here it is to be noted that a decrease in the transonic wave drag without loss in lift would result in an increased lift to drag ratio, which is a key range parameter that can potentially increase both the range and endurance of the aircraft. The major geometric bump parameters such as length, height and span are altered for both the two-dimensional and three-dimensional bumps in order to obtain the optimum location and shape of the bump. Once an optimum standalone three-dimensional bump is acquired, an array of bumps is manually placed spanwise of an unswept supercritical wing and analyzed under fully turbulent flow conditions. Different configurations are tested with varying three-dimensional bump spacing in order to determine the contribution of bump spacing on overall performance. The results show a 14% drag reduction and a consequent 16% lift to drag ratio rise at the design Mach number for the optimum arrangement of bumps along the wing span.

STRATEGY AND IMPLEMENTATION FOR HIGH-SPEED TORQUE ENHANCEMENT OF BRUSHLESS DC MOTOR

Serious commutation lag occurs when a Brushless DC Motor(BLDCM) operates at high speeds,and this leads to torque decline with ripple.In this paper,an advanced conduction control scheme is proposed which can accelerate the commutation and enhance the torque production remarkably.Besides,an on line adjusting algorithm based on the Golden Section Method is adopted to search the optimal advanced conduction angle.Simulation and experimental results verify the feasibility and effectivity of the scheme proposed.

Study on Lateral Aerodynamic Characteristics of Hypersonic Lifting-Configuration

To have a deep understanding of the lateral stability of hypersonic lifting-configurations, wind-tunnel tests of roll static and dynamic stability for typical hypersonic lifting-configurations are carried out. The results show the roll is static unstable in small angles; the roll dynamic test curves present obvious non-linearity characteristics, and the model vibrates violently even When the angle of attack is small, which may be provoked by the non-symmetry transition from the small transverse flow around the nose of model. Subsequent research adopts longitudinal trips to generate symmetry transition at the fore-body of the model. As a result, the lateral stability of the aircrafts is apparently improved. The results show that the lateral stability of hypersonic aircrafts is very weak, and the main reason for this is lateral perturbation of flow over the nose, among which asymmetric transition weighs the most. Adoption of longitudinal trips could spur fixed transition of lateral flow, reduce the transition asymmetry of lateral flow, and strengthen the lateral stability of hypersonic aircrafts at the same time.

Time-resolved two-photon excitation fluorescence spectroscopy and microscopy using a high repetition rate streak camera

We present a time-resolved two-photon excitation fluorescence spectroscopy and a simultaneous time- and spectrum- resolved multifocal multiphoton microscopy system that is based on a high repetition rate picosecond streak camera for providing time- and spectrum- resolved measurement and imaging in biomedicine. The performance of the system is tested and characterized by the fluorescence spectrum and lifetime analysis of several standard fluorescent dyes and their mixtures. Spectrum-resolved fluorescence lifetime images of fluorescence beads are obtained. Potential applications of the system include clinical diagnostics and cell biology etc.

Application of an Analytical Method to Locate a Mixing Plane in a Supersonic Compressor

In order to achieve greater pressure ratios, compressor designers have the opportunity to use transonic configurations. In the supersonic part of the incoming flow, shock waves appear in the front part of the blades and propagate in the upstream direction. In case of multiple blade rows, steady simulations have to impose an azimuthal averaging （mixing plane） which prevents these shock waves to extend upstream. In the present paper, several mixing plane locations are numerically tested and compared in a supersonic configuration. An analytical method is used to describe the shock pattern. It enables to take a critical look at the CFD （computational fluid dynamics） steady results. Based on this method, the shock losses are also evaluated. The good agreement between analytical and numerical values shows that this method can be useful to wisely forecast the mixing plane location and to evaluate the shift in performances due to the presence of the mixing plane.

Counterformal contacts of full toroidal continuously variable transmission

The point and the line contacts of a toroidal continuously variable transmission (CVT) are studied. The contact shapes between the roller and input and output disks are formulated by using the classical Hertz contact theory. Based on the formulated equations, different system factors affecting the maximum Hertz stress in the elliptical and strip contacts of the full toroidal CVT are explored, which include the properties of the contacting material (Young’s modulus), operating condition (pushing load) and geometrical parameters (aspect cavity ratio, aspect roller ratio). The comparative results reveal the relations between the maximum Hertz stress and the speed ratio in the form of graphs. These graphs give useful information for designer to know the maximum Hertz stress during operation in such systems.

A Study on the Structure of Linear Synchronous Motor for 600 km/h Very High Speed Train

Recently, an interest in a hybrid system combining only the merits of the conventional wheel-rail system and Maglev propulsion system is growing as an alternative to high-speed maglev train. This hybrid-type system is based on wheel-rail method, but it enables to overcome the speed limitation by adhesion because it is operated through a non-contact method using a linear motor as a propulsion system and reduce the overall construction costs by its compatibility with the conventional railway systems. Therefore, a comparative analysis on electromagnetic characteristics according to the structural combinations on the stator-mover of LSM （linear synchronous motor） for VHST （very high speed train） maintaining the conventional wheel-rail method is conducted, and the structure of coreless superconducting LSM suitable for 600 km/h VHST is finally proposed in this paper.

Recent Advances in the Theoretical and Applied Study on Compressible Turbulent Flow over Aerospace Vehicles

This paper focused on the fundamental and applied research of turbulent flows encountered in the hypersonic flight of aerospace vehicles,which take place in the boundary layer and mixing layer.As to the plate boundary layer,LES approach has been used to simulate the flows over compression corners and incident shock waves,revealing that turbulent flows would significantly inhibit the boundary layer separation caused by shock wave-boundary layer interaction(SWBLI).The boundary layer transition over a circular cone has been analyzed through stability analysis and wind-tunnel test,by which the angle-of-attack effect in case of small angle of attack has been studied.Non-linear evolution process and secondary instability structure in the supersonic mixing layer(Mc=0.5) were initially figured out through the study of mixing layer,and knowledge of the flow control mechanism of the boundary layer and mixing enhancement mechanism of the mixing layer has been obtained through this research.Artificial boundary-layer transition technique based on subharmonic resonance has been proposed and applied to the flow control in a scramjet inlet,inhibiting the flow separation of the boundary layer while improving the inlet performance.To guarantee the mixing of kerosene and supersonic airflow in the scramjet combustor,the mixing enhancement method based on subharmonic resonance has been adopted and a concept of combustor with smooth wall and low internal drag has been proposed for ignition and stable combustion.Finally,future turbulence research and technological development of aerospace vehicles is predicted.

Experimental Study of the Gas Triggered Switch's Breakdown by Optical Measurement

In this paper the main technical data of the high speed camera(HSFC-PRO),components of gas triggered switch and the primary experimental results of the breakdown of gas triggered switch using high speed camera are introduced.Four photographs totaling in 24 nanoseconds in single trigger mode manifest that the breakdown consists of two phases,which are the breakdowns of the trigger electrode with positive and negative electrode successively. This phenomenon is consist with the electric field distribution simulation result with the help of the software ANSYS. Eight photographs in double trigger mode prove that the breakdown time of the gas triggered switch is above 10.5 microseconds.The elementary results show that high speed camera is a very efficient apparatus to study the discharge characteristics.This optical measuring technique is helpful to profoundly study the breakdown of high voltage switch. More studies and experiments would be continued in future.

Lessons from Rotor 37

NASA rotor 37 was used as a ’blind’ test case for turbomachinery CFD by the Turbimachinery Com-mittee of the IGTI. The rotor is a transonic compressor with a tip speed of 454 m/s (15OO ft/s) anda relatively high pressure ratio of 2.1. It was tested in isolation with a circumferentially uniform inletflow so that the flow through it should be steady apart from any effects of passage to passage geometry variation and mechanical vibration. As such it represents the simplest possible type of test forthree-dimensional turbomachinery flow solvers. However, the rotor still presents a real challenge to3D viscous flow solvers because the shock wave-boundary layer interaction is strong and the effects ofviscosity are dominant in determining the flow deviation and hence the pressure ratio. Eleven ’blind’solutions were submitted and in addition a ’non-blind’ solution was used to prepare for the exercise-This paper reviews the fiow in the test case and the comparisons of the CFD solutions with the testdata. Lessons for both the Flow Physics in transonic has and for the application of CFD to suchmachines are pointed out.

Conceptual design and aerodynamic evaluation of hypersonic airplane with double flanking air inlets

To aim at design requirements of high lift-to-drag ratio as well as high volumetric efficiency of next generation hypersonic airplanes,a body-wing-blending configuration with double flanking air inlets layout is presented.Moreover,a novel forebody design methodology which by rotating and assembling two waverider-based surfaces is firstly introduced in this paper.Some typical configurations are designed and their aerodynamic performances are evaluated by computational fluid dynamics.The results for forebodies analysis show that large volumetric efficiency,high lift-to-drag ratio,and uniformly distributed flowfield at the inlet cross section can be assured simultaneously.Furthermore,results of numerical simulation of four integrated configurations with various leading edge shapes,including three power-law curves and a cosine curve clearly show the advantage of high lift-to-drag ratio.Besides,the high pressure generated by the side wall of the airframe can be partly captured by the reasonably designed wings in the condition of small flight attack angle.Then the order of lift-to-drag ratio of four configurations at 0 degree flight attack angle is completely different from the condition of 4-degree flight attack angle.This result demonstrates that the curve shape of the leading edge is very important for the lift-to-drag ratio of the aircraft,and it should be further optimized under the cruising attack angle in future work.

Prediction of hypersonic boundary layer transition with variable specific heat on plane flow

When an aircraft flies at a hypersonic speed,the temperature of gas inner boundary layer near the wall is so high that the specific heat is no longer a constant but dependent upon the temperature.It is necessary to consider its effect on transition location.In this paper,the transition locations of hypersonic plane boundary layer are predicted with the improved e N method,and the results of the specific heat dependent upon temperature are compared with those of constant specific heat.The flow parameters are taken as those corresponding to the condition at a height of 40 km and the Mach numbers of oncoming flow are 6,7,and 8,respectively.It is found that the transition locations calculated by the variable specific heat are closer to the leading edge than those by the constant specific heat.The deviations in most cases are around 30 percent.All the results prove that the real gas effect should be taken into consideration when one predicts transition location for hypersonic flow.Whether the first or second mode wave determines the transition location relies on the oncoming flow Mach number and the wall condition.

Drag force investigation of cavities with different geometric configurations in supersonic flow

In order to prolong the residence time of the flow retaining in the supersonic flow, wall cavity has been widely applied in the scramjet combustor, and this affects the aerodynamic surface and imposes additional drag force on the hypersonic propulsion system. The two-dimensional coupled implicit Reynolds Averaged Navier-Stokes (RANS) equations and the RNG k?ε turbulent model were employed to investigate the flow fields of cavities with different geometric configurations, namely the classical rectangular, triangular and semi-circular, and the cavities with the fixed depth and length-to-depth ratio. At the same time, the drag force performances of the cavities were estimated and compared. The obtained results show that the numerical results are in very good agreement with the experimental data, and the different scales of grid make only a slight difference from the numerical results. The intensity of the trailing shock wave is much stronger than that of the leading one, and the area around the trailing edge of the cavities plays an important role in the chemical reaction in the scramjet combustor. With the fixed depth and length-to-depth ratio, the triangular cavity can strengthen the turbulent combustion in the scramjet combustor further, but impose the most additional drag force on the scramjet engine. The classical rectangular one can impose the least additional drag force on the engine, but the function of strengthening the combustion is the weakest. The influence of the semi-circular one is the moderate, but the machining process is more complex than the other two configurations.

A hypersonic lift mechanism with decoupled lift and drag surfaces

In the present study, we propose a novel lift mechanism for which the lifting surface produces only lift. This is achieved by mounting a two-dimensional shock-shock interaction generator below the lifting surface. The shock-shock interaction theory in conjunction with a three dimensional correction and checked with computational fluid dynamics (CFD) is used to analyze the lift and drag forces as function of the geometrical parameters and inflow Mach number. Through this study, though limited to only inviscid flow, we conclude that it is possible to obtain a high lift to drag ratio by suitably arranging the shock interaction generator.

Three-dimensional nonlinear coupling guidance for hypersonic vehicle in dive phase

Three-dimensional(3D)nonlinear diving guidance strategy considering the coupling between longitudinal and lateral motions for hypersonic vehicle is investigated in this paper.It constructs the complete nonlinear coupling motion equation without any approximations based on diving relative motion relationship directly,and converts it into linear state space equation with the same relative degree by feedback linearization.With the linear equation,slide mode control with strong robustness is employed to design the guidance law,and 3D diving guidance law which can satisfy terminal impact point and falling angle constraints with high precision is obtained by substituting the previous control law into the origin nonlinear guidance system.Besides,regarding lateral overload as the standard,hybrid control strategy which can take full advantage of the excellent characters of both bank-to-turn(BTT)and skid-to-turn(STT)controls is designed to improve the guidance accuracy further.Finally,the results of CAV-H vehicle guidance test show that the algorithm can realize high accuracy guidance even if serious motion coupling exists,and has strong robustness to the path disturbances and navigation errors as well.

Progress in research on mixing techniques for transverse injection flow fields in supersonic crossflows

The transverse injection flow field has an important impact on the flowpath design of scramjet engines. At present a combination of the transverse injection scheme and any other flame holder has been widely employed in hypersonic propulsion systems to promote the mixing process between the fuel and the supersonic freestream; combustion efficiency has been improved thereby, as well as engine thrust. Research on mixing techniques for the transverse injection flow field is summarized from four aspects, namely the jet-to-crossflow pressure ratio, the geometric configuration of the injection port, the number of injection ports, and the injection angle. In conclusion, urgent investigations of mixing techniques of the transverse injection flow field are pro- posed, especiaUy data mining in the quantitative analytical results for transverse injection flow field, based on results from multi-objective design optimization theory.

Numerical exploration on jet oscillation mechanism of counterflowing jet ahead of a hypersonic lifting-body vehicle

Numerical investigation of a supersonic jet from the nose of a lifting-body vehicle opposing a hypersonic flow with the freestream Mach number being 8.0 at 40 km altitude was carried out by solving the three-dimensional, time-accurate Navier-Stokes equations with a hybrid meshes approach. Based on the analysis of the flow field structures and aerodynamic characteristics, the behaviours relevant to the LPM jet were discussed in detail, including the drag reduction effect, the periodic oscillation and the feedback loop. The obtained results show that the flow oscillation characteristic of the LPM jet is low-frequency and high-amplitude while that of the SPM jet is high-frequency and low-amplitude. Compared with the clearly dominant frequencies of the LPM jet, the SPM jet exhibits a broad-band structure. The LPM jet can sustain drag reduction effect until the angle of attack is 8°, and the lift-to-drag ratio of the vehicle is effectively improved by 6.95% at angle of attack of 6°. The self-sustained oscillation process was studied by a typical oscillating cycle of the drag force coefficient and the variation of the instantaneous pressure distribution,which reveals an off-axial flapping motion of the conical shear layer. The variation of the subsonic recirculation zone ahead of the vehicle nose strengthens the understanding of the jet behavior including the source of instability in the long penetration mode and the mechanism of the feedback loop. The aim of this paper is to advance the technology readiness level for the counterflowing jet applied as an active control technology in hypersonic flows by gaining a better insight of the flow physics.