Youth Symphony

Ayoung orchestra is very active in playing variousChinese and foreign musical compositions in thecity's big concert halls. The performers are sofamiliar with the music that they play it very well. Founded inApril,1995, the orchestraaffiliated withtheCivil Aviation Shanghai Polytechnic School once heldorchestra concerts at 2001 and 2002 Shanghai SpringInternational Music Festival as an amateurart troupe. Theirperformance was praised bymusicians and musical fans. The achievementshould bepar…     

Ningwu——An Ancient Pass On The Plateau

Ningwu situated on the Loess Plateau in north of Shanxi Province is one of the three passes along the Great Wall. The other two are the Pian Pass in the west and the Yanmen Pass in the east. In the ancient times, it had been a key military town in the northern Chinese borders.     

Performance investigation of intercooler operating in wet condition using distributed parameter model

The performance of a marine gas turbine intercooler operating in wet condition was evaluated.The intercooler was a cross-flow plate-fin heat exchanger that used air and pure water as its working fluids at the hot and cold sides,respectively.The heat transfer performance and the water vapor condensation were investigated for a relative humidity of the inlet air that reached 100% during warship cruise.The condensation of the water vapors increased the hot side outlet temperature by a certain amount,which could in turn influence the performance of the compressor downstream.The condensate film thickness and the void fraction were calculated based on an annular two-phase flow model.It is found that water vapor condensation in hot flow channel increases the outlet temperature with a maximum value of 7.3℃ in the case of 100% relative humidity.The calculated liquid film thickness reaches a maximum value of 4μm,which indicates negligible thermal resistance to heat transfer.The results of liquid film thicknesses also provide a qualitative prediction of the diameter distribution of the condensate water droplets.     

Overloading of Landing Based on the Deformation of the Lunar Lander

Along with the progress of sciences and technologies, a lot of explorations are taken in many countries or organizations in succession. Lunar, the natural satellite of the earth, become a focus of the space discovery again recently because of its abundant resource and high value in use. Lunar exploration is also one of the most important projects in China. A primary objective of the probe in lunar is to soft-land a manned spacecraft on the lunar surface. The soft-landing system is the key composition of the lunar lander. In the overall design of lunar lander, the analysis of touchdown dynamics during landing stage is an important work. The rigid-flexible coupling dynamics of a system with flexible cantilevers attached to the main lander is analyzed. The equations are derived from the subsystem method. Results show that the deformations of cantilevers have considerable effect on the overloading of the lunar lander system.     

DUTCH R&B

I have forgotten who had said: "Music has no boundary." In the Netherlands, we met with the four boys of the bandRe-Play by accident. As we talked about the "Tornado," they,who were grown up in the Netherlands, sang it in the Dutchlanguage. We felt very surprised.It was the year of 1994 when four guys from Rotterdam,the Netherlands, decided to take part in a Dutch singing contest,     

Ameco-Beijing——a big name in a booming market

Catching up with the fast development of worldeconomy,China pulled up its bamboo curtain andsponsored an even more faster revolution of economytill 1978.The cooperation with German Lufthansa isone of China’s major steps to upgrade its civil avia-tion industry.The Aircraft Maintenance＆EngineeringCo.-Beijing(Ameco-Binjing),a partnership start-ed in 1989 by Air China and German Lufthansa is thelargest and the most powerful civil aircraft mainte-nance company in China.     

Numerical analysis for the matching of the core driven compression system in a double bypass engine

The numerical analysis for the matching of the core driven compression system in a double bypass variable cycle engine was presented in this paper.The system consists of a one-stage-core driven fan stage(CDFS),an inner bypass duct and a five-stage high pressure compressor(HPC),providing two basic operating modes: the single bypass mode and the double bypass mode.Variable vanes are necessary to realize the mode switch of the system.The correct matching in the double bypass mode requires a proper combination of the mass flow,total pressure ratio and blade speed.The work capacity of the system decreases in the double bypass mode and the pressure ratio tends to decrease more for the CDFS and the front stages of the HPC.The overall system efficiency is higher in the double bypass mode.The radial distributions of aerodynamic parameters are similar in different modes.The notable redistribution of mass flow downstream the CDFS in the single bypass mode leads to strong radial flows and additional mixing losses.The absolute flow angles into the inner bypass increase for the inner span and decrease for the outer span when the system is switched from the single bypass mode to the double bypass mode.     

Variable-fidelity optimization with design space reduction

Advanced engineering systems, like aircraft, are defined by tens or even hundreds of design variables. Building an accurate surrogate model for use in such high-dimensional optimization problems is a difficult task owing to the curse of dimensionality. This paper presents a new algorithm to reduce the size of a design space to a smaller region of interest allowing a more accurate surrogate model to be generated. The framework requires a set of models of different physical or numerical fidelities. The low-fidelity (LF) model provides physics-based approximation of the high-fidelity (HF) model at a fraction of the computational cost. It is also instrumental in identifying the small region of interest in the design space that encloses the high-fidelity optimum. A surrogate model is then constructed to match the low-fidelity model to the high-fidelity model in the identified region of interest. The optimization process is managed by an update strategy to prevent convergence to false optima. The algorithm is applied on mathematical problems and a two-dimen-sional aerodynamic shape optimization problem in a variable-fidelity context. Results obtained are in excellent agreement with high-fidelity results, even with lower-fidelity flow solvers, while showing up to 39% time savings.     

Airport City——A visit to Amsterdam Schiphol Airport in the Netherlands

Gerlack J Cerfontaine, president and chief executive officer of Schiphol Group in the Netherlands, announced at the New Year's Press Conference that Amsterdam Schiphol Airport handled 42.5 million passengers in 2004, up 6.5 percent over 2003. Its cargo volume broke the record to reach 1.4 milliontons, an increase of 8.5 per cent over the previous year.The airport handled 402,700 flights, a rise of 2.5 percent.It ranked fourth in carrying passengers and third in ca…     

Topological Studies of Three-dimensional Flows in a High Pressure Compressor Stator Blade Row without and with Boundary Layer Aspiration

This paper presents a numerical study of the flow topologies of three-dimensional (3D) flows in a high pressure compressor stator blade row without and with boundary layer aspiration on the hub wall. The stator blade is representative of the first stage operating under transonic inlet conditions and the blade design encourages development of highly complex 3D flows. The blade has a small tip clearance. The computational fluid dynamics (CFD) studies show progressive increase of hub corner stall with the increase in incidence. Aspiration is implemented on the hub wall via a slot in the corner between the hub wall and the suction surface. The CFD studies show aspiration to be sensitive to the suction flow rate; lower rate leads to very complex flow structures and increased level of losses whereas higher rate renders aspiration effective for control of hub corner separation. The flow topologies are studied by trace of skin friction lines on the walls. The nature of flow can be explained by the topological rules of closed separation. Furthermore, a deeper analysis is done for a particular case with advanced criterion to test the non-degeneracy of critical points in the flow field.     

Investigation on the Hydro-forming of SUS304 Stainless Steel Dome

The dome hydro-forming was studied theoretically and experimentally. The theoretical analysis shows that the process of dome hydro-forming can be divided into two stages, i.e., firstly forming a hemi-sphere and secondly forming a hemi-toroidal. Theoretically, being larger than those in the outer area of a hemi-toroidal shell, the radial tensile stresses take place in the inner area where fracture is more likely to occur in the forming process. The required hydraulic pressure to form the dome should be determined by the deformation in the outer area, hitting about 12 MPa in theory. The experimental results show that the dome could be produced in one operation by hydro-forming which needs a hydraulic pressure of about 9 MPa. The experimental results prove to agree well with the theoretical analysis. In order to avoid wrinkling and fracture, the closing force acted on the die should be adjusted properly in accordance with the hydraulic pressure.     

Reliability Analysis of Aircraft Condition Monitoring Network Using an Enhanced BDD Algorithm

The aircraft condition monitoring network is responsible for collecting the status of each component in aircraft. The reliability of this network has a significant effect on safety of the aircraft. The aircraft condition monitoring network works in a real-time manner that all the data should be transmitted within the deadline to ensure that the control center makes proper decision in time. Only the connectedness between the source node and destination cannot guarantee the data to be transmitted in time. In this paper, we take the time deadline into account and build the task-based reliability model. The binary decision diagram (BDD), which has the merit of efficiency in computing and storage space, is introduced when calculating the reliability of the network and addressing the essential variable. A case is analyzed using the algorithm proposed in this paper. The experimental results show that our method is efficient and proper for the reliability analysis of the real-time network.     

Detailed modeling of aluminum particle combustion——From single particles to cloud combustion in Bunsen flames

A numerical model for aluminum cloud combustion which includes the effects of interphase heat transfer, phase change, heterogeneous surface reactions, homogeneous combustion,oxide cap growth and radiation within the Euler–Lagrange framework is proposed. The model is validated in single particle configurations with varying particle diameters. The combustion process of a single aluminum particle is analyzed in detail and the particle consumption rates as well as the heat release rates due to the v...     

Robust Control for Static Loading of Electro-hydraulic Load Simulator with Friction Compensation

Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness test of aircraft actuation systems. The tracking performance of the static loading is studied in this paper. Firstly, the nonlinear mathematical models of the hydraulic load simulator are derived, and the feedback linearization method is employed to construct a feed-forward controller to improve the force tracking performance. Considering the effect of the friction, a LuGre model based friction compensation is synthesized, in which the unmeasurable state is estimated by a dual state observer via a controlled learning mechanism to guarantee that the estimation is bounded. The modeling errors are attenuated by a well-designed robust controller with a control accuracy measured by a design parameter. Employing the dual state observer is to capture the different effects of the unmeasured state and hence can improve the friction compensation accuracy. The tracking performance is summarized by a derived theorem. Experimental results are also obtained to verify the high performance nature of the proposed control strategy.     

Time-domain modeling of a cutter exiting a workpiece in the slot milling process

In a milling operation, there must be processes of a cutter entering and exiting the work-piece boundary. The cutter exit is usually in the feed direction and the dynamic response is different from that in the normal cutting process. This paper presents a new time-domain modeling of mechanics and dynamics of the cutter exit process for the slot milling process. The cutter is assumed to exit the workpiece for the first time with one tooth right in the feed direction. The dynamic chip thickness is summed up along the feed direction and compared with the remaining workpiece length in the feed direction to judge whether the cutter is ready to exit the workpiece or not. The developed model is then used for analyzing the cutting force and machining vibration in the cutter exit process. The developed mathematical model is experimentally validated by comparing the simulated forces and vibrations against the measured data collected from real slotting milling tests. The study shows that stable cutting parameters cannot guarantee stable cutting in a cutter exit process and further study can be performed to control the vibration amplitude in this specific process.     

Modeling and Backstepping-based Nonlinear Control Strategy for a 6 DOF Quadrotor Helicopter

In this article, a nonlinear model of an underactuated six degrees of freedom （6 DOF） quadrotor helicopter is derived on the basis of the Newton-Euler formalism. The derivation comprises determining equations of the motion of the quadrotor in three dimensions and approximating the actuation forces through the modeling of aerodynamic coefficients and electric motor dynamics. The derived model composed of translational and rotational subsystems is dynamically unstable, so a sequential nonlinear control strategy is used. The control strategy includes feedback linearization coupled with a PD controller for the translational subsystem and a backstepping-based PID nonlinear controller for the rotational subsystem of the quadrotor. The performances of the nonlinear control method are evaluated by nonlinear simulation and the results demonstrate the effectiveness of the proposed control strategy for the quadrotor helicopter in quasi-stationary flights.     

An experimental system for release simulation of internal stores in a supersonic wind tunnel

Aerodynamic parameters obtained from separation experiments of internal stores in a wind tunnel are significant in aircraft designs. Accurate wind tunnel tests can help to improve the release stability of the stores and in-flight safety of the aircrafts in supersonic environments.A simulative system for free drop experiments of internal stores based on a practical project is provided in this paper. The system contains a store release mechanism, a control system and an attitude measurement system. The release mechanism adopts a six-bar linkage driven by a cylinder, which ensures the release stability. The structure and initial aerodynamic parameters of the stores are also designed and adjusted. A high speed vision measurement system for high speed rolling targets is utilized to measure the pose parameters of the internal store models and an optimizing method for the coordinates of markers is presented based on a priori model. The experimental results show excellent repeatability of the system, and indicate that the position measurement precision is less than0.13 mm, and the attitude measurement precision for pitch and yaw angles is less than 0.126°, satisfying the requirements of practical wind tunnel tests. A separation experiment for the internal stores is also conducted in the FL-3 wind tunnel of China Aerodynamics Research Institute.     

SEPARATED FLOW AROUND BENT-NOSE BICONIC IN HYPERSONIC FLOW

This article investigates the separated flow around the bent-nose biconic, in which the second ordered TVD(Total Variation Diminishing) method is applied. The governing cqua-tion is a thin layer Navier-Stokes equation. The surface pressure distribution at the leeward side is a little higher in the vicinity of the symmetrical plane. This seems to be caused by the development of the vortex at the leeward side due to the separated flow. The location of a separation line and the size are in very good agreement with the experiment. Also the secondary separation is captured very clearly.     

Aeroelastic effect on aerothermoacoustic response of metallic panels in supersonic flow

A finite element formulation is presented for the analysis of the aeroelastic effect on the aerothermoacoustic response of metallic panels in supersonic flow. The first-order shear deforma-tion theory (FSDT) and the von Karman nonlinear strain-displacement relationships are employed to consider the geometric nonlinearity induced by large deflections. The piston theory and the Gaus-sian white noise are used to simulate the mean flow aerodynamics and the turbulence from the boundary layer. The thermal loading is assumed to be steady and uniformly distributed, and the material properties are assumed to be temperature independent. The governing equations of motion are firstly formulated in structural node degrees of freedom by using the principle of virtual work, and then transformed and reduced to a set of coupled nonlinear Duffing oscillators in modal coor-dinates. The dynamic response of a panel is obtained by the Runge-Kutta integration method. The results indicate that the increasing aeroelastic effect can lead the panel vibration from a random motion to a highly ordered motion in the fashion of diffused limit cycle oscillations (LCOs), and remarkably alter the stochastic bifurcation and the spectrum of the aerothermoacoustic response. On the other hand there exists a counterbalance mechanism between the external random loading and the aeroelastic effect, which mainly functions through the nonlinear frequency-amplitude response. It is surmised that the aeroelastic effect must be considered in sonic fatigue analysis for panel structures in supersonic flow.     

Effects of splined shaft bending rigidity on cylinder tilt behaviour for high-speed electro-hydrostatic actuator pumps

High-speed axial piston pumps are hydraulic power supplies for electro-hydrostatic actuators(EHAs). The efficiency of a pump directly affects the operating performance of an EHA, and an understanding of the physical phenomena occurring in the cylinder/valve plate interface is essential to investigate energy dissipation. The effects of the splined shaft bending rigidity on the cylinder tilt behaviour in an EHA pump need to be considered, because the deflection and radial expansion of a steel shaft rotating at a high speed cannot be ignored. This paper proposes a new mathematical model to predict the cylinder tilt behaviour by establishing a quantitative relationship between the splined shaft deflection, the cylinder tilt angle, and the tilt azimuth angle. The moments exerted by the splined shaft are included in the equilibrium equation of the cylinder. The effects of solid and hollow splined shafts equipped in an EHA pump prototype are compared at variable speeds of 5000–10,000 r/min. With a weight saving of 29.7%, the hollow shaft is experimentally found to have almost no influence on the volumetric efficiency, but to reduce the mechanical efficiency by 0.6–2.4%. The results agree with the trivial differences of the simulated central gap heights of the interface between the two shafts and the enlargement of the simulated tilt angles by the hollow shaft. The findings could guide designs of the cylinder/valve plate interface and the splined shaft to improve both the efficiency and power density of an EHA pump.