基于速度分布法的离心通风机叶片结构优化分析

叶片的结构形式对离心通风机运行中的能量利用率具有重要的影响,采用速度分步法对叶片的结构形式进行优化设计,并对优化后的通风机性能进行分析。结果表明,采用速度分步法优化的叶片中以模型C的通风机性能最佳,其在减小通风机能量损失的同时,可提高通风机在额定工况及小流量工况下的性能。

GDI喷油器喷雾碰壁的基础试验研究

为了研究直喷汽油机喷雾碰壁可能导致的机油稀释与碳烟排放增加问题，对某款直喷汽油机喷油器进行改造，使用相位多普勒激光测试系统（phase Doppler analyzer， PDA）研究了不同壁面条件下，近壁面处喷雾液滴的粒径分布与法向速度分布特点。研究结果表明：碰壁过程对距壁面较近的液滴径向发展有显著影响，自由喷雾表现为由轴线向外液滴特征粒径减小，而喷雾碰壁则为增大趋势；壁面温度对液滴粒径概率分布和法向速度分布影响显著，壁面加热条件下粒径集中于10 μm范围内，而绝大多数液滴法向速度趋近于0；壁面干湿条件的影响主要表现在粒径概率分布、特征粒径径向发展和法向速度分布，粒径概率分布形态产生变化，特征粒径径向发展呈现为由轴线向外先减小后略有增大的趋势，法向速度在10~30 m/s范围内的液滴数量明显减小。此外，碰壁位置是影响液滴分布的关键因素，碰壁位置距喷嘴越远，液滴粒径分布越趋向均匀。

不同叶片结构的离心通风机性能对比研究

基于通风机整体运行效率不高的问题,采用速度分布法及载荷分布法两种设计方法对离心通风机的叶片结构进行优化设计,并采用有限元仿真的形式对优化后的通风机性能进行仿真分析。结果表明,由速度分布法设.计的叶片结构对通风机的运行效率及安全性能具有较大的提升,可作为离心通风机优化设计的首选方法。

An algorithm for moving target detection in IR image based on grayscale distribution and kernel function

A fast algorithm based on the grayscale distribution of infrared target and the weighted kernel function was proposed for the moving target detection(MTD) in dynamic scene of image series. This algorithm is used to deal with issues like the large computational complexity, the fluctuation of grayscale, and the noise in infrared images. Four characteristic points were selected by analyzing the grayscale distribution in infrared image, of which the series was quickly matched with an affine transformation model. The image was then divided into 32×32 squares and the gray-weighted kernel(GWK) for each square was calculated. At last, the MTD was carried out according to the variation of the four GWKs. The results indicate that the MTD can be achieved in real time using the algorithm with the fluctuations of grayscale and noise can be effectively suppressed. The detection probability is greater than 90% with the false alarm rate lower than 5% when the calculation time is less than 40 ms.

Failure mechanism of large-diameter shield tunnels and its effects on ground surface settlements

A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism.Furthermore,the shape of blocks between the failure surface and the tunnel face was considered as an entire circle,and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth.The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.

A DYNAMICAL INTERPRETATION OF THE WIND FIELD IN TROPICAL CYCLONES

Based on the primitive equations in polar coordinates and with the supposition that parcel velocity in tropical cyclones is in linear variation and that the distribution of surface pressure agrees with the Fujita formula, a set of equations are derived, which describe the impact of perturbations of central pressure, position of tropical cyclones, direction and velocity of movement of tropical cyclones on the wind field. It is proved that the second order approximation of the kinetic energy of tropical cyclones can be described by the equations under linear approximation. Typhoon Wipha (2007) is selected to verify the above interpretation method, and the results show that the interpretation method of the wind field could give very good results before the landfall of tropical cyclones, while making no apparent improvement after the landfall. The dynamical interpretation method in this paper is applicable to improving the forecasts of the wind field of tropical cyclones close to the coast.

A calculation method for low dynamic vehicle velocity based on fusion of optical flow and feature point matching

Aming at the problem of the low accuracy of low dynamic vehicle velocity under the environment of uneven distribution of light intensity,an improved adaptive Kalman filter method for the velocity error estimate by the fusion of optical flow tracking and scale mvaiant feature transform(SIFT)is proposed.The algorithm introduces anonlinear fuzzy membership function and the filter residual for the noise covariance matrix in the adaptive adjustment process.In the process of calculating the velocity of the vehicle,the tracking and matching of the inter-frame displacement a d the vehicle velocity calculation a e carried out by using the optical fow tracing and the SIF'T methods,respectively.Meanwhile,the velocity difference between theoutputs of thesetwo methods is used as the observation of the improved adaptive Kalman filter.Finally,the velocity calculated by the optical fow method is corrected by using the velocity error estimate of the output of the modified adaptive Kalman filter.The results of semi-physical experiments show that the maximum velocityeror of the fusion algorithm is decreased by29%than that of the optical fow method,and the computation time is reduced by80%compared with the SIFT method.

Particle Paths of Lagrangian Velocity Distribution Simulating Yin-Yang Balance in Ancient Tai-Chi Diagram

The particle paths of the Lagrangian flow field simulate very well the interface curve of the Yin-Yang balance in the ancient Tal-Chi diagram. There are four forms called the ＂four states＂ in the Tai-Chi diagram. Of the four states, under Yang are the Major Yang and the Minor Yin, and under Yin are the Major Yin and the Minor Yang. The present study provides the proper positions of the four states in the ancient Tal-Chi diagram. The Fu Xi＇s Eight Trigrams Chart located along the ancient Tai-Chi diagram is also developed in the present study. The interface curve of Yin-Yang in the ancient Tai-Chi diagram has never been described mathematically. It can now be formulated by the equations describing the particle paths in the Lagrangian flow field.

Sound speed profile inversion using a horizontal line array in shallow water

It is better to use a simple configuration to enhance the matched-field inversion method based on a horizontal line applicability of ocean environment inversion in shallow water. A array （HLA） is used to retrieve the variation of sound speed profile. The performance of the inversion method is verified in the South China Sea in June, 2010. An HLA laid at bottom was used to receive signals from a bottom-mounted transducer. Inverted mean sound speed profiles from 9-hour long acoustic signals are in good agreement with measurements from two temperature chains at the sites of the source and receiver. The results show that an HLA can be used to monitor the variability of shallow-water sound speed profile.

Convergence proof of the DSMC method and the Gas-Kinetic Unified Algorithm for the Boltzmann equation

This paper investigates the convergence proof of the Direct Simulation Monte Carlo(DSMC) method and the Gas-Kinetic Unified Algorithm in simulating the Boltzmann equation.It can be shown that the particle velocity distribution function obtained by the DSMC method converges to a modified form of the Boltzmann equation,which is the equation of the gas-kinetic unified algorithm to directly solve the molecular velocity distribution function.Their convergence is derived through mathematical treatment.The collision frequency is presented using various molecular models and the local equilibrium distribution function is obtained by Enskog expansion using the converged equation of the DSMC method.These two expressions agree with those used in the unified algorithm.Numerical validation of the converging consistency between these two approaches is illustrated by simulating the pressure driven Poiseuille flow in the slip transition flow regime and the two-dimensional and three-dimensional flows around a circular cylinder and spherical-cone reentry body covering the whole flow regimes from low speed micro-channel flow to high speed non-equilibrium aerothermodynamics.