汽车空调用铝合金超薄多孔扁管生产技术

以20×2mm规格汽车空调用多孔扁管为例,详细介绍了超薄多孔扁管单孔模具的三种设计方案及配套挤压工艺技术,通过研制结果比较分析,确定了适合超薄多孔扁管单孔模具的设计方案,为今后超薄多孔扁管多孔模具积累了经验。

Simulation of porous medium engine using a detailed chemical kinetics model

The Senkin code of package is used to simulate the the Chemkin chemical kinetics combustion process of a porous medium（PM） engine fueled by n-heptane. The code is modified to incorporate the Woschni heat transfer correlation and heat transfer model within a porous medium. A detailed chemistry mechanism of NOx formation is coupled with the detailed chemical kinetics mechanism of n-heptane. The code is applied to a zero- dimensional single-zone model of engine combustion. Influences of operating parameters on the performance of the PM engine are discussed. With the increase in the intake temperature and compression ratio, or with the decrease of the excess air ratio, the ignition timing of the PM engine obviously advances. It is found that the porous medium acting as a heat recuperator can considerably preheat the fuel-air mixture, which promotes the ignition and combustion in the cylinder. And the initial PM temperature is a critical factor controlling the compression ignition of the mixture.

Investigation of Mode and Modulation Responses in Semiconductor PS-DFB Lasers:Use of a Vector-Newton Method

A numerical model for steady state analysis and analytical expressions for the AM and FM modulation responses of DFB lasers are presented.The small signal modulation responses of 3 phase shift(PS) DFB is investigated for the first time.A new method(Vector Newton method) to obtain multiple longitudinal mode of DFB lasers is used.It is demonstrated that this method is suitable for obtaining multiple solution of high nonlinear equations.Longitudinal photon density distribution and multiple longitudinal mode of 3PS DFB and simple DFB lasers are analyzed.The results show that modulation response characteristics of 3PS DFB laser is as good as that of DFB,and PS can weaken the longitudinal spatial hole burning (LHSB) effect and is in favor of single longitudinal mode operating of lasers.

Simulation of the pore size distribution function for a deformable soil

In order to obtain an indirect estimation method of the pore size distribution function(PSDF)for a deformable soil,both the soil-water characteristic curve in the form of gravimetric water content(w-SWCC)and the shrinkage curve(SC)are used as the input parameters.The w-SWCC defines the relationship between the gravimetric water content and soil suction.The SC illustrates the variation of the void ratio with respect to different water contents.10 points in the w-SWCC were selected as initial conditions.By adopting different void ratios,a group of soil-water characteristic curve in the form of the degree of saturation(S-SWCC)can be obtained.Based on Kelvin's capillary law,the S-SWCCs can be converted into a group of PSDFs.In the group of PSDFs,each PSDF represents the geometric pore space in soil corresponding to a given void ratio.From the proposed methodology,it is observed that a bimodal PSDF can be gradually changed into a unimodal PSDF when the soil is compressed.The Chataignier clay is selected as the verification and it shows that the simulation results agree well with the measured results from the mercury intrusion porosimetry(MIP)test.In addition,the discrepancies between both direct measurement data using the MIP test and the indirect estimated results from the proposed method are also discussed.

Effects of porosity on tensile mechanical properties of porous FeAl intermetallics

Uniaxial tensile tests and scanning electron microscopy(SEM)experiments were carried out on the porous FeAl intermetallics(porosities of 41.1%,44.2%and 49.3%,pore size of 15−30μm)prepared by our research group to study the macroscopic mechanical properties and microscopic failure mechanism.The results show that the tensileσ−εcurves of the porous FeAl with different porosities can be divided into four stages:elasticity,yielding,strengthening and failure,without necking phenomenon.The elastic modulus,ultimate strength and elongation decrease with the increase of porosity and the elongation is much lower than 5%.A macroscopic brittle fracture appears,and the microscopic fracture mechanism is mainly intergranular fracture,depending on the Al content in the dense FeAl intermetallics.In addition,the stochastic porous model(SPM)with random pore structure size and distribution is established by designing a self-compiling generation program in FORTRAN language.Combined with the secondary development platform of finite element software ANSYS,the effective elastic moduli of the porous FeAl can be determined by elastic analysis of SPM and they are close to the experimental values,which can verify the validity of the established SPM for analyzing the elastic properties of the porous material.

Numerical simulation of flow field of single-hole oxygen lance jet

The numerical simulation of jet flow field in Laval tube was carried out first by commercial software CFX4.4, and it is used to determine inlet pressure condition out of nozzle in order to its numerical simulation. The decay rule of jet middle line velocity of axial symmetry turbulence jet and cross section＇s expand situation out of the tube in different stagnation pressure and surrounding temperature were analyzed systematically. The result showed that K-e model is suitable for numerical simulation. The conclusion will have important guide and referent function to research of two important craft parameters, impact depth and the impact area which are related to steel-making production practice.