连杆裂解加工力参数数值分析

为了确定合适的连杆裂解工艺中裂解力参数,采用数值分析的方法建立了53d斜切口连杆裂解加工的数值模型。对裂纹尖端的节点采用了1/4节点技术用于模拟裂纹尖端应力场的奇异性,分析得到了裂解力与应力强度因子的关系曲线。根据连杆材料的临界应力强度因子KIc,确定了连杆裂解加工所需的裂解力。结果表明：裂纹1的裂解力为851 kN,裂纹2的裂解力818 kN。与实际生产中的裂解力860-880 kN相比,其误差小于10%。

基于应力强度因子的发动机连杆裂解力数值模拟分析

目的为获得合适的裂解力,以某款轿车发动机连杆为研究对象,应用扩展有限元法(Extended Finite Element Method,XFEM)对裂解工艺中的裂解力进行计算分析。方法根据部件的实际尺寸建立预制初始微裂纹条件下的连杆裂解有限元模型,确定相关的材料参数,并进行有限元网格划分,确定部件之间的约束类型。以应力强度因子大于材料断裂韧度,裂纹即扩展为依据,反复试算得出应力强度因子达到断裂韧度时的裂解力,进而通过大量计算和数据拟合得出初始微裂纹长度与裂解力之间的关系。分析裂解力对塑性区的影响,为裂解力阈值确定给出参考。结果当裂解力能够满足裂解工艺要求时,预制的初始微裂纹长度应尽可能小。结论最为理想的裂解力为材料断裂韧度对应的裂解力。文中提出的分析方法也适合于求解各类连杆的裂解力。

发动机连杆裂解加工初始裂纹槽几何参数研究

分析比较了裂纹槽的设计位置、几何形状以及预制方法;对含有预制裂纹槽的C70S6钢连杆的裂解加工过程进行了数值模拟分析和连杆断裂剖分实验,给出裂纹槽几何参数对裂解力水平的影响规律.结果表明,在其他参数不变的条件下,裂纹槽深度对裂解力的影响最为显著,随着槽深增大裂解力锐减;提高锐度及减小张角可降低裂解力,但曲率半径为0.1-0.3 mm或张角〉30°时,裂解力增幅较小且趋于稳定.研究结果对合理设计裂纹槽、降低切槽成本、提高连杆裂解质量具有参考价值.

连杆裂解加工数值分析

裂解力的选择是发动机连杆裂解加工成败的关键。为获得合适的裂解力,利用MSC.MARC软件对捷达轿车连杆起裂过程进行了数值分析,得出了裂解力与J积分的关系曲线。根据冲击韧性与断裂韧性的关系,确定了临界J积分值,并采用线性插值的方法获得了裂解力。试验结果表明:此种数值分析方法适合对不同类型和材料的连杆裂解力的确定。

连杆厚度对裂解的影响分析

结合理论分析与数值模拟研究了连杆厚度对裂解加工的影响，给出了断裂韧性、裂纹区塑性区状态与连杆厚度的关系，并讨论了连杆厚径比对裂解的影响。结果表明：在启裂工步，随连杆厚度的增加，裂纹区的VonMises应力由狭长的、多个分散集中状态逐渐过渡到趋向中面唯一分布的集中状态，裂尖附近的最大主应力均值逐渐增加，分析了连杆厚度及厚径比与裂解力的关系，得出某规格连杆的厚径比D／R最佳设计范围为3．312～3．438。

连杆背压裂解加工方法

通过数值模拟与实验相结合的方法对准静态加载条件下的连杆裂解过程进行分析,确定了C70S6连杆裂解的临界J积分值,并对背压裂解过程进行数值模拟分析,对背压力对于连杆裂解J积分、韧带区场变量及裂解力的影响进行探索。模拟结果表明:背压力使沿连杆裂纹槽长度方向的裂尖J积分梯度增大,使应力更快、更有效地集中在裂纹槽中部,有利于裂纹槽起裂和裂纹快速扩展,可减少因裂纹分叉、交汇异常等引起的裂解加工缺陷,但是背压力增加的同时也增大了胀断主动力和裂解力,建议背压力设定为胀断主动力的1/4。

发动机曲轴箱轴承座裂解加工数值分析

预先精确计算裂解力参数,对于裂解设备设计及工艺过程的制定至关重要。应用MSC.MARC软件对捷达轿车发动机主轴承座(以RuT380材料为例)起裂过程进行数值模拟,得出了裂解力与J积分的关系曲线。根据J积分值与断裂韧性的关系,确定了临界J积分,采用线性插值的方法获得了裂解力,并进行了实验研究。实验结果表明:此方法也适用于不同结构、不同材料的其他分体类零件裂解加工时裂解力的确定。

塑料加工过程的力化学分析

塑料成型加工过程是力和热共同作用的过程,塑料在这两种能量作用下将发生一系列的物理及化学变化.以力降解、力活化为主体的力化学过程,直接影响着从原料到制品的整个加工工艺过程和制品质量.力化学作用有益于塑料共混改性的效果,但对一般塑料成型加工过程则有着不利影响.

Reactive Molecular Dynamics Simulation on Thermal Decomposition of n-Heptane

The thermal decomposition of n-heptane is an important process in petroleum industry. The theoretical investigations show that the main products are C2H4, H2, CH4, and C3H6, which agree well with the experimental results. The products populations depend strongly on the temperature. The quantity of ethylene increases quickly as the temperature goes up. The conversion of n-heptane and the mole fraction of primary products from reactive molecular dynamic and chemical kinetic modeling are compared with each other. We also investigated the pre-exponential factor and activation energy for thermal decomposition of n-heptane by kinetic analysis from the reactive force field simulations, which were extracted to be 1.78×10^14 s^-1 and 47.32 kcal/mol respectively.

CFD Simulation of Propane Cracking Tube Using Detailed Radical Kinetic Mechanism

In the radiant section of cracking furnace,the thermal cracking process is highly coupled with turbulent flow,heat transfer and mass transfer.In this paper,a three-dimensional simulation of propane pyrolysis reactor tube is performed based on a detailed kinetic radical cracking scheme,combined with a comprehensive rigorous computational fluid dynamics(CFD)model.The eddy-dissipation-concept(EDC)model is introduced to deal with turbulence-chemistry interaction of cracking gas,especially for the multi-step radical kinetics.Considering the high aspect ratio and severe gradient phenomenon,numerical strategies such as grid resolution and refinement,stepping method and relaxation technique at different levels are employed to accelerate convergence.Large scale of radial nonuniformity in the vicinity of the tube wall is investigated.Spatial distributions of each radical reaction rate are first studied,and made it possible to identify the dominant elementary reactions.Additionally,a series of operating conditions including the feedstock feed rate,wall temperature profile and heat flux profile towards the reactor tubes are investigated.The obtained results can be used as scientific guide for further technical retrofit and operation optimization aiming at high conversion and selectivity of pyrolysis process.

Side lobes of wavelets impact identification of thin sand bodies

Recently, we found that side lobes of wavelets have a large impact on the identification of thin sand reservoirs when studying some gas fields in a basin in Northwest China. Reflections from the top of the H Formation, in which there are gas-bearing thin sand bodies, have the main wavelet lobe between two weak peak side lobes. The lower one always mixes with another peak reflected from the top of a thin sand reservoir. That makes it difficult to identify the sand reservoir. In order to solve this, many forward models were set up using typical well logs. 2D synthetic profiles were produced using Ricker wavelets to study the relationships between the effects of wavelet side lobes and thin sand position and frequency and between amplitude and the thin sand body. We developed the following conclusions： First, it is easier to identify thin sands in a shallower position. Second, a good way to tell sand body reflections from side lobes is by comparing profiles with different frequency windows. Third, it is helpful and effective to describe sand extent using amplitude attributes.

A Hybrid Algorithm Based on Differential Evolution and Group Search Optimization and Its Application on Ethylene Cracking Furnace

To find the optimal operational condition when the properties of feedstock changes in the cracking furnace online,a hybrid algorithm named differential evolution group search optimization(DEGSO) is proposed,which is based on the differential evolution(DE) and the group search optimization(GSO).The DEGSO combines the advantages of the two algorithms:the high computing speed of DE and the good performance of the GSO for preventing the best particle from converging to local optimum.A cooperative method is also proposed for switching between these two algorithms.If the fitness value of one algorithm keeps invariant in several generations and less than the preset threshold,it is considered to fall into the local optimization and the other algorithm is chosen.Experiments on benchmark functions show that the hybrid algorithm outperforms GSO in accuracy,global searching ability and efficiency.The optimization of ethylene and propylene yields is illustrated as a case by DEGSO.After optimization,the yield of ethylene and propylene is increased remarkably,which provides the proper operational condition of the ethylene cracking furnace.

Establishment of Kinetic Model for Catalytic Pyrolysis of Daqing Atmospheric Residue

An 8-lump kinetic model was proposed to predict the yields of propylene, ethylene and gasoline in the catalytic pyrolysis process of Daqing atmospheric residue. The model contains 21 kinetic parameters and one for catalyst deactivation. A series of experiments were carded out in a riser reactor over catalyst named LTB-2. The ki- netic parameters were estimated by using sub-model method, and apparent activation energies were calculated according to the Arrhenius equation： The predicted yields coincided well with the experimental values. It shows that the kinetic parameters estimated by using the sub-model method were reliable.

Near Crack Line Elastic-Plastic Analysis for an Infinite Plate Loaded by a Pair of Point Shear Forces

The near crack line analysis method was used to investigate a crack loaded by a pair of point shear forces in an infinite plate in an elastic-perfectly plastic solid. The analytical solution was obtained, that is the elastic-plastic fields near crack line and law that the length of the plastic zone along the crack line is varied with external loads. The results are sufficiently precise near the crack line and are not confined by small scale yielding conditions.

Numerical Simulation of Mechanical Behaviors of Degradable Porous Bioceramics with Cracks

Hydroxyapatite bioceramics is simulated by using finite element method （FEM）. The influences of porosity, hole shape, angle of crack and other parameters on the ceramics are analyzed. The results show that with the increase of the angle between crack and horizontal direction, the stress intensity factor KⅠ decreases gradually, but stress intensity factor KⅡ increases at first and then it decreases. The value of KⅡ reaches maximum when the angle between crack and horizontal direction is 45°. KⅠ and KⅡ rise with the increase of porosity, and they are almost the same for the circular and hexagonal holes. For elliptical holes, KⅠ and KⅡ reach maximum when the long axis of ellipse is perpendicular to the loading direction and they reach minimum when the same axis is parallel to the loading direction. Moreover, with the increase of the angle between the long axis and loading direction, KⅠ and KⅡ increase gradually.

Role of N/Z in Pre-scission Neutrons as an Observable of Nuclear Friction

A dynamical Langevin model is employed to evaluate the excess of the neutron emission in the fission ofheavy nuclei ^(240)Cf,^(246)Cf,^(254)Cf,^(240)U relative to the standard statistical-model prediction at various saddle-to-scissionfriction strengths.It is shown that when the neutron-to-proton ratio N/Z of the system increases,the sensitivityof the excess to the friction decreases substantially,and it almost disappears for ^(240)U.We suggest that using thosecompound systems with low N/Z favors an accurate determination for the saddle-to-scission friction strength based onthe measurement of the pre-scission neutron multiplicity.

Expression, Characterization and Antimicrobial Ability of a Variant T4 Lysozyme in Pichia pastoris

T4 lysozyme was engineered with disulfide bonds and expressed in Pichia pastoris. The secreted proteins were purified and made into powder by lyophiliza-tion. Recombinant protein purity was more than 70% measured by HPLC. The lytic activity of variant T4-lysozyme was measured by the lysis of the cel wal of Xan-thomonas oryzae pv. oryzae, X. oryzae pv. oryzicola, Ralstonia solanacearum comb. nov, Clavibacter michiganensis subsp. michiganensis, X. campestris pv. mal-vacearum, Fusarium oxysporium sp. vasinfectum, Verticil ium dahliae kleb. Inhibition zone assay showed that variant T4 lysozyme significantly inhibited X. o. oryzicola and X. c. malvacearum. The antifungal activities of this protein against F. o. vasin-fectum and V. d. kleb were also analyzed.

Testing of separating catalyst from resid fluid catalytic cracking slurry by 10 mm hydrocyclones

The paper focuses on removing catalyst solids from oil slurry using 10 mm hydrocyclones, and aims to test the feasibility of the solution. An industrial sidetrack tester of residual oil separation by hydrocyclones was set up in 1.8 Mt/a resid fluid catalytic cracking （RFCC） unit, the effect of pressure drop, separation efficiency and inlet flowrate were studied. It was observed that an increase in feed flowrate will decrease the pressure drop ratio, and with an increase in feed flowrate, separation efficiency increases gradually. Under the condition that feed fiowrate was ranging from 250L/h to 270L/h, the separation efficiency was 45.77%-82.80%, the recovery rate of catalyst solid panicles was increased from 10 20% of electrostatic catalyst separator to 50 80%. Thus, it is feasible to separate the slurry by using the miniature hydrocyclones in RFCC unit.

Geochemical evolution during the cracking of crude oil into gas under different pressure systems

Two comparative simulation experiments(a normal atmospheric-pressure opening system and a 20 MPa closed system)were conducted to study the geochemical evolution of n-alkane,sterane,and terpane biomarkers in the process of oil cracking into gas under different pressures.With an initial experimental temperature set at 300°C,the temperature was increased to 650°C at a heating rate of 30°C/h.The products were tested every 50°C starting at 300°C,and a pressure of 20 MPa was achieved using a water column.The low-maturity crude oil sample was from the Paleogene system in the Dongying sag in eastern China.The threshold temperature obtained for the primary oil cracking process in both pressure systems was 450°C.Before the oil was cracked into gas,some components,including macromolecular n-alkanes,were cracked into medium-or small-sized n-alkanes.The secondary oil cracking of heavy hydrocarbon gases of C2–5to methane mainly occurred between 550°C to 650°C,and the parameters Ln(C1/C2)and Ln(C1/C3),as well as the dry coefficients,increased.Overpressure inhibited the oil cracking process.In the 20 MPa system,the oil conversion rate decreased,the temperature threshold for gas generation rose,and oil cracking was inhibited.Compared with the normal pressure system,high-carbon n-alkanes and other compounds in the 20 MPa pressure system were reserved.Furthermore,the parameters∑C21-/∑22+,Ln(C1/C2),and Ln(C1/C3),as well as the dry coefficients,decreased within the main temperature range.During secondary oil cracking(550°C to 600°C),the Ph/nC18and Pr/nC17decreased.High pressure influenced the evolution of the biomarkers Ts and Tm,C31homohopane,C29sterane,and their related maturity parameters to different extents during oil cracking under different temperature ranges.

Power generation and heat sink improvement characteristics of recooling cycle for thermal cracked hydrocarbon fueled scramjet

In order to further investigate how much fuel heat sink could be increased and how much power generation could be obtained by using recooling cycle for a regeneratively cooled scramjet,the energy conversion from heat to electricity and the fuel heat sink increase in recooling cycle are experimentally investigated for fuel conversion rate and components of gas cracked fuel products at different fuel temperatures.The results indicate that the total fuel heat sink(i.e.,physical+chemical+recooling) of a recooling cycle is obviously higher than the heat sink of fuel itself,and the maximum heat sink increment is as high as 0.4 MJ/kg throughout the recooling cycle.Furthermore,the cracked fuel mixture has a significant capacity of doing work.The thermodynamic power generation scheme,which adopts the cracked fuel gas mixture as the working fluid,is a potential power generation cycle,and the maximum specific power generation is about 500 kW/kg.Turbine-pump scheme using cracked fuel gas mixture is also a potential fuel feeding cycle.