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分析了200MW汽轮机调速器φ60错油门上弹簧刚度下降时对速度变动率、中间滑阀和同步器工作的影响。 相似文献
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通过试验研究,介绍了不同类型、不同压缩状态的变刚度气门弹簧组的固有特性变化规律,及其对配气系统动态特性的影响,为配所系统动态理论分析和变刚度气门弹簧的选型设计提供依据。 相似文献
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分析某机型改进过程中,由于排气背压的增加导致气门反跳的现象,并对新机型重新校核弹簧特性参数;分析了增加弹簧预紧力对配气机构运动学和动力学特性的影响,证明适当增加弹簧预紧力能有效地解决反跳问题,并对整个配气机构特性影响不大。 相似文献
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采用试验的方法,研究弹簧分离装置输出性能随温度的变化规律及高低温长期贮存对弹簧分离装置输出性能的影响.最终得出弹簧刚度随温度的变化关系,不锈钢丝剪切模量的温变系数及特定温度下剪切模量的计算公式,具有工程实用价值;证明了高低温长期贮存不会影响弹簧分离装置输出性能. 相似文献
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用矩阵来描述活塞的径向刚度,并在试验台架上对不同位置加载,测得规定点处的变形量,从而确定活塞整体刚度的分布情况。利用建立的动力学模型分析活塞刚度变化对二阶运动、敲击动能及摩擦功损失等的影响,为确保活塞温度场、热变形及缸套安装变形等边界条件的准确性,使用硬度塞测温试验、缸孔轮廓仪等得到的实测数据对模拟过程进行标定和验证。计算结果表明:活塞动力学分析要同时考虑缸套和活塞刚度的影响,否则计算得到的活塞摆角偏小,摩擦损失偏大,而敲击动能则随着曲轴转角的不同而与实际情况产生周期性偏差,有些偏差值甚至会达到70%;改变活塞结构会改变活塞的刚度,通常当裙部刚度增大后,活塞在每个换向时刻的最大摆角会减小,同时在每个敲击时刻的敲击能量峰值也会减小。 相似文献
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本文对高压共轨泵用燃油计量阀的结构和原理进行了分析,对3种相同预紧力不同刚度的复位弹簧和同一刚度不同预紧力的复位弹簧进行了对比试验,从而为复位弹簧的确定提供了参考。 相似文献
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为研究螺旋钢弹簧刚度对频率的响应,采用动态刚度矩阵法研究螺旋钢弹簧在不同频率的外加载荷下刚度发生变化的规律。计算结果表明,弹簧刚度的变化主要由弹簧自身共振行为引起,载荷频率越高,对弹簧刚度的影响越显著。考虑弹簧自身质量分布的特性,用多质量块串联的弹簧-质量系统来代替连续螺旋弹簧,结果表明该等效算法在多刚体动力学时域计算中能准确反映弹簧刚度随频率变化的特性。 相似文献
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System dynamics software STELLA is used to obtain mass and thermal balances of a spring in the Orakeikorako geothermal field, New Zealand, based on field measurements of water level, barometric pressure, rainfall and spring temperature. The model identifies the interactions of the principal influences on spring behaviour of rainfall, groundwater, geothermal steam and barometric pressure. The geothermal steam inflow estimated from the model, of about 0.022 kg/s, confirms the existence of a weak hydraulic connection with a deeper geothermal reservoir. 相似文献
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Jin-Yuan Qian Zhi-Xin Gao Jian-Kai Wang Zhi-Jiang Jin 《International Journal of Hydrogen Energy》2017,42(27):17192-17201
Valves are widely used for fluid flow control, not only for conventional fluid like water, gas and oil, but also for hydrogen under high pressure and so forth. Under these new conditions, the response time and energy consumption of valves are closely related to the whole performance of the piping system. Pilot-control globe valve (PCGV) is a novel quick response valve, which can utilize the pressure difference before and after the valve core to control the open/close states of the main valve. In this paper, the effects of spring stiffness inside PCGV on the flow and the valve core movement are carried out, respectively. To begin with, the experimental setup is introduces and the 3D numerical model is established. The simulation is carried out in software FLUENT with RNG k-ε turbulence model, User Defined Function method and dynamic mesh regeneration methods under transmit state. Then, a comparison of steady valve core displacements between experiment and simulation is carried out. After that, the effects of spring stiffness on flow characteristics, valve core movement and response times during opening and closing periods are presented. Finally, a spring chosen correction equation is proposed. This work can benefit the further design work of PCGVs or similar valves with springs, and it can be also referred by someone dealing with novel control valves design or flow control issues. 相似文献
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扩散系数在化工设计和研究中是不可缺少的传递特性。但其数据却相对缺乏,因此需要寻找一种方法来预测这个特性就显得十分重要。利用分子动力学方法模拟了简单流体的自扩散系数。模拟分别采用Green-Kubo法(VACF:velocity autocorrelation function)和Einstein法(MSD:mean square displacement)。模拟结果与实验数据吻合较好,误差在10%左右。两种方法的平均值与实验结果误差在7%左右。同时还模拟了流体自扩散系数随温度的变化关系。结果表明,自扩散系数与温度满足Arrenhius关系,数据相关性在0.99以上,计算得到的自扩散激活能分别为1 258 J/mol(VACF)、1 272 J/mol(MSD)和平均值1 265 J/mol。 相似文献
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The diffusion coefficient is indispensable to chemical engineering design and research. In practical engineering and research, there is still a great lack of available data. Therefore, methods need to be developed to solve this problem. In this paper, a molecular dynamics simulation method is used to predict the self‐diffusion coefficient for a simple fluid by using the Green– Kubo relation (VACF) and the Einstein relation (MSD). The simulation results are in good agreement with experimental findings except for an error of about 10%. The algorithm average of the two methods (AV) reduces the error to 7%. The relationship of the diffusion coefficient with temperature has also been simulated. According to the simulation data, whose correlation is all above 0.99, the diffusion coefficient agrees well with temperature following the Arrenhius relationship. Activation energy for self‐diffusion has been calculated and the result were 1258(VACF), 1272(MSD), and 1265(AV) J/mol separately. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(2): 86–93, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20191 相似文献
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通过对CKD7F型机车曲线通过能力的分析计算,查明了该型机车钩尾框变形和裂纹的原因,据此对相关结构进行了改进,取得了良好效果。 相似文献
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Kookil Han Bo Ki HongSae Hoon Kim Byung Ki AhnTae Won Lim 《International Journal of Hydrogen Energy》2010
The effects of gas diffusion layer’s (GDL’s) anisotropic bending stiffness on the electrochemical performances of polymer electrolyte membrane fuel cells have been investigated for carbon fiber-felt and -paper GDLs. The bending stiffness values of all GDLs in the machine direction are higher than those in the cross-machine direction. We have prepared GDL sheet samples such that the machine direction of GDL roll is aligned with the major flow field direction of a metallic bipolar plate at angles of 0° (parallel: ‘0° GDL’) and 90° (perpendicular: ‘90° GDL’). The I–V performances of all the 5-cell stacks with 90° GDLs are higher than those with 0° GDLs. All the 5-cell stacks with 90° GDLs show lower values of high-frequency resistance (HFR) than those with 0° GDLs. However, the gas pressure differences at both anode and cathode of 5-cell stacks with 90° GDLs appear to be similar to or slightly lower than those with 0° GDLs, making the lower HFR as a dominant factor for the improved I–V performances. This may result from the reduced intrusion of 90° GDLs into gas channels than 0° GDLs as observed by less thickness reduction under compression of 90° GDLs. A 45° GDL (skew alignment) also shows better performances than the 0° GDL. 相似文献
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《International Journal of Hydrogen Energy》2019,44(36):19474-19483
Molecular dynamics simulation on the reaction of nano-aluminum particle and water were performed by ReaxFF force field. The different reaction rates of aluminum with H2O and D2O indicate that the effect of kinetic isotope effect (KIE) is obvious. The generation rate of H2 is 20% higher than that of D2. The mechanism of formation and consumption of AlH3 as well as the generation of Al2O3 are elucidated. Specifically, the most frequent reaction pathways throughout the full period are clarified based on the changes of numbers of intermediate and final products. The reactions in the early period are endothermic and release isolated H atoms, which involves Al +3H2O → Al(OH)3 + 3H and 3Al + 2H2O → 2AlO + AlH3 + H. Afterwards, the reactions release a large amount of energy and generate H2 molecules in the later period, in accordance with the equations of 2AlO + H2O → Al2O3 + H2, Al(OH)3 + AlH3 → Al2O3 + 3H2 and 2AlH3 + 3H2O → Al2O3 + 6H2. The initial pathways are in agreement with early DFT investigations. The diffusion coefficients of the different atoms show that the replacement of H2O by D2O reduces the diffusion rate of all the atoms (5%) in the system. The KIE is confirmed, and the results agree with experiments. In addition, the simulations were performed under different maximum temperatures. Results show that the solid residues become more disperse in space as the temperature increase. 相似文献
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Kookil HanBo Ki Hong Sae Hoon KimByung Ki Ahn Tae Won Lim 《International Journal of Hydrogen Energy》2011,36(19):12452-12464
The effects of gas diffusion layer’s (GDL’s) anisotropic bending stiffness on the degradation behavior of polymer electrolyte membrane fuel cells have been investigated under freezing conditions. We have prepared GDL sheet samples such that the higher stiffness direction of GDL roll is aligned with the major flow field direction of a metallic bipolar plate at angles of 0° (parallel: ‘0° GDL’) and 90° (perpendicular: ‘90° GDL’). The I-V performances before and after 1000 temperature cycles between −10 and 1 °C of 90° GDL stack are higher than those of 0° GDL stack, and the voltages of 90° GDL stack are decreased slower than those of 0° GDL stack, indicating a higher durability of 90° GDL stack. Furthermore, the values and increasing rates of high-frequency resistance of 90° GDL stack are lower than those of 0° GDL stack. However, the H2 and air pressure differences before and after 1000 temperature cycles of 90° GDL stack are very similar to those of 0° GDL stack. The surface of anode catalyst layer (CL) of membrane-electrode assembly (MEA) with catalyst-coated membrane type in 0° GDL stack appears to be more severely damaged than that in 90° GDL stack, especially under the channels, whereas the surfaces of cathode CLs of MEAs in both 0° and 90° GDL stacks are slightly damaged after 1000 temperature cycles. 相似文献