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针对高速开关阀流量小且不连续的缺陷,设计一种新型的两级数字流量阀。其先导级为电机驱动的高速开关转阀,主级为三位四通滑阀。高速开关转阀的启闭频率较高,可以显著减小主阀流量波动。基于两级阀的结构和工作原理,建立数学模型和流量波动模型。在AMESim软件中建立了两级数字流量阀的动态仿真模型,对主阀进行动态位移特性和动态流量特性仿真计算,分析主阀供油压力、面积比、节流槽宽度等参数对主阀阀芯位移动态响应特性的影响以及先导流量、控制腔体积、启闭频率等参数对主阀流量稳定性的影响。结果表明:增大供油压力、启闭频率,减小面积比、节流槽宽度可以提高阀的响应速度;增加启闭频率、增大控制腔体积以及减小先导流量都可以降低主阀流量波动,提高输出流量的稳定性。 相似文献
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为突破高速开关阀阀芯行程对开关频率的限制,提出一种阀芯旋转式高速开关阀。采用理论计算与CFD仿真相结合的方法,研究不同阀芯旋转角度下阀芯结构参数变化对阀口过流面积、流量系数、射流角及液动力矩的影响,得到了液动力矩的变化规律。研究结果表明:液动力矩与阀口压差及流量的二次方成正比;压差一定时,液动力矩与阀口过流面积及射流角余弦值成正比,随着阀芯旋转角度增大,液动力矩先增大后减小;流量一定时,液动力矩与阀口过流面积成反比,随着阀芯旋转角度增大,液动力矩逐步减小为零。通过调整阀芯沟槽高度来改变射流角,达到补偿液动力矩的目的。 相似文献
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相较负载敏感系统,采用泵阀协同压力流量复合控制系统时流量控制更加精准,系统压损更小。但采用压力传感器检测阀口前后压差、实时调节阀口开度来实现流量精准调节,当阀口压力高频波动时会引起阀芯振荡,从而导致压力冲击和流量不稳定。针对这种情况,提出一种提高系统阻尼比的压差-位移检测装置,实现在压力高频波动时抑制阀芯振荡以提高系统稳定性。利用AMESim软件建立电子压力补偿的控制系统模型并验证;建立具有该装置的控制系统仿真模型,通过仿真研究该装置对系统特性的影响。结果表明:该装置中的弹簧刚度、黏性阻尼系数、活塞质量对系统特性的影响依次减小;当负载频率小于50 Hz时,不采用压差-位移检测装置可以保证流量的稳定以及准确;当负载频率为50~80 Hz时,采用压差-位移检测装置的输出流量的波动减小了15%~30%;主阀芯的振荡减小了约85%。 相似文献
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给出直动式溢流阀结构简图及工作原理,建立其流量连续性方程和阀芯动态力平衡方程,结合数学模型基于AMESim仿真软件建立其动态仿真模型,系统研究结构参数对其动态性能的影响规律。仿真结果表明:阀芯质量增大,超调略有增大,动态压力稳定时间延长;弹簧刚度增大,超调减小,稳定压力增大,阀芯位移变化不大;阀芯阻尼增大,压力超调增大,稳定时间延长;阀座直径减小,压力超调减小,稳定压力增大,阀芯位移增大;阶跃流量增大,压力超调增大,稳定压力增大。 相似文献
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结合水的理化性质,建立动座式节流阀阀口计算流体力学模型,对其水力特性包括流场、压力场、气蚀、流量压差特性、液动力特性等进行研究。在此基础上,研制一种新型的动座式水液压节流阀,该阀阀座台阶面上压力相等,使阀座所受轴向静压力得以平衡,采用伞状阀座有效补偿由于水冲击振动所引起的液动力;在流体经阀座进入阀芯的喷入口处,设计阀芯中杆结构,使喷出流体的液动力通过阀芯中杆传导在阀芯上,降低了液动力对阀座的冲击和侵蚀。采用Fluent软件建立相应的仿真模型,并就输入压力、阀芯锥角和阀口尺寸对系统动态特征的影响进行仿真分析,在此基础上搭建水液压试验台对仿真结果进行试验验证。研究结果表明:动座式节流阀阀口处压力迅速降低,开度越小,压降越大;二级阀口处压力变化大而低,易发生气穴现象;引流孔、合适的阀芯锥角及二级阀口结构可有效降低主阀口的工作压差及液动力,减少阀口的气蚀,能有效地提高节流阀的工作性能和使用寿命。 相似文献
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Deng-Kui Zhang Guo-Qing Wang Ai-Ping Wu Ji-Guo Shan Yue Zhao Tian-Yi Zhao Dan-Yang Meng Jian-Ling Song Zhong-Ping Zhang 《金属学报(英文版)》2019,32(6):684-694
In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone. 相似文献
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After nearly two years'tense construction the first phase of industrialized base of Shenyang Research Institute of Foundry 《中国铸造》2008,5(1):63-64
After nearly two years' tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry (SRIF), located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation. 相似文献
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Z. Sun S.L. Zheng Y. Zhang 《金属学报(英文版)》2007,20(3):187-192
Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process. 相似文献
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R. González-Martínez 《金属学报(英文版)》2007,20(4):235-240
The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke. 相似文献
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The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C). 相似文献
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The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel. 相似文献
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This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before. 相似文献
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Chao Yang He-Fei Huang Massey de los Reyes Long Yan Xing-Tai Zhou Tian Xia De-Liang Zhang 《金属学报(英文版)》2015,28(7):809
Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties. 相似文献
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Lei Li Bo Xu Wei-Ping Tong Hui Zhang Chun-Yan Ban Li-Zi He Zhi-Hao Zhao Yu-Bo Zuo Qing-Feng Zhu Jian-Zhong Cui 《金属学报(英文版)》2015,28(6):725
A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed. 相似文献
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综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。 相似文献