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掺杂对甲醛气敏元件气敏特性的改善 总被引:1,自引:0,他引:1
纳米材料SnO2对大多数VOC气体具有敏感性.文中以SnO2为基料制作了旁热式甲醛气敏元件,为改善甲醛气敏元件的气敏特性,选择了2%Sb,3%Sb,2%Pd,3%Pd,4种比例的掺杂材料,并以低体积分数甲醛作为测试气体,对SnO2气敏元件的气敏特性进行了测试.结果显示:掺杂2%Pd的气敏元件气敏特性良好. 相似文献
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提出一种新型可倾气封。与传统固定式气封相比,可倾气封块在气流力作用下可以绕支点作自适应摆动,当气封块达到平衡位置时,切向激振力减小,从而提高稳定性。试验采用不平衡同频激励法测定可倾气封的动力特性,研究和比较了可倾气封和传统固定式气封的动静态性能。试验结果表明,两种气封泄漏量相当,可倾气封内产生的切向气流力比固定气封小。低压比下两种气封动力特性系数相近,随着压比的增大,动力特性系数差异逐渐增大。以气流力对气缸的做功量大小为综合评判依据,发现可倾气封做功量明显小于固定气封,压比越大,做功量差异也越大,可倾气封的稳定性较高。对于大型旋转机械而言,气封进出口压比很大,两种气封动力特性的差异将会更大。 相似文献
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在气体辅助成型工艺中,常常遇到一种缺陷是“气指”,气泡穿过气道形成指状分支,严重的“气指”会降低注塑件的强度,造成气辅成型技术的失败,或者不能发挥气辅成型技术的优势。为了消除或减少这种缺陷的产生,本文采用数值模拟方法和正交试验方法对气辅成型制品“气指”缺陷进行了研究。研究了对“气指”缺陷影响最重要的6个工艺参数:熔体短射量、气体注射延迟时间、气体注射压力 、模具温度、熔体温度以及气体注射时间对气辅成型制品“气指”缺陷的影响关系。结果表明,影响“气指”最重要的工艺参数依次是气体注射延迟时间、熔体温度和气体注射压力。因此优先选择合理的延时,熔体温度和注气压力参数尤为重要,为控制气指行为建议在相同熔体温度下适当延长气体注射延迟时间。 相似文献
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气凝胶具有极低的热导率,是目前已知热导率最低的固体材料,是一种理想的轻质隔热材料。主要介绍了SiO2气凝胶、Al2O3气凝胶、ZrO2气凝胶耐高温性能的研究进展,同时对耐高温气凝胶隔热材料的发展方向进行了探讨。 相似文献
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随着钢材市场的细分和用户对带钢表面质量要求的不断提高,热轧除鳞工艺及设备有了长足的发展,从上世纪30年代的低压水系统到现在的高压水系统,工程师们一直在寻求和开发高效的除鳞工艺及设备,并讨论了除鳞系统重要部件的性能和特点,通过优化设计和设备,可以提高系统效率. 相似文献
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变压差自动恒流阀常用于阀门的气液联动驱动装置,具有流量大、出口压力基本恒定、可自动调节开度等优点。介绍了变压差自动恒流阀的结构和工作原理,建立了其数学模型。在此基础上,应用AMESim软件对变压差自动恒流阀进行仿真分析,得到不同弹簧弹性系数、弹簧预紧力、初始状态槽口开度对流量和出口压力的影响规律,为变压差自动恒流阀的机械设计提供依据。 相似文献
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Chang-Hoon Shin Jong-Man Ha Cheol-Gu Lee 《Journal of Mechanical Science and Technology》2008,22(2):374-381
Typically, a Pressure Control Valve (PCV) system is constructed with 3 to 4 PCV lines in order to prepare for both a future
demand increase and a continuous supply of power after an emergency shutdown of the operating line. However, some operation
failure cases that do not follow the original design concepts of a PCV system have been reported in the field. In this study,
an accurate 1-D PCV system numerical model was built and a 1-D compressible flow theory was introduced for analytic valve
modeling to find solutions for this problem. Several numerical analyses were successfully performed to examine the generation
and propagation characteristics of the transient pressure and to clarify the relationships between the transient pressure
or surge wave and each factor or parameter relating to fluid dynamics behavior in a PCV system. The relationship between the
transient pressure and other factors, such as the size of pipe and header linked after a PCV, the pipe size of the added components
linked after the header, and the generation time of the transient pressure and influence of the Slam Shut Valve were investigated
in detail. Finally, in order to reduce the strength of the transient pressure and to delay its propagation, this study demonstrates
the benefit both of enlargement of the pipe linked to the component added after the PCV system, and the installation of a
dissipation component between the operation line and the other lines. 相似文献
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在对安全阀校验现状进行分析的基础上,较详细地叙述了安全阀校验测试仪的设计。该测试仪可以安全阀校验过程中压力和位移进行实时测量,自动识别和显示安全阀的开启压力和开启高度,并具有RS485数据通讯功能。 相似文献
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考虑阀口误差的阀控非对称液压缸系统建模、仿真与试验 总被引:3,自引:0,他引:3
从解决比例阀控制非对称缸系统存在的超压问题入手,分析因加工误差引起的各阀口重叠量不一致这一非线性因素对系统性能的影响,建立考虑阀口误差的阀控非对称缸系统的非线性状态方程模型和键图模型。应用这两种非线性数学模型分析一实际非对称阀控制非对称缸系统的压力特性,与试验结果的对比分析验证了所建的非线性数学模型的正确性。仿真和试验研究揭示比例阀控制非对称缸系统的阀口误差对系统性能影响较大,往往是引起有杆腔压力超过供油压力的主要原因。通过大量仿真研究获得了阀口误差与系统超压之间的关系,研究表明适当提高比例阀阀口的加工精度有利于消除超压现象和提高系统的性能,进而建议将某些比例阀阀口误差控制在最大阀位移的0.5%以内。给出的两种非线性数学模型具有通用性,可用于对各类阀控缸系统进行系统仿真、设计和控制策略等方面的理论研究工作。 相似文献
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为了改善目前钢铁企业正在使用的各类煤气放散阀在高风温、高压力的条件下密封性的问题,采用了球面密封,提高了放散周密封压力及使用寿命,确保高炉高压生产. 相似文献
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This paper presents the results of numerical and experimental performance evaluation of the rotary tubular spool valve. The aim of this work is to develop further the novel design of the tubular spool valve by confirming experimentally the validity of the simulation model and its results, thereby proving the valve's potential to represent a feasible and more efficient alternative to conventionally used translation spool valves avoiding the use of two stage valve configurations. In this research the valve performance is assessed through numerical modelling and experimental studies of its metering characteristic and pressure losses. This paper demonstrates that the used valve model yields the results, which agree well with the conducted experimental study. Therefore, validation of the numerical model and the modelling results in the form of theoretical valve characteristics was accomplished. Firstly, the paper presents details of a numerical approach employed to evaluate valve performance and then analyzes the simulation results. Next, the valve performance is experimentally validated by testing a prototype valve on a hydraulic test rig capable of measuring the volume flow rate, pressure levels in up- and downstream lines of the valve across the entire spool angular stroke. Initially, average discrepancies between modelling and test results were 52.46% for the metering and 82.78% for the pressure loss characteristics. Correcting the model geometry aimed at eliminating differences between the valve model and the practically used prototype-test rig system enabled reduction of the error between experiment and modelling by 47.75% for the pressure loss function. This confirmed validity of the simulated characteristics of the valve. The benchmark comparison of pressure losses confirmed average 71.66% energy dissipation reduction compared to the industry-available analogue valve. 相似文献
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二通插装阀方向控制回路分析 总被引:1,自引:0,他引:1
高压、大流量是液压系统的发展趋势,二通插装阀的应用势必越来越多.本文对2种比较典型的由插装阀组成的方向控制油路进行了比较细致的分析,对加深理解和实际应用插装阀具有一定的参考价值. 相似文献
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对半圆形、单三角形、三角半圆形和双半圆形节流槽阀口的流量系数进行了研究。基于阀口的流量压差特性试验,在已实现程序化计算阀口通流面积的基础上,获得了上述4种节流槽阀口的流量系数及其变化规律,对节流槽滑阀的设计及其流量精确预测具有重要实用价值。 相似文献
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本文介绍油泵隔离泵阀箱渗漏的原因,能过对阀盖0型圈沟槽的改进及采取乐泰密封胶替牛油盘根进行密封,解决了阀箱渗漏的问题。 相似文献