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在大型循环流化床装置上,以200mm×12500mm提升管为对象,使用FCC催化剂颗粒粉料,实验测量了提升管内气固两相流的动态压力,分析了提升管内气固两相流的压力脉动特性和产生的机理。实验结果表明,提升管内气固两相流的压力脉动由两种不同成分的脉动叠加构成,一种为低频高幅值脉动,是由提升管的不稳定进料引起的;另一种为高频低幅值脉动,是颗粒簇运动、气固相互作用、气体速度脉动等多种因素耦合作用的结果。压力脉动的标准偏差分析和功率谱分析表明,压力脉动的强度随颗粒质量流率的增加而增大,但沿提升管轴向有一定程度衰减。压力脉动的量纲1和功率谱分析表明,低频高幅值的脉动在提升管轴向具有一定的相似性。 相似文献
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在压力26~30 MPa,时均质量流速420 kg·m~(-2)·s~(-1)、热通量0~130 kW·m~(-2)工况范围内,对垂直上升并联双通道内超临界水的脉动传热特性进行了实验研究。根据实验数据分析了流量脉动对壁温的影响,脉动振幅率(A_f)和脉动频率数(Wo)对时均Nusselt数的影响,并将脉动时均Nu与超临界传热关联式进行了比较。结果表明:壁温随流量脉动而波动,脉动周期相同,相位相反,流量脉动振幅越大,壁温波动也越大;低频脉动时均Nu随脉动振幅率的增大逐渐减小,随脉动频率数的增大先减小后基本不变;高频脉动时均Nu随脉动振幅率的增大而缓慢增大,随脉动频率数的增大而减小;关联式预测的Nu较实验值普遍偏高。 相似文献
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在压力26~30 MPa,时均质量流速420 kg·m-2·s-1、热通量0~130 kW·m-2工况范围内,对垂直上升并联双通道内超临界水的脉动传热特性进行了实验研究。根据实验数据分析了流量脉动对壁温的影响,脉动振幅率(Af)和脉动频率数(Wo)对时均Nusselt数的影响,并将脉动时均Nu与超临界传热关联式进行了比较。结果表明:壁温随流量脉动而波动,脉动周期相同,相位相反,流量脉动振幅越大,壁温波动也越大;低频脉动时均Nu随脉动振幅率的增大逐渐减小,随脉动频率数的增大先减小后基本不变;高频脉动时均Nu随脉动振幅率的增大而缓慢增大,随脉动频率数的增大而减小;关联式预测的Nu较实验值普遍偏高。 相似文献
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基于质量与能量守恒方程,以转子压缩机几何模型为基础,建立反映中间压力形成过程的变容量双级压缩系统压缩机动态耦合模型,并利用实验对模型进行了校核。基于模拟和实验结果,分析了中间压力随时间的变化及其变工况特性。结果表明,中间压力具有脉动特性,但脉动幅值相对于时均值较小;在影响中间压力的因素中,低高压压缩机理论输气量比的影响最为显著,冷凝温度的影响明显小于蒸发温度的影响;系统制热量随中间压力的升高近似呈线性增加,而系统制热COP随中间压力升高具有先升高后降低的趋势,且存在最优值。 相似文献
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采用欧拉双流体模型模拟了加压下二维鼓泡床内的气固流动特性,结果表明:在相同的表观气速下,加压使气泡体积分数增大,气泡相与乳化相间的分解越发明显,气固两相流动、混合剧烈;同时,床层中上部颗粒轴向速度的径向分布不均匀性增强:中心区颗粒速度增加,近壁区下降;随着操作压力变大,流化床膨胀高度增大,相应地,整体气含率增大,床层下部的颗粒浓度减小,而上部颗粒浓度增加,固含率在轴向上的分布更均匀;床层压力波动主要由两种成分构成:低频率高幅值和低幅值高频率成分.压力脉动强度随床高的增加呈现先增大后迅速减小的趋势;此外,加压下床层压力脉动强度变大,即床压波动更加剧烈;而且加压下颗粒拟温度增大,即颗粒速度脉动增强. 相似文献
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为了提高脉动热管的传热效率,实现更加高效的传热效果,研究了单环闭式循环脉动热管的动力学特性。首先本文建立了弹簧-质量-阻尼模型,通过Matlab程序进行理论计算,得到了脉动热管内工质位移随时间变化的理论计算结果;然后建立仿真模拟的数值模型,计算得到了不同加热功率下液柱的位移等参数随时间的变化规律。结果表明:脉动热管内液柱的振荡频率随加热功率的增大而增大;当管内最大压力与最小压力的差值小于某一临界值时,管内工质做振荡运动,反之,工质做循环运动;脉动热管内工质的运动具有同步化现象。 相似文献
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研究了螺杆轴向振动对熔体注射过程中各个阶段能耗的影响,建立了振动力场作用下熔体流经圆锥形浇口流道和圆盘充模的物理模型和数学模型,并求得上述两个过程中功耗的解析式;通过实验验证了振动力场的引入使得注射过程能耗减小,在振动强度系数达到0.45以后,注射过程功耗减小的趋势更明显。 相似文献
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研究了聚合物电磁动态注射成型过程中熔体在轴向振动力场作用下在圆柱形流道中的流动情况。从理论上分析了动态熔体流动过程,为研究聚合物熔体的动态充模过程提供流道系统压力降。得出在施加了轴向振动的情况下,熔体的压力梯度有明显的降低,并且随着振动强度的增强,降低的幅度加大。 相似文献
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《Journal of Adhesion Science and Technology》2013,27(3-4):267-286
In this study the three-dimensional transient vibration attenuation of an adhesively-bonded cantilevered single-lap joint was controlled using actuators. First, the vibration attenuation of the adhesive joint, which was disturbed by applying a concentrated load to the free edge of the lower adherend, was determined without a control force. In order to reduce displacement level and vibration attenuation time, a variable transverse control force was applied to a point on the lower adherend surface using an actuator. The transient variation of the control force was expressed by a periodic function so that the damped vibration of the adhesive joint was decreased. The optimal transient variation of the control force applied by the actuator is an optimization problem requiring the minimization of the objective function including the total elastic strain and kinetic energies, and the actuator work. In addition, the optimum placement of the actuator on the surface of the lower adherend is the second optimization problem. Optimal transient control force history and optimal actuator position were determined using the Open Loop Control Approach and Genetic Algorithm. The peak displacement reduced by 69.6% and the attenuation time decreased by 33%. In addition, the control performance of two actuators was investigated. Thus, the first actuator was located at the optimal position of a single actuator case, and then the optimal transient variations of the control forces applied by both actuators and the optimal position of the second actuator were determined. An additional decrease of 30% in the total energy of the adhesive joint and in the total work of both actuators in comparison to the single actuator case was found, whereas the difference in the vibration attenuation time of the adhesive joint was minor. 相似文献
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《Journal of Adhesion Science and Technology》2013,27(2):339-359
In this study, the loss factors of an adhesively-bonded double containment cantilever joint were determined for different plate and support lengths. The response of the adhesive joint subjected to a transverse excitation force was measured with a contactless eddy-current sensor and the first bending natural frequency was determined using the Fast Fourier Transform method. The loss factor was calculated using the half-power bandwidth method based on the power spectrum of the joint vibration. After an excitation force was applied to the joint, the damped free vibration analysis was carried out using the finite element method and its measured loss factor. The transverse vibration attenuation was actively controlled with different numbers of actuators located on the top surface of the plate. The optimal control of the vibration attenuation was achieved based on a performance index by considering the strain energy, the kinetic energy, the work done on the adhesive joint by the actuators as well as the vibration attenuation time. Genetic Algorithm was implemented to this optimization problem in which the optimal control force histories, the optimal locations and the optimal numbers of the actuators were searched. Eight actuators exhibited the best control force history minimizing the performance index to 3.34 × 10–2. Thus, the attenuation time was reduced from 16 s to 0.15 s and the absolute displacement was decreased from 13.1 mm to 17.15 × 10–3 mm for 0.15 s. In addition, the modal strain energy and kinetic energy were found to be at lowest levels. As the actuator number was increased only a minor decrease in the performance index was observed after four actuators. 相似文献
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往复式压缩机的管道振动主要是由于气流脉动引起的,尤其是当压缩机的激振频率接近管道固有频率时,管线系统会发生共振,严重影响管道的安全运行。新疆油田公司采气一厂的克75天然气处理站有3台压缩机的管道自安装运行后一直存在较为严重的振动问题。本文首先对克75往复压缩机撬的管线振动情况进行了测量,获得了管道振动危险点的振幅值和振动频率。然后建立了管线的CAESAR Ⅱ模型,计算了往复压缩机管线的固有频率,分析了产生振动的原因主要是由共振引起的。然后本文并提出切实可行的改进措施,通过改变支撑的位置和刚度,调整管线系统的固有频率消除共振。改造后的振动测量表明,减振措施取得了良好的效果,消除了装置运行的一大隐患,为同类型装置振动问题的解决提供了可以参考借鉴的方案。 相似文献
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通过对水表PMMA字轮盒的结构和成型工艺分析,设计了其热流道注塑模具的总体结构。并详细介绍了热流道系统的结构和先复位机构。采用该模具成功实现了以热流道形式对字轮盒进行大批量自动化生产。 相似文献