共查询到19条相似文献,搜索用时 156 毫秒
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螺旋波纹管尺寸参数与流体在其内部的压损之间的关系尚未明确,针对超导电缆用的Φ 40 mm以上的大尺寸波纹管也缺乏相应的试验数据。本文搭建了大尺寸波纹管流动特性试验平台,并参照已有的超导电缆结构,对标称外径分别为Φ 90 mm和Φ 60 mm、尺寸规格不同的四个空芯螺旋波纹管样品进行水介质的流动特性试验研究,从试验上得到了不同流量下的压损数据。结果表明,波纹管内压损随流速的增大呈接近于平方的关系增大。在流速相同情况下,外径规格相同的样品,波深越深,压损值越大;波深相同的样品,外径越小压损越大。利用上述试验数据,推导出每个样品摩擦系数f与雷诺数Re的关系式。关系式计算值与实验值最大偏差值为16.77%,可在一定误差范围内对摩擦系数f进行估算。 相似文献
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生物质高压密相输送特性试验研究 总被引:3,自引:0,他引:3
生物质气流床气化技术是一项新技术,生物质加压密相输送是需要解决的关键问题之一。本文在大型中试高压密相试验装置上进行两种特殊生物质粉料的输送试验,研究物料特性和操作参数对其流动特性的影响。试验结果表明,本试验系统输送生物质稳定可靠,质量流量随着输送差压和发料罐压力的升高增大。随表观气速增大两种生物质弯管当量长度系数K近似为定值,生物质1的K值大于生物质2,且生物质1的K值随输送差压的增加而增大;两种生物质的固相摩擦系数随着体积分数和接收罐压力的增大逐渐增大。 相似文献
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信息熵、玻尔兹曼熵以及克劳修斯熵之间的关系--兼论玻尔兹曼熵和克劳修斯熵是否等价 总被引:6,自引:0,他引:6
论述了信息熵、玻尔兹曼熵以及克劳修斯熵之间的关系;由不涉及具体系统的方法从玻尔兹曼关系、信息熵推导出了克劳修斯熵的表达式;指出玻尔兹曼熵与克劳修斯熵不是等价关系,而是玻尔兹曼熵包含克劳修斯熵,信息熵又包含玻尔兹曼熵。 相似文献
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G.S.Agarwal and K.Tara发现了一个具有负P表示的非经典光场,而此前发现非经典光场的P表示都是奇异的.本文研究了这类负P表示光场的信息熵随场参数m和平均光子数的关系.结果显示,负P表示的非经典光场的Wehrl熵随着场参数m的增大而减小;而当平均光子数增大时,Wehrl熵亦随其增大而减小.同时本文用数值计算的方法研究了负P表示光场的Shannon熵与平均光子数的关系.发现当场参数m一定时,Shannon熵随着平均光子数的增大反而愈来愈小.以上结果表明,当场参数m一定时,随着平均光子数的增大,负P表示光场的非经典性增强;当平均光子数一定时,随着场参数m的增大,负P表示光场的非经典性亦越来越强.这是因为,当m 趋于零时,该光场则演化为经典的热光场;当平均光子数趋于无穷时,该光场则变为Fock态光场. 相似文献
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利用全量子理论计算方法,探究了在强度关联耦合下两个二能级原子与单模Pólya态光场相互作用系统中原子线性熵粒子布局数反转以及信息熵压缩随时间的演化规律.分析了原子初态、光场参量p和r以及Lamb-Dicke参量η对原子线性熵、粒子布局数反转以及信息熵压缩的影响.结果表明:当原子处于不同的初态时,相互作用系统表现出完全不同的量子特性;光场参量p增大使得各个物理量振荡周期增大;光场参量r增大,使振幅发生变化,破坏粒子布局数反转崩塌-复原现象以及信息熵压缩效应. 相似文献
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《工程热物理学报》2016,(6)
本文以完全气体为流动工质,进行离心透平级的气动设计与性能研究。采用数值模拟方法,对所设计的离心透平级进行设计工况及变工况条件下的三维稳态流场分析。结果表明:在设计工况下,流道内的流场合理,流线流畅,气动性能符合预期;在变工况条件下,当转速一定,随着背压的降低,流量缓慢增大,效率先缓慢下降,再迅速下降。随着背压的升高,流量和效率都是先缓慢下降,再迅速下降;涡流的出现会导致变工况点的效率的迅速下降;转速增大对流量几乎没有影响,转速增大可使最佳效率点向压比p_2/p_1小的方向移动;转速减少对流量也几乎没有影响,转速减少可使最佳效率点向压比p_2/p_1大的方向移动;进口温度的变化对级效率影响较小,质量流量随进口温度的增大而降低。 相似文献
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采用数值模拟的方法对比研究了定常、方波脉冲、正弦脉冲这3种喷流对Ma=2流动激波/边界层干扰的控制效果, 分析了不同喷流方式对受控流动流场结构、压力分布的影响. 结果表明, 不同喷流方式都能够实现对受控流动的有效控制, 可以增大激波距离, 减弱激波强度, 减小激波发生器壁面压力. 在控制效果方面, 定常喷流效果最佳, 方波脉冲喷流效果次之, 但定常喷流所需要的质量流量也最大, 方波脉冲质量流量次之. 3种喷流的控制效果与所需质量流量的关系表明, 控制收益的增加随着质量流率的增大而减小. 相似文献
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本文分析了非晶铁模型中原子能量分布的信息维和位形熵随压力的变化。计算了原子相互作用能的粒子数分布,将其分布的信息维作为非晶态位形熵的度量。计算结果表明,原子能量分布曲线和位形熵与统计时所取能量间隔有关;位形熵与能量间隔之间具有分形标度关系。用介于由能量间隔的下截止限和上截止限所确定的无标度区内的平均值表示各压力下的位形熵。模拟结果表明,原子能量分布的信息维是描述非晶系统无序状态的另一有效参量;压力对非晶金属结构无序及分维值的影响呈较复杂的波动变化趋势。
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高温高压下湿空气的焓和熵计算 总被引:2,自引:0,他引:2
本文以湿空气透平和压缩空气储能系统中的工质-湿空气为研究对象,运用所提出的一个适合计算高温高压湿空气热力学性质的对应态维里方程,对湿空气的偏差焓和偏差熵进行了计算.在湿度0≤ W≤1 kg/kg(A),温度小于573.15 K,压力小于5 MPa时,与ASHRAE用的多项式维里方程计算得到的偏差焓和偏差熵进行了比较,误差很小.用这个对应态维里方程外推计算了温度和压力分别达到600 K和15 MPa的湿空气焓和熵.计算结果表明对湿空气而言压力和湿度越大,偏差焓和偏差熵越大;温度越高,偏差焓和偏差熵越小. 相似文献
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It is widely accepted that the frictional pressure drop is impossible to be negative for pipe flow. However, the negative frictional pressure drops were observed for some cases of two-phase slug and churn flows in pipes, challenging the general sense of thermodynamic irreversibility. In order to solve this puzzling problem, theoretical investigations were performed for the entropy generation in slug and churn flows. It is found that the frictional pressure drop along with a buoyancy-like term contributes to the entropy generation due to mechanical energy loss for steady, incompressible slug and churn flows in vertical and inclined pipes. Experiments were conducted in a vertical pipe with diameter as 0.04 m for slug and churn flows. Most of the experimental data obtained for frictional pressure drop are negative at high gas–liquid ratios from 100 to 10,000. Entropy generation rates were calculated from experimental data. The results show that the buoyancy-like term is positive and responsible for a major part of entropy generation rate while the frictional pressure drop is responsible for a little part of entropy generation rate, because of which the overall entropy generation due to mechanical energy loss is still positive even if the frictional pressure drop is negative in vertical slug and churn flows. It is clear that the negative frictional pressure drops observed in slug and churn flows are not against the thermodynamics irreversibility. 相似文献
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Present study investigates entropy generation analysis for peristaltic motion of hybrid nanofluid. Hybrid nanofluid is composed of iron-oxide and copper nanoparticles suspended in water. Effects of Hall current, Ohmic heating and mixed convection are taken into account. Governing equations are simplified by utilizing lubrication approach. The numerical solutions for resulting system of differential equations are obtained with the aid of Shooting method. Attention has been given to the analysis of hybrid nanoparticles, Hall parameter and Grashoff number on entropy generation, heat transfer rate, velocity profile and pressure gradient. Outcomes reveal that insertion of nanoparticles decreases the temperature of hybrid nanofluid. It is found that increase in Hall parameter reduces the heat transfer rate at wall. Increment in Hall parameter reduces the entropy generation. Velocity and pressure gradient increases by enhancing Grashoff number. It is believed that the present flow model can prove useful in improving the efficiency of similar thermodynamical systems. 相似文献
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Wei He Qiaofeng Xie Zifei Ji Zhuming Rao Bing Wang 《Proceedings of the Combustion Institute》2019,37(3):3433-3442
The sampled pressure signals in continuously rotating detonation combustors have the inherence of nonlinear dynamics. To dig out more information on combustion modes, the nonlinear time series analysis method is thus applied to the pressure-time series obtained at a hydrogen/air rotating detonation combustor by using the phase space reconstruction and wavelet entropy algorithm. The variation of wavelet entropy is approved to be associated with the periodicity variation of pressure signals. Different structures of attractor as well as wavelet entropy distribution in the phase diagram can distinguish the deflagration mode from the unstable and stable detonation modes under the conditions of different air flow rates. The limit-cycle oscillation is exhibited in the phase space diagram with a very low flow rate, here 25 g/s. The mean wavelet entropy of pressure-time series can be a quantitative index of different combustion modes occurring in the combustor. The present study is expected to enhance the understanding of the physical mechanism of continuously rotating detonation and contribute on the development of detonation propulsion technology. 相似文献
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声制冷机是一种新型制冷机,具有无机械运动部件,可靠性高寿命长,采用惰性气体为工质无污染等优点.驻波型热声制冷机的声功泵热效应是不可逆过程,内部不可逆损失导致热声制冷机效率偏低,制约了热声制冷机的发展和应用.本文研究了线性范围内驻波型制冷机换热器和回热器内的可压缩振荡流动与传热过程的熵产,分析了板间距,振荡频率和温度梯度对熵产的影响。 相似文献