Linear stability of Rayleigh–Benard–Poiseuille convection for electrochemical system

The effect of Poiseuille flow on the convective stability of electrochemical system is considered. It is found that the effect is destabilizing in the case of oscillatory instability in the system. It is shown that this effect is caused by the fact that the problem is not self-conjugate, because the system is multicomponent. In addition, it is found that the effect of Reynolds number on the stability of these systems is linear at small Reynolds number, in contrast to the self-conjugate Rayleigh–Benard problem, where the effect is quadratic.     

压力对泡沫驱封堵能力及气泡大小的影响

空气泡沫驱油工艺中,泡沫对孔喉的封堵能力主要受气泡尺寸大小的影响。通过室内驱替实验研究了压力对空气泡沫渗流过程中的封堵能力和气泡大小的影响。实验装置为自制可视化填砂管模型．实验用起泡剂为有效浓度为0．5％的zY起泡体系。在不同压力下,用精密压力表测定填砂管首尾测压点（p。和P。）和填砂管中间的两个测压点（p2和P3）压力数值;p2和P3之间相距1m,距填砂管首尾两端距离都为0．5m。结果表明：①泡沫的封堵能力与压力成正比,压力越大,泡沫产生的阻力系数越大,封堵能力越强;压力为0．1MPa、5MPa和IOMPa时,泡沫产生的阻力系数分别为48、58和70。②气泡的直径与压力成反比,常压（0．1MPa）时,气泡平均直径约为7．381xrn;压力为5MPa时,气泡平均直径约为5．46μm。③压力为5MPa时,气泡与孔喉的匹配性比常压（0．1MPa）时更好。     

Exergy analysis of a 1.2 MW waste heat power generation project

According to systematic features, analysis method based on exergy balance is established. Basic indicators in the system, the subsystem, and facilities are put forward in this paper. By using this method to analyze the generation system of megawatt‐scale in one chemical enterprise, it is found that the objective exergy efficiency of the system is 35.67%, and exergy loss of organic Rankine cycle (ORC) is the highest. The thermal efficiency of the total system is 9.61%. For the condenser, the thermal efficiency is 91.18%, and the exergy efficiency is only 23.44%. The objective exergy efficiency of the evaporator is 74.04%. The influence coefficient of exergy loss of condenser is higher than that of pump and expander, but input exergy of the condenser is lower than that of the expander. It is revealed that ORC subsystem is the part which needs to be focused on, and the condenser is the most important component of ORC subsystem which should be optimized firstly.     

发电厂湿法脱硫系统烟气挡板门密封风系统的节能改造

火力发电厂普遍采用烟气湿法脱硫系统来脱除锅炉燃烧产生的二氧化硫,湿法脱硫系统的挡板需要持续通入热空气,避免挡板受到烟气的腐蚀。一般采用电加热的方法来加热空气,实际运行中发现存在耗电量大和加热器的电热丝容易烧断的问题。通过计算发现使用发电厂辅助蒸汽来加热空气比采用电加热的方法具有更高的经济性。文中介绍了湿法脱硫系统烟气挡板门密封风节能改造方法,及其经济性分析结果。     

Fu''s experiment and the generalized Gibbs distribution

It is pointed out that the distribution of electrons in Fu's experiment is not the Boltzmann distribution, but the generalized Gibbs distribution. The generalized Gibbs distribution is derived from Liouville's theorem and also from the requirement that the entropy of a closed system be maximum. It is shown that in the case of the generalized Gibbs distribution, the increase of entropy of the system is not equivalent to the second law of thermodynamics. Therefore, the second law is violated in Fu's experiment, but the principle of increase of entropy is still held. The electric current is calculated by using the generalized Gibbs distribution and the result agrees with the experiment. A new experiment which is more convenient to make than Fu's experiment is suggested.     

进气喷射不同辛烷值燃料的HCCI燃烧爆震试验分析

HCCI燃烧是化学动力学控制的均匀稀混合气的压缩自燃,大量的浓混合气同时着火燃烧导致燃烧速度过快而爆震。致力于能够描述或量化HCCI爆震程度方法的研究,进而建立HCCI爆震强度评价标准。不同辛烷值掺比燃料在不同工况的HCCI燃烧压力信号的频谱对比分析结果表明：不同辛烷值燃料的HCCI燃烧爆震具有相近的爆震特征频带,其能量集中的主要爆震特征频带位于4～12kHz;确定HCCI燃烧缸压信号在4～12kHz频带处带通滤波的峰值压力Pbps为HCCI爆震强度评价标准,当Pbps日大于0．15MPa,断定HCCI燃烧出现爆震。据此找出不同辛烷值的混合掺比燃料HCCI燃烧的安全运行范围。     

叶片振动的灰色可靠性研究

在叶片的实际振动中存在着大量部分已知、部分未知或信息不完全的灰色信息，借助灰色理论所需建模数据量较少，研究解决小样本、贫信息不确定问题的优点，将灰色理论与方法引入叶片的振动可靠性评估，提出了叶片振动的灰色可靠性概念，建立了叶片振动的灰色可靠性模型，并将其应用于实际叶片的振动可靠性研究，研究结果表明该法是可行的，具有较高的实用推广价值。     

垂直对称四叶片风力机气动特性仿真研究

采用CFD计算软件对垂直轴风力机气动性能进行计算.首先,使用ICEM软件对模型进行前处理,通过Fluent软件进行数值模拟,分析不同计算时间步长和湍流模型对风力机气动特性仿真结果的影响,确定符合该研究模型的计算方法.随后,对顺流垂旋型垂直轴风力机在不同叶尖速比下进行计算,发现该风力机在叶尖速比为0.42时获得最大功率系...     

Comments on the equation of state of the products of high density explosives

The problem of the thermal equation of state of the products of solid explosives is considered. It is assumed that the products are in chemical equilibrium, that the specific chemical heat released is independent of the loading density, and that the detonation density is proportional to the loading density. Using the energy conservation equation and thermodynamic relationships, it is then shown that the thermal equation of state must satisfy the following relationship:

$F[T^{(1?K)/2K}\upsilon ;{\upsilon }^{(1+K)/(1?K)}p]=0$

. where K is a constant and F is an arbitrary function of its two arguments. It is then argued that the experimental knowledge of detonation velocity, pressure, density, and particle velocity versus loading density is not enough to check the validity of an assumed thermal equation of state of the products and to compute the detonation temperature. In particular, it is explained why similar detonation pressures, densities, and particle velocities, but completely different detonation temperatures have been calculated by various authors, using similar detonation velocity data but different thermal equations of state.     

发动机左后盖有限元优化分析

左后盖是发动机的重要部件之一,其结构强度历来是发动机设计者关注的重要指标之一。本文对发动机左后盖若干极端工况下受力过程进行简要分析,进而用MSC.Nastran软件进行强度计算,分析了其应力分布规律,并提出了改进措施。进一步计算表明,结构改进后的左后盖安全系数大大提高。     

锅炉憋压/节流运行技术的热力学分析

对锅炉憋压 /节流运行技术提高热网运行效率的方法给予了详细的阐述 ,它产生于塔里木油田某转油站 ,并成功地应用于该油田的其它转油站。锅炉憋压运行技术的研究是基于工程热力学理论、流体力学理论和传热学理论。在供热系统中热动力式疏水器在原始的运行系统下蒸汽流失严重 ,而在新的运行系统下只疏水不疏汽 ,蒸汽损失较小 ;通过对外输原油所需热量、换热器换热量、实际用汽量以及转油站所需锅炉加热量等的比较计算分析 ,论证了锅炉憋压运行技术对高出力、低负荷运行 锅炉热网具有一定的节能效果 ,操作简单且不需要对系统进行改造     

考虑源荷不确定性的电热系统联合调度

针对风电和电热负荷不确定的问题,提出计及源荷不确定性的旋转备用容量的优化方法,建立考虑电热备用耦合影响的调度模型.在日前阶段,以能源与负荷的预测量制定机组的出力方案,风电由于其预测精度较低,利用Beta概率密度函数来拟合风电出力,从而确定风电的不确定性带来的旋转备用容量,利用机会约束规划来处理不确定问题;负荷有较高的预...     

Numerical investigation on porous media heat transfer in a solar tower receiver

In order to investigate the steady heat transfer characteristics of a porous media solar tower receiver developed in China, this paper applies the steady heat and mass transfer models of the porous media to solar receivers, chooses the preferable volume convection heat transfer coefficient model, solves these equations by using the numerical method, and analyzes the typical influences of the porosity, average particle diameter, air inlet velocity, and thickness on the temperature distribution. The following conclusions have been drawn: in the same position or relative position along the downstream, the bigger the average particle diameter is, the higher the solid matrix dimensionless temperature is, the higher the air dimensionless temperature is. The bigger the porosity is, the lower the solid matrix dimensionless temperature is, the bigger the porosity is, the higher the air dimensionless temperature is. The bigger the thickness is, the lower the solid matrix dimensionless temperature is, the higher the air dimensionless temperature is. In a certain depth, the bigger the air inlet velocity is, the higher the solid matrix dimensionless temperature is. After a certain depth, the bigger the air inlet velocity is, the lower the solid matrix dimensionless temperature is, and the bigger the air inlet velocity is, the higher the air dimensionless temperature is. The paper can provide a reference for this type of receiver design and reconstruction.     

AA-CAES+CSP系统性能及关键参数分析

为深入分析耦合太阳能辅热的先进绝热压缩空气储能(AA-CAES+CSP)系统的运行特性,在先进绝热压缩空气储能(AA-CAES)系统基础上建立相关模型,对比分析这2个系统性能,并探究关键参数对AA-CAES+CSP系统性能影响。结果表明:相比于AA-CAES系统,AA-CAES+CSP系统循环效率提高7.90%,储能密度提高4.46%;当压缩机级数N1=膨胀机级数N2=级数N时,循环效率和储能密度最高,N1与N2相差越小,系统性能越优;随着储气室对流换热系数hc的增大,循环效率先大幅度降低,后缓慢增大,储能密度则持续增大,且在hc较小时,N越大,循环效率越低,而当hc较大时则相反,储能密度则随N的增大而持续增大,但N越大,同一hc对系统性能的影响越小;循环效率随储气室最大压比的增大而减小,储能密度则相反,且在最大压比较小时,N越大,循环效率越小,储能密度越大,但当N较大时,N越大,循环效率和储能密度均越大。     

膜片管通道流动与换热过程的数值模拟

采用SIMPLE算法模拟膜片管通道中的流动与换热,分析流场中出现的非线性现象以及不同管束排列方式对换热的影响。物理模型长度为185. 6 mm,高度为92. 8 mm,圆管直径为32 mm。烟气入口温度为400 K,上下两侧固体壁面温度为300 K。假设流动与换热进入充分发展阶段,雷诺数(Re)的取值范围是3 000～25 000,通入不同流速的烟气与两侧的壁面进行换热。结果表明:采用雷诺应力模型(RSM)所得的努塞尔数(Nu)与实验关联式结果最吻合,而且相对误差在5%～17%间;采用直接模拟(DNS)模拟时,稳态到非稳态的临界Re是100;在同一Re时,随着管间距减小,Nu是逐渐增加的,当Re取为25 000,管束水平间距和竖直间距均取为43. 2 mm时,通道换热能力达到最大且相应的Nu是195. 23。     

双水平井SAGD预热阶段温度场计算

采用满足质量守恒的流函数方法,编制有限容积法程序,模拟计算了双水平井蒸汽辅助重力泄油(steam assisted gravity draining,SAGD)蒸汽循环启动预热阶段温度场演化情况。对比了纯导热与导热及热对流共同作用下所需预热时间的差别,给出了单位长度井散热速度和两井中间位置温度随时间的变化,同时,也分析了井间距对预热时间的影响。结果表明,单位井长度的散热速度随时间的延长逐渐减少,在初始阶段变化较快,然后以较慢的速度降低。这表明,以井筒恒热流边界条件的温度叠加原理分析方法,建立预测阶段温度分布模型,预测热联通需要的加热时间是不合适的。不同井间距工况预热阶段数值计算表明,影响预热时间的主要因素为两井间距,间距扩大一倍,需要的预热时间延长约为原来的4倍;原油黏度很大且随温度变化不太敏感或井间距较小的情况,自然对流换热作用很弱,在预测预热时间时可以按照纯导热模型处理,而相对不太黏稠的原油或井间距较大时热对流作用强,不能忽略对流传热的影响,自然对流换热可大大缩短预热时间。     

天然气制氢尾气碳减排工艺设计与优化

开发多种类分离膜与压缩冷凝耦合的梯度回收工艺,实现H₂和CO₂等组分高价值利用。考察压力、产品浓度和不同氢膜单元对工艺的影响。通过Aspen HYSYS对10000 Nm³/h处理量的工艺优化模拟得出：采用单级氢膜单元和一级二段氢膜单元,尾气进膜压力2700 kPa和H₂产品浓度60%时,工艺经济性最佳,分别实现H₂回收率81%和90%、CO₂回收率58%和60%、燃气热值16.7 MJ/Nm³和18.2 MJ/Nm³、投资回收期26.1 个月和24.4 个月。采用二级氢膜单元投资最少,最佳投资回收期16.5 个月时,氢气产品纯度为52%,低于制氢吸附装置设计要求。     

转轮式干燥冷却系统的参数分析与性能预测

以若干有代表性的参数对干燥冷却系统各部件的作用进行了分析，阐述了换热器在气流冷却过程中的突出作用，给出以ＲＤ硅胶为吸附剂时系统的具体性能。在原有系统基础上增加预冷装置，使系统性能有明显提高。     

循环流化床锅炉二次风机节能改造

300 MW循环流化床（CFB）锅炉二次风机设计余量偏大且为恒速运行风机。机组在低负荷运行时,送风量需求减少,风机入口挡板开度很小,风机效率低,电耗大。通过对300 MWCFB锅炉二次风机电机进行加装变频器的节能技术改造,二次风机运行时入口调节挡板全开,通过变频器调节二次风机电机转速来调节送风量,尤其是在机组低负荷运行期间,能提高风机运行效率,实现了厂用电率的大幅降低,达到了节电降耗的目的。且风机运行调节平滑及精度高,有利于锅炉安全、经济运行。风机经变频调速运行后,运行转速下降较多,故又能降低噪音,延长风机使用寿命。     

Operation analysis of a photovoltaic lighting system with battery and heater

An operation analysis is presented for a photovoltaic system consisting of the photovoltaic generator, the battery, the light, and the heater. An optimal resistive load for lighting is determined according to the characteristics of the battery. The working domain of the battery is marked out to display the range of the battery charge supplied by the photovoltaic generator. Before sunrise and after sunset, the battery supplies power to the light with an optimal resistive load. When the sun is above the horizon but sunset or not sunrise for the tilled photovoltaic module, the system is at rest. If the beam radiation is really incident on the surface of the module and induces a characteristic inside the working domain, all power will charge the battery. Once the characteristic is outside of the working domain, the resistive load is chosen to balance the currents of photovoltaic generator, battery charge, and heater. It is the only situation of concurrence. If the open-circuit voltage of the photovoltaic array under insolation is less than the zero-current voltage of the battery at the fractional state of charge, or if the battery is at full charge, the battery is disconnected from the photovoltaic system and the power output of the photovoltaic array to the heater is found by the method of maximum power point tracking.