开式燃气轮机中冷循环热力学优化

调整质量流率(或沿通流路径压力损失)和中间压比的分配可以优化开式燃气轮机中冷循环的热力学性能。分析表明,分别存在最佳的燃料流率(或沿通流路径压力损失)和中间压比使循环输出功率最大,最大功率输出对总压比有附加的最大值。给定质量流率和动力装置尺寸的情况下,通过合理分配压气机入口和透平出口之间的流通面积,循环输出功率和效率可以再次得到优化。     

回收内燃机余热的布雷顿循环分析

对回收内燃机余热的布雷顿循环进行了分析,导出了循环比功、循环效率和各个部件损失的表达式,分析了余热温度、循环压比和换热器有效度对循环比功、效率的影响,得到了该循环的效率特性和输出比功特性,确定了损失最大的位置。结果表明,循环比功和效率随着换热器有效度和余热温度的增加而增加,分别存在最佳循环压比使循环效率和循环比功达到最大值。研究为余热回收型燃气轮机性能的改进提供方向。     

余热利用式燃气轮机循环热力学分析

燃气轮机循环能用于回收钢厂生产过程中熔渣所产生的余热资源,为了研究余热利用式燃气轮机循环的性能,建立了该循环的经典热力学模型,分析了余热回收温度对循环功率和热回收效率的影响,并以循环功率最大为优化目标,对循环的功率进行了优化,给出了最大功率、最大热回收效率及相应的最佳空气质量流率和最佳压比等经典热力学优化结果。     

带涡轮进气冷却的燃气轮机循环分析

对带涡轮进气冷却的燃气轮机循环进行了分析,导出了循环效率和损失的表达式,分析了循环温比和质量流率比对循环效率和循环输出比功的影响。得到了该循环的效率特性和输出比功特性,确定了损失最大的位置,研究对燃气轮机循环的设计有一定指导意义。     

基于火电机组循环水负荷段经济背压自动调节应用研究

冷端损失是火电机组占比最大的能量损失,其中机组背压是影响冷端损失最重要的因素之一,长久以来火电行业一直存在最佳背压的理论,也就是在用来冷却蒸汽的循环水电耗与机组背压之间存在一个最经济的平衡点。基于上述思路,以内蒙某电厂超临界350MW循环流化床机组为研究对象,机组可在循环水泵变频运行基础上,通过对机组最佳经济背压的寻优,根据不同工况凝汽器热负荷、主机循环水温度及背压对机组功率的影响,利用DCS控制系统对循环水泵频率进行自动实时调控,实现机组在优化的经济背压下运行。     

柴油机中冷器的结构与设计研究

在内燃机车当中,柴油机中冷器的功能是使柴油机在运行时增压状态下的空气温度得以降低,同时使空气的密度增加,进而增加柴油机的循环进气量。在热负荷增加的情况下,中冷器可以有效提高柴油机的运行功率,实现资源的合理利用,减少有害气体的排放量。通过对柴油机中冷器的优化设计,可以使设备的优势得到更为充分地发挥,促进柴油机性能的优化与提升。     

百叶窗角度对管带式中冷器传热与阻力特性影响研究

根据影响中冷器综合性能的因素,建立了四组不同开窗角度的百叶窗翅片计算模型,采用Fluent软件,SIMPLE算法和标准k-ε模型对传热特性和阻力特性进行了仿真分析,得到不同开窗角度下中冷器空气侧的温度、压力和换热系数,及中冷器综合性能评价因子。研究发现换热主要集中在百叶窗前端,阻力损失主要集中在翅片区域;压降随着开窗角度的增大而增大;在相同的工况条件下,开窗角度为27°时,翅片表面传热系数最大,具有更好的综合性能。计算结果为中冷器散热带结构设计提供了参考。     

弧齿锥齿轮摩擦功率损失影响因素分析

建立了弧齿锥齿轮摩擦功率损失计算模型,采用正交试验法分析了压力角、中点螺旋角、大端端面模数、齿宽、输入转速和输入功率对弧齿锥齿轮摩擦功率损失的影响及各因素的影响程度。结果表明,中点螺旋角和压力角影响最大,并得到使功率损失最小的优化参数组合。     

过零调速型控制式差动无级变速器中回流功率的优化分配研究

控制式差动无级变速器的出现克服了传统变速器调速范围小的缺点,但是在扩大调速范围的同时也带来了封闭循环功率的问题。装置中的循环功率是无法避免的,在这种情况下,针对过零调速型装置进行循环功率流优化分配研究,达到装置内功率损失最小的原则,提高传动效率,以此来达到最佳传动效果,为此类装置的优化设计提供了依据。     

柴油机整机与零部件机械损失的评价指标及实验分析

用倒拖法对6110型直喷柴油机整机及各零部件的机械损失进行测量，提出了发动机的整机机械损失功率比和零部件机械损失功率比评价指标。分析了发动机各零部件和整机的机械损失功率比、机械损失功率、机械效率和平均机械损失压力随发动机转速和润滑油温度变化的规律。实验结果表明，发动机机械损失功率比和其他评价指标一样，不仅可以评价整机的机械损失的大小，也可以评价各零部件的机械损失大小。     

恒温热源实际布雷顿循环的功率密度优化

计入工质与高、低温侧换热器的热阻损失及压气机和涡轮机中的不可逆压缩和膨胀损失，用有限时间热力学方法导出了恒温热源条件下实际不可逆布雷顿循环功率密度与压比间的解析式，借助于数值计算研究了高、低温侧换热器的最优热导率分配对最大功率密度的影响。     

换热管内微型液轮机研究

换热设备积垢热阻大,能耗高,换热设备污垢使中国工业生产蒙受的损失每年达百亿元以上。发明了换热管内微型液轮机用以实现换热设备在线除垢、防垢并强化传热。当管内液体流动时,液轮机自行运动。由于转子不断刷洗换热管,换热管内很难结垢;如果原有积垢,也可除垢;而且滞流边界层受到不断地扰动,强化了传热。工厂试验证明,换热管内微型液轮机在线除垢防垢效果好。该技术对节能有重要意义。介绍了换热管内微型液轮机的工作原理、转速特性、流阻特性及在线除垢工业试验。     

Heat transfer enhancement for fin-tube heat exchanger using vortex generators

Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin-circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of fin-flat tube heat exchanger without vortex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger. At the same time, pressure losses for four types of heat exchanger is measured and compared.     

进排气压力损失耦合作用下的船用燃气轮机性能研究

基于不同的燃气轮机运行工况,获得进排气系统的压力损失变化规律。运用容积惯性法建立了三轴燃气轮机动态仿真模型,考虑船用燃气轮机进排气压力损失作用,对燃气轮机的性能进行仿真研究。数值实验结果表明:随着燃气轮机工况(其值为运行工况功率与额定工况功率之比)的增加,进排气系统的压力损失按近二次方规律增加;燃气轮机的输出功率损失也随工况增加而增大,并呈现非线性特性;热效率同样因进排气压力损失的影响而下降,但在0.8工况左右损失最大,总体也呈现非线性特性。所得结果可为燃气轮机的性能修正、运行管理和优化设计提供参考。     

地面及飞行通用的燃气轮机最佳循环参数简化解及其应用

本文系统地推导出对地面及飞行燃气轮机通用的、各最佳循环参数的定比热循环参数的定比热简化解,包括前所未见的较繁的耗油率最佳压比的解,与压气机及涡轮定等熵效率或定多变效率的两种变比热准确作比较。从而看出：简化解可初估性能随压比变化的趋势及各最佳压比,可作准确解的起步,也可初估各最佳压比及其性能受部件参数及飞行条件影响的趋势;此外,简化解简捷地探求新循环的作用,也值得注意。     

Effect of particle ingestion on the fouling reduction and heat transfer enhancement of a No-Distributor-Fluidized heat exchanger

To overcome the fouling problem that is common in heat exchangers for waste heat recovery, a new type of fluidized heat exchanger was devised and tested. Fluidized bed heat exchangers are considered to be a good candidate for waste heat recovery flue gases due to their demonstrated ability to avoid fouling or to clean out deposition on heat transfer surfaces, but have a major drawback with significant pressure losses. These pressure drops typically associated with the distributor plate, which is a key component in constructing any conventional fluidized bed system, limit the applicability of fluidized bed heat exchangers for use as an energy saving device. In a new design, however, dilute gassolid particulate is maintained without having a distributor plate. The main feature of this no-distributor-fluidized (NDF) heat exchanger is the self-cleaning action by ingested circulating particles at minimal additional pressure loss. In the present study, a multi riser NDF heat exchanger of 7,000 kcal/hr capacity was built to evaluate its heat transfer performance and fouling reduction characteristics. To experimentally simulate the fouled condition, fuel rich combustion gas with soot was introduced to the heat exchanger, then a cleaning test was performed by introducing glass bead particles (600μm) inside the gas passage of the heat exchanger unit. Through the present experimental study, the performance degradation due to fouling was successfully demonstrated and the cleaning role of particle circulation was identified. It was also demonstrated that small amounts of circulating particles contribute not only to the fouling reduction on the gas side, but also to the heat transfer enhancement. Experimental operation data for 50 hours including accelerated fouling are obtained to simulate the long-term behavior of the system.     

使用条缝翅片管换热器的空气源热泵机组除霜特性研究

对试验使用条缝翅片换热器及R410A工质的空气源热泵空调器的除霜特性进行了试验研究,测量了除霜过程中热泵样机的制热量、输入功率、室外换热器进出口温度及压力等参数的动态变化,分析了不同工况下热泵样机的除霜损失.试验结果表明:随着室外环境温度和相对湿度的降低,热泵机组在除霜过程中消耗的能量及从空调房间中吸收的热量增大,尤其在环境温度低于0℃时,除霜过程中的损失增大更快.由于随着环境相对湿度的增大霜层增长速度加快,除霜过程中的损失占结霜/除霜循环总耗能及总制热量的比例增加,因此热泵机组结霜/除霜循环的平均制热量及COP迅速减小.与使用平翅片换热器的热泵机组除霜性能的比较表明,随环境相对湿度的增加,条缝片换热器热泵机组的结霜/除霜循环平均性能衰减速度要快的多.     

An effectiveness-NTU method for triple-passage counterflow heat exchangers

A new effectiveness-NTU method is developed for a special type of heat exchangers. in which the fluid of a passage is in simultaneous thermal contact with two separate fluids flowing in the opposite direction. An extensive amount of numerical simulations are carried out by an iterative method for wide ranges of dimensionless parameters such as ratios of capacity rates, NTU’s, or a dimensionless inlet temperature. The large body of resulting data are then effectively reduced to a small number of simple equations and graphs by introducing a new effectiveness, ε. ε is defined as the ratio of actual heat transfer to the maximum heat transfer obtained when the NTU’s become very large while the ratio of two NTU’s is kept constant. The developed method is readily applicable to the cycle analysis and design, in the same way as the ε-NTU method for the usual double-passage heat exchangers.     

Torque loss in a gearbox lubricated with wind turbine gear oils

In this study, four different fully formulated ISO VG 320 wind turbine gear oils were select: a mineral oil‐based, a polyalphaolefin‐based, an ester‐based and a polyalkyleneglycol‐based fluids. Their physical properties (viscosity, thermoviscosity, piezoviscosity etc.) were characterised for a wide range of operating temperatures. A two‐stage multiplying gearbox, with helical gears, was selected to evaluate the influence of the wind turbine gear oil formulation on torque loss with the gearbox operating at low speed (130–230 rpm) and high torque (500–1000 Nm). The results obtained showed that each wind turbine gear oil formulation generated very different torque losses, evacuated heat flows and operating temperatures, with differences above 20 °C under the most severe operating conditions. A numerical model was developed, simulating all power loss mechanisms inside the gearbox, in particular the churning and friction losses. The coefficients of friction, between gear teeth and between rolling elements and bearing raceways, were calculated for all the tested oils. Copyright © 2013 John Wiley & Sons, Ltd.