汽轮机调节级固体颗粒冲蚀的数值模拟

对于不同机组,汽轮机调节级内部结构不尽相同,其中的固体颗粒冲蚀规律也会有区别.以某600MW汽轮机调节级叶栅为研究对象,采用欧拉-拉格朗日法,数值模拟了调节级静、动叶栅通道内固体颗粒的运动特性,研究了固体颗粒的运动规律,分析了固体颗粒对喷嘴叶片、动叶片的冲蚀.研究发现不同粒径的固体颗粒对叶片的冲蚀有着不同的影响,大粒径粒子造成的冲蚀占主要比例,小粒子甚至未对叶面发生碰撞;喷嘴内的冲蚀区集中在压力面的中后部;动叶内的冲蚀区位于压力面中后部以及柱形前缘,压力面中后部靠近叶尖部位的地方冲蚀最为严重.     

考虑气固单向耦合作用的燃气轮机流场数值模拟

基于颗粒随机轨道模型,将烟气看成连续相,将颗粒视为离散相,采用气固单向耦合方法,应用Fluent软件对某船用增压锅炉燃气轮机级多叶片流道内的气固两相流动特性进行了数值模拟,重点分析了不同直径固体颗粒在动静叶栅通道中的运动轨迹分布特点、颗粒对叶片表面的碰撞作用。研究结果可为燃气轮机叶片抗磨损能力的优化设计提供理论依据。     

超临界汽轮机再热第一级叶片固粒冲蚀特性的数值分析

采用数值方法计算与分析了超临界汽轮机再热第一级的固体颗粒三维运动特性,根据固体颗粒撞击叶片的位置、速度与撞击角以及叶片材料的抗冲蚀性能综合分析了静叶与动叶的冲蚀机理及冲蚀特性,指出静叶吸力面冲蚀是从动叶反弹回来的固粒撞击所引起的。此外,还分析了动静叶轴向间距及机组负荷对反弹至静叶的颗粒数量的影响,结果表明,随着轴向间距的减小和负荷的降低,反弹回静叶的颗粒数量增加。     

子午面成型对超临界汽轮机调节级喷嘴固体颗粒冲蚀特性的影响

建立了氧化铁颗粒撞击12Cr材料高温的冲蚀率模型,并与叶栅的三维流场和固体颗粒运动特性的数值计算方法一道,计算与分析了1台超临界汽轮机调节级喷嘴顶部采用平直子午面和收缩子午面两种情况下,氧化铁颗粒对于喷嘴叶片的撞击区域和撞击参数以及喷嘴表面的冲蚀量分布,结果表明:子午面收缩能够有效地减小叶片表面上受严重侵蚀的范围并降低最大当地冲蚀量。与平直子午面喷嘴相比,受严重侵蚀的区域面积降低约60%,最大当地冲蚀量降低约1 3。图13参7     

汽轮机静叶栅表面颗粒沉积特性数值模拟研究

采用计算流体力学CFD方法(computational fluid dynamics)并结合汽轮机静叶栅处实际运行参数对静叶栅表面颗粒的沉积特性进行数值模拟研究。模拟计算基于三维定常不可压缩流体的N-S方程,在连续相流场的基础上引入离散相模型DPM(discrete phase model),并忽略盐类析出的化学过程,对流场内固体颗粒的沉积轨迹及在叶片表面的沉积率进行数值模拟。模拟结果表明:汽轮机静叶栅处的沉积部位主要位于压力面的尾缘处,且随着颗粒直径的变大,沉积率变大,同时在压力面处的沉积范围也增大;随着颗粒质量流量增大,沉积率增大,但是沉积范围没有变化。     

固体颗粒磨蚀的数值模拟计算分析

论述了蒸汽中的固体颗粒对汽轮机喷嘴叶片磨蚀作用的产生机理及危害;采用流体力学软件对叶栅流场进行了详细的全三维数值模拟;并对结果进行了计算分析,总结出了固粒磨蚀的特点,为解决固粒磨蚀提供了一定的理论依据。     

叶片弯曲对扩压叶栅出口流场的影响

通过由常规直叶片、正弯曲叶片、反弯曲叶片组成的三种矩型扩压叶栅在低速风洞上的实验研究,测得了叶栅出口流场、研究了零冲角下常直叶栅、正弯曲叶栅、反弯曲叶栅对出口总压损失分布情况和二次流速度矢量的影响,讲座了叶片弯曲对扩压叶栅出口流场的改善作用。     

端壁相对运动对压气机叶栅间隙流场影响的数值模拟

压气机端壁与叶片间的相对运动是影响叶顶间隙气流流动的重要因素.采用数值模拟的方法考察了端壁运动对不同叶顶间隙压气机叶栅内三维流场的影响.结果表明:端壁相对运动改变了叶栅间隙流场结构,叶栅通道内出现向相邻叶片压力面运动的刮削泄漏涡,上通道涡及叶顶分离涡受到抑制,叶尖负荷增大,间隙泄漏流量增加,叶栅总损失由于叶顶区掺混损失减少而减少.     

冲角对不同掠型压气机叶栅扩压因子的影响

对直、前掠、弯掠和后掠叶片组成的压气机叶栅进行了实验研究,结合叶栅出口能量损失分布和叶片表面静压系数的分布及叶片负荷的变化,讨论了冲角变化对不同掠型压气机叶栅扩压因子的影响以及叶栅扩压因子与叶栅能量损失和叶片负荷的相互关系。结果表明,前掠和弯掠叶栅显著改善了叶栅根部的流动．能够有效防止气流减速造成流动分离的可能;这两种叶栅轴向逆压梯度长度和叶片负荷大小的综合作用是其扩压因子在叶片两端部小于直叶栅的原因。     

非光滑叶片对叶栅出口能量损失系数的影响

在低速平面叶栅风洞中对４种具有不同几何尺寸流向微槽的非光滑叶片叶栅进行了实验研究,主要研究非光滑叶片对叶栅出口能量损失系数的影响。实验结果表明,采用非光滑叶片可以减少叶栅损失,相对减少最多１６．５％,最少９．１％。     

唱响春天里的歌

春的脚步蹒跚将至。春节刚过。料峭春寒中,2月9日、12日,北京终于迎来入冬以来久违的降雪。在故宫墙外,在北海公园,人们拿着相机记录着今冬的雪,享受着银装素裹下红墙碧瓦的美丽。心情就像一只只快活的小鹿在一望无垠的草地上时而奔跑,时而嘻戏,时而偎依在母亲身旁。人们的心里、喉咙里唱着春天里的歌。     

通用外径检具在气缸套加工中的应用

1引言气缸套是发动机的核心零部件,气缸套质量直接影响到发动机的功率和排放指标,国家修订的气缸套标准越来越等同于欧标排放标准,随着近几年进军多缸机的厂家逐步扩大,我国大中型柴油机厂猛增几十家,     

节能量的计算方法及在节能审核中的应用

节能量的准确计算在节能审核中越来越重要。文中详细阐述节能量的计算、边界确定和在实际中的应用,增加审核的可靠性、真实性,同时介绍在燃煤锅炉(窑炉)、余热余压利用项目、电机系统节能、及能量优化系统优化项目的计算方法。     

Understanding the ROC transfer payment in the renewable obligation with the recycling mechanism in the United Kingdom

The Renewable Obligation scheme was implemented to promote renewable energy for electricity supply in the UK over 15 years from 2002 to 2017. Renewable Obligation Certificates (ROCs) were allocated to accredited generators for receiving additional revenues from selling those certificates to electricity suppliers. In particular, a recycling mechanism was employed in this scheme. That is, the penalties on missing ROCs from all suppliers are paid into the buy-out fund, which is then redistributed to suppliers in proportion to the number of ROCs they presented. This mechanism complicated the ROC trading in three aspects. First, the recycling mechanism induces strategic behaviour between suppliers in fulfilling the obligation of purchase of ROCs, leading to the equilibrium of a lower transfer payment from suppliers to generators, compared with the scenario without the mechanism. Secondly, under the recycling mechanism, the existence of vertical integration encourages upstream competition between generators, reducing ROC prices and the transfer payment. Thirdly, suppliers may strategically collude with each other to take the advantage of the recycling mechanism, but the existence of vertical integration weakens the collusion and prevents the worst case of nearly zero transfer payment.     

Energy efficiency and the slump in labour productivity in the USA

Energy consumption is included in an aggregate Cobb-Douglas production function for the USA. The data suggest that energy conservation has not reduced the growth rate for real GNP by more than 0.3 percentage points and that less than one-fifth of the overall slump in labour productivity since 1973 should be attributed to higher energy prices.     

Estimating the agricultural demand for electricity in the presence of measurement error in the data

This paper begins by discussing some of the problems frequently encountered in obtaining demand elasticity estimates. To these problems is added that associated with inaccuracy in the measurement of the dependent variable and one or more of the independent variables that impact upon the quantity demanded. Two diagnostics — the regression coefficient bounds and the bias correction factor — are introduced to assess the effect that such a measurement error has on the estimated coefficients of demand relationships. Use of these diagnostics aids in assessing the integrity of the estimates obtained. In considering the demand for electricity for irrigation and the demand for electricity for other (non-irrigation) uses by farmers in the USA, both the quantity demanded and the unit price data available for demand model estimation purposes contain measurement errors. The regression coefficient bounds diagnostic is used to indicate a range over which the true price responsiveness of farmers to changes in energy prices lies. The results suggest that each 1% increase (decrease) in the price of energy will result in between a 0·51 and 0·35% decrease (increase) in the quantity of electricity demanded for irrigation and between a 0·43 and 0·17% decrease (increase) in the quantity of electricity demanded for other uses. The bias correction factor is computed to evaluate the magnitude of the under-estimation of the responsiveness of the quantity of electricity demanded for irrigation and electricity for other uses to a change in the number of acres irrigated and the number of acres planted. For electricity for irrigation, the under-estimation was 14·1% while, for electricity for other uses, it was 13·9%.     

Meeting the challenges in the transport sector

This paper provides an industry leader's perspectives on the potential for transportation fuel cells, reviewing their development progress, describing their advantages and barriers, and identifying paths to successful commercial deployment. UTC Power has developed proton exchange membrane (PEM) fuel cell technology for transportation since 1998, building upon applicable innovations from the company's space fuel cell and stationary fuel cell programs. PEM fuel cell durability improvements are discussed, highlighting achievements in the understanding of decay mechanisms and the design of effective mitigations. The potential for high-volume production to make automotive fuel cells cost competitive with internal combustion engines is explained. The paper underscores the important role that initial deployment of PEM technology for transit buses can play, although development of automotive fuel cells must continue in parallel as the hydrogen infrastructure develops. Suggestions are offered on how policies and regulations, communication and education, and improved codes and standards can all help to promote the widespread use of fuel cells in transportation.     

可调式汽封在215MW 机组汽封改造中的应用

可调式汽封可以减少动静间的碰磨造成的汽封磨损,保持较小的汽封间隙,使泄漏蒸汽量减少,提高机组运行热效率,同时,也能够增加机组的安全可靠性。     

叶片动应力计算的重要改进及其在不调频叶片设计上的应用

叶栅流场中的叶片受流道中汽流力的作用，同时也承受了流道中谐波汽流力的激振。由于谐波汽流力沿周向波动，其对叶片的激振力应该是流道宽度内谐波激振力的积分。本着这一观念对ASME早期发表的动应力基本方程进行改进，重新作了推导，并指出了降低叶片共振应力的途径。多年来已取得了成功应用，其中涉及带冠单叶片的动强度特性及不调频叶片事故处理的材料综合抗振强度对比分析，对工程实践具有一定的参考借鉴的价值。     

地源热泵制冷工况间歇运行的实验研究

地下埋管内的水温主要与埋管换热器的长度、地下土壤温度、土壤的热物性及系统运行模式等因素有关。如果能找出系统最佳运行模式,对于地下温度场的恢复、系统运行优化以及减少埋管换热器的造价都有重要意义。本文就是基于这样的目的,通过人为控制机组的运行模式,探求连续运行及间歇运行模式下埋管换热器内水温的变化规律,以期找到地下换热系统运行优化的最佳手段。