Investigation of the steam-cooled blade in a steam turbine cascade

With the increasing demand for electricity,an efficiency improvement and thereby reduced CO2 emissions of the coal-fired plants are expected in order to reach the goals set in the Kyoto protocol.It can be achieved by a rise of the process parameters.Currently,live steam pressures and temperatures up to 300 bars and 923 K are planned as the next step.Closed circuit steam cooling of blades and vanes in modern steam turbines is a promising technology in order to establish elevated live steam temperatures in future steam turbine cycles.In this paper,a steam-cooled test vane in a cascade with external hot steam flow is analyzed numerically with the in-house code CHTflow.A parametric analysis aiming to improve the cooling effectiveness is carried out by varying the cooling mass flow ratio.The results from two investigated cases show that the steam cooling technique has a good application potential in the steam turbine.The internal part of the vane is cooled homogeneously in both cases.With the increased cooling mass flow rate,there is a significant improvement of cooling efficiency at the leading edge.The results show that the increased cooling mass flow ratio can enhance the cooling effectiveness at the leading edge.With respect to trailing edge,there is no observable improvement of cooling effectiveness with the increased cooling mass flow.This implies that due to the limited dimension at the trailing edge,the thermal stress cannot be decreased by increasing the cooling mass flow rate.Therefore,impingement-cooling configuration at the trailing edge might be a solution to overcome the critical thermal stress there.It is also observed that the performance of the cooling effective differs on pressure side and suction side.It implicates that the equilibrium of the cooling effectiveness on two sides are influenced by a coupled relationship between cooling mass flow ratio and hole geometry.In future work,optimizing the hole geometry and cooling steam supply conditions might be the solutions for an equivalent cooling effectiveness along whole profile.      

Designing a power plant with highest efficiency:results from SFB 561

The goal of Collaborative Research Centre(SFB) 561 "thermally highly loaded,porous and cooled multi-layer systems for combined cycle power plants" is to expand the current technological and scientific knowledge on power plants in order to achieve total efficiencies of 65% in a combined cycle power plant in the year 2025.Therefore,the aero-thermomechanical,structural-mechanical,materials' scientific and production fundamentals for the development of steam and gas turbine components that are able to withstand highest thermal loads are being worked out within this SFB.This means for the gas turbine that combustion chamber outlet temperatures of 1520℃ at 1.7MPa are to be attained.In order to control these high temperatures,it is not only required to develop new materials' solutions,including thermal barrier coatings,but also to apply improved cooling techniques,as for example effusion cooling.This novel cooling concept is to be realised through open-porous structures.These structures can consist of drilled open-porous multi-layer systems or open-porous metallic foams.The development of graded multi-layer systems is also extremely important,as the grading will enable the use of coolant in dependence of the requirements.The live steam parameters in the high pressure turbine are expected to be increased up to approximately 700℃ with pressure of 30MPa.These elevated steam parameters can be encountered with Ni-base alloys,but this is a costly alternative,associated with many manufacturing difficulties.Therefore,the SFB proposes cooling the highly loaded turbines instead,as this would necessitate the application of far less Ni-base alloys.To protect the thermally highly loaded casing,a sandwich material consisting of two thin face sheets with a core of a woven wire mesh is used to cover the walls of the steam turbine casing.The current state of the research shows that by utilising innovative cooling technologies a total efficiency of 65% can be reached without exceeding the maximum allowable material temperature,thereby prolonging the life-span.      

几种导弹弹射动力系统内弹道性能比较

介绍并比较了几种导弹弹射动力系统的特点,在一定假设的基础上对几种弹射动力系统进行了内弹道模型的设计、编制程序并针对某型导弹及内弹道指标进行计算,计算结果显示了在不同弹射动力下,发射筒内工质气体状态参数随时间变化的规律和导弹在发射筒内运动加速度、速度、位移随时间变化的规律.通过比较分析所得的内弹道性能曲线,得出燃气-蒸汽式弹射动力系统所需工质流量小,结构简单,压力及加速度变化平稳,温度适中,导弹速度及位移增加快,发射时间短,内弹道参数较理想,具有很大的优势和发展前景.为导弹弹射动力系统的设计和方案选择提供参考依据.     

汽轮机真空值偏高的原因分析及处理

针对充矿科澳公司南屯电厂4#机组的汽轮机真空值偏高的现状,在充分调查和分析原因的基础上,对降低汽轮机真空值展开研究．在19个影响原因中确定4个为主要原因,并采取相应措施。实施效果表明,与改造前相比,机组负荷由原来到80％（即40MW）就因汽机真空值高而带不上去,到现在满负荷运转时,真空≤-0．091Mpa,完全达到了改造前的目标。     

甲烷水蒸气重整强化管内换热的数值模拟

以圆管内壁催化剂薄层内发生甲烷水蒸气重整反应为研究对象,对层流条件下反应及换热进行了数值模拟,分析了催化剂活性、薄层厚度、入口气体流量、入口压力、入口温度以及反应物组分比对反应和换热的影响.结果表明:催化剂薄层内的吸热反应可以有效地增强换热,降低壁面温度;提高催化剂活性和增加薄层厚度,可以增加化学反应吸热量,降低壁面温...     

重整制氢反应器的种类和研制进展

介绍了重整制氢的方法和重整制氢反应器的种类及其特点.重整制氢的方法有3种:水蒸汽重整、部分氧化重整、自热重整.重整制氢反应器有3种:管式反应器、板式反应器和微通道反应器.管式反应器结构简单;板式反应器易于拆装和扩大规模,并且传热效率高,其研究受到了广泛关注;微通道反应器在传热、恒温等性能方面的表现明显优于管式反应器和板式反应器,有较好的发展前景.     

蛇型冷却通道中的蒸汽流动与换热特性研究

采用CFX软件数值计算了带肋蛇形冷却通道内的空气流动与换热特性,验证了计算模型和方法,比较了湍流模型的适用性;在此基础上,数值计算了蛇形冷却通道内蒸汽的流动与换热特性,分析了蒸汽过热度、肋片角度和V型肋片对蒸汽流动与换热性能的影响。结果表明:SSG湍流模型的计算结果与实验数据吻合较好;蒸汽过热度对换热效果的影响较小;相对于光滑通道,带肋通道的弯道效应影响降低;V型肋片的换热效果好于平行斜肋。     

Flow and Heat Transfer Characteristics in Rotating Two-pass Channels Cooled by Superheated Steam

In a modern gas turbine,using superheated steam to cool the vane and blade for internal convection cooling is a promising alternative to traditional compressor air.However,further investigations of steam cooling need to be performed.In this paper,the three-dimensional flow and heat transfer characteristics of steam are numerically investigated in two-pass square channels with 45° ribbed walls under stationary and rotating conditions.The investigated rotation numbers are 0 and 0.24.The simulation is carried out by solving the Reynolds averaged Navier-Stokes equations employing the Reynolds stress turbulence model,especially considering two additional terms for Coriolis and rotational buoyancy forces caused by the rotating effect.For comparison,calculations for the air-cooled channels are done first at a Reynolds number of 25 000 and inlet coolant-to-wall density ratio of 0.13.The results are compared with the experiment data.Then the flow and heat transfer in steam-cooled channels are analyzed under the same operating conditions.The results indicate that the superheated steam has better heat transfer performance than air.Due to the combined effect of rotation,skewed ribs and 180° sharp turn,the secondary flow pattern in steam-cooled rotating two-pass channels is quite complex.This complex secondary flow pattern leads to strong anisotropic turbulence and high level of anisotropy of Reynolds stresses,which have a significant impact on the local heat transfer coefficient distributions.     

某型燃气轮机燃气一蒸汽联合循环方案分析

燃气-蒸汽联合循环是利用燃气侧高温吸热和蒸汽侧低温放热来扩大循环平均吸放热温差,促进能源的梯级利用,以提高循环效率。分析了某燃气轮机采用余热锅炉型联合循环后性能改善情况。简述了余热锅炉型燃气-蒸汽联合循环的工作原理,采用能量平衡法分析联合循环机组的热效率及其影响因素,采用Gat eCycle软件搭建联合循环模型,分析给出适合该型燃气轮机的联合循环方案。     

蒸汽动力分布式集成智能故障决策支持系统

船舶蒸汽动力故障决策支持系统是一个复杂的系统决策问题。文章借鉴RODOS系统（核事故应急决策支持系统）的思想,将分布式系统结构、系统集成思想以及智能运作机制引入到决策支持系统之中,提出船舶蒸汽动力系统分布式集成智能故障决策支持系统的理论框架和结构。系统可充分利用分布式集成智能理论的自主性、反应性和自觉性,对蒸汽动力系统故障时的处置决策提供有效支持。