Concept of turbines for ultrasupercritical,supercritical, and subcritical steam conditions

The article describes the design features of condensing turbines for ultrasupercritical initial steam conditions (USSC) and large-capacity cogeneration turbines for super- and subcritical steam conditions having increased steam extractions for district heating purposes. For improving the efficiency and reliability indicators of USSC turbines, it is proposed to use forced cooling of the head high-temperature thermally stressed parts of the high- and intermediate-pressure rotors, reaction-type blades of the high-pressure cylinder (HPC) and at least the first stages of the intermediate-pressure cylinder (IPC), the double-wall HPC casing with narrow flanges of its horizontal joints, a rigid HPC rotor, an extended system of regenerative steam extractions without using extractions from the HPC flow path, and the low-pressure cylinder’s inner casing moving in accordance with the IPC thermal expansions. For cogeneration turbines, it is proposed to shift the upper district heating extraction (or its significant part) to the feedwater pump turbine, which will make it possible to improve the turbine plant efficiency and arrange both district heating extractions in the IPC. In addition, in the case of using a disengaging coupling or precision conical bolts in the coupling, this solution will make it possible to disconnect the LPC in shifting the turbine to operate in the cogeneration mode. The article points out the need to intensify turbine development efforts with the use of modern methods for improving their efficiency and reliability involving, in particular, the use of relatively short 3D blades, last stages fitted with longer rotor blades, evaporation techniques for removing moisture in the last-stage diaphragm, and LPC rotor blades with radial grooves on their leading edges.     

600MW超临界机组汽轮机低压转子末级叶片损坏原因分析

介绍某发电厂发生的一起超临界机组低压转子末级叶片损坏事故,宏观检查发现是因为反向第6级蜂窝汽封跌落引起的。进一步开展材质分析、力学性能试验、金相试验,并对蜂窝汽封的加工工艺综合分析,得出如下结论:钎焊工艺影响了汽封体的原始热处理状态,使汽封体的综合机械性能下降,而且汽封体结构不合理,加上运行蒸汽的冲击,导致汽封体跌落断裂,造成末级叶片损坏。分析结论对汽轮机的检修、改造具有指导意义。     

汽轮机末级叶片司太立6连铸铸棒钴基合金焊接修复

吴泾第二发电有限责任公司1号机组在2007年10月的大修中,实现了在汽轮机低压转子末级叶片入口表面用司太立6连铸铸棒钴基合金氩弧焊堆焊代替原来司太立合金片钎焊,成功地对叶片水蚀进行了修复,大大提高了叶片的抗水蚀能力.     

Achieving More Efficient and Reliable Operation of Geothermal Turbines by Using a Secondary Flash Steam Superheating System

Problems encountered in operation of saturated steam geothermal turbine units that stem from the specific features of a geothermal heat carrier are considered. A two-phase state, increased content of salts, and corrosiveness of geothermal working medium have a negative influence on the efficiency and reliability of the turbine’s first and last stages. Owing to high concentrations of impurities in the liquid phase, the first stages suffer from intense generation of deposits. The resulting decrease in the power output is due to both fouling of the flow path and significantly growing roughness of the turbine cascade blades. The flow of wet steam in the geothermal turbine flow path is accompanied by droplet impingement erosion of the last-stage blades and corrosion fatigue of the metal of rotor elements. In addition, the losses due to steam wetness in the flow path cause an essential decrease of the geothermal turbine efficiency. The article gives examples of erosioninduced damage inflicted to the last-stage rotor blades, corrosion fatigue of the metal of integrally-machined shroud elements, and deposits in the nozzle vane cascades of geothermal turbine stages. The article also presents the results from numerical investigations of the effect that the initial steam wetness has on the silicic acid concentration in the wet steam flow liquid phase in a 4.0 MW geothermal turbine’s stages. A method for achieving more efficient and reliable operation of the geothermal turbine low-pressure section by applying a secondary flash steam superheating system with the use of a hydrogen steam generator is proposed. The article presents a process arrangement for preparing secondary flash steam supplied to the geothermal turbine low-pressure section in which the flash steam is evaporated and superheated through the use of a hydrogen steam generator. The technical characteristics of the system for preparing secondary flash steam to be used in the intermediate inlet to the turbine were preliminarily assessed (taking the upgrading of the Mutnovsk geothermal power plant as an example), and it has been shown from this assessment that the wetness degree in the low-pressure section can be decreased down to its final value equal to 2.0%.     

Development of High-Powered Steam Turbines by OAO NPO Central Research and Design Institute for Boilers and Turbines

The article provides an overview of the developments by OAO NPO TsKTI aimed at improvement of components and assemblies of new-generation turbine plants for ultra-supercritical steam parameters to be installed at the power-generating facilities in service. The list of the assemblies under development includes cylinder shells, the cylinder’s flow paths and rotors, seals, bearings, and rotor cooling systems. The authors consider variants of the shafting–cylinder configurations for which advanced high-pressure and intermediate-pressure cylinders with reactive blading and low-pressure cylinders of conventional design and with counter-current steam flows are proposed and high-pressure rotors, which can increase the economic efficiency and reduce the overall turbine plant dimensions. Materials intended for the equipment components that operate at high temperatures and a steam cooling technique that allows the use of cheaper steel grades owing to the reduction in the metal’s working temperature are proposed. A new promising material for the bearing surfaces is described that enables the operation at higher unit pressures. The material was tested on a full-scale test bench at OAO NPO TsKTI and a turbine in operation. Ways of controlling the erosion of the blades in the moisture–steam turbine compartments by the steam heating of the hollow guide blades are considered. To ensure the dynamic stability of the shafting, shroud and diaphragm seals that prevent the development of the destabilizing circulatory forces of the steam flow were devised and trialed. Advanced instrumentation and software are proposed to monitor the condition of the blading and thermal stresses under transient conditions, to diagnose the vibration processes, and to archive the obtained data. Attention is paid to the normalization of the electromagnetic state of the plant in order to prevent the electrolytic erosion of the plant components. The instrumentation intended for monitoring the relevant electric parameters is described.     

1000 MW机组汽轮机低压转子现场车削技术

针对某电厂1 000 MW汽轮机低压转子经检修发现存在的动静碰摩现象,研制了低压转子现场车削装置,比较了低压转子返厂车削和现场车削两种方案,成功实施了转子现场车削,消除了设备隐患.     

超低负荷工况下大功率汽轮机低压缸内温度场分布特性研究

超低负荷下,汽轮机低压缸内的温度分布情况直接影响汽轮机的安全运行。为了更加清晰地分析蒸汽在低压缸内的温度分布特性,采用非平衡凝结流动模型、SST k-ω湍流模型对某300MW汽轮机极低负荷工况下的低压缸流场进行数值模拟,分析了整个低压缸内蒸汽流动特性、做功能力、温度分布以及近零功率时冷却蒸汽参数变化对温度场的影响。结果表明:汽轮机在30%机组热耗验收工况(turbine heat acceptance,THA)时,末级动叶根部出现了回流。在20%THA左右时,末级已经出现了鼓风现象,动静叶顶部出现漩涡,温度明显上升,且此时末级做功为负功率输出。在近零工况下时,低压缸排汽温度与冷却蒸汽流量和冷却蒸汽温度呈线性变化趋势,与冷却蒸汽流量负相关,与冷却蒸汽温度正相关,因此需设置合理的冷却蒸汽流量和温度来控制末两级叶片的出口温度。研究成果可为超低负荷工况下汽轮机的运行提供参考。     

Development and improvement of the operating diagnostics systems of NPO CKTI works for turbine of thermal and nuclear power plants

The work results on the development and improvement of the techniques, algorithms, and software–hardware of continuous operating diagnostics systems of rotating units and parts of turbine equipment state are presented. In particular, to ensure the full remote service of monitored turbine equipment using web technologies, the web version of the software of the automated systems of vibration-based diagnostics (ASVD VIDAS) was developed. The experience in the automated analysis of data obtained by ASVD VIDAS form the basis of the new algorithm of early detection of such dangerous defects as rotor deflection, crack in the rotor, and strong misalignment of supports. The program-technical complex of monitoring and measuring the deflection of medium pressure rotor (PTC) realizing this algorithm will alert the electric power plant staff during a deflection and indicate its value. This will give the opportunity to take timely measures to prevent the further extension of the defect. Repeatedly, recorded cases of full or partial destruction of shrouded shelves of rotor blades of the last stages of low-pressure cylinders of steam turbines defined the need to develop a version of the automated system of blade diagnostics (ASBD SKALA) for shrouded stages. The processing, analysis, presentation, and backup of data characterizing the mechanical state of blade device are carried out with a newly developed controller of the diagnostics system. As a result of the implementation of the works, the diagnosed parameters determining the operation security of rotating elements of equipment was expanded and the new tasks on monitoring the state of units and parts of turbines were solved. All algorithmic solutions and hardware-software implementations mentioned in the article were tested on the test benches and applied at some power plants.     

Improvement in the corrosive fatigue damage to the low-pressure steam turbine blades due to unbalanced currents

This paper presents two improved methods for the corrosive fatigue damage to the blades of low-pressure steam turbines due to corrosive operating environments and power system unbalance. Two blade materials as AISI-403 and 17-4PH are chosen into the investigation, which provides an enhanced understanding on the effect of materials to reduce the corrosion fatigue damage of blades. To verify the validity of the proposed methods, simulated results of a 951 MW operating turbine generator for the corrosive fatigue damage are presented in this paper. From the simulated results, it can be found that the corrosive fatigue damage to the low-pressure steam turbine blades is significantly reduced. In addition, the effects of unbalanced currents (I₂) on the corrosive fatigue damage to the steam turbine blades are estimated when turbine generators operate in various stress concentration factors and corrosive conditions. The estimations may provide with the safe operating standard on the new or designed generator sets under corrosive environments.     

汽轮机低压转子末级叶片断裂分析

1台135MW机组在正常运行时突然发生汽轮机低压转子末级叶片断裂,被迫停机检修。为了查明叶片断裂的原因,通过对叶片断口进行宏观、微观试验,并结合运行参数分析,排除了叶片遭水击断裂的可能性,得出叶片断裂的主要原因是叶片局部区域受到外来高温热源击伤,造成局部金属材料组织发生变化,形成疲劳裂纹源所致。     

Investigation of the fatigue and short-term mechanical properties of 13% chromium steel and titanium alloys after welding or treatment with high-frequency currents as applied to steam-turbine blades

We present the results of a study on comparing the structural strength of rotor blades made of stainless 13% chromium steels for their design versions in which wear-resistant straps made of cast VZK stellite are soldered or welded on the blade inlet edges. It is shown that treatment of VT6 alloy with high-frequency currents increases the endurance limit of the zone subjected to strengthening and makes the alloy more resistant to erosion. The worn blades of a 48-T4 titanium alloy repaired with the use of welding technologies have operational characteristics at least as good as those of newly manufactured ones.     

Some perspective decisions for the regeneration system equipment of the thermal and nuclear power plants decreasing the probability of water ingress into the turbine and rotor acceleration by return steam flow

The regeneration system heaters are one of the sources of possible ingress of the water into the turbine. The water penetrates into the turbine either at the heaters overflow or with the return flow of steam generated when the water being in the heater boils up in the dynamic operation modes or at deenergization of the power-generating unit. The return flow of steam and water is dangerous to the turbine blades and can result in the rotor acceleration. The known protective devices used to prevent the overflow of the low-pressure and high-pressure heaters (LPH and HPH), of the horizontal and vertical heaters of heating-system water (HWH and VWH), as well as of the deaerators and low-pressure mixing heaters (LPMH) were considered. The main protective methods of the steam and water return flows supplied by the heaters in dynamic operation modes or at deenergization of the power-generating unit are described. Previous operating experience shows that the available protections do not fully prevent water ingress into the turbine and the rotor acceleration and, therefore, the development of measures to decrease the possibility of ingress of the water into the turbine is an actual problem. The measures allowing eliminating or reducing the water mass in the heaters are expounded; some of them were designed by the specialists of OAO Polzunov Scientific and Development Association on Research and Design of Power Equipment (NPO CKTI) and are efficiently introduced at heat power plants and nuclear power plants. The suggested technical solutions allow reducing the possibility of the water ingress into the turbine and rotor acceleration by return steam flow in the dynamic operation modes or in the case of power generating unit deenergization. Some of these solutions have been tested in experimental–industrial exploitation and can be used in industry.     

320 MW机组的振动分析与解决

天津大港发电厂2号机组2004年12月锅炉改造投产以来一直存在轴瓦振动超标的问题.利用在机组甩负荷试验期间,对2、3、4号瓦振动超标进行了现场动平衡处理.从最终的效果看,造成3、4号瓦振动异常的原因并不是转子的残余不平衡引起的,主要原因是由于低压转子轴承座系悬臂支撑方式,相对来说动刚度较低,同时末级叶片司太立合金严重冲蚀,导致蒸汽激振力增加,致使机组在30 MW负荷以下或空负荷时瓦振正常,在30 MW以上机组振动随负荷升高而增大.     

半速汽轮机轴位移和胀差传感器的安装与调整

轴位移和胀差是反映汽轮机动静间隙的两项重要监视参数。采用半速机组轴位移和胀差的测量原理和测量方法,对红沿河核电厂1号机组存在的轴位移传感器测量值偏大、高中乐转子膨胀测量传感器安装间隙不足和暖机过程中低压转子膨胀量过大等问题的解决过程进行了系统论述。通过对红沿河核电厂1号机组轴位移和胀差实际运行数据和变化规律的分析,说明传感器的安装过程和调整方法正确,实现了对汽轮发电机的可靠监视和保护。     

Prospects of using two-tier low-pressure cylinders in steam-turbine power units

Possible ways for increasing the throughput capacity of the low-pressure cylinders of the condensing steam turbines are discussed. It is shown that the use of two-tier low-pressure cylinders allows the flowrate of steam through them to be increased by 65–70% without the need of increasing the length of last-stage blades.     

汽轮机动叶片氯腐蚀的分析与对策

汽轮机动叶片因腐蚀而引起的断裂事故严重威胁汽轮发电机组的安全经济运行，而氯腐蚀又是动叶片腐蚀的重要原因。为此，通过对某电厂300MW机组叶片断裂事故的分析，探讨动叶片氯腐蚀的机理与特点，并提出相应的对策，即通过对铬合金钢叶片进行表面强化．严格监视给水的pH值，加强水处理，降低氯离子的浓度，来防止汽轮机动叶片的氯腐蚀。     

A numerical analysis of the serial design of the T-250/300-23.5 cogeneration turbine low-pressure cylinder’s exhaust hood

A mathematical model of the low-pressure cylinder’s exhaust compartment used in the serial design version of the T-250/300-23.5 turbine is constructed. The exhaust compartment consists of the turbine flow path last stage, a moisture removal chamber, and an exhaust hood (the EH stage). The effect of individual elements of the low-pressure cylinder exhaust compartment’s flow path on its gas dynamic characteristics in condensing modes of operation is numerically modeled for a wide range of steam flow rates. For the compartment with the exhaust hood completely filled with its inner elements, the flow patterns are calculated in partial modes of operation with presenting data on losses and flow-averaged integral characteristics at the diffuser inlet. The calculation results have been verified against the data of full-scale and model tests.     

极端严寒气候下直接空冷机组的冷态启动

国电电力大同发电有限责任公司的空冷机组在-20℃左右,首次实现了汽轮机历时16h的冷态启动。文章介绍了启动过程,分析了高中压联合启动中存在的问题,要求汽轮机数字电液调节系统（DEH）、旁路系统以及空冷凝汽器（ACC）三者的控制要匹配。启动中应预防空冷凝汽器管束内部大量结冰冻堵,文章对冷态启动中出现的问题进行了分析,如汽轮机维持额定转速时出现转速上升、采用功率闭环控制在33％综合阀位附近出现负荷晃动、优化汽轮机背压控制程序等。     

Investigation of Technical and Economic Viability of the 450-MW CCGT Unit’s Operation in the GTU Based CHP Mode

Technical viability and economic feasibility of improving the technology of a 450-MW CCGT unit’s participation in power load leveling of the power system operating in a GTU based CHP mode by transferring a 450-MW CCGT T-125/150 steam turbine to the driving mode instead of its shutdown are considered. It is shown that the shutdown of the steam turbine is associated with increased fuel consumption under start-up conditions, delayed steam turbine loading and the CCGT unit as a whole, and a loss of steam turbine life characteristics. The technology of transferring the 450-MW CCGT unit to the GTU based CHP mode, possible schemes of high- and low-pressure steam distributions between line water heaters, and methods and results of calculation of power parameters of the 450-MW CCGT unit with the turbine shutdown and transferring it to the driving mode in the absence and presence of peak-load heaters in the heat balance are presented. It is shown that switching the 450-MW CCGT unit from the base 290 MW electric load and 1006 GJ/h heat production to the GTU based CHP mode leads to a decrease in electric capacity of the CCGT unit by 90 MW and an increase in heat production by 335–348 GJ/h. Comparative graphs of the steam turbine start-up and the CCGT unit rated loading in the comparable variants after its operation in the GTU based CHP mode for 8–10 h are given. Evaluation techniques and results of the economic efficiency of the generator driving mode are compared with the shutdown of the steam turbine. Based on the performed calculations, it is shown that, for various combinations of fuel equivalent and electricity costs and heating tariffs, the expedient time for switching the steam turbine to the driving mode is 10–18 h. Additional advantages of the driving mode are noted, such as improvement of the steam turbine reliability due to the elimination of cyclic temperature variations of its steam-inlet elements and vibrational oscillations in the final stages of the low-pressure cylinder and the possibility of the steam turbine generator to operate as a synchronous condenser.     

汽轮机低压转子叶片静态频率试验研究

机组检修期间,需要对所有叶片的状况进行宏观检查和频率测试,检查转子叶片的固有频率是否在长期运行过程发生改变。针对某电厂#8汽轮机低压转子末级调频叶片,通过测试结果,分析存在的问题,提出处理的意见,并为下次检修期间转子叶片静态频率测试提供对比依据,从而保证机组的安全运行。