我国发展燃气轮机的问题及途径

论述了大功率燃气轮机在我国的应用条件及开发燃机所存在的问题,以及在设计及制造大功率,高性能燃气轮机方面需突破的技术难题和可行的解决方案,涉及了开发大流量高压比压气机,大焓降涡轮,降低有害排放量,解决高温叶片的材料,冷却,保护涂层及单晶叶片铸造等主要问题,并确认了一些关键的制造技术。     

Analysis of thermal stress evolution in the steam drum during start-up of a heat recovery steam generator

A program to predict the transient characteristics of the heat recovery steam generator (HRSG) is constructed and the start-up behavior of the high-pressure part of an HRSG is analyzed with a special focus on the estimation of the thermal stress in the steam drum. Three HRSG start-up procedures (steady gas turbine without gas bypass, steady gas turbine with gas bypass, start-up gas turbine) are simulated. The gas bypass is conducted during the initial stage of the start-up. Estimation of the maximum thermal stress makes it possible to optimize the gas bypass mode. It is shown that bypassing part of the gas flow lowers the peak stress much in case of the steady gas turbine exhaust condition. Examples of the scheduling of the gas flow increase using the step and ramp modes are demonstrated. In case of the simultaneous start-up, the peak stress is considerably low due to the gradual increase of gas temperature and mass flow and bypassing just a small portion of gas flow is enough to keep it under the allowable limit.     

考虑气体压缩性的液力透平内气液两相流场分析

为研究在气液两相条件下液力透平内部的流动规律,选择比转速为55.7的单级单吸离心泵反转作液力透平(Pumps as Turbines,PAT),在考虑气体可压缩的基础上对该模型在不同流量、不同含气率下进行数值计算。分析含气率对液力透平外特性和液力透平各过流部件内流场的影响规律,总结不同工况下液力透平内气液两相流动规律。研究发现:随着含气率的增大,液力透平的效率和功率逐渐减小、扬程逐渐增加,气体的存在对液力透平效率影响较大;液力透平叶片进口有明显的旋涡,随着流量和含气率的增大,混合介质的相对速度均增加;含气率从液力透平进口到出口逐渐增大,叶片背面的含气率要比工作面大,过流部件内的气体分布不对称,随着含气率的变大,气体分布的均匀性变差。     

Numerical heat transfer predictions and mass/heat transfer measurements in a linear turbine cascade

The effect of secondary flows on mass transfer from a simulated gas turbine blade and hubwall is investigated. Measurements performed using naphthalene sublimation provide non-dimensional mass transfer coefficients, in the form of Sherwood numbers, that can be converted to heat transfer coefficients through the use of an analogy. Tests are conducted in a linear cascade composed of five blades having the profile of a first stage rotor blade of a high-pressure turbine aircraft engine. Detailed mass transfer maps on the airfoil and endwall surfaces allow the identification of significant flow features that are in good agreement with existing secondary flow models. These results are well suited for validation of numerical codes, as they are obtained with an accurate technique that does not suffer from conduction or radiation errors and allows the imposition of precise boundary conditions. The performance of a RANS (Reynolds-Averaged Navier–Stokes) numerical code that simulates the flow and heat/mass transfer in the cascade using the SST (Shear Stress Transport) k–ω model is evaluated through a comparison with the experimental results.     

基于气液两相的导叶对液力透平内部流动规律的影响

为了研究气液两相条件下导叶对液力透平内部流动特性的影响,现选取比转速为55.7的离心泵反转作为液力透平,并在液力透平叶轮进口添加一组负曲率导叶,设计出含导叶的水力模型,研究含气工况下导叶对液力透平性能的影响。研究发现:添加导叶前蜗壳和叶轮流道内压力分布和气相分布不均匀,且含气率越高均匀性越差,过流部件内流动较为紊乱,蜗壳和叶轮流道内出现了旋涡;添加导叶后,在较高含气率工况下叶轮流道内压力分布相对均匀且混合介质的流动情况得到改善,水力损失减少;添加导叶后透平最优效率点的值要高于未添加导叶的最优效率点的值,但随着含气率的提高,添加导叶的液力透平效率比未添加导叶的透平效率下降快。     

带回热微型燃气轮机系统动态过程分析

分析了微型燃气轮机的动态数学模型,利用解析方法,求解了带回热单轴燃气轮机动态方程,对定转速和变转速两种情况下微型燃气轮机负荷变化和甩负荷的动态过程进行了仿真,提出了机组变工况动态性能优化和控制优化的途径。该研究能够为实际机组的运行和系统性能参数的合理匹配提供理论指导。     

高精度燃气轮机控制器在回路的仿真研究

采用容积法建立了非迭代和模块化的燃气轮机实时模型,并提出其实时求解算法;同时还建立了通用的燃气轮机控制器在回路的实时仿真平台,并在PC机上获得了高精度实时时钟.基于该实时模型和平台,进行了高、低压压气机和涡轮共轴的燃气轮机起动、升降负荷和甩负荷仿真试验,并通过整定PID控制器参数获得了理想的燃气轮机动态响应特性.结果表明:该实时模型、算法和平台可满足高精度燃气轮机控制器在回路的仿真需要,具有工程应用价值.     

长短叶片水轮机转轮气液两相流的数值模拟

为降低水轮机运行过程中的空化现象并提高经济效率,以长短叶片混流式水轮机HLA351 LJ 170原型机为研究对象,采用完整的空化流模型和商用CFD软件FLUENT中的Mixture多相流无滑移模型,在大流量工况下对长短叶片混流式水轮机进行了气液两相流数值模拟。计算结果表明,该工况下长短叶片水轮机转轮流速、压力分布合理,水力性能较好。由此预测了长短叶片水轮机空化发生的部位和程度,对水轮机优化设计或改型等具有重要的指导意义。     

Performance of vertical axis water turbine with eye-shaped baffle for pico hydropower

A series of inline pico hydropower systems, which could be used in confined space, especially for water distribution networks (WDNs), was designed and investigated. The turbine with an eye-shaped vertical water baffle was developed to evaluate the hydraulic performance. A three-dimensional dynamic mesh was employed and the inlet velocity was considered as the inlet boundary condition, whereas the outlet boundary was set as the outflow. Then, numerical simulations were conducted and the standard k-ε turbulence model was found to be the best capable of predicting flow features through the comparison with the experimental results. The effects of the opening diameter of the water baffle and installation angle of the rotor on the flow field in the turbine were investigated. The results suggested that the water baffle opening at d = 30 mm and the rotor at a 52° angle could achieve the highest efficiency of 5.93%. The proper eye-shaped baffle not only accelerates the fluid flow and generates positive hydrodynamic torque, but also eliminates the flow separation. The scheme proposed in this paper can be exploited for practical applications in the water pipelines at various conditions and power requirements.     

混合太阳能微型燃气轮机性能限制分析与优化

为研究混合太阳能燃气轮机系统的现实应用需构建实验系统,通常的思路是采用目前性能较好的型号燃气轮机与太阳能集热加热组件耦合,但耦合后的系统性能指标相对型号燃气轮机受到限制。对此限制的原因进行热力学性能原理分析,并利用EBSILON软件建立型号燃气轮机仿真模型和混合太阳能微型燃气轮机实验系统计算模型,通过计算验证热力学性能原理分析结果,发现燃烧室通流能力是系统性能指标的主要限制因素,并提出增加压气机压比和提高燃烧室通流能力、更好地组织燃烧可作为系统优化方向。     

透平静叶栅中间叶高处水滴尺寸测量及临界韦伯数分析

通过测量获得了多种工况下试验透平叶栅进出口平均叶高处可能带来水蚀危害的水滴的尺寸,揭示并分析了静叶栅后水滴尺寸比叶栅前大大减小且水滴平均直径随气流流速增大而减小的原因。结合试验测试数据和对叶栅尾迹区气相流场的数值模拟结果,更精确地推算出了静叶尾迹区粗大水滴形成二次雾化的临界韦伯数范围,建议取为20。提供了一个推导临界韦伯数的详细示例。由于试验条件更接近实际汽轮机,所得汽轮机湿蒸汽级内的水滴尺寸及分析获得的临界韦伯数更加确切和可靠。这些都有助于更准确地预测叶片的水蚀和选择合理的防水蚀措施。图7参6     

Note on a real gas model for OWC performance

Oscillating water column (OWC) are devices for wave energy extraction equipped with turbines for energy conversion. The purpose of the present work is to study the thermodynamic of a real gas flow through the turbine and its differences with respect to the ideal gas hypothesis, with the final goal to be applied to OWC systems. The effect of moisture in the air chamber of the OWC entails variations on the atmospheric conditions near the turbine, modifying its performance and efficiency. In this work we study the influence of humid air in the performance of the turbine. Experimental work is carried out and a real gas model is asserted, in order to take a first approach to quantify the extent of influence of the air–water vapour mixture in the turbine performance. The application of a real gas model and the experimental study confirmed the deviations of the turbine performance from the expected values depending on flow rate, moisture and temperature.     

Effects of Various Geometric Features on the Performance of a 7:1 Pressure Ratio Deeply Scalloped and Split Radial Turbine in a Gas Turbine Engine

A 2 MW gas turbine engine has been developed for the distributed power market.This engine features a 7:1 pressure ratio radial inflow turbine.In this paper,influences of various geometry features are investigated including turbine tip and backface clearances.In addition to the clearances,the effects of the inducer deep scallop and exducer rounded trailing edge are investigated.Finally,geometric features associated with a split rotor(separate inducer and exducer)are studied.These geometry features are investigated numerically using CFD.Part of the numerical results is also compared to experimental data acquired during engine test to validate the CFD results.     

基妻相似理论估算PFBC—CC燃气轮机变工况性能

文章基于相似理论方法分析燃气轮机变工况性能,提出采用一流量修正系数修正参考工况点的无因次准则数,用来模拟燃气轮机共同工作线,并对一增压流化床联合循环电站的燃气轮机机组由于环境状况和负荷要求变化引起的变工况分别作了示例计算,结果表明本方法可以用作缺乏设备详细性能特性时,燃气轮机变工况性能的近似估算。     

数值模拟环形燃烧室两相反应流场

在任意曲线坐标系下,采用一种整体分区结合法,对包扩压器和火焰筒在在内的环形燃烧室三维两相反应流进行了数值模拟。所相采用Ｅｕｌｅｒ方法处理,并采用标准ｋ－ε双方程紊流模型、ＥＢＵ－Ａｒｒｈｅｎｉｕｓ紊流燃烧模型,六通量热辐射模型;液相采用Ｌａｇｒａｎｇｅ法处理。在非交错网格体系下,气相用ＳＩＭＰＬＥ法求解,液相采用颗粒群轨道模型,并用ＰＳＩＣ算法对其进行数值求解,计算结果表明这种新方法是可行的。     

A theoretical framework for calculating full-scale jet fires induced by high-pressure hydrogen/natural gas transient leakage

Previous experimental results on full-scale jet fires induced by high-pressure hydrogen/natural gas transient leakage can only be suitable for solving practical engineering problems, or testing the limitation of previous models. Thus, this paper presents a theoretical framework for the high-pressure hydrogen/natural gas leakage and the subsequent jet fire. The proposed framework consists of a transient leakage model, a notional nozzle model, a jet flame size model, a radiative fraction correlation and a line source radiation model. The framework is validated by comparing the model predictions and experimental measurements of mass flow rate, total flame height and thermal radiation field of hydrogen, natural gas, hydrogen/natural gas mixture jet fires with a flame height up to 100 m. The comparison shows that the theoretical framework can give considerable predictions to properties of full-scale jet fires induced by high-pressure hydrogen/natural gas transient leakage.     

Numerical model validation and prediction of mist/steam cooling in a 180-degree bend tube

To achieve higher efficiency target of the advanced turbine systems, the closed-loop steam cooling scheme is employed to cool the airfoil. It is proven from the experimental results at laboratory working conditions that injecting mist into steam can significantly augment the heat transfer in the turbine blades with several fundamental studies. The mist cooling technique has to be tested at gas turbine working conditions before implementation. Realizing the fact that conducting experiment at gas turbine working condition would be expensive and time consuming, the computational simulation is performed to get a preliminary evaluation on the potential success of mist cooling at gas turbine working conditions. The present investigation aims at validating a CFD model against experimental results in a 180-degree tube bend and applying the model to predict the mist/steam cooling performance at gas turbine working conditions. The results show that the CFD model can predict the wall temperature within 8% of experimental steam-only flow and 16% of mist/steam flow condition. Five turbulence models have been employed and their results are compared. Inclusion of radiation into CFD model causes noticeable increase in accuracy of prediction. The reflect Discrete Phase Model (DPM) wall boundary condition predicts better than the wall-film boundary condition. The CFD simulation identifies that mist impingement over outer wall is the cause for maximum mist cooling enhancement at 45° of bend portion. The computed results also reveal the phenomenon of mist secondary flow interaction at bend portion, adding the mist cooling enhancement at the inner wall. The validated CFD simulation predicts that average of 100% mist cooling enhancement can be achieved by injecting 5% mist at elevated GT working condition.     

Performance evaluation of a tri-generation system with simulation and experiment

A test rig for a tri-generation system was set up in the laboratory to investigate the system performance and application feasibility. The rig was composed of three modules, a power component containing a microturbine, a refrigeration unit consisting of an absorption chiller with gas pipe connection, and a supermarket section containing a display cabinet. This system was supposed to be effectively applied into a supermarket energy control system where cooling, heating and electricity power are simultaneously required and subsequently, valuable test results have been produced. In the mean time, a simulation model for the particular tri-generation system has been established by integrating the component models of the system in accordance with the components’ actual flow paths and energy streams. These component models, which include a compressor, recuperator, combustion chamber, gas turbine, electric generator, gas pipes, generator (desorber), rectifier, absorbers, condenser and evaporator etc., were developed based upon the balance of heat and mass. The calculations of heat transfer and phase equilibrium were included in the component models and chemical reaction balances were considered in the model of the combustion chamber. The system model has been validated with the test results and has consequently been used to predict the system performance at different operating and design conditions, such as varied ambient temperature, fuel flow rate and pressure ratio etc. The ultimate results of the performance analysis formulated by the system model can contribute significantly to the optimal component and system designs in various practical applications.     

Flowfield and heat transfer past an unshrouded gas turbine blade tip with different shapes

This paper describes the numerical investigations of flow and heat transfer in an unshrouded turbine rotor blade of a heavy duty gas turbine with four tip configurations. By comparing the calculated contours of heat transfer coefficients on the flat tip of the HP turbine rotor blade in the GE-E³ aircraft engine with the corresponding experimental data, the κ-ω turbulence model was chosen for the present numerical simulations. The inlet and outlet boundary conditions for the turbine rotor blade are specified as the real gas turbine, which were obtained from the 3D full stage simulations. The rotor blade and the hub endwall are rotary and the casing is stationary. The influences of tip configurations on the tip leakage flow and blade tip heat transfer were discussed. It’s showed that the different tip configurations changed the leakage flow patterns and the pressure distributions on the suction surface near the blade tip. Compared with the flat tip, the total pressure loss caused by the leakage flow was decreased for the full squealer tip and pressure side squealer tip, while increased for the suction side squealer tip. The suction side squealer tip results in the lowest averaged heat transfer coefficient on the blade tip compared to the other tip configurations.     

Modeling and optimization of a novel pressurized CHP system with water extraction and refrigeration

A novel cooling, heat, and power (CHP) system has been proposed that features a semi-closed Brayton cycle with pressurized recuperation, integrated with a vapor absorption refrigeration system (VARS). The semi-closed Brayton cycle is called the high-pressure regenerative turbine engine (HPRTE). The VARS interacts with the HPRTE power cycle through heat exchange in the generator and the evaporator. Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration unit, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration in an amount that depends on ambient conditions. Water produced as a product of combustion is intentionally condensed in the evaporator of the VARS, which is designed to provide sufficient cooling for the inlet air to the high-pressure compressor, water extraction, and for an external cooling load. The computer model of the combined HPRTE/VARS cycle predicts that with steam blade cooling and a medium-sized engine, the cycle will have a thermal efficiency of 49% for a turbine inlet temperature of 1400°C. This thermal efficiency, is in addition to the large external cooling load, generated in the combined cycle, which is 13% of the net work output. In addition, it also produces up to 1.4 kg of water for each kg of fuel consumed, depending upon the fuel type. When the combined HPRTE/VARS cycle is optimized for maximum thermal efficiency, the optimum occurs for a broad range of operating conditions. Details of the multivariate optimization procedure and results are presented in this paper. Copyright © 2008 John Wiley & Sons, Ltd.