有机工质朗肯循环向心透平设计与流动特性研究

发布时间：2018-03-29 23:17

本文选题：有机工质朗肯循环　切入点：向心透平　出处：《华北电力大学》2017年硕士论文

【摘要】：有机工质朗肯循环(ORC)发电技术在回收工业废热、利用太阳能和地热能等方面发挥了重要作用。而向心透平作为低温余热发电技术循环系统中的重要部件,有着较小的余速损失和流动损失,结构简单和运行范围较宽等优点受到越来越多的关注。本文以ORC向心透平为研究对象,对其设计方法和流动特性进行研究,主要研究内容如下:以环己烷为工质,对200kW向心透平进行热力设计,确定静叶和动叶的几何气动参数和结构尺寸。采用ANSYS-CFX对透平进行数值计算,分析透平的整体性能和内部的流动情况。结果表明,所设计的向心透平热力参数与数值模拟结果基本吻合,所有参数误差都控制在3%之内,验证了设计方法的正确性,同时获得了较高的透平效率;模拟结果能真实地反映透平内部流动特性。透平整体性能较好,压降分布和马赫数分布较为合理,没有出现较大的流动分离现象。研究了有机工质向心透平内流动特性,针对ORC向心透平静叶栅,分析了工质在静叶栅内的流动损失机理和主要损失分布,分析了下上端壁流动分布和叶栅通道内的各种涡系的表现形式,给出了总压损失系数的分布规律。数值结果表明,叶栅通道存在压力面和吸力面之间的横向流动,但通道涡并没有形成,通道涡并不是ORC向心透平静叶栅内二次流涡流形式中的重要涡系结构;主要总压损失在轴向弦长方向集中在叶栅后40%流道,在叶高方向集中在上下端壁,在周向方向聚集在吸力面附近。针对动叶进行了优化设计,通过改变形状设计参数来得到叶轮不同扭曲变化规律,分析动叶轮扭曲规律对透平效率的影响。数值计算结果表明,叶轮的扭曲程度会影响叶轮流道形状和出口气流与轴向的夹角,不同的叶轮扭曲规律使透平轮周效率的最大变化范围达到了2.44%,是叶轮结构优化设计的重要影响因素。研究了不同工况下透平入口温度、出口压力、转速对透平效率性能和通流性能的影响。结果表明,在设计工况点下,各个变量对透平效率和流量的影响最小,并且效率能保持在较高水平。在三个变化因素中,转速对透平效率的影响最大,效率最大变化值达到了10.88%。在120%转速和120%背压情况下流量变化范围较大。整体来看,有机工质向心透平性能受变工况的影响较大,控制好合理的进出口参数和转速水平对透平的高效运行至关重要。
[Abstract]:The organic refrigerant Rankine cycle (ORC) power generation technology plays an important role in recovering industrial waste heat, utilizing solar energy and geothermal energy, etc. The centripetal turbine is an important component in the circulating system of low-temperature waste heat power generation technology. More and more attention has been paid to the advantages of small residual velocity loss and flow loss, simple structure and wide range of operation. In this paper, the design method and flow characteristics of ORC centripetal turbine are studied. The main research contents are as follows: with cyclohexane as working medium, the thermodynamic design of 200kW centripetal turbine is carried out, and the geometric aerodynamic parameters and structural dimensions of static and moving blades are determined. The turbine is numerically calculated by ANSYS-CFX. The overall performance and internal flow of the turbine are analyzed. The results show that the thermodynamic parameters of the designed centripetal turbine are in good agreement with the numerical simulation results, and the errors of all the parameters are controlled within 3%, which verifies the correctness of the design method. At the same time, a higher turbine efficiency is obtained, and the simulation results can truly reflect the internal flow characteristics of the turbine. The overall performance of the turbine is better, and the pressure drop distribution and Mach number distribution are more reasonable. In this paper, the flow characteristics of organic working fluid in the centripetal turbine are studied. The flow loss mechanism and main loss distribution of the working fluid in the static cascade are analyzed according to the ORC centripetal transparent calm cascade. In this paper, the flow distribution of the upper wall and the form of vortex system in the cascade channel are analyzed, and the distribution law of the total pressure loss coefficient is given. The numerical results show that there is a transverse flow between the pressure surface and the suction surface in the cascade channel. However, the channel vortex was not formed, and the channel vortex was not an important vortex system in the form of secondary vortex in the ORC concentric calm cascade, and the main total pressure loss was concentrated in the axial chord length direction in the 40% channel behind the cascade, and in the upper and lower end wall in the high direction of the blade. The optimum design of moving blade is carried out in the vicinity of the suction surface in the circumferential direction. By changing the shape design parameters, the different distortion law of the impeller is obtained, and the influence of the twist law on the turbine efficiency is analyzed. The numerical results show that the influence of the twisting law of the impeller on the turbine efficiency is obtained by changing the shape design parameters. The twist of the impeller affects the shape of the impeller passage and the angle between the outlet airflow and the axial flow. The maximum variation range of turbomachinery circumference efficiency is 2.44, which is an important factor in the optimization design of impeller structure. The turbine inlet temperature and outlet pressure under different working conditions are studied. The effect of rotating speed on turbine efficiency and flow performance. The results show that, at the design working conditions, each variable has the least effect on turbine efficiency and flow rate, and the efficiency can be maintained at a high level. The effect of rotating speed on turbine efficiency is the greatest, and the maximum variation value of efficiency reaches 10.88. The flow rate varies greatly under 120% rotating speed and 120% back pressure. Overall, the performance of organic working fluid centripetal turbine is greatly affected by variable working conditions. It is very important to control the reasonable import and export parameters and speed level for the efficient operation of the turbine.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM617

【参考文献】