摘要
为探究二氧化碳和水蒸气工质在透平叶栅中损失特性的异同,采用数值方法研究了2种工质在轴流透平静叶栅以及级内的流动特性,获得了亚音速条件下透平级高效运行的最佳马赫数。结果表明:随着马赫数增大,流动损失先增大后减小;当马赫数较低时,扩压段范围较大且易回流,使得壁面边界层增厚并分离,总体流动损失增大;当马赫数较高时,通道内二次流强度较大,且在叶片尾缘附近产生激波,其流动损失主要源于二次流和激波;与水蒸气相比,二氧化碳的动力黏度略大,密度约是水蒸气的2倍,在相同马赫数时其主流速度较低,边界层较厚,因此在马赫数较低时其壁面摩擦损失较大,总体损失较大;马赫数低于0.30时,以二氧化碳为工质的透平级总总等熵效率较低,马赫数高于0.50时,二氧化碳的效率略高于水蒸气;在叶型最佳出口马赫数约为0.60时,2种介质在级环境下的总总等熵效率均达到最高。该研究结果将为进一步提高水蒸气和二氧化碳轴流透平的设计水平以及深入理解不同介质在透平级内的流动特性提供参考。
In order to explore the similarities and differences of the loss characteristics of carbon dioxide and steam in turbine cascades,the flow characteristics of the two kinds of working fluids in stator cascade and stage were studied by numerical methods.And the optimal Mach number for efficient operation of turbine stage under subsonic condition was obtained.The results show that with the increase of Mach number,the flow loss first increases and then decreases.When the Mach number is lower,the diffuser has a large range and is easy to backflow,which makes the wall boundary layer thicken and separate,and increases the overall flow loss.When the Mach number is higher,the strength of the secondary vortex in passage is larger,and the shock wave will be generated near the trailing edge of blades.The reason for the larger flow loss is the secondary flow and shock wave.Compared with steam,the dynamic viscosity of carbon dioxide is slightly higher,and its density is about twice that of steam.Under the same Mach number condition,the mainstream velocity is lower,the boundary layer is thicker,and the overall loss is larger.When the Mach number is lower than 0.30,the total-total efficiency of turbine stages with carbon dioxide is lower.While the Mach number is higher than 0.50,the efficiency of carbon dioxide is slightly higher than that of steam.When the optimal outlet Mach number of balde is about 0.60,the efficiency of both is the highest.The research results will provide a reference for further improving the design level for axial flow turbines of steam and carbon dioxide,and further understanding the loss characteristics of different medium in turbine stage.
作者
杨国英
邓清华
徐伯洲
张永海
李军
丰镇平
YANG Guoying;DENG Qinghua;XU Bozhou;ZHANG Yonghai;LI Jun;FENG Zhenping(School of Energy and Power Engineering,Xi'an Jiaotong University,Xi'an 710049,China;Xi'an Thermal Power Research Institute Co.Ltd.,Xi'an 710054,China)
出处
《热力发电》
CAS
CSCD
北大核心
2023年第6期52-62,共11页
Thermal Power Generation
基金
国家自然科学基金联合基金资助项目(U20A20303)
国家重点研发计划资助项目(2017YFB0601804)。
关键词
水蒸气
二氧化碳
透平级
马赫数
流动特性
steam
carbon dioxide
turbine stage
Mach number
flow characteristics
