【作者】 曹丽华；

【导师】 周云龙；

【作者基本信息】 华北电力大学 ， 热能工程， 2012， 博士

【摘要】 汽轮机通流部分的损失严重影响着汽轮机的经济性,研究汽轮机通流部分损失产生的机理和诊断应达值的确定,实现汽轮机通流部分的热经济性诊断,对于提高汽轮机的效率,促进电厂的节能减排,具有非常重要的意义。首先,针对目前汽轮机转子转速对汽封内流场影响尚无定论的现状,对汽轮机隔板汽封的泄漏机理及隔板汽封间隙内蒸汽的流动特性作深入的研究,重点研究转速对汽封内蒸汽流场的影响程度。结果表明,汽轮机转子的转动效应对汽封内部流动及漏汽量的影响要远远小于汽封结构参数的影响。其次,利用数值模拟方法研究叶顶间隙变化对泄漏量和泄漏涡运行轨迹的影响、叶顶泄漏流在吸力面出口与主流的掺混情况、以及叶顶泄漏涡强度沿转子轴向的变化规律,并探讨了大涡模拟方法在这方面的应用。结果表明,叶顶泄漏流造成了主流通道内流体的非定常流动。泄漏流对主流所造成的影响经历了从弱变强再从强变弱的周期性变化过程。通道内的二次涡则经历了靠近吸力面到远离吸力面再到靠近吸力面的过程；二次涡的影响范围经历了从弱变强再从强到弱的周期性过程。随着叶顶间隙的增大,泄漏涡的强度和影响范围也在增大。大涡模拟可以很好的捕捉泄漏涡的形成、脱落和尾涡的相互作用,对研究泄漏涡和各涡系之间的非定常相互干涉有很好的帮助。同时,对排汽缸和带有内置式低压加热器及汽动给水泵小汽机排汽的凝汽器喉部内的流动进行耦合数值分析,考虑湿蒸汽热力行为及不同进汽条件,更加真实准确的反映排汽通道内流场的分布情况。结果表明,随着进汽湿度的增加,排汽通道内流动的能量损失系数逐渐降低；随着旋流强度增加,排汽通道内流动的能量损失系数降低；随着进汽角增大,排汽通道能量损失系数也下降。最后,对汽轮机通流部分热经济性诊断的指标及其应达值的确定方法进行研究。结果表明,汽轮机采用回热循环或再热循环后,汽轮机的相对内效率和理想循环热效率之间存在较强的耦合性,汽轮机的相对内效率不能准确反映通流部分的运行经济状态。建议采用级组的相对内效率来反映通流部分的运行经济状态,并给出了级组的相对内效率应达值的确定方法。尤其针对处于湿蒸汽区的最末级组的相对内效率应达值很难确定的问题,提出采用BP神经网络方法进行解决,为实现汽轮机通流部分的热经济性诊断奠定了基础。更多还原

【Abstract】 Economy of steam turbine is severely affected by the flow passage losses. It is very important to study the mechanism of flow passage losses and normal value of diagnose in order to evaluate the operating condition of steam turbine flow passage. And this research will be helpful to improve the relative internal efficiency of steam turbine and promote the energy conservation and pollution reduction.First, aimed at no final conclusion of the rotor speed of steam turbine influenced on steam flow characteristics of seal at present, mechanism and flow characteristics of clearance leakage of diaphragm gland are deeply researched. The focus is the effect of the rotor speed on flow field of seal. The results show that the effects of rotation on the internal flow and leakage are much smaller than structural parameters of seal.Second, the change rule of the leakage flow, the trajectory of leakage vortex, the mixing degree of tip leakage and main flow at outlet of suction surface and the vortex strength along axial direction with the blade tip clearance are studied by numerical simulation method. And, a comparative study is made by using large eddy simulation method. The results show that the unsteady of main stream is caused by the tip leakage flow. The effects of tip leakage flow on main stream appear some regularity, from weak to strong, and then from strong to weak. The secondary vortex of flow passage changes near the suction surface to away from the suction surface, then the other. The incidence of leakage vortex is recurring process that from weak to strong, and then from strong to weak. The leakage vortex is strengthened with the increase of the tip clearance, and the range affected by leakage vortex increases. The large eddy simulation method can better capture the formation, shedding of the leakage vortex and the interaction with the wake vortex. So the large eddy simulation method is good to study the unsteady interference between the leakage vortex and all kinds of vortexes.At the same time, the flow field of the exhaust hood and condenser throat which has inner heaters and exhaust of turbine driven feed pump is studied by coupling numerical simulation method based on the thermodynamic behavior of wet steam and the different inflow condition, in order to study the real flow condition of wet steam in the exhaust channel. The results show that the energy loss coefficient of exhaust channel decreases with increasing the inlet wetness, the intensity of swirl flow and the inflow angle.Finally, the index for thermal economic diagnosis of steam turbine flow passage and its normal value are studied. The results show that the relative internal efficiency is coupled to ideal cycle thermal efficiency, when the regeneration system or reheated temperature system is used in steam turbine. The relative internal efficiency of steam turbine cannot accurately reflect the economic performance of the flow passage in operation. It is recommended that the flow passage condition of steam turbine be estimated by relative internal efficiency of stage groups. And, a method to determine the norm of relative internal efficiency of stage groups is proposed. It is difficult to determine the norm relative internal efficiency of the last stage group lying in wet steam region. A method based on BP neural network to determine the normal value is proposed. The studying results fall foundations for thermal economic diagnosis of steam turbine flow passage.更多还原