汽轮机转子涡动汽流激振力分析与CFD数值模拟

汽轮机转子涡动时轴心偏离静子中心产生轴系失稳的Thomas/Alford汽流激振力,传统的叶顶间隙激振力公式对此不能全面准确评估。该文综合考虑转子涡动以及围带汽封二次流,在动叶通道,根据蒸汽做功分析涡动效应激振力;在叶顶围带汽封,用CFD数值模拟泄漏蒸汽三维粘性流场,确定蒸汽激振力。研究结果表明小的静偏心和动偏心条件下,转子涡动动偏心在动叶通道诱发的激振力要大于静偏心激振力;围带汽封汽流预旋速度对间隙激振力有重要影响;调门不对称进汽也是蒸汽激振力的另一个重要来源。

Analysis and CFD (Computational Fluid Dynamics) Numerical Simulation of Steam Flow Excitation Force Leading to a Whirling of Steam Turbine Rotors

During the whirling of a steam turbine rotor, its shaft center will deviate from that of the stator, thus producing a Thomas/Alford steam-flow excitation force leading to a loss of stability due to vibrations. In such a case, however, the calculation formula of a traditional blade-tip clearance excitation force can not provide an overall and a correct evaluation of the above force. With the whirling of the rotor and the secondary flow around the blade shroud being comprehensively taken into account in rotating blade passages, the whirling-caused excitation force was analyzed based on the work done by the steam. In the gland seal of the blade tip shroud, CFD values were used to simulate a three-dimensional viscous flow field of the leaking steam, thus determining the magnitude of the steam excitation force. The research results show that under the condition of a small static and dynamic eccentricity, the excitation force in the rotating blade passages induced by the dynamic eccentricity of the rotor whirling is greater than that induced by the static eccentricity, and the pre-swirling velocity of steam flows in the shroud gland has an important influence on the excitation force in the clearance. The non-symmetric steam admission is another important source of the steam excitation force.