船舶燃机大子午扩张变几何涡轮全工况端区非稳态流动机理研究

The variable-geometry turbine technology is one of the effective means to improve the off-design performance of marine gas turbines. However, the high endwall angle variable-geometry turbine has the following serious issues for modern marine gas turbines: the variable-geometry vane clearance and losses are very large, the vane turning induces large incidence endwall flows, and the vane turning process can cause the risk of airflow oscillation. All these seriously degrade the full-condition performance of variable-geometry turbines. Therefore, the full-condition unsteady endwall flow mechanisms in a high endwall angle variable-geometry turbine for marine gas turbines will be revealed, which is considered as the starting point of the project. By means of experimental and numerical methods, the following aspects will be investigated: the multi-condition evolution processes of endwall leakage flows in a high endwall angle variable-geometry vane, the inherent relation between variable-geometry vane endwall flow interaction and vane turning angle, the evolution mechanism of endwall transient flows during the vane turning, and the off-design endwall flow mechanism of downstream blade rows under various vane turning angles. Through the above investigations, the space-time evolution mechanism of endwall vortex flow structures and its relationships with the vane turning angle and turning process will be clarified, the cascade transfer characteristics of the additional losses generated by the vane turning will be obtained, and then the high-efficiency full-condition aerodynamic design strategies and programs will be explored. The research results can provide the theoretical basis and technical support for the aerodynamic design of high-efficiency variable-geometry turbines and the control of full-condition endwall losses, and thus promote the development of the aerodynamic design technology for high endwall angle variable-geometry turbines.

变几何涡轮技术是有效提高船舶燃机变工况性能的手段之一，但现代船舶燃机大子午扩张变几何涡轮存在可调静叶端部间隙及损失过大、静叶转动引起大攻角端区流动甚至转动过程会引起气流振荡危险等难题，严重恶化变几何涡轮全工况性能。为此，本项目以揭示大子午扩张变几何涡轮全工况端区非稳态流动机理为切入点，通过试验和数值模拟等手段，对大扩张角端壁可调静叶端区泄漏流场的多工况演化过程、可调静叶级端区流动干涉与静叶开度的内在联系、静叶转动过程中端区瞬变流场演化机制和静叶转动引起下游各叶片列端区变工况流动的机理进行研究。通过研究，澄清大子午扩张变几何涡轮端区复杂涡系结构的时空演化机制与静叶开度及转动过程的关联关系，获得静叶转动引起附加损失的级联传递特性，进而探求其高效全工况气动设计策略和方案。研究结果能为高效变几何涡轮研发和全工况端区损失控制提供理论依据和技术支撑，从而促进大子午扩张变几何涡轮气动设计技术的发展。

变几何涡轮技术是有效提高船舶燃气轮机变工况性能的手段之一，但现代船舶燃气轮机大子午扩张变几何涡轮存在可调静叶端部间隙及损失过大、静叶转动引起大冲角端区流动甚至转动过程会引起气流振荡危险等难题，严重恶化变几何涡轮全工况气动性能。.本项目以揭示大子午扩张变几何涡轮全工况端区非稳态流动机理为切入点，通过可调扇形叶栅试验、定常与非定常精细数值模拟结合理论分析等手段，首先深入研究了变几何涡轮端区定常与非定常流动特性及损失机制，包括可调导叶级端区流动特性及损失机制，1.5级变几何涡轮非定常流动特性以及多级变几何涡轮流场及其气动特性。建立了变几何涡轮过渡态特性的数值计算与试验方法，重点探讨了基于导叶转动的变几何涡轮过渡态特性。针对变几何涡轮的大子午扩张特征，从叶顶、机匣处理角度探讨了大扩张角端壁可调导叶端区损失控制方法。在对变几何涡轮内部流场结构及损失特性有清晰认识的基础上，建立了变几何涡轮宽工况叶型/叶片气动设计优化方法。与此同时，通过理论分析结合程序编制构建了变几何涡轮一维性能预测方法及气动设计参数选取规律。.本项目的研究结果能为高效变几何涡轮研发和全工况端区损失控制提供理论依据和技术支撑，从而促进大子午扩张变几何涡轮气动设计技术的发展。