空化和自由表面吸气条件下喷水推进器内和环境气液两相非定常流动及其推力特性研究

The unsteady characteristics of waterjet propulsion inner and ambient gas-liquid two phase flow and thrust dynamic features under cavitation and free surface gas entrainment are going to be studied in this project. The piecewise linear interface reconstruction (PLIC) method will be used to simulate the gas entrainment through the free surface, and the partially averaged Navier-Stokes (PANS) equations and mass transfer equation will be combined to calculate the cavitation characteristics. The two simulation steps can accomplish the unsteady gas liquid two phase flow calculation for both cavitation and free surface gas entrainment. A high-speed photography system for the loop test rig and a planar laser induced fluorescence (PLIF) technology for bollard conditions will be performed to obtain the unsteady flow information. A specially designed gas pipe and a transparent and resin housing will be used to control and measure the gas entrainment accurately. Transfer matrix will be calculated according to the pressure date through high frequency sensor and be used to depict the geometry feature and the inner flow structures of the waterjet propulsion. Vortex energy will be used as a threshold criterion to express the unsteady feature of the gas liquid two phase. The efforts will reveal the unsteady characteristics of waterjet propulsion inner and ambient gas-liquid two phase flow and thrust dynamic features under cavitation and free surface gas entrainment as well as their relationship, and the results will afford theoretical and technological support for the modern waterjet propulsion research and development, and for the high speed, high efficient and stable control and cruising of high performance vehicles.

针对喷水推进器的具体运行环境，拟研究在空化和吸气条件下喷水推进器内和环境两相流动的非定常特性及相应的推力动态特性。采用分段线性界面重构PLIC算法计算自由表面吸气。组合采用PANS方程和传质方程计算空化特性。分两步走的数值计算方法实现了包含自由表面吸气和空化特性的两相流非定常特性计算；在管路回路试验以及静水拖曳水池试验中采用高速摄影和PLIF技术获取非定常流动信息和气相浓度信息，采用专门设计的通气管以及透明箱体对喷水推进器的吸气量进行调节控制和准确测量。应用状态传递函数描述喷水推进器的几何性质以及内部流动结构，应用涡量能量作为判据表征气液两相流动的非定常特性。项目预期揭示喷水推进器在空化和吸气条件下的流动非定常特性及推力的动态特性以及二者的联系，本项目的研究成果可为用于我国高性能船舶的现代喷水推进器研发、为实现高性能船舶高速、高效及稳定控制和巡航提供理论依据。

喷水推进器的优势直到20世纪末才被特别关注并积极应用于船舶推进。高速和安全是喷水推进器的两个显著优势。这两个优点与其叶轮包裹在壳体内部这一结构形式密切相关。由于叶轮被壳体包裹，(1) 船舶前进运动为叶轮进口提供能量。因此理论上只要船—机配合合理，喷水推进器的进口就能够具有足够的有效净正吸头（考虑经济性，喷水推进器推进的船舶速度为每小时25节~55节）；(2) 被包裹的叶轮不会对水中的动植物产生伤害。对于战斗登陆艇而言，不会对涉水战士造成伤害；(3)在水力性能上防缠绕、易操作、工况宽、噪音低也就是隐身性能（安全性）优越。预计到本世纪中叶，该新型推进装置有望在很多领域换代更替螺旋桨。.喷水推进器的优势在现代高性能船舶的应用中体现得尤为明显。与传统排水型船舶相比，高性能船舶的航行姿态随着航速的变化而变化：高速时吃水浅、阻力小。水陆两栖等特种车船也属于高性能船舶的范畴。本项目针对应用于高性能船舶的喷水推进器系统地开展了理论分析和试验研究等工作。取得的成果有：.基本理论方面：构筑了包括(1)喷水推进器系统工作原理、(2)喷水推进器推力特性与水力性能参数联系、(3)喷水推进器相似理论等基本内容和构架的喷水推进器理论体系。.技术方面：攻克了(1) 经验nD值对喷水推进器运行的限制、(2)基于管路数据和台架试验获取喷水推进器“航速—推力—功率”谱图的关键技术。.试验研究工作：开展了系列管路回路试验、（具有自主知识产权的）台架试验和在船试验工作。.同期研发的产品已应用于体育、救援、遥感测绘与测量船、无人船等诸多领域并出口乌兹别克斯坦，真正做到了把科研成果写在祖国大地（江河湖海）上。.2022年12月，课题组完成的“喷水推进器基础理论及关键技术研究”项目经由中国机械工业联合会组织鉴定，认为该成果整体达到国际先进水平，其中在喷水推进器高效运行控制策略方面达到国际领先水平。.本项目的研究成果构筑了完善的喷水推进器基础理论、对其技术开发和性能评价提供了基准。