带旋流器的燃油喷嘴工作特性及火焰筒头部数值模拟

对带空气旋流器的燃油喷嘴工作特性进行了试验研究,得到了该喷嘴的供油特性、喷雾锥角的变化特点和液滴尺寸及其分布规律。应用Fluent软件模拟了在最大工作状态下火焰筒头部和喷嘴喷雾的相互作用,重点计算了火焰筒头部的空气流场、浓度场和油滴轨迹。通过喷嘴试验和数值模拟,真实地反映火焰筒头部的物理化学过程,为该喷嘴和火焰筒的改进提供了重要依据。     

加力燃烧室双层喷油杆内冷却气流动特性

对新型外涵引气冷却双层壁加力喷油杆的冷气流动特性进行了模拟实验,为双层喷油杆结构设计和冷却性能研究提供基础.通过对8套不同结构尺寸实验件的研究,得到了双层喷油杆冷却套管内气流流阻系数随来流质量流量的变化规律、流阻系数随双层喷油杆结构尺寸的变化规律和冷却套内气流雷诺数随进口总压的变化规律等.对8套实验件结果进行比较,综合三个因素最终选择了较为合理的新型双层喷油杆结构尺寸.这种尺寸的喷油杆流阻系数为1.2,迎风尺寸宽16mm较为合适,相同工况下冷却气的雷诺数最大.      

压电驱动自耦合射流冲击冷却特性的实验

利用热线风速仪测量了二维狭缝自耦合射流的速度和湍流度变化,获得了激发器输入电压、频率对自耦合射流的影响规律,获得了激发器的最佳激励电压和频率值;并将自耦合射流应用于冲击换热,通过红外热像仪得到了不同加热功率下加热靶板对流换热系数分布。实验结果表明:(1)在冲击间距比小于20时,射流处于发展区内,冲击冷却效果较差;(2)冲击间距比大于20以后,射流完全形成并趋于稳定后,冲击靶板的换热效果较好;(3)但由于射流速度随着距离增大而衰减,换热效果在冲击间距比为80时达到最佳。      

旋转对冲击射流流动及换热影响的数值研究

为了探究旋转对动叶前缘冲击射流流动及换热的影响机制,采用数值模拟的方法对比分析了静止条件和三种不同旋转转速下的流场结构与换热情况.结果表明:冲击靶面的平均努塞尔数随转速的增大而减小,最高转速下,靶面平均努塞尔数下降约16％.另一方面,压力面和吸力面侧对旋转的敏感性不同.高转速下,换热的削弱主要集中在吸力面和压力面无量纲...     

Integration of high-fidelity model of forward variable area bypass injector into zero-dimensional variable cycle engine model

Forward Variable Area Bypass Injector (FVABI) is one of key components which contributes to modulate the cycle parameters of Variable Cycle Engine (VCE) under various operation conditions. The modeling method of zero-dimensional FVABI was reviewed and its deficiency was analyzed based on FVABI flow characteristic. In order to improve the accuracy of VCE performance simulation, the high-fidelity modeling method of FVABI was developed based on its working characteristics. Then it was coupled with the zero-dimensional VCE model and the multi-level VCE model was built. The results indicate that the geometric and aerodynamic parameters can affect the interaction between the two airflows and the zero-dimensional FVABI model is too simple to predict the component performance accurately, especially when the FVABI inner bypass is chocked. Based on the performance curves for single bypass mode and the regression model of multi-scale support vector regression for double bypass mode, the high-fidelity model can predict FVABI performance accurately and rapidly. The integration of high-fidelity FVABI model into zero-dimensional VCE model can be done by adjusting iterative variables and balance equations. The multi-level model has good convergence and it can predict VCE performance when the FVABI inner bypass is chocked.     

供油瞬态喷油杆内燃油结焦机理及规律数值研究

为获得喷油杆通断循环供油工作模式下,供油瞬间燃油结焦速率陡增机理,本文建立起沿喷杆轴向的一维非稳态热-流-固耦合换热与燃油结焦计算模型.获得不同时刻壁温、油温与结焦速率等参数轴向分布.通过与连续供油模式下的结果对比,来分析供油瞬间灼热喷杆内壁对燃油热冲击的影响,以获得结焦速率陡增机理.结果表明:通断供油模式下,供油瞬间...     

变推力发动机仿真计算分析

分析了变推力发动机采用的双调模式,用流量调节器控制推进剂流量。流量定位针栓式喷注器控制喷注压降,保证喷注速度基本不变。根据发动机系统特点建立了主要组件的数学模型,并根据模型进行了仿真计算,最后对发动机前管路流阻影响进行了分析。     

Experimental study of hydrogen-rich/oxygen-rich gas-gas injectors

Five types of coaxial injectors were investigated experimentally using hot hydrogen-rich gas and oxygen-rich gas, which were respectively provided by a GH2/GO2 hydrogen-rich perburner and a GH2/GO2 oxygen-rich preburner. The injectors were the shear coaxial injector, the oxidizer post expansion coaxial injector, the fuel impinging coaxial injector, the central body coaxial injector, and the shear tri-coaxial injector. The characteristic velocity efficiency and the combustor＇s wall temperatures were obtained for different design parameters through the experiments. It can be con- cluded that angles of the oxidizer post expansion and the fuel impinging have little influence on the combustion performance and the wall temperatures. The contact area between fuel and oxidizer and the mass flow rate have significant impacts on the combustion performance. The shear tri-coaxial injector has the best combustion performance but also the highest wall temperatures among the five types of injectors.     

针栓式喷注单元雾化角模型分析

为了实现不同径向孔形的针栓式喷注器雾化角的准确预测，从动量守恒方程出发建立了液膜撞击液膜和液膜撞击液束的雾化角理论修正模型。对于液膜撞击液膜的喷注单元，模型中通过理论推导引入了2个变形因子，将撞击的几何变形效应与雾化角关联；对于液膜撞击液束，通过引入阻塞率定义有效撞击动量比，同时将液束入口孔形的影响隐含考虑在变形因子中，最后根据高速摄影试验结果和数值仿真结果获得了对应的变形因子组合系数，使得新的雾化角模型适应性更广、准确性更高。结果表明：引入变形因子和阻塞率的理论模型预测值与试验及数值仿真结果吻合很好；对于液膜撞击液膜，变形因子基本维持在0.9~1.1，根据试验结果及仿真结果，变形因子推荐值为C₁=0.99和C₂=1.06；对于液膜撞击液束，变形因子推荐值为C₁=0.75和C₂=1.25。该模型根据实际出口的轴向动量和合成总动量计算雾化角，隐含考虑了撞击作用造成的影响，较根据撞击前入口的轴向动量和合成总动量计算雾化角的常用模型预测值准确度显著提高，为针栓式喷注器的理论研究和工程设计提供了重要参考。     

A high-fidelity design methodology using LES-based simulation and POD-based emulation: A case study of swirl injectors

Engineering design is undergoing a paradigm shift from design for performance to design for affordability, operability, and durability, seeking multi-objective optimization. To facilitate this transformation, significantly extended design freedom and knowledge must be available in the early design stages. This paper presents a high-fidelity framework for design and optimization of the liquid swirl injectors that are widely used in aerospace propulsion and power-generation systems. The framework assembles a set of techniques, including Design Of Experiment (DOE), high-fidelity Large Eddy Simulations (LES), machine learning, Proper Orthogonal Decomposition (POD)-based Kriging surrogate modeling (emulation), inverse problem optimization, and uncertainty quantification. LES-based simulations can reveal detailed spatiotemporal evolution of flow structures and flame dynamics in a high-fidelity manner, and identify important injector design parameters according to their effects on propellant mixing, flame stabilization, and thermal protection. For a given a space of design parameters, DOE determines the number of design points to perform LES-based simulations. POD-based emulations, trained by the LES database, can effectively explore the design space and deduce an optimal group of design parameters in a turn-around time that is reduced by three orders of magnitude. The accuracy of the emulated results is validated, and the uncertainty of prediction is quantified. The proposed design methodology is expected to profoundly extend the knowledge base and reduce the cost for initial design stages.