利用自激振荡脉冲特性实现双腔室射流喷嘴的超微雾化机理

Spray removing dust is one of the effective ways to reduce PM2.5, PM10 of fog and haze, how to achieve spraying fluid efficient atomization in the low energy consumption is a great difficult problem urgently resolved. It is found that the injection peak pressure of the self excited oscillation pulsed jet is increased by 10%-15% higher than the traditional injection pressure because of the special chamber and the specific boundary conditions of the nozzle. Based on that, the research ideas have been innovatively proposed by using self-excited oscillation pulsed characteristics to realize fluid ultramicro atomization. The resonance effects, cavitation phenomenon and pneumatic atomization generated during the pulsed jet as the main factors are studied and at that time the internal function and rules that using the self-excited oscillation pulsed characteristics to improve jet atomization effects are analyzed deeply; on this basis, the double-chamber jet nozzle is designed, the spraying dynamics models are established and numerically solved, after that, experimental chamber structure parameters are optimized by the artificial neural network algorithm; Combined with the calculation results, the experiments of self-excited oscillation pulsed jet continuous spraying and flow characteristics spraying are carried out under the multi-factor coupling, and the calculated prediction models between the dimensionless structure parameters of the chamber and the average particle size of the ultramicro droplets is built. The findings of the research will lay the theoretical foundations for riching fluid ultramicro spraying technology, and provide the scientific references for design theory and method of novel spraying equipments in the practical application. It is of great significance to build energy efficient and environment-protecting society in our country.

喷雾抑尘是降低雾霾PM2.5、PM10的有效途径之一，如何实现喷射流体的低能耗高效雾化是其中急需解决的重大难题。研究发现：自激振荡脉冲射流依靠喷嘴自身特殊腔室和特定边界条件使喷射脉冲峰值压力比传统喷射压力增大10%-15%。基于此，本项目创新性地提出利用自激振荡脉冲特性实现流体超微雾化的研究思路。拟从射流产生的共振效应、空化现象和气动雾化等主要因素展开研究，深入分析利用自激振荡脉冲特性提高射流雾化效果的内在作用与规律；在此基础上，设计双腔室射流喷嘴并建立其喷雾动力学模型进行数值求解，利用人工神经网络算法进行实验用腔室结构参数优化；结合计算结果，完成多因素耦合下脉冲射流连续性喷雾和流场特性喷雾实验，构建腔室无量纲结构参数与超微雾滴平均粒径的计算预测模型。项目研究将对丰富流体超微喷雾技术奠定理论基础，并为实际应用中新型喷雾装备设计理论及方法提供科学依据，对我国建立节能型、环保型社会有重要意义。

项目融合当前利用喷雾抑尘技术降低PM2.5、PM10相关研究的热点和难点，对影响射流超微雾化效果的自激振荡脉冲特性主要因素、自激振荡脉冲射流喷嘴设计与计算流体动力学建模、多因素耦合下自激振荡脉冲射流喷雾特性三个方面进行探讨。主要研究工作包括：.（1）分析了射流来流速度和脉动压力对自激振荡脉冲喷嘴出口流道空化效应的影响，提出利用来流雷诺数和脉动特征值表征喷嘴出口流道空化程度，得到了喷嘴出口流道较好空化状态的来流雷诺数和喷嘴腔室长径比；根据空化泡和涡结构的状态本质，提出了空化云新定义，分析了空化云在自激振荡脉冲腔室单个周期内的演变过程和形态。.（2）依据涡环在自激振荡腔室内的蓄能及释能状态，分析了自激振荡脉冲涡量助推效应。利用大涡模拟数值计算方法，分析了入口压力为1MPa时自激振荡瞬时涡量初生时刻扰动变化、一个脉动周期内瞬时流向涡量变化和自激振荡腔室下游出口流道流速变化规律。.（3）提出一种考虑剪切应力和由湍动能产生的压力脉动对空化初生影响的修正空化模型，并对不同压力工况下的空化初生能力进行了研究；推导并联式自激振荡喷嘴的固有频率和系统频率方程，分析了并联式自激振荡脉冲喷嘴的频率特性。.（4）提出基于空化汽囊能量最大化的雾化喷嘴腔室壁面结构设计方法，利用Bezier曲线重构了腔室壁面四角过渡形状，设计了次生涡衰减的新型雾化喷嘴自激振荡腔室壁面结构；采用中心复合实验方法进行试验设计，通过响应面法建立喷嘴近嘴区初次雾化的近似数学模型，结合NSGA-II遗传算法和灰色理论进行了喷嘴结构参数多目标优化设计。.（5）基于多相流模型，计算得到了振荡周期100ms内自激振荡脉冲射流的空化泡破碎、腔室内多相分布、湍动能分布和速度分布等数值计算结果；使用DPM模型和Rosin-Rammler分布，获得了新型喷嘴结构雾化效果在20μm-50μm的雾滴比例。.项目研究将对丰富流体超微喷雾技术奠定理论基础，并为实际应用中新型喷雾装备设计理论及方法提供科学依据，对我国建立节能型、环保型社会有重要意义。