How does primary liquid break-up determine the downstream spray characteristics of airblast atomisers?

更好的燃油喷雾(例如，更小的液滴尺寸以改善蒸发，更好的“模式”--以及及时的低液滴“聚集”--以避免产生碳烟和氮氧化物的燃料富集区，在空闲到满负荷之间保持这些品质)是已知的更环保航空发动机设计的关键。尽管燃油雾化是一项古老的技术，但几乎没有基本的知识可以可靠地回答这个简单的问题：考虑到这种喷雾器的形状，我会产生什么样的燃油喷雾？答案必须能够解释对雾化器进行几分之一毫米量级的修改是如何以及为什么从根本上改变喷雾的。为了给出答案，我们需要比以往更好、更广泛地测量“基本”过程：我们必须提高计算流动(波浪、不稳定性、韧带形成、‘夹断’等)的能力。该提案的总体目标是为喷雾器中液体射流的雾化过程生成新的计算流体动力学(CFD)建模策略，重点是燃烧系统和航空发动机中使用的几何形状。我们的方法将是使用光学仪器对同流和横流雾化器配置的主要破碎区域中的液体、喷雾和气体运动进行新颖的时间和空间分辨率测量。我们将使用这些来评估基于开源CFD代码的两种雾化器几何形状的大涡模拟(LES)的结果，以预测雾化过程的时间发展，包括内部液体流动和周围气体流动、液体破碎和液体喷射完整长度下游的喷雾特性。我们打算确定CFD在多大程度上可以预测这些几何形状的初级雾化过程中的三个转变--从波到韧带再到液滴，这是完全未经测试和未知的。我们将使用评估后的代码进行“数值实验”，重点放在稠密的液核上，在那里很难进行测量，以进一步阐明物理原理。

Better fuel sprays {e.g. smaller drop sizes to improve evaporation, better 'patterns' - and low droplet 'clustering' in time - to avoid fuel rich zones for soot and NOx production, maintaining these qualities between idle to full power } are known to be a key to the design of greener aeroengines. Although fuel atomization is an old technology, remarkably little fundamental knowledge exists which would reliably answer the simple question: given this shape of atomizer, what kind of fuel spray would I produce? The answer must be able to explain how and why modifications of the order of a fraction of a millimeter to the atomiser radically changes the spray. To formulate the answer, we need better and more extensive measurement of the 'fundamental' processes than hitherto: and we must advance our ability to calculate the flow (waves, instabilities, ligament formation, 'pinch-off', etc.) from first principles - and check the advance against fundamental, simple yet representative sprays.The overall aim of the proposal is to generate new computational fluid dynamic (CFD) modelling strategies for the atomisation process of liquid jets in airblast atomisers with an emphasis to geometries used in combustion systems and aero-engines. Our approach will be to make novel time- and spatially- resolved measurements of the liquid, spray and gas motions in the primary breakup regions of co-flowing and cross-flow atomiser configurations using optical instrumentation. We will use these to evaluate the results of Large eddy simulations (LES) of two atomiser geometries, based on an open source CFD code, to predict the temporal development of the atomisation process, in terms of internal liquid flow and surrounding gas flow, liquid breakup and spray characteristics downstream of liquid jet intact length. We intend to establish the extent to which CFD can predict the three transitions - waves to ligaments to droplets - in primary atomization in these geometries, which is as yet completely untested and unknown. We will use the evaluated code to perform 'numerical experiments' with emphasis on the dense liquid core, where measurements are hard to make, to further elucidate the physics.