Fundamental studies on combustion and microfluidics

------------------ 1.氨作为燃气轮机的替代燃料 - 氨在世界范围内都很容易获得，并且在适当的压力下很容易液化，便于储存和运输。它的热值与甲醇相似，但纯氨的燃烧特性较差。但是，它可以在相对较低的温度下部分分解，自行产生一些氢气，从而消除这个问题。氨燃烧中不含碳是消除温室气体的重要一步，但氮氧化物（NOx）仍然是一个关键问题。拟议的实验设施将包括一个催化氨分解室和一个燃烧管与多排孔的二次空气喷射。部分分解的氨和预热的一次空气将通过具有反涡流的同轴管引入燃烧室，并将在燃烧室沿着的各个位置监测温度和氮氧化物水平。最终目标是为超清洁氨燃料燃气涡轮机燃烧器开发分级燃烧策略。------------------ 2.通道内的微尺度流动与传热 - 微尺度管道流的行为与宏观尺度管道流的行为非常不同。对于气体，稀薄导致壁面处的速度滑移和温度跃变，从而导致较低的摩擦系数和传热系数。此外，由于气体的可压缩性和粘性耗散的影响变得重要。液体在很大程度上不受压缩性和稀疏性的影响，但由于壁附近存在带电区域，因此可能会经历电动和电渗效应。在电动装置中，该区域内的过量电荷随着流体移动，以通过跨通道施加压力差来产生电流。在电渗装置中，通过施加外部电场来移动过量电荷，从而产生液体泵。在本研究中，将利用数值方法研究矩形和梯形微通道内气体和液体的流动行为。

------------------     1. AMMONIA AS AN ALTERNATIVE FUEL FOR GAS TURBINES     ------------------ Ammonia is readily available worldwide, and is easily liquefied at modest pressures for storage and transportation. It has a calorific value similar to methanol, but pure ammonia has poor combustion characteristics. However, it can be partially decomposed at relatively low temperatures to self-generate some hydrogen, thus eliminating this problem. The absence of carbon in the combustion of ammonia is a major step towards eliminating greenhouse gases, but nitrogen oxides (NOx) remain a critical concern. The proposed experimental facility will consist of a catalytic ammonia decomposition chamber and a combustion tube with multiple rows of holes for secondary air injection. Partially decomposed ammonia and preheated primary air will be introduced into the combustion chamber through co-axial tubes with counter-swirl, and temperatures and NOx levels will be monitored at various locations along the combustion chamber. The ultimate goal is to develop staged-combustion strategies for ultra-clean ammonia fuelled gas turbine burners. ------------------     2. MICRO-SCALE FLOWS AND HEAT TRANSFER IN CHANNELS     ------------------ Micro-scale duct flows behave very differently from their macro-scale counterparts. For gases, rarefaction causes velocity-slip and temperature-jump at the walls, resulting in lower friction and heat transfer coefficients. Furthermore, effects due to gas compressibility and viscous dissipation become important. Liquids are largely immune to compressibility and rarefaction, but may experience electro-kinetic and electro-osmotic effects due to the presence of an electrically charged region near the walls. In an electro-kinetic device, the excess charge within this region is moved with the fluid to create an electric current by the application of a pressure difference across the channel. In an electro-osmotic device, the excess charge is moved by the application of an external electric field, thereby creating a liquid pump. In the proposed research, the behavior of gas and liquid flows in rectangular and trapezoidal micro-channels will be investigated using numerical methods.