Fundamental studies on combustion and microfluidics

1. 氨作为燃气轮机的替代燃料------------------氨在世界各地都很容易获得，并且在适度的压力下很容易液化，用于储存和运输。它的热值与甲醇相似，但纯氨的燃烧特性较差。然而，它可以在相对较低的温度下部分分解，自行产生一些氢气，从而消除了这个问题。在氨的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。该实验装置将由一个催化氨分解室和一个带有多排二次空气喷射孔的燃烧管组成。部分分解的氨和预热过的一次空气将通过带反旋的同轴管引入燃烧室，并在燃烧室的各个位置监测温度和NOx水平。最终目标是开发超清洁氨燃料燃气轮机燃烧器的分级燃烧策略。------------------      2。微尺度流动和通道内的传热------------------微尺度的管道流动与其宏观尺度的管道流动表现非常不同。对于气体来说，稀薄会导致壁面的速度滑移和温度跳变，从而降低摩擦系数和传热系数。此外，气体可压缩性和粘性耗散的影响也很重要。液体在很大程度上不受可压缩性和稀薄性的影响，但由于在壁附近存在带电区域，可能会经历电动力学和电渗透效应。在电动装置中，该区域内的多余电荷随着流体移动，通过施加跨通道的压差产生电流。在电渗透装置中，通过施加外电场移动多余的电荷，从而产生液体泵。在提出的研究中，气体和液体在矩形和梯形微通道中的流动行为将采用数值方法进行研究。

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.