Engineering Research Equipment Grant: UV-Imaging Equipment

一种新的基于准分子激光的诊断方法正在开发中，该方法可以在高温介质中产生瞬时的二维温度和密度场，例如在明火或内燃机中发生的情况。由于该方法具有良好的时间分辨率(10 Ns)，是湍流燃烧分析的理想方法。它使用激光诱导荧光，但采用了一种新的方法，消除了碰撞猝灭的问题，通常情况下，碰撞猝灭将LIF限制在低于0.01大气压的压力下。一种强大的窄带紫外线激光将分子激发到预解离状态，这种状态是如此短暂，以至于没有时间来熄灭碰撞。提出了获取紫外像增强器和自扫描阵列相机以获得荧光的二维图像的方案。然后，人们可以从字面上拍摄单个选定量子态的密度分布的“快照”。通过使用两个摄像系统比较两个这样的状态的密度，可以用一次激光拍摄来计算温度分布。例如，激光技术在用于优化燃烧系统、最小化污染物排放或最大化燃油经济性的探测器/计算机组合技术方面尤其有前景。这里提出的方法将把LIF扩展到一个更有用的压力区域，从而将我们引向这个方向。

A new excimer-laser based diagnostic method is being developed that should yield instantaneous two-dimensional temperature and density fields in high-temperature media such as occur in open flames or in internal combustion engines. Because the method has excellent time resolution ( 10ns), it is ideal for analysis of turbulent burning. It uses laser induced fluorescence, but with a novel approach that eliminates the problem of collisional- quenching that normally limits LIF to pressures less than 0.01 atmosphere. A powerful narrow-band UV laser excites molecules to predissociating states that are so short-lived that there is no time for quenching collisions. It is proposed to acquire a UV image intensifier and a self scanned array camera to obtain two-dimensional images of the fluorescence. One can then literally take "snapshots" of the density distribution of a single selected quantum state. By comparing the densities of two such states using two camera systems, the temperature distribution can be calculated with a single laser shot. Laser techniques are particularly promising for combined detector/computer technologies for optimization of combustion system, minimizing pollutant emissions or maximizing fuel economy for example. The method proposed here will lead us in that direction by extending LIF to a more useful pressure regime.