Study on the Development of Automatc Line-Heating System

为了实现线加热过程的自动化，提出了一种火焰与板间传热的估计方法。得到的主要结果如下。1)通过计算非燃烧碰撞射流代替燃烧火焰的热流，可以估计出板附近的温度分布。在这种方法中，需要给出喷嘴出口虚拟非燃烧气体的温度和速度作为计算条件。对于二维气体火焰，将火焰内的最高温度和喷嘴上游混合气的速度作为出口虚拟气体的温度和速度时，板表面附近的观测温度与计算温度吻合较好。2)发现局部换热系数可以用对数定律（壁律）来计算。实验证明了该公式对二维气体火焰的适用性。3)利用高性能lif测量系统，详细测量了管道加热过程中气体火焰内部的瞬态三维温度分布。研究发现，火炬周围气体温度的相对分布与现场加热时几乎相同。还发现，无论钢板温度升高与否，这种相对分布几乎不变。这些结果使我们提出了一个新的假设，即在管道加热过程中，火炬周围气体温度和局部换热系数的相对分布保持不变，与现场加热过程几乎相同。基于这一假设，提出了一种新的热输入估算方法。

In order to automate Line-heating process, an estimation method of heat transfer between flame and plate is developed. The major results obtained are as follows.1) It is found that the temperature distribution near the plate can be estimated by calculating the heat flow of non-combustion impinging-jet in place of the combustion flame. In this approach, it is needed to give the temperature and velocity of the Virtual non-combustion gas at the nozzle exit as the calculation Conditions. For 2-dimensional gas flame, close agreement, between observed and calculated temperature near the plate surface was obtained when the highest temperature within the flame and the velocity of gas mixture at the upstream side of the nozzle was employed as the temperature and velocity of the virtual gas at the exit.2) It is found that the local heat transfer coefficient can evaluated by the logarithmic law (wall law). Appropriateness of this formulation was proved experimentally for 2-dimensional gas flame.3) The transient 3-dimensional temperature distribution within the gas flame during line heating is measured in detail by a high performance L.I.F. measurement system. It has been found that the relative distribution of gas temperature around the torch is almost the same as that in spot heating. It has also been found that this relative distribution is almost unchanged regardless of the temperature increase in the steel plate. These results lead us to a new hypothesis that the relative distributions of gas temperature and local heat transfer coefficient around the torch remain unchanged and they are almost the same as those in spot heating during line heating process. A new method of heat input estimation for line heating process based on this hypothesis has been propounded.