Combustion chamber wall heat transfer is a major contributor to efficiency losses in diesel engines. In this context, thermal swing materials (adapting to the surrounding gas temperature) have been pinpointed as a promising mitigative solution. In this study, experiments are carried out in a high-pressure/high-temperature vessel to (a) characterise the wall heat transfer process ensuing from wall impingement of a combusting fuel spray, and (b) evaluate insulative improvements provided by a coating that promotes thermal swing. The baseline experimental condition resembles that of Spray A from the Engine Combustion Network, while additional variations are generated by modifying the ambient temperature as well as the injection pressure and duration. Wall heat transfer and wall temperature measurements are time-resolved and accompanied by concurrent high-speed imaging of natural luminosity. An investigation with an uncoated wall is carried out with several sensor locations around the stagnation point, elucidating sensor-to-sensor variability and setup symmetry. Surface heat flux follows three phases: (i) an initial peak, (ii) a slightly lower plateau dependent on the injection duration, and (iii) a slow decline. In addition to the uncoated reference case, the investigation involves a coating made of porous zirconia, an established thermal swing material. With a coated setup, the projection of surface quantities (heat flux and temperature) from the immersed measurement location requires additional numerical analysis of conjugate heat transfer. Starting from the traces measured beneath the coating, the surface quantities are obtained by solving a one-dimensional inverse heat transfer problem. The present measurements are complemented by CFD simulations supplemented with recent rough-wall models. The surface roughness of the coated specimen is indicated to have a significant impact on the wall heat flux, offsetting the expected benefit from the thermal swing material.

燃烧室壁的热传递是导致柴油发动机效率损失的主要因素。在这种情况下，热摆材料（适应周围的气体温度）已被确定为有希望的缓解方案。在这项研究中，我们在高压/高温容器中进行了实验，以（a）表征燃烧的燃料喷雾撞击壁后产生的壁传热过程，以及（b）评估由涂料提供的隔热性能促进热摆动。基线实验条件类似于来自发动机燃烧网络的喷雾A的条件，而通过改变环境温度以及喷射压力和持续时间会产生其他变化。壁传热和壁温测量是时间分辨的，并伴随着自然光度的高速成像。使用停滞点周围的几个传感器位置进行了无涂层壁的研究，阐明了传感器之间的可变性和安装对称性。表面热通量分为三个阶段：（i）一个初始峰，（ii）取决于注入持续时间的略低的平稳期，和（iii）缓慢下降。除了未涂层的参考案例外，研究还涉及由多孔氧化锆（一种成熟的热摆动材料）制成的涂层。使用涂层装置时，从浸没的测量位置投影表面量（热通量和温度）需要对共轭传热进行额外的数值分析。从涂层下面测得的痕迹开始，通过解决一维逆传热问题来获得表面量。当前的测量结果通过CFD模拟得到补充，并补充了最新的粗糙壁模型。指示涂层样品的表面粗糙度对壁热通量有显着影响，抵消了热摆材料的预期收益。