In situ imaging of 4D fire events in a ground vehicle testbed using customized fiber-based endoscopes

Understanding the dynamics of fire events in ground vehicles is critical to improving crew survivability. To advance our understanding, four dimensional (4D) measurements are sorely needed to resolve both the temporal and spatial dynamics of fire events. However, there are several key challenges toward such measurements, including equipment requirements and optical access. 4D measurements, especially with sufficient temporal resolution, can be equipment intensive. Such equipment requirements are further compounded by the relatively hostile environments encountered in vehicular testbeds. Moreover, there is often very limited optical access available for obtaining such measurements within vehicular environments. This work describes the design and implementation of a customized fiber-based endoscope (FBE) setup to overcome these challenges in order to enable 4D flame measurements in a ground vehicle testbed located at the Army Research Laboratory, Aberdeen Proving Ground. Using a customized 9-to-1 FBE bundle, 4D imaging of relatively large-scale fire events was demonstrated at 500 Hz in a volume of 35 cm (width) x 35 cm (depth) x 29 cm (height), with a single camera located at a safe distance outside the vehicle. The measurements were then processed by volumetric tomography techniques to resolve the temporal dynamics and spatial structures of the target flame within the vehicle testbed. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.