Multi-scale analyses of wildland fire combustion processes: Small-scale field experiments – Transportable Analyzer for Calorimetry Outside (TACO)

The United States Department of Defense (DoD) Strategic Environmental Research and Development Program (SERDP) funded project: "Multi-scale Analyses of Wildland Fire Combustion Processes in Open-canopied Forests using Coupled and Iteratively Informed Laboratory-, Field-, and Model-based Approaches (RC-2641)" small-scale field experiments were designed to investigate how contrasting fuel conditions (e.g., fuel load, particle type, bulk density), fire spread type (e.g., heading vs. backing), and ambient conditions (e.g., seasonality, moisture, flow, temperature) influenced physical processes associated with combustion (e.g., heat transfer, flame propagation, flow) and the scale-dependent coupling of these processes. Additionally, these experiments provide 1) a linkage between small-scale laboratory combustion experiments and large-scale operational prescribed fires, and 2) archived datasets for further model development and evaluation. Our experimental design incorporates complementary approaches, methods, and instrumentation employed at these other scales, to quantify critical properties of the experimental fires’ physics domains (e.g., fuels and ambient conditions) and processes associated with combustion (e.g., heat transfer, flame propagation, flow). The small-scale field experiments include a series of highly instrumented, intermediate-scale experiments conducted on 100 square meter plots at the Silas Little Experimental Forest, New Lisbon, New Jersey. This dataset contains data collected in 2018 and 2019 from a Transportable Analyzer for Calorimetry Outside (TACO). TACO measurements were conducted at a single measurement location within the plot. The TACO system consists of an exhaust collection hood and duct, with a gas sample line extracting from the duct. The TACO exhaust duct was not operational until burn 8. From burns 8-13 (6 burns) the exhaust duct radius was 0.1016 meters (m). After burn 13 the exhaust duct was altered changing the duct radius to 0.0508 m for burns 14-35 (15 burns). The exhaust duct pressure difference was measured using a 25-millimeter (mm) diameter bi-directional pressure probe connected to a Sensirion SDP810-125Pa air pressure sensor. The exhaust gas temperature was measured using a 0.25 mm K-type thermocouple. Oxygen concentration was measured using an AO2 CiTiceL oxygen cell, while carbon dioxide and carbon monoxide concentrations were measured using a Non-Dispersive Infrared Sensor (NDIR) on the Crestline Instruments 7911 Automotive Gas Analyzer. These data were collected at 1 hertz (Hz).
Many DoD facilities utilize low intensity prescribed fire to manage hazardous fuels, restore ecological function and historic fire regimes, and encourage the recovery of threatened and endangered species in the forests they manage. Current predictive models used to simulate fire behavior during low-intensity prescribed fires (and wildfires) are empirically based, simplistic, and fail to adequately predict fire outcomes because they do not account for variability in fuel characteristics and interactions with important meteorological variables. This study used a suite of measurements at the fuel particle, fuel bed, field plot, and stand scales to quantify how variability in fuel characteristics and key meteorological factors interact to drive fire behavior during low intensity prescribed burns. These experiments were designed to inform the development and evaluation of physics-based models that explicitly account for combustion, turbulent transfer, and energy exchange by coupling and scaling individual component processes. These datasets provide measurements to improve the understanding of, and ability to accurately predict, fire behavior under a wide range of management scenarios.
A summary of the SERDP Project RC-2641 can be found at the RC-2641 Project Overview (serdp-estcp.org): https://www.serdp-estcp.org/Program-Areas/Resource-Conservation-and-Resiliency/Air-Quality/Fire-Emissions/RC-2641. Please reference the plot layout and documentation data publication (Gallagher et al. 2022) as these data provide burn summaries, detailed descriptions of data collected, and the locations of sensors within each burn.