National Fire Research Laboratory: Advanced Metrology

Summary

The National Fire Research Laboratory (NFRL) is the premier facility in the world for conducting research at realistic scales to accurately quantify fire behavior and the response of structural systems to fire.  It provides controlled laboratory conditions for project investigators to study full‑scale fires as they propagate through simulated configurations of built and natural habitats. The project coordinates research activities to implement state-of-the-art technology in support of advancing fire research and reducing the risk of fire, develop best practices for generating the most accurate data characterizing fire behavior, and implement new technology as innovative solutions to the challenges of fire metrology.

Description

Verification burn using a natural gas burner under the 20 MW exhaust hood in the National Fire Research Laboratory.  

Credit: R. Bryant/NIST

Objective
Develop a robust system of measurement capabilities and best practices to serve as a model for advancing fire metrology, generate accurate and high‑quality data, and enable solutions for a wide range of fire problems. 

Technical Idea
The National Fire Research Laboratory is a unique facility allowing the study of real-scale fires, ranging from 50 kW to 20 MW, under controlled conditions.  Fires are generated using natural gas, flammable liquids, wood cribs, building systems and contents, as well as vehicles as fuel sources.  Innovative leveraging of NFRL’s unique capabilities to generate new insight into the behavior of full-scale fires and the response of structures to fire is the new technical idea.  These capabilities include:

• precisely controlled burns
• controlled hydraulic loading of structures
• complete capture of fire effluents for calorimetry and emissions control
• accurate measurements of the thermal environment, structural response, and performance of fire safety systems

This combination of capabilities enables the execution of fire experiments not possible previously.  Using state-of-the-art measurement methods, high‑fidelity data can be produced for new and routine fire experiments to support the development of standards and predictive simulation tools.

Research Plan
This project coordinates the research activities to create an infrastructure of high‑fidelity measurements in support of research projects with the goal of reducing fire risk.  Using state-of-the-art technology, the measurements will provide high-quality reference data and serve as benchmarks for developing best practices and evaluating new measurement methods. Focus is placed on improving the capabilities of the large fire calorimeters to measure heat release rate, the primary measure of the fire hazard, and improving measurements relevant to structural performance, such as strain and displacement.

Accurate characterization of the fire environment is necessary to gain new insight into fire behavior, and to correlate the performance of structural and fire safety systems to thermal loading.  State-of-the-art measurement capabilities will be implemented to:

• characterize gas and particle emissions from real-scale fires
• quantify the thermal impact of fire to the surroundings
• correlate localized fire events to specific parameters of fire behavior
• measure the deformation and strain on structures exposed to fire
• characterize the transport of heat and toxic products using robust flow measurements

Techniques capable of remotely probing the fire to provide in‑situ measurements have potential to improve accuracy and provide further insight.  New instrumentation will be evaluated for their potential to:

• generate accurate full-field images of thermal data
• provide strain and displacement measurements over large regions of a specimen
• characterize gas species production in real-time

Statistical methods will be used to quantify measurement uncertainty and systematically improve measurement accuracy.  Detailed characterizations of existing and newly implemented measurements will be conducted to provide benchmarks for quality controls and evaluating the performance of new techniques.  Useful best practices will be developed as technology transfer to the communities of fire research and fire safety testing.  Ultimately a world class measurement system will generate high‑fidelity data to advance fire safety education, validate and develop predictive models, and provide scientific support for the development of standards.

Major Accomplishments

• Documented the measurement uncertainty for NFRL’s system of oxygen consumption calorimeters.
• Verified the accuracy of NFRL’s exhaust flow measurement using independent measurement techniques.
• Developed a system of precise positioning probes for detailed characterizations of fire experiments.
• Demonstrated the benefits the S-probe, an off-the-shelf technology, as an alternative to the bi‑directional probe for flow measurements in fire.