Instrumentation Design for HRR Measurements in a Large-Scale Fire Facility

Abstract

Carleton University's experimental atrium and tunnel facilities share a fan chamber and three large exhaust fans. Using oxygen consumption calorimetry, the Heat Release Rates (HRR) of fires in either of these facilities can be calculated. This paper focuses on the design of the instrumentation in the fan chamber, which was carried out using the Fire Dynamics Simulator (FDS) and manual velocity measurements. Due to a high amount of mixing and turbulence and a long travel distance, the temperature and gas concentration profiles are relatively uniform. However, for the same reason, the velocity profile had to be looked at very closely to find an optimum combination of bi-directional probes. The analysis indicated that acceptable HRR measurements can be obtained using an array of six thermocouples, four bidirectional velocity probes and a gas sampling grid. Results from the preliminary tests are presented. The system shows a reasonable estimate of the HRR as compared to the propane calibration burner.

Study of smoke backlayering during suppression in tunnels

“…For accurate measurements of HRR, the instrumentation of the HRR measurement system was designed based on extensive analysis of various CFD simulations of the flow pattern in the tunnel facility as well as analysis of manual measurements of the velocity profile in the fan chamber [13]. A series of calibration tests was conducted to evaluate the accuracy of the system for various fire sizes under different ventilation conditions.…”

A study of the heat release rate of tunnel fires and the interaction between suppression and longitudinal air flows in tunnels

“…In order to measure the HRR of a burning item, all combustion products must be However, for the same reason, the velocity profile had to be looked at very closely to find an optimum combination of bi-directional probes. More details about this are published in [79].…”

“…5 (a) Probe constant as function of Re (b) standard design of the probe[88].. Bi-directional probe dimensions used in the current study (D=24.6 mm, L=46.25 mm, D'=6.3 mm, and L'=7.6 mm) Model Vertical temperature profiles from a 10 MW fire in the tunnel under different fan speeds (Note: -1.25 and 1.25 refer 1.25 m left and 1.25 m right from the centre, respectively)[79] Vertical profiles of oxygen mass fraction of the flow from a 10 MW fire in the tunnel under different fan speeds (Note: -1.25 and 1.25 refer 1.25 m left and 1.25 m right from the centre, respectively)[79] 10 Vertical velocity profiles at 50% fan speed without and with a 2.5 MW fire in the tunnel (Note: -1.25 and 1.25 refer 1.25 m left and 1.25 m right from the centre, respectively)[79] 11 Vertical velocity profiles at 50% fan speed from a atrium simulation and manual measurements (Note: -1 25. and 1.25 refer 1.25 m left and 1.25 m right from the centre, respectively) [79] 12 the fire most accurate velocity probe combinations [79] 13 Comparison of the fire most accurate velocity probe combinations [79] 16 Real-time HRR calculations and display system flow chart Test arrangement for Heptane and propane fire The front panel of the real time HRR measurement calculation and display system (captured during a test, 5 MW 50% fan speed) HRR results from a calibration test A5 of the HRR measurement system using propane burners (50% fan speed, 5 MW) The correction factor matching JQ to E from a calibration test A5 (50% fan speed, 5 MW) Comparisons of the system response to 5 MW calibration fire for different fan speeds Results from a calibration test P13 of the HRR measurement system using propane burners (100% fan speed, 13 MW, for 40 seconds) Results from a calibration test of the HRR measurement system using propane burners and heptane pool fire (100% fan speed, 23 MW) Correction factors with respect to 02 concentration Corrected HRR calculation for Test Bl 1 (25%, 8-2 MW Type B propane test, correction factor = 0.83) Uncertainty contributions by each component (averaged results from 11 tests) Performance of the HRR measurement system Test set-up in the tunnel 125 Flow straightening vanes at the main opening 125 Sprinkler system and instrumentation in the tunnel 129 The propane burners and heptane pool for the fire test of 15 MW 131 Plate thermometer (the manufacture provided) 133 Arrangement of buckets 134 Bucket test 135 The collected water spray rate normalised to the nominal water spray rate of3 1/min/m 2 under an air flow of 0 m/s 137 The collected water spray rate normalised to the nominal water spray rate of 3 1/min/m 2 under an air flow of 2.7 m/s (Fan speed 100%) 137 10 The collected water spray rate normalised to the nominal water spray rate of 9 1/min/m 2 under an air flow of 0 m/s 138 11 The collected water spray rate normalised to the nominal water spray rate of 9 1/min/m 2 under an air flow of 2.7 m/s (Fan speed 100%) 138 12 A photo taken during the suppression test 139 13 The measured HRR and O2 concentration over time for 10 MW fire with a 9 9…”

“…Lower Chamber ! i 1 Q\ Tunnel 37 5m by 10 0 rn (floor area) and 5,6 m high partition waii 1-i-i-r -~r uppar chamber 3.Schematic of Carleton laboratory facility[79] To develop a HRR measurement system for the facility, a preliminary study was conducted to obtain insight into the flow characteristics in the fan chambers using Computational Fluid Dynamics (CFD) modelling of the facility. Detailed model descriptions are presented in Chapter 3.3.1.…”

“…Vertical temperature profiles from a 10 MW fire in the tunnel under different fan speeds (Note: -1.25 and 1.25 refer 1.25 m left and 1.25 m right from the centre, respectively)[79] …”