A Novel and Cost Effective Radiant Heatflux Gauge

Samim Safaei M.S. Candidate Worcester Polytechnic Institute, Worcester, MA [email protected]

Outline

 Background

 Fundamentals

 Methodology

 Results

 Next Steps

2

Background: Research Context

 Objective:

 To develop a cost effective and practical tool for analysis and detection purposes.

 Background:

 B.Eng., University of British Columbia (UBC), Canada, 2012 – Electrical and Mechanical Engineering

 Independently conceived technology during B.Eng.

 Currently validating technology for M.S. Thesis in Fire Protection Engineering at Worcester Polytechnic Institute (WPI)

 Patent-Pending

 Collaborators:

 Ali S. Rangwala, Associate Professor, Supervisor, WPI

 V. Raghavan & T. Muruganandam, Co-supervisors, Mech. & Aero. Eng., Indian Institute of Technology Madras, IITM

 L. Genovesi, CEO, Global Fire Products Inc. 3 Background: Current Technologies

 Radiant heatflux (light) communicates a wealth of information remotely and instantly.  Radiative heatflux  Geometries/dynamics Parameter Device Physics Spectra Unit Cost Requires  Temperature Radiant Schmidt-Boelter Thermo- UV, Vis, 1000 - Continuous  Chemical characteristics heatflux / Gardon Gauge electric SWIR, 5000 cooling  Fire hazards = OFD effect MWIR, LWIR Radiant Thermal Thermo- UV, Vis, 1000 - Cooling,  Fundamental sensor physics heatflux + Imaging electric SWIR, 100000 Specialized Temperature Cameras effect MWIR, operation limit current tools: LWIR  Resource intensive Radiant Prototype Photo- SWIR 10 - 100 N/A  Data sparse heatflux + electric  Cost prohibitive Temperature + effect Soot fraction,

speed… Figure 1. Technology Comparison 4

Fundamentals: Flame Radiation

General Combustion Reaction:

CnH2n + Oxidizer Soot (Carbon Intermittents) H2O + CO2 + … Chemiluminescene Thermal Radiation Photoluminescence (Small, Fuel Dependant) (Fuel Dependant) Visible

x10

[2] G.P. Smith, et al. “Low pressure flame determinations [1] “Spectrum of Typical of rate constants for OH(A) and CH(A) chemiluminescence”, Hydrocarbon Flame”, NFPA 72, Figure A.17.8.2.1 Combustion and Flame, Volume 131 (1–2), 2002, p.59-69

>>>For all carbonaceous diffusion flames, soot radiation dominates. 5 Fundamentals: Thermal Radiation

 All objects emit light-energy as a strong UV V SWIR MWIR LWIR function of their Temperature; E=f(T4). 100000

] 1500K 2  Function also influenced by: 80000 1300K  Surface properties (emissivity, reflectance, …) 1100K  Geometries (emission area and orientation) 60000 900K

 Emissions distributed over a range of 40000 700K wavelengths; tending towards shorter 500K wavelengths as Temperature increases. 20000

[W/m E(T) Power, Emissive

 Visible light makes up a minor portion 0 of this range, only visible when emission 0 1 2 3 4 5 6 7 8 9 10 source passes 900K (1200 F). Light Wavelength [μm]

F.P. Incropera, D.P. DeWitt, “Fundamentals of Heat and Mass Transfer”, Wiley, 1996, p.723-780 6

Methodology: Validation Approach

Prototype, Gn Measured Established Experimental Platform ? Theoretical, Gn Computed

 Gn is the Sensible Irradiance on a sensor 7 Methodology: Experimental Platform

Soot & Temperature Data from published co-flow Ethylene-Air Partially-Premixed Laminar Flames [1]

ri = 0.5 cm

Equivalence Ratio Pure Diffusion ~Stoic. Premix

[1] C.P. Arana, S. Sen, I.K. Puri, “Field measurements of soot volume fractions in laminar partially premixed coflow

ethylene/air flames” Combustion and Flame 138 362–372 (2004) 8 Methodology: Prototype

Irradiance Lens Sensor “n” Circuit Sensor • Stabilize, ADC E(T) Signal

Digital Signal • Amplify, R ϴ + - Recorded Data, X • DAQ Total incoming Proprietary low cost Off-The-Shelf Sensor n radiative flux lens focuses view to output proportional to 2 [W/m ] ϴ, filters excess heat sensible Irradiance; Cn

Blackbody Calibrator:

E(T)  Gn(T)

푮풏 = 푪풏(푹(푨푫푪(푿풏))) Verify sensor constant Cn 9 Methodology: Theoretical Model

Radial Soot Distribution 40000 1 Abel Transform 0.9 (Line of Sight Average) 0.8 30000 0.7 Integrated Soot Fraction 0.6 20000 0.5 0.4 0.3 10000 0.2

Sensible Emissions 0.1 0 0 Portion visible 0.5 1.5 2.5 3.5 4.5 to Sensor; 1/tan2ϴ Wavelength

Effective Emissivity: Ds

1 ϴ ϵ 0.75 ∞ ∞ 0.5 푬 ≡ { ( 푬(흀) ∗ 푺 흀 − 흉 )풅흉} 풅흀 0.25 v 풏 ퟎ −∞ 풏 v

0 Effective Emissivity, Effective 0 0.2 0.4 0.6 0.8 1 Flame Thickness, Ds [meters] 퐶표 −퐶 풇풗푻풔푫풔 10 ε = 1 − 푒 2 [1] C. Tien, K. Lee, A. Stretton, “Radiation Heat Transfer”, SFPE HB, (2002) Results: Flame Comparison

 Flame heights and thermocouple measurements were very comparable (<10% error) Axial Flame Temperature

1700

1600 1500 1400

1300 Lit. High

Lit. [1] 1200 Thermocouple Correction: Lit. Low 4 [2] 1100  tT t Measured Tg  Tt 

Corrected Soot Temperature [K] Temperature Soot Corrected h t 1000 [2] D. Bradley, K.J. Matthews, 0.1 0.3 0.5 0.7 0.9 “Measurement of High Temperature Gas Normalized Height Above Burner [z/H] with Fine Gauge Thermocouples”, Journal of Mechanical Engineering Science, 10 (4) 1968 [1] C.P. Arana, S. Sen, I.K. Puri, “Field measurements of soot volume fractions in laminar partially premixed coflow ethylene/air flames” Combustion and Flame 138 362–372 (2004) 11 Results: Radiation Comparison

 Measured and Computed Irradiance are comparable. 0.005

푮풏 = 푪(푹(푨푫푪(푿풏)))

] Measured = H 2 0.0045 휺 × 푬 × 푭 Computed 푮 ≡ 풏

0.004 풏 ퟏퟔ × 퐭퐚퐧ퟐ 휽

[W/m

n 0.0035 G 0.003 0.0025 0.002 0.0015 0.001

Sensible Irradiance, Irradiance, Sensible 0.0005 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Normalized Height Above Burner [z/H]

12 Results: Sources of Error

Hypothesized Source Description Estimated % Error Proposed Solution

Sensor specification Variation in specification to actual <50 -Consult manufacturers performance -Change sensors -Rigorous calibration Soot temperature input Effective soot temperature at local <30 -Move to larger flames regions is difficult to measure & -Use radiant heatflux error is amplified drastically gauge measurements to avoid thermocouple input Build limitations Optical alignment & attenuation, <20 -Revise circuit for stability electronic component accuracy -Revise optics for accuracy -Self-contain for integrity Soot fraction Input Not directly measured; limited <10 -Move to large flames to accuracy of literature interpolation avoid input requirement

13 Next Steps: Application to Real Fires

 Large-Scale Liquid Pool Fires  Crude oil fuel; Multi-component hydrocarbon  Optically thick; Effective emissivity=1; Less inputs  Turbulence; Time fluctuating micro-scale gradients [1]

[1] Prateep Chatterjee , John L de Ris , Yi Wang, Niveditha Krishnamoorthy and Sergey B Dorofeev, “Laminar Smoke Point Based Sub-grid Soot Radiation Modeling Applied to LES of Buoyant Turbulent Diffusion Flames”, FM Global Research Division, 2012 J. Phys.: Conf. Ser. 369

14 Thank you - Questions?

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