scholarly journals Sensitivity Analysis of FDS Results for the Input Uncertainty of Fire Heat Release Rate

2016 ◽  
Vol 31 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Jae-Ho Cho ◽  
Cheol-Hong Hwang ◽  
Joosung Kim ◽  
Sangkyu Lee
Keyword(s):  
Sensitivity Analysis ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Input Uncertainty

Adjoint Methods for Elimination of Thermoacoustic Oscillations in a Model Annular Combustor via Small Geometry Modifications

2018 ◽  
Author(s):  
José G. Aguilar ◽  
Matthew P. Juniper
Keyword(s):  
Sensitivity Analysis ◽  
Time Delay ◽  
Heat Release ◽  
Combustion Chamber ◽  
Heat Release Rate ◽  
Release Rate ◽  
Gas Turbines ◽  
Acoustic Pressure ◽  
Annular Combustor ◽  
Thermoacoustic Oscillations

In gas turbines, thermoacoustic oscillations grow if moments of high fluctuating heat release rate coincide with moments of high acoustic pressure. The phase between the heat release rate and the acoustic pressure depends strongly on the flame behaviour (specifically the time delay) and on the acoustic period. This makes the growth rate of thermoacoustic oscillations exceedingly sensitive to small changes in the acoustic boundary conditions, geometry changes, and the flame time delay. In this paper, adjoint-based sensitivity analysis is applied to a thermoacoustic network model of an annular combustor. This reveals how each eigenvalue is affected by every parameter of the system. This information is combined with an optimization algorithm in order to stabilize all thermoacoustic modes of the combustor by making only small changes to the geometry. The final configuration has a larger plenum area, a smaller premix duct area and a larger combustion chamber volume. All changes are less than 6% of the original values. The technique is readily scalable to more complex models and geometries and the inclusion of further constraints, such that the combustion chamber itself should not change. This demonstrates why adjoint-based sensitivity analysis and optimization could become an indispensible tool for the design of thermoacoustically-stable combustors.

scholarly journals Effects of User Dependence on the Prediction Results of Visibility in Fire Simulations

2021 ◽  
Vol 35 (3) ◽  
pp. 14-22
Author(s):  
Ho-Sik Han ◽  
Sun-Yeo Mun ◽  
Cheol-Hong Hwang
Keyword(s):  
Sensitivity Analysis ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Large Change ◽  
Fire Simulation ◽  
Input Parameters ◽  
Measurement Uncertainties ◽  
Safety Assessments ◽  
In Fire

To improve the reliability of safety assessments in domestic performance-based designs (PBDs), the problem of the input parameters being dependent on fire-simulation users was quantitatively analyzed. Thus, the results of statistical analyses of domestic PBD reports evaluated over the last 5 years were examined. It was determined that the uncertainties of the input parameters might have a relatively larger influence on the statistical deviations than the measurement uncertainties. Accordingly, a sensitivity analysis was performed by considering the statistical deviations of the input parameters that could greatly influence the prediction results of visibility, which are important for the available safe egress time. The main results were as follows: a large change in visibility was observed owing to deviations of the heat release rate and soot yield. Based on this study, it is expected that more accurate results can be obtained if the objectivity of input parameters determined by user dependence can be secured in domestic PBDs.

Scale Modeling on the Effect of Air Velocity on Heat Release Rate in Tunnel Fire

2008 ◽  
Vol 18 (2) ◽  
pp. 111-124 ◽  
Author(s):  
C. Chen ◽  
L. Qu ◽  
Y. X. Yang ◽  
G. Q. Kang ◽  
W. K. Chow
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Air Velocity ◽  
Tunnel Fire ◽  
Scale Modeling

scholarly journals Effects of Discharge Area and Atomizing Gas Type in Full Cone Twin-Fluid Atomizer on Extinguishing Performance of Heptane Pool Fire under Two Heat Release Rate Conditions in an Enclosed Chamber

2021 ◽  
Vol 11 (7) ◽  
pp. 3247
Author(s):  
Dong Hwan Kim ◽  
Chi Young Lee ◽  
Chang Bo Oh
Keyword(s):  
Heat Release ◽  
Flow Rate ◽  
Heat Release Rate ◽  
Release Rate ◽  
Water Mist ◽  
Pool Fire ◽  
Sauter Mean Diameter ◽  
Discharge Area ◽  
Fire Extinguishing ◽  
Enclosed Chamber

In this study, the effects of discharge area and atomizing gas type in a twin-fluid atomizer on heptane pool fire-extinguishing performance were investigated under the heat release rate conditions of 1.17 and 5.23 kW in an enclosed chamber. Large and small full cone twin-fluid atomizers were prepared. Nitrogen and air were used as atomizing gases. With respect to the droplet size of water mist, as the water and air flow rates decreased and increased, respectively, the Sauter mean diameter (SMD) of the water mist decreased. The SMD of large and small atomizers were in the range of approximately 12–60 and 12–49 μm, respectively. With respect to the discharge area effect, the small atomizer exhibited a shorter extinguishing time, lower peak surface temperature, and higher minimum oxygen concentration than the large atomizer. Furthermore, it was observed that the effect of the discharge area on fire-extinguishing performance is dominant under certain flow rate conditions. With respect to the atomizing gas type effect, nitrogen and air appeared to exhibit nearly similar extinguishing times, peak surface temperatures, and minimum oxygen concentrations under most flow rate conditions. Based on the present and previous studies, it was revealed that the effect of atomizing gas type on fire-extinguishing performance is dependent on the relative positions of the discharged flow and fire source.

scholarly journals Heat release rate shaping for optimal gross indicated efficiency in a heavy-duty RCCI engine fueled with E85 and diesel

Fuel ◽  
2021 ◽  
Vol 288 ◽  
pp. 119656
Author(s):  
Robbert Willems ◽  
Frank Willems ◽  
Niels Deen ◽  
Bart Somers
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Heavy Duty ◽  
Rate Shaping

scholarly journals Experimental and Simulation of Diesel Engine Fueled with Biodiesel with Variations in Heat Loss Model

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1622
Author(s):  
Daniel Romeo Kamta Legue ◽  
Zacharie Merlin Ayissi ◽  
Mahamat Hassane Babikir ◽  
Marcel Obounou ◽  
Henri Paul Ekobena Fouda
Keyword(s):  
Heat Release ◽  
Heat Loss ◽  
Heat Release Rate ◽  
Release Rate ◽  
Diffusion Combustion ◽  
Cylinder Wall ◽  
Compression Ignition Engine ◽  
Experimental Conditions ◽  
Load Range ◽  
Combustion Phase

This study presents an experimental investigation and thermodynamic 0D modeling of the combustion of a compression-ignition engine, fueled by an alternative fuel based on neem biodiesel (B100) as well as conventional diesel (D100). The study highlights the effects of the engine load at 50%, 75% and 100% and the influence of the heat loss models proposed by Woschni, Eichelberg and Hohenberg on the variation in the cylinder pressure. The study shows that the heat loss through the cylinder wall is more pronounced during diffusion combustion regardless of the nature of the fuels tested and the load range required. The cylinder pressures when using B100 estimated at 89 bars are relatively higher than when using D100, about 3.3% greater under the same experimental conditions. It is also observed that the problem of the high pressure associated with the use of biodiesels in engines can be solved by optimizing the ignition delay. The net heat release rate remains roughly the same when using D100 and B100 at 100% load. At low loads, the D100 heat release rate is higher than B100. The investigation shows how wall heat losses are more pronounced in the diffusion combustion phase, relative to the premix phase, by presenting variations in the curves.

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