Assessment of Halon-free agents for fire safety application in aircraft propulsion system
Bibliographic record
Abstract
Abstract Halon 1301 is an effective total flooding fire suppression agent which is widely employed in aircraft cargo and propulsion systems for emergency fire scenarios. The production of Halon 1301 was banned by the Montreal Protocol in 1994 due to its environmental impact on ozone depletion and long atmospheric lifetime. Thus, a credible alternative is required for fire safety application on-board aircrafts. This study forms a follow-up to the work published by A. Dinesh et.al [14] and M. Diakostefanis et.al [16] which studied halon-free fire suppression in aircraft cargo bay through CFD and experimental validation respectively. Due to constraints in cost and logistics of testing fire suppression in a gas turbine engine, a computer modelled fire zone of a hypothetical high-bypass turbofan engine was used to simulate and evaluate the fire suppression performance of three Halon-free agents - HFC-125, HFC-227ea and FIC-13I1. Halon 1301 was also simulated to provide baseline comparison to the alternative agents. The capacity to inert was based on the distribution of agent concentrations subjected to a heptane-based fuel fire. Simulations were conducted at ISASLS and 40,000 feet to represent the engine’s operating environment. Overall, it was found that HFC-125 and HFC-227ea satisfactorily suppressed fire at both ambient scenarios. It was found that agent density and suppression concentration significantly influenced the agent’s ability to mix with ambient air and flood the fire zone. Density of the agent combined with higher inertion concentrations also influenced formation of localised recirculation zones which influenced mixture distribution in the fire zone. The simulations enabled identification of individual changes to agent flow characteristics at different operating conditions and demonstrated the performance criteria of Halon 1301 along with the proposed alternative agents for successful fire suppression. Through this study, it was found that all the agents except FIC-13I1 passed the minimum suppression criteria making HFC-125 and HFC-227ea suitable agents for replacement of Halon 1301. The failure of FIC-13I1 was attributed to the complex design in fire zone and could be overcome by considering a higher factor of safety for this design and injecting higher mass flow rate of the agent into the fire zone. The outcome of this study proposes further work to be carried out through experimental validation of the CFD simulations which will be key to progress the technology to higher TRL and meet aviation certification requirements. Further work may also explore blended agent configurations to tailor the agent characteristics to meet suppression requirements for maintaining safety and reliability of the system.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".