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1
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- Ariam C. Luers, Gerard G. Back, Scott A. Hill
- Hughes Associates, Inc.
- Baltimore, MD
- Dr. Patricia Tatem, Dr. Frederick Williams
- Naval Research Laboratory
- Washington, DC
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2
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- Background
- Previous testing conducted to develop systems and technologies to help
reduce the number of personnel required for Damage Control operations on
a Navy ship.
- Water mist used to provide boundary cooling for spaces surrounding the
fire compartment.
- Traditional means of boundary cooling was accomplished by spraying water
on the bulkhead – using fire hoses and/or sprinklers.
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3
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- Background
- During the reduced manning tests, we learned that any water in the
damaged space was beneficial to cooling the compartment.
- Wanted to develop a system that could survive in the damaged
compartment.
- Concept of using sidewall nozzles introduced.
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4
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5
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6
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- Water Mist Attributes
- Thermal Management
- Reduced Vent Flow
- Oxygen dilution by water vapor and vitiated gases.
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7
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- Test Objectives
- Scoping tests to conducted to evaluate the ability of low pressure and
high pressure water mist systems to:
- Thermally manage the compartments directly damaged by the weapons hit.
- Prevent fire spread to adjacent spaces.
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8
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- Measures of Performance
- Thermal management
- Limit fire spread (i.e., compartment temps < 250°C)
- Prevent flashover (i.e., compartment temps < 500°C)
- Fire extinguishment
- Localized heating effects
- Energy absorbed by water mist system
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9
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10
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11
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12
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- 0.6 MW
- 1.2 MW
- 2.0 MW
- 4.0 MW
- Multiple Fires
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13
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- Test Variables
- Pan Location (Forward, Aft)
- Proximity Effects
- Vent Openings (5 Outboard, 2 Inboard)
- Obstructions
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14
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- Test Results
- Over 70 tests conducted.
- Baseline tests (i.e., no mist) conducted for the fire scenarios.
- Nozzle performance compared against baseline to evaluate systems.
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15
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- Test Results – Summary of System Performance
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16
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17
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- Test Results – Thermal Management
- 0.6 MW Fires – Upper layer temps did not exceed fire spread criteria
250°C.
- 1.2 MW Fires – Upper layer temps above 250°C. Fire spread criteria exceeded during
some high pressure tests and all of the low pressure tests.
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18
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- Test Results – Thermal Management
- 2.0 MW Fires – Baseline exceeded 250°C.
High pressure – 17 of 24 met goal; Low pressure – none met goal.
- 4.0 MW Fires – Baseline exceeded 500°C.
Flashover prevention was achieved during all tests. Fire spread criteria exceeded for all
tests.
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19
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- Test Results – Fire Extinguishment
- Larger fires easier to extinguish than smaller fires.
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20
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- Summary/Conclusions
- Overall high pressure better than low pressure – in terms of fires
extinguished and thermal management.
- Example - 2.0 MW fire scenario – average overhead temperatures exceeded
fire spread criteria during all of low pressure tests (100%) and less
than half of high pressure tests (30%).
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21
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- Summary/Conclusions
- For systems with equivalent flow rates, high pressure performed better
than low pressure.
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22
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- Summary/Conclusions
- For systems with equivalent flow rates, high pressure performed better
than low pressure.
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23
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- Summary/Conclusions
- Nozzle design (pattern, flow, projection) has an impact on thermal
management – flow rate alone is not an indicator of performance.
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24
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- Summary/Conclusions
- Overall, both high pressure and low pressure water mist systems were
shown to be effective in terms of thermal management.
- It is important to note that none of the water mist systems were
optimized.
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25
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- Summary/Conclusions
- Additional testing is currently being conducted to further evaluate low,
medium and high pressure water mist systems.
- These tests will evaluate different types of fires (i.e., Class A and
Class B), various types of nozzles, and different nozzle spacings.
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Notes
