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NACA-TN-3829
Effect of pressure on the spontaneous ignition temperature of liquid fuels
Year: 1956
Abstract: Spontaneous ignition temperatures from 1 to 9 atmospheres were measured in air for n-heptane (straight-chain paraffin), isooctane (branched-chain paraffin), benzene (aromatic), and JP-4 and JP-5 fuels. A 125-cc Erlenmeyer flask was employed as the ignition chamber, and fuel was injected in a solid stream (no spray) into the flask enclosed in a bomb. Fuel charges were varied to obtain the lowest temperature at which ignition occurs. Time lags before ignition were measured at each pressure for all fuels.
All fuels that were tested showed a decrease in the spontaneous ignition temperature as the pressure was raised; the rate of decrease was greatest in the range of 1 to 3 atmospheres. The total decrease of the spontaneous ignition temperature over the pressure range considered was 276° C for benzene, 236° C for isooctane, 60o C for n-heptane and JP-4 fuel, and 41° C for JP-5 fuel.
The difference in the spontaneous ignition temperature of two fuels at 1 atmosphere becomes less at a higher pressure. For example, JP-4 and JP-5 fuels differ by 25o C at 1 atmosphere and by 8° C at 9 atmospheres.
Two jet fuels that were specified as JP-4 showed a constant difference of about 20° C in the spontaneous ignition temperature over the experimental pressure range. By percolation of the fuel samples through silica gel, the spontaneous ignition temperature of the fuel with the higher value was reduced by approximately 10° to 12° C.
From a limited number of ignition lag experiments with n-heptane, the lag was found to decrease with increasing pressure. Experiments were performed with three fuel charges, and ignition lags were measured at three pressures with each charge. Semilogarithmic plots of the time lag against the reciprocal of the absolute temperature gave lines showing some curvature. Activation energies were calculated from the slope of these curves, and were found essentially invariant with variation of fuel charge and pressure. The average activation energy was approximately 21,000 calories per mole.
All fuels that were tested showed a decrease in the spontaneous ignition temperature as the pressure was raised; the rate of decrease was greatest in the range of 1 to 3 atmospheres. The total decrease of the spontaneous ignition temperature over the pressure range considered was 276° C for benzene, 236° C for isooctane, 60o C for n-heptane and JP-4 fuel, and 41° C for JP-5 fuel.
The difference in the spontaneous ignition temperature of two fuels at 1 atmosphere becomes less at a higher pressure. For example, JP-4 and JP-5 fuels differ by 25o C at 1 atmosphere and by 8° C at 9 atmospheres.
Two jet fuels that were specified as JP-4 showed a constant difference of about 20° C in the spontaneous ignition temperature over the experimental pressure range. By percolation of the fuel samples through silica gel, the spontaneous ignition temperature of the fuel with the higher value was reduced by approximately 10° to 12° C.
From a limited number of ignition lag experiments with n-heptane, the lag was found to decrease with increasing pressure. Experiments were performed with three fuel charges, and ignition lags were measured at three pressures with each charge. Semilogarithmic plots of the time lag against the reciprocal of the absolute temperature gave lines showing some curvature. Activation energies were calculated from the slope of these curves, and were found essentially invariant with variation of fuel charge and pressure. The average activation energy was approximately 21,000 calories per mole.
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| contributor author | NASA - National Aeronautics and Space Administration (NASA) | |
| date accessioned | 2017-09-04T15:38:14Z | |
| date available | 2017-09-04T15:38:14Z | |
| date copyright | 01/01/1956 | |
| date issued | 1956 | |
| identifier other | OXONEEAAAAAAAAAA.pdf | |
| identifier uri | https://yse.yabesh.ir/std/handle/yse/40295 | |
| description abstract | Spontaneous ignition temperatures from 1 to 9 atmospheres were measured in air for n-heptane (straight-chain paraffin), isooctane (branched-chain paraffin), benzene (aromatic), and JP-4 and JP-5 fuels. A 125-cc Erlenmeyer flask was employed as the ignition chamber, and fuel was injected in a solid stream (no spray) into the flask enclosed in a bomb. Fuel charges were varied to obtain the lowest temperature at which ignition occurs. Time lags before ignition were measured at each pressure for all fuels. All fuels that were tested showed a decrease in the spontaneous ignition temperature as the pressure was raised; the rate of decrease was greatest in the range of 1 to 3 atmospheres. The total decrease of the spontaneous ignition temperature over the pressure range considered was 276° C for benzene, 236° C for isooctane, 60o C for n-heptane and JP-4 fuel, and 41° C for JP-5 fuel. The difference in the spontaneous ignition temperature of two fuels at 1 atmosphere becomes less at a higher pressure. For example, JP-4 and JP-5 fuels differ by 25o C at 1 atmosphere and by 8° C at 9 atmospheres. Two jet fuels that were specified as JP-4 showed a constant difference of about 20° C in the spontaneous ignition temperature over the experimental pressure range. By percolation of the fuel samples through silica gel, the spontaneous ignition temperature of the fuel with the higher value was reduced by approximately 10° to 12° C. From a limited number of ignition lag experiments with n-heptane, the lag was found to decrease with increasing pressure. Experiments were performed with three fuel charges, and ignition lags were measured at three pressures with each charge. Semilogarithmic plots of the time lag against the reciprocal of the absolute temperature gave lines showing some curvature. Activation energies were calculated from the slope of these curves, and were found essentially invariant with variation of fuel charge and pressure. The average activation energy was approximately 21,000 calories per mole. | |
| language | English | |
| title | NACA-TN-3829 | num |
| title | Effect of pressure on the spontaneous ignition temperature of liquid fuels | en |
| type | standard | |
| page | 22 | |
| status | Active | |
| tree | NASA - National Aeronautics and Space Administration (NASA):;1956 | |
| contenttype | fulltext |