This test method is intended for use as a guide in cases where experimental determination of heat of combustion is not available and cannot be made conveniently and where an estimate is considered satisfactory. It is not intended as a substitute for experimental measurements of heat of combustion. Table 1 shows a summary for the range of each variable used in developing the correlation. The mean value and an estimate of its distribution about the mean, namely the standard deviation, is shown. This indicates, for example, that the mean density for all fuels used in developing the correlation was 779.3 kg/m3 and that two thirds of the samples had a density between 721.4 and 837.1 kg/m3, that is, plus or minus one standard deviation. The correlation is most accurate when the values of the variables used are within one standard deviation of the mean, but is useful up to two standard deviations of the mean. The use of this correlation may be applicable to other hydrocarbon distillates and pure hydrocarbons; however, only limited data on non-aviation fuels over the entire range of the variables were included in the correlation.
Note 48212;The procedures for the experimental determination of the gross and net heats of combustion are described in Test Methods D 240
The calorimetric methods cited in Note 4 measure gross heat of combustion. However, net heat is used in aircraft calculations because all combustion products are in the gaseous state. This calculation method is based on net heat, but a correction is required for condensed sulfur compounds.
TABLE 1 Mean and Standard Deviation of the Variables
| Variable | Mean | Standard Deviation |
|---|---|---|
| Aromatics, volume % | 13.5 | 23.9 |
| Density, kg/m3 [°API] | 779.3 [50.0] | 58.0 [13.5] |
| Volatility, °C [°F] | 171.11 [340] | 57.2 [103] |
| Heat of combustion, MJ/kg [Btu/lb] | 43.421 [18 668] | 0.862 [371] |
1.1 This test method covers the estimation of the net heat of combustion (megajoules per kilogram or [Btu per pound]) of aviation gasolines and aircraft turbine and jet engine fuels in the range from 40.19 to 44.73 megajoules per kilogram or [17 280 to 19 230 Btu per pound]. The precision for estimation of the net heat of combustion outside this range has not been determined for this test method.
1.2 This test method is purely empirical and is applicable to liquid hydrocarbon fuels that conform to the specifications for aviation gasolines or aircraft turbine and jet engine fuels of grades Jet A, Jet A-1, Jet B, JP-4, JP-5, JP-7, and JP-8.
Note 18212;The experimental data on heat of combustion from which the Test Method D 3338 correlation was devised was obtained by a precision method similar to Test Method D 4809
Note 28212;The estimation of the net heat of combustion of a hydrocarbon fuel is justifiable only when the fuel belongs ......
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