ASTM D3338

ASTM D3338 – Standard Test Method for Estimation of Net Heat of Combustion of Aviation Fuels

Description:

Significance and Use

5.1 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 kg/m³ 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 4: The procedures for the experimental determination of the gross and net heats of combustion are described in Test Methods D240 and D4809.

5.2 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.

Scope

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 MJ/kg to 44.73 MJ/kg or [17 280 Btu/lb to 19 230 Btu/lb]. 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 1: The experimental data on heat of combustion from which the Test Method D3338 correlation was devised was obtained by a precision method similar to Test Method D4809.

Note 2: The estimation of the net heat of combustion of a hydrocarbon fuel is justifiable only when the fuel belongs to a well-defined class for which a relation between heat of combustion and aromatic and sulfur contents, density, and distillation range of the fuel has been derived from accurate experimental measurements on representative samples of that class. Even in this case, the possibility that the estimates may be in error by large amounts for individual fuels should be recognized. The fuels used to establish the correlation presented in this method are defined as follows:

Fuels:

Aviation gasoline—Grades 100/130 and 115/145 (1, 2)2

Kerosenes, alkylates, and special WADC fuels (3)

Pure hydrocarbons—paraffins, naphthenes, and aromatics (4)

Fuels for which data were reported by the Coordinating Research Council (5).

Note 3: The property ranges used in this correlation are as follows:

Aromatics—from 0 % by mass to 100 % by mass

API Gravity—from [25.7° to 81.2°API]

Volatility—from [160 °F to 540 °F], average boiling point

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.3.1 Although the test method permits the calculation of net heat of combustion in either SI or inch-pound units, SI units are the preferred units.

1.3.2 The net heat of combustion can also be estimated in inch-pound units by Test Method D1405 or in SI units by Test Method D4529. Test Method D1405 requires calculation of one of four equations dependent on the fuel type with a precision equivalent to that of this test method. Test Method D4529 requires calculation of a single equation for all aviation fuels with a precision equivalent to that of this test method. Unlike Test Method D1405 and D4529, Test Method D3338/D3338M does not require the use of aniline point.