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Temperature conversion of ethanol-gasoline mixtures


In order to enable legally required temperature conversion also for bio fuels and mixtures of bio fuels with conventional fuels PTB carried out first investigations of the temperature-density behaviour of these liquids.

Due to legal requirements the use of bio ethanol or the use of mixtures of conventional fuels and bio ethanol increases rapidly. However the parameters necessary for temperature conversion, required in some EC member states, are unknown for different mixtures of gasoline and ethanol. That’s why PTB has started with the experimental determination of the temperature-density behaviour of selected mixtures of gasoline and ethanol. Aim of the investigations is to cover a temperature range from -15°C to 50°C in steps of 5 K and a range of the volumetric mixing ratio from 100/0 (100% ethanol and 0% gasoline) to 0/100 (0% gasoline and 100% ethanol) in steps of 5%.
The temperature dependent density variation has experimentally been determined using oscillation-type density meters. The measurement uncertainty is 0.05 kg/m³ (k = 2).
The single measurement values are approximated by a 3rd degree polynomial where T0 is the base temperature (15 °C) and ?0 the density at base temperature:

temperature-density behaviour of selected mixtures of gasoline and ethanol

The first experimental results of the wide spreaded mixing ratios E80 (80% ethanol, 20% gasoline) and E85 (85% ethanol, 15% gasoline) are presented in the following table

first experimental results of the widespread mixing ratios E80 and E85

From the experimental data the following coefficients A1 to A3 of the polynomial have been obtained:

coefficients of the polynomial

The relative deviations of the approximated data from the experimental values are smaller than 5·10-5.
However, the users of the experimental data are free to apply a different method of approximation.

Contact person:

H. Wolf, FB 3.3, AG 3.32, Email: henning.wolf@ptb.de,
M. Rinker, FB 1.5, AG 1.51, Email: michael.rinker@ptb.de