Review on the Relationship Between Liquid Aerospace Fuel Composition and Their Physicochemical Properties

Abstract

The development of advanced air transportation has raised new demands for high-performance liquid hydrocarbon fuels. However, the measurement of fuel properties is time-consuming, cost-intensive, and limited to the operating conditions. The physicochemical properties of aerospace fuels are directly influenced by chemical composition. Thus, a thorough investigation should be conducted on the inherent relationship between fuel properties and composition for the design and synthesis of high-grade fuels and the prediction of fuel properties in the future. This work summarized the effects of fuel composition and hydrocarbon molecular structure on the fuel physicochemical properties, including density, net heat of combustion (NHOC), low-temperature fluidity (viscosity and freezing point), flash point, and thermal-oxidative stability. Several correlations and predictions of fuel properties from chemical composition were reviewed. Additionally, we correlated the fuel properties with hydrogen/carbon molar ratios (nH/C) and molecular weight (M). The results from the least-square method implicate that the coupling of H/C molar ratio and M is suitable for the estimation of density, NHOC, viscosity and effectiveness for the design, manufacture, and evaluation of aviation hydrocarbon fuels.

Chemical Composition and Low-Temperature Fluidity Properties of Jet Fuels

“…In particular, the hydrocarbons of class 3 with a carbon number between C9 and C13 (K3C9-K3C13) had a weight percentage greater than 8.7%. According to Wang et al [8], the low-temperature fluidity properties strongly depend on the hydrocarbon class. For a given carbon number, n-paraffins exhibit the highest freezing point and so crystallization onset temperature was comparable with those of other hydrocarbon classes, whereas iso-paraffins with more compact and symmetry molecular structure start to form crystals at lower temperatures.…”

“…This requirement stems from two main aspects: the search for alternative fuels that allow a transition to cleaner energy sources and the desire to design and operate high-performance engines using knowledge of fuel composition as a control criterion [2]. This has led to the development of improved analytical techniques for aviation fuel analysis [3][4][5][6] and the development of correlations and mathematical models for predicting fuel properties as a function of chemical composition [7,8].…”

“…Several research works have been performed to develop reliable composition-property relationships of petroleum-derived fuels, especially jet and diesel fuels. However, it is still difficult to accurately predict the fuel properties due to the complexity in fuel composition [8]. With respect to jet fuels, it is worth mentioning the pioneering work of Cookson and his colleagues [10,11].…”

“…They proposed several multiple nonlinear correlations between the freezing point and the composition of fuel blends for the design of optimum fuel compositions that meet the ASTM specifications. To simplify the relationship between the freezing point and molecular structure of aviation fuels, Wang et al [8] attempted to correlate the freezing point with H/C molar ratios and molecular weight; however, they found difficulties in obtaining a suitable model, probably given the difficulty of reflecting molecular symmetry and intermolecular forces. Joubert [14] developed a QSAR (structure-activity relationship (SAR) and quantitative structure-activity relationship) model to predict the freezing point of different classes of hydrocarbons.…”

“…To identify patterns in the analyzed data, a correlation matrix was calculated. Since it is widely accepted that the freezing point behavior of the various hydrocarbon classes is mostly erratic, as no clear behavioral trends have been clearly identified [7][8][9][10][11][12][13][14], the main aim of this work is to provide a tool that allows identifying individual or types of hydrocarbon components that directly affect the low-temperature fluidity properties of jet fuels. This information can be especially useful for manufactures of additives or conventional or alternative aviation fuels.…”