Heat of combustion of commercial diesel and biodiesel fuels and their blends: effect of water content

I. Fernandez1, E. Alvarez1, F. Cerdeira2, M. Vazquez2 and M. Iris3

1Chemical Engineering Department, University of Vigo, Spain
2Mechanical Engineering, Thermal Machines and Motors & Fluids Department, University of Vigo, Spain
3Galician Automotive Technology Centre, Porriño, Spain

Keywords: bomb calorimeter
property: heat of combustion; water content
material: commercial biodiesel; diesel fuel

Fuel quality is one of the key factors which has an impact upon the operational performance of the engine. The properties of fuels may be split into three groups: the first one is represented by the operational properties; the second group includes properties related to the safety of fuels within transportation and storage, and finally those related to environmental specifications. One of these properties, the heat of combustion, is important for engine design. Knowledge of this value is essential when considering the thermal efficiency of equipment for producing either power or heat.

The heat of combustion of a fuel is commonly referred to as the heating value or calorific value, and briefly defined as the amount of heat released during the combustion of a specified amount of it, being a characteristic for each fuel. The heating value of a fuel may be categorized as either the higher heating value (HHV) or the lower heating value (LHV), depending if the latent heat of vaporization of the water is considered or not. Heating value is commonly determined using a bomb calorimeter[1].

In this paper, the quality of commercial diesel and biodiesel, and their blends, is evaluated through the heat of combustion and water content. Nineteen different blends were prepared from the pure commercial biodiesel and diesel, varying the percentage of biodiesel in steps of 5%. The heat of combustion was measured using an automatic bomb calorimeter, which operates according to the European Standard test method[2]. In all cases, it is observed that the heat of combustion increases by decreasing the concentration of biodiesel. On the other hand, the heat of combustion varies with the water content of the blend. For this reason, correlations between the heat of combustion and water content or biodiesel mass fraction have been established in this study.

This study is include in a greater project financed by the Galician Regional Government (Grant:08REM004CT), carried out by CTAG and the University of Vigo, where it is tried to give to the user, a study of the properties and the impact of the biodiesel on car engine

  1. S. M. Akers et al. J. Chem. Educ. 83, 260 (2006)

  2. ASTM D 240-09. Standard test method for heat of combustion of liquid hydrocarbon fuels by bomb calorimeter (2009)

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