Paliva (Fuels) is a scientific journal issued quarterly by the Faculty of Environmental Technology, ICT Prague. Fuels publishes papers on a broad range of topics covering exploitation, processing, upgrading, and utilization of various types of fuels, and power engineering.
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Comparison of hydrogen quality from different production technologies

Jan Hadrava, Roman Vokatý, Tomáš Hlinčík, Daniel Tenkrát

This paper is focused on conventional methods of hydrogen production using the reforming of fossil fuels. We also discussed the alternative methods of production which are still in research. Nowadays, the steam reforming is used as a dominant source of hydrogen. The reason is the high ratio of CO in gas inlet from the initial steps of high–temperature conversion. Most of the technology processes require desulfurization which causes higher price of the final product. Fossil fuels transformed by steam reforming produce 70-80 vol. % of Hydrogen in contrast to partial oxidation that produces only 35 vol.%.

3/2013 - pages 79 - 83DOI: 10.35933/paliva.2013.03.01

The use of Rancimat test for determination of oxidation stability of biofuels

Sabina Tomašíková, Milan Pospíšil, Pavel Šimáček

The one of more important property of diesel fuel is oxidation stability. The purpose of this paper is to describe determination of oxidation stability by test Rancimat. According with the standard EN 14112+A1 (2010), the oxidation stability is the value of the time expressed in hours, which passes between the moment when the measurement is started and the moment when the formation of oxidation products rapidly begins to increase. The oxidation stability was measured in a 743 Rancimat apparatus. Experiments showed the influence of biodiesel blending in a decrease of diesel fuel stabil-ity and negative influence of impurity on oxidation stability of biodiesel.

3/2013 - pages 84 - 86DOI: 10.35933/paliva.2013.03.02

Utilization of a Pressure DSC for Determination of Oxidation Stability of Biodiesel

Sabina Tomašíková, Milan Pospíšil, Zlata Mužíková, Jaroslav Černý

Biodiesel is an alternative fuel for diesel engines made from renewable biological sources such as vege-table oils and animal fats. The one of more important property of biodiesel is oxidation stability. This work is focused on possibility for determination of oxidation stability of biodiesel by using a pressure DSC method.

3/2013 - pages 87 - 90DOI: 10.35933/paliva.2013.03.03

Measuring of a discharge coefficient of orifices with irregular edges

Ondřej Novák, Ilona Pasková, Václav Koza
In this paper we proposed measurements of the discharge coefficient for several types of orifices with irregular shapes of their opening and irregular edges of the opening. In addition we measured special type of orifices that extends measuring of discharge coefficient of the two – dimensional orifices to the measuring of the discharge coefficient of orifices with a three – dimensional lift. They can be found on ruptured pipelines during pipeline accidents caused by puncturing the pipeline from outer side.
We proposed an apparatus, which was built from widely available industrial parts. The apparatus consists of high pressure supply tanks, a working pressure vessel with volume of 0.16 m3, several thermocouples, an electronic pressure sensor and a flange for tested orifices. We used a theoretic approach to determine the temperature of the gas inside the vessel during measured discharge process. Methane was used during our measurements. Results show that the discharge coefficient of a lifted orifice is lower than the discharge coefficient of a two-dimensional orifice with comparable area and shape of opening. The discharge coefficient of the lifted orifice grows with the increasing angle of the lift. The influence of an irregular shape of the opening on the discharge coefficient of the orifice is lower than the influence of a lifted part of the orifice material over its opening area.
3/2013 - pages 91 - 99DOI: 10.35933/paliva.2013.03.04

The Effect of potassium carbonate on Thermal Oxidation of Cokes and Carbonaceous Materials

Silvie Vallová, Eva Plevová, Věra Valovičová, Martin Hummel

The effect of K2CO3 on thermal oxidation of the blast furnace cokes and carbonaceous materials in the air was investigated by means of thermal analysis. The results obtained from the thermal analysis showed that coke contains two carbonaceous structures. The addition of K2CO3 affected mainly oxidation of a less ordered structure while the second stage oxidation went without changes. With increasing concentration of an additive, a decrease of both the characteristic temperatures and the values of activation energy occurred together with enhancement of reaction heat. The catalytic effect of potash on the oxidation of materials with variously ordered carbonaceous structure grows with no order of carbonaceous matter. In all cases (except graphite) the addition of potash caused a decrease of activation energies.

3/2013 - pages 100 - 104DOI: 10.35933/paliva.2013.03.05

The use of E85 in fuel systems of common spark ignition engines

Daniel Maxa

In case of cars equipped with spark ignition en-gines, the increase if biofuel consumption according to EU directives can be ensured either with bulk increase in ethanol concentration in petrol, or with broader use of high-percentage ethanol blends, e.g. E85. However, it requires larger expansion of flex-fuel vehicles fleet, or the use of engine retrofit systems enabling the use of E85 in conventional SI engines. The most important role of such systems is to increase fuel injection time according to different E85 properties. The paper sum-marises differences in composition and properties of petrol and E85, and gives theoretical and experimental background for calculation of relative injection time increment.

3/2013 - pages 105 - 108DOI: 10.35933/paliva.2013.03.06

technical support editor-in-chief