International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The experience of foreign companies on conversion of diesel vehicles for natural gas operation was analyzed. The results of computer simulations of the gas engine and diesel duty cycle were presented. The features of the gas engine power system converted from the D-243 tractor diesel are shown. The efficiency of the entire range of speed and load modes of a gas engine converted from D-243 diesel to run on natural gas has been experimentally confirmed by reducing the compression ratio from 16 to 12 and equipping it with a gas supply system and ignition system. Its effective power is close to that of a base diesel engine, equivalent to a specific fuel efficiency of up to 25% higher than that of a diesel engine. There is no carbon black in the exhaust gas of the gas engine. The emissions of certain harmful substances in some modes of operation of the gas engine are higher than that of the diesel, but the total toxicity of the exhaust gases resulting from carbon monoxide in the gas engine is 1.96 times lower than that of the diesel.

Natural gas in Republic of Croatia is being produced from three main regions: Sjeverni Jadran, Duboka Podravina and Međimurje. The natural gas produced from Međimurje region has been taken as an example for modelling the dehydration process because, compared to natural gas from Duboka Podravina region, it contains higher amount of acid gases. The associated gas with much smaller content of acid gases, currently being flared at region site called Istočna Hrvatska, has been taken as a second example. The comparison of these two cases has shown the effect of acid gases to the dehydration process efficiency. In both cases, absorption by triethylene glycol is chosen. Due to a large discrepancy in acid gas content, water content difference observation is much easier. Modelling of the dehydration process has been made in Aspen Hysys software.

The article is devoted to the problem of comprehensive evaluation of the efficiency of the use of various alternative fuels obtained from natural gas (NG) in a total life cycle (TLC). Despite the fact that all types of motor fuel under consideration are produced from NG, the energy and environmental consequences of their use may vary significantly. Goals of this research are: developing TLC mathematical models of a power unit operating on motor fuels obtained from NG (compressed NG, liquefied NG, methanol, dimethyl ether, synthetic diesel fuel and hydrogen) and conducting a simulation in order to determine energy and environmental indicators for the use of the considered fuel types. The results of simulation allow to choose the most promising types of alternative fuels according to the criteria of energy efficiency and a level of environmental pollution by harmful substances and greenhouse gases.