The paper presents studies on a high-speed diesel engine driven by added CNG (compressed natural gas) in order to increase its power. The effects of the amount of CNG added on the engine performance have been studied. Throughout the tests the effective performance and pollution emission indicators of ICE (Internal Combustion Engine), the cylinder pressure, etc. were measured. Under all operating conditions the diesel fuel consumption per hour and the rotation speed have remained constant. The amount of CNG added is variable. As a result of the research, relations have been established concerning the overall efficiency, the air to fuel ratio for steady-state performance and smoke opacity. An increase in CO, NOx and HC emissions has been recorded and at the same time the amount of CO₂ released has decreased. Both the maximum pressure in the combustion chamber and the pressure rise rate increase which results in rising the engine performance harshness. When CNG has been added in quantity about 47% of the total amount of fuel, the peak value is achieved. The influence of the amount of added gas fuel on the calculated gross heat release rate has been determined. The maximum heat release rate does not change significantly. The nature of the combustion process does not change either. In conclusion, findings validate the possibility to achieve up to 30 % higher maximum rated power by adding 56% CNG mass fraction of the total amount of fuel. Provided the amount of CNG is up to 48% of the total amount of fuel, the ICE ecological indicators have not been deteriorated, furthermore the power has been increased by up to 20%.

Propanol isomers, which are oxygen-rich fuels, possess superior octane ratings and energy density in comparison to methanol and ethanol. Recently, due to advancements in fermentation techniques, these propanol isomers have garnered increased interest as additives for engines. They are being explored to decrease emissions and reduce the usage of conventional fossil fuels. This study delves into this emerging field. One of the alternatives is the use of alcohol fuels in their pure state or as additives to traditional fuels. Alcohols, due to their higher volumetric energy density, are better fuels for spark ignition engines than hydrogen and biogas. Alcohol-blended fuels or alcohol fuels in their pure state may be used in gasoline engines to reduce exhaust emissions. The current research emphasizes the effect of isopropanol gasoline blends on the performance and emissions characteristics of a gasoline direct injection (GDI) engine. This investigation was conducted with different blends of isopropanol and gasoline (by volume: 10% isopropanol [IP10], 20% isopropanol [IP10], 30% isopropanol [IP30], 40% isopropanol [IP40], and 50% isopropanol [IP50]). The reviewed results showed that with increasing isopropanol in the fuel blends, engine brake power increased while BSFC decreased. In terms of emissions, with the increase in isopropanol in the fuel blends, CO and HC emissions decreased while CO₂ and NOx emissions increased.

Alternative fuels appeared soon after the first internal combustion engines were designed. The history of alternative fuels is basically as long as the history of the automotive industry. Initially, fuels whose physicochemical properties allowed for a change in parameters of the combustion process in order to achieve greater efficiency and reliability were searched for. Nowadays, there are significantly more variables; in addition to the above mentioned parameters, alternative fuels are being sought that will ensure environmental protection during vehicle operation and improve the ergonomics of use. This article outlines the results of the authors’ own comparative tests of vibrations of a vibroacoustic character. Based on a popular engine model, the vibration–acoustic responses of a system powered by two types of fuel, namely, diesel and biodiesel (B10), are compared. The research consists of comparing vibrations in both time and frequency domains. In the case of the time domain, the evaluation was performed with vibrations as a function of engine torque and speed. In the case of frequency analysis, the focus was on changes in the frequency response for the tested fuels. The research shows that the profile of vibroacoustic vibrations changes in the case of biodiesel power supply in relation to standard fuel. The vibration profile changes significantly as a function of speed and only slightly in relation to the engine load. The results presented in this article show different vibroacoustic responses of an engine powered by diesel and biodiesel; the change is minor for lower speeds but significant (other harmonics are dominant) for higher speeds (changes in the dominant harmonic magnitude of up to 10% at a crankshaft speed of 3000 rpm).

The article is focused on the potential and application of biogas, as an alternative fuel from Renewable Energy Sources, for use mainly in gas-generator stations. Biogas fuel is basically a mixture of methane and carbon dioxide. Its composition depends on the type of raw material used for its production. Methane concentration in biogas is between 50÷80%. To be possible engine to work with maximum efficiency with different biogas fuels, it is necessary to modify specific adjustment parameters depending on the concentration of methane in the mixture. This requires the creation of a biogas simulation system for different concentrations of the main components. The aim is to investigate and determine the optimum and permissible biofuel blend concentrations and their impact on engine performance and fuel consumption. Biogas can be used as a fuel to produce electricity, heat or steam or as fuel for internal combustion engine, and its use will help to reduce harmful emissions into the atmosphere.

The article explores the possibilities of using biogas for power purposes. First of all, it studies the use of biogas as fuel of great potential and significant socio-economic benefits, being a renewable energy source at the same time. Second the utilization of biogas could contribute to a considerable reduction in harmful emissions into the atmosphere. In addition, biogas is an extremely important greenhouse gas characterized by a high methane and carbon dioxide content of the ratios of around 60/40%. It can then be concluded that all these aspects result in the obligatory utilization of biogas for power purposes in the sites of its production such as urban landfills, various farms and places of anaerobic decomposition of organic matter.

The paper presents a study of the variation of ignition advance when the engine works with methane and a comparison with values when the engine runs on gasoline. It is known that methane has a lower burning velocity than gasoline, and therefore, to obtain a maximal efficiency from the working process (the maximum value of cylinder pressure p_z should be 7-15 degrees after TDC), ignition advance should be increased, as for different operating regimes this angle should be increased with different values. A gasoline engine has been studied and were measured and analysed the ignition advance at work with gasoline and methane, with optimal air-fuel ratio (α) for both fuels. Three-dimensional graphics of ignition advance variation across the rpm and load range were made. In conclusion, on the basis of the experiments, a table is produced, which presents the values of coefficients for change of base parameters of ignition advance for all engine operating modes, in dependence on rpm and load of the engine.