The global policy solution seeks to reduce the usage of fossil fuels and greenhouse gas (GHG) emissions, and biogas (BG) represents a solutions to these problems. The use of biogas could help cope with increased amounts of waste and reduce usage of fossil fuels. Biogas could be used in compressed natural gas (CNG) engines, but the engine electronic control unit (ECU) needs to be modified. In this research, a spark ignition (SI) engine was tested for mixtures of biogas and hydrogen (volumetric hydrogen concentration of 0, 14, 24, 33, and 43%). In all experiments, two cases of spark timing (ST) were used: the first for an optimal mixture and the second for CNG. The results show that hydrogen increases combustion quality and reduces incomplete combustion products. Because of BG’s lower burning speed, the advanced ST increased brake thermal efficiency (BTE) by 4.3% when the engine was running on biogas. Adding 14 vol% of hydrogen (H₂) increases the burning speed of the mixture and enhances BTE by 2.6% at spark timing optimal for CNG (CNG ST) and 0.6% at the optimal mixture ST (mixture ST). Analyses of the rate of heat release (ROHR), temperature, and pressure increase in the cylinder were carried out using utility BURN in AVL BOOST software.

This study presents an experimental investigation into the impact of blending bioethanol (E100) with conventional gasoline (E0), incrementally increasing biofuel levels up to E10, E50, and E70. The test was carried out in two stages: Stage I assessed the engine’s performance under fixed speeds (n = 2000 rpm and n = 2500 rpm) and fixed throttle positions (15%, 20%, and 25%) to measure changes in engine torque, efficiency, and environmental metrics by varying the concentration of bioethanol in the fuel. Stage II aimed to enrich the initial findings by conducting an additional test, running the engine at a fixed speed (n = 2000 rpm) and braking torque (M_B = 80 Nm) and varying the ignition timing. Results indicated slight improvements in engine brake torque and thermal efficiency (up to 1.7%) with bioethanol content increased to 70%, and a notable reduction in incomplete combustion byproducts—carbon monoxide and hydrocarbons emissions (up 15% and 43%). Nitrogen oxide emissions were reduced by up to 23%, but carbon dioxide emissions decreased by a mere 1.1%. In order to increase thermal efficiency by adding higher bioethanol blend concentrations, adjusting the ignition timing to counter the longer ignition delay is necessary; however, higher emissions of nitrogen oxides and hydrocarbons are a major drawback of such a strategy. The results of the research are important in determining the optimal concentration of bioethanol in the mixture with gasoline for the energy and environmental sustainability of a spark ignition engine.

Biogas is one of the alternative solutions that could reduce the usage of fossil fuels and production of greenhouse gas emissions, as biogas is considered as an alternative fuel with a short carbon cycle. During biogas production, organic matter is decomposed during an anaerobic digestion process. Biogas mainly consists of methane and carbon dioxide, of which the ratio varies depending on the raw material and parameters of the production process. Therefore, engine parameters should be adjusted in relationship with biogas composition. In this research, a spark ignition engine was tested for mixtures of biogas with 0 vol%, 20 vol%, 40 vol% and 50 vol% of CO₂. In all experiments, two cases of spark timing (ST) were used; the first one is a constant spark timing (26 crank angle degrees (CAD) before top dead center (BTDC)) and the second one is an advanced spark timing (optimal for biogas mixture). Results show that increasing the CO₂ concentration and using constant spark timing increases the mass burned fraction combustion duration by 90%, reduces the in-cylinder pressure and leads to a reduction in the brake thermal efficiency and nitrogen oxides emissions at all measurement points. However, the choice of optimal spark timing increases the brake thermal efficiency as well as hydrocarbon and CO₂ emission.

This paper investigates the emission characteristics of hydrogen-enriched gasoline (95G5H₂) under dynamic driving situations in order to fulfill the growing need for cleaner and more efficient automobile fuels. This study aimed to investigate the impact of hydrogen addition on pollutant-specific emissions, including CO, CO₂, HC, and NO_x, using a Nissan Qashqai that ran on both pure gasoline (100G) and 95G5H₂. Emission statistics were obtained by computer simulations of the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) applied using AVL CRUISE software. The paper presents a method of comparing the characteristics of pollutants emitted by the combustion engine and comparing the pollutants emitted when powered by regular fuel and fuel with hydrogen. The tests were performed in real conditions, and the presented method shows the amount of pollutants emitted when the vehicle is directly in motion, which allows for effective comparison of the amount of pollutants emitted for different fuels. 95G5H₂ sharply reduces CO-, CO₂-, and HC-specific emissions by 22.19%, 14.55%, and 35.46%, respectively, when compared to 100G. However, NO_x-specific emissions increased by 20.17%, suggesting a compromise between higher combustion efficiency and higher burning temperatures. The study shows that 95G5H₂ fuel performs better in urban driving cycles, including plenty of acceleration and deceleration, which usually results in incomplete combustion. Although additional refinement is needed to cut NO_x-specific emissions, the results demonstrate that hydrogen-enriched fuels have considerable potential to lower vehicle-specific emissions. The significant conclusions of the study on the advantages of hydrogen-enriched fuels, both practically and environmentally, will help in the future development of environmentally friendly transportation solutions.

This paper presents a study on the energy efficiency and emissions of a converted high-revolution bore 79.5 mm/stroke 95 mm engine with a conventional fuel injection system for operation with dual fuel feed: diesel (D) and natural gas (NG). The part of NG energy increase in the dual fuel is related to a significant deterioration in energy efficiency $\left({\eta }_i\right)$ , particularly when engine operation is in low load modes and was determined to be below 40% of maximum continuous rating. The effectiveness of the D injection timing optimisation was established in high engine load modes within the range of a co-combustion ratio of NG $\le$ 0.4: with an increase in ${\eta }_i$ , compared to D, the emissions of ${\mathrm{NO}}_{\mathrm{x}}+$ HC decreased by 15% $\mathrm{to}$ 25%, while those of ${\mathrm{CO}}_2$ decreased by 8% to16%; the six-fold $\mathrm{CO}$ emission increase, up to 6 g/kWh, was unregulated. By referencing the indicated process characteristics of the established NG phase elongation in the expansion stroke, the combustion time increase as well as the associated decrease in the cylinder excess air ratio (α) are possible reasons for the increase in the incomplete combustion product emission.