Incomplete combustion leads to the formation of solid particles composed of carbon, organic compounds, and metal oxides, increasing smoke and its harmful impact on health and the environment [20]. Hydrocarbons resulting from incomplete combustion contribute to a bluish exhaust tint, indicating issues with temperature or mixture quality [21]. While carbon monoxide does not directly affect visible smoke, its presence reflects oxygen deficiency and correlates with PM formation. Nitrogen oxides, although not visible, indicate high combustion temperatures conducive to PM generation. Sulfur compounds from low-quality fuels increase the smoke density and produce a pungent odor [22]. Smoke levels also vary with the engine load and temperature: high loads with insufficient air raise the PM output, and cold starts increase hydrocarbon and PM emissions. Poor fuel quality and mechanical wear, such as faulty injectors or cylinder damage, further elevate smoke levels [23]. Thus, smoke density serves as a key indicator of combustion quality and emission cleanliness, and reducing it is essential to improving diesel engine environmental performance. There are numerous methods and technologies aimed at reducing harmful emissions from diesel engines, generally classified into two main categories: engine design improvements and technological advancements in exhaust gas cleaning systems. Engine design improvements include the use of exhaust gas recirculation systems (EGRs), which reduce nitrogen oxide (NO\({}_{\rm x}\)) emissions by recirculating a portion of the exhaust gases back into the intake manifold [24]. High-precision fuel injection systems (such as common rail or piezoelectric injectors) allow for accurate fuel dosing, thereby improving the combustion efficiency and reducing hydrocarbon (HC) and carbon monoxide (CO) emissions [25; 26]. Turbocharging combined with an intercooler increases engine power and efficiency while lowering emissions, and a higher compression ratio improves the combustion process, resulting in reduced PM formation [27]. On the other hand, technological advancements in exhaust gas aftertreatment include diesel particulate filters (DPF) that trap solid particles (soot) from the exhaust stream, selective catalytic reduction (SCR) systems that lower NOx emissions by injecting urea, converting harmful compounds into nitrogen and water, and diesel oxidation catalysts (DOCs), which reduce hydrocarbons, CO, and some organic compounds [28]. Additionally, two-stage filtration systems that combine DPF and SCR technologies offer maximum efficiency in emissions [29]. However, existing technological solutions for reducing harmful emissions from diesel engines have several significant drawbacks that not only complicate the engine design and operation but also increase the maintenance costs. Exhaust gas recirculation (EGR) systems reduce the engine power due to decreased oxygen availability in the cylinders, increase the thermal load on the cooling system, and may cause deposit buildup in the valves and intake manifold, requiring regular cleaning [30; 31]. High-precision fuel injection systems, such as common rail or piezoelectric injectors, are expensive, difficult to maintain and repair due to their complex design and sensitivity, and heavily dependent on fuel quality, which poses challenges in regions with low fuel standards [32]. Turbocharging with an intercooler, while enhancing engine performance, increases the system complexity, the risk of turbocharger failure, and the requirements for oil and coolant quality, resulting in higher maintenance costs [33; 34]. Although a higher compression ratio improves combustion and reduces PM formation, it also increases the mechanical stress on engine components [35]. In terms of exhaust gas aftertreatment, diesel particulate filters (DPFs) involve high installation and maintenance costs, require periodic regeneration that raises fuel consumption, and are prone to clogging under low-load conditions or during frequent short trips [36; 37].