Optimizing combustion efficiency and emission reduction in low temperature combustion engines using biodiesel-nano additive alcohol blends: A review

Abstract

The increasing levels of harmful emissions and the depletion of fossil fuel resources have sparked global interest in biodiesel as an alternative fuel. This review explores the potential of biodiesel derived from non-edible resources and waste products, enhanced by nano-additives and higher alcohol fuels, to support Low Temperature Combustion (LTC) engine technologies. Nano-additives like titanium dioxide and magnesium oxide enhance fuel properties, while higher alcohols reduce soot and hydrocarbon (HC) emissions. Advanced combustion modes are used to minimize nitrogen oxide (NOx) and particulate emissions. This review underscores the significant role of biodiesel with additives in enhancing lower combustion, although Low temperature combustion engines demand advanced control over fuel composition and combustion conditions for optimal performance. Effective strategies like Exhaust Gas recirculation (EGR) and Variable Injection Timing helps in controlling the harmful emission levels in LTC Engines. EGR reduces NOx emissions but increases HC and CO beyond 30 %. Early injection rates (before 23° BTDC) increased NOx, while late injection (after 27° BTDC) increases HC and CO. Combining EGR (15–25 %) with optimized injection timing (23°-27° BTDC) provides the best emission control in LTC engines. Hence Blending biodiesel, alcohols, and nano-additives helps to reduce emissions in LTC engines. It was found that Higher alcohols improve combustion efficiency, reduce NOx & PM, but increase CO & HC at high blends while with addition of Nanoparticles optimization of combustion, lower emissions, and enhancement of thermal efficiency are achieved. n-Pentanol and Copper Oxide (CuO) were found to be better Alcohol and Nanoparticle additive with respect to High energy content, Better Volatility and Stability, enhanced combustion and Emission control. Within the LTC strategies RCCI was found to be best with respect to maximum thermal efficiency, lower emissions, superior load adaptability which is a concern in HCCI and PCCI modes and fuel flexibility to be used in a wide range of fuel combinations to optimize combustion efficiency, emissions, and performance. However, trade off exists between NOx and HC levels even with enhanced combustion which can be controlled with optimized combustion chamber design, optimized fuel injection system with proper Air Fuel Ratio and after treatment systems like SCR and DPF.