Utilization of catalytically cracked waste transformer oil in compression ignition engines: Effects of combustion chamber geometry on efficiency and emission characteristics

Research on alternative fuels has received increased attention in recent years because they not only address the sustainability issues associated with fossil fuels but also mitigate the harmful gases released during combustion. This study focuses on the use of recycled transformer oil (WTO) in diesel engines, aiming to harness its energy content, which is typically discarded as waste. The WTO was recycled via catalytic cracking, and CCWTO50 (a 50 % CCWTO and 50 % neat diesel blend) was used as the test fuel. Furthermore, a re-entrant combustion chamber (RCC) and a hemispherical open-type combustion chamber (HCC) were employed to investigate the combustion and emission characteristics of WTO. The combustion characteristics, engine performance, and exhaust gas emission levels were recorded when the CCWTO50 powered the engine for both HCC and RCC geometries. The results indicate that CCWTO50 improved engine performance and reduced emissions compared to diesel fuel. Further improvements were observed when RCC was employed. A higher heat release rate of 169.3 kJ/m 3 /°C and a peak pressure of 61.54 bar were observed for CCWTO50-RCC. CCWTO50-RCC improved brake thermal efficiency by 3 % compared to diesel-HCC. In addition, CCWTO50-RCC reduced emissions of hydrocarbons (HC), carbon monoxide (CO), and smoke by 8 %, 6 %, and 5 %, respectively, compared to diesel-HCC. Thus, the authors suggest that CCWTO50 with RCC can be effectively used in diesel engines to enhance engine performance and reduce exhaust gas emissions. • Studied catalytically cracked waste transformer oil in diesel engines with different combustion chamber designs. • Identified optimal chamber design for improved efficiency and reduced emissions. • Provided practical recommendations for sustainable fuel utilization and future research directions.