Comparative analysis of Diesel, B50, and H50 fuels in a diesel engine employing air-fuel ratio and exhaust gas recirculation

Abstract

Past research has mostly concentrated on the utilization of hydrogen or biodiesel in various proportions when blended with diesel fuel. Despite considerable research conducted on the utilization of fuel blends consisting of hydrogen and biodiesel. Currently, there is a lack of research that has conducted a comparative analysis regarding the impact of air-fuel ratio on the performance of diesel fuel blended with Hydrogen and FAME. This research article examines three fuel blends to determine four critical diesel engine parameters (BTE, Brake Torque, NOx concentration, and BMEP) at five distinct air-fuel ratios spanning from 14 to 65. The present study aims to enhance the comprehension of the intricate characteristics of air-fuel mixtures, specifically rich, stoichiometric, and lean, by conducting an extensive analysis. Additionally, the investigation focuses on the impact of the exhaust gas recirculation technique on the NOx concentration. This article presents a mono-cylinder diesel engine model developed in the Ricardo wave program, simulated in three cases: I) Diesel only, II) B50(Blend of 50 % Diesel and 50 % FAME), and III) H50(Blend of 50 % Diesel and 50 % Hydrogen) at a compression ratio 21 with an rpm ranging from 500 to 2500.Fair agreement with peak results deviating in a few percent revealed that H50 significantly enhances brake thermal efficiency (BTE) measured to Diesel and B50, with improvements of up to 5.6 % and 5 %, respectively. When Hydrogen is mixed with Diesel, the combustion process quickens and becomes more complete, and ultimately, an improved combustion quality is achieved. H50 generates 13 % and 12 % higher levels of NOx in comparison to Diesel and B50, respectively. Increased engine speed triggers the in-cylinder temperature to rise, promoting NOx generation. The heat release rate is a significant parameter for assessing combustion efficiency. Diesel releases more heat than B50 at a particular crank angle. However, from 15-64° CA, B50 keeps generating more heat than Diesel. Thereby, B50 releases more heat than the Diesel overall. The Brake torque and BMEP decrease with the increase in AFR for each case. In conclusion, H50 and B50 generate higher BTE than Diesel. Meanwhile, this comes at the cost of a rise in NOx concentration. When the exhaust gas recirculation is applied at 25 %, the NOx concentration is reduced drastically, and it is further deduced that the rate of change of EGR is inversely proportional to the NOx concentration.