Optimizations of Vane Height of Guide Vane Swirl and Tumble Device to Improve in Cylinder Airflow Characteristics of a Diesel Engine Running with Vegetable Oil

Abstract

Generally, compression ignition engine operating on neat vegetable oil and its blend with diesel fuel experience a reduction of engine performance and increase in exhaust emissions due to higher viscosity and lower volatility of vegetable oil than diesel fuel. Vegetable oil is less prone to evaporate, diffuse and mix with the in-cylinder air which eventually reduces the combustion efficiency and produces more emissions of CO and unburned HC. Therefore, this research investigated the potential of guide vane swirl and tumble device (GVSTD) to guide the air entrance to create more organized turbulence inside the fuel injected region to enhance the mixing process of air and vegetable oil. In order to do so, a base model of 3D computational fluid dynamic of internal combustion engine simulation was developed, verified and then simulations were carried with different GVSTD models. The results of turbulent kinetic energy, velocity, vorticity and swirling strength were compared to determine the optimum vane height. This research found that the 2 mm vane height was the optimum vane height with 35° twist angle, four vanes being arranged perpendicularly to each other and 30 mm vane length. Other different heights of vanes also showed improvement but 2 mm height showed the highest number of improvements. This could be due to the airflow pattern in bowl-inpiston head shape was amplified by the airflow pattern produced by the guide vane of 2 mm vane height. The extra turbulence, swirl, vorticity and velocity in the fuel injected region created by the 2 mm height vane is expected to enhance the mixing of vegetable oils with air to improve combustion and reduce CO and unburned HC emissions.