A review on improving airflow characteristics inside the combustion chamber of CI engines to improve the performance with higher viscous biofuels

Performances of diesel engines run on biodiesel and vegetable-based fuels are not satisfactory mainly due to higher viscosity, and they are termed as higher viscous fuels (HVFs). Researchers have developed different techniques to improve the performance of diesel engines run on HVFs such as preheating HVFs, blending with lighter fuels, and changing injection strategy. These techniques improved the performance with HVFs, but the performances are still lower than diesel. Another technique, improving the in-cylinder airflow characteristics can create more turbulence inside the combustion chamber to break up HVFs and mix better with the in-cylinder air to improve the performance of the engine. Most reviews show that the performances of diesel engines are improved with higher turbulence though with diesel, but few papers show that this technique can improve the performance of diesel engines with HVFs as well. Based on literatures, the in-cylinder turbulence can be increased using guide vanes and throttling the intake manifold and modifying the combustion chamber and intake manifold. It is found that about 1.3-2.8% efficiency improved by improving the in-cylinder turbulence by using guide vanes when the engines ran on HVFs. Some researchers have also reported around 12% improvement in brake specific fuel consumption (bsfc) by improving the swirl of the air inside the combustion chamber. This paper reviews different techniques to improve the in-cylinder airflow characteristics in IC engines and reviews a handful of papers with HVFs to show that increasing in-cylinder turbulence can improve the performance of the CI engines with HVFs.