Methods for improving the in-cylinder airflow characteristics for sustainable transportation using fuels with higher viscosity: A review

Numerous research studies have been persistently conducted to improve the performance of diesel engines (CI engines) running on alternative fuels. The poor performance of CI engines due to the high viscosity of alternative fuels limits their applications. Several techniques and measures have been introduced, such as preheating the fuel before being supplied to the engine, changing the injection methods, altering the combustion chamber design, and modifying the piston to improve engine performance while running on higher viscosity fuel. These techniques effectively enhanced engine performance and reduced emission, but their performance is still lower than those of petro-diesel engines. Improving the in-cylinder airflow characteristics in the combustion chamber could potentially address the problem of poor performance. Nevertheless, studies investigating the appropriate methods to overcome poor performance are limited. The in-cylinder airflow characteristics are vital for improving the air-fuel mixing process. Changes in the airflow characteristics can generate more turbulence inside the combustion chamber. An increase in the turbulent flow in the combustion chamber will enable the break-up of higher viscosity fuel during injection and mix well with the in-cylinder airflow. From the literature, the commonly used methods to enhance and stimulate the turbulent flow in the combustion chamber are by using a guide vane device, throttling the intake manifold, modifying the combustion chamber, and changing the intake manifold design. This paper briefly reviews various techniques for improving the in-cylinder airflow characteristics in CI engines running on fuel with higher viscosity (FHVs).