Effect of intake manifold design on the mixing of air and bio-CNG in a port-injected dual fuel diesel engine

The awareness for an effective utilization of renewable energy and alternative fuels has been increasing. As alternative fuels, both liquid and gaseous biofuels have huge resources. A bio-CNG is a form of biogas with increased methane content. The present study comprises the development of intake manifold with the port fuel injector and investigate the mixing characteristics of air and bio-CNG. The aim of the study is to analyse the effect the R/D ratio on the flow behaviour and mixture formation of air and bio-CNG. The four configurations of intake manifold are investigated. The ratio of radius of curvature of manifold bend (R) to the diameter of manifold (D) is varied as 1, 1.5, 1.75 and 2. The port fuel injector for bio-CNG induction is placed at 200 mm from the manifold. The objective is to optimize the intake manifold to deliver the homogeneous mixture of air and bio-CNG inside the engine cylinder. As the bio-CNG is new age fuel, being produced to reduce the import of conventional CNG, the work for optimization of port injector and intake manifold are hardly available. The geometries are made in PTC-Creo 3.0, followed by CFD simulation in ANSYS Fluent. The different configurations are analysed for the comparison of the parameters such as, pressure, velocity, turbulence kinetic energy, helicity and mass fraction of CH₄. The results show that the distribution of bio-CNG near the outlet of the manifold is uniform and homogeneous for the manifold with R/D ratio of 1.75 and 2.