Effects of compressed natural gas (CNG) injector position on intake manifold towards diesel-CNG dual fuel (DDF) engine performance

Abstract

In Diesel-CNG (Compressed Natural Gas) Dual Fuel (DDF) system, CNG is generally inducted in the intake manifold by CNG injector which is mounted on the intake manifold whereas diesel fuel is directly injected into engine cylinder using existing diesel fuel injector system. Status quo of optimum CNG injector position on intake manifold will provide better gaseous fuel mixing quality, produce high turbulence kinetic energy and thus improve the performance of the diesel engine under DDF system. Thus, under full load condition at 2750 rpm, the engine performance and exhaust gas emissions tests such as nitric oxides (NOx), carbon dioxide (CO2), carbon monoxide (CO) and hydrocarbon (HC) were conducted on a diesel engine under DDF system for optimization of CNG injector position. Four CNG injector position on intake manifold were selected and optimum position of CNG injector was found to be at "position 2" which results in higher power output and less exhaust gas emissions. Further analysis by Computational Fluid Dynamics (CFD) shows that CNG injector at "position 2" exhibit better quality of homogeneous CNG-air mixture and higher turbulence kinetic energy compared to other position. Based on the findings, an optimization of CNG injector position on intake manifold provide promising modification method due to the simple, cheaper and commercially acceptable