The performance and emissions of a conventional natural gas/diesel duel fuel engine at various operating conditions 2019-01-1158
Dual fuel combustion mode is an attractive alternative to standard spark ignition (SI) or compression ignition (CI) combustion modes due to potential benefits in terms of lower CO2 emission, lower fuel costs and usage of fuel with alternative supply chain. Besides the potential benefits, dual fuel combustion mode also has its challenges, especially at high and low load, and since there are limited data given in the literature that shows how the performance of the dual fuel engine changes over the engine map at various injection pressures and natural gas substitution ratios this paper presents a comprehensive set of experimental results obtained with the conventional dual fuel operation (diesel/natural gas) at ambient intake conditions. The results are obtained from a single cylinder CI experimental engine converted to run in conventional dual fuel mode with full flexibility of choosing injection parameters (injection pressure, injection timing, and injection duration) of both directly injected and port injected fuel. Instead of natural gas, methane from the pressure cylinders is used as the alternative fuel and is injected into the intake port, while the standard diesel from the gas station is directly injected by a conventional common rail system and used as an ignition source. The presented results are obtained at optimized operating points in terms of start of injection timing, where the criterion in the optimization was a maximum indicated efficiency. The tests are performed at three different engine speeds (1200, 1600 and 2000 rpm), three different diesel injection pressures (300, 500 and 700 bar), three different loads (IMEP = 2, 4 and 7 bar) and at three different natural gas substitution ratios (0%, 50% and 90%). The obtained results show how injection parameters and natural gas substitution ratios influence various engine performance and emission results at different operating points in the engine map.
Darko Kozarac, Mario Sremec, Mladen Bozic, Ante Vucetic