PR179-22207-R01 Improved In-Cylinder Mixing Injection Pressure Sensitivity

Large-bore, natural gas-fueled engines are used for gas compression at over 1700 compression stations across the US, and methane emissions have presented a challenge to their optimization over the years. A significant root of this problem has been linked to the level of air-fuel mixing in the main combustion chamber of these engines as poor mixing results in low combustion efficiency. High-pressure fuel injection is believed to be a significant way to improve air-fuel mixing in natural gas engine combustion chambers. The purpose of this present study is to determine the sensitivity of in-cylinder mixing to injection pressures, using CFD simulations, determine the limits of high-pressure fuel injection, and explore the possibility of improving low-pressure fuel injection. The engine modeled using CONVERGE Studio for CFD was the large 4-cylinder GMV 4TF engine. The model was simulated for four major sets of configured cases – baseline establishment, ideal mixing case development, injection pressure variation, and low-pressure, high-momentum cases. The results of this work show that improved mixing potentially reduces the amount of methane emissions by half and high-pressure fuel injection also improves the in-cylinder mixing in the main combustion chambers of large bore engines. The optimal timing for the injection at different injection pressures was determined and the limitations in each case were identified. It was concluded that fuel injection at 700 psi at -110 degrees BTDC gave the best mixing case. The level of mixing in low-pressure fuel injection systems was also found to be improved by up to 39% by having high-momentum fuel injection using increased flow areas at injection.