Durability Effects of Gas Nozzle Shape on Marine Two-Stroke Dual-Fuel Engines Using Numerical Analysis

To comply with rules on air pollutants released by ships, two-stroke dual-fuel engines with liquefied natural gas (LNG) as the primary fuel have been marketed and offered to the market. However, there are still reports of gas-injection nozzles being damaged after they have been put on the market. Damage to the nozzles might result in secondary accidents in addition to worsening engine combustion conditions from improper injection. This study aims to gather fundamental information regarding the impact of different types of gas-injection nozzles on durability and to pinpoint the prerequisites for an ideal nozzle design. The results of total deformation and equivalent stress were examined for 27 nozzles that each variable was applied to in order to compare and confirm the durability by changing the nozzle shape. The cause of the nozzle temperature change according to the change in nozzle length was found to have the biggest impact on the total deformation, and it was confirmed that the effect was increased at higher temperatures. As the nozzle length increased and decreased by 2 mm, the average temperature of the nozzle increased by 47% and decreased by 53%, but the total deformation increased by 100% and decreased by 70%. It was verified that the equivalent stress was determined by the complicated interplay between the pressure inside the nozzle and turbulent kinetic energy impacted by a change in the nozzle shape. The factor that has the largest influence on the equivalent stress is the adjustment of the nozzle hole pipe angle, and the difference in equivalent stress according to this factor was found to be up to 118% and at least 44%. As a result, it has been proven that shortening the nozzle length, increasing the hole pipe angle, and enlarging the hole diameter are the most effective and expected to be used as basic data for future nozzle development.