이중 연료 엔진의 급기관 폭발 손상 방지용 릴리프 밸브 설계 및 성능 평가

Abstract

The purpose of this study is to predict the pressure rise when liquefied natural gas (LNG) explodes in the charge air chamber of a dual fuel engine used to meet environmental regulations and to evaluate the performance of the relief valve installed in the charge air chamber. For the numerical analysis of the explosion, a commercial computational fluid dynamics (CFD) code ANSYS FLUENT 2020 R2 was used, and the validity was verified with an error of less than 5% by comparing the experimental results and results of numerical analysis by installing the relief valve in the cylindrical chamber. The charge air chamber of a dual fuel engine was modeled in a cylindrical shape and numerical analysis results were analyzed. As a result of numerical analysis, the pressure increased to a maximum of 29.5 barg without the relief valve. This result exceeds the 10 barg design pressure recommended by the engine manufacturer. The relief valve with a free area of 499 ㎠ was installed in the charge air chamber and the results of numerical analysis were analyzed when an explosion occurred at three-positions. The result of the maximum explosion pressure was 14.75 barg at the position of turbocharger, 8.57 barg at the position of the charge air chamber center, and 10.9 barg at the position of the relief valve. When one relief valve was installed, the pressure results in the charge air chamber were reduced by operating the relief valve, but the pressure results exceeds the design pressure by 10 barg at the turbocharger and relief valve positions. As a result of numerical analysis by installing two relief valves with a free area of 346 ㎠ in the air inlet and the charge air chamber, the maximum pressure was 8.02 barg, and the pressure was reduced below the design pressure by operating the relief valve. Through the results of this study, it was possible to design a relief valve for the charge air chamber of a dual fuel engine, and the effect of the presence, size, and number of relief valves on the explosion pressure in the charge air chamber was confirmed. In the future, it is expected that the performance evaluation results of this study will be utilized to develop relief valves.