In order to design a diesel engine system and to predict its performance, it is necessary to analyze the gas flow of the intake and exhaust system. Gas flow analysis in a three-dimensional (3D) format needs a high-resolution workstation and an enormous amount of time for analysis. Calculation using the method of characteristics (MOC), which is a gas flow analysis in a one-dimensional (1D) format, has a fast calculation time and can be analyzed with a low-resolution workstation. However, there is a problem with poor accuracy in certain areas. It was assumed that the reason was that 1D could not implement the shape. The error that occurs in the shape of the bent pipe used in the intake and exhaust ports of the diesel engine was analyzed and to find a solution to the low accuracy, the results of the experiment and 1D analysis were compared. The discharge coefficient was calculated using the average mass flow rate, and as a result of applying it, the accuracy was improved for the maximum negative pressure by 0.56–1.93% and the maximum pressure by 3.11–7.86% among the intake pipe pressure results. The difference in phase of the exhaust pipe pressure did not improve. It is considered as a limitation of 1D analysis that does not improve even by applying the discharge coefficient. In the future, we intend to implement a bent pipe that cannot be realized in 1D using a 3D format and to prepare a method to supplement the reliability by using 1D–3D coupling.
Devices for reducing environmental pollutant emissions are being installed in ship compression ignition (CI) engines; alternatively, the designs of intake and exhaust pipes and ports are being modified to tune the performance according to the user’s needs. In both cases, substantial computation time and cost are required to simulate the gas flow of the CI engine with an air-intake system. In order to simulate the air-intake system of the CI engine, which changes according to the user’s needs, at a low cost and in a short time, we aimed to analyze the gas flow using a 1D–3D coupled method. The 1D zone was analyzed using the method of characteristics, and the 3D zone was analyzed using the commercial computational fluid dynamics (CFD) code Ansys Fluent R15.0, whereas their coupling was achieved by applying the developed 1D–3D coupling algorithm to Ansys Fluent R15.0 using user-defined functions (UDFs). In the comparison of the pressure of the intake pipe with the experimental result, the average error was 0.58%, thereby validating the approach. In addition, when analyzing the intake pipe and port in a 3D zone, the results of the velocity and pressure were expressed as contours, allowing them to be visualized. It is expected that the 1D–3D coupling algorithm of the air-intake system can be used to reflect the user’s needs and can be used as a method to quickly and accurately calculate the gas flow within tens of minutes.
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