JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25EDU10301

Subject Category: Space and Astronautical Science

PDF (to be added)

• Responsible Representative: Hiroaki Kobayasi,Professor
• Contact Information: Shie Sato,Teikyo Univercity(25fm100170x@stu.teikyo-u.ac.jp)
• Members: Shie Sato

Abstract

JAXA/ISAS is currently conducting research and development of a reusable sounding rocket called the Atmospheric Assist Rocket. This vehicle is equipped with an ATRIUM engine, which combines a rocket engine and an air-turbo engine. This engine burns hydrogen/oxygen in a fuel-rich state as the primary combustion, and then the secondary combustion occurs in the secondary combustion chamber, where the fuel is combusted with air. Teikyo University has focused on this secondary combustion chamber and conducted combustion tests using a subscale test chamber. These tests revealed that modifying the tip of the cylindrical section through which the fuel gas passes (fuel injection tip shape) improves the combustion efficiency of the secondary combustion chamber, approaching 100%. However, there are still some unknowns, such as the degree of influence of the tip shape and the influence of conducting experiments at a subscale rather than a full-scale model. Therefore, we conducted computational fluid dynamics analysis to elucidate the mechanism of the secondary combustion chamber in the subscale test chamber and the influence of scale changes.

Reference URL

N/A

Reasons and benefits of using JAXA Supercomputer System

In this study, the flow around the complicated shape of the fuel injection tip and combustion phenomena are analyzed in three dimensions. CHARIOT was used for the calculations, and JSS3, which is capable of large-scale calculations, was used to handle the complex combustion phenomena. Furthermore, Pointwise can be used in JSS3, which was used for grid division.

Achievements of the Year

As a tutorial, we used a supercomputer to create a grid and perform numerical calculations for a sub-scale single-element combustor using a coaxial injector. These tasks were carried out with the guidance of experts. A grid of 61,750 cells was created using Pointwise, and the domains were divided into 18 (Figure 1). Calculations were performed using CHARIOT to obtain the combustion temperature, velocity, pressure, heat release rate, and mole fraction when hydrogen and oxygen were burned. Figure 2 shows the temperature distribution obtained. It can be seen that the flame spreads in a pleated pattern.

Next, to reproduce the combustion tests conducted using Teikyo University's sub-scale test chamber, we performed an analysis on a protrusion, which is the simplest injection shape. We decided to first perform the analysis in 2D before conducting an actual 3D analysis. As in the tutorial, we used Pointwise to create a total of 89 domains and 217,500 cells in a grid (Figures 3 and 4). Based on the experts' opinions, we created a finer grid in the protrusion area and a coarser grid in the buffer area to allow for a smooth transition in grid size. Currently, the boundary conditions have been set and calculations are being performed using CHARIOT.

In the future, we will proceed with a 3D analysis of the protrusion shape. After that, we will proceed with analysis of shapes that actually produced high combustion efficiency, in order to clarify what phenomena are occurring inside the sub-scale test chamber and what effect changes in shape have on combustion efficiency.

Fig.1: Coaxial injector grid

Fig.2: Temperature distribution in hydrogen/oxygen combustion.

Fig.3: Secondary combustion chamber (protrusion) grid

Fig.4: Enlarged view of the protrusion

Publications

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Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: OpenMP
• Number of Processes: 1 - 13
• Elapsed Time per Case: 1.5 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.00

Details

Please refer to System Configuration of JSS3 for the system configuration and major specifications of JSS3.

*1: Fraction of Usage in Total Resources: Weighted average of three resource types (Computing, File System, and Archiver).

*2: Fraction of Usage：Percentage of usage relative to each resource used in one year.

ISV Software Licenses Used

*2: Fraction of Usage：Percentage of usage relative to each resource used in one year.

JAXA Supercomputer System Annual Report February 2025-January 2026