新着論文

スクラムジェットエンジンの燃料の強制着火用に用いられているマイクロロケットトーチ（点火器）を対象とした，トーチ内部の燃焼及び固体熱伝導の連成シミュレーション手法を新たに開発しました．実験結果との検証解析結果より，本解析手法の有用性を明らかにしました．詳細については，下記の学術論文をご覧ください．

論文タイトル：Coupled simulation of gas-phase combustion and solid heat conduction in a hydrogen-oxygen micro-rocket torch igniter

著者：Shinichiro Ogawa, Yuya Hirayama

掲載論文：CEAS Space Journal (2025)

DOI: https://doi.org/10.1007/s12567-025-00685-w

Abstract:

Hydrogen–oxygen torch igniters are widely used to promote ignition and flame holding during high-speed propulsion. However, the coupled internal reaction flow and solid heat conduction processes that govern their thermal limits remain insufficiently quantified. We developed a conjugate framework that couples a one-dimensional plug-flow reactor for gas-phase H₂/O₂ chemistry with an axisymmetric transient heat conduction model of a noncooled copper micro-rocket torch. The inner/outer wall boundary conditions account for gas-to-wall convection, external natural convection, and radiation. The solver was verified against the analytical solution for an infinitely long cylinder with convective cooling, yielding a small and decaying RMSE (~ 10^-2 - 10^-3), which supports the fidelity of temporal/spatial discretization and boundary implementation. Simulations at Φ = 1.14 show post-ignition chamber temperatures near 3100 K and near-exit temperatures that decrease with increasing internal heat-transfer coefficient h_inner [50–500 W/(m²・K)] from ≈ 3180 to 2930 K. A comparison with the wall thermocouple data at 3 and 6 cm from the tip indicates h_inner ≈ 100 - 200 W/(m²・K), which is consistent with the Nusselt-based estimates for nominally laminar flow (Re_d≈1690). Despite strong internal heating, the torch temperature-rise rate remained < 4 K/s and diminished over time, implying thermal robustness for at least 15 s of operation under the present conditions. The gas-phase radiation inside the chamber is negligible because of the small p_H2OL, whereas the external radiation becomes comparable to natural convection near ~ 600 K and must be included in the design. The framework enables quantitative assessment of gas–wall coupling and provides actionable guidance for selecting operating windows and material/thickness choices to balance ignition strength against structural heating in scramjet and liquid/hybrid-rocket torch igniters.