Thermoacoustic phenomena and their nonlinear behaviors due to instability of heat flow

2018 Fiscal Year Final Research Report

• Project/Area Number: 26289036
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Fluid engineering
• Research Institution: Kansai University
• Principal Investigator: SUGIMOTO Nobumasa 関西大学, システム理工学部, 教授 (20116049)
• Co-Investigator(Kenkyū-buntansha): 清水 大 福井工業大学, 工学部, 教授 (40448048)
• Project Period (FY): 2014-04-01 – 2019-03-31
• Keywords: 熱流体力学 / 熱音響 / 不安定性 / 非線形波動・振動 / 熱機関 / エネルギーハーベスティング

Outline of Final Research Achievements

This project aims at establishing theoretical framework to deal with nonlinear behaviors in thermoacoustic phenomena resulting from instability of heat flow, and also at making experiments to verify the theoretical findings. The framework of theoretical treatments of weakly nonlinear wave propagation in a flow passage subjected to a temperature gradient has been established. The theories are expected to be applicable to quantitative clarification of emergence of self-excited oscillations including shock waves and acoustic streamings. In parallel, experiments are performed by using a closed, straight tube and a looped tube, in which a heat flow is produced by imposing a temperature gradient on a stack. The experimental results are checked against the theories. In addition, electricity generation from self-excited oscillations is also attempted in view of one means of energy harvesting.

Free Research Field

熱流体力学

Academic Significance and Societal Importance of the Research Achievements

熱音響現象は熱的な要因で発生する音の発生を意味するが、本研究では熱流の不安定化による気体の強い振動が自然に生じる現象を取り扱う。この現象を定量化することは難しく、振幅が微小な場合の解析だけがこれまで行われてきたが、不安定化後の振幅が大きくなった場合に適用できる理論はこれまでなかった。本研究では、粘性や熱伝導性による拡散の影響と圧力振幅の大きさに応じた理論体系を構築した。これにより、不安定化から自励振動の発生の定量化が可能になる。また、直管やループ管路を用いて自励振動を実験でも発生させ、理論の根拠や結果について調べた。こうした研究は将来の環境・エネルギー問題の解決への試みとなる。