Amplification of self-excited thermoacoustic traveling waves by effects of elbow curvature and stack positions

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03863
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Fukui University of Technology
• Principal Investigator: Shimizu Dai 福井工業大学, 工学部, 教授 (40448048)
• Co-Investigator(Kenkyū-buntansha): 杉本 信正 大阪大学, 大学院工学研究科, 招へい教授 (20116049)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 熱音響自励振動 / 基本振動モード / 2次振動モード / 曲管 / 曲率半径 / 進行波 / 定在波成分

Outline of Final Research Achievements

Experiments are performed to investigate effects of elbow curvature and the location of the stack on self-excited thermoacoustic oscillations in an air-filled looped tube. The tube is composed of two curved sections and two straight sections. Use is made of three looped tubes having different curvatures with tube's total length along the centerline kept constant. Traveling-wave type of thermoacoustic oscillations are excited spontaneously by inserting a stack consisting of many square pores sandwiched between hot and cold heat exchangers to impose a steep temperature gradient along it. It is revealed that as the radius of curvature becomes small, the location of the stack has significant effects on onset of instability, amplitude, mode and spatial profiles of self-excited oscillations.

Free Research Field

熱音響工学

Academic Significance and Societal Importance of the Research Achievements

従来の研究では，入手の容易さから，管の径と比較して曲率半径が極めて小さい 90度エルボ管を用いた実験結果に基づいて議論が進められ，管の曲率が，自励振動に与える影響は議論されてこなかった．自励振動のpp値がスタックの挿入位置に依存することは知られていたが，管の曲率への依存性は注目されてこなかった．本研究により，発生する自励振動のpp値に加え，振動モードや含まれる定在波成分の割合も管の曲率に依存していることが明らかになった．進行波型の熱音響自励振動を応用した冷凍機や原動機では，進行波成分の増大や振動モードが出力の増大に直結することから，本研究成果は学術的意義に加え，社会的意義も非常に大きい．