Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
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CFD (Computational Fluid Dynamics) Study on Partial-Load Combustion Characteristics of a 4-Step-Grate Wood Pellet Boiler

4단 화격자 목재 펠릿 보일러의 부분부하 연소해석

  • Ahn, Joon (School of Mechanical Systems Engineering, Kookmin Univ.) ;
  • Jang, Jun Hwan (Dept. of Mechanical Engineering, Graduate School, Kookmin Univ.)
  • 안준 (국민대학교 기계시스템공학부) ;
  • 장준환 (국민대학교 대학원 기계공학과)
  • Received : 2013.08.14
  • Accepted : 2014.02.19
  • Published : 2014.04.01
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Abstract

A numerical simulation was conducted for the combustion chamber of a 4-step grate-firing boiler for wood pellet fuel. The flame is extended to the exit of combustion chamber, which is reproduced by present numerical method based on a homogeneous reaction model. Flow field from the simulation shows a strong recirculation flow at the upstream corner of the chamber, along which the flame is extended to the exit. These combustion and flow characteristics remain unchanged for partial load operations, which suggest modification of the combustion chamber structure rather than resizing should be effective to improve combustion characteristics. Possible modifications for combustion chamber are suggested such as relocating its exit, increasing the number of grate steps or installing internals such as guide baffles.

본 연구에서는 4단 화격자로 구성된 목재 펠릿 보일러의 연소실에 대하여 수치해석을 수행하였다. 목재 펠릿의 화염은 화격자에서 연소실 출구까지 신장되는 데 이 현상이 균질 반응에 기반한 수치해석 기법으로 잘 예측되었다. 수치해석으로 구한 유동장을 보면 연소실 상류에서 출구쪽으로 강한 재순환 유동이 형성되는데 이 유동을 따라 화염이 신장된다. 이와 같은 유동 및 연소 형태는 부분부하 조건에 대하여 수치해석을 수행하였을 때도 유지되었다. 따라서 연소실의 체적을 변경하는 것보다 연소실의 구조를 변경하는 것이 연소 효율을 개선하는 데 도움이 될 것으로 보인다. 본 연구에서는 수치해석 결과를 바탕으로 연소 효율을 높이기 위하여 연소실 출구 위치 변경하거나 화격자 개수를 늘이는 방안 또는 격벽과 같은 내부 구조물을 설치하는 방안을 제안하였다.

Keywords

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