Journal of the Korean Institute of Gas (한국가스학회지)

The Korean Institute of GAS (한국가스학회)
권호 표지
DOI QR코드

DOI QR Code

Characteristics of Entrainment Flow Rate in a Coanda Nozzle with or without Coaxial Contractor

코안다 노즐에서 중심 축소관 유무에 따른 유입량 특성

  • Received : 2014.01.23
  • Accepted : 2014.04.14
  • Published : 2014.04.30
Download PDF
⟨ Previous Next ⟩

Abstract

A MILD(Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used a coanda nozzle for the exhaust gas recirculation in a MILD combustor. A numerical analysis was accomplished to elucidate the effect of exhaust gas entrainment toward the furnace with or without a coaxial contractor. The result of the present CFD analysis showed that the entrainment mass flow rate without a coaxial contractor had 18% larger than that with a coaxial contractor when the mixed gas outlet pressure was ambient pressure. On the other hand, if the outlet pressure increased, the mass flow rate with a contractor was larger than that without a contractor. It could be analysed by the entrainment driving force composed with the nozzle throat pressure, inlet and outlet pressures and flow cross sectional area.

MILD 연소는 고온의 배기가스를 연소로 내에 재유입 되는 양에 따라 질소산화물 저감 특성에 많은 영향을 받는다. 본 연구에서는 MILD 연소로에서 고온의 배기가스를 연소로 내에 재순환하기 위해 코안다 노즐을 사용하였는데. 코안다 노즐의 중심에 중심 축소관을 설치한 경우와 설치하지 않은 경우에 고압공기 유량, 배기가스 유입량 특성을 수치해석을 통해 살펴봄으로써 최적의 코안다 노즐 형상을 도출하는 것을 연구의 목적으로 하였다. 본 연구의 전산 해석의 결과는 혼합가스 출구의 압력이 대기압일 때는 중심축소관이 없을 때가 배기가스 유입량이 약 18% 크게 나타나고 혼합가스 출구 압력이 증가하면 중심축소관이 있을 때가 유입량이 더 큼일 알 수 있었다. 이에 대한 분석은 노즐 목에서의 압력, 유입가스 입구와 혼합가스 출구 압력 그리고 유동 단면적으로 구성한 유입 구동력으로 해석 가능하였다.

Keywords

References

  1. J.A. Wuuning and J.G. Wunning, "Flameless oxidation to reduce thermal NO-formation", Prog. Energy Combust.Sci., vol.23, 81-97, (1997) https://doi.org/10.1016/S0360-1285(97)00006-3
  2. M. Katsuki, T.Hasegawa, "The science of technology of combustion in highly preheated air", 27 Symp (Int) Combustion, 3135-3146, (1998)
  3. A. Cavaliere, M. De Joannon, R. Ragucci, "Mild combustion of high temperature reactants", 2nd International Symposium on High Temperature Air Combustion, (1999)
  4. T. plessing, N. Peters, J.G. Wunning, "Laseroptical investigation of highly preheated combustion with strong exhaust gas recirculation", 27 Symp (Int) Combustion, 3197-3204, (1998)
  5. Frazan, H., Maringo, G. J., Riggs, J. D., Yagiela, A. S. and Newell, R. J., "Reburning with Powder River Basin Coal to Achieve $SO_2\;an\;NO_x$ Compliance", Proc. of the Power - Gen Sixth International Conference, Dallas, 175-187, (1993)
  6. Ji Soo Ha, Tae Kwon Kim and Sung Hoon Shim, "A numerical study of the air fuel ratio effect on the combustion characteristics in a MILD combustor", Korean Society of Environmental Engineers, Vol. 32, No. 6, 587-592, (2010)
  7. Tae Kwon Kim, Sung Hoon Shim, Hyuk Sang Chang and Ji Soo Ha, "A numerical study of the combustion characteristics in a MILD combustor with the change of the fuel and air nozzle position and air mass flow rate", Korean Society of Environmental Engineers, Vol. 33, No. 5, 325-331, (2011) https://doi.org/10.4491/KSEE.2011.33.5.325
  8. Sung Hoon Shim and Ji Soo Ha, "A study on the flow entrainment characteristics of a coaxial nozzle used in a MILD combustor with the change of nozzle position and flow condition", Korean Society of Environmental Engineers, Vol. 34, No. 2, 103-108, (2012) https://doi.org/10.4491/KSEE.2012.34.2.103
  9. S.V. Patankar, Numerical Heat Transfer and Fluid Flow, McGraw Hill Book, New York, (1980)