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Title: Mixing and chemical reaction in an idealized swirl chamber

Abstract

A vorticity-based, low-Mach-number model for simulating combustion in closed chambers is constructed. Numerical scheme is based on a mixed finite-difference pseudo-spectral discretization of the governing equations. Discrete evolution equations are integrated in time using a predictor-corrector scheme, while discrete elliptic systems are inverted with the help of fast-Poisson solver. Scheme is applied to analyze mixing and combustion in an idealized swirl cavity, which consists of the annular space between a spinning inner cylinder and a stationary reaction. To this end, we assume that the oxidizer and fuel are initially separated by a thin mixed region, and carefully control mixing levels by varying the duration of the swirl-driven mixing period. The mixture is then ignited along the boundary of the inner cylinder. When pre-mixing is complete, an axisymmetric flame front is established, and the reactants are consumed as the front propagates radially outwards. When the charge is partially mixed, combustion in the early stages predominantly occurs within a non-uniform premixed front. As this non-uniform front approaches the outer cylinder, a transition to a distributed combustion regime occurs. Following the transition, the remaining fuel burns at a slow rate within non-premixed flames which wrap around the inner cylinder. Results show that themore » mixing time has substantial effects on the pressure rise within the cavity and on the evolution of the burnt fraction, and that these effects become more pronounced as the Damkoehler number increases.« less

Authors:
;  [1];  [2]
  1. Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Mechanical Engineering
  2. Sandia National Labs., Livermore, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States); Department of Defense, Washington, DC (United States)
OSTI Identifier:
234597
Report Number(s):
SAND-96-8529C; CONF-960772-1
ON: DE96006765
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: 26. international symposium on combustion, Naples (Italy), 28 Jul - 2 Aug 1996; Other Information: PBD: Jan 1996
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; 40 CHEMISTRY; COMBUSTION CHAMBERS; MIXING; VORTEX FLOW; ROTATION; OXIDIZERS; FUELS; IGNITION

Citation Formats

Knio, O M, Worlikar, A S, and Najm, H N. Mixing and chemical reaction in an idealized swirl chamber. United States: N. p., 1996. Web.
Knio, O M, Worlikar, A S, & Najm, H N. Mixing and chemical reaction in an idealized swirl chamber. United States.
Knio, O M, Worlikar, A S, and Najm, H N. 1996. "Mixing and chemical reaction in an idealized swirl chamber". United States. https://www.osti.gov/servlets/purl/234597.
@article{osti_234597,
title = {Mixing and chemical reaction in an idealized swirl chamber},
author = {Knio, O M and Worlikar, A S and Najm, H N},
abstractNote = {A vorticity-based, low-Mach-number model for simulating combustion in closed chambers is constructed. Numerical scheme is based on a mixed finite-difference pseudo-spectral discretization of the governing equations. Discrete evolution equations are integrated in time using a predictor-corrector scheme, while discrete elliptic systems are inverted with the help of fast-Poisson solver. Scheme is applied to analyze mixing and combustion in an idealized swirl cavity, which consists of the annular space between a spinning inner cylinder and a stationary reaction. To this end, we assume that the oxidizer and fuel are initially separated by a thin mixed region, and carefully control mixing levels by varying the duration of the swirl-driven mixing period. The mixture is then ignited along the boundary of the inner cylinder. When pre-mixing is complete, an axisymmetric flame front is established, and the reactants are consumed as the front propagates radially outwards. When the charge is partially mixed, combustion in the early stages predominantly occurs within a non-uniform premixed front. As this non-uniform front approaches the outer cylinder, a transition to a distributed combustion regime occurs. Following the transition, the remaining fuel burns at a slow rate within non-premixed flames which wrap around the inner cylinder. Results show that the mixing time has substantial effects on the pressure rise within the cavity and on the evolution of the burnt fraction, and that these effects become more pronounced as the Damkoehler number increases.},
doi = {},
url = {https://www.osti.gov/biblio/234597}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 1996},
month = {Mon Jan 01 00:00:00 EST 1996}
}

Conference:
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