Velocity fields of fuel lean premixed turbulent opposed jet flames

Abstract Velocity measurements in the turbulent reacting flow created by an opposed nozzle configuration are reported with emphasis on the axis and stagnation plane. The instrumentation comprised particle image velocimetry (PIV) with Al2O3 particles and silicon oil droplets added upstream of both nozzles and with the laser sheet passing through the axis between the nozzles. Results are reported for a set of fuel lean (0.7 ⩽ ϕ ⩽ 0.9) turbulent premixed counterflow CH4, C2H4 and C3H8 flames covering a range of Reynolds numbers (4900 ⩽ Re ⩽ 13,700). The study extends past work featuring single point measurements to include comparisons of mean and fluctuating velocity components along the stagnation point streamline and stagnation plane. The study permits a more detailed assessment of flame structures for a comparatively wide range of conditions and experimental results are further compared with computations using eddy viscosity and comprehensive second moment closures for velocity and scalar fields. The effects of closure approximations and boundary conditions were explored and it is shown that a primary sensitivity is associated with the prescribed initial length scale of turbulence. The study also shows that modifications, based on the ratio of the turbulent to mean strain timescale, do not have a significant impact in the current flow. However, sensitivities to closure approximations relating to mean and fluctuating pressure gradient terms are confirmed. Comparisons with data obtained for the corresponding isothermal flows show that the recorded levels of anisotropy are strongly affected by heat release.

[1]  P. Libby,et al.  Premixed flames in stagnating turbulence part III—The k - ε theory for reactants impinging on a wall , 1992 .

[2]  K. Sreenivasan.  On the scaling of the turbulent energy dissipation rate , 1984 .

[3]  P. Libby,et al.  Pre-mixed flames in stagnating turbulence , 2001 .

[4]  J. Whitelaw,et al.  Control of NOx Emissions in Confined Flames by Oscillations , 1998 .

[5]  L. Kostiuk,et al.  Experimental study of premixed turbulent combustion in opposed streams. Part II—Reacting flow field and extinction , 1993 .

[6]  Carl D. Meinhart,et al.  Vortex organization in the outer region of the turbulent boundary layer , 2000, Journal of Fluid Mechanics.

[7]  Large-eddy simulation of a counterflow configuration with and without combustion , 2000 .

[8]  R. Lindstedt,et al.  Second moment modeling of premixed turbulent flames stabilized in impinging jet geometries , 1998 .

[9]  Measurement volume defined by peak-finding algorithms in cross-correlation particle image velocimetry , 2001 .

[10]  R. Lindstedt,et al.  Modeling of premixed turbulent flames with second moment methods , 1999 .

[11]  Manuel V. Heitor,et al.  Simultaneous velocity and temperature measurements in a premixed flame , 1985 .

[12]  R. Cheng,et al.  The influence of burner geometry on premixed turbulent flame propagation , 1991 .

[13]  Pascale Domingo,et al.  Laminar flamelet expressions for pressure fluctuation terms in second moment models of premixed turbulent combustion , 2000 .

[14]  C. Sung,et al.  Thermophoretic Effects on Seeding Particles in LDV Measurements of Flames , 1994 .

[15]  J. Westerweel,et al.  The effect of a discrete window offset on the accuracy of cross-correlation analysis of digital PIV recordings , 1997 .

[16]  F. Williams,et al.  Turbulent Reacting Flows , 1981 .

[17]  J. B. Moss,et al.  Unified modeling approach for premixed turbulent combustion—Part I: General formulation , 1985 .

[18]  S. Pope,et al.  A pdf modeling study of self‐similar turbulent free shear flows , 1987 .

[19]  L. Kostiuk,et al.  Premixed turbulent combustion in counterflowing streams , 1989 .

[20]  C. Law,et al.  Velocity and scalar fields of turbulent premixed flames in stagnation flow , 1988 .

[21]  H. Sung,et al.  Development of a near-wall turbulence model and application to jet impingement heat transfer , 2000 .

[22]  C. Mounaïm-Rousselle,et al.  Strain effects on the structure of counterflowing turbulent premixed flames , 1994 .

[23]  S. Orszag,et al.  Development of turbulence models for shear flows by a double expansion technique , 1992 .

[24]  M. G. Mungal,et al.  Simultaneous measurements of velocity and CH distributions. Part 1: jet flames in co-flow , 2003 .

[25]  Robert K. Cheng,et al.  Experimental study of premixed turbulent combustion in opposed streams. Part I—Nonreacting flow field , 1993 .

[26]  Ronald J. Adrian,et al.  Dynamic ranges of velocity and spatial resolution of particle image velocimetry , 1997 .

[27]  R. Lindstedt,et al.  Velocity and Strain-Rate Characteristics of Opposed Isothermal Flows , 2005 .

[28]  C. Sung,et al.  Further studies on effects of thermophoresis on seeding particles in LDV measurements of strained flames , 1996 .

[29]  R. Adrian,et al.  Effect of resolution on the speed and accuracy of particle image velocimetry interrogation , 1992 .

[30]  Stephen B. Pope,et al.  A generalized Langevin model for turbulent flows , 1986 .

[31]  J. H. Whitelaw,et al.  Extinction timescales of periodically strained, lean counterflow flames , 1999 .

[32]  Acoustic-wave interactions with counterflow single- and twin-premixed flames: Finite-rate kinetics, heat release and phase effects , 2007 .

[33]  Francis H. Harlow,et al.  Transport Equations in Turbulence , 1970 .

[34]  Piotr Wolanski,et al.  Particle image velocimetry (PIV) analysis of flame structure , 2001 .