Nitrogen-Diluted Methane Flames in the Near-and Far-Field

With the increased utilization of multicomponent fuels, such as natural gas and biogas, in industrial applications, there is a need to be able to effectively model and predict the properties of jet flames for mixed fuels. In addition, the interaction of these diluted fuels with outside influences (such as differing levels of coflow air) is a primary consideration. Experiments were performed on methane jet flames under the influence of varying levels of nitrogen dilution, from low Reynolds number lifted regimes to blowout, observing the influence of the nitrogen on lifted flame height and flame chemiluminesence images. These findings were analyzed and compared with existing lifted jet flame relations, such as the flammable region approximation proposed by Tieszen et al., as well as to undiluted flames. The influence of nitrogen dilution was seen to have an effect on the liftoff height of the flame, as well as the blowout velocity of the flame, but was seen to have a less pronounced effect compared with flames with coflowing air.

Download Full-text

Volumetric PIV and 2D OH PLIF imaging in the far-field of a low Reynolds number nonpremixed jet flame

Measurement Science and Technology ◽

10.1088/0957-0233/24/2/024003 ◽

2012 ◽

Vol 24 (2) ◽

pp. 024003 ◽

Cited By ~ 16

Author(s):

M Gamba ◽

N T Clemens ◽

O A Ezekoye

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Far Field ◽

Jet Flame ◽

Low Reynolds

Download Full-text

Steady approach of unsteady low-Reynolds-number flow past two rotating circular cylinders

Journal of Fluid Mechanics ◽

10.1017/jfm.2013.503 ◽

2013 ◽

Vol 736 ◽

pp. 414-443 ◽

Cited By ~ 5

Author(s):

Y. Ueda ◽

T. Kida ◽

M. Iguchi

Keyword(s):

Reynolds Number ◽

Circular Cylinder ◽

Stokes Equations ◽

Low Reynolds Number ◽

Vortex Method ◽

The Self ◽

Circular Cylinders ◽

Far Field ◽

Flow Past ◽

Low Reynolds

AbstractThe long-time viscous flow about two identical rotating circular cylinders in a side-by-side arrangement is investigated using an adaptive numerical scheme based on the vortex method. The Stokes solution of the steady flow about the two-cylinder cluster produces a uniform stream in the far field, which is the so-called Jeffery’s paradox. The present work first addresses the validation of the vortex method for a low-Reynolds-number computation. The unsteady flow past an abruptly started purely rotating circular cylinder is therefore computed and compared with an exact solution to the Navier–Stokes equations. The steady state is then found to be obtained for $t\gg 1$ with ${\mathit{Re}}_{\omega } {r}^{2} \ll t$, where the characteristic length and velocity are respectively normalized with the radius ${a}_{1} $ of the circular cylinder and the circumferential velocity ${\Omega }_{1} {a}_{1} $. Then, the influence of the Reynolds number ${\mathit{Re}}_{\omega } = { a}_{1}^{2} {\Omega }_{1} / \nu $ about the two-cylinder cluster is investigated in the range $0. 125\leqslant {\mathit{Re}}_{\omega } \leqslant 40$. The convection influence forms a pair of circulations (called self-induced closed streamlines) ahead of the cylinders to alter the symmetry of the streamline whereas the low-Reynolds-number computation (${\mathit{Re}}_{\omega } = 0. 125$) reaches the steady regime in a proper inner domain. The self-induced closed streamline is formed at far field due to the boundary condition being zero at infinity. When the two-cylinder cluster is immersed in a uniform flow, which is equivalent to Jeffery’s solution, the streamline behaves like excellent Jeffery’s flow at ${\mathit{Re}}_{\omega } = 1. 25$ (although the drag force is almost zero). On the other hand, the influence of the gap spacing between the cylinders is also investigated and it is shown that there are two kinds of flow regimes including Jeffery’s flow. At a proper distance from the cylinders, the self-induced far-field velocity, which is almost equivalent to Jeffery’s solution, is successfully observed in a two-cylinder arrangement.

Download Full-text

Aspect Ratio Effects of Elliptic Co-Flow on Turbulent Jet Flame Structures

Engineering Technology Conference on Energy, Parts A and B ◽

10.1115/etce2002/cae-29008 ◽

2002 ◽

Author(s):

Ahsan R. Choudhuri ◽

Sayela P. Luna ◽

S. R. Gollahalli

Keyword(s):

Reynolds Number ◽

Aspect Ratio ◽

Flame Structure ◽

Major Axis ◽

Combustion Characteristics ◽

Flame Height ◽

Pollutant Emission ◽

Jet Flame ◽

Fuel Jet ◽

Emission Flame

The aspect ratio effects of elliptic co-flow on the structure of a turbulent propane diffusion flame from a circular tube have been presented. Pollutant emission, flame radiation, flame structure, and soot concentration have been measured. The fuel jet exit Reynolds number is 2700, and the exit Reynolds number for the co-flow is 4010 and 8025 based on the minor and major axis respectively. The results are compared with the measurements from the experiments in a circular co-flow, which is the baseline condition for the present study. The pollution characteristics and the structure of the flame in the elliptic co-flow are significantly different from those in the circular co-flow. The NO emission is higher and the CO emission is lower in the elliptic co-flow. Elliptic co-flow flame produces less soot than circular co-flow flame. The study shows that the elliptic co-flow aspect ratio has a controlling influence on various combustion characteristics. In general, it is seen that as the aspect ratio of the elliptic co-flow is increased from 2:1 to 4:1, the entrainment of air increases and thus the combustion characteristics are enhanced. Compared to 2:1 AR co-flow flames, the flames with 4:1 AR co-flow are more stable, have a lower flame height, produce more NO and less CO, the flame peak temperature is higher, are less sooty, and radiate less. Flame spectral measurements show that the 4:1 aspect ratio flames produce more OH, CH, C2 and H2O radicals in the near-burner region than the 2:1 co-flow flames as a result of higher fuel oxidation.

Download Full-text

Low-Reynolds-number flow through two-dimensional shunts

Journal of Fluid Mechanics ◽

10.1017/jfm.2013.99 ◽

2013 ◽

Vol 723 ◽

pp. 21-39 ◽

Cited By ~ 3

Author(s):

A. Setchi ◽

A. J. Mestel ◽

K. H. Parker ◽

J. H. Siggers

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Industrial Applications ◽

Two Dimensional ◽

Low Reynolds Number Flow ◽

Reynolds Number Flow ◽

Flow Profiles ◽

Number Flow ◽

Flow Through ◽

Low Reynolds

AbstractMotivated by numerous biological and industrial applications relating to bypasses, mixing and leakage, we consider low-Reynolds-number flow through a shunt between two channels. An analytical solution for the streamfunction is found by matching biorthogonal expansions of Papkovich–Fadle eigenfunctions in rectangular subregions. The general solution can be adapted to model a variety of interesting problems of flow through two-dimensional shunts by imposing different inlet and outlet flux distributions. We present several such flow profiles but the majority of results relate to the particular problem of a side-to-side anastomosis in the small intestine. We consider different flux fractions through the shunt with particular emphasis on the pressure and recirculating regions, which are important factors in estimating health risks pertaining to this surgical procedure.

Download Full-text