A swirl burner with different length to rim diameter ratio L/D. A three ratios 1,2 and 3 were studied. The results show that a change in the L/D ratio will effect on the stabilization position of the flame in downstream. The equivalence ratio of the mixture was taken a constant for the comparison sake. The flame stabilizes closer to the rim with an increase of the rim length.

1. Effect of rim geometry on burner stability
Jameel T. Al-naffakh1; Mohammed Al-fahham, PhD2; Qhatan Adnan Abed, PhD2
2AL-Furat Al-Awsat Technical University, Najaf Technical College
Jameel T. Al-Naffakh
AL-NAJAF ALASHRAF GOVERNORATE
Email: jameeltawfiq@gmail.com
Website: https://www.facebook.com/jameel.tawfiq
Phone: 07801008086
Contact
1. M. Konle and T. Sattelmayer, "Interaction of heat release and vortex breakdown during flame flashback driven by combustion induced vortex breakdown,"
Experiments in Fluids, vol. 47, no. 4, p. 627, 2009/05/24 2009.
2. I. M. Lasky, A. J. Morales, J. Reyes, K. A. Ahmed, and I. G. Boxx, "The Characteristics of Flame Stability at High Turbulence Conditions in a Bluff-Body
Stabilized Combustor," in AIAA Scitech 2019 Forum(AIAA SciTech Forum: American Institute of Aeronautics and Astronautics, 2019
3. M. Al-Fahham, F. A. Hatem, A. S. Alsaegh, A. Valera Medina, S. Bigot, and R. Marsh, "Experimental Study to Enhance Resistance for Boundary Layer
Flashback in Swirl Burners Using Microsurfaces," no. 50848, p. V04AT04A030, 2017.
4. S. Bauer, B. Hampel, and T. Sattelmayer, "Operability Limits of Tubular Injectors With Vortex Generators for a Hydrogen-Fueled Recuperated 100 kW Class
Gas Turbine," Journal of Engineering for Gas Turbines and Power, vol. 139, no. 8, pp. 082607-082607-8, 2017.
5. J. A. Lovett and W. J. Mick, "Development of a Swirl and Bluff-Body Stabilized Burner for Low-NOx, Lean-Premixed Combustion," no. 78804, p.
V003T06A033, 1995.
References
A swirl burner with different length to rim diameter
ratio L/D. A three ratios 1,2 and 3 were studied. The
results show that a change in the L/D ratio will effect
on the stabilization position of the flame in
downstream. The equivalence ratio of the mixture was
taken a constant for the comparison sake. The flame
stabilizes closer to the rim with an increase of the rim
length.
Abstract
The experimental tests focused in the first stage on
the effect of the rim length (L) to the diameter (D)
the results show that for a stable flame. The
equivalence ratio (ɸ) of the mixture was taken to be
0.9 where the system is stable and far away from
blowoff and flashback. The position of stabilization
downstream is effected significantly by the L/D ratio.
The burner with L/D equal 1 the flame stabilized
increase in L/D will stabilize the flame closer to the
burner rim. The increase L/D ratio cause the flame
front moves towards the upstream and stabilizing
closer to the rim Fig 2. The increase of rim length in
internal swirl flow caused to increase the swirl decay
which reduces the flow turbulence. The increase of
turbulence in the downstream flow will increase the
stability.
Introduction
The experimental rig is a swirl burner shown in Fig
1. The air is delivered tangentially from a blower.
The maximum airflow rate around 160l/s. The air
then mixed with LPG in the bottom of the burner
then the mixture goes through a swriler plate to
swirl the mixture and produce a premixed fuel. The
rest of the burner geometry is a divergent shape
which slows the flow to give the mixture the time to
be fully mixing, then the premixed fuel accelerated
through a convergent part and go through the
burner rim. The burner rim diameter is 5cm and the
length of the rim is variable (5cm, 10cm and 15cm)
to ensure L/D ratios (1,2 and 3). A pilot flame is
produced by a secondary ignition system consist
from a central nozzle with an adjustable length,
where it is ensured that the top of the pilot ignition
system nozzle lay at the same level of the burner
rim top edge. The flame stability is captured using a
1000 fps camera. The LPG is supplied from a
pressurized cylinder through a high-pressure plastic
hose connected to a bank of roto_meters.
Methods and Materials
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Discussion
The main point that concluded from the
experiments that the increase in the length of the
burner rim causes more decay in swirl strength
which reduce the coherence of the flow
downstream, such weakness in flow structure will
move the flame front closer to the rim and make
the system more vulnerable to the flashback issues.
Conclusions
The flame stability issues such as blow off and
flashback are the main challenges in the way to switch
fuel in main power plants. The swirl flame structure is
complicated and parameters that have an influence on
the swirling flame are not completely understood. The
CIVB is dominant flashback mechanism in swirl burner,
where a flame bubble is developed and the center of
the flow and propagate upstream. Many techniques
have been studied to avoid the CIVB[1]. Bluff body is
used to stabilizing the flame in downstream through
increase the turbulence of the flow in recirculation
zone witch help to reduce the tendency of a system to
flashback[2]. Although the bluff body is sold geometry
impeded in the central of the flow the bluff body
could be used to produce a central fuel or air flow[3,
4]. In boundary layer flashback the flame propagates
upstream in the low-velocity region near burner walls
or bluff body walls[5]. In more recent work use
stainless steel wire screen as a liner at the inner wall
of burner rim to alter the boundary layer[4], from
another hand the combination of the central injector
and wire mesh produce more balanced effect
between CIVB and BLF[6]. However, the aerodynamic
characteristics of the burner rim and their effects on
the burner stability still not clarified. In recent work,
the effect of the burner length to diameter ratio (L/D)
on the flame stability were studied.
Results
Figure 3. The flame front height at different rim
length (L) a) 5cm b) 10cm c) 15cm..
Figure 2. Experimental rig
1 Liter of Diesel is equivalent to 0.796 KG of LPG
(roughly). In other words, to produce a specific
amount of energy, around 20% less LPG would be
used as compared to diesel e.g. To produce 2000
MMBtus, roughly 56000 Liters of Diesel would be used
whereas roughly 44000 kg of LPG would be used to
produced same energy. 1 kg of LPG (1.85 liter) cost
370 ID. 1 kg of diesel (1.3 liter) costs 520 ID.
In total using LPG will cut fuel cost by 41%.
Why LPG ?
Figure1. LPG and Diesel Heating value