14th North American Waste to Energy Conference
May 1-3, 2006, Tampa, Florida USA
NAWTEC14-3195
Pulse Combustion Technology
Gene Plavnik
Heat Technologies, Inc.
PO Box 88413, Atlanta, GA 30356
Tel (770) 804 9309
Abstract: Pulse combustion has been used in a variety of ways since first being
discovered in 1877. This a combustion process that occurs under oscillatory conditions
with changing state variables, such as pressure, temperature and velocity. This paper
looks at the historic uses of pulse combustion, and it provides an overview of this unique
process.
Pulse combustion has been used to amplify thrust power with the German V-I
rockets. Pulse combustion has been used to optimize flame efficiencies, and it is now re­
emerging in many new industrial applications including some for Waste to Energy.
What is Pulse Combustion?
Furthermore, acoustic oscillations
Pulsating Combustion is a combustion
generated in the combustion process are
process that occurs under oscillatory
coupled with heat and released into the
conditions. That means, that the state
process at the same time.
variables, such as pressure, temperature,
velocity of combustion gases, etc., that
The first known example of pulse
describe the condition in the combustion
combustion is so called" singing flame"
zone, vary periodically with time.
discovered by Dr. Higgins in 1 777.
Fig 1. Discovery of a Singing Flame by Dr. Higgins, 1777
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Copyright © 2006 by ASME
His studies were followed by Deluc,
The first known attempts to utilize pulse
Chladni, Faraday, Tybdall, Rayleigh,
combustion process occurred at the tum
which showed that sound of
of 20th century. The most well known
considerable amplitude can be generated
application is German V-I rocket motor,
when a gas flame is placed in a larger
or a buzz bomb. Another good example
diameter tube. The observations also
of a pulse combustion device is a
indicated that when a certain set of
Helmholz burner. The principle of this
conditions is satisfied, an interaction
burner is utilized by several boiler
between the burner-flame and generated
companies in their commercial products.
acoustic oscillations can take place.
Fig. 2 An
unmanned
airplane with a pulse rocket engine: the V-I "buzz bomb."
Helmholtz and Schmidt combustors of
How Does Pulse Combustion Work?
flapper valves on air and fuel lines. In
All pulse burners can be divided in three
contrast, the other type of pulse burners
sections: the inlet, the combustion
(including our version), have no flapper
chamber, and the exhaust section. The
valves but consists of aerdynamic air
inlet section can consist, in case of the
inlet on the air side.
Copyright © 2006 by ASME
144
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Fig 3. Schematic Diagram and Operation of a Pulse Burner
To start the operation, the combustion
and fuel into the combustion chamber
reactants are delivered into the
where it is re-ignited by the hot
combustion chamber via air and fuel
environment. The negative pressure
lines or flapper valves, where a spark
created in the burner volume also creates
plug or a pilot ignites the mixture. The
reversal motion of the part of the exhaust
initiation of the combustion process
gases back into the combustion chamber
creates a sudden pressure rise that closes
which facilitate ignition of fresh charge
flapper valves and combustion gases
of the combustion reactants and next
move downstream towards the end of the
pressure rise in the combustion system.
exhaust tube. This movement, in turn,
The combustion process now repeats
produces a negative pressure in the
itself indefinitely without spark plug and
burner itself and allows flapper valves to
the operation is controlled by acoustic
open and allow next portion of the air
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Copyright © 2006 by ASME
laws and takes place at a created single
frequency.
the three Ts.
Pulse Combustion and Heat Transfer
The three Ts are Time,
Turbulence and Temperature.
High reversible velocities of combustion
gases in pulse combustion have potential
Let us try to look at three Ts, and
for improvement of heat transfer.
emissions in conjunction with each
other.
This could be accomplished by
introducing pulse combustion process in
As it is known from the classical theory
the area where the combined heat
of Zeldovich, there are three different
transfer process is present, for example
type of NO x:
a)
convective radiant and conductive type.
Thermal NOx formed during
combustion process
Reversible motion of combustion gases
allows diminish boundary layer formed
b)
Fuel NOx
on the heat transfer surfaces, and, in
c)
Prompt NOx
tum, allow better heat transfer from
combustion gases to the surfaces itself,
Time. Term time really means residence
resulting in increase of conductive heat
time of combustion reactants to
transfer as well. Some works show
complete the combustion and"become"
improvements in heat transfer by the
combustion gases. Typically residence
factor of 2.5 depending on application.
time of a high velocity steady state
burner is about 20 milliseconds. The
same residence time in a pulse burner is
Pulse Combustion and Emissions.
2-8 milliseconds. The short residence
In general, any combustion technology is
time, in tum, leaves less time for thermal
characterized by its NOx and CO
NOx to be formed.
emissions, and burner equivalence ratio
or coefficient of excess of air. Also any
Turbulence: This is rather relates to
combustion technology is dependent on
advanced mixing formed by reversible
flows of combustion gases. Pulse
Copyright © 2006 by ASME
146
combustion takes oxygen that is
As it was mentioned above, part of the
available for combustion and converts it
exhaust gases is invited back into the
into "usable" oxygen, thus allowing
combustion process. In addition to the
combustion process with very low
reducing of the flame temperature, this
coefficient of excess of air. In addition,
part of the combustion gases creates
the same high reversible velocities of the
natural automatic flue gas re-circulation,
combustion gases are responsible for the
where NOx oxides are already formed,
high heat and mass transfer rates within
thus, reduces further formation of the
the process.
NOx.
Temperature. This term relates to the
All of the factors above create very
temperature of the flame. Usually the
specific conditions of the combustion
thermal NOx are formed around
that naturally creates lower level of NOx
stoichiometric temperature when the
ellllSSlOns.
excess of air is low and the combustion
is close to its complete conditions. Pulse
Current Applications
combustion process creates reversible
flow where fresh portion of the
Today pulse combustion technology is
combustion reactant is continuously and
successfully applied in boilers of
oscillatory is brought into the
commercial scale, spray, and conveyer
combustion zone, which decreases the
drying. There were efforts to utilize this
average flame temperature, as the
technology in cement pyro-processing,
research show, by four hundred degrees
waste incineration and there are efforts
and creates less favorable conditions for
to apply this technology to the waste-to­
the thermal NOx formation.
energy systems.
Add ional factor that is present in pulse
Potential Benefits of Utilization of the
combustion and is attributive to its low
Pulse Combustion Technology in the
emissions is Automatic Natural Flue
field of Waste-To-Energy Systems
Gas Re-circulation.
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Copyright © 2006 by ASME
The pulse combustion systems can be
The pulse combustion systems can serve
successfully applied as an alternative to
a powerful heat transfer booster of"in­
soot blowers. It generates a lot more
situ" type where it appears necessary.
powerful level of sound (about 300
The pulse combustion systems can serve
times) and can be tailor-designed to the
as fast and very powerful ignitor of the
specifics of the area to be cleaned
main combustion process.
References:
1.
Tyndall, J. Sound. D. Appleton & Company, New York
2.
Keller, J. O. Pulse Combustion: The Mechanism of NO x Production. Combustion
and Flame 80, 219-237, 1990.
3.
P. A. Eibeck, et al. Pulse Combustion: Impinging Heat Transfer Enhancement.
Combustion Science and Technology Volume 94, 1-6, 1993
4.
Pulse Combustion Boiler, Fulton Thermal Products Co, Product Brochure
5.
C. Pope et al. Control of NO x Emissions in Confined Flames by Oscillations.
Combustion and Flame 113 : 13-26, 1998
6.
Plavnik, Z. et al. Pulse Combustion System and Method, US Patent 6,210,149 Bl,
2001
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