Pulse Combustion Technology - Columbia Engineering

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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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.


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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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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


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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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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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