Liquid fuel burner

Disclosed is a burner for burning liquid fuel that is able to obtain a long flame in which the proportion of the luminous flame portion is large, and thereby particularly effective for radiant heat transfer. This liquid fuel burner is composed of a fuel feed pipe (4) having a fuel spray nozzle (3) at its distal end, a combustion-assisting gas feed pipe (6) provided concentrically on the outside of the fuel feed pipe (4) to form a combustion-assisting gas passage (5), and an orifice member (7) arranged within the above-mentioned fuel feed pipe (4) at an interval from the distal end of the fuel feed pipe (4). In addition, the orifice (9) of the orifice member (7) and the fuel spray nozzle (3) of the above-mentioned fuel feed pipe (4) are mutually eccentric.

TECHNICAL FIELD 
The present invention relates to a liquid fuel burner, and more 
particularly, to a liquid fuel burner suitable for various types of 
furnaces using radiant heat transfer from a flame, such as a glass melting 
furnace. 
BACKGROUND ART 
In glass melting furnaces, a burner has conventionally been used in which a 
liquid fuel, such as fuel oil or kerosene, is burned in air for uniform 
temperature rise and heating of the glass. In these furnaces, a melting 
method is employed whereby the flame is not brought in direct contact with 
the glass, but rather the glass is heated primarily by transfer of radiant 
heat. 
However, when air is used as the combusting-assisting gas, the volume of 
exhaust gas increases since nitrogen is contained in the air that does not 
contribute to combustion. Moreover, the heat loss due to the exhaust gas 
carried away from the furnace also increases, thus resulting in poor 
thermal efficiency. In addition, the NOX emission level produced is also 
very high. 
The use of oxygen for the combusting-assisting gas is then considered. When 
oxygen is used for the combustion-assisting gas, since the amount of 
combustion exhaust gas is reduced to roughly 1/5 in comparison with that 
in the case of using air, the amount of heat carried away by the 
combustion exhaust gas is also reduced to roughly 1/4 to 1/5. Together 
with this resulting in higher thermal efficiency, the amount of NOX 
produced is also considerably reduced. 
However, the flame produced by a conventional liquid fuel burner that uses 
oxygen gas for the combustion-assisting gas is extremely disadvantageous 
for use as melting means consisting primarily of radiant heat transfer 
from the flame. The following provides a detailed description of this. 
As disclosed in, for example, the specification of U.S. Pat. No. 4,216,908, 
liquid fuel gas burners of the prior art that use oxygen gas for the 
combusting-assisting gas are composed of a fuel feed pipe having a fuel 
spray nozzle at its distal end, a combusting-assisting gas feed pipe 
provided concentrically on the outside of said fuel supply pipe to form a 
combusting-assisting gas passage, a swirler arranged within the 
above-mentioned fuel supply pipe in close proximity to the above-mentioned 
fuel spray nozzle, and a plurality of combustion-assisting gas spray 
nozzles provided continuous with the above-mentioned combustion-assisting 
gas passage around the above-mentioned fuel spray nozzle. 
Together with liquid fuel being sprayed in the form of a mist from the 
above-mentioned fuel spray nozzle at a large angle of 30 degrees, or more, 
through the swirler, oxygen gas is flowed from the above-mentioned 
combustion-assisting nozzles at a velocity of from 50 to 200 m/sec 
followed by combustion of the sprayed liquid fuel. 
With this structure, the liquid fuel is vigorously mixed with the oxygen 
gas and burned at high speed. As a result, a high-temperature flame having 
a short flame length is formed producing at a temperature 600.degree. to 
800.degree. C. higher than the case of using air. By then directing this 
high-temperature flame onto the object to be heated, the object to be 
heated can be heated to a high temperature. Moreover, since the radical 
substances contained in the flame generate heat when they change to stable 
substances of carbon dioxide and water after colliding with the object to 
be heated, the object to be heated can be heated to even higher 
temperatures. 
Thus, although burners of the prior art that use oxygen gas for the 
combustion-assisting gas are effective for direct heat melting of the 
object to be heated, since velocity of oxygen gas flowed from the 
above-mentioned combustion-assisting gas nozzles is rapid, mixing of the 
liquid fuel and oxygen gas is accelerated. Since the burning velocity 
becomes correspondingly faster, flame length becomes shorter. Moreover, 
since the proportion of the luminous flame portion of the flame that is 
effective in radiant heat transfer is short at about 40 to 60% of flame 
length (in the case of using a petroleum-based liquid fuel, such as fuel 
oil or kerosene), there were problems when this is used for melting means 
consisting primarily of radiant heat transfer from a flame. 
Therefore, it is an object of the present invention to provide a liquid 
fuel burner that is able to increase combustion efficiency to a high level 
by using gas having an oxygen concentration of 50% or more for the 
combustion assisting gas, and that is able to obtain a flame that is long 
and of which a large proportion is composed of a luminous flame portion no 
be effective in radiant heat transfer, while simultaneously taking 
advantage of the merit of being able to reduce NOX. 
DISCLOSURE OF THE INVENTION 
The liquid fuel burner of the present invention is composed of a fuel feed 
pipe having a fuel spray nozzle at its distal end, a combustion-assisting 
gas feed pipe provided concentrically on the outside of said fuel feed 
pipe to form a combustion-assisting gas passage, and an orifice member 
arranged within the fuel feed pipe at an interval from the distal end of 
said fuel feed pipe; wherein the orifice of said orifice member and the 
fuel spray nozzle of the fuel feed pipe are mutually eccentric. 
In addition, according to the present invention, there is provided a blade 
for swirling the combustion-assisting gas in the combusting-assisting gas 
passage of the combustion-assisting gas feed pipe of an improved fuel gas 
burner, as described above. 
Moreover, in the present invention, the eccentricity ratio as determined by 
the ratio of the distance between the center line of the fuel spray nozzle 
and the center line of the orifice to the distance in the axial direction 
between said fuel spray nozzle and said orifice is 1.0 to 4.0. 
In addition, in the present invention, the nozzle velocity of 
combustion-assisting gas flowed from the combusting-assisting gas passage 
is 1 to 20 m/sec. 
Moreover, the combusting-assisting gas of the present invention has an 
oxygen concentration of 50% or more. 
As described above, according to the liquid fuel burner of the present 
invention, liquid fuel is sprayed from a fuel spraying nozzle after being 
diffused in a gap between the orifice member and the distal end of the 
fuel feed pipe after passing through the orifice. At this time, since the 
orifice and the fuel spray nozzle are mutually eccentric, the liquid fuel 
is sprayed from the fuel spray nozzle at a spraying angle smaller than 
that of the prior art, thus increasing the distance over which the sprayed 
liquid fuel is projected. On the other hand, the combustion-assisting gas 
is sprayed from the open end of the combustion-assisting gas passage so as 
to envelope the atomized liquid fuel. Since the liquid fuel is then burned 
in this state, a flame is obtained in which the flame length is long and 
the proportion of the luminous flame portion is large. 
The flame length is increased because the liquid fuel that has been 
projected over a greater distance burns over its entire length as a result 
of being sprayed at an acute angle from the above-mentioned fuel spray 
nozzle. The proportion of the luminous portion of the flame is increased 
because, in the liquid fuel burner of the present invention, the mixing 
rate of the liquid fuel and combustion-assisting gas is slower than in 
liquid fuel burners of the prior art in which the liquid fuel is burned 
all at once. As a result, the manner in which the liquid fuel burns is 
thought to be less intense. Incidentally, if a gas, such as air having an 
oxygen gas concentration of less than 50% is used for the 
combusting-assisting gas, it becomes difficult to completely burn the 
liquid fuel. Since this results in the production of soot caused by 
incomplete combustion, in the present invention, it is preferable to use 
an oxygen-rich gas having an oxygen gas concentration of 50% or more, or 
high purity oxygen, for the combustion-assisting gas, as described above. 
This is because a better flame can be formed in the case where the 
concentration of oxygen higher. 
Thus, since the liquid fuel burner of the present invention is able to 
obtain a flame having a long flame length and a large proportion of 
luminous flame portion, in the case of being used for glass melting, and 
so forth, consisting primarily of radiant heat transfer, melting effects 
are improved and the amounts of liquid fuel and oxygen gas used can be cut 
down. In addition, since the combustion flame has a narrow spindle-shape, 
the heat load due to combustion on the end of the burner is reduced. 
Consequently, it becomes possible to eliminate the need for a water 
cooling jacket, which was indispensable in liquid fuel burners of the 
prior art that used oxygen gas. 
In addition, the liquid fuel burner of the present invention is 
concentrically provided with a combustion-assisting gas feed pipe for 
forming a secondary combustion-assisting gas passage on the outside of the 
combustion-assisting gas feed pipe for forming a primary 
combustion-assisting gas passage. 
Moreover, in the present invention, the ratio of the flow volume of 
combusting-assisting gas of the primary combustion-assisting gas passage 
to the flow volume of the combustion-assisting gas of the secondary 
combustion-assisting gas passage is 0.25 to 1.0. 
In addition, in the present invention, the ratio of the nozzle velocity of 
combustion-assisting gas of the primary combustion-assisting gas passage 
to the nozzle velocity of the combustion-assisting gas of the secondary 
combusting-assisting gas passage is 0.3 to 1.0. 
Moreover, in the present invention, the nozzle velocity of the 
combustion-assisting gas of the primary combustion-assisting gas passage 
is 10 to 40 m/sec in terms of the state of a temperature of 0.degree. C. 
and atmospheric pressure of 1 atm. 
The liquid fuel burner of the present invention is able to form an even 
longer combustion flame by providing a combustion-assisting gas feed pipe 
for forming a secondary combustion-assisting gas passage concentrically on 
the outside of the combustion-assisting gas feed pipe for forming a 
primary combustion-assisting gas passage. Moreover, nearly all of the 
combustion flame is composed of a luminous flame portion, which further 
improves melting effects in the case of being used for glass melting, and 
so on, consisting primarily of radiant heat transfer.

BEST MODE FOR CARRYING OUT THE INVENTION 
The best mode for carrying out the invention will be described below in 
detail by referring to the drawings. 
FIG. 1 is a cross-sectional view of the essential portion indicating a 
first embodiment of the liquid fuel burner of the present invention. This 
liquid fuel burner 1 is composed of a fuel feed pipe 4 having a fuel spray 
nozzle 3 at the distal end thereof continuous with a fuel passage 2, a 
combustion-assisting gas feed pipe 6 provided concentrically on the 
outside of said fuel feed pipe 4 to form a combustion-assisting gas 
passage 5, and an orifice-containing member 7 arranged within said fuel 
feed pipe 4 located at an interval from the distal end of said fuel feed 
pipe 4. The above-mentioned fuel spray nozzle 3 is formed with its axis on 
a center line 8 of the fuel feed pipe 4. A plurality of orifices 9 in the 
member 7, for example three, are formed at positions wherein their axes 
are eccentric to the axis of the fuel spray nozzle 3. The three orifices 9 
are each of the same diameter, and are arranged with their axes at equal 
intervals about the circumference centering on the center line 8. 
The interval between the orifice-containing member 7 and the end of the 
fuel feed pipe 4 serves as a fuel atomization portion 10. The distal end 
of the combustion-assisting gas passage 5 is a combustion-assisting gas 
exit port 11. 
Various types of liquid fuels can be used for the liquid fuel, examples of 
which include kerosene, gas oil and fuel oil. 
If a gas such as air having an oxygen gas, concentration of less than 50%, 
is used for the combustion-assisting gas, it becomes difficult to 
completely combust the liquid fuel. Since soot is produced due to 
incomplete combustion, in the present invention it is desirable to use an 
oxygen-rich gas having an oxygen gas concentration of 50% or more, or high 
purity oxygen, for the combusting-assisting gas. This is because a better 
flame can be formed in the case where the concentration of oxygen is 
higher. 
According to the above-mentioned constitution, the liquid fuel and 
combustion-assisting gas are supplied by a known means to passages 2 and 
5, respectively. The liquid fuel passes through the orifices 9 and 
diffuses in the atomization portion 10. Next, it is sprayed from the fuel 
spray nozzle 3, after which it is combusted after mixing with 
combustion-assisting gas that flows from the combusting-assisting gas exit 
port 11 of combustion-assisting gas passage 5. 
Although varying slightly according to the length (L) and surface area of 
the fuel spray nozzle 3, it was experimentally confirmed that the spraying 
angle of liquid fuel sprayed from said fuel spray nozzle 3 changes mainly 
according to the ratio of the distance (M) between the center line of the 
fuel spray nozzle 3 and the center line of the orifice 9, to the distance 
(S) in the axial direction between said fuel spray nozzle 3 and said 
orifice 9, namely the gap of fuel atomization portion 10. In other words, 
this changes according to the value of M/S (referred to as eccentricity). 
If this eccentricity is less than 1.0, although the projected distance of 
the fuel increases, since diffusion (atomization) of the liquid fuel 
sprayed from the above-mentioned fuel spray nozzle 3 becomes inadequate, a 
portion of the liquid fuel remains unburned. On the other hand, if 
eccentricity is in excess of 4.0, diffusion of the liquid fuel is good. 
However, the spraying angle of the liquid fuel increases, resulting in 
shorter flame length. Based on such findings, by setting eccentricity to 
within a range of 1.0 to 4.0, the spraying angle of the liquid fuel can be 
reduced to 5 to 10 degrees while still obtaining adequate diffusion. Thus, 
a long flame can be obtained. 
FIG. 2 is a cross-sectional view of the essential portion indicating a 
second embodiment of the present invention. In a liquid fuel burner 21 of 
this embodiment, only the number and positional relationship of fuel spray 
nozzles 23 of fuel feed pipe 4 and an orifice 29 of orifice member 7 
differ from the liquid fuel burner 1 of the first embodiment shown in the 
above-mentioned FIG. 1. Other constituents are the same as liquid fuel 
burner 1 of the first embodiment. 
The above-mentioned orifice 29 is formed with its axis in the center of the 
above-mentioned orifice member 7, namely on the center line 8 of the 
above-mentioned fuel feed pipe 4. A plurality of fuel spray nozzles 23 are 
formed with their axis at locations eccentric to the above-mentioned 
orifice 29. This plurality of fuel spray nozzles 23 each have the same 
diameter, and are arranged at equal intervals about the circumference 
centering an the above-mentioned center line 8. 
Eccentricity in this case is expressed as the ratio of the distance (M) 
between the center line of the above-mentioned fuel spray nozzles 23 and 
the center line of the above-mentioned orifice 29, to the distance (S) in 
the axial direction between said fuel spray nozzles 23 and said orifice 
29, namely the gap of fuel atomization portion 10. In other words, this is 
expressed as M/S. 
In the case of this second embodiment as well, by setting eccentricity 
within a range of 1.0 to 4.0, the spraying angle of the liquid fuel can be 
reduced to 5 to 10 degrees while still obtaining adequate diffusion. Thus, 
a long flame can be obtained. 
In order to maintain the above-mentioned eccentricity at the prescribed 
value, either the case of providing one fuel spray nozzle and one orifice, 
the case of providing a plurality of orifices 9 to one fuel spray nozzle 
3, or the case of providing one orifice 29 to a plurality of fuel spray 
nozzles 23 can be used. In either case, the cross-sectional area of the 
above-mentioned orifice (total cross-sectional area when using a plurality 
of orifices) should be made to be larger than the cross-sectional area of 
the fuel spray nozzle (total cross-sectional area when using a plurality 
of fuel spray orifices). In the case of providing a plurality of fuel 
spray nozzles or orifices, it is desirable in terms of forming a good 
flame to make them all of the same diameter and arrange them at equal 
intervals on the circumference centering about center line 8. However, as 
long as eccentricity is set within the prescribed range as described 
above, even if other conditions change slightly, the same diameter is not 
used or the fuel spray nozzles and orifices are not arranged at equal 
intervals, the spraying angle of the fuel burner can be made to be smaller 
than that of burners of the prior art. 
Experimental Example 1 
In order to confirm effects according to eccentricity between the 
above-mentioned fuel spray nozzle 3 and orifices 9, combustion was 
performed in atmosphere using the liquid fuel burner 1 having the 
structure shown in FIG. 1 (liquid fuel burner of the present invention) 
and a liquid fuel burner A of the prior art previously described (liquid 
fuel burner of the prior art), and the shape of the flame was confirmed. 
Incidentally, the eccentricity in the liquid fuel burner 1 of the present 
invention was set at 3.0. Kerosene was allowed to flow into the fuel 
passage of the above-mentioned burner as liquid fuel at the rate of 50 
liters/hour. Oxygen gas (oxygen gas concentration: 98%) was allowed to 
flow into the combusting-assisting gas passage at the rate of 100 Nm.sup.3 
/hour (where Nm.sup.3 will refer to the volume of the gas at a temperature 
of 0.degree. C. and pressure of 1 atm). Incidentally, since the 
cross-sectional area of the combusting-assisting gas passages differs 
between the liquid fuel burner 1 of the present invention and the liquid 
fuel burner A of the prior art, the nozzle velocity of oxygen gas in the 
liquid fuel burner 1 of the present invention is 6 m/sec, while that in 
the liquid fuel burner A of the prior art is 100 m/sec. These results are 
shown in Table 1. In addition, the states of the flames that were formed 
are shown in FIG. 3. FIG. 3(a) indicates the flame produced by the liquid 
fuel burner 1 of the present invention, while FIG. 3(b) indicates the 
flame produced by the liquid fuel burner A of the prior art. The 
temperatures of the flames were determined by measuring the temperature of 
the luminous flame portion with a radiation thermometer. 
TABLE 1 
______________________________________ 
Liquid Fuel Burner 
1 of the Present 
Liquid Fuel Burner 
Invention A of the Prior Art 
______________________________________ 
Flame Length (mm) 
2500 1500 
Length of Luminous 
2500 600 
Flame Portion (mm) 
Flame Temperature 
2400 2700 
(.degree.C.) 
______________________________________ 
As is clear from the above-mentioned Table 1 and FIG. 3, in the case of 
liquid fuel burner A of the prior art, the mist of liquid fuel that 
spreads out from the fuel spray nozzle results in the formation of a flame 
by being held in by oxygen gas flowing from its outside. Since the liquid 
fuel and oxygen gas are mixing vigorously, a short flame is obtained 
having a temperature higher than that of the liquid fuel burner 1 of the 
present invention. As shown in FIG. 3(b), luminous flame portion B was 
partially formed near the end of the burner, and a long pale blue 
non-luminous flame portion C, which was thought to be the result of 
combustion of gas formed by vaporization of the fuel, was formed closer to 
the end from said luminous flame portion B. 
On the other hand, in the case of liquid fuel burner 1 of the present 
invention, a flame was obtained that was longer than that of the liquid 
fuel burner A of the prior art, and the luminous flame portion B was 
extended throughout the entire flame, as shown in FIG. 3(a). 
As has been described above, according to the liquid fuel burner 1 of the 
present invention, a favorable flame is obtained having greater radiant 
heat transfer than liquid fuel burner A of the prior art, and, by 
controlling the nozzle velocity of combustion-assisting gas flowed from 
the above-mentioned combustion-assisting gas exit port 11 to within a 
range of 1 to 20 m/sec, and particularly 2 to 12 m/sec, a flame is 
obtained that is optimal for practical use. Furthermore, various types of 
means known in the prior art can be used for the means for controlling the 
velocity of the combustion-assisting gas, examples of which include 
adjusting the cross-sectional surface area of the combustion-assisting gas 
passage according to the amount of combustion-assisting gas used, and 
providing a flow regulator in the feed pipe to the combustion-assisting 
gas passage. 
Experimental Example 2 
Next, in order to investigate the relationship between the nozzle velocity 
of the oxygen gas and the flame, a flame was formed by spraying oxygen gas 
at various velocities while maintaining the amount of oxygen gas supplied 
constant and using the liquid fuel burner 1 having the structure shown in 
FIG. 1 as well as the burners having different surface areas for 
combustion-assisting gas passage 5. These results are shown in FIG. 4. In 
this graph, D indicates the length of the flame, and E indicates the 
proportion of the length of the luminous flame portion to the length of 
the flame (proportion of the luminous flame portion). Flame length D is 
plotted on the left vertical axis in centimeters, while the proportion of 
the luminous flame portion E is plotted on the right vertical axis as a 
percentage. 
As is clear from FIG. 4, when the velocity of oxygen gas is low at less 
than 1 m/sec, the proportion of the luminous flame portion is high, but 
the flame is short. This is thought to be due to the velocity of the 
oxygen gas being excessively slow so that at the distal end of the flame, 
the state of mixing of liquid fuel and oxygen gas is poor, thus resulting 
in the production of unburned components. A substantially favorable flame 
is obtained when the nozzle velocity of oxygen gas is increased to 2 m/sec 
or more. 0n the other hand, if the nozzle velocity of the oxygen gas is in 
excess of 12 m/sec, the proportion of the luminous flame portion 
decreases. In particular, when the nozzle velocity of oxygen gas is 
increased to a high rate in excess of 20 m/sec, the proportion of the 
luminous flame portion decreases remarkably, although flame length does 
not change much. This is thought to be due to the velocity of oxygen being 
too fast, which results in excessive promotion of mixing of liquid fuel 
and oxygen gas. As a result, a portion of the liquid fuel is vaporized due 
to combustion near the distal end of the flame, thus preventing the 
formation of a luminous flame since the liquid fuel is burned in the 
vaporized state. Based on the above results, in the case of the liquid 
fuel burner of the present invention, it is desirable to control the 
velocity of oxygen gas to 1 to 20 m/sec, and preferably 2 to 12 m/sec, 
from the viewpoint of practical use. 
Next, FIGS. 5 and 6 indicate a third embodiment of the present invention. 
FIG. 5 is a cross-sectional view depicting the pipe on the outside that 
forms the combustion assisting gas passage 5 cut away. FIG. 6 is a view 
taken along lines VI--VI shown by arrows in FIG. 5. 
A liquid fuel burner 31 of this embodiment is provided with a blade 32 for 
swirling the combustion-assisting gas in the above-mentioned 
combustion-assisting gas passage 5 of combustion-assisting gas feed pipe 
6. Other constituents are the same as the liquid fuel burner 1 of the 
first embodiment. 
As shown in FIG. 6, the above-mentioned blade 32 for swirling the 
combustion-assisting gas is composed of four blade elements. These four 
blade elements are arranged at equal intervals within the 
combustion-assisting gas passage 5, and have a prescribed angle with 
respect to said combustion-assisting gas passage 5. Incidentally, although 
4 blade elements are used in this example, any number of blade elements 
can be used. 
As a result of employing the above-mentioned constitution, 
combustion-assisting gas flowing through the combustion-assisting gas 
passage 5 is subjected to swirling force when it passes between each of 
the blade elements of blade 32, and is flowed out in the swirled state 
from the combustion-assisting gas spray pore 11. As a result, although 
flame length hardly changes at all, a combustion flame is produced that 
has a luminous flame portion with high-temperature, thus improving radiant 
heat transfer effects. This is thought to be due to the 
combustion-assisting gas subjected to this swirling force being mixed with 
liquid fuel while swirling around the liquid fuel that has been atomized 
and sprayed from the fuel spray nozzle 3, thus enabling suitable mixing 
with the liquid fuel. 
Experimental Example 3 
Next, the effect of blade 32 was confirmed by using the liquid fuel burner 
of the third embodiment, setting the conditions for the velocity of the 
liquid fuel and combustion-assisting gas to be the same as in Experimental 
Example 1, and changing the inclination of the blade elements of blade 32 
with respect to the combustion-assisting gas passage 5. The 
above-mentioned inclination of the blade elements was defined such that an 
inclination of 0 degrees corresponds to the state in which the blade 
elements are parallel with the combustion-assisting gas passage 5, while 
an inclination of 90 degrees corresponds to the state in which the blade 
elements are perpendicular to the combustion-assisting gas passage 5. 
These results are shown in Table 2. 
TABLE 2 
______________________________________ 
Inclination 
(.degree.) 0 20 40 
______________________________________ 
Flame Length 
2500 2500 2450 
(mm) 
Length of 2500 2500 2450 
Luminous 
Flame Portion 
(mm) 
Flame 2400 2450 2500 
Temperature 
(.degree.C.) 
______________________________________ 
As is clear from Table 2, the results are the same as those of the burner 
of FIG. 1 when the inclination is 0 degrees. When the inclination is 
increased to 20 and 40 degrees, both flame length and the luminous flame 
portion remain almost the same with the temperature of the flame 
increasing. When the inclination is increased to 45 degrees and beyond, 
however, there is essentially no change. In this case, it becomes 
necessary to increase the supply pressure of the oxygen gas, since the 
blade 32 becomes an opposition to the flow of oxygen gas. Thus, it is 
preferable that the inclination of the above-mentioned blade elements be 
set to a suitable value of 40 degrees or less corresponding to the actual 
conditions of use. 
Incidentally, since Experimental Examples 1 through 3 described above were 
conducted in atmosphere, the distal end of the flame was pointing upward 
due to buoyancy, as shown in FIG. 3. In the case of use in an actual 
furnace, however, due to the high temperature inside the furnace, the 
difference between the temperature inside the furnace and the temperature 
of the flame is small. Thus, buoyancy is reduced resulting in the 
obtaining of a substantially horizontal flame. 
Experimental Example 4 
Subsequently, a burner in which the inclination of the above-mentioned 
blade elements was set to 0 degrees and a burner in which the inclination 
of the above-mentioned blade elements was set to 40 degrees were installed 
in a test combustion furnace, and the temperature inside the furnace was 
measured. The liquid fuel burner A of the prior art used in Experimental 
Example 1 was used for comparison purposes. 
The state of flame formation differs between the burner 31 as an embodiment 
of the present invention and the burner A of the prior art as shown in 
FIG. 3. Thus, in the case of burner 31, in contrast to the distal end of 
the burner being able to be arranged towards the outside of a burner 
insertion port 34 continuous with the inside of a furnace 33 as shown in 
FIG. 7(a), it must be inserted to the back of burner insertion port 34 in 
the case of liquid fuel burner A of the prior art. Consequently, it is 
necessary to provide a water cooling jacket that is water-cooled, for 
example, on the outer periphery of the end of the burner in liquid fuel 
burner A of the prior art so as not to subject the burner tiles affixed to 
the inside wall of the burner insertion port 34 to wear. In contrast, in 
the case of burner 31, as a result of forming a long, thin flame, the heat 
load of the distal end of the burner caused by combustion is reduced, thus 
offering the advantage of eliminating the need to cool the vicinity of the 
end of the burner. 
FIG. 8 is a graph that resulted from forming a flame using a burner F with 
the inclination of the above-mentioned blade elements set to 0 degrees, a 
burner G with the inclination of the above-mentioned blade elements set to 
40 degrees, and the burner A of the prior art, and then measuring the 
temperature at the crown (ceiling) of the furnace at a prescribed location 
from the end of the opening of the furnace of burner insertion port 34. As 
is clear from FIG. 8, the temperature inside the furnace can be seen to 
increase in the order of burner A of the prior art, the burner F and the 
burner G. 
FIG. 9 is a cross-sectional view of the essential portion of a liquid fuel 
burner indicating a fourth embodiment of the present invention. 
A liquid fuel burner 41 of this embodiment is provided concentrically with 
a second combustion-assisting gas feed pipe 42 on the outside of the 
above-mentioned combustion-assisting gas feed pipe 6 of the burner of the 
first embodiment. Other constituents are the same as those of liquid fuel 
burner 1 of the first embodiment. 
A primary combustion-assisting gas passage 43 is then formed between the 
above-mentioned fuel feed pipe 4 and the combustion-assisting gas feed 
pipe 6, while a secondary combustion-assisting gas passage 44 is formed 
between the above-mentioned combustion-assisting gas feed pipe 6 and the 
above-mentioned combustion-assisting gas feed pipe 42. 
FIG. 10 is a cross-sectional view of the essential portion of a liquid fuel 
burner indicating a fifth embodiment of the present invention. 
A liquid fuel burner 51 of this embodiment is provided concentrically with 
a second combustion-assisting gas feed pipe 52 on the outside of the 
above-mentioned combustion-assisting gas feed pipe 6 of the burner of the 
second embodiment. Other constituents are the same as those of liquid fuel 
burner 21 of the second embodiment. 
A primary combustion-assisting gas passage 53 is then formed between the 
above-mentioned fuel feed pipe 4 and the combustion-assisting gas feed 
pipe 6, while a secondary combustion-assisting gas passage 54 is formed 
between the above-mentioned combustion-assisting gas feed pipe 6 and the 
above-mentioned combustion-assisting gas feed pipe 52. 
By providing a secondary combustion-assisting gas passage on the outer 
periphery of a primary combustion-assisting gas passage as described 
above, a primary combustion-assisting gas flow sprayed from the primary 
combustion-assisting gas passage is formed around fuel sprayed at a small 
angle from the fuel spray nozzle, while a secondary combustion-assisting 
gas flow sprayed from the secondary combustion-assisting gas passage is 
formed around said primary combustion-assisting gas flow. As a result, a 
long flame having a large luminous flame portion is obtained. In addition, 
the length of the flame can be changed by changing the ratios of flow 
volume and velocity between the primary combusting-assisting gas flow and 
secondary combustion-assisting gas flow. 
It should be noted that the above-mentioned ratios of the flow volume and 
velocity are defined as the ratio of the primary combustion-assisting gas 
flow to the secondary combustion-assisting gas flow, namely 
[primary]/[secondary]. 
An experimental example using a liquid fuel burner as a fourth embodiment 
of the present invention shown in FIG. 9 will be given below. 
Experimental Example 5 
Combustion properties in the case of changing the flow volume when kerosene 
at 35 liters/hour and oxygen at 70 Nm.sup.3 /hour were burned in 
atmosphere were as shown in Table 3. Incidentally, the oxygen velocity on 
the primary side was 20 Nm/sec (where Nm is to indicate the value 
converted for a temperature of 0.degree. C. and pressure of 1 atm, the 
same shall apply hereinafter) and that on the secondary side was 33 
Nm/sec. 
TABLE 3 
______________________________________ 
Flow Volume Ratio 
0.11 0.25 0.54 1.00 2.33 
______________________________________ 
Flame Length (mm) 
Large 1500 1700 1500 1200 
unburned 
portion 
Luminous Flame 1500 1700 1500 1200 
Portion (mm) 
Flame Temperature 
2100 2400 2500 2550 2600 
(max, .degree.C.) 
______________________________________ 
Based on the above results, it is preferable to set the flow volume ratio 
to within a range of 0.25 to 1.0, and particularly to roughly 0.54. 
Incidentally, when the oxygen burner of the prior art was used under the 
same conditions, flame length was 900 mm, the luminous flame portion was 
600 mm, and the maximum flame temperature was 2700.degree. C. 
Experimental Example 6 
Combustion properties in the case of changing velocity while setting the 
flow volume ratio in Experimental Example 5 to 0.54 were as shown in Table 
4. In this case, the primary oxygen velocity was 20 Nm/sec. 
TABLE 4 
__________________________________________________________________________ 
Velocity Ratio 
0.1 0.2 
0.3 
0.5 
0.6 
0.8 
1.0 
1.2 
1.5 
__________________________________________________________________________ 
Flame Large 1100 
1500 
1600 
1700 
1700 
1600 
1200 
1100 
Length unburned 
(mm) portion 
Luminous 1050 
1500 
1600 
1700 
1700 
1600 
1100 
1000 
Flame 
Portion 
(mm) 
Flame 2100 2300 
2400 
2500 
2500 
2500 
2550 
2600 
2650 
Temp. (.degree.C.) 
__________________________________________________________________________ 
Based on the above results, it is preferable to set the velocity ratio to 
within a range of 0.3 to 1.0, and particularly to 0.6 to 0.8. 
Experimental Example 7 
Combustion properties in the case of varying the primary oxygen velocity 
while setting the flow volume ratio in Experimental Example 5 to 0.54 were 
as shown in Table 5. Incidentally, secondary oxygen velocity was varied 
over the application range of 0.3 to 1.0 for the velocity ratios confirmed 
in Experimental Example 6. 
TABLE 5 
__________________________________________________________________________ 
Primary 
5 10 20 40 50 60 70 
Oxygen 
Velocity 
Secondary 
5-17 10-33 
20-67 
40- 50- 60- 70- 
Oxygen 133 150 150 150 
Velocity 
Range 
Primary/ 
0.3-1 
0.3-1 
0.3-1 
0.3-1 
0.33- 
0.4-1 
0.46- 
Secondary 1 1 
Flow Volume 
Ratio 
Flame 1200- 
1450- 
1500- 
1400- 
1200- 
1100- 
900- 
Length (mm) 
1300 1700 1700 1600 1300 1200 1000 
Flame 1200- 
1450- 
1500- 
1400- 
1200- 
1000- 
900- 
Luminous 
1300 1700 1700 1600 1300 1200 1000 
Portion 
(mm) 
Flame 2100- 
2400- 
2400- 
2450- 
2500- 
2600- 
2600- 
Temperature 
2200 2500 2550 2550 2650 2700 2700 
(.degree.C.) 
__________________________________________________________________________ 
* Units for the range of primary oxygen velocity and secondary oxygen 
veloxity are Nm/sec. 
Based on the above results, it is preferable to set the primary oxygen 
velocity to within a range of 10 to 40 Nm/sec, and particularly to 10 to 
20 Nm/sec. 
As has been mentioned above, the liquid fuel burners of the fourth and 
fifth embodiments are able to realize a low angle of spraying of liquid 
fuel by employing a structure providing the above-mentioned fuel 
atomization portion 10 and a primary combustion-assisting gas passage and 
secondary combusting-assisting gas passage concentrically on the outer 
periphery of said atomization portion 10. Moreover, they are also able to 
obtain preferable combustion properties by controlling a 
combustion-assisting gas supply means. Namely, the flow volume ratio is 
controlled to within a range of 0.25 to 1.0, the velocity ratio is 
controlled to within a range of 0.3 to 1.0, and the primary 
combustion-assisting gas velocity is controlled to within a range of 10 to 
40 Nm/sec.