US3610537A

US3610537A - Liquid fuel combustion device

Info

Publication number: US3610537A
Application number: US794221*A
Authority: US
Inventors: Masayoshi Nakagawa; Toshihiro Hirai; Yuji Suzuki; Ryozaburo Kimura; Masamichi Okahara
Original assignee: Daido Sanso Co Ltd
Current assignee: Daido Sanso Co Ltd
Priority date: 1968-01-25
Filing date: 1969-01-27
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05
Also published as: FR2000773A1; GB1256951A; US3733165A; DE1903595A1

Abstract

Through a combination of A. THE SUPPLY OF OXYGEN SUBSTANTIALLY IN THE FORM OF PURE OXYGEN IN AN AMOUNT FAR LESS THAN THAT THEORETICALLY REQUIRED FOR COMBUSTION OF LIQUID FUEL TO BE BURNED IN SUCH A MANNER AS TO ATTAIN A VERY RAPID COMBUSTION TEMPERATURE RISE, B. WITH THE STRONG ACTIVATION OF THE LIQUID FUEL BY MIXING AND ATOMIZATION OF A PART OF THE FUEL LIQUID SUFFICIENTLY WITH THE OXYGEN, LIMITED IN QUANTITY, CLOSELY ADJACENT TO A LIQUID FUEL NOZZLE THEREBY TO FORM A HIGH-TEMPERATURE CENTER FLAME VERY CLOSE TO THE NOZZLE, C. A HIGH-TEMPERATURE FLAME HAVING A LARGE POTENTIAL HEAT PER UNIT VOLUME THEREOF, THAT IS, A FLAME OF EXTREMELY HIGH INTENSITY, IS OBTAINED EFFICIENTLY WITH A SMALL SUPPLY OF OXYGEN.

Description

United States Patent [72] Inventors MasayoshiNakagawa Nishinomiya;

Toshihiro Hirai, Sakai; Yuji Suzuki, Amagasaki; Ryozaburo Kimura, 'lakarazuka; Masamichi Okahara,

Takarazuka, all of Japan [21] Appl. No. 794,221

[22] Filed Jan. 27, 1969 [45] Patented Oct. 5, I971 [73] Assignee Daido Sanso Kabushiki Kaisha Banchi, Japan [32] Priority Jan. 25, 1968, Feb. 23, 1968, Aug. 27,

[33] Japan [31] 43/4,712, 43/11,674 and 43/74,096

[54] LIQUID FUEL COMBUSTION DEVICE 1 Claim, 16 Drawing Figs.

52 user 239/4193, 239 424.5, 239 429 511 Int.Cl ..F23d13l40 so FieldofSearch 239 403, 405,406,4l9,4l9.3,422,424.5,428,429,430,

Primary Examiner-M. Henson Wood, Jr. Assistant Examiner.lohn J. Love Attorney-Edwin E. Greigg ABSTRACT: Through a combination of a. the supply of oxygen substantially in the form of pure oxygen in an amount far less than that theoretically required for combustion of liquid fuel to be burned in such a manner as to attain a very rapid combustion temperature rise,

b. with the strong activation of the liquid fuel by mixing and atomization of a part of the fuel liquid sufficiently with the oxygen, limited in quantity, closely adjacent to a liquid fuel nozzle thereby to form a high-temperature center flame very close to the nozzle,

c. a high-temperature flame having a large potential heat per unit volume thereof, that is, a flame of extremely high intensity, is obtained efficiently with a small supply of oxygen.

PATENTEDUET SIS?! $610,537

SHEET 5 BF 5 s54 5 9 5 7 see 5 8 LIQUID FUEL COMBUSTION DEVICE BACKGROUND OF THE INVENTION Combustion devices for burning liquid fuel by the addition of oxygen are required to minimize the issue and consumption of expensive oxygen gas for the combustion of the fuel, completely burn the liquid fuel issuing from the orifice, and produce a high-temperature, intense flame (with a highcalorific value per unit volume of the flame).

ln conventional devices of the type described, the combustion efficiency and flame temperature can be increased by oxygen enrichment (i.e., by the addition of oxygen gas to air in order to bring a corresponding decrease of the amount or proportion of nitrogen in the air which takes part in the combustion). However, the combustion efficiency depends largely upon the manner in which the enrichment is made.

For example, some devices are so designed that oxygen gas is passed into the central part of the flame and, because the oxygen gas and liquid fuel are separately supplied without being premixed, the increase of the nozzle velocity of oxygen gas above a certain value produces a jet of oxygen gas fast enough to blow the merging or mixing point of the gas and liquid fuel away from the nozzle tip. Consequently, oxygen gas and liquid fuel cannot be diffused and mixed thoroughly and rapidly notwithstanding the addition of oxygen gas. The arrangement is thus disadvantageous in that the oxygen gas fed in is only partly utilized and the flame thus obtained is not of a sufficiently elevated temperature.

As described above, it has hitherto been in practice to atomize liquid fuel beforehand and allow the atomized fuel to issue from an orifice in such a way as to simply entrain oxygen gas and carry-it into the flame. Efforts have thus been centered on direct promotion of the combustion of the main flame through the addition of or enrichment with oxygen. Here it may appear at a first glance that the preatomization of liquid fuel will produce a high-temperature, high-intensity flame, but in reality the practice is merely contributory to complete combustion of liquid fuel. By the complete atomization the liquid fuel is widely difiused in the space, and the flame produced by combustion of this diffused liquid fuel is so thick and long. that the calorific value per unit volume is below the level otherwise attained with the same quantity of heat, and the flame intensity is accordingly decreased. The flame of very large size also causes dissipation of heat over a wide area with a consequent drop of the flame temperature.

As will be appreciated from the foregoing, there has been no method and device for effecting the combustion of liquid fuel with a high flame intensity by the mere addition of a very small amount of pure oxygen.

This invention is directed to the provision of a liquid fuel combustion device which can satisfy all of the requirements above mentioned.

According to the present invention, the aforementioned disadvantages of the convention devices are eliminated in the following way. First, a part of liquid fuel is burned with pure oxygen in an amount of less than the chemical equivalent in the central part of the nozzle tip of the combustion device to effeet the combustion in an entirely pure oxygen atmosphere so as to produce a high-temperature, stable center flame there. The remainder of liquid fuel is then ejected through nozzle means so as to envelop the center flame and is instantaneously vaporized and decomposed by the extremely high heat of reaction of the center flame to produce, at the same time, a large amount of active radicals which rapidly diffuse in air serving to form a main flame. Altogether, a high-temperature flame of extremely great intensity is thus obtained. In other words, the combustion system of the invention is characterized in that the flame thereby produced includes a center flame and a main flame and that the pure oxygen added is not directly consumed for the combustion of the entire flame but it serves to form a center flame of an ultrahigh temperature by the combustion of fuel in a totally pure oxygen atmosphere and then indirectly promotes the burning of the main flame with the aid of the center flame.

As a modification of the above combustion system, the amount of oxygen is naturally increased where a flame of a still higher temperature is desired. In such a case, it is of course possible to pass the entire amount of liquid fuel through an oxygen nozzle which is being supplied with pure oxygen in an amount of less than the chemical equivalent so as to vaporize and decompose the total amount of liquid fuel within the center flame by virtue of the high temperature of the flame, and supply combustion-sustaining air from around the center flame to cause rapid diffusion and combustion of the gaseous mixture so that a flame of high intensity at an ultrahigh temperature can be produced with a center flame much larger than that formed by the combustion system described above.

SUMMARY OF THE INVENTION The liquid fuel combustion device according to the present invention pertains to a liquid fuel burner.

The device of the invention is'charactcrized by a method and arrangement as represented by the first embodiment thereof, wherein an oxygen nozzle and a liquid fuel nozzle are separately provided in the central part of the combustion device, surrounded by a line for air or steam or their mixture, and a mixing chamber is provided near the tip of the oxygen nozzle in which a part of the liquid fuel is mixed with oxygen gas.

In this way it is made possible, in mixing and burning the liquid fuel with oxygen gas, to feed a part of the liquid fuel into the mixing chamber thereby to atomize, mix and burn the part of liquid fuel in that chamber, and also effect almost complete volatilization and decomposition of the rest of liquid fuel by the heat of reaction due to the partial combustion so that a flame as a whole at a high temperature and having a great intensity and stability can be produced.

As is well known, active radicals have important bearings upon the promotion of combustion. In accordance with the present invention, the active radicals are produced in a large quantity as the remainder or most of the liquid fuel is volatilized and decomposed around the stabilized center flame by the heat of reaction (i.e., the heat of combustion) of the center flame. This production of active radicals is combined with the transfer of heat from the high-temperature center flame that exists very close to the nozzle tip to promote the combustion of the main flame (i.e., the flame formed by the combustion of most of the liquid fuel in mixture with air or the like supplied through the gas line).

Thus, the combustion of a part of liquid fuel atomized and mixed with oxygen in the mixing chamber produces a small, highly stable center flame at a high temperature at the nozzle tip, and the heat of reaction of the center flame in turn volatilizes and decomposes most of the liquid fuel to form a main flame around the center flame and very close thereto by the combustion upon diffusion with air or the like. Thus, a flame as a whole which is short in length can be obtained. By shortening the overall flame length in this way, the flame temperature can be raised and the quantity of heat per unit volume of the flame can be increased so as to heighten the flame intensity.

In the second embodiment of the present invention, the amount of pure oxygen that issues from the oxygen nozzle is controlled to a range (2 to 15 percent) that is far less than the theoretical amount of oxygen required for the combustion of the liquid fuel.

It is thus only necessary to supply from 2 to 16 percent of pure oxygen on the basis of the theoretical oxygen requirement in order to obtain a flame of high intensity.

According to the third embodiment of the invention, a pressure-reducing portion is provided at the front end or in the vicinity thereof in the oxygen nozzle, and a passage or passages branched from a frontward part of the liquid fuel nozzle are open in theportion, thus forming a mixing chamber there.

The provision of the pressure-reducing portion permits rapid expansion and diffusion of oxygen gas with a consequent decrease of the gas density and formation of turbulence near the sidewall of the flow passage. This leads to an improvement of the mixing action of a part of liquid fuel and oxygen gas in the mixing chamber and to a remarkable promotion of the atomizing action of the liquid fuel in the same chamber.

ln the fourth embodiment of the invention, a portion to cause a turbulent flow is formed along the boundary between the flow of oxygen and the flow of liquid fuel at the front end or in the vicinity thereof in the oxygen nozzle, and a passage or passages branched from the forward portion of the liquid fuel nozzle are open in a part of the portion where the turbulent flow of oxygen is formed, thus defining a mixing chamber.

In this turbulence-inducing portion oxygen is mixed with most of the liquid fuel in an atomized and dispersed state. The fuel as mixed in this way is almost completely vaporized, decomposed and burned by the heat of reaction of the flame. This in turn facilitates the combustion of the center flame at an elevated temperature and with a high flame intensity.

In accordance with the fifth embodiment of the invention, a tapered portion is formed at the front end or in the vicinity thereof in the oxygen nozzle in such a manner as to expand toward the tip of the nozzle, and a passage or passages branched from the forward portion of the liquid fuel nozzle are open in a part of the tapered portion, thus defining a mixing chamber.

This tapered portion prevents backward flow of oxygen gas to the liquid fuel side through the openings of the branched passages and avoids backfire. Also, the stream of oxygen gas by suction carries a part of the liquid fuel into the mixing chamber to an adequate extent in addition to the fact that the branched passages are so narrow that the liquid fuel introduced therethrough can be easily atomized.

Thus, the liquid fuel intake can be automatically regulated to the amount of the oxygen jet and a stable center flame corresponding in size to the rate of oxygen supply can be maintained.

According to the sixth embodiment of the invention, a pressure-reducing portion is formed at the front end or in the vicinity of the oxygen nozzle, and a passage or passages branched from a forward portion of the liquid fuel nozzle are open in a part of the pressure-reducing portion, thus defining a mixing chamber, and further the amount of pure oxygen emitted from the oxygen nozzle is controlled to a level far less than the theoretical requirement, or to a rate of from 2 to percent of the theoretical oxygen amount required for the combustion of the liquid fuel.

With this construction it is possible to obtain a flame of a high flame intensity by merely supplying from 2 to 15 percent of pure oxygen on the basis of the theoretical requirement.

In the seventh embodiment of the invention, the oxygen nozzle is disposed inside the liquid fuel nozzle coaxially or substantially coaxially therewith, and an orifice portion for abruptly changing the pressure of oxygen gas thereby to cause a sudden increase of the oxygen flow velocity is formed in the central portion of the oxygen gas passage inside the oxygen nozzle away from the opening at the tip of the nozzle and at a point upstream of the flow direction of the oxygen gas, and a flow passage or passages branched from the liquid fuel nozzle are open in the oxygen nozzle at a point between the orifice portion and front end of the oxygen nozzle.

The orifice portion produces vortices of oxygen wherein a part of the liquid fuel is mixed. As a result, the mixing of the liquid fuel and oxygen gas is promoted and the ignitability is much improved and further a stabilized center flame is thereby formed.

In the eighth embodiment of the invention, the oxygen nozzle is disposed inside the liquid fuel nozzle coaxially or substantially coaxially therewith, an orifice portion for abruptly changing the pressure of oxygen gas thereby to cause a sudden increase of the oxygen flow velocity is formed in the central portion of the oxygen gas passage inside the oxygen nozzle away from the opening at the tip of the nozzle and at a point upstream of the flow direction of the oxygen gas, a flow passage or passages branched from the liquid fuel nozzle are open in the oxygen nozzle at a point between the orifice portion and the front end of the oxygen nozzle, and further the amount of pure oxygen to be emitted from the oxygen nozzle is controlled to a level far less than the theoretical requirement, or in the range of from 2 to 15 percent of the theoretical oxygen amount required for the combustion of the liquid fuel.

it is therefore possible to obtain a flame of a high intensity by merely supplying from 2 to 15 percent of pure oxygen on the basis of the theoretical requirement.

According to the ninth embodiment of the invention, the oxygen nozzle and liquid fuel noule are arranged together, the former being disposed inside the latter coaxially or substantially coaxially therewith, and the tip opening of the inner nozzle for oxygen is protruded frontwardly from the tip opening of the other nozzle.

Thus, an oxygen jet emerges from the inner nozzle while liquid fuel issues from the outer nozzle. When the liquid fuel is to be atomized by air or steam or a gaseous mixture of both, it is directed toward the periphery of the inner nozzle tip and is thereby atomized. in this manner it becomes possible to vaporize and decompose most or all of the liquid fuel without having any adverse effect upon the center flame.

In the atomization of the liquid fuel, therefore, the stability of the center flame is protected against any disturbance that may otherwise be caused by the jet or liquid fuel, and hence a highly stabilized center flame can be produced with the complete volatilization and decomposition of the liquid fuel thereby promoted.

In the tenth embodiment of the invention, the oxygen nozzle and liquid fuel nozzle are arranged together, the former being disposed inside the latter coaxially or substantially coaxially therewith, and the tip opening of the inner nozzle for oxygen is protruded frontwardly from the tip opening of the nozzle, and further the amount of pure oxygen to be emitted from the oxygen nozzle is controlled to a level far less than the theoretical requirement, or in the range of from 2 to l5 percent of the theoretical oxygen amount required for the combustion of the liquid fuel.

A flame of high intensity can therefore be obtained by supplying pure oxygen merely in an amount of from 2 to I5 percent of the theoretical requirement.

The eleventh embodiment of the invention is such that the oxygen nozzle and liquid fuel nozzle are arranged together, the former being disposed inside the latter coaxially or substantially coaxially therewith, and the tip opening of the inner nozzle for oxygen is protruded frontwardly from the tip opening of the other nozzle, and the periphery of the tip opening of the protruded nozzle is expanded outwardly.

Because of the provision of this outwardly expanded periphery of the tip opening, the stream of gaseous mixture of oxygen and liquid fuel in the center flame, which is formed at the nozzle tip by the jet action of air or steam supplied for the atomization purpose, begins a reverse flow after it is emitted from the nozzle tip toward the expanded periphery. As a result, the center flame expands to a bulbous shape near the nozzle tip. in this way a short, thick and ignitable center flame is formed and at the same time, the main flame is shortened and laterally expanded with desirable stability. This is particularly advantageous in certain applications, for example, where difficulties are involved in ignition, transverse or lateral expanse of flame is required, or a short flame is needed to meet particular operating conditions.

In the twelfth embodiment of the invention, the oxygen nozzle and liquid fuel nozzle are arranged together, the former being disposed inside the latter coaxially or substantially coaxially therewith, the tip opening of the inner nozzle for oxygen extending frontwardly from the tip opening of the other nozzle, the periphery of the tip opening of the protruding noule being expanded outwardly, and further the amount of pure oxygen emitted from the oxygen nozzle being controlled to a the first to the twelfth. These embodiments to be described hereunder are invariably simplified in construction with an arrangement adapted to introduce the total amount of liquid fuel into the mixing chamber of the oxygen nozzle and use oxygen in a relatively large amount, though less than the chemical equivalent, so that a flame at an ultrahigh temperature, e.g., at about two thousand and several hundred degrees Centigrade, can be produced. These embodiments will now be described one after another.

In accordance with the thirteenth embodiment of the invention, the oxygen nozzle is disposed outside the liquid fuel nozzle coaxially or substantially coaxially therewith, and the tip of the oxygen nozzle is projected a suitable length outwardly of the tip of the liquid fuel nozzle, and an annular step is formed in the oxygen passage of the oxygen nozzle, upstream of the flow direction of oxygen gas from the tip opening of the liquid fuel nozzle, protruding from the inner periphery of the oxygen nozzle toward the outer periphery of the liquid fuel nozzle, the portion of the oxygen gas passage constricted by the step fonning an orifice which increases the flow velocity of the oxygen gas that flows therethrough to an extremely high velocity and enables the jet of oxygen to spout toward the tip opening of the liquid fuel nozzle, and a mixing chamber wherein the liquid fuel and oxygen gas are mixed is formed adjacent to the step and on the side of the tip opening of the oxygen nozzle.

The orifice causes vortex flow of oxygen jet in the mixing chamber. Since the vortex flow of oxygen gas draws the liquid fuel thereinto and intermixes therewith, the liquid fuel is completely atomized. As a result, very good ignitability is attained, the flame stability is improved, a high-temperature flame is obtained, and the portion of liquid fuel that has remained unreacted with the oxygen added can be completely vaporized and decomposed, and moreover a large amount of active radicals are produced.

Because the mixing chamber is immediately open to the atmosphere and creates a large pressure difference upstream of the drastic changing portion, backward flow of the gaseous mixture of oxygen gas and liquid fuel or of the liquid fuel into the oxygen line is reduced to zero, with the result that the dangers of damage and explosion of the device by backfire or the like is completely precluded, and accordingly, the degree of safety is noticeably increased.

In the fourteenth embodiment of the invention, the oxygen nozzle is disposed outside the liquid fuel nozzle coaxially or substantially coaxially therewith, and the tip of the oxygen nozzle projects a suitable length outwardly of the tip of the liquid fuel nozzle, and a step is formed in the oxygen passage of the oxygen nozzle, upstream of the flow 'direction of oxygen gas from the tip opening of the liquid fuel nozzle, protruding from the inner periphery of the oxygen nozzle toward the outer periphery of the liquid fuel nozzle, the portion of the oxygen gas passage constricted by the step forming an orifice which increases the flow velocity of the oxygen gas that flows therethrough to an extremely high velocity and enables the jet of oxygen to spout toward the tip opening of the liquid fuel nozzle, and a mixing chamber wherein the liquid fuel and oxygen gas is intermixed is formed adjacent to the step and on the side of the tip opening of the oxygen nozzle, and the amount of pure oxygen to issue from the oxygen nozzle is controlled to a level less than the theoretical amount required for the combustion of the liquid fuel in the range of from to 70 percent of the theoretical requirement.

Accordingly, by supplying pure oxygen only in an amount ranging from 30 to 70 percent of the theoretical amount, a flame of high intensity can be obtained.

Another embodiment of the invention, the fifteenth, is characterized in that the oxygen nozzle is disposed outside the liquid fuel nozzle coaxially or substantially coaxially therewith, and a swirl generator for injecting liquid fuel in the expanding, conical and helical direction into the oxygen flow passage is formed in the vicinity of the tip opening of the liquid fuel nozzle.

The provision of the swirl generator enables the liquid fuel injected from the tip of the liquid fuel nozzle to be spread under pressure to a conical and helical shape while being injected. This combines with the actions and effects already described to improve the ignitability and stability of the flame.

In the sixteenth embodiment of the invention, the oxygen nozzle is disposed outside the liquid fuel nozzle coaxially or substantially coaxially therewith, and a swirl generator for injecting liquid fuel in the expanding, conical and helical direction into the oxygen flow passage is formed in the vicinity of the tip opening of the liquid fuel nozzle, and the amount of pure oxygen to issue from the oxygen nozzle is controlled to a level less than the theoretical amount required for the cornbustion of the liquid fuel in the range of from 30 to 70 percent of the theoretical requirement.

Thus, by supplying pure oxygen only in an amount ranging from 30 to 70 percent of the theoretical amount, a flame of high intensity can be obtained.

In the seventeenth embodiment of the invention, the oxygen nozzle is disposed outside the liquid fuel nozzle coaxially or substantially coaxially therewith, the tip of the oxygen nozzle extends a suitable length outwardly of the tip of the liquid fuel nozzle, a swirl generator for injecting liquid fuel in the expanding, conical and helical direction into the oxygen flow passage is formed in the vicinity of the tip opening of the liquid fuel nozzle, a forced air supply duct is provided outside the oxygen nozzle coaxially or substantially coaxially therewith, the tip opening of said air duct being formed near the tip opening of the oxygen nozzle, and vane means for air swirling are provided which inject air in a turbulent state and in a helical direction into a forced airflow passage of the air duct.

Since the forced air supply duct is positively provided in the manner described, the large amount of active radicals produced in the center flame and the high-temperature combustible gases (H C H C li C H etc.) produced by the vaporization and decomposition of the liquid fuel with the effect that oxygen is forcibly mixed up with air, so that the combustion can be accomplished rapidly and completely at a high temperature and high intensity nearly equivalent to those attained with the flame by combustion of heavy oil in pure oxygen alone. The mixing of the gaseous mixture is accomplished all the more thoroughly because air is intermingled with the combustible gases as the former is injected in a turbulent state and in a helical direction with respect to the latter by the vane means for turbulent air injection.

According to the eighteenth embodiment of the invention, the oxygen nozzle is disposed outside the liquid fuel nozzle coaxially or substantially coaxially therewith, the tip of the oxygen nozzle is protruded a suitable length outwardly of the tip of the liquid fuel nozzle, a swirl generator for injecting liquid fuel in the expanding, conical and helical direction into the oxygen flow passage is formed in the vicinity of the tip opening of the liquid fuel nozzle, a forced air supply duct is provided outside the oxygen nozzle coaxially or substantially coaxially therewith, the tip opening of said air duct being formed near the tip opening of the oxygen nozzle, vane means for air swirling are provided which inject air in a turbulent state and in a helical direction into a forced air flow passage of the air duct, and the amount of pure oxygen arranged to be issued from the oxygen nozzle is controlled to a level less than the theoretical amount required for the combustion of the liquid fuel, in the range of from 30 to 70 percent of the theoretical requirement.

A flame of high intensity can thus be obtained by supplying pure oxygen only in an amount ranging from 30 to 70 percent of the theoretical amount.

In the nineteenth embodiment of the invention, the oxygen nozzle is disposed outside the liquid fuel nozzle which injects a part of the liquid fuel, another liquid fuel nozzle is provided outside the oxygen nozzle, an atomizing gas nozzle for air or steam or a gaseous mixture of both is provided outside the outer liquid fuel nozzle, and a forced air-supplying duct is provided outside the atomizing gas nozzle, in such a manner that the inner liquid fuel nozzle, oxygen nozzle, outer liquid fuel noule, atomizing gas supplying nozzle, and forced air-supplying duct are disposed coaxially or substantially coaxially with one another, the tip of the oxygen nozzle being extended outwardly a suitable length from the tip of the inner liquid fuel nozzle, the tip openings of the outer liquid fuel nozzle, atomizing gas nozzle, and forced air-supplying duct being formed in the vicinity of the tip opening of the oxygen nozzle, and a swirl generator for injecting liquid fuel in the expanding, conical and helical direction into the oxygen gas passage is formed in the vicinity of the tip opening of the inner liquid fuel nozzle, and further vane means for air swirling are provided which inject air for combustion in a turbulent state and in a helical direction into a forced air passage of the air duct.

When the liquid fuel is injected in such large volume, perfect combustion cannot be realized with devices as described hereinbefore in embodiments l-l3, due to incomplete mixing of such large volume fuel with oxygen gas. According to the present invention, however, a fraction of the liquid fuel to be burned is perfectly mixed with oxygen gas at the central portion along the oxygen flow path, in order to form a very stable center flame, while the rest of the liquid fuel, constituting a large portion thereof, is atomized, vaporized and decomposed around the said center flame whose heat effectively serves for this purpose. Therefore, even when a liquid fuel is injected in such large volume that the complete mixing with oxygen gas may not be expected with means as described hereinbefore in embodiments 1-13, at very stable center flame can hereby be formed, and the vaporization and decomposition of the large volume of the liquid fuel of the low mixing efficiency are accomplished positively and completely. This results in the formation of a stable and large flame which has a high flame intensity.

In accordance with this embodiment, therefore, a liquid fuel combustion device of a large capacity with quite excellent performance can be obtained.

In the twentieth embodiment of the invention, the oxygen nozzle is disposed outside the liquid fuel nozzle which injects a part of the liquid fuel, another liquid fuel nozzle is provided outside the oxygen nozzle, and atomizing gas nozzle for air or steam or a gaseous mixture of both is provided outside the outer liquid fuel nozzle, and a forced air-supplying duct is provided outside the atomizing gas nozzle in such a manner that the inner liquid fuel nozzle, oxygen nozzle, outer liquid fuel nozzle, atomizing gas supplying nozzle, and forced air-supplying duct are disposed coaxially or substantially coaxially with one another, the tip of the oxygen nozzle being protruded outwardly a suitable length from the tip of the inner liquid fuel noule, the tip openings of the outer liquid fuel nozzle, atomizing gas nozzle, and forced air-supplying duct being formed in the vicinity of the tip opening of the oxygen nozzle, and a swirl generator for injecting liquid fuel in the expanding, conical and helical direction into the oxygen gas passage is formed in the vicinity of the tip opening of the inner liquid fuel nozzle, vane means for air swirling are provided which inject air for combustion in a turbulent state and in a helical direction into a forced air passage of the air duct, and the amount of pure oxygen to issue from the oxygen nozzle is controlled to a level less than the theoretical amount required for the combustion of the liquid fuel in the range of from 2 to percent of the theoretical requirement.

Thus, a flame of high intensity can be formed by supplying pure oxygen only in an amount ranging from 2 to 15 percent of the theoretical amount.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows in longitudinal section the essential part of the first embodiment of the liquid fuel combustion device of the present invention;

FIG. 2 is an enlarged longitudinal section of the oxygen nozzle shown in FIG. 1;

FIG. 3 is a view explanatory of the pattern of flame according to the first embodiment;

FIG. 4 is an enlarged longitudinal section of the oxygen nozzle in the third embodiment;

FIG. 5 is an enlarged longitudinal section of the oxygen nozzle in the fourth embodiment;

FIG. 6 is an enlarged longitudinal section of the oxygen nozzle in the fifth embodiment;

FIG. 7 is a longitudinal section of the essential part of the seventh embodiment;

FIG. 8 is an enlarged longitudinal section illustrating the essential part in operation;

FIG. 9 is a longitudinal section of the essential part of the ninth embodiment;

FIG. 10 is a longitudinal section of the essential part of the eleventh embodiment;

FIG. 11 is a longitudinal section of the essential part of the thirteenth embodiment;

FIG. 12 is a section taken along the line I--I of FIG. 11;

FIG. 13 is a side view, partly in section, of the nozzle of FIG. 11 in operation;

FIG. 14 is a longitudinal section of the essential part of the fifteenth embodiment;

FIG. 15 is a longitudinal section of the essential part of the seventeenth embodiment; and

FIG. 16 is a longitudinal section of the essential part of the nineteenth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the liquid fuel combustion device according to the present invention will now be described in conjunction with FIG. 1 showing the first embodiment thereof. In the center of the device shown there is provided an oxygen line 51 to the front end of which is fitted an oxygen nozzle 52. The two members are connected to each other through the engagement of threaded portions 53 detachably to the axis of the oxygen line 51. This detachability of the oxygen nozzle 52 permits selective use of a plurality of interchangeable oxygen nozzles 52. Through the oxygen line 51 and oxygen nozzle 52 high purity oxygen gas passes usually under a low pressure of about 0.3 to 2.0 kg./cm G and is emitted from the tip 54 of the oxygen nozzle 52.

Oxygen line 51 is surrounded by a liquid fuel line 56, to the front end of which is also fitted a liquid fuel nozzle 58 as if to envelop the oxygen nozzle 52. This liquid fuel nozzle 58 is connected through the engagement of threaded portions 57 to the liquid fuel line 56 in such a manner that it can be detached therefrom. The detachability of this liquid fuel nozzle 58 serves the same purposes as those of the oxygen nozzle 52 already described. Through the liquid fuel line 56 and liquid fuel nozzle 58 flows a heavy oil such as a liquid fuel.

Liquid fuel line 56 is further surrounded by a gas line 59 which is connected at the front end with a gas nozzle 61 enveloping the liquid fuel nozzle 58, detachably from the line through the engagement of threaded portions 60. The detachability of this gas nozzle 61 permits the same functions as those of the oxygen nozzle 52 and liquid fuel nozzle 58. Through the gas line 59 and gas nozzle 61 and via another line 67 passes air or steam or their mixture for atomizing the heavy oil. This gas for atomization use need not always be kept at a high pressure or run at a high velocity. Therefore; the feed arrangement may be of a relatively simple structure. Displacement of the nozzles with respect to one another enables the supply of gas to be shut off or adjusted where necessary.

Near the tip 54 of the oxygen nozzle 52 there is formed a mixing chamber wherein a part of the heavy oil is mixed with oxygen gas. As shown in an enlarged longitudinal section in FIG. 2, the oxygen nozzle 52 is formed with one or a plurality of passages 62 for the introduction of the heavy oil that are open in the bore of the nozzle 52 close to the tip 54. Thus, a mixing chamber 63 is defined which attracts a part of the heavy oil into the oxygen nozzle 52 by the injector action of the apertures under the influence of the flow of oxygen gas through the oxygen nozzle 52 at a flow rate within a certain range, and thus mixes the heavy oil so attracted by suction with the oxygen gas.

With the construction above described, the burner 64 is accommodated in a combustion-sustaining air line 69 coaxially or substantially coaxially therewith, usually penetrating altogether through a furnace wall 68 with the front end portion held inside the furnace.

Oxygen gas that flows through the oxygen nozzle 52 issues from the tip 54 past the mixing chamber 63. As it passes along the heavy oil-introducing passages 62, it induces an injector action thereby to attract by suction a part of the heavy oil in the liquid fuel nozzle 58 through the passages 62 into the oxygen nozzle 52. The fraction of heavy oil thus attracted is atomized and mixed up by the oxygen gas passing through the mixing chamber 63 and in the atomized and mixed state it is thus blown out of the tip 54. As shown in FIG. 3, this atomized mixture upon ignition forms a high-temperature and well-stabilized center flame 65 due to combustion with pure oxygen gas adjacent to the tip center of the burner 64.

The remainder of the heavy oil is emitted from the tip of the liquid fuel nozzle 58 into the atmosphere along the periphery of the center flame 65. At this time, the heavy oil is atomized and dispersed by the gas also issuing out of the gas nozzle 61 surrounding the liquid fuel nozzle 58. The liquid fuel thus atomized and dispersed is vaporized and decomposed around the center flame 65 by the high heat of reaction thereof and gives ofi' a large amount of active radicals. The increased volume of active radicals combines with the high heat of reaction of the center flame 65 to promote the combustion of most of the liquid fuel so vaporized and decomposed. Around the center flame 65 and at a point quite close thereto, the vaporized and decomposed liquid fuel is burned in a state diffused by and mixed with the combustion air supplied from the combustion-sustaining air line 69, thus forming a main flame 66. On account of the high temperature of the center flame 65, the mixing of the atomized liquid fuel after vaporization with oxygen in the surrounding air is rapidly accomplished due to the high molecular velocity. in this manner the gaseous mixture is burned at a high burning velocity.

Accordingly, the main flame 66 having the high-temperature center flame 65 at the tip of the burner 64 is so formed that the main flame 66 itself has a short overall length. The quantity of heat being the same, the short main flame 66 has a higher calorific value per unit volume than ordinary flames, and hence a greater flame intensity. Because the flame is short and the surface area is small, the heat-radiating area is accordingly limited and the heat of combustion can be supplied to a desired zone concentrically and efficiently without waste. Further, because the flame length is short and the main flame 66 is formed near the burner 64, flame stability is attained without the possibility of lifting.

Combustion-sustaining air need not always be supplied through the air line 69 as illustrated in this embodiment, but it may be introduced from a separate route. In any case, it is most desirable that the air be fed in the direction toward the tip of the burner 64 or around the center flame 65.

For the reasons above stated, it is possible according to the present invention that through a combination of a. the supply of oxygen substantially in the form of pure oxygen in an amount far less than that theoretically required for combustion of liquid fuel to be burned so that a very rapid combustion temperature rise can be attained,

c. a high-temperature flame having a large calorific value v per unit volume thereof, that is, a flame of extremely high intensity, is obtained efficiently with a small supply of oxygen.

It is further to be noted that the nozzles are fitted to be ad- 10 justable relative to one another in the longitudinal direction by means of adjustment setting of the respective regulating handle (not shown in the drawings). This adjustment, together with readjustment of the respective fluid pressure, enables a single type of nozzle to meet any material changes in the amount of fuel oil and oxygen to be added, and permits adjustments of flame contour over an extensive range.

In the second embodiment, the device of the construction according to the first embodiment is so modified in design as to supply pure oxygen in an amount from 2 to 15 percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about l,700 to about 2,200 C., or the flame has a correspondingly high intensity.

The construction of the third embodiment will now be described with reference to FIG. 4. An oxygen nozzle 102 having a threaded portion 101 at one end is provided with an axial hole as an oxygen line 103. Upstream of the flow direction of oxygen from the tip 104 at the end of the oxygen line 103 there is formed a pressure-reducing portion 105. By the provision of this pressure-reducing portion 105, the bore of the tip 104 is made larger than that upstream of the flow direction of oxygen gas through the oxygen line 103. In the large bore section and in the neighborhood of the pressure-reducing portion 105 is provided one or a plurality of passages 106 for the introduction of heavy oil (liquid fuel) through passages branched from the forward portion of the liquid fuel nozzle. The pressure-reducing portion 105 and the tip 104 define a mixing chamber 107 therebetween. The heavy oil passages 106 are formed at an angle, as shown, so that they can open in the mixing chamber 107 in the oxygen flow direction.

Thus, the oxygen gas that flows through the oxygen line 103 is injected out of the tip 104 via the mixing chamber 107. As it passes through the pressure-reducing portion 105, the oxygen gas is thereby expanded and reduced in the flow velocity. Accordingly, the mixing action of a part of heavy oil and oxygen gas in the mixing chamber 107 is improved and the atomizing action of the liquid fuel in the mixing chamber 107 is remarkably increased. As a result, the gaseous mixture forms a more readily ignitable and stabilized high-temperature center flame.

Referring now to FIG. 5 showing the construction of the fourth embodiment, an oxygen nozzle 152 having a threaded portion 151 at one end is provided with an axial hole as an oxygen line 153. Upstream of the flow direction of oxygen from the tip 154 at the end of the oxygen line 153 there is formed an oxygen turbulence-generating portion 155. By the provision of this oxygen turbulence-generating portion 155, the bore of the tip 154 is made larger than that upstream of the flow direction of oxygen gas through the oxygen line 153. In part of the oxygen turbulence-generating portion 155 is provided one or a plurality of passages 156 for the introduction of heavy oil (liquid fuel) through passages branched from the forward portion of the liquid fuel nozzle. The oxygen turbulence-generating portion 155 and the tip 154 define a mixing chamber 157 therebetween. The heavy oil passages 156 are formed at an angle so that they can open in the mixing chamber 157 in the oxygen flow direction.

Thus, the oxygen gas that flows through the oxygen line 153 is injected out of the tip 154 via the mixing chamber 157. As it passes through the oxygen turbulence-generating portion 155, the oxygen gas is expanded, reduced in pressure, and made turbulent. This turbulent oxygen gas mixes up with most of the liquid fuel introduced therein through the heavy oil passages 156 and then forms a more readily ignitable and stabilized high temperature.

The construction of the fifth embodiment will now be described with reference to FIG. 6. An oxygen nozzle 202 having a threaded portion 201 at one end is provided with an axial hole as an oxygen line 205. A tapered portion 204 is formed at the front end of the oxygen line 205 or in the vicinity thereof in such a manner as to expand toward the tip 203 at the other end of the oxygen nozzle 202. By the provision of this tapered portion 204, the bore of the tip 203 is made larger than that upstream of the flow direction of oxygen gas through the oxygen line 205. Midway the tapered portion 204 is provided one or a plurality of passages 206 for the introduction of heavy oil (liquid fuel) through passages branched from the forward portion of the liquid fuel noule. The tapered portion 204 and the tip 203 define a mixing chamber 207 therebetween. The heavy oil passages 206 are formed in the oxygen nozzle 202 with the other port open in the mixing chamber 207 at an angle with respect to the oxygen gas flow direction.

Thus, the oxygen gas that flows through the oxygen line 205 is injected out of the outlet port 203 via the tapered portion 204 and mixing chamber 207. As it passes through the tapered portion 204, the oxygen gas is thereby rapidly diffused and reduced in density. Accordingly, in view of the reduced oxygen density, the mixing action of a part of the heavy oil and oxygen gas in the mixing chamber 207 is improved. The dispersion and mixing in the chamber are thus accomplished positively and satisfactorily, and homogeneously mixed gaseous mixture is injected out of the tip 203. Accordingly, the gaseous mixture is rendered highly ignitable, and the center flame formed on combustion is all the more increased in stability and temperature. Moreover, because the openings of the heavy oil passages 206 in the mixing chamber 207 are provided in the tapered portion 204 diagonally rearward of the oxygen gas flow direction, any backward flow of oxygen gas through the heavy oil passages 206 to the liquid fuel line is avoided and hence backfire is precluded.

Further, because the oxygen stream by its suction introduces a part of heavy oil into the mixing chamber 207, the heavy oil can be urged into the chamber in an adequate amount in addition to the fact that the branched flow passages 206 are so thin that the oil flowing therethrough is easily atomized.

With the construction above described, the feed of heavy oil can be suitably increased or decreased automatically in accordance with the variation of the rate of oxygen injection within a certain range and, at the time of combustion, the amount of heavy oil to be burned is automatically controlled depending on the oxygen supply. For example, any possibility of an excessive supply of oxygen with consequent outward flow of a part of the oxygen jet through the center and main flame is eliminated and the oxygen gas can be completely and effectively used. in this way a stabilized center flame is obtained which corresponds to the amount of oxygen supplied that is all converted into heat.

The turbulent condition of the combustible mixture varies depending on changes of the taper angle of the tapered portion 204.

In the sixth embodiment, the device of the construction according to the third embodiment is so modified in design as to supply pure oxygen in amount of from 2 to percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about l,700 to about 2,200 C., or the flame has a correspondingly high intensity.

The construction of the seventh embodiment will now be explained in conjunction with FIGS. 7 and 0.

To an oxygen line 251 disposed in the central part of the device is connected an oxygen nozzle 253 through a nozzle joint 252. Surrounding this oxygen line 251 there is provided a liquid fuel line 254, to the front end of which is connected a liquid fuel nozzle 256. The liquid fuel line 254 and liquid fuel nozzle 256 are arranged outside the oxygen line 251 and oxygen nozzle 253 coaxially or substantially coaxially therewith. Further outside the liquid fuel line 254 an air line 257 is disposed which has an air nozzle 258 at its front end. In the middle part of the oxygen gas passage 259 in the oxygen nozzle 253 there is formed an orifice 261 integrally with the oxygen nozzle 253 and which protrudes axially at a point fairly upstream of the oxygen flow direction from the tip 260 of the nozzle 253 and in the direction approaching the center of the oxygen flow passage 259 so that it can abruptly increase the flow velocity of oxygen gas. By the provision of this orifice 261 an abruptly changing portion 262 is formed in the oxygen flow passage 259. in the space defined between the abruptly changing portion 262 and tip 260 of the oxygen nozzle 253 is pro vided one or a plurality of heavy oil passages 263 which are flow passages branched from the liquid fuel nozzle 256, inclined or substantially perpendicular to the axis of the device. Inside the oxygen flow passage 259 of the oxygen nozzle 253 there is formed a mixing chamber 264 between the orifice 261 and tip 260.

A burner 267 of the foregoing construction is held in a combustion-sustaining air line 269 coaxially or substantially coaxially therewith, with the frontal part usually penetrating through a furnace wall 268 and extending into the furnace.

With such an arrangement, a part of the heavy oil is fed into the oxygen nozzle 253 through the passages 263 and mixed with oxygen gas in the mixing chamber 264 and then the mixture is injected out of the tip 260 and burned to form a center flame 265. The remainder of the heavy oil is injected from the tip of the liquid fuel nozzle 256 and is atomized by the atomizing air issuing from the air nozzle 258 and is then burned together with the combustion sustaining air supplied from the air line 269, whereby a main flame 266 is formed enveloping the center flame 265. This condition will be more fully described with reference to FIG. 8. The oxygen gas forced from the oxygen flow passage 259 toward the mixing chamber 264 is collected in the zone along the axial center of the oxygen flow passage 250 by means of the abruptly changing portion 262. The oxygen gas so collected is abruptly injected into the mixing chamber 264 along the axial center zone thereof. A part of oxygen gas surrounding the outer periphery of the jet is abruptly introduced into the chamber where it is made turbulent in the mixing chamber 264 and caused to form a vortex flow therein. The heavy oil fed through the passages 263 is involved in the vortex of oxygen gas, and the oxygen gas and heavy oil in the vortex flow move toward the tip opening 260 while being thoroughly mixed and perfectly atomized in the mixing chamber 264 before the gaseous mixture issues from the tip 260.

Thus, the orifice 261 produces a fairly intense vortex flow and permits vigorous suction of liquid fuel through the passages 263 and very thorough dispersion and mixing of the liquid fuel with oxygen gas. The resulting mixture attains very good ignitability and flame stability within an extremely wide range of oxygen flow rate.

In the eighth embodiment, the device of the construction according to the seventh embodiment is so modified in design to supply pure oxygen in an amount of from 2 to 15 percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame tem' perature is as high as about l,700 to about 2,200 C., or the flame has a correspondingly high intensity.

The construction according to the ninth embodiment is as shown in FIG. 9. In the middle part of the device there is provided an oxygen nozzle 302 which has an oxygen flow passage 301. This oxygen nozzle 302 is enveloped by a liquid fuel nozzle 304 having a liquid fuel passage 303. Further, the liquid fuel nozzle 304 is enveloped by an air nozzle 306 having an air flow passage 305. The oxygen nozzle 302, liquid fuel noule 304 and air nozzle 306 are arranged coaxially and substantially coaxially with one another. These

nozzles

302 and 304 are slidably displaceable with respect to one another. The oxygen nozzle 302 is protruded so that the innermost tip opening, i.e. the tip opening 307 of the oxygen nozzle 302 extends ahead of the other nozzle tip openings, i.e., the

tip openings

308 and 309 of the liquid fuel nozzle 304 and air nozzle 306. At the front end of the oxygen nozzle 302 or in the vicinity thereof, there is formed a tapered portion 315 that expands toward the tip opening 307. Midway of this tapered portion 315 is provided one or a plurality of heavy oil passages 313 which are passages branched from the liquid fuel line 303. Within the oxygen flow passage 301, a mixing chamber 314 is defined by the tapered portion 315 and the tip opening 307. Vane means 319 for turbulent air injection are provided in the air flow passage 305. A burner 316 of the construction as above described is held in a combustion-sustaining air line 318 coaxially or substantially coaxially therewith, with the frontal part usually penetrating through a furnace wall 317 into the furnace.

A part of the heavy oil which is the liquid fuel in the liquid fuel passage 303 is introduced into the mixing chamber 314 through the heavy oil passages 313. Inside the chamber 314, the oil is mixed with and atomized by oxygen gas and is injected through the tip opening 307 and, at the same time, burned to form a center flame 311. The air that flows through the air passage 305 is injected in a vortex flow from the tip opening 309 and thereby atomizes most of the heavy oil that flows through the liquid fuel passage 303 and issues from the tip opening 308, thus causing the mixture to be emitted from the tip opening 309. During the course of this atomization of heavy oil, the air and heavy oil tend to move toward the tip opening 307 of the oxygen nozzle 302 but, because the oxygen nozzle 302 extends frontwardly ahead of the other nozzles, the mixture is injected and atomized along the protruded periphery 310.

This construction serves to avoid deterioration of the center flame stability due to disturbance by the momentum of injection of atomizing air in the course of atomization, as would occur when the tip opening of an inner nozzle should be flush with the tip opening of outwardly located nozzles or when the tip opening of the inner nozzle should be positioned rearwardly of the other nozzles with respect to the material flow. In other words, the embodiment enables heavy oil to be atomized and dispersed in the neighborhood of the nozzle tip without affecting the center flame unfavorably. While the vaporization and decomposition of the heavy oil by the center flame 311 are being remarkably promoted, a highly stabilized main flame 312 is produced. The heavy oil and air hit against the same outer periphery 310 and this creates a colliding and vaporizing action in addition to the blowing and atomizing action already described, hence ensuring a better and more positive atomizing action of the heavy oil.

In the tenth embodiment, the device of the construction according to the ninth embodiment is so modified in design as to supply pure oxygen in an amount of from 2 to 15 percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about 1,700 to about 2,200 C., or the flame has a correspondingly high intensity.

The construction of the eleventh embodiment will now be described with reference to FIG. 10.

To an oxygen line 351 disposed in the central part of the device is connected an oxygen nozzle 353 through a nozzle joint 352. This oxygen line 351 is enveloped by a liquid fuel line 354 which is connected at the front end with a liquid fuel nozzle 356. The liquid fuel line 354 and liquid fuel nozzle 356 are arranged outside the oxygen line 351 and oxygen nozzle 353 coaxially or substantially coaxially therewith. Further, the liquid fuel line 354 is enveloped by an air line 357 which has an air nozzle 358 at its front end. In the middle part of the oxygen gas passage 368 in the oxygen nozzle 353 there is formed an orifice 360 integrally with the oxygen nozzle 353 and which protrudes axially at a point fairly upstream of the oxygen flow direction from the tip 359 of the nozzle 353 and in the direction approaching the center of the oxygen flow passage 368 so that it can abruptly increase the flow velocity of oxygen gas. By the provision of this orifice 360 an abruptly changing portion 369 is formed in the oxygen flow passage 368. In the space defined between the abruptly changing portion 369 and tip 359 of the oxygen nozzle 353 is provided one or a plurality of heavy oil passages 361 which are flow passages branched from the liquid fuel nozzle 356, inclined or substantially perpendicular to the axis of the device. lnside the oxygen flow passage 368 of the oxygen nozzle 353 there is formed a mixing chamber 362 between the orifice 360 and tip 359. The oxygen nozzle 353 is elongated so that the tip opening of the inner nozzle, i.e., the tip opening 359 of the oxygen nozzle 353, extends ahead of other nozzle tip openings, i.e., the

tip openings

363 and 364 of the liquid fuel nozzle 356 and air nozzle 358.

The end periphery of the protruded tip opening 359 of oxygen nozzle 353 extends outwardly with an annular extension or flange 365 which is formed in one piece with the oxygen nozzle 353. Constructed in this way, the burner 355 is positioned in a combustion-sustaining air line 371 coaxially or substantially coaxially therewith, usually penetrating altogether through a furnace wall 370 with the front end portion held inside the fumace.

Then the mixture of oxygen and part of the heavy oil mixed in the mixing chamber 362 issues from the tip opening 359. At this time, the flange 365 causes most of the heavy oil and air to flow divergently outward simultaneously with the injection, and the mixture upon injection from the tip opening 359 reapproaches the opening 359 by convection due to a reverse flow phenomenon. This mixture is burned while involving the backward flow and, as a result, the center flame 366 thereby formed contains the backward flow, and the unburned mixture issuing from the tip opening 359 is ignited by this backward flow. Consequently, the ignitability and stability of the center flame 366 are greatly improved and at the same time, the main flame 367 is shortened and laterally expanded with high stability. This construction is particularly advantageous in certain cases where ignition is rendered difficult under particular operating conditions, for example, due to a too low-fumace temperature, or where an expanse of flame is required, or where a short wide flame is required.

In the twelfth embodiment, the construction of the eleventh embodiment is modified in design so that pure oxygen is supplied only in an amount of from 2 to 15 percent the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about l,700 to about 2,200 C., and the flame has an accordingly high flame intensity.

Referring to FIGS. 11 to 13, the construction of the thirteenth embodiment will be described below.

To the front end of a liquid fuel line 401 disposed in the central part of the device is connected a liquid fuel nozzle 402 through an oil gun joint 405. The liquid fuel line 401 is enveloped by an oxygen gas line 403, the front end of which in turn is connected to an oxygen nozzle 404 via a nozzle joint 406. The oxygen gas line 403 and oxygen nozzle 404 are arranged outside the liquid fuel line 401 and liquid fuel nozzle 402, respectively, either coaxially or substantially coaxially therewith. The liquid fuel nozzle 402 is so located that its tip opening 407 is retracted from the tip 408 of the oxygen nozzle 404, upstream of the injective direction of liquid fuel stream. lnside the oxygen nozzle 404 and in the vicinity of the tip 408 there is defined a mixing chamber 409. In the oxygen gas passage 414 of the oxygen nozzle 404 and in the vicinity upstream of the oxygen flow direction from the tip opening 407 of the liquid fuel nozzle 402, there is formed an annular step 410 which protrudes from the inner wall of the oxygen nozzle 404 toward the outer wall of the liquid fuel nozzle 402 at a point near the tip opening 407 and upstream of the oxygen flow direction, integrally with the oxygen nozzle 404. The part ofthe oxygen flow passage 414 constricted by this step 410 represents an abruptly changing portion 41 l, and a dead space 415 is defined outwardly thereof. Enveloping the oxygen gas line 403, a water line 412 is connected to the nozzle joint 406, and a water jacket 413 is defined by the nozzle joint 406.

Heavy oil, or the liquid fuel that is supplied from the liquid fuel line 401 to the liquid fuel nozzle 402 via the oil joint 405 is injected from the tip opening 407 of this nozzle 402 to the mixing chamber 409 and divergently toward the discharging direction. On the other hand, the oxygen gas supplied to the oxygen flow passage 414 in the oxygen line 403 is injected into the mixing chamber 409 through the oxygen nozzle 404. The heavy oil and oxygen gas are mixed in the mixing chamber 409 and the mixture is injected from the tip 408 of the oxygen nozzle 404. Then, the mixture is ignited and burned to form a flame. Here, as shown more fully in FIG. 13, the oxygen gas is injected from the oxygen flow passage 404 into the mixing chamber 409 toward the axial center thereof, in the form of a stream extremely increased in speed by means of the abruptly changing portion 411 of the oxygen flow passage 414. At the same time, a part of the oxygen gas therearound is made turbulent to form vortices in the dead space 415. The heavy oil injected from the liquid fuel nozzle 402 is therefore involved in the vortices of oxygen gas, and thus the oxygen gas and heavy oil are thoroughly mixed in the dead space 415 and mixing chamber 409. In this way the heavy oil is completely atomized and mixed before injection into the atmosphere.

Because of the thorough atomization and mixing, the mixture has excellent ignitability, great flame intensity and is maintained at a high temperature.

The mixing chamber 409 is immediately open to the atmosphere, and the abruptly changing portion 411 provides a marked difference in pressure between the mixing chamber 409 and the space in the oxygen flow passage 414 that is upstream from the abruptly changing portion 411. This eliminates the possibility of the heavy oil flowing backward to the oxygen gas line 403. As a result, the dangers of damage of the device and explosion due to backfire and the like are completely avoided, and a remarkable improvement in safety is attained over a very extensive range of oxygen flow rate.

In the fourteenth embodiment of the invention, the device of the construction according to the thirteenth embodiment is modified in design so that pure oxygen is supplied only in an amount of from 30 to 70 percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about 2,200 to about 2,700 C. or the flame has a correspondingly high intensity. Specifically in this embodiment, the supply of pure oxygen may be increased to 100 percent for added beneficial effect.

The construction of the fifteenth embodiment will now be described in conjunction with FIG. 14.

To the front end of a liquid fuel line 451 disposed in the central part of the device is connected a liquid fuel nozzle 452 through an oil gun joint 455. The liquid fuel line 451 is enveloped by an oxygen gas line 453, the front end of which in turn is connected to an oxygen nozzle 454 via a nozzle joint 456. The oxygen gas line 453 and oxygen nozzle 454 are arranged outside the liquid fuel line 451 and liquid fuel nozzle 453, respectively, either coaxially or substantially coaxially therewith. The liquid fuel nozzle 452 is so located that its tip opening 457 is retracted from the opening 458 of the oxygen nozzle 454, upstream of the injective direction of liquid fuel stream. Inside the oxygen nozzle 454 and in the vicinity of the opening 458 there is defined a mixing chamber 459. In the oxygen gas passage 464 of the oxygen nozzle 454 and in the vicinity upstream of the oxygen flow direction from the opening 457 of the liquid fuel nozzle 452, there is formed an orifice 460 integrally with the oxygen nozzle 454 and which protrudes toward the axial center in the direction approaching the tip opening 457 of the liquid fuel nozzle 452, thereby to cause a sudden increase in the flow velocity of oxygen gas. The orifice 460 defines an abruptly changing portion 461 in the oxygen flow passage 464. Enveloping the oxygen gas line 453, a water line 462 is connected to the nozzle joint 456, and a water jacket 463 is defined by the nozzle joint 456. Near the tip opening 457 of the liquid fuel nozzle 452, a swirl generator 466 is formed inside the liquid fuel passage 465 in such a manner as to inject the liquid fuel in a divergent, conical and helical direction.

Thus, heavy oil which is the liquid fuel supplied from the liquid fuel line 451 to the liquid fuel nozzle 452 via the oiljoint 455 is injected from the tip opening 457 of this nozzle 452 to the mixing chamber 459 and divergently toward the direction of discharge. Meanwhile, the oxygen gas that flows through the oxygen flow passage 464 is accelerated in the flow velocity by the abruptly changing portion 461 of the oxygen flow passage 464 and is injected toward the axial center of the mixing chamber 459. The oxygen gas so injected is made turbulent to form vortices near the outward end of the mixing chamber 459 and the vortices in turn involve the heavy oil injected from the liquid fuel nozzle 462. The mixture of oxygen gas and heavy oil is then injected from the tip opening 458. At this time, the heavy oil that flows through the liquid fuel passage 465 is caused to swirl in a turbulent state by the pressure exerted thereupon and by the action of the swirl generator 466. The fuel is then injected from the tip opening 457 in an expanding, conical and helical direction.

The provision of swirl generator 466 ensures quicker and more uniform mixing of the fuel with oxygen gas than otherwise in the mixing chamber 459 so that the ignitability of the gas mixture is improved and the flame is formed in a stabilized state adjacent to the tip of the burner device to attain the object of the present invention all the more satisfactorily.

1n the sixteenth embodiment, the device of the construction according to the fifteenth embodiment is modified in design so that pure oxygen is supplied only in an amount of from 30 to 70 percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about 2,200 to about 2,700 C. or the flame has a correspondingly high intensity. It is further possible, specifically in this embodiment to increase the pure oxygen supply to percent for further beneficial effect.

Now the construction of the seventeenth embodiment will be explained in connection with FIG. 15.

To the front end of a liquid fuel line 501 disposed in the central part of the device is connected a liquid fuel nozzle 502 through an oil gun joint 505. The liquid fuel line 501 is enveloped by an oxygen gas line 503, the front end of which in turn is connected to an oxygen nozzle 504 via a nozzle joint 506. The oxygen gas line 503 and oxygen nozzle 504 are arranged outside the liquid fuel line 501 and liquid fuel nozzle 502, respectively, either coaxially or substantially coaxially therewith. The liquid fuel nozzle 502 is so located that its tip opening 507 is retracted from the opening 508 of the oxygen nozzle 504, upstream of the injective direction of liquid fuel stream. Inside the oxygen nozzle 504 and in the vicinity of the opening 508 is defined a mixing chamber 509. in the oxygen gas passage 514 of the oxygen noule 504 and in the vicinity upstream of the oxygen flow direction from the opening 507 of the liquid fuel nozzle 502, there is formed an orifice 510 integrally with the oxygen nozzle 504 and which protrudes toward the axial center in the direction approaching the tip opening 507 of the liquid fuel nozzle 502 thereby to cause a sudden increase in the flow velocity of oxygen gas. The orifice 510 defines an abruptly changing portion 511 in the oxygen flow passage 514. Enveloping the oxygen gas line 503, a water line 512 is connected to the nozzle joint 506, and a water jacket 513 is defined by the nozzle joint 506. Near the tip opening 507 of the liquid fuel nozzle 502, a swirl generator 516 is formed inside the liquid fuel passage 515 in such a manner as to inject the liquid fuel in the divergent, conical and helical direction.

Outside the oxygen noule 504, a forced air supply duct 517 is disposed coaxially or substantially coaxially therewith. The tip opening 518 of this air duct 517 is provided in the neighborhood of the tip opening 507 of the oxygen nozzle 504. Between the oxygen gas line 503 and air duct 517 is defined a forced air passage 519 which communicates with a blower, not shown. In this forced air passage 519 are provided vane means 520 for turbulenTa imjection. The air duct 517 is enveloped by a water jacket 522 via a tip ring 521. Constructed as above, the burner 523 is partly held in a furnace with the front end portion penetrating through the furnace wall 524.

Thus, the heavy oil or the liquid fuel that is supplied from the liquid fuel line 501 to the liquid fuel nozzle 502 via the oil joint 505 is injected from the tip opening 507 of this nozzle 502 to the mixing chamber 509 and divergently toward the direction of discharge. Meanwhile, the oxygen gas that flows through the oxygen flow passage 514 is accelerated in the flow velocity by the abruptly changing portion 511 of the oxygen flow passage 514 in being injected toward the axial center of the mixing chamber 509. The oxygen gas so injected is made turbulent to form vortices near the outward end of the mixing chamber 509, and the vortices in turn involve the heavy oil injected from the liquid fuel nozzle 502. The mixture of oxygen gas and heavy oil is then injected from the tip opening 508. At this time, the heavy oil that flows through the liquid fuel passage 512 is caused to swirl in a turbulent state by the pressure exerted thereupon and by the action of the swirl generator 516, then injected from the tip opening 507 in an expanding and helical fashion. The combustion-sustaining air which is forced forward through the air duct 517 is caused to swirl as it is moved in the forced air passage 519 by the pressure exerted and the action of the vane means 520 for the turbulent air injection and, in the swirling condition, it is injected into the atmosphere.

Since the oxygen supply is far less than the equivalent required for the forming of the center flame to accomplish the volatilization and decomposition of the liquid fuel, the rest of oxygen necessary for the complete combustion is obtained from air. Here, because the forced air supply duct is positively provided, the large amount of active radicals produced in the center flame and the high-temperature combustible gases (H C,l-l,, C H C,H etc.) formed on the volatilization and decomposition of the liquid fuel are forcibly mixed with air so that the combustion can be accomplished rapidly and completely at a temperature and intensity almost as high as those attained with the flame by combustion of the liquid fuel in pure oxygen alone.

While the provision of the cooling means 512 and 522 at suitable points as illustrated in connection with this embodiment is, in itself, a customary practice in the art, the means are specifically described here because they are incorporated in the embodiment in a most definite and practical way.

In the eighteenth embodiment of the invention, the device of the construction according to the seventeenth embodiment is modified in design so that pure oxygen is supplied only in an amount of from to 70 percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about 2,200to about 2,700" C., or the flame has a correspondingly high intensity. It is appreciated particularly in this embodiment that the pure oxygen supply may be increased to 100 percent in order to attain an even more improved effect.

Next, the construction of the nineteenth embodiment of the invention will be described with reference to FIG, 16.

To the front end of a liquid fuel line 551 disposed in the central part of the device is connected a liquid fuel nozzle 552 through an oil gun joint 555. The liquid fuel line 551 is enveloped by an oxygen gas line 553, the front end of which in turn is connected to an oxygen nozzle 556 via a nozzle joint 554. From the nozzle joint 554, a water line 557 extends as if to envelope the oxygen gas line 553, and a water jacket is formed in the nozzle joint 554. Surrounding the water line 557 there is disposed a liquid fuel line 559, at the front end of which is provided a liquid fuel nozzle. These three

nozzles

552, 556 and 560 are fitted in one another coaxially or substantially coaxially. Further, outside the liquid fuel line 559 is arranged an air duct 561 provided with an air nozzle 562 at the front end. The inner liquid fuel nozzle 552 is so located that its tip opening 563 is retracted from the opening 564 of the oxygen nozzle 556, upsfream of the injective direction of liquid fuel stream, and inside the oxygen nozzle 556 and in the vicinity of the opening 564 is defined a mixing chamber 565. In the oxygen gas passage 566 of the oxygen nozzle 556, and in the vicinity upstream of the oxygen flow direction from the opening 563 of the liquid fuel nozzle 552, there is formed an orifice 567 integrally with the oxygen nozzle 556 and which protrudes toward the axial center in the direction approaching the tip opening 563 of the liquid fuel nozzle 552, thereby to cause a sudden increase in the flow velocity of oxygen gas. The orifice 567 defines an abruptly changing portion 568 in the oxygen flow passage 566. Near the tip opening 563 of the inner liquid fuel nozzle 552, a swirl generator 570 is formed inside the liquid fuel passage 569 in such a manner as to inject the liquid fuel in the divergent, conical and helical direction. Outside the air nozzle 562 a forced air supply duct 57! is disposed coaxially or substantially coaxially therewith. The tip opening 572 of this forced air duct 571 is provided in the neighborhood of the tip opening 564 of the oxygen nozzle 556. Between the air duct 561 and the forced air supply duct 571 is defined a forced air passage 573 which communicates with a forced blower, not shown. In this forced air passage 573 are provided vane means 574 for turbulent air injection in the helical direction. The forced air duct 571 is enveloped by a water jacket 576 via a tip ring 575. The tip openings of the outer liquid fuel nozzle 560, atomizing gas supply nozzle 562 and forced air duct 571 are provided in the vicinity of the tip opening 564 of the oxygen nozzle 556. Constructed as above described, the burner 577 is partly held in a furnace with the front end portion penetrating through the furnace wall 578.

Thus, the heavy oil or the liquid fuel that is supplied from the liquid fuel line 551 to the liquid fuel nozzle 552 via the oil joint 555 is injected from the tip opening 563 of this nozzle 552 to the mixing chamber 565 and divergently toward the discharging direction. Meanwhile, the oxygen gas that flows through the oxygen flow passage 566 is accelerated in the flow velocity by the abruptly changing portion 568 of the oxygen flow passage 566 by being injected toward the axial center of the mixing chamber 565. The oxygen gas so injected is made turbulent to form vortices near the outward end of the mixing chamber 565, and the vortices in turn involve the heavy oil injected from the inner liquid fuel nozzle 552. The mixture of oxygen gas an heavy oil is then injected from the tip opening 564. At this time, the heavy oil that flows through the liquid fuel passage 569 is caused to swirl in a turbulent state by the pressure exerted thereon and by the action of the swirl generator 570,- and then injected from the tip opening 563 in an expanding and helical fashion. The gaseous mixture is then ignited to form the center flame. The heavy oil that is injected from the outer liquid fuel nozzle 560 spurts around the center flame. At this point, the oil does so in a state atomized and dispersed by the gaseous jet from the air nozzle 562 which surrounds the fuel nozzle. Around the center flame, the liquid fuel is vaporized and decomposed by the high heat of reaction of the center flame and gives off a large amount of active radicals. The increased production of active radicals combines with the high heat of reaction of the center flame to promote the combustion of the liquid fuel thus vaporized and decomposed. This vaporized and decomposed liquid fuel is burned around the center flame while being diffused by and mixed with the combustion-sustaining air forcibly supplied from the forced air supply passage 573. In this way the main flame is formed. The combustion-sustaining air which is urged forward through the forced air passage 573 is caused to swirl by the pressure so applied and the action of the vane means 574 for turbulent air injection and, in the swirling condition, it is shifted in the delivery pattern and injected around the center flame. The diffusion and mixing above described are thus accomplished all the more vigorously.

When the large center flame is being formed, the oxygen nozzle 556 and the parts in theproximity thereof are heated to fairly high temperatures, but to prevent overheating they are cooled by water that runs through the water jacket 558. Outer jacket 576 is provided if desired.

If an extremely large naEEHfie formed by injection of a large volume of liquid fuel, the mixing efficiency of the liquid fuel and oxygen gas is badly affected for the following reason. In the combustion device to burn such large volume of liquid fuel, required oxygen supply is accordingly large, and the oxygen nozzle must therefore be of large diameter. In this case, if a combustion means as described hereinbefore in embodiments 1 to 13 is used, it will become difficult to realize complete mixing of the liquid fuel with oxygen gas.

According to the present embodiment, however, a part of the large volume of liquid fuel to be injected is injected from the inner liquid fuel nozzle into the central part of the oxygen gas stream being injected from the oxygen nozzle. Also, this part of liquid fuel injected is caused to pass through the swirl generator so that it swirls while expanding in the divergent and spiral direction to reduce its own density. 1n the manner described, the part of liquid fuel is completely atomized and mixed in the oxygen gas to form a stead, stabilized center flame. In this state, most of the liquid fuel is injected from the outer liquid fuel nozzle and, together with the atomizing gas from the atomizing air nozzle, the most of the liquid fuel is directed to the center flame and is vaporized and decomposed efficiently around the center flame. The combustion-sustaining air issuing from the forced air supply duct is rendered turbulent by the vane means and is fed around the flame. When the liquid fuel is injected in such large volume, perfect combustion cannot be realized with devices as described hereinbefore in embodiments 1-13, on account of incomplete mixing of such large volume fuel with oxygen gas. According to the present invention, however, fraction of the liquid fuel to be burned is perfectly mixed with oxygen gas at the central portion along the oxygen flow path, in order to form a very stable center flame, while the rest of the liquid fuel, constituting large portion thereof, is atomized, vaporized and decomposed around the said center flame whose heat effectively serves for this purpose. Therefore, even when a liquid fuel is injected in such large volume that the complete mixing with oxygen gas may not be expected with means as described hereinbefore in embodiments 1-13, a very stable center flame can hereby be formed and the main flame so produced is stable and large and has a high flame intensity.

The present embodiment thus permits provision of a large capacity liquid fuel combustion device with excellent performance.

In the twentieth embodiment of the invention, the construction of the nineteenth embodiment is modified in design so that the pure oxygen supply may be limited to from 2 to 15 percent of the theoretical oxygen requirement. Accordingly, notwithstanding the stability and largeness, the flame is maintained at a temperature as high as about 1,700 C. to about 2,200 C with a very high-flame intensity.

Of the preferred embodiments of the present invention hereinabove elucidated, the thirteenth through the eighteenth embodiments easily produce short and high-temperature flames and are most adapted for that reason for such applications as melting scrap metal charged in a melting furnace, for example, and which is located near the tip of the burner according to the invention.

What is claimed is:

l. A liquid fuel combustion device comprising concentrically disposed oxygen, liquid fuel and gas feed lines having threaded entry ends, the terminus of said threaded entry ends lying in substantially the same vertical plane, an axially perforated oxygen control nozzle means threaded at one end for attachment to said oxygen feed line, said noule means further including an end portion and being provided with angularly disposed passages substantially medially of its length, said passages permitting oxygen passing through said oxygen feed line to suck thereinto liquid fuel arranged to pass through the concentric fuel line disposed thereabout, an axially perforated liquid fuel control nozzle means having a terminal end portion secured to the terminus of said threaded fuel feed line, said terminal end portion of said fuel control nozzle means ter' minating in the same vertical plane as the end portion of said oxygen nozzle means, and an axially perforated gas control nozzle means having a terminal end portion secured to the terminus of said threaded gas feed line, said terminal end portion of said gas control nozzle means terminating in the same vertical plane as the end portion of said liquid fuel control nozzle means, whereby upon combustion a center flame of high temperature is formed, said center flame being surrounded by a main flame of higher calorific value.

Patent No.

Inventor(s Dated October 5, 1971 Masayoshi Nakagawa et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 18,

V (SEAL) Attest:

EDWARD M.FLETCHER,JR LAttesting Officer line 67,

line

line 38,

line 44,

line 18,

Signed "16" should read l5 change "250" to --259-- change "an to --and-- change "stead" to steadyand sealed this 12th day of September 1972.

ROBERT GOTTSCHALK Commissioner of Patents