US3816055A - Reigniter means for power combustors - Google Patents

Abstract

Reigniter means for combustors of vapor generators used in eternal combustion engine systems. The combustors provide heat in response to engine power demand to vaporize liquid in boiler tubes. Combustion emissions are with low noxious pollutant content over the power operating range of the engine system. Internal arrangements in the combustors maximize burning up of fuel that is injected into the primary combustion zone. Portions of the combustor that may reach above 2,100*F are minimized to inhibit the formation of nitrous oxide. Regions that might fall below 1,500*F are controlled to minimize quenching that would result in the formation of carbon monoxide and unburned hydrocarbon particles. The flow of combusted gases is moderated by arranging incoming air to be in the counter direction. Air and fuel particles are thoroughly intermixed towards complete combustion. An important feature is a tower positioned in the route of the gases out of the combustor, for reigniting combustible particles that have not fully burned.

Description

United States Patent [1 1 [111 3,816,055 June 11, 1974 Lear 1 1 REIGNITER MEANS FOR POWER COMBUSTORS [75] Inventor: William P. Lear, Verdi, Nev.

[73] Assignee: Lear Motors Corporation, Reno,

Nev.

[22] Filed: June 15, 1972 [21] Appl. No.: 263,108

Related US. Application Data [63] Continuation-impart of Ser. No. 261,691, June 12,

[52] US. Cl 431/171, 431/347, 431/350 [51] Int. Cl. F23m 9/06 [58] Field of Search 431/168, 169, 171, 172, 431/347, 350,352, 353; 110/97 R; 122/155 A [56] References Cited UNITED STATES PATENTS 704,600 7/1902 Van der Borght 122/155 A 1,712,699 5/1929 Grefenstette 110/97 R 2,606,604 8/1952 Witherell 431/353 2,712,352 7/1955 Manor etal. 431/171 3,364,968 1/1968 Mutchler 431/347 Primary Examiner-Carroll B. Dority, Jr. Attorney, Agent, or Firm-Richard A. Marsen 5 7 ABSTRACT Reigniter means for combustors of vapor generators used in eternal combustion engine systems. The combustors provide heat in response to engine power demand to vaporize liquid in boiler tubes. Combustion emissions are with low noxious pollutant content over the power operating range of the engine system. Internal arrangements in the combustors maximize burning up of fuel that is injected into the primary combustion zone. Portions of the combustor that may reach above 2,100F are minimized to inhibit the formation of nitrous oxide. Regions that might fall below 1,500F are controlled to minimize quenching that would result in the formation of carbon monoxide and unburned hydrocarbon particles. The flow of combusted gases is moderated by arranging incoming air to be in the counter direction. Air and fuel particles are thoroughly intermixed towards complete combustion. An important feature is a tower positioned in the route of the gases out of the combustor, for reigniting combustible particles that have not fully burned.

4 Claims, 5 Drawing Figures REIGNITER MEANS FOR POWER COMBUSTORS CROSS REFERENCE This patent application is a continuation-in-part of my copending application for Vapor Generators With Low Pollutant Emission, Ser. No. 261,691 filed June 12, 1972, and assigned to the assignee hereof.

BACKGROUND OF THE INVENTION The basic engine power cycles in current use were originated before the turn of the century. The Rankine cycle involves the vapor engine principle, wherein the engines are fueled externally (ECE). Most of todays cars, buses and trucks are fueled internally, as combustion engines (ICE). The Otto cycle uses carbureted gasoline air/fuel mixtures that are exploded against the engines pistons. Gas turbines function generally on the Brayton cycle. Other variations are the Stirling and the Diesel engine cycles. Nevertheless, none of these engine cycles transform the heat energy that is generated into practical work with high efficiency. The Carnot cycle delineates the theoretical limits of such power conversion from heat energy.

The automakers have thoroughly masteredthe mass production of ICE piston engines using liquid petroleum fuel. The automobile industryv has thoroughly developed gasoline fueled ICE engines so that they cost less, weigh less, requireless space, and use less fuel for given output ratings than otherengine types currently available. Internal combustion engines however present a high noxious pollution factor. In operation, measured fuel and air mixtures are fed into each cylinder successively, exploded, then exhausted to the. atmosphere, all at many times per minute. Their pistons convert the explosion energyinto work. The air/fuel mixture often is improperly carbureted, and upon entering the cylinders only some portions of the charge burn well, while other portions have too little or too much fuel for the contained air. Another important defect is the relatively cooler cylinder walls that cause incompletely burned fuel therein.

The portions of the air/fuel charges that burn poorly, or not at all, containv carbon monoxide and hydrocarbons. The higher temperatures in the explosions cause the oxygen and, nitrogen of air in the charge to form unwanted oxides of nitrogen (N To date, researchers have determined that these inherent faults of the ICE systems may be moderated but not sufficiently as to their noxious pollution. Therelatively high adverse pollutant emissions from ICE engines are today a significant cause of smog and unhealthy city climates. The present invention is directed towards improved and practical vapor generators of superheated vapor athigh temperature and high pressure with relatively low resultant pollution for powering, ECE systems. In ECE steam there is no disintegration of fluid or vapor, or fowling of ECE system components. Superheated steam is generated by the combustor or burner as at the order of l,000F, and high pressure as at the order of 1,000 pounds per square inch (psi). The flow of the superheated steam to the vapor power expander is controlled through a throttle valve.

The combustor/vapor generator hereof is of simple construction; and rugged, reliable and efficient. It assures relatively clean emission operation from idling through top power demand. The combustor thereof has full vaporization and combustion of commercially available fuels, such as gasoline, kerosene. fuel oil and aircraft f uel. A combustor/vapor generator constructed with sufficient gross output, to power passenger cars fated at 120 HP, can be made the size of a spare tire,

systems, the, generated heat through fuel as heated gas is presented to the power expander, as a vapor turbine through a different medium, namely vapor or steam. The combustor/vapor. generator is apart from the power expander in the ECE system and independent thermodynamically.

SUMMARY OF THE INVENTION Water producing superheated steam has been found preferable to any available organic fluid as fluorocarbons. Water is stable at superheat. With water and about 26 inches in diameter. One for a bus, with 240 HP engine gross output, is of the same diameter, with less than twice the height.

The combustor has low noxious pollutant emission over the wide power range of its vehicle in use. The feedwater is fed into the vapor generator by a suitable pump in general proportion to output power demand. The result is a steam flow rate that is rapidly responsive to power demands on the ECE system as a whole. The respective steam and fuel and air mass flows, and their controls herein are continuous and continual while the engine system is ON, and provides a power drive basis for the vehiclethat is assmooth and effective as commercial ICE cars, buses and trucks.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in perspective of the exemplary vapor generator, as seen from below.

FIG. 2.is a cross-sectional view through the combustor/vapor generator of FIG. 1.

FIG. 3, is aview in perspective of a modified combustor/vapor generator of FIGS. 1 and 2, with the boiler tubes removed.

FIG. 4 is an enlarged plan view of reigniter device hereof.

FIG. 5 is a partial view device of FIG. 4.

THE COMBUSTOR-VAPOR GENERATOR of amodified portion of the ther, these factors remain operative over the power demand. and. operating range upon the vapor generator 30. Operation of the combustor (55) system is maintained with air and fuel injection at a given relative mass ratio, as 30, with an operative tumdown range of at least 20 to l. Referenceis made to my aforesaid copending patent application for details of an ECE system with a combustor-vapor generator of the type hereof.

The combustor system 55, may be designed to use fuels that are currently generally available, including automotive gasoline, kerosene, Diesel No. l and Jet A fuel, as well as for Unleaded gasoline, and .lP-4 aircraft class fuel. The overall efficiency of vapor generation hereof is found to be in the order of 95 percent at the lower power level of 50 HP, as at idling condition with accessory drive by a 240 HP unit; to the order of 90 percent at its top power level. Vapor generator 30 and combustor 55 are of relatively simple construction, rugged and reliable. The temperature of its gaseous exhaust is acceptably warm to the touch, as are the outer exposed surfaces. The vapor generator and combustor hereof (30,55) are suitable for mass production, of relatively inexpensive material, at reasonable unit cost.

Combustor 55 is of the axial flow turbulent vortex type. Combustion therein is accomplished with a 15 inch diameter chamber 132 for firewall 135: 15 inches high in the size for the 50 passenger bus; 7% inches high in the passenger car unit of hereof. The combustion gases are inert before they propel over top level l56 of firewall 135, and on to the convection bank of fluid/vapor tubing 160. The volume of the bus combustor (55) is 1.5 cubic feet. Its heat release at a 28 gallon per hour fuel rate provides approximately 2.l X 10 BTU per cubic foot per hour.

The fuel is herein atomized by a spinning cup 60 at the bottom center of the combustor. An atomizer nozzle or equivalent may instead by used. Fuel is introduced to the center of cup 60 through U-tube 61. Tube 61 is sized to supply the fuel at pressures below 10 psi. Spin cup 60 is rotated at 12,000 rpm for a rim velocity sufficient to atomize all of the fuel fed even at its high flow rate. Spin cup 60 and its motor 62 are cooled by air injected into its well 135. Such air is diverted from scroll 72 through duct 137, flowing passed spin cup 60 inwardly into the combustion zones.

Air enters the primary combustion zone 133 and secondary zone 132 above it through a grid of apertures 140 contained in cylindrical firewall 135. The exemplary grid 140 comprises an array of the order of 2,800 holes in the larger bus unit, consisting of rows of 94 holes each on a 0.5 inch grid. The six bottom rows of apertures (140) substantially form the air inlet for primary combustion zone 133, and are three-sixteenths inches in diameter. The remaining apertures are the bulk of the air inlet'supporting combustion in the secondary zone 132, and are one-eighth inches in diameter. Other grid arrays and apertures diameters are feasible therefor, as to number, position and construction.

An important component of combustor 55 is the annular air deflector-baffle system. Baffles 145 comprise a series of spaced conical downwardly directing air deflection plates 146. Deflection baffles I45 contribute to the preheating, the intermixing of inlet air with atomized fuel, and control the velocity distribution of gases within combustor 31, to promote rapid and full combustion of the atomized fuel and even of fuel droplets that may have formed therein, as will now be set forth.

Fuel combustion initiates in the lower region 133 as the primary zone. Combustion therein occurs under relatively fuel rich conditions, thereby retarding the formation of oxides of nitrogen. The active addition of ample secondary air into the next upper and adjacent zone 132 completes combustion of the hydrocarbon species and carbon monoxide, while avoiding sufficient residence time at reaction temperatures that might form objectionable quantities of nitrogen oxides. Air

input air from scroll 72 through the upper grid of holes inwardly into the secondary zone 132, but importantly also downwardly towards and into the lower primary combustion zone 133, see arrows a. Towards this end the downwardly oriented conical lips 146 of deflectors are at 45. The atomized fuel spreads away from cup 60, in annular array in primary zone 133, and the air supplied through the lower few baffles (145) is towards and into the atomized fuel as the primary combustion zone 133.

It is noted that the aforesaid air flow is 360 around. This occurs up and down within the firewall 135, all downwardly but in the opposite direction to that of prior combustion gas flow. This latter flow is from lower zone 133 up through zone 132, and out above the combustor 55, namely to the combustion gaseous zone 134 centrally of tube bundle 160. In prior art combustors, the input air generally was introduced and directed along in and with the general path of the primary combusted gases, herein from zones 133 to 132 to 134. The process of the examplary combustor propels distinct tubular. streams of air from grid 140 downwardly in the direction of the sprayed fuel and also opposite to the flow direction of the primary combusted fuel from zone 133 up through zone 132 and to top zone 134. The pre-swirled air in scroll 72 contributes to the vorticity in this process. The downwardly baffled tubular streams of air enhances the molecular turbulence of the atomized fuel'enhancing the combustion process in the primary zone 133, and from then on.

Further, the baffles 145 direct the incoming swirling air stream into the generally central secondary combustion zone 132 to further turbulate and mix-up uncombusted fuel droplets, as well as combustible pollutants and particles that move up thereto from primary zone 133. This action enhances the surrounding of and intermixing with oxygen these particles to be combusted towards their complete burning with low noxious emission.

By maintaining the overall air/fuel mass ratio at twice stoichiometric as aforesaid, and turbulating the air streams with the basic atomized fuel, small packets of air and fuel are formed. This results in full burn of the fuel, with resultant pollutants in the overall gaseous emission from the combustor-vapor generator through exhaust ducts 65, 65' being kept well within the EPA Emission Standards referred to. Creation of such turbulance in the secondary combustion zone 132 enhances such result. The central reigniter tower still further contributes to full combustion. It comprises, in the exemplary form, an assembly of five annular horizontal discs 151 supported in vertical posts 152. The posts 152 are specially supported in the combustor 55, described hereinafter.

As shown in the perspective view of FIG. 3, the tower 150 is positioned altemativelysomewhat above its top level 156. The tower 150 thereof illustrates the plural holes 155 in each disc 151. The reigniter tower 150 may be positioned differently in the combustor. In FIG. 3 it projects above the top 156 of the firewall by a small amount. Tower 150 may be located somewhat lower, extending into primary zone 133. Optimum location in a particular design can be readily determined for lowest noxious pollutant results. In the exemplary tower 150, stanchions 152 contribute somewhat to the combustion process turbulance hereof. The apertures 154 in discs 155 turbulate the air and fuel to generate the aforesaid packets.

The practical effect and result of the vigorous intermixing, turbulating and chopping-up of the atomized fuel and air streams, in the stated air/fuel ratio, in the combustion process hereof is to burn the fuel as completely as feasible. This is particularly effective due .to the multitude of small fuel/air packets formed. The fuel and air rate fed in, and the travel path provided assures the combustion at the order of 2,l and below, with negligable hot spots thereat, to hold NO production below the target minimum over the power operating range, e.g. l0 parts-per-million (ppm) in the exhaust.

Fuel particles and droplets, and incompletely burned particulates and pollutants, that emerge from the primary combustion zone 133 encounter reigniter tower 150 in the secondary combustion zone 132. Besides the turbulance and further breakups in that caused by tower 150 as aforesaid, the glowing state of its compo-' nents 151, 152, ignite particles, particulates and pollutants that impinge. This tower reignition action assures cleanliness of the. exhaust gases with a minimum of noxious pollutants. The deflector baffles 145 also are at sufficiently high temperatures to similarly serve as reigniters. The baffles 145 and the components 151, 152 of tower 150 are arrangedto operate in the cherryred to light orange temperaure range, namely the order of 1,300F to 1,850F, the tower ranging higher. The conical baffles 145 made of lnconel No. 601 material are structurally intact in combustor 55. The tower 150 not being directly cooled, is constructed of columbium alloy material as set forth hereinafter.

Minimization of quenching in the combustion process is accomplishedin the combustor-vapor generator (30,55). The downwardly air projecting baffles 145 are somewhat cooled by the air incoming, which keeps them from rising much above light orange at 1,850F. The baffles 145 thoroughly preheat the incoming air and thereby inhibit the air from quenching, or only partially burning in the fuel combustion process hereof. An important feature of the set of baffles 145 is that they are arranged so that their inner downwardly directed portions 146 are sufficiently long to inhibit heat in radiation form from the combustion zones 132, 133 from reaching out to the firewall 135. For this purpose, also the length of their annular horizontal shelf portions 147 is suitably proportioned with the angle and length of the downwardly directing portions 146. Such radiation protection of firewall .135, together with its intimate contact with the much cooler incoming swirling Y air in the scroll 72 that surrounds it, prevents it from exceeding a cherry red temperature.

The radially inner bank of superheatsteam tubes 161 are preferably provided with fins 162 along their surface. These fins 162 are hit by the initial hottest phase of the convection heat flow 175. They may even run cherry red. Nevertheless, their presence prevents these tubes from lowering to quenching temperature, and also serves a reigniting function.

The convection bank 160 is a counter flow heat exchanger. The feedwater is injected at 29 into the outermost coil in the radial group, and the superheated steam is extracted from the end 31 of the innermost coil. Thus the hottest combustion gases heat the hottest fluid (vapor and the coldest combustion gases heat the coldest fluid (water). As the combustion gases flow through convection bank 160 as indicated by arrows 175, and give up their heat, the tubes thereof in turn transfer the heat into the vapor or fluid therein, as the case may be. As the water flows from the outside coils towards the center, picking up increasing gaseous heat and velocity, the internal diameter of the tubing (161) becomes progressively larger to minimize flow pressure drop.

The two outermost rows of tubing carrying initial water, are arranged to have water flow in parallel, also to reduce flow pressure drop. The boiler 160 is all monotube in the evaporation and inner superheatregion to avoid pressure imbalance. Heat transfer into tube bundle 160 is by the use of finned tubing which also provides an internal burst strength many times that of the bare tubing per se. The use of predetermined fin height also accurately allocates the gas flow cross sectional areas such that the heat transfer coefficient can be varied to obtain the most efficient enthalpy rise in particular portions of vapor generator 30. Further, the outside fin heights per seon the respective tube sections of tube bundle l60are increasingly higher in the path of the combustion gases along arrows 175. This arrangement recoverslowerlevels of heat energy of the gases alongroutes 175 until entering as exhaust 176 into plenum 177, through openings 179. The boiler housing, 178, 180 may advantageously be made of 1010 steel. The tubing (160) is constructed of relatively inexpensive No. 18-8 corrosion resistant steels. The exhaust ducts 65, 65' are made large to avoid excessive combustion pressure drop. The exhaust velocity is thus so low that a silencing device is not required.

It is noted that combustor 55 is arrayed with tube bundle 160 whereby its central opening surrounds the upper section of firewall 135. The combustor 55 projects substantially into vapor generator 30, and the hot combustion. gases from within the combustor exit into centralzone 134: and out along paths indicated at 175 through. tube. bundle 160, as aforesaid. Such pancake tube arrangement, and it central overhang about the combustor. 55, provide efficient heat flow and heat transfer to tubes 160. It further lends towards compactness, a feature that is advantageous for its assembly with the VTE system in passenger cars.

A dome 165 is mounted above heat transfer zone 134 over combustor 5S. Dome 165 reflects heat back and minimizes radiation out through lid 180. Heat insulation 172, as Kaowool," is packed behind dome 165, and also at l73.underrlid 180. Dome 165 is formed as two annular sections: 166, 167.. Its apex 170 is welded to central disc 169 after" insulation 172 is packed-in. A disc 168 is mounted on top of tube bundle 160, and supports dome .165 at welds 171. Kaowool is a ceramic fiber wool. filler that is stable at high temperature. It is a heat seal, and assists in holding down the temperature of cover 180. The bottom 178 of the boiler 30 has a layer of insulation 156 on it for the same purpose.

Cover 180 is sealed in annular lip 181, and is secured to housing 178 by bolts 182. Cross-rods 183 are for crane hook or chain attachment. Channels 184 attached under housing 178facilitates mounting of the vapor generator with the system structure. The blower input air is inserted to scroll 72 via flexible connector 158 and duct 159. Scroll 72 is welded to base 178 across its mounting flange 185.

THE REIGNITER TOWER structural integrity in such turbulent high heat high power operation, the exemplary discs 151 and posts 152 are made of columbium alloy material, as No. C- 103. Such columbium sheeting withstands the temperatures encountered in combustion zones 132, 133 without weakening or warping. As is known, contact of columbium surfaces with ferrous material results in oxidization and deterioration of the columbium. Also, tower 150 requires firm mechanical construction and support in the combustor to prevent its being buffeted by the mass of the gases that rapidly swirl about it.

Towards this end, a plurality of posts 152, four herein, have slotsthat engage adjacent edges of the annular discs 151. As the posts and discs are of columbium alloy, they are safely welded together at their contacting regions to constitute a rigid tower assembly (150). No part of tower 150 is close to the interior edges of baffle plates 145 within combustor 55. Posts 152 extend to the floor 194 of the combustor, and are firmly secured thereto with individual support mounts 190. Mounts 190 are stable in the high temperatures of primary combustion zone 133. Further, they hold posts 152 apart from the ferrous base 194 and provide secure mechanical attachment therewith. v

Each support mount 190 grips the associate post 152 at its leg 191 that projects from the bottom thereof. Posts 152 extend through openings in auxiliary base 195 that is above floor 194. Input air from passage 72 passes through side apertures (not shown) in the shallow side wall of floor panel 194, and across mounts 190 to prevent their overheating. Each leg 191 is sandwiched between two washers 192, 192 ofinert thermal insulation material. Exemplary washers 192 are made of Fiberfrax, a ceramic fiber insulation material manufactured by the Carborundum Company. Exemplary washers 192 are built-up of three 0.05 inch layers of Fiberfrax No. 970-F. Cap screw 193 is of I-Iastalloy. A washer of Inconel is used under the head of screw 193 to ease pressure on the upper washer 192. The lower washer 192 presses onto base 194. Nutplates lock with the ends of the cap screws 193. A shallow bronze ring (not shown) is positioned about each leg 191 to physically isolate it from the shank of the central screw 193. An aperture 196 in each leg 191, is sufficiently large to include such ring therebetween, see FIG. 4. Conventional coatings are applied to the surfaces of columbium discs 151 and posts 152 to inhibit their oxidizing in the presence of the high temperatures.

FIG. 4 is an enlarged plan view of reigniter discs 151. They are symmetrically supported by stanchions 152. Extending leg flats 191 of posts 152 are sandwiched between the insulation washers 192. The plurality of holes 155 enhance the turbulence of the gases flowing passed the tower. The rectangular shape of posts 152 does the same, as does their semi-circular shape in said copending application. The high temperatures that discs 151 and posts 152 acquire in operation reignite unburned gas and fuel particles that contact them in such flow action. FIG. 5 is a partial view of an alternative disc 155. Radial slots 157 in modified disc 155 permit localized distortion while maintaining overall mechanical viability for the tower.

What is claimed is:

1. A reigniter tower for a fuel combustor comprising a series of plates supported therein in the path of combusted gas flow, said plates being spaced apart and attaining temperatures that reignite unburned gas particles contacting them, said plates being proportioned to provide ready gas flow around them in the combustor, a substantial in-line opening centrally of each plate for gas flow therethrough, and a series of apertures about the periphery of each plate whereby gas flowing through the apertures is broken into smaller packets to assist in the combustion process. I

2. A reigniter tower as claimed in claim 1, in which said plates are of annular form.

3. A reigniter tower as claimed in claim 2, in which said annular plates have radial slots that permit local distortion thereof under high temperatures.

4. A reigniter tower for afuel combustor comprising a series of plates supported therein in the path of combusted gas flow, said plates being spaced apart and attaining temperatures that reignite unburned gas particles contacting them, said plates being proportioned to provide ready gas flow around them in the combustor and being of annular form with each central opening in-line for gas flow therethrough, said plates having slots at their peripheral regions that permit local distortion thereof under-high temperatures.

Claims (4)

1. A reigniter tower for a fuel combustor comprising a series of plates supported therein in the path of combusted gas flow, said plates being spaced apart and attaining temperatures that reignite unburned gas particles contacting them, said plates being proportioned to provide ready gas flow around them in the combustor, a substantial in-line opening centrally of each plate for gas flow therethrough, and a series of apertures about the periphery of each plate whereby gas flowing through the apertures is broken into smaller packets to assist in the combustion process.

2. A reigniter tower as claimed in claim 1, in which said plates are of annular form.

3. A reigniter tower as claimed in claim 2, in which said annular plates have radial slots that permit local distortion thereof under high temperatures.

4. A reigniter tower for a fuel combustor comprising a series of plates supported therein in the path of combusted gas flow, said plates being spaced apart and attaining temperatures that reignite unburned gas particles contacting them, said plates being proportioned to provide ready gas flow around them in the combustor and being of annular form with each central opening in-line for gas flow therethrough, said plates having slots at their peripheral regions that permit local distortion thereof under high temperatures.

Images