US 3846065 A
Vapor generators for powering external combustion engine systems. Their combustor generates heat in full response to engine system power demands. Emissions have low noxious pollutant content over the wide power demands of a vehicle on the road. Internal arrangements maximize combustion of the fuel that is atomized in the primary combustion zone. Hot spots above 2,100 DEG F in the combustor are minimized to inhibit the formation of nitrous oxide. Further, quenching spots below 1,500 DEG F are controlled to minimize the formation of carbon monoxide and unburned hydrocarbon particles. An important feature in the combustor section is that the direction of flow of input air is opposite to that of the flow of the hot combusted gases. This moderates the rate of gas flow, and turbulates to intermix the gases towards their complete combustion. A wide range of available fuels may be used, and operation over at least a 20:1 range of air to fuel input is effected. The combustor-vapor generator hereof meets the Emission Standards for 1976 set by the Environmental Protection Agency. It is suitable for mass production at reasonable unit cost with relatively inexpensive materials.
Claims available in
Description (OCR text may contain errors)
Unite States Patent 1 1 1 11 memes Lear 1 1 Nov. 5, 1974 1 1 VAPOR GENERATORS WITH LOW Primary Examiner-Carroll B. Dority, Jr.
POLLUTANT EMISSION Assistant Examiner-Larry I. Schwartz 75 lnventor: William P. Lear, Verdi, Nev. Mars  Assignce: Lear Motors Corporation, Reno,  ABSTRACT Nev.
 Filed: June 12, 1972 1211 Appl. No.: 261,691
Related US. Application Data  Continuation-in-part of Ser. No. 261,158, June 2,
152] US. Cl 431/347, 431/168, 431/352  Int. Cl. F23d 13/12.  Field of Search 431/347, 351, 352,171, 431/190, 168; 60/3965  References Cited UNITED STATES PATENTS 976,221 11/1910 Scrimgeour 431/347 2,398,654 4/1946 Lubbock et a1 431/352 2,973,727 3/1961 Northcote 431/173 3,306,333 2/1967 Mock 431/352 FOREIGN PATENTS OR APPLICATIONS 189,130 4/1962 Sweden 431/352 Vapor generators for powering external combustion engine systems. Their combustor generates heat in full response to engine system power demands. Emissions have low noxious pollutant content over the wide power demands of a vehicle on the road. Internal arrangements maximize combustion of the fuel that is atomized in the primary combustion zone. l-lot spots above 2,100 E in the combustor are minimized to inhibit the formation of nitrous oxide. Further, quenching spots below 1,500 F are controlled to minimize the formation of carbon monoxide and unburned hydrocarbon particles. An important feature in the combustor section is that the direction of flow of input air is opposite to that of the flow of the hot combusted gases. This moderates the rate of gas flow, and turbulates to intermix the gases towards their complete combustion. A wide range of available fuels may be used, and operation over at least a 20:1 range of air to fuel input is effected. The combustor-vapor generator hereof meets the Emission Standards for 1976 set by the Environmental Protection Agency. It is suitable for mass production at reasonable unit cost with relatively inexpensive materials.
6 Claims, 10 Drawing Figures PMENIEDW 51914 3L846L065 sm so: a
VAPOR GENERATORS WITH LOW POLLUTANT EMISSION CROSS-REFERENCE: This patent application is related to copending application Ser. No. 261,158 filed June 9, 1972, for Low Pollution Vapor Engine Systems, and is a continuation-in-part thereof.
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 arefueled 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. I
The automakers have thoroughly mastered the mass production of ICE piston engines using liquid petroleumfuel. The automobile industry has thoroughly developed gasoline fueled ICE engines so that they cost less, weigh less, require less space, and use less fuel for given output ratings than other engine 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 energy into 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, contain 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. The relatively high adverse pollutant emissions from ICE engines are today a significant cause of smog and unhealthy city climates. The present inventionis directed towards improved and practical ECE engines operated by superheated steam at high temperature and high pressure with relatively low resultant pollution. A single stage vapor turbine drive is used as the exemplary expander thereof.
The gas turbine, and the vapor turbine system hereof,
stand this, resulting in a cost comparable to that of a whole conventional passenger ICE engine. Far less'expensive parts and materials are required for the ECE vapor turbine hereof, as its operating temperature is far less than in a gas turbine. The combustor/vapor generator is apart from the turbine expander in the VTE sysboth burn fuel in a continuous manner, and in proporwheel. Important components of the gas turbine thus are operated at relatively high temperatures. The gas turbine blades often glow at cherry red, well above 2,000 F. They are fabricated of exotic metals to withtern and independent thermodynamically. This factor permits better control of fuel combustion over the VTE power operating range, permitting better fuel economy and lower noxious pollutant emission than possible in commercial gas turbine systems.
There is considerable development activity on devices to minimize pollutant emission from ICE systems, and from gas turbines as well. These involve catalytic converters, manifold security and after-burners. Such devices add to cost, space and weight, and still are quite difficult to keep maintained. The powering of the vapor turbine engine hereof is in a closed fluid cycle with negligible water or vapor depletion. The ECE engine systems can be readily fitted into the engine compartments of conventional cars, buses, boats and trucks. Their fuel efficiency is comparable to that of ICE systems; and cost less to manufacture, particularly when exhaust cleaning devices are included in the ICE installations. Future engine systems will have to'be low noxious polluters. The Environmental Protection Agency and the Clean Air Act are presently forcing the issue. Ecological emission is becoming an important factor in the design and construction of engine systems for the future. The engine system of the present invention is directed towards that goal.
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 steam there is no disintegration of fluid or vapor, or
fowling of system components. This is of vital importance. The VTE system hereof comprises a combustor/vapor generator, a feedwater pump, throttle valve control, vapor turbine (the power expander), output reduction gearing, and a torque converter as mechanical transmission to the output shaft and wheels. Superheated steam is generated by the combustor or burner as at the order of 1,000 F, and high pressure as at the order of 1,000 pounds per square inch (psi). The flow of the superheated steam to the vapor turbine is manually controlled through a throttle valve. The steam enters the turbine nozzles, and at supersonic velocity against the turbine blades, impelling the rotor to high speeds. Operating high speed of the turbine may well be 60,000 to 65,000 rpm. The resultant ease of vehicle operation, its smoothness, quietness'and sensitive refeedpump to the boiler of the vapor generator. Temperature, pressure and rotational speed sensors are utilized to coordinate'the operation and safety of the components of the ECE engine system hereof. These, in association with mechanical, electrical and electronic controls automatically maintain predetermined system tem controls for each such type of installation are closely related.
An important component of the exemplary ECE engine system, is its unique combustor/vapor generator 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 fuel. A combustor/vapor generator constructed with sufficient gross output, to power passenger cars rated at 120HP, canbe made the size of a spare tire, about 26 inches in diameter. One for a bus, with 240 HPgross engine output, is of the same diameter, with less than twice the height.
A further important feature of the exemplary ECE engine system is its control of vapor flow in its impacting of the vapor turbine in proportion to power output demand. The steam throttle is operator-responsive as by linkage to the accelerator pedal, and controls the volume of ambient superheated steam to the impulse turbine wheel. Automatic controls maintain substantially rated temperature and pressure of the steam output of the vapor generator. The combustor is fueled through controlled air/fuel into it, the latter being held in general proportion to throttle position over a wide range, over 20 to 1, direct or transient torque and power output requirements.
The combustor hereof has low noxious pollutant emission over the wide power range of the 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. In the combustor of the present invention the air is supplied to both the primary and secondary combustion zones in a tubular flow, and swirled to enhance turbulence and the creation of small packets of air and fuel. Further and importantly, the air input is in the direction against the normal outflow of the gases of combustion. The resultant exhaust emission contains a proportion of noxious pollutants within the EPA Standards of 1976.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the exemplary vapor turbine engine (VTE) system, as installed in a coach or passenger bus.
FIG. 2 is a cross-sectional view through the exemplary combustor/vapor generator of the VTE system of FIG. 1.
FIG. 2A is a partial view of the interior of the dome of the combustor.
FIG. 2B is an enlarged showing, in schematic, of some tubes of the boiler section.
FIG. 3 is a view in perspective of the combustor/vapor generator of FIG. 2, with the boiler tube bundle removed, and with the central combustor element modified.
FIG. 3A is an enlarged cross-sectional view partially through a modified combustor arrangement.
FIG. 4 is a view in perspective of the assembled vapor generator of FIG. 2, as seen from below.
FIGS. 5,6 and 7 are respective rear, plan and side elevational views of the VTE engine system of FIG. 1 as installed in the bus.
THE VAPOR ENGINE SYSTEM The exemplary power vapor turbine engine system 10 is shown schematically in FIG. 1 as applied to a passenger bus. The fluid water from make-up tank 15 is drawn by boost pump 14, and a positive inlet pressure is maintained along main fluid supply lines 16 and 17 to high pressure feedpump 20, and startup of the vapor generator. A small portion of the high pressure fluid is divertable through normalizers 18, 19 for generator control, used intermittenly for steam over-temperature safety in a manner to be described. The main fluid flow is through feedpump. 20 at sufficiently high pressure to main fluid lines 21, 22, 23, and through regenerators 24, 24'. As the water passes through regenerators 24, 24' it is heated by exhaust steam therein from turbine 25, as later described. The heated fluid flows along main lines 26, 27, 28 to inlet 29 of the vapor generator 30. The operation of the novel vapor generator 30 with integral combustor 55 hereof is described in detail hereinafter in connection with FIGS. 2, 3 and 4.
The water is rapidly converted into superheated steam in vapor generator 30. Superheated steam emerges in outlet line 31, as in the order of l,000 F and 1,000 psia. The steam outlet 31 connects with vapor lines 32 and 33, towards the input of power turbine (expander) 25. The exemplary turbine 25 has been found best to be of the impulse type, a single blade-wheel stage; as well as one of the Curtis type with two spaced turbine blade sets on a single wheel and stator therebetween. Rapid response to power demands, up and down, is provided thereby due to the relatively low rotational inertia of such single turbine wheel, as well as its having good power conversion efficiency herein over the power range. The steam expands through the turbine which, through reduction gearbox 35 powers the vehicle and the system accessory devices. Also, its low inertia permits more efficient and practical idling stage, with its prompt stopping and restart feasible.
Exhaust steam from turbine 25 passes into exhaust plenum 36 and via steam lines 37, 37' through the vapor side of regenerators 24, 24. The main feedwater fluid flow from output line 23 is through the regenerators 24, 24' via schematically indicated connection lines 38, 38', to return main fluid lines 26, 27, 28. Heat transfer to the feedwater passed through the regenerators improves cycle efficiency of the VTE system, and reduces the condenser cooling load. The bus VTE system 10 involves generation of up to the order of 240 are desirably used at the air inlet position to condensers 40, 40 to avoid excessive fluid cooling at low power condition, which would reduce cycle efflciency. The
fluid phase from condensers 40, 40' is returned to make-up tank via output lines 43, 44 through line 45. The position of shutters 42, 42' is herein controlled through compressed air on the bus by respective electrically actuated solenoid valves 78, 78 and cylinder/- piston units 79, 79.
The pressure of the water and steam in vapor generator 30 is of the order of 1,000 psi. The feedwater is thus fed at sufficient pressure into the boiler tubes of vapor generator 30, via inlet 29. Boost pump 14 initiates the fluid from tank 15. The exemplary feedpump is of the positive and variable displacement type. The feedwater is controllably directed into the inlet 29 by the feedpump 20. Pump 20 is driven through pulley 46. Actuator 47 couples to lever 48 extending from pump 20. The position of lever 48 controls the rate of feedwater pumped. I
Pump actuator 47 is control-operated through a small servo-motor therein, connected to control signals by leads 49. The control signals therefor are derived from system power/torque demand as determined from the vapor mass flow via throttle setting into turbine 25. Fluid output of feedwater pump 20 is directed to fluid line 21, in series with surge tank 52 and filter 53, as of l0 micron size. The main fluid enters input line 29 of vapor generator 30- at sufficient pressure to replace evaporating water in the boiler tubes.
Vapor generator 30 converts the fed-in feedwater into high-temperature high-pressure vapor, as superheated steam. Combustor 55 is constructed integrally with vapor generator 30. Combustor 55 is flred with a continual flow of fuel held mixed with air in generally predetermined mass proportion, as will be explained. Towards this end, fuel tank 56 connects to electric fuel pump drive 57. The fuel is directed through solenoid 58 to U-shaped feed nozzle 61 into spin cup 60. An electric motor 62 of small power spins cup 60 at a predetermined rate as 12,000 rpm, atomizing the fuel that impinges thereon into a radially spread-out fine spray-in torroidal shape within combustor 55. Once ignited by spark-plug 63 an intense combustion starts and is maintained therein.
The combustor 55v is unique, and is arranged and constructed to have particularly low proportions of noxious pollutants in its exhaust emission. Tests in actual operation in a SO-passenger bus have shown that its exhaust safely meets the 1976 Standards of the EPA Clean Air Act referred to. Its gaseous exhaust passes through ducts 65, 65' arranged to emit them generally from the rear of the vehicle. Fuel pump 57 is electrically operated through its terminals 59 by electric control current derived in proportion to the setting of throttle lever 51 or equivalent power demand signals, whereby the fuel feed into cup 60 is directly consonant with output power/torque demand.
more readily maintain the vapor close to predetermined levels. In essence then, the superheated steam is rapidly generated in mass and volume at a rate proportional to that requisite to drive the turbine expander (25) as determined by output demand and throttle setting by the operator. The VTE system 10 utilizes superheated steam generated in the order of l,000 F at a pressure input to the turbine 25 of the order of 1,000 psia. In operation, the combustor/vapor generator hereof can be steamed-up from initial ignition start to full rated condition for vehicle drive well within 20 seconds.
Should the combustion process flame out, or not take hold for any reason, unburned fuel drops to the floor of combustor and exits in drain tube 67' directly into flame arrest device 67 that prevents its ignition. From there it drains out through tube 67" to back to fuel tank 56. A photocell flame detector 64 mounted in the combustor frame. It connects to a fail-safe circuit that promptly disconnects fuel flow and stops other activity in the system if the detector indicates no-flame at anytimewhen it should be ON.
Ambient air is directed into combustor 55 by blower 70 that draws in air through inlet duct 71. The exemplary blower system couples to the combustion chamber by scroll shaped surround 72, see FIGS. 2, 3 and 4. The air is swirled into combustor 55, and broken into numerous thin streams that are powerfully intermixed with the atomized fuel sprayed-out by spin cup 60, to be described in detail. The objective and result are to produce multitudes of tiny packets of atomized fuel surrounded by ample oxygen to burn-up thoroughly without producing incompleted noxious products of combustion. Full fuel combustion results in benign compounds, as H 0 and CO and in higher net efficiency.
Towards this end, air is blown into combustor 55 in controlled amount to insure optimum combustion of the fuel as fed-in concurrently. A safe ratio of air quantity to fuel quantity is maintained for this purpose. Such ratio is the order of twice the basic stoichiometric ratio.v A practical air-fuel mass ratio used is 30:1 for particular fuels over the operating range, presenting sufficient oxygen for complete fuel combustion at about 2,l00 F or less. This upper temperature limit minimizes the generation of oxides of nitrogen, as well as unburned HC and CO. Adjustable inlet guide vanes 73 are settable to maintain safe air/fuel ratio as directed into combustor 55. Actuator 74 controls the setting of vanes 73 for blower air. This is accomplished through actuator 74 coupled to the vanes 73, and through its electrical terminals connected to the amplifier control responsive to the mass vapor flow as by throttle demand position.
its lead terminals 81, or alternatively to local bus compressed air. Its outputpulley 82 drives belt 83 and pulley 84 at the blower. An overrunning clutch (ORC) 85 couples pulley 84 to blower pulley 76 and thereby to belting 77. Thus, initial starter 80 operation as by the ignition key, directly starts up blower and the feedwater pump 20(At the same time, these lower powered fuel and spin cup motors 57 and 62 are electrically connected to the battery. They perform fuel pumping and sition the throttle passes vapor to the turbine 25 in idling status. The idle drive of the gearing in reduction gearbox 35 occurs. Such turning of this gearing 35 directly rotates auxiliary drive shafting 90. A pulley 91 thereon drives belt 92 which operates pulley 93 of 1:1 90 gear unit 94. Gear unit 94 in turn drives pulley 95 through overrunning clutch 96. The initiation of gearbox 35 rotation by the idling power of turbine 25 is thus by starter motor 80 as just described. When at suffi-- cient power level shafting 90 drives gear unit 94 and its pulley 95, and takes over the operation of blower 70 at,
its pulley 76, and feedpump 20 at its pulley 46. ORC 85 at pulley 76 thereupon mechanically disconnects starter 80. Conversely, during starter 80 use, ORC 96 at pulley 95 disconnects the belt 77 drive from gear unit 94 and thus also shaft 90. In system switch-off of starter 80 power is effected when the vapor pressure generated reaches 750 psi.
The other auxiliary units of VTE system 10 are driven by the shafting 90 upon its rotation during the idling mode of turbine 25, and also throughout the operational course under driver control of lever 51, of throttle 50. As shown in. FIG. 1, these auxiliaries include the transmission oil pump 97 through pulleys 98, 99', alternator 100 through pulleys 101, 102; fans 41, 41' of condensers 40, 40' through bevel gearing unit 103; and in turn air compressor 105 (optional in a bus) through pulleys 106', 107'. A take-off line 86 from main fluid supply line 16 passes through filter 87, 10 micron size, to line 88 supplying seal purge fluid to turbine 25. Fluid drain from turbine 25 passes through line 110, pressure relief valve 111,'and drain line 112 on to the make-up tank input line 45. A fluid holding tank 113 of about one gallon capacity is in series therewith, together with check valve 114.
Fluid drain from turbine exhaust plenum 36 enters drain line 115, and return line 112. Non-condensable gas from condensers 40, 40' are directed to make-up tank by conduits 116, 117, 118. A check valve 119 and a finned cooler 120 is in series therewith. It is practicable to provide heating for the whole bus by inserting finned tubing 121 in the hot return fluid in make-up tank 15, for heat transfer and heating-up of fluid contained in the tubing 121. The bus heating system 122 is schematically indicated, through which this heated fluid is transmitted via tubes 123, 124, as will now be understood.
The vapor turbine 25 hereof, takes-up a relatively small volume of the VTE system, particularly for a 240 gross horsepower system for the bus. The single wheel of the exemplary turbine is only 5.4 inches diameter, with 80 blades only 0.3 inch long. It is designed for supersonic nozzle velocity and impulse action, with good performance substantially over its normal operating speed range of 10,000 to 65,000 rpm. A double reduction gear train 35 reduces this top operating speed to a ratio that permits coupling to a standard automatic transmission (125 namely a torque converter to transmit its output drive 126 to the differential gearing, and the vehicle wheels. Such automatic stepped transmission (125) used for the 50 passenger bus hereof is an Allison Model PIT-7400. In place of such automatic transmission (125) it is contemplated to use a hydromechanical transmission unit to derive even smoother power and speed variationfor the vehicle output drive. A suitable hydromechanical transmission therefor are shown in US. Pat. Nos. 2,830,468 and 3,411,381. The stepped transmission 125 utilizes savenger/pressure oil pump 97 with oil lines 127 and 128, and oil cooler/oil resevoir unit 129.
An electronic control unit 106 is shown mechanically coupled with throttle lever 51 through linkage 107 and arm 108. The throttle demand position oflever 51 is thereby translated to arm 108 and in turn into a corresponding electrical signal modifier in unit 106, as a potentiometer. The amplified output 109 thereof connects with leads 49 to control the setting of actuator 47 for feedpump 20, as aforesaid; as well as with control actuator 74 for setting blower vanes 73 by connection with lead 75. The rate control of fuel pump drive motor 57 through leads 59 is also arranged with master control unit 106. To assure proportionality of mass vapor flow to the turbine in accordance with the throttle 50 demand position 51, the speed of blower motor fan 70 and that of feedpump 20 is provided, as through their respective pulleys from shaft 90 and compensation feedback of their respective speeds to their actuator operational controls, as understood by those skilled in the art. In this manner, the mass flow of superheated steam vapor, at predetermined system temperature and pressure, to turbine 25 remains substantially proportional to vehicle power/torque demand through throttle settings 51 as aforesaid.
An electrical temperature sensor/transducer T is placed in the vapor path in pipe 33 to throttle 50; as is electrical pressure sensor/transducer P. These may be direct parameter readouts for the system control network. The circuits are preset to provide differential or error-temperature and error-pressure signal outputs; or combined with readouts on the basic parameters as well. The normalizer tubes 18, 19 divert feedwater controllably through their indicated solenoid valves 78", 79" should vapor temperature rise substantially above the system value, as 1,000 F, and thus avoid excess vapor temperature. Other approaches to overall system control to maintain smooth delivery of power and torque as required, from idle to full power, transient and sustained, may be used with the basic VTE system hereof. In essence, the system 10 provides for rapid response in generating superheated steam to the turbine 25 on demand. The combustor has low noxious pollutant emission over the operating steam demand range. It utilizes fuel in proportion to the mass of the steam required corresponding to feed water insertion, as well as maintain an air/fuel mass ratio of twice stoichiometric for the clean emission. Deviation from preset system vapor temperature (as l,000 F), and from system vapor pressure (as 1,000 psi) are directly correctable by auxiliary, control and trim means, that may readily be integrated with the feedwater data and fuel rate controls.
There are further elements incorporated as safe 68 at overspeed, as at above 80,000 rpm. Valve 68 directly discharges superheated vapor from line 32, preferably into exhaust ducts 65, 65' as indicated at 89; and valve 68' directly discharges main fluid from line 27 into make-up tank 15. The turbine thereupon slows and promptly stops; the auxiliaries thus stopping as well, to shut down the VTE power and operation. The vapor turbine 25 hereof has been tested to failsafe condition in that even at engine runaway condition when the turbine wheel could spin faster than 95,000 rpm during no load, it did not disintegrate. A safety pressure relief valve 69 is in vapor delivery line 33 should the superheated vapor pressure exceed a given high design valve, as 1,300 psi. The vapor is preferably directed into the exhaust ducts 65, 65 as schematically indicated at 89. Other safety sensors, check valves and relief valves are utilized, some of which are indicated in FIG. 1, which are not further discussed as they are not significant for the patentable aspects hereof.
The vapor impulse-type vapor turbine 25 hereof is powered by the superheated steam admitted thereto through the throttle 50 with variable area vapor control. The number of supersonic nozzles used are determined by the position of driver control lever 51, which then direct the superheated vapor onto the single wheel turbine blades. This arrangement is uniquely advantageous in the VTE system (10) hereof for vehicles, as compared with an engine system with a plurality of turbine wheels. Use of several stages of bladed wheels results in the turbine quite rapidly dropping off in efficiency when operating off its optimum speed. The single stage turbine (25) combined with the reducing gearbox (35) operates with good efficiency over the wide speed range of vehicles. The throttle area changing or modulation is under driver control (51). This directly determines the superheated vapor volume to .turbine 25 and the power/torque output of the single stage turbine (25) hereof. The vapor, at substantially rated temperature and pressure, is under variable mass flow control by the throttle 50. It exits from the number of turbine nozzles that are exposed to the vapor, at supersonic velocity. The plural nozzles involved at any power setting by lever 51 imparts energy directly to the turbine wheel blades, at high efficiency herein. Such throttle area control, with plural nozzle selection directly to the turbine wheel is an effective power output to demand response. It is also effective with a Curtis type turbine referred to. In both cases control is by direct nozzle impacting based upon throttle (50) area exposure through throttle lever (51) position, with power output substantially proportional to demand, throttle position (51) through the corresponding mass flow of the vapor. As an engine unit for an ECE system the turbine/gearbox (25, 35) hereof is relatively light in weight, efficient, small in volume, and inexpensive. The high-speed geared-turbine (25, 30) hereof offers good reliability and life, at relatively lower operating and fuel cost. This factor also involves low rotational inertia, and ties in with simplification of the control approach for the VTE system hereof, and its effective operation.
COMBUSTOR-VAPOR GENERATOR The exemplary vapor generator 30 and integrally assembled combustor 55 are in cross-sectional view in FIG. 2, and in external perspective view in FIG. 4. Its novel internal construction and combustion process are arranged to maximize fuel combustion and to minimize hot spots above about 2,l00 F to keep formation of NO, below the requisite minimum to meet the EPA Emission Standards. These factors are also arranged to minimize undue quenching therein at relative coldspots, e.g. below about l,500 F, to keep the formation of CO and hydrocarbons within these Standards. Fur ther, these factors remain operative over the power demand and operating range upon the vapor generator 30. Operation of the combustor system is maintained with air and fuel injection at a given relative mass ratio, as 30, with an operative turndown range of at least 20 to l.
The combustor system 55 may be designed to use fuels that are currently generally available, including automotive gasoline, kerosene, Diesel No. 1 and Jet A fuel, as well as for unleaded gasoline, and W4 aircraft class fuel. The overall efficiency of vapor generation hereof is found to be in the order of 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.
Comb'ustor 55 is of the axial flow turbulent vortex type. Combustion therein is accomplished within a 15 inches diameter chamber 132 for firewall 15 inches high in the size for the 50-passenger bus; 7 /2 inches high in the passenger car unit hereof. The combustion gases are inert before they propel over top level 156 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 2.15 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 be 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 sec ondary zone 132 above it through a grid of apertures 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 30 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 3/16 inch in diameter. The remaining apertures are the bulk of the air inlet supporting combustion in the secondary zone 132, and are /a inch 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 comprise a series of spaced conical downwardly directing air deflection plates 146. Deflection baffles 145 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 baffle/deflector assembly 145 is arranged to direct the input air from scroll 72 through the upper grid of holes (140) 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 145 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 exemplary 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 150 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. Suitable tierods 153 secure the tower assembly 150 in the combustor. Alternative support for tower 150 is indicated by dashed line mounting posts 154.
As shown in the perspective view into the modified combustor 55' of FIG. 3, the tower 150 is positioned alternatively somehwat above its top level 156. The tower 150 thereof illustrates the plural holes 155 in each disc 151, and the semicircular shape 157 of posts 152. 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 159 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 are semicircular to contribute to the combustion process turbulance hereof. The apertures 154 in discs 155 also 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,l00 and below, with negligable hot spots thereat, to hold NO, production below the target minimum over the power operating range, e.g. l0 parts-permillion (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 components 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 also are at sufficiently high temperatures to similarly serve as reigniters. The baffles 145 and the components 151, 152 of tower are arranged to operate in the cherryred to light orange temperature range, namely the order of l,300 to 1,850 F, and not much above 2,l00 F. For structural integrity these parts 145, 151, 152 are preferably made of Income] No. 601, a commercial high temperature corrosion resistant material.
Another significant accomplishment of the invention combustor-vapor generator (30,55) is its minimization of quenching in the combustion process. Thus the downwardly air projecting baffles 145 are somewhat cooled by the sufficiently incoming, which keeps them from rising much above light orange at l,850 F. The baffles 145 thoroughly preheat the incoming air and thereby inhibit the air from quenching, or only directing 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 suffiently 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 directly portions 146. Such radiation protection of firewall 135, together with its intimate contact with the much cooler incoming swirling air in the scroll 72 that surrounds it, prevents it from exceeding a cherry red temperature.
The radially inner bank of superheat steam 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 prevent these tubes from lowering to quenching temperature, and also serves a reigniting function.
The feedwater is preheated in regenerators 24, 24' as stated hereinabove, exchanging heat with the hot turbine exhaust. 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 mono-' tube in the evaporation and inner superheat region 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 pre-determined 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 se on the respective tube sections of tube bundle 160 are increasingly higher in the path of the combustion gases along arrows 175. This arrangement recovers lower levels of heat energy of the gases along routes 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 central zone 134 and out along paths indicated at 175 through tube bundle 160, as aforesaid. Such pancake tube arrangement, and its 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 l65'is mounted above heat transfer zone 134 over combustor 55. 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 173 under lid 180. Dome is formed as two annular sections 166, 167. Its apex 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 at tached under housing 178 facilitates connection in the VTE system. 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.
An alternate manner'of mounting tower 150 in the combustor is shown in FIG. 3A. Tower 150a is positioned lower into the combustion chamber than in FIG. 2, extending into primary zone 133. Tower 150a has more turbulence discs 151a, and fewer support posts 152a than does tower 150. It is supported by radial ribs 195. Slits 197 in ribs engage adjacent the rims of discs 151a. Ribs 195 are welded at 195 to the adjacent inner rims of baffle rings 145. Further, ribs 195 are welded at 194 to base plate 193 of the combustor.
The baffles 145 are directly exposed to the high heat and flame in combustion zones 132, 133. Baffles of commercial Inconel No. 601 0.018 inch thick are structurally sound herein. Input air through apertures 140 strikes their outer surfaces, moderating the temperature of baffles 145. Rings 146 and shoulders 147 maintain at cherry red, between 1,300 F and l,850 F. The incoming ambient air is thereby preheated en route to the combustion zones, and quenching conditions are avoided at the baffles. Also, the cherry red state of the baffle rings 146 serves to reignite fuel particles and packets that they encounter.
The lower set of the baffle rings are exposed to flame in and at the vicinity of primary combustion zone 133. They each contain an added Inconel ring 148, as seen in FIG. 3A. Rings 148 herein are on the lowest four full 45 baffles, and ring 148' on bottom 60 ring 146. Rings 148, 148' are welded onto the conical rings 146, 146'. The oxidized layers normally on Inconel rings (146, 148) serve to thermally isolate them from adja cent rings 146, 146' thereof. Such isolation permits outer rings 148, 148' to rise to somewhat higher temperatures, and serve as reigniters of impinging fuel, particularly in the primary combustion zone.
FIGS. 5, 6 and 7 are respective rear, top and side views of the VTE system 10 as installed in the rear compartment of a SO-passenger bus. Its major mechanical and thermodynamic components are arranged for compactness, full performance, and for maintenance 188. The fans 41, 41' are respectively supported in the 15 bus through spoked frames, partially indicated at 189, 189.
The vapor generator 30 is firmly mounted on girders 190, 191 in bus structure 192, secured with its crossbeams 184, 184. The assembled mechanical components of VTE system are shown in their practical configurations and relative dimensions for a 240 HP bus installation. The same numerals for its components are as used in FIG. 1. Gaseous emission from combustor '55 exits through ducts 65, 65'. The superheated high-temperature high-pressure steam out of boiler 160 connects to throttle 50 and-in turn to turbine 25 via piping 33. The power output of the turbine rotor is through gearbox 35 to automatic transmission 125, and on to the wheels (not shown).
What is claimed is:
1. A combustor comprising a firewall containing a combustion chamber, means for presenting fuel into the combustion zone of said chamber constituting its primary zone, means for injecting air into said primary combustion zone and the successive secondary combustion zone of said chamber, means associated with said firewall for directing major portions of the injected air generally counter to the flow direction of the combusted gases from said primary to the secondary zones and outwardly of said chamber, said air injecting means including apertures in the firewall that admit the air into said chamber as tubular streams, and baffle means arranged within the firewall adjacent its apertures, said baffle means being shaped to effect said counter direction of the injected air. v
2. A combustor as claimed in claim 1, in which said baffle means includes a series of air passages along the firewall that communicate with its apertures and are oriented in directions generally towards said primary combustion zone.
3. A combustor as claimed in claim 1, said baffle means being mounted along the firewall and formed of i a series of inclined annular members that are directed generally towards said primary combustion zone.
4. A combustor as claimed in claim 3, further including annular shelves that support said members apart from said firewall, said shelves and members being proportioned to minimize radiation from the chamber to the firewall.
5. A combustor as claimed in claim 3, further including annular elements attached along some of said members, said elements being arranged in substantial thermal isolation to become independently heated during the combustion process and reignite contacting uncombusted gaseous particles.
6. A. combustor comprising a firewall containing a combustion chamber, means for presenting fuel into the combustion zone of said chamber constituting its primary zone, means for injecting air into said primary combustion zone and the successive secondary combustion zone of said chamber, means associated with said firewall for directing major portions of the injected air generally counter to the flow direction of the cornbusted gases from said primary to the secondary zone and outwardly of said chamber, said air injecting means including apertures in the firewall that admit the air into said chamber as tubular streams, baffle means arranged within the firewall adjacent its apertures, said baffle means being directed to effect said counter direction of the air injected into said chamber, and duct means surrounding said firewall and arranged to swirl the air injected into the chamber to form gas vortexes therein for facilitating gaseous fuel combustion, said duct means constituting an air passageway of substantially spiralconfiguration about the firewall with its air inlet at the further radial position thereof.