Abstract:
A carburetion system, without complicated control systems, functions uniformly throughout the range of engine load and incremental increases of power demand to provide efficient stable engine performance for a natural gas fired, internal combustion engine using EGR. A cogeneration system for supplying distributed generation of electricity and process/utility heat, employs a system for engine cooling and effective heat transfer to a cogeneration client, reduces engine head temperature, thereby reducing fuel consumption and reducing pollutants, as well as delivering substantially increased heat to a cogeneration process/utility heat facility by use of a carburetion system which employs at least a pair of spaced apart venturi positioned in series proximate one to another such that a first exhaust recycled gas venturi is upstream of a fuel venturi where fuel and air/exhaust gas are admixed prior to the resultant gas being introduced into a turbocharger. The distance between the exhaust venturi and fuel venturi is affective to provide a given amount of exhaust gas to air ratio prior to entering the fuel venturi inlet. Unexpectedly the spatial relationship between the two venturi, one to the other, affectively regulates exhaust gas air mixture, as well as the air/fuel/exhaust gas mixture to the engine by means solely of pressure increase and decrease (vacuum) of the engine intake system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to carburetion systems for natural gas fueled internal combustion engines; and, more particularly, to venturi carburetion systems for natural gas fueled internal combustion engines using recycled exhaust gas.  
           [0003]    2. Description of Related Art  
           [0004]    Electric energy generation in this country has lagged behind demand. There are a number of reasons for this, but chief among them is failure of traditional energy producers to replace spent units and capitalize new plants. This has been, in part, due to increased air quality regulations. In addition, new challenges face electric generation security. Events of Sep. 11, 2001 showed this nation its vulnerability to terrorist attack. Vital operations, such as police, medical and civil defense that relied upon the electric power “grid” for service, realized that their needs were susceptible to disruption and viewed stand-alone units, as well as micro grids as a possible solution. These alternatives are fraught with their own problems. Chief among the reasons is a drastic increase in demand. Thus, while energy demand has increased, generating capabilities have not.  
           [0005]    In addition to the mismatch between demand and generating capacity, the physical transmission infrastructure necessary to deliver power from geographically remote generating facilities to the consumer&#39;s location is unable to support the increased load. Even under today&#39;s operating conditions, the transmission grid is subject to stress and occasional failure.  
           [0006]    One reason for the growth in demand is the increased use of computers and other technology for industrial and business purposes, as well as personal use. As computer usage continues to grow, the use of power-consuming peripheral technologies, such as printers, cameras, copiers, photo processors, servers, and the like, keep pace and even expand. As business use of computer based equipment continues to rise, as do the number of in-house data servers, outsourced data storage facilities, financial systems, and Internet-related companies requiring constant electrical uptime and somewhat reducing traditional peak demand times, requirement for reliable, cheap, environmentally compliant electrical power, continues to grow.  
           [0007]    Other technological advances have also increased electrical energy demand. Increased use of power consuming devices in every aspect of life, from medical to industrial manufacturing robots, as well as innovations in almost every research and industrial field, are supported by increasingly complex technology, which requires more electrical power to function. CAT scans, NMRs, side looking X-rays, MRIs and the like, all take electrical power.  
           [0008]    Further, security and reliability of source has become of increasing concern. Grid system vulnerability is a real threat. Strategic industries are looking to cut energy costs, increase reliability, and assure security. This has lead to an interest in distributed market technologies. The potential market for distributed generation has become vast without adequate means for fulfilling this need. Again, inefficiency, reliability, and environmental concerns are major barriers. The compelling economics are made on engine efficiency without the financial benefit of waste heat usage, yet with all of the same customer reluctance to accept hassles. Industry estimates indicate that the existing market for distributed generation is $300 billion in the United States and $800 billion worldwide.  
           [0009]    Although most existing distributed generation sites use small gas turbine or reciprocating engines for generation, there are many alternatives that are being considered over the longer term. Technologies, such as micro-turbines, are currently available, but only used at a relatively small number of sites. These newer generators offer some inherent advantages, including built-in communications capabilities. It is anticipated that fuel cells will be available in the next five years, which will provide some highly appealing, environmentally friendly options.  
           [0010]    As it stands today however, small gas turbine and reciprocating engines comprise a substantial proportion of existing generator technology in the market and will for some time to come for a number of reasons. Engines provide the best conversion efficiency (40%), and they can operate using non-pressurized gas. Micro-turbines, on the other hand, require compressed gas and conversion efficiency is lower (approximately 30%). These latter generators tend to be used in wastewater and landfill and other specialty sites, where a conventional prime mover is unable to stand up to poor fuel quality. Therefore, for utilities to truly benefit from a distributed generation scheme over the short term, they must look to the existing generator technology to provide a sustainable and affordable solution.  
           [0011]    Waste heat utilization or cogeneration is one way to increase overall system efficiency. In the case of most power generation, the waste heat is not used, and the economics are based largely on the cost of the electricity produced (i.e. heat rate is paramount), with little consideration for improved reliability or independence from the electric grid. The anticipated fluctuation in energy costs, reduced reliability, and increasing demand has led end users to consider maximizing efficiency through use of heat from generation of on-site generating-heat capture systems, i.e. cogeneration, or “Combined Heating and Power” (CHP).  
           [0012]    Cogeneration of electricity and providing client service heat for space heating and/or hot water from the same unit is one solution. Cogeneration provides both electricity and usable process or utility heat from the formerly wasted energy inherent in the electricity generation. With cogeneration, two problems are solved for the price of one. In either case, distributed electricity generation systems must meet stringent local air quality standards, which are typically much tougher than EPA (nation wide) standards.  
           [0013]    On-site cogeneration represents a potentially valuable resource for utilities by way of distributed generation. A utility can increase capacity by turning to a “host” site (e.g. industrial user) with an existing generator, and allow them to parallel with the grid and use their generator capacity to handle peak volumes as well as provide utility and space heat to the host site customers. From the utility&#39;s point of view, the key advantages to a distributed generation solution are twofold: improved system reliability and quality; and the ability to defer capital costs for a new transformer station.  
           [0014]    For customers who can use the process/utility waste heat, the economics of cogeneration are compelling. The impediment to widespread use is reliability, convenience, and trouble free operation. Cogeneration products empower industrial and commercial entities to provide their own energy supply, thus meeting their demand requirements without relying on an increasingly inadequate public supply and infrastructure.  
           [0015]    Unfortunately, to date, the most widespread and cost-effective technologies for producing electricity require burning hydrocarbon-based fuel. Other generating technologies are in use, including nuclear and hydroelectric energy, as well as alternative technologies, such as solar, wind, and geothermal energy. However, burning fuel remains the primary method of producing electricity. Unfortunately, the emissions associated with burning hydrocarbon fuels are generally considered damaging to the environment, and the Environmental Protection Agency has consistently tightened emissions standards for new power plants. Green house gases, as well as entrained and other combustion product pollutants, are environmental challenges faced by hydrocarbon-based units.  
           [0016]    Of the fossil fuels, natural gas is the least environmentally harmful. Most natural gas is primarily composed of methane and combinations of Carbon Dioxide, Nitrogen, Ethane, Propane, Iso-Butane, N-Butane, Iso Pentane, N-Pentane, and Hexanes Plus. Natural gas has an extremely high octane number, approximately 130, thus allowing higher compression ratios and broad flammability limits. A problem with using natural gas is reduced power output when compared to gasoline, due mostly to the loss in volumetric efficiency with gaseous fuels. Another problem area is the emissions produced by these natural gas engines. Although, the emissions are potentially less than that of gasoline engines, these engines generally require some types of emissions controls such as exhaust gas recirculation (EGR), positive crankcase ventilation (PCV), and/or unique three-way catalyst.  
           [0017]    Still another problem with using natural gas is the slow flame speed, which requires that the fuel be ignited substantially before top dead center (BTDC). In general, most internal combustion engines running on gasoline operate with a spark advance of approximately 35 degrees BTDC where as the same engine operating on natural gas will require an approximate advance of 50 degrees BTDC. The slower burn rate of the fuel results in reduced thermal efficiency and poor burns characteristics.  
           [0018]    It is well known that emission reduction for natural gas engines can be accomplished by EGR to make the engines run lean. Numerous systems have been devised to recycle exhaust gas into the fuel-air induction system of an internal combustion engine for the purposes of pre-heating the air-fuel mixture to facilitate its complete combustion in the combustion zone, for re-using the unignited or partially burned portions of the fuel, which would otherwise pass to exhaust and into the atmosphere, and for reducing the oxides of nitrogen emitted from the exhaust system into the atmosphere. It has been found that approximately 15 to 20 percent of exhaust gas recycling is required at moderate engine loads to substantially reduce the nitrogen oxide content of the exhaust gases discharged in the atmosphere, that is, to below about 1,000 parts per million.  
           [0019]    Although, the prior art systems have had the desired effect of reducing nitrogen oxides in the exhaust by reducing the maximum combustion temperature as a consequence of diluting the fuel-air mixture with recycled exhaust gases during certain operating conditions of the engine, these systems have not been commercially acceptable from the standpoints of both cost and operating efficiency and have been complicated by the accumulation of gummy deposits, which tend to clog the restricted bypass conduit. Recycling the exhaust systems have also been complicated by the desirability of reducing the recycling during conditions of engine idling when nitrogen oxide emission is a minor problem and progressively increasing wide open throttle when maximum power is required, while progressively increasing the recycling exhaust gases with increasing engine load.  
           [0020]    In the usual hydrocarbon fuel type engine, fuel combustion can take place at about 1,200° F. The formation of nitrogen oxides does not become particularly objectionable until the combustion temperature exceeds about 2,200° F., but the usual engine combustion temperature, which increases with engine load or the rate of acceleration at any given speed frequently, rises to about 2,500° F. It is known that the recycling of at least one-twentieth and not more than one-fourth of the total exhaust gases through the engine, depending on the load or power demand, will reduce the combustion temperature to less than 2,200° F. Contaminants in the exhaust resulting from fuel additives desired for improved combustion characteristics normally exit in a gaseous state at combustion temperatures exceeding about 1,700° F., but tend to condense and leave a gummy residue that is particularly objectionable at the location of metering orifices and valve seats in the exhaust recycling or bypass conduit. The thermal nitrogen oxide emission is a direct function of combustion temperature and for that reason is less critical during engine idling when the rate of fuel combustion and the consequent combustion temperature are minimal but tends to be problematic during throttle-up and extended full speed operation.  
           [0021]    Thus, prior art cogeneration systems employing internal combustion engines, and specifically, natural gas fueled engines have suffered from the myriad of problems including elevated head temperatures and inability to deliver large quantities of process and/or utility heat to the cogeneration client. Excessive head temperatures lead to inefficient operation and unacceptable environmental conditions, which include excessive use of fuel, as well as significant NO x  production.  
           [0022]    Some of the inherent problems with natural gas fueled engines, which utilize EGR techniques to reduce pollution, are a result of carburetion problems, which prevent them from running “lean.” Specifically, the natural gas regulators have been unable to supply natural gas to the engine throughout the load cycle while maintaining a fuel to air ratio, which does not starve the engine or alternatively run it to rich. In the former case, the engine stalls; in the later, fuel efficiency and NO x  production become out of limits.  
           [0023]    Prior art internal combustion engines operating on natural gas and used as power units to spin electric generators use various types of fuel carburetion, regulation, and introduction systems. One device for carburetion uses a diaphragm, which opens under engine vacuum, to operate a fuel-metering valve, allowing fuel to enter an air-mixing chamber, where it is mixed with air and exhaust gas for combustion. The mixture of fuel/air/recycle gas from the mixing chamber then passes through a throttle regulator, which regulates the flow of the mixture to the engine as a function of load. The diaphragm regulates fuel flow by responding to the changes in vacuum (pressure) at the intake manifold of the engine. In some configurations, an exhaust gas driven turbocharger is used to pre-compress the mixture prior to injection into the cylinder. The use of a turbocharger increases the vacuum on the carburetion unit.  
           [0024]    These systems have inherent drawbacks. For one, the diaphragm must be several times the size of the gas inlet. For example, a three-inch diameter inlet could require a diaphragm of 15-18 square inches. For a second, when recycled exhaust gas is used the recycle gas tends to erode the diaphragm. Finally, these systems are prone to diaphragm rupture from engine backfire through the intake system. If the engine is turbocharged, the air/recycle gas/fuel mixture passes through the turbocharger, and then, preferably, through an engine intercooler to cool the compressed air/recycle gas/fuel mixture and into the engine cylinders. The combination of a large diaphragm section, mixing section, and throttle section in the carburetion unit make for a large and bulky apparatus, which must be mounted directly on the engine intake.  
           [0025]    Therefore, a more fuel-efficient balanced venturi style fuel/air mixing unit was developed. This style of fuel introduction is now utilized on most natural gas fired, internal combustion engines because it is easy to obtain parts, assemble, and mount to the engine. One drawback is that a separate gas shut-off valve must be installed upstream of the venturi for engine shutdown. Another is flooding from pressurized fuel sources. Finally, the load variations on these systems make fuel regulation upstream of the venturi compelling.  
           [0026]    Engines, which utilize this venturi fuel carburetion system, utilize a series of small ports of a size determined by the fuel requirement. Air is drawn into a venturi-mixing chamber by vacuum. If the fuel is under a positive pressure, the chamber floods prior to ignition, which prevents ignition of the engine. Again, a regulator is required upstream of the venturi. One type of regulator employs one or more diaphragms, which respond to variation in engine or burner vacuum. For most applications, this vacuum operated devise works reasonably well because, like a burner, the requirement for fuel is full on or full off.  
           [0027]    Prior art EGR carburetion systems have been plagued with a myriad of problems. First, the exhaust gas is usually recycled at elevated temperatures, which increases the head temperature of the engine, unless the gas is cooled. In addition, when the engine is turbocharged, the temperature of the intake admixture is elevated even further by compression. Thermal NO x  is a function of head temperatures, as previously described. Thus, elevated temperatures of intake gases contribute to thermal NO x  production.  
           [0028]    Second, carburetion systems for natural gas internal combustion engines that utilize recycled gas must mix recycled exhaust gas in proportion to ambient air in proportion to fuel to affect stoicheiometric conditions in the engine, while maintaining low thermal NO x  and overall energy efficiency. In cogeneration units, where electric load automatically throttles the engine, these ratios of air-to-exhaust and gas-to-fuel can easily become out of proportion because of rapid acceleration/deceleration of the engine.  
           [0029]    Thus, carburetion systems for internal combustion natural gas fired exhaust gas recycled engines have, heretofore, been complicated and involved electronic, dynamic feed back, control systems for regulating the fuel, as well as the recycled gas in response to changing engine demands. Since the intake mixture varies with load, too much fuel or too much recycled gas will “choke” the engine. Like wise, too little fuel will “starve” the engine and too little recycle gas will increase thermal NO x  production. All of these conditions cause the engine to be unstable, inefficient, and out of emission compliance.  
           [0030]    Therefore, it would be advantageous to have a simple carburetion system, which does not involve complicated control feed back systems, which must be maintained and tuned; eliminates need for mechanical or digital control of varying EGR flow over changing load or RPM; and/or the need for mechanically or electrically driven pumps to properly modulate EGR over changing loads. In addition, it would be advantageous to have a system, which mechanically responds to the engine load requirements by dynamically regulating the fuel, air, recycled gas ratio in the intake mixture as a function, solely of the pressure change created by acceleration/deceleration of the engine. Further, it would be advantageous if such system would operate without creating engine instability in response to almost instantaneous electrical load change. It would also be advantageous to accomplish all of the aforementioned without complicated mechanical linkage or excess parasitic power demands.  
           [0031]    It would further be advantageous to have a cogeneration system with reduced fuel consumption, as well as NO x  production, while delivering substantial heat to the process/utility heat cogeneration system. In addition, it would be advantageous to run a lean burning engine using EGR, which results, in not only a lean burn, but also reduced head temperatures, leading to reduced thermal emissions and greater efficiency.  
         SUMMARY OF THE INVENTION  
         [0032]    It has now been unexpectedly discovered that a carburetion system, without complicated control systems, functions uniformly throughout the range of engine loads and incremental increases of power demand to provide efficient stable engine performance for a natural gas fired, internal combustion engine using EGR. In accordance with the invention, a cogeneration system for supplying distributed generation of electricity and process/utility heat, employs a system for engine cooling and effective heat transfer to a cogeneration client, reduces engine head temperature, thereby reducing fuel consumption and reducing pollutants, as well as delivering substantially increased heat to a cogeneration process/utility heat facility. The cooling cycles and process/utility heat radiation configurations of the inventive system maintain cylinder inlet temperature resulting in improved efficiency, reduced thermal NO x  and longer engine life. This allows operation of the engine at optimum inlet and outlet temperatures regardless of cogeneration process/utility heat system requirements, without excessive parasitic pump loads.  
           [0033]    In accordance with the invention a cogeneration system for supplying distributed generation of electricity and process/utility heat employs a carburetion system for a natural gas fired internal combustion engine employing EGR. The carburetion system employs at least a pair of spaced apart venturi positioned in series proximate one to another such that a first exhaust recycled gas venturi is upstream of a fuel venturi where fuel and air/exhaust gas are admixed prior to the resultant gas being introduced into a turbocharger. The distance between the exhaust venturi and fuel venturi is affective to provide a given amount of exhaust gas to air ratio prior to entering the fuel venturi inlet.  
           [0034]    It has been unexpectedly discovered that the relationship of the two venturi, one to the other, can be used to affectively regulate exhaust gas air mixture, as well as the air/fuel/exhaust gas mixture to the engine by means solely of pressure increase and decrease (vacuum) of the engine intake system.  
           [0035]    In accordance with another aspect of the invention, a fuel regulator device communicates with the fuel venturi such that the fuel gas venturi, the exhaust gas venturi, and the gas regulator operate in concert to fuel the engine throughout the load range without need for complex electronic control systems. This system responds to the increase or decrease in pressure created by opening and closing the throttle to create a vacuum through the turbocharger. The system allows the engine to run stoicheiometricaly throughout the load range, while reducing thermal NO x  emissions and maintaining the engine power curve without the necessity of complicated control feed back systems such as electronic solenoids, transducers, computers, and the like.  
           [0036]    In accordance with a preferred embodiment, the cogeneration system of the instant invention employs an engine cooling and heating system, which includes a first coolant loop, which directs coolant through the engine block, and a second loop, which directs coolant through the at least one exhaust manifold in cooperation with the first loop, such that the coolant inlet temperature of the first loop is substantially reduced to maintain appropriate engine head temperatures to reduce thermal NO x  while maintaining efficiency. The two loops then merge at a process heat exchanger such that the combined output heat contained in the liquid of the two loops is effective to deliver increased heat to the cogeneration process/utility heat system without an increase in parasitic load, i.e. using the engine internal pump only.  
           [0037]    Advantageously, the coolant loops each carry different quantities of coolant to assure engine performance. In one embodiment, the loops can be balanced by means of a dynamic feed back valving to assure head temperatures within a specified range.  
           [0038]    In accordance with another aspect of the instant invention, a turbo intercooler/heat exchanger is used to reduce the temperature of compressed engine intake gas, emerging from the turbocharger, prior to its entry into the intake manifold of the engine such that the inlet gas temperature is reduced to retard the formation of thermal NO x . Thus, the engine driven coolant pump can be utilized exclusively for the coolant loop, reducing the parasitic load, while drastically reducing cylinder inlet temperature resulting in improved efficiency, lower thermal NO x  and longer engine life.  
           [0039]    In another aspect an EGR cooling circuit using air finned heat exchangers is used to reduce the temperature of the recycled exhaust gas, prior to its mixing with the intake gases for combustion. This further reduces cylinder inlet temperature resulting in improved efficiency, lower thermal NO x , and longer engine life.  
           [0040]    In accordance with the invention, a dump/balance radiator is used to remove heat not transferred to the cogeneration process/utility heat system such that engine efficiency is maintained even in the absence of the cogeneration process/utility heat system load. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0041]    The following drawings form part of the present specification and are included to further demonstrate certain embodiments. These embodiments may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.  
         [0042]    [0042]FIG. 1 is a flow chart detail of an example integration of EGR air venturi; the exhaust gas recycle/air-fuel venturi; the fuel regulator system of the instant invention with a turbocharger intercooler radiator loop interface, the engine intake gas system and the engine exhaust system.  
         [0043]    [0043]FIG. 2 is a sectional view, along the direction of gas flow, of the upstream venturi for admixing recycled exhaust gas with air in accordance with the instant invention;  
         [0044]    [0044]FIG. 3 is a sectional view, along the direction of gas flow, of the downstream venturi for admixing recycled exhaust gas and air with fuel in accordance with the instant invention;  
         [0045]    [0045]FIG. 4 is a sectional view, along the direction of fuel flow, of the fuel regulator in accordance with the instant invention; and,  
         [0046]    [0046]FIG. 5 is a is a flow chart of the heat transfer systems for cogeneration of the instant invention; 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0047]    In accordance with the instant invention a natural gas fueled, internal combustion engine, employing EGR, delivers power to spin a coupled electric turbine, as well as heat of combustion, through a heat exchanger, to a cogeneration process/utility heat loop for on site use as heat for process water, utility heat, space heat, potable hot water, and the like. This is accomplished with the instant system by increasing the transfer of engine heat to the cogeneration process/utility heat loop while maintaining the engine, and, especially, the head temperature low enough to increase efficiency and reduce thermal NO x  to acceptable levels, even in the presence of the EGR. Even in the presence of EGR, moreover, there is substantially no increase in parasitic power requirements, such as adding external pumps to increase the flow through the heat exchanger.  
         [0048]    Further, the carburetion system of the instant invention employs two venturi in a spaced apart relationship, which deliver air, fuel, and recycle exhaust gas to the engine in response to increase and decrease in intake manifold pressure as the engine responds to increased and decreased loads. A fuel regulator for natural gas fired cogeneration unit regulates natural gas, under pressure, from a remote fuel source, such as a tank, to an carburetion device where the fuel is mixed with air and exhaust gas for intake into the cylinders of an internal combustion engine.  
         [0049]    In accordance with one aspect of the invention, recycle exhaust gas is admixed with the air and fuel to reduce NO x  emissions from the engine, as will be further explained below. In accordance with a further aspect, the engine is supercharged by, for example, an exhaust gas driven turbocharger, to enhance engine performance. When the engine is turbocharged using EGR, the exhaust gas is mixed with combustion air upstream of the fuel venturi, and then admixed with fuel by, for example, a fuel venturi. Advantageously, the turbocharged mixture of hot exhaust gas, fuel, and air is cooled prior to entrance into the engine cylinder to reduce head tempeture, and thus, NO x  emissions from the engine.  
         [0050]    The fuel regulator can comprise one or more sections or elements to regulate flow of the pressurized fuel into the carburetor. In accordance with the invention, a first gas metering chamber is provided to meter the flow of gas, dynamically, in response to the requirements of the engine by means of incremental changes in vacuum pressure from the carburetion device. A second gas flow-restricting chamber, downstream of the metering chamber, but in gas communication therewith, is provided to restrict the flow of gas by means of a manual set valve, which is used to “tune” the engine and is manually set and maintained. An upper diaphragm responds to incremental vacuum changes from load variation and induces the lower diaphragm to modulate fuel flow to the venturi to maintain engine RPM during load changes.  
         [0051]    In accordance with the invention, an engine coolant loop flow is split so that a first portion flows through the engine block, by way of the engine oil cooler, and through a thermal valve control to the fluid process heat exchanger. A second portion flows to at least one fluid cooled exhaust manifold by way of the engine oil cooler, for example, through the inlet ports of the left and right liquid cooled exhaust manifolds and then the inlet port of the fluid cooled turbocharger where it merges with the liquid from the first loop prior to going through the fluid process heat exchanger, which delivers heat to the cogeneration process/utility heat system.  
         [0052]    Thus, in accordance with one embodiment, the coolant flows through a cooling loop by way of an engine driven pump through the oil heat exchanger. Exiting the oil heat exchanger, it splits into two parallel loops. One loop follows a path through the engine block, and the other through the coolant manifold, and then the coolant cooled turbocharger. Both coolant flow loops converge at the thermal control valve where they blend back together to form a single stream prior to flowing through the fluid process heat exchanger. The thermal control valve senses the blended stream temperature and bypasses the fluid process heat exchanger if the temperature is below the threshold engine block inlet tempeture of, for example, 175° F. This closed loop prohibits flow through the fluid/process heat exchanger and dump/balance radiator to retard heat loss until optimum engine block inlet temperature is achieved. When the temperature is greater than, for example, 175° F., flow through the control valve is first diverted partially to the fluid/process heat exchanger and then fully to the fluid/process heat exchanger as operating temperatures are reached.  
         [0053]    The combined flow is, thus, through the coolant/process heat exchanger for use in heat exchange with the cogeneration process/utility heat system. This parallel cooling loop increases the engine cooling loop heat available to the process/utility heat system, significantly, while maintaining favorable engine operating conditions. In this manner, the coolant through the second loop is at a higher tempeture, but a lower flow rate, while the coolant through the first is at a slightly lower tempeture, but a higher flow rate to keep the cylinder heads cooler, thus, increasing efficiency and reducing thermal NO x  emissions.  
         [0054]    In accordance with a further aspect, the system employs a separate loop to cool supercharged engine inlet feed. This separation of the intercooler liquid coolant loop from the engine coolant loop provides a separate heat exchanger upstream of the engine intake manifold to reduce engine intake temperatures, drastically reducing head temperatures within the engine. Likewise, in a further aspect, the exhaust recycle gas is cooled by at least one air cooled radiator prior to admixing it with air and fuel, which is then compressed in the supercharger.  
         [0055]    The power source compatible with the instant invention is a natural gas fueled, internal combustion liquid cooled engine, wherein at least a portion of the exhaust gas is recycled to reduce NO x  For example, a Deutz brand Engine Model BE 8 M1015 GC engine manufactured by Deutz. The natural gas fired internal combustion engine is the prime mover of the electrical generation system, having liquid coolant flow system with a required return coolant at a temperature to reduce head temperature to less than about 1,800° F. The internal engine pump moves the coolant through the various engine components and then through the process heat exchanger to transfer heat to the cogeneration process/utility the system.  
         [0056]    Carburetion/Exhaust System  
         [0057]    As shown in FIG. 1, there is carburetion/exhaust system  10 . In accordance with carburetion/exhaust system  10 , there is an upstream EGR venturi  200 , a downstream fuel/air venturi  100 , and a fuel regulator  300 , which comprise the carburetion system of the instant invention. As further shown in FIG. 1, the intake loop interfaces with the turbo intercooler  34  cooling circuit, the turbocharger  428 , the engine intake manifold  38 , and the recycled exhaust gas (EGR) system. This interaction is advantageous in that head temperatures, gas inlet temperatures, and exhaust gas recycle temperatures can be tuned. It is also advantageous in that the throttle linkage from electrical generator opens and closes a valve, for example, a butterfly valve, which increases or decreases the engine intake of fuel/air/EGR and, in turn, creates a pressure variation at the outlet of fuel/air venturi  100  as will be further described herein.  
         [0058]    In accordance with FIG. 1, ambient outside air passes through air filter  20  and intake conduit  22  to EGR venturi  200 , where air is mixed with recycled exhaust gas from conduit  66 , as will be more fully described. EGR venturi  200  is upstream of fuel/air venturi  100 . Mixed air and exhaust gas exits EGR venturi  200  through intake conduit  26  into fuel/air venturi  100  where the air/exhaust gas mixture entrains fuel from fuel regulator  300 . Fuel regulator  300  is connected to a fuel source (not shown) by means of conduit  12 . Fuel regulator  300  communicates with fuel/air venturi  100  by means of fuel line  16 . The fuel/air/exhaust gas mixture exits fuel/air venturi  100  via turbocharger intake conduit  28  and is compressed in turbocharger  428 . The turbocharger, which is operated by engine exhaust, creates a vacuum on turbocharger intake conduit  28  which is translated back through the system to operate the fuel regulator, as will be further described.  
         [0059]    The compressed fuel/air/recycled exhaust gas mixture exits turbocharger  428  through turbo intercooler intake conduit  32  into turbo intercooler  34  where it is cooled from 400° F. to 165° F. Intercooler radiator  70 , pump  72 , and coolant circulating conduit  74  continually circulate coolant, in a closed loop, through turbo intercooler  34  to cool the compressed fuel/air/recycled exhaust gas mixture. The cooled intake gas (exhaust gas/air/fuel) exits turbo intercooler  34  into engine intake manifold  38  via engine intake conduit  36  and through engine intake manifold  38  into engine cylinders  40 .  
         [0060]    Exhaust gas from engine cylinders  40  exits into fluid cooled manifold  420 , as more fully described below, and enters the turbine side of turbocharger  428  through exhaust conduit  46  to power the turbocharger  428 , thus compressing the fuel/air/recycled exhaust gas mixture entering turbocharger  428  by means of turbo intercooler intake conduit  32 , as previously described. As can be seen, exhaust gas exiting turbocharger  428  is split into a recycled stream and an exhaust stream. The exhaust stream, moved via conduit  50 , enters three-way catalyst  52  and then by way of conduit  54  to exhaust heat recovery silencer  456 . One skilled in the art will realize that the exhaust heat recovery silencer  456  is on the cogeneration process/utility heat system and provides additional heat recovery for that system (see FIG. 5). A portion of the exhaust gas to be recycled passes through conduit  58  to primary air cooled EGR cooler  60 ; and, if necessary, secondary air cooled EGR cooler  64  by means of conduit  62  and then passes into EGR venturi  200  through conduit  66 .  
         [0061]    The pressurization of the air/exhaust gas/fuel mixture by turbocharger  428  creates a vacuum upstream, as previously described. As fuel is pulled through fuel/air venturi  100 , it creates a vacuum, which is transferred through fuel line  16  to fuel regulator  300  of the carburetion/exhaust system  10 , in accordance with the instant invention.  
         [0062]    Venturi System  
         [0063]    As shown in FIG. 2, there is a fuel/air venturi  100  having an air EGR inlet port  102  narrowing to a throat  104  wherein fuel from a fuel regulator (See FIG. 4) flows through fuel line  16  and enters by means of conduit  106  through an opening in the venturi housing to circumferentially disposed fuel distribution conduit  108 , which communicates with numerous fuel injection ports  110 . The air EGR admixture entering air EGR inlet port  102  is compressed through throat  104  wherein fuel from fuel injection ports  110  is admixed there with to form an air/EGR/fuel mixture, which exits throat  112  to turbocharger  458 , as seen in FIG. 1. In operation, the engine is throttled by means of an appropriate valve to open an intake manifold inlet on the engine (not shown) to cause the turbocharger  458  to provide increased fuel/gas/EGR admixture, thus creating a vacuum at air EGR inlet port  102 . The fuel in circumferentially disposed fuel distribution conduit  108 , under pressure, is continually regulated by a fuel regulator  300 , described herein below, to cause appropriate portions of fuel and air/exhaust gas to be admixed in fuel/air venturi  100 .  
         [0064]    Turning to FIG. 3, there is shown an EGR venturi  200 , which is located upstream of fuel/air venturi  100 , having an EGR inlet conduit  202  which communicates with mixing chamber  204 , as shown. Air from an air filter  20  (FIG. 1) enters rear venturi throat  206  and passes by way of mixing chamber  204  passed the end of EGR inlet conduit  202 , which protrudes into the air stream created in mixing chamber  204  to aspirate EGR from EGR inlet conduit  202 . The air/EGR admixture then passes into exit throat  208  and by means of a intake conduit  26  enters fuel/air venturi  100 , as previously described.  
         [0065]    In operation, upstream EGR venturi  200  and downstream fuel/air venturi  100  are placed in a spaced apart relationship, one to the other, wherein the distance from the EGR inlet conduit  202  and the fuel injection ports  110  is affective to create an aspiration of EGR to provide sufficient EGR (about 20%) to maintain a lean burn condition in the engine (not shown). Thus, EGR venturi  200  and fuel/air venturi  100  operate in concert with fuel gas regulator, as described below. Turbocharger inlet pressure regulates the flow of EGR gas ratio to air and subsequently EGR/air ratio to fuel in order to stoicheiometricaly fire the internal combustion engine.  
         [0066]    Gas Regulator  
         [0067]    Turning to FIG. 4, there is shown a cutaway of fuel regulator  300 . FIG. 4 shows the internal workings of the fuel regulator  300  when the solenoid is activated. Inlet-coupling element  312  carries threaded nipple  313  and communicates with gas metering/shutoff component  318 , as shown. Gas metering/shutoff component  318  has mounted thereon a solenoid housing  320 , which contains a solenoid (not shown) to actuate solenoid actuation rod  336 , and a diaphragm housing  334 , containing the gas regulating membranes, as will be further described.  
         [0068]    Solenoid actuation rod  336 , the end of which contacts metal contact plate  338 , which, in turn, is seated upon fuel regulating valve  340 . Fuel regulating valve  340  sealably engages valve seat  342 , when the solenoid housing  320  is de-energized (not shown), all gas flow is shut-off through fuel regulator  300 . Within gas metering/shutoff component  318  is a solid partition  344 , which divides gas metering/shutoff component  318  into an upper gas receiving chamber  384  and a lower gas receiving chamber  386  and contains valve seat  342  therein, such that when fuel regulating valve  340  is fully seated in valve seat  342 , gas flow is shut off. In operation, with the solenoid energized, as shown in FIG. 4, the solenoid actuation rod  336  is retracted allowing fuel regulating valve  340  to open and close by means of valve stem  346 .  
         [0069]    Valve stem  346  communicates with, and is advantageously attached to the bottom portion of, fuel regulating valve  340  on one end and upper diaphragm  348  on the other. The upper diaphragm assembly includes upper diaphragm  348 , which is sealably housed in diaphragm housing  334  and an upper diaphragm seating spring  350 , which engages the underside of upper diaphragm  348  and rests on platform  352 . Platform  352  is sealably supported by the sidewalls of diaphragm housing  334 . The underside of upper diaphragm  348  and platform  352  in cooperation with the sidewalls of diaphragm housing  334  forms an upper diaphragm chamber  356 .  
         [0070]    A lower diaphragm assembly resides in the diaphragm housing  334 , beneath the upper diaphragm assembly. The lower diaphragm assembly, includes lower diaphragm  360 , which is sealably housed in diaphragm housing  334 , and a lower diaphragm seating spring  362 , which engages the underside of lower diaphragm  360  and rests on the bottom closure of diaphragm housing  334  to form a sealed unit. The upper side of lower diaphragm  360  and the lower side of platform  352  in cooperation with the sidewalls of diaphragm housing  334  form a first lower diaphragm chamber  358 . The underside of lower diaphragm  360 , and the bottom closure of diaphragm housing  334  in cooperation with the sidewalls of diaphragm housing  334  form a second lower diaphragm chamber  367 .  
         [0071]    Platform  352  has a pressure equalization port  354 , which communicates between the upper diaphragm chamber  356  and first lower diaphragm chamber  358 . A pressure equalization tube  364  communicates with second lower diaphragm chamber  367  and ambient. These two devices equalize the pressure between the chambers as the diaphragms deform in operation.  
         [0072]    Modulating element  326  sealably attaches to gas metering/shutoff component  318  such that pressure-modulating chamber  366  communicates with lower gas receiving chamber, interior of gas metering/shutoff component  318  and modulating element  326  sealably attaches to manual fuel trim valve assembly housing  328  such that pressure-modulating chamber  366  communicates with the upper gas receiving chamber  376  interior of manual fuel trim valve assembly housing  328 .  
         [0073]    Manual fuel trim valve assembly housing  328  contains a valve stem  368 , which is capped by valve adjustment settings screw  330  and threadably engages treaded sleeve  332 . The lower end of valve stem  368  is attached to metal valve plate  370  seated on fuel regulating valve  372 . Within manual fuel trim valve assembly housing  328  is a solid separating membrane  374 , which divides the manual fuel trim valve assembly housing  328  into an upper gas receiving chamber  376  and a lower gas exiting chamber  378  and contains valve seat  380  therein, such that when fuel regulating valve  372  is fully seated in valve seat  380 , gas flow is shut off. Outlet-coupling element  314  carries threaded nipple  382  for connection to a fuel line  16 , as seen in FIG. 1.  
         [0074]    In operation, the solenoid, which is de-energized so that solenoid actuation rod  336  is in the fully extended position, closes fuel regulating valve  340 . Upon ignition of the engine, the solenoid is energized (as shown in FIG. 4) and solenoid actuation rod  336  is fully retracted, allowing modulated opening and closing of fuel regulating valve  340  in response to movement of upper diaphragm  348 . Fuel entering, under pressure, through inlet-coupling element  312 , passes into upper gas receiving chamber  384  of gas metering/shutoff component  318 , through valve seat  342  into lower gas receiving chamber  386 , through pressure-modulating chamber  366 , into upper gas receiving chamber  376  in manual fuel trim valve assembly housing  328 , through valve seat  380 , into lower gas exiting chamber  378  and exits outlet-coupling element  314  to fuel line  16  The fuel regulating valve  372  is manually set by means of threadably adjusting valve adjustment settings screw  330  to regulate the maximum gas flow rate through the manual fuel trim valve assembly housing  328 .  
         [0075]    The pressurization of the air/exhaust gas/fuel mixture by turbocharger  428  creates a vacuum upstream, as previously described. As fuel is pulled through fuel/air venturi  100 , it creates a vacuum, which is transferred through fuel line  16  to fuel regulator  300 . The vacuum reduces pressure in lower gas exiting chamber  378  and upper gas receiving chamber  376  through pressure-modulating chamber  366  and in lower gas receiving chamber  386 . The reduced pressure in lower gas receiving chamber  386  causes upper diaphragm  348  to deform, as shown in FIG. 3, moving valve stem  346  upwardly to open fuel regulating valve  340 , as shown. Likewise, the reduction in pressure of upper diaphragm chamber  356  causes a corresponding reduced pressure to equalize through pressure equalization port  354  to create a vacuum in the first lower diaphragm chamber  358  causing lower diaphragm  360  to deform. Pressure equalization tube  364  allows equalization pressure into second lower diaphragm chamber  367  below lower diaphragm  360 . Thus, as the vacuum pressure pulled on the fuel in fuel supply conduit  390  fluctuate upper diaphragm seating spring  350  and lower diaphragm seating spring  362  cooperate to attempt to reduce the deformity of upper diaphragm  348  and lower diaphragm  360 , respectively, re-seating fuel regulating valve  340  in valve seat  342 .  
         [0076]    Advantageously, two diaphragms are used, as shown in FIG. 4. This arrangement prevents a harmonic or “fluttering” of the first diaphragm as a vacuum serge is experienced by the fuel regulator device. However, it will be realized by one skilled in the art that a single diaphragm apparatus would be operative in accordance with the instant invention.  
         [0077]    Thus, in accordance with the invention, fuel under pressure is introduced into the upper gas receiving chamber  384 . Fuel regulating valve  340  is modulated by movement of upper diaphragm  348  in response to vacuum applied to the system by varied throttling of the engine. The fuel regulating valve  372  is manually set to maintain as lean a burn condition as permissible at full load as well as at engine starting to preclude a “too rich” setting causing miss-firing of the sparkplugs and/or damage to the three-way catalyst during engine warm-up. During operation, as the generator experiences a change in load with corresponding changes in engine throttle position, the corresponding increase or decrease in vacuum pressure causes the fuel modulating diaphragm to deform or return to its non-deformed position due to the action of the seating spring. These changes in vacuum cause the diaphragm to slightly “over compensate” for the fuel required for that load change. Rapid, or large load changes with corresponding pressure changes on the fuel-modulating diaphragm cause engine instability.  
         [0078]    The pressure modulation chamber, in accordance with the instant invention, unexpectedly modulates the rapid pressure changes reducing the wide variations in the deformation of the fuel modulating diaphragm, which dampens the amplitude of the fuel regulating valve yielding less “overcompensation” to produce smoother engine operation over the full range of load conditions. Thus, rather than dynamically manipulating the valve adjustment settings screw by means of a control system, the modulating chamber allows the system to adjust to surges stabilizing engine operation throughout the full load range. The volume of the chamber and the spacing between the valves caused by inserting the chamber depends upon the system. Modulating element, having a thickness (height) in the range of ¾ to 1.5″, is useful in accordance with the system described. Diameters of from about 1.5 to 2.0 inches at the above referenced thickness are found to provide the required volume.  
         [0079]    Thus, in accordance with the invention, ambient air (70° F.) flows through air filter to EGR venturi where it is mixed with up to 20% cooled exhaust gas (140° F.) at 100% load. The percent of recycled exhaust gas utilized is a function of engine load. This mixture (120° F.) then passes through the fuel/air venturi where fuel is drawn from the gas regulator and mixed with the ambient air and exhaust gas to be flowed to the intake side of the turbocharger. The fuel/air/recycle exhaust gas mixture is then pressurized by an exhaust gas-powered turbine to a pressure of 15 PSIG of at a temperature of 400° F. This pressurized mixture passes through the turbocharger intercooler, which reduces the pressurized, high temperature mixture to about 165° F. to be introduced into the intake manifold and then to the engine cylinders.  
         [0080]    Following combustion, exhaust gas from the cylinders (1100° F.) passes through the coolant-cooled manifolds (FIG. 1) to recover heat, which reduces the exhaust gas tempeture to about 940° F. The exit exhaust gas enters the exhaust (turbine section) of the turbocharger and, upon exiting, passes through a “T” with about 80% of the gas being flowed through a catalyst and a heat recovery silencer or muffler as previously described, and exhausted to atmosphere. A second portion comprising about 20% of the exhaust gas is passed through air coolers, as previously described, to the EGR venturi for introduction to the air/fuel intake system. The recycled exhaust gas is cooled by the air coolers to about 110° F. prior to admixing with air in the EGR venturi.  
         [0081]    Cooling System  
         [0082]    Turning to FIG. 5, in an engine coolant system  411 , an engine block  412  contains fluid cooling ports, through which cooling fluid travels by means of internal fluid pump  414  located upstream of oil heat exchanger  416 , which is ideally housed within the engine. As shown, oil heat exchanger  416  is in fluid communication with the inlet port of engine block  412  by means of conduit  418  and with inlet of fluid cooled manifold  420  by means of conduit  422 . Preferably, oil heat exchanger  416  is contained within engine block  412  and is an integral part thereof. The outlet of engine block  412  communicates with the inlet of thermal control valve  424  by means of conduit  426 .  
         [0083]    The outlet of fluid cooled manifold  420  communicates with the manifold inlet of fluid cooled turbocharger  428  by means of conduit  430 . The outlet of fluid cooled turbocharger  428  communicates with a second inlet of thermal control valve  424  through conduit  432 . In a bypass circuit for engine warm up, the outlet of thermal control valve  424  communicates through internal fluid pump  414  with oil heat exchanger  416  through conduit  434 . Alternately, during operation thermal control valve  424  communicates through internal fluid pump  414  with oil heat exchanger  416  by way of fluid process/heat exchanger  436  via conduit  438  and dump/balance radiator  440  via conduit  442  and then a T connect of conduit  444  with conduit  434 .  
         [0084]    This fluid loop comprises the coolant system  411  of the present invention. In operation, internal fluid pump  414  is driven by engine block  412  to flow coolant at a tempeture of about 175° F. and a flow rate of about 106 GPM through oil heat exchanger  416  and simultaneously through conduit  418  to the inlet of engine block  412  at a tempeture of about 182° F. and a flow rate of about 91 GPM and conduit  422  at a tempeture of about 182° F. and a flow rate of about 26 GPM to inlet of fluid cooled manifolds  420 .  
         [0085]    As shown in FIG. 5, there are two fluid cooled manifolds. The first, fluid cooled manifold  420  and the second fluid cooled turbocharger  428 . It will be realized that one or more liquid cooled manifolds for removing heat from the engine exhaust can be utilized. The function of these manifolds is to cool exhaust and generate heat to the cooling fluid, which will be transferred to the cogeneration client as described below.  
         [0086]    Coolant, exiting from exhaust-manifolds at a tempeture of about 210° F. and a flow rate of about 26 GPM, flows to thermal control valve  424 , which functions to limit fluid circulation back to inlet of the engine block  412  until operating temperature of the system is attained, and thereafter through conduit  438  to fluid process/heat exchanger  436 . Coolant exiting from engine block  412  at a tempeture of about 198° F. and a flow rate of about 91 GPM, flows to thermal control valve  424  where is merges with the coolant from fluid cooled manifold  420 . Dump/balance radiator  440  serves as a cooling radiator for the system to balance coolant inlet temperature to the oil heat exchanger  416  if fluid process/heat exchanger  436  removes insufficient heat or is turned off.  
         [0087]    As shown in FIG. 5, fluid process/heat exchanger  436  is a radiator which allows heat transfer from coolant system  411  to cogeneration process/utility heat system  413 . Cogeneration process/utility system comprises a closed loop to circulate fluid, which is heated in fluid process/heat exchanger  436 , by means of pump  446 . Fluid process/heat exchanger  436  communicates with primary facility load  448  and secondary facility load  450  by means of conduit  452  and return conduit  454 .  
         [0088]    In operation, fluid process/heat exchanger  436  which contains coolant fluid at a tempeture of about 206° F. at a flow rate of about 106 GPM, provides heat exchange between coolant system  411  and cogeneration process/utility heat system  413 , which provides heated liquid to the client in a cogeneration configuration. Thus, the cogeneration client receives transferred heat from the coolant system  411  by way of fluid process/heat exchanger  436  to the cogeneration process/utility heat system  413 . The coolant in coolant system  411  is then heat balanced, if necessary, in the dump/balance radiator  440  to return through internal fluid pump  414  to oil heat exchanger  416  to loop at a tempeture of about 175° F. at a flow rate of about 106 GPM.  
         [0089]    Thus, for example heat in coolant flow, through the coolant/process heat exchanger, is captured for the cogeneration client use by counter flowing process/utility water flowing through the coolant/process heat exchanger. Thermal regulating valves can be used to regulate process/utility water temperature to insure appropriate water temperature delivery to the cogeneration use.  
         [0090]    In accordance with one aspect of the invention, as shown in FIG. 1 an exhaust heat recovery silencer  456 , further cools the exhaust from the engine block  412  through three-way catalyst  52  and communicates through client absorption chiller  458  (FIG. 5) by means of conduit  460  and return conduit  462 , as will be further described below. In operation, internal fluid pump  414  is driven by engine block  412  to flow coolant at a tempeture of about 175° F. and a flow rate of about 106 GPM through oil heat exchanger  416  and simultaneously through conduit  18  to the inlet of engine block  412  at a tempeture of about 182° F. and a flow rate of about 91 GPM and conduit  422  at a tempeture of about 182° F. and a flow rate of about 426 GPM to inlet of fluid cooled manifold  420 .  
         [0091]    Returning to FIG. 1, fluid process/heat exchanger  436  is a radiator, which allows heat transfer from coolant system  411  to cogeneration process/utility heat system  413 . Cogeneration process/utility system comprises a closed loop to circulate fluid, which is heated in fluid process/heat exchanger  436 , by means of pump  446 . Fluid process/heat exchanger  436  communicates with primary facility load  448  and secondary facility load  450  by means of conduit  452  and return conduit  454 .  
         [0092]    Thus, for example heat in coolant flow, through the coolant/process heat exchanger, is captured for the cogeneration client use by counter flowing process/utility water flowing through the coolant/process heat exchanger. Thermal regulating valves can be used to regulate process/utility water temperature to insure appropriate water temperature delivery to the cogeneration use.  
         [0093]    The foregoing discussions, and examples, describe only specific embodiments of the present invention. It should be understood that a number of changes might be made, without departing from its essence. In this regard, it is intended that such changes—to the extent that they achieve substantially the same result, in substantially the same way would still fall within the scope and spirit of the present invention.