Abstract:
A natural gas fuel regulator for a natural gas fueled internal combustion engine for driving a co-generation plant, which allows exhaust recycled gas combustion while maintaining lower head temperatures to reduce thermal NO x  emissions. The gas regulator has a modulation chamber, which modulates incremental pressure changes from the carburetion system to allow the engine to respond to load changes without the necessity for dynamic control feed back valve. In one aspect, a non-diaphragm venturi fuel/air-mixing unit with post turbo charger throttle adjustment is downstream of the natural gas fuel regulator to provide lean burn, low thermal NO x  operation of the co-generation unit from no load to full load electrical generation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to fuel regulators for engines in co-generation units; and, more particularly, natural gas regulators for internal combustion engine driven co-generation units. 
     2. Description of Related Art 
     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. 
     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. 
     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. 
     As a result, the Federal Government deregulated power generation, and a number of states have begun to establish competitive retail energy markets. Unfortunately, the deregulation process has not provided adequate incentives for industry entities to construct generating facilities, upgrade the transmission grid, or provide consumers with price signals to enable intelligent demand-side management of energy consumption. With the deregulation in the utility market, energy (kWh) has become a commodity item that can be bought or sold. However, swings in supply and demand leave end users open to fluctuations in the cost of electricity. 
     According to the ETA, to meet projected increases in demand over the next 20 years, at least 393 GW of additional generating capacity must be added. In some areas, the growth in demand is much higher than the projected two percent average (e.g., California&#39;s peak electricity demand grew by 18 percent between 1993 and 1999, while generating capacity increased by only 0.3 percent.) Despite California&#39;s highly publicized energy situation, a similar problem exits for other states as well; the New York Independent System Operator recently stated that 8600 MW of additional generating capacity (a 25 percent increase) must be added by 2005 to avoid widespread shortages that may lead to blackouts. 
     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. 
     Further, security and reliability of source has become of increasing concern. Grid system vulnerability and blackouts have become more commonplace. 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. 
     The need to leverage existing technology while transitioning to alternative energy sources is an important consideration for meeting this challenge. 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. 
     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. 
     Waste heat utilization or co-generation is one way to meet this challenge. In the case of 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. co-generation, or “Combined Heating and Power” (CHP). 
     Co-generation of electricity and client service heat to provide 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 generating process. With cogeneration, two problems are solved for the price of one. In either case, the electricity generation must meet stringent local air quality standards, which are typically much tougher than EPA (nation wide) standards. 
     On-site co-generation 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. 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. 
     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. 
     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. 
     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 reticulation (EGR), positive crankcase ventilation (PCV), and/or unique three-way catalyst. 
     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. 
     It is well known that emission reduction for natural gas engines can be accomplished by recycling of exhaust gases 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. 
     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 provided for recycling the exhaust, and have also been complicated by the desirability of reducing the recycling during conditions of both engine idling when nitrogen oxide emission is a minor problem and wide open throttle when maximum power is required, while progressively increasing the recycling of exhaust gases with increasing engine load. 
     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. 
     Thus, prior art co-generation 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 co-generation 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. 
     Some of the inherent problems with natural gas fueled engines, which utilize exhaust gas recycle 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. 
     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 for combustion. The diaphragm regulates fuel flow by responding to the changes in vacuum pulled by the engine. 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. 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. In some configurations an exhaust gas driven turbocharger is used to pre-compresses the mixture prior to injection into the cylinder. The use of a turbocharger increases the vacuum on the carburetion unit. 
     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. 
     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. 
     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 chamber surrounding the venturi by vacuum. If the fuel is under a positive pressure, the chamber floods prior to ignition, which prevents ignition of the engine. Thus, 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, these vacuum operated devises work reasonably well because, like a burner, the requirement for fuel is full on or full off. 
     However, when engines such as turbocharged natural gas fueled internal combustion engines are employed, regulators must respond to a myriad of incremental changes in RPM of the engine to fulfill electrical generation load requirements of the electrical system. Because this requires carburetion of the fuel over a fairly broad range of intake settings, some gas regulation devises have employed dynamic feed back control gas regulator devises that work upon incremental movement of an electrically actuated valve. Such devises, while effective, require complicated control circuitry, as well as transducers, to modulate current-flow to the electric valve. Unless these valves are substantially analog, the carburetion of the engine is not smooth, leading to inefficiencies, especially with co-generation units. When exhaust gas recycle is employed in the intake gas to reduce thermal NO x , the regulation of the natural gas fuel stream becomes even more critical. This is especially true with so called “lean burn” operations. 
     Therefore, it would be advantageous to have a simple fuel regulator device, which operates solely on engine intake gas manifold pressure, including pressures upstream of a turbocharger, to incrementally regulate fuel flow to the carburetion unit throughout the operating range of the engine. In this manner, no external circuitry would be required to regulate the gas flow of the device, yet, the response could be sensitive enough to maintain the turbocharged fuel/air/recycled exhaust gas to the engine over a range from idle to full throttle, with little deviation of proportion of the mixture. In this manner “lean burn” engines could operate in this configuration substantially through the entire operating range of the engine. It would be further advantageous to employ the metering accuracy of a spring-tensioned diaphragm without the deterioration or the large inlet port to diaphragm size ratio. 
     SUMMARY OF THE INVENTION 
     A natural gas regulator for a natural gas fueled internal combustion engine co-generation plant, which allows efficient, “lean burn” operation of the engine from no load to full load generation without the requirement of adjusting fuel restricting valves has now been discovered. The gas regulator of the instant invention employs a pressure modulation chamber, which dampens incremental pressure changes from the engine carburetion system and allows a fuel flow-regulating valve to respond uniformly throughout the acceleration range of the engine. In one aspect, a non-diaphragm venturi fuel/exhaust gas/air-mixing unit, with post turbocharger throttle adjustment, is downstream of the natural gas fuel intake regulator to provide lean bum operation of the co-generation unit, through exhaust gas recycle to maintain lower head temperatures thereby reducing thermal NO x  emissions. 
     In one embodiment, the pressurized inlet natural gas source passes through a small micron fuel gas filter into a housing with an electric solenoid to maintain a fuel shut-off valve in an open position. Two metering valves, one with diaphragm for sensing small vacuum changes delivered to the chamber by load variations of the engine to induce a second manual trim valve set to a single position to moderate fuel flow to the air/exhaust gas/fuel venturi. A pressure modulating chamber mounted between the diaphragm chamber and a manual trim valve chamber provides pressure modulation of the pressure generated by the engine carburetion system to stabilize engine performance throughout the performance range of the engine and particularly to variation in load. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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. 
     FIG. 1 is a perspective view of the fuel regulator of the instant invention; 
     FIG. 2 is a an exploded view of the flow chart of the engine cooling loop of the fuel regulator of the instant invention; 
     FIG. 3 is a cut away along lines  3 — 3  of FIG. 1.; 
     FIG. 4 is a cut away of the fuel regulating chamber in accordance with the instant invention with the solenoid deactivated; and, 
     FIG. 5 is a flow chart detail of an example integration of the fuel regulator of the instant invention with a turbocharger intercooler radiator loop interface, the engine intake gas system and the engine exhaust system including the exhaust recycle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A fuel regulator for natural gas fired co-generation unit regulates natural gas, under pressure, from a remote fuel source, such as a tank, to an engine carburetor where the fuel is mixed with air for intake into the cylinders of an internal combustion engine. 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 recycle exhaust gas, the exhaust gas is mixed with combustion air upstream of the carburetor, then admixed with fuel by, for example, fuel aspiration. The turbocharger places an extra vacuum load on the engine side of the carburetor. 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. 
     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. 
     Placed between the first gas metering chamber and the second gas flow-restricting chamber is a modulating chamber in gas communication with both the gas metering chamber and the second preset gas flow-restricting chamber. As will be further described below, the modulating chamber acts to modulate the pressure of intake gas and the vacuum pressure from the carburetor to provide a smooth transition from intake to outlet of the gas, as it is metered by the preset gas-metering chamber in response to engine demands as communicated to the regulator by varying vacuum pressure from the carburetor. 
     Advantageously, the metering chamber contains at least one spring-tensioned diaphragm, which opens under engine vacuum to operate a fuel-metering valve allowing fuel to enter a gas-metering chamber. The metering chamber contains a pressure balance line to ambient pressure, which allows the substantially instantaneous deformation of the diaphragm in response to incremental changes in pressure within the chamber. Changes in engine vacuum increasing or decreasing from engine load changes impart very small vacuum changes that cause the metering chamber diaphragm to open and close the fuel inlet valve to allow appropriate fuel flow through the regulator to pass to the carburetor through the preset gas regulating chamber. 
     There is shown in FIG. 1 an illustrative view of the fuel regulator device  10  in accordance with the instant invention. The fuel regulator device  10  comprises an inlet-coupling element  12  and outlet-coupling element  14  as better seen in FIG.  2 . Inlet-coupling element  12  has a threaded nipple  13  adopted to receive a 1.5″ fuel line, which nominally operates at from about 1.5 to 2.0 PSIG. Fuel from a pressurized source (not shown) communicates with the inlet-coupling element  12 . A micron mesh fuel filter  16  connects inlet-coupling element  12  to gas metering/shutoff component  18 . The filter prevents entrained contaminants from entering the system through the fuel source. Gas metering/shut off component  18  carries a solenoid housing  20 , which contains a standard electrically operated solenoid (not shown.) Solenoid housing  20  is held in place on gas metering/shut off component  18  by retaining nut  22 . By means of electrical connection  24 , a standard electrical solenoid operates a solenoid actuation rod  36  as seen in FIGS. 3 and 4. 
     The solenoid is a “dead-man” shutdown switch. As better seen in FIG. 4, when the solenoid is de-energized, the fuel regulating valve  40  is closed, and gas is precluded from flowing through the regulator, as will be further explained with respect to FIG. 3. A modulating element  26  contains a pressure-modulating chamber  66  and sealably abuts gas metering/shut off component  18  and the manual fuel trim valve assembly housing  28 . Valve adjustment setting screw  30 , which threadably engages threaded sleeve  32  on the exterior of manual fuel trim valve assembly housing  28  is manually set to “tune” the engine by means of a fuel-regulating valve  72  as will be further described below. Outlet-coupling element  14  sealably abuts manual fuel trim valve assembly housing  28  and carries threaded nipple  82  for connection to carburetor fuel line as is better seen in FIG.  5 . 
     As better seen in FIG. 2, which is a side looking exploded view of FIG. 1, where like elements contain like numbers, there is shown the individual elements of fuel regulator device  10  as assembled. Micron mesh fuel filter  16  is advantageously used to provide clean fuel to the system but is not required. As seen in FIG. 2, each component is bolted together, thus providing ease of exchange components, as well as cleaning and maintenance. 
     Turning to FIG. 3, there is shown a cutaway of FIG. 1 along line  3 — 3 . FIG. 3 shows the internal workings of the fuel regulator device  10  when the solenoid is activated. FIG. 3 does not show the optional micron mesh fuel filter  16 . Inlet-coupling element  12  carries threaded nipple  13  and communicates with gas metering/shutoff component  18 , as shown. Gas metering/shutoff component  18  has mounted thereon a solenoid housing  20 , which contains a solenoid (not shown) to actuate solenoid actuation rod  36 , and a diaphragm housing  34 , containing the gas regulating membranes as will be further described. 
     Solenoid actuation rod  36 , the end of which contacts metal contact plate  38 , which in turn is seated upon fuel regulating valve  40 . Fuel regulating valve  40  sealably engages valve seat  42 , when the solenoid housing  20  is de-energized, as shown in FIG.  4 . In this configuration, all gas flow is shut-off through fuel regulator device  10 . Within gas metering/shutoff component  18  is a solid partition  44 , which divides gas metering/shutoff component  18  into an upper gas receiving chamber  84  and a lower gas receiving chamber  86  and contains valve seat  42  therein, such that when fuel regulating valve  40  is fully seated in valve seat  42 , gas flow is shut off. In operation, with the solenoid energized, as shown in FIG. 3, the solenoid actuation rod  36  is retracted allowing fuel regulating valve  40  to open and close by means of valve stem  46 . 
     Valve stem  46  communicates with, and is advantageously attached to the bottom portion of, fuel regulating valve  40  on one end and upper diaphragm  48  on the other. The upper diaphragm assembly includes upper diaphragm  48 , which is sealably housed in diaphragm housing  34  and an upper diaphragm seating spring  50 , which engages the underside of upper diaphragm  48  and rests on platform  52 . Platform  52  is sealably supported by the sidewalls of diaphragm housing  34 . The underside of upper diaphragm  48  and platform  52  in cooperation with the sidewalls of diaphragm housing  34  forms an upper diaphragm chamber  56 . 
     A lower diaphragm assembly resides in the diaphragm housing  34 , beneath the upper diaphragm assembly. The lower diaphragm assembly, includes lower diaphragm  60 , which is sealably housed in diaphragm housing  34 , and a lower diaphragm seating spring  62 , which engages the underside of lower diaphragm  60  and rests on the bottom closure of diaphragm housing  34  to form a sealed unit. The upper side of lower diaphragm  60  and the lower side of platform  52  in cooperation with the sidewalls of diaphragm housing  34  form a first lower diaphragm chamber  58 . The underside of lower diaphragm  60  and the bottom closure of diaphragm housing  34  in cooperation with the sidewalls of diaphragm housing  34  form a second lower diaphragm chamber  67 . 
     Platform  52  has a pressure equalization port  54 , which communicates between the upper diaphragm chamber  56  and first lower diaphragm chamber  58 . A pressure equalization tube  64  communicates with second lower diaphragm chamber  67  and ambient. These two devices equalize the pressure between the chambers as the diaphragms deform in operation. 
     Modulating element  26  sealably attaches to gas metering/shutoff component  18  such that pressure-modulating chamber  66  communicates with lower gas receiving chamber, interior of gas metering/shutoff component  18  and modulating element  26  sealably attaches to manual fuel trim valve assembly housing  28  such that pressure-modulating chamber  66  communicates with the upper gas receiving chamber  76  interior of manual fuel trim valve assembly housing  28 . 
     Manual fuel trim valve assembly housing  28  contains a valve steam  68 , which is capped by valve adjustment settings screw  30  and threadably engages treaded sleeve  32 . The lower end of valve steam  68  is attached to metal valve plate  70  seated on fuel regulating valve  72 . Within manual fuel trim valve assembly housing  28  is a solid separating membrane  74 , which divides the manual fuel trim valve assembly housing  28  into an upper gas receiving chamber  76  and a lower gas exiting chamber  78  and contains valve seat  80  therein, such that when fuel regulating valve  72  is fully seated in valve seat  42 , gas flow is shut off. Outlet-coupling element  14  carries threaded nipple  82  for connection to a carburetor fuel line  92  as seen in FIG.  5 . 
     In operation, the solenoid, which is de-energized so that solenoid actuation rod  36  is in the fully extended position, closes fuel-regulating valve  40 , as shown in FIG.  4 . Upon ignition of the engine, the solenoid is energized and solenoid actuation rod  36  is fully retracted, allowing modulated opening and closing of fuel regulating valve  40  in response to movement of upper diaphragm  48 . Fuel entering, under pressure, through inlet-coupling element  12 , passes into upper gas receiving chamber  84  of gas metering/shutoff component  18 , through valve seat  42  into lower gas receiving chamber  86 , through pressure-modulating chamber  66 , into upper gas receiving chamber  76  in manual fuel trim valve assembly housing  28 , through valve seat  72 , into lower gas exiting chamber  78  and exits outlet-coupling element  14  to fuel line  92 . The valve seat  72  is manually set by means of threadably adjusting valve adjustment settings screw  30  to regulate the maximum gas flow rate through the manual fuel trim valve assembly housing  28 . 
     To better understand the invention in operation, FIG. 5 shows the interfaces between the turbo intercooler cooling circuit, the turbocharger, the engine intake manifold, and the recycled exhaust gas system. This interaction is important in that head temperatures, gas inlet temperatures, and exhaust gas recycle temperatures can be tuned. Ambient outside air passes through air filter  96  and intake conduit  98  to EGR venturi  104 , where air is mixed with recycled exhaust gas from conduit  180 , as will be more fully described. Mixed air and exhaust gas exits EGR venturi  104  through intake conduit  106  into fuel/air venturi  108  where the air/exhaust gas mixture entrains fuel from fuel regulator device  10 . Fuel regulator device  10  is connected to a fuel source (not shown) by means of conduit  90 . Fuel regulator device  10  communicates with fuel/air venturi  108  by means of fuel line  92 . The fuel/air/exhaust gas mixture exits fuel/air venturi  108  via turbocharger intake conduit  112  and is compressed in turbocharger  114 . The turbocharger, which is operated by engine exhaust, creates a vacuum on turbocharger intake conduit  112  which is translated back through the system to operate the fuel regulator as will be further described. 
     The compressed fuel/air/recycled exhaust gas mixture exits turbocharger  114  through turbo intercooler intake conduit  116  into turbo intercooler  110  where it is cooled from 400° F. to 165° F. Intercooler radiator  100 , pump  102 , and coolant circulating conduit  94  continually circulate coolant, in a closed loop, through turbo intercooler  110  to cool the compressed fuel/air/recycled exhaust gas mixture. The cooled intake gas exits turbo intercooler  110  into engine intake manifold  118  via engine intake conduit  122  and through intake manifold  118  into engine cylinders  120 . 
     Exhaust gas from engine cylinders  120  exits into fluid cooled manifold  124  and enters turbocharger  114  through exhaust conduit  126  to power the turbocharger  114 , thus compressing the fuel/air/recycled exhaust gas mixture entering turbocharger  114  by means of turbo intercooler intake conduit  116 , as previously described. As can be seen, exhaust gas exiting turbocharger  114  is split into a recycled stream and an exhaust stream. The exhaust stream  128  enters three-way catalyst  130  and then exhaust heat recovery silencer  132 . It will be realized by one skilled in the art that the exhaust heat recovery silencer  132  is on the co-generation process/utility heat system and provides additional heat recovery for that system. A portion of the exhaust gas to be recycled passes through conduit  134  to primary air cooled EGR cooler  136 ; and, if necessary, secondary air cooled EGR cooler  138  by means of conduit  134  and then passes into EGR venturi  104  through conduit  180 . 
     The pressurization of the air/exhaust gas/fuel mixture by turbocharger  114  creates a vacuum upstream, as previously described. As fuel is pulled through fuel/air venturi  108 , it creates a vacuum, which is transferred through fuel line  92  to fuel regulator device  10 . The vacuum reduces pressure in lower gas exiting chamber  78  and upper gas receiving chamber  76  through pressure-modulating chamber  66  and in lower gas receiving chamber  86 . The reduced pressure in lower gas receiving chamber  86  causes upper diaphragm  48  to deform, as shown in FIG. 3, moving valve stem  46  upwardly to open fuel regulating valve  40 , as shown. Likewise, the reduction in pressure of upper diaphragm chamber  56  causes a corresponding reduced pressure to equalize through pressure equalization port  54  to create a vacuum in lower diaphragm chamber  58  causing lower diaphragm  60  to deform. Pressure equalization tube  64  allows equalization pressure into second lower diaphragm chamber  67  below lower diaphragm  60 . Thus, as the vacuum pressure pulled on the fuel in fuel supply conduit  90  fluctuate upper diaphragm seating spring  50  and lower diaphragm seating spring  62  cooperate to attempt to reduce the deformity of upper diaphragm  48  and lower diaphragm  60 , respectively, re-seating fuel regulating valve  40  in valve seat  42 . 
     Advantageously, two diaphragms are used as shown in FIG.  3 . This arrangement prevents a harmonic or “fluttering” of the first diaphragm as a vacuum serge is experiences 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. 
     Thus, in accordance with the invention, fuel under pressure is introduced into the upper gas-receiving chamber  84 . Fuel regulating valve  40  is modulated by movement of upper diaphragm  48  in response to vacuum applied to the system by varied throttling of the engine. The fuel-regulating valve  72  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. 
     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″ are 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. 
     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. 
     Following combustion, exhaust gas from the cylinders (1100° F.) passes through the coolant-cooled manifolds (not shown) to recover heat, which reduces the exhaust gas tempeture to about 940° F. The exit exhaust gas enters the exhaust (turbine driving 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. 
     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.