Patent Publication Number: US-2023148398-A1

Title: Mass-flow throttle for large natural gas engines

Description:
CLAIM OF PRIORITY TO PRIOR APPLICATION 
     This application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 62/636,382, filed on Feb. 28, 2018, entitled “Mass-Flow Throttle for Large Natural Gas Engines,” the entire disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention primarily relates to a throttle for large natural gas engines. Particularly, it pertains to a throttle for controlling the mass flow rate to the combustion chambers for large gaseous fuel spark-ignited internal combustion engines, particularly for stationary industrial applications, and more particularly while operating in low pressure non-choked flow. 
     BACKGROUND 
     Throttle valves have long been used in large natural gas engines, but existing control strategies tend to be lacking. More accurate flow control is needed in order to obtain optimally efficient fuel combustion based on the demands of an Engine Control Module (ECM). Precisely controlled mass flowrates are difficult to achieve, especially with non-choked flow. Electronic throttles are commonly used in large engines to control the mass flow rates of fuel and air. ECM advancements have vastly improved the ability to optimize efficiency and performance and minimize emission concerns with spark-ignited internal combustion engines. By continuously monitoring numerous sensors and inputs, ECM&#39;s can balance the current operator commands against performance conditions to determine the most ideal supply flowrates needed for the engine at any given instant. 
     Knowing the ideal flowrate and delivering it, however, are two very different things. Even though modern ECMs can know the ideal at any given instant, practical prior art fuel supplies are not able to consistently deliver it instantaneously on demand across their entire range of operation. The very best of available controls claim to provide 1% setpoint accuracy, which means they claim to deliver an actual supply flowrate within about 1% of the demanded flowrate. The ability to consistently deliver a gaseous supply flowrate with 1% setpoint accuracy is considered extremely accurate and would be ideal, but claims to that effect tend to only be part of the story. 
     With the prior art, extreme setpoint accuracies tend to only be attained within a limited range of operation, which means that claimed accuracies are generally unreliable, especially for engines having large dynamic power ranges. (An engine&#39;s “dynamic power range” is the ratio of maximum power to minimum power over which the engine will operate as specified, which is dependent largely on the effective turndown ratio of the associated fuel supply system.) For a fuel supply delivering 25 grams/second at the top end of its operating range, for instance, one percent would be a quarter-gram/second (0.25 g/s). While calibrating one of the best available valves to a quarter-gram/second error can be manageable for moderate flowrates, the same fuel supply often needs to also idle at about a quarter-gram/second at the opposite end of its operating range, such that the same quarter-gram/second error would be tremendously inaccurate for near-idle flowrates. Although accurate control is sometimes considered easier to achieve with lower flowrates, 1% setpoint accuracy at a quarter-gram/second idle flowrate would require accuracy to within ±0.0025 g/s. So, while prior art gas flow throttles claim to deliver extremely accurate flowrates at specified portions of their overall operating range, it has long been unattainable to achieve as much for both ends of the operating range and everything in between, especially for such large ranges in real-world operation. 
     The complex interaction of too many real-world variables frustrates the pursuit of consistently high, full-range setpoint accuracies for gaseous supply mass flowrates. Wear and tear, leaks, lag times, glitches, clogs, noise, artifacts, and general variability all tend to happen in the real world. External temperatures and wide variability in gaseous fuel and air compositions further compound the challenges. 
     Moreover, even if perfection was achievable within a gaseous supply&#39;s flowrate control itself, flowrate accuracies can be thwarted by upstream and downstream pressure fluctuations as well, especially when the flow through the throttle is not choked. Because gaseous fluids are compressible, downstream events related to combustion or valve and piston movements can cause pressure waves that create sizable flowrate fluctuations. Upstream pressure fluctuations can be equally problematic, especially when controlling the flowrate of vaporized liquid fuels (e.g., LNG or LPG) or of boosted or turbocharged systems. 
     Thus, there has long been a need for a throttle that can accurately and consistently deliver ECM-demanded mass flow rates in the field of gaseous supply systems for large spark-ignited engines, even while controlling non-choked flows, which are common with low-pressure supply flows but which also occur in many high pressure scenarios as well. For more background in light of choked mass flow control, refer to U.S. Pat. No. 9,957,920, a copy of which is incorporated herein by reference in its entirety. 
     SUMMARY OF THE INVENTION 
     It will become evident to those skilled in the art that thoughtful use of the invention and embodiments disclosed herein will resolve the above-referenced and many other unmet difficulties, problems, obstacles, limitations, and challenges, particularly when contemplated in light of the further descriptions below considered in the context of a comprehensive understanding of the prior art. 
     The present invention accomplishes as much by enabling fast-acting, highly accurate gaseous supply flowrate control for large spark-ignited internal combustion engines, which is particularly beneficial for engines that use natural gas as a fuel source. The gaseous fuel is preferably derived from either a liquefied natural gas (LNG) or compressed natural gas (CNG) storage state. A large engine is defined here as any engine that is 30 liters or greater. The engine is preferably used in stationary applications such as generator sets (hereinafter “gensets”). Alternatively, the engine may be used in large mobile applications such as mining trucks, ships, trains or other heavy-duty vehicles. Although preferred embodiments typically operate to control non-choked flow, often in low pressure applications, they nonetheless achieve highly accurate mass flow control. Our objectives include enabling such flow control in response to instantaneous demand signals from the engine&#39;s ECM while consistently maintaining extreme accuracy over large dynamic power ranges, despite most upstream, downstream and even midstream pressure fluctuations. 
     Possible embodiments can manifest in numerous different combinations and in numerous different kinds of improved machines, internal combustion engines, gaseous supply control systems, and the like. Other possible embodiments are manifest in methods for operating and optimizing such machines, engines, systems and the like, as well as in other types of methods. All of the various multifaceted aspects of the invention and all of the various combinations, substitutions and modifications of those aspects might each individually be contemplated as an invention if considered in the right light. 
     The resulting combinations of the present invention are not only more versatile and reliable, but they are also able to achieve greater accuracy despite rapidly changing conditions over a larger dynamic power range than has ever been achieved with such a simple system. The various embodiments improve on the related art, including by optimizing reliability, manufacturability, cost, efficiency, ease of use, ease of repair, ease of adaptability, and the like. Although the embodiments referenced below do not provide anything remotely near an exhaustive list, this specification describes select embodiments that are thought to achieve many of the basic elements of the invention. 
     In accord with many of the teachings of the present invention, a throttle is provided in a form that is readily adaptable to the power demands of numerous applications and is readily capable of achieving highly accurate setpoint accuracy for controlling gaseous supply flowrates across very large dynamic power ranges in internal combustion engines. Such flowrate control throttles and related fuel systems materially depart from the conventional concepts and designs of the prior art, and in so doing provide many advantages and novel features which are not anticipated, rendered obvious, suggested, or even implied by any of the prior art, either alone or in any obvious combination thereof. 
     Through its innovative combination of features and elements, a throttle according to the teachings of the invention is able to consistently and reliably achieve highly accurate mass flow control for various large engine applications, even with non-choked flow. Some of the features and elements that enable that result include the use a unitary block assembly for the throttle, and a fast-acting actuator, plus a single unitary and rigid rotary shaft for driving a throttle blade, supported by three different bearing assemblies along the length of the shaft, as well as a commonly-contained assembly of the control circuitry together with the rotary actuator as well as the throttle itself, all of which help minimize slop in the control. In addition, the invention is preferably embodied with multiple pressure sensors that are at least partially redundant, which enables the controller to self-check the various sensors in real time. 
     To be all encompassing, many other aspects, objects, features and advantages of the present invention will be evident to those of skill in the art from a thoughtful and comprehensive review of the following descriptions and accompanying drawings in light of the prior art, all to the extent patentable. It is therefore intended that such aspects, objects, features, and advantages are also within the scope and spirit of the present invention. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various expansions, changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     Indeed, the present invention will ultimately be defined relative to one or more patent claims or groups of claims that may be appended to this specification or to specifications that claim priority to this specification, as those claims may be amended, divided, refined, revamped, replaced, supplemented or the like over time. Even though the corresponding scope of the invention depends on those claims, these descriptions will occasionally make references to the “invention” or the “present invention” as a matter of convenience, as though that particular scope is already fully understood at the time of this writing. Indeed, multiple independent and distinct inventions may properly be claimed based on this specification, such that reference to the “invention” is a floating reference to whatever is defined by the ultimate form of the corresponding patent claims. Accordingly, to the extent these descriptions refer to aspects of the invention that are not separately required by the ultimate patent claims, such references should not be viewed as limiting or as describing that variation of the invention. 
     The invention, accordingly, is not limited in its application to the details of construction and to the arrangements of the components set forth in the following descriptions or illustrated in the drawings. Instead, the drawings are illustrative only, and changes may be made in any specifics illustrated or described, especially any referenced as “preferred.” Such changes can be implemented while still being within the spirit of the invention. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting. Other terminology and language that describes the invention and embodiments and their function will be considered as within the spirit of the invention. 
     The invention is capable of many other embodiments and of being practiced and carried out in numerous other ways. It should also be understood that many other alternative embodiments are not shown or referenced that would still be encompassed within the spirit of the invention, which will be limited only by the scope of claims that may be original, added, or amended in this or any other patent application that may in the future claim priority to this application. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       Various features and advantages of the invention will now be described with reference to the drawings of certain preferred and alternative embodiments, which are intended to illustrate and not to limit the invention, where reference numbers may refer to like elements. 
         FIG.  1 A  and  FIG.  1 B  are perspective views of the preferred mass flow throttle  10 . 
         FIG.  2 A  is a front view of the preferred large engine throttle  10 . 
         FIG.  2 B  is a sectional view of the preferred large engine throttle  10  of  FIG.  2 A , centrally sectioned through sectional plane B-B of  FIG.  2 A . 
         FIG.  3    is an exploded perspective view of the preferred large engine throttle  10 . 
         FIG.  3 A  is an exploded perspective view of large engine throttle  10 ′, which is an alternative embodiment of the throttle  10  of  FIG.  3   . 
         FIG.  4    is a perspective view of the throttle body assembly  20 . 
         FIG.  5    is an exploded perspective view of spring assembly  50 . 
         FIG.  5 A  is an exploded perspective view of spring assembly  50 ′ of the alternative embodiment of large engine throttle  10 ′ of  FIG.  3 A . 
         FIG.  6    is an exploded perspective view of thermistor assembly  60 . 
         FIG.  7    is an exploded perspective view of motor and throttle shaft assembly  70 . 
         FIG.  8    is an exploded perspective view of intermediate housing assembly  80 . 
         FIG.  9    is an exploded perspective view of PCB assembly  90 . 
         FIG.  10    is a block diagram illustrating a preferred embodiment of a gaseous fuel supply system with a large engine MFG throttle  20 , operatively integrated with an internal combustion engine  102  to provide highly accurate control of the gaseous fuel supply to that engine  102  in accordance with various teachings of the present invention. 
     
    
    
     DETAILED DESCRIPTIONS OF ILLUSTRATED EMBODIMENTS 
     The following examples are described to illustrate preferred embodiments for carrying out the invention in practice, as well as certain preferred alternative embodiments to the extent they seem particularly illuminating at the time of this writing. In the course of understanding these various descriptions of preferred and alternative embodiments, those of skill in the art will be able to gain a greater understanding of not only the invention but also some of the various ways to make and use the invention and embodiments thereof. 
     Wording Conventions 
     For purposes of these descriptions, a few wording simplifications should be understood as universal, except to the extent otherwise clarified in a particular context either in the specification or in any claims. For purposes of understanding descriptions that may be basic to the invention, the use of the term “or” should be presumed to mean “and/or” unless explicitly indicated to refer to alternatives only, or unless the alternatives are inherently mutually exclusive. When referencing values, the term “about” may be used to indicate an approximate value, generally one that includes a standard deviation of error for any particular embodiments that are disclosed or that are commonly used for determining or achieving such value. Reference to one element, often introduced with an article like “a” or “an”, may mean one or more, unless clearly indicated otherwise. Such “one or more” meanings are most especially intended when references are made in conjunction with open-ended words such as “having,” “comprising” or “including.” Likewise, “another” may mean at least a second or more. Other words or phrases may have defined meanings either here or in the accompanying background or summary descriptions, and those defined meanings should be presumed to apply unless the context suggests otherwise. 
     These descriptions occasionally point out and provide perspective as to various possible alternatives to reinforce that the invention is not constrained to any particular embodiments, although described alternatives are still just select examples and are not meant to represent an exhaustive identification of possible alternatives that may be known at the time of this writing. The descriptions may occasionally even rank the level of preference for certain alternatives as “most” or “more” preferred, or the like, although such ranked perspectives should be given little importance unless the invention as ultimately claimed irrefutably requires as much. Indeed, in the context of the overall invention, neither the preferred embodiments nor any of the referenced alternatives should be viewed as limiting unless our ultimate patent claims irrefutably require corresponding limits without any possibility for further equivalents, recognizing that many of the particular elements of those ultimate patent claims may not be required for infringement under the U.S. Doctrine of Equivalents or other comparable legal principles. Having said that, even though the invention should be presumed to cover all possible equivalents to the claimed subject matter, it should nonetheless also be recognized that one or more particular claims may not cover all described alternatives, as would be indicated either by express disclaimer during prosecution or by limits required in order to preserve validity of the particular claims in light of the prior art. 
     As of the date of writing, the structural and functional combinations characterized by these examples are thought to represent valid preferred modes of practicing the invention. However, in light of the present disclosure, those of skill in the art should be able to fill-in, correct or otherwise understand any gaps, misstatements or simplifications in these descriptions. 
     For descriptive reference, we categorize supply flowrate setpoint accuracy as being “generally accurate” if it is consistently within 5% of the demanded flowrate across its entire operating range. When consistently within 3% of the demanded flowrate across the entire range, setpoint accuracy can be categorized as “highly accurate.” At the extreme, when setpoint accuracy is consistently within about 1% of the demanded flowrate across the entire operating range, it can be classified as “extremely accurate.” 
     It is also notable that, while many embodiments may be used for mass flow control of either air or fuel, or combinations of air and fuel, these descriptions will commonly refer to control of a “supply flow”, which should generally be understood to refer to control of any such supply flow, whether it be air, fuel, or a combination. It will be understood, nonetheless, that a throttle according to these descriptions that is intended strictly for controlling the fuel supply flow will be plumbed at a different location than one that is plumbed for just controlling air. Likewise, a throttle according to these descriptions that is deployed for controlling mass flow of air without fuel will be plumbed at a different location than one that is plumbed for controlling the mixture of fuel and air. We presently prefer to include one throttle for controlling just the gaseous fuel supply flow, to achieve highly accurate control of the mass flow of the fuel (sometimes referred to as mass-flow-gas, or “MFG”), together with another throttle further downstream for controlling the supply flow after air has been mixed with the supply flow of fuel (which is sometimes referred to as mass-flow-air, or “MFA”, irrespective of the inclusion of the fuel in the same flow). Nonetheless, complete and highly accurate mass flow control can also be achieved by combining an MFG throttle together with an MFA throttle that is plumbed in the air supply upstream of the fuel-air mixer. Moreover, generally accurate overall control might also be attainable by just controlling the mass flow of the fuel, without actively controlling the mass flow of the air if other reliable data is used to calculate that mass flow of the air, such as through use of oxygen sensors in combination with pressure, temperature and the like. Whatever the choice for a specific application, we trust that those of skill in the art will understand where and how to include such throttles for the different purposes to achieve the different combinations for overall mass flow control. 
     With respect to any valve, throttle or actuator, “fast-acting” is a term that is generally understood by those of skill in the art, and the term should be presumed to generally mean that it is designed to act or respond considerably faster or quicker than most throttles, valves or actuators. More limited definition may be applied to the phrase to the extent expressly disclaimed during prosecution or to the extent necessary for preserving validity of particular claims in light of the prior art. Despite the presumed broader meaning, fast-acting actuators referenced in these descriptions are preferably operable to move the actuated throttle element through most of its entire operable range of motion (preferably from 20% to 80% of that operable range), if not all of that operable range, in fifty milliseconds or less, although many other types of actuators are still likely to be suitable as alternatives, especially to the extent particular claim elements are not expressly disclaimed to require particular fast-acting characteristics. 
     The term “large engine throttle”  10  is used herein to describe the mass-flow throttle of numerous preferred embodiments and it refers to the throttle and throttle control system rather than merely the throttle body  20  or the butterfly valve (or throttle blade)  210  therein. Despite the “large engine” descriptor for throttle  10 , the reader should understand that various aspects of such large engine throttle may be beneficial for smaller engines as well, such that the reference to “large engine” should not be considered as limiting unless estoppel, validity in view of the prior art, or other legal principles clearly require an interpretation that is limited to large engines. The simpler term “throttle”  20  is used herein interchangeably with the term “throttle body assembly”  20 . With respect to fuels, the term “fluid” is used herein to mean either a liquid or a gas, although liquid fuel embodiments are preferably adapted to vaporize the liquid phase of the fuel before the flow reaches the large engine throttle  10 . In the context of a supply flowrate control, a “continuous fluid passage” refers to a fluid passageway of any sort, whether defined through tubes, channels, chambers, baffles, manifolds or any other fluid passageway that is uninterrupted by fully closed valves, pistons, positive displacement pumps or the like during its normal operative mode of controlling the fuel flowrate, such that gaseous fluid is generally able to continually flow through a continuous fluid passage whenever a pressure gradient is present to cause such flow. It should be recognized, though, that a continuous fluid passage in this context can be regulated to zero flowrate by reducing the effective area of an opening to zero, while the passage would still be considered as a continuous fluid passage in this context. In addition, absent clear disclaimer otherwise, equivalent structures can be fully closed when not operating to control the flowrate, and equivalent structures may also have parallel or alternate passageways where one or more may be interrupted without discontinuing the overall flow. 
     Exploded and Unexploded Views of Large Engine Throttle  10   
     Turning to  FIGS.  1 A and  1 B , there are shown perspective views of the preferred large engine throttle  10 . As shown therein, large engine throttle  10  includes an inlet adapter  30  and an outlet adapter  40 . Inlet adapter  30 , in part, defines supply inlet  390 , which is configured to allow supply flow into large engine throttle  10 . Outlet adapter  40 , in part, defines supply outlet  170  (shown in  FIGS.  2 B and  10   ), which is configured to allow supply flow out of large engine throttle  10 . Screws  31 - 34  are paired with machine nuts  31   a - 34   a  for securing inlet adapter  30  to housing assembly  20  (shown in more detail in  FIGS.  2 A- 4   ). Similarly, screws  41 - 44  are paired with machine nuts  41   a - 44   a  for securing outlet adapter  40  to housing assembly  20 . Detailed descriptions of assemblies and components of the preferred embodiment are provided in ensuing paragraphs. 
     With reference to  FIG.  2 A , there is shown a two-dimensional view of the large engine throttle  10 . A coolant port  220  can be seen in the front of housing assembly  20  (shown in dashed-line box) and another coolant port  221  (not shown) is located on the opposite side. Especially when throttle  10  is used as an air-fuel (MFA) throttle, hot gasses may flow through throttle  10 . To cope with the temperature of such hot gasses, and particularly to guard against thermal damage to the control circuitry associated with PCB  900  or to the motor  700 , a heat dissipator (not numbered) is located within the unitary block assembly  99  between main throttle body  20  and motor  700  as well as PCB  900 . The heat dissipater preferably is in the form of an aluminum component enclosing one or more flow-through passageways with relatively large surface areas for enabling liquid coolant to circulate therethrough and thereby cool the aluminum component. As will be understood by those of skill in the art, heat dissipators are commonly used on turbocharged applications like the large engine throttle  10 . The coolant ports  220  and  221  enable coolant to enter and flow around the large engine throttle  10  to keep the brushless motor  700  (shown in  FIG.  7   ) and main PCB  900  (shown in  FIG.  9   ) from overheating. 
     With reference to  FIG.  2 B , there is shown a cross-section, indicated by line B-B, of the embodiment illustrated in  FIG.  2 A  rotated clockwise 90 degrees. The throttle shaft  710  (sometimes referred to as an actuator “drive shaft”) controls movement of the throttle blade  210 , with minimal opportunity for slop or other errors. The upstream pressure P 1  (upstream of throttle blade  210 ) is measured at port  230  by pressure sensor  951  on PCB  900 , as the stovepipe of sensor  951  is connected in open fluid communication with port  230 , through an open passage (not shown) that runs through the unitary block assembly and a tube between port  230  and the stovepipe of sensor  951 . Likewise, the downstream pressure P 2  (downstream of throttle blade  210 ) is measured at port  240  by pressure sensor  952  on PCB  900 , as the stovepipe of sensor  952  is connected in open fluid communication with port  240 , through an open passage (not shown) that runs through the unitary block assembly and a tube between port  240  and the stovepipe of sensor  952 . 
     Each of ports  230  and  240  have fluid passage segments in close proximity to the ports that are oriented perpendicular to the flowline of the throttle fluid passage of throttle  10 , to minimize stagnation or suction pressures due to their orientation relative to flow. However, the next adjacent segments of each are oriented to slope slightly upwardly relative to gravity in order to minimize the risk of clogging. The temperature of the fluid is measured at port  250  using a thermistor  600  (shown in  FIG.  6   ). Screws  201 - 204  unite throttle body assembly  20  with intermediate housing assembly  80 . 
     With reference to  FIG.  3   , dashed-line boxes are used to depict some of various assemblies of and within an embodiment of the unitary block assembly  99  of throttle  10 . Assemblies that rigidly unite to form the unitary block assembly  99  include the walls  22  of central throttle body  20 , the spring return cover  550  of spring return assembly  50  at the end toward the right in  FIG.  3   , control circuitry cover  901  at the other end toward the left in  FIG.  3   , with the intermediate housing  800  of motor enclosure  80  positioned between throttle body  20  and the PCB space. In addition, as will be understood, numerous screws are used to rigidly unite the sub-blocks of the embodiment of  FIG.  3    together, preferably with inset seals to ensure a sealed union between each of the various subblocks. Two additional subblocks—namely the inlet extension and the flow outlet extension are also united to the unitary block assembly  99  of  FIG.  3   . Analogously, the unitary block assembly  99 ′ of the embodiment shown if  FIG.  3 A  is also very similar to assembly  99  of  FIG.  3   . 
     More particularly, the unitary block assembly is composed of various sub-blocks and covers that are preferably all of predominantly aluminum composition in the preferred embodiment. The resulting unitary block assembly of throttle  10  defines the inner and outer surfaces of throttle  10 . That unitary block assembly is illustrated as a billet type assembly of aluminum parts evident in the various views of  FIGS.  1 - 4   , although it should be understood that preferred embodiments may also be formed through larger castings having fewer sub-blocks in order to reduce costs for volume production. These assemblies are illustrated in greater detail in the figures that follow. In  FIG.  3    there is shown an inlet adapter  30  above a throttle body assembly  20  (more particularly shown in  FIG.  4   ). Four screws  31 - 34  (three shown) unite the inlet adapter  30  to the throttle body assembly  20  with a circular seal  35 , to sealingly enable mass flow from upstream into the throttle body assembly  20 . Similarly, the outlet adapter  40  is united with throttle body assembly  20  using screws  41 - 44  with a circular seal  45 , to sealingly enable mass flow downstream from the throttle body assembly  20 . Although of secondary importance, it may be noted that the inlet adapter  30  and outlet adapter  40  are more beneficial when throttle  10  is being used as an MFG throttle, as opposed to when it is being used as an MFA throttle. 
     Although each of the plurality of spaces defined by the unitary block assembly and that collectively contain the rotary shaft  710 —namely the PCB space, the motor space of intermediate housing  800 , the throttle body space, and the spring return assembly space of assembly  50 —are formed by sealed uniting of adjacent sub-blocks, leakage may still occur from one such space to the next due to the imperfect seals around a rotating shaft  710 . Accordingly, to protect the control circuitry of PCB  900  from the corrosive effects of gaseous fuel supplies, electronic components of PCB  900  are coated with a coating that is protective of such electronic components against the otherwise corrosive characteristics of gaseous fuels. 
     To the right of throttle body  20  is a spring assembly  50  (shown in detail in  FIG.  5   ). The spring assembly  50  operates as a torsion type spring that winds up while the block assembly  10  is powered on. When the block assembly  10  is powered off, the spring assembly  50  winds down and returns to a closed position or, more preferably, to a substantially closed position. To the left of throttle body  20  is a thermistor assembly  60  (shown in detail in  FIG.  6   ) that senses temperature. Also, to the left of throttle body assembly  20  is a motor and throttle shaft assembly  70  (shown in detail in  FIG.  7   ) that controls the movement of the throttle (shown in  FIG.  4   ). An intermediate housing assembly  80  (shown in detail in  FIG.  8   ) unites the motor and throttle shaft assembly  70  and a printed circuit board (PCB) assembly  90  (shown in detail in  FIG.  9   ). 
     As an alternative to the embodiments of  FIGS.  3  and  5   ,  FIGS.  3 A and  5 A  show a comparable but alternative embodiment. However, due to the close similarities of throttle  10 ′ as compared to throttle  10 , the parts in each of  FIGS.  3 A and  5 A  are numbered similarly to the comparable parts of  FIGS.  3  and  5   , with the main difference being the addition of a prime symbol (“′”) for the components of the embodiment of  FIGS.  3 A and  5 A . Particularly, with reference to  FIG.  3 A , most all the subassemblies of the throttle  10 ′ are practically similar to those of throttle  10  of  FIG.  3   , with the most notable exception being the spring return assembly  500 ′, which has components analogous but different from those of spring return assembly  500 . 
     Nonetheless, details of  FIG.  5 A  are different enough from those similar details of  FIG.  5    that some description may be helpful. Particularly, component  510 ′ of  FIG.  5 A  is a shaft seal. In this embodiment, seal retainer  511 ′ and  512 ′ are merged as one component. Part  501 ′ is a bushing separator that supports spring  500 ,′ and screw  531 ′ screws the assembly  50 ′ to the end of the throttle shaft  710 . D-shaped cutout in the screw  531 ′ tend to orient the spring assembly to the desired orientation on the shaft  710 . Bearing assembly  513 ′ is a conventional bearing assembly much like bearing assembly  513  and element  520 ′ is a bearing freeload spring. Part  530 ′ is spring return for returning throttle blade  210  to a five-degrees-from-fully closed position. Each end of the spring  500 ′ has projecting flare that engages mating notches and the like to drive the spring-biased return of throttle blade  210 , in a manner that is generally common for many spring-biased returns for automotive throttles. 
     Throttle Body Assembly  20   
     With reference to  FIG.  4   , there is shown an isometric view of the throttle body assembly (also referred to as “gaseous supply throttle”)  20 . As previously discussed, a throttle body assembly  20  may be used for controlling fuel flow rates, air flow rates, or fuel-air mixture flow rates. The cylindrically shaped volume of space from the top to the bottom of throttle body assembly  20  is defined herein as the throttle chamber  205 . For fuel throttles, the throttle orifice  200  is preferably between 50 millimeters and 76 millimeters in diameter. For fuel-air throttles, the throttle orifice  200  is preferably between 60 millimeters and 120 millimeters in diameter. Note that, although throttle orifice  200  is a circular-faced orifice in a preferred embodiment, other shapes may be used in alternative embodiments such as a square-shaped orifice. 
     Spring Assembly  50   
     With reference to  FIG.  5   , there is shown an exploded view of the spring assembly  50 . On the left side of  FIG.  5    is a throttle shaft seal  510  (with insert) that seals the throttle shaft  710  (shown in  FIG.  7   ). A throttle seal spacer  511  separates the throttle shaft seal  510  from a seal retainer washer  512 . A roller bearing  513  is located between the seal retainer washer  512  and a wave spring  520 . A spring guide bearing  501  prevents torsional spring  500  from contacting or rubbing against the body of throttle  10 . A larger spring guide bearing  502  separates the torsional spring  500  from a spring return flange  530 . A screw-like perpendicular pin  531  located in the center of flange  530  of the spring assembly  50  serves to transmit the neutrally biasing force of spring  500  to the shaft  710  and, in turn, to throttle blade  210 . Screws  551 - 554  fasten the spring return cover  550  to the throttle body assembly  20 , and an O-ring  540  sealingly unites the assemblies. With reference to the alternative embodiment of  FIG.  5 A , there is shown another exploded view of a spring assembly  50 ′, which is structured comparably and functions in a manner generally comparable to spring assembly  50 . 
     Thermistor Assembly  60   
     With reference to  FIG.  6   , there is shown an exploded view of the thermistor assembly  60 . In one embodiment, the thermistor  600  has a temperature measurement range from −70° C. to 205° C. The thermistor assembly  60  has two O-ring gaskets  603  and  604  that function as sealants. Lead wires  611  and  612  are soldered to thermistor PCB  610 , extend (not shown) through the intermediate housing assembly  80 , and are also soldered to the main PCB  900 . An epoxy overmolding  620  is used to protect the thermistor  600  and thermistor PCB  610 . A thermistor tube  630  encloses the epoxy overmolding  620 , thermistor  600 , and thermistor PCB  610 . The thermistor tube  630  is united with the throttle body assembly  20  using a screw  640 . 
     Motor and Throttle Shaft Assembly  70   
     With reference to  FIG.  7   , there is shown the motor and throttle shaft assembly  70 . A brushless motor  700  controls the movement of the throttle shaft  710 . On the right side of  FIG.  7    is a throttle shaft seal (with insert)  711 . A throttle seal spacer  712  separates the throttle shaft seal  711  from the throttle shaft  710 . Four screws  701 - 704  (three shown) unite the brushless motor  700  and the throttle shaft  710  with the throttle body assembly  20 . The throttle shaft  710  extends all the way through the brushless motor  700  and connects to a rotor arm  720 . There are two rotary bearing assemblies  705  and  706  within motor  700  such that, together with the rotary bearing assembly  513  (or  513 ′ in the embodiment of  FIG.  3 A ), three bearing assemblies support the rotatable movement of shaft  710 . A screw  730  integrally fastens the rotor arm  720  to an end of the throttle shaft  710  that protrudes into the PCB space from the left side (as viewed in  FIG.  7   ) of the brushless motor  700 . The rotor arm  720  has a permanent magnet  740  permanently attached to a radially outward portion of rotor arm  720 , such that arm  720  can be used in conjunction with a magnet  740  to indirectly measure the position of the throttle blade  210  in its range of rotatable motion. 
     Intermediate Housing Assembly  80   
     With reference to  FIG.  8   , there is shown the intermediate housing assembly  80 . A large open space  810  is used for housing the brushless motor  700 . A smaller circular opening  820  at the bottom left is used for housing the controller-area-network (CAN) pin connector that protrudes from the main PCB  900 . One small opening  830  at the top of the assembly  80  houses a reverse flow check valve  840 , to protect sensors from over-pressurization. Another smaller opening  850  houses a forward flow check valve  860  to protect sensors from over-pressurization. An in-groove seal  870  shaped to fit the intermediate housing assembly  80  sealingly unites assembly  80  to the throttle body assembly  20 . 
     Printed Circuit Board (PCB) Assembly  90   
     With reference to  FIG.  9   , there is shown the PCB assembly  90 , which sealingly contains PCB  900 . The PCB  900  is enclosed in a space (the “PCB space”) defined between a PCB housing cover  901  and intermediate housing  800 , which are united by screws  915 - 920  in a sealed manner. The sealed union between cover  901  and intermediate housing  800  is partially enabled by an in-groove elastic seal  902  positioned perimetrically around the PCB space in the interface between intermediate housing  800  and PCB housing cover  901 . Twelve screws  903 - 914  securely fasten the PCB  900  and pressure sensors  950 - 952  to the PCB housing  901 . Six screws  915 - 920  (three shown) and a PCB housing seal  902  sealingly unite the PCB assembly  90  with the intermediate housing assembly  80  (shown in  FIG.  8   ). Such sealed integration enables optimal control and helps minimize extraneous artifacts or other influences that might otherwise affect its operation. 
     PCB  900  comprises a microcontroller  930 , which can be any commercially available microcontroller with a memory that is capable of receiving machine readable code, i.e., software. The microcontroller  930  provides the “brains” of the large engine throttle  10 . Microcontroller  930  receives throttle position signals from Hall Effect sensors  940   a - e , pressure signals from pressure sensors  950 - 952 , temperature signals from the thermistor  600 , and control signals from the ECM  100 . The microcontroller  930  uses an algorithm to calculate throttle position in order to achieve the instantaneously desired mass flow rates and then outputs pulse width modulated and H-bridge signals to motor  80  to cause motor  700  to properly control the position of throttle blade  210 , while also outputting measured data to the ECM. 
     PCB  900  has five pairs of identical Hall Effect sensors  940   a - e  which are part of a position sensor assembly for indirectly detecting the position of throttle blades  210 . With cross reference to  FIG.  10   , these sensors are collectively named “Blade Position Sensor”  940 . As the throttle shaft  710  rotates, the rotor arm  720  which is an integral part of shaft  710  rotates within the PCB space and this causes the magnet  740  to move relative to the Hall Effect sensors  940   a - e , which are able to detect the resulting changes in the magnetic field. These sensors  940   a - e  vary their output voltage in response to magnetic field changes and these electrical signals are processed by the microcontroller  930 . The sensors  940   a - e  are used for calibrating the location of the throttle blade  210  relative to the strength of the magnetic field given by the magnet  740 . 
     Delta-P sensor  950  is a double-sided pressure transducer that measures the differential pressure (“Delta-P”) between the upstream pressure port  230  and downstream pressure port  240 . Two pressure sensor gaskets  950   a  and  950   b  seal Delta-P sensor  950 . Upstream pressure sensor  951  measures the absolute upstream pressure (“P 1 ”) and has pressure sensor gasket  951   a . Downstream pressure sensor  952  measures the absolute downstream pressure (“P 2 ”) and has pressure sensor gasket  952   a . The Delta-P sensor  950  is significantly more accurate in measuring the differential pressure than the method of mathematically subtracting the difference between P 1  and P 2 . However, there are conditions when the throttle operates at pressures out of range of the Delta-P sensor  950 . When the Delta-P sensor  950  begins to peg (ie, approaches its maximum reliable limits), the microcontroller  930  will begin using pressure sensors  951  and  952  to calculate the differential pressure. Once the maximum pressure range is exceeded, the microcontroller  930  will stop using Delta-P sensor  950  and switch entirely to pressure sensors  951  and  952  in addition, PCB  900  will troubleshoot other instances whenever P 1 , P 2  and/or Delta-P do not conform to rationality checks, in such cases a false signal is sent to ECM  100 . 
     Pressure sensors  951  and  952  are conventional pressure transducers, although non-conventional ones (or even sensors or the like for fluid conditions other than pressure) can be considered for use as alternatives for some of the same purposes. Pressure transducers  951  and  952  are preferably of the type that can be and are mounted to PCB  900  and have stiff tube connectors (sometimes called “stove pipes”) extending from their bases, through which the transducers access the pressure to be sensed. 
     To neutralize some of the effects of pressure fluctuations—particularly downstream pressure fluctuations—the control algorithms of microcontroller  930  preferably use time-averaged pressure readings from the pressure sensors  950 - 952  rather than instantaneous pressure readings. More particularly, based on the number of cylinders and the current RPM of the engine, as received by microcontroller  930  from ECM  100 , microcontroller  930  continuously determines the stroke cycle time for the pistons of engine  102   
     FIG.  10 —Block Diagram 
     In the illustrative block diagram of  FIG.  10   , there are four main segments of supply flow depicted for preferred embodiments: (1) an upstream gaseous fuel supply  350  depicted on the left; (2) a large engine throttle  10  depicted within the dashed-line box in the middle; and (3) an engine  102  depicted in the smaller dashed-line box further to the right. The three segments  350 ,  10 , and  102  are operatively connected to provide rotary shaft power for any number of large engine applications, with fuel supply  350  serving as the basic gaseous fuel supply for engine  102 , and with large engine throttle  10  serving to provide accurate control of the gaseous fuel flowrate from that fuel supply  350  to engine  102 , in accordance with various teachings of the present invention. 
     Upstream Fuel Supply  350   
     As illustrated in  FIG.  10   , fuel supply  350  preferably includes a fuel tank  360  serving as the source for fluid fuel, together with a mechanical pressure regulator  370  and other conventional components such as a shut-off gate valve  380 . Valve  380  is preferably controlled by ECM  100 , although independent control may be utilized in alternative embodiments. The gaseous fuel supply  350  is equipped and adapted to deliver a gaseous fuel supply to supply inlet  390  at desired pressure levels. 
     More preferably, the gaseous fuel supply  350  is a natural gas or vaporized propane fuel supply that delivers natural gas or propane stored in fuel tank  360 . Though not shown in  FIG.  10   , fuel tank  360  may be equipped with vaporization subassemblies and controls to manage LNG (liquefied natural gas) or propane vaporization and resulting pressure within fuel tank  360  and the associated lines  365 ,  375  and  376 . Such vaporization subassemblies and controls for LNG preferably prime tank  360  by pre-circulating some of the stored LNG through a heat exchange loop that increases the temperature of the pre-circulated LNG to the point of partial or complete vaporization, thereby creating a vapor phase with an adequate pressure head within tank  360 . Line  365  preferably also includes a second heat exchanger downstream of the fuel tank  360 , to further aid in complete vaporization of the LNG or propane once gaseous fuel is allowed to flow from fuel supply  350  to large engine throttle  10 . 
     Downstream of the heat exchanger in line  365 , the gaseous fuel is directed sequentially through a mechanical pressure regulator  370 , a downstream fuel shut-off valve  380 , and a line quick-disconnect assembly (not shown) prior to entry into large engine throttle  10 . In this embodiment, initial fuel pressure is supplied by the tank  360 , although the initial pressure from tank  360  is preferably regulated by mechanical pressure regulator  370  before reaching supply inlet  390  of large engine throttle  10 . Mechanical pressure regulator  370  is able to manage the low pressures from tank  360  and includes one or more conventional pressure regulators that use pressure-balanced diaphragms to vary effective orifice sizes and thereby control the pressure to within the preferred range at supply inlet  390 . Mechanical pressure regulator  370  preferably includes an integrated pressure sensor for providing upstream pressure data (i.e., equivalent to the pressure “P 1 ” at supply inlet  390 ) to ECM  100  via control link  371 . Whether or not a pressure sensor is integrated with regulator  370 , the preferred embodiment includes a pressure transducer  951  that measures the pressure at port  230 , which is upstream of throttle blade  210  and which is in fluidic proximity to supply inlet  390 , such that it is the same as P 1 , for reliable input on the actual pressure of the gaseous supply entering throttle  10 . 
     Assuming all lines  365 ,  375  and  376  are operatively sealed and connected to direct supply flow therethrough, supply flow from fuel supply  350  to large engine throttle  10  is enabled or disabled by On/Off operation of a mechanical shut-off valve  380 . Although manual valves may be used in certain alternative embodiments, valve  380  is preferably motor or solenoid actuated via oversight control by ECM  100 , as illustrated by the dotted-line control link  381  in  FIG.  10   . When shut-off valve  380  is open, gaseous supply flow is induced by an operable pressure gradient between tank  360  and supply inlet  390 . Hence, with valve  380  open, fuel first moves through the heat exchanger and the mechanical pressure regulator(s)  370 , and the fuel is then directed through the valve  380  and into the fuel inlet  390 . 
     Despite vaporization subassemblies and controls, the potential exists for the passage of vaporized natural gas or propane fuel that also contains droplets of liquid phase LNG or propane, which may occur for instance if the ports or conduits for heat exchange fluids become clogged. If any LNG or propane droplets remain in the fuel stream downstream from the mechanical pressure regulator(s)  370 , their subsequent vaporization may introduce dramatic pressure spikes into large throttle engine  10 , which would overwhelm large throttle engine  10 . In order to compensate for the possible introduction of LNG or propane droplets downstream of the heat exchanger, a pressure control loop may be inserted into the system in a position intermediate between the pressure regulator(s)  370  and the supply inlet  390  to large engine throttle  10 , preferably downstream of the heat exchanger and mechanical pressure regulator(s)  370 . 
     In the event any errant droplets of LNG or propane enter into large engine throttle  10 , the delayed vaporization would likely lead to a spike of increased pressure at the supply inlet  390  of the large engine throttle  10 . If such a pressure spike is produced, the inserted pressure control loop preferably buffers the spike by venting back to the upstream side of the mechanical pressure regulator  370 . As other alternatives, one or more overpressure vents or bypass check valves can be included in line  375  and/or  376  to help divert vaporization spikes that would otherwise propagate and disrupt the control of large engine throttle  10 . Similarly, pressure spikes due to fuel vaporization upstream of the mechanical pressure regulator can also be vented to atmosphere and/or diverted to other containment further upstream in fuel supply  350 . 
     By providing a multi-faceted strategy for control of such errant pressure spikes, namely through the inclusion of a heat exchanger in line  365  as well as one or more of the vents, check valves or the like as discussed above, preferred embodiments control and modulate the pressure introduced to the supply inlet  390  to reduce or prevent overwhelming the flowrate control of large engine throttle  10 . 
     The fuel tank  360  may alternatively be embodied as any of a number of commonly available gaseous fuel sources, such as stationary gas pipelines, compressed gas cylinders, or other types of liquefied storage tanks with vaporization controls, together with conventional pressure regulators and the like. Preferably, most such alternatives still include some form of a fuel storage tank  360  that feeds fuel to large engine throttle  10  via a high-pressure mechanical pressure regulator  370  which regulates the pressure to a desired range for the supply inlet  390 . 
     Again, from the high-pressure mechanical pressure regulator  370 , the fuel is fed through a fuel tube or supply line  375 , which preferably includes a shut-off gate valve  380  as shown. Downstream from shut-off gate valve  380 , the fuel supply line  376  is connected to the large engine throttle  10  at supply inlet  390 , at which point the fuel is preferably introduced into the gaseous supply throttle  20  of large engine throttle  10 . 
     As will be understood by those of skill in the art, the supply line  375  may also include a fuel filter (not shown) or other conventional systems for monitoring and/or optimizing fuel supply conditions prior to introduction into large engine throttle  10 . Such other systems may include, for instance, fuel quality sensors connected to the engine control module (ECM)  100  and/or the PCB  900  of large engine throttle  10  for anticipating operating needs. The fuel supply  350 may also include a combination of several independent pressure regulators  370  (rather than just one) or may include additional pressure regulators that are integral to the fuel storage tank  360 . 
     Referring again to the preferred embodiment as illustrated in  FIG.  10   , the large engine throttle  10  includes a fuel supply  350 . Downstream of that large engine throttle  10 , the supplied fuel flow is then blended with air  160  for supplying a gaseous fuel-air mix  150  to internal combustion engine  102 . While the  FIG.  10    arrangement is preferred, alternative embodiments in line with some broader teachings of the present invention may alternatively introduce some or all of the required air into the fuel upstream of large engine throttle  10  (as suggested by alternate air mixing flow arrow  260 ′), albeit with corresponding challenges and possible compromises given that corresponding adjustments may be needed to account for the air flow introduction at whichever point it is introduced. 
     Gaseous Supply Throttle  20   
     Linked to the ECM  100  of engine  102  via the communication link illustrated by dotted line  101 , gaseous supply throttle  20  is adapted to provide rapid and highly accurate control of the actual {dot over (m)} supply flowrate at its outlet  170  in response to the {dot over (m)} flowrate signal  105 , for controlled delivery of the fuel supply to the fuel-air mixer  161  and subsequently the engine  102 . By its nature, gaseous supply throttle  20  is used to control gaseous supply flow from a primary fuel supply  350  (on the left in  FIG.  10   ) to an internal combustion engine  102  (on the right in  FIG.  10   ). Accordingly, gaseous supply throttle  20  is operatively positioned downstream of the fuel supply  350  and upstream of the fuel-air mixer  161  and engine  102 , such that it is plumbed and sealed to be part of a fluidly continuous fuel supply system during operation of engine  102 , with gaseous supply throttle  20  being intermediate the fuel supply  350  and the engine  102 . A detailed description of large engine throttle  10  with references to additional figures is made in ensuing paragraphs. 
     For further optimization, the in-block microcontroller  930  and related control circuitry are preferably embodied on a single printed circuit board  900  (also visible in  FIG.  9   ). The in-block microcontroller  930  of PCB  900  is connected via data link  101  to receive the {dot over (m)} data signal  105  (and all other available data, including a P 3  data signal  121 , if needed, as discussed elsewhere herein) from ECM  100 . Data link  101  connects to ECM  100  and its control network, which is a CAN network in the preferred embodiment. Using the received data signals  105 ,  120 , the printed circuit board  900  controls large engine throttle  10 , preferably without any external communication other than power and data connection  101  to the engine&#39;s ECM  100 . Although “CAN” is technically an acronym for controller-area-network, the “CAN” reference is a commonly used technical word that refers to a CAN network or to data received via a CAN network. On that note, it should be recognized that although a CAN network is the preferred communication link for communication of all commands, variables and other data received through line  101  by microcontroller  930  from outside of throttle system  10 , wireless, analog signals, digital signals, or other communication means may be used as alternatives while still embracing many aspects of the present invention. 
     Also located on the PCB  900  is the CAN network connector  960  (visible in  FIG.  2 B ). As will be understood by those of skill in the art, CAN network connector  960  is a five-pin connector. The five pins comprise a power pin, a ground pin, a CAN plus pin, a CAN minus pin, and a CAN termination pin. As will be understood by those of skill in the art, alternative embodiments could be direct (0-5V or 5-20 milliamp) data connections or any other known alternative for data connections that are otherwise suitable for an application such as large engine throttle  10 . Alternative embodiments may have eight pin connectors instead of the five pins for a CAN network. 
     In the preferred embodiment, optimal fluid condition feedback is obtained from double sided transducer (“Delta-P sensor”)  950  by positioning the tips of its stove pipes (or a tube therefrom, as an alternative) in direct fluid contact with throttle chamber  205  (shown in  FIG.  4   ), while the base of transducer  950  is mounted directly on PCB  900 . With cross-reference to  FIG.  2 B , Delta-P sensor  950  measures the differential pressure (“Delta-P”) between the upstream pressure port  230  and downstream pressure port  240 . Pressure sensor  951  measures the absolute upstream pressure (“P 1 ”) from port  230 . Pressure sensor  952  measures the absolute downstream pressure (“P 2 ”) from port  240 . With further cross-reference to  FIG.  2 B , the stove pipe tips of pressure sensors  951  and  952  extend from PCB  900  through appropriately positioned sensor ports  230  and  240  in a side wall of throttle chamber  205 . To minimize clogging or other fouling of transducers  950 - 952 , ports  230  and  240  are preferably in a side compartment of throttle chamber  205  and are shielded through use of downwardly sloping passages or other measures as are known for use as contamination preventers. 
     With cross-reference to  FIG.  6   , optimal fluid condition feedback is obtained by positioning the sensor tip  601  of thermistor  600  directly within throttle chamber  205 , while the base  602  of thermistor  600  is soldered directly to thermistor PCB  610 . Thermistor  600  is a conventional thermistor that senses temperature at its tip  601  and has wire leads extending to the sensor tip  601 , although other forms of temperature sensors (or even sensors or the like for fluid conditions other than temperature) can be considered for use as alternatives for some of the same purposes. 
     Throughout the control of in-block microcontroller  930 , embodiments of the present invention address long felt unresolved needs in the field through innovative approaches that overcome many of the limitations and challenges of the prior art. In accord with many of the teachings of the present invention, the industry is enabled to provide solutions manifested in large engine control systems that are readily adaptable to the power demands of numerous applications and are readily capable of highly accurately and precisely controlling supply flow across sizable dynamic power ranges in internal combustion engines. 
     Engine  102   
     With reference again to  FIG.  10   , Engine  102  is a large spark-ignited internal combustion engine  102  of a type that uses gaseous fuel as its primary energy source, most preferably of a type that uses natural gas (NG) or vaporized propane (LPG) as its fuel. A large engine is defined here as any engine that is 30 liters or greater. Engine  102  is preferably used in stationary applications such as generator sets (hereinafter “gensets”) on natural gas compression skids. Alternatively, engine  102  may be used in large mobile applications such as trains, ships, mining trucks or other heavy-duty vehicles. As is conventional, engine  102  has an ECM  100  or the equivalent, which continually monitors the operating conditions of various parts of engine  102  and its peripheral systems. Such an engine  102  may be operatively incorporated in any number of powered applications in alternative embodiments, as well as many other applications that may be now or in the future known in the art for being powered by spark-ignited gaseous-fuel internal-combustion engines. 
     ECM  100  of engine  102  is connected via data communication lines  181 - 182  or other conventional means to monitor pressures, temperatures and operating states in or around numerous subsystems of engine  102 , such as its fuel-air handling system (that preferably includes a turbo charger  172 ), a fuel-air throttle  140 , its ignition system, its combustion chambers  180 , its coolant system, its oil pressure, and its exhaust system, amongst others as are known in the art. Although alternative embodiments may use wireless connections for some or all of the data connections between ECM  100  and the various subsystems of engine  102 , preferred embodiments of ECM  100  are connected to send and receive analog or digital signals through wire harnesses or other forms of communication lines  101 ,  181 ,  182 ,  182   a ,  182   b ,  371 , and  381 . Though represented in  FIG.  10    by the various dotted-line communication links directly between the various components, communication lines  101 ,  181 ,  182 ,  182   a ,  182   b ,  371 , and  381  are preferably embodied in the form of a conventional data network, such as a controller-area-network (“CAN”) network. 
     As will be understood by those skilled in the art, ECM  100  is programmed to operate, in part, to determine the desired supply flowrate (“{dot over (m)}” or “mdot”)  105  at any given instant in time, based on current operating conditions of engine  102  in comparison to current user demands. As the desired {dot over (m)} flowrate is determined by ECM  100 , the ECM produces a corresponding {dot over (m)} data signal  105  that represents the current {dot over (m)} flowrate demand for engine  102 . As the desired {dot over (m)} flowrate is determined by ECM  100 , the corresponding {dot over (m)} data signal  105  is conveyed by communication link  101  to the microcontroller  930  of large engine throttle  10 , and large engine throttle  10  operatively serves to instantaneously and accurately deliver as much from throttle system outlet  170 . 
     After the flow control by large engine throttle  10 , the controlled flow of gaseous supply from the throttle system outlet  170  is directed to fuel-air mixer  161  where it is preferably mixed with air  160 , to produce a combustible fuel-air mix  150 . Preferred embodiments use a flow of filtered air  160 . The intake air  160  that is directed into the fuel-air mixer  161  may be drawn from ambient air in alternative embodiments, with or without pressure compensators, albeit with performance compromises. Fuel-air mixer  161  is preferably a venturi-like mixer or another type that does not use moving parts in the supply flow, thereby maximizing durability and fuel/air mixture homogeneity of flow conditions actually delivered to combustion chambers  180 . Most preferably, fuel-air mixer  161  is in a form that includes a fuel ring, to help preserve the benefit of the accurate {dot over (m)} flowrate control provided by throttle system  10 . 
     Once the proper fuel-air mixture  150  is provided by fuel-air mixer  161 , that mixture  150  flows toward engine  102 . The fuel-air mixture  150  passes through a turbocharger  172 . The turbocharger  172  takes in recirculated gas from the pre-turbo exhaust  171 , mixes it with fuel-air mixture  150  and compresses it. After leaving the turbocharger  172 , the fuel-air mixture  150  passes through a turbo aftercooler  174 . The turbo aftercooler  174  cools fuel-air mixture  150  before it enters the engine  102 . It is necessary to reduce the temperature of the fuel-air mixture to allow for a denser intake to the engine  102 , thereby increasing the output of the engine  102 . The post turbo exhaust gas  173  flows into a three-way catalytic converter (TWC)  175 . As will be understood by those of skill in the art, the TWC  175  reduces pollutants prior to the exhaust gas being released to the environment. Although not illustrated in the drawings, those of skill in the art will understand that preferred embodiments would include various components that are not shown. Moreover, other components like filters and pressure relief valves are also not shown. With respect to any such simplifications and omissions from the drawings, it should be understood that preferred embodiments include them in such character and configuration as would be generally understood within the discretion of those of skill in the art. 
     The flow of fuel-air mixture  150  is controlled by fuel-air throttle  140 , which is preferably an electronic throttle that further facilitates preservation of the highly accurate flowrate control provided by the supply throttle  10  in  FIG.  10   . Accordingly, fuel-air throttle  140  is preferably also constructed with the same basic structure and software as throttle  10 , albeit preferably with adaptations to accommodate the different pressure ranges that would be experienced downstream of mixer  161  and perhaps with less protection of internal components against the corrosive effects of more concentrated fuels, as would be encountered upstream of mixer  161 . Because  FIG.  10    plumbs and uses throttle  10  to control the mass flowrate of the fuel itself, that type of throttle deployment is sometimes referred to as mass-flow-gas throttle (or an “MFG” throttle). In contrast, the fuel-air throttle  140  that is used to achieve highly accurate control of the mass flow of the fuel-air mixture  150  is sometimes referred to as a mass-flow-air throttle, or an “MFA” throttle, irrespective of whether or not the fuel is mixed with the air at the point of that control. 
     Preferably, the fuel-air throttle  140  is also constructed according to the teachings of the present invention, with the same basic structure as the supply flow throttle  10  that is used as an MFG throttle to control the mass flow of the fuel by itself. Hence, the highly accurate fuel supply flow of the MFG throttle  10  in  FIG.  10    is preferably combined with highly accurate air supply mass flow control achieved by a fuel air throttle  140  constructed according to the same basic teachings as the MFG throttle  10 . Alternatively, complete and highly accurate mass flow control can also be achieved by combining an MFG throttle together with an MFA throttle that is plumbed in the air supply  160  upstream of the fuel-air mixer  161 . Either such combination, either the one illustrated in  FIG.  10    or the alternative combination of using a similar throttle to control the mass flow of air  160  by itself, enables comprehensive mass flow control of all supply flows for combustion. Moreover, generally accurate overall control might also be attainable by just controlling the mass flow of the fuel, without actively controlling the mass flow of the air if other reliable data is used to calculate that mass flow of the air, such as through use of oxygen sensors in combination with pressure, temperature and the like. Whatever the choice for a specific application, we trust that those of skill in the art will understand where and how to include such throttles for the different purposes to achieve the different combinations for overall mass flow control. 
     Whatever the choice, the resulting fuel-air mixture  150  is then operatively introduced into combustion chambers  180  of engine  102  under the control of ECM  100 . Within combustion chambers  180 , the fuel-air mixture  150  is then operatively spark-ignited to cause working combustion. 
     Surprisingly, the use of such an MFG throttle together with such an MFA throttle enables a dramatically streamlined development cycle for engines. Whereas large natural gas spark-ignited internal combustion engines have historically required considerable time and expense to finalize and validate the engine design prior to commercial release, the highly accurate mass flow control of the present invention enables a greatly simplified development, conceivable without any test cell expense. Although the industry will likely continue the use of test cells for finalizing designs, the accurate controls enabled by the present invention will allow much more relaxed standards in the process, not to mention the ability to achieve highly accurate mass flow control despite highly variable quality in fuel quality, air composition, and other environmental factors. 
     Throttle Control Strategy 
     As will be understood by those of skill in the art, the following mass flow rate equations are used to describe the non-choked flow of gases through an orifice. Equation (1) is the mass flow rate equation for ideal gases and equation (2) uses a gas compressibility factor “Z” to correct for the mass flow rate of real gases. 
     
       
         
           
             
               
                 
                   
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                   2 
                   ) 
                 
               
             
           
         
       
     
     In these equations, “{dot over (m)}” is the mass flow rate; “C” is the dimensionless orifice flow coefficient; “A 2 ” is the cross-sectional area of the orifice hole (“effective area”); “ρ 1 ” is the upstream real gas density; “P 1 ” is the upstream gas pressure; “k” is specific heat ratio; “P 2 ” is the downstream gas pressure; “M” is the gas molecular mass; “T 1 ” is the absolute upstream gas temperature; “Z” is the dimensionless gas compressibility factor at “P 1 ” and “T 1 ”; and “R” is the universal gas law constant. 
     With reference to  FIG.  10   , the throttle control algorithm  990  determines the A 2  “effective area” needed to achieve the desired {dot over (m)} flowrate using equation (2). P 2 , P 1 , and T 1  are measured as previously described and these values are used in equation (2). The microcontroller  930  is constantly utilizing the throttle control algorithm  990  to attain precise {dot over (m)} flowrates while the parameters change. Once the “effective area” A 2  is determined by throttle control algorithm  990 , a signal is transmitted to brushless motor  700 . Brushless motor  700  is an actuator that controls the movement of throttle shaft  710 , thereby adjusting throttle blade  210  of gaseous supply throttle  20  until the desired “effective area” A 2  is achieved. Brushless motor  700  is preferably a fast-acting actuator, preferably operable to move the throttle blade  210  through its entire range of motion in fifty milliseconds or less. Fast-acting actuators are preferably operable to move the actuated element through most of its operable range of motion (preferably from 20% to 80% of stroke), if not all of that operable range, in fifty milliseconds or less, although many other types of actuators are still likely to be suitable as alternatives, especially to the extent particular claim elements are not expressly disclaimed to require particular fast-acting characteristics. 
     Operating Pressures—Low Pressure 
     Although it will be understood that adaptations may be made for other upstream conditions, the pressure in the supply line  376  at the supply inlet  390  is preferably controlled by mechanical pressure regulator  370  to be approximately at a gauge pressure slightly above one atmosphere, although when throttle  10  is used as an MFG throttle, pressures could be as high as 2.5 bar absolute or, in the case of MFA application, as high as four bar absolute. 
     Although not necessary for highly accurate mass flow control, some methods of controlling large engine throttle  10  may also be further tuned to achieve the desired control depending in part on actual or estimated fluid conditions even further downstream, such as by a downstream sensor  121  monitoring pressure (designated as “P 3 ” for our purposes) that is monitored by ECM  100  and for which a representative data signal  120  is continuously available from ECM  100  (or from the data network associated with ECM  100 ). The particular P 3  value of data signal  120  represents any available data stream from engine  102  that is characteristic of pre-combustion fluid pressure within engine  102 . Such a downstream sensor  121  may be a conventional temperature and manifold absolute pressure (TMAP) sensor module located in the engine&#39;s intake manifold downstream from fuel-air throttle  140 . In addition to, or as an alternative to, a conventional TMAP sensor  121 , downstream data can also be gathered from a conventional throttle inlet pressure (TIP) sensor module upstream of fuel-air throttle  140 . Again, though, despite the plausible benefits of knowing the further downstream pressure P 3  for some variations of the invention, most preferred embodiments of throttle  10  omit consideration of P 3  data from sensor  121  as unnecessary, opting instead for simplicity and cost saving. 
     Alternative Fuels 
     Gaseous fuel for these purposes means a fuel that is in the gaseous state at standard operating temperatures and pressures. In presently preferred embodiments, the gaseous fuel is natural gas, derived from either a liquefied natural gas (LNG) or compressed natural gas (CNG) storage state. While the most preferred embodiments are adapted for use with these fuels, adaptations will be evident to those of skill in the art for use of aspects of this invention with other fuels in alternative embodiments. Such alternative embodiments are adapted, for instance, for use with hydrogen or other gaseous fuels such as propane, butane or other gas mixtures, including those common with liquefied petroleum gas (LPG) mixtures. Indeed, although the present invention is focused on the particular fields to which the preferred embodiments apply, it may also well be that some aspects of the invention may be found revolutionary in other fields as well. 
     Alternatives in General 
     While the foregoing descriptions and drawings should enable one of ordinary skill to make and use what is presently considered to be the best mode of the invention, they should be regarded in an illustrative rather than a restrictive manner in all respects. Those of ordinary skill will understand and appreciate the existence of countless modifications, changes, variations, combinations, rearrangements, substitutions, alternatives, design choices, and equivalents (“Alternatives”), most if not all of which can be made without departing from the spirit and scope of the invention. 
     Therefore, the invention is not limited by the described embodiments and examples but, rather, encompasses all possible embodiments within the valid scope and spirit of the invention as claimed, as the claims may be amended, replaced or otherwise modified during the course of related prosecution. Any current, amended, or added claims should be interpreted to embrace all further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments that may be evident to those of skill in the art, whether now known or later discovered. In any case, all equivalents should be considered within the scope of the invention, to the extent expressly disclaimed during prosecution or to the extent necessary for preserving validity of particular claims in light of the prior art.