Patent Application
20110214643
The invention relates to a system and method for heating fuel supplied to an internal combustion engine.
High pressure fuel delivery systems utilize a common rail to accumulate and distribute fuel to fuel injectors at high-pressure while minimizing pressure fluctuations among the injectors. The rail functions as an accumulator to allow for precise control of high-pressure injection of fuel by an engine control unit (ECU) into the cylinders of an internal combustion engine at timing that is independent from the engine speed. Such high pressure fuel delivery systems are susceptible to leakage from the fuel line or elsewhere in the delivery system. If fuel leakage occurs, the leaking fuel can spray onto high temperature surfaces of an engine and cause a fire. To control fuel leakage when it does occur, a low pressure containment system has been used to channel leaking fuel to a containment tank or to return the leaking fuel to the fuel tank or the fuel pump. One such conventional containment system uses a double wall structure, which encloses a high pressure fuel line with an outer wall to form a low pressure passage between the inner high pressure line and the outer wall. A fuel leak that may develop in the high pressure fuel line would be contained in the low pressure passage.
Additionally, recent fuel systems have modified the accumulator of the common rail from a single tube-like structure from which fuel is supplied to multiple injections to a more modular approach in which a fuel injector body itself includes a volume that functions as an accumulator with pressures maintained as high as 23,000 psi (1600 bar). These modular components eliminate the need for a costly long external fuel rail by maintaining a highly pressurized fuel volume within the injector.
A system for heating fuel and method of heating fuel supplied to an internal combustion engine is provided by the invention.
More particularly, embodiments consistent with the claimed invention relate to a system for heating fuel supplied by a common rail fuel supply to an internal combustion engine. The system includes a high pressure fuel line, plural fuel injectors connected in series along the high pressure fuel line in the common rail, and a continuous low pressure passage including a heat exchanging portion in close proximity to the high pressure fuel line. A heated fluid source operative to fluidly communicate with the continuous low pressure passage and circulate heated fluid to heat fuel present in the high pressure fuel line prior to, and during a cold start operation of the internal combustion engine.
In other embodiments consistent with the invention, a method of providing fuel to an internal combustion engine includes sensing the temperature of fuel supplied to a fuel system of the internal combustion engine and determining whether the sensed fuel temperature is greater than a predetermined value. If the sensed fuel temperature is less than or equal to a predetermined value, the method recirculates fluid through a continuous low pressure circuit to heat fuel present in a high pressure fuel line. If the sensed fuel temperature is greater than the predetermined value, the method evacuates fluid for heating fuel from a portion of the continuous low pressure passage and the evacuated portion of the continuous low pressure passage is fluidly connected to a fuel leakage detection device.
In accordance with other embodiments consistent with the invention, an internal combustion engine includes an engine block including plural cylinders, where each cylinder contains a piston movable in a reciprocating manner. The internal combustion engine includes a fuel line for supplying fuel under high pressure to plural fuel injectors, where each fuel injector is controlled to deliver timed charges of atomized fuel to an associated one of the cylinders. A high pressure fuel pump fluidly communicates with the fuel line, an electronic controller, and a heated fluid recirculating circuit. The heated fluid recirculating circuit includes a heated fluid source, a feed line fluidly communicating with the heated fluid source, a heat exchanger having a low pressure passageway surrounding a portion of the fuel line and first and second distal ends. The first distal of the heat exchanger fluidly communicates with the feed line, and a return line fluidly communicates between the second distal end and the heated fluid source. The electronic controller is operative to cause the heated fluid recirculating circuit to circulate heated fluid from the heated fluid source through the low pressure passageway of the heat exchanger to heat fuel under high pressure in fuel line prior to, and during a cold start operation of the internal combustion engine.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and exemplary only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention that together with the description serve to explain the principles of the invention. In the drawings:
The various aspects are described hereafter in greater detail in connection with a number of exemplary embodiments to facilitate an understanding of the invention. However, the invention should not be construed as being limited to these embodiments. Rather, these embodiments are provided so that the disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Descriptions of well-known functions and constructions are omitted for clarity and conciseness. Further, it should be emphasized that the terms “comprises” and “comprising,” when used in this specification, are taken to specify the presence of stated elements, features, integers, steps or components; but the use of these terms does not preclude the presence or addition of one or more other elements, features, integers, steps, components or groups thereof.
Standby power generation units as well as industrial, mobile and marine engines may be required to go from a cold soak cold start condition (−30° F.) to full rated speed and power within a few seconds of starting. For example, the NFPA (National Fire Prevention Association) requirement is 85% of rated speed to accept load within 10 seconds of cold start. By cold start condition is meant a condition of the internal combustion engine determined based on input(s) from one or more sensors provided on or around the engine that can be relayed to a controller, such as an engine control module (ECM) or electronic engine controller (EEC). For example, an ECM, EEC or other controller can determine the existence of a cold start condition by comparing one or more engine parameters to predetermined threshold values. For example, a cold start condition can be determined to exist by the comparison of fuel temperature and/or engine coolant temperature with a predetermined temperature threshold. Likewise, other engine conditions may be utilized for determining cold start conditions, such as catalyst temperature, ambient temperature, etc. These engine parameters can include, for example, oil temperature, exhaust temperature, intake air temperature, ambient temperature, and so forth. A cold start operation includes starting and/or operating an internal combustion engine while in a cold start condition.
During the transient period from zero speed and fueling to full rated speed and fueling, cold viscous fuel from the fuel lines, fuel pump and low pressure filtration system can pass by a flow limiter or flow fuse provided in the high pressure portion of the fuel line supply. For example,
Referring now to
As shown in
Each double walled segment 120 includes an inner line 121 that forms a portion of a high pressure fuel passage 122 that extends at least the length of the heat exchanging portion 112, and an outer line 123 surrounding the inner line 121 to form an annular shaped low pressure passage 124 that is part of a low pressure circuit extending beyond the heat exchanging portion. As will be described below in detail, heated fluid can be circulated through the low pressure passage 124 to heat fuel supplied in the high pressure fuel passage 122. The number of double walled segments 120 can correspond to the number, n, of fuel injectors, for example, a number that is equal to the number of cylinders 104 included in a bank of cylinders of an engine, although some applications can include additional segments or only one segment for an engine having a single cylinder. For example, embodiments can include modular elements of various shapes and lengths that provide increased flexibility in applications requiring different fuel routing paths and/or branches to multiple paths, or to permit insertion of intermittent elements, such as sensors and valves.
As shown in
The annular shaped low pressure passage 124 is part of a heated fluid circuit that includes a heated fluid reservoir 140, a low pressure (LP) pump 142, and feed line 144 for providing the heated fluid from the heated fluid reservoir 140 to an inlet 146 of the coupler 130. After the heated fluid enters the coupler 130, it flows through the heat exchanging portion 112 in the direction of solid tailed arrows depicted in
The recirculated heated fluid flowing through the heat exchanging portion 112 keeps fuel residing in the high pressure passage 122 and the injectors 113 warm and at low viscosity. For example, a target viscosity can be under 6 centistokes, which is approximately 40° F. for straight #2 diesel fuel (e.g., ASTM D975 #2), although the temperature for maintaining fuel below a target viscosity would depend on the type of fuel being used. For instance, respective temperatures required for maintaining a target viscosity would increase for the following fuels in the order of: jet fuel, typical #1 diesel, typical #2, moderate #2, and high viscosity #2. Viscosities above this range can close a flow limiter associated with a fuel injector, so maintaining fuel viscosity below about 6 centistokes by applying heat to the fuel can prevent unintended closings. However, a target viscosity for a fuel also can depend on a type of fuel system, type of flow limiter, or another physical structure associated with a fuel's path in a high pressure fuel system.
To prevent heat loss from the flowing heated fluid, insulation can be added to the outside of the double wall segments 120, couplings 126, 128 and 130, the feed and return lines 144, 149, and/or all exposed surfaces of the injectors 113. Other heating means such as electrical tape or other active heating may also be used to augment the effect of the heated fluid recirculation.
To form the low pressure passage 124, a second end portion of the coupler body 254 includes a bushing 262 that can be compressed in sealing engagement with an outer surface portion of the low pressure outer line 123 and the coupler body 354 by screwing a cap 264 onto threads 263 of the coupler body. The outlet 148 of the coupler 126 includes a rotatably adjustable sleeve portion 148a provided over the coupler body 254 with sealing elements 265, such as O-rings, provided therebetween and on both sides of at least one opening 266 provided in the coupler body 254. The opening 266 provides a communication path to the low pressure return line 149 via the outlet 148. The return line 149 and the outlet 148 are connected via a threaded engagement 267, and one or more sealing elements 268 provide a seal between the outlet 148 and the return line 149. A continuous low pressure passage 124 is thus formed from the annular area between the inner high pressure line 121 and the outer low pressure line 123, the area between the high pressure line 121 and the coupler body 254, the opening 266, and the extent of the low pressure return line 149.
At a second end of the coupler body 354, a bushing 362 is compressed against an end portion of the low pressure outer line 123 by screwing a cap 364 onto the threads 363 of the coupler body 354. A continuous low pressure passage 124 is formed from the annular area between the inner high pressure line 121 and the outer low pressure line 123, the annular area between the high pressure line 121 and the coupler body 354, the channel 360, and the inlet or outlet port of the fuel injector T piece 127. Each fuel injector T piece 127 can include one or more low pressure passageway extending from its inlet port to its outlet port to provide continuity of the low pressure passage 124 through the T piece 127. Hence, heated fluid recirculated from the reservoir 140 can flow across the T piece 127 and the coupler 128 to exchange heat with fuel in the high pressure passage 122.
Similar to coupler 126 of
To seal the low pressure passage 124 between the coupler body 454 and the plug 132a, the plug 132a can be sealingly engaged with a second end portion of the coupler body 454 by compressing a bushing 462 via screwing a cap 464 onto threads 463 of the coupler body 454. The inlet 146 of the coupler 130a includes a rotatably adjustable sleeve portion 146a provided over the coupler body 454 with sealing elements 465, such as O-rings, provided therebetween and on both sides of at least one opening 466 in the coupler body 454. The opening 466 provides a flow path for the heated fluid from the low pressure feed line 144 via the inlet 146. The heated fluid feed line 144 and the inlet 146 of the coupler 130a can be connected via a threaded engagement 467, and one or more sealing elements 468 can sealingly engage the outlet 148 and the return line 149. A continuous low pressure passage 124 is thus formed from the feed line 144, the opening 466, the area between the high pressure line 121 and the coupler body 254, and the low pressure passageway of the fuel injector T piece 127. As the couplers 126, 128, and double walled segments 120 described above, the coupler 130a can provide a high degree of modularity and efficiency in manufacturing. For example, comparing the coupler body 252 of
Referring again to
The arrows with solid tails in
Some current fuel systems utilize double wall segments as a way to avoid potential hazards or undesirable situations that can occur with a rupture of the inner high pressure line, such as spraying high pressure fuel onto hot surfaces of an engine. In these systems, the low pressure outer line is a shell arrangement that captures this high pressure fuel spray or leakage and routes it back to a drain hose or sensor to detect the leakage and warn the operator that a fuel leakage has occurred. In normal operation of current systems, no fluid of any kind should exist in an area between the inner high pressure line and the outer low pressure line. By contrast, embodiments consistent with the claimed invention permit heated fluid, for example, hot engine coolant, to be circulated in that low pressure space during extended cold soak shutdown to keep the high pressure lines warm, and thus reduce the viscosity of fuel in these heated lines to avoid problems related to unintended flow limiter closings.
Rather than simply plugging an end of the double walled segment, embodiments include a new coupling to the last injector in the bank of daisy chained injectors to provide a low pressure heated fluid loop ingress or egress. A similar coupling can be installed near the outlet 117 of the high pressure fuel pump 116. These couplings can be connected by a flexible hose system to the circulation pump and coolant heater reservoir to form a heated fluid circuit.
In some embodiments, a fuel supply system can include one or more thermostats, actuators and valves that allow heated fluid to circulate through the closed low pressure loop including the heat exchanger, such as the double walled configuration described above, only when a cold start condition exists. When the fuel supply system is warmed through operation or the ambient environment, the low pressure loop can be opened to allow heated fluid to return to the heat fluid reservoir. This would enable switching, or converting portions of the low pressure passage including the heat exchanger between a first heated fluid recirculation mode, such as in embodiments described above, and a second dry mode where, in the event of fuel leakage from a rupture of the high pressure fuel line, leaking fuel is redirected to a leakage detection device, such as a low pressure fuel sensor and/or a tell-tale port that provides a visual indication that the heated fluid is present and the heating system.
In the second dry mode, which can be activated or active when a cold start condition does not exist (i.e., when the fuel is at or less than a target viscosity), a portion of the low pressure loop including the heat exchanger/fuel containment housing 612 is purged of any heated fluid, and heated fluid is prevented from entering the purged portion of the low pressure loop. In this way, the purged portion of the low pressure loop is converted to a dry configuration that can contain fuel leakage in the event of a rupture in the high pressure fuel line portion 621.
To control conversion between the first and second modes, a temperature sensor (not shown) can be provided at a point along a low pressure or a high pressure portion of the fuel supply to sense the temperature of fuel supplied to the high pressure fuel line 621, although temperature sensors can be provided elsewhere, for example, in the fuel system, the ambient environment, and/or the engine, to determine whether a cold start condition exists. A control module 634 can monitor the sensed temperature and control the LP pump 642 based on the sensed temperature. For example, if the control module 634 determines the sensed temperature is above a predetermined threshold value for maintaining viscosity at below a target value, the control module 634 can turn off the LP pump 642, which causes the heated fluid source to cease circulating heated fluid. The system can then be purged using a multi-port valve 680 positioned along the path of the feed line 644. For example, two ports of the valve 680 can permit flowing circulated heated fluid from the LP pump 642 to the heat exchanger/fuel containment housing 612 during the first mode (i.e., during a cold start condition), but in the second mode the valve 680 shuts off the low pressure path leading from the LP pump 642 and momentarily allows pressurized gas from a pressurized gas source 682 that is fluidly connected to a third port of the valve 680 to enter the low pressure feed line 644, the heat exchanger/fuel containment housing 612, and the return line 649 to force the heated fluid in these portions into the heated fluid reservoir 640. A vent 684 can be provided at the heated fluid reservoir 640 to vent compressed gas blown into it during the momentary purge period. The pressurized gas source 682 can be an air compressor that supplies compressed air, for example, a shop compressor, although stationary and mobile applications can use other sources of pressurized gas, such as an air pump electrically or mechanically driven by the engine, exhaust gas from an operating engine's exhaust, stored compressed gas, etc.
After purging the heat exchanger/fuel containment housing 612 of heated fluid, the valve 680 shuts off the pressurized gas while continuing to close the path to the LP pump 642. Another valve 686 can be provided downstream of the heat exchanger/fuel containment housing 612 in the return line 649 and closed after purging the heated fluid to completely isolate the heated fluid reservoir 640 and LP pump 642 from the heat exchanger/fuel containment housing 612.
In some embodiments, the valve 680 and/or valve 686 can include a sufficient number of ports to provide fluid communication between the heat exchanger/fuel containment housing 612 and at least one fuel leakage detection device, although one or more fuel detection devices may be positioned elsewhere in the low pressure path of the low pressure feed line 644 downstream of the valve 680, the heat exchanger/fuel containment housing 612, and upstream of valve 686 in the return line 649.
Any of the above embodiments described with respect to
The inner high pressure line and outer low pressure line material should be compatible with any type of fluids that can come into contact with them for long periods under the operating conditions (temperatures, pressures, pH etc.) to minimize deterioration such as corrosion. When selecting line material, characteristics to consider is strength, thermal-conductivity, and corrosion-resistance. Exemplary high quality line materials typically includes metals, such as copper alloy, stainless steel, carbon steel, non-ferrous copper alloy, Inconel, nickel, Hastelloy and titanium. Poor choice of line material can result in a leak through an inner high pressure line between the outer low pressure line shell, which can cause fluid cross-contamination and loss of pressure.
The fuel heating system and method described herein can be used in any of a variety of applications requiring an internal combustion engine, such as mobile and stationary heavy duty machines, vehicles including heavy and light duty trucks and automobiles, construction equipment and the like. Although a limited number of embodiments is described herein, one of ordinary skill in the art will readily recognize that there could be variations to any of these embodiments and those variations would be within the scope of the appended claims. For example, embodiments consistent with the present description can include a double walled configuration such as described in U.S. Pat. No. 6,928,984, the entire disclosure of which is hereby incorporated herein by reference. In this configuration, the common rail comprises double walled segments joined to one another and separated from each fuel injector by a flow limiter that taps the high pressure line of a double walled segment. From the present disclosure, modifications necessary to create a recirculation circuit including heated fluid consistent with the claimed subject matter would be readily apparent. Thus, it will be apparent that the invention described herein can be applied to fuel systems having plural injectors with one inlet port that are not configured in a daisy chain arrangement, such as described above with respect to
In addition to coolant as heated fluid in the above embodiments, heated fluid can include hot oil, hot water, steam, hot air or any other hot liquid or gas that can be circulated through the low pressure heated fluid loop. For example, standby power generators generally have a block heater that heats the oil and coolant contained therein to about 100° F., so a heater and heated fluid reservoir is already present in such existing applications.
Thus, it will be apparent to those skilled in the art that various changes and modifications can be made to the fuel heating system and method described herein without departing from the scope of the appended claims and their equivalents.
| Number | Date | Country | |
|---|---|---|---|
| 61304959 | Feb 2010 | US |
