Patent ID: 12234758

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears.

FIG.1illustrates an engine100with a water-cooled exhaust assembly, according to at least one example. The engine100may be any engine configured to generate electricity and/or mechanical energy using a gaseous fuel, for example, such as an internal combustion engine. Gaseous fuels are fuels that are in a gaseous state under ordinary conditions such as at standard temperature and pressure. Gaseous fuels may include, for example, methane, ethane, liquified natural gas (LNG), propane, blends of these, and the like.

Though described herein with reference to gas engines, the systems and methods described herein may be implemented with other systems that are water-cooled, oil-cooled, or otherwise liquid-cooled and may experience a hot shutdown event. Though described herein with respect to water and water-based coolants, in some examples the coolant may be oil-based or other types of coolant. Additionally, such systems as described herein may include an exhaust gas recirculation cooler, turbo, and other such systems.

The engine100includes an exhaust manifold102that receives exhaust gases from the combustion chamber of the engine100. The exhaust manifold102may include a water-cooled exhaust manifold to lower surface temperatures of the gas engine, for example. The exhaust manifold102includes ports for receiving exhaust gases from the gas engine, for example through exhaust ports of the engine. The ports provide conduits for exhaust gases to travel from the engine exhaust ports to an exhaust conduit of the exhaust manifold102. The exhaust manifold102provides an exit114for transporting exhaust gases away from the gas engine for treatment and/or dispersal. The exhaust manifold102also includes a coolant exit for transporting heated coolant away from the exhaust manifold102.

The exhaust manifold102includes a water-cooled sleeve that surrounds a central exhaust conduit. The water-cooled sleeve may be fed by coolant through supply lines to provide coolant circulation into and away from the exhaust manifold102, for example to transport heat away from the exhaust manifold102. The coolant circulation may be forced through the use of a coolant pump system of the engine100and/or an external pump system. The coolant circulation may cause coolant to flow along the length of the exhaust manifold102to absorb heat energy and transport heat energy away from the exhaust manifold102. The water-cooled sleeve contains a coolant volume used to absorb heat energy from the exhaust gases and provide temperature control and cooling of the exhaust manifold102.

The exhaust manifold102is designed with steel and cast-iron components, in some examples. The coolant may flow into and out of the water-cooled sleeve through the supply lines. During operation of the engine, the coolant is actively flowing (e.g., pumped) through the supply lines to supply coolant to the water-cooled sleeve and control the temperature of the exhaust manifold102. When the gas engine is shut down from a full-load or high operating load, the coolant may cease to flow through the supply lines as the pump may be coupled and/or run with and/or by the engine100(e.g., due to the coolant pump being shutdown by shutdown of the engine) and result in stagnant coolant within the water-cooled sleeve of the exhaust manifold102.

In typical systems, stagnant coolant within the water-cooled sleeve may result in local vapor pockets as the coolant continues to absorb heat from the exhaust manifold102and is not circulated through the supply lines. Such vapor pockets may result, in typical systems, in stresses and damages to the exhaust manifold102.

If the exhaust manifold102is dry, especially for more than an incidental period of time, then the engine100may be at risk of natural gas auto ignition due to elevated temperatures that may spike at the exhaust manifold102. The water-cooled sleeve mitigates this risk by reducing the temperatures at the exhaust manifold102. Additionally, the water-cooled sleeve of the exhaust manifold102reduces a turbo turbine inlet temperature, which increases altitude capability and enables operating at increased rotational rates.

Coolant for the engine100passes through the engine heads and into the water-cooled sleeve of the exhaust manifold102, which maintains the outer metal surface of the exhaust manifold102within a predetermined range. The exhaust manifold102has internal metal mass due to exhaust tubes and radiation shields (such as shown and described herein) that heats up to near exhaust temperatures while the engine100is operating. These components may be considerable hotter compared to the inner shell of the water-cooled sleeve that is continuously being cooled by the coolant flow. At shutdown, the coolant flow stops, and the internal heat of the exhaust manifold102begins to transfer into the inner shell and coolant. In some typical systems, the coolant in the manifold may boil after shutdown. Boiling causes vapor to build up in the top portion of the manifold, which can result in an air gap at the top portion of the manifold. This results in the inner coolant shell temperature increasing higher than the outer coolant shell, which results in different thermal expansion, high stresses, metal cracking, and leaks. The existing coolant lines and vent lines of typical systems do not allow for sufficient venting of vapor, therefore, the thermosiphon effect, a passive thermal management that relies on natural convection, is not effective at mitigating boiling after shutdown in such typical systems.

The exhaust manifold102and engine100described herein are equipped with an expansion tank104(e.g., a phase separation tank) via one or more vent lines. The one or more vent lines may include conduit106. The engine100includes an expansion tank104(which may include one or more expansion tanks) that rest at a height above a height of the exhaust manifold102. The conduit106passes from the liquid passage of the water-cooled sleeve of the exhaust manifold102and to the expansion tank104. In operation, as vapor bubbles form in the exhaust manifold102(e.g., in the water-cooled sleeve), the vapor bubbles travel along the conduit106to the expansion tank104, thereby separating the vapor bubbles from the coolant and preventing dry manifold conditions. Accordingly, the conduit106has a positive slope from the exhaust manifold102to the expansion tank104. The conduit106extends from a port108at the exhaust manifold102where the conduit106is in fluid communication with the water-sleeve of the exhaust manifold102.

In some examples, and as illustrated inFIG.1, the engine100may include a second expansion tank110. The second expansion tank110may be positioned adjacent a first end of the exhaust manifold102while the expansion tank104may be adjacent a middle portion or second end of the exhaust manifold102. In addition to providing additional capacity, the second expansion tank110may enable the conduit106and the conduit112that passes from the exhaust manifold102(e.g., at the port116) to the second expansion tank110to be substantially vertical (e.g., having a near-vertical slope). In some examples, the slope of the conduit106and the conduit112is positive across the entire length of the conduit such that vapor travels along the conduit106and the conduit112to the expansion tank104and the second expansion tank110, respectively.

The expansion tank104and the second expansion tank110may each contain a volume that may be occupied by liquid as well as vapor. For instance, the expansion tank104and the second expansion tank110may each have a first portion occupied by coolant and a second portion occupied by gas. As vapor travels from the exhaust manifold102to the expansion tank104and/or the second expansion tank110, the coolant contained therein may travel in the opposite direction along the conduit106and the conduit112to replace the volume previously occupied by the vapor at the exhaust manifold102. In this manner, the water-cooled sleeve is not emptied or dry, but maintains liquid, even as vapor boils away and travels to the expansion tank104and the second expansion tank110.

The conduit106and the conduit112may have a first diameter that enables vapor to travel from the exhaust manifold102to the expansion tank104and/or the second expansion tank110and simultaneously enables liquid coolant to travel in the opposite direction. The first diameter may be in a range of three-quarters of an inch to one and one-quarter inches or more. In an example, the first diameter may be one inch. This first diameter enables natural flow of gases (e.g., vapor) due to buoyancy and flow of the more (relatively) dense liquid coolant in the opposite direction. In some examples, such as when oil-based fluid is used as the coolant, the first diameter may be larger due to the increased viscosity as compared with water-based coolant. Accordingly, to accomplish the bidirectional travel through a conduit106having a single passageway may require a diameter greater than one inch.

In some examples, such as depicted inFIG.1, multiple conduits106may travel from each exhaust manifold102to the expansion tank104. In some examples, and due to the natural flow of the vapor and coolant, one or more of the multiple conduits106may include flow only in a single direction while a second conduit of the multiple conduits106may include flow in a single direction opposite the flow direction (e.g., into or out of the expansion tank) of the other conduit.

In some examples, each exhaust manifold102may have one or more expansion tanks. Accordingly, in a system where each exhaust manifold has two expansion tanks, the engine100may have four expansion tanks distributed across the exhaust manifolds102.

The expansion tank104and the second expansion tank110may each couple to a coolant reservoir, such as a shunt tank, or other portion of the cooling system such that coolant is always available at the expansion tank104and the second expansion tank110. The expansion tank and second expansion tank110may be coupled to the coolant reservoir through a second set of conduits (not pictured inFIG.1) that have a second diameter. The second diameter is less than the first diameter. The second diameter may be in a range of up to three-quarters of an inch and/or in a range of one-quarter of an inch to three-quarters of an inch. The second diameter is smaller than the first diameter such that the coolant system does not bypass through the expansion tank104but instead provides for the coolant system of the engine100to operate as designed, while also enabling use of the expansion tank104. A larger diameter conduit to the coolant reservoir may result in natural convection causing bypass flows that would alter the performance of the coolant system for the engine100.

Accordingly, the expansion tank104, provides for preventing overheating of the exhaust manifold during or after a hot shutdown of the engine100. Accordingly, heat stored within the exhaust manifold102(e.g., within the metal) may be absorbed by coolant and may result in boiling of the coolant. The vapor may then rise up the conduit106and out of the exhaust manifold to the expansion tank104, and be replaced within the exhaust manifold by coolant from the expansion tank104that flows down along the conduit106due to gravity and natural pressures within the system. The internal structure of the exhaust manifold102may provide for such benefits, as shown inFIG.4.

In examples and systems described herein, the exhaust manifold102may be implemented in any gas engine system without requiring any changes to the gas engine or downstream exhaust system. As such, the exhaust manifold assemblies designed with the heat capacitance ratios described herein may be retrofitted to existing systems as well as implemented on new systems of gas engines.

FIG.2illustrates a side view of the water-cooled exhaust assembly200of the engine100ofFIG.1including expansion tanks, according to at least one example. The water-cooled exhaust assembly200includes an exhaust manifold202which may be the same or similar to the exhaust manifold102ofFIG.1. In some examples, the exhaust manifold202may instead be replaced by any other actively cooled component that is cooled through contact with a coolant such as water or oil. The exhaust manifold202delivers exhaust gases from the engine to an exit206where the exhaust gases may be released and/or used to feed into a turbocharger system.

The exhaust manifold202is a water-cooled manifold that includes a sleeve around the exhaust conduit of the exhaust manifold202. In particular, the exhaust manifold202may include an inner conduit that has an axis about which the inner conduit is disposed. The water sleeve is disposed radially outward of the inner conduit such that coolant contained by the water sleeve at least partially surrounds the inner conduit. In some examples, the exhaust manifold202may include a radiation shield between the inner conduit and the water sleeve, such as depicted inFIG.4.

The exhaust manifold202receives coolant at an inlet204where the coolant is provided by a coolant system of the engine. The coolant system may pump the coolant or otherwise provide for flow of the coolant such that the coolant actively circulates to cool the exhaust manifold202and/or additional other components of the engine. An outlet of the exhaust manifold provides for coolant to leave the exhaust manifold202to travel to a subsequent system such as a radiator or other component included in the coolant system of the engine.

The water-cooled exhaust assembly200includes a first expansion tank208and a second expansion tank214. The first expansion tank208and the second expansion tank214may be formed of any suitable material including metals, plastics, composites, or other such materials that may withstand the temperatures of the vapor and the coolant. The first expansion tank208fluidly couples with the exhaust manifold202, specifically with the water sleeve of the exhaust manifold202. The first pipe210provides a first conduit from at or near a first end of the exhaust manifold to the first expansion tank208. A second pipe212provides a second conduit from a middle portion of the exhaust manifold202to the first expansion tank208. A third pipe216provides a third conduit from at or near a second end of the exhaust manifold202to the second expansion tank214. The first pipe210, second pipe212, and third pipe216may be formed of a hydraulic line, rubber line, plastic line, metal, or other liquid and gas-tight material that may withstand the temperatures of the coolant and vapor.

The first expansion tank208and the second expansion tank214may each contain a volume that may be occupied by liquid as well as vapor. For instance, the first expansion tank208and the second expansion tank214may each have a first portion occupied by coolant and a second portion occupied by gas. As vapor travels from the exhaust manifold202to the first expansion tank208and/or the second expansion tank214, the coolant contained therein may travel in the opposite direction along the conduits to replace the volume previously occupied by the vapor at the exhaust manifold202. In this manner, the water-cooled sleeve of the exhaust manifold202is not emptied or dry, but maintains liquid, even as vapor boils away and travels to the first expansion tank208and the second expansion tank214.

The first pipe210, second pipe212, and third pipe216are shown in a particular configuration and orientation, but may be connected to the exhaust manifold at any position. In one embodiment, the pipes couple to the exhaust manifold202at an upper surface of the water sleeve such that as vapor is formed within the water sleeve the gases travel along the pipes to the expansion tanks. The pipes may have a first diameter that enables vapor to travel from the exhaust manifold202to the first expansion tank208and/or the second expansion tank214and simultaneously enables liquid coolant to travel in the opposite direction. The first diameter may be in a range of three-quarters of an inch to one and one-quarter inches or more. In an example, the first diameter may be one inch. This first diameter enables natural flow of gases (e.g., vapor) due to buoyancy and flow of the more (relatively) dense liquid coolant in the opposite direction. In some examples, such as when oil-based fluid is used as the coolant, the first diameter may be larger due to the increased viscosity as compared with water-based coolant. Accordingly, to accomplish the bidirectional travel through a single conduit may require a diameter greater than one inch.

The first expansion tank208and the second expansion tank214are positioned at a first height and a second height relative to a height of the exhaust manifold202. The first height and the second height are greater than the height of the exhaust manifold such that vapor will flow to the expansion tanks from the exhaust manifold202through the conduits. The first height and the second height may be different and/or the same in various embodiments, so long as the first height and the second height are greater than a height of the exhaust manifold202. Additionally, as described herein, the conduits have a positive slope along the length of the conduits from the exhaust manifold202to the expansion tanks such that the vapor may travel solely due to buoyancy and not be trapped within the pipes. Further the conduits couple to the expansion tanks at a bottom surface and/or near a bottom surface of the expansion tanks such that the liquid coolant of the expansion tanks is at the entrance of the conduits into the expansion tanks and able to flow downwards along the conduits to the exhaust manifold202.

The first expansion tank208and the second expansion tank214may each couple to a coolant reservoir, such as a shunt tank, or other portion of the cooling system such that coolant is provided to the first expansion tank208and the second expansion tank214to maintain a level of coolant within the expansion tanks such that as vapor is generated within the exhaust manifold the volume of the vapor may be replaced by coolant from the expansion tanks. The first expansion tank208and second expansion tank214may be coupled to the coolant reservoir through a second set of conduits that have a second diameter. For instance, the first expansion tank208couples through a tube218and the second expansion tank214couples to the coolant reservoir through a tube220. The second diameter is less than the first diameter. The second diameter may be in a range of up to three-quarters of an inch and/or in a range of one-quarter of an inch to three-quarters of an inch. The second diameter is smaller than the first diameter such that the coolant system does not bypass through the expansion tank but instead provides for the coolant system of the engine to operate as designed, while also enabling use of the expansion tank. A larger diameter conduit to the coolant reservoir may result in natural convection causing bypass flows that would alter the performance of the coolant system for the engine.

The coolant within the water sleeve of the exhaust manifold202absorbs heat from the exhaust gases to control the temperature at the manifold and/or exhaust gases for one or more purposes, such as to prevent reignition, maintain temperatures at a turbocharger, or other such reasons.

FIG.3illustrates a perspective view of a water-cooled exhaust assembly300and coolant system, according to at least one example. The water-cooled exhaust assembly300includes exhaust manifolds302similar and/or identical to the exhaust manifolds102and/or exhaust manifolds202described herein. The water-cooled exhaust assembly300further includes exhaust exits304where exhaust gases are directed to exit the exhaust manifolds302. The water-cooled exhaust assembly300further includes coolant inlets306and coolant exits324for the coolant system of an engine or other system to actively circulate coolant through the exhaust manifolds302.

The water-cooled exhaust assembly300includes a first expansion tank308, a second expansion tank310, and a coolant reservoir320. The first expansion tank308and the second expansion tank310may be similar and/or identical to the first expansion tank208and the second expansion tank214ofFIG.2, respectively. The first expansion tank308fluidly couples with the exhaust manifolds302through pipes312and the second expansion tank310fluidly couples with the exhaust manifolds302through pipes314and316. Though depicted as having two expansion tanks with three sets of tubes, the water-cooled exhaust assembly300may have more or fewer numbers of expansion tanks (e.g., one, two, three, four, five, six, or more). Additionally, the first expansion tank308and the second expansion tank310are depicted as coupled to both exhaust manifolds302. In some examples, each of the exhaust manifolds302may have separate expansion tanks. In some examples, the expansion tanks may each have one, two, three, four, or more tubes that couple to the exhaust manifolds302.

The first expansion tank308fluidly couples with a coolant reservoir320through a pipe318. The second expansion tank310fluidly couples with the coolant reservoir320through a pipe322. The coolant reservoir320may be positioned or stored in a separate area within an implementation of the water-cooled exhaust assembly300. The coolant reservoir320may be capable of providing coolant to the expansion tanks to maintain a level of coolant within the expansion tanks. The level of coolant may be controlled through the use of level measurement systems such as laser level indicators, floats, and the like. In some examples, the pipe318and the pipe322may include one or more valves that may be actuated to provide coolant into the expansion tanks. The valves may be actuated manually in some examples to increase the level of coolant to a desired level. The valves may be actuated automatically based on a control system that receives sensor data from a float or level sensor within the expansion tanks. The valves may also be actuated to open upon a shutoff of the engine to provide coolant to the expansion tanks upon a hot shutdown event. The coolant reservoir320may provide coolant to the expansion tanks through a pumping or circulation system of the engine. In some examples the coolant may be pumped or circulated into the expansion tanks as part of the coolant circulation within the engine. The relatively smaller diameter of the pipe318and pipe322as compared with the pipes312, pipes314, and pipes316results in free natural convection and circulation through the pipes312, pipes314, and pipes316(as described herein) while natural convection and flow through pipe318and pipe322may be limited to prevent bypassing the coolant system of the engine.

FIG.4illustrates a cross-section view illustrating a water-cooled exhaust assembly400with an expansion tank418, according to at least one example. The water-cooled exhaust assembly400includes an exhaust manifold402that has an exhaust conduit406for transporting exhaust gases, a radiation shield404disposed radially outward from the exhaust conduit, and a water-cooled sleeve408that contains coolant from the coolant system.

The water-cooled exhaust assembly400further includes a conduit412from an upper surface of the water-cooled sleeve408to an expansion tank418. The expansion tank418is shown having a first portion420with liquid coolant and a second portion424with gas or vapor.

The inner shell of the water-cooled sleeve408is oriented annularly about an axis that lies along a center of the exhaust conduit406and radially outward of the radiation shield404. The coolant (water, for example) flows into the water-cooled sleeve408that may have an annular shape. Exhaust gases may, in some examples, flow through the annular passage between the radiation shield404and the inner shell of the water-cooled sleeve408and/or the exhaust conduit406. In such examples, the exhaust conduit406and/or radiation shield404may each define one or more passages, openings, or conduits to enable exhaust gases to travel from the exhaust conduit to the interstitial spaces between the exhaust conduit406, radiation shield404, and inner shell of the water-cooled sleeve408.

The expansion tank418has a conduit426that provides a fluid connection to a coolant reservoir. The conduit426has a diameter428that is less than the diameter414. The conduit412may have a diameter414that enables vapor410that forms in the exhaust manifold402to travel from the exhaust manifold402to the expansion tank418and simultaneously enables liquid coolant to travel in the opposite direction. The diameter414may be in a range of three-quarters of an inch to one and one-quarter inches or more. In an example, the diameter414may be one inch. This diameter414enables natural flow of gases (e.g., vapor) due to buoyancy and flow of the more (relatively) dense liquid coolant in the opposite direction. In some examples, such as when oil-based fluid is used as the coolant, the diameter414may be larger than one inch due to the increased viscosity as compared with water-based coolant. Accordingly, to accomplish the bidirectional travel through the conduit412may require a diameter greater than one inch. The expansion tank418may couple to a coolant reservoir, such as a shunt tank, or other portion of the cooling system such that coolant is always available at the expansion tank418. The expansion tank418may be coupled to the coolant reservoir through the conduit426that has a diameter428. The diameter428is less than the diameter414. The diameter428may be in a range of up to three-quarters of an inch and/or in a range of one-quarter of an inch to three-quarters of an inch. The diameter428is smaller than the diameter414such that the coolant system does not bypass through the expansion tank418but instead provides for the coolant system of the engine to operate as designed, while also enabling use of the expansion tank418. A larger diameter conduit to the coolant reservoir may result in natural convection causing bypass flows that would alter the performance of the coolant system for the engine.

The coolant within the water-cooled sleeve408passes through the engine heads and into the water-cooled sleeve408of the exhaust manifold402, which maintains the outer metal surface of the exhaust conduit406and/or the exhaust manifold402within a predetermined range. The exhaust manifold402has internal metal mass due to exhaust tubes and radiation shields (such as shown and described herein) that heats up to near exhaust temperatures while the engine is operating. These components may be considerable hotter compared to the inner shell of the water-cooled sleeve408that is continuously being cooled by the coolant flow. At shutdown, the coolant flow stops, and the internal heat of the exhaust manifold402begins to transfer into the coolant. In some typical systems, the coolant in the manifold may boil after shutdown. Boiling causes vapor410to build up in the exhaust manifold402, specifically within the water-cooled sleeve408, which can result in an air gap at the top portion of the water-cooled sleeve408. The vapor416travels, instead of gathering, up the conduit412and into the expansion tank418. At the same time, coolant from the first portion420flows down the conduit412into the water-cooled sleeve408to prevent overheating of the exhaust manifold402.

INDUSTRIAL APPLICABILITY

The present disclosure provides systems and methods for preventing coolant boiling in post-shutdown environments of water-cooled exhaust manifolds to reduce damage to parts and components. In typical systems, stagnant coolant within the water-cooled sleeve of the manifold may result in local vapor pockets as the coolant continues to absorb heat from the exhaust manifold assembly and is not circulated through coolant supplies. Such vapor pockets may result, in typical systems, in stresses and damages to the exhaust manifold assembly. Such stressed and damages lead to excessive part wear and costly downtime for equipment.

Accordingly, the exhaust manifold assembly described herein, provides for preventing creation of the vapor pockets by having an expansion tank and at or near vertical conduits that have a diameter sufficient to allow bidirectional simultaneous travel of vapor and coolant between the manifold and the expansion tank to prevent collection of vapor within the water-cooled manifold that would otherwise result in overheating and damage to the exhaust manifold. Accordingly, heat stored within the exhaust manifold assembly (e.g., within the metal) may be absorbed by coolant and as coolant vaporizes, it is replaced by coolant from the expansion tank such that the coolant does not boil away and leave the exhaust manifold with vapor pockets during a hot shutdown event.

In one illustrative example, the engine is a Caterpillar G3500 gas engine used to convert landfill gas into electrical energy. The engine includes a water-cooled exhaust manifold. The manifold includes an exhaust tube defining a main exhaust passage. The exhaust tube includes one or more holes in the end of the tube opposite an exhaust outlet. The exhaust enters the manifold through several exhaust inlets and flows from the inlets to the exhaust outlet. A water jacket is oriented radially outward of the exhaust tube and configured to carry water to provide cooling for exhaust surfaces. The water jacket and exhaust tube may be separated by a radiation shield. The exhaust flows from the hole, through the passage, to the exhaust outlet during steady state operation of the engine. After a hot shutdown event, the water jacket contains coolant and connection to an expansion tank such that residual heat that causes coolant boiling allows vapor to collect away from the exhaust manifold and be replaced by liquid coolant at the exhaust manifold flowing from the expansion tank and thereby preventing associated damage to engine components.

While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.