EXHAUST ASSEMBLY HEAT MITIGATION SYSTEM

Abstract

This disclosure describes, in part, systems and structures for an exhaust assembly that includes an exhaust tube and an insulation structure surrounding the exhaust tube. The insulation structure is offset from the exhaust tube to create an air gap around the exhaust tube and the insulation structure. The air gap is used to transport forced air by a fan system to mitigate and remove heat from the exhaust tube to a disposal location. The insulation structure includes an inner shell and an outer shell that contain an insulation component to provide a reduced surface temperature during steady state operation within a threshold range.

Claims

1. An exhaust assembly comprising: an exhaust tube defining a substantially central axis, wherein the exhaust tube is configured to direct an exhaust gas away from an engine to which the exhaust tube is fluidly connected; an insulation structure positioned concentrically around the exhaust tube, the insulation structure including: a standoff coupled to the exhaust tube and providing an air gap between the exhaust tube and the insulation structure; an inner shell coupled to the standoff and concentric about the exhaust tube; an outer shell concentric about the inner shell; and an insulation layer disposed between the inner shell and the outer shell; and a forced air system that drives air through the air gap along a length of the exhaust tube.

2. The exhaust assembly of claim 1, wherein the insulation layer comprises aerogel.

3. The exhaust assembly of claim 1, wherein the standoff comprises a porous metal mesh disposed in the air gap between the inner shell and the exhaust tube.

4. The exhaust assembly of claim 1, wherein the insulation layer comprises rock wool insulation.

5. The exhaust assembly of claim 1, wherein the exhaust gas travels along the exhaust tube in a first direction and the forced air system drives the air in a second direction opposite the first direction.

6. The exhaust assembly of claim 1, wherein the exhaust gas travels along the exhaust tube in a first direction and the forced air system drives the air in a second direction parallel to the first direction.

7. The exhaust assembly of claim 1, wherein the forced air system comprises a fan at a first end of the insulation structure configured to pull air through the air gap from a second end to the first end.

8. An exhaust insulation system comprising: an inner shell disposed radially outward from an exhaust tube; an outer shell disposed radially outward from the inner shell; an insulation layer disposed between the inner shell and the outer shell; a support coupled between the inner shell and the exhaust tube that supports the inner shell and provides an air gap between the inner shell and the exhaust tube; and a forced air system comprising: a first opening at a first end of the exhaust insulation system providing access to the air gap; a second opening at a second end of the exhaust insulation system providing access to the air gap; and a fan positioned adjacent the first opening and configured to drive air through the air gap.

9. The exhaust insulation system of claim 8, wherein the insulation layer comprises shredded aerogel insulation.

10. The exhaust insulation system of claim 8, wherein the fan is configured to drive the air through the air gap in a first direction opposite a direction of travel of exhaust within the exhaust tube.

11. The exhaust insulation system of claim 8, wherein the fan is configured to drive the air through the air gap in a second direction opposite a direction of travel of exhaust within the exhaust tube.

12. The exhaust insulation system of claim 8, wherein the support comprises metal fins coupled between the exhaust tube and the inner shell.

13. The exhaust insulation system of claim 8, further comprising a radiation shield positioned in the air gap between the exhaust tube and the inner shell, the radiation shield defining one or more openings.

14. The exhaust insulation system of claim 8, wherein the support comprises a metal mesh.

15. The exhaust insulation system of claim 8, wherein the inner shell and the outer shell define a plurality of openings along a length of the exhaust tube.

16. A system comprising: an internal combustion engine; and an exhaust assembly fluidly connected with the internal combustion engine, wherein the exhaust assembly comprises: an exhaust tube oriented about an axis, wherein an exhaust gas is configured to flow through the exhaust tube away from the internal combustion engine; an insulation structure positioned concentrically around the exhaust tube, the insulation structure including: a standoff coupled to the exhaust tube and providing an air gap between the exhaust tube and the insulation structure; an inner shell coupled to the standoff and concentric about the exhaust tube; an outer shell concentric about the inner shell; and an insulation layer disposed between the inner shell and the outer shell; and a forced air system that drives air through the air gap along a length of the exhaust tube.

17. The system of claim 16, wherein the insulation layer comprises a shredded aerogel insulation.

18. The system of claim 16, wherein the standoff comprises a porous metal mesh.

19. The system of claim 16, wherein the forced air system is configured to drive the air through the air gap in a direction parallel with a direction of travel of the exhaust gas.

20. The system of claim 16, wherein the forced air system is configured to drive the air through the air gap in a direction opposite a direction of travel of the exhaust gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items or features.

[0010] FIG. 1 illustrates an exhaust assembly with a heat mitigation and insulation system for an internal combustion engine, according to at least one example.

[0011] FIG. 2 illustrates a section view of an exhaust assembly with a heat mitigation system for an internal combustion engine, according to at least one example.

[0012] FIG. 3 illustrates a cross-section view illustrating an exhaust assembly with a heat mitigation system for an internal combustion engine, according to at least one example.

[0013] FIG. 4 illustrates a cross-section view illustrating a portion of an exhaust assembly with a heat mitigation system, according to at least one example.

[0014] FIG. 5 illustrates a cross-section view illustrating a portion of an exhaust assembly with a heat mitigation system, according to at least one example.

[0015] FIG. 6 illustrates a detail view of a heat mitigation system for an exhaust assembly, according to at least one example.

DETAILED DESCRIPTION

[0016] 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.

[0017] FIG. 1 illustrates an exhaust manifold 102 for an internal combustion engine 101, according to at least one example. The internal combustion engine 101 may be any engine configured to generate electricity and/or mechanical energy using a fuel. Fuels for the internal combustion engine 101 may include fuels such as diesel, hydrogen, gaseous fuels, and other such fuels used to power internal combustion engines. Gaseous fuels may include fuels that are in a gaseous state under ordinary conditions such as at standard temperature and pressure. Gaseous fuels may include, for example, hydrogen, methane, ethane, liquified natural gas (LNG), propane, blends of these, and the like.

[0018] Though described herein with reference to internal combustion engines, the systems and methods described herein may be implemented with other heat-generating systems that may need heat mitigation to reduce wear and thermal stresses that lead to failure of components. For example, such systems may include an exhaust gas recirculation cooler, turbo, and other such systems.

[0019] The exhaust manifold 102 may include an insulation structure that provides for heat mitigation as well as lower surface temperatures of the internal combustion engine 101, for example. The exhaust manifold 102 includes ports 104 for receiving exhaust gases from the internal combustion engine 101, for example through exhaust ports of the internal combustion engine 101. The ports 104 provide conduits for exhaust gases to travel from the engine exhaust ports to an exhaust tube 106 of the exhaust manifold 102. The exhaust manifold 102 provides an exit 108 for transporting exhaust gases away from the internal combustion engine 101 for treatment and/or dispersal.

[0020] In some examples, the insulation may be effective at preventing the exterior temperature of the exhaust assembly from exceeding 300 degrees Celsius. The use of aerogel or other such insulation may make such a temperature differential possible in a compact space such that the thickness of the insulation and the thickness of the air gap is less than a thickness of a typical insulation that may have a lower thermal resistance than the aerogel. Accordingly, the configuration included herein provides for a more compact profile surrounding the exhaust assembly while maintaining or exceeding the performance of typical exhaust systems.

[0021] The exhaust manifold 102 includes an insulation structure 110 that surrounds the exhaust tube 106. The insulation structure 110 includes multiple layers and provides for heat mitigation through forced convection as well as reduced surface temperatures and radiation to surrounding components. The insulation structure 110 provides for forced convection through an air gap 118 between the exhaust tube 106 and an insulation layer 120. The forced convection is a result of fans 112 that draw air 114 into the air gap 118 at a first end of the exhaust manifold 102 and expels the air 116 at a second end of the exhaust manifold 102. The forced convection provides heat mitigation as heat is transferred to the air as it is forced through the air gap 118 and expelled at a waste heat disposal location. In some examples, the fan 112 may force the air away from the internal combustion engine 101 such as out of an engine compartment and/or past a radiator or other heat transfer system. In some examples, the air gap 118 may have a thickness of approximately five millimeters around the exhaust tube 106 such that the insulation layer 120 is offset from the exhaust conduit by approximately five millimeters around the circumference of the exhaust conduit.

[0022] The insulation layer 120 may be positioned concentrically about the exhaust tube 106 by one or more standoffs positioned between the insulation layer 120 and the exhaust tube 106. The standoffs may include fins, pins, or structural members that span the air gap 118 without blocking and/or preventing airflow through the air gap 118. The standoffs may, for example include stainless steel or other ribs that couple to an inner shell of the insulation layer 120 and to the exhaust tube 106. In some examples, the standoffs may include a metal mesh or other porous material that fills a gap between the insulation layer 120 and the exhaust tube 106 and supports the insulation layer 120 being spaced away from the exhaust tube 106. In an example, the metal mesh may include a stainless steel mesh that is porous to allow airflow through the air gap 118 while also providing support for maintaining the position of the insulation layer 120 relative to the exhaust tube 106. In an example, the metal mesh may include an open-cell metal foam, metal webbing, or other such material that allows airflow while also providing structural support to the insulation layer 120.

[0023] In some examples, the metal mesh and/or other standoff may provide for additional heat transfer to the air in the air gap 118 as air is forced through the air gap 118. As the air flows through the air gap 118, the additional surface area of the standoffs may enable heat transfer from the exhaust tube 106 to the air to be carried away from the exhaust system for disposal.

[0024] In some examples, the standoffs may include a heat bridge interruption to prevent or reduce heat transferred from the exhaust tube 106 to the insulation layer 120 through the standoffs. For example, the standoffs may include a material having a low thermal conductivity, for example at a middle portion of the standoff and/or be formed of a material with a relatively (compared with stainless steel) low thermal conductivity.

[0025] The exhaust manifold 102 is designed with steel, stainless steel, and/or cast-iron components, in some examples. The exhaust manifold 102 may reach temperatures up to and in excess of 760 degrees Celsius. The high temperatures may cause typical insulation to break down or fail and/or cause a high temperature gradient across a short distance that results in expansion and stresses and failure in the exhaust manifold 102.

[0026] The exhaust manifold 102 and/or the insulation layer (e.g., the inner shell and the outer shell) may include expansion gaps and/or flexible portions to allow for thermal expansion during operation at elevated temperatures.

[0027] The insulation structure 110 provides for a step down in temperature between the surface of the exhaust tube 106 and the insulation layer 120 such that an insulating material such as an aerogel may be used for the insulation layer. Aerogel insulation, such as silica-based aerogel and composite pyrogels may operate and be effective up to a temperature of about 650 degrees Celsius. Accordingly, the insulations structure 110 provides an ability to implement insulation such as aerogels within the insulation layer 120 without the insulation breaking down or failing. The insulation structure includes the air gap 118 with forced convection occurring through the air gap 118 and resulting in a stepped down temperature occurring at the insulation layer 120.

[0028] The insulation layer 120 may be sandwiched between an inner layer and an outer layer, such as an inner shell and an outer shell. In an example, the inner layer or inner shell and the outer layer or outer shell for the insulation layer 120 may be formed for stainless steel or another suitable material. The insulation layer 120 may have a thickness of up to ten millimeters in some examples, such as examples that include an aerogel insulation in the insulation layer 120. The thickness of the insulation layer 120 may be based on reducing the external surface temperature to approximately 300 degrees Celsius or less. In some examples, the insulation layer 120 may be greater than ten millimeters to reach a desired temperature on the outer shell.

[0029] The insulation layer 120 may include aerogel, as mentioned previously, and may include shredded aerogel particles fit between the inner shell and the outer shell, for example by filling a space between the shells with the aerogel particles. The space may be sealed off to retain the aerogel particles, for example with end caps connecting between the inner shell and the outer shell. In some examples, the insulation layer 120 may include an aerogel blanket with aerogel particles suspended or retained in an organic binder. In some examples, the insulation layer 120 may include other types of insulation such as mineral wool insulation, rock wool insulation, vacuum insulation between the inner shell and the outer shell, and other suitable insulation that may withstand the temperatures of the exhaust manifold 102.

[0030] The air gap 118 provides for air to be forced or driven through the air gap 118, heated by proximity with the exhaust tube 106, and expelled at an end and/or an exit of the insulation structure 110. The air gap 118 may extend along a length of the exhaust tube 106, and may include along an entire length of the exhaust tube 106, across a portion of a length of the exhaust tube 106, and/or include multiple insulation structures to span the length of the exhaust tube 106. An entry for air 114 at one end of the exhaust tube 106 and/or insulation structure 110 allows air to enter the air gap 118 from an air source. In some examples, the air source may be connected to ducting to provide air from an external source rather than a local source, such as within an engine compartment. The air source may be external to a vehicle and/or engine compartment and may pass through ducting and/or filters before reaching the air gap 118. The filter may prevent particles, impurities, oils, fuels, and other contaminants from contacting the exhaust tube 106 and potentially igniting.

[0031] The fans 112 are depicted drawing air 114 through the entry and expelling air 116 from the air gap 118 at an exit. The fans 112 may be configured to pull air through the air gap 118 as depicted and/or to push air through the air gap 118 (e.g., in the opposite direction pictured in FIG. 1. The fans may be driven by a power source, and may include electric fans or fans driven using a belt connected to an output shaft of the internal combustion engine 101. In some examples, the fans 112 may include cooling fans for the internal combustion engine 101, with ducting leading from the air gap 118 to the existing cooling fans, such as fans at or adjacent a radiator for a cooling system of the internal combustion engine 101. The fans 112 may also include passive fans, such as fans driven by passive means such as a heat engine. For instance, the fans 112 may include fans driven based on a heat difference such as by a Peltier device and/or Stirling engine that use a heat difference and/or dissimilar metals to produce a voltage for powering the fan and/or use a heat difference to expand and compress a working gas to produce motion of the fans 112. The fans 112 may be positioned at or near the end of the insulation structure 110 with a hot end positioned against and/or adjacent the exhaust tube 106 and a cold end including one or more radiator fins extending away from the exhaust tube 106 such as into the engine compartment.

[0032] FIG. 2 illustrates a section view of an exhaust manifold 102, according to at least one example. The exhaust manifold 102 includes, within the insulation structure 110, an inner shell 124 and an outer shell 126. The inner shell 124 and the outer shell 126 define volume for containing insulation 122 such as the insulation layer 120 described with respect to FIG. 1. The insulation 122 may have a consistent thickness and/or a variable thickness (such as depicted in FIG. 2) around the circumference of the exhaust tube 106. The exhaust manifold 102 extends along an axis, e.g., an axis that aligns with or follows the direction of flow of the exhaust within the exhaust tube 106.

[0033] The inner shell 124 and the outer shell 126 may be joined together at ends of the insulation structure 110 such as with end caps or plates that enclose the insulation 122 within the volume formed between the inner shell 124 and the outer shell 126. In some examples, the insulation may include aerogel, shredded aerogel, aerogel particles, mineral wool insulation, rock wool insulation, aerogel blanket, or other such insulative particles and/or blankets. In an example, the insulation 122 may include vacuum insulation. For instance, in the example, the inner shell 124 and the outer shell 126, when coupled with the end caps of the insulation layer 120, may enclose the insulation 122 such that the volume may be evacuated to provide vacuum insulation across the insulation structure. In some examples, the end caps may be formed, at least partially of an insulative material to prevent heat being transferred across the end caps of the insulation structure 110.

[0034] In examples and systems described herein, the exhaust manifold 102 may be implemented in any internal combustion engine 101 without requiring any changes to the internal combustion engine 101 or downstream exhaust system.

[0035] FIG. 3 illustrates a cross-section view illustrating an exhaust manifold 102 for an internal combustion engine 101, according to at least one example. The exhaust manifold 102 includes an exhaust tube 300 and an insulation structure 302 that may be similar and/or identical to the insulation structure 110 described with respect to FIGS. 1 and 2. The exhaust manifold 102 includes exhaust inlets 306 a-306 h, an exhaust outlet 308, and an exhaust conduit 316. Exhaust gases are received through the exhaust inlets 306 a-306 h, for example, and flow to the exhaust outlet 308 through the exhaust conduit 316.

[0036] The insulation structure 302 includes an inner shell 312 and an outer shell 314. Inner shell 312 and the outer shell 314 enclose the insulation 320. The insulation 320 may include the insulation described herein, such as aerogel particles and other such insulation products. For example, the insulation 320 may include aerogel insulation, such as silica-based aerogel and composite pyrogels may operate and be effective up to a temperature of about 650 degrees Celsius. Accordingly, the insulations structure 302 provides an ability to implement insulation 320 without the insulation breaking down or failing. The insulation structure includes the air gap 304 with forced convection occurring through the air gap 304 and resulting in a stepped down temperature occurring at the insulation 320.

[0037] The insulation structure 302 is retained in position about the exhaust tube 300 by one or more standoffs 322. The standoffs 322 position the insulation structure 302 radially outward of the exhaust tube 300. The standoffs 322 may include fins, pins, or structural members that span the air gap 304 without blocking and/or preventing airflow through the air gap 304. The standoffs 322 may, for example include stainless steel or other ribs that couple to the inner shell 312 and to the exhaust tube 300. In some examples, the standoffs 322 may include a metal mesh or other porous material that fills a gap between the inner shell 312 and the exhaust tube 300 and supports the insulation 320 being spaced away from the exhaust tube 300. In an example, the metal mesh may include a stainless steel mesh that is porous to allow airflow through the air gap 304 while also providing support for maintaining the position of the inner shell 312 and/or the insulation 320 relative to the exhaust tube 300. In an example, the metal mesh may include an open-cell metal foam, metal webbing, or other such material that allows airflow while also providing structural support to the insulation 320.

[0038] In some examples, the metal mesh and/or other standoff 322 may provide for additional heat transfer to the air in the air gap 304 as air is forced through the air gap 304. As the air flows through the air gap 304, the additional surface area of the standoffs 322 may enable heat transfer from the exhaust tube 300 to the air to be carried away from the exhaust system for disposal.

[0039] In some examples, the standoffs 322 may include a heat bridge interruption to prevent or reduce heat transferred from the exhaust tube 300 to the insulation 320 through the standoffs 322. For example, the standoffs 322 may include a material having a low thermal conductivity, for example at a middle portion of the standoff and/or be formed of a material with a relatively (compared with stainless steel) low thermal conductivity.

[0040] The insulation 320 is positioned between the inner shell 312 and the outer shell 314. In an example, the inner shell and the outer shell may be formed for stainless steel or another suitable material. The insulation 320 may have a thickness of up to ten millimeters or more in some examples, such as examples that include an aerogel insulation in the insulation 320. The thickness of the insulation 320 may be based on reducing the external surface temperature to approximately 300 degrees Celsius or less. In some examples, the insulation 320 may be greater than ten millimeters to reach a desired temperature on the outer shell.

[0041] The insulation 320 may include aerogel, as mentioned previously, and may include shredded aerogel particles fit between the inner shell and the outer shell, for example by filling a space between the shells with the aerogel particles. The space may be sealed off to retain the aerogel particles, for example with end caps connecting between the inner shell and the outer shell. In some examples, the insulation 320 may include an aerogel blanket with aerogel particles suspended or retained in an organic binder. In some examples, the insulation 320 may include other types of insulation such as mineral wool insulation, rock wool insulation, vacuum insulation between the inner shell and the outer shell, and other suitable insulation that may withstand the temperatures of the exhaust manifold 102.

[0042] The exhaust manifold 102 also includes an air system 310 that enables forced convection through the air gap 304 between the exhaust conduit 316 and the inner shell 312. The forced convection is a result of the air system 310 that draws air into the air gap 304 at a first end of the exhaust manifold 102 and expels the air at a second end of the exhaust manifold 102. The forced convection provides heat mitigation as heat is transferred to the air as it is forced through the air gap 304 and expelled at a waste heat disposal location. In some examples, the fan air system may force the air away from the internal combustion engine 101 such as out of an engine compartment and/or past a radiator or other heat transfer system. In some examples, the air gap 304 may have a thickness of approximately five millimeters around the exhaust conduit 316 such that the insulation 320 and/or inner shell 312 is offset from the exhaust conduit by approximately five millimeters around the circumference of the exhaust conduit. In some examples, the air gap 304 may be spaced less than or greater than about five millimeters from the exhaust conduit 316.

[0043] The air gap 304 provides for air to be forced or driven through the air gap 304, heated by proximity with the exhaust conduit 316, and expelled at an end and/or an exit of the insulation structure 302. The air gap 304 may extend along a length of the exhaust tube, and may include along an entire length of the exhaust tube, across a portion of a length of the exhaust tube, and/or include multiple insulation structures to span the length of the exhaust tube. An entry for air at one end of the exhaust tube and/or insulation structure allows air to enter the air gap 304 from an air source. In some examples, the air source may be connected to ducting to provide air from an external source rather than a local source, such as within an engine compartment. The air source may be external to a vehicle and/or engine compartment and may pass through ducting and/or filters before reaching the air gap 304. The filter may prevent particles, impurities, oils, fuels, and other contaminants from contacting the exhaust tube and potentially igniting.

[0044] The air system is depicted drawing air through the air gap 304 in a first direction opposite the direction of travel 318 of the exhaust gases. The direction of travel of the air through the air gap 304 may be in the same direction or the opposite direction of the direction of travel 318.

[0045] A section 324 of the exhaust manifold 102 provides a detail view as depicted in FIGS. 4-6, of the layers of the air gap 304, inner shell 312, insulation 320, and outer shell 314.

[0046] FIG. 4 illustrates a cross-section view illustrating a portion of an exhaust manifold 102 with a heat mitigation system, according to at least one example. The exhaust manifold 102 includes components described above such as the exhaust tube 300, air gap 304, inner shell 312, outer shell 314, insulation 320, standoff 322, and other such components as described herein. As seen in FIG. 4, the exhaust tube 300 is oriented annularly about an axis CL.

[0047] The inner shell 312 is oriented annularly about the axis CL and radially outward of the exhaust tube 300 and of an optional radiation shield (not depicted) that may be positioned in the air gap 304 between the exhaust tube 300 and the inner shell 312 and supported by the standoffs 322. The outer shell 314 is radially outward of the inner shell 312. The insulation 320 is positioned between the inner shell 312 and the outer shell 314 in a passage that may have an annular shape.

[0048] The air 402 flows into the air gap 304 as described herein and travels in a first direction 404. Exhaust gases flow through the exhaust tube in a second direction 406. The first direction and second direction may be opposite to each other such that the air 402 flows in the opposite direction of the exhaust gases. In some examples, the first direction 404 and the second direction 406 may be parallel with an in the same direction as each other such that the air 402 flows in the same direction as the exhaust gases.

[0049] FIG. 5 illustrates a cross-section view illustrating a portion of an exhaust manifold 102 with a heat mitigation system, according to at least one example. The exhaust manifold 102 includes components described above such as the exhaust tube 300, air gap 304, inner shell 312, outer shell 314, insulation 320, standoff 322, and other such components as described herein. As seen in FIG. 5, the exhaust tube 300 is oriented annularly about an axis CL.

[0050] In FIG. 5, the standoffs are shown as a mesh 502. In some examples, such as depicted in FIG. 5, the standoffs may include a metal mesh or other porous material that fills a gap between the inner shell 312 and the exhaust tube 300 and supports the inner shell 312 being spaced away from the exhaust tube 300. In an example, the mesh 502 may include a stainless steel mesh that is porous to allow airflow through the air gap 304 while also providing support for maintaining the position of the insulation structure relative to the exhaust tube 300. In an example, the mesh 502 may include an open-cell metal foam, metal webbing, or other such material that allows airflow while also providing structural support to the insulation 320.

[0051] FIG. 6 illustrates a detail view of a heat mitigation system for an exhaust manifold 102 for example at section 324 of FIG. 3, according to at least one example. The detail view shows the structure and layers of the insulation structure 302 including at least the exhaust tube 300, air gap 304, exhaust conduit 316, inner shell 312, outer shell 314, insulation 320 as described above. The detail view shows an example of the spacing between the exhaust tube 300 and the insulation structure including at least a height or thickness of the air gap 304 and the thickness of the inner shell 312 and the outer shell 314.

[0052] The air gap is depicted with a thickness 608 indicating a distance between the inner shell 312 and the exhaust tube 300. The thickness 608 may be in a range of up to five millimeters. In some examples the thickness may be in a range of up to about ten millimeters. In some examples the thickness may be in a range of up to about fifteen millimeters. In some examples the thickness may be in a range of up to about twenty millimeters. The air gap 304 provides enough space to cause a decrease in temperature between the exhaust tube 300 and the inner shell 312 such that the insulation 320 remains below a degradation temperature of the insulation 320. The insulation 320, as described herein may include aerogels or other such insulation and/or organic binders that may break down at temperatures at or above 650 degrees Celsius. Accordingly, the air gap 304 may have the thickness 608 sized such that the temperature of the inner shell remains below the threshold temperature.

[0053] The insulation 320 may have a thickness 610 from an interior of the inner shell 312 to an interior of the outer shell 314 in a range of up to ten millimeters. In some examples, the thickness 610 may be in a range of ten to fifteen millimeters. In some examples, the thickness 610 may be in a range of fifteen to twenty millimeters. In some examples, the thickness 610 may be greater than twenty millimeters. The inner shell 312 may similarly have a thickness 604 that may be less than three millimeters, less than two millimeters, less than one millimeter, or any other suitable range.

[0054] In some examples, the insulation 320 may be effective at preventing the exterior temperature of the exhaust assembly from exceeding 300 degrees Celsius. The use of aerogel or other such insulation may make such a temperature differential possible in a compact space such that the thickness 610 of the insulation 320 and the thickness 608 of the air gap 304 is less than a thickness of a typical insulation that may have a lower thermal resistance than the aerogel. Accordingly, the configuration included herein provides for a more compact profile surrounding the exhaust assembly while maintaining or exceeding the performance of typical exhaust systems.

INDUSTRIAL APPLICABILITY

[0055] The present disclosure provides systems and methods for providing insulation to exhaust assemblies to provide heat mitigation without complex insulation systems and techniques such as liquid cooling that involves pumps or insulation that may be bulky or occupy excessive space in an engine compartment. The insulation systems involve the use of insulations types that may have operating temperatures below the range of temperatures typically experienced in an exhaust system. The insulation systems use an air gap and forced convection to step down the temperature between the exhaust tube and the insulation to a level that is within the operating range of the insulation and thereby use a more effective insulation that may otherwise be unavailable for such uses.

[0056] Accordingly, the exhaust manifold assembly described herein, provides for preventing thermal buildup in and around the exhaust system and thereby prevents thermal stresses and cracking in the exhaust assemblies by using forced air in an air gap surrounded by an insulation structure to provide an external surface temperature at or below a threshold such as 300 degrees Celsius without additional complexity of liquid cooling or bulky insulation systems.

[0057] The systems and techniques described herein provide for a thermal insulative and heat mitigation system that is inexpensive, simple, and resistant to failure. Retaining heat increases thermal stress on the exhaust tube and therefore heat must be mitigated and removed. Accordingly, the use of a fan to pull air through the air gap between the insulation and the exhaust tube allows the air to be moved to a location where heat can be dissipated. Further, shells surrounding the insulation provide for the use of different insulation types including particulate, blanket, granular, fibrous, and other such insulation types that may not otherwise be possible to implement. The shells surrounding the insulation additionally provide for the heat to be stepped down or reduced to a level where insulation such as aerogels may be used without causing degradation.

[0058] 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.