A thermal barrier coating exhaust duct with anti-backfire function and its installation method

Abstract

This invention proposes a thermal barrier coating exhaust duct with anti-backfire function and its installation method, relating to the technical fields of thermal barrier coatings and diesel engine exhaust ducts. It includes an exhaust duct body coated with a thermal barrier coating, which consists of a first adhesive layer, a ceramic layer, and a second adhesive layer from the outside to the inside. The first and second adhesive layers are made of the same material. An exhaust duct heat exchanger is installed on the exhaust duct body, and a spiral static mixer is installed on the inner side of the exhaust duct body. This invention, by designing an exhaust duct with a spiral mixing structure, can effectively promote the mixing of incompletely combusted exhaust gases. Furthermore, a heat exchange channel is provided on the outside of the exhaust duct, and the heat exchange channel and the outer wall of the exhaust duct are coated with a thermal barrier coating. This design can reduce the heat transferred from the high-temperature cylinder head to the exhaust duct, while simultaneously removing heat from the high-temperature wall of the exhaust duct. The combination of these two methods effectively reduces the temperature of the exhaust duct wall while avoiding excessively high local combustion gas concentrations.

Description

Technical Field

[0001] This invention relates to the field of thermal barrier coatings and diesel engine exhaust systems, and particularly to a thermal barrier coating exhaust system with backfire prevention function and its installation method. Background Technology

[0002] As diesel engine technology continues to evolve towards higher strength, lighter weight, compactness, and lower emissions, the exhaust manifold, as a critical heat-load component, faces significant challenges. Traditional cast iron and aluminum alloys can no longer meet the performance requirements of modern high-efficiency, low-emission diesel engines. Therefore, high-temperature nickel-based alloys and stainless steel, due to their excellent high strength and high-temperature resistance, are gradually becoming the preferred materials. However, the low thermal conductivity of these materials leads to increased surface temperature on the inner surface of the exhaust manifold. Insufficient cooling can cause localized high temperatures, thermal damage, and carbon buildup. In severe cases, unburned exhaust gases can enter the exhaust manifold, causing backfire and affecting the diesel engine's performance and reliability. Therefore, current methods typically involve coating the inner and outer walls of the exhaust manifold with thermal barrier coatings or adding a cooling oil chamber within the cylinder head to reduce the heat load. However, current exhaust manifold optimization technologies often have the following drawbacks.

[0003] (1) After the thermal barrier coating is applied to the inner and outer walls of the exhaust duct, it significantly reduces heat conduction, resulting in an increase in the temperature of the exhaust duct wall. The high-temperature wall surface is in direct contact with the exhaust gas, which can easily ignite residual fuel and accelerate flame propagation and oxidation reaction, thereby increasing the risk of flame backfire in the exhaust system.

[0004] (2) Although the addition of the oil cooling chamber in the cylinder head can effectively reduce the temperature of the exhaust port wall, excessive cooling will lead to a large temperature difference, increase the heat load, and may cause thermal cracks under the coupling effect of high pressure exhaust gas, thus reducing the fatigue strength of the exhaust port.

[0005] (3) The cooling oil chamber inside the cylinder head carries away a large amount of heat generated by the cylinder head. However, since the cylinder head is in direct contact with the combustion chamber, excessive heat dissipation from the cooling oil chamber may lead to a significant decrease in the combustion chamber temperature. This temperature drop will affect the efficiency of the combustion process, thereby significantly reducing the overall thermal efficiency of the diesel engine. In addition, excessive heat dissipation may also lead to incomplete combustion of fuel, increasing exhaust emissions and fuel consumption.

[0006] (4) The cooling oil chamber within the cylinder head significantly affects its structure. The presence of the cooling oil chamber reduces the overall mechanical strength of the cylinder head. This structural weakening can lead to deformation or cracking of the cylinder head under high temperature and pressure conditions, thus affecting the normal operation and reliability of the diesel engine. Furthermore, the decrease in mechanical strength can trigger a series of serious consequences, including seal failure, combustion chamber pressure leakage, and potential engine damage. Therefore, this invention proposes a thermal barrier coating exhaust passage with anti-backfire function and its installation method to solve the problems existing in the prior art. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a thermal barrier coating exhaust duct with anti-backfire function and its installation method. This thermal barrier coating exhaust duct and its installation method with anti-backfire function can effectively promote the mixing of incomplete combustion exhaust gases, thus solving the problems existing in the prior art.

[0008] To achieve the objectives of this invention, the invention is implemented through the following technical solution: a thermal barrier coating exhaust duct with anti-backfire function, comprising an exhaust duct body, wherein a thermal barrier coating is coated on the exhaust duct body, and the thermal barrier coating consists of a first adhesive layer, a ceramic layer and a second adhesive layer from the outside to the inside, wherein the first adhesive layer and the second adhesive layer are made of the same material, an exhaust duct heat exchanger is installed on the exhaust duct body, and a spiral static mixer is installed on the inner side of the exhaust duct body.

[0009] A further improvement is that the exhaust heat exchanger includes an exhaust heat exchange wall and heat exchange holes. The exhaust heat exchange wall is provided with heat exchange holes, and several groups of heat exchange holes are evenly arranged, with the groups of heat exchange holes connected to each other.

[0010] A method for installing a thermal barrier coating exhaust duct with anti-backfire function, characterized by comprising the following steps:

[0011] Step 1: Cleaning the inner and outer walls of the exhaust duct body

[0012] The surface residue on the inner and outer walls of the exhaust duct body is polished and removed with sandpaper to ensure a smooth and flat surface. Then it is rinsed with deionized water, dehydrated with alcohol, and dried.

[0013] Step 2: Installation of the spiral mixer and exhaust heat exchanger

[0014] Install the spiral mixer into the bend of the exhaust duct, then heat the outer wall of the exhaust duct to 100°C using an external heating device, then evenly apply thermal conductive adhesive to the outer wall of the exhaust duct, then install the exhaust heat exchanger, and allow it to cool naturally at room temperature until the wall is completely adhered.

[0015] Step 3: Cylinder head treatment

[0016] Prepare the cylinder head for which the exhaust manifold body needs to be installed, and use sandpaper to sand the exhaust manifold cavity of the cylinder head, and then drill a hole from the top of the cylinder head to the exhaust manifold cavity.

[0017] Step 4: Prepare the adhesive layer material

[0018] High-density polyethylene powder, NiCrAlY alloy powder, and 0.1-0.2 wt% high-purity Dy powder were mixed for 15 minutes using a mechanical mixing method. After the mixture was homogeneous, the powder was placed in a high-temperature oven for baking.

[0019] Step 5: Preparation of ceramic layer material

[0020] YSZ powder was poured into 400-500 ml of high-purity ethanol and placed in an ultrasonic cleaner to form a YSZ suspension. La(NO3)3·6(H2O) and ZrOCl2·8(H2O) were added and stirred evenly. Then, sodium linear alkylbenzene sulfonate was added and the pH value was adjusted. After standing for 30-60 minutes, the mixture was filtered and the precipitate was placed in a thermoelectric furnace and treated at a high temperature of 500-600℃ for 1 hour to obtain a mixed powder of YSZ and La2Zr2O7.

[0021] Step 6: Apply thermal barrier coating

[0022] A 100μm adhesive layer material was uniformly coated on the outer wall of the exhaust heat exchanger by plasma spraying. Then, a 300μm ceramic layer material was coated on the adhesive layer surface by electron beam physical vapor deposition. Finally, a 100μm adhesive layer material was coated on the outermost layer by plasma spraying.

[0023] Step 7: Install the exhaust duct

[0024] After cleaning off any remaining coating material from the exhaust manifold body, align it with the mounting holes on the cylinder head and install the exhaust manifold body.

[0025] A further improvement is made in step four, where the baking conditions are: temperature 1100℃~1300℃, time 3~4h.

[0026] A further improvement is made in step four, where the specific composition of the NiCrAlY alloy powder is: 23wt% Co, 17wt% Cr, 12wt% Al, 0.5wt% Y, and 47.5wt% Ni.

[0027] A further improvement is made in step four, where the particle size of the powder material is 30–60 μm.

[0028] A further improvement is made in step five, where the particle size of the mixed powder is 30–100 nm.

[0029] A further improvement is made in step five, which comprises 2 parts by weight of YSZ powder, 2.5 parts by weight of La(NO3)3·6(H2O), 1 part by weight of ZrOCl2·8(H2O), and 1.5 parts by weight of sodium linear alkylbenzene sulfonate.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) The present invention employs an exhaust heat exchanger design, which can effectively reduce the temperature of the exhaust duct wall, thereby reducing the risk of exhaust duct backfire. In addition, it can reduce the thermal stress on the exhaust system and surrounding components, thereby extending their service life.

[0032] (2) By using a spiral mixer, the present invention can promote the mixing of incomplete combustion exhaust gas, effectively avoid the problem of excessively high concentration of incomplete combustion exhaust gas in some areas, and reduce the risk of backfire in the exhaust duct.

[0033] (3) The present invention can reduce exhaust temperature and improve the working efficiency of after-treatment equipment such as SCR (selective catalytic reduction) and DPF (diesel particulate filter).

[0034] (4) The present invention uses a thermal barrier coating to avoid the cylinder head conducting heat to the exhaust port, while reducing the thermal stress caused by the difference in thermal expansion coefficients between metal layers, thus extending the service life of the exhaust port.

[0035] (5) The present invention has little impact on the structure of the engine cylinder head and is more stable and reliable than the traditional cylinder head cooling system. Attached Figure Description

[0036] Figure 1 This is a side view of the end of the exhaust duct body of the present invention.

[0037] Figure 2 This is a front view of the exhaust manifold body and cylinder head after installation according to the present invention.

[0038] Figure 3 This is a partially enlarged front view of the exhaust duct body of the present invention after installation.

[0039] Figure 4 This is a schematic diagram of the thermal barrier coating structure of the present invention.

[0040] The components are: 1. Exhaust duct body; 2. Thermal barrier coating; 3. First adhesive layer; 4. Ceramic layer; 5. Second adhesive layer; 6. Exhaust duct heat exchanger; 7. Spiral static mixer; 8. Exhaust duct heat exchange wall; 9. Heat exchange hole; 10. Cylinder head. Detailed Implementation

[0041] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0042] according to Figures 1-4As shown, this embodiment proposes a thermal barrier coating exhaust duct with anti-backfire function, including an exhaust duct body 1, on which a thermal barrier coating 2 is coated. The thermal barrier coating 2 consists of a first adhesive layer 3, a ceramic layer 4, and a second adhesive layer 5 from the outside to the inside. The first adhesive layer 3 and the second adhesive layer 5 have the same thickness and are made of the same material. An exhaust duct heat exchanger 6 is installed on the exhaust duct body 1, and a spiral static mixer 7 is installed on the inner side of the exhaust duct body 1. The exhaust duct heat exchanger 7 includes an exhaust duct heat exchange wall 8 and heat exchange holes 9. The exhaust manifold body 1 has heat exchange holes 9, and several groups of heat exchange holes 9 are evenly arranged and connected to each other. In this embodiment, four groups of heat exchange holes 9 are evenly arranged. A spiral static mixer 7 is provided in the exhaust manifold body 1. This spiral mixing structure promotes the mixing of incompletely combusted exhaust gases, effectively preventing excessively high concentrations of incompletely combusted exhaust gases in certain areas and reducing the risk of exhaust manifold backfire. The introduction of the exhaust manifold heat exchanger 7 effectively reduces the wall temperature of the cylinder head 10 exhaust chamber (used to install the exhaust manifold body 1), thereby reducing the risk of exhaust manifold backfire. Furthermore, it reduces the thermal stress on the exhaust system and surrounding components, thus extending their service life. Further, the use of a thermal barrier coating 2 prevents heat conduction from the cylinder head to the exhaust manifold while reducing thermal stress caused by the difference in thermal expansion coefficients between metal layers, further extending the service life of the exhaust manifold.

[0043] A method for installing a thermal barrier coating exhaust duct with anti-backfire function includes the following steps:

[0044] Step 1: Cleaning the inner and outer walls of the exhaust duct body

[0045] The exhaust duct body's inner and outer wall surfaces are polished and cleaned by sanding. Specifically, 80-grit sandpaper is used for coarse sanding to remove large residues and uneven areas, followed by 240-grit sandpaper for fine sanding to ensure a smooth and flat surface. Then, deionized water is used to rinse the surface to remove all dust and residues, followed by alcohol dehydration and drying.

[0046] Step 2: Installation of the spiral mixer and exhaust heat exchanger

[0047] Insert the spiral mixer into the bend of the exhaust duct, then heat the outer wall of the exhaust duct to 100°C using an external heating device. Apply thermally conductive adhesive evenly to the outer wall of the exhaust duct, then install the exhaust heat exchanger and allow it to cool naturally at room temperature (25°C±2°C) until the wall is completely adhered.

[0048] Step 3: Cylinder head treatment

[0049] Prepare the cylinder head for which the exhaust manifold body needs to be installed, and use sandpaper to sand the exhaust manifold cavity of the cylinder head. Specifically, sand the exhaust manifold cavity of the cylinder head according to the exhaust manifold size to ensure that the exhaust manifold cavity can correctly accommodate the entry of the exhaust manifold body. Then, drill a hole from the top of the cylinder head to the exhaust manifold cavity. The drilling position is the pre-set position.

[0050] Step 4: Prepare the adhesive layer material

[0051] High-density polyethylene (HDPE) powder, NiCrAlY alloy powder, and 0.1–0.2 wt% high-purity Dy (dysprosium) powder were mechanically mixed for 15 minutes. After uniform mixing, the powder was placed in a high-temperature oven for baking. The particle size of the powder material was 30–60 μm. The specific composition of the NiCrAlY alloy powder was: 23 wt% Co, 17 wt% Cr, 12 wt% Al, 0.5 wt% Y, and 47.5 wt% Ni. The baking conditions were: temperature 1100℃–1300℃, time 3–4 h. In this embodiment, the preferred temperature was 1200℃ and the preferred time was 3.5 h.

[0052] Step 5: Preparation of ceramic layer material

[0053] YSZ (yttrium-stabilized zirconium oxide) powder was poured into 400-500 ml of high-purity ethanol and placed in an ultrasonic cleaner. Ultrasonic treatment was used to help the YSZ powder disperse evenly in the ethanol, forming a YSZ suspension. La(NO3)3·6(H2O) (lanthanum nitrate hexahydrate) and ZrOCl2·8(H2O) (zirconium oxychloride octahydrate) were added, and the mixture was stirred thoroughly with a glass rod. Then, sodium linear alkylbenzene sulfonate was added dropwise while continuously stirring. The pH value is then adjusted to be between 10 and 11, preferably 10 in this embodiment. After standing for 30 to 60 minutes, preferably 45 minutes in this embodiment, until no more precipitate appears, the mixture is filtered. The precipitate is then placed in a thermoelectric furnace and treated at a high temperature of 500 to 600°C for 1 hour, preferably 450°C in this embodiment, to obtain a mixed powder of YSZ and La2Zr2O7 with a particle size of 30 to 100 nm, indicating that the ceramic layer material is a nanomaterial.

[0054] The mixture consists of 2 parts by weight of YSZ powder, 2.5 parts by weight of La(NO3)3·6(H2O), 1 part by weight of ZrOCl2·8(H2O), and 1.5 parts by weight of sodium linear alkylbenzene sulfonate. In this embodiment, each part by weight corresponds to 1g.

[0055] Step 6: Apply thermal barrier coating

[0056] A 100μm adhesive layer material is uniformly coated on the outer wall surface of the exhaust heat exchanger (excluding heat exchange holes) by plasma spraying. Before coating, the surface to be coated is preheated to 280℃~300℃, preferably 290℃ in this embodiment. Then, a 300μm ceramic layer material is coated on the adhesive layer surface (excluding heat exchange holes) by electron beam physical vapor deposition. Finally, a 100μm adhesive layer material is coated on the outermost layer by plasma spraying.

[0057] Step 7: Install the exhaust duct

[0058] After cleaning off any remaining coating material from the exhaust manifold body, align it with the mounting holes on the cylinder head and install the exhaust manifold body.

[0059] This invention, through the design of an exhaust manifold with a spiral mixing structure, effectively promotes the mixing of incompletely combusted exhaust gases. Furthermore, a heat exchange channel is provided on the outer side of the exhaust manifold, and a thermal barrier coating is applied to both the heat exchange channel and the outer wall of the exhaust manifold. This design reduces the heat transferred from the high-temperature cylinder head to the exhaust manifold while simultaneously removing heat from the high-temperature walls of the exhaust manifold. The combination of these two aspects effectively reduces the temperature of the exhaust manifold walls while preventing excessively high localized fuel gas concentrations. This prevents incompletely combusted exhaust gases from igniting upon encountering the high-temperature walls, thereby effectively suppressing backfire.

[0060] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its framework and scope of application, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for installing a thermal barrier coating exhaust duct with anti-backfire function, characterized in that: The thermal barrier coating exhaust duct includes an exhaust duct body (1), on which a thermal barrier coating (2) is coated. The thermal barrier coating (2) consists of a first adhesive layer (3), a ceramic layer (4), and a second adhesive layer (5) from the outside to the inside. The first adhesive layer (3) and the second adhesive layer (5) are made of the same material. An exhaust duct heat exchanger (6) is installed on the exhaust duct body (1), and a spiral static mixer (7) is installed on the inner side of the exhaust duct body (1). The exhaust duct heat exchanger (7) includes an exhaust duct heat exchange wall (8) and heat exchange holes (9). The exhaust duct heat exchange wall (8) is provided with heat exchange holes (9), and several groups of heat exchange holes (9) are evenly arranged, and the several groups of heat exchange holes (9) are connected to each other. Its installation method includes the following steps: Step 1: Cleaning the inner and outer walls of the exhaust duct body The surface residue on the inner and outer walls of the exhaust duct body is polished and removed with sandpaper to ensure a smooth and flat surface. Then it is rinsed with deionized water, dehydrated with alcohol, and dried. Step 2: Installation of the spiral mixer and exhaust heat exchanger Install the spiral mixer into the bend of the exhaust duct, then heat the outer wall of the exhaust duct to 100°C using an external heating device, then evenly apply thermal conductive adhesive to the outer wall of the exhaust duct, then install the exhaust heat exchanger, and allow it to cool naturally at room temperature until the wall is completely adhered. Step 3: Cylinder head treatment Prepare the cylinder head for which the exhaust manifold body needs to be installed, and use sandpaper to sand the exhaust manifold cavity of the cylinder head, and then drill a hole from the top of the cylinder head to the exhaust manifold cavity. Step 4: Prepare the adhesive layer material High-density polyethylene powder, NiCrAlY alloy powder, and 0.1-0.2 wt% high-purity Dy powder were mixed for 15 minutes using a mechanical mixing method. After the mixture was homogeneous, the powder was placed in a high-temperature oven for baking. Step 5: Preparation of ceramic layer material YSZ powder was poured into 400-500 ml of high-purity ethanol and placed in an ultrasonic cleaner to form a YSZ suspension. La(NO3)3·6(H2O) and ZrOCl2·8(H2O) were added and stirred evenly. Then, sodium linear alkylbenzene sulfonate was added and the pH value was adjusted. After standing for 30-60 minutes, the mixture was filtered and the precipitate was placed in a thermoelectric furnace and treated at a high temperature of 500-600℃ for 1 hour to obtain a mixed powder of YSZ and La2Zr2O7. Step 6: Apply thermal barrier coating A 100μm adhesive layer material was uniformly coated on the outer wall of the exhaust heat exchanger by plasma spraying. Then, a 300μm ceramic layer material was coated on the adhesive layer surface by electron beam physical vapor deposition. Finally, a 100μm adhesive layer material was coated on the outermost layer by plasma spraying. Step 7: Install the exhaust duct After cleaning off any remaining coating material from the exhaust manifold body, align it with the mounting holes on the cylinder head and install the exhaust manifold body.

2. The installation method of a thermal barrier coating exhaust duct with anti-backfire function according to claim 1, characterized in that: In step four, the baking conditions are: temperature 1100℃~1300℃, time 3~4h.

3. The installation method of a thermal barrier coating exhaust duct with anti-backfire function according to claim 1, characterized in that: In step four, the specific composition of the NiCrAlY alloy powder is: 23wt% Co, 17wt% Cr, 12wt% Al, 0.5wt% Y and 47.5wt% Ni.

4. The installation method of a thermal barrier coating exhaust duct with anti-backfire function according to claim 1, characterized in that: In step four, the particle size of the powder material is 30–60 μm.

5. The installation method of a thermal barrier coating exhaust duct with anti-backfire function according to claim 1, characterized in that: In step five, the particle size of the mixed powder is 30–100 nm.

6. The installation method of a thermal barrier coating exhaust duct with anti-backfire function according to claim 1, characterized in that: In step five, the following components are used: 2 parts by weight of YSZ powder, 2.5 parts by weight of La(NO3)3·6(H2O), 1 part by weight of ZrOCl2·8(H2O), and 1.5 parts by weight of sodium linear alkylbenzene sulfonate.

Images