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[0001] This application claims priority from the following Chinese patent applications: “Dissipative Automobile Exhaust Mufflers” filed on “Apr. 24, 2003”, having a Chinese Application No. 03114334.2; and “Automobile Exhaust Catalytic Converter Devices”, filed on “Apr. 30, 2003”, and having a Chinese Application No.: 03114399.7; and “Automobile Exhaust Muffler and Purifying Devices, filed on “Dec. 26, 2003”, and having a Chinese Application No.:200320125349.5. All of the above applications are incorporated here by reference.
[0002] This invention relates to muffler devices, catalytic converter devices, and combination muffler catalytic converter devices for the exhaust system of an engine. More particularly, it relates to the use of porous metal as the sound absorption material and the substrate for the catalyst for muffler devices, catalytic converter devices, and combination muffler catalytic converter devices for the exhaust system of engines.
[0003] The removal of environmental contaminants from an engine's exhaust and the muffling of engine noise are all integral functions of the exhaust system of an engine. At present, for machines operated by engines such as automobiles, two separate devices perform these functions. The muffler is used to reduce engine noise while the catalytic converter is used to purify the exhaust by the removal of environmentally harmful contaminants. Having two separate devices to perform these two functions not only causes a decrease in engine efficiency, it also increases the cost of production of the exhaust system by the increase in the cost of the production and installation of the two devices.
[0004] Catalytic converters often use ceramic and metal as the substrate for the catalyst. Honeycombed ceramic substrates have many disadvantages when compared with metal substrates. They generally operate at lower temperatures since ceramic softens at about 1400° C. Their walls are thicker. They preheat slower and the exhaust pressure in systems with these catalytic converters is higher. For these reasons, many countries are conducting research on the use of metal substrates. The wall of a metal substrate is only a quarter as thick as that of the ceramic substrate. As a result, exhaust pressure is lowered and the substrate for the catalyst can be made smaller. Metal substrates can be heated efficiently since they have a small capacity and can be electrically preheated. Moreover, metal substrates can adapt well to temperature changes.
[0005] Existing metal substrates of automobile exhaust catalytic converter mainly use combinations of various structures of corrugated metal. Their resistance to heat and mechanical impact are low. At high temperatures, their anti-oxidation ability is insufficient, thereby affecting life of the devices. In addition, the specific surface area of these corrugated metal substrate are limited and their capacity for the catalyst to be adsorbed is inadequate, limiting the efficiency of these devices.
[0006] At present, automobile exhaust muffler system customarily use reactive type mufflers because these systems are constructed of metal with simple structures that are durable and can withstand high temperature, corrosion, and impact from the flow of exhaust. However, the spectrum of sound absorption for the reactive type muffler is narrow with sound absorption better at low frequencies and worse at high frequencies. In order to compensate for the weakness in high frequency sound absorption, multi-stage combinations structures such as, multi-stage mufflers or dissipative and reactive combination mufflers are often used to achieve better results. These devices are complex and increase the cost for the production of mufflers.
[0007] Alumina felt and asbestos felt are commonly used materials for sound absorption. They can resist high temperature and corrosion and can be firmly secured to a surface protecting structure. However, they are not durable as their ability to resist impact, humidity, and dust is low. Their sound absorption capability is also insufficient. Therefore, at present, they are not widely used in the automobile industry.
[0008] Due to the limitations of the prior art, it is therefore desirable to have novel devices that would have better sound absorption as well as good exhaust purification, is simple to make and easy to fabricate, and is durable by being resistant to high temperature, corrosion, and impact from the flow of the exhaust.
[0009] An object of this invention is to provide a muffler that is effective in sound absorption over a wide spectrum of frequencies.
[0010] Another object of this invention is to provide a catalytic converter that is efficient in the removal of environmental contaminants from the exhaust.
[0011] Still another object of this invention is to provide a muffler and catalytic converter device that is effective in sound absorption over a wide spectrum of frequencies and efficient in the removal of environmental contaminants from the exhaust.
[0012] Yet still another object of this invention is to provide a muffler, a catalytic converter, or a muffler and catalytic converter having properties including simplicity in construction, easy and cheap to fabricate, durable and having a long useable lifespan resulting from its resistance to high temperature, corrosion, and impact from the flow of exhaust.
[0013] The present invention relates to the use of baffles of porous metal with large specific surface area as the sound absorption material and as the substrate for the catalyst in the catalytic converter. The large specific surface area of the porous metal enables effective sound absorption and provides a large area for the catalyst to be adsorbed resulting in efficient exhaust purification. By using the same type of material for the sound absorption and exhaust purification, it is possible not only to construct separate muffler and catalytic converter devices but also to combine these two devices into one.
[0014] The advantages of the devices of this invention are that they are effective in sound absorption over a wide spectrum of frequencies, efficient in the removal of environmental contaminants from the exhaust, simple to construct and fabricate for industrial production, durable, and has a long useable life as they are resistant to high temperature, corrosion, and impact from the flow of the exhaust.
[0015] The foregoing and other objects, aspects and advantages of the invention will be better understood from the following detailed description of preferred embodiments of this invention when taken in conjunction with the accompanying drawings in which:
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
[0022]
[0023]
[0024] This invention provides in several embodiments a muffler and catalytic converter device, a muffler, and a catalytic to absorb, muffle or reduce noise and to purify the exhaust by the removal of environmental contaminants from the exhaust of an engine. Baffles of sound absorption material, which can also act as the substrate for the catalyst coating, are used. These baffles can be made from porous metal with predetermined pore diameter and pore density to achieve desired results for the conversion of exhaust contaminants and for sound absorption.
[0025] As shown in
[0026] Electroplating is used to fabricate the porous metal with pores diameters between 50 to 1200 micrometers and pore density between 80% and 98%. High temperature oxidation, electrochemical anodic oxidation, etching with heated organic acid, or other methods are used to form a thin dense oxide layer on the surface of the substrate. This not only increases the adhesion between the substrate and the catalyst coating including the oxide layer such as aluminum oxide, zirconium oxide and cerium oxide, but also increases the substrate's ability to resist high temperature oxidation and increases the catalyst's purification efficiency and lifespan.
[0027] In embodiments of this invention, baffles of porous metal can be placed in sections across the direction of the exhaust flow, i.e., the flow from the intake opening to the outtake opening, with gaps between the baffles. A baffle can be typically placed across the direction of exhaust flow when the planes tangential to its surfaces (that are not touching the inside surfaces of the outer shell) forms an angle between π/4 radians and π/2 radians with the direction of exhaust flow.
[0028] The thickness of a baffle can be measured as the average distance between the planes tangential to the surfaces of the baffles that are not touching the surface of the outer shell. The thickness of a gap between two neighboring baffles can be measured as the average distance between neighboring planes tangential to the surfaces of the neighboring baffles that are not touching the surface of the gaps. The thickness of a gap between an inner surface of the outer shell and its neighboring baffle can be the average distance between the plane tangential to the surface of the baffle not touching the outer shell and the outer shell. For baffles of variable shapes, it is understood that the thickness of the baffles and the thickness of the gaps can vary but that they all fall within a pre-determined thickness. For the disc shaped baffles in
[0029] In embodiments where two baffles are placed perpendicular to the flow of exhaust, a preferred ratio of the three gaps are: 1: between 1 and 10: between 1 and 2.
[0030] In another embodiment of this invention, the baffles of porous metal can also be placed either in single or multiple layers in the direction along the direction of the flow of the exhaust, leaving gaps between the layers of porous metal, and between the inside of the outer shell and the layers of porous material. A baffle is placed along the direction of exhaust flow when the planes tangential to its surfaces that are not touching the inside surfaces of the outer shell forms an angle between 0 radians and π/4 radians with the direction of exhaust flow. The baffles can be positioned as shown in
[0031] In yet another embodiment spiral shaped baffles of porous metal can be placed inside an outer shell. An example of this embodiment is shown in
[0032] In some embodiments of this inventions that are mufflers, catalytic converters, or muffler and catalytic converter devices, said porous metal, a metal or an alloy, is one or more metals selected from the following group: nickel, iron, or titanium.
[0033] In other embodiments of this invention that are mufflers, catalytic converters, or muffler and catalytic converter devices, said porous metal is an alloy with two components, A and B, where component A is between 55 wt % and 95% wt. % of the porous metal and is one or more of the following: nickel, iron, or titanium. The B component is between 5 wt. % and 45 wt. % of the porous metal and is one or more of the following: chromium, Cr, aluminum, Al, cobalt, Co, molybdenum, Mo, and zinc, Zn.
[0034] For some embodiments that are mufflers, said porous metal is a metal alloy containing two components, A and B, where said A component is between 55 wt % to 95 wt % of said porous metal and is one or more of the following: nickel, iron, and titanium and said B component is between 5 wt. % to 45 wt. % of the porous metal and is one or more of the following: chromium, Cr, aluminum, Al, cobalt, Co, molybdenum, Mo, zinc, Zn, zirconium, Zr, vanadium, V, cerium, Ce, lanthanum, La, and Neodymium, Nd.
[0035] For embodiments that are catalytic converters or muffler and catalytic converter devices, the composition of the catalyst coating includes an active ingredient, an assisting ingredient, and a stabilizer. The active ingredient is one ore more rare earth metals from the following: cerium, Ce, lanthanum, La, praseodymium, Pr, and neodymium, Nd and small quantities of one or more precious metals from the following: palladium, Pd or Pa, platinum, Pt, rhodium, Rh, and ruthenium, Ru. The assisting ingredient is one or more of the following: manganese, Mn, calcium, Ca, barium, Ba, magnesium, Mg, zinc, Zn, and aluminum, Al. The stabilizer is one or more of the following: zirconium, Zr, potassium, K, sodium, Na, and lithium, Li.
[0036] The effectiveness of the sound absorption and exhaust purification of the embodiments is highly dependent on the properties of the porous metal, namely, the pore diameter and the pore density. Examination of the sound absorption and exhaust purification results of different embodiments leads to the following conclusions.
[0037] The effectiveness of the exhaust purification is highly dependent on the size of the pore diameter of the porous metal. When the pore diameter is between 50 μm and 1200 μm, the purification results are good. The purification results are the best when the pore diameter is between 400 μm and 800 μm.
[0038] The sound absorption ability is also highly dependent on the size of the pore diameter. Seven groups of experiments were conducted in order to determine the preferred parameters for the pore diameter. The results are shown in Table 1.
TABLE 1 Pore coefficient of sound absorption Diamter for different frequencies Group (μm) 100 Hz 500 Hz 1500 Hz 2500 Hz 4000 Hz 1 50 0.14 0.24 0.32 0.28 0.26 2 100 0.22 0.37 0.45 0.42 0.36 3 200 0.28 0.54 0.68 0.72 0.73 4 400 0.35 0.62 0.75 0.72 0.74 5 800 0.35 0.68 0.71 0.72 0.75 6 1200 0.32 0.61 0.72 0.72 0.65 7 1600 0.26 0.41 0.52 0.62 0.55
[0039] Table 1 shows that the sound absorption coefficient of the device increases as the pore diameter increases exhibiting a trend to first increase from low to high and then decrease from high to low. The best results for sound absorption are obtained between 200 μm to 1200 μm. At the same time, the sound absorption results are better at high frequencies than low frequencies.
[0040] To achieve better sound absorption characteristics, especially at lower frequencies, methods such as leaving gaps between baffles of the sound absorption material and reasonably increasing the thickness of the material are used. Theoretically, gaps can also have the effect of increasing the material's thickness. This is equivalent to increasing the effective length of the capillaries. This method will decrease the use of materials, lower cost, and improve the material's sound absorption properties, especially at the lower frequencies. To improve the sound absorption, gaps are also left between the sound absorption material (
[0041] The pore density of the porous metal material significantly determines the specific surface area of the substrate that the catalyst is attached to, the purification and sound absorption characteristics, and the air resistance. Generally speaking, large pore density has the advantage of decreasing air resistance and increasing the sound absorption. However, if the pore density of the material is increased to above 98%, the technology of fabricating the porous metal is more difficult and uneconomical. Too high a pore density would also affect the mechanical strength of the porous metal by lowering its ability to resist impact from the exhaust. Therefore, the preferred specification is to limit the pore density of the porous material to be between 80% and 90%.
[0042] The pore density of the different baffles of sound absorption material gap can vary. In addition, the size of the gap between the sections can vary. The sound absorption can be increased in a wider spectrum of frequencies by adjusting the pore density of the different sections and the thickness of the different gaps.
[0043] To fabricate the muffler and catalytic converter device of this embodiment, electroplating is used to first fabricate the baffles of porous nickel chromium alloy. Then the catalyst coating is fabricated on the porous metal alloy. The baffles of porous metal with catalyst coating are then inserted into a metal outer shell with a cushioning layer to form the final device.
[0044] (1) Fabrication and Pre-treatment of the Porous Nickel Chromium Metal Alloy:
[0045] In this embodiment, electroplating is used to fabricate the porous nickel chromium alloy to a thickness of 1.5 mm to 3.0 mm, a pore density of between 95% and 98%, and a pore diameter of 400 μm. This porous metal alloy has good mechanical strength and flexibility. There are no sealed pores and the pore diameter is distributed evenly. The specifications and the formula metal plating to fabricate the nickel chromium alloy are shown in Table 2.
TABLE 2 Specifications (g/L) chromium chloride 50˜80 nickel chloride 20˜75 formic acid (mL/L) 10˜95 boric acid 20˜50 sodium citrate 25˜100 ammonia chloride 30˜120 sodium bromide 40˜90 pH level 1˜4 Temperature ° C.) 20˜60 current density (A/dm2) 2˜10 plating time (hour) 1˜6
[0046] The ingredients listed in Table 2 are stirred to completely dissolve in de-ionized water to form the electrolyte. The pH is then adjusted to approximately 3.5. To improve the quality of the plating layer, an additive such as sodium dedocyl sulphonate or coumarin is added.
[0047] An inert graphite is used for the positive electrode while the negative electrode is a commercially available porous sponge-like material coated with a conducting agent with predetermined pore diameter and pore density. The plated porous metal obtained with this process contains 60% to 90% nickel and 10-40% chromium.
[0048] After said porous nickel chromium alloy is fabricated as described above, it is pretreated by etching with heat in organic acid for 1 to 5 hours before it is ready to be used as a substrate for the catalyst in the muffler and catalytic converter device. The etching with heat in organic acid forms a thin, dense layer of oxidized material on the surface of the porous nickel chromium alloy. Other methods such as high temperature oxidation or electrochemical anodic oxidation can also be used to form this oxide layer.
[0049] (2) Fabrication of the Catalyst Coating
[0050] The composition of the catalyst coating includes an active ingredient, an assisting ingredient, and a stabilizer. The active ingredient is at least one rare earth metals selected from the following group: cerium, Ce, lanthanum, La, praseodymium, Pr, and neodymium, Nd and small quantities of at least one precious metal selected from the following group: palladium, Pd (?Pa), platinum, Pt, rhodium, Rh, and ruthenium, Ru. The assistant? Ingredient is at least one of the following: magnesium, Mn, manganese, calcium, Ca, barium, Ba, magnesium, Mg, zinc, Zn, and aluminum, Al. The stabilizer is at least one of the following: zirconium, Zr, potassium, K, sodium, Na, and lithium, Li.
[0051] The catalyst coating of this embodiment contains a mixture of nanometer γ alumina and nanometer zirconia in the ratio of between 0:3 and 3:0. To fabricate the catalyst coating, a pre-determined ratio of a slurry mixture of powdered oxides of aluminum and zirconium is immersed in a saturated solution of cerium salt at a temperature of 30° C. to 80° C. for about to 2 hours to 5 hours to form a slurry. At that temperature, the porous metal substrate that has been etched with heat in organic acid is immersed in said slurry for 2 hours to 4 hours. Then, pressurized air or centrifuge is used to remove excess slurry from the substrate. The porous metal substrate is heated at 400° C. to 600° C. for 1 to 8 hours and then cooled to room temperature.
[0052] After cooling, the porous metal alloy substrate that has been calcined is heat treated in organic acid, then immersed in a solution containing soluble cerium salt, rhodium salt and small amounts of manganese salt at a temperature of between 30° C. and 80° C. for 2 hours to 4 hours. The calcinations process described above is then repeated to obtain the catalyst coating on the substrate for the muffler and catalytic converter device.
[0053] As illustrated in
[0054] The fabrication of the porous nickel chromium metal alloy and the pretreatment of the porous metal alloy remains the same as Embodiment 1.
[0055] To fabricate the catalyst coating layer, the porous nickel chromium metal alloy substrate that has been pretreated in organic acid to form an oxide layer is immersed in a solution that include a pre-determined ratio of a mixture of soluble aluminum salt, zirconium salt, cerium salt, rhodium salt. After immersion, excess solution is removed and the substrate coated with said mixture is heat dried. The porous metal alloy with catalyst coating is heated at 400° C. to 600° C. for 2 hours to 6 hours and then cooled to room temperature. The above described processes, etching with organic acid, immersion, heat dry, and calcinations are repeated to form multi-layers of oxidized material on the surface of the substrate until the porous metal alloy with catalyst coating reaches the pre-determined technical specification.
[0056] As illustrated in
[0057] Nickel chromium metal alloy with a thickness of 1.5 mm to 3.0 mm, a pore density of 95% to 98%, and a pore diameter of 50 μm is used as the substrate for the catalyst coating in this embodiment. Other than this, the fabrication of the muffler and catalytic device remains the same as Embodiment 1.
[0058] Nickel chromium metal alloy with a thickness of 1.5 mm to 3.0 mm, a pore density of 95% to 98%, and a pore diameter of 200 μm is used as the substrate for the catalyst coating in this embodiment. Other than this, the fabrication of the muffler and catalytic device remains the same as Embodiment 1.
[0059] Nickel chromium metal alloy with a thickness of 1.5 mm to 3.0 mm, a pore density of 95% to 98%, and a pore diameter of 600 μm is used as the substrate for the catalyst coating in this embodiment. Other than this, the fabrication of the muffler and catalytic device remains the same as Embodiment 1.
[0060] Nickel chromium metal alloy with a thickness of 1.5 mm to 3.0 mm, a pore density of 95% to 98%, and a pore diameter of 800 μm is used as the substrate for the catalyst coating in this embodiment. Other than this, the fabrication of the muffler and catalytic device remains the same as Embodiment 1.
[0061] Nickel chromium metal alloy with a thickness of 1.5 mm to 3.0 mm, a pore density of 95% to 98%, and a pore diameter of 1000 μm is used as the substrate for the catalyst coating in this embodiment. Other than this, the fabrication of the muffler and catalytic device remains the same as Embodiment 1.
[0062] Nickel chromium metal alloy with a thickness of 1.5 mm to 3.0 mm, a pore density of 95% to 98%, and a pore diameter of 1200 μm is used as the substrate for the catalyst coating in this embodiment. Other than this, the fabrication of the muffler and catalytic device remains the same as Embodiment 1.
[0063] The above-described embodiments were placed in automobiles and their conversion rates of exhaust contaminants were measured. Their conversion rates for CO, HC, NOx after test driving for 30,000 km are listed in the Table 3.
TABLE 3 Pore Diameters and Conversion Rates Embodi- Embodi- Embodi- Embodi- Embodi- Embodi- Embodi- Embodi- ment 1 ment 2 ment 3 ment 4 ment 5 ment 6 ment 7 ment 8 Pore 400 400 50 200 600 800 1000 1200 diameter (μm) CO 91 94 80 83 95 93 87 75 Conversion Rate (%) HC 94 93 75 76 93 90 83 70 Conversion Rate (□) Nox 72 70 50 55 74 73 71 60 Conversion Rate (□)
[0064]
[0065] In this embodiment, there are two baffles of sound absorbing material made from porous nickel fabricated by electroplating that are secured in two sections to the inside of the outer metal shell and placed perpendicular to the direction of the exhaust flow. Gaps are left between the porous metal and the outer shell and between the different sections of the baffles of porous metal. The pore density is between 80% and 98%. Best sound absorption results are obtained when the pore density is between 95% and 98%. The pore diameter of the porous metal is 200 μm. The thickness of the porous metal is between 10 mm and 100 mm and the thickness of the gaps is between 10 mm and 150 mm. The porous nickel fabricated by electroplating has evenly spaced pores, with no sealed pores. Therefore, this material has high structural strength and pre-determined flexibility.
[0066] In this embodiment, the pore diameter of the porous nickel is 400 μm. All other specifications are the same as Embodiment 9.
[0067] In this embodiment, the pore diameter of the porous nickel is 800 μm. All other specifications are the same as Embodiment 9.
[0068] In this embodiment, the pore diameter of the porous nickel is 1200 μm. All other specifications are the same as Embodiment 9.
[0069] In this embodiment, the porous nickel chromium alloy containing 55 wt. % of nickel and 45 wt. % of chromium has a pore diameter of 200 μm. All other specifications remain the same. This embodiment is more durable and has a longer useable life since the porous nickel chromium is strong with a high resistance to oxidation and heat corrosion.
[0070] In this embodiment, the porous nickel chromium alloy containing 75 wt. % of nickel and 25 wt. % of chromium has a pore diameter of 200 μm. All other specifications remain the same.
[0071] In this embodiment, the porous nickel chromium alloy containing 95 wt. % of nickel and 5 wt. % of chromium has a pore diameter of 200 μm. All other specifications remain the same.
[0072] Embodiments 9 through 15 were placed in automobiles and the their sound absorption properties were tested using the Automobile Standard Noise Measuring Method (GB/T 14365-93) and External Noise Limit and Testing Method for Automobile Acceleration (GB 1495-2002), the noise level were all lower than 76 dB and 73 dB, all lower than the national standards. In addition, the useable lives for embodiments of this invention using porous metal alloy are longer than those using a single metal element as the porous metal material.
[0073]
[0074] Said porous metal material, a metal or an alloy, is at least one of the metals selected from the following group: nickel, iron, or titanium. In the alternative, the porous metal can also be composed on an alloy with two components, A and B, where the A component is 55 wt. % to 95% wt. % of the porous metal and is at least one of the following: nickel, iron, or titanium. The B component is 5 wt. % to 45 wt. % of the porous metal and is at least one of the following: chromium, Cr, aluminum, Al, cobalt, Co, molybdenum, Mo, and zinc, Zn.
[0075] The composition of the catalyst coating includes an active ingredient, an assisting ingredient, and a stabilizer. The active ingredient is at least one rare earth metals selected from the following group: cerium, Ce, lanthanum, La, praseodymium, Pr, and neodymium, Nd and small quantities of at least one precious metal selected from the following group: palladium, Pd or Pa, platinum, Pt, rhodium, Rh, and ruthenium, Ru. The assistant ingredient is at least one element selected from the following: manganese, Mn, calcium, Ca, barium, Ba, magnesium, Mg, zinc, Zn, and aluminum, Al. The stabilizer is at least one element selected from the following: zirconium, Zr, potassium, K, sodium, Na, and lithium, Li.
[0076] Referring
[0077] As shown in
[0078] As
[0079] As
[0080] As
[0081] Embodiments 16 through 21 are placed inside common sedans. When tested according to government standards (GB/T3845-93) during vehicle operation, the purification efficiency are all over 95% for HC, CO, and Nox. When tested according to European Exhaust Testing Standards #11, for Embodiments 16 through 21, their CO exhaust volume is less than 1.9 g/km, total exhaust volume for HC and Nox is less than 0.4 g/km.
[0082] The sound absorption properties of the embodiments of this invention are excellent and no additional mufflers are needed to achieve sound absorption. When the insertion loss reaches 20 to 30 dB, less than 5% of the engine efficiency is lost and the exhaust backpressure is less than 15 Kpa.
[0083] While the present invention has been described with reference to certain preferred embodiments, it is to be understood that the present invention is not limited to such specific embodiments. Rather, it is the inventor's contention that the invention be understood and construed in its broadest meaning as reflected by the following claims. Thus, these claims are to be understood as incorporating not only the preferred embodiments described herein but all those other and further alterations and modifications as would be apparent to those of ordinary skilled in the art.