Processing

Please wait...

Settings

Settings

Goto Application

1. WO2012064194 - HOT GAS HANDLING DEVICE AND MOTORIZED VEHICLE COMPRISING THE DEVICE

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

Hot gas handling device and motorized vehicle comprising the device

The invention relates to a hot gas handling device, and particularly to an exhaust. The invention also relates to a motorized vehicle comprising the device, in particular the exhaust.

Exhausts are widely used in multiple types of motorized vehicles, such as cars, motorbikes, buses, boats etcetera. Exhausts transport hot gasses discharged under pressure from an internal combustion engine away from the engine. Depending on the overall exhaust design, the exhaust gas may flow through one or more of a cylinder head and exhaust manifold, a turbocharger to increase engine power, a catalytic converter to reduce air pollution and a silencer to reduce noise. Exhausts are subject to diverse conditions, such as mechanical loads (shock loads, mechanical vibrations and bending), high temperatures up to 1100° C and above, arising from the exhaust gasses and moisture. Known exhausts are made from metals, such as stainless steel, which are strong, durable, but are also heavy. Moreover, the known exhaust produces noise at such levels that additional devices such as silencers and mufflers need to be employed in the exhaust system. These additional devices add further weight, which increases fuel consumption.

It has been proposed to use fiber-reinforced materials in some parts of an exhaust system. For example, the silencer in exhausts of motorbikes can be made from carbon fibres embedded in a high temperature resistant resin. However, the temperature of the exhaust gasses discharged from the engine has significantly decreased as they enter the silencer. This also holds for components like a catalytic converter for instance.

It is an object of the present invention to provide a hot gas handling device, in particular an exhaust, which is lighter than the known exhausts made from steel.

According to the invention, this object is achieved by a device for handling hot gasses, and in particular by an exhaust for exhaust gasses discharged from an internal combustion engine, the device comprising a housing, enclosing a space for transporting the hot (exhaust) gasses, wherein the housing is provided with an entrance-opening for the hot gasses discharged from the engine and an exit-opening for transporting the hot gasses away from the engine, wherein the housing comprises a flexible thermal insulating layer, which insulating layer is arranged for resisting the temperature of the hot gasses discharged from the engine, and a supporting structure at a side of the insulating layer opposite from the space, which supporting structure is made of reinforcing fibres embedded in a matrix, wherein the housing further comprises a liner facing the space, the liner comprising a porous fibrous structure.

In an embodiment of the invention, the liner of the device comprises metal and/or mineral fibers, such as glass fibers.

Another embodiment of the invented device is characterized in that the liner comprises a fibrous spiral, a fibrous mesh and/or a fibrous braid.

The insulating layer allows the use of a supporting structure made of fibres embedded in a matrix, which results in a device for handling hot gasses, and in particular an exhaust, which is lighter than the known devices made from steel. In addition, the use of a flexible insulating layer allows for the deformation of the insulating layer. Increasing pressure of exhaust gasses in the exhaust will deform the insulating layer, thereby increasing the cross-section of the exhaust. This leads to a decrease of the pressure of exhaust gasses, which results in an increase of power of the engine. By exhaust is in particular meant the header-back, which is the part of the exhaust from the outlet of the manifold to the final vent to open air. However, the manifold itself may also be part of the exhaust according to the invention. Several insulating materials may be suitable for insulating the support structure. All that is required is that the insulating layer is arranged for resisting the temperature of the exhaust gasses discharged from the engine. The insulating layer and the support structure can be designed as separate parts. The insulating layer and the support structure can also be integrally formed, e.g. by using a pile fabric, wherein the lower side of the pile fabric is embedded in the matrix of the support structure, thereby forming the reinforcing part of the support structure.

Due to the use of a liner in the form of a porous fibrous structure in combination with the (porous) thermally insulating layer and a housing of fiber reinforced material, noise generated by the hot gasses flowing at high speeds is unexpectedly well damped. In particular the high frequency harmonics are well damped. The use of noise reduction

means such as mufflers and silencers is no longer required, which makes the whole hot gas handling device considerably lighter and of simpler construction than the known device. Further, it turns out that, contrary to expectations, it becomes possible to reduce the very high temperatures at the inside of the device or exhaust to manageable temperatures at the outside thereof, typically from 700-950 °C and more inside the exhaust device to 150-250 °C at the outside.

The liner further offers resistance to ablation, especially in corners and/or bends of the device.

The use of a housing made from fiber-reinforced composites allows to change the cross-sectional shape of the device, in particular the exhaust tube, at will. A further advantage in this respect is that the fundamental of the noise wave can be attenuated or damped easily by changing the shape of the cross-section.

Still another advantage is that the device and the exhaust in particular can be fastened to a substructure such as a vehicle in a rigid way. A metal exhaust for instance needs to be fastened in a flexible way such that the important thermal expansion in the length direction of the exhaust (several cm) can be accommodated. A flexible attachment produces low frequency noise waves that are not easily dampened. The device according to the invention does not have this drawback.

In another embodiment of the device of the invention, the flexible thermal insulating layer comprises a first layer facing the space, arranged for withstanding a first temperature and a second layer at a side of the first layer opposite from the space, arranged for withstanding a second temperature, wherein the first temperature is higher than the second temperature, and wherein the second layer comprises a specific heat capacity higher than 0,5 (kJ/(kg*K)), preferably higher than 0,6 (kJ/(kg*K)) and most preferably higher than 0.7 (kJ/(kg*K)). Such a thermal insulating layer comprising a first and second layer allows for more design flexibility of the exhaust. In this embodiment the second layer can be chosen to have higher heat capacity at the expense of a lower heat resistance, due to the presence of the first layer facing the space. As a result, for a given temperature of the exhaust gasses, the temperature of the support structure is lower due to the increased heat capacity of the second layer. As a result a larger variety of materials, both the reinforcing fibres as well as the matrix, can be selected, thereby giving more freedom to design. Surprisingly, the second layer provides for sufficient specific heat capacity, while being sufficiently heat resistant, wherein the second layer can be designed low weight and thin.

In a preferred embodiment the first insulating layer is a permeable fibrous structure, comprising fibres selected from the group consisting of: steel, silicium, calcium, aluminium, titanium, zirconium, platinum and combinations thereof. Surprisingly, an insulating layer made from such materials can be designed relatively thin while providing high heat insulation. A thin insulation layer allows for the use of a smaller support structure for a given space, which leads to a more lightweight exhaust. A particular suitable material is Superwool®, from the company Thermal ceramics.

Superwool® is composed of silicium (50-82 wt%), calcium and magnesium (18-43 wt%), aluminium, titanium and zirconium (less than 6 wt%), and trace oxides.

In another embodiment the second layer comprises a material with a closed cell structure. This allows for a moisture barrier from the exhaust gasses towards the support structure and may increase the durability of the exhaust.

The second layer may also comprise a material with an open-cell structure, which provides the second layer for increased elastic properties. For a given pressure, the second layer will deform more, thereby increasing the effective cross-section of the exhaust for transporting the exhaust gasses, which provides the engine with increased power.

In a preferred embodiment the second layer comprises an aerogel. An aerogel comprises a high heat capacity and is lightweight, as it comprises a relative high percentage of air, up to 90%. Aerogel is a silicum-based substance, derived from silicum gel. Aerogel can have a density as low as 1 mg/cm3. For comparison the density of air is 1.2 mg/cm3. Aerogel combines good thermal insulating properties with high a heat capacity.

For increasing design flexibility and strength of the second insulation layer, the second insulation layer preferably comprises micro-fibres. Preferred fibres are metallic, carbon, silicium and glass fibres.

The supporting structure may comprise varying reinforcing fibres. Preferably the reinforcing fibres are sufficiently heat resistant to resist the temperature as conducted through the insulation layer. Sufficiently heat resistant reinforcing fibres have a melting temperature of at least 200 °C, preferably at least 300 °C, and most preferably at least 400°C. When the used reinforcing fibres are amorphous, such as in the case of glass fibres, a melting temperature cannot clearly be indicated or determined. Sufficiently heat resistant amorphous fibres are able to withstand the temperatures indicated above in a tensile test conducted at these temperatures and at a tensile stress of 10% of their room temperature tensile strength for an hour.

In an embodiment the support structure comprises reinforcing fibres selected from the group consisting of: polyamide fibres, polyester fibres such as Vectran®, carbon fibres, PBO-fibres (Poly(p-phenylene-2,6-benzobisoxazole)), aramide-fibres, steel-fibres, platinum- fibres, PBI fibres (Polybenzimidazole), glass fibres, silicon carbide fibres and combinations thereof. Such fibres combine low weight with high strength and temperature resistance. Combinations of the reinforcing fibres provide for further increased design flexibility and may increase impact resistance of the support structure. The support structure may comprise fibres different from the first insulating layer.

However, the support structure may also comprise the same fibres as the first insulating layer, or a mixture of fibres different from the first insulating layer and the same fibres as the first insulating layer.

The supporting structure may comprise varying matrix materials. Preferably, the matrix material is sufficiently heat resistant to resist the temperature as conducted through the insulation layer. With sufficiently heat resistant is meant that the matrix material has a glass transition temperature Tg of at least 90°C, preferably at least 140 °C, and most preferably at least 190°C. In an embodiment the matrix of the supporting structure comprises a matrix, which is composed of a polymeric material, and more preferred of a material elected from the group consisting of poly-imides, epoxy, phenol- formaldehyde, melamine and combinations thereof. In another embodiment the matrix comprises a mineral polymer. Preferred mineral polymers are described in WO0024690 and in US6103007, both documents being incorporated in their entirety by reference in the present application. Such a matrix comprising a mineral polymer shows good

temperature and oxidative resistance, allows for easy processing and is environment-friendly.

In an embodiment the first and/or second layer comprises a textile structure comprising fibres, such as a braid, a woven fabric and the like. This provides for design flexibility, in that the shape, in particular the cross-sectional shape, of the exhaust along its length may be varied depending on design requirements. An example is to design the exhaust such that a catalyst is positionable in the inner space of the exhaust or an additional muffler. This embodiment also provides for an easier integration of the function of the manifold as the shape of the manifold and in particular the part of the manifold for coupling to the engine can be adjusted.

Although it is assumed that the inner side of the housing facing the space should be smooth for reducing noise and to ensure a homogeneous airflow, it is surprisingly found that this is not required. As a result during use the exhaust according to the present invention leads to decreased pressurization and as a result the performance in terms of power of the combination of the engine and the exhaust increases. In yet another embodiment the housing is provided with a ceramic coating on the side of the thermal insulating layer facing the space to further improve the performance in terms of power of the combination of the engine and the exhaust increases. In addition such a coating may improve the sound insulating properties of the exhaust. In other words, the function of a silencer, also named muffler has been integrated in the exhaust.

The exhaust according to the invention can be fitted directly with an engine, for example in the case the engine comprises only one cylinder. The exhaust according to invention is particularly suitable to be used in combination with a manifold connected to the engine, wherein the exhaust is connectable downstream to the manifold. Although it may be more difficult to manufacture, the exhaust may also be adapted to be connected to the cylinder exits from the engine. In an embodiment therefore the exhaust comprises at least two housings, whether or not mutually interconnected, each enclosing a space for transporting the exhaust gasses and wherein each housing is provided with an entrance-opening for the exhaust gasses discharged from a manifold connected to the engine and an exit-opening for transporting the exhaust gasses away from the engine. As a result no manifold is needed anymore, leading to easier assembly of the exhaust

and the engine and in a more lightweight exhaust. In other words, the function of the manifold has been integrated in the exhaust.

For allowing for an easy connection to the engine or to the manifold the exhaust comprises at least one coupling element, for connecting the exhaust to a manifold directly to an internal combustion engine.

The invention also relates to a motorized vehicle provided with an internal combustion engine and an exhaust according to the invention connected to the engine or a manifold of the engine. For the advantages of the vehicle according to the invention see the advantages as described in relation to the exhaust according to the invention.

The invention will now be further elucidated with reference to the following schematic figures, without however being limited thereto.

Figure 1 schematically shows a perspective view of an exhaust according to the invention, Figure 2 schematically shows an exploded view of an embodiment of the exhaust according to figure 1 ,

Figure 3 schematically shows a perspective view of another embodiment of the exhaust according to the invention,

Figure 4 schematically represents a graph of temperature versus time as obtained with an exhaust of the invention, and

Figure 5 schematically represents a graph of the sound attenuation versus frequency as obtained with an exhaust of the invention.

With reference to figure 1 an exhaust 1 for exhaust gasses discharged from an internal combustion engine is shown. The exhaust comprises a tubular housing 2, which housing 2 encloses a space 3 for transporting the exhaust gasses. The housing 2 is further provided with an entrance-opening 4 for the exhaust gasses discharged from the engine and an exit-opening 5 for transporting the exhaust gasses away from the engine, according to arrow PI . The housing 2 comprises a flexible thermal insulating layer facing the space 3, which insulating layer is arranged for resisting exhaust gasses discharged from the engine. The flexible thermal insulating layer comprises a first layer 6 facing the space 3, which is arranged for withstanding a first temperature, and a second layer 7 at a side of the first insulating layer opposite from the space 3, arranged for withstanding a second temperature, wherein the first temperature is higher than the second temperature. The second layer 7 comprises a material having a specific heat capacity higher than 0,5 (kJ/(kg*K)), preferably higher than 0,6 (kJ/(kg*K)) and most preferably higher than 0.7 (kJ/(kg*K)). Further the housing 2 comprises a supporting structure 8 at a side of the insulating layer opposite from the space 3, which supporting structure 8 is made of reinforcing fibres embedded in a matrix.

In the embodiment shown, the first layer 6 is made of Superwool®, manufactured by the company Thermal ceramics. Superwool is composed of silicium (50-82 wt%), calcium and magnesium (18-43 wt%), aluminium, titanium and zirconium (less than 6 wt%), and trace oxides. The second layer 7 is made of the open-cell structure material Aerogel, comprising micro fibers and is manufactured by the company Aspen Aerogels. The support structure 8 comprises carbon fibres embedded in matrix made from phenol-formaldehyde .

Further the housing 2 is provided with a ceramic coating (not shown in Figure 1) on the side of the thermal insulating layer facing the space 3 of the exhaust 1.

With reference to figure 2 an embodiment of the exhaust 1 of figure 1 is shown. The exhaust 1 comprises a coupling element 9 near the entrance-opening 4 and an exit-opening 5 for connecting the exhaust 1 to a manifold or an internal combustion engine (not shown). The coupling elements 9 are manufactured from steel and comprise a cylindrical part 9a, which is dimensioned to be at least partly within the positioned into the space 3 surrounded by the first layer 6. Distal from the housing 2 the coupling elements 9 are provided with a plate 9b manufactured from steel, which plate 9b is provided with holes 9c, for connecting the exhaust 1 to a manifold or engine (not shown).

Figure 3 shows another embodiment of the device according to the invention. The materials used are the same as those shown in Figure 1. However, the exhaust 1 further comprises a liner 16 facing the space 3. The liner 16 comprises a mesh of steel fibers and is a.o. used to hold the first and second layers (6, 7) into place. It also provides additional ablation resistance and cooling. The mesh 16 can be made by several methods, for instance by braiding metal fibers to form a braid that is easily applied onto the thermal insulation layers 6 and 7. A typical temperature in the inside space 3 of the exhaust 1 is 950 °C, while a typical temperature at the outside of the exhaust is 200 °C, showing the excellent insulation of the exhaust.

Figure 4 shows a graph of the temperature 20 versus time 21 for the embodiment shown in Figure 3, when tested on a V12 engine. Graph 23 represents the temperature of the exhaust gasses inside the space 3, while graph 24 represents the temperature as measured on a known steel exhaust, while graph 25 represents the temperature as measured on the outside skin of the exhaust shown in Figure 3. It is clear that the particular arrangement of the exhaust in accordance with the invention yields very low temperatures at the outer skin, when compared to the steel skin which has temperatures in excess of 850 °C. It should be noted that the skin temperatures were measured close to the transition of the fiber-reinforced composite housing to a metal adapter piece used to connect the exhaust to other parts of the exhaust system. Skin temperatures measured further away on the composite housing were even lower and around 100 °C. An exhaust in accordance with the invention does not need heat shields, which may lead to a weight reduction of tenths of kg.

Due to the use of the metal mesh liner 16 in combination with the porous thermally insulating layers 6 and 7, and the fiber reinforced supporting structure 8, noise generated by the hot gasses flowing at high speeds through space 3 is damped beyond expectations. This is shown in figure 5 where the attenuation 30 in dB is shown versus frequency 31. The data were obtained by inputting a sound wave with a frequency of about 150 Hz. Graph 32 shows the attenuation in a known steel exhaust tube, while graph 33 represents the attenuation obtained with the exhaust of Figure 3. From comparing graphs 32 and 33 can easily be inferred that the exhaust according to the invention attenuates sound by -50dB in the range of 1500-3000 Hz. A muffler is therefore not necessary and omitting a muffler may save weight and reduces

manufacturing complexity and cost. The use of a housing made from fiber-reinforced composites allows to change the cross-sectional shape of the device, in particular the exhaust tube, at will. A further advantage in this respect is that the fundamental of the sound wave - which in the example given is around 150 Hz - can also be attenuated by changing the circular shape of the cross-section into an elliptic cross-section. Such shapes are easily manufactured by adopting a support structure of fiber-reinforced composite materials.

There are several methods of manufacturing the exhaust according to the invention. An example of manufacturing the exhaust according to the invention is as follows:

The second layer 7 from aerogel is shaped into its correct tubular dimensions, where after a piece of Superwool® forming the first layer 6 is cut into the correct dimensions and positioned within the second layer 7 in the tubular form. Then, layers of carbon fibres are positioned around the second layer 7 of the two halves of the support structure 8. Finally, the layers of carbon fibres are injected in the matrix and cured, thereby forming a consolidated support structure 8.

The invention has been described by the above examples, but is not limited thereto, and different modifications can be made within the scope of the invention, as defined by the attached claims. The device for handling hot gases according to the invention may advantageously be used in exhaust systems for vehicles, in helicopters and in aircraft, in turbines and the like.