Abstract:
The present invention is generally directed towards an air induction system in a motor vehicle and more specifically to a methane storage device connectable to the air induction system. The methane storage device comprises a housing having an inner chamber. A reticulated material is located within the housing. The reticulated material is capable of trapping any hydrocarbon especially methane.

Description:
TECHNICAL FIELD 
     This invention generally relates to a methane storage device to store methane emitted into an air induction system of an engine in an automobile. 
     BACKGROUND 
     The emission standard limits the, amount of hydrocarbons, carbon dioxide and particulate matter that can be emitted from the vehicle&#39;s tailpipe. Due to laws requiring the reduction of the levels of hydrocarbons that vehicles may emit into the atmosphere, it is necessary for automotive designers to consider alternate fuel technology to control emissions. One such alternate fuel technology that has been developed is the use of natural gas to run vehicles. 
     Natural gas which contains primarily over 70% methane is one of the cleanest fuels known in the automotive industry. Natural gas is used on vehicles as compressed natural gas (CNG), as the gas is compressed at over 3000 psi and stored in a fuel cylinder aboard the vehicle. Exhaust emissions from Natural Gas Vehicles (NGV) are much lower than those from equivalent gasoline-powered vehicles. For instance, NGV emissions of carbon monoxide are approximately 70% lower, non-methane organic gas emissions are 89% lower, and oxides of nitrogen emissions are 87% lower. In addition to these reductions in pollutants, NGVs also emit significantly lower amounts of greenhouse gases and toxins than gasoline vehicles do. 
     Although tailpipe emissions are significantly lower for NGV, hydrocarbons including methane are released from the engine, even when the engine is not operating. Hydrocarbons, primarily methane remaining from engine reactions can leak out of the engine through the engine&#39;s air intake systems. Although such emissions are not as significant as the tailpipe emissions, it is desirable to reduce the amount of methane leaked from the air intake systems as methane is known to cause green house effect. 
     Typically, hydrocarbons emitted from the engine&#39;s air intake system are controlled by placing a hydrocarbon adsorbing material in the air intake tube. Typically these hydrocarbon adsorbing materials are formed from carbon or zeolite and are capable of adsorbing most of the hydrocarbons released by the engine. However, methane has a very low efficiency of storage in hydrocarbon adsorbing materials. This low efficiency of storage is primarily due to the non reactive nature of the methane molecule. Although it may be possible to store methane in these hydrocarbon adsorbing materials it requires expensive processes. 
     Therefore there is a need in the automotive industry, primarily NGV&#39;s to reduce the amount of evaporative methane released from the engine&#39;s air intake system. According, there is a need to find solutions where methane can be stored at atmospheric pressure at or near room temperature. 
     SUMMARY 
     In one aspect of the invention, an air induction system of an automotive internal combustion engine comprises a methane storage device for storing evaporative methane emitted by the engine. In yet another aspect of the present invention, the methane storage device is connected to the air intake tube of the air induction system. 
     In yet another aspect of the present invention, the methane storage device has a housing having an interior chamber. The interior chamber is substantially filled with a reticulated material that is capable of trapping methane. 
     In yet another aspect of the present invention, the housing is provided with an inlet port to introduce methane inside the interior chamber. The housing is also provided with an outlet port to purge the methane vapors to the engine. 
     In yet another aspect of the present invention, a method of trapping methane in the air induction system is provided. 
    
    
     Further features and advantages of the invention will become apparent from the following discussion and the accompanying drawings in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block representation of the various components of an air induction system of an automobile&#39;s internal combustion engine, having a first embodiment of a methane storage device; 
     FIG. 2 is a block representation of the various components of an air induction system of an automobile&#39;s internal combustion engine, with an alternate embodiment of a reticulated material inside the methane storage device; 
     FIG. 3 is block representation of the air induction system and the methane storage device of FIG. 1, wherein the inlet and the outlet ports are on opposite ends of the methane storage device; 
     FIG. 4 is block representation of the air induction system and the methane storage device of FIG. 1, wherein the inlet port is at a higher level than the outlet port of the methane storage device; and 
     FIG. 5 is a block representation of the various components of an air induction system of an automobile&#39;s internal combustion engine, showing a second embodiment of a methane storage device. 
    
    
     DETAILED DESCRIPTION 
     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention or its application or uses. 
     Referring in particular to FIG. 1, an air induction system installed in the vicinity of an internal combustion engine  11  in an automobile is generally shown and represented by reference numeral  10 . The air induction system  10 , functions to filter and meter the air intake flow from the outside into the engine  11 . The direction of the air flow from the outside to the engine  11  is shown by reference numeral  12 . 
     The air induction system  10  comprises a dirty air duct  13  for drawing ambient air, an air cleaner  14  for cleaning the ambient air and an air intake duct  16 . One end  18  of the air intake duct  16  is connected to the air cleaner  14  and the other end  20  to an intake manifold  22  of the engine  11 . The air induction system  10  may comprise other components such as a mass air flow sensor, a flow conditioning device and a throttle body. During operation; the air  12  enters the air induction system  10  through the dirty air duct  13 , located upstream of the intake manifold  22 . 
     In case of natural gas vehicles (NGV) or hybrid vehicles using both gasoline fuels and natural gas fuel, the natural gas is compressed at about 3000 psi and stored in a fuel container aboard the vehicle installed in the rear, undercarriage, or on the roof (not shown). When natural gas is required by the engine, the natural gas leaves the cylinders and travels through a high-pressure fuel regulator located in the engine compartment. The natural gas is injected at atmospheric pressure through a specially designed natural gas mixer  24  where it is properly mixed with air  12  injected by the intake manifold  22 . Natural gas then flows into the engine&#39;s combustion chamber and is ignited to create the power required to drive the vehicle. 
     As clearly shown in FIG. 1, when the engine is shut off, unburnt methane vapor, shown by broken arrows  26 , present in the engine  11  has a tendency to flow into the air induction system  10  via the air intake duct  16  and finally to the environment through the dirty air duct  13 . In order to trap the methane vapors  26 , the air intake duct  16  is connected to a methane storage device  30 . 
     As seen in FIG. 1, the methane storage device  30  is formed of a housing  32 . Although in the drawing a rectangular housing is shown and described, it must be understood that the housing can be various shapes such as a cylinder, conical etc. For the sake of understanding this invention, the housing  32  has an upper portion  34  and a lower portion  36 . The upper portion  34  and the lower portion  36  have been divided by an imaginary line  35 . Upper portion  34  and lower portion  36  of the housing  32  are described relative to the air intake duct  16 . The portion of the housing  32  away from the air intake duct  16  is the upper portion  34  and the portion of the housing  32  towards the air intake duct  16  is the lower portion  36  of the housing. As clearly shown in FIG. 1, the housing  32  defines a sealed interior chamber  38 . Preferably, the housing  32  is formed of metal such as aluminum etc. Alternatively, it could be formed of plastic or plastic composites. 
     In order to trap the methane vapors  26  emitted from the engine  11  into the air intake duct  16 , the interior chamber  38  of the housing  32  is provided with a reticulated material  40 . In this invention, a reticulated material is any material having a complex net like structure such that a complex pathway is created for the methane vapors and facilitates the trapping of the methane vapors in the net like structure. Preferably, the reticulated material  40  is medium to high density foam material, having a density in the range of 40 to 100 ppi. Alternatively, as shown in FIG. 2, the reticulated material  40  may also be provided with baffles or ribs  42  such that the methane vapors  26  have to travel a longer distance inside the chamber. The travel path of the methane vapors inside the reticulated material  40  with baffles  42  is shown by reference number  44 . As clearly shown in FIG. 1, the reticulated material  40  is tightly packed inside the interior chamber  38  of the housing  32 , such that there is minimum or no flow rate between the reticulated material  40  and the interior chamber  38 . 
     In order to introduce the methane vapors  26  into the methane storage device  30 , the housing  32  is provided with an inlet port  46 . The inlet port  46  is connected to the air intake duct  16  with an inlet line  48 . Similarly, to purge the methane vapors  26  back to the engine  11  when the engine is turned on, the housing  32  is provided with an outlet port  50 . The outlet port  50  is connected to the air intake duct  16  with an outlet line  52 . As clearly shown in FIG. 1, the inlet port  46  and the outlet port  50  extend into the interior chamber  38  of the housing  32  such that the methane vapors  26  are directly introduced into the reticulated material  40 . 
     Preferably, the inlet port  46  formed on the housing  32  is spaced apart from the outlet port  50 . As shown in FIG. 1, both the inlet port  46  and the outlet port  48  are located in the lower portion  36  of the housing  32  and on a bottom wall of the housing. Alternatively, as shown in FIG. 3, the inlet port  46  and the outlet port  50  are positioned on opposite walls of the housing  32  such that the methane vapors  26  enter the housing  32  on one side and exit the housing  32  on the other side. 
     As clearly shown in FIG. 1, since methane is lighter than air, it has a tendency to rise inside the housing  32  towards the upper portion  34  of the housing. Therefore, to effectively store methane vapors  26  in the methane storage device  30 , it is preferred that the outlet port  50  be located lower than the inlet port  46 , such that the methane vapors do not enter the outlet port  50  and are stored away from the outlet port  50 . It is preferred that the outlet port  50  is located in the lower portion  36  of the housing  32 . As clearly shown in FIG. 4, the inlet port  4 ,  46  is located at the upper portion  34  of the housing  32 . Therefore, the methane vapors  26  are trapped away from the outlet port  50 , which is located on the lower portion  36  of the housing  32 . 
     Referring again to. FIG. 1, to ensure that the methane vapors  26  enter the methane storage device  30 , the air intake duct  16  is provided with a first valve  54 . Preferably, the first valve  54  is positioned in the air intake duct  16  upstream, from the inlet line  48 . When the engine is shut off, the first valve  54  also shuts off such that methane vapors  26  are forced into the methane storage device  30  through the inlet line  48 . In order to prevent methane vapors from escaping the methane storage device  30  from the outlet port  50 , the outlet port  50  is provided with a second valve  56 . Therefore, when the engine  11  is shut off, the second valve  56  closes such that no methane vapor  26  escapes the methane storage device  30 . Alternatively, the second valve  56  can be located in the air intake duct  16 , downstream from the first valve  54 . 
     In order to effectively store methane vapor  26  in the methane storage device  30  described above, the methane vapor is introduced through the inlet port  46  at a very slow rate. Preferably, the rate of introduction of the methane vapor is less than  15  sccm. A slow introduction rate will help methane vapors  26  to migrate to the upper portion  34  of the housing  32  and away from the outlet port  50 . Higher the methane vapors are in the housing  32 , more efficient is the storage of the methane vapors. 
     Additionally, the preferred embodiment of the methane storage device  30  is also self-regenerating. Rather than adsorbing methane and trapping them in until the methane storage device  30  is saturated, the methane vapors may be relatively easily released from the device. The release occurs when the engine is operating and pulling air into the air intake duct  16  at a moderate to high rate. Preferably, to remove the vapor, the air has a higher flow rate than the rate at which methane vapor was introduced into the methane storage device  30 . When air passes through the methane storage device  30  at a moderate to high rate, the methane vapors  26  trapped in the reticulated material  40  are pulled out and travel down the housing  32  to the outlet port  50  into the air intake duct  16  to the engine  11 , where they are burned off. By allowing the methane vapors  26  to be released from the methane storage device  30 , the preferred embodiment of the invention is self-regenerating, and the methane storage device  30  does not have to be replaced over the lifetime of the vehicle as a result of hydrocarbon build-up. 
     FIG. 5, represents an alternate embodiment of the methane storage device and is represented by reference numeral  100 . The various components of the air induction system  10  are represented by the same reference numeral as the previous embodiment. Like the first embodiment, methane storage device  100  also has a housing  110 . The housing  110  has an upper portion  112  and a lower portion  114  and defines an interior chamber  116 . The hydrocarbon vapors released into the air intake duct  16  are trapped by a reticulated material  118 . The reticulated material  118  is identical to the reticulated material  40  described above. 
     In order to introduce the hydrocarbon vapors into the methane storage device  100 , the methane storage device  100  is provided with a first inlet port  120  formed on the housing. The first inlet port  120  is connected to the air inlet duct by an inlet line  122 . The vapors are released back to the air intake duct  16  through an outlet port  124  formed on the housing  110  and spaced apart from the first inlet port  120 . The outlet port  124  is connected to the air intake duct  16  through an outlet line  126 . The methane storage device  100  is different from the first embodiment in that it is provided with a second inlet port  128 . As clearly shown in FIG. 5, the second inlet port  128  is preferably located away from the first inlet port  120  and the outlet port  124 . The second inlet port  128  is connected to the air intake duct  16 , through a second inlet line  130 . Like the first inlet port  120 , the second inlet port  128  is used to introduce hydrocarbon vapors such as methane or other hydrocarbons into the methane storage device  100 . Preferably, the second inlet port is located on the upper portion of the housing  110 . 
     As seen from above, the present invention provides for an efficient way of storing methane at ambient temperature and pressure. This is achieved by providing a methane storage device and connecting the device to the air induction system  10 . A reticulated material in the methane storage device helps trap and release the vapors stored. Although the invention has been described with repect to storing of methane gas released by the engine into the air induction system, it must be understood that any hydrocarbon released may be stored using the device. 
     As any person skilled in the art will recognize from the previous description and from the figures and claims, modifications and changes can be made to the preferred embodiment of the invention without departing from the scope of the invention as defined in the following claims.