Abstract:
Provided is an internal combustion engine system ( 1 ) capable of obtaining sufficient quantity of ethanol by separating a gasoline-ethanol composite fuel to gasoline and ethanol without being affected by components of gasoline. The internal combustion engine system ( 1 ) includes a composite fuel storing tank ( 2 ), a separation membrane ( 3 ) configured to separate a composite fuel to a gasoline component and an ethanol component, and a supplying unit ( 9 ) configured to supply the gasoline component and the ethanol component to an internal combustion engine respectively according to operation conditions. The separation membrane ( 3 ) is prepared to permeate aromatic hydrocarbons together with ethanol.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an internal combustion engine system using a composite fuel of gasoline and ethanol. 
         [0003]    2. Description of the Related Art 
         [0004]    In recent years, it has been called on to reduce emitted amount of carbon dioxide, which has been considered as a contribution factor to prevention of global warming. Therefore, there has been considered to use a composite fuel of ethanol and liquid hydrocarbons such as gasoline or the like as a fuel for an automobile. As the ethanol, bio-ethanol prepared from fermentation of plant substances, for example, agricultural crops such as sugar cane, corn and the like can be used. 
         [0005]    A raw material plant in the plant substances has absorbed carbon dioxide through photosynthesis; when the ethanol prepared from the raw material plant is burned, the emitted amount of carbon dioxide is equal to the absorbed amount of carbon dioxide by the raw material plant itself. In other words, the so-called carbon neutral effect can be achieved since the total emitted amount of carbon dioxide is theoretically equal to zero. Thereby, by using the composite fuel of gasoline-ethanol, namely the bio-ethanol, as a fuel for the internal combustion engine of an automobile or the like, the emitted amount of carbon dioxide can be reduced, which contributes to prevention of global warming. 
         [0006]    There has been studied an internal combustion engine system which is configured to separate the gasoline-ethanol composite fuel to gasoline and ethanol and supply the obtained gasoline and ethanol mixed at an arbitrary proportion to the engine. The ethanol has a higher octane number in comparison with the gasoline; therefore, by mixing the gasoline and the ethanol at an arbitrary proportion, it is possible to supply the engine a fuel having an appropriate octane number according to a required engine load. 
         [0007]    There has been known an internal combustion engine system using a separation membrane such as an ethanol permeation membrane to separate the gasoline-ethanol composite fuel to gasoline and ethanol (for example, refer to Japanese Patent Laid-open No. 2009-150397). A pervaporation membrane (permeation-evaporation membrane), for example, can be used as the ethanol permeation membrane to permeate ethanol to a secondary side at higher permeability than gasoline. 
         [0008]    However, in the internal combustion engine system using the ethanol permeation membrane, a separated quantity of ethanol decreases according to the components of gasoline, causing a problem that ethanol can not be obtained at a required quantity. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been accomplished in view of the aforementioned problems, and it is therefore an object of the present invention to provide an internal combustion engine system capable of obtaining sufficient quantity of ethanol by separating a gasoline-ethanol composite fuel to gasoline and ethanol without being affected by components of gasoline. 
         [0010]    According to committed researches on reasons causing a separated quantity of ethanol to degrade according to components of gasoline, the inventors of the present invention found that the separated quantity of ethanol degrades if aromatic hydrocarbons are contained in gasoline composed of hydrocarbons. 
         [0011]    In general, in a separation membrane which separates a component from the other components, firstly, the component to be permeated is absorbed to a primary side of the separation membrane, then, the component is permeated from the primary side to a secondary side thereof. Thereafter, the permeated component detaches from the separation membrane due to evaporation at the secondary side of the separation membrane and diffuses. 
         [0012]    The reason why the separated quantity of ethanol degrades if aromatic hydrocarbons are contained in gasoline composed of hydrocarbons has been considered that aromatic hydrocarbons are absorbed by priority to the primary side of the separation membrane, hindering the absorption and permeation of ethanol. 
         [0013]    To attain an object described above, the present invention provides an internal combustion engine system comprising: a composite fuel storing tank configured to store a composite fuel of gasoline and ethanol; a separation membrane configured to separate the composite fuel stored in the composite fuel storing tank to a gasoline component and an ethanol component; and a supplying unit configured to supply the gasoline component and the ethanol component separated by the separation membrane to an internal combustion engine according to operation conditions, respectively; wherein the separation membrane is prepared to permeate aromatic hydrocarbons together with ethanol. 
         [0014]    In the internal combustion engine system of the present invention, the separation membrane permeates aromatic hydrocarbons together with ethanol; thus, the aromatic hydrocarbons absorbed to the primary side of the separation membrane by priority is permeated immediately through the separation membrane, without hindering the absorption and permeation of ethanol. Therefore, according to the internal combustion engine system of the present invention, even if the gasoline in the gasoline-ethanol composite fuel contains aromatic hydrocarbons, the separated quantity of ethanol can be prevented from degrading. 
         [0015]    Although the separated quantity of ethanol can be prevented from degrading according to the internal combustion engine system of the present invention, if the quantity of ethanol itself is originally low in the gasoline-ethanol composite fuel, it is possible that the required quantity of ethanol may not be assured. 
         [0016]    In this regarding, it is preferred that the supplying unit in the internal combustion engine system of the present invention is configured to supply the ethanol component and the aromatic hydrocarbons separated by the separation membrane concurrently to an internal combustion engine according to the operation conditions. Similar to the ethanol component, the aromatic hydrocarbons also have a higher octane number and therefore are extremely appropriate substance to prevent irregular combustion such as knocking or the like in an internal combustion engine. Thereby, according to the internal combustion engine system of the present invention, the shortage of ethanol can be compensated by supplying the ethanol component together with the aromatic hydrocarbons to the internal combustion engine through the supplying unit. 
         [0017]    According to the internal combustion engine system of the present invention, when the engine load becomes high, supplying the ethanol component together with the aromatic hydrocarbons to the internal combustion engine can prevent irregular combustion such as knocking or the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is an explanatory diagram illustrating a structural example of an internal combustion engine system of the present invention. 
           [0019]      FIG. 2  is a diagram illustrating temporal variation of a separated quantity of ethanol separated by a conventional ethanol permeation membrane from an isooctane-ethanol composite fuel. 
           [0020]      FIG. 3  is a diagram illustrating temporal variation of a separated quantity of ethanol separated by a conventional ethanol permeation membrane from a toluene-ethanol composite fuel. 
           [0021]      FIG. 4  is a diagram illustrating temporal variation of a separated quantity of ethanol separated by an ethanol permeation membrane of the present invention from a toluene-ethanol composite fuel. 
           [0022]      FIG. 5  is an explanatory diagram illustrating another structural example of an internal combustion engine system of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 
         [0024]    As illustrated in  FIG. 1 , an internal combustion engine system  1  according to a first embodiment of the present invention is provided with a main tank  2  serving as a composite fuel storing tank to store a composite fuel of gasoline and ethanol, a separation device  4  having a separation membrane  3  configured to separate the composite fuel to a gasoline component and an ethanol component, a first conduit  6  configured to supply the gasoline component separated by the separation membrane  3  to an engine  5 , and a second conduit  7  configured to supply the ethanol component separated by the separation membrane  3  to the engine  5 . The engine  5 , for example, is a flexible fuel engine. The first conduit  6  is connected to the engine  5  via a first injector  8   a,  and the second conduit  7  is connected to the engine  5  via a second injector  8   b.  The injectors  8   a  and  8   b  are controlled by a controller  9  such as an electronic control unit (ECU) or the like. 
         [0025]    The separation membrane  3  may be any membrane capable of permeating aromatic hydrocarbons together with ethanol, for example, a carbon membrane described in the embodiment 1 of Published PCT International Application 2009/001970 can be used after a heat treatment known heretofore is performed thereon in oxidative atmosphere. The carbon membrane is prepared from a precursor solution obtained by dissolving a commercially available phenol resin in an organic solvent. The heat treatment in oxidative atmosphere, for example, may be one described in Industrial &amp; Engineering Chemistry Research vol. 36 (1997), No. 6, page 2134 to 2140. 
         [0026]    According to the internal combustion engine system  1  of the present embodiment, the gasoline-ethanol composite fuel stored in the main tank  2  is supplied to the separation device  4  to be separated to the gasoline component and the ethanol component. The separation device  4  is provided with the separation membrane  3  for permeating aromatic hydrocarbons together with ethanol, therefore, even though aromatic hydrocarbons are contained in the gasoline of the gasoline-ethanol composite fuel, sufficient quantity of ethanol can be permeated. 
         [0027]    In the separation device  4 , firstly, aromatic hydrocarbons in the supplied gasoline-ethanol composite fuel are absorbed to the primary side of the separation membrane  3  by priority. The aromatic hydrocarbons are permeated through the separation membrane  3  immediately, without hindering the absorption and permeation of ethanol. As a result thereof, components abound in gasoline can be obtained at the primary side of the separation membrane  3 , and meanwhile, components abound in ethanol and aromatic hydrocarbons can be obtained at the secondary side of the separation membrane  3 . In the present specification, the components abound in ethanol and aromatic hydrocarbons obtained at the secondary side of the separation membrane  3  are described as the ethanol component, and the components abound in gasoline obtained at the primary side of the separation membrane  3  are described as the gasoline component. 
         [0028]    The gasoline component is supplied to the engine  5  from the first conduit  6  via the first injector  8   a,  and the ethanol component is supplied to the engine  5  from the second conduit  7  via the second injector  8   b.  The supplied quantities of the gasoline component and the ethanol component are adjusted by the controller  9  according to a required load of the engine  5 . Specifically, the supplied quantity of the ethanol component is adjusted greater as the required load of the engine  5  becomes larger. 
         [0029]    The ethanol component contains the aromatic hydrocarbons and the aromatic hydrocarbons have a higher octane number similar to ethanol; therefore, the aromatic hydrocarbons can be used similar to ethanol according to the required load of the engine  5 . 
         [0030]    Hereinafter, descriptions will be carried out on the ethanol permeability of the separation membrane  3 . 
         [0031]    Firstly, as a contrast, a separation membrane capable of permeating ethanol but not aromatic hydrocarbons (for example, a carbon membrane described in embodiment 1 of Published PCT International Application 2009/001970 (prepared from a precursor solution for the carbon membrane obtained by dissolving a commercially available phenol resin in an organic solvent)) is used in place of the separation membrane  3  to separate an isooctane-ethanol composite fuel consisting of 10% (w/w) ethanol and 90% (w/w) isooctane. The isooctane-ethanol composite fuel is prepared in imitation of a gasoline-ethanol composite fuel containing substantially no aromatic hydrocarbons. The result thereof is shown in  FIG. 2 . 
         [0032]    Subsequently, the same separation membrane as that in  FIG. 2  is used to separate a toluene-ethanol composite fuel consisting of 10% (w/w) ethanol and 90% (w/w) toluene. The toluene-ethanol composite fuel is prepared in imitation of the gasoline-ethanol composite fuel containing aromatic hydrocarbons in which gasoline is composed of aromatic hydrocarbons only (toluene in this case). The result thereof is shown in  FIG. 3 . 
         [0033]    From  FIG. 2  and  FIG. 3 , it is obvious that when the separation membrane capable of permeating ethanol but not aromatic hydrocarbons is used, sufficient ethanol can be separated from the gasoline-ethanol composite fuel containing substantially no aromatic hydrocarbons, but the separated quantity of ethanol from the gasoline-ethanol composite fuel containing aromatic hydrocarbons is drastically decreased. 
         [0034]    Thereafter, the separation membrane  3  of the present embodiment is used to separate the toluene-ethanol composite fuel consisting of 10% (w/w) ethanol and 90% (w/w) toluene. The result thereof is shown in  FIG. 4 . 
         [0035]    From  FIG. 4 , it is obvious that when the separation membrane  3  capable of permeating aromatic hydrocarbons together with ethanol is used, the same quantity of ethanol as that in  FIG. 2  can be separated, and the separated quantity of aromatic hydrocarbons is remarkably increased in comparison with that in  FIG. 3 . 
         [0036]    A second embodiment of the present invention will be described hereinafter. 
         [0037]    As illustrated in  FIG. 5 , the internal combustion engine system  11  of the second embodiment of the present invention has completely the same configuration as the internal combustion engine system  1  illustrated in  FIG. 1  except that a sub tank  12  serving as the ethanol component tank for storing the ethanol component is disposed intermediately in the second conduit  7 . 
         [0038]    When the gasoline-ethanol composite fuel consists of, for example, 90% (w/w) gasoline and 10% (w/w) ethanol, the absolute quantity of ethanol is low. Thus, even though the separation membrane  3  is used to separate ethanol effectively, enough quantity of ethanol component sufficient for the required load of the engine  5  may not be obtained. 
         [0039]    However, according to the internal combustion engine system  11 , by preliminarily storing the ethanol component in the sub tank  12 , sufficient quantity of ethanol can be assured even though the proportion of ethanol contained in the gasoline-ethanol composite fuel is low.