Internal combustion engine system with hydrogen generation capability

A dehydrogenated fuel tank 32 which is replenished with an organic hydride-contained hydrogenated fuel and a gasoline tank 48 which is replenished with normal gasoline are provided. In order to separate the hydrogenated fuel into a hydrogen rich gas and dehydrogenation product, a dehydrogenation reactor 22 and a separator 40 are provided. The hydrogen rich gas flows into a hydrogen pipe 44 and is supplied into the intake pipe 12. A dehydrogenation product pipe 42 is provided with a flow separator 46. The dehydrogenation product is guided into the gasoline tank 48 until the mixed ratio of the dehydrogenation product reaches the maximum allowable ratio in the gasoline tank 48. Only if the ratio reaches the maximum allowable ratio, the dehydrogenation product is collected into a dehydrogenation product tank 50.

TECHNICAL FIELD

The present invention relates to an internal combustion engine system with a hydrogen generation capability. In particular, the invention relates to a hydrogen generation capability-equipped internal combustion engine system which is run by using both hydrogenated fuel and normal gasoline.

BACKGROUND ART

As disclosed in, for example, Japanese Patent Laid-Open No. 2003-343360, internal combustion engine systems provided with hydrogen generation capability are known. Specifically, the system includes a mechanism to generate a hydrogen rich gas and dehydrogenation products such as naphthalene from a hydrogenated fuel containing organic hydrides such as Decalin as well as a hydrogen engine which runs using the generated hydrogen rich gas as fuel.

In the system disclosed in the above-mentioned publication, while the hydrogen engine is operating, the hydrogenated fuel is separated into a hydrogen rich gas and dehydrogenation products by utilizing the heat generated by the operation. Then, only the hydrogen rich gas is extracted and used as fuel. The remaining dehydrogenation products are collected into a recovery tank. The recovery tank has a discharge pipe through which the dehydrogenation products can be discharged to the outside.

As described above, this prior art system can generate by itself hydrogen for use as fuel. It is therefore possible to realize a hydrogen-fueled system without having to install a high pressure hydrogen tank or the like.

Including the above-mentioned document, the applicant is aware of the following documents as a related art of the present invention.

By the way, for an internal combustion engine to output large power, it is effective to supply both gasoline and hydrogen to the internal combustion engine. This function can be implemented by, for example, applying the above-mentioned prior art system to a gasoline-fueled ordinary internal combustion engine.

In the above-mentioned prior art system, however, dehydrogenation products which are by-products of generating hydrogen rich gas are discharged for disposal. Thus, if the system is simply applied to an ordinary internal combustion engine, dehydrogenation products will have to be discharged frequently, requiring the user to do troublesome maintenance/management operations.

DISCLOSURE OF INVENTION

The present invention has been made to solve the above-mentioned problem. It is an object of the present invention to provide a hydrogen generation capability-equipped internal combustion engine which can use both hydrogen rich gas and normal gasoline as fuel without requiring troublesome maintenance/management operations.

The above object is achieved by a first aspect of the present invention. The first aspect of the present invention relates to an internal combustion engine system with a capability to generate hydrogen. The system includes a hydrogenated fuel tank which is replenished with an organic hydride-contained hydrogenated fuel. The system also includes a gasoline tank which is replenished with a normal gasoline. A fuel separating unit is provided for separating the hydrogenated fuel into a hydrogen rich gas and a dehydrogenation product. A hydrogen rich gas consuming mechanism is provided for consuming the hydrogen rich gas. A dehydrogenation product mixing unit is provided for mixing the dehydrogenation product with the normal gasoline. Further, the system includes a fuel supplying unit by which a mixed fuel composed of the normal gasoline and the dehydrogenation product is supplied to an internal combustion engine.

The above object of the present invention is also achieved by a second aspect of the present invention. The second aspect of the present invention relates to the internal combustion engine system according to the first aspect. In this aspect, the dehydrogenation product mixing unit includes a dehydrogenation product guiding mechanism for guiding the dehydrogenation product into the gasoline tank, a mixed ratio detecting unit for detecting the mixed ratio of the dehydrogenation product in the gasoline tank, and a dehydrogenation product stopping unit for prohibiting the dehydrogenation product from flowing into the gasoline tank if the mixed ratio exceeds the maximum allowable mixed ratio.

The above object of the present invention is further achieved by a third aspect of the present invention. The third aspect of the present invention relates to the internal combustion engine system according to the second aspect of the present invention. In this aspect, a dehydrogenation product tank is further provided to pool the dehydrogenation product. The dehydrogenation product guiding unit includes a flow separator capable of implementing a first state in which the dehydrogenation product is guided into the gasoline tank and a second state in which the dehydrogenation product is guided into the dehydrogenation product tank. The dehydrogenation product stopping unit includes flow separator control unit which sets the flow separator to the second state if the mixed ratio exceeds the maximum allowable mixed ratio. The system further includes an alarming unit which if the amount of the dehydrogenation product pooled in the dehydrogenation product tank reaches the maximum allowable amount, issues an alarm about the condition.

According to a first aspect of the present invention, it is possible to generate a hydrogen rich gas and dehydrogenation product by separating a hydrogenated fuel. While the hydrogen rich gas is consumed, the dehydrogenation product can be mixed into a normal gasoline and supplied to the internal combustion engine as part of the mixed fuel. It is therefore possible to reduce the frequency of discharging the dehydrogenation product.

According to a second aspect of the present invention, it is possible to prohibit the dehydrogenation product from flowing into a gasoline tank if the mixed ratio of the dehydrogenation product in the gasoline tank exceeds the maximum allowable mixed ratio. If the mixed ratio of the dehydrogenation product rises excessively, the mixed fuel deteriorates in combustibility, making it impossible for the internal combustion engine to stably run. The present invention can prevent such a situation from occurring.

According to a third aspect of the present invention, it is possible to guide the dehydrogenation product into a dehydrogenation product tank if the mixed ratio of the dehydrogenation product exceeds the maximum allowable mixed ratio. Thus, it is possible to continue generating hydrogen rich gas without excessively raising the mixed ratio of the dehydrogenation produce in the mixed fuel. Further, in case the amount of the dehydrogenation product pooled in the tank reaches the maximum allowable amount, it is possible to issue an alarm to urge its disposal (discharge).

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

Configuration of First Embodiment

FIG. 1is provided to explain the configuration of an internal combustion engine system according to a first embodiment of the present invention. This system has an internal combustion engine10. An intake pipe12and an exhaust pipe14are communicated with the internal combustion engine10.

The intake pipe12is provided with a throttle valve16to control the amount of air to be suctioned. Downstream of the throttle vale16, a hydrogen injector18is disposed. In addition, a gasoline injector20is disposed at the intake port of the internal combustion engine10.

The hydrogen injector18, as described later, is supplied with hydrogen rich gas at a certain pressure. Receiving a drive signal from the outside, the hydrogen injector18opens the valve to inject hydrogen rich gas into the intake pipe12. The amount of hydrogen rich gas to be injected is in accordance with the valve opening duration. Although the hydrogen injector18is disposed at the intake pipe12in the system ofFIG. 1, the configuration is not limited to this arrangement. Specifically, the hydrogen injector18may also be mounted on the main body of the internal combustion engine so as to inject hydrogen into the cylinder.

The gasoline injector20, as described later, is supplied with gasoline (strictly, mixed fuel) at a certain pressure. Receiving a drive signal from the outside, the gasoline injector20opens its valve to inject gasoline into the intake port12. The amount of gasoline to be injected is in accordance with the valve opening duration.

A dehydrogenation reactor22is attached to the exhaust pipe14. In addition, a hydrogenated fuel injector24is mounted to the top of the dehydrogenation reactor22. The hydrogenated fuel injector24, as described later, is supplied with organic hydride-contained hydrogenated fuel at a certain pressure.

Here, “organic hydrides” mean Decalin, cyclohexane and other hydrocarbon components which show dehydrogenation at temperatures around 300° C. Further, for convenience of explanation, it is assumed that a fuel which contains only methylcyclohexane C7H14, that is, a fuel which is substantially 100% composed of methylcyclohexane is used as “hydrogenated fuel” in this embodiment.

Receiving a drive signal from the outside, the hydrogenated fuel injector24opens its valve to inject hydrogenated fuel into the dehydrogenation reactor22. The amount of hydrogenated fuel to be injected is in accordance with the valve opening duration. The dehydrogenation reactor22can separate the thus supplied hydrogenated fuel into a hydrogen rich gas and dehydrogenation product by utilizing the heat emitted from the exhaust pipe14, and sending them out from the bottom.

In this embodiment, as mentioned above, hydrogenated fuel is composed 100% of methylcyclohexane C7H14. Methylcyclohexane C7H14is separated into hydrogen H2and toluene C7H8through a dehydrogenation reaction as below:
C7H14→C7H8+3H2(1)

Thus, in this embodiment, if hydrogenated fuel is injected from the hydrogenated fuel injector24, hydrogen rich gas and toluene C7H8are sent out from the bottom of the dehydrogenation reactor22.

An O2sensor26and a NOx sensor28are mounted in the exhaust pipe14downstream of the dehydrogenation reactor22. Based on the amount of oxygen in the exhaust gas, the O2sensor26provides an output which represents the exhaust air-fuel ratio. In addition, the NOx sensor28provides an output which represents the NOx concentration in the exhaust gas. A catalyst30is disposed downstream of these sensors26and28to purify the exhaust gas.

The system of the present embodiment includes a hydrogenated fuel tank32. The hydrogenated fuel tank32is a tank which should be refueled with hydrogenated fuel and pools the hydrogenated fuel. In other words, the system of the present embodiment requires filling the hydrogenated fuel tank32with the above-mentioned hydrogenated fuel, namely, 100% methylcyclohexane.

A hydrogenated fuel supply pipe34is connected with the hydrogenated fuel tank32. The hydrogenated fuel supply pipe34is provided with a pump36halfway in its route and communicated with the hydrogenated fuel injector24at its end. During operation of the internal combustion engine, hydrogenated fuel is pumped up from the hydrogenated fuel tank32and supplied to the hydrogenated fuel injector24at a certain pressure.

As mentioned above, receiving a drive signal from the outside, the hydrogenated fuel injector24can inject hydrogenated fuel into the dehydrogenation reactor22from its top. The dehydrogenation reactor22, as mentioned above, separates the hydrogenated fuel into a hydrogen rich gas and a dehydrogenation product, namely, hydrogen rich gas and toluene C7H8.

The bottom of the dehydrogenation reactor22communicates with a separator40via a pipe38. The separator40has the capability to separate the high temperature hydrogen rich gas and dehydrogenation product (toluene) supplied from the dehydrogenation reactor22by cooling them. In the bottom of the separator40, there is a liquid reservoir space to pool the cooled and thereby liquefied dehydrogenation product therein. Above this reservoir space, there is a vapor reservoir space to pool the hydrogen rich gas still in vapor phase. A dehydrogenation product pipe42communicated with the separator40gives communication to the liquid reservoir space. Likewise, a hydrogen pipe44gives communication to the vapor reservoir space.

The dehydrogenation product pipe42is communicated with a flow separator46. The flow separator46is connected to a gasoline tank48and a dehydrogenation product tank50. Receiving a drive signal from the outside, the flow separator46can switch its state between a first state in which the dehydrogenation product pipe42communicates with the dehydrogenation product tank50and a second state in which the hydrogenation product pipe42communicates with the gasoline tank48. In this system embodiment, it is therefore possible to supply the dehydrogenation product into the gasoline tank48by setting the flow separator46to the first state. It is also possible to guide the dehydrogenation product into the dehydrogenation product tank50by setting the flow separator46to the second state.

The dehydrogenation product tank50includes a liquid level sensor52and a discharge valve54. The liquid level sensor52provides an output which reflects the amount of the dehydrogenation product collected in the dehydrogenation product tank50. The discharge valve54is a valve mechanism by which dehydrogenation product pooled in the dehydrogenation product tank50is discharged to the outside.

The gasoline tank48is a tank which should be replenished with normal gasoline which contains organic hydrides such as cyclohexane and Decalin at some 40%. That is, the system of the present embodiment is designed so that the hydrogenated fuel tank32is replenished with hydrogenated fuel and the gasoline tank48is filled with normal gasoline.

When the flow separator46is in the first state, the dehydrogenation product, namely, toluene generated in the separator40, is supplied into the gasoline tank. In the gasoline tank48, a mixed fuel composed of the replenished normal gasoline and the dehydrogenation product introduced from the flow separator46is therefore pooled.

In this embodiment, the gasoline tank48includes a weight sensor56and a level sensor58. The weight sensor56provides an output which reflects the amount of the mixed fuel pooled in the gasoline tank50. Meanwhile, the level sensor58provides an output which reflects the volume of the mixed fuel there. The specific gravity of the normal gasoline is different from that of the dehydrogenation product. If both weight and volume of the mixed fuel pooled there are known, it is therefore possible to calculate the ratio of the normal gasoline content and the dehydrogenation product content from these values. In the system of the present embodiment, the ratio of the dehydrogenation product content in the mixed fuel pooled in the gasoline tank48can be detected based on the output of the weight sensor56and that of the level sensor58.

A gasoline pipe60is communicated with the gasoline tank48. The gasoline pipe60is provided with a pump62halfway in its route and communicated with the gasoline injector20at its end. During operation of the internal combustion engine, the mixed fuel stored in the gasoline tank48is pumped up by the pump62at a certain pressure and supplied to the gasoline injector20.

The hydrogen pipe44is communicated with a hydrogen buffer tank64. The hydrogen pipe44is provided with a pump66and a relief valve68. From the separator40, hydrogen rich gas is pumped into the hydrogen buffer tank64by the pump66. The relief valve68prevents the delivery pressure of the pump66from rising excessively. With the pump66and the relief valve68, hydrogen rich gas can be supplied into the hydrogen buffer tank64without causing the internal pressure to rise excessively.

The hydrogen buffer tank64includes a pressure sensor70. The pressure sensor70provides an output which reflects the internal pressure of the hydrogen buffer tank64. According to the output of the pressure sensor70, it is possible to estimate the amount of hydrogen rich gas pooled in the hydrogen buffer tank64.

A hydrogen supply pipe72is communicated with the hydrogen buffer tank64. The hydrogen supply pipe72is provided with a regulator74halfway in its route and communicated with the hydrogen injector18at its end. In this configuration, hydrogen rich gas is supplied to the hydrogen injector18at a pressure regulated by the regulator74as long as hydrogen rich gas is pooled enough in the hydrogen buffer tank64.

The system in the present embodiment includes an ECU80. The outputs of various sensors including the above-mentioned O2sensor26, NOx sensor28, liquid level sensor52, liquid weight sensor56, liquid level sensor58and pressure sensor70are connected to the ECU80. In addition, the actuators of the above-mentioned flow separator46, pumps36,62and66and injectors18,20and24, an alarm lamp82and others are connected to the ECU80. By performing routine processing based on the sensor outputs, the ECU80can appropriately drive these actuators and turn on the alarm lamp82to notify that the amount of the dehydrogenation produce pooled has exceeded the upper limit if so.

Summary of Operation of First Embodiment

When the internal combustion engine10starts, the ECU80begins to calculate the amounts of hydrogen rich gas and gasoline (mixed fuel) to be supplied to the internal combustion engine10. These targeted values are calculated based on the operating condition according to predefined rule. During operation of the internal combustion engine10, the hydrogen injector18and the gasoline injector20are driven so as to realize these target values. Consequently, the hydrogen rich gas pooled in the hydrogen buffer tank64and the mixed fuel pooled in the gasoline tank48are appropriately injected into the intake pipe12and the intake port, respectively.

If both hydrogen and gasoline are supplied to the internal combustion engine10at the same time, it is possible to obtain greatly larger power than when only hydrogen is used as the fuel. In addition, since this greatly raises the upper limit of the air excess ratio at which stable combustion can be assured as compared with a case in which only gasoline is used as the fuel, it is possible to remarkably improve the fuel efficiency and emission performance. Thus, the system of the present embodiment can realize an internal combustion engine10superior in terms of fuel efficiency, output power performance and emission.

The dehydrogenation reactor22in this system embodiment becomes able to separate the hydrogenated fuel to a hydrogen rich gas and dehydrogenation product when its internal temperature is raised to 300° C. or so. After the internal combustion engine10is started, the ECU80judges whether the dehydrogenation reactor22has become ready to perform the separating process based on the temperature of the internal combustion engine10. Then, if it is judged that the process can be performed, the ECU80allows the hydrogenated fuel injector24to start injecting an appropriate amount of hydrogenated fuel.

After the hydrogenated fuel begins to be injected, a high temperature gas of a mixture of a hydrogen rich gas and dehydrogenation product (toluene) begins to flow out from the bottom of the dehydrogenation reactor22. This high temperature gas is cooled in the separator40, thereby the dehydrogenated product begins to flow in the dehydrogenation product pipe42and the hydrogen rich gas begins to flow in the hydrogen pipe44, respectively.

The hydrogen rich gas in the hydrogen pipe44flows into the hydrogen buffer tank64under pressure by the pump66. Normally, the ECU80controls the generative amount of hydrogen rich gas, i.e., controls the amount of hydrogenated fuel to be injected from the hydrogenated fuel injector24so that the internal pressure of the hydrogen buffer tank64is kept within a desired range. The system of the present embodiment can therefore reliably run the internal combustion engine10using the hydrogen rich gas and the mixed fuel, while always keeping an appropriate amount of hydrogen rich gas in the hydrogen buffer tank64.

Dehydrogenation product, namely, toluene flows in the dehydrogenation product pipe42and is guided into the gasoline tank48or the dehydrogenation product tank50depending on the state of the flow separator46. Dehydrogenation products such as toluene can not solely be used as fuel for the internal combustion engine10since their octane numbers are excessively high. However, a dehydrogenation product is inevitably generated as a by-product in the system of the present embodiment since hydrogen is generated by decomposing a hydrogenated fuel.

One considerable method for treating such a dehydrogenated product is simply collecting the product into a recovery tank, and discharging the dehydrogenated product to the outside from the recovery tank when some volume is accumulated. In this method, however, it is necessary to either frequently discharge the dehydrogenated product or use a larger recovery tank in order to reduce the frequency.

Alternatively, although toluene and other dehydrogenation products can not solely be used as fuel for the internal combustion engine10, they may be mixed into a normal gasoline as octane boosters. That is, since dehydrogenation products are stable in composition, adding a dehydrogenation product to normal gasoline at an appropriate proportion can boost the octane number without deteriorating the combustibility of the gasoline. Consequently, such a mixed fuel can improve the output power of the internal combustion engine10since the possibility of knocking is lower than when normal gasoline is solely used.

Further, in the system of the present embodiment, as already described, the ratio of the dehydrogenation product content in the mixed fuel pooled in the gasoline tank48can be detected based on the output of the weight sensor56and that of the liquid level sensor58. Thus, the system of the present embodiment is configured so that the dehydrogenation product is guided into the gasoline tank48by setting the flow separator46to the first state until the above mentioned ratio reaches a predetermined upper limit and the dehydrogenation product is collected into the dehydrogenation product recovery tank50by setting the flow separator to the second state only while the ratio is higher than the upper limit.

Practical Processing in the Second Embodiment

FIG. 2is the flowchart of a routine which is executed by the ECU80to implement the above-mentioned functions in this embodiment. In the routine shown inFIG. 2, firstly, the volume and weight of the mixed fuel in the gasoline tank48are obtained based on the outputs of the weight sensor56and liquid level sensor58(step100).

Then, based on these obtained results, the ratio of the dehydrogenated content or toluene content in the mixed fuel is calculated (step102). Then, it is judged whether the calculated ratio is equal to or higher than a predetermined threshold (step104). This predetermined threshold is the upper limit of the toluene content range in which the internal combustion engine10shows good combustion.

If the ratio of the toluene content is judged equal to or larger than the predetermined threshold in the above-mentioned step104, it is considered that the mixed fuel may loose its adequateness as fuel if the dehydrogenation product (toluene) is further supplied into the gasoline tank48. In this case, the flow separator46is set to the second state so as to prevent the dehydrogenation product from flowing into the gasoline tank48(step106).

On the other hand, if the toluene content is judged smaller than the predetermined threshold in the above-mentioned step104, it is considered that further supply of the dehydrogenation product (toluene) into the gasoline tank48is allowed. In this case, the flow separator46is set to the first state to allow further supply (step108).

According to the processing mentioned above, the hydrogenated fuel can be separated into a hydrogen rich gas and dehydrogenation product during operation of the internal combustion engine10so as to compensate for the amount of hydrogen rich gas consumed. As well, some of the generated dehydrogenation product can be consumed as part of the mixed fuel without deteriorating the adequacy of the mixed fuel as fuel. Therefore, as compared with a system where a normal gasoline is directly injected from the gasoline injector20, the system of the present embodiment can improve the output power performance of the internal combustion engine10and, further, lighten the system maintenance/management burden by reducing the frequency of discharging the dehydrogenation product.

In addition, as described above, if the amount of the dehydrogenation product collected in the dehydrogenation product tank50exceeds the upper storage limit, this system embodiment can turn on the alarm lamp82to urge the system user to discharge the dehydrogenation product. According to the system of the present embodiment, it is therefore possible to realize an easy-to-use dual-fueled internal combustion engine10.

Note that although it is assumed in the aforementioned first embodiment that the fuel used as the hydrogenated fuel contains 100% of an organic hydride, the present invention is not limited to this. Although the higher the ratio of the organic hydride content in the hydrogenated fuel, the more preferable for generating hydrogen efficiently, the ratio is not necessarily limited to 100%. The ratio of the organic hydride content inof the hydrogenated fuel is only required to be higher than that of normal gasoline.

Also note that although it is assumed in the aforementioned first embodiment that the hydrogen rich gas generated by decomposing the hydrogenated fuel is consumed by the internal combustion engine10as fuel, the hydrogen gas may also be consumed for other purposes. Namely, the hydrogen rich gas generated together with the dehydrogenation product may also be added to the exhaust gas of the internal combustion engine10in order to improve the emission. Further, the gas may be consumed by not only the internal combustion engine10but also other different devices (auxiliary hydrogen engine, fuel cell system and the like).

In addition, although it is assumed in the aforementioned first embodiment that the dehydrogenation product is mixed with normal gasoline in the gasoline tank48, the mixing place is not limited to the gasoline tank48. That is, the dehydrogenation product may be mixed with the normal gasoline in some place of the gasoline supply pipe before the gasoline injector20.

Further, although it is assumed in the aforementioned first embodiment that if the amount of the dehydrogenation produce pooled reaches the upper limit, the alarm lamp82is used to notify of it, the alarming means is not limited to a lamp. For example, alarming may also be done using an alarm buzzer, voice guidance or the like.

It should be noted that the dehydrogenation reactor22and the separator40in the aforementioned first embodiment correspond to “fuel separating unit” in the first aspect of the present invention. Likewise, the internal combustion engine10corresponds to “hydrogen rich gas consuming mechanism” and the gasoline supply pipe60, the pump62and the gasoline injector20correspond to “fuel supplying unit”. In addition, “dehydrogenation product mixing unit” in the first aspect of the present invention is implemented by the ECU80which sets the flow separator46to the first state by executing step108as aforementioned.

Also it should be noted that in the aforementioned first embodiment, the flow separator46corresponds to “dehydrogenation product guiding mechanism” in the second aspect of the present invention. In addition, “mixed ratio detecting unit” in the second aspect of the present invention is implemented by the ECU80which executes steps100and102as aforementioned. Likewise, “dehydrogenation product stopping unit” in the second aspect of the present invention is implemented by the ECU80which sets the flow separator46to the second state by executing step108as aforementioned.

Also it should be noted that in the aforementioned first embodiment, “flow separator control means” in the third aspect of the present invention is implemented by the ECU80which sets the flow separator46to the second state by executing step106as mentioned above. Likewise, “alarming unit” in the third aspect of the present invention is implemented by the ECU80which turns on the alarm lamp82if the amount of the dehydrogenation product pooled in the dehydrogenation product tank50reaches the maximum allowable amount.