JP5916109B2 - Ethanol engine system - Google Patents

Description

  The present invention relates to an ethanol engine system using ethanol as a fuel.

Ethanol can be obtained as so-called biofuel from biomass such as sugar cane and corn. Such carbon neutral ethanol can reduce CO ₂ by substituting for petroleum fuel. However, ethanol has a higher market price than petroleum fuel, which has hindered the widespread use of ethanol as a fuel.

  By the way, the production process of biomass-derived ethanol is roughly divided into a saccharification process, a fermentation process, and a dehydration process. Predetermined energy is required to carry out each of these processes, but the dehydration process is about 25% of the total energy required for the manufacturing process. Therefore, if the aqueous ethanol solution can be used as fuel without performing the dehydration process, the amount of energy required for the alcohol production process can be reduced, and the price of ethanol can be kept low.

  On the other hand, an engine widely used as a power source in various fields can effectively achieve high efficiency by recovering the exhaust heat. In particular, an exhaust heat recovery system using fuel reforming is less important than other exhaust heat recovery systems and can be implemented at low cost. Therefore, it is considered important to improve engine efficiency. .

  Conventionally, as an ethanol engine system using an ethanol reformed gas as a fuel, a reformer that generates an reformed gas using an ethanol aqueous solution as a raw material and utilizing exhaust heat of the engine is supplied from the reformer. It is possible to supply reformed gas to the engine from the engine that generates power by combustion of the reformed gas and until the exhaust heat of this engine reaches the reforming temperature in the reformer. Until then, there is known an ethanol injection means for injecting high-concentration ethanol into an intake pipe of an engine to generate power in the engine (see, for example, Patent Document 1).

JP 2009-74439 A

  However, in the conventional ethanol engine system (for example, refer to Patent Document 1), the ethanol aqueous solution for reforming has an ethanol concentration much lower than that of ethanol for combustion. There was a problem that two types of ethanol for combustion had to be used. Therefore, the conventional ethanol engine system requires at least two tanks to store the reforming ethanol aqueous solution and the combustion ethanol, respectively, and there is a problem that the system itself becomes large.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ethanol engine system that can use a common aqueous ethanol solution as a fuel from the start of the engine to a steady operation that operates at a predetermined rotational speed and a predetermined load. is there.

Ethanol engine system of the present invention, a storage tank of ethanol aqueous solution, a reformer for generating a reformed gas to the raw material aqueous ethanol solution supplied from the storage tank, is stored in the storage tank to solve the problem An aqueous ethanol solution is directly injected into the combustion chamber and reformed gas is supplied from the reformer, and ethanol and reformed gas contained in the aqueous ethanol solution are combusted in the combustion chamber to generate power. An engine, and a reformed gas sent from the reformer and an aqueous ethanol solution containing unreformed ethanol are separated between the reformer and the engine. Provided with a separation device for returning to the storage tank, provided in the middle of the extension of an ethanol return pipe connecting the separation device and the storage tank. A flow rate adjusting device for adjusting the flow rate of the aqueous ethanol solution flowing through the ethanol return pipe, and detecting at least one of the concentrations of the aqueous ethanol solution sent from the storage tank to the engine and the reformer comprising a ethanol concentration detector, the flow control device is characterized that you adjust the flow rate of the ethanol aqueous solution flowing through the ethanol return pipe according to the concentration of the aqueous ethanol solution is detected by the ethanol concentration detector .
The ethanol engine system of the present invention that solves the above-described problems includes a storage tank for an aqueous ethanol solution, a reformer that generates a reformed gas from the aqueous ethanol solution supplied from the storage tank, and a storage tank that stores the reformed gas. The generated aqueous ethanol solution is directly injected into the combustion chamber and reformed gas is supplied from the reformer, and the ethanol and reformed gas contained in the aqueous ethanol solution are combusted in the combustion chamber to generate power. The reformed gas sent from the reformer and the aqueous ethanol solution containing unreformed ethanol are separated between the reformer and the engine, and the separated aqueous ethanol solution is provided. Is provided in the middle of the extension of the ethanol return pipe that connects the separation device and the storage tank. A flow rate adjusting device for adjusting the flow rate of the aqueous ethanol solution flowing through the ethanol return pipe, and at least one of the concentrations of the aqueous ethanol solution sent from the storage tank to the engine and the reformer When the ethanol concentration detected by the ethanol concentration detector exceeds a predetermined threshold, the engine generates power only by the combustion of ethanol in the aqueous ethanol solution supplied to the engine. When the ethanol concentration detected by the ethanol concentration detector is below a predetermined threshold, power is generated by combustion of ethanol and reformed gas.

  ADVANTAGE OF THE INVENTION According to this invention, the ethanol engine system which can use common ethanol aqueous solution as a fuel can be provided from the time of engine starting to the time of the steady driving | running operated with a predetermined | prescribed rotational speed and a predetermined | prescribed load.

1 is a configuration explanatory diagram of an ethanol engine system according to an embodiment of the present invention. FIG. It is a partial expansion schematic diagram showing typically the cylinder head neighborhood of the engine which constitutes the ethanol engine system concerning the embodiment of the present invention. (A) is sectional drawing of the reformer which comprises the ethanol engine system which concerns on embodiment of this invention, (b) is sectional drawing of the reaction cell incorporated in a reformer, (c) is It is sectional drawing of the reaction sheet incorporated in the reaction cell. 1 is a configuration explanatory diagram of a separation device constituting an ethanol engine system according to an embodiment of the present invention. FIG. It is a graph which shows the relationship between the ethanol density | concentration [mass%] of the ethanol aqueous solution used as a fuel with the ethanol engine system which concerns on embodiment of this invention, and the ratio of the latent heat of vaporization with respect to a low fuel calorific value. It is a graph which shows the ratio of the latent heat of vaporization with respect to low fuel calorific value of ethanol aqueous solution used as fuel in the ethanol engine system concerning the embodiment of the present invention by contrast with other fuels (gasoline, toluene). It is a graph which shows the relationship between the ethanol concentration of molar conversion, and the ethanol concentration of mass conversion of the ethanol aqueous solution used as a fuel with the ethanol engine system which concerns on embodiment of this invention. It is a flowchart which shows the procedure which the control part which comprises the ethanol engine system which concerns on embodiment of this invention performs. It is composition explanatory drawing of the 1st modification of the ethanol engine system of the present invention. It is composition explanatory drawing of the 2nd modification of the ethanol engine system of the present invention. It is the partial expansion schematic diagram which shows typically the modification of the engine used for the ethanol engine system of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
The ethanol engine system according to the embodiment of the present invention generates power when a reformed gas using ethanol as a carbon source and an aqueous ethanol solution are supplied to the engine. Hereinafter, the configuration of the ethanol engine system, the aqueous ethanol solution used as the reforming raw material and fuel, and the operation of the ethanol engine system will be described.

<Configuration of ethanol engine system>
FIG. 1 is a configuration explanatory diagram of an ethanol engine system according to an embodiment of the present invention.
As shown in FIG. 1, the ethanol engine system S according to this embodiment includes a storage tank 4 for storing an ethanol aqueous solution, which will be described later, an engine 1, a reformer 2, a separation device 3, a control unit 7, It is configured with. In FIG. 1, reference numerals I ₁ , I ₂ , and I ₃ are injectors, reference numeral P ₁ is a low-pressure pump, reference numeral P ₂ is a high-pressure pump, reference numeral V ₁ is a valve, reference numeral 5 Is a throttle, and symbol D is an ethanol concentration sensor. Hereinafter, these symbols are the same.

≪Engine≫
As shown in FIG. 1, an ethanol aqueous solution is supplied to the engine 1 from a storage tank 4 via a low pressure pump P ₁ , a high pressure pump P ₂ , and an injector I ₁ , and reformed gas is supplied from the reformer 2. It is supplied via the separation device 3 and the injector I ₃ . As a result, the engine 1 is configured to generate power by combustion of ethanol and reformed gas contained in the aqueous ethanol solution.

FIG. 2 to be referred to next is a partially enlarged schematic view schematically showing the vicinity of the cylinder head of the engine constituting the ethanol engine system according to the embodiment of the present invention.
As shown in FIG. 2, the engine 1 includes a piston 11 that reciprocates in a cylinder 10, and an intake pipe 13 and an exhaust pipe 14 are connected to a combustion chamber 12 in the cylinder 10. Reference numeral 15 is a spark plug disposed so as to face the combustion chamber 12, reference numeral 13a is an intake valve, and reference numeral 14a is an exhaust valve.

  Incidentally, the cylinder 10 in the present embodiment is made of ceramic that has better heat insulation than conventional metal ones. Incidentally, a ceramic liner (not shown) having a heat insulating property may be provided in the cylinder 10 in place of the ceramic cylinder 10. Moreover, about the piston 11, it can also be set as the structure which provided the ceramic coating which has heat insulation on the surface. The ceramic cylinder 10 and the ceramic liner, and the ceramic coating of the piston 11 correspond to a heat radiation suppression mechanism in the claims.

As will be described later, such a heat dissipation suppression mechanism efficiently burns the aqueous ethanol solution injected into the combustion chamber 12 and discharges it from the exhaust pipe 14 toward the reformer 2 (see FIG. 1). The temperature of the exhaust gas that is produced can be kept high.
In addition, as this heat radiation | emission suppression mechanism, it can also be set as the structure which maintains the temperature of the coolant which flows into a water jacket (illustration omitted) high, for example.

As will be described in detail later, the injector I ₁ uses an aqueous ethanol solution to burn the engine 1 at a predetermined injection pulse width corresponding to the ethanol concentration of the aqueous ethanol solution in the storage tank 4 and the torque required by the operator for the engine 1. Inject directly into the chamber 12. The injector I ₃ injects the reformed gas into the intake pipe 13 as will be described in detail later. Air is introduced into the intake pipe 13 through the throttle 5 (see FIG. 1) when the engine 1 is started.
Incidentally, as will be described later, the opening degree of the throttle 5 is controlled by the control unit 7 in accordance with the ethanol concentration of the ethanol aqueous solution in the storage tank 4 and the required torque.

≪Reformer≫
As shown in FIG. 1, the reformer 2 is supplied with an aqueous ethanol solution from a storage tank 4 via a low-pressure pump P ₁ and an injector I ₂ , and exhaust gas is supplied from the engine 1. As a result, the reformer 2 generates a reformed gas using an aqueous ethanol solution as a raw material.

More specifically, the reformer 2 is warmed up by the exhaust gas of the engine 1 and becomes a reformed gas mainly composed of carbon monoxide and hydrogen by exchanging heat with the aqueous ethanol solution. The reforming reaction is shown in the following formula (1).
C ₂ H ₅ OH + H ₂ O (ethanol aqueous solution) → 2CO + 4H ₂ (reformed gas) −298 kJ Formula (1)

As shown in the formula (1), the reaction for reforming an ethanol aqueous solution into carbon monoxide (CO) and hydrogen (H ₂ ) is an endothermic reaction, and 1 mol of ethanol (C ₂ H ₅ OH) is modified. The energy of 298 kJ is absorbed.

The supply amount of the aqueous ethanol solution to the reformer 2, is regulated according to the temperature and pressure of the reformer 2, reforming injected from the injector I ₃ is set according to the demand torque of the engine 1 If it can adjust in the range which can ensure gas amount, there will be no restriction | limiting in particular.
Incidentally, the reforming temperature of ethanol is lower than the reforming temperature of other fuels such as gasoline and toluene, and is about 200 ° C. to 400 ° C. Therefore, the standard for determining the end of the warm-up process of the reformer 2 by the exhaust gas of the engine 1 in the present embodiment is, for example, the temperature of the reaction cell 21 (see FIG. 3A) described later of the reformer 2. When the temperature reaches about 200 ° C. to 400 ° C. Further, the injection control of the injector I ₃ can also be performed based on the temperature of the reaction cell 21 of about 200 ° C. to 400 ° C.

  FIG. 3A to be referred to next is a cross-sectional view of a reformer constituting the ethanol engine system according to the embodiment of the present invention, and FIG. 3B is a cross-sectional view of a reaction cell built in the reformer. FIG. 3C is a cross-sectional view of the reaction sheet built in the reaction cell.

As shown in FIG. 3A, the reformer 2 includes a plurality of reaction cells 21 whose outer shape has a columnar shape, and a cylindrical first casing 22 that accommodates the plurality of reaction cells 21. Yes.
And the ethanol aqueous solution in the storage tank 4 flows through each reaction cell 21. Further, the high-temperature exhaust gas discharged through the exhaust pipe 14 (see FIG. 2) of the engine 1 flows outside the reaction cell 21 and in the first casing 22.

The first casing 22 and the second casing 24 to be described later are made of metal (for example, SUS) so as to have high thermal conductivity.
In addition, the shape of the 1st casing 22 and the 2nd casing 24 is not limited to cylindrical shape, For example, a square cylinder shape and a polygonal cylinder shape may be sufficient.

As shown in FIG. 3B, the reaction cell 21 includes a plurality of stacked reaction sheets 23 and a second casing 24 that houses the plurality of reaction sheets 23.
As shown in FIG. 3C, each reaction sheet 23 includes a base metal foil 25, a porous layer 26 formed on each surface of the metal foil 25, and a catalyst 27 supported on the porous layer 26. And.

That is, each reaction sheet 23 has a three-layer structure in which a porous layer 26 carrying a catalyst 27, a metal foil 25, and a porous layer 26 carrying a catalyst 27 are laminated in this order.
Note that a gap is formed between the reaction sheets 23 adjacent to each other in the thickness direction so that an ethanol aqueous solution, generated hydrogen (H ₂ ), and carbon monoxide (CO) can flow therethrough.

Further, since the reaction sheet 23 is in the form of a sheet, its heat capacity is small, heat is quickly conducted through the reaction sheet 23, and the temperature of the catalyst 27 is quickly raised to a temperature at which the catalyst function is satisfactorily exhibited.
Thus, the efficiency of decomposing the decomposition reaction of ethanol aqueous hydrogen and (H ₂₎ and carbon monoxide (CO) is higher.

Furthermore, each reaction sheet 23 has a plurality of through holes 23a.
Thereby, the heat of the exhaust gas is conducted well in the thickness direction, and the ethanol aqueous solution, the generated hydrogen (H ₂ ), and carbon monoxide (CO) are also flowed well in the thickness direction. It has become.

  The metal foil 25 is made of, for example, an aluminum foil and has a thickness of about 50 to 200 μm. However, the metal foil 25 may not be provided, or instead of the metal foil 25, a porous layer serving as a base may be provided, and the entire reaction sheet 23 may have a porous structure.

The porous layer 26 is a layer for supporting the catalyst 27 and has a plurality of pores through which an aqueous ethanol solution, generated hydrogen and carbon monoxide can flow.
Such a porous layer 26 is made of an oxide mainly composed of alumina, niobium oxide, zirconium oxide or the like, for example.

The catalyst 27 is a catalyst for decomposing an ethanol aqueous solution and generating a reformed gas (hydrogen, carbon monoxide) as shown in the above formula (1).
Such a catalyst 27 is, for example, at least one selected from platinum, nickel, palladium, rhodium, iridium, ruthenium, molybdenum, rhenium, tungsten, vanadium, osmium, chromium, cobalt, iron, niobium, copper, zinc and the like. Consists of.

≪Separation device≫
The separation device 3 (see FIG. 1) is a device that separates the reformed gas (hydrogen, carbon monoxide) generated in the reformer 2 (see FIG. 1) and the unreformed ethanol aqueous solution.
The separation device 3 in the present embodiment cools the reformed gas, ethanol vapor, and mixed gas containing steam and water vapor sent from the reformer 2 (see FIG. 1), and reformed gas and condensed ethanol ( Boiling point: 78 ° C.) and water (boiling point: 100 ° C.) are separated.

Next, FIG. 4 to be referred to is a configuration explanatory diagram of a separation device constituting the ethanol engine system according to the embodiment of the present invention.
As shown in FIG. 4, the separation device 3 includes a condenser 31 and a drain tank 32 in a predetermined housing 30. Although not shown, the separation device 3 stores a condensed ethanol aqueous solution separately from the sensor (for example, a water level sensor) that detects the amount of the condensed ethanol aqueous solution stored in the drain tank 32 and the drain tank 32. And a reserve tank.

  The condenser 31 heat-exchanges the mixed gas sent from the reformer 2 (see FIG. 1) and a predetermined coolant CL, and condenses ethanol vapor and water vapor contained in the mixed gas as described above. It is something to be made. In addition, there is no restriction | limiting in particular as coolant CL, For example, liquid refrigerants, such as water and ethylene glycol, are mentioned. In addition, the condenser 31 may be an air-cooled heat exchanger provided with heat radiation fins, although not shown.

The drain tank 32 separates ethanol and water condensed in the condenser 31 from the reformed gas and gas and liquid. The reformed gas separated in the drain tank 32 is supplied to the engine 1. Condensed ethanol and water, that is, an aqueous ethanol solution, are extracted from the bottom of the drain tank 32 and returned to the storage tank 4 (see FIG. 1) via the valve V ₁ (see FIG. 1).

Incidentally, since the space between the separation device 3 and the storage tank 4 is sealed by the aqueous ethanol solution stored in the drain tank 32, the reformed gas does not flow into the storage tank 4 from the separation device 3. Further, the control unit 7 determines the amount of the aqueous ethanol solution in the drain tank 32 based on the detection signal of the above-described sensor (for example, a water level sensor) so that the sealing with the aqueous ethanol solution is more reliably performed. a structure for controlling the opening and closing of the valve V _{1 (see} FIG. 1) so as to quantify. Note that the valve V ₁ in the present embodiment is assumed to be a normally closed on-off valve (for example, a valve that opens when the solenoid of the valve V ₁ is energized and is normally in a closed state). Yes. The valve V ₁ corresponds to a “flow rate adjusting device” in the claims together with a valve V ₁ as a flow rate adjusting valve exemplified later.

The ethanol concentration of the aqueous ethanol solution stored in the storage tank 4 often varies as the aqueous ethanol solution is returned from the separation device 3 to the storage tank 4. Such a change in ethanol concentration can be monitored by an ethanol concentration sensor D shown in FIG.
The ethanol concentration sensor D in the present embodiment is provided at the outlet of the storage tank 4 that sends out an aqueous ethanol solution from the storage tank 4 toward the low-pressure pump P ₁ (see FIG. 1).
Examples of the ethanol concentration sensor D include one that detects the ethanol concentration by measuring the density of the aqueous ethanol solution, and one that detects the ethanol concentration by measuring the pH of the aqueous ethanol solution.

  The position where the ethanol concentration sensor D is provided is not limited to the outlet of the storage tank 4. For example, in the storage tank 4, piping connecting the storage tank 4 and the engine 1 (see FIG. 1), the storage tank 4. And a pipe connecting the reformer 2 (see FIG. 1).

  Incidentally, the variation tendency of the ethanol concentration of the aqueous ethanol solution in the storage tank 4 is determined by the ethanol concentration of the initial aqueous ethanol solution (before the start of reforming) stored in the storage tank 4.

  More specifically, in the reforming reaction represented by the above formula (1), the stoichiometry is modified by a reaction of 1 mol of ethanol and 1 mol of water (reaction of an ethanol aqueous solution having an ethanol concentration of 50 mol%). A gas (2 moles of carbon monoxide and 4 moles of hydrogen gas) is produced. On the other hand, when the initial ethanol concentration of the aqueous ethanol solution stored in the storage tank 4 is less than 50 mol%, equimolar ethanol and water used for reforming in the reformer 2 are consumed. Therefore, the ethanol concentration of the aqueous ethanol solution returned from the separation device 3 to the storage tank 4 is lower than the initial ethanol concentration.

Then, in the ethanol engine system S according to the present embodiment, the control unit 7 controls the injection pulse width of the aqueous ethanol solution (fuel) by the injector I ₁ based on the ethanol concentration detected by the ethanol concentration sensor D as described later. To control.

Further, in the ethanol engine system S according to the present embodiment, when the ethanol concentration detected by the ethanol concentration sensor D falls below a predetermined threshold (for example, a first threshold C1 described later), the control unit 7 , as described later, by closing the valve V _1, the ethanol concentration of the ethanol aqueous solution in the storage tank 4 is prevented from lowering further. The aqueous ethanol solution separated by the separation device 3 is stored in the above-described reserve tank (not shown) separate from the drain tank 32.

In the ethanol engine system S according to the present embodiment, when the ethanol concentration detected by the ethanol concentration sensor D exceeds a predetermined threshold (for example, a second threshold C2 described later), the control unit 7 The valve V ₁ is closed and the injectors I ₂ and I ₃ are turned off. That is, the ethanol engine system S obtains power only by supplying the ethanol aqueous solution to the engine 1 through the injector I ₁ by interrupting the generation of the reformed gas in the reformer 2.
The second threshold C2 corresponds to a “threshold” in the claims.

  Further, in the ethanol engine system S according to the present embodiment, when the ethanol concentration detected by the ethanol concentration sensor D is, for example, lower than the first threshold value C1 or higher than the second threshold value C2, that is the case. Display means such as a lamp that is lit so as to be recognized by the operator can also be provided.

≪Control part≫
Next, the control part 7 (refer FIG. 1) which electronically controls this ethanol engine system S is demonstrated.
The control unit 7 includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and comprehensively controls the ethanol engine system S according to a program stored therein. The control unit 7 controls the injectors I ₁ , I ₂ , I ₃ , the low pressure pump P ₁ , the high pressure pump P ₂ , the valve V ₁ , and the throttle 5 shown in FIG. Yes. The procedure executed by the control unit 7 will be described in detail later together with the description of the operation of the ethanol engine system S.

<Ethanol aqueous solution>
In the ethanol engine system S according to the present embodiment shown in FIG. 1, an aqueous ethanol solution directly injected into the combustion chamber 12 (see FIG. 2) of the engine 1 by the injector I ₁ and the reaction of the reformer ₂ by the injector I ₂ . As the ethanol aqueous solution injected into the cell 21 (see FIG. 3A), a common ethanol aqueous solution supplied from the storage tank 4 is used.

Next, an aqueous ethanol solution used in the ethanol engine system S will be described.
When the aqueous ethanol solution is injected into the combustion chamber 12 (see FIG. 2) of the engine 1 and burned, the ethanol required for vaporization in the combustion chamber 12 with respect to the calorific value of the ethanol in the combusted aqueous ethanol solution (low fuel calorific value) It is desirable that the ratio of the latent heat of vaporization of the aqueous solution be a predetermined value or less. In general, considering that the heat released from the engine (for example, gasoline engine) to the engine cooling water is 30% to 40% at the maximum with respect to the calorific value of the supplied fuel, the ethanol fuel level is low. The ratio of the latent heat of vaporization of the ethanol aqueous solution to the calorific value can be set to be smaller than the above-mentioned range of “30% to 40%”.
FIG. 5 to be referred to next is the latent heat of vaporization with respect to the ethanol concentration [mass%] and the lower heating value (LHV) of the ethanol aqueous solution used as fuel in the ethanol engine system according to the embodiment of the present invention. It is a graph which shows the relationship with ratio.

  As shown in FIG. 5, the ethanol concentration of the aqueous ethanol solution injected into the combustion chamber 12 (see FIG. 2) of the engine 1 in the present embodiment is within the range of “30% to 40%” (the vertical axis in FIG. 5). It was set to 20% by mass or more (horizontal axis of 20% by mass or more in FIG. 5) corresponding to an arbitrary value in the range of the axis 0.3 to 0.4. Incidentally, the value of 20% by mass of the ethanol concentration of the aqueous ethanol solution corresponds to the first threshold value C1 in the present embodiment, and is the lower limit value of the ethanol concentration of the aqueous ethanol solution injected into the combustion chamber 12.

Incidentally, the ethanol aqueous solution to be directly injected into the combustion chamber 12 of the engine 1 has a relatively large ratio of latent heat of vaporization to the lower heating value of the fuel than other fuels.
FIG. 6 is a graph showing the ratio of latent heat of vaporization to the lower fuel heating value of the aqueous ethanol solution used as fuel in the ethanol engine system according to the embodiment of the present invention in comparison with other fuels (gasoline and toluene). is there.

  As shown in FIG. 6, when comparing the ratio of the latent heat of vaporization to the lower fuel calorific value of gasoline, toluene, and ethanol (the latent heat of vaporization / lower calorific value of fuel), The ratio is larger than gasoline and toluene, which are hydrocarbon fuels. This is because the latent heat of vaporization of ethanol containing oxygen in the molecular structure is relatively large. Further, as shown in FIG. 6, the ratio of “the latent heat of vaporization / the lower heating value of fuel” increases as the aqueous ethanol solution containing more noncombustible water (the lower the ethanol concentration, the higher the ethanol aqueous solution).

  Accordingly, it is generally considered that an ethanol aqueous solution having a lower ethanol concentration is insufficiently vaporized in the combustion chamber 12. On the other hand, in the ethanol engine system S according to this embodiment, the ethanol aqueous solution is directly applied to the combustion chamber 12. The present inventors have confirmed that when the compression ratio of the engine 1 is set to 14 or higher, vaporization of the aqueous ethanol solution is promoted and stable combustion is possible. Incidentally, in the case of a normal spark ignition engine, there is a possibility that knocking may occur when the compression ratio is 14 or more, but the ethanol aqueous solution used in this embodiment has a ratio of “evaporation latent heat / low fuel calorific value” and Since the sensible heat is high and the octane number of ethanol itself is as high as 111, there is an advantage that knocking does not occur even if the compression ratio is large.

  The upper limit of the ethanol concentration of the aqueous ethanol solution injected into the combustion chamber 12 of the engine 1 can be set to 100% by mass. The ethanol concentration of the aqueous ethanol solution supplied to the reformer 2 is as follows. It is desirable that the concentration be explained.

The aqueous ethanol solution is injected using the injector I ₂ to the reformer 2 shown in FIG. 1, with reference to the reforming reaction represented by the formula (1), its ethanol concentration to stoichiometric ethanol A 50 mol% aqueous ethanol solution having the same number of moles of water and water is desirable.
Next, FIG. 7 to be referred to is a graph showing the relationship between the molar equivalent ethanol concentration and the mass equivalent ethanol concentration of the aqueous ethanol solution used as fuel in the ethanol engine system according to the embodiment of the present invention.

As shown in FIG. 7, when the ethanol concentration of the ethanol aqueous solution is 50 mol%, it is about 72 mass% in terms of mass. On the other hand, when the ethanol concentration exceeds 72% by mass (50 mol%), when reforming of the aqueous alcohol solution is performed in the reformer 2 (see FIG. 1), in the reforming reaction represented by the above formula (1). Impurities may accumulate on the surface of the catalyst 27 (see FIG. 3C) due to a shortage of stoichiometric water (H ₂ O). For this reason, the performance of the catalyst 27 may be reduced, and the reforming efficiency of the aqueous alcohol solution may be reduced. Thereby, the ethanol concentration of the aqueous ethanol solution injected into the reaction cell 21 (see FIG. 3A) of the reformer 2 in this embodiment is set to 70% by mass or less. Incidentally, the value of 70% by mass of the ethanol concentration of the aqueous ethanol solution corresponds to the second threshold value C2 in the present embodiment, and the upper limit value of the ethanol concentration of the aqueous ethanol solution injected into the reaction cell 21 of the reformer 2 is It has become.

  As described above, in the ethanol engine system S according to the present embodiment, it is assumed that the ethanol concentration of the ethanol aqueous solution stored in the storage tank 4 is set to 20% by mass to 70% by mass. Is not intended to limit the ethanol concentration of the aqueous ethanol solution stored in the storage tank 4, but on the premise that various conditions such as engine temperature, compression ratio, fuel injection pulse width, required air volume are ideally realized, Theoretically, the ethanol concentration can be appropriately set within a range of more than 0% by mass and less than 100% by mass, preferably within a range of 20% by mass or more and less than 100% by mass.

<Operation of ethanol system>
Next, the operation of the ethanol engine system S according to this embodiment will be described.
In the following description of the operation, an ethanol engine system S in which a 70 mass% ethanol aqueous solution (ethanol aqueous solution having an ethanol concentration of less than 50 mol%) is stored in the storage tank 4 and the compression ratio of the engine 1 is set to 14 is used. Assumed.

First, when an operator operates an ignition key (not shown) to turn on a starter switch, a starter motor (not shown) is driven. At this time, the control unit 7 determines the fuel amount on the basis of the required air amount at startup (initial opening of the throttle 5) set in advance at the time of startup by a conventional method. Next, the control unit 7 obtains the fuel pressure at the time of fuel injection by a fuel pressure sensor (not shown), and determines the fuel injection pulse width in the injector I ₁ so that an appropriate fuel amount is obtained according to the pressure. The control unit 7 also performs ignition by reading a value determined in advance by the rotational speed of the engine 1 from a predetermined constant table for the ignition timing by the ignition plug 15 (see FIG. 2).
FIG. 8 is a flowchart showing a procedure executed by the control unit constituting the ethanol engine system according to the embodiment of the present invention. The following description will be given with reference to FIG. 1 as appropriate with reference mainly to FIG.

When the engine 1 is started, the ethanol aqueous solution in the storage tank 4 is turned on by the low pressure pump P ₁ , the high pressure pump P ₂ , and the injector I ₁ as shown in FIG. 8 (step S1). The fuel is directly injected into the combustion chamber 12 of the engine 1 through the injector I ₁ and burned.

In addition, the control unit 7 turns off the injectors I ₂ and I ₃ and sets the valve V ₁ to a control-off state (a state in which control is not performed). When the valve V ₁ was not performed control has become a closed state. (Normally, the valve is closed) (step S1). In step S1, since I ₂ and I ₃ are turned off, the liquid level in the drain tank 32 does not change. Therefore, as described above, the valve V ₁ is in the control-off state.

Incidentally, when the control of the valve V ₁ is ON (control is performed), as described above, it is performed based on the detection signal of the sensor (not shown) provided in the drain tank 32, If the amount of ethanol solution is less than the predetermined amount, the control unit 7, when the valve V ₁ and a closed state, the amount of aqueous ethanol drain tank 32 to reverse a predetermined amount or more, the valve V ₁ And the ethanol aqueous solution is extracted from the bottom of the drain tank 32 and returned to the storage tank 4. That By the control on the valves V ₁ (performs control), a state of an aqueous ethanol solution in the drain tank 32 is always a predetermined amount reservoir. Thereby, it is possible to prevent the aqueous ethanol solution from overflowing from the drain tank 32 and the reformed gas from flowing into the storage tank 4.

  And the high temperature exhaust gas discharged | emitted from the engine 1 is supplied to the reformer 2 (step S2), and the reformer 2 is warmed up.

  On the other hand, the control unit 7 determines whether or not the reformer 2 has been warmed up to a predetermined reforming temperature by a temperature sensor (not shown) disposed at an appropriate position of the reaction cell 21 (see FIG. 3A) of the reformer 2. Is determined (step S3). Incidentally, the control unit 7 in this embodiment determines whether or not the engine has been warmed up based on a preset threshold within a range of 200 ° C. to 400 ° C. as a guideline for determining the end of the warming-up process described above. To do.

When the controller 7 determines that the warming up of the reformer 2 has not been completed (No in step S3), the control unit 7 executes steps S2 and S3 again and determines that the warming up has been completed. (Yes in step S3), the injectors I ₂ and I ₃ are turned on and the control of the valve V ₁ is turned on (step S4). As a result, the aqueous ethanol solution in the storage tank 4 is supplied to the reformer ₂ via the low-pressure pump P ₁ and the injector I ₂ . In the reaction cell 21 of the reformer 2, the reforming reaction represented by the formula (1) proceeds to generate a reformed gas.
Incidentally, in the injectors I ₂ and I ₃ in this embodiment, the injection pulse width is controlled so that the temperature of the reaction cell 21 (see FIG. 3A) is about 200 ° C. to 400 ° C., and the reformer The supply amount of the ethanol aqueous solution to 2 is controlled.

Next, the reformed gas and the unreformed ethanol aqueous solution (ethanol vapor and water vapor) are sent from the reformer 2 to the separation device 3 and separated into the reformed gas and the ethanol aqueous solution by the separation device 3. . Then, the reformed gas is injected into the intake pipe 13 (see FIG. 2) of the engine 1 via the injector I ₃ (see FIG. 2). That is, in the combustion chamber 12 of the engine 1, the ethanol contained in the aqueous ethanol solution injected by the injector I ₁ and the reformed gas supplied to the intake pipe 13 by the injector I ₃ are combusted.

On the other hand, aqueous ethanol solution separated in the separation device 3 is returned to the storage tank 4 via a valve V ₁ became open. At this time, the ethanol concentration of the returned ethanol aqueous solution is lower than the initial ethanol concentration as described above. Therefore, the ethanol concentration in the storage tank 4 gradually decreases in proportion to the length of operation time of the ethanol engine system S.

At this time, the ethanol concentration sensor D disposed at the outlet of the storage tank 4 detects the ethanol concentration that gradually decreases and outputs the detection signal to the control unit 7.
On the other hand, the control unit 7 controls the injector I ₁ according to the ethanol concentration detected by the ethanol concentration sensor D and the torque required for the engine 1 by the operator's predetermined input device (for example, accelerator operation element). Correction of the fuel injection pulse width, correction of the opening of the throttle 5 and the like are performed (see step S5).

And the control part 7 judges whether ethanol concentration is more than a threshold value (1st threshold value C1 prescribed | regulated as said lower limit of the said ethanol concentration) (step S6). If a result, the ethanol concentration is determined to be smaller than the first threshold value C1 (No in step S6), and the control unit 7 turns off the control of the valve V ₁ proceeds to step S7 (usually closed) And The control off of the valve V _1, the ethanol concentration of the ethanol aqueous solution in the storage tank 4 is prevented from continuing to drop.
Incidentally, in conjunction with that the valve V ₁ is closed, an aqueous ethanol solution separated by the separating apparatus 3, instead of the drain tank 32, so that the stored destination to the preliminary tank (not shown) is changed. Also, when the capacity of the auxiliary tank has been filled, or in ethanol engine system S which is not provided with the auxiliary tank itself, the control unit 7, and turns off (usually closed) the control of the valve V ₁ In addition, the injectors I ₂ and I ₃ can be turned off. That is, the supply of the ethanol aqueous solution to the reformer 2 is stopped, and the engine 1 is operated using only the ethanol aqueous solution as fuel.
Then, after executing such step S7, the control unit 7 proceeds to the next step S8.

If it is determined that the ethanol concentration detected by the ethanol concentration sensor D is equal to or higher than the threshold (the first threshold C1) (Yes in step S6), the process proceeds to the next step S8.
In step S8, it is determined whether or not a stop command for the ethanol engine system S has been input by the operator (whether or not a stop command has been received). At this time, if the control unit 7 determines that there is no stop command (No in step S8), the control unit 7 returns to step S5 again and continues the operation of the ethanol engine system S.

If it is determined that a stop command has been issued (Yes in step S8), the control unit 7 stops the low-pressure pump P ₁ and the high-pressure pump P ₂ and turns off the injectors I ₁ , I ₂ , and I _3. together, the valve _{V 1} is closed (step S9). As a result, a series of operations of the ethanol engine system S is completed.

Next, effects of the ethanol engine system S according to the present embodiment will be described.
According to the ethanol engine system S according to this embodiment as described above, the reforming temperature of ethanol is about 200 to 400 ° C., which is lower than other fuels, and can be reformed at the exhaust temperature of the engine 1. In addition, the amount of heat absorbed during reforming of ethanol increases by performing steam reforming using water. Then, by using the exhaust heat of the engine 1 for the generation of reformed gas, the amount of energy recovered into the reformed gas (fuel) increases. Therefore, the ethanol engine system S can improve the efficiency of the engine 1. Further, since ethanol is easily dissolved in water, an aqueous ethanol solution as fuel can be stably stored in the storage tank 4.

  In addition, according to the ethanol engine system S, unlike the conventional ethanol engine system (see, for example, Patent Document 1), the engine 1 is started from the time of starting to the time of steady operation at a predetermined rotational speed and a predetermined load. A common aqueous ethanol solution can be used as a fuel. Therefore, it is not necessary to use a plurality of concentrations of ethanol, so there is no need to provide a plurality of storage tanks 4. Therefore, unlike the conventional ethanol engine system (see, for example, Patent Document 1), the system itself can be made compact.

  Moreover, according to the ethanol engine system S according to the present embodiment, an ethanol aqueous solution is used as a fuel, so that a dehydration step at the time of ethanol production is not required, which is effective for promoting the spread of bioethanol. Further, when the concentration of water is high (the ethanol concentration is low), the aqueous ethanol solution becomes a legal non-hazardous material and is easy to handle.

  Further, according to the ethanol engine system S according to the present embodiment, when the wall surface temperature of the combustion chamber 12 is low, for example, when the engine 1 is started, the compression of the piston 11 causes the combustion chamber 12 to have a boiling point equal to or higher than the boiling point of the aqueous ethanol solution. It becomes a high temperature state. Therefore, the engine 1 can be started even when a relatively low concentration aqueous ethanol solution is used as fuel.

  Further, according to the ethanol engine system S according to the present embodiment, when the temperature of the combustion chamber 12 becomes equal to or higher than the boiling point of the aqueous ethanol solution after the engine 1 is started, the aqueous ethanol solution is stably vaporized for each cycle of the engine 1. Combustion efficiency is improved.

  In general, the temperature of the combustion chamber wall surface is maintained at a predetermined temperature by an engine cooling mechanism such as a water jacket. According to the ethanol engine system S according to the present embodiment, the latent heat of vaporization with respect to the heating value of the aqueous ethanol solution Since the sensible heat is large, the wall surface temperature of the combustion chamber 12 can be cooled from the inside of the combustion chamber 12 of the engine 1. Thereby, according to ethanol engine system S concerning this embodiment, an engine cooling mechanism can be omitted.

  Further, according to the ethanol engine system S according to the present embodiment, since the engine cooling mechanism can be omitted, most of the exhaust heat from the engine 1 can be collected in the exhaust gas. Therefore, according to the ethanol engine system S, exhaust heat exergy can be improved. This means that the ability to generate power by exhaust heat recovery is increased.

  Further, according to the ethanol engine system S according to the present embodiment, the ethanol contained in the ethanol aqueous solution and the reformed gas are combusted in the combustion chamber 12, so that the combustion of the ethanol contained in the ethanol aqueous solution is reformed. Promoted by hydrogen in the gas. Thereby, even an ethanol aqueous solution having a low ethanol concentration can be reliably and stably burned.

Further, since hydrogen in the reformed gas has a higher combustion speed and a wider flammable range than hydrocarbon fuels such as gasoline, combustion with excess air (lean combustion) is possible.
Therefore, according to the ethanol engine system S according to the present embodiment, it is not necessary to squeeze the air even under the low-load operation condition of the engine 1, the pumping loss can be reduced, and the thermal efficiency of the engine 1 is further improved. Can do. And since the working gas of the engine 1 becomes excessive in air, the specific heat ratio of the working gas is improved, and this also improves the thermal efficiency of the engine 1.

Further, according to the ethanol engine system S according to the present embodiment, the reformed gas is supplied to the engine 1 via the separation device 3, so that an unmodified ethanol aqueous solution is supplied to the engine 1 from the intake pipe 13. Can be prevented.
Further, the temperature of the reformed gas supplied to the engine 1 can be lowered by the reformed gas passing through the separation device 3. As a result, the ethanol engine system S can prevent backfire due to hydrogen and can also prevent a reduction in the amount of intake air to the engine 1.

  Such an ethanol engine system S according to the present embodiment can be applied to anything that requires a power source. Specifically, it is used for a generator such as a vehicle or a ship, a generator, a construction machine, or the like. can do.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It can implement with a various other form. In addition, although other embodiment of this invention is described below, the same code | symbol is attached | subjected about the component same as the said embodiment, and the detailed description is abbreviate | omitted.

In the ethanol engine system S according to the above embodiment, the high temperature exhaust gas of the engine 1 is used to improve the ethanol aqueous solution to improve the exhaust heat exergy. It is also possible to adopt a configuration in which an exhaust heat recovery mechanism is also provided. FIG. 9 referred to here is a configuration explanatory diagram of a first modification of the ethanol engine system of the present invention, and FIG. 10 is a configuration explanatory diagram of a second modification of the ethanol engine system of the present invention. In FIGS. 9 and 10, the description of the control unit 7 is omitted for the convenience of drawing, but the low pressure pump P ₁ , the high pressure pump P ₂ , and the injectors I ₁ and I _{2 in} FIGS. 9 and 10 are omitted. , I ₃ are controlled by the control unit 7 in the same manner as the low pressure pump P ₁ , high pressure pump P ₂ , and injectors I ₁ , I ₂ , I _{3 of} FIG.

As shown in FIG. 9, the ethanol engine system S according to the first modification is configured to include a turbocharger 6 on a path for supplying air to the engine 1 via the throttle 5. The turbocharger 6 uses exhaust gas supplied from the engine 1 toward the reformer 2 for intake air compression of the engine 1.
The configuration is the same as that of the ethanol engine system S according to the embodiment except that the reformed gas from the reformer 2 is supplied to the upstream side of the turbocharger 6 via the separator 3.

According to the first modification, the pressure of the reformed gas supplied via the injector I _3, can be kept lower than ethanol engine system S according to the embodiment.
Further, according to the first modification, the torque of the engine 1 is improved, so that the range of application to the engine field requiring high torque, such as construction machinery, is expanded.

Incidentally, the gasoline has an octane number of about 90 to 100, and the compression ratio is set to 14 or more because the ratio of “latent heat of vaporization / low heating value of fuel” (see FIG. 6) is small as described above. Knocking occurs when the engine is operated with the intake pressure increased under certain conditions.
On the other hand, the ethanol aqueous solution has a large ratio of “latent heat of vaporization / low fuel heating value” and a high octane number. Therefore, in the ethanol engine system S according to the first modification, even if the turbocharger 6 is provided in the configuration in which the compression ratio of the engine 1 is set to 14 or more, high torque and high output are achieved without causing knocking. be able to.
Moreover, in this invention, it can replace with the turbocharger 6 in this 1st modification, and can also be set as the structure which provided together with the other waste heat recovery means using Rankine cycles, such as a steam turbine.

Next, an ethanol engine system S according to a second modification will be described.
As shown in FIG. 10, in the second modification, a part of the exhaust gas of the engine 1 is returned to the intake pipe 13 (see FIG. 2) of the engine 1 for exhaust gas recirculation (EGR). A pipe (indicated by EGR in FIG. 10) is provided. The pipe EGR branches from the middle of the connection pipe between the engine 1 and the reformer 2, and the tip of the pipe EGR merges with the intake pipe 13 of the engine 1. This pipe EGR is flow regulating valve V ₂ is provided for the control unit by a conventional method (not shown) to adjust the flow rate of the exhaust recirculation gas.
A configuration similar to that of the ethanol engine system S according to the above embodiment except that the reformed gas from the reformer ₂ is supplied to the pipe EGR on the downstream side of the flow rate adjustment valve V2 via the separation device 3. It has become.

According to such a second modification, the combustion temperature in the engine 1 can be lowered by supplying the reformed gas and the exhaust gas recirculation gas to the engine 1. Thereby, in the ethanol engine system S according to the second modification, the amount of NOx in the exhaust gas can be reduced under a wide range of operating conditions.
Further, in the second modification, the reformed gas can be supplied to the engine 1 through the pipe EGR through which the exhaust gas recirculation gas flows, so that the reformed gas is supplied from the separation device 3 to the engine 1. The length of the piping can be shortened. Thereby, ethanol engine system S of the 2nd modification can be made into a more compact composition.
Moreover, in this 2nd modification, it can be set as the structure which provides in this piping EGR the heat exchanger which heat-exchanges with the exhaust gas recirculation gas which flows through piping EGR, and cools this exhaust gas recirculation gas.

  In the present invention, the reformed gas generated by the reformer 2 may be supplied to the engine 1 together with the exhaust gas recirculation gas. That is, in the present invention, exhaust gas recirculation gas and reformed gas are supplied to the engine 1 by flowing a part of the exhaust gas together with the aqueous ethanol solution inside the reaction cell 21 shown in FIG. can do.

  In the operation of the ethanol engine system S in the embodiment (see FIG. 8), the case where an aqueous ethanol solution having an ethanol concentration of less than 50 mol% is used as the fuel has been described. However, in the present invention, an ethanol aqueous solution having an ethanol concentration exceeding 50 mol% can also be used.

For example, when an ethanol aqueous solution having an ethanol concentration exceeding 50 mol% or 100% ethanol is used, the control unit 7 (see FIG. 1) detects the ethanol concentration by the ethanol concentration sensor D. At this time, the control unit 7, the ethanol concentration sensor ethanol concentration detected by D is the second threshold value C2 (e.g., 70 wt%) Judging exceeded, closes the valve V ₁ shown in FIG. 1, the injector I _2, to turn off the _{I 3.} That is, the ethanol engine system S obtains power only by supplying the ethanol aqueous solution to the engine 1 through the injector I ₁ by interrupting the generation of the reformed gas in the reformer 2.

When it is determined that the ethanol concentration detected by the ethanol concentration sensor D has become equal to or less than the second threshold value C2 (for example, 70% by mass), the valve V1 shown in FIG. ₁ is opened again and the injector I _{2 is used.} , to turn on the _{I 3.} That is, the reformed gas and the ethanol aqueous solution are supplied to the engine 1.

  In such an ethanol engine system S, the storage tank 4 is filled with a high-concentration ethanol aqueous solution (including an azeotropic ethanol aqueous solution) or 100% ethanol in advance, and the high amount consumed by the operation of the ethanol engine system S. An amount of water corresponding to the concentration ethanol aqueous solution or 100% ethanol may be replenished from a separately provided water tank. According to such an ethanol engine system S, it is possible to construct a system that automatically switches from power generation by only ethanol combustion to power generation by ethanol and reformed gas combustion.

  The ethanol engine system S is operated in a state where the storage tank 4 is filled with an ethanol aqueous solution of 70% by mass or less (less than 50 mol%), and then high-concentration ethanol is poured into the storage tank 4. The same automatic switching operation is possible.

  Further, as a method for adjusting the ethanol concentration in the storage tank 4, for example, when the value is lower than the first threshold C1 or exceeds the second threshold C2, it is lit so that the operator can recognize it. It is not excluded that the operator adds water or high-concentration ethanol to the storage tank 4 on the basis of the display means such as the lamp to be operated.

In the above-described embodiment, the ethanol engine system S in which the reformed gas is supplied to the intake pipe 13 of the engine 1 has been described. However, the present invention has a configuration in which the reformed gas is supplied to the auxiliary combustion chamber of the engine 1. be able to. FIG. 11 referred to next is a partially enlarged schematic view schematically showing a modification of the engine used in the ethanol engine system of the present invention.
As shown in FIG. 11, the engine 1 according to this modification is provided with a sub-combustion chamber 16 in the cylinder head portion. Then, the sub-combustion chamber 16, is disposed so as to face the spark plug 15 and the injector I _3.
According to such a modification, even if there is less reformed gas, it can be burned efficiently. This is because the aqueous ethanol solution supplied to the combustion chamber 12 (main combustion chamber) of the engine 1 can be ignited by the combustion flame of the reformed gas, so that the air and fuel supplied to the engine 1 (the sum of the reformed gas and ethanol) ) Ratio (air-fuel ratio) can be increased. That is, since the lean combustion can be performed, the efficiency improvement can be achieved. In particular, the effect is large in a low load region where pumping loss is large.

The valve V ₁ of the the above embodiment, it is assumed that on-off valve, the present invention is, instead of the opening and closing flight, the valve V as a flow rate of aqueous ethanol adjustable flow control valve for flowing ₁ may be used. The valve V ₁ as the flow rate adjusting valve corresponds to the “flow rate adjusting device” in the claims together with the valve V ₁ as the on-off valve in the embodiment.

DESCRIPTION OF SYMBOLS 1 Engine 2 Reformer 3 Separator 4 Storage tank 5 Throttle 6 Turbocharger 7 Control part 10 Cylinder 11 Piston 12 Combustion chamber 13 Intake pipe 14 Exhaust pipe 16 Subcombustion chamber D Ethanol concentration sensor EGR piping I ₁ Injector I ₂ Injector I ₃ injectors P ₁ low pressure pump P ₂ high pressure pump S ethanol engine system

Claims (6)

A storage tank for an aqueous ethanol solution;
A reformer that generates reformed gas from the ethanol aqueous solution supplied from the storage tank, and
The ethanol aqueous solution stored in the storage tank is directly injected into the combustion chamber and the reformed gas is supplied from the reformer, and the ethanol and the reformed gas contained in the ethanol aqueous solution are combusted in the combustion chamber. An engine that generates power by
With
Between the reformer and the engine, the reformed gas sent from the reformer and the ethanol aqueous solution containing unreformed ethanol are separated, and the separated ethanol aqueous solution is returned to the storage tank. Equipped with a separating device,
Provided in the middle of the extension of the ethanol return pipe connecting the separation device and the storage tank, the flow rate adjusting device for adjusting the flow rate of the aqueous ethanol solution flowing through the ethanol return pipe,
An ethanol concentration detector that detects at least one of the concentrations of the aqueous ethanol solution sent from the storage tank to the engine and the reformer;
The ethanol flow rate adjusting device adjusts the flow rate of the aqueous ethanol solution flowing through the ethanol return pipe according to the concentration of the aqueous ethanol solution detected by the ethanol concentration detector. The ethanol engine system according to claim 1,
The ethanol engine system further includes a heat dissipation suppression mechanism that suppresses heat dissipation of combustion heat generated in the combustion chamber. The ethanol engine system according to claim 2 ,
An ethanol engine system characterized by omitting the engine cooling mechanism. A storage tank for an aqueous ethanol solution;
A reformer that generates reformed gas from the ethanol aqueous solution supplied from the storage tank, and
The ethanol aqueous solution stored in the storage tank is directly injected into the combustion chamber and the reformed gas is supplied from the reformer, and the ethanol and the reformed gas contained in the ethanol aqueous solution are combusted in the combustion chamber. An engine that generates power by
With
Between the reformer and the engine, the reformed gas sent from the reformer and the ethanol aqueous solution containing unreformed ethanol are separated, and the separated ethanol aqueous solution is returned to the storage tank. Equipped with a separating device,
Provided in the middle of the extension of the ethanol return pipe connecting the separation device and the storage tank, the flow rate adjusting device for adjusting the flow rate of the aqueous ethanol solution flowing through the ethanol return pipe,
An ethanol concentration detector that detects at least one of the concentrations of the aqueous ethanol solution sent from the storage tank to the engine and the reformer;
When the ethanol concentration detected by the ethanol concentration detector exceeds a predetermined threshold, the engine generates power only by the combustion of ethanol in the ethanol aqueous solution supplied to the engine, and the ethanol detected by the ethanol concentration detector An ethanol engine system that generates power by combustion of ethanol and reformed gas when the concentration is below a predetermined threshold. The ethanol engine system according to claim 4,
  The ethanol engine system further includes a heat dissipation suppression mechanism that suppresses heat dissipation of combustion heat generated in the combustion chamber. The ethanol engine system according to claim 5,
An ethanol engine system characterized by omitting the engine cooling mechanism.

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