JP5551964B2 - Internal combustion engine system - Google Patents

Description

  The present invention relates to an internal combustion engine system including an internal combustion engine to which a hydrogen-containing gas containing hydrogen is added.

  Conventionally, as disclosed in, for example, Patent Documents 1 and 2, by adding highly flammable hydrogen to an internal combustion engine that burns fuel such as gasoline and light oil, output and the like are improved, and exhaust gas (emission) A technique for reducing the above is known.

Japanese Patent No. 4103867 Japanese Patent No. 4196897

However, conventionally, even if hydrogen is added to fuel such as gasoline and light oil, the indexes (ignition index) such as octane number and cetane number related to ignitability and flammability have been treated as fixed values.
That is, it is known that when hydrogen is added to gasoline and light oil, ignition of the fuel is suppressed, knocking is suppressed in the case of gasoline, and the ignition delay period is extended in the case of light oil, which can be premixed. Actually, the octane number and cetane number seem to fluctuate, but conventionally, the octane number and cetane number due to hydrogenation are not considered, that is, constant regardless of whether or not hydrogenation is performed. Was treated as a fixed value.

Here, in the case of a gasoline engine, a high octane fuel is desired in the high load region in order to suppress knocking. In the case of a diesel engine, a low cetane number fuel that promotes premixed combustion is desired in order to reduce exhaust gas (emission) in a middle and high load region.
Since both the high octane number fuel and the low cetane number fuel have low ignitability, a low ignitability fuel is desired in a high load region in both gasoline engines and diesel engines.

  Therefore, an object of the present invention is to provide an internal combustion engine system in which hydrogen is added while taking into account fluctuations in ignitability and combustibility, and the thermal efficiency of the internal combustion engine is high.

  In view of the above problems, the inventor of the present application diligently studied the combustion of hydrogenated fuel in an internal combustion engine. Hydrogen has a low ignitability, but has a high combustion speed, and has a robustness for combustion (combustion robustness). Since it has the characteristic that it is high, when hydrogen was added, the ignitability became low, the combustion rate was large, and the combustion robustness became high.

That is, by controlling the amount of hydrogen added, the knowledge that the ignitability of the whole fuel after hydrogen addition can be optimized, the combustion speed can be increased, the combustion robustness can be improved, and the thermal efficiency can be improved. .
And when combustion speed became large and robustness became high, since the combustion fluctuation rate became small, the EGR rate could also be raised and the exhaust gas (emission) could be reduced. In addition, the inventors have found that knocking becomes difficult as the combustion rate increases.

Based on such knowledge, as means for solving the above problems, the present invention includes a diesel internal combustion engine that burns light oil , and a hydrogen-containing gas addition means that adds a hydrogen-containing gas containing hydrogen to the diesel internal combustion engine. A hydrogen addition amount determining means for determining a hydrogen addition amount by the hydrogen-containing gas addition means based on hydrogen addition amount data set in consideration of a change in octane number and cetane number due to hydrogen addition, and the diesel internal combustion engine A combustion state detection means for detecting the combustion state in the engine, and an EGR amount control means for controlling the EGR amount based on the combustion state detected by the combustion state detection means so that the combustion in the diesel internal combustion engine becomes slow. wherein the EGR quantity control means, after controlling the EGR amount 35 to 45%, and the hydrogen amount determining means, said combustion state detection Based on the detected burning state means such that said combustion in a diesel engine is slowed, which is an internal combustion engine system and determining the 4 vol% of hydrogen addition amount with respect to the intake.

Here, the hydrogen-containing gas includes high-purity hydrogen and a reformed gas containing hydrogen.
According to such an internal combustion engine system, the hydrogen addition amount determining means determines and determines the hydrogen addition amount based on the hydrogen addition amount data set in consideration of fluctuations in the octane number and cetane number due to hydrogen addition. The hydrogen-containing gas adding means adds the hydrogen-containing gas so that the amount of hydrogen added becomes the same.

Thus, since the hydrogen addition amount is determined based on the hydrogen addition amount data set in consideration of the fluctuation of the octane number and cetane number, that is, the ignition index (such as the octane number and cetane number of the fuel after hydrogen addition) Since the hydrogen addition amount is appropriately determined in consideration of (ignitability, combustibility), the ignitability / combustibility of the fuel after hydrogen addition is appropriate.
Further, the addition of hydrogen increases the combustion speed and increases the combustion robustness, so that the combustion fluctuation rate in the internal combustion engine can be reduced, the thermal efficiency of the internal combustion engine can be increased, and NOx and the like in the exhaust gas can be reduced.

  In the internal combustion engine system, the hydrogen addition amount determining means determines the hydrogen addition amount in consideration of an EGR amount.

According to such an internal combustion engine system, since the hydrogen addition amount determining means determines the hydrogen addition amount in consideration of the EGR amount, the hydrogen addition amount can be made more appropriate.
Note that if the EGR amount (rate) increases, it becomes difficult to ignite and the combustion fluctuation rate tends to increase. Therefore, when the EGR amount (rate) increases, the hydrogen addition amount is increased and the combustion fluctuation rate is, for example, 5%. It is preferable to control to be as follows.

  In the internal combustion engine system, when knocking occurs in the internal combustion engine after adding the hydrogen-containing gas at the hydrogen addition amount determined by the hydrogen-containing gas addition means, the hydrogen addition amount determination means It is characterized by increasing.

  According to such an internal combustion engine system, when knocking occurs in the internal combustion engine after adding the hydrogen-containing gas, the hydrogen addition amount determining means increases the hydrogen addition amount, so that the combustibility is improved and the subsequent knocking is performed. Can be suppressed.

  Further, in the internal combustion engine system, after adding the hydrogen-containing gas at the hydrogen addition amount determined by the hydrogen-containing gas addition means, the hydrogen addition amount determination means has an ignition delay time in the internal combustion engine of a predetermined time or more. Thus, the hydrogen addition amount is corrected.

  According to such an internal combustion engine system, the hydrogen addition amount determining means corrects the hydrogen addition amount so that the ignition delay time in the internal combustion engine is equal to or longer than a predetermined time, and therefore, the ignition delay time can be secured at a predetermined time or longer. .

  According to such an internal combustion engine system, the combustion in the internal combustion engine is slow based on the combustion state detected by the combustion state detection means (in the embodiment described later, the in-cylinder pressure detected by the pressure sensor). The EGR amount is controlled such that the EGR amount (rate) is increased.

  In this way, when the EGR amount increases, the thermal efficiency in the internal combustion engine is hardly lowered (see FIG. 15 described later), and the heat generation rate with respect to the crank angle of the internal combustion engine is delayed (see FIGS. 16A to 16D described later). ), (DP / dθ) max and maximum in-cylinder pressure Pmax can be decreased (see FIGS. 13 and 14 described later), and NO in the exhaust gas of the internal combustion engine can be decreased (refer to FIG. 17 described later).

  According to such an internal combustion engine system, the hydrogen addition amount determination means determines the hydrogen addition amount based on the combustion state detected by the combustion state detection means so that the combustion in the internal combustion engine becomes slow, that is, Increase the amount of hydrogenation. Then, the hydrogen-containing gas adding means adds the hydrogen-containing gas according to the increased hydrogen addition amount.

  In this way, when the hydrogen addition amount increases, (dP / dθ) max and the maximum in-cylinder pressure Pmax are lowered (see FIGS. 13 and 14 described later), and the heat generation rate with respect to the crank angle is further delayed (as described later). 16A to FIG. 16D), CO, THC (Total Hydro Carbon) and Soot in the exhaust gas can be reduced (see FIGS. 18 to 20 described later).

  According to such an internal combustion engine system, after the EGR amount control means controls the EGR amount to 35 to 45%, the hydrogen addition amount determination means is based on the combustion state detected by the combustion state detection means. Since the hydrogen addition amount is determined so that the combustion becomes slow, the combustion in the internal combustion engine can be made closer to the slow combustion.

  According to the present invention, it is possible to provide an internal combustion engine system in which hydrogen is added while taking into account fluctuations in ignitability and combustibility and the internal combustion engine has high thermal efficiency.

It is a figure which shows the structure of the internal combustion engine system which concerns on a 1st reference form. It is a flowchart which shows operation | movement of the internal combustion engine system which concerns on 1st Embodiment . It is a map which shows the relationship between an engine speed, a required torque (load) of an engine, and the amount of hydrogen addition. It is a graph which shows the relationship between the hydrogenation rate (calorific value%) at the time of hydrogenation to gasoline, and the octane number of hydrogenated gasoline. It is a graph which shows the relationship between the hydrogen addition amount (vol%) to intake air, and OH radical generation amount. It is a graph which shows the relationship between the EGR rate (%) and combustion fluctuation rate (%) in a gasoline engine. It is a graph which shows the relationship between the compression ratio and thermal efficiency (%) in a gasoline engine. It is a flowchart which shows operation | movement of the internal combustion engine system which concerns on a 2nd reference form. It is a graph which shows the relationship between the hydrogenation rate (calorific value%) at the time of hydrogenation to light oil, and the cetane number of the hydrogenated light oil. It is a graph which shows the relationship between the cetane number and light octane number in light oil. It is a graph which shows the relationship between nitric oxide (g / kWh) and smoke (%) in the exhaust gas of a diesel engine. It is a flowchart which shows operation | movement of the internal combustion engine system which concerns on 1st Embodiment. It is a graph which shows the relationship between an EGR rate and a hydrogenation rate, and (dP / dθ) max. It is a graph which shows the relationship between a crank angle, an EGR rate, a hydrogen addition rate, and in-cylinder pressure. It is a graph which shows the relationship between an EGR rate, a hydrogenation rate, and thermal efficiency. It is a graph which shows the relationship between a crank angle and a hydrogen addition rate, and a heat release rate in case an EGR rate is 0%. It is a graph which shows the relationship between a crank angle and a hydrogenation rate, and a heat release rate in case an EGR rate is 20%. It is a graph which shows the relationship between a crank angle and a hydrogenation rate, and a heat release rate in case an EGR rate is 30%. It is a graph which shows the relationship between a crank angle and a hydrogenation rate, and a heat release rate in case an EGR rate is 40%. It is a graph which shows the relationship between EGR rate and hydrogenation rate, and NO in exhaust gas. It is a graph which shows the relationship between EGR rate and hydrogenation rate, and CO in exhaust gas. It is a graph which shows the relationship between an EGR rate and a hydrogenation rate, and THC in exhaust gas. It is a graph which shows the relationship between an EGR rate, a hydrogenation rate, and Soot (煤).

≪First Reference Form≫
Hereinafter, a first reference embodiment of the present invention will be described with reference to FIGS.

≪Configuration of internal combustion engine system≫
Internal combustion engine system 1 according to the first reference embodiment shown in Figure 1, is mounted on a vehicle, not shown.
The internal combustion engine system 1 introduces a gasoline engine 10A (internal combustion engine) that burns gasoline (fuel), a fuel supply system (fuel supply means) that supplies gasoline to the gasoline engine 10A, and a part of exhaust gas to an intake system. An exhaust gas recirculation (EGR) system that circulates exhaust gas, a hydrogen addition system (hydrogen-containing gas addition means) that adds hydrogen (hydrogen-containing gas) to the gasoline engine 10A, and a control that electronically controls these systems ECU70 (Electronic Control Unit) which is means.

<Gasoline engine>
The gasoline engine 10A is a four-stroke engine that repeats four cycles (intake, compression, combustion / expansion, and exhaust), and reciprocates in the cylinder 11a and a cylinder block 11 in which a cylinder 11a (cylinder) is formed. The piston 12 includes a head cover 13 in which an intake port 13a and an exhaust port 13b are formed, an intake valve 14 provided in the intake port 13a, and an exhaust valve 15 provided in the exhaust port 13b.
For simplicity, only one cylinder 11a is shown in FIG. 1, but the number of cylinders 11a, the arrangement of cylinders 11a, and the displacement of the gasoline engine 10A can be freely changed.

An intake pipe 21a is connected to the intake port 13a. When the gasoline engine 10A is operated, the air outside the vehicle is naturally sucked and goes to the intake port 13a through the intake pipe 21a.
An exhaust pipe 31a is connected to the exhaust port 13b. The exhaust gas from the gasoline engine 10A passes through the exhaust pipe 31a and is discharged outside the vehicle.

In addition, a pressure sensor 16 (combustion state detection means), a crank angle sensor 17, and a knock sensor 18 are attached to the gasoline engine 10A. The pressure sensor 16 detects the pressure (cylinder pressure) in the cylinder 11 a and outputs it to the ECU 70. The crank angle sensor 17 detects the angle (crank angle) of a crankshaft (not shown) and outputs it to the ECU 70. The knock sensor 18 detects the knocking state of the gasoline engine 10 </ b> A and outputs it to the ECU 70.
In addition, an ignition plug (not shown) is attached to the gasoline engine 10A. The timing of ignition by the spark plug is controlled by the ECU 70 based on the crank angle input from the crank angle sensor 17.

<Fuel supply system>
The fuel supply system includes a fuel tank 41 that stores gasoline, a fuel pump 42 that pumps gasoline, and a fuel injector 43 (fuel injector) that injects gasoline.
The fuel tank 41 is connected to the fuel injector 43 via a pipe 41a, a fuel pump 42, and a pipe 42a. When the fuel pump 42 operates according to a command from the ECU 70, the gasoline in the fuel tank 41 is pumped to the fuel injector 43.

The fuel injector 43 is attached to the head cover 13, and when operated (opened) according to a command from the ECU 70, gasoline is directly injected into the cylinder 11a. However, the injection position is not limited to this, and may be configured to be injected into the intake port 13a.
The fuel injector 43 is a linear solenoid type normally closed electromagnetic valve electronically controlled by the ECU 70. As a result, the fuel injector 43 is opened / closed with high accuracy in accordance with a command from the ECU 70, so that the gasoline injection amount, injection timing, and injection time are controlled with high accuracy.

<EGR system>
The EGR system includes an EGR valve 51 that is a flow rate control valve capable of controlling the flow rate of exhaust gas returned to the intake side.
The middle of the exhaust pipe 31a is connected to the intake pipe 21a via the pipe 51a, the EGR valve 51, and the pipe 51b. Next, the opening degree of the EGR valve 51 is controlled by the ECU 70, whereby a part of the exhaust gas is returned to the intake side, the exhaust gas is recirculated, and the EGR rate (exhaust gas addition ratio) is controlled. It is like that.

<Hydrogenation system>
The hydrogen addition system includes a hydrogen tank 61 in which hydrogen is sealed at a high pressure, a regulator 62 (pressure reducing valve) for reducing the pressure of hydrogen to a predetermined pressure, and a hydrogen injector 63 (hydrogen injector).
The hydrogen tank 61 is connected to the hydrogen injector 63 via a pipe 61a, a regulator 62, and a pipe 62a. The hydrogen in the hydrogen tank 61 is decompressed by the regulator 62 and then supplied to the hydrogen injector 63. It has become.

  The hydrogen injector 63 is attached to the head cover 13, and when operated (opened) in accordance with a command from the ECU 70, hydrogen is injected into the intake port 13a.

Similarly to the fuel injector 43, the hydrogen injector 63 is a linear solenoid type normally closed solenoid valve. As a result, the hydrogen injector 63 is opened / closed with high accuracy in accordance with a command from the ECU 70, so that the hydrogen injection amount, injection timing, and injection time are controlled with high accuracy.
Therefore, in the first reference embodiment, the hydrogen-containing gas addition means for adding hydrogen (hydrogen-containing gas) to the gasoline engine 10A (internal combustion engine) includes the hydrogen tank 61, the hydrogen injector 63, and the ECU 70. ing.

<ECU>
The ECU 70 (control means) is a control device that electronically controls the internal combustion engine system 1 and includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and according to a program stored therein, Demonstrates various functions and controls various devices.
Further, the accelerator opening (throttle opening) detected by the accelerator opening sensor 81 is input to the ECU 70.

<ECU-Hydrogen addition amount determination function>
In addition, the ECU 70 (hydrogen addition amount determining means) is configured so that the rotational speed of the gasoline engine 10A, the required torque (output) required for the gasoline engine 10A, and the map (hydrogen addition amount data) stored in FIG. Based on the above, a function for determining the amount of hydrogen addition is provided.
A specific method will be described later.

≪Operation of internal combustion engine system≫
Next, the operation of the internal combustion engine system 1 will be described with reference to the flowchart of FIG.
Note that the control process shown in FIG. 2 is periodically executed, for example, at every constant crank angle.

In step S <b> 101, the ECU 70 calculates a required torque (load) that the gasoline engine 10 </ b> A should take as a target value based on the accelerator opening from the accelerator opening sensor 81.
In this calculation, a map in which the accelerator opening is associated with the required torque is referred to, and the required torque increases as the accelerator opening increases.

In step S102, the ECU 70 calculates the hydrogen addition amount based on the necessary torque calculated in step S101, the rotation speed of the gasoline engine 10A, and the map (hydrogen addition amount data) of FIG. 3 stored therein. To do.
The rotational speed of the gasoline engine 10A is calculated based on the crank angle input from the crank angle sensor 17.

<Hydrogen addition amount data-gasoline engine>
FIG. 3 is a map that schematically illustrates the optimum hydrogen addition amount at the rotation speed and the required torque of the gasoline engine 10A at a certain EGR rate (for example, 20%) divided into a plurality of regions for convenience. is there.
That is, the ECU 70 stores a plurality of maps similar to FIG. 3 for each EGR rate, such as EGR rates of 15%, 20%, 25%, and 30%. Then, the ECU 70 selects a map to be referred to based on the current EGR rate, and calculates the current hydrogen addition amount based on the necessary torque (load) and the rotational speed in the selected map. Yes.

In FIG. 3, the target hydrogenation amount tends to increase as the required torque increases as the rotation speed increases from the lower left to the upper right.
Note that in FIG. 3, the amount of hydrogen addition is shown in shades of hatching, indicating that the amount of hydrogen addition increases as the region becomes darker.

Here, for the gasoline engine 10A, a method of setting the region will be described as shown in FIG.
First, in the gasoline engine 10A, for example, the EGR rate is increased in order to reduce the pumping loss (intake resistance loss), but simply increasing the EGR rate increases the combustion fluctuation rate (C.O.V.IMEP). By adding hydrogen, the combustion fluctuation rate can be suppressed.

When hydrogen is added in this manner, the combustion fluctuation rate is reduced because hydrogen has low ignitability, but the combustion rate is high, so when hydrogen is added, the overall combustion rate after addition increases. It is.
Note that an increase in the combustion speed means that the robustness (combustion robustness) of combustion is increased.

  That is, as shown in FIG. 4, when the amount of hydrogen added to gasoline increases, the overall octane number after the addition increases, the ignitability decreases, the combustion speed increases, and the combustion robustness increases. Therefore, the Y-axis title “octane number of hydrogenated gasoline” in FIG. 4 is an index (parameter) indicating the ignitability, combustibility (combustion speed), and combustion robustness of the entire gasoline after hydrogen addition. .

FIG. 4 is a graph showing the relationship between the hydrogen addition rate to commercial regular gasoline and the octane number of regular gasoline to which hydrogen is added. The addition rate of hydrogen is given by the ratio of hydrogen in the calorific value of the whole regular gasoline hydrogenated. According to “SAE Paper 2004-01-0975”, the octane number of hydrogen is 140.
FIG. 4 shows that assuming that the octane number of regular gasoline to which hydrogen is not added is 90, the octane number of regular gasoline after addition of 10% of hydrogen having an octane number of 140 is 95. (Refer to the arrows in FIG. 4).

Here, it is considered that the hydrogen addition increases the combustion rate and the combustion robustness because the hydrogen combustion rate is high and hydrogen has a high combustion robustness. This is probably because hydrogen generates OH radicals (intermediates) that are strong oxidants during the combustion reaction process, and the amount of OH radicals increases as the amount of hydrogen added increases (see FIG. 5).
FIG. 5 shows that the amount of OH radicals generated increases as the amount of hydrogen added to the intake air (vol%) increases.

Thus, when the hydrogen addition amount increases, the combustion speed increases, the robustness increases, and the combustion fluctuation rate decreases. And since a combustion fluctuation rate becomes small, a pumping loss can be made small while raising an EGR rate and lowering combustion temperature, and it becomes possible to raise a fuel consumption.
Moreover, since octane number (combustion speed) improves by hydrogenation, knocking is suppressed.
Further, the synergistic effect of the decrease in combustion temperature and the increase in octane number makes it possible to increase the compression ratio and further increase the fuel consumption.

Therefore, the hydrogenation amount is determined by considering the rotational speed of the gasoline engine 10A for each EGR rate (for example, 15%, 20%, 25%, and 30%) by a preliminary test or the like in consideration of these effects due to the hydrogenation. Corresponding to the required torque, the combustion fluctuation rate is set to be 5% or less, for example.
The map shown in FIG. 3 shows the hydrogen addition amounts set in this way and is divided into regions for convenience.

Returning to FIG. 2, the description will be continued.
In step S103, the ECU 70 controls the hydrogen injector 63 to add hydrogen so that the hydrogen addition concentration calculated in step S102 is obtained.

  In step S104, the ECU 70 controls the EGR valve 51 so that a desired EGR rate is obtained. The target EGR rate is set to 30%, for example, so that the exhaust gas temperature does not become too high based on the exhaust gas temperature or the like.

The ECU 70 controls the EGR rate in this way, and based on the current EGR rate, the rotation speed and required torque of the gasoline engine 10A, and the map of FIG. 3 corresponding to the current EGR rate, the combustion fluctuation The hydrogenation concentration is calculated again so that the rate is 5% or less. Specifically, when the EGR rate increases, that is, when the amount of exhaust gas mixed into the intake air increases, the hydrogen addition concentration is increased in order to reduce the combustion fluctuation rate.
The combustion fluctuation rate is calculated based on the in-cylinder pressure input from the pressure sensor 16.

In step S105, the ECU 70 controls the hydrogen injector 63 to add hydrogen so that the hydrogen addition concentration calculated in step S104 is obtained.
Here, since the map of FIG. 3 is set so that the combustion fluctuation rate is 5% or less by a preliminary test or the like, hydrogen is added in step S105 according to the hydrogen addition amount calculated in step S104. Thus, the combustion fluctuation rate is suppressed to 5% or less (see FIG. 6).

In step S <b> 106, the ECU 70 determines whether knocking has been detected via the knock sensor 18.
If it is determined that knocking has been detected (S106, Yes), the processing of the ECU 70 proceeds to step S107. On the other hand, if it is determined that knocking has not been detected (No at S106), the ECU 70 returns to the start through a return.

In step S107, the ECU 70 controls the hydrogen injector 63 to add and add hydrogen.
Thus, when knocking is detected, by adding hydrogen, that is, by increasing the amount of hydrogen addition, the overall octane number and combustion speed after hydrogen addition increase, and as a result, compression in the gasoline engine 10A. The ratio is increased and the thermal efficiency is improved (see FIG. 7). The amount of hydrogen addition is preferably increased as the frequency of detection of knocking increases, for example.

  Thereafter, the processing of the ECU 70 returns to the start through a return.

≪Effect of internal combustion engine system≫
According to such an internal combustion engine system 1, the following effects are obtained.
Based on the required torque (load) and rotation speed of the gasoline engine 10A, the hydrogenation concentration is determined and hydrogenated so that the ignitability, octane number, combustion speed, combustion robustness, etc. of the gasoline after hydrogen addition are optimized. (S102, S103) Furthermore, since the hydrogen addition amount corresponding to the current EGR rate is determined and hydrogenation is performed (S104, S105), the combustion fluctuation rate is set to 5% or less and the operation range (EGR rate) is wide. Low temperature combustion of the gasoline engine 10A can be realized (see FIG. 6).

That is, by controlling in this way, it is possible to suppress intake resistance loss (pumping loss) due to a large amount of EGR (high EGR rate) and knocking. That is, as shown in FIG. 6, when the EGR rate is increased, the combustion fluctuation rate is increased. However, by adding hydrogen as in the present embodiment, the combustion speed and the combustion robustness are increased, and the EGR rate is increased. Even if it is 30%, the combustion fluctuation rate is within 5%, and the gasoline engine 10A can be operated with a high EGR rate (see the embodiment in FIG. 6).
If hydrogen is not added, as shown in the comparative example of FIG. 6, if the EGR rate exceeds 20%, the combustion fluctuation rate exceeds 5%. That is, in the first reference embodiment, the robustness is remarkably improved as compared with the comparative example.

  Further, when such a high EGR rate is used, the combustion temperature can be lowered and low-temperature combustion can be performed. As a result, the compression ratio can be further increased, intake resistance loss (pumping loss) can be reduced, thermal efficiency can be improved, and exhaust gas can be reduced.

  Furthermore, when knocking is detected (S106 / Yes), hydrogen having a high octane number is further added (S107), whereby the octane number is increased, and the compression ratio can be increased as shown in FIG. As a result, the thermal efficiency of the gasoline engine 10A can be increased.

≪Modification≫
The first reference embodiment of the present invention has been described above, but the present invention is not limited to this, and can be appropriately combined with the embodiments described later, or can be modified as follows.
Although the direct injection type gasoline engine 10A in which gasoline is directly injected into the cylinder 11a is illustrated in the above-described embodiment, the port injection type gasoline engine 10A in which gasoline is injected into the intake port 13a may be used.

In the above-described embodiment, the configuration in which gasoline for vehicles is used as the fuel is exemplified. However, for example, light oil, biofuel, DME (Dimethyl ether), GTL (gas to liquids), and mixed fuel in which these are mixed Can also be used.
The hydrocarbons contained in the fuel are, for example, alkanes, alkenes, alkynes, aromatic compounds, alcohols, aldehydes, and esters. Biofuels are ethanol, fatty acid methyl ester, etc., for example.

  In the above-described embodiment, the configuration in which the hydrogen-containing gas addition unit is a hydrogen addition system including the hydrogen tank 61, the hydrogen injector 63, and the like is exemplified. However, instead of the hydrogen addition system (the hydrogen tank 61, the hydrogen injector 63, and the like). The hydrogen-containing gas addition means may be configured by a reformed gas addition system for adding a reformed gas containing hydrogen (hydrogen-containing gas).

  In this case, the reformed gas addition system (hydrogen-containing gas addition means) includes a reformer that reforms the fuel and generates a reformed gas containing hydrogen, a pump that pumps the reformed gas, and a reformer that contains hydrogen. And a reformed gas injector (hydrogen-containing gas injector) for injecting gas.

  And the reformer is based on a known technique, and the reforming reaction is (1) a steam reforming method, (2) a partial oxidation method, and (3) a combination of a steam reforming method and a partial oxidation method. It is configured to be generated based on at least one of an autothermal reforming method and (4) a method in which a gas generated by rich combustion of the internal combustion engine is subjected to a water gas shift reaction.

  Further, the reformer performs the reforming reaction in at least one gas atmosphere of the exhaust gas of the gasoline engine 10A, air, oxygen-enriched air, nitrogen-enriched air, oxygen, and water vapor. Composed.

≪Second reference form≫
Next, a second reference embodiment of the present invention will be described with reference to FIGS. 1, 3, and 8 to 11. FIG.

≪Configuration of internal combustion engine system≫
The internal combustion engine system 2 according to the second reference embodiment includes a diesel engine 10B (diesel internal combustion engine) that burns light oil instead of the gasoline engine 10A (see FIG. 1).
Here, the diesel engine 10B self-ignites by compressing the light oil injected into the cylinder 11a and does not include a spark plug. However, the diesel engine 10B includes a cylinder block 11, a piston 12, a head cover 13, an intake valve 14, and an exhaust valve 15 similarly to the gasoline engine 10A.

In the second reference embodiment, light oil is stored in the fuel tank 41, and the fuel pump 42 pumps the light oil to the fuel injector 43. The fuel injector 43 directly injects light oil into the cylinder 11a.

≪Operation of internal combustion engine system≫
Next, the operation of the internal combustion engine system 2 will be described with reference to the flowchart of FIG.
In the second reference form, the ECU 70 executes the processes of steps S101 to S103 as in the first reference form.
Incidentally, in the second reference form, in step S102, the ECU 70 adds the hydrogen based on the required torque, the rotational speed of the diesel engine 10B, the current EGR rate, and the map of FIG. 3 corresponding to the current EGR rate. Calculate the amount.

<Hydrogen addition amount data-diesel engine>
Here, as for the diesel engine 10B, a method of setting the region will be described as shown in FIG.
First, in the diesel engine 10B, for example, a low cetane number fuel that promotes premixed combustion is desired in order to reduce exhaust gas (emission, NOx) and soot in a middle and high load region. Premixing is performed to increase the ignition delay time.
Therefore, in the second reference embodiment, hydrogen with low ignitability is added to the light oil to control the ignition delay time and premixed combustion, thereby reducing exhaust gas and the like.

  That is, as shown in FIG. 9, when the amount of hydrogen added to light oil increases, the overall cetane number after the addition decreases, the ignitability decreases, the combustion rate increases, and the combustion robustness increases. Thus, the Y-axis title “cetane number of hydrogenated gas oil” in FIG. 9 is an index (parameter) indicating the ignitability, combustibility (combustion speed), and combustion robustness of the entire diesel oil after hydrogenation. Become.

FIG. 9 is a graph showing the relationship between the addition rate of hydrogen to commercially available light oil and the cetane number of light oil to which hydrogen has been added. The addition rate of hydrogen is given by the ratio of hydrogen in the calorific value of the entire hydrogenated gas oil.
FIG. 9 shows that when the cetane number of light oil to which hydrogen is not added (JIS No. 2 light oil) is 55, 10% of hydrogen estimated to have a cetane number of −57 is added. It shows that the cetane number of light oil is estimated to be 40 (see arrow in FIG. 9).

  Incidentally, the fact that the cetane number of hydrogen is −57 indicates that the octane number of hydrogen is 140 according to the graph of FIG. 10 showing the relationship between the cetane number and the octane number in commercially available light oil and “SAE Paper 2004-01-0975”. Is estimated based on the fact (see the arrow in FIG. 10).

Therefore, the amount of hydrogen added is determined by an ignition delay corresponding to the rotational speed and required torque of the diesel engine 10B for each EGR rate (for example, 15%, 20%, 25%, 30%, 40%) by a preliminary test or the like. The time is set so as to be a predetermined time or more.
The predetermined time is set to increase as the required torque (load) of the diesel engine 10B increases. This is because, as the required torque (load) of the diesel engine 10B increases, especially in the middle and high load regions, the exhaust gas is reduced. Therefore, hydrogen with low ignitability is added to lengthen the ignition delay time and good before combustion. This is for premixing.
The map shown in FIG. 3 shows the hydrogen addition amounts set in this way and is divided into regions for convenience.

  In step S103, the ECU 70 adds hydrogen by controlling the hydrogen injector 63 so that the hydrogen addition concentration calculated in step S102 is obtained.

  Subsequently, in step S204, the ECU 70 controls the EGR valve 51 so that a desired EGR rate is obtained. The target EGR rate is set to, for example, 30% to 40% based on the exhaust gas temperature or the like so that the exhaust gas temperature does not become too high.

  Then, while controlling the EGR rate in this way, the ECU 70 controls the ignition delay based on the current EGR rate, the rotational speed and required torque of the diesel engine 10B, and the map of FIG. 3 corresponding to the current EGR rate. The hydrogenation concentration is calculated (corrected) again so that the time becomes equal to or longer than the predetermined time.

  The current ignition delay time is calculated based on a change in the in-cylinder pressure detected via the pressure sensor 16. In addition, it is good also as a structure which calculates ignition delay time based on the electric current value change of the in-cylinder pressure sensor which an electric current sensor (not shown) detects.

  In step S205, the ECU 70 controls the hydrogen injector 63 to add hydrogen so that the hydrogen addition concentration calculated in step S204 is obtained.

In step S206, the ECU 70 determines an optimal light oil injection timing while ensuring an ignition delay time of a predetermined time or more.
The optimum light oil injection timing is determined to be a timing at which the thermal efficiency of the diesel engine 10B becomes larger and (dP / dθ) max becomes a smaller value. (DP / dθ) max is the maximum value of the pressure increase rate (dP / dθ) of the in-cylinder pressure per unit crank angle. When (dP / dθ) max decreases, the noise / vibration of the diesel engine 10B decreases. .

  In step S207, the ECU 70 controls the fuel injector 43 according to the injection timing determined in step S206, and injects light oil.

≪Effect of internal combustion engine system≫
According to such an internal combustion engine system 2, the following effects are obtained.
By adding hydrogen with low ignitability, the ignition delay time is secured for a predetermined time or more (S102, S103, S204, S205), so that light oil and air are easily premixed. As a result, as shown in FIG. 11, the smoke and soot contained in the exhaust gas can be reduced while reducing NOx (nitrogen oxide) in the exhaust gas.

In addition, although hydrogen has low ignitability, as described above, it has a high combustion rate and high combustion robustness. Therefore, by adding hydrogen, the EGR rate can be increased, and as a result, it is burned at a low temperature. Therefore, NOx can be reduced.
In addition, as shown in the comparative example of FIG. 11, conventionally, NOx increases when smoke is reduced, and conversely, when NOx is reduced, smoke increases. is there.

  Moreover, since the light oil injection timing is optimized while ensuring the ignition delay time at a predetermined time or longer (S206, S207), the thermal efficiency of the diesel engine 10B can be improved.

«First embodiment»
Next, a first embodiment of the present invention will be described with reference to FIGS.
The internal combustion engine system according to the first embodiment differs from the second reference embodiment in that the program set in the ECU 70 is partially different and the operation thereof is partially different. Only the different parts will be described below.

As shown in FIG. 12, in the first embodiment, the processing of the ECU 70 proceeds to step S301 after step S103.
In step S301, the ECU 70 determines the diesel engine based on (dP / dθ) max calculated based on the in-cylinder pressure input from the pressure sensor 16 (combustion state detection means) and the graph (map) of FIG. The opening degree of the EGR valve 51 is controlled so that the EGR rate (amount) is 35 to 45%, preferably about 40% so that the combustion at 10B becomes slow.

Therefore, in the first embodiment, the EGR amount control means for controlling the EGR amount includes the EGR valve 51 and the ECU 70 for controlling the EGR valve 51.
FIG. 13 illustrates the case where the injection pressure of light oil is 150 (MPa) and the injection amount Q per stroke is 29.8 (mm ³ / stroke). Other injection pressures and injection amounts This graph (map) is also stored in the ECU 70 in advance.

  In step S302, the ECU 70 determines that the ignition delay time is equal to or longer than a predetermined time based on the current EGR rate, the rotational speed and required torque of the diesel engine 10B, and the map of FIG. 3 corresponding to the current EGR rate, and The hydrogenation concentration is again calculated (corrected) so that (dP / dθ) max decreases. That is, the ECU 70 corrects the increase / decrease in the amount of hydrogen addition using the current EGR rate, rotation speed, required torque, the map in FIG. 3 and the in-cylinder pressure (pressure signal) input from the pressure sensor 16 as control indices. .

  Thereafter, the processing of the ECU 70 proceeds to step S205.

≪Effect of internal combustion engine system≫
According to the internal combustion engine system according to the first embodiment, the following effects are obtained.
Since the EGR rate (amount) is controlled to 35 to 45%, preferably about 40% (S301), (dP / dθ) max and Pmax can be lowered to approach buffered combustion (FIG. 13). FIG. 14). Further, since hydrogen is further added, (dP / dθ) max and Pmax can be lowered to approach buffered combustion (see FIGS. 13 and 14).

  In this way, since the maximum in-cylinder pressure Pmax can be reduced, the skeleton of the diesel engine 10B can be reduced in weight, and fuel consumption and friction can be suppressed.

  Further, when the EGR rate (amount) is increased, as shown in FIGS. 15 and 16A to 16D, the heat generation rate with respect to the crank angle is delayed, that is, the thermal efficiency is made equal (see FIG. 15). it can.

  When hydrogen is further added, the heat generation rate is further retarded to promote premixing, and slow combustion can be performed (see FIGS. 16A to 16D). Thus, when hydrogen is added, the heat generation rate is further retarded, but as shown in FIG. 13, the thermal efficiency is substantially the same as when hydrogen is not added (hydrogen 0 vol%). This is thought to be due to the fact that heat loss was reduced by slow combustion and the robustness was increased by the addition of hydrogen.

16A to 16D, the light oil injection amount is 29.8 (mm ³ / stroke), and the fuel injection timing is BDTC (Before Top Dead Center) 2 deg. The case is shown as an example.

  Furthermore, since (dP / dθ) max can be lowered (see FIG. 13) while maintaining the same thermal efficiency (see FIG. 15), the noise and vibration of the diesel engine 10B can be greatly reduced in the medium and high load regions. As a result, the number of pilot injections can be reduced, or pilot injection itself can be omitted, and fuel consumption can be suppressed.

Furthermore, by increasing the EGR rate (amount), as shown in FIG. 17, NO in the exhaust gas can be reduced, and by adding hydrogen, NO can be further reduced.
This is thought to be due to the fact that the local high-temperature combustion portion is reduced by approaching slow combustion.

  Further, when hydrogen is added, CO and THC in the exhaust gas can be reduced (see FIGS. 18 and 19). This is presumably because the robustness of combustion is increased by adding hydrogen.

Further, when hydrogen is added, soot in the exhaust gas can be reduced (see FIG. 20). Here, when hydrogen is not added, soot increases as the EGR rate increases, but by adding hydrogen, soot (煤) can be reduced to approximately 0%.
This is because, by adding hydrogen, (1) premixing is promoted, (2) the robustness is increased, and the portion with a small local equivalence ratio on the φ-T map is reduced, and (3) it is also slow. Since it approaches combustion, the portion with a small local equivalent ratio on the φ-T map is reduced. (4)
It can be considered that the addition of hydrogen has made it difficult to generate soot.

1, 2 Internal combustion engine system 10A Gasoline engine (gasoline internal combustion engine)
10B Diesel engine (diesel internal combustion engine)
16 Pressure sensor (combustion state detection means)
41 Fuel tank (fuel supply means)
42 Fuel pump (fuel supply means)
43 Fuel injector (fuel supply means, fuel injector)
51 EGR valve 61 Hydrogen tank (means for adding hydrogen-containing gas)
62 Regulator (means for adding hydrogen-containing gas)
63 Hydrogen injector (hydrogen-containing gas addition means, injector for hydrogen-containing gas)
70 ECU (hydrogen addition amount determination means, EGR amount control means)
81 Accelerator position sensor

Claims (4)

A diesel internal combustion engine that burns light oil ;
A hydrogen-containing gas addition means for adding a hydrogen-containing gas containing hydrogen to the diesel internal combustion engine;
A hydrogen addition amount determining means for determining the hydrogen addition amount by the hydrogen-containing gas addition means based on hydrogen addition amount data set in consideration of fluctuations in octane number and cetane number due to hydrogen addition;
Combustion state detection means for detecting a combustion state in the diesel internal combustion engine;
EGR amount control means for controlling the EGR amount based on the combustion state detected by the combustion state detection means so that the combustion in the diesel internal combustion engine becomes slow,
Equipped with a,
After the EGR amount control means controls the EGR amount to 35 to 45%,
The hydrogen addition amount determining means determines the hydrogen addition amount to be 4 vol% with respect to the intake air based on the combustion state detected by the combustion state detecting means so that the combustion in the diesel internal combustion engine becomes slow. An internal combustion engine system. The internal combustion engine system according to claim 1, wherein the hydrogen addition amount determining means determines the hydrogen addition amount in consideration of an EGR amount. When knocking occurs in the internal combustion engine after the hydrogen-containing gas addition means has added the hydrogen-containing gas at the determined hydrogen addition amount,
The internal combustion engine system according to claim 1 or 2, wherein the hydrogen addition amount determining means increases the hydrogen addition amount. After adding the hydrogen-containing gas at the determined hydrogen addition amount by the hydrogen-containing gas addition means,
The internal combustion engine system according to claim 1 or 2, wherein the hydrogen addition amount determining means corrects the hydrogen addition amount so that an ignition delay time in the internal combustion engine is equal to or longer than a predetermined time.

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