Engine device

Abstract

To provide an engine device capable of suppressing an amount of nitrogen oxide emission to a target value without providing an expensive sensor and regardless of a proportion of hydrogen mixed in fuel gas.SOLUTION: An engine system 1, which is powered by fuel gas mixed with hydrogen, includes a control unit 8 that controls an excess air ratio and / or ignition parameters of an engine 2 based on the excess air ratio of the mixture of fuel gas and air supplied to the engine 2, and an exhaust temperature of exhaust gas from the engine 2, so as to suppress nitrogen oxides contained in the exhaust gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine device that is driven by fuel gas containing hydrogen. [Background technology]

[0002] Conventionally, some engine systems are driven by fuel gas whose fuel composition changes over time, and the fuel gas is supplied to the engine as a mixture with air. In such engine systems, combustion of the fuel gas produces exhaust gas containing nitrogen oxides (NOx). Furthermore, engine systems are required to suppress nitrogen oxide emissions to satisfy emission regulations and maintain stable operation, regardless of changes in the fuel composition of the fuel gas supplied to the engine.

[0003] For example, Patent Document 1 discloses a control method for an engine that uses fuel composed of multiple different components, the concentration of each component changing over time. This control method controls a first control variable that can adjust the air-fuel ratio so that the air-fuel ratio is within a band including the stoichiometric air-fuel ratio, and detects a second control variable that determines the air flow rate or the mixture flow rate, thereby performing constant air-fuel ratio control so that the air-fuel ratio is maintained at the stoichiometric air-fuel ratio. Here, the first control variable is the opening of a fuel control valve that controls the flow rate of fuel supplied to a mixer, and the second control variable is the opening of a throttle valve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5667413 Summary of the Invention [Problem to be solved by the invention]

[0005] Some engine devices are driven by fuel gas containing hydrogen, such as natural gas supplied from a pipeline, which is a fuel gas whose composition changes over time. However, while the same air-fuel ratio control according to the conventional technology disclosed in Patent Document 1 can accommodate variations in fuel composition in engines that use hydrocarbon-based fuel gas, it cannot accommodate variations in the hydrogen mixing ratio in engines that use hydrogen-containing fuel gas, because this increases nitrogen oxide (NOx) emissions in addition to reducing fuel efficiency.

[0006] Furthermore, in engines that use fuel gas mixed with hydrogen, combustion characteristics change significantly depending on the hydrogen content, so it is necessary to control fuel supply and engine operating conditions after understanding the hydrogen content. However, in this case, expensive sensors such as hydrogen sensors and NOx sensors must be installed to understand the hydrogen content, which increases costs and may complicate the device.

[0007] An object of the present invention is to provide an engine device that can suppress nitrogen oxide emissions to a target value without using an expensive sensor and regardless of the proportion of hydrogen mixed in the fuel gas. [Means for solving the problem]

[0008] In order to solve the above problems, the engine device of the present invention is an engine device that is driven by feeding a fuel gas having a variable fuel composition into the engine, and is characterized by including a control unit that controls the supply pressure of a mixture of fuel gas and air to the engine and the ignition parameters of the engine based on the exhaust temperature of exhaust gas from the engine. [Effects of the Invention]

[0009] According to the present invention, an engine device is provided that can be operated so as to suppress nitrogen oxide emissions to a target value, regardless of the hydrogen content of the fuel gas, without requiring an expensive sensor. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating an example of an engine device according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating an example of an engine device according to an embodiment of the present invention. [Figure 3] 1 is a graph showing the relationship between the average pressure of an engine and the amount of nitrogen oxide emissions in an engine system. [Figure 4] 1 is a graph showing the relationship between the ignition timing of an engine and the excess air ratio when the amount of nitrogen oxide emissions is adjusted to a predetermined target value in an engine device. [Figure 5] 1 is a graph showing the relationship between the ignition timing of an engine and the exhaust temperature when the amount of nitrogen oxide emissions is adjusted to a predetermined target value in an engine device. [Figure 6] 10 is a graph showing the relationship between the excess air ratio and the exhaust temperature of an engine when the amount of nitrogen oxide emissions is adjusted to a predetermined target value in an engine device according to an embodiment of the present invention. [Figure 7] 4 is a flowchart showing an example of an operation of combustion control by a control unit in the engine device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] An engine system 1 according to an embodiment of the present invention will be described with reference to the drawings. As shown in Figures 1 and 2, the engine system 1 includes an engine 2, an intake passage 3, an exhaust passage 4, a fuel supply device 5, an air excess ratio control device 6, an ignition device 7, and a control unit 8.

[0012] Particularly in this embodiment, the engine device 1 is a gas engine that is driven by fuel gas having a fuel composition that changes over time, such as natural gas supplied from a pipeline and mixed with hydrogen, being introduced into the combustion chamber 12a of the engine 2. For example, the engine device 1 supplies fuel gas containing a hydrocarbon fuel such as diesel oil, kerosene, or heavy oil as a main component and / or a non-hydrocarbon fuel such as ammonia, and further mixed with hydrogen, to the engine 2 by the fuel supply device 5. The fuel gas is supplied to the combustion chamber 12a as a mixture with air.

[0013] The engine 2 is, for example, a four-stroke engine, and is configured with a cylinder block 11 having a plurality of cylinders 12, but only one cylinder 12 is shown in Figures 1 and 2. As shown in Figures 1 and 2, each cylinder 12 is configured with a cylinder 13, a piston 14, and a cylinder head 15, and an ignition device 7 is provided for each cylinder 12.

[0014] The cylinder 13 is formed, for example, in a cylindrical shape within the cylinder block 11, and the piston 14 is slidably housed within the cylinder 13. The cylinder head 15 is attached to the upper side of the cylinder 13, and the cylinder 13 and the cylinder head 15 form a combustion chamber 12a therein.

[0015] Below the cylinder 13, a crankshaft 19 is connected to the piston 14 via a connecting rod 18, and the reciprocating motion of the piston 14 is converted into the rotational motion of the crankshaft 19 via the connecting rod 18.

[0016] The cylinder 13 is provided with a rotation speed sensor 20 such as an encoder that detects the rotation speed of the crankshaft 19, i.e., the rotation speed of the engine 2, and the rotation speed sensor 20 transmits the detection result to the control unit 8. The cylinder 13 is provided with a torque sensor 21 near the crankshaft 19 that detects the engine load (engine torque) of the engine 2, and the torque sensor 21 transmits the detection result to the control unit 8.

[0017] The cylinder head 15 also has an intake port 22 and an exhaust port 23 that communicate with the combustion chamber 12a of the cylinder 13, and is equipped with an intake valve 24 and an exhaust valve 25 that open and close the intake port 22 and the exhaust port 23, respectively, to the combustion chamber 12a.

[0018] The intake port 22 is connected to the intake passage 3 and introduces the air-fuel mixture supplied from the intake passage 3 into the combustion chamber 12a, while the exhaust port 23 is connected to the exhaust passage 4 and discharges the exhaust gas generated in the combustion chamber 12a into the exhaust passage 4. By opening the intake valve 24, the air-fuel mixture can be taken into the combustion chamber 12a through the intake port 22, while by opening the exhaust valve 25, the exhaust gas generated in the combustion chamber 12a can be exhausted through the exhaust port 23.

[0019] In other words, the intake passage 3 is connected to the intake port 22 of each cylinder 12 of the engine 2, and supplies compressed and cooled air to each cylinder 12 via the intake port 22. The exhaust passage 4 is connected to the exhaust port 23 of each cylinder 12 of the engine 2, and exhaust gas generated in each cylinder 12 is discharged via the exhaust port 23.

[0020] 1 and 2 show an example in which the intake passage 3 and the intake port 22 are directly connected, but in order to connect the intake passage 3 to each of the intake ports 22 of the multiple cylinders 12, an intake manifold having branch passages branching from the intake passage 3 to the multiple cylinders 12 may be provided between the intake passage 3 and the engine 2. Also, while Figures 1 and 2 show an example in which the exhaust passage 4 and the exhaust port 23 are directly connected, in the case of connecting the exhaust passage 4 to each of the exhaust ports 23 of the multiple cylinders 12, an exhaust manifold having branch passages branching from the exhaust passage 4 to the multiple cylinders 12 may be provided between the exhaust passage 4 and the engine 2.

[0021] The intake passage 3 may be provided with an air filter (not shown) that purifies fresh air and introduces it into the intake passage 3, and an intercooler (not shown) that cools the air flowing through the intake passage 3.

[0022] The intake passage 3 is provided with a throttle valve 6a as an excess air ratio control device 6 for adjusting the amount of air or mixture delivered to the intake port 22. The throttle valve 6a has its opening adjusted by a control unit 8, and the amount of air or mixture delivered to the intake port 22 is adjusted according to the opening of the throttle valve 6a. In this way, the throttle valve 6a functions as an excess air ratio control device 6 that adjusts the amount of air supplied from the intake passage 3 to the engine 2, thereby adjusting the excess air ratio of the mixture supplied to the engine 2.

[0023] An exhaust temperature sensor 27 is provided in the exhaust passage 4 to detect the exhaust temperature of the exhaust gas discharged from the engine 2 into the exhaust passage 4, and the exhaust temperature sensor 27 transmits the detection result to the control unit 8. In addition, an oxygen concentration sensor 28 is provided in the exhaust passage 4 to detect the oxygen concentration of the exhaust gas discharged from the engine 2 into the exhaust passage 4, and the oxygen concentration sensor 28 transmits the detection result to the control unit 8.

[0024] The fuel supply device 5 is provided in the intake passage 3 and is controlled by a control unit 8 to supply fuel gas supplied from a fuel supply section 9 such as a pipeline to the intake passage 3. A mixture of air supplied from the upstream side of the intake passage 3 and fuel gas supplied from the fuel supply section 9 is supplied to the combustion chamber 12a from the intake port 22. The control unit 8 controls the amount and timing of supply of fuel gas, etc., of the fuel supply device 5.

[0025] 1, the fuel supply device 5 is configured as a mixer type, and includes, as fuel control valves for controlling the amount of fuel gas supplied to the intake passage 3, a fuel flow rate adjustment valve 5a that adjusts the flow rate of fuel gas, and a venturi mixer 5b that mixes fuel gas with air flowing through the intake passage 3. Alternatively, as shown in FIG. 2, the fuel supply device 5 may be configured as an injection type, and include, as a fuel control valve, an admission valve 5c that injects fuel gas toward the intake passage 3, or an injector or the like may be included as a fuel control valve instead of the admission valve 5c.

[0026] Fuel control valves such as the fuel flow rate control valve 5a and the admission valve 5c function as an air excess ratio control device 6 that adjusts the air excess ratio of the mixture supplied to the engine 2 by adjusting the amount of fuel gas supplied to the intake passage 3.

[0027] The ignition device 7 is provided in the cylinder head 15 of each cylinder 12. The ignition device 7 is, for example, a spark ignition device using an ignition plug. In the spark ignition ignition device 7, the timing and duration of energization of the spark plug are controlled by a control unit 8, and ignition parameters such as ignition timing according to the energization timing and ignition energy according to the energization duration are controlled.

[0028] Alternatively, the ignition device 7 may be a micro-pilot type device that injects a small amount of liquid fuel, and is composed of an injector or the like that injects liquid fuel supplied from a liquid fuel tank (not shown) into the combustion chamber 12a (sub-chamber) below the cylinder head 15. In the micro-pilot type ignition device 7, the timing and duration of energization of the injector are controlled by the control unit 8, and the injection timing (ignition timing) according to the energization timing and the fuel injection amount according to the energization duration, i.e., ignition energy and other ignition parameters are controlled.

[0029] The control unit 8 is a computer such as an ECU (Engine Control Unit) that controls the operation of the engine 2, and is equipped with a CPU, ROM, RAM, etc., and is configured to control each part of the engine 2. The control unit 8 may store various programs for controlling the engine 2, and control the engine 2 by reading and executing the programs.

[0030] As a base control, the control unit 8 of this embodiment controls the opening of fuel control valves such as the fuel flow rate adjustment valve 5a and admission valve 5c or the throttle valve 6a so that the mixture flow rate is determined by the engine load and engine speed.

[0031] When the engine speed, load, or excess air ratio changes due to a change in the fuel gas composition, etc., the opening of fuel control valves such as fuel flow control valve 5a and admission valve 5c or throttle valve 6a is corrected based on the detection results from the speed sensor 20 and torque sensor 21 and the detection results from the oxygen concentration sensor 28 attached to the exhaust passage 4 so that the target speed, load, and excess air ratio are achieved.

[0032] Furthermore, the control unit 8 controls the combustion of the engine 2 so as to suppress the amount or proportion of nitrogen oxides contained in the exhaust gas based on the excess air ratio of the mixture supplied to the engine 2 from the intake passage 3 and the exhaust temperature of the exhaust gas discharged from the engine 2.

[0033] First, we will explain the combustion control of the engine 2. In an engine system 1 that uses fuel gas mixed with hydrogen as in the present invention, the hydrogen content of the supplied fuel gas changes. The nitrogen oxides contained in the exhaust gas of the engine system 1 vary depending on the hydrogen content of the fuel gas input to the engine 2, as well as the engine speed, load, excess air ratio, and ignition timing of the engine 2.

[0034] 3 shows the correlation between the average pressure of the combustion gas in the combustion chamber 12a and the amount of nitrogen oxide emissions for each hydrogen content of the combustion gas when the engine device 1 is operated under the same operating conditions. According to this correlation, the higher the hydrogen content of the combustion gas in the combustion chamber 12a, the greater the amount of nitrogen oxide emissions. Even if the hydrogen content is the same, the amount or percentage of nitrogen oxide emissions can be reduced by retarding the ignition timing or leaning the fuel gas in the air-fuel mixture, i.e., by increasing the excess air ratio.

[0035] Furthermore, Figure 4 shows the correlation between the ignition timing of the engine 2 and the excess air ratio of the mixture supplied to the engine 2 for each hydrogen content of the combustion gas when the engine system 1 is operated so that the nitrogen oxide emissions reach a predetermined target value. According to the correlation shown in Figure 4, the excess air ratio relative to the ignition timing (ignition timing relative to the excess air ratio) when the nitrogen oxide emissions reach a predetermined target value differs depending on the hydrogen content, but the tendency for the excess air ratio to decrease as the ignition timing is retarded is the same linear correlation regardless of the hydrogen content.

[0036] Figure 5 shows the correlation between the ignition timing of the engine 2 and the exhaust temperature of the exhaust gas from the engine 2 for each hydrogen content ratio of the combustion gas when the engine device 1 is operated so that the nitrogen oxide emissions reach a predetermined target value. According to the correlation shown in Figure 5, the exhaust temperature relative to the ignition timing (ignition timing relative to the exhaust temperature) when the nitrogen oxide emissions reach a predetermined target value differs depending on the hydrogen content ratio, but the characteristic that the more retarded the ignition timing, the higher the exhaust temperature tends to be is the same linear correlation regardless of the hydrogen content ratio.

[0037] Furthermore, based on the correlations in Figures 4 and 5, Figure 6 shows the correlation between the excess air ratio of the mixture supplied to the engine 2 and the exhaust temperature of the exhaust gas from the engine 2, for each hydrogen content in the combustion gas, when combustion is performed at each ignition timing when the engine system 1 is operated so that the nitrogen oxide emissions reach a predetermined target value. According to Figure 6, the correlation between the excess air ratio and the exhaust temperature when the nitrogen oxide emissions reach a predetermined target value is characterized by a tendency for the exhaust temperature to decrease as the excess air ratio increases, and is a substantially linear correlation regardless of the hydrogen content. In other words, if the excess air ratio and the exhaust temperature have a linear correlation as shown in Figure 6, the engine system 1 will achieve a predetermined target value for the nitrogen oxide emissions.

[0038] Therefore, in the engine system 1, a target line L for when the engine system 1 is operating is set based on the linear correlation between the excess air ratio and exhaust temperature for each hydrogen mixing ratio shown in Fig. 6, and is stored as a map for each target value of nitrogen oxide emissions. Note that the correlation between the excess air ratio and exhaust temperature may be a linear correlation having a certain width that allows a certain range (width) of exhaust temperature (or a certain excess air ratio) for a certain excess air ratio (or a certain exhaust temperature). In other words, the target line L for when the engine system 1 is operating may have a certain width.

[0039] In addition, in the engine device 1, the correlation between the excess air ratio and the exhaust temperature varies depending on the operating conditions of the engine 2, such as the engine speed and engine load, so the target line L when the engine device 1 is operating is stored as a map for each operating condition of the engine device 1.

[0040] If the excess air ratio and exhaust temperature detected during operation of the engine device 1 deviate from the correlation between the excess air ratio and the exhaust temperature as described above, the nitrogen oxides in the exhaust gas of the engine device 1 will no longer meet the specified target value.

[0041] Therefore, in the engine device 1 of this embodiment, as combustion control of the engine 2, the control unit 8 controls each part so that the excess air ratio and the exhaust temperature maintain a constant correlation based on the excess air ratio of the fuel gas and the exhaust temperature of the exhaust gas during operation, as well as the engine speed and engine load of the engine 2.

[0042] Specifically, the control unit 8 controls the excess air ratio of the engine 2 and ignition parameters (ignition timing, ignition energy, etc.) when igniting the engine 2, thereby suppressing nitrogen oxides contained in the exhaust gas and satisfying emission regulation values ​​regardless of the hydrogen mixing ratio, or improving the fuel efficiency of the fuel gas supplied to the engine 2. At this time, the control unit 8 feedback-controls the excess air ratio and ignition parameters of the engine 2 so that the excess air ratio and exhaust temperature detected during operation satisfy the correlation between the excess air ratio and exhaust temperature as described above.

[0043] The engine device 1 can improve fuel economy by advancing the ignition timing and / or enriching the fuel gas (reducing the excess air ratio) regardless of the hydrogen mixing ratio. Also, the engine device 1 can reduce nitrogen oxide emissions by retarding the ignition timing and / or leaning the fuel gas (increasing the excess air ratio) regardless of the hydrogen mixing ratio.

[0044] In the engine system 1 of this embodiment, correlation information such as a relational expression or a map showing the correlation between the excess air ratio and the exhaust temperature is stored in the control unit 8. For example, the correlation between the excess air ratio and the exhaust temperature may be obtained from data detected when the engine system 1 is operated experimentally, and the correlation information may be constructed in advance. Alternatively, the correlation information may be obtained from data detected when the engine system 1 is operated practically, and the correlation information may be constructed in real time. Furthermore, in the engine system 1, correlation information showing the correlation between the excess air ratio and the exhaust temperature is stored in the control unit 8 for each operating condition of the engine 2, such as the engine speed and engine load (for example, for each combination of engine speed and engine load).

[0045] Furthermore, the engine device 1 estimates the hydrogen mixing ratio based on the correlation between the ignition timing and the excess air ratio, and the ignition timing and excess air ratio during operation, calculates a correction amount for the ignition timing and excess air ratio based on the estimated hydrogen mixing ratio, and corrects the ignition timing and excess air ratio based on the correction amount.

[0046] Next, a specific example of combustion control of the engine 2 by the control unit 8 will be described with reference to the flowchart of FIG.

[0047] First, the control unit 8 assumes that the proportion of hydrogen mixed in the combustion gas supplied to the engine 2 is 0 (step S1).

[0048] During operation of the engine device 1, the control unit 8 detects the engine speed of the engine 2 using the speed sensor 20, and detects the engine load of the engine 2 using the torque sensor 21. Then, the control unit 8 reads out correlation information between the excess air ratio and the exhaust temperature that corresponds to the detected engine speed and engine load of the engine 2 from the stored correlation information between the excess air ratio and the exhaust temperature.

[0049] During operation of the engine device 1, the control unit 8 detects the oxygen concentration of the exhaust gas discharged from the engine 2 to the exhaust passage 4 using the oxygen concentration sensor 28, and calculates the excess air ratio of the fuel gas supplied from the intake passage 3 to the engine 2 based on the oxygen concentration. Additionally, during operation of the engine device 1, the control unit 8 detects the exhaust temperature of the exhaust gas discharged from the engine 2 to the exhaust passage 4 using the exhaust temperature sensor 27 (step S2).

[0050] Then, the control unit 8 compares the air excess ratio and the exhaust temperature (the current air excess ratio and the current exhaust temperature) with the read correlation information between the air excess ratio and the exhaust temperature, and determines whether the current air excess ratio and the current exhaust temperature match the correlation information (step S3). For example, the control unit 8 determines whether the current air excess ratio and the current exhaust temperature are on a target line L between the air excess ratio and the exhaust temperature, which is the correlation information as shown in FIG.

[0051] If the current excess air ratio and the current exhaust temperature are on the target line L (step S3: Yes), the control unit 8 ends the flow without correcting the excess air ratio and the ignition parameters.

[0052] On the other hand, if the current excess air ratio and the current exhaust temperature are not on the target line L (step S3: No), the control unit 8 corrects the excess air ratio and the ignition parameters, for example, by advancing or retarding the ignition timing, so that the excess air ratio and the exhaust temperature are on the target line L (step S4).

[0053] Furthermore, the control unit 8 estimates the hydrogen mixing ratio based on the relationship between the ignition timing and the excess air ratio (step S5). For example, the control unit 8 estimates the hydrogen mixing ratio corresponding to the corrected ignition timing and the current excess air ratio based on the relationship between the ignition timing and the excess air ratio for each hydrogen mixing ratio as shown in Fig. 4. At this time, the control unit 8 may estimate the hydrogen mixing ratio from the graph of each hydrogen mixing ratio in Fig. 4 that is closest to the position of the corrected ignition timing and the current excess air ratio.

[0054] Furthermore, the control unit 8 corrects the excess air ratio to an optimum value based on the estimated hydrogen mixing ratio (step S6). For example, the control unit 8 corrects the excess air ratio to an optimum value corresponding to the corrected ignition timing in the graph of the estimated hydrogen mixing ratio in Fig. 4.

[0055] Thereafter, the control unit 8 returns to step S2 and continues to operate the engine 2 with the corrected ignition timing and excess air ratio.

[0056] As described above, according to this embodiment, the engine device 1 is an engine device 1 that is driven by fuel gas mixed with hydrogen, and includes a control unit 8 that controls the excess air ratio of a mixture of fuel gas and air supplied to the engine 2 and / or ignition parameters of the engine 2 so as to suppress nitrogen oxides contained in the exhaust gas, based on the excess air ratio of the mixture of fuel gas and air supplied to the engine 2 and the exhaust temperature of exhaust gas from the engine 2. For example, the control unit 8 controls the amount or ratio of nitrogen oxides contained in the exhaust gas.

[0057] In engine system 1 that burns hydrogen, compared to a normal gas engine, it is necessary to adjust the fuel gas to be lean (increase in excess air ratio) and the ignition timing to retard in order to suppress nitrogen oxide emissions. In this case, the amount of adjustment of the excess air ratio and ignition timing changes depending on the hydrogen content of the fuel gas, but the hydrogen content of the fuel gas is unknown and fluctuates, and measuring the hydrogen content requires an expensive sensor. In contrast, engine system 1 can suppress nitrogen oxide emissions to a predetermined target value without using an expensive sensor by adjusting the excess air ratio and ignition timing to maintain the correlation between the excess air ratio and exhaust temperature regardless of the hydrogen content of the fuel gas.

[0058] Furthermore, according to this embodiment, the control unit 8 controls the air excess ratio and / or the ignition parameters based on the air excess ratio and exhaust temperature, the ignition parameters, and the engine speed and / or the engine load so as to suppress nitrogen oxides contained in the exhaust gas.

[0059] As a result, the engine device 1 can utilize the relationship between the excess air ratio and the exhaust temperature that corresponds to various operating conditions, even if the relationship between the excess air ratio that suppresses nitrogen oxide emissions and the exhaust temperature differs depending on the operating conditions of the engine speed and engine load.

[0060] Furthermore, according to this embodiment, the control unit 8 stores in advance correlation information between the excess air ratio and the exhaust temperature at which nitrogen oxides become constant, based on the operating conditions corresponding to the engine speed and / or the engine load, and controls the excess air ratio and / or the ignition parameters based on the correlation information.

[0061] As a result, the engine device 1 has correlation information between the excess air ratio and the exhaust temperature for each operating condition in the form of a map or the like, and based on the correlation information between the excess air ratio and the exhaust temperature according to the operating conditions during operation, the engine device 1 controls the excess air ratio and ignition parameters so as to correct deviations from the actual measured values ​​of the excess air ratio and the exhaust temperature, thereby making it possible to suppress nitrogen oxide emissions to a predetermined target value.

[0062] Furthermore, according to this embodiment, the control unit 8 estimates the hydrogen mixture ratio in the fuel gas based on the operating conditions and the excess air ratio and / or the correction amount of the ignition parameters.

[0063] This allows the engine device 1 to grasp the hydrogen mixing ratio without having to equip it with an expensive sensor for measuring the hydrogen mixing ratio of the fuel gas, and further allows combustion control to be performed based on the estimated hydrogen mixing ratio.

[0064] Furthermore, according to this embodiment, in the engine system 1, the engine 2 is a four-stroke engine and includes an ignition device 7 that ignites the engine 2 by a spark ignition system or a micro-pilot system, a fuel supply device 5 that supplies fuel gas to the intake side of the engine 2 by an injection system or a mixer system, and an air excess ratio control device 6 that adjusts the air excess ratio using at least one of a fuel flow control valve 5a and a throttle valve 6a based on the oxygen concentration in the exhaust gas.

[0065] In such an engine system 1, the control unit 8 adjusts the excess air ratio by controlling at least one of the opening degree of the fuel flow rate control valve 5a and the opening degree of the throttle valve 6a.

[0066] This allows the engine system 1 to more accurately control the excess air ratio to satisfy the relationship between the excess air ratio and the exhaust temperature.

[0067] In addition, in such an engine system 1, the control unit 8 controls the timing of energizing the spark ignition plug, thereby controlling the ignition parameters.

[0068] This allows the engine system 1 to more accurately control the ignition parameters to satisfy the relationship between the excess air ratio and the exhaust temperature.

[0069] According to this embodiment, the engine device 1 supplies fuel containing hydrocarbons as a main component to the engine 2 as fuel gas.

[0070] As a result, the engine device 1 can be operated with fuel gas in which hydrogen is mixed into fuel mainly composed of hydrocarbons so that the amount of nitrogen oxide emissions satisfies the regulated value.

[0071] In the above embodiment, an example has been described in which the hydrogen mixing ratio is estimated based on the correlation between the ignition timing and the excess air ratio, and the ignition timing and excess air ratio during operation in the engine system 1, and the estimated hydrogen mixing ratio is used to calculate the correction amounts for the ignition timing and excess air ratio, but the present invention is not limited to this example.

[0072] In another embodiment, in the engine system 1, the control unit 8 determines whether the hydrogen content of the fuel gas is increasing or decreasing based on correlation information between the excess air ratio and the exhaust temperature. Then, the control unit 8 adjusts the excess air ratio and / or the ignition timing by a predetermined amount in accordance with the determination result, thereby performing feedback control of the excess air ratio and / or the ignition timing.

[0073] For example, the control unit 8 detects the current excess air ratio and the current exhaust temperature, and determines that the hydrogen mixing ratio is increasing if the exhaust temperature is lower than the target exhaust temperature based on the correlation information between the excess air ratio and the exhaust temperature and the current excess air ratio and / or the current exhaust temperature.Furthermore, the control unit 8 determines that the hydrogen mixing ratio is decreasing if the exhaust temperature is higher than the target exhaust temperature.

[0074] When the control unit 8 determines that the hydrogen mixing ratio is on the rise, it executes at least one of increasing the excess air ratio by a predetermined amount and retarding the ignition timing by a predetermined amount. When the control unit 8 determines that the hydrogen mixing ratio is on the fall, it executes at least one of decreasing the excess air ratio by a predetermined amount and advancing the ignition timing by a predetermined amount.

[0075] Thereafter, the control unit 8 again detects the current excess air ratio and the current exhaust temperature, and determines whether the hydrogen mixing ratio is increasing or decreasing based on the correlation information between the excess air ratio and the exhaust temperature. If the hydrogen mixing ratio is neither increasing nor decreasing, the control unit 8 ends the feedback control of the excess air ratio and the ignition timing, and if the hydrogen mixing ratio is increasing or decreasing, the control unit 8 repeats the feedback control of the predetermined amount of the excess air ratio and the ignition timing.

[0076] As described above, according to the engine system 1 of another embodiment, when the proportion of hydrogen mixed in the fuel gas is on the rise based on the correlation information between the air excess ratio and the exhaust temperature, the control unit 8 performs at least one of increasing the air excess ratio and retarding the ignition timing, which is an ignition parameter.

[0077] In the engine system 1, an increase in the proportion of hydrogen mixed in leads to an increase in the amount of nitrogen oxide emissions. In contrast, in another embodiment, by making the fuel gas lean (increasing the excess air ratio) and retarding the ignition timing so as to maintain the relationship between the excess air ratio and the exhaust temperature, it is possible to suppress the amount of nitrogen oxide emissions to a target value while aiming to improve fuel economy.

[0078] Furthermore, according to the engine system 1 of another embodiment, the control unit 8, when the proportion of hydrogen mixed in the fuel gas is on a decreasing trend, based on the correlation information between the excess air ratio and the exhaust temperature, At least one of the following is performed: reducing the excess air ratio and advancing the ignition timing, which is an ignition parameter.

[0079] In the engine system 1, when the hydrogen mixing ratio decreases, the amount of nitrogen oxide emissions decreases but fuel economy deteriorates. In contrast, in another embodiment, by enriching the fuel gas (reducing the excess air ratio) and advancing the ignition timing so as to maintain the relationship between the excess air ratio and the exhaust temperature, it is possible to prevent excessive deterioration in fuel economy and keep the amount of nitrogen oxide emissions to a target value.

[0080] In addition, the engine device 1 may be a gas engine that can be driven by feeding fuel gas mixed with hydrogen into the engine 2, or may be a dual-fuel engine that can be driven by feeding at least one of fuel gas mixed with hydrogen and liquid fuel such as light oil or heavy oil into the engine 2.

[0081] Furthermore, the present invention can be modified as appropriate within the scope that does not contradict the gist or idea of ​​the invention that can be read from the claims and the entire specification, and engine devices that involve such modifications are also included in the technical idea of ​​the present invention.

[0082] [Appendix to the invention] The following is a summary of the invention extracted from the above-described embodiment. Note that the configurations and processing functions described in the following supplementary notes can be selected and combined as desired.

[0083] <Appendix 1> An engine device driven by fuel gas containing hydrogen, An engine device comprising a control unit that controls the excess air ratio of a mixture of fuel gas and air supplied to the engine and / or ignition parameters of the engine based on the exhaust temperature of exhaust gas from the engine.

[0084] <Appendix 2> 2. The engine device according to claim 1, wherein the control unit controls the amount or ratio of nitrogen oxides contained in the exhaust gas.

[0085] <Appendix 3> The engine device described in Appendix 1, characterized in that the control unit controls the air excess ratio and / or the ignition parameters based on the air excess ratio and the exhaust temperature, the ignition parameters, and engine speed and / or engine load.

[0086] <Appendix 4> The engine apparatus according to claim 3, wherein the control unit pre-stores correlation information between the air excess ratio and the exhaust temperature at which the nitrogen oxides become constant, based on operating conditions corresponding to the engine speed and / or the engine load, and controls the air excess ratio and / or the ignition parameters based on the correlation information.

[0087] <Appendix 5> The engine device according to claim 4, wherein the control unit estimates the proportion of hydrogen mixed in the fuel gas based on the operating conditions and the correction amount of the excess air ratio and / or the ignition parameter.

[0088] <Appendix 6> the engine is a four-stroke engine, an ignition device that ignites the engine using a spark ignition system or a micro-pilot system; a fuel supply device that supplies the fuel gas to the intake side of the engine by an injection method or a mixer method; An engine device according to any one of claims 1 to 5, further comprising an air excess ratio control device that adjusts the air excess ratio using at least one of a fuel flow control valve and a throttle valve based on the oxygen concentration in the exhaust gas.

[0089] <Appendix 7> 7. The engine device according to claim 6, wherein the control unit adjusts the excess air ratio by controlling at least one of an opening degree of the fuel flow control valve and an opening degree of the throttle valve.

[0090] <Appendix 8> 8. The engine device according to claim 6, wherein the control unit controls the ignition parameters by controlling the timing of energization of the spark ignition type spark plug.

[0091] <Appendix 9> 9. The engine device according to any one of claims 1 to 8, wherein a fuel containing a hydrocarbon as a main component is fed to the engine as the fuel gas.

[0092] <Appendix 10> The engine device according to any one of appendices 1 to 9, wherein the control unit, when the proportion of hydrogen mixed in the fuel gas is on the rise based on correlation information between the excess air ratio and the exhaust temperature, executes at least one of increasing the excess air ratio and retarding the ignition timing, which is the ignition parameter.

[0093] <Appendix 11> The engine device according to any one of appendices 1 to 10, wherein the control unit, when the proportion of hydrogen mixed in the fuel gas is on a decreasing trend based on correlation information between the excess air ratio and the exhaust temperature, performs at least one of reducing the excess air ratio and advancing the ignition timing, which is the ignition parameter. [Explanation of symbols]

[0094] 1 Engine equipment 2 engines 3 Intake passage 4 Exhaust passage 5 Fuel supply device 5a Fuel flow control valve 5b Venturi Mixer 5c Admission Valve 6. Air Excess Ratio Control Device 6a Throttle valve 7 Ignition device 8. Control Unit 9 Fuel supply section 11 Cylinder block 12 cylinders 12a Combustion chamber 13 cylinders 14 Piston 15 Cylinder head 18 Connecting rod 19. Crankshaft 20 RPM sensor 21 Torque sensor 22 Intake port 23 Exhaust port 24 intake valve 25 Exhaust valve 27 Exhaust gas temperature sensor 28 Oxygen concentration sensor

Claims

1. An engine device driven by fuel gas containing hydrogen, An engine device comprising a control unit that controls the excess air ratio of a mixture of fuel gas and air supplied to the engine and / or ignition parameters of the engine based on the exhaust temperature of exhaust gas from the engine.

2. 2. The engine device according to claim 1, wherein the control unit controls the amount or ratio of nitrogen oxides contained in the exhaust gas.

3. 2. The engine apparatus according to claim 1, wherein the control unit controls the air excess ratio and / or the ignition parameters based on the air excess ratio and the exhaust temperature, the ignition parameters, and the engine speed and / or the engine load.

4. 4. The engine apparatus according to claim 3, wherein the control unit pre-stores correlation information between the excess air ratio and the exhaust temperature at which the nitrogen oxides become constant, based on operating conditions corresponding to the engine speed and / or the engine load, and controls the excess air ratio and / or the ignition parameters based on the correlation information.

5. 5. The engine apparatus according to claim 4, wherein the control unit estimates the proportion of hydrogen mixed in the fuel gas based on the operating conditions and the correction amount of the excess air ratio and / or the ignition parameter.

6. the engine is a four-stroke engine, an ignition device that ignites the engine using a spark ignition system or a micro-pilot system; a fuel supply device that supplies the fuel gas to the intake side of the engine by an injection method or a mixer method; 2. The engine apparatus according to claim 1, further comprising an air excess ratio control device that adjusts the air excess ratio by at least one of a fuel flow control valve and a throttle valve based on the oxygen concentration in the exhaust gas.

7. 7. The engine device according to claim 6, wherein the control unit adjusts the excess air ratio by controlling at least one of the opening degree of the fuel flow control valve and the opening degree of the throttle valve.

8. 7. The engine apparatus according to claim 6, wherein the control unit controls the ignition parameters by controlling the energization timing of the spark ignition type spark plug.

9. 2. The engine device according to claim 1, wherein the fuel gas is a fuel containing a hydrocarbon as a main component.

10. 2. The engine apparatus according to claim 1, wherein the control unit executes at least one of increasing the excess air ratio and retarding the ignition timing, which is the ignition parameter, when the proportion of hydrogen mixed in the fuel gas tends to increase based on correlation information between the excess air ratio and the exhaust temperature.

11. 2. The engine device according to claim 1, wherein the control unit executes at least one of reducing the excess air ratio and advancing the ignition timing, which is the ignition parameter, when the proportion of hydrogen mixed in the fuel gas is on a decreasing trend based on correlation information between the excess air ratio and the exhaust temperature.

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