JP2013047495A - Engine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs, to simplify a configuration, and to operate an engine stably by maintaining an air ratio of an air-fuel mixture to a desired air ratio even if a heating value of fuel gas changes significantly.SOLUTION: An engine system includes: an engine output control part H1 for controlling an opening of an air-fuel mixture flow regulating valve 10 so that an engine output becomes a target output; an air-fuel mixture pressure control part H2 for controlling openings of a first fuel gas flow regulating valve 8 and a second fuel gas flow regulating valve 9 so that air-fuel mixture pressure becomes target pressure; and a fuel gas supply state switching control part H3 for switching a first fuel gas supply state of supplying only first fuel gas G1 to a mixer 2 and a mixed fuel gas supply state of supplying mixed fuel gas of the first fuel gas G1 and second fuel gas G2 to the mixer 2 on the basis of opening information on the first fuel gas flow regulating valve 8 and the second fuel gas flow regulating valve 9 in a state that control by the air-fuel mixture pressure control part H2 is performed.

Description

  The present invention comprises a mixer that mixes fuel gas and combustion air to generate an air-fuel mixture, and an air-fuel mixture supply path that supplies the air-fuel mixture generated by the mixer to the engine, The first fuel gas having the first calorific value or the mixed fuel gas obtained by mixing the second fuel gas having the second calorific value higher than the first calorific value and the first fuel gas is used for the mixing. The present invention relates to an engine system that operates an engine by burning an air-fuel mixture supplied in an air supply path.

  In the engine system as described above, for example, a biogas which is a first fuel gas is used as a fuel gas, and an air-fuel mixture obtained by mixing the biogas and combustion air is supplied to the engine and burned. . However, since the calorific value of biogas varies depending on its generation conditions, it is difficult to stably operate the engine while obtaining a desired engine output. For example, in a lean engine that burns by supplying a lean mixture (fuel mixture with a low fuel gas concentration) to the engine, misfiring occurs if the air ratio of the mixture supplied to the engine becomes too lean than the desired air ratio. On the contrary, if the concentration is higher than the desired air ratio, the problem arises that the NOx concentration in the exhaust gas becomes too high. Therefore, in order to stably operate the engine while obtaining a desired engine output, it is required to maintain the air ratio of the air-fuel mixture supplied to the engine at a desired air ratio, but the calorific value of the fuel gas varies. Since the theoretical air amount of the fuel gas also fluctuates, for example, if the flow rate ratio between the fuel gas and the combustion air is kept constant, the air ratio of the air-fuel mixture supplied to the engine will be This causes a problem as described above.

  Therefore, conventionally, even when a fuel gas whose calorific value fluctuates is used, in order to prevent the occurrence of the above-described problems, a fuel gas that can be supplied with an adjustable amount of fuel gas supplied to the mixer through the fuel gas supply path There is a gas amount adjusting valve that controls the opening degree of the fuel gas amount adjusting valve so that the air-fuel mixture pressure supplied to the engine becomes a predetermined target pressure with respect to the engine output (for example, a patent) Reference 1). In the engine system described in Patent Document 1, the case where coal mine methane gas, which is the first fuel gas, is used as the fuel gas, but in the case where biogas, which is the first fuel gas, is used as the fuel gas, is shown. Is also useful for preventing the occurrence of the above-described problems.

In another conventional engine system, a mixed fuel gas obtained by mixing two types of fuel gas, that is, a biogas that is the first fuel gas and a city gas that is the second fuel gas, is used as the fuel gas. There is also an engine in which an air-fuel mixture obtained by mixing fuel gas and combustion air is supplied to an engine and burned (see, for example, Patent Document 2).
In the system described in Patent Document 2, a mixed fuel gas supply path that supplies a mixed fuel gas obtained by mixing biogas and city gas to a mixer, and a mixed fuel gas that is supplied to the mixer through the mixed fuel gas supply path And a fuel control valve capable of adjusting the flow rate of the mixed fuel gas supplied to the mixer through the mixed fuel gas supply path. Then, the opening of the throttle valve, which can adjust the flow rate of the air-fuel mixture supplied to the engine, is controlled and supplied to the engine so that the power generation amount of the generator driven by the engine becomes a predetermined target power generation amount. The opening degree of the fuel control valve is controlled so as to maintain the air ratio of the air-fuel mixture at a desired air ratio. For the control of the opening of the fuel control valve, the estimated heat consumption per unit time consumed by the engine is obtained using the power generation amount of the generator driven by the engine, and the obtained estimated heat consumption and flow rate are obtained. The estimated calorific value per unit volume of the mixed fuel gas is obtained using the flow rate measured by the meter, and the opening of the fuel control valve is controlled so that the target opening obtained from the obtained calorific value is obtained. ing.

Japanese Patent No. 4452092 JP 2010-72120 A

  In the system described in Patent Document 1, even if the calorific value of the fuel gas varies, the opening of the fuel gas amount adjusting valve is controlled so that the mixture pressure supplied to the engine becomes the target pressure. The air ratio of the air-fuel mixture supplied to is maintained at a desired air ratio. However, when the calorific value of the fuel gas changes significantly, the air ratio of the air-fuel mixture supplied to the engine cannot be maintained at a desired air ratio simply by adjusting the opening of the fuel gas amount adjusting valve. That is, when the heat generation amount of the fuel gas decreases, the opening degree of the fuel gas amount adjustment valve is adjusted to the open side. However, when the heat generation amount of the fuel gas greatly decreases, the fuel gas amount Even if the opening degree of the regulating valve is adjusted to full open, the mixture pressure supplied to the engine cannot be set as the target pressure. As a result, the air ratio of the air-fuel mixture supplied to the engine cannot be maintained at a desired air ratio, causing problems such as misfires and excessively high NOx concentration in the exhaust gas. Cannot drive. Therefore, in order to operate the engine stably, there is a problem that the range of the calorific value of the fuel gas is limited to a narrow range, and when the calorific value of the fuel gas is greatly reduced, the engine is not operated. It becomes a situation that must be stopped.

  In the system described in Patent Document 2, when the calorific value of the mixed fuel gas changes significantly, for example, the supply of biogas to the mixer is stopped, and only the city gas is supplied to the mixer to supply the fuel gas to the city. By using only gas, the air ratio of the air-fuel mixture supplied to the engine can be maintained at a desired air ratio. However, in the system described in Patent Document 2, the fuel gas is basically a mixed fuel gas obtained by mixing biogas and city gas, and the mixed fuel gas and combustion air are mixed. The air-fuel mixture is supplied to the engine and burned. Thus, when using a mixed fuel gas of biogas and city gas, the mixed fuel gas supply path is provided with a flow meter, and the fuel control valve is opened using the flow rate of the mixed fuel gas measured by the flow meter. By controlling the degree, the air ratio of the air-fuel mixture supplied to the engine is maintained at a desired air ratio. Therefore, an expensive flow meter must be provided, which increases the cost and complicates the configuration.

  The present invention has been made paying attention to such a point, and its purpose is to reduce the cost and simplify the configuration, and to supply the engine even if the calorific value of the fuel gas changes greatly. An object of the present invention is to provide an engine system that can maintain a desired air ratio and can operate the engine stably.

In order to achieve this object, the characteristic configuration of the engine system according to the present invention includes a mixer that mixes fuel gas and combustion air to generate an air-fuel mixture, and an air-fuel mixture generated by the mixer to the engine. And a first fuel gas having a first calorific value, or a second fuel gas having a second calorific value higher than the first calorific value and the first fuel gas. In an engine system that uses a mixed fuel gas mixed with a fuel gas and operates the engine by burning the mixture supplied in the mixture supply path,
As the mixer, the first fuel gas supplied through the first fuel gas supply path, or the mixed fuel gas obtained by mixing the first fuel gas and the second fuel gas supplied through the second fuel gas supply path And a single mixer that mixes the combustion air with each other to generate an air-fuel mixture, is provided in the first fuel gas supply path, and the flow rate of the first fuel gas supplied to the mixer is adjustable A first fuel gas flow rate adjustment valve, a second fuel gas flow rate adjustment valve provided in the second fuel gas supply path and capable of adjusting a flow rate of the second fuel gas supplied to the mixer, and the air-fuel mixture A mixture flow rate adjustment valve provided in the supply path and capable of adjusting the flow rate of the mixture supplied to the engine, and an engine output for controlling the opening of the mixture flow rate adjustment valve so that the engine output becomes a target output Control unit and said mixing An air-fuel mixture pressure control unit that controls the opening degrees of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve so that the air-fuel mixture pressure supplied to the engine in the supply path becomes a target pressure; Regarding the supply state of the fuel gas to the mixer, the first fuel gas flow rate adjustment valve is opened, and the second fuel gas flow rate adjustment valve is closed, and only the first fuel gas is supplied to the mixer. Mixing to supply a mixed fuel gas of the first fuel gas and the second fuel gas to the mixer with both the supply state and the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve opened. The degree of opening of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve can be switched between fuel gas supply states and controlled by the mixture pressure control unit. Based on, in that it includes a fuel gas supply state switching control unit for switching between the said mixed fuel gas supply with said first fuel gas supply state.

According to this feature, the fuel gas supply state switching control unit switches between the first fuel gas supply state and the mixed fuel gas supply state with respect to the supply state of the fuel gas to the mixer. The engine can be operated while switching between the case where only the first fuel gas is used and the case where the mixed fuel gas of the first fuel gas and the second fuel gas is used.
Even when the fuel gas supply state switching control unit switches between the first fuel gas supply state and the mixed fuel gas supply state, the engine output control unit performs mixing so that the engine output becomes the target output. Since the opening degree of the air flow rate adjusting valve is controlled, the engine output can be maintained at the target output to obtain a desired engine output, and the mixture pressure control unit can adjust the mixture pressure so that the mixture pressure becomes the target pressure. Since the opening degree of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve is controlled, the air ratio of the air-fuel mixture supplied to the engine can be maintained at a desired air ratio.

  When the fuel gas supply state to the mixer is switched between the first fuel gas supply state and the mixed fuel gas supply state, the fuel gas supply state switching control unit is in a state where the control is performed by the mixture gas pressure control unit. The first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve are switched based on the opening information. For example, when the supply state of the fuel gas to the mixer is switched to the first fuel gas supply state, if the calorific value of the fuel gas is significantly reduced, the second fuel gas flow rate adjustment valve is controlled by the mixture pressure control unit. The opening degree of the first fuel gas flow rate adjustment valve is controlled to the open side while maintaining the closed state. Therefore, the fuel gas supply state switching control unit determines, for example, from what the opening degree of the first fuel gas flow rate adjustment valve the opening degree of the first fuel gas flow rate adjustment valve has reached. I can grasp it. When the fuel gas supply state switching control unit determines that the opening degree of the first fuel gas flow rate adjustment valve has reached a set opening degree before full opening, for example, the supply state of the fuel gas to the mixer is changed to the first state. The fuel gas supply state can be switched to the mixed fuel gas supply state. Thereby, before the opening degree of the first fuel gas flow rate adjustment valve reaches full open, the supply state of the fuel gas to the mixer is switched from the first fuel gas supply state to the mixed fuel gas supply state, and the mixture pressure control unit By performing the control, it is possible to prevent the mixture pressure supplied to the engine from becoming the target pressure. As described above, even when the fuel gas supply state to the mixer is switched to the mixed fuel gas supply state, the control by the engine output control unit and the control by the mixture pressure control unit are performed, and the engine output is output to the target output. The air ratio of the air-fuel mixture supplied to the engine can be maintained at a desired air ratio while maintaining a desired engine output.

Therefore, even when the calorific value of the fuel gas changes significantly, the first fuel gas flow rate adjustment valve and the second fuel gas flow rate when the fuel gas supply state switching control unit performs control by the mixture gas pressure control unit. Switching between the first fuel gas supply state and the mixed fuel gas supply state based on the opening information of the regulating valve can maintain the engine output at the target output and obtain a desired engine output. However, the air ratio of the air-fuel mixture supplied to the engine can be maintained at a desired air ratio, and the engine can be operated stably.
Moreover, according to this feature configuration, as in the system described in Patent Document 2, it is not necessary to provide an expensive flow meter for measuring the flow rate of the mixed fuel gas of the first fuel gas and the second fuel gas. Cost reduction and simplification of the configuration can be achieved. Moreover, since only a single mixer is provided instead of a plurality of mixers, the cost can be reduced and the configuration can be simplified from this point.

  According to a further characteristic configuration of the engine system according to the present invention, the fuel gas supply state switching control unit performs control by the mixture pressure control unit when the fuel gas supply state switching control unit is switched to the first fuel gas supply state. When the opening of the fuel gas flow rate adjustment valve reaches the opening setting opening on the opening side, the first fuel gas supply state is switched to the mixed fuel gas supply state. Here, the opening set opening can be set in advance, for example, an opening before the full opening.

  When the fuel gas supply state switching control unit switches the fuel gas supply state to the mixer to the first fuel gas supply state, the first fuel gas flow rate adjustment valve is opened and the second fuel gas flow rate adjustment valve is opened. When the control is performed by the mixture gas pressure control unit, the first fuel gas flow rate adjustment is performed so that the mixture gas pressure becomes the target pressure while the second fuel gas flow rate adjustment valve is maintained in the closed state. The opening of the valve is controlled. Therefore, according to the present characteristic configuration, the fuel gas supply state switching control unit starts the mixed fuel gas from the first fuel gas supply state when the opening of the first fuel gas flow rate adjustment valve reaches the opening set opening on the open side. Since the switching to the supply state is performed, the supply state of the fuel gas to the mixer is appropriately switched from the first fuel gas supply state to the mixed fuel gas supply state before the opening degree of the first fuel gas flow rate adjustment valve reaches full open. The air ratio of the air-fuel mixture supplied to the engine can be appropriately maintained at a desired air ratio.

  According to a further characteristic configuration of the engine system according to the present invention, the fuel gas supply state switching control unit performs control by the mixture pressure control unit when the fuel gas supply state switching control unit is switched to the mixed fuel gas supply state. When the opening degree of the fuel gas flow rate adjustment valve or the opening degree of both the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve reaches the closed set opening degree on the closing side, the mixed fuel gas supply state is It is the point which is comprised so that switching to the said 1st fuel gas supply state may be performed. Here, the closing opening degree can be set in advance, for example, an opening degree before full closing, and the closing opening degree for the first fuel gas flow rate adjustment valve and the closing setting for the second fuel gas flow rate adjustment valve. The opening can be set to the same opening or different opening.

When the fuel gas supply state to the mixer is switched to the mixed fuel gas supply state, the calorific value of the first fuel gas may increase. At this time, for example, the opening degree of the first fuel gas flow rate adjustment valve is fixed at a constant opening degree, and the opening degree of the second fuel gas flow rate adjustment valve is controlled so that the mixture pressure becomes the target pressure. When the control by the mixture pressure control unit is performed, the opening degree of the second fuel gas flow rate adjustment valve is controlled to the closed side. Further, when performing control by the mixture pressure control unit so as to control the opening degree of both the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve so that the mixture gas pressure becomes the target pressure, The opening degree of both the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve is controlled to the closed side.
Therefore, according to this characteristic configuration, when the fuel gas supply state switching control unit switches to the mixed fuel gas supply state, the opening degree of the second fuel gas flow rate adjustment valve or the first fuel gas flow rate adjustment valve and the second When the opening degree of both of the fuel gas flow rate adjustment valves reaches the closed set opening degree on the closing side, the mixed fuel gas supply state is switched to the first fuel gas supply state. 2 The fuel gas supply state to the mixer can be appropriately switched from the mixed fuel gas supply state to the first fuel gas supply state before the opening degree of the fuel gas flow rate adjustment valve reaches the fully closed state. The air-to-air ratio can be appropriately maintained at a desired air ratio.

  A further characteristic configuration of the engine system according to the present invention is that the fuel gas supply state switching control unit switches the first fuel gas flow rate adjusting valve when the fuel gas supply state switching control unit switches from the first fuel gas supply state to the mixed fuel gas supply state. And the opening amounts of both the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve so that the opening amounts of both the second fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve are set to a predetermined mixed fuel gas target opening degree. The first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment are performed so that the mixture pressure supplied to the engine through the mixture supply path becomes the target pressure by the mixture pressure control unit. It is in the point comprised so that the opening degree of a valve may be controlled.

  According to this characteristic configuration, when the supply state of the fuel gas to the mixer is switched to the mixed fuel gas supply state, the control by the mixture pressure control unit is temporarily interrupted, and first the first fuel gas flow rate adjustment valve and the second Since the opening degree of both of the fuel gas flow rate adjusting valves is controlled to a predetermined mixed fuel gas target opening degree and switched to the mixed fuel gas supply state, the switching to the mixed fuel gas supply state can be performed smoothly. And in the state which made the opening degree of both the 1st fuel gas flow rate adjustment valve and the 2nd fuel gas flow rate adjustment valve into the predetermined mixed fuel gas target opening degree, the mixed gas pressure control part makes the mixed gas pressure the target pressure. Since the opening degree of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve is controlled so as to become, the mixed fuel gas target opening degree is changed to the opening degree for setting the mixture pressure to the target pressure. Can be controlled smoothly. Therefore, when the supply state of the fuel gas to the mixer is switched to the mixed fuel gas supply state, the air ratio of the air-fuel mixture supplied to the engine can be shifted relatively quickly to a stable state where the desired air ratio can be maintained.

  A further characteristic configuration of the engine system according to the present invention is that when the mixture gas pressure control unit is switched to the mixed fuel gas supply state by the fuel gas supply state switching control unit, the first fuel gas flow rate adjustment is performed. The second fuel gas flow rate adjusting valve is configured such that the opening of the valve is fixed to a preset setting opening for fixing, and the mixture pressure supplied to the engine through the mixture supply path becomes a target pressure. It is in the point comprised so that the opening degree of may be controlled.

  According to this configuration, when the fuel gas supply state to the mixer is switched to the mixed fuel gas supply state, the mixture pressure control unit sets the opening of the first fuel gas flow rate adjustment valve to the fixed setting opening. While fixing the flow rate of the first fuel gas to the mixer, the opening of the second fuel gas flow rate adjustment valve is controlled so that the mixture pressure becomes the target pressure, and the second fuel gas flow rate to the mixer is controlled. The flow rate is controlled. Therefore, the engine can be operated using the mixed fuel gas obtained by mixing the first fuel gas and the second fuel gas while effectively using the first fuel gas having a smaller calorific value than the second fuel gas. Even when the calorific value of the first fuel gas changes, the flow rate of the second fuel gas is controlled so that the mixture pressure becomes the target pressure, and the air ratio of the mixture supplied to the engine is maintained at the desired air ratio. Stable operation can be performed.

Schematic configuration diagram of the engine system Flowchart showing operations of mixture pressure control and fuel gas supply state switching control

An embodiment of an engine system according to the present invention will be described with reference to the drawings.
The engine system 100 includes a mixer 2 that mixes fuel gas G and combustion air A to generate an air-fuel mixture M, and an air-fuel mixture supply path that supplies the air-fuel mixture M mixed in the mixer 2 to the engine 1. 3 is provided. In the engine system 100, the mixture M of the fuel gas G and the combustion air A supplied to the engine 1 is a lean mixture having a low fuel gas concentration. The engine system 100 mixes, as the fuel gas G supplied to the engine 1, a first fuel gas G1 having a first heat value and a second fuel gas G2 having a second heat value higher than the first heat value. Two types of fuel gas, that is, only the fuel gas and the first fuel gas G1, can be used. The first fuel gas G1 is, for example, biogas obtained by anaerobic fermentation of biomass such as sewage sludge and organic factory wastewater, and the second fuel gas G2 is, for example, city gas.

  The engine system 100 includes a combustion air supply path 4 for supplying combustion air A to the mixer 2, a first fuel gas supply path 5 for supplying the first fuel gas G1 to the mixer 2, and a second fuel gas G2 for mixing. The mixer 2 is connected to a joining portion where the first fuel gas supply passage 5 and the second fuel gas supply passage 6 are joined together. As the mixer 2, the first fuel gas G1 supplied through the first fuel gas supply passage 5 or the second fuel gas G2 supplied through the second fuel gas supply passage 6 and the first fuel gas G1 were mixed. A single mixer 2 for mixing the mixed fuel gas with the combustion air A is provided. Although a detailed description and illustration of the configuration of the mixer 2 are omitted, a suction force is generated by a suction action by a venturi along with the flow of the combustion air A, and the fuel gas G is transferred to the combustion air A by the suction force. , And a Venturi type that generates an air-fuel mixture M of combustion air A and fuel gas G.

  The first fuel gas supply path 5 is connected at its upstream end to a first fuel gas storage section 7 for storing a first fuel gas G1 (biogas) generated by a biogas generator (not shown). The first fuel gas G1 stored in the first fuel gas storage unit 7 is configured to be freely supplied to the mixer 2. A middle portion of the first fuel gas supply path 5 is provided with a first fuel gas flow rate adjustment valve 8 capable of adjusting the flow rate of the first fuel gas G1 supplied to the mixer 2.

A middle portion of the second fuel gas supply path 6 is provided with a second fuel gas flow rate adjustment valve 9 that can adjust the flow rate of the second fuel gas G2 supplied to the mixer 2.
In the air-fuel mixture supply path 3, the air-fuel mixture flow rate adjusting valve 10, which can adjust the flow rate of the air-fuel mixture supplied to the engine 1, in order from the upstream side in the flow direction of the air-fuel mixture M, An air-fuel mixture pressure sensor 11 that detects the air-fuel mixture pressure supplied to 1 is provided.

  In the engine system 100, an engine output of the engine 1 is obtained by operating the engine 1, for example, a generator is driven using the engine output as a drive source. The engine system 100 is provided with engine output detection means 12 for detecting engine output. The engine output detection means 12 includes, for example, a rotation speed sensor that detects the rotation speed of the engine 1, a load detection sensor that detects the engine load, and the like, and detects the engine output from the detection information of these sensors. It is configured. Here, for example, when the generator is driven using the engine output as a drive source, the engine output can also be detected from the generated power of the generator.

  The engine system 100 is provided with a control device H to which detection information of the engine output detection means 12 and detection information of the gas mixture pressure sensor 11 can be input, and the control device H operates the engine system 100. Configured to control. The control device H includes an engine output control unit H1 that performs engine output control, an air-fuel mixture pressure control unit H2 that performs air-fuel mixture pressure control, and a fuel gas supply state switching control unit H3 that performs fuel gas supply state switching control. Is provided.

  The engine output control unit H1 is configured to perform engine output control for controlling the opening of the air-fuel mixture flow rate adjustment valve 10 so that the engine output detected by the engine output detection means 12 becomes a target output. The target output can be set constant or changed. For example, when the generator is driven using the engine output as a driving source, the generated power of the generator is changed according to the power consumption of the power consuming device, so the target output is changed and set according to the generated power of the generator. be able to.

  The mixture pressure control unit H2 controls the opening degrees of the first fuel gas flow rate adjustment valve 8 and the second fuel gas flow rate adjustment valve 9 so that the mixture pressure detected by the mixture gas pressure sensor 11 becomes the target pressure. The mixture pressure control is performed. The target pressure is set so that the air ratio of the lean air-fuel mixture M supplied to the engine 1 becomes a desired air ratio (for example, 1.5 to 2.0), and the target pressure increases as the engine output increases. The target pressure is set according to the engine output, such as increasing. For example, for each engine output, the air-fuel mixture pressure for maintaining the air ratio of the lean air-fuel mixture at a desired air ratio is obtained by experiment, and the relationship between the engine output obtained by the experiment etc. and the target pressure Is set in advance, and the target pressure is set according to the engine output using the relationship.

The fuel gas supply state switching control unit H3 is capable of switching between the first fuel gas supply state and the mixed fuel gas supply state with respect to the supply state of the fuel gas G to the mixer 2, and the mixture gas pressure control unit H2 Based on the opening information of the first fuel gas flow rate adjustment valve 8 and the second fuel gas flow rate adjustment valve 9 in the state in which the control is performed according to the above, between the first fuel gas supply state and the mixed fuel gas supply state The fuel gas supply state switching control for switching is performed.
In the first fuel gas supply state, the first fuel gas flow rate adjustment valve 8 is opened and the second fuel gas flow rate adjustment valve 9 is closed, and only the first fuel gas G1 is supplied to the mixer 2. In the mixed fuel gas supply state, both the first fuel gas flow rate adjustment valve 8 and the second fuel gas flow rate adjustment valve 9 are opened, and the mixed fuel gas of the first fuel gas G1 and the second fuel gas G2 is supplied to the mixer 2. Supply.

  Hereinafter, operations of the engine output control by the engine output control unit H1, the mixture pressure control by the mixture pressure control unit H2, and the fuel gas supply state switching control by the fuel gas supply state switching control unit H3 will be described.

First, engine output control by the engine output control unit H1 will be described.
The engine output control is performed to maintain the engine output at the target output, and the engine output control unit H1 always performs the engine output control while the engine 1 is operating.
In this engine output control, when the engine output detected by the engine output detecting means 12 is smaller than the target output, the opening of the mixture flow rate adjusting valve 10 is opened according to the difference between the engine output and the target output. Control to the side. On the contrary, when the engine output detected by the engine output detecting means 12 is larger than the target output, the opening of the air-fuel mixture flow adjustment valve 10 is set to the closed side according to the difference between the engine output and the target output. I have control. In this way, the engine output is maintained at the target output to obtain a desired engine output.

Next, operations of the mixture pressure control by the mixture pressure control unit H2 and the fuel gas supply state switching control by the fuel gas supply state switching control unit H3 will be described based on the flowchart of FIG.
When the first fuel gas G1 is stored in the first fuel gas storage unit 7, the first fuel gas G1 can be supplied to the mixer 2. Therefore, the fuel gas supply state switching control unit H3 is connected to the mixer 2. The fuel gas G supply state is switched to the first fuel gas supply state (step # 1). At this time, the fuel gas supply state switching control unit H3 temporarily interrupts the mixture pressure control by the mixture pressure control unit H2, and the first fuel gas whose opening degree of the first fuel gas flow rate adjustment valve 8 is set in advance is set. The first fuel gas that supplies only the first fuel gas G1 to the mixer 2 with the target opening (for example, opening 70%) and the second fuel gas flow rate adjusting valve 9 closed (opening 0%). Switching to the supply state. Then, the fuel gas supply state switching control unit H3 switches to the first fuel gas supply state so that the fuel gas G is only the first fuel gas G1, and the mixture M of the first fuel gas G1 and the combustion air A is obtained. Is supplied to the engine 1 and combusted to operate the engine 1.

  When the fuel gas supply state switching control unit H3 switches to the first fuel gas supply state, the suspension of the mixture pressure control by the mixture pressure control unit H2 is canceled, and the mixture pressure control unit H2 performs the mixture pressure control. Control is performed (step # 2). In this air-fuel mixture pressure control, the second fuel gas flow rate adjustment valve 9 is closed (opening degree 0%) by switching to the first fuel gas supply state by the fuel gas supply state switching control unit H3. The opening degree of the first fuel gas flow rate adjusting valve 8 is controlled by maintaining the gas flow rate adjusting valve 9 in the closed state. That is, when the mixture pressure detected by the mixture pressure sensor 11 is smaller than the target pressure, the opening degree of the first fuel gas flow rate adjustment valve 8 is closed according to the difference between the mixture pressure and the target pressure. Control to the side. Conversely, when the mixture pressure detected by the mixture pressure sensor 11 is larger than the target pressure, the opening of the first fuel gas flow rate adjustment valve 8 is set according to the difference between the mixture pressure and the target pressure. Control to open side. Thereby, the air ratio of the lean air-fuel mixture M is maintained at a desired air ratio, thereby preventing the occurrence of misfires and the problem that the NOx concentration in the exhaust gas becomes too high.

  In this way, when the first fuel gas supply state is switched, the mixture pressure control unit H2 performs the mixture pressure control, whereby the opening degree of the first fuel gas flow rate adjustment valve 8 is controlled. However, when the opening K1 of the first fuel gas flow rate adjusting valve 8 becomes equal to or larger than the opening set opening degree Ka on the opening side due to a large decrease in the amount of heat generated by the first fuel gas G1, the fuel gas supply state switching control is performed. The section H3 switches the supply state of the fuel gas G to the mixer 2 from the first fuel gas supply state to the mixed fuel gas supply state (in the case of Yes in step # 3, step # 4). Here, the opening setting opening degree Ka can be set in advance to an opening degree before the full opening, for example, the opening degree is set to 90%. As a result, when the calorific value of the first fuel gas G1 is significantly reduced, the mixture pressure control unit H2 performs mixture pressure control, so that the opening on the opening side over the opening set opening degree Ka such as full opening is increased. Before controlling the opening K1 of the first fuel gas flow rate adjusting valve 8 every time, the fuel gas supply state switching control unit H3 switches from the first fuel gas supply state to the mixed fuel gas supply state, and By simply controlling the opening K1 of the gas flow rate adjusting valve 8, the mixture pressure cannot be made the target pressure, and the air ratio of the mixture M can be prevented from being maintained at the desired air ratio.

  At this time, the fuel gas supply state switching control unit H3 temporarily interrupts the mixture pressure control by the mixture pressure control unit H2, and the first fuel gas whose opening degree of the first fuel gas flow rate adjustment valve 8 is set in advance is set. The mixed fuel gas target opening degree (for example, 85% opening degree) and the opening degree of the second fuel gas flow rate adjusting valve 9 is set to the preset mixed fuel gas target opening degree (for example, for example). , The opening degree of both the first fuel gas flow rate adjusting valve 8 and the second fuel gas flow rate adjusting valve 9 is controlled so that the first fuel gas G1 and the second fuel are supplied to the mixer 2. It is switched to the mixed fuel gas supply state for supplying the mixed fuel gas with the gas G2. Then, the fuel gas supply state switching control unit H3 switches to the mixed fuel gas supply state, so that the fuel gas G becomes the mixed fuel gas of the first fuel gas G1 and the second fuel gas G2, and the mixed fuel gas and the combustion gas The air-fuel mixture M with air A is supplied to the engine 1 and combusted to operate the engine 1.

  When the fuel gas supply state switching control unit H3 switches to the mixed fuel gas supply state, the suspension of the mixture pressure control by the mixture pressure control unit H2 is released, and the mixture pressure control unit H2 controls the mixture pressure control. (Step # 5). In this mixture pressure control, the opening of the first fuel gas flow rate adjustment valve 8 is fixed to a preset fixed opening, and the mixture pressure detected by the mixture pressure sensor 11 is the target pressure. Thus, the opening degree of the second fuel gas flow rate adjusting valve 9 is controlled. Here, for the fixed set opening, for example, the same opening (for example, 85% opening) as the mixed fuel gas target opening for the first fuel gas is set. That is, the flow rate of the first fuel gas G1 is kept constant without being changed. When the mixture pressure detected by the mixture pressure sensor 11 is smaller than the target pressure, the opening of the second fuel gas flow rate adjustment valve 9 is closed according to the difference between the mixture pressure and the target pressure. Control to the side. Conversely, when the mixture pressure detected by the mixture pressure sensor 11 is larger than the target pressure, the opening degree of the second fuel gas flow rate adjusting valve 9 is set according to the difference between the mixture pressure and the target pressure. Control to open side. Thereby, while effectively using the biogas that is the first fuel gas G1, even when the calorific value of the first fuel gas G1 changes, by controlling the flow rate of the city gas that is the second fuel gas G2, The air ratio of the lean air-fuel mixture M is maintained at a desired air ratio to prevent the occurrence of misfires and the problem that the NOx concentration in the exhaust gas becomes too high.

  As described above, when the supply state of the fuel gas G to the mixer 2 is switched to the mixed fuel gas supply state, for example, the heating value of the first fuel gas G1 may increase. In this case, the mixture pressure control unit H2 performs the mixture pressure control, so that the opening degree of the second fuel gas flow rate adjusting valve 9 is controlled to the closed side. Therefore, when the mixed fuel gas supply state is switched, the mixture pressure control by the mixture pressure control unit H2 is performed, so that the opening K2 of the second fuel gas flow rate adjusting valve 9 is closed on the closing side. If it is less, the fuel gas supply state switching control unit H3 switches the supply state of the fuel gas G to the mixer 2 from the mixed fuel gas supply state to the first fuel gas supply state (Yes in step # 6). Step # 1). Here, the closing opening degree can be set to an opening degree before the full closing, for example, the opening degree is set to 5%. Thereby, when the calorific value of the first fuel gas G1 is increased, the mixture pressure control unit H2 performs the mixture pressure control so that the opening degree is less than the closing set opening degree Kb on the closing side, such as full closing. Before the opening K2 of the second fuel gas flow rate adjusting valve 9 is controlled, the fuel gas supply state switching control unit H3 switches from the mixed fuel gas supply state to the first fuel gas supply state, and the second fuel gas By simply controlling the opening degree K2 of the flow rate adjusting valve 9, the mixture pressure cannot be made the target pressure, and the air ratio of the mixture M can be prevented from being maintained at a desired air ratio.

  In this way, when the first fuel gas G1 is stored in the first fuel gas storage section 7, the engine 1 can be operated by effectively using the first fuel gas G1, Even if a change in the heat generation amount of the first fuel gas G1 occurs, the first fuel gas flow rate adjustment valve 8 and the second fuel gas supply state switching control unit H3 perform the control by the mixture pressure control unit H2 and the second fuel gas flow rate control valve H2. Based on the opening information of the fuel gas flow rate adjusting valve 9, the supply state of the fuel gas G to the mixer 2 is switched between the first fuel gas supply state and the mixed fuel gas supply state, and the air of the mixture M The ratio is maintained at a desired air ratio so that the engine 1 can be operated stably.

Incidentally, in the flowchart of FIG. 2, the case where the first fuel gas G1 is stored in the first fuel gas storage unit 7 has been described. For example, the first fuel gas G1 is stored in the first fuel gas storage unit 7. If not, the engine 1 can be operated with only the second fuel gas G2 as the fuel gas G2.
In this case, for example, the fuel gas supply state switching control unit H3 closes the first fuel gas flow rate adjustment valve 8 and opens the second fuel gas flow rate adjustment valve 9 for the supply state of the fuel gas G to the mixer 2. As a state, the mixer 2 is switched to the second fuel gas supply state in which only the second fuel gas G2 is supplied.

[Another embodiment]
(1) In the above embodiment, when the fuel gas supply state switching control unit H3 switches to the mixed fuel gas supply state, the mixture gas pressure control by the mixture gas pressure control unit H2 is temporarily interrupted, and the first fuel gas flow rate Both the first fuel gas flow rate adjustment valve 8 and the second fuel gas flow rate adjustment valve 9 are opened so that the opening amounts of both the adjustment valve 8 and the second fuel gas flow rate adjustment valve 9 become the target opening for the mixed fuel gas. After the degree is controlled, the mixture pressure control by the mixture pressure control unit H2 is performed.
Instead, when the fuel gas supply state switching control unit H3 switches to the mixed fuel gas supply state, the first fuel gas flow rate adjustment valve 8 has a predetermined opening degree of the first fuel gas mixed fuel gas target. While controlling the opening degree of the first fuel gas flow rate adjusting valve 8 so as to be the opening degree (for example, the opening degree is 85%), the mixture pressure control by the mixture pressure control unit H2 is performed in the mixture supply path 3. The opening degree of the second fuel gas flow rate adjusting valve 9 may be controlled so that the mixture pressure supplied to the engine 1 becomes the target pressure. In this way, when the supply state of the fuel gas G to the mixer 2 is switched to the mixed gas fuel gas supply state, the first fuel gas flow rate adjustment valve 8 is controlled to open to the mixed fuel gas target opening. At the same time, with respect to the second fuel gas flow rate adjustment valve 9, the mixture pressure control by the mixture pressure control unit H2 can be performed. When the mixture gas fuel gas supply state is switched, the mixture gas pressure control unit H2 performs the mixture gas pressure control.

(2) In the above embodiment, the first fuel gas G1 is a biogas. However, for example, the first fuel gas G1 can be a coal mine gas.

(3) In the above embodiment, when the fuel gas supply state switching control unit H3 switches the supply state of the fuel gas G to the mixer 2 to the mixed fuel gas supply state, the mixture pressure control unit H2 controls the mixture pressure control. As described above, the first fuel gas flow rate adjusting valve 8 is fixed at a predetermined fixed opening, and the mixture pressure detected by the mixture pressure sensor 11 is set to the target pressure. The opening degree of the fuel gas flow rate adjusting valve 9 is controlled.
Instead of this, for example, as the mixture pressure control, the mixture pressure control unit H2 controls the first fuel gas flow rate adjusting valve 8 and the mixture gas pressure detected by the mixture pressure sensor 11 to be the target pressure. The opening degree of both of the second fuel gas flow rate adjusting valves 9 can also be controlled. In this case, since the opening degree of both the first fuel gas flow rate adjustment valve 8 and the second fuel gas flow rate adjustment valve 9 changes, the fuel gas supply state switching control unit H3 performs the mixing by the mixture pressure control unit H2. By performing the air pressure control, when the opening degree of both the first fuel gas flow rate adjustment valve 8 and the second fuel gas flow rate adjustment valve 9 reaches the closed set opening degree on the closed side, the first state is changed from the mixed fuel gas supply state to the first. Switch to the fuel gas supply state. At this time, the closing set opening for the first fuel gas flow rate adjusting valve 8 and the closing set opening for the second fuel gas flow rate adjusting valve 9 can be set to the same opening or different opening.

  The present invention comprises a mixer that mixes fuel gas and combustion air to generate an air-fuel mixture, and an air-fuel mixture supply path that supplies the air-fuel mixture generated by the mixer to the engine, The first fuel gas having the first calorific value or the mixed fuel gas obtained by mixing the second fuel gas having the second calorific value higher than the first calorific value and the first fuel gas is used for the mixing. Even if the calorific value of the fuel gas changes drastically, the air-fuel mixture supplied to the engine is operated while the engine is operated by burning the air-fuel mixture supplied in the air supply path to reduce costs and simplify the configuration. The air ratio can be maintained at a desired air ratio and can be applied to various engine systems capable of operating the engine stably.

DESCRIPTION OF SYMBOLS 1 Engine 2 Mixer 3 Mixture supply path 5 First fuel gas supply path 6 Second fuel gas supply path 8 First fuel gas flow rate adjustment valve 9 Second fuel gas flow rate adjustment valve 10 Mixture flow rate adjustment valve A Combustion air G Fuel gas G1 First fuel gas (biogas)
G2 Second fuel gas (city gas)
H1 Engine output control unit H2 Mixture pressure control unit H3 Fuel gas supply state switching control unit M Mixture

Claims (5)

A mixer that mixes fuel gas and combustion air to generate an air-fuel mixture, and an air-fuel mixture supply passage that supplies the air-fuel mixture generated by the mixer to the engine, and the fuel gas has a first heating value. Or a mixed fuel gas in which a second fuel gas having a second calorific value higher than the first calorific value and the first fuel gas are mixed, and the mixed gas supply path is used. An engine system for operating an engine by burning an air-fuel mixture supplied
As the mixer, the first fuel gas supplied through the first fuel gas supply path, or the mixed fuel gas obtained by mixing the first fuel gas and the second fuel gas supplied through the second fuel gas supply path And a single mixer that mixes the combustion air with each other to generate an air-fuel mixture,
A first fuel gas flow rate adjusting valve provided in the first fuel gas supply path and capable of adjusting a flow rate of the first fuel gas supplied to the mixer;
A second fuel gas flow rate adjustment valve provided in the second fuel gas supply path and capable of adjusting a flow rate of the second fuel gas supplied to the mixer;
An air-fuel mixture flow adjustment valve provided in the air-fuel mixture supply path and capable of adjusting the flow rate of the air-fuel mixture supplied to the engine;
An engine output control unit that controls the opening of the mixture flow rate adjustment valve so that the engine output becomes a target output;
An air-fuel mixture pressure control unit that controls the opening degrees of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve so that the air-fuel mixture pressure supplied to the engine in the air-fuel mixture supply path becomes a target pressure. When,
Regarding the supply state of the fuel gas to the mixer, the first fuel gas flow rate adjustment valve is opened and the second fuel gas flow rate adjustment valve is closed to supply only the first fuel gas to the mixer. The mixed fuel gas of the first fuel gas and the second fuel gas is supplied to the mixer with both the gas supply state and the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve opened. Opening degrees of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve in a state that can be switched between the mixed fuel gas supply state and controlled by the mixed gas pressure control unit An engine system comprising: a fuel gas supply state switching control unit configured to switch between the first fuel gas supply state and the mixed fuel gas supply state based on information.   When the fuel gas supply state switching control unit is switched to the first fuel gas supply state, the opening degree of the first fuel gas flow rate adjustment valve is set to the open side by performing control by the mixture pressure control unit. 2. The engine system according to claim 1, wherein the engine system is configured to switch from the first fuel gas supply state to the mixed fuel gas supply state when an opening set opening degree is reached.   When the fuel gas supply state switching control unit is switched to the mixed fuel gas supply state, the fuel gas supply state switching control unit controls the opening of the second fuel gas flow rate adjusting valve or the first fuel by performing control by the mixture gas pressure control unit. When the opening degree of both the gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve reaches the closing set opening degree on the closing side, the mixed fuel gas supply state is switched to the first fuel gas supply state. The engine system of Claim 1 or 2 comprised by these.   The fuel gas supply state switching control unit opens both of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve when switching from the first fuel gas supply state to the mixed fuel gas supply state. After controlling the opening degree of both the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve so that the degree is a predetermined mixed fuel gas target opening degree, the mixture pressure control unit The opening degree of the first fuel gas flow rate adjustment valve and the second fuel gas flow rate adjustment valve is controlled so that the mixture pressure supplied to the engine in the mixture supply path becomes a target pressure. The engine system according to any one of claims 1 to 3.   When the fuel gas supply state switching control unit switches to the mixed fuel gas supply state, the air-fuel mixture pressure control unit opens the first fuel gas flow rate adjustment valve in a preset setting for fixing. And the degree of opening of the second fuel gas flow rate adjustment valve is controlled so that the mixture pressure supplied to the engine in the mixture supply path becomes a target pressure. Item 5. The engine system according to any one of Items 1 to 4.

Images