JP2013087716A - Control device of premixed type gas engine, control method of premixed type gas engine, and premixed type gas engine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve stable operation of a premixed type gas engine having a bypass line.SOLUTION: This premixed type gas engine system 100 includes a premixed type gas engine for supplying mixed gas formed by mixing fuel gas and air, and a control device 300. The gas engine includes a combustion chamber 111, a throttle valve 150 for adjusting the amount of the mixed gas to be supplied to the combustion chamber 111, a supercharger 170 for compressing and supplying the mixed gas to the throttle valve 150, and a bypass valve 160 for bypassing a part of the mixed gas supplied to the throttle valve 150 to an air supply passage of the supercharger 170 from a delivery passage of the supercharger 170. The control device 300 variably sets a target value of a pressure difference before and behind the throttle valve 150 in accordance with a load of the gas engine, to adjust opening of the bypass valve 160 so that opening of the throttle valve 150 is maintained within a predetermined range.

Description

  The present invention relates to a control device for a premixed gas engine in which fuel gas and air are mixed in advance and supplied to a combustion chamber, a control method for the premixed gas engine, and a premixed gas engine system.

  Effective utilization of biogas such as pyrolysis gas and digestion gas is required as an alternative to fossil energy. As one of the utilization methods of biogas, a power generation system using a gas engine using biogas as a fuel has attracted attention.

  In a gas engine, the ratio (air-fuel ratio) between fuel gas and combustion air is an important adjustment factor. If there is too much air relative to the fuel gas, misfires and combustion fluctuations will occur, and if there is too little air, combustion abnormal phenomena such as exhaust temperature rise and knocking will occur, and stable operation cannot be continued. For this reason, in a premixed gas engine, a target air-fuel ratio is set in advance, and the air-fuel ratio is kept constant by measuring the amount of air-fuel mixture. In this case, the set value of the air-fuel ratio is set using a typical characteristic of fuel gas determined in advance.

  For example, in the gas engine described in Japanese Patent Application Laid-Open No. 2009-36111 (Patent Document 1), the target value of the air-fuel ratio is set at the start of operation using a high calorie gas (for example, LPG (liquefied natural gas), city gas). Is set to the value of the stoichiometric air / fuel ratio at which the fuel reacts without excess or deficiency. When switching from high-calorie gas to low-calorie gas (biogas), the target value of air-fuel ratio is set to the theoretical air-fuel ratio value, or to avoid the possibility of misfiring because the air-fuel mixture becomes lean all at once. Is set to be richer than the theoretical air-fuel ratio.

JP 2009-36111 A

  In a premixed gas engine, the amount of mixed gas supplied to a combustion chamber is generally determined by adjusting the opening of a throttle valve. In addition, the amount of mixed gas discharged from the supercharger changes depending on the ambient temperature such as the air temperature, and particularly when the temperature is low such as in winter, the amount of mixed gas discharged from the supercharger increases. The throttle valve is closed to adjust the engine output. As a result, the supercharger discharge pressure increases, and so-called surging may occur in which the amount of the mixed gas discharged from the supercharger rapidly decreases.

  In order to prevent such surging, a bypass line of the mixed gas is provided on the inflow side to the throttle valve, and by adjusting the opening degree of the bypass valve, a part of the mixed gas is released, and the pressure difference between the throttle valve ( That is, the amount of fuel gas supplied to the combustion chamber is adjusted by controlling the difference between the supply pressure of the mixed gas supplied to the throttle valve and the discharge pressure of the mixed gas supplied from the throttle valve to the combustion chamber. In some cases, a configuration is employed.

  In the gas engine having the bypass line as described above, it is necessary to appropriately control the throttle valve and the bypass valve in order to ensure a stable operation state.

  The present invention has been made to solve such problems, and an object thereof is to stably operate a premixed gas engine having a bypass line.

  A control device for a premixed gas engine according to the present invention is a control device for controlling a premixed gas engine to which a mixed gas obtained by mixing fuel gas and air is supplied. The gas engine is provided with a combustion chamber for burning the mixed gas, a throttle valve provided in an air supply path to the combustion chamber, for adjusting the supply amount of the mixed gas to the combustion chamber, and an exhaust gas from the combustion chamber The supercharger configured to compress the mixed gas and supply it to the throttle valve is connected to the discharge path of the supercharger and the supply path of the mixed gas to the supercharger. And a bypass valve for bypassing a part of the mixed gas supplied to the throttle valve. The control device includes a pressure detector for detecting a pressure difference between the supply pressure and the discharge pressure of the throttle valve, and a gas so that the opening of the throttle valve is maintained within a predetermined range. A control unit that variably sets the target value of the pressure difference according to the engine load and adjusts the opening of the bypass valve so that the pressure difference becomes the set target value.

  Preferably, the control unit sets the target value of the pressure difference used when starting the gas engine to a value higher than the target value of the pressure difference used during operation of the gas engine.

  Preferably, a control part sets the target value of the pressure difference used at the time of starting of a gas engine in the range of 50-70 kPa.

  Preferably, the control unit sets the target value of the pressure difference used during operation of the gas engine to be equal to or higher than the value when the load factor is low when the load factor of the gas engine is high.

  Preferably, a control part sets the target value of the pressure difference used during a driving | operation of a gas engine in the range of 10-35 kPa.

  Preferably, the predetermined range for the opening of the throttle valve is set to a range in which the control sensitivity is relatively high in the characteristics of the throttle valve.

  Preferably, the predetermined range for the opening of the throttle valve is set to 30 to 60% of the opening when the throttle valve is fully opened.

  Preferably, the predetermined range for the opening of the throttle valve is set to 40 to 45% of the opening when the throttle valve is fully opened.

  Preferably, the control unit controls the opening degree of the bypass valve by feedback control, and when the target value of the pressure difference is set variably, the control unit performs feedback control compared to the case where the target value of the pressure difference is a fixed value. Set the gain to be used small.

  Preferably, a control part performs feedback control by PID control. The control unit uses a proportional gain, an integral gain, and a differential gain as the gain, and sets the proportional gain in the range of 0.01 to 0.1.

  Preferably, a control part performs feedback control by PID control. The control unit uses a proportional gain, an integral gain, and a differential gain as the gain, and sets the integral gain in the range of 0.01 to 0.1.

  Preferably, a control part performs feedback control by PID control. The control unit uses a proportional gain, an integral gain, and a differential gain as the gain, and sets the differential gain in the range of 1 to 100.

  Preferably, a control part performs feedback control by PID control. The control unit uses a proportional gain, an integral gain, and a differential gain as gains, sets the proportional gain to 0.05, sets the integral gain to 0.05, and sets the differential gain to 98.

  A control method for a premixed gas engine according to the present invention is a control method for a premixed gas engine to which a mixed gas obtained by mixing fuel gas and air is supplied. The gas engine is provided with a combustion chamber for burning the mixed gas, a throttle valve provided in an air supply path to the combustion chamber, for adjusting the supply amount of the mixed gas to the combustion chamber, and an exhaust gas from the combustion chamber The supercharger configured to compress the mixed gas and supply it to the throttle valve is connected to the discharge path of the supercharger and the supply path of the mixed gas to the supercharger. And a bypass valve for bypassing a part of the mixed gas supplied to the throttle valve. The control method includes a step of detecting a pressure difference between the supply pressure and the discharge pressure of the throttle valve, and a load of the gas engine so that the opening degree of the throttle valve is maintained within a predetermined range. Accordingly, there are provided a step of variably setting the target value of the pressure difference and a step of adjusting the opening degree of the bypass valve so that the pressure difference becomes the set target value.

  A premixed gas engine system according to the present invention includes a premixed gas engine to which a mixed gas obtained by mixing fuel gas and air is supplied, and a control device for controlling the gas engine. The gas engine is provided with a combustion chamber for burning the mixed gas, a throttle valve provided in an air supply path to the combustion chamber, for adjusting the supply amount of the mixed gas to the combustion chamber, and an exhaust gas from the combustion chamber The supercharger configured to compress the mixed gas and supply it to the throttle valve is connected to the discharge path of the supercharger and the supply path of the mixed gas to the supercharger. And a bypass valve for bypassing a part of the mixed gas supplied to the throttle valve. The control device includes a pressure detector for detecting a pressure difference between the supply pressure and the discharge pressure of the throttle valve, and a gas so that the opening of the throttle valve is maintained within a predetermined range. And a control unit that variably sets the target value of the pressure difference according to the engine load and adjusts the opening degree of the bypass valve so that the pressure difference becomes the set target value.

  According to the present invention, a premixed gas engine having a bypass line can be stably operated.

1 is an overall block diagram of a premixed gas engine system according to the present embodiment. It is a figure which shows an example of the flow characteristic of a butterfly valve. It is a functional block diagram which shows an example of a structure of the control apparatus in the premix type gas engine system according to this Embodiment. It is a figure which shows an example of the setting table of the excess air ratio memorize | stored in the memory | storage part of the air fuel ratio control part of FIG. It is a figure which shows an example of the setting map of the target pressure difference memorize | stored in the memory | storage part of the pressure control part of FIG. It is a figure for demonstrating the feedback control performed by the control signal generation part of the pressure control part of FIG. In this Embodiment, it is a flowchart for demonstrating the pressure difference control process of the throttle valve performed with a pressure control part. It is a flowchart which shows an example of the detail of the pressure difference target value calculation process in S130 of FIG. It is a figure for demonstrating the effect at the time of applying the pressure difference setting control at the time of a start in the pressure difference control process according to this Embodiment. It is a 1st figure for demonstrating the effect at the time of applying the pressure difference setting control according to load in the pressure difference control process according to this Embodiment. It is a 2nd figure for demonstrating the effect at the time of applying the pressure difference setting control according to load in the pressure difference control process according to this Embodiment. It is a figure for demonstrating the effect at the time of applying the gain change control in feedback control in the pressure difference control process according to this Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Basic configuration of premixed gas engine system]
FIG. 1 is an overall block diagram of a premixed gas engine system 100 according to the present embodiment. The premixed gas engine system 100 includes an engine main body 110, an air filter 120, a fuel gas amount adjuster 130, a mixer 140, a throttle valve 150, a bypass valve 160, and a supercharger that constitute a gas engine. Machine 170. The premixed gas engine system 100 includes a control unit 310 and pressure gauges 340 and 350 that form a control device for controlling the gas engine. Control unit 310 includes an air-fuel ratio control unit 320 and a pressure control unit 330.

  The gas engine is a premixed gas engine in which a mixed gas in which fuel gas and air are mixed in advance is sucked into the combustion chamber 111. In the gas engine in the present embodiment, biogas such as pyrolysis gas and digestion gas can be used as fuel gas. The sucked mixed gas is ignited and burned in the combustion chamber 111, and the piston 112 is driven by the generated heat energy. An output shaft (not shown) of the gas engine is coupled to, for example, a generator (not shown), and power is generated using the driving force of the gas engine.

  The mixer 140 mixes the air supplied through the air filter 120 and the fuel gas adjusted by the fuel gas amount adjuster 130 to generate a mixed gas. The air filter 120 removes dust and the like contained in the air supplied to the mixer 140. The fuel gas amount adjuster 130 is controlled by a control signal GSR from the air-fuel ratio controller 320 and adjusts the flow rate of fuel gas supplied from an external fuel tank (not shown) or the like.

  The supercharger 170 is an exhaust turbine driven supercharger (so-called turbocharger). The supercharger 170 includes, for example, a turbine 171 and a compressor 172 coupled to the same rotating shaft. The turbine 171 is rotated by the exhaust gas discharged from the combustion chamber 111. The compressor 172 rotates in conjunction with the rotation of the turbine 171, pressurizes the mixed gas generated by the mixer 140, and supplies the mixed gas to the combustion chamber 111 via the throttle valve 150.

  The throttle valve 150 is provided in a path through which the mixed gas flows between the compressor 172 of the supercharger 170 and the combustion chamber 111. The throttle valve 150 adjusts the opening according to the output of the engine body 110 and adjusts the flow rate of the mixed gas supplied to the combustion chamber 111.

  The bypass valve 160 is provided in a path (bypass line) that communicates the mixed gas discharge path from the compressor 172 to the throttle valve 150 and the mixed gas inflow path from the mixer 140 to the compressor 172. When the bypass valve 160 is opened, a part of the mixed gas supplied from the compressor 172 to the throttle valve 150 is bypassed to the inflow path of the compressor 172 through the bypass valve 160. By controlling the opening degree of the bypass valve 160, the inflow pressure of the mixed gas supplied to the throttle valve 150 can be adjusted.

  Although not shown in FIG. 1, the air-fuel ratio control unit 320 and the pressure control unit 330 included in the control unit 310 include a CPU (Central Processing Unit), a storage device, and an input / output buffer. The air-fuel ratio control unit 320 and the pressure control unit 330 output control signals to the respective devices based on the input of signals from the sensors and the like, thereby controlling the respective devices of the gas engine. Note that these controls are not limited to processing by software, and can be processed by dedicated hardware (electronic circuit).

  The air-fuel ratio control unit 320 sets the excess air ratio according to the rotational speed NRE of the engine main body 110 and the load factor (the ratio of the current engine output to the rated output) LDR. The air-fuel ratio control unit 320 sets the target value of the air-fuel ratio by multiplying the theoretical air amount set in advance according to the type of fuel gas by the excess air ratio. Then, the air-fuel ratio control unit 320 calculates the flow rate of the mixed gas from the pressure detected by the pressure gauge 350, and further calculates the air amount from the current supply gas amount, so that the air-fuel ratio in which the actual air-fuel ratio is set is calculated. A control signal GSR to the fuel gas amount regulator 130 is generated so that the target value of the fuel ratio is obtained. Based on the control signal GSR, the fuel gas amount adjuster 130 is controlled to adjust the flow rate of the fuel gas.

  The pressure gauge 340 is provided in the flow path on the inflow side of the throttle valve 150, detects the pressure of the mixed gas supplied to the throttle valve 150 (that is, the discharge pressure of the supercharger 170), and pressure-controls the detected value PIN. To the unit 330. The pressure gauge 350 is provided on the discharge side path of the throttle valve 150, detects the pressure of the mixed gas supplied from the throttle valve 150 to the combustion chamber 111, and outputs the detected value POUT to the pressure control unit 330.

  Pressure controller 330 receives inflow pressure PIN and discharge pressure POUT of throttle valve 150 detected by pressure gauges 340 and 350. Based on these pieces of information, the pressure controller 330 generates a control signal SIG and controls the opening degree of the bypass valve 160.

[Problems of gas engine system]
In the premixed gas engine system, as described above, the amount of the mixed gas supplied to the combustion chamber is adjusted by adjusting the opening of the throttle valve. The amount of the mixed gas discharged from the supercharger varies depending on the ambient temperature such as the air temperature, and the amount of the mixed gas discharged from the supercharger decreases as the temperature increases as in summer. Then, the throttle valve opens its opening to adjust the engine output. If the gas mixture is still insufficient, the engine output may decrease. Conversely, when the temperature is low, such as in winter, the amount of mixed gas discharged from the supercharger increases. Then, the throttle valve closes its opening to adjust the engine output. As a result, the supercharger discharge pressure becomes high, and so-called surging may occur in which the mixed gas supplied from the supercharger rapidly decreases.

  In order to prevent such surging, a mixed gas bypass line is provided on the inflow side to the throttle valve as shown in FIG. 1, and a part of the mixed gas is released by adjusting the opening of the bypass valve. In some cases, a method of reducing the discharge pressure of the supercharger is employed.

  For example, a butterfly valve may be used as the throttle valve. As shown in FIG. 2, the flow rate characteristic with respect to the opening degree of the butterfly valve is generally a flow rate change amount with respect to the opening change amount when the valve opening degree is an area AR1 (30 to 60%) near the center. Is large (that is, the control sensitivity is high) and the controllability is improved. Conversely, when the valve opening is small (0 to 30%) or when the valve opening is large (60 to 100%), the control sensitivity is relatively low. Therefore, when adjusting the flow rate of the mixed gas with good response to load fluctuations, it is desirable to use an operating range (30 to 60%) in which the controllability of the throttle valve becomes high. In particular, it is more preferable that the valve opening be in the operating range of 40 to 45%.

  The flow rate of the mixed gas is largely determined by the engine output. If the amount of the mixed gas is the same, the opening degree of the throttle valve is generally determined by the pressure difference before and after the throttle valve. In the flow control of the mixed gas in the gas engine having the bypass line as shown in FIG. 1, the pressure difference before and after the throttle valve is set to a predetermined pressure difference (fixed value) by adjusting the opening degree of the bypass valve. In some cases, a method of controlling the throttle valve and adjusting the opening of the throttle valve according to the load fluctuation may be employed.

  However, in such a case, when the pressure difference setting is adapted to a low load condition, the throttle opening is too open at a high load, and when the pressure difference is adapted to a high load condition, the throttle opening is too closed at a low load. Thus, the operating range in which the controllability of the throttle valve becomes high cannot be used over the entire engine load state. If so, there may be a case where a stable operating state of the engine cannot be maintained.

  In addition, since the bypass valve opens when the gas engine is started, there is a possibility that the amount of mixed gas necessary for starting the engine cannot be sufficiently secured, and the engine speed and load cannot be increased. .

  Therefore, in the present embodiment, the pressure difference before and after the throttle valve is variably set according to the load state, and thus the throttle valve is used in an operating range where the controllability is enhanced over the entire load state of the engine. Control the flow rate of the mixed gas.

[Description of control configuration]
FIG. 3 is a functional block diagram showing an example of the configuration of control device 300 in premixed gas engine system 100 according to the present embodiment. In particular, detailed configurations of air-fuel ratio control unit 320 and pressure control unit 330 are shown. It is. Each functional block shown in FIG. 3 is realized by hardware or software processing.

  Referring to FIGS. 1 and 3, air-fuel ratio control unit 320 includes an excess air ratio setting unit 321, a storage unit 322, and a control signal generation unit 323.

  The excess air ratio setting unit 321 receives the rotational speed NRE and the load factor LDR of the engine main body 110 from an engine control unit (not shown). Based on such information, the excess air ratio setting unit 321 sets the excess air ratio AIR using a setting table or a setting map as shown in FIG. 4 stored in advance in the storage unit 322. Then, the excess air ratio setting unit 321 outputs the set excess air ratio AIR to the control signal generation unit 323.

  The control signal generation unit 323 receives the excess air ratio AIR from the excess air ratio setting unit and the pressure POUT detected by the pressure gauge 350. The control signal generator 323 calculates the flow rate FLW of the mixed gas supplied to the combustion chamber 111 from the pressure POUT. In addition, the control signal generation unit 323 determines a target air-fuel ratio from a theoretical air amount that is predetermined according to the type of fuel gas and an excess air ratio AIR. The control signal generation unit 323 then supplies the fuel gas supplied from the fuel gas amount regulator 130 so that the calculated air-fuel ratio is obtained according to the air amount obtained from the calculated flow rate FLW and the current supply gas amount. A control signal GSR for adjusting the flow rate of is generated.

  The pressure control unit 330 includes a target pressure difference setting unit 331, a storage unit 332, a pressure difference calculation unit 333, an opening degree setting unit 334, and a control signal generation unit 335.

  Target pressure difference setting unit 331 receives load factor LDR from an engine control unit (not shown). Based on the load factor LDR, the target pressure difference setting unit 331 sets the target pressure difference ΔPR using a setting table or setting map stored in advance in the storage unit 332, and sends the set value to the opening setting unit 334. Output.

  FIG. 5 is a diagram illustrating an example of a setting map of the target pressure difference ΔPR stored in the storage unit 332. In the setting map of FIG. 5, pressure difference target values ΔPR P0 to P5 corresponding to six points from the load factor LDR from L0 (= 0%) to L5 (= 100%) are set. For example, when the acquired load factor LDR is Lx between L1 and L2, the target value is a value corresponding to a point on a straight line obtained by linearly complementing P1 and P2 (Px in FIG. 5). ). Note that the setting map of FIG. 5 is an example, and the pressure difference target value ΔPR can be arbitrarily set according to the characteristics of the engine main body 110. Further, instead of the map as shown in FIG. 5, it may be set using a predetermined arithmetic expression or a setting table as shown in FIG.

  Referring to FIG. 3 again, the pressure difference calculation unit 333 calculates the actual pressure difference ΔPA before and after the throttle valve 150 from the pressures PIN and POUT detected by the pressure gauges 340 and 350, respectively. The pressure difference calculation unit 333 outputs the pressure difference ΔPA obtained by the calculation to the opening degree setting unit 334.

  The opening setting unit 334 receives the pressure difference target value ΔPR from the target pressure difference setting unit 331 and the pressure difference actual value ΔPA from the pressure difference calculation unit 333. The opening setting unit 334 performs feedback control using PID control (proportional integral derivative control) based on the pressure difference target value ΔPR and the actual pressure difference ΔPA, and sets the opening target value OPR of the bypass valve 160. The set value is output to the control signal generator 335.

  The control signal generator 335 generates a control signal SIG for driving the bypass valve 160 based on the opening target value OPR from the opening setting unit 334.

  FIG. 6 is a diagram for explaining feedback control executed by the control signal generation unit 335. 3 and 6, control signal generation unit 335 includes a subtraction unit 200, coefficient units 210, 220, and 230, an integration unit 240, a differentiation unit 250, and an addition unit 260.

  The subtraction unit 200 subtracts the pressure difference ΔPA detected by the pressure difference calculation unit 333 from the pressure difference target value ΔPR set by the target pressure difference setting unit 331, and calculates a deviation thereof. The coefficient unit 210 multiplies the calculated deviation by a proportional gain (1 / Kp). The coefficient unit 220 multiplies the calculated deviation by an integral gain (1 / Ki). Then, the output of the coefficient unit 220 is integrated by the integration unit 240. The coefficient unit 230 multiplies the calculated deviation by a differential gain (Kd). The output of the coefficient unit 230 is differentiated by the differentiation unit 250. The adding unit 260 generates a control signal SIG for driving the bypass valve 160 by adding outputs from the coefficient unit 210, the integrating unit 240, and the differentiating unit 250.

  By the above operation, the control signal SIG corresponding to the set opening target value OPR is set.

  FIG. 7 is a flowchart for explaining the pressure difference control process of the throttle valve 150 executed by the pressure control unit 330 in the present embodiment. In the flowchart shown in FIG. 7 and FIG. 8 described below, the processing is realized by a program stored in advance in the pressure control unit 330 being called from the main routine and executed in a predetermined cycle. Alternatively, for some steps, it is also possible to construct dedicated hardware (electronic circuit) and realize processing.

  Referring to FIGS. 1 and 7, pressure control unit 330 sets feedback gains Kp, Ki, and Kd at step (hereinafter, step is abbreviated as S) 100. The feedback gains Kp, Ki, Kd at this time are preferably set to be lower than when the pressure difference is set to a fixed value regardless of the load factor. This is because, in the pressure difference control of the present embodiment, the throttle valve 150 is used in an operating range with high control sensitivity, and therefore, when these feedback gains Kp, Ki, and Kd are set high, the response is high. This is to prevent hunting and the like from becoming unstable.

  As the set values of the feedback gains Kp, Ki, and Kd, for example, when the pressure difference is set to a fixed value and Kp = 1, Ki = 1, and Kd = 100, in this control, Kp = 0 .01 to 0.1, Ki = 0, 01 to 0.1, and Kd = 1 to 100 are preferable. More preferably, Kp = 0.05, Ki = 0.05, and Kd = 98 may be set.

  Thereafter, in S110, the pressure control unit 330 determines whether or not the engine main body 110 is being activated. In addition, the case where the engine is started includes a case where the engine main body 110 is started (started) and a case where the operation is continued.

  If engine main body 110 is not in operation (NO in S110), the pressure difference control is not necessary, and pressure control unit 330 skips the subsequent processes and ends the process.

  If engine body 110 is being activated (YES in S110), the process proceeds to S120, and pressure control unit 330 acquires the current load factor LDR of engine body 110. In step S130, the pressure control unit 330 calculates the pressure difference target ΔPR corresponding to the load factor LDR using the acquired load factor LDR. Detailed control in S130 will be described later with reference to FIG.

  Thereafter, in S140, the pressure control unit 330 calculates the current actual pressure difference ΔPA from the pressure detection values PIN and POUT detected by the pressure gauges 340 and 350, respectively. In S150, the pressure control unit 330 calculates the opening command value of the bypass valve 160 using the pressure difference target value ΔPR and the actual pressure difference ΔPA, and performs feedback control as shown in FIG. The opening degree of the bypass valve 160 is controlled.

  And the pressure control part 330 advances a process to S160, and determines whether the engine main-body part 110 was stopped.

  If engine body 110 is not stopped and operation is continued (NO in S160), the process returns to S120, and pressure controller 330 opens bypass valve 160 in accordance with load factor LDR. Continue degree control.

  When engine main body 110 is stopped (YES in S160), pressure control unit 330 ends the process.

  Next, details of the calculation process of the pressure difference target value ΔPR in step S130 of FIG. 7 will be described with reference to FIG. In FIG. 8, a case where the setting map shown in FIG. 5 is used will be described as an example.

  Referring to FIG. 8, in S200, pressure control unit 330 determines whether or not load factor LDR acquired in S120 of FIG. 7 is L5 or more (LDR ≧ L5).

  If load factor LDR is equal to or greater than L5 (YES in S200), the process proceeds to S205, and pressure control unit 330 sets pressure difference target value ΔPR to P5. And the pressure control part 330 advances a process to S140 of FIG.

  If load factor LDR is less than L5 (NO in S200), the process proceeds to S210, and pressure controller 330 determines whether or not load factor LDR is greater than or equal to L4 and less than L5 (L4 ≦ LDR <L5). judge.

  If load factor LDR is greater than or equal to L4 and less than L5 (YES in S210), the process proceeds to S215, and pressure control unit 330 acquires on a straight line obtained by linearly complementing points A4 and A5 in FIG. The pressure difference target value ΔPR corresponding to the obtained load factor LDR is calculated by the following equation (1), and then the process proceeds to S140.

ΔPR = {(P5−P4) / (L5−L4)} · (LDR−L4) + P4 (1)
If load factor LDR is less than L4 (NO in S210), the process proceeds to S220, and pressure controller 330 determines whether load factor LDR is equal to or greater than L3 and less than L4 (L3 ≦ LDR <L4). Determine.

  When load factor LDR is not less than L3 and less than L4 (YES in S220), the process proceeds to S225, and pressure control unit 330 calculates pressure difference target value ΔPR by the following equation (2), and thereafter The process proceeds to S140.

ΔPR = {(P4−P3) / (L4−L3)} · (LDR−L3) + P3 (2)
If load factor LDR is less than L3 (NO in S220), the process proceeds to S230, and pressure control unit 330 determines whether load factor LDR is greater than or equal to L2 and less than L3 (L2 ≦ LDR <L3). Determine.

  If load factor LDR is not less than L2 and less than L3 (YES in S230), the process proceeds to S235, and pressure control unit 330 calculates pressure difference target value ΔPR by the following equation (3), and thereafter The process proceeds to S140.

ΔPR = {(P3−P2) / (L3−L2)} · (LDR−L2) + P2 (3)
If load factor LDR is less than L2 (NO in S230), the process proceeds to S240, and pressure controller 330 determines whether load factor LDR is greater than or equal to L1 and less than L2 (L1 ≦ LDR <L2). Determine.

  When load factor LDR is not less than L1 and less than L2 (YES in S240), the process proceeds to S245, and pressure control unit 330 calculates pressure difference target value ΔPR by the following equation (4), and thereafter The process proceeds to S140.

ΔPR = {(P2−P1) / (L2−L1)} · (LDR−L1) + P1 (4)
When load factor LDR is less than L1 (NO in S240), the process proceeds to S250, and pressure control unit 330 calculates pressure difference target value ΔPR by the following equation (5), and then the process To S140.

ΔPR = {(P1−P0) / (L1−L0)} · (LDR−L0) + P0 (5)
Here, when the load factor LDR is 0%, it indicates the time when the engine main body 110 is started, and the pressure target value ΔPR at this time is compared with that during operation of the engine main body 110 where the load factor LDR is greater than zero. It is set large. As explained in the above-mentioned problem, the bypass valve 160 is opened when the engine is started, so that the amount of mixed gas supplied to the combustion chamber 111 is reduced, and the engine cannot be started properly. This is to prevent this. That is, the bypass valve 160 is closed by increasing the pressure target value ΔPR.

  The pressure difference target value ΔPR is appropriately set in a range of about 10 to 35 kPa, for example, during engine operation (P1 to P5), while being set in a range of about 50 to 70 kPa at the time of engine start (P0). More preferably, the pressure difference target value ΔPR at the time of starting the engine is set to about 60 kPa.

  In addition, about the process of step S130 shown by FIG. 8, it changes suitably according to the setting map, setting formula, and setting table which are employ | adopted.

  By performing the control according to the above-described process, in the premixed gas engine system with a supercharger having a mixed gas bypass line, the target value of the pressure difference between the supply pressure of the throttle valve and the discharge pressure is set to gas. The opening degree of the bypass valve can be adjusted so that the pressure difference becomes a target value by variably setting according to the engine load. As a result, the amount of gas mixture at the start of the gas engine can be secured, and while the gas engine is operating, the throttle valve opening is maintained within a high control sensitivity range. It is possible to perform well and stable operation.

[Execution example when this embodiment is applied]
Hereinafter, the effect when this embodiment is applied will be described with reference to FIGS. 9 to 12. These drawings show the results of simulation comparing the case where the control of the present embodiment is applied and the case of a comparative example where a part of the control is not applied.

  9 to 12, the horizontal axis represents time, and the vertical axis represents the pressure difference target value ΔPR and actual value ΔPA (upper stage), and the valve opening of the throttle valve and bypass valve (middle stage). , And the engine speed and generated power (lower). In the figure, the solid line indicates the case where the control of the present embodiment is applied, and the broken line indicates the case of the comparative example.

(Effect of setting pressure difference target value at start-up)
FIG. 9 shows a case where the pressure difference target value ΔPR at the time of starting the engine is set higher than that during other operations as in the control of the present embodiment, and in the case of a comparative example in which the pressure difference target value ΔPR is comparable to that during other operations. It is a figure which shows a simulation result.

  Referring to FIG. 9, the engine is started at time 0. At this time, in the comparative example, the pressure difference target value ΔPR is set lower than the solid line W10 as indicated by the broken line W11 in the upper graph.

  When the engine is started, the comparative example (middle broken line W17) starts moving faster than the case where the control of the present embodiment is applied (middle solid line W16) with respect to the bypass valve opening. As a result, the mixed gas is bypassed and the amount of the mixed gas flowing into the throttle valve decreases, so that the increase in the pressure difference ΔPA before and after the throttle valve is delayed (upper broken line W13).

  In response to this, the throttle valve opening amount is increased in order to increase the amount of mixed gas supplied to the combustion chamber, but the throttle valve opening amount reaches the opening upper limit UL (middle broken line W15), As a result, the gas engine immediately after start-up is stagnant in a low state (lower broken line W20).

  On the other hand, when the control according to the present embodiment is applied, the pressure difference target value ΔPR at the time of starting is high, and the opening degree of the bypass valve immediately after starting the engine gradually increases (solid solid line W16). The pressure difference ΔPA rises quickly (upper solid line W12). Then, the throttle valve opening does not reach the upper limit and operates within a relatively high control sensitivity (middle solid line W14). Thereby, the stagnation of the engine output immediately after the start is suppressed.

(Effect of pressure difference target value setting according to load-1)
FIG. 10 shows a comparative example in which the pressure difference target value ΔPR is changed according to the load as in the control of the present embodiment, and the pressure difference target value ΔPR is fixed to a value when adapted at a low load. It is a figure which shows the simulation result in a case. In order to clarify the difference, the pressure difference target value ΔPR at the start in the comparative example is set in the same manner as in the present embodiment.

  Referring to FIG. 10, after the engine is started, when the engine output is low and the load is low, the pressure difference target value ΔPR is appropriately set, and thus the same behavior as the control of the present embodiment is shown. . However, since the pressure difference target value ΔPR is adapted at the time of low load, the pressure target value ΔPR becomes lower than the optimum value as the load increases (upper broken line W31). In response to this, in order to reduce the supply pressure to the throttle valve, the bypass valve opening becomes larger than the optimum state (middle broken line W37).

  Then, in order to increase the amount of gas mixture, the throttle valve opening increases and reaches the opening upper limit UL (middle broken line W35). As a result, the required amount of mixed gas cannot be secured, and the engine output is reduced (lower broken line W40).

  On the other hand, when the control according to the present embodiment is applied, the pressure difference target value ΔPR at the time of high load is set higher than that at the time of low load (upper solid line W30). An increase in the opening of the valve is suppressed (middle solid line W36). Then, the throttle valve opening does not reach the upper limit and operates in a range where the control sensitivity is relatively high (middle solid line W34). Thereby, the stagnation of the engine output at the time of high load is suppressed (lower solid line W39).

(Effect of pressure difference target value setting according to load -2)
FIG. 11 shows a comparative example in which the pressure difference target value ΔPR is changed according to the load as in the control of the present embodiment, and the pressure difference target value ΔPR is fixed to a value when adapted at high load. It is a figure which shows the simulation result in a case.

  Referring to FIG. 11, in this case, the pressure difference target value ΔPR is adapted at the time of high load, so that the target value is set higher than the optimum target value at the time of low load (the upper broken line) W51). Therefore, optimal control is performed in a high load state, but at a low load immediately after the engine is started, the bypass valve opening is set small (middle broken line W57), and the actual pressure difference ΔPA increases ( Upper broken line W53). Then, the throttle valve opening is set to be small in order to reduce the amount of gas mixture into the combustion chamber (middle broken line W55). As a result, the operating range of the throttle valve becomes a region with low control sensitivity, so that the engine output becomes unstable (lower broken line W60).

  In contrast, when the control of the present embodiment is applied, the pressure difference target value ΔPR at the time of low load is set lower than that at the time of high load (upper solid line W50). It is suppressed that the opening degree of the valve becomes small (middle solid line W56), and the control sensitivity is operated within a relatively high range without being lowered (open solid line W54). Thereby, the stagnation of the engine output at the time of high load is suppressed (lower solid line W59).

(Effect of feedback gain reduction)
FIG. 12 is a diagram illustrating a simulation result in the case of reducing the feedback gain as in the control of the present embodiment and in the comparative example in which the feedback gain is set high.

  Referring to FIG. 12, the pressure difference target value ΔPR is the same as that in the control in the present embodiment in the comparative example (upper W70, W71), but the feedback gain is set high in the comparative example. Therefore, the change of the opening degree of the bypass valve is quick, and it becomes over-controlled and enters the hunting state (middle broken line W77). As a result, the actual pressure difference ΔPA also changes in an oscillating manner (upper broken line W73). Then, in response to the change in the pressure difference ΔPA, the throttle valve opening changes (middle broken line W75), and as a result, the engine output also becomes unstable (lower broken line W80).

  On the other hand, when the control of the present embodiment is applied, setting the feedback gain to a small value prevents the bypass valve opening from being overcontrolled (interrupt solid line W76). Changes in the actual pressure difference and the throttle valve opening are suppressed (upper solid line W72, middle solid line W74), and engine output hunting is suppressed (lower solid line W80).

  As described above, by applying the control of the present embodiment to a premixed gas engine system with a supercharger having a mixed gas bypass line, compared to the case where the control is not applied, A stable gas engine can be operated.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 100 Gas engine system, 110 Engine main part, 111 Combustion chamber, 112 Piston, 120 Air filter, 130 Fuel gas quantity regulator, 140 Mixer, 150 Throttle valve, 160 Bypass valve, 170 Supercharger, 171 Turbine, 172 Compressor, 200 subtraction unit, 210, 220, 230 coefficient unit, 240 integration unit, 250 differentiation unit, 260 addition unit, 300 control device, 310 control unit, 320 air-fuel ratio control unit, 321 excess air ratio setting unit, 322, 332 storage unit , 323, 335 Control signal generation unit, 330 Pressure control unit, 331 Target pressure difference setting unit, 333 Pressure difference calculation unit, 334 Opening setting unit, 340, 350 Pressure gauge.

Claims (15)

A control device for controlling a premixed gas engine to which a mixed gas obtained by mixing fuel gas and air is supplied,
The gas engine
A combustion chamber for burning the mixed gas;
A throttle valve provided in an air supply path to the combustion chamber, for adjusting a supply amount of the mixed gas to the combustion chamber;
A turbocharger that is driven using exhaust gas from the combustion chamber and is configured to compress and supply the mixed gas to the throttle valve;
A bypass valve disposed so as to connect the discharge path of the supercharger and the supply path of the mixed gas to the supercharger, and for bypassing a part of the mixed gas supplied to the throttle valve Including
The controller is
A pressure detector for detecting a pressure difference between a supply pressure and a discharge pressure of the throttle valve;
The target value of the pressure difference is variably set according to the load of the gas engine so that the opening degree of the throttle valve is maintained within a predetermined range, and the target in which the pressure difference is set And a control unit that adjusts the opening degree of the bypass valve so as to be a value.   2. The premix according to claim 1, wherein the control unit sets a target value of the pressure difference used when starting the gas engine to a value higher than a target value of the pressure difference used during operation of the gas engine. Type gas engine control device.   The said control part is a control apparatus of the premix type gas engine of Claim 2 which sets the target value of the said pressure difference used at the time of the start of the said gas engine in the range of 50-70 kPa.   The said control part sets the target value of the said pressure difference used during the driving | operation of the said gas engine more than the value when the said load factor is low, when the load factor of the said gas engine is high, or. 2. The control device for the premixed gas engine according to 2.   The said control part is a control apparatus of the premix type gas engine of Claim 4 which sets the target value of the said pressure difference used during the driving | operation of the said gas engine in the range of 10-35 kPa.   The control device for a premixed gas engine according to claim 1, wherein the predetermined range for the opening of the throttle valve is set to a range in which control sensitivity is relatively high in the characteristics of the throttle valve.   The control device for a premixed gas engine according to claim 6, wherein the predetermined range for the opening of the throttle valve is set to 30 to 60% of the opening when the throttle valve is fully opened.   The control device for a premixed gas engine according to claim 7, wherein the predetermined range for the opening of the throttle valve is set to 40 to 45% of the opening when the throttle valve is fully opened.   The control unit controls the opening degree of the bypass valve by feedback control, and when the target value of the pressure difference is variably set, the feedback is compared with the case where the target value of the pressure difference is a fixed value. The control device for a premixed gas engine according to claim 1, wherein a gain used for control is set to be small. The control unit executes the feedback control by PID control,
10. The premixed gas engine according to claim 9, wherein the control unit uses a proportional gain, an integral gain, and a differential gain as the gain, and sets the proportional gain in a range of 0.01 to 0.1. Control device. The control unit executes the feedback control by PID control,
The premixed gas according to claim 9 or 10, wherein the control unit uses a proportional gain, an integral gain, and a differential gain as the gain, and sets the integral gain in a range of 0.01 to 0.1. Engine control device. The control unit executes the feedback control by PID control,
The premixing formula according to any one of claims 9 to 11, wherein the control unit uses a proportional gain, an integral gain, and a differential gain as the gain, and sets the differential gain in a range of 1 to 100. Gas engine control device. The control unit executes the feedback control by PID control,
The control unit uses a proportional gain, an integral gain, and a differential gain as the gain, sets the proportional gain to 0.05, sets the integral gain to 0.05, and sets the differential gain to 98. The control device for a premixed gas engine according to claim 9. A control method of a premixed gas engine to which a mixed gas obtained by mixing fuel gas and air is supplied,
The gas engine
A combustion chamber for burning the mixed gas;
A throttle valve provided in an air supply path to the combustion chamber, for adjusting a supply amount of the mixed gas to the combustion chamber;
A turbocharger that is driven using exhaust gas from the combustion chamber and is configured to compress and supply the mixed gas to the throttle valve;
A bypass valve disposed so as to connect the discharge path of the supercharger and the supply path of the mixed gas to the supercharger, and for bypassing a part of the mixed gas supplied to the throttle valve Including
The control method is:
Detecting a pressure difference between an air supply pressure and a discharge pressure of the throttle valve;
Setting the target value of the pressure difference variably according to the load of the gas engine, so that the opening of the throttle valve is maintained within a predetermined range,
And a step of adjusting the opening of the bypass valve so that the pressure difference becomes a set target value. A premixed gas engine to which a mixed gas in which fuel gas and air are mixed is supplied;
A control device for controlling the gas engine,
The gas engine
A combustion chamber for burning the mixed gas;
A throttle valve provided in an air supply path to the combustion chamber, for adjusting a supply amount of the mixed gas to the combustion chamber;
A turbocharger that is driven using exhaust gas from the combustion chamber and is configured to compress and supply the mixed gas to the throttle valve;
A bypass valve disposed so as to connect the discharge path of the supercharger and the supply path of the mixed gas to the supercharger, and for bypassing a part of the mixed gas supplied to the throttle valve Including
The controller is
A pressure detector for detecting a pressure difference between a supply pressure and a discharge pressure of the throttle valve;
The target value of the pressure difference is variably set according to the load of the gas engine so that the opening degree of the throttle valve is maintained within a predetermined range, and the target in which the pressure difference is set And a control unit that adjusts the opening of the bypass valve so as to be a value.

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