JP2017110566A - Control method and device of gas engine, and gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue an operation by eliminating instability and abnormal combustion by minimizing transient variation of an engine rotating speed due to sudden fluctuation of heat quantity of a gas fuel during the operation.SOLUTION: A control device of a gas engine includes an air supply system 10, a fuel gas supply system 20, mixing means (carburetor 30) for mixing air and a fuel gas, a throttle valve 50 for adjusting a supply amount of the air-fuel mixture, engine rotating speed measurement means (rotating speed sensor 62), air-fuel ratio measurement means (Osensor 80), an electric power transducer 72, and control means (engine controller 100). When the engine rotating speed changed though a signal value of the electric power transducer 72 is not changed in controlling the gas engine in which a fuel supply amount is controlled by at least a fuel gas flow rate adjustment valve 24 disposed on the fuel gas supply system 20, a control value of the fuel gas flow rate adjustment valve 24 is temporarily corrected only by a time when the engine rotating speed is stabilized.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas engine control method, apparatus, and gas engine. In particular, the present invention relates to an unstable or abnormal state by minimizing transient fluctuations in engine speed due to sudden heat quantity fluctuations of gas fuel during self-sustaining operation. The present invention relates to a gas engine control method and apparatus capable of eliminating combustion and continuing operation, and a gas engine using the same.

  Gasoline and diesel engine fuels are standardized liquid fuels such as gasoline and light oil, and their quality is very stable.

  On the other hand, a gas engine configured to mix gas fuel and air at a required air-fuel ratio in a gas mixer, supply the mixture (mixed gas) to an engine combustion chamber through an air supply pipe, and perform ignition combustion. It has been put into practical use. In such gas engines, in addition to city gas with high calorific value as fuel, in recent years, sludge digestion gas generated in the process of treating sewage sludge, biomass gas generated from biological resources derived from animals and plants, A wide variety of gases are used, such as waste combustion gas and coke oven gas generated in the iron making process. However, depending on the gas fuel used, not only the theoretical air amount but also the combustibility such as the combustion speed, the combustion temperature, and the combustion pressure are different, so the specifications of the gas engine are also different.

Currently, systems such as gas cogeneration using city gas as fuel and emergency power generation are also widespread. Although the calorific value of city gas is stable, a rapid variation in calorific value of 40 to 46 MJ / m ³ is expected in a few seconds due to diversification of gas fuel as a raw material.

  Naturally, this variation in the amount of heat is accompanied by a change in the composition, so there is a concern that the engine may stall due to a large variation and a sudden change in the stoichiometric air-fuel ratio, and a technique for operating the gas engine in a stable manner is desired. .

  For this purpose, Patent Document 1 installs a gas engine for calorific value measurement in addition to the main engine, operates the measurement engine and the main engine at the same time, takes operation data from the measurement engine, It is described that the operating conditions of the main engine are controlled based on the operating data.

  Further, Patent Document 2 discloses that the type of fuel gas is determined from the engine speed increase speed when the same speed control is performed at the time of start-up and reflected in the operating conditions, and when the engine speed fluctuates. Adjusting the opening of the throttle valve to control fluctuations in the engine speed, and if the adjusted opening of the throttle valve is outside the allowable range, adjust the opening of the fuel gas flow control valve to adjust the adjusted fuel gas It is described that if the valve opening degree of the flow control valve exceeds a threshold value, the opening characteristic of the throttle valve and the opening characteristic of the fuel gas flow control valve are switched to other fuel gas characteristics.

JP-A-2005-226621 (Claim 1) Japanese Patent Laying-Open No. 2005-299451 (Claim 1, paragraph 0040)

  However, none of the techniques copes with a sudden change in the calorific value of the fuel gas during the independent operation.

In the gas engine, the air-fuel ratio changes due to fluctuations in the calorific value of the fuel gas, and is affected by combustibility such as the combustion speed, combustion temperature, and combustion pressure. Specifically, when the calorific value of the fuel gas is reduced and the calorific value is reduced, the theoretical air amount of the fuel gas is reduced, so if the gas engine controller does not support the reduction of calorie, the actual excess air ratio As λ increases, it becomes impossible to produce an output sufficient to carry the load, and the engine speed decreases. In order to cope with this, the controller of the gas engine usually instructs the speed governor to open the throttle valve and increase the amount of air-fuel mixture. Furthermore, an air-fuel ratio sensor such as an O ₂ sensor or an intake pressure sensor is used to control the fuel gas pressure regulating valve and the fuel gas flow rate adjustment valve so that the excess air ratio λ of the mixture becomes an optimum value for the fuel gas at that time. ing. However, the engine speed changes transiently until the control works stably.

The calorific value fluctuation of city gas, which is one of the gas fuels, is expected to be abrupt fluctuation of about 40 to 46 MJ / m ^{3 in} a few seconds in the future. The control which detected the state change of is necessary.

  The present invention was made to solve the above-mentioned conventional problems, and in a self-sustained operation of a gas engine generator, suppressing transient fluctuations in engine speed due to sudden heat fluctuations of gas fuel during operation, The task is to eliminate unstable and abnormal combustion so that operation can be continued.

  The present invention includes an air supply system, a fuel gas supply system, a mixing means for mixing air and fuel gas, a throttle valve for adjusting the supply amount of the air-fuel mixture, an engine speed measuring means, and an air-fuel ratio measurement Means, a power transducer, and a control means, and at the time of controlling a gas engine whose fuel supply amount is controlled by at least a fuel gas flow rate adjustment valve provided in the fuel gas supply system so that the engine speed is constant, When the engine speed fluctuates even though the signal value of the power transducer does not change, the control value of the fuel gas flow rate adjustment valve is temporarily corrected only until the engine speed stabilizes, It solves the problem.

  Further, when the engine speed fluctuates even though the signal value of the power transducer does not change, at least one of the control values of the ignition timing and the ignition energy is temporarily changed only until the engine speed is stabilized. It can be corrected. Here, the control value is a control signal from the control circuit including the engine map, and is a control signal that is always transmitted to the control device target instead of transiently.

  The present invention also includes an air supply system, a fuel gas supply system, a mixing unit that mixes air and fuel gas, a throttle valve for adjusting the supply amount of the mixture, an engine speed measuring unit, A gas comprising a fuel ratio measurement means, a power transducer, and a control means, and the fuel supply amount is controlled by a fuel gas flow rate adjustment valve provided at least in the fuel gas supply system so that the engine speed is constant. When the engine speed fluctuates even though the signal value of the power transducer does not change, the control value of the fuel gas flow control valve is temporarily changed until the engine speed stabilizes. The above-mentioned problem is solved in the same manner by a gas engine control device provided with correction means for automatically correcting.

  Further, when the engine speed fluctuates even though the signal value of the power transducer does not change, the correction means controls at least one of ignition timing and ignition energy only until the engine speed stabilizes. The value can also be corrected temporarily.

  The present invention further includes an air supply system, a fuel gas supply system, a mixing means for mixing air and fuel gas, a throttle valve for adjusting the supply amount of the air-fuel mixture, an engine speed measurement means, The fuel ratio measurement means, the power transducer, the control means for controlling the fuel supply amount by at least the fuel gas flow rate adjusting valve provided in the fuel gas supply system so that the engine speed is constant, and the signal value of the power transducer is Correction means for temporarily correcting the control value of the fuel gas flow control valve only until the engine speed stabilizes when the engine speed fluctuates without changing. A gas engine is provided.

  In the present invention, the case where the engine speed fluctuates even though the signal value of the power transducer does not change is regarded as the fuel gas calorie fluctuation in a short time, and in addition to the control by the control value according to the normal map and feedback control, Only until the engine speed is stabilized, at least one of the control value, the fuel gas flow rate adjustment valve provided in the fuel gas supply system, and, if necessary, the ignition timing and ignition energy temporarily. to correct. This shortens the time until the engine speed returns to stable operation, minimizes fluctuations in engine speed, eliminates unstable and abnormal combustion, and allows the operation to continue. Become.

The figure which shows an example of the whole structure of the gas engine to which this invention is applied The time chart which shows an example of the control in 1st Embodiment of this invention The time chart which shows an example of the control in 2nd Embodiment of this invention A time chart showing an example of ignition energy

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the content described in the following embodiment and an Example. In addition, the constituent elements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in the so-called equivalent range. Furthermore, the constituent elements disclosed in the embodiments and examples described below may be appropriately combined or may be appropriately selected and used.

An example of a spark ignition and premixed combustion type gas engine to which the present invention is applied is shown in FIG. The gas engine includes an air supply system 10, a fuel gas supply system 20 including a fuel gas pressure regulating valve 22 and a fuel gas flow rate adjustment valve (FCV) 24 that adjust the fuel gas supply pressure using, for example, a step motor, and the air supply system. 10 and the carburetor 30 which is a mixing means for uniformly mixing the air and the fuel gas supplied from the fuel gas supply system 20 and the supercharger turbine 40 disposed in the exhaust system of the engine body 60, and the carburetor A supercharger blower 42 for compressing the air-fuel mixture mixed at 30; an intercooler 44 for cooling the air-fuel mixture heated by the compression of the supercharger blower 42; and excessive mixing when the air-fuel mixture is excessive A turbo bypass valve (TBV) 46 for returning the air to the inlet of the supercharger blower 42, and a throttle valve 5 for adjusting the supply amount of the air-fuel mixture A speed governor 52 for controlling the opening degree of the throttle valve 50, an intake pressure sensor 54 for detecting the pressure in the intake pipe on the inlet side of the engine body 60, and an engine crankshaft, for example. A rotational speed sensor 62 such as a crank angle sensor for detecting the rotational angle of the engine, an engine body 60 having a spark plug 64, for example, a piezoelectric cylinder pressure sensor 66, and an amplifier 68 paired with the cylinder pressure sensor 66; A generator 70 that is rotationally driven by an output (crank) shaft of the engine body 60 (a gas engine), a power transducer (also referred to as a kW transducer) 72, and an exhaust pipe provided in the exhaust pipe of the engine body 60, for example. An O ₂ sensor 80 which is an air-fuel ratio sensor for detecting the air-fuel ratio from the oxygen concentration in the inside, and a throttle valve A valve opening is mechanically adjusted, for example, with a differential pressure of about 50, a wastegate valve 90 for bypassing excess exhaust after the turbocharger turbine 40, the intake pressure sensor 54, the rotational speed sensor 62, an amplifier 68, By controlling the fuel gas pressure regulating valve 22, FCV 24, TBV 46, throttle valve 50, ignition device 110 with variable ignition energy function, etc. according to inputs from the power transducer 72, the O ₂ sensor 80, etc. And an engine controller 100 that performs control.

  The engine controller 100 includes a control circuit 102 including an engine map and a correction circuit 104 according to the present invention in addition to a general computer configuration such as a CPU, ROM, and RAM.

  The fuel gas is mixed with air in the carburetor 30 and is sent to the engine body 60 after supercharging.

  The ignition device 110 with variable ignition energy function applies a predetermined ignition energy pattern to the ignition plug 64 at the ignition timing (IT) received from the engine controller 100 to ignite the air-fuel mixture.

  Since this gas engine is a lean combustion system, the excess air ratio λ changes from about 1 (low output) to about 1.8 (high output) depending on the engine output.

  Therefore, in the independent operation, the engine controller 100 controls the opening degree of the throttle valve 50 in order to keep the engine speed constant regardless of the load of the generator 70. Specifically, when the load increases, the throttle valve 50 is opened so that the engine speed does not drop. Therefore, unless there is a sudden fluctuation such as load application or load interruption, fluctuations in the engine speed that cause problems such as engine stall and deterioration in the quality of generated electricity do not occur.

On the other hand, since the optimal excess air ratio λ varies depending on the load, it is necessary to control the excess air ratio λ. The control of the excess air ratio λ is performed by adjusting the fuel gas supply amount with respect to the supply air flow rate in the air supply system 10 so that the output value of the O ₂ sensor 80 corresponding to the excess air ratio λ becomes a predetermined value. This is performed by controlling the fuel gas supply pressure by the pressure valve 22 and the fuel gas flow rate by the FCV 24. The control value of the excess air ratio λ is determined by comparing the engine speed and the value of the power transducer 72 at this time with the control circuit 102 including the engine map.

  As is well known, in self-sustained operation, load fluctuations such as load application and load interruption appear as fluctuations in the engine speed following changes in the output signal of the power transducer 72.

  On the other hand, when a change in the fuel gas calorific value (the amount of heat generated by the fuel gas) occurs during operation, there is no load change as when the load is turned on or off, so the signal of the power transducer 72 changes. Does not appear. That is, a situation in which the engine speed fluctuates even when the output value of the power transducer 72 does not change occurs at least at the initial stage of fluctuation of the fuel gas heat quantity.

  In the first embodiment of the present embodiment, when the engine speed fluctuates even though the signal value of the power transducer does not change, it is determined that the amount of heat generated by the fuel gas has changed, and the FCV24 opening degree control value is transient. A correction coefficient (correction coefficient 1) as shown in FIG. 2 is added. That is, when the amount of heat increases and the engine speed increases, the fuel gas flow rate is transiently reduced by adding a correction coefficient in the closing direction to the control value of the opening degree of the FCV 24, and conversely, the amount of heat decreases. When the engine speed decreases, the fuel gas flow rate is increased transiently by adding a correction coefficient in the opening direction to the control value of the opening degree of the FCV 24 in a transitional manner and opening a large amount. In this way, by correcting the control value of the fuel supply amount in a transient manner, it is possible to advance the time until the stable operation is reached after the unstable combustion due to the heat amount fluctuation.

  That is, when the engine speed fluctuates due to heat fluctuations, the opening of the FCV 24 is corrected in the opening direction or the closing direction, the combustion is changed by changing the excess air ratio λ, and the setting of the engine speed is accelerated. . Specifically, when the engine speed fluctuates even though the signal value of the power transducer 72 does not change, the stepwise correction coefficient as shown in FIG. 2 is added to the control value of the FCV 24 depending on the magnitude of the fluctuation of the engine speed. (Correction coefficient 1) is added.

  On the other hand, fluctuations in engine speed may not be sufficiently suppressed only by correcting the fuel supply amount by the FCV 24 or the fuel gas pressure regulating valve 22. Therefore, the second embodiment of the present invention has a function of adding correction coefficients (correction coefficients 2 and 3) as shown in FIG. 3 to the control values of the ignition timing IT and ignition energy when the fuel gas calorific value fluctuates. . In the present embodiment, by correcting the ignition timing IT and the ignition energy, the time from the unstable combustion accompanying the heat fluctuation to the stable operation is advanced.

  That is, when the engine speed increases (or decreases) due to heat fluctuation, the ignition timing IT is retarded (or advanced) to the excess side, and the ignition energy is increased (or decreased) to generate sparks. The combustion is changed by changing so as to keep the period longer (shorter), and the settling of the engine speed is accelerated.

  Specifically, when a change in heat quantity is detected due to a change in engine speed, a stepwise correction coefficient 2 as shown in FIG. 3 is added to the control value of the ignition timing IT and ignition energy depending on the magnitude of the change in engine speed. And 3 are added.

  Here, as illustrated in FIGS. 4A and 4B, the horizontal axis represents time and the vertical axis represents current, so that the time at which the ignition current is generated can be maintained and controlled as a period rather than an instant, and the generation of sparks By adjusting the period, the integral value of the ignition current, that is, the ignition energy can be increased or decreased.

  In the above embodiment, the present invention is applied to a lean combustion type gas engine. However, the application target of the present invention is not limited to this, and a stoichiometric gas having an excess air ratio λ of about 1 is used. The same applies to engines.

  Moreover, in the said embodiment, although this invention was applied to the supercharged gas engine provided with the supercharger, the application object of this invention is not limited to this, The natural air supply which does not have a supercharger The same applies to a gas engine.

DESCRIPTION OF SYMBOLS 10 ... Air supply system 20 ... Fuel gas supply system 22 ... Fuel gas pressure regulation valve 24 ... Fuel gas flow control valve (FCV)
30 ... Carburetor 40 ... Supercharger turbine 42 ... Supercharger blower 44 ... Intercooler 46 ... Turbo bypass valve (TBV)
50 ... throttle valve 52 ... speed governor 54 ... intake pressure sensor 60 ... engine body 62 ... rotational speed sensor 64 ... spark plug 66 ... cylinder pressure sensor 68 ... amplifier 70 ... generator 72 ... power transducer 80 ... O ₂ (air) Sensor 90 ... Wastegate valve 100 ... Engine controller 102 ... Control circuit including engine map 104 ... Correction circuit 110 ... Ignition device with variable ignition energy function

Claims (6)

An air supply system, a fuel gas supply system, a mixing means for mixing air and fuel gas, a throttle valve for adjusting the supply amount of the air-fuel mixture, an engine speed measuring means, an air-fuel ratio measuring means, an electric power When controlling a gas engine, which includes a transducer and a control means, and whose fuel supply amount is controlled by at least a fuel gas flow rate adjustment valve provided in the fuel gas supply system so that the engine speed is constant,
When the engine speed fluctuates even though the signal value of the power transducer does not change, the control value of the fuel gas flow rate adjustment valve is temporarily corrected only until the engine speed stabilizes. To control the gas engine.   When the engine speed fluctuates even though the signal value of the power transducer does not change, at least one of the control values of ignition timing and ignition energy is temporarily corrected only until the engine speed stabilizes. The method for controlling a gas engine according to claim 1. An air supply system, a fuel gas supply system, a mixing means for mixing air and fuel gas, a throttle valve for adjusting the supply amount of the air-fuel mixture, an engine speed measuring means, an air-fuel ratio measuring means, an electric power A gas engine control device comprising a transducer and a control means, wherein the fuel supply amount is controlled by at least a fuel gas flow rate adjusting valve provided in the fuel gas supply system so that the engine speed is constant. And
When the engine speed fluctuates even though the signal value of the power transducer does not change, correction means for temporarily correcting the control value of the fuel gas flow control valve only until the engine speed stabilizes is provided. A control device for a gas engine.   When the engine speed fluctuates even though the signal value of the power transducer does not change, at least one of the control values of the ignition timing and the ignition energy is not changed until the correction means stabilizes the engine speed. The control device for a gas engine according to claim 3, wherein correction is performed temporarily. An air supply system;
A fuel gas supply system;
Mixing means for mixing air and fuel gas;
A throttle valve for adjusting the supply amount of the air-fuel mixture;
An engine speed measuring means;
Air-fuel ratio measuring means;
A power transducer;
Control means for controlling the fuel supply amount by at least a fuel gas flow rate adjusting valve provided in the fuel gas supply system so that the engine speed is constant;
Correction means for temporarily correcting the control value of the fuel gas flow control valve only until the engine speed is stabilized when the engine speed fluctuates even though the signal value of the power transducer does not change;
A gas engine characterized by comprising:   When the engine speed fluctuates even though the signal value of the power transducer does not change, at least one of the control values of the ignition timing and the ignition energy is not changed until the correction means stabilizes the engine speed. The gas engine according to claim 5, wherein the correction is temporarily performed.

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