JP2015132206A - Gas engine controller, gas engine control method, and gas engine equipped with controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the reduction in engine speed due to rapid load increase, with a simple configuration.SOLUTION: A controller 51 comprises: a required-gas-flow calculation unit 54 calculating a required gas flow Qg_d necessary to keep an engine speed constant from a deviation between the engine speed and a target engine speed; a throttle-valve-opening calculation unit 55 calculating a throttle opening in response to the required gas flow Qg_d; an air-gas-mixture-flow calculation unit 56 calculating an air-gas mixture Qm from the engine speed, an intake pressure, an intake temperature, an engine displacement, and the like; a gas-flow-command-value calculation unit 57 calculating a necessary gas flow command value Qt_t to be proportional to a target air excess rate λ during normal operation from the air-gas mixture flow Qm and the target air excess rate λ; and a revision calculation unit 58 revising the target air excess rate λ downward so as to satisfy required gas flow Qg_d=gas flow command value Qg_t if the required gas flow Qg_d is greater than the gas flow command value Qg_t.

Description

  The present invention relates to a control device and a control method for a gas engine, and a gas engine provided with the control device, in which a decrease in the rotational speed due to an increase in load is suppressed.

  In an independently operated power generation engine that is not linked to a commercial power system, such as a private power generator, the engine speed is directly the power frequency, so control to keep the engine speed constant to keep the power frequency constant. There is a need to do. At the same time, it is necessary to keep the air-fuel ratio (ratio of air and fuel) constant in order to achieve high efficiency and achieve the exhaust gas regulation value.

  Various control methods have been studied so far for control of gas engines that use gas such as LPG as fuel. As a typical example, a throttle valve is mainly used to improve responsiveness to load fluctuations. A method of controlling the engine speed and performing air-fuel ratio control with a gas flow rate control valve is known. That is, this is a method of determining the gas flow rate command value so that the air-fuel ratio matches the target value after adjusting the throttle valve opening so that the engine speed matches the target speed.

  With this control method, good response can be obtained for small load fluctuations, but there is a problem that the engine speed is greatly reduced for a large load increase in which the throttle is fully opened transiently. is there. This is because if the throttle is greatly opened and the differential pressure before and after the throttle is reduced, it becomes impossible to increase the flow rate of the air-fuel mixture even if the throttle is further opened, so the amount of gas flowing into the cylinder cannot be increased. This is because the engine output is insufficient.

  Due to this phenomenon, when the engine speed is greatly reduced during the single operation, the power supply frequency is lowered, which may adversely affect the connected electrical equipment. In order to solve this problem, the following methods are known.

  As a known method, there is a method of operating with a margin in the throttle valve opening. This method is a method in which the throttle is controlled by adjusting the throttle in preparation for load fluctuations, and a control allowance for the throttle valve opening is ensured. However, this method has a problem that the pressure loss due to the throttle increases because the throttle is throttled during steady operation, and the power generation efficiency (fuel consumption) of the engine deteriorates.

  Patent Document 1 proposes a method of increasing the gas flow rate so as to comprehend the nonlinearity in which the flow rate characteristic of the throttle valve is grasped in advance and the flow rate does not increase in a portion where the throttle valve opening is large.

  On the other hand, in an automobile engine whose output is controlled by a throttle valve, control is generally performed to thicken the fuel when the load increases (acceleration). In this control, the fuel injection amount is stored in a map having the accelerator opening, the engine speed, etc. as inputs, and the fuel is set to be concentrated in an operation region where the load is large.

Japanese Patent No. 4142477

  However, in the control method proposed in Patent Document 1, the flow rate characteristic of the throttle valve changes depending on environmental conditions and aging conditions, so that there is a possibility that compensation accuracy becomes a problem.

  On the other hand, in the engine engine control method, the engine is subjected to high load temporarily during acceleration or climbing, whereas the generator engine is based on steady operation at high load. When the control for thickening the fuel at a high load is applied to the engine, the steady fuel efficiency and exhaust gas performance tend to deteriorate. Since the problem with the power generation engine that is the subject of the present invention is not the magnitude of the load itself but the magnitude of the load input and the accompanying engine speed fluctuation, it is possible to apply the above-mentioned automobile engine control technology. Can not.

  The present invention has been made in view of such circumstances, and has a control device, a control method, and a control device for a gas engine that can suppress a decrease in engine speed due to an increase in engine load with a simple configuration. An object is to provide a gas engine provided.

  In order to solve the above problems, a gas engine control device according to the present invention is a gas engine control device that improves the response of the engine speed to load fluctuations in a gas engine operated by gas fuel, Based on the deviation between the engine speed and the target engine speed, a required gas flow rate calculation unit for calculating a required gas flow rate required to keep the engine speed constant, and a throttle valve opening according to the required gas flow rate. Throttle valve opening calculation unit for calculating, mixture flow rate calculation unit for calculating the mixture flow rate from the engine speed, intake pressure, intake air temperature, engine exhaust amount, etc., the mixture flow rate, and steady operation Gas flow rate required to match the target air excess ratio and / or the target air-fuel ratio from the target air excess ratio and / or the target air-fuel ratio at the time A gas flow rate command value calculation unit for calculating a command value; and, when the required gas flow rate is larger than the gas flow rate command value, the target excess air ratio and / or the required gas flow rate = the gas flow rate command value. And a correction calculation unit for correcting the target air-fuel ratio downward.

  In order to solve the above-mentioned problems, a gas engine control method according to the present invention is a gas engine control method for improving the response of the engine speed to load fluctuations in a gas engine operated by gas fuel. A required gas flow rate calculating step for calculating a required gas flow rate required to keep the engine rotational speed constant from a deviation between the engine rotational speed and the target engine rotational speed, and a throttle valve according to the required gas flow rate A throttle valve opening calculating step for calculating an opening; an air-fuel flow calculating step for calculating an air-fuel flow from the engine speed, intake pressure, intake air temperature, engine displacement, etc .; The target excess air ratio and / or the target air-fuel ratio in steady operation agrees with the target excess air ratio and / or the target air-fuel ratio. A gas flow rate command value calculating step for calculating a gas flow rate command value necessary for adjusting the required gas flow rate and the gas flow rate command value, and determining whether or not the required gas flow rate is greater than the gas flow rate command value. When the comparison determination step and the determination result in the comparison determination step are affirmative determination, the target excess air ratio and / or the target air-fuel ratio are corrected downward so that the required gas flow rate = the gas flow rate command value. A downward correction step.

  According to the gas engine control device and the gas engine control method configured as described above, the required gas flow rate calculation unit calculates the required gas flow rate necessary to keep the engine speed constant, and according to the required gas flow rate. The throttle valve opening calculation unit calculates the throttle valve opening. Further, the mixture flow rate is calculated by the mixture flow rate calculation unit.

  Further, the gas flow rate command value calculation unit calculates a gas flow rate command necessary for making the target air excess rate or the target air-fuel ratio equal to the target air excess rate or the target air-fuel ratio from the air-fuel mixture flow rate and the target air excess rate or target air-fuel ratio during steady operation. The value is calculated. Then, when the required gas flow rate is larger than the gas flow rate command value, the correction arithmetic unit corrects the target excess air ratio or the target air-fuel ratio downward so that the required gas flow rate becomes equal to the gas flow rate command value.

  When the target excess air ratio or the target air-fuel ratio decreases, the gas flow rate command value increases accordingly, so that the ratio of gas fuel in the mixture (air-fuel ratio) increases and the engine output improves. For this reason, it can suppress that an engine speed falls, when an engine load increases.

  The above control device (control method) can be implemented only by changing the software (programming), and no additional hardware is required, so the configuration is not complicated and the simple configuration is maintained. Can do.

  In addition, the flow rate characteristic of the throttle valve that changes depending on environmental conditions and aging conditions can be ignored and controlled. For this reason, the flow rate characteristics of the throttle valve are compared with the conventional method in which the flow rate characteristics of the throttle valve are grasped and the gas flow rate is increased so as to compensate for the non-linearity in which the flow rate does not increase when the throttle opening is large. Can be controlled easily and reliably.

  The control device for a gas engine according to the present invention further includes an ignition timing delay unit that delays the ignition timing of the gas engine when the target excess air ratio and / or the target air-fuel ratio is corrected downward. It is characterized by.

  As described above, when the target excess air ratio and / or the target air-fuel ratio is corrected downward and the ratio of the gas fuel in the mixture (air-fuel ratio) increases, knocking due to abnormal combustion is likely to occur. At this time, since the ignition timing of the engine is delayed by the ignition timing delay unit, the occurrence of knocking is suppressed.

  The control device for a gas engine according to the present invention further includes a fuel type correction unit that gives a fuel type correction coefficient to the target excess air ratio and / or the target air-fuel ratio according to the type and composition of the gas fuel. It is characterized by that.

  Since the gas fuel used in the gas engine has different types and components depending on the region, the theoretical air-fuel ratio in the gas engine also changes. In order to cope with this, a fuel type correction unit is provided to apply a correction coefficient to the target excess air ratio and the target air-fuel ratio in accordance with the type of gas fuel. As a result, the target excess air ratio and the target air-fuel ratio suitable for the type of gas fuel can be calculated, and the above-described control for suppressing the engine speed reduction can be stably performed.

  A gas engine according to the present invention includes the above-described control device. For this reason, the amount of decrease in engine speed due to an increase in engine load can be suppressed with a simple configuration.

As described above, according to the gas engine control device, the control method, and the gas engine including the control device according to the present invention, it is possible to suppress a decrease in engine speed due to an increase in engine load with a simple configuration. .
For this reason, especially when applied to a power generation engine, it is possible to prevent the engine speed, that is, the power supply frequency from fluctuating due to fluctuations in load.

1 is a schematic configuration diagram illustrating an example of a one-stage supercharging gas engine to which a control device according to the present invention can be applied. It is a schematic block diagram which shows an example of the gas engine of the two-stage supercharging system which can apply the control apparatus which concerns on this invention. It is a graph which shows the state where the amount of air-fuel mixture does not increase even if the opening amount of the throttle valve is large and the amount of air-fuel mixture increases, and a nonlinear region occurs in the gas flow rate. It is a functional block diagram of a control device concerning a 1st embodiment of the present invention. It is a flowchart which shows the control method which concerns on 1st Embodiment of this invention. (A), (b) shows the conventional engine characteristic, (c) is a graph which shows the engine characteristic of this invention. It is a functional block diagram of the control apparatus which concerns on 2nd Embodiment of this invention. It is a functional block diagram of a control device concerning a 3rd embodiment of the present invention. It is a functional block diagram of a control device concerning a 4th embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic configuration diagram showing an example of a one-stage supercharging gas engine to which a control device according to the present invention can be applied. This gas engine is for driving a generator (not shown), for example.

  In the gas engine 1, an intake port 5 that is opened and closed by an intake valve 4 and an exhaust port 7 that is opened and closed by an exhaust valve 6 are connected to a cylinder 3 in which a piston 2 slides. A combustion chamber 8 is defined between the cylinder 3 and the piston 2, and a spark plug 9 is provided in the combustion chamber 8.

  An intake manifold 11 is connected to the intake port 5, and a compressor 12c of the supercharger 12 is connected to the upstream end thereof. A throttle valve 14 and an intercooler 15 are connected to an intermediate portion of the intake manifold 11. A gas flow rate adjusting valve 18 for supplying gas fuel is connected to an intermediate portion of the intake pipe 17 connected to the compressor 12c, and an air cleaner 19 is connected to the upstream end.

  On the other hand, an exhaust manifold 22 is connected to the exhaust port 7, and a turbine 12t of the supercharger 12 is connected to the downstream end thereof. The compressor 12c and the turbine 12t of the supercharger 12 rotate together via a rotating shaft 12s. An exhaust pipe 24 is connected to the turbine 12 t, and a bypass exhaust valve 26 is provided in a bypass exhaust passage 25 connecting the exhaust pipe 24 and the exhaust manifold 22.

  In the gas engine 1 configured as described above, the air sucked from the air cleaner 19 is injected with gas fuel at the gas flow rate adjusting valve 18 to become a fuel mixture, compressed by the compressor 12 c of the supercharger 12, and intake The gas engine 1 is operated by being supercharged to the cylinder 3 through the manifold 11. The flow rate of the fuel mixture is adjusted by the throttle valve 14, and the compression heat is cooled by the intercooler 15.

  Further, the exhaust gas discharged from the cylinder 3 is supplied to the turbine 12t of the supercharger 12 through the exhaust manifold 22, and rotates the turbine 12t at high speed. This rotation drives the compressor 12c at high speed via the rotating shaft 12s, and continues the compression and supercharging of fresh air.

  In addition, as shown in FIG. 2, it is good also as the gas engine 101 of the two-stage supercharging system provided with 12 A of superchargers for low pressures, and the supercharger 12B for high pressures. In this example, a sub-throttle valve 29 is provided in a bypass intake passage 28 that directly connects the intake pipe 17 and the intake manifold 11 without passing through the superchargers 12A and 12B. On the other hand, a bypass exhaust passage 25a and a bypass exhaust valve 26a connecting between the superchargers 12A and 12B and the exhaust manifold 22 are added on the exhaust side.

  In such gas engines 1 and 101, the engine speed is controlled by the throttle valve 14 and the air-fuel ratio control is performed by the gas flow rate control valve 18 in order to improve the response to the load fluctuation. . That is, the control for determining the gas flow rate command value to the gas flow rate adjusting valve 18 so that the air-fuel ratio matches the target value after adjusting the opening degree of the throttle valve 14 so that the engine speed matches the target speed. It has become a method.

  However, with this control method, good responsiveness can be obtained for small load fluctuations, but the engine speed greatly decreases for a large load increase in which the throttle valve 14 is transiently fully opened. There is a problem. This is because if the throttle valve 14 is greatly opened and the differential pressure before and after the throttle valve 14 is reduced, it becomes impossible to increase the flow rate of the air-fuel mixture even if the throttle valve 14 is opened further. This is because the amount of gas cannot be increased and the engine output is insufficient.

  For this reason, as shown in FIG. 3, even if the opening degree of the throttle valve 14 is increased, the flow rate of the air-fuel mixture does not increase, and the flow rate of the air-fuel mixture does not increase. A non-linear region NL occurs in the flow rate, and the engine output does not increase. As a result, the engine speed tends to drop and stall. The control device 51 shown in FIG. 4 solves such a problem.

  The control device 51 includes a required gas flow rate calculation unit 54 (PL controller), a throttle valve opening calculation unit 55 (P gain), an air-fuel mixture flow rate calculation unit 56, a gas flow rate command value calculation unit 57, and a correction calculation. Part 58.

  The required gas flow rate calculation unit 54 is a functional unit that calculates a required gas flow rate Qg_d necessary for keeping the engine speed constant from the deviation between the engine speed and the target engine speed.

  The throttle valve opening calculation unit 55 is a functional unit that calculates the opening of the throttle valve 14 in accordance with the required gas flow rate Qg_d.

ここで、pinは吸気圧力［Pa］、即ちインテークマニホルド１１の内圧、Tinはインテークマニホルド１１の温度［K］、ηvは体積効率、Neはエンジン回転数［rpm］、Veはエンジン排気量［m3］、Rは気体定数［Pa・m3/kg/K］である。 The air-fuel mixture flow rate calculation unit 56 mixes the engine speed, the intake pressure, that is, the internal pressure (negative pressure) in the intake manifold 11 between the throttle valve 14 and the cylinder 3, the intake air temperature, the engine displacement, and the like. This is a functional unit that calculates the air flow Qm. This air-fuel mixture flow rate Qm [m3 / sec] is derived by the following equation (1).

Here, pin is the intake pressure [Pa], that is, the internal pressure of the intake manifold 11, Tin is the temperature [K] of the intake manifold 11, ηv is volumetric efficiency, Ne is the engine speed [rpm], Ve is the engine displacement [m3 ] And R are gas constants [Pa · m3 / kg / K].

The gas flow rate command value calculation unit 57 is a functional unit that calculates a gas flow rate command value Qg_t required to match the target air excess rate λ from the mixture flow rate Qm and the target air excess rate λ during steady operation. is there. This gas flow rate command value Qg_t is derived by the following equation (2).

ここで、λdは要求空気過剰率、λtは空気過剰率指令値、AFRthは理論空燃比である。 The correction calculation unit 58 is a functional unit that downwardly corrects the target excess air ratio λ so that the required gas flow rate Qg_d = the gas flow rate command value Qg_t when the required gas flow rate Qg_d is larger than the gas flow rate command value Qg_t. . The correction value Δλ for this downward correction is derived from the following equation (3).

Here, λd is the required excess air ratio, λt is the excess air ratio command value, and AFRth is the stoichiometric air-fuel ratio.

  In this control device 51, as described above, when the engine load increases and the opening of the throttle valve 14 increases and the air-fuel mixture cannot be increased, the target value of the excess air ratio λ is decreased. The gas concentration (air / fuel ratio) is increased to control the required gas flow rate. For example, in this embodiment, the target excess air ratio λ, which is the ratio between the actual air amount and the theoretical air amount, is used as the control amount, but the air flow ratio (AFR) that is the ratio between the actual air amount and the fuel is controlled. It is good as quantity. With this method, it is possible to reduce the decrease in the engine speed with respect to the load increase without increasing the pressure loss in the throttle valve 14.

  Next, the operation of the control device 51 will be described with reference to the flowchart of FIG.

When this control starts, first, in step S1, the required gas flow rate calculation unit 54 calculates the required gas flow rate Qg_d (required gas flow rate calculation step).
Next, in step S2, the throttle valve opening calculation unit 55 calculates the opening of the throttle valve 14 (throttle valve opening calculation step).
Next, in step S3, the mixture flow rate Qm is calculated by the mixture flow rate calculation unit 56 (mixture flow rate calculation step).

  Further, in step S4, the gas flow rate command value calculation unit 57 causes the gas flow rate command value necessary to match the target air excess rate λ from the mixture flow rate Qm and the target air excess rate λ during steady operation. Qg_t is calculated (gas flow rate command value calculation step).

  In step S5, the correction calculation unit 58 compares the required gas flow rate Qg_d with the gas flow rate command value Qg_t, and determines whether or not the required gas flow rate Qg_d> the gas flow rate command value Qg_t. That is, it is determined whether or not a non-linear region NL is generated in the gas flow rate also shown in the graph of FIG. 3 (comparison determination step).

  If the determination result in step S5 is affirmative (Yes), that is, the rotational speed deviation of the gas engine 1 (101) is large and the required gas amount is large, that is, the opening of the throttle valve 14 is large, so the mixture flow rate does not increase. In this case, the process proceeds to step S6, and the target excess air ratio λ is corrected downward so that the required gas flow rate Qg_d = gas flow rate command value Qg_t (downward correction step). The correction value Δλ of the target excess air ratio λ at this time is derived from the above-described equation (3).

Thereafter, the process proceeds to step S7, where the throttle valve 14 controls the rotation speed of the gas engine 1 (101) and the gas flow rate adjustment valve 18 controls the air-fuel ratio. Then, the routine of steps S1 to S7 is repeated.
If the determination result in step S5 is negative (No), that is, if the rotational speed deviation of the gas engine 1 (101) is small and the required gas amount is small, the process proceeds to step S7 and the operation is continued. The

  According to the control device 51 and the control method, the required gas flow rate calculation unit 54 calculates the required gas flow rate Qg_d required to keep the engine speed constant, and the throttle valve opening degree is determined according to the required gas flow rate Qg_d. The opening of the throttle valve 14 is calculated by the calculation unit 55. Further, the air-fuel mixture flow rate calculation unit 56 calculates the air-fuel mixture flow rate Qm.

  Further, the gas flow rate command value calculation unit 57 calculates the gas flow rate command value Qg_t necessary to match the target air excess rate λ from the mixture flow rate Qm and the target air excess rate λ during steady operation. The Then, when the required gas flow rate Qg_d is larger than the gas flow rate command value Qg_t, the correction calculation unit 58 calculates the correction value Δλ so that the required gas flow rate Qg_d becomes equal to the gas flow rate command value Qg_t, and the target air excess The rate λ is corrected downward.

  When the target excess air ratio λ decreases, the gas flow rate command value Qg_t increases accordingly, so the ratio of gas fuel (air-fuel ratio) in the mixture increases and the engine output improves. For this reason, it can suppress that an engine speed falls, when an engine load increases.

FIGS. 6A and 6B show the characteristics of a conventional gas engine, and FIG. 6C is a graph showing the characteristics of the gas engine of the present embodiment.
As shown in FIG. 6 (a), even in a conventional gas engine, when the load increase is small, the air-fuel mixture / gas flow rate can be increased by increasing the throttle valve opening, and the engine speed The decline of was small.

  However, when the increase in load is large, as shown in FIG. 6B, the throttle valve opening is fully opened (point A), or the throttle opening is large, so the opening is further reduced. Even if it is increased, an increase in the air-fuel mixture flow rate cannot be expected (point B). Conventionally, the target excess air ratio λ remains constant (point C). For this reason, the gas flow rate is not greatly increased (D point). As a result, the engine output is insufficient, the engine speed is greatly reduced (point E), and there is a concern that the engine stalls.

  On the other hand, in the gas engine of the present embodiment shown in FIG. 6 (c), when the load increases greatly, the throttle valve opening degree is fully opened (point A) or mixed with the increase of the throttle opening degree. The point where the air flow rate does not increase (point B) is the same as in the prior art. However, when the target excess air ratio λ is corrected downward (point F), the ratio (air-fuel ratio) of the gas fuel in the air-fuel mixture relatively increases (point G). For this reason, the engine output is improved, and as a result, the amount of decrease in the engine speed is reduced (H point). Therefore, when generating power by driving a generator with a gas engine, it is possible to prevent power supply frequency from fluctuating and perform stable power generation.

  The control device 51 and the control method described above can be implemented only by software change (programming), and no additional hardware is required, so that the configuration is not complicated and the simple configuration is maintained. Can do. Note that no additional hardware or the like is required even for the two-stage supercharging gas engine 101 shown in FIG.

  In addition, the flow rate characteristic of the throttle valve 14 that changes depending on environmental conditions and aging conditions can be ignored and controlled. For this reason, control is easier than the conventional method of grasping the flow rate characteristics of the throttle valve 14 and increasing the gas flow rate so as to compensate for the non-linearity in which the flow rate does not increase in a portion where the throttle opening is large. And it can be performed reliably.

  By the way, when the engine load increases and the downward correction of the target excess air ratio λ is performed, the correction amount (Δλ) of the target excess air ratio λ becomes 0 by the following process after a while. Return to rate λ.

  That is, after the load is increased, the air-fuel mixture flow rate increases as the engine speed returns from the drop. As a result, the exhaust energy increases, the energy flowing into the turbine 12t increases, the compressor work increases, the boost pressure increases, and the mixture flow rate increases, and the mixture flow rate and boost pressure increase. I will do it. Then, the gas flow rate command value increases as the mixture flow rate increases due to this cycle, and as a result, the gas flow rate command value Qg_t = required gas flow rate Qg_d, so that the steady state is restored and the target excess air ratio λ is corrected. The value Δλ becomes zero.

  For this reason, the period during which the air-fuel mixture becomes rich is only a very short time of several seconds to several tens of seconds from the time when the load increases. Therefore, there is no concern that the fuel consumption of the gas engine increases and the running cost increases.

[Second Embodiment]
FIG. 7 is a functional block diagram of a control device according to the second embodiment of the present invention. The control device 61 differs from the control device 51 of the first embodiment shown in FIG. 4 in that the control device 51 uses the excess air ratio λ, which is the ratio of the actual air amount and the theoretical air amount, as the control amount. In the control device 61, the air-fuel ratio (Air Flow Ratio: AFR), which is the ratio between the actual air amount and the fuel, is used as the control amount.

For this reason, the gas flow rate command value calculation unit 57 calculates the gas flow rate command value Qg_t based on the target air-fuel ratio AFR and the air-fuel mixture flow rate Qm in the steady state. This gas flow rate command value Qg_t is derived by the following equation (4).

Further, when the required gas flow rate Qg_d is larger than the gas flow rate command value Qg_t, the correction calculation unit 58 corrects the target air-fuel ratio AFR downward so that the required gas flow rate Qg_d = the gas flow rate command value Qg_t. The correction value ΔAFR for this downward correction is derived from the following equation (5).

Here, AFRd is a required air-fuel ratio, and AFRt is an air-fuel ratio command value.
Since other parts are the same as those of the control device 51 of the first embodiment, the same reference numerals are given to the respective parts and the description thereof is omitted.

  According to this control device 61, the required gas flow rate calculation unit 54 calculates the required gas flow rate Qg_d necessary for keeping the engine speed constant, and the throttle valve opening calculation unit 55 according to the required gas flow rate Qg_d. Thus, the opening degree of the throttle valve 14 is calculated. Further, the air-fuel mixture flow rate calculation unit 56 calculates the air-fuel mixture flow rate Qm.

  Further, the gas flow rate command value calculation unit 57 calculates a gas flow rate command value Qg_t necessary to match the target air-fuel ratio AFR from the air-fuel mixture flow rate Qm and the target air-fuel ratio AFR during steady operation. Then, when the required gas flow rate Qg_d is larger than the gas flow rate command value Qg_t, the correction value ΔAFR is calculated by the correction calculation unit 58 so that the required gas flow rate Qg_d becomes equal to the gas flow rate command value Qg_t, and the target air-fuel ratio AFR is revised downward.

  When the target air-fuel ratio AFR decreases, the gas flow rate command value Qg_t increases accordingly, so that the ratio of gas fuel in the mixture (air-fuel ratio) increases and the engine output improves. For this reason, it can suppress that an engine speed falls, when an engine load increases. Therefore, when generating power by driving a generator with a gas engine, it is possible to prevent power supply frequency from fluctuating and perform stable power generation.

[Third Embodiment]
FIG. 8 is a functional block diagram of a control device according to the third embodiment of the present invention. The control device 71 is different from the control device 51 of the first embodiment shown in FIG. 4 in that an ignition timing delay unit 72 is provided. In addition, although the knock sensor 73 is provided with the ignition timing delay part 72, the knock sensor 73 is also equipped with a general engine, and it is not something new.

  The ignition timing delay unit 72 delays the ignition timing of the gas engine 1 (101) when the engine load increases rapidly and the target excess air ratio λ (or the target air-fuel ratio AFR) is corrected downward as described above. Is a functional part that works like For example, the ignition timing delay amount (from the retard map having the target air excess ratio λ correction amount (or the target air-fuel ratio AFR correction amount shown in FIG. 7) determined by the above-described logic and the intake manifold 11 pressure as inputs is input. (Retard amount) is determined, added to the other retard amounts, and transmitted to the ignition device. In the retard map, the larger the correction amount of the target excess air ratio λ, the greater the retard amount, so that knocking due to a decrease in the in-cylinder target excess air ratio λ is suppressed. Since the ignition timing is delayed when the air-fuel mixture becomes rich in this way, knocking can be suppressed and smooth operation can be performed.

[Fourth Embodiment]
FIG. 9 is a functional block diagram of a control device according to the fourth embodiment of the present invention. The control device 81 is different from the control device 51 of the first embodiment shown in FIG. 4 in that a fuel type correction unit 82 is provided. The fuel type correction unit 82 is a functional unit that gives a fuel type correction coefficient to the target excess air ratio λ and the target air-fuel ratio AFR according to the type and components of the gas fuel.

  Since gas fuel used in a gas engine has different types and components depending on regions, the theoretical air-fuel ratio (AFRth) in the gas engine also changes. In order to cope with this, the fuel type correction unit 82 applies a correction coefficient to the target excess air ratio and the target air-fuel ratio according to the type of gas fuel. As a result, the target excess air ratio and the target air-fuel ratio suitable for the type of gas fuel can be calculated, and the above-described control for suppressing the engine speed reduction can be stably performed.

  The theoretical air-fuel ratio is corrected from the component of the gas fuel, and the gas flow rate command value calculation and the target excess air ratio λ correction calculation are performed using the corrected theoretical air-fuel ratio. Alternatively, a correction coefficient corresponding to each type of gas fuel may be stored in the fuel type correction unit 82 in advance, and the operator of the gas engine may be switched. When the target air-fuel ratio AFR in the steady state is used as the control amount, as in the control device 61 shown in FIG. 7, the target air-fuel ratio AFR in the steady state can be changed to correspond to the type of gas fuel. Can do.

  As described above, the gas engine control devices 51, 61, 71, 81 according to the above-described embodiment, the gas engine control method, and the gas engine 1, 101 including the control devices 51, 61, 71, 81 are provided. Accordingly, it is possible to suppress a decrease in engine speed due to an increase in engine load with a very simple configuration. For this reason, especially when applied to a power generation engine, it is possible to prevent the engine speed, that is, the power supply frequency, from fluctuating due to fluctuations in the load, and to perform stable power generation.

  It should be noted that the present invention is not limited to the configuration of the embodiment described above, and can be appropriately modified or improved within the scope not departing from the gist of the present invention. The form is also included in the scope of the right of the present invention.

  For example, it is good also as a structure which combined said some embodiment. Moreover, although the said embodiment demonstrated as a gas engine for electric power generation, this technique is applicable also to motive power engines, such as a vehicle and a ship. In particular, it is also suitable for vehicles and ships that generate electricity with a gas engine and run or sail with a motor.

1,101 Gas engine 11 Intake manifold 12 Supercharger 14 Throttle valve 51, 61, 71, 81 Control device 54 Required gas flow rate calculation unit 55 Throttle valve opening calculation unit 56 Mixture flow rate calculation unit 57 Gas flow rate command value calculation unit 58 Correction calculation unit 72 Ignition timing delay unit 82 Fuel type correction unit S1 Required gas flow rate calculation step S2 Throttle valve opening calculation step S3 Mixture flow rate calculation step S4 Gas flow rate command value calculation step S5 Comparison determination step S6 Downward correction step
AFR target air-fuel ratio
AFRth Theoretical air / fuel ratio
Qg_d Required gas flow rate
Qg_t Gas flow command value
Qm Mixture flow rate λ Target air excess rate

Claims (5)

In a gas engine operated by gas fuel, a control device for a gas engine that improves the responsiveness of engine speed to load fluctuations,
A required gas flow rate calculation unit for calculating a required gas flow rate required to keep the engine speed constant from a deviation between the engine speed and the target engine speed;
A throttle valve opening calculator that calculates the throttle valve opening in accordance with the required gas flow rate;
A mixture flow rate calculation unit for calculating a mixture flow rate from the engine speed, intake pressure, intake temperature, engine displacement, etc .;
A gas for calculating a gas flow rate command value required to match the target excess air ratio and / or the target air-fuel ratio from the mixed gas flow rate and the target excess air ratio and / or the target air-fuel ratio in steady operation A flow rate command value calculator,
When the required gas flow rate is greater than the gas flow rate command value, a correction calculation unit that downwardly corrects the target excess air ratio and / or the target air-fuel ratio so that the required gas flow rate = the gas flow rate command value;
A control device for a gas engine, comprising:   2. The gas engine according to claim 1, further comprising an ignition timing delay unit that delays an ignition timing of the gas engine when the target excess air ratio and / or the target air-fuel ratio is corrected downward. Control device.   3. The fuel type correction unit according to claim 1, further comprising a fuel type correction unit that applies a fuel type correction coefficient to the target excess air ratio and / or the target air-fuel ratio in accordance with a type and a component of the gas fuel. Gas engine control device.   A gas engine comprising the control device for a gas engine according to claim 1. In a gas engine operated by gas fuel, a gas engine control method for improving responsiveness of engine speed to load fluctuations,
A required gas flow rate calculating step for calculating a required gas flow rate required to keep the engine speed constant from a deviation between the engine speed and a target engine speed;
A throttle valve opening calculation step for calculating a throttle valve opening according to the required gas flow rate;
A mixture flow rate calculating step for calculating a mixture flow rate from the engine speed, intake pressure, intake air temperature, engine displacement, etc .;
A gas for calculating a gas flow rate command value required to match the target excess air ratio and / or the target air-fuel ratio from the mixed gas flow rate and the target excess air ratio and / or the target air-fuel ratio in steady operation Flow rate command value calculation step;
A comparison determination step of comparing the required gas flow rate with the gas flow rate command value and determining whether the required gas flow rate> the gas flow rate command value;
When the determination result in the comparison determination step is affirmative determination, a downward correction step of correcting the target excess air ratio and / or the target air-fuel ratio downward so that the required gas flow rate = the gas flow rate command value;
A control method for a gas engine, comprising:

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