JP4247842B2 - Gas engine knocking control device - Google Patents

Description

  The present invention relates to a knocking control device for a gas engine whose main fuel is a gas fuel such as natural gas or city gas.

  In recent years, a clean energy source has been demanded from the viewpoint of environmental conservation. From this viewpoint, power generation facilities using a gas engine whose main fuel is a gas fuel such as natural gas or city gas is becoming widespread.

  However, due to the characteristics of the fuel, it is relatively difficult to operate this gas engine in a stable state. To perform stable and highly efficient operation, abnormal combustion such as knocking or misfiring is promoted early. It is necessary to detect and avoid this.

In order to detect this abnormal combustion at an early stage, there is a device that detects knocking using a vibration sensor attached to a cylinder (see, for example, Patent Document 1). In addition to this, a detection method and a detection device for early detection of knocking are also disclosed (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 08-177603 JP 2005-42583 A

  However, the inventions described in Patent Document 1 and Patent Document 2 described above are for determining whether or not knocking has actually occurred based on the generation signal, and for coping with it early. Is not predicted in advance, that is, before occurrence, to prevent the occurrence of knocking. And once knocking occurs, it may lead to engine damage.

  The present invention has been made to solve such problems, and can prevent the occurrence of knocking of the gas engine in advance, and can perform a stable and highly efficient operation of the gas engine. It is an object of the present invention to provide a knocking control device.

  In order to solve the above problems, the means employed by the present invention includes a knock degree detection means for detecting the knock degree, which is the degree of knocking, for each cylinder, and the knock degree detected by the knock degree detection means has a predetermined knock degree. In a knock control device for a gas engine, comprising: a controller that calculates an evaluation knocking frequency, which is an exceeding frequency; and a knocking prevention unit capable of performing measures for preventing the occurrence of knocking for each cylinder based on an instruction from the controller The controller is to cause the knocking prevention means to take measures for preventing the occurrence of knocking for each cylinder when the numerical value related to the evaluation knocking frequency exceeds a predetermined frequency.

  Thus, according to the knock control device for a gas engine of the present invention, when the occurrence frequency of the evaluation knock exceeds a predetermined frequency, the controller prevents the knock prevention means from occurring for each cylinder. Since the measures are taken, a knock prevention measure can be taken in advance for the cylinder where the possibility of occurrence of knocking is increased, and the occurrence thereof can be prevented in advance.

  This evaluation knocking is a virtual knocking state in a broad sense, including not only knocking that damages the engine but also a precursor phenomenon of knocking in particular. By changing the above-mentioned predetermined knock degree, the magnitude of the evaluation knocking, that is, the degree of knocking of the target for which knock prevention measures are taken can be freely adjusted, and by changing the above-mentioned predetermined frequency, The frequency at which the knocking prevention measure is activated can be freely adjusted. Therefore, by appropriately setting the predetermined knock degree and the predetermined frequency, the gas engine can be operated stably and efficiently without causing knocking.

  Preferably, the knocking prevention means includes a gas injection amount adjusting mechanism capable of adjusting a gas injection amount of fuel for each cylinder, and the controller uses the evaluation knocking frequency as the numerical value and the evaluation knocking frequency exceeds a predetermined frequency. The gas injection amount adjusting mechanism is instructed to reduce the gas injection amount of the cylinder whose evaluation knocking frequency exceeds a predetermined frequency.

  Preferably, the engine has a plurality of cylinders, the knocking prevention means includes a gas injection amount adjustment mechanism capable of adjusting a gas injection amount of fuel for each cylinder, and the controller evaluates the plurality of cylinders. When the average value of the knocking frequency is calculated and the difference value obtained by subtracting the average value from the evaluation knocking frequency is the above numerical value, and the difference value exceeds the predetermined frequency, the difference value is calculated with respect to the gas injection amount adjusting mechanism. An instruction is given to reduce the gas injection amount of the cylinder exceeding the predetermined frequency.

  In any of the above preferred embodiments, by reducing the gas injection amount in this way, the fuel concentration in the unburned gas mixture in the cylinder can be particularly lowered, and the occurrence of knocking can be prevented in advance and reliably. can do.

  More preferably, the controller calculates an average value of the evaluation knocking frequencies of the plurality of cylinders, and when the difference value obtained by subtracting the evaluation knocking frequency from the average value exceeds a predetermined frequency, the gas injection amount adjustment mechanism Is instructed to increase the gas injection amount of the cylinder whose difference value exceeds a predetermined frequency.

  That is, when there is a cylinder that is particularly unlikely to cause knocking compared to other cylinders, the balance between the cylinders is adjusted to always maintain the average value at an appropriate value.

Preferably, the gas engine is a pilot fuel ignition type gas engine, the knocking prevention means includes a pilot fuel injection timing adjustment mechanism for adjusting a pilot fuel injection timing, and the controller sets the evaluation knocking frequency as the numerical value. When the evaluation knocking frequency exceeds a predetermined frequency, the pilot fuel injection timing adjustment mechanism is instructed to delay the pilot fuel injection timing of the cylinder whose evaluation knocking frequency exceeds the predetermined frequency.
Or
The gas engine is a spark ignition type gas engine, and the knocking prevention means includes a spark ignition timing adjustment mechanism for adjusting a spark ignition timing, and the controller uses the evaluation knocking frequency as the numerical value and the evaluation knocking frequency is predetermined. When the frequency is exceeded, the spark ignition timing adjusting mechanism is instructed to delay the spark ignition timing of the cylinder whose evaluation knocking frequency exceeds a predetermined frequency.

Preferably, the engine is a pilot fuel ignition type gas engine having a plurality of cylinders, the knocking preventing means includes a pilot fuel injection timing adjusting mechanism for adjusting a pilot fuel injection timing, and the controller includes a plurality of cylinders. When the average value of the evaluation knocking frequency is calculated and the difference value obtained by subtracting the average value from the evaluation knocking frequency is the above numerical value, and the difference value exceeds the predetermined frequency, the pilot fuel injection timing adjustment mechanism is Instructing to delay the pilot fuel injection timing of the cylinder in which this difference value exceeds a predetermined frequency,
Or
The engine is a spark ignition type gas engine having a plurality of cylinders, and the knocking prevention means includes a spark ignition timing adjusting mechanism for adjusting a spark ignition timing, and the controller is configured to calculate an average of evaluation knocking frequencies of the plurality of cylinders. When the difference value exceeds the predetermined frequency with the difference value obtained by subtracting the average value from the evaluation knocking frequency as the above numerical value, this difference value is set to the predetermined frequency for the spark ignition timing adjustment mechanism. Instruct to delay the spark ignition timing of the cylinder that has exceeded.

  In any of the above preferred embodiments, in the pilot fuel ignition type gas engine, the ignition timing of the air-fuel mixture is delayed by delaying the pilot fuel injection timing, and in the spark ignition type gas engine, the spark ignition timing is set. By delaying, the ignition timing of the air-fuel mixture is delayed, thereby suppressing the pressure increase in the cylinder in particular and suppressing the temperature increase of the unburned air-fuel mixture. Thereby, the occurrence of knocking can be prevented in advance and reliably.

More preferably, the controller calculates an average value of the evaluation knocking frequencies of the plurality of cylinders, and when the difference value obtained by subtracting the evaluation knocking frequency from the average value exceeds a predetermined frequency, the pilot fuel injection timing adjustment mechanism Instructing the pilot fuel injection timing of the cylinder whose difference value exceeds a predetermined frequency to be advanced,
Or
The controller calculates an average value of the evaluation knocking frequencies of a plurality of cylinders, and when the difference value obtained by subtracting the evaluation knocking frequency from the average value exceeds a predetermined frequency, this difference is given to the spark ignition timing adjustment mechanism. An instruction is given to advance the spark ignition timing of the cylinder whose value exceeds a predetermined frequency.

  That is, when there is a cylinder that is particularly unlikely to cause knocking compared to other cylinders, the balance between the cylinders is adjusted to always maintain the average value at an appropriate value.

  The knock control device for a gas engine according to the present invention includes a knock degree detection unit that detects a knock degree, which is a degree of knocking, for each cylinder, and an evaluation knock that is a frequency at which the knock degree detected by the knock degree detection unit exceeds a predetermined knock degree. In a knock control device for a gas engine, comprising: a controller for calculating a frequency; and a knocking prevention device capable of taking measures for preventing the occurrence of knocking for each cylinder based on an instruction from the controller. When the numerical value related to the frequency exceeds a predetermined frequency, the knocking prevention means takes measures for preventing the occurrence of knocking for each cylinder, so that the occurrence of knocking of the gas engine can be prevented in advance. Stable and highly efficient operation , It exhibits the excellent effect that.

  The best mode for carrying out the invention of the knocking control device for a gas engine according to the present invention will be described in detail with reference to FIGS.

FIG. 1 shows one (j-th) cylinder 2 of a multi-cylinder (L-cylinder) gas engine 1. An intake valve 6 is interposed on the intake side of the cylinder 2 and an intake pipe 6 is disposed on the exhaust side. Exhaust pipes 10 are connected to each other through a valve 8. The intake pipe 6 is connected to the intake main pipe 12 and receives supply of external air.

  A fuel gas pipe 14 is connected to the intake pipe 6 between the intake valve 4 and the intake main pipe 12, and the fuel gas pipe 14 is connected to the fuel gas main pipe 16 to receive the supply of fuel gas. A fuel gas injection valve 18 is inserted on the intake pipe 6 side of the fuel gas pipe 14. The fuel gas is injected into the intake pipe 6 through the fuel gas injection valve 18, and an air-fuel mixture of the injected fuel gas and external air is supplied into the cylinder 2 through the intake valve 4.

  A pilot fuel injection valve 20 is attached to the cylinder 2 of the gas engine 1. In the gas engine 1, a lean burn system is becoming mainstream in order to reduce nitrogen oxides (NOx) in exhaust gas and improve fuel efficiency, and supercharging intake air in order to improve output In many cases, the in-cylinder pressure of the gas engine is increased. From the viewpoint of effective energy use, some gas engines use low-calorie special gases such as digestion gas generated from sewage treatment plants and biomass gas made from dust and waste as the main fuel. is there.

  In this way, under conditions where the in-cylinder pressure is high or the main fuel is a low-calorie special gas, an ignition method capable of generating large ignition energy is required to achieve stable ignition of the main fuel. It came to be. For this reason, an ignition system by pilot fuel injection that generates ignition energy several thousand times that of a spar plug is becoming mainstream from a spark ignition system by a general spar plug, and this pilot fuel injection is performed by a pilot fuel injection valve 20. Done.

  The pilot fuel injection valve 20 described above is connected to the common rail 24 via the fuel pipe 22. The common rail 24 is for supplying high-pressure liquid fuel to the pilot fuel injection valve 20 of each cylinder. A knock sensor 26 for monitoring the occurrence of knocking is attached to the head of each cylinder 2. Examples of the knock sensor 26 include a sensor that detects the occurrence of knocking by measuring the vibration of the cylinder 2.

  Knock sensor 26 is electrically connected to engine controller 40 via combustion diagnostic unit 28. The pilot fuel injection valve 20 described above is electrically connected to the engine controller 40 via the pilot fuel injection valve driver 30 and receives a command related to pilot fuel injection from the engine controller 40.

  The fuel gas injection valve 18 described above is electrically connected to the engine controller 40 via the fuel gas injection valve driver 32, and receives a command relating to fuel gas injection from the engine controller 40. In addition, the engine controller 40 receives engine output, crank angle, TDC, crank rotational speed, crank phase, and the like.

  Next, the operation of the knocking control device for a gas engine according to the present invention will be described with reference to FIGS.

  A knock sensor 26 monitors the occurrence of knocking in each cylinder 2. Specifically, knock sensor 26 measures the vibration of jth (j = 1 to L) cylinder 2. Then, the combustion diagnosis unit 28 converts the magnitude of vibration measured by the knock sensor 26 into a numerical value in the range of 0 to 1 as the knock degree k of the j-th cylinder 2.

The engine controller 40 detects the knock degree k of the j-th cylinder 2 from the combustion diagnosis unit 28 (step S2), and determines whether or not the knock degree k exceeds a preset threshold value ko (predetermined knock degree). (Step S4). This threshold value ko is set, for example, as a numerical value of about 0.6, and in this case, about 60% of the maximum knocking (k = 1) is set as the evaluation knocking subject to the following preventive measures. Note that an example of the method of calculating the knock degree k is disclosed in the above-described Patent Document 2, and thus the description thereof is omitted.

  If the determination result in step S4 is affirmative (Yes), the number of evaluation knocking occurrences is counted by the following equation (1), assuming that the evaluation knocking has occurred once (step S6).

K i = K i +1 (1)
After step S8 is executed or when the determination result in step S4 is negative (No), the number of cycles is counted by the following equation (2) (step S8).

C = C + 1 (2)
Next, it is determined whether or not the cycle number C has reached the predetermined cycle number Co (step S10). If the determination result in step S10 is negative, that is, the cycle number C has reached the predetermined cycle number Co. If not, the above steps S2 and after are repeated.

  On the other hand, if the determination result in step S10 is affirmative, that is, if the cycle number C reaches the predetermined cycle number Co, the evaluation knocking frequency Fj of the j-th cylinder 2 is calculated by the following equation (3) (step S12). ).

Fj = ΣKi / (n · Co) (3)
However, ΣKi = K1 + K2 +... + K (n−1) + Kn
Here, ΣKi is an integrated value of the number of evaluation knocking occurrences for the j-th cylinder during n predetermined cycles.
Next, the average value Fm of the evaluation knocking frequencies of all cylinders is calculated, and the absolute value of the difference (Fj−Fm) between the evaluation knocking frequency Fj of the jth cylinder 2 and the average value Fm of the evaluation knocking frequencies of all the cylinders is calculated. Then, it is determined whether or not a preset threshold value F1 (predetermined frequency) is exceeded (step S14).

  Alternatively, it is determined whether or not the evaluation knocking frequency Fj of the j-th cylinder 2 exceeds a preset threshold value F2 (predetermined frequency) (step S14). Which of the relative determination method with respect to the average value Fm of the evaluation knocking frequencies of all the cylinders or the absolute determination method based on the evaluation knocking frequency Fj itself is appropriately determined according to the characteristics of the engine 1 or the like.

  If the determination result in step S14 is affirmative, that is, if it is determined that the evaluation knocking frequency Fj of the jth cylinder 2 is relatively or absolutely large and there is a possibility of occurrence of knocking to a certain extent, the engine The controller 40 takes the following measures.

  When the difference value (Fj−Fm) between the evaluation knocking frequency Fj of the jth cylinder 2 and the average value Fm of the evaluation knocking frequencies of all the cylinders exceeds the threshold value F1, or the evaluation knocking frequency Fj of the jth cylinder 2 is the threshold value F2. Is exceeded, the fuel gas injection valve driver 32 is actuated to reduce the valve opening period of the fuel gas injection valve 18 of the jth cylinder 2, and the injection amount of the fuel gas mixed with the intake air is reduced (step S16). ).

  Combustion of a gas engine is generally a premixed combustion method. In this premixed combustion method, combustion is started by ignition by pilot injection or spark ignition, and then combustion proceeds by spark propagation. If combustion progresses by spark propagation to the end, normal combustion is achieved, but the unburned air-fuel mixture spontaneously ignites during the combustion process, and combustion may occur before the flame propagates. This is a phenomenon called knocking.

Factors involved in the occurrence of knocking include the fuel concentration in the unburned mixture, the temperature of the unburned mixture, the reaction time until self-ignition, and the higher the fuel concentration in the unburned mixture, the less The higher the temperature of the fuel mixture and the longer the reaction time until self-ignition, the more likely knocking occurs.

  By reducing the fuel gas injection amount in step S16, the fuel concentration in the unburned gas mixture in the cylinder can be lowered, and the occurrence of knocking in the jth cylinder 2 can be prevented in advance and reliably. .

  At the same time, the engine controller 40 operates the pilot fuel injection valve driver 30 to delay the pilot fuel injection timing of the pilot fuel injection valve 20 of the jth cylinder 2 (step S18). Due to the delay of the pilot fuel injection timing, the ignition timing of the air-fuel mixture is delayed. In particular, the pressure increase in the cylinder is suppressed, and the temperature increase of the unburned air-fuel mixture is suppressed. This also makes it possible to prevent knocking of the jth cylinder 2 in advance and reliably.

  As described above, in the present embodiment, since the decrease in the valve opening period of the fuel gas injection valve 18 and the delay of the pilot fuel injection timing described above are performed simultaneously for the jth cylinder 2, The occurrence of knocking can be prevented more reliably.

  On the other hand, when the difference value (Fm−Fj) obtained by subtracting the evaluation knocking frequency Fj of the jth cylinder 2 from the average value Fm of the evaluation knocking frequencies of all the cylinders exceeds the above-described threshold value F1, The fuel gas injection valve driver 32 is actuated to increase the valve opening period of the fuel gas injection valve 18 of the j-th cylinder 2 and increase the injection amount of the fuel gas mixed with the intake air (step S16). Further, the pilot fuel injection valve driver 30 is operated to advance the pilot fuel injection timing of the pilot fuel injection valve 20 of the jth cylinder 2 (step S18).

  This is because when the evaluation knocking frequency Fj of the j-th cylinder 2 is small compared to other cylinders and the possibility of occurrence of knocking is considered to be particularly low, the engine controller 40 determines that the fuel gas of the j-th cylinder 2 This is because the balance between the cylinders 2 is adjusted by increasing the injection amount and advancing the pilot fuel injection timing of the pilot fuel injection valve 20 of the j-th cylinder 2. Thereby, the said average value Fm can always be maintained appropriately.

  The threshold for evaluating the difference value (Fj−Fm) obtained by subtracting the evaluation knocking frequency Fj of the j-th cylinder 2 from the average value Fm of the evaluation knocking frequencies of all the cylinders is not necessarily limited to the above-described threshold F1. Of course, any more appropriate threshold value F3 (predetermined frequency) may be used.

  When the determination result of step S14 is negative, and when the above-described steps S16 and S18 are executed, the above-described evaluation knocking occurrence number Kn and cycle number C are reset and both are set to zero (step S20). Thereafter, the above steps S2 and after are repeated again.

  Thus, according to the knocking control device for a gas engine of the present invention, the engine controller 40 is a numerical value related to the evaluation knocking frequency when (Fj−Fm) exceeds the predetermined frequency F1, or a numerical value related to the evaluation knocking frequency. When a certain Fj itself exceeds the predetermined frequency F2, measures are taken in advance for each cylinder 2 to prevent the occurrence of knocking, so that the occurrence of knocking can be prevented in advance and reliably, and the stability of the gas engine And efficient operation can be performed.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the gas engine 1 described above has a pilot fuel injection valve 20, and the occurrence of knocking is prevented in advance by delaying the injection timing of the pilot fuel injection valve 20.

  However, some gas engines employ a spark ignition system, and in this spark ignition system gas engine, the ignition timing of the air-fuel mixture is delayed by delaying the spark ignition timing in the above-described step S18, so that the pressure in the cylinder 2 is increased. The rise is suppressed, and the temperature rise of the unburned mixture is suppressed. Thereby, the occurrence of knocking can be prevented in advance and reliably.

  On the other hand, when the possibility of knocking is low compared to the other cylinders 2, measures are taken to advance the spark ignition timing and the balance between the cylinders 2 is adjusted. Others are the same as those of the gas engine 1 having the pilot fuel injection valve 20 described above.

  Further, the average value Fm of the evaluation knocking frequencies described above is not necessarily the average value of the evaluation knocking frequencies of all the cylinders 2, and may be the average value of the evaluation knocking frequencies of a plurality of specific cylinders.

  Furthermore, together with the knocking control device for the gas engine of the present invention, when the knocking actually occurs, the conventional knocking control device for the gas engine that detects the knocking early and takes measures to prevent knocking is simultaneously implemented. Of course, it is also good.

1 is a schematic diagram showing a best mode for carrying out a knocking control device for a gas engine of the present invention. FIG. FIG. 3 is a front part of a flowchart showing the operation of the knocking control device for the gas engine of FIG. 1. FIG. It is a rear part of the flowchart of FIG.

Explanation of symbols

1 Gas Engine 2 Cylinder 4 Intake Valve 6 Intake Pipe 8 Exhaust Valve 10 Exhaust Pipe 12 Intake Main Pipe 14 Fuel Gas Pipe 16 Fuel Gas Main Pipe 18 Fuel Gas Injection Valve 20 Pilot Fuel Injection Valve 22 Fuel Pipe 24 Common Rail 26 Knock Sensor 28 Combustion Diagnostic Unit 30 Pilot fuel injector driver 32 Fuel gas injector driver 40 Engine controller C Number of cycles Co Predetermined number of cycles Fj Evaluation knocking frequency Fm Evaluation knocking frequency average values F1, F2 Threshold values (predetermined frequency)
k knock degree ko threshold (predetermined knock degree)
K i evaluation knocking occurrences

Claims (3)

Knock degree detection means (26, 28) for detecting the knock degree (k), which is the degree of knocking, for each cylinder (2), and the knock degree detected by the knock degree detection means exceeds a predetermined knock degree (ko). A controller (40) for calculating an evaluation knocking frequency (Fj), which is a frequency, and a knocking prevention means capable of taking measures for preventing the occurrence of the knocking for each cylinder based on an instruction from the controller. In the knocking control device of the gas engine (1), the engine has a plurality of the cylinders, and the knocking prevention unit adjusts the gas injection amount of fuel for each cylinder (18). 32), and the controller has an average value (Fm) of the evaluation knocking frequencies (Fj) of the plurality of cylinders. Calculated, the cylinder difference value with respect to the gas injection amount adjusting mechanism when the difference value obtained by subtracting the average value from the evaluation knocking frequency exceeds a predetermined frequency (F1) is greater than said predetermined frequency Instructing the gas injection amount to decrease, and when the difference value obtained by subtracting the evaluation knocking frequency from the average value exceeds a predetermined frequency (F1, F3), the gas injection amount adjustment mechanism A knocking control device for a gas engine, characterized in that an instruction is given to increase the gas injection amount of a cylinder whose difference value exceeds the predetermined frequency. Knock degree detection means (26, 28) for detecting the knock degree (k), which is the degree of knocking, for each cylinder (2), and the knock degree detected by the knock degree detection means exceeds a predetermined knock degree (ko). A controller (40) for calculating an evaluation knocking frequency (Fj), which is a frequency, and a knocking prevention means capable of taking measures for preventing the occurrence of the knocking for each cylinder based on an instruction from the controller. In the knocking control device of the gas engine (1), the engine is a pilot fuel ignition type gas engine having a plurality of the cylinders, and the knocking preventing means adjusts a pilot fuel injection timing. (20, 30), and the controller has the evaluation of the plurality of cylinders. Kkingu average frequency (Fj) to (Fm) calculated, relative to the pilot fuel injection timing adjusting mechanism when the difference value obtained by subtracting the average value from the evaluation knocking frequency exceeds a predetermined frequency (F1) When the difference value obtained by subtracting the evaluation knocking frequency from the average value exceeds the predetermined frequency (F1, F3) while instructing to delay the pilot fuel injection timing of the cylinder whose difference value exceeds the predetermined frequency A gas engine knocking control apparatus for instructing the pilot fuel injection timing adjustment mechanism to advance the pilot fuel injection timing of a cylinder whose difference value exceeds the predetermined frequency. Knock degree detection means (26, 28) for detecting the knock degree (k), which is the degree of knocking, for each cylinder (2), and the knock degree detected by the knock degree detection means exceeds a predetermined knock degree (ko). A controller (40) for calculating an evaluation knocking frequency (Fj), which is a frequency, and a knocking prevention means capable of taking measures for preventing the occurrence of the knocking for each cylinder based on an instruction from the controller. In the knocking control device for a gas engine (1), the gas engine is a spark ignition type gas engine having a plurality of the cylinders, and the knocking prevention means has a spark ignition timing adjusting mechanism for adjusting a spark ignition timing. The controller calculates an average value (Fm) of the evaluation knocking frequencies (Fj) of the plurality of cylinders. Calculated, and the cylinder difference values for the spark ignition timing adjustment mechanism when the difference value obtained by subtracting the average value from the evaluation knocking frequency exceeds a predetermined frequency (F1) is greater than said predetermined frequency instructs to delay the spark ignition timing, the difference values for the spark ignition timing adjustment mechanism when the difference value of said average value by subtracting the evaluation knocking frequency is greater than a predetermined frequency (F1, F3) is A knocking control device for a gas engine, characterized by instructing to advance the spark ignition timing of a cylinder exceeding the predetermined frequency.