Natural gas engine system and nozzle injection quantity correction method

Abstract

Disclosed is a control unit for a natural gas engine system. The control unit is configured to: during a nozzle injection quantity detection process, control each nozzle to sequentially supply natural gas to the engine and calculate the injection quantity for each nozzle by detecting engine exhaust gas indicators; compare the calculated injection quantity for each nozzle with the required injection quantity to determine the injection quantity deviation for each nozzle; determine an injection quantity correction factor for each nozzle based on the injection quantity deviation for each nozzle; and, during normal engine operation, control the actual injection quantity of each nozzle based on the corresponding injection quantity correction factor. Also disclosed is a natural gas nozzle injection quantity correction method for the natural gas engine system.

Description

Technical Field

[0001] The present application relates to a natural gas engine system and a method for correcting the injection quantity of a natural gas nozzle thereof. Background Art

[0002] Natural gas engines are engines that use natural gas as fuel. Compared with fuel engines, natural gas engines also produce significantly lower pollutants in their exhaust, so natural gas engines are of great significance in improving air quality.

[0003] For multi-cylinder natural gas engines, natural gas from the gas tank is delivered to each cylinder through multiple nozzles in the distributor. Because each nozzle inevitably has initial structural differences (due to production and component tolerances), and the injection volume of each nozzle drifts over time (the degree of drift varies from nozzle to nozzle), there is a deviation between the actual injection volume of each nozzle and the required injection volume. Furthermore, there are differences in injection volume between nozzles, resulting in a deviation between the actual and required natural gas intake volume for each cylinder, which in turn affects the performance and emissions of the entire engine. Summary of the Invention

[0004] An object of the present application is to provide a natural gas engine system and a method for correcting the injection quantity of a natural gas nozzle thereof, which can detect and correct the injection quantity deviation of each nozzle.

[0005] To this end, the present application provides, in one aspect, a control unit for a natural gas engine system, the natural gas engine system comprising a gas storage tank, a natural gas distributor, and an engine, the natural gas distributor comprising a plurality of nozzles; the control unit is configured to:

[0006] During the nozzle injection quantity detection process, each nozzle is controlled to supply natural gas to the engine in turn, and the injection quantity of each nozzle is calculated by detecting the engine exhaust index;

[0007] comparing the calculated injection amount of each nozzle with the required injection amount to determine the injection amount deviation of each nozzle;

[0008] determining an injection amount correction coefficient for each nozzle based on the injection amount deviation of each nozzle; and

[0009] During normal engine operation, the actual injection quantity of each nozzle is controlled based on the corresponding injection quantity correction coefficient.

[0010] According to a possible implementation manner, the control unit is configured to perform a nozzle injection quantity detection process when the engine is running at a low speed.

[0011] According to a possible embodiment, the control unit is configured to perform a nozzle injection quantity detection process during an idling operation after the engine is started and thereby determine the injection quantity correction coefficient.

[0012] According to a possible implementation, during the nozzle injection quantity detection process, the control unit calculates the injection quantity of each nozzle by detecting the oxygen content in the engine exhaust.

[0013] According to a feasible embodiment, the engine includes a plurality of cylinders, and during the nozzle injection quantity detection process, the control unit controls a corresponding nozzle in each detection period to supply natural gas to all cylinders in sequence.

[0014] According to a possible embodiment, the control unit is configured to determine a corresponding correction coefficient based on the injection quantity deviation of each nozzle, and to correct the actual injection quantity of the corresponding nozzle based on the correction coefficient during normal operation of the engine.

[0015] According to a possible embodiment, the control unit is configured to perform injection quantity correction only for injection nozzles whose injection quantity deviation falls outside the deviation limit.

[0016] According to a possible embodiment, the control unit is configured to issue a prompt when the injection amount deviation of one or more nozzles exceeds a first threshold; and

[0017] When the injection quantity deviation of one or more nozzles exceeds a second threshold whose absolute value is greater than the first threshold, compulsory measures are taken on the engine, such as limiting the engine output torque and / or speed.

[0018] According to a feasible implementation manner, the control unit is configured to wirelessly transmit the injection quantity deviation of each nozzle to a background monitoring station.

[0019] In another aspect, the present application provides a natural gas engine system, comprising a gas storage tank, a natural gas distributor, an engine, and the control unit as described above.

[0020] In one aspect, the present application provides a natural gas nozzle injection amount calibration method for a natural gas engine system, the natural gas engine system comprising a gas storage tank, a natural gas distributor, and an engine, the natural gas distributor supplying natural gas from the gas storage tank to the engine through a plurality of nozzles of the natural gas distributor;

[0021] The nozzle injection amount correction method includes:

[0022] During the nozzle injection quantity detection process, each nozzle is controlled to supply natural gas to the engine in turn, and the injection quantity of each nozzle is calculated by detecting the engine exhaust index;

[0023] comparing the calculated injection amount of each nozzle with the required injection amount to determine an injection amount deviation of each nozzle; and

[0024] During normal engine operation, the actual injection quantity of each nozzle is corrected based on the injection quantity deviation of the corresponding nozzle.

[0025] According to the present application, the actual injection amount of each nozzle in the natural gas engine system is detected and compensated accordingly to make the actual injection amount of each nozzle as close as possible to the required injection amount, thereby improving the performance and emission quality of the entire engine and extending the engine life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The foregoing and other aspects of the present application will be more fully understood and appreciated through the following detailed description made with reference to the accompanying drawings, in which:

[0027] Figure 1 is a schematic diagram of a natural gas engine system according to a feasible embodiment of the present application;

[0028] Figure 2 、 3 is a schematic diagram of a method for detecting the injection amount of each nozzle in a natural gas engine system according to the present application;

[0029] Figure 4 It is a schematic diagram reflecting the injection amount of each nozzle;

[0030] Figure 5 This is a schematic diagram of the injection amount compensation coefficient for each nozzle. DETAILED DESCRIPTION

[0031] The present application generally relates to a natural gas engine system, such as Figure 1 The natural gas engine system includes a gas storage tank 1, a natural gas distributor 2, an engine 3 and a control unit 4.

[0032] Compressed or liquefied natural gas is stored in the gas tank 1 and is equipped with a valve (not shown). When the valve is opened, the gas tank 1 supplies natural gas to the engine 3 via the distributor 2.

[0033] The gas storage tank 1 may include a single tank body. Alternatively, the gas storage tank 1 may include multiple tank bodies. The multiple tank bodies may be arranged in series and store the same type of natural gas. Alternatively, the multiple tank bodies may be arranged in parallel and store different types of natural gas, so as to supply a mixture of different natural gases to the engine 2.

[0034] The dispenser 2 includes an air rail 5, a delivery chamber 6, and n nozzles I1, I2, ..., I arranged between the air rail 5 and the delivery chamber 6. n Gas tank 1 through pipeline LNG Connected to gas rail 5, pipeline L NG A pressure regulator (not shown) is arranged in the middle. The gas tank 1 is connected to the air tank 1 through the pipeline L NG Natural gas is supplied to the gas rail 5. The natural gas in the gas rail 5 is injected into the delivery chamber 6 through each nozzle. Each nozzle may be a high-volume injection nozzle (HFI).

[0035] The engine 3 includes n cylinders C1, C2...C n In general, the number of nozzles in the distributor 2 is equal to the number of cylinders in the engine 3. The distribution chamber 6 is connected to the distribution chamber 6 by supply pipes L1, L2...L n Connected to the corresponding cylinders. Each supply pipe leads to the corresponding cylinder's intake manifold (not shown). During the intake stroke of each cylinder, natural gas from the distribution chamber 6 mixes with air drawn into the intake manifold through the corresponding supply pipe and enters the cylinder. The operating cycles of the various cylinders are separated by a phase angle of 720° / n. Exhaust gas from the engine 3 is discharged through the exhaust pipe 7. The exhaust pipe 7 is equipped with an oxygen sensor 8 and other sensors (not shown).

[0036] Control unit 4 is connected to gas tank 1, natural gas distributor 2, and engine 3 to control their operation. Specifically, it controls the opening and closing timing and duration of each nozzle in distributor 2 based on the operating cycle of each cylinder in engine 3. The duration of each nozzle's opening determines the amount of natural gas injected by that nozzle.

[0037] The control unit 4 is also connected to various sensors in the engine system (including the oxygen sensor 8) to receive data from these sensors, thereby monitoring the operating status of the engine system and making any necessary adjustments. The control unit 4 includes a memory 9 for storing various engine system data, including sensor data, engine system settings and operating parameters, and so on.

[0038] Based on the description in the background section, it can be understood that the injection amount of each nozzle may deviate from the required injection amount, and that drift of the injection amount over time may increase this deviation. This application proposes regularly detecting the injection amount (injection capacity) of each nozzle and compensating the injection amount of each nozzle so that the actual injection amount of each nozzle is as close as possible to the required injection amount.

[0039] The present application tests the injection quantity (injection capacity) of each nozzle in the following manner: During the nozzle testing process, the control unit 4 controls each nozzle to sequentially supply natural gas to all cylinders of the engine 3, and determines the injection quantity (injection capacity) of each nozzle based on the oxygen content in the engine exhaust gas detected by the oxygen sensor 8. This testing process is preferably performed when the engine 3 is operating at a low speed (e.g., idling, especially idling after each engine start), for example, during idling after each engine start.

[0040] The above detection process of the control unit 4 is Figure 2 、 3 First, Figure 2 As shown, in the first detection period Period 1, the control unit 4 controls the nozzle I1 to sequentially inject water into each cylinder C1, C2...C n The first detection period Period 1 may include several engine operating cycles.

[0041] Figure 2 The step-shaped curve in Figure 2 shows the sequential actuation control (opening, remaining open, and closing) of nozzle I1 for each cylinder's operating cycle. The duration of nozzle I1's opening is consistent throughout each cylinder's operating cycle, resulting in a substantially equal amount of natural gas supplied to each cylinder through nozzle I1. While nozzle I1 is injecting fuel for all cylinders, the other nozzles remain closed.

[0042] In the first detection period Period 1, the control unit 4 receives the oxygen content of the exhaust gas in the exhaust pipe 7 from the oxygen sensor 8 and calculates the injection quantity of the nozzle I1 based on the oxygen content of the exhaust gas. The calculated injection quantity of the nozzle I1 is recorded in the memory 9.

[0043] After the first detection period Period 1 ends, the control unit 4 switches the nozzle to the nozzle I2, so that in the second detection period Period 2, only the nozzle I2 is used to supply fuel to each nozzle. Figure 3 Schematically illustrated in FIG. Injector I2 is controlled in the same manner as previously described for nozzle I1. During the second detection period, Period 2, control unit 4 similarly receives the oxygen content of the exhaust gas in exhaust pipe 7 from oxygen sensor 8 and calculates the injection quantity of nozzle I2 based on the oxygen content in the exhaust gas. The calculated injection quantity of nozzle I2 is recorded in memory 9.

[0044] After the second detection period Period 2 ends, the control unit 4 switches the nozzle to nozzle I3, and so on, until all nozzles are rotated. In this way, the injection amount of each nozzle is calculated and recorded in the memory 9.

[0045] It should be pointed out that as an alternative or additional measure to determining the injection amount (injection capacity) of each nozzle by detecting the oxygen content in the engine exhaust, the control unit 4 can calculate the injection amount of each nozzle through other detected indicators of the exhaust (such as the content of other components in the exhaust, exhaust temperature, pressure, etc.).

[0046] According to one possible embodiment, each nozzle is in the form of a solenoid valve, which opens when powered on and closes when powered off. The control process for each nozzle involves applying a high voltage / current to the solenoid valve to open the nozzle, then switching to a low voltage / current to maintain the nozzle open. After the nozzle remains open for a period of time, the solenoid valve is de-energized to close the nozzle. Of course, each nozzle can also be actuated in other ways.

[0047] Figure 4 The figure schematically illustrates the calculated injection quantity Q for each nozzle and the required injection quantity Q0 for each nozzle. It should be noted that the required injection quantity Q0 may not be a fixed value but may vary with factors such as engine speed. The calculated injection quantity Q for each nozzle represents its current injection capacity.

[0048] The control unit 4 compares the calculated nozzle injection quantity Q with the required injection quantity Q0 to determine the deviation between the calculated nozzle injection quantity Q and the required injection quantity Q0. It is understood that the injection quantity of some nozzles may be lower than the required injection quantity due to factors such as structural deviations, injection channel blockage, etc. Alternatively, the injection quantity of some nozzles may be higher than the required injection quantity due to factors such as structural deviations, injection channel corrosion, etc. Of course, the injection quantity of some nozzles may be substantially equal to the required injection quantity, i.e., the injection quantity deviation is within a certain deviation limit (e.g., ±3%).

[0049] Then, the control unit 4 applies the injection amount compensation coefficient F to each nozzle, for example, Figure 5 Schematic representation. The compensation factor F of each nozzle is related to its calculated injection quantity.

[0050] After determining the compensation coefficient F for each nozzle, during the subsequent normal operation of the engine system (for example, during the driving of a vehicle equipped with the engine system), the control unit 4 corrects the injection amount of each nozzle based on the compensation coefficient F of each nozzle, for example, corrects the opening time length of each nozzle.

[0051] It should be noted that during normal engine system operation, depending on the engine load, more than two nozzles may be required to participate in injection simultaneously. When more than two nozzles are involved in injection simultaneously, each nozzle is usually opened sequentially, and when one nozzle is not closed, another nozzle is opened.

[0052] According to a feasible implementation, the compensation coefficient F is a simple multiplication factor, for example Figure 5 As shown in , control unit 4 multiplies the set opening time of each nozzle by the corresponding compensation coefficient F to obtain the actual opening time, and then controls the opening of the corresponding nozzle based on the actual opening time. In this way, the actual injection amount of each nozzle is corrected, making the actual injection amount of each nozzle as close as possible to the required injection amount.

[0053] It should be noted that injection amount correction can be performed only for nozzles whose injection amount deviation falls outside the deviation limit (for example, higher than 3% or lower than -3%); injection amount correction is not performed for nozzles whose injection amount deviation is within the deviation limit (for example, ±3%).

[0054] The deviation in the injection quantity (injection capacity) of each nozzle indicates the condition of the nozzle. Excessive deviation in injection quantity indicates that the nozzle requires maintenance (e.g., cleaning) or replacement. To this end, the control unit 4 records the deviation in injection quantity (injection capacity) of each nozzle and the compensation factor F determined thereby in the memory 9. If the injection quantity deviation or the compensation factor F exceeds a predetermined threshold, the control unit 4 issues a corresponding prompt and, if necessary, initiates appropriate mandatory measures.

[0055] For example, a first threshold (e.g., ±5%) and a second threshold (e.g., ±10%) whose absolute value is greater than the first threshold can be set. When the control unit 4 determines that the injection quantity deviation of a particular nozzle exceeds the first threshold but does not reach the second threshold (e.g., between 5% and 10%, or -5% to -10%), the control unit 4 prompts the user that appropriate maintenance is required, such as by displaying a prompt on the vehicle's dashboard. When the control unit 4 determines that the injection quantity deviation of a particular nozzle exceeds the second threshold (e.g., greater than 10%, or less than -10%), the control unit 4 can take mandatory measures, such as limiting engine output torque and / or speed, activating a "limp-home" mode for the vehicle in the central engine system, and so on. This protects the engine from damage, thereby extending engine life and reducing maintenance costs.

[0056] Furthermore, the control unit 4 can also transmit the injection quantity deviation of each nozzle to a backend monitoring station via a wireless networking device. The backend monitoring station can monitor the status of the engine system based on the received injection quantity deviation of each nozzle. When the injection quantity deviation of a particular nozzle exceeds a predetermined threshold (such as the first or second thresholds described above), the backend monitoring station can send a corresponding message to the user or monitoring agency to prompt the user or monitoring agency to take appropriate measures.

[0057] The above describes some feasible implementations of the natural gas engine system and its control unit 4 of the present application. It is understood that under the principles of the present application, those skilled in the art can make various adaptive modifications to the various details described above according to specific application conditions.

[0058] This application also provides a natural gas nozzle injection quantity calibration method for a natural gas engine system, which implements the detection and correction process described above for the natural gas engine system and its control unit 4. The various control-related features described above for the natural gas engine system and its control unit 4 are also applicable to the natural gas nozzle injection quantity calibration method of this application and will not be repeated here.

[0059] It should be noted that the natural gas nozzle injection amount correction scheme of this application is fundamentally different from conventional closed-loop adjustments to natural gas intake based on engine exhaust oxygen content measurements. This closed-loop adjustment scheme for natural gas intake is characterized by real-time detection of the engine exhaust oxygen content during normal engine operation and real-time control of the engine's natural gas intake based on the detected oxygen content. The natural gas nozzle injection quantity correction scheme of the present application is characterized in that a nozzle injection quantity detection process is performed periodically (for example, after each engine start-up, during which each nozzle is controlled to supply natural gas to the engine in turn, and then the injection quantity of each nozzle is calculated by detecting the engine exhaust index, thereby determining the injection quantity deviation of each nozzle and the injection quantity correction coefficient for correcting the injection quantity deviation; during normal operation of the engine, it is only necessary to control the actual injection quantity of each nozzle based on the corresponding injection quantity correction coefficient, and there is no need to determine the injection quantity deviation and injection quantity correction coefficient of each nozzle in real time. Therefore, in essence, according to the present application, during normal operation of the engine, it is no longer necessary to perform closed-loop adjustment of the natural gas intake quantity in real time as in the prior art. Therefore, the natural gas nozzle injection quantity correction scheme of the present application (without closed-loop adjustment) is simpler than the closed-loop adjustment scheme of the prior art.

[0060] Although the present application is described herein with reference to specific embodiments, the scope of the present application is not limited to the details shown. Various modifications may be made to these details without departing from the basic principles of the present application.

Claims

1. A control unit for a natural gas engine system, the natural gas engine system comprising a gas storage tank (1), a natural gas distributor (2) and an engine (3), the natural gas distributor comprising a gas rail (5), a distribution chamber (6) and a plurality of nozzles arranged between the gas rail (5) and the distribution chamber (6), natural gas being sprayed into the distribution chamber (6) through the respective nozzles, the distribution chamber (6) being connected to a corresponding cylinder of the engine (3) through a supply pipe, and during an intake stroke of each cylinder, natural gas from the distribution chamber (6) is mixed with air sucked into an intake pipe through the corresponding supply pipe and then enters the cylinder; the control unit is configured to: During the nozzle injection amount detection process, each nozzle is controlled to supply natural gas to all cylinders of the engine through the distribution chamber (6) and the corresponding supply pipe in sequence, and the injection amount of each nozzle is calculated by detecting the engine exhaust index; comparing the calculated injection amount of each nozzle with the required injection amount to determine the injection amount deviation of each nozzle; determining an injection quantity correction coefficient for each nozzle based on an injection quantity deviation of each nozzle; as well as During normal engine operation, the actual injection quantity of each nozzle is controlled based on the corresponding injection quantity correction coefficient.

2. The control unit according to claim 1, wherein: The control unit is configured to perform a nozzle injection amount detection process when the engine is operated at a low speed.

3. The control unit according to claim 1, wherein: The control unit is configured to perform a nozzle injection quantity detection process during an idling operation after the engine is started and thereby determine an injection quantity correction coefficient.

4. The control unit according to claim 1, wherein: During the nozzle injection quantity detection process, the control unit calculates the injection quantity of each nozzle by detecting the oxygen content in the engine exhaust.

5. The control unit according to any one of claims 1 to 4, wherein: The engine includes a plurality of cylinders, and during a nozzle injection amount detection process, the control unit controls a corresponding nozzle in each detection period to supply natural gas to all cylinders in sequence.

6. The control unit according to any one of claims 1 to 4, wherein: The control unit is configured to determine a corresponding correction coefficient based on the injection quantity deviation of each nozzle, and to correct the actual injection quantity of the corresponding nozzle based on the correction coefficient during normal operation of the engine.

7. The control unit according to claim 6, wherein: The control unit is configured to perform injection quantity correction only for nozzles whose injection quantity deviation falls outside the deviation limit.

8. The control unit according to any one of claims 1 to 4, wherein: The control unit is configured to issue a prompt when the deviation of the injection amount of one or more nozzles exceeds a first threshold; and When the injection quantity deviation of one or more nozzles exceeds a second threshold value whose absolute value is greater than the first threshold value, a mandatory measure is taken on the engine.

9. The control unit according to claim 8, wherein: The engine output torque and / or speed is limited when the injection amount deviation of one or more injectors exceeds a second threshold value whose absolute value is greater than the first threshold value.

10. The control unit according to any one of claims 1 to 4, wherein: The control unit is configured to wirelessly transmit the injection amount deviation of each nozzle to a background monitoring station.

11. A natural gas engine system comprising a gas storage tank (1), a natural gas distributor (2), an engine (3) and a control unit according to any one of claims 1 to 10.

12. A method for calibrating the injection amount of a natural gas nozzle for a natural gas engine system, the natural gas engine system comprising a gas storage tank (1), a natural gas distributor (2) and an engine (3), the natural gas distributor comprising a gas rail (5), a distribution chamber (6) and a plurality of nozzles arranged between the gas rail (5) and the distribution chamber (6), natural gas being injected into the distribution chamber (6) through each nozzle, the distribution chamber (6) being connected to a corresponding cylinder of the engine (3) through a supply pipe, and during the intake stroke of each cylinder, natural gas from the distribution chamber (6) is mixed with air sucked into an intake pipe through the corresponding supply pipe and then enters the cylinder; The nozzle injection amount correction method includes: During the nozzle injection amount detection process, each nozzle is controlled to supply natural gas to all cylinders of the engine through the distribution chamber (6) and the corresponding supply pipe in sequence, and the injection amount of each nozzle is calculated by detecting the engine exhaust index; comparing the calculated injection amount of each nozzle with the required injection amount to determine an injection amount deviation of each nozzle; and During normal engine operation, the actual injection quantity of each nozzle is corrected based on the injection quantity deviation of the corresponding nozzle.

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