Natural gas engine system and its nozzle injection control method

Abstract

Disclosed is a natural gas engine system, which includes a gas storage tank (1), a natural gas dispenser (2) and an engine (3). The engine includes a plurality of cylinders, and the natural gas dispenser includes a plurality of nozzles. The control unit is configured to supply natural gas from the gas storage tank to the engine through the nozzles of the natural gas dispenser; the control unit is configured to: within a period of time, supply natural gas to all cylinders of the engine in sequence using the same nozzle. Also disclosed is a natural gas nozzle injection control method for a natural gas engine system.

Description

Technical Field

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

[0002] A natural gas engine is an engine that uses natural gas as fuel. Compared with a fuel engine, the pollutants in the tail gas of a natural gas engine are also significantly reduced. Therefore, natural gas engines are of great significance in improving air quality.

[0003] For a natural gas engine including multiple cylinders, natural gas from a gas storage tank is delivered to each cylinder through multiple nozzles in a distributor. Under certain working conditions (such as the low load condition of the engine), the injection timing of each nozzle corresponds to the intake stroke of a corresponding cylinder, so as to realize the delivery of natural gas to the corresponding cylinder through each nozzle.

[0004] Generally, when the engine is running smoothly, the opening time length of each nozzle is the same. Due to structural differences between nozzles (production tolerance, part tolerance, installation tolerance, etc.), there will be differences in the natural gas intake of each cylinder, resulting in different working performances of each cylinder, and further affecting the performance and emissions of the entire engine. Summary of the Invention

[0005] An object of the present application is to provide a natural gas engine system and a method for controlling the injection of its nozzles, which can reduce the difference in the natural gas intake of each cylinder.

[0006] To this end, in one aspect of the present application, there is provided a control unit for a natural gas engine system. The natural gas engine system includes a gas storage tank, a natural gas distributor, and an engine. The engine includes multiple cylinders, and the natural gas distributor includes multiple nozzles. The control unit is configured to supply natural gas from the gas storage tank to the engine through the nozzles of the natural gas distributor;

[0007] The control unit is configured to execute the following natural gas injection control process:

[0008] Under the low load condition of the engine, within a period of time during the operation of the engine, use the same nozzle to sequentially supply natural gas to all cylinders of the engine.

[0009] According to a feasible implementation manner, the control unit is configured to: in each working cycle of the engine, for the intake stroke of each cylinder, sequentially control each nozzle to maintain an equal opening time length.

[0010] According to a feasible implementation manner, the control unit is configured to: determine the opening time length of each nozzle according to the natural gas intake request of the engine.

[0011] According to a feasible implementation manner, the control unit is configured to: execute the natural gas injection control process under all operating conditions in the low-load condition of the engine; or execute the natural gas injection control process under some operating conditions in the low-load condition of the engine.

[0012] According to a feasible implementation manner, the low-load condition of the engine is calibratable.

[0013] According to a feasible implementation manner, the low-load condition of the engine is: the engine speed is below 1000 RPM and the torque is below 500 Nm.

[0014] According to a feasible implementation manner, the partial operating conditions include: the engine runs at a low speed, and / or there are factors affecting the emission quality of the engine.

[0015] According to a feasible implementation manner, the control unit is configured to, after the passage of the time period, switch another nozzle of the natural gas distributor to execute the natural gas injection control process within the corresponding time period, thereby sequentially rotating the use of each nozzle.

[0016] In another aspect of the present application, there is provided a natural gas engine system, which includes a gas storage tank, a natural gas distributor, an engine, and the control unit as described above. The engine includes a plurality of cylinders, the natural gas distributor includes a plurality of nozzles, and the control unit is configured to supply natural gas from the gas storage tank to the engine through the nozzles of the natural gas distributor. Wherein, in the low-load condition of the engine, within a time period during the engine operation, the same nozzle of the natural gas distributor is used to sequentially supply natural gas to all cylinders of the engine.

[0017] According to a feasible implementation manner, the number of the nozzles is the same as or different from the number of the cylinders.

[0018] In still another aspect of the present application, there is provided a natural gas nozzle injection control method for a natural gas engine system, which can be executed by the control unit as described above or applied to the natural gas engine system as described above; the natural gas injection control method includes the following natural gas injection control process:

[0019] In the low-load condition of the engine, within a time period, the same nozzle of the natural gas distributor in the natural gas engine system is used to sequentially supply natural gas to all cylinders of the engine in the natural gas engine system.

[0020] According to a feasible implementation, the natural gas nozzle injection control method further includes: after the passage of the time period, switching to another nozzle of the natural gas dispenser to perform the natural gas injection control process within the corresponding time period, thereby sequentially rotating the use of each nozzle of the natural gas dispenser.

[0021] According to the present application, under the low load condition of the engine, especially when the requirement for the natural gas injection accuracy is high, such as when the engine is idling, a single nozzle is controlled to supply natural gas to all cylinders in sequence. In this way, the difference in the natural gas intake of each cylinder caused by the structural differences between the nozzles can be reduced, thereby improving the performance and emissions of the engine.

[0022] According to a further implementation, after a certain nozzle has worked alone for a period of time (which can be calibrated), it is switched to another nozzle to supply natural gas to all cylinders, so that each nozzle is rotated for use, which can ensure the uniformity of the use of each nozzle, thereby reducing the differences in the performance and emissions of the engine during the use of different nozzles. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The foregoing and other aspects of the present application will be more fully understood and appreciated by the following detailed description with reference to the accompanying drawings, in which:

[0024] Figure 1 is a schematic diagram of a natural gas engine system according to a feasible implementation of the present application;

[0025] Figure 2 、 3 is a schematic diagram of the injection strategy for each working cycle of the natural gas engine system according to the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present application generally relates to a natural gas engine system, as Figure 1 schematically shown. The natural gas engine system includes a gas storage tank 1, a natural gas dispenser 2, an engine 3, and a control unit 4.

[0027] The gas storage tank 1 stores compressed or liquefied natural gas and is equipped with a valve (not shown). When the valve is opened, the gas storage tank 1 supplies natural gas to the engine 3 through the dispenser 2.

[0028] 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 in order to supply a mixture of different natural gases to the engine 2.

[0029] The dispenser 2 includes a gas rail 5, a distribution chamber 6, and n nozzles I arranged between the gas rail 5 and the distribution chamber 61 、I 2 …I n 。The gas storage tank 1 is connected to the gas rail 5 through the pipeline L NG and a pressure regulator (not shown) is arranged in the pipeline L NG 。The gas storage tank 1 supplies natural gas to the gas rail 5 through the pipeline L NG 。The natural gas in the gas rail 5 is sprayed into the distribution chamber 6 through each nozzle

[0030] The engine 3 includes n cylinders C 1 、C 2 …C n 。Generally, the number of nozzles in the dispenser 2 is equal to the number of cylinders in the engine 3. The distribution chamber 6 is connected to the corresponding cylinders through the supply pipes L 1 、L 2 …L n 。Each supply pipe leads to the intake pipe (not shown) of the corresponding cylinder. During the intake stroke of each cylinder, the natural gas from the distribution chamber 6 is mixed with the air inhaled into the intake pipe through the corresponding supply pipe and enters the cylinder. The working cycles of the individual cylinders are separated by a phase angle of 720° / n respectively

[0031] The control unit 4 is connected to the gas storage tank 1, the natural gas dispenser 2, and the engine 3 to control their operations, especially to control the opening and closing of the individual nozzles of the dispenser 2 according to the working cycles of the cylinders of the engine 3

[0032] According to the basic principle of the present application, at least under certain operating conditions of the engine 3, the control unit 4 controls a single nozzle to supply natural gas to all the cylinders of the engine 3 in turn during each working period

[0033] This control process of the control unit 4 can be implemented for all low-load operating conditions of the engine 3. Alternatively, under certain specific conditions in low-load operating conditions, such as when high precision of natural gas injection is required and the engine 3 is running at low speed (e.g., idling speed), the control unit 4 implements this control process

[0034] The control unit 4 usually controls the opening time length of each nozzle according to the natural gas intake request of the engine 3 (e.g., based on the degree of depression of the accelerator pedal by the driver in a vehicle with the engine 3, the intake demand calculated based on the vehicle speed during autonomous driving, etc.), thereby controlling the amount of natural gas injected each time each nozzle is opened

[0035] A feasible implementation manner of the above control process of the control unit 4 is schematically shown in Figure 2 。As Figure 2 shown, in the first working period Cycle 1 of the engine 3, the control unit 4 controls the nozzle I 1Natural gas is supplied to each cylinder C 1 、C 2 …C n in sequence.

[0036] Figure 2 The actuation control (open, keep open, close) applied to the nozzle I 1 for each cylinder's working cycle is shown as a stepped curve in sequence. The nozzle I 1 keeps open for the same length of time for each cylinder in one working cycle of the engine. In this way, the amount of natural gas supplied to each cylinder through the nozzle I 1 is basically equal. During the injection operation of the nozzle I 1 for all cylinders in sequence, other nozzles remain closed.

[0037] According to the change in the natural gas intake request of the engine 3, the control unit 4 adjusts the natural gas intake of each cylinder by changing the length of time the nozzle I 1 keeps open in each cylinder's working cycle.

[0038] After the nozzle I 1 has been used for a period of time, the control unit 4 switches the nozzle to the nozzle I 2 , so that in the second working period Cycle 2 of the engine 3, only the nozzle I 2 is used to supply fuel to each nozzle, as schematically shown in Figure 3 . The control mode of the nozzle I 2 is the same as that of the nozzle I 1 described above. After the nozzle I 2 has been used for a period of time, the control unit 4 switches the nozzle to the nozzle I 3 , and so on, until all nozzles have been rotated and used in sequence. Then, the control unit switches the nozzle back to the nozzle I 1 . By rotating and using the nozzles in this way, the uniformity of nozzle use can be ensured, thereby reducing the differences in engine performance and emissions during the use of different nozzles, and reducing the differences in nozzle wear, and improving the service life of the engine system.

[0039] The time period for each nozzle to be used each time can be calibrated. For example, the time period for each nozzle to be used each time can be calibrated to be equal to each other. Or, it can be calibrated separately for each nozzle, so that the time period for a certain nozzle or some nozzles to be used each time is slightly different from that of other nozzles.

[0040] According to a feasible implementation manner, 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 is as follows: apply a high voltage / current to the solenoid valve to open the nozzle, then change to apply a low-high voltage / current to keep the nozzle open. After the nozzle has been open for a period of time, power off the solenoid valve to close the nozzle. The length of time to keep it open depends on the natural gas intake request of the engine 3.

[0041] Of course, each nozzle can also be actuated in other ways.

[0042] As mentioned above, the above nozzle control process can be implemented under all low-load conditions of the engine 3. Or, the above nozzle control process can be implemented only in some cases of low-load conditions. Under high-load conditions of the engine 3, if single-nozzle injection can meet the natural gas intake demand, the above nozzle control process can also be implemented. If single-nozzle injection cannot meet the natural gas intake demand, then two or more, or even all nozzles need to participate in injection simultaneously (usually with different injection timings, that is, when one nozzle has not closed, another nozzle has been opened). In this case, the above nozzle control process is not implemented.

[0043] The low-load conditions of the engine 3 mentioned here respectively refer to the load of the engine 3 being below a predetermined load value. For example, the engine speed of the engine 3 is below 1000 RPM and the torque is below 500 Nm. The low-load conditions of the engine 3 are calibratable, that is, the above values of the predetermined load value, such as the engine speed and torque of the engine 3, can be adjusted.

[0044] In the case of high requirements for natural gas injection accuracy, such as when there are factors that may cause a decline in the engine emission quality, such as climate factors, altitude factors, natural gas quality factors, etc., or in some cases that may cause a decline in emission quality, such as low-speed operation, etc., controlling the uniformity of the natural gas intake of each cylinder of the engine 3 is crucial for engine performance and emissions. It is difficult to ensure the uniformity of the natural gas intake of each cylinder by using the existing technology of injecting natural gas into the corresponding cylinder with each nozzle. Especially when the engine 3 is running at a low speed (such as idling), the opening time of each nozzle is short each time, and it is more difficult to ensure the uniformity of the natural gas intake of each cylinder by using the existing technology. According to the present application, using the same nozzle to supply natural gas to all cylinders in sequence reduces the difference in the intake of each cylinder caused by the structural differences between different nozzles in the existing technology. Therefore, it is easier to ensure the uniformity of the natural gas intake of each cylinder.

[0045] According to a further embodiment of the present application, considering that during a certain period of operation of the engine 3, natural gas is sequentially supplied to all cylinders of the engine 3 using the same nozzle of the natural gas dispenser 2, therefore, the number of nozzles in the natural gas dispenser 2 can be designed to be different from the number of cylinders in the engine 3. The number of nozzles mainly depends on factors such as the natural gas intake demand of each cylinder in the engine 3 and the designed service life of the nozzles, etc.

[0046] The nozzles in the natural gas dispenser 2 can be high-flow nozzles (HFI).

[0047] The present application also provides a natural gas nozzle injection control method for a natural gas engine system, which can execute the control process described above based on the nozzles of the natural gas dispenser 2. Generally speaking, the natural gas injection control method includes: within a period of time, using the same nozzle to sequentially supply natural gas to all cylinders of the engine.

[0048] In the natural gas nozzle injection control method, further, after the period of time has passed, switch to another nozzle of the natural gas dispenser to execute the natural gas injection control process, thereby sequentially rotating the use of each nozzle of the natural gas engine system.

[0049] The natural gas injection control method is applicable to the natural gas engine system described above and can be executed by means of the control unit 4 described above. Therefore, all the control-related features described above for the natural gas engine system and its control unit 4 also apply to the natural gas nozzle injection control method of the present application, and will not be repeated here.

[0050] Although the present application has been described here with reference to specific embodiments, the scope of the present application is not limited to the details shown. Various modifications can 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 including a gas storage tank (1), a natural gas dispenser (2) and an engine (3), the engine including a plurality of cylinders, the natural gas dispenser including a plurality of nozzles, the control unit being configured to supply natural gas from the gas storage tank to the engine through the nozzles of the natural gas dispenser; The control unit is configured to perform the following natural gas injection control process: Under low load conditions of the engine, within a period during the engine operation, supply natural gas to all cylinders of the engine in sequence using the same nozzle.

2. The control unit according to claim 1, wherein, The control unit is configured to: in each working cycle of the engine, for the intake stroke of each cylinder, control the same nozzle to maintain an equal opening time length in sequence.

3. The control unit according to claim 1, wherein, The control unit is configured to: determine the opening time length of the nozzle according to the natural gas intake request of the engine.

4. The control unit according to claim 1, wherein, The control unit is configured to: perform the natural gas injection control process under all operating conditions under low load conditions of the engine; or perform the natural gas injection control process under some operating conditions under low load conditions of the engine.

5. The control unit according to claim 4, wherein, The low load conditions of the engine are calibrated.

6. The control unit according to claim 5, wherein, The low load conditions of the engine are: the engine speed is below 1000 RPM and the torque is below 500 Nm.

7. The control unit according to any one of claims 1 to 6, wherein, The control unit is configured to, after the elapse of the period, switch to another nozzle of the natural gas dispenser to perform the natural gas injection control process within the corresponding period, thereby alternately using each nozzle in sequence.

8. A natural gas engine system, including a gas storage tank (1), a natural gas dispenser (2), an engine (3) and the control unit according to any one of claims 1 to 7, the engine including a plurality of cylinders, the natural gas dispenser including a plurality of nozzles, the control unit being configured to supply natural gas from the gas storage tank to the engine through the nozzles of the natural gas dispenser, wherein, Under low load conditions of the engine, within a period during the engine operation, supply natural gas to all cylinders of the engine in sequence using the same nozzle.

9. The natural gas engine system according to claim 8, wherein, The number of the nozzles is the same as or different from the number of the cylinders.

10. A natural gas nozzle injection control method for a natural gas engine system, performed by the control unit according to any one of claims 1 - 6, including the following natural gas injection control process: Under low load conditions of the engine, within a period, supply natural gas to all cylinders of the engine in the natural gas engine system in sequence using the same nozzle of the natural gas dispenser in the natural gas engine system.

11. The natural gas nozzle injection control method according to claim 10, wherein, The natural gas nozzle injection control method further includes: after the passage of the time period, switching to another nozzle of the natural gas dispenser to perform the natural gas injection control process within the corresponding time period, thereby sequentially rotating the use of each nozzle of the natural gas dispenser.

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