Engine gas supply system and EGR rate determination method

Abstract

The invention belongs to the technical field of engine gas supply, and discloses an engine gas supply system and an EGR rate determining method.The engine gas supply system comprises an engine, a gas inlet pipe, an exhaust pipe and an EGR assembly, the engine is provided with multiple cylinders, the gas inlet pipe communicates with the gas inlet ends of the multiple cylinders, and the exhaust pipe communicates with the exhaust ends of the multiple cylinders; the EGR assembly comprises a gas storage tank, a main control valve, an EGR main pipe and a plurality of EGR branch pipes, the first end of the EGR main pipe is communicated with the exhaust pipe through the main control valve, the second end of the EGR main pipe is communicated with the gas storage tank, the gas storage tank is communicated with the gas inlet ends of the cylinders through the EGR branch pipes, and each EGR branch pipe is provided with an EGR control valve; the EGR rate determination method is applied to the engine gas supply system. According to the air supply system of the engine, it is ensured that the pressure of waste gas supplied to the air cylinders of the engine subsequently does not fluctuate, and the uniformity of the EGR rate of each air cylinder is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of engine air supply, and in particular to an engine air supply system and an EGR rate determination method. Background Art

[0002] During the operation of the engine, each cylinder works alternately, and during the exhaust process, the pressure in the exhaust pipe fluctuates. Therefore, after the EGR pipe takes air from the exhaust pipe, there is also pressure fluctuation in the EGR pipe. The exhaust gas in the EGR pipe will enter the cylinder of the engine together with the fresh air. Due to the pressure fluctuation of the EGR pipe, the EGR rate of the exhaust gas and fresh air mixed at different times changes, which in turn causes the EGR rate in each cylinder to be uneven, affecting the reliability of the engine. Summary of the invention

[0003] The purpose of the present invention is to provide an engine air supply system, in which the exhaust gas can be temporarily stored after being taken from the exhaust pipe, and the pressure of this part of the gas can be stabilized, and then it is supplied to each cylinder through the corresponding EGR branch pipe, ensuring that the pressure of the exhaust gas supplied to the engine cylinder is stable and does not fluctuate, and an EGR control valve is arranged on each EGR branch pipe, which can control the opening and closing of the corresponding EGR branch pipe to adjust the exhaust gas intake time of each cylinder, thereby ensuring the uniformity of the EGR rate of each cylinder.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] An engine air supply system, comprising:

[0006] An engine having a plurality of cylinders;

[0007] An intake pipe connected to the intake ends of the plurality of cylinders;

[0008] An exhaust pipe connected to the exhaust ends of the plurality of cylinders;

[0009] The EGR component includes an air storage tank, a main control valve, an EGR main pipe and multiple EGR branch pipes. The first end of the EGR main pipe is connected to the exhaust pipe through the main control valve, the second end of the EGR main pipe is connected to the air storage tank, and the air storage tank is connected to the intake ends of multiple cylinders through multiple EGR branch pipes. An EGR control valve is provided on each of the EGR branch pipes.

[0010] Preferably, the EGR control valve is configured to unidirectionally connect the EGR branch pipe from the gas tank to the cylinder.

[0011] Preferably, an intercooler is provided on the intake pipe, and an EGR cooler is provided on the exhaust pipe between the gas storage tank and the main control valve.

[0012] Preferably, it further comprises a turbine and a compressor, wherein the turbine is connected to the compressor, the turbine is arranged on the exhaust pipe, and the compressor is arranged on the intake pipe.

[0013] The present invention also provides an EGR rate determination method, which applies the above-mentioned engine air supply system and can effectively improve the uniformity of the EGR rate of each cylinder of the engine.

[0014] A method for determining an EGR rate is applied to the above-mentioned engine air supply system, and the method for determining an EGR rate comprises the following steps:

[0015] S100, formulating an EGR rate and assigning an EGR rate calculation value α;

[0016] S200, obtaining the duration t0 during which the pressure P1 in the gas storage tank is greater than the pressure P2 in the cylinder of the engine according to α;

[0017] S300, obtaining the opening time t of the EGR control valve to be determined, and determining whether the following is satisfied: t<t0;

[0018] If yes, proceed to step S400;

[0019] If not, adjust the pressure P1 in the gas storage tank and / or the spray hole cross-sectional area A of the injector and then return to step S200;

[0020] S400, evaluate the performance indicators and determine whether the evaluation requirements are met;

[0021] If so, the EGR rate is determined to be complete;

[0022] If not, a new EGR rate is re-set and assigned to α, and then the process returns to step S200.

[0023] Preferably, in step S200, the duration t0 during which the pressure P1 in the gas storage tank is greater than the pressure P2 in the cylinder is obtained by calculation using GT-POWER software.

[0024] Preferably, the pressure P1 in the gas storage tank and the pressure P2 in the cylinder are acquired by a pressure sensor.

[0025] Preferably, in step S300, the opening time t of the EGR control valve is obtained as follows:

[0026] Get the mass m of the EGR gas in the cylinder e and mass flow rate q m ,but in,

[0027] m1 is the fresh air intake mass of the cylinder, m is the fresh air intake mass flow rate of the cylinder, and n is the speed of the engine;

[0028] ρ is the gas density in the gas tank; T1 is the gas temperature in the gas tank; R is the gas constant.

[0029] Preferably, step S400 is specifically as follows: determining the NO in the exhaust gas of the exhaust pipe. X And whether the SOOT values ​​meet the requirements.

[0030] As a preferred method, the NO in the exhaust gas of the exhaust pipe is judged X And whether the smoke density values ​​meet the requirements:

[0031] Determine whether it meets the following conditions: 1g / (kW·h)<NO X The content is less than 2g / (kW·h) and 5mg / m 3 <Smoke density value<10mg / m 3 .

[0032] Beneficial effects:

[0033] The engine air supply system provided by the present invention is provided with an air storage tank, so that part of the exhaust gas discharged from the exhaust pipe can enter the air storage tank through the main control valve and the EGR main pipe. This part of the exhaust gas can be temporarily stored in the air storage tank, and the pressure of this part of the gas is stabilized, and then it is supplied to each cylinder through multiple EGR branch pipes, ensuring that the pressure of the exhaust gas supplied to the engine cylinder is stable and does not fluctuate. In addition, an EGR control valve is provided on each EGR branch pipe, which can control the opening and closing of the corresponding EGR branch pipe to adjust the exhaust gas intake time of each cylinder, ensuring the uniformity of the EGR rate of each cylinder.

[0034] The EGR rate determination method provided by the present invention applies the above-mentioned engine air supply system, obtains the duration t0 that the pressure P1 in the air storage tank is greater than the pressure P2 in the cylinder of the engine, and compares t0 with the opening time t of the EGR control valve, adjusts the pressure P1 in the air storage tank and / or the cross-sectional area A of the spray hole of the injector according to the comparison result, and continuously iterates the EGR rate in the subsequent performance index evaluation process, so as to determine the optimal EGR rate value, realize the controllable quality of the EGR exhaust gas entering each cylinder, and improve the uniformity of the EGR rate of each cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the engine air supply system provided by the present invention;

[0036] Figure 2 It is a flow chart of the EGR rate determination method provided by the present invention.

[0037] In the figure:

[0038] 1. Engine; 11. Cylinder;

[0039] 21. Intake pipe; 22. Exhaust pipe; 23. Intercooler; 24. EGR cooler;

[0040] 31. Gas storage tank; 32. Main control valve; 33. EGR main pipe; 34. EGR branch pipe; 35. EGR control valve;

[0041] 41. Turbine; 42. Compressor. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0043] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0045] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0046] This embodiment provides an engine air supply system. Figure 1 As shown, the engine air supply system includes an engine 1, an intake pipe 21, an exhaust pipe 22 and an EGR component, wherein the engine 1 has a plurality of cylinders 11, the intake pipe 21 is connected to the intake ends of the plurality of cylinders 11, the exhaust pipe 22 is connected to the exhaust ends of the plurality of cylinders 11, the EGR component includes an air storage tank 31, a main control valve 32, an EGR main pipe 33 and a plurality of EGR branch pipes 34, a first end of the EGR main pipe 33 is connected to the exhaust pipe 22 through the main control valve 32, a second end of the EGR main pipe 33 is connected to the air storage tank 31, the air storage tank 31 is connected to the intake ends of the plurality of cylinders 11 through a plurality of EGR branch pipes 34, and an EGR control valve 35 is provided on each EGR branch pipe 34.

[0047] In this embodiment, the engine air supply system is provided with an air storage tank 31 in the EGR component. During the exhaust process of the exhaust pipe 22, part of the exhaust gas discharged from the exhaust pipe 22 can enter the air storage tank 31 through the main control valve 32 and the EGR main pipe 33. This part of the exhaust gas can be temporarily stored in the air storage tank 31, and the pressure of this part of the gas is stabilized. Then, it is supplied to each cylinder 11 through multiple EGR branch pipes 34 to ensure that the pressure of the exhaust gas supplied to the cylinder 11 of the engine 1 is stable and avoids fluctuations. In addition, an EGR control valve 35 is provided on each EGR branch pipe 34, which can control the opening and closing of the corresponding EGR branch pipe 34 to adjust the exhaust gas intake time of each cylinder 11, and ensure the uniformity of the EGR rate of each cylinder 11.

[0048] In this embodiment, the EGR control valve 35 is configured to unidirectionally conduct the EGR branch pipe 34 from the gas tank 31 to the cylinder 11. Such a configuration plays a role in unidirectionally conducting the exhaust gas, avoiding the exhaust gas backflow, further ensuring that each cylinder 11 of the engine 1 works stably and reliably, and avoiding pressure fluctuations caused by backflow.

[0049] Optionally, the main control valve 32 is configured as a solenoid valve.

[0050] Optionally, the EGR control valve 35 is provided as a solenoid valve.

[0051] Specifically, the intake pipe 21 includes an intake manifold and a plurality of intake branch pipes, the plurality of intake branch pipes are connected to the intake manifold, and the plurality of intake branch pipes are connected to the plurality of cylinders 11 in a one-to-one correspondence.

[0052] Specifically, an intercooler 23 is provided on the intake pipe 21, and an EGR cooler 24 is provided on the exhaust pipe 22 between the air storage tank 31 and the main control valve 32. Specifically, the intercooler 23 is provided on the intake manifold, and the provision of the intercooler 23 can cool the fresh air in the intake pipe 21. The provision of the EGR cooler 24 can cool the exhaust gas in the EGR manifold 33.

[0053] Specifically, the engine air supply system further includes a turbine 41 and a compressor 42. The turbine 41 is connected to the compressor 42. The turbine 41 is arranged on the exhaust pipe 22, and the compressor 42 is arranged on the intake pipe 21. Specifically, the exhaust gas in the exhaust pipe 22 is discharged, driving the turbine 41 to rotate, and the compressor 42 is driven by the turbine 41 to work, so that the fresh air is pressurized and sent into the intake pipe 21.

[0054] Continue to refer to Figure 1 to Figure 2 As shown, this embodiment also provides an EGR rate determination method, which applies the above-mentioned engine air supply system. The EGR rate determination method mainly includes the following steps:

[0055] S100, formulating an EGR rate and assigning an EGR rate calculation value α;

[0056] S200, obtaining the duration t0 during which the pressure P1 in the gas storage tank 31 is greater than the pressure P2 in the cylinder 11 of the engine 1 according to α;

[0057] S300, obtaining the opening time t of the EGR control valve 35 to be determined, and judging whether the condition satisfies: t<t0;

[0058] If yes, proceed to step S400;

[0059] If not, adjust the pressure P1 in the gas storage tank 31 and / or the spray hole cross-sectional area A of the injector and then return to step S200;

[0060] S400, evaluate the performance indicators and determine whether the evaluation requirements are met;

[0061] If so, the EGR rate is determined to be complete;

[0062] If not, a new EGR rate is re-set and assigned to α, and then the process returns to step S200.

[0063] Specifically, in order to ensure that the cylinder 11 can obtain the largest possible EGR rate and evenly mix, the opening time of the EGR control valve 35 is during the opening process of the intake valve of each cylinder 11. When the pressure in the air tank 31 is greater than the pressure in the cylinder 11, the EGR control valve 35 is opened to allow the exhaust gas to enter the corresponding cylinder 11. In the subsequent intake compression process, the exhaust gas and fresh air are mixed with the help of the air flow movement in the cylinder 11. The method applies the above-mentioned engine air supply system, obtains the duration t0 when the pressure P1 in the air tank 31 is greater than the pressure P2 in the cylinder 11 of the engine 1, and compares t0 with the opening time t of the EGR control valve 35, adjusts the pressure P1 in the air tank 31 and / or the spray hole cross-sectional area A of the injector according to the comparison result, and continuously iterates the EGR rate in the subsequent performance index evaluation process, so as to determine the optimal EGR rate value, realize the controllable quality of the EGR exhaust gas entering each cylinder 11, and improve the uniformity of the EGR rate of each cylinder 11.

[0064] Specifically, an initial EGR rate is firstly prepared, the pressure P1 in the air tank 31 and the pressure P2 in the cylinder 11 of the engine 1 are obtained, and the GT-POWER software is used to calculate the duration t0 during which the pressure P1 in the air tank 31 is greater than the pressure P2 in the cylinder 11. Specifically, the pressure P1 in the air tank 31 and the pressure P2 in the cylinder 11 are obtained by the pressure sensor.

[0065] Then, the opening time t of the EGR control valve 35 is obtained using the previously planned initial EGR rate. Specifically:

[0066] Get the mass m of the EGR gas in cylinder 11 e and mass flow rate q m ,but in,

[0067] m1 is the fresh air intake mass of cylinder 11, m is the fresh air intake mass flow rate of cylinder 11, and n is the speed of engine 1;

[0068] ρ is the gas density in the gas tank 31; T1 is the gas temperature in the gas tank 31; and R is the gas constant.

[0069] According to the above parameters, the initial EGR rate α is substituted into the equation to obtain

[0070] In order to ensure that the exhaust gas can fully enter the cylinder 11, the EGR control valve 35 time should be less than or equal to the duration that P1 is greater than P2.

[0071] Determine whether t satisfies: t<t0.

[0072] If the judgment is yes, then a subsequent performance indicator evaluation is performed;

[0073] If the answer is no, the pressure P1 in the air storage tank 31 and / or the spray hole cross-sectional area A of the fuel injector are adjusted and the process returns to step S200 to continue calculating a new t0 until the requirement of t<t0 is finally met.

[0074] In this embodiment, the pressure P1 in the gas storage tank 31 is adjusted by adjusting the model of the compressor 42 .

[0075] Furthermore, the performance index evaluation mainly includes test simulation evaluation based on simulation software and experimental evaluation based on real conditions, which requires both simulation and experimental evaluation.

[0076] Specifically, the performance index is evaluated to determine whether the evaluation requirements are met. Specifically, the NO in the exhaust gas of the exhaust pipe 22 is determined. X And whether the smoke density values ​​meet the requirements.

[0077] It is understandable that different regulations have different reference thresholds according to different emission regulations. Taking the non-road stage 4 regulations as an example: the NO of a 260 horsepower model NRSC emission cycle is X The content requirement of NO in the exhaust gas of the exhaust pipe 22 is 1.398 g / (kW·h). X The requirements for smoke density are as follows: Determine whether it meets the following requirements: 1g / (kW·h)<NO X The content is less than 2g / (kW·h) and 5mg / m 3 <Smoke density value<10mg / m 3 If the answer is yes, it indicates that the EGR rate is determined; if the answer is no, it is necessary to re-formulate a new EGR rate and assign it to α, then return to step S200, and go through the above steps again, that is, iterate the EGR rate until the optimal EGR rate is determined, so as to achieve controllable quality of EGR exhaust gas entering each cylinder 11 and improve the uniformity of the EGR rate of each cylinder 11.

[0078] In some other optional implementations, the performance index evaluation can also use other indicators as a reference. Take the marine diesel engine emission regulations as an example: it is stipulated that for the first category of marine engines (single cylinder displacement less than 5L), the equivalent displacement is between 1.2L and 5L, the HC+NOx limit is 5.8, and the PM limit is 0.3g / kWh.

[0079] The EGR rate determination method provided by the present invention applies the above-mentioned engine air supply system, obtains the duration t0 during which the pressure P1 in the air tank 31 is greater than the pressure P2 in the cylinder 11 of the engine 1, and compares t0 with the opening time t of the EGR control valve 35, adjusts the pressure P1 in the air tank 31 and / or the spray hole cross-sectional area A of the injector according to the comparison result, and continuously iterates the EGR rate in the subsequent performance indicator evaluation process, so as to determine the optimal EGR rate value, realize the controllable quality of the EGR exhaust gas entering each cylinder 11, and improve the uniformity of the EGR rate of each cylinder 11.

[0080] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An engine air supply system, characterized in that: include: An engine (1) having a plurality of cylinders (11); An air intake pipe (21) connected to the air intake ends of the plurality of cylinders (11); An exhaust pipe (22) connected to the exhaust ends of the plurality of cylinders (11); An EGR component comprises an air storage tank (31), a main control valve (32), an EGR main pipe (33) and a plurality of EGR branch pipes (34); a first end of the EGR main pipe (33) is connected to the exhaust pipe (22) through the main control valve (32); a second end of the EGR main pipe (33) is connected to the air storage tank (31); the air storage tank (31) is connected to the intake ends of a plurality of cylinders (11) through the plurality of EGR branch pipes (34); and each of the EGR branch pipes (34) is provided with an EGR control valve (35).

2. The engine air supply system according to claim 1, characterized in that: The EGR control valve (35) is configured to unidirectionally conduct the EGR branch pipe (34) from the gas storage tank (31) to the cylinder (11).

3. The engine air supply system according to claim 1, characterized in that: An intercooler (23) is provided on the intake pipe (21), and an EGR cooler (24) is provided on the exhaust pipe (22) between the gas storage tank (31) and the main control valve (32).

4. The engine air supply system according to claim 1, characterized in that: It also includes a turbine (41) and a compressor (42), wherein the turbine (41) is connected to the compressor (42), the turbine (41) is arranged on the exhaust pipe (22), and the compressor (42) is arranged on the intake pipe (21).

5. A method for determining an EGR rate, applied to the engine air supply system according to any one of claims 1 to 4, characterized in that: The EGR rate determination method comprises the following steps: S100, formulating an EGR rate and assigning an EGR rate calculation value α; S200, obtaining, based on α, a duration t0 during which the pressure P1 in the gas storage tank (31) is greater than the pressure P2 in the cylinder (11) of the engine (1); S300, obtaining the opening time t of the EGR control valve (35) to be determined, and judging whether the condition t<t0 is satisfied; If yes, proceed to step S400; If not, adjust the pressure P1 in the gas storage tank (31) and / or the spray hole cross-sectional area A of the fuel injector and then return to step S200; S400, evaluate the performance indicators and determine whether the evaluation requirements are met; If so, the EGR rate is determined to be complete; If not, a new EGR rate is re-set and assigned to α, and then the process returns to step S200.

6. The EGR rate determination method according to claim 5, characterized in that: In step S200, the GT-POWER software is used to calculate and obtain the duration t0 during which the pressure P1 in the gas storage tank (31) is greater than the pressure P2 in the cylinder (11).

7. The EGR rate determination method according to claim 5, characterized in that: The pressure P1 in the gas storage tank (31) and the pressure P2 in the cylinder (11) are obtained through a pressure sensor.

8. The method for determining the EGR rate according to claim 5, characterized in that: In step S300, the opening time t of the EGR control valve (35) is obtained as follows: Obtain the mass m of the EGR gas of the cylinder (11) e and mass flow rate q m ,but in, m1 is the fresh air intake mass of the cylinder (11), m is the fresh air intake mass flow rate of the cylinder (11), and n is the rotation speed of the engine (1); ρ is the gas density in the gas storage tank (31); T1 is the gas temperature in the gas storage tank (31); and R is the gas constant.

9. The method for determining the EGR rate according to claim 5, characterized in that: Step S400 specifically comprises: determining the NO in the exhaust gas of the exhaust pipe (22) X And whether the SOOT values ​​meet the requirements.

10. The method for determining the EGR rate according to claim 9, characterized in that: Determine the NO in the exhaust gas of the exhaust pipe (22) X And whether the smoke density values ​​meet the requirements: Determine whether it meets the following conditions: 1g / (kW·h)<NO X The content is less than 2g / (kW·h) and 5mg / m 3 <Smoke density value<10mg / m 3 .

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