阅读说明：本技术 一种提高增压柴油机废气再循环率的装置及其控制方法 (Device for improving exhaust gas recirculation rate of supercharged diesel engine and control method thereof ) 是由 李振国 钟祥麟 高继东 邬斌扬 吴撼明 郑雪龙 任晓宁 邵元凯 于 2020-08-24 设计创作，主要内容包括：本发明涉及一种提高增压柴油机废气再循环率的装置及其控制方法,装置包括发动机、涡轮增压器、电控离合器和EGR压气机；发动机分别连接进气总管和排气总管；涡轮增压器包括同轴设置的涡轮机和压气机,涡轮机的进气口通过二号排气管与排气总管连通,涡轮机的排气口通过三号排气管与大气连通；EGR压气机通过电控离合器连接压气机；上述装置可解决增压柴油机低速中高负荷等工况下进气压力大于或等于排气压力,废气难以顺利引入进气管的问题,使EGR系统应用工况范围更加广泛。同时可根据实际工况控制上述装置EGR阀、旁通阀和电控离合器,实现有无EGR、有无EGR增压、EGR增压度的控制,提高发动机效率。(The invention relates to a device for improving the exhaust gas recirculation rate of a supercharged diesel engine and a control method thereof, wherein the device comprises an engine, a turbocharger, an electric control clutch and an EGR (exhaust gas recirculation) compressor; the engine is respectively connected with the air inlet main pipe and the air outlet main pipe; the turbocharger comprises a turbine and a compressor which are coaxially arranged, an air inlet of the turbine is communicated with an exhaust main pipe through a second exhaust pipe, and an exhaust port of the turbine is communicated with the atmosphere through a third exhaust pipe; the EGR gas compressor is connected with the gas compressor through an electric control clutch; the device can solve the problems that the air inlet pressure is greater than or equal to the air outlet pressure under the working conditions of low speed, medium and high load and the like of the supercharged diesel engine, and the waste gas is difficult to smoothly introduce into the air inlet pipe, so that the application working condition range of the EGR system is wider. Meanwhile, the EGR valve, the bypass valve and the electric control clutch of the device can be controlled according to actual working conditions, the control of EGR absence, EGR pressurization and EGR pressurization degree is realized, and the efficiency of the engine is improved.)

1. The device for improving the exhaust gas recirculation rate of the supercharged diesel engine is characterized by comprising an engine (1), a turbocharger (8), an electric control clutch (11) and an EGR compressor (12); the engine (1) is respectively connected with an air inlet main pipe (20) and an air outlet main pipe (2); the exhaust main pipe (2) is connected with a first exhaust pipe (4) and a second exhaust pipe (5); the turbocharger (8) comprises a turbine (6) and a compressor (10) which are coaxially arranged, an air inlet of the turbine (6) is communicated with the exhaust manifold (2) through a second exhaust pipe (5), and an exhaust port of the turbine (6) is communicated with the atmosphere through a third exhaust pipe (7); an air inlet of the compressor (10) is communicated with an air filter (9), and an air outlet of the compressor (10) is communicated with an air inlet header pipe (20) through a first air inlet pipe (17);

the EGR compressor (12) is connected with the compressor (10) through an electric control clutch (11), an air inlet of the EGR compressor (12) is communicated with a first exhaust pipe (4) through a bypass pipe (13), and an exhaust outlet of the EGR compressor (12) is sequentially communicated with a fourth exhaust pipe (16), the first exhaust pipe (4) and a first air inlet pipe (17).

2. The apparatus for increasing an exhaust gas recirculation rate of a supercharged diesel engine according to claim 1, characterized in that: a bypass valve (15) is arranged on the bypass pipe (13), and the bypass valve (15) is used for controlling the flow of the exhaust gas passing through the bypass pipe (13).

3. The apparatus for increasing an exhaust gas recirculation rate of a supercharged diesel engine according to claim 1, characterized in that: an EGR valve (3), an EGR pre-pressure intercooler (14) and an EGR post-pressure intercooler (19) are arranged on the first exhaust pipe (4); EGR presses intercooler (14) before to be located bypass pipe (13) and exhaust pipe (4) interface before, EGR presses aftercooler (19) to be located No. four exhaust pipe (16) and exhaust pipe (4) interface back.

4. The apparatus for increasing an exhaust gas recirculation rate of a supercharged diesel engine according to claim 3, characterized in that: no. one blast pipe (4) with intake pipe (17) intercommunication, be equipped with air intake intercooler (18) on intake pipe (17).

5. The apparatus for increasing an exhaust gas recirculation rate of a supercharged diesel engine according to claim 4, characterized in that: and the air intake intercooler (18) is positioned in front of the joint of the first exhaust pipe (4) and the first air intake pipe (17).

6. The control method of an apparatus for increasing an exhaust gas recirculation rate of a supercharged diesel engine as claimed in claims 1 to 5, characterized in that the engine cooling water temperature, the exhaust pressure, the intake pressure, the engine load signal and the engine speed signal are collected separately by the ECU control unit and controlled according to a preset MAP.

7. The control method of an apparatus for increasing a egr rate of a supercharged diesel engine according to claim 6, characterized in that: when the engine (1) is in a cold start, warm-up or idle working condition, the EGR valve (3) and the bypass valve (15) are closed, and the electric control clutch (11) is disconnected.

8. The control method of an apparatus for increasing a egr rate of a supercharged diesel engine according to claim 6, characterized in that: when the engine (1) is in a low-rotating-speed and small-load working condition, a medium-speed working condition and a high-speed working condition, the EGR valve (3) is opened, the bypass valve (15) is closed, the electronic control clutch (11) is disconnected, and the recirculated exhaust gas enters the first air inlet pipe (17) through the first exhaust pipe (4) to be mixed with fresh air.

9. The control method of an apparatus for increasing a egr rate of a supercharged diesel engine according to claim 6, characterized in that: when the engine (1) is in a low rotating speed and a high load, if the air inlet pressure of the engine (1) is detected to be larger than or equal to the exhaust pressure, the EGR valve (3) and the bypass valve (15) are opened, the electronic control clutch (11) is connected, the turbine (6) simultaneously drives the air compressor (10) and the EGR air compressor (12) to rotate, the recirculating exhaust gas enters a first air inlet pipe (17) through a fourth exhaust pipe (16) and a first exhaust pipe (4) after being pressurized by the EGR air compressor (12), and is mixed with fresh air pressurized by the air compressor (10) to enter a cylinder of the engine (1).

10. The control method of the apparatus for increasing a egr rate of a supercharged diesel engine according to claims 6-9, characterized in that: the ECU controls the flow rate of the recirculated exhaust gas by controlling the opening and closing angles of the EGR valve (3) and the bypass valve (15), and achieves a target EGR rate.

Technical Field

The invention belongs to the field of engine control, and particularly relates to a device for improving the exhaust gas recirculation rate of a supercharged diesel engine and a control method thereof.

Background

Exhaust Gas Recirculation (EGR) refers to the introduction of a portion of the Exhaust gases from the engine back into the intake pipe and again into the cylinder together with fresh mixture. Because the waste gas contains a large amount of CO₂、H₂Polyatomic gases such as O, and CO₂On one hand, the gases absorb a large amount of heat due to high specific heat capacity, on the other hand, the combustion chemical reaction rate is reduced due to low oxygen concentration, so that the maximum combustion temperature of the mixed gas is reduced, and the generation amount of NOx emission is reduced.

As for the connection method of the EGR loop of the single-stage supercharged diesel engine, there are three types: (1) turbine inlet → compressor inlet; (2) turbine outlet → compressor inlet; (3) turbine inlet → intake pipe after intercooler.

The first two modes are referred to as low pressure EGR and because the exhaust gas is introduced into the compressor inlet and a positive pressure differential is established between the exhaust gas and the intake air with the aid of a back pressure valve, the desired EGR rate is relatively easily achieved over a relatively wide operating range of the engine. However, the main problem of the low-pressure EGR system is that EGR exhaust gas enters a compressor to cause supercharger pollution and affect the reliability of an engine, and a DPF is generally required to be additionally installed to filter the exhaust gas; on the other hand, the exhaust back pressure is higher at high rotating speed, and the pumping loss is larger.

The third mode is referred to as high pressure EGR, and is also the more commonly used form of EGR. For a supercharged diesel engine, under the working conditions of low speed, medium load and the like, the intake pressure is greater than or equal to the exhaust pressure, and the exhaust gas is difficult to smoothly flow into an intake pipe, so that the performance and the emission level of the engine are influenced.

The existing method for improving the exhaust gas recirculation rate mainly reduces the pressure of an air inlet pipe by installing a throttle valve on the air inlet pipe, so that the exhaust gas flows into the air inlet pipe under the action of differential pressure. With the increase of the load of the supercharged diesel engine, the maximum pressure difference of the intake and the exhaust provided by the diesel engine is small, and the exhaust back pressure is increased through the technologies of an exhaust gas throttle valve, a VGT (variable geometry turbine) and the like to obtain a high EGR rate, so that the oil consumption of the engine can be improved. For the above reasons, the improvement of the supercharged diesel engine exhaust gas recirculation rate is limited.

Disclosure of Invention

In view of the above, the invention provides a device for improving the exhaust gas recirculation rate of a supercharged diesel engine, so as to solve the problem that the exhaust gas is difficult to smoothly introduce into an air inlet pipe when the air inlet pressure is greater than or equal to the exhaust pressure under the working conditions of low speed, medium and high load and the like, so that more exhaust gas enters the air inlet pipe, and the application working condition range of an EGR system is wider.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a device for improving the exhaust gas recirculation rate of a supercharged diesel engine comprises an engine 1, a turbocharger 8, an electric control clutch 11 and an EGR compressor 12; the engine 1 is respectively connected with an air inlet main pipe 20 and an exhaust main pipe 2; the exhaust main pipe 2 is connected with a first exhaust pipe 4 and a second exhaust pipe 5; the turbocharger 8 comprises a turbine 6 and a compressor 10 which are coaxially arranged, an air inlet of the turbine 6 is communicated with the exhaust manifold 2 through a second exhaust pipe 5, and an air outlet of the turbine 6 is communicated with the atmosphere through a third exhaust pipe 7; an air inlet of the compressor 10 is communicated with an air filter 9, and an air outlet of the compressor 10 is communicated with an air inlet header pipe 20 through a first air inlet pipe 17;

the EGR compressor 12 is connected with the compressor 10 through an electric control clutch 11, an air inlet of the EGR compressor 12 is communicated with the first exhaust pipe 4 through a bypass pipe 13, and an air outlet of the EGR compressor 12 is sequentially communicated with the fourth exhaust pipe 16, the first exhaust pipe 4 and the first air inlet pipe 17.

Preferably, a bypass valve 15 is provided on the bypass pipe 13, and the bypass valve 15 is used to control the flow rate of the exhaust gas passing through the bypass pipe 13.

Preferably, the first exhaust pipe 4 is provided with an EGR valve 3, an EGR pre-pressure intercooler 14 and an EGR post-pressure intercooler 19; the intercooler 14 before EGR pressure is positioned at the front of a joint of the bypass pipe 13 and the first exhaust pipe 4, and the intercooler 19 after EGR pressure is positioned at the back of a joint of the fourth exhaust pipe 16 and the first exhaust pipe 4.

Preferably, the first exhaust pipe 4 is communicated with the first air inlet pipe 17, and an air inlet intercooler 18 is arranged on the first air inlet pipe 17.

Preferably, the intake intercooler 18 is located before the interface between the first exhaust pipe 4 and the first intake pipe 17.

The invention also provides a control method of the device for improving the exhaust gas recirculation rate of the supercharged diesel engine, which is characterized in that an ECU (electronic control Unit) is used for respectively collecting the cooling water temperature, the exhaust pressure, the intake pressure, the engine load signal and the engine rotating speed signal of the engine and controlling according to a preset MAP (MAP).

Preferably, when the engine 1 is in a cold start, warm up or idle condition, the EGR valve 3 and the bypass valve 15 are closed and the electronically controlled clutch 11 is disengaged.

Preferably, when the engine 1 is in a low-speed and small-load working condition, a medium-speed working condition and a high-speed working condition, the EGR valve 3 is opened, the bypass valve 15 is closed, the electrically controlled clutch 11 is disconnected, and the recirculated exhaust gas enters the first air inlet pipe 17 through the first exhaust pipe 4 to be mixed with fresh air.

Preferably, when the engine 1 is in a low rotating speed and a medium-high load, if the air inlet pressure of the engine 1 is detected to be greater than or equal to the air outlet pressure, the EGR valve 3 and the bypass valve 15 are opened, the electrically controlled clutch 11 is engaged, the turbine 6 simultaneously drives the compressor 10 and the EGR compressor 12 to rotate, the recirculated exhaust gas enters the first air inlet pipe 17 through the fourth exhaust pipe 16 and the first exhaust pipe 4 after being pressurized by the EGR compressor 12, and is mixed with the fresh air pressurized by the compressor 10 to enter the cylinder of the engine 1.

Preferably, the ECU control unit controls the recirculated exhaust gas flow rate by controlling the opening and closing angles of the EGR valve 3 and the bypass valve 15, to achieve the target EGR rate.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention is different from a common EGR system, adopts an EGR pressurization mode by utilizing exhaust gas turbocharging, an EGR compressor is connected with a compressor of a turbocharger through an electric control clutch, a turbine of the turbocharger drives the compressor and the EGR compressor at the same time, and the recirculated exhaust gas is pressurized by the EGR compressor and then is input into an air inlet pipe to be mixed with fresh air pressurized by the compressor to enter an air cylinder. The problem of under low-speed medium high load, inlet pressure is greater than or equal to the exhaust pressure, and waste gas is difficult to flow into the intake pipe smoothly is solved for more the entering of waste gas volume is in the intake pipe, and the operating mode range of EGR system application is wider.

2. The EGR compressor is connected with the bypass pipe in parallel, and the recirculated exhaust gas can smoothly flow into the air inlet pipe without pressurizing the exhaust gas under the working condition of the forward pressure difference, namely under the condition that the exhaust pressure is greater than the air inlet pressure. The exhaust back pressure of the engine is reduced, and the oil consumption of the engine is further reduced.

3. The invention is provided with an EGR valve, an electric control clutch and a bypass valve, and can realize the control of EGR-free, EGR-pressurized and EGR-pressurized degree by controlling the valve and the clutch. High control precision and wide application range.

4. When the recirculated exhaust gas is pressurized, the turbine drives the gas compressor and the EGR gas compressor at the same time, so that the load of the turbine is increased, the highest rotating speed of the turbine can be effectively reduced, and the overspeed of the turbocharger is prevented.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic structural diagram of the present invention.

Icon: 1. an engine; 2. an exhaust manifold; an EGR valve; 4. a first exhaust pipe; 5. a second exhaust pipe; 6. a turbine; 7. a third exhaust pipe; 8. a turbocharger; 9. an air cleaner; 10. a compressor; 11. an electrically controlled clutch; 12, an EGR compressor; 13. a bypass pipe; EGR pre-pressure intercooler; 15. a bypass valve; 16. a fourth exhaust pipe; 17. a first air inlet pipe; 18. an air intake intercooler; an EGR post-pressure intercooler; 20. an intake manifold.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "connected," and "connected" are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The invention is described in further detail below with reference to the figures and specific examples.

Referring to fig. 1, an apparatus for improving an exhaust gas recirculation rate includes an engine 1, a turbocharger 8, an electronically controlled clutch 11, and an EGR compressor 12. The engine 1 is respectively connected with an air inlet main pipe 20 and an exhaust main pipe 2; the exhaust main pipe 2 is connected with a first exhaust pipe 4 and a second exhaust pipe 5; the turbocharger 8 comprises a turbine 6 and a compressor 10 which are coaxially arranged, an air inlet of the turbine 6 is communicated with the exhaust manifold 2 through a second exhaust pipe 5, and an air outlet of the turbine 6 is communicated with the atmosphere through a third exhaust pipe 7; an air inlet of the compressor 10 is communicated with an air filter 9, and an air outlet of the compressor 10 is communicated with an air inlet manifold 20 through a first air inlet pipe 17.

The EGR compressor 12 is connected with the compressor 10 through an electric control clutch 11, an air inlet of the EGR compressor 12 is communicated with the first exhaust pipe 4 through a bypass pipe 13, and an air outlet of the EGR compressor 12 is sequentially communicated with the fourth exhaust pipe 16, the first exhaust pipe 4 and the first air inlet pipe 17.

A bypass valve 15 is arranged on the bypass pipe 13.

And an EGR valve 3, an EGR pre-pressure intercooler 14 and an EGR post-pressure intercooler 19 are arranged on the first exhaust pipe.

The EGR pre-pressure intercooler 14 is positioned in front of the joint of the bypass pipe 13 and the first exhaust pipe 4.

And the EGR post-pressure intercooler 19 is positioned behind the interface of the fourth exhaust pipe 16 and the first exhaust pipe 4.

The first exhaust pipe 4 is communicated with the first air inlet pipe 17.

And an air intake intercooler 18 is arranged on the first air inlet pipe 17.

Preferably, the intake intercooler 18 is located before the interface between the first exhaust pipe 4 and the first intake pipe 17.

The engine 1 of the present invention is preferably a diesel engine.

The principle of the invention is illustrated as follows:

for supercharged diesel engines, the demand for EGR rate is different when the engine is in different operating conditions. When the diesel engine is in working conditions of cold start, warm-up, idling and the like, EGR needs to be closed; when the diesel engine is in a working condition of low rotating speed, small load, medium and high rotating speed and large load, a small EGR rate is needed to be used; when the diesel engine is operated at a low rotation speed and a high load, it is necessary to use a large EGR rate, and at this time, the intake pressure is greater than or equal to the exhaust pressure, and it is difficult for the recirculated exhaust gas to directly flow into the intake pipe.

In order to meet the demand of the supercharged diesel engine on the EGR rate under different working conditions and enlarge the application range of EGR, the invention provides an EGR supercharging mode by utilizing exhaust gas turbocharging, which comprises the following steps: when the diesel engine does not need EGR, the EGR valve 3 and the bypass valve 15 are closed; when the diesel engine needs EGR and does not need to pressurize the recirculated exhaust gas, the EGR valve 3 is opened, the bypass valve 15 is closed, the recirculated exhaust gas is directly mixed with fresh air pressurized by the compressor 10 into the cylinder through the first exhaust pipe 4 and the first air inlet pipe 17; when the diesel engine needs EGR and the recirculated exhaust gas needs to be pressurized, the EGR valve 3 is opened, the bypass valve 15 is opened, the EGR compressor 12 is connected with the compressor 10 of the turbocharger 8 through the electric control clutch 11, the turbine 6 of the turbocharger 8 drives the compressor 10 and the EGR compressor 12 simultaneously, the recirculated exhaust gas enters the first air inlet pipe 17 through the fourth exhaust pipe 16 and the first exhaust pipe 4 after being pressurized by the EGR compressor 12, and the recirculated exhaust gas is mixed with fresh air pressurized by the compressor 10 and enters the cylinder of the engine 1.

The EGR valve 3, the electric control clutch 11 and the bypass valve 15 are switched on and off to realize the opening and closing of EGR and EGR pressurization functions, and the specific control method comprises the following steps:

the ECU control unit respectively collects the cooling water temperature, the exhaust pressure, the intake pressure, the diesel engine load signal, the diesel engine rotating speed signal and the like of the engine and controls according to a preset MAP (MAP data processing) diagram:

(1) when the engine 1 is in the working conditions of cold start, warm-up, idling and the like, the in-cylinder combustion temperature is low, the generation amount of NOx is small, and in order to enable the engine 1 to start more smoothly and operate smoothly, the EGR function is closed under the working conditions. At this time, the EGR valve 3 and the bypass valve 15 are in the closed state, and the electronically controlled clutch 11 is disengaged.

(2) When the engine 1 is in a low-speed and low-load working condition, a small EGR rate is used due to the fact that the fuel injection quantity is small and the combustion temperature is not high; when the engine 1 is in the middle, high speed, large load condition, the EGR rate should also be reduced in order to obtain higher output power. These conditions should turn on the EGR function, but not boost the recirculated exhaust gas. At the moment, the EGR valve 3 is opened, the bypass valve 15 is closed, the electrically controlled clutch 11 is disconnected, and the recirculated exhaust gas directly enters the first air inlet pipe 17 through the first exhaust pipe 4 to be mixed with fresh air.

(3) When the engine 1 is at a low rotation speed and a high load, the temperature in the combustion chamber is high, the amount of NOx produced is large, the EGR rate does not greatly affect the indexes such as HC and CO emissions, the fuel consumption, and the output torque, and the NOx emission can be reduced by using a large EGR rate. Under these conditions, the exhaust gas is pressurized so that the intake pressure is greater than or equal to the exhaust pressure, the exhaust gas is difficult to flow smoothly into the intake pipe, the EGR function should be turned on, and the recirculated exhaust gas is pressurized. When the ECU detects that the diesel intake pressure is close to the exhaust pressure, the EGR valve 3, the bypass valve 15 are opened, and the electronically controlled clutch 11 is engaged. The turbine 6 drives the compressor 10 and the EGR compressor 12 to rotate at the same time, the recirculated exhaust gas enters the first air inlet pipe 17 through the fourth exhaust pipe 16 and the first exhaust pipe 4 after being pressurized by the EGR compressor 12, and is mixed with fresh air pressurized by the compressor 10 to enter the cylinder of the engine 1.

(4) The ECU controls the recirculated exhaust gas flow rate by controlling the opening and closing angles of the EGR valve 3 and the bypass valve 15, and achieves the target EGR rate.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.