CN211549860U - An exhaust gas recirculation system - Google Patents

Abstract

The utility model discloses an exhaust gas recirculation system, which relates to the technical field of engines, comprising an exhaust pipe, an EGR cooler, an EGR valve, an intake pipe, a venturi pipe, a temperature sensor, a pressure sensor, a differential pressure sensor and an engine ECU; The venturi tube is arranged between the EGR cooler and the EGR valve, and is provided with two input lumen, which are respectively connected with the inlet and the throat; the temperature sensor is arranged on the EGR cooler and the intake pipe On the connecting pipeline between, the pressure sensor is arranged on the straight section of the inlet or outlet of the venturi tube, and the two input nozzles of the differential pressure sensor are respectively arranged on the two input tubes of the venturi tube. cavity; the temperature sensor, pressure sensor, differential pressure sensor and EGR valve are respectively connected with the engine ECU through lines. The utility model realizes closed-loop control of the opening degree of the EGR valve by measuring the exhaust gas flow under different opening degrees of the EGR valve.

Description

An exhaust gas recirculation system

technical field

The utility model relates to the technical field of engines, in particular to an exhaust gas recirculation system.

Background technique

The existing EGR system usually does not have an EGR exhaust gas flow measurement device, and only controls and calculates the EGR rate through the opening degree of the EGR valve. The method of controlling and calculating the EGR rate through the opening of the EGR valve is used for the models required by the national 5 emission regulations. Only controlling the EGR rate through the opening of the EGR valve belongs to open-loop control. After the emission is upgraded to the national 6, the emission Higher requirements are put forward for the emission of harmful substances such as nitrogen oxides and soot particles in the exhaust gas. The control accuracy of open-loop control cannot meet the requirements. In the case of open-loop control, the emission cannot meet the requirements of China 6 regulations. The EGR system of the model needs to add a measuring device that can measure the EGR rate to perform closed-loop control of the EGR rate.

The prior art realizes different EGR rates corresponding to different working conditions by controlling the opening degree of the EGR valve, and defines the opening degree of the EGR valve under each working condition through test calibration, and the EGR valve finds the closed position through self-learning of the zero point position. of zero. Even if there is wear and tear in use, it can be adjusted to adapt to the zero position. This EGR control technology can meet the requirements of emission regulations for models with emission requirements below China 5. However, with the upgrade of emission regulations to China 6, the EGR technology route is only calculated and controlled by the EGR valve opening and the control accuracy cannot meet the emission requirements.

There is also a method to calculate the exhaust gas flow by measuring the pressure difference before and after the EGR valve. This method is theoretically feasible, but the control accuracy is difficult to meet the national 6 emission control requirements, because the EGR valve airflow is unstable, and the pressure difference between the front and rear is affected by the change of the valve opening. The deviation between the exhaust gas flow calculated by this method and the actual value will be very large. The requirements of the national 6 emission for the measurement progress of the exhaust gas flow are within ±1%, which requires a high-precision processing flowmeter to achieve.

Chinese invention patent application CN 109209688 A

Utility model content

In view of the problems existing in the prior art, the utility model provides an exhaust gas recirculation system, which realizes closed-loop control of the opening degree of the EGR valve by measuring the exhaust gas flow under different opening degrees of the EGR valve.

For realizing the above-mentioned purpose of the utility model, the technical scheme of the present utility model is as follows:

An exhaust gas recirculation system, comprising an exhaust pipe, an EGR cooler, an EGR valve and an intake pipe connected in sequence through a pipeline, the system further comprising: a venturi, a temperature sensor, a pressure sensor, a differential pressure sensor and an engine ECU;

The venturi tube is arranged between the EGR cooler and the EGR valve, including an inlet and a throat, and the wall of the venturi tube is provided with two input lumens, which are respectively communicated with the inlet and the throat;

The temperature sensor is arranged on the connecting pipeline between the EGR cooler and the intake pipe, the pressure sensor is arranged on the straight section of the inlet or outlet of the venturi, and the differential pressure sensor is two. The input nozzles are respectively arranged in the two input lumens of the venturi;

The temperature sensor, pressure sensor, differential pressure sensor and EGR valve are respectively connected with the engine ECU through communication lines.

Further, one or two input lumens of the Venturi tube are axially inclined relative to the Venturi tube.

Further, the temperature sensor is arranged on the connecting pipe between the EGR cooler and the venturi or on the connecting pipe between the venturi and the EGR valve.

Further, the temperature sensor is arranged at a position biased towards the venturi.

Compared with the prior art, the utility model has the following beneficial effects:

1. The utility model adds a temperature sensor, a pressure sensor, a differential pressure sensor and a Venturi tube. The engine ECU can calculate the EGR valve under different opening degrees according to the exhaust gas temperature, exhaust gas pressure and differential pressure collected by these three sensors. EGR flow value, closed-loop control of EGR valve opening. Compared with the existing technology, it has higher control precision and good control response. Through closed-loop control, the EGR flow can be adjusted in real time, the emission consistency is good, and the emission of pollutants can be minimized;

2. The utility model is arranged for the EGR valve at the cold end. The exhaust gas is first cooled by the cooler and then enters the EGR valve. The EGR valve does not need to have a cooling water circuit, and the arrangement is compact and the cost is low;

3. The input lumen of the Venturi tube and the two input nozzles of the differential pressure sensor are inclined and set to ensure that there are equal diameter straight sections of a certain length before and after the pressure taking port of the Venturi tube, so as to stabilize the airflow at the pressure taking port. At the same time, it can make the Venturi tube compact, improve the flexibility and adaptability of the Venturi tube to its layout space, and save costs at the same time;

4. The system has simple structure and low cost, and realizes complex control and measurement requirements through simple structure, and has good economical practicability;

5. The utility model reduces the burden of post-processing by improving the contribution of the EGR system to emission control, and reduces the development difficulty and cost of post-processing;

6. The EGR valve is arranged behind the venturi tube and is closest to the intake port, so the EGR system has a high response and avoids the knocking phenomenon of the gas engine.

Description of drawings

Fig. 1 is the structural representation of one embodiment of the utility model;

2 is a schematic structural diagram of a venturi tube according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of an outflow coefficient curve according to an embodiment of the present invention.

In the figure, 1-exhaust pipe, 2-EGR cooler, 3-EGR valve, 4-venturi pipe, 41-pressure port 1, 42-pressure port 2, 43-inlet, 44-throat port, 45 - Input lumen, 5- intake pipe, 6- engine ECU, 7- temperature sensor, 8- pressure sensor, 9- differential pressure sensor.

Detailed ways

In order to describe in detail the technical content, achieved objects and effects of the present invention, the following descriptions are given with reference to the embodiments and the accompanying drawings.

As shown in FIG. 1, an exhaust gas recirculation system includes an exhaust pipe 1, an EGR cooler 2, an EGR valve 3 and an intake pipe 5 that are sequentially communicated through pipelines; it also includes a venturi 4, a temperature sensor 7, Pressure sensor 8 , differential pressure sensor 9 and engine ECU 6 .

The venturi tube 4 is arranged between the EGR cooler 2 and the EGR valve 3, and includes an inlet 43 and a throat 44. The wall of the venturi tube 4 is provided with two input lumens 45, which are respectively connected to the inlet 43. and the throat 44 is communicated.

The temperature sensor 7 , the pressure sensor 8 , the differential pressure sensor 9 and the EGR valve 3 are respectively connected with the engine ECU 6 through communication lines.

The role of the EGR cooler 2 is to cool the EGR exhaust gas. -

The function of the EGR valve 3 is to control the size of the EGR exhaust gas flow by receiving a control command from the engine ECU 6 and adjusting the opening of the valve plate.

The venturi 4 is provided with a pressure-taking port 41 and a pressure-taking port 42 at the connection between the inlet 43, the throat port 44 and the input lumen 5, respectively. There is a pressure difference between them, the specific structure is shown in Figure 2.

The temperature sensor 7 is used to monitor the exhaust gas temperature of the EGR valve 3 under different opening degrees, and send the exhaust gas temperature to the engine ECU 6 .

The pressure sensor 8 is used to monitor the exhaust gas pressure of the EGR valve 3 under different opening degrees, and send the exhaust gas pressure to the engine ECU 6 .

The differential pressure sensor 9 monitors the pressure taking ports 41 and 41 of the Venturi tube 4 under different opening degrees of the EGR valve 3 through the two input nozzles disposed in the two input lumens 5 of the Venturi tube 4 . The pressure difference between the pressure ports 42 is taken and sent to the engine ECU 6 .

The temperature sensor 7 is arranged on the connecting pipeline between the EGR cooler 2 and the intake pipe 5. In order to improve the control accuracy, the temperature sensor should be placed as close as possible to the venturi 4 when the space allows. 7 is arranged on the connecting pipe between the EGR cooler 2 and the venturi 4 or on the connecting pipe between the venturi 4 and the EGR valve 3, the best solution is to place all the Described temperature sensor 7 is arranged in the position that is biased to described venturi tube 4; Described pressure sensor 8 is arranged on the straight section of the inlet or outlet of described Venturi tube 4, this position air flow is stable, avoids air flow fluctuation to affect test, guarantees Test stability. In this embodiment, the temperature sensor 7 is arranged on the connecting pipeline between the venturi 4 and the EGR valve 3 , and the pressure sensor 8 is arranged on the straight section of the outlet of the venturi 4 .

The sudden change in the diameter of the inner lumen of the venturi tube 4 will cause a large fluctuation in the pressure of the exhaust gas flow, thereby affecting the measurement accuracy. There must be a certain length range of equal diameters before and after the pressure taking port 41 and the pressure taking port 42 of the Venturi tube 4. In order to make the Venturi tube 4 compact, improve the flexibility and adaptability of the Venturi tube 4 to its layout space, and save costs, two or one input lumen of the Venturi tube 4 can be opposite to each other. The Venturi tube 4 is arranged obliquely in the axial direction. In this embodiment, the input lumen corresponding to the inlet 43 is arranged obliquely, as shown in FIG. 2 .

The exhaust gas is first cooled from the exhaust pipe 1 through the EGR cooler 2, then the exhaust gas pressure difference is measured through the Venturi pipe 4, and then the exhaust gas flow is controlled through the EGR valve 3, and finally enters the intake pipe. 5. The exhaust gas is first cooled by the EGR cooler 2 and then enters the EGR valve 3. The EGR valve 3 does not need to have a cooling water circuit, and the layout is compact and the cost is low. The EGR valve 3 is arranged behind the Venturi tube 4 and is closest to the intake port 5, so the EGR system has high responsiveness and avoids the knocking phenomenon of the gas engine.

其中：Calculation principle of exhaust gas flow value:

in:

Q _m - mass flow of exhaust gas, the mass of exhaust gas passing through the exhaust gas recirculation system per unit time, in kg/s;

C-outflow coefficient, which represents the coefficient of the relationship between the actual flow through the system and the theoretical flow;

β-diameter ratio, the ratio of the diameter of the throat 44 of the venturi tube 4 to the diameter of the inlet 43;

ε-expansibility coefficient;

d-Venturi 4 throat 43 diameter, unit m;

Δp-pressure difference, the static pressure difference measured between the inlet 43 and the throat 44 of the venturi 4, the signal is measured by the pressure difference sensor 9, the unit Pa;

ρ-exhaust gas density, obtained by calculating the exhaust gas temperature and pressure, in kg/m ³ .

P1为废气压力，T为废气温度，R为热力学气体常数。

P1 is the exhaust gas pressure, T is the exhaust gas temperature, and R is the thermodynamic gas constant.

计算流量Q_c，标准流量台架实际废气流量与测量计算流量Q_c的比值就算出流出系数C，计算出不同流量下对应的流出系数C值，绘制成一条曲线，曲线示意图如图3所示，X轴表示文丘里管4不同目标流量，单位为kg/h，Y轴表示对应的流出系数C(流量20以内小流量时压差较小，流出系数有偏差不考虑在内)。When calculating the mass of exhaust gas passing through the venturi tube 4 using the above formula, the value of the outflow coefficient C is first determined according to the corresponding relationship between the target flow rate and the outflow coefficient C. The value of the outflow coefficient C can be calibrated off-line. A Venturi tube (the structure is the same as that of the Venturi tube 4) is set up on the standard flow bench, and the corresponding differential pressure sensor, pressure sensor and temperature sensor are connected to the Venturi tube. 5, 10, 15, 20…….kg/h exhaust gas flow, according to the formula (

Calculate the flow rate Q _c , the ratio of the actual exhaust gas flow rate of the standard flow bench to the measured and calculated flow rate Q _c to calculate the outflow coefficient C, calculate the corresponding outflow coefficient C value under different flow rates, and draw a curve. The schematic diagram of the curve is shown in Figure 3 , the X axis represents the different target flow rates of the Venturi tube 4, the unit is kg/h, the Y axis represents the corresponding outflow coefficient C (the pressure difference is small when the flow rate is less than 20, and the deviation of the outflow coefficient is not considered).

During engine operation, the engine ECU 6 calculates the EGR of the EGR valve 3 under different opening degrees according to the exhaust gas temperature, exhaust gas pressure and differential pressure transmitted by the temperature sensor 7 , the pressure sensor 8 and the differential pressure sensor 9 . Exhaust gas flow value; ECU 6 compares the calculated exhaust gas flow value with the target flow rate, and controls and adjusts the opening of the EGR valve 3 according to the comparison difference, so that the EGR flow rate is infinitely close to the target flow rate, thereby realizing precise closed-loop control of the EGR flow rate. . Compared with the prior art, it has higher measurement accuracy and control accuracy, and has good control correspondence. Through closed-loop control, the EGR flow can be adjusted in real time, and the emission consistency is good, and the emission of pollutants can be minimized. The contribution of the EGR system to emission control is improved, the burden of post-processing is reduced, and the development difficulty and cost of post-processing are reduced.

The system has a simple structure and low cost, realizes complex control and measurement requirements through a simple structure, and is economical and practical.

Although the present utility model has been described in detail above with specific embodiments, some modifications or improvements can be made on the basis of the present utility model, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention belong to the scope of protection of the present invention.

Claims (4)

1. An exhaust gas recirculation system, comprising an exhaust pipe (1), an EGR cooler (2), an EGR valve (3) and an intake pipe (5) that are sequentially communicated through pipelines, characterized in that, also comprising: Venturi tube (4), temperature sensor (7), pressure sensor (8), differential pressure sensor (9) and engine ECU (6); The venturi tube (4) is arranged between the EGR cooler (2) and the EGR valve (3), including an inlet (43) and a throat (44), and the wall of the venturi tube (4) is provided with There are two input lumen (45), which are respectively communicated with the inlet (43) and the throat (44); The temperature sensor (7) is arranged on the connecting pipeline between the EGR cooler (2) and the intake pipe (5), and the pressure sensor (8) is arranged on the venturi (4) On the straight section of the inlet or outlet of the differential pressure sensor (9), the two input nozzles of the differential pressure sensor (9) are respectively arranged in the two input lumens (45) of the Venturi tube (4); The temperature sensor (7), the pressure sensor (8), the differential pressure sensor (9) and the EGR valve (3) are respectively connected with the engine ECU (6) through communication lines. 2. The exhaust gas recirculation system according to claim 1, characterized in that: one or two of the input lumen (45) of the venturi (4) are axially inclined relative to the venturi (4). set up. 3. The exhaust gas recirculation system according to claim 1, wherein the temperature sensor (7) is arranged on the connecting pipe between the EGR cooler (2) and the venturi (4) Or on the connecting pipe between the Venturi tube (4) and the EGR valve (3). 4. The exhaust gas recirculation system according to claim 3, characterized in that the temperature sensor (7) is arranged at a position biased towards the venturi (4).

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