CN116906155A - Electric heating system and electric heating control method for vehicle SCR exhaust thermal management - Google Patents

Abstract

The invention discloses an electric heating system and an electric heating control method for thermal management of automobile SCR tail gas, wherein the electric heating control method controls the electric heating system, and the electric heating control method comprises the following steps: the vehicle-mounted computer monitors the exhaust flow, the vehicle speed, the ambient temperature, the post-treatment temperature, the urea temperature, the PTO, the brake, the clutch and the battery voltage, and controls the heating state of the EHC electrode through the electric heating relay switch according to the exhaust flow state, the vehicle speed state, the ambient temperature state, the post-treatment temperature state, the urea temperature state, the PTO state, the brake state, the clutch state and the battery voltage state. The electric heating control method can reach the temperature range of the optimal conversion efficiency of the SCR catalyst, thereby reducing NOx emission and further meeting the requirements of the emission regulations of the next stage.

Description

Electric heating system and electric heating control method for vehicle SCR exhaust thermal management

Technical field

The present invention relates to the field of post-processing of engine emissions, and in particular to an electric heating system and electric heating control method for vehicle SCR exhaust thermal management.

Background technique

With the gradual tightening of emission regulations for mobile source vehicles, the National VI post-treatment solution is "DOC (Diesel Oxidation Catalyst) + DPF (Diesel Particulate Filter) + SCR (Selective Catalytic Reduction Device) + ASC (Ammonia Oxidation Catalyst) "The technical route can no longer meet future regulatory requirements. In order to meet the NOx "near-zero emissions" required by future regulations, the current National VI aftertreatment engine body thermal management can no longer meet the emissions of cold cycle and low-load LLC cycles of future regulations. According to regulatory limits, an electric heating device needs to be installed in the front stage of the National VI post-processing DOC+DPF+SCR+ASC, as shown in Figure 1. The thermal management of the engine body cannot quickly heat the SCR catalyst in the WHTC cold cycle. After the electric heating device is installed, the temperature of the SCR catalyst in the WHTC cycle and LLC cycle quickly rises to reach the optimal conversion efficiency temperature range of the SCR catalyst, thereby reducing For NOx emissions, to meet the next stage of emission regulations, the following application problems need to be solved:

1: Exhaust temperature management and control during the cold start phase. If the exhaust temperature is lower than the set value, the electric heating is turned on - the temperature is set too low and the catalytic converter temperature is not in the high-efficiency zone and emissions are difficult to meet the standard. If the exhaust temperature is higher than the set value, the pipe heating is turned off - If the temperature is set too high, fuel consumption will seriously deteriorate.

2: When the exhaust flow rate is lower than a certain value, turning on the electric heating may easily cause the electric heating wire to be too hot and burned.

3: When the ambient temperature and urea temperature are lower than a certain value, the urea solution is in a solid state, the SCR catalytic converter temperature reaches the high efficiency zone, no liquid urea enters the catalytic converter, and NOx cannot be converted. Turning on electric heating can easily cause engine fuel consumption to deteriorate.

4: When the voltage supplied to the electric heating wire is too high, it is easy to cause the electric heating wire current to exceed the rated current and burn the heating wire. When the voltage is too low, turning on the electric heating is easy to cause other electrical components of the vehicle to fail to work normally, etc.

The current methods to increase the post-processing temperature are:

Exhaust gas recirculation (EGR), air intake throttling, and fuel post-injection, etc.

The method for the EGR valve to increase the exhaust temperature is to reduce the air-fuel ratio in the engine combustion chamber, lower the temperature in the combustion chamber, decrease the combustion efficiency, and increase the exhaust temperature.

The method of increasing the exhaust temperature by throttling the intake air is to reduce the amount of fresh air in the engine burner, thereby reducing the air-fuel ratio, decreasing the combustion efficiency, and increasing the exhaust temperature.

The method of post-injection of fuel to increase exhaust temperature is: part of the fuel is burned during the after-combustion period, which reduces the combustion efficiency of the fuel in the combustion chamber and increases the exhaust temperature of the engine.

The current emission regulations have no technical requirements for cold cycle and low load cycle. Due to the single-stage injection low load cycle in the current post-treatment plan, the SCR catalyst bed temperature cannot reach the catalytic converter in the first 600 seconds of the cold cycle. efficiency window, the SCR catalytic converter cannot convert NOx pollutants into harmless N2 in the first 600 seconds of the cold cycle. The current thermal management solution cannot meet the exhaust thermal management technology of cold cycle and low load cycle in future regulations. Require.

The information disclosed in this Background section is merely intended to enhance an understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art that is already known to a person of ordinary skill in the art.

Contents of the invention

The purpose of the present invention is to provide an electric heating system and electric heating control method for vehicle SCR exhaust thermal management, which can achieve the optimal conversion efficiency temperature range of the SCR catalytic converter, thereby reducing NOx emissions and thereby meeting the next stage of emission regulations. requirements.

In order to achieve the above object, the present invention provides an electric heating system for vehicle SCR exhaust gas thermal management, which is integrated in the ccSCR of a vehicle SCR dual-stage urea injection device to reduce NOx. The electric heating system includes a T8 temperature sensor, a T9 temperature Sensor, EHC electrode and electric heating relay switch; T8 temperature sensor is set at the SCR inlet and behind the urea nozzle. The T8 temperature sensor is used to monitor the temperature at the urea nozzle; T9 temperature sensor is set at the SCR outlet to monitor the SCR The temperature at the outlet; the EHC electrode is set at the SCR inlet and in front of the urea nozzle. The EHC electrode is used to heat the ccSCR; the electric heating relay switch is electrically connected to the EHC electrode.

In a preferred embodiment, the distance between the T8 temperature sensor and the front end of the SCR mixer is 50 mm, and the distance between the T9 temperature sensor and the rear end of the SCR mixer is 50 mm.

In a preferred embodiment, the depth of the EHC electrode inserted into the SCR is between 50 and 90 mm.

In a preferred embodiment, the electric heating relay switch controls the heating of the EHC electrode according to the exhaust flow state, vehicle speed state, ambient temperature state, after-treatment temperature state, urea temperature state, PTO state, braking state, clutch state and battery voltage state. state.

In order to achieve the above object, the present invention provides an electric heating control method for vehicle SCR exhaust gas thermal management, which is controlled by the electric heating system as mentioned above. The electric heating control method includes: the on-board computer controls the exhaust flow, vehicle speed, Monitoring of ambient temperature, after-treatment temperature, urea temperature, PTO, brake, clutch and battery voltage, and based on exhaust flow status, vehicle speed status, ambient temperature status, after-treatment temperature status, urea temperature status, PTO status, brake status, The clutch status and battery voltage status control the heating status of the EHC electrode through the electric heating relay switch.

In a preferred embodiment, the electric heating control method also includes the total amount of heat that the EHC electrode needs to generate when the EHC electrode meets the target temperature, and the rated power value of the EHC motor is derived according to the basic formula of P=Q/t; where Q refers to the EHC The total amount of heat that the electrode needs to generate, t refers to the heating time, and P refers to the electric heating power value.

In a preferred embodiment, the target temperature that the EHC electrode needs to meet is 250°, and the time for the EHC electrode to reach the target temperature is within 0 to 300 seconds.

In a preferred embodiment, the heat generated by the EHC electrode is mainly used for the heat absorption needs of the EHC carrier, the need to increase the circulating air temperature and other heat losses, where:

Endothermic demand of EHC carrier Q1=C _ehc m _ehc ΔT;

Increase the circulating air temperature requirement Q2=C _exhaust q tΔT;

P=(Q1+Q2+Q3)/t;

Among them, Q3 refers to other heat losses, C _ehc refers to the specific heat capacity of the EHC carrier, m _ehc refers to the weight of the electric heating carrier, ΔT refers to the elevated temperature value, C _exhaust refers to the specific heat capacity of the engine exhaust, q refers to the engine exhaust flow, t refers to the heating time, P refers to the electric heating power value.

Compared with the prior art, the electric heating system and electric heating control method for vehicle SCR exhaust thermal management of the present invention have the following beneficial effects: after the electric heating device is installed, the SCR catalyst temperatures in the WHTC cycle and LLC cycle increase rapidly, The optimal conversion efficiency temperature range of the SCR catalytic converter can be reached, thereby reducing NOx emissions and meeting the requirements of the next stage of emission regulations.

Description of the drawings

Figure 1 is a schematic diagram of an exhaust heat pipe according to an embodiment of the prior art;

Figure 2 is a schematic diagram of an exhaust heat pipe according to an embodiment of the present invention;

Figure 3 is an enlarged schematic diagram of an electric heating system according to an embodiment of the present invention;

Figure 4 is a schematic diagram of the control principle of an electric heating system according to an embodiment of the present invention.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

Unless expressly stated otherwise, throughout the specification and claims, the term "comprises" or its variations such as "comprises" or "comprising" will be understood to include the stated elements or components, and to Other elements or other components are not excluded.

As shown in Figures 2 to 3, according to a preferred embodiment of the present invention, an electric heating system for vehicle SCR exhaust gas thermal management is integrated into the ccSCR of a vehicle SCR dual-stage urea injection device for reducing NOx. The electric heating system Including T8 temperature sensor, T9 temperature sensor, EHC electrode of the electric heating system and electric heating relay switch; T8 temperature sensor is set at the SCR inlet and located behind the urea nozzle. The T8 temperature sensor is used to monitor the temperature at the urea nozzle; T9 temperature The sensor is set at the SCR outlet to monitor the temperature at the SCR outlet; the EHC electrode is set at the SCR inlet and in front of the urea nozzle. The EHC electrode is used to heat the ccSCR; the electric heating relay switch is electrically connected to the EHC electrode.

In some embodiments, the T8 temperature sensor is 50 mm from the front end of the mixer of the SCR, and the T9 temperature sensor is 50 mm from the rear end of the mixer of the SCR.

In some embodiments, the EHC electrode is inserted into the SCR to a depth ranging from 50 to 90 mm.

In some embodiments, the electric heating relay switch controls the heating state of the EHC electrode according to the exhaust flow state, vehicle speed state, ambient temperature state, aftertreatment temperature state, urea temperature state, PTO state, braking state, clutch state and battery voltage state. .

As shown in Figure 4, according to an electric heating control method for vehicle SCR exhaust thermal management according to a preferred embodiment of the present invention, it is controlled by the electric heating system as mentioned above. The electric heating control method includes: the on-board computer controls the exhaust gas Monitoring of flow, vehicle speed, ambient temperature, aftertreatment temperature, urea temperature, PTO, brake, clutch and battery voltage, and based on exhaust flow status, vehicle speed status, ambient temperature status, aftertreatment temperature status, urea temperature status, PTO status , braking status, clutch status and battery voltage status control the heating status of the EHC electrode through the electric heating relay switch.

In some embodiments, the electric heating control method also includes the total amount of heat that the EHC electrode needs to generate when the EHC electrode meets the target temperature, and deriving the rated power value of the EHC motor according to the basic formula of P=Q/t; where Q refers to the EHC electrode. The total amount of heat to be generated, t refers to the heating time, and P refers to the electric heating power value.

In some embodiments, the target temperature that the EHC electrode needs to meet is 250°, and the time for the EHC electrode to reach the target temperature is within 0 to 300 seconds.

In some embodiments, the heat generated by the EHC electrode is mainly used for the heat absorption needs of the EHC carrier, the need to increase the circulating air temperature, and other heat losses, where:

Endothermic demand of EHC carrier Q1=C _ehc m _ehc ΔT;

Increase the circulating air temperature requirement Q2=C _exhaust q tΔT;

P=(Q1+Q2+Q3)/t;

Among them, Q3 refers to other heat losses, C _ehc refers to the specific heat capacity of the EHC carrier, m _ehc refers to the weight of the electric heating carrier, ΔT refers to the elevated temperature value, C _exhaust refers to the specific heat capacity of the engine exhaust, q refers to the engine exhaust flow, t refers to the heating time, P refers to the electric heating power value.

To sum up, the electric heating system and electric heating control method for vehicle SCR exhaust thermal management of the present invention have the following beneficial effects: by installing the electric heating device, the SCR catalyst temperatures of the WHTC cycle and LLC cycle are rapidly raised, which can achieve The optimal conversion efficiency temperature range of the SCR catalytic converter can reduce NOx emissions and meet the requirements of the next stage of emission regulations.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and illustration. These descriptions are not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical applications, thereby enabling others skilled in the art to make and utilize various exemplary embodiments of the invention and various different applications. Choice and change. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims (8)

1. An electric heating system for vehicle SCR exhaust gas thermal management, which is integrated in the ccSCR of a vehicle SCR dual-stage urea injection device to reduce NOx. It is characterized in that the electric heating system includes: T8 temperature sensor, which is arranged at the SCR inlet and located behind the urea nozzle. The T8 temperature sensor is used to monitor the temperature at the urea nozzle; T9 temperature sensor, which is installed at the SCR outlet to monitor the temperature at the SCR outlet; An EHC electrode is provided at the inlet of the SCR and located in front of the urea nozzle, and the EHC electrode is used to heat the interior of the ccSCR; and An electric heating relay switch is electrically connected to the EHC electrode. 2. The electric heating system according to claim 1, characterized in that the distance between the T8 temperature sensor and the front end of the mixer of the SCR is 50 mm, and the distance between the T9 temperature sensor and the rear end of the mixer of the SCR is 50 mm. 50mm. 3. The electric heating system according to claim 1, wherein the EHC electrode is inserted into the SCR to a depth ranging from 50 to 90 mm. 4. The electric heating system according to claim 1, characterized in that the electric heating relay switch is configured according to exhaust gas flow status, vehicle speed status, ambient temperature status, after-treatment temperature status, urea temperature status, PTO status, and brake status. , clutch state and battery voltage state control the heating state of the EHC electrode. 5. An electric heating control method for vehicle SCR exhaust thermal management, which is controlled by the electric heating system according to any one of claims 1 to 4, characterized in that the electric heating control method includes: a vehicle-mounted computer By monitoring the exhaust flow, vehicle speed, ambient temperature, after-treatment temperature, urea temperature, PTO, brake, clutch and battery voltage, and based on the exhaust flow status, vehicle speed status, ambient temperature status, after-treatment temperature status, urea temperature status, PTO status, braking status, clutch status and battery voltage status control the heating status of the EHC electrode through the electric heating relay switch. 6. The electric heating control method according to claim 5, characterized in that it also includes the total amount of heat that the EHC electrode needs to generate when the EHC electrode meets the target temperature, which is derived according to the basic formula of P=Q/t. The rated power value of the EHC motor; Q refers to the total amount of heat that the EHC electrode needs to generate, t refers to the heating time, and P refers to the electric heating power value. 7. The electric heating control method according to claim 6, wherein the target temperature that the EHC electrode needs to meet is 250°, and the time for the EHC electrode to reach the target temperature is within 0 to 300 seconds. 8. The electric heating control method according to claim 6, characterized in that the heat generated by the EHC electrode is mainly used for the heat absorption needs of the EHC carrier, the need to increase the circulating air temperature and other heat losses, wherein: Endothermic demand of EHC carrier Q1=C _ehc m _ehc ΔT; Increase the circulating air temperature requirement Q2=C _exhaust q tΔT; P=(Q1+Q2+Q3)/t; Among them, Q3 refers to other heat losses, C _ehc refers to the specific heat capacity of the EHC carrier, m _ehc refers to the weight of the electric heating carrier, ΔT refers to the elevated temperature value, C _exhaust refers to the specific heat capacity of the engine exhaust, q refers to the engine exhaust flow, t refers to the heating time, P refers to the electric heating power value.