阅读说明：本技术 针对柴油机热管理系统的doc快速起燃加热装置及方法 (DOC rapid ignition heating device and method for diesel engine heat management system ) 是由 黄志宏 吴锋 姚栋伟 于 2019-07-30 设计创作，主要内容包括：本发明公开了针对柴油机热管理系统的DOC快速起燃加热装置及方法,该装置包括DOC载体、电热丝、绝缘筒、保温筒、车载电源、DOC入口温度传感器、DOC出口温度传感器、排气管、温度控制模块、固态继电器。电热丝螺旋缠绕在DOC载体外表面,并嵌入在绝缘筒的内壁上。DOC入口温度传感器、DOC出口温度传感器均与温度控制模块的输入端连接,温度控制模块的输出端与固态继电器连接。温度控制模块通过控制PWM波形的占空比来控制加热功率的大小,进而实时控制DOC载体的加热过程。DOC快速起燃加热装置的控制方法包括数据采集与计算并进行逻辑判定与执行。本发明解决了柴油机排气温度控制中的瓶颈问题,扩大了排气温度控制的范围。(The invention discloses a DOC rapid ignition heating device and a DOC rapid ignition heating method for a diesel engine thermal management system. The heating wire is spirally wound on the outer surface of the DOC carrier and is embedded in the inner wall of the insulating cylinder. And both the DOC inlet temperature sensor and the DOC outlet temperature sensor are connected with the input end of the temperature control module, and the output end of the temperature control module is connected with the solid-state relay. The temperature control module controls the heating power by controlling the duty ratio of the PWM waveform, so that the heating process of the DOC carrier is controlled in real time. The control method of the DOC rapid ignition heating device comprises the steps of data acquisition and calculation, logic judgment and execution. The invention solves the bottleneck problem in the exhaust temperature control of the diesel engine and enlarges the exhaust temperature control range.)

1. The DOC rapid ignition heating device is characterized by comprising a DOC carrier, a heating wire, an insulating cylinder, a heat preservation cylinder, a vehicle-mounted power supply, a DOC inlet temperature sensor, a DOC outlet temperature sensor, a temperature control module and a solid-state relay.

The electric heating wire is spirally wound on the outer surface of the DOC carrier and embedded in the inner wall of the insulating cylinder, and the insulating cylinder and the heat-insulating cylinder are integrated; the vehicle-mounted power supply is connected with the electric heating wire.

DOC entry temperature sensor, DOC export temperature sensor all are connected with temperature control module's input, and temperature control module's output and solid state relay are connected.

The temperature control module controls the heating power by controlling the duty ratio of the PWM waveform, so that the heating process of the DOC carrier is controlled in real time.

2. The DOC rapid ignition heating device for the thermal management system of the diesel engine as claimed in claim 1, wherein the insulation cylinder is assembled with the outer surface of the DOC carrier wound with the heating wire through bosses at both ends.

3. The DOC rapid ignition heating device for the thermal management system of the diesel engine according to claim 1, wherein the vehicle-mounted power supply supplies power to the heating wire, and a PID controller with feedforward is adopted to control the duty ratio of the PWM waveform, so as to control the heating power until the carrier temperature reaches the DOC ignition temperature.

4. The DOC rapid ignition heating device for the thermal management system of the diesel engine according to claim 1, wherein when the temperature in the DOC carrier is lower than the DOC ignition temperature, the temperature control module outputs a PWM wave high level, the solid state relay switch is closed, and the heating power is controlled by controlling the PWM wave duty ratio; when the DOC carrier temperature is higher than the DOC ignition temperature value, the temperature control module outputs the low level of the PWM waveform, and the solid state relay switch is switched off.

5. A control method based on a DOC rapid ignition heating device for a diesel engine thermal management system is characterized by comprising the following steps:

(1) data acquisition and calculation part

And (1.1) reading the message by the temperature control module through the CAN bus. Collecting temperatures T of DOC inlet and outlet temperature sensors at equal time intervals_in ⁱ、T_ou ⁱWherein i represents the current sampling frequency, i is more than or equal to 1 and less than or equal to N, and N is a preset sampling frequency freq; obtaining the current exhaust mass flow m by checking an exhaust mass flow MAP measured in the calibration process of the complete machine when the engine leaves a factory_exh。

(1.2) calculating the average temperature T of the DOC outlet and the DOC inlet by using a filter average temperature calculation module_in、T_ouThe calculation formula is as follows:

assuming that the temperature in the DOC carrier has uniformity in the axial direction, then according to the convective heat transfer formula:

C_P，g*m_exh*(T_ou-T_in)＝h*A*(T_doc-(T_ou+T_in)/2)

calculating the temperature T of the DOC carrier_doc. Wherein C is_P，gIs the specific heat capacity of the diesel exhaust; h is the convective heat transfer coefficient between the DOC carrier and the exhaust gas flow, and can be obtained by calibration; a is the contact area between the DOC carrier and the exhaust gas stream, and is available from the DOC manufacturer.

And (1.3) logically judging that the step (2) is executed when the calculated DOC carrier temperature is less than the DOC light-off temperature value. Otherwise, executing the step (1), and continuing to collect and calculate;

(2) logic start and execute section

(2.1) during the operation of the Diesel Engine, if the temperature T of the DOC carrier is lower than the temperature T of the DOC carrier_docAnd when the temperature value is smaller than the DOC ignition temperature value, the temperature control module outputs PWM wave high level, the solid state relay switch is closed, and the heating power is controlled by controlling the duty ratio of the PWM wave. The feedforward control is calculated as follows.

Wherein a is₀Which represents the feed-forward duty cycle,the DOC carrier has energy, and the above formula can be used for steady-state treatment in one period of the action of the relay. The duty cycle of the feedforward control output is calculated by the following equation.

Wherein f represents the working frequency of the solid-state relay, U represents the voltage of the vehicle-mounted power supply, R represents the thermal resistance of the heating wire, m represents the mass of the DOC carrier, c represents the specific heat capacity of the DOC carrier, and T represents the specific heat capacity of the DOC carrier_Light-offRepresenting DOC light-off temperature values.

(2.2) calculating the duty ratio by adopting a position type PID algorithm, wherein the calculation formula is as follows:

e_k＝T_light-off-T_doc

Wherein e_kDenotes the difference between the current DOC carrier temperature and the DOC light-off temperature, subscript k denotes the time series, a denotes the duty cycle, k denotes the_p、k_i、k_dRespectively representing a proportional coefficient, an integral coefficient and a differential coefficient in the PID control, and T is a sampling period in the PID control.

Controlling the heating power P according to the duty ratio a, wherein the formula is as follows:

and (3) repeating the step (1) and the step (2) until the duty ratio a is equal to 0 and the DOC is ignited.

6. The control method based on DOC rapid ignition heating device for the thermal management system of the diesel engine according to claim 5, characterized in that in the step (1.1), the current exhaust mass flow m of the diesel engine is_exhThe exhaust mass flow MAP measured in the calibration process of the whole engine when the engine leaves the factory can be checked according to the rotating speed value and the torque value and obtained by a median difference method.

Technical Field

The invention relates to the field of diesel engine tail gas aftertreatment, in particular to a DOC rapid ignition heating device and method for a national six-heat-management system of a diesel engine.

Background

With the proposal of national six-emission regulations of diesel engines, the requirements on the diesel engine after-treatment system are more and more strict. In order to meet the requirements of emission regulations, diesel exhaust after-treatment systems must adopt a DOC-DPF-SCR (diesel oxidation catalyst-diesel particulate trap-selective catalytic reduction) technical route.

The bottleneck problem encountered in the DOC-DPF-SCR technical route realization process is the control of the exhaust temperature of the diesel engine, the exhaust temperature needs to be kept to a certain value under low load in the diesel engine to ensure the catalytic conversion efficiency of the SCR, and the exhaust temperature needs to be raised to a certain value to ensure the stable and safe regeneration of the DPF when the DPF is regenerated. At present, diesel engine cylinder internal secondary post injection or tail pipe injection diesel oil is mostly adopted at home and abroad, so that the diesel oil generates catalytic oxidation heat release in DOC to control the exhaust temperature.

The difficulty encountered in the technical route of controlling the exhaust temperature by the heat release of diesel oil oxidized by DOC is that a certain temperature threshold is required for the catalytic oxidation reaction of DOC, and the exhaust temperature cannot reach the temperature for the reaction of DOC under the low-load of a diesel engine, particularly under the test cycle specified by the national six-emission regulation, so that the temperature control strategy is invalid, the emission is deteriorated, and the DPF cannot be safely and effectively regenerated. It is desirable to have a preheating device that heats the DOC-carriers to a temperature that quickly reaches the DOC light-off temperature when the temperature of the DOC-carriers is less than the DOC light-off temperature.

Disclosure of Invention

Aiming at the DOC ignition problem of the diesel engine in the national six aftertreatment temperature control, the invention provides a DOC rapid ignition heating device and a DOC rapid ignition heating method for a national six thermal management system of the diesel engine, which are used for rapidly increasing the temperature of a DOC carrier under the working condition of low and medium load of the diesel engine, so that the DOC is subjected to oxidation reaction, and the exhaust temperature control range of the diesel engine is expanded.

The purpose of the invention is realized by the following technical scheme: the DOC rapid ignition heating device is characterized by comprising a DOC carrier, a heating wire, an insulating cylinder, a heat preservation cylinder, a vehicle-mounted power supply, a DOC inlet temperature sensor, a DOC outlet temperature sensor, a temperature control module and a solid-state relay.

The electric heating wire is spirally wound on the outer surface of the DOC carrier and embedded in the inner wall of the insulating cylinder, and the insulating cylinder and the heat-insulating cylinder are integrated; the vehicle-mounted power supply is connected with the electric heating wire.

DOC entry temperature sensor, DOC export temperature sensor all are connected with temperature control module's input, and temperature control module's output and solid state relay are connected.

The temperature control module is integrated into the DCU, and controls the heating power by controlling the duty ratio of the PWM waveform, so as to control the heating process of the DOC carrier in real time.

Further, the insulation cylinder is assembled with the outer surface of the DOC carrier wound with the heating wire through bosses at both ends.

Furthermore, the vehicle-mounted power supply supplies power to the heating wire, and the duty ratio of the PWM wave is calculated by adopting a position type PID algorithm to control the heating power, so that the heating process of the DOC carrier is controlled in real time.

Further, when the temperature in the DOC carrier is lower than the DOC ignition temperature, the temperature control module outputs PWM wave high level, the solid-state relay switch is closed, and the heating power is controlled by controlling the duty ratio of the PWM wave; when the DOC carrier temperature is higher than the DOC ignition temperature value, the temperature control module outputs the low level of the PWM waveform, and the solid state relay switch is switched off.

Further, the method comprises the steps of:

(1) data acquisition and calculation part

And (1.1) reading the message by the temperature control module through the CAN bus. Collecting temperatures T of DOC inlet and outlet temperature sensors at equal time intervals_in ⁱ、T_ou ⁱWherein i represents the current sampling frequency, i is more than or equal to 1 and less than or equal to N, and N is a preset sampling frequency freq; obtaining the current exhaust mass flow m by checking an exhaust mass flow MAP measured in the calibration process of the complete machine when the engine leaves a factory_exh。

(1.2) calculating the average temperature T of the DOC outlet and the DOC inlet by using a filter average temperature calculation module_in、T_ouThe calculation formula is as follows:

assuming that the temperature in the DOC carrier has uniformity in the axial direction, then according to the convective heat transfer formula:

C_P，g*m_exh*(T_ou-T_in)＝h*A*(T_doc-(T_ou+T_in)/2)

calculating the temperature T of the DOC carrier_doc. Wherein C is_P，gIs the specific heat capacity of the diesel exhaust; h is the convective heat transfer coefficient between the DOC carrier and the exhaust gas flow, and can be obtained by calibration; a is the contact area between the DOC carrier and the exhaust gas stream, and is available from the DOC manufacturer.

And (1.3) logically judging that the step (2) is executed when the calculated DOC carrier temperature is less than the DOC light-off temperature value. Otherwise, executing the step (1), and continuing to collect and calculate;

(2) logic start and execute section

(2.1) during the operation of the Diesel Engine, if the temperature T of the DOC carrier is lower than the temperature T of the DOC carrier_docAnd when the temperature value is smaller than the DOC ignition temperature value, the temperature control module outputs PWM wave high level, the solid state relay switch is closed, and the heating power is controlled by controlling the duty ratio of the PWM wave. The feedforward control is calculated as follows.

During one cycle of relay action, the above equation can be processed in steady state. The duty cycle of the feedforward control output is calculated by the following equation.

Wherein a is₀Which represents the feed-forward duty cycle,representing the energy possessed by the DOC carrier, f TableShowing the working frequency of the solid-state relay, U showing the voltage of the vehicle-mounted power supply, R showing the thermal resistance of the heating wire, m showing the mass of the DOC carrier, c showing the specific heat capacity of the DOC carrier, and T_Light-offRepresenting DOC light-off temperature values.

(2.2) calculating the duty ratio by adopting a position type PID algorithm, wherein the calculation formula is as follows:

e_k＝T_light-off-T_doc

Wherein e_kDenotes the difference between the current DOC carrier temperature and the DOC light-off temperature, subscript k denotes the time series, a denotes the duty cycle, k denotes the_p、k_i、k_dRespectively representing a proportional coefficient, an integral coefficient and a differential coefficient in the PID control, and T is a sampling period in the PID control.

Controlling the heating power P according to the duty ratio a, wherein the formula is as follows:

and (3) repeating the step (1) and the step (2) until the duty ratio a is equal to 0 and the DOC is ignited.

Further, in the step (1.1), the current exhaust mass flow m of the diesel engine is_exhThe exhaust mass flow MAP measured in the calibration process of the whole engine when the engine leaves the factory can be checked according to the rotating speed value and the torque value and obtained by a median difference method.

The invention has the beneficial effects that: according to the invention, the electric heating wire is uniformly wound on the outer surface of the DOC, and the insulating layer is arranged outside the insulating cylinder, so that the electric heating effect is good. The heating wire is embedded in the inner surface of the insulating cylinder, only two ports are exposed, and the heating wire is directly connected with a vehicle-mounted power supply, so that the space arrangement is convenient. The heating process of the DOC carrier is controlled in real time by adopting the position type PID algorithm with feedforward, the temperature of the DOC carrier can be quickly increased to the light-off temperature of the DOC, the emission of CO, HC and the like of a diesel engine can be reduced, the bottleneck problem in the exhaust temperature control of the diesel engine is solved, and the exhaust temperature control range is expanded.

Drawings

FIG. 1 is a schematic view of a DOC rapid light-off heating device of a national six-heat management system of a diesel engine;

FIG. 2 is a schematic diagram of a temperature control process;

FIG. 3 is a schematic diagram of a specific control method in the temperature control module;

in the figure, 1, an exhaust pipe; a DOC inlet temperature sensor; DOC outlet temperature sensing; DOC carrier; 5. a solid state relay; 6. a vehicle-mounted power supply; 7. a slide rheostat; 8. an electric heating wire; 9. an insulating cylinder; 10. a heat-preserving cylinder; 11. and a temperature control module.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and control method.

As shown in figure 1, the invention discloses a DOC rapid ignition heating device for a national six-heat management system of a diesel engine, which comprises an exhaust pipe 1, a DOC inlet temperature sensor 2, a DOC outlet temperature sensor 3, a DOC, a heating wire 8 wound on the DOC, an insulating cylinder 9 and a heat-insulating cylinder 10, wherein the heating wire 8 is embedded in the inner wall of the insulating cylinder 9, only two ports are exposed, and the heat-insulating cylinder 10 is tightly attached to the outer wall of the insulating cylinder 9, so that the energy of electric heating is not basically dissipated into the air. The device also comprises a temperature control module 11, a solid-state relay 5, a vehicle-mounted power supply 6 and a sliding rheostat 7, wherein the anode of the vehicle-mounted power supply 6 is connected with one end of the heating wire 8 through the sliding rheostat 7, and the cathode of the vehicle-mounted power supply 6 is connected with the other end of the heating wire 8 through the solid-state relay 5.

As shown in fig. 2, a DOC inlet temperature sensor 2 and a DOC outlet temperature sensor 3 are respectively arranged at a DOC inlet and a DOC outlet, the two temperature sensors are connected with a temperature control module 11, and meanwhile, exhaust working condition parameters of an exhaust pipe 1 are input into the temperature control module 11; the temperature control module 11 is connected with the solid-state relay 5. In the running process of the diesel engine, if the temperature of the DOC carrier is lower than the DOC ignition temperature, the temperature control module 11 outputs the high level of the PWM waveform, the switch of the solid-state relay 5 is closed, and the heating power is controlled to reach the DOC ignition temperature value by controlling the duty ratio. If the temperature in the DOC carrier is higher than the DOC ignition temperature, the temperature control module 11 outputs the low level of the PWM waveform, the switch of the solid-state relay 5 is switched off, and the heating device does not work.

As shown in fig. 3, the specific control method of the temperature control module 11 of the present invention is as follows: a position type PID control algorithm with feedforward is adopted, temperature values of a DOC inlet and an DOC outlet are calculated by adopting an average filtering module according to two temperature sensors and current working condition changes of a diesel engine, and then the temperature of a DOC carrier is calculated according to the knowledge of convective heat transfer; carrying out logic judgment according to the obtained DOC carrier temperature, starting a heating device to heat the DOC carrier if the DOC carrier temperature is lower than the DOC ignition temperature, and controlling the heating power by adopting a position type PID control algorithm with feedforward; otherwise, the heating device is not started. The specific control process comprises the following steps:

(1) data acquisition and calculation part

And (1.1) reading the message by the temperature control module through the CAN bus. Collecting temperatures T of DOC inlet and outlet temperature sensors at equal time intervals_in ⁱ、T_ou ⁱWherein i represents the current sampling frequency, i is more than or equal to 1 and less than or equal to N, and N is a preset sampling frequency freq; obtaining the current exhaust mass flow m by checking an exhaust mass flow MAP measured in the calibration process of the complete machine when the engine leaves a factory_exh。

(1.2) calculating the average temperature T of the DOC outlet and the DOC inlet by using a filter average temperature calculation module_in、T_ouThe calculation formula is as follows:

assuming that the temperature in the DOC carrier has uniformity in the axial direction, then according to the convective heat transfer formula:

C_P，g*m_exh*(T_ou-T_in)＝h*A*(T_doc-(T_ou+T_in)/2)

calculating the temperature T of the DOC carrier_doc. Wherein C is_P，gIs the specific heat capacity of the diesel exhaust; h is the convective heat transfer coefficient between the DOC carrier and the exhaust gas flow, and can be obtained by calibration; a is the contact area between the DOC carrier and the exhaust gas stream, and is available from the DOC manufacturer.

And (1.3) logically judging that the step (2) is executed when the calculated DOC carrier temperature is less than the DOC light-off temperature value. Otherwise, executing the step (1), and continuing to collect and calculate;

(2) logic start and execute section

(2.1) during the operation of the Diesel Engine, if the temperature T of the DOC carrier is lower than the temperature T of the DOC carrier_docAnd when the temperature value is smaller than the DOC ignition temperature value, the temperature control module outputs PWM wave high level, the solid state relay switch is closed, and the heating power is controlled by controlling the duty ratio of the PWM wave. The feedforward control is calculated as follows.

During one cycle of relay action, the above equation can be processed in steady state. The duty cycle of the feedforward control output is calculated by the following equation.

Wherein a is₀Which represents the feed-forward duty cycle,representing the energy of the DOC carrier, f representing the working frequency of the solid-state relay, U representing the voltage of the vehicle-mounted power supply, R representing the thermal resistance of the electric heating wire, m representing the mass of the DOC carrier, c representing the specific heat capacity of the DOC carrier, and T_Light-offRepresenting DOC light-off temperature values.

(2.2) calculating the duty ratio by adopting a position type PID algorithm, wherein the calculation formula is as follows:

e_k＝T_light-off-T_doc

Wherein e_kDenotes the difference between the current DOC carrier temperature and the DOC light-off temperature, subscript k denotes the time series, a denotes the duty cycle, k denotes the_p、k_i、k_dRespectively representing a proportional coefficient, an integral coefficient and a differential coefficient in the PID control, and T is a sampling period in the PID control.

Controlling the heating power P according to the duty ratio a, wherein the formula is as follows:

and (3) repeating the step (1) and the step (2) until the duty ratio a is equal to 0 and the DOC is ignited.

The above-described embodiments are intended to illustrate rather than to limit the invention, and any modifications and variations of the present invention are within the spirit of the invention and the scope of the appended claims.