Diesel preheating system utilizing high-temperature waste gas and control method

Abstract

The invention discloses a diesel preheating system utilizing high-temperature waste gas, which relates to a mini-tiller and comprises a heater, a tail gas pipe section, a cooling liquid tank and a controller, the heater is installed at the bottom in the diesel oil tank, the tail gas pipe section is installed in the diesel oil tank above the heater, one end of the tail gas pipe section is communicated with an exhaust pipe of a diesel engine, the other end of the tail gas pipe section penetrates through and extends to the outer side of the diesel oil tank, and a first gas flow valve is installed in the tail gas pipe section. A liquid level sensor is arranged in the diesel tank above the tail gas pipe section; a circulating pipe is arranged between the liquid inlet end and the liquid outlet end of the cooling liquid tank and provided with a pipe section located in the diesel oil tank, a flow pump is installed in the circulating pipe, a temperature sensor is installed in the diesel oil tank, and the liquid level sensor, the temperature sensor, the first gas flow valve and the flow pump are connected with a controller at the same time. The invention further discloses a control method of the diesel preheating system utilizing the high-temperature waste gas. Diesel oil can be sprayed more evenly, ignition is easier, and therefore the combustion efficiency is improved.

Description

Technical Field

[0001] The invention relates to a micro-tillage machine, and more particularly to a diesel preheating system and a control method utilizing high-temperature exhaust gas. Background Art

[0002] Micro-tillage machines have great advantages in greenhouses, dry land, deep water fields, small plots and other areas, and are also one of the most popular and best-selling models in the agricultural machinery market. In areas with hard soil such as mountains and dry land, gasoline micro-tillage machines often lack horsepower and have low working efficiency, so consider running higher-power diesel micro-tillage machines. In some low-temperature working environments, diesel has a high viscosity problem due to its own properties. After the diesel engine is started, the diesel condenses and the spraying is uneven, resulting in incomplete combustion and low thermal efficiency. Therefore, how to improve the combustion efficiency of diesel engines in low-temperature environments has become an urgent problem to be solved by current micro-tillage machines. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a diesel preheating system and a control method using high-temperature exhaust gas in view of the deficiencies of the prior art, thereby improving the uniformity of diesel injection and thus improving combustion efficiency.

[0004] A diesel preheating system utilizing high-temperature exhaust gas described in the present invention comprises a heater, an exhaust pipe section, a coolant tank and a controller; the heater is installed at the bottom of the diesel tank, the exhaust pipe section is installed in the diesel tank above the heater, one end of the exhaust pipe section is connected to the exhaust pipe of the diesel engine, the other end of the exhaust pipe section penetrates and extends to the outside of the diesel tank, a gas flow valve 1 is installed in the exhaust pipe section, and a liquid level sensor is provided in the diesel tank above the exhaust pipe section; a circulation pipe is provided between the inlet and outlet liquid ends of the coolant tank, and the circulation pipe has a pipe section located in the diesel tank, a flow pump is installed in the circulation pipe, a temperature sensor is installed in the diesel tank, and the liquid level sensor, temperature sensor, gas flow valve 1 and flow pump are connected to the controller at the same time.

[0005] Preferably, the exhaust pipe section located in the diesel tank is a spiral coil.

[0006] Preferably, a three-way catalytic converter is installed in the pipe section of the exhaust pipe section extending to the outside of the diesel tank.

[0007] Preferably, a second gas flow valve and a second three-way catalytic converter are installed on the exhaust pipe of the diesel engine.

[0008] Preferably, the pipe section of the circulation pipe located in the diesel tank is located between the exhaust pipe section and the heater.

[0009] Preferably, a pressure relief mechanism is provided on the top of the diesel tank.

[0010] Preferably, the controller is electrically connected to an oil level warning light.

[0011] A control method based on the diesel preheating system, the method comprising:

[0012] The diesel engine is started, and the temperature of the diesel in the diesel tank is obtained by the temperature sensor. If the temperature of the diesel is lower than a preset oil temperature preheating threshold, the heater is started to heat the diesel;

[0013] The liquid level of diesel in the diesel tank is obtained by the liquid level sensor. If the liquid level is detected to be higher than the liquid level sensor, the gas flow valve 1 is opened to allow the exhaust gas to enter the exhaust pipe section; if the liquid level is lower than the liquid level sensor, the gas flow valve 1 is closed;

[0014] When the diesel temperature is higher than the oil temperature preheating threshold, the valve ratio of the gas flow valve 1 is calculated, and the opening of the gas flow valve 1 is controlled to keep the diesel temperature between the oil temperature preheating threshold and the preset maximum oil temperature threshold.

[0015] Preferably, the valve ratio of the gas flow valve 1 is calculated by the following formula:

[0016]

[0017] In the formula, K p is the proportionality coefficient; E k is the difference sample, E k =T v -X k , T v is the target temperature, X k is the diesel temperature; T is the sampling time; T i is the integration time; T d is the differential time; out0 is the compensation constant.

[0018] Preferably, the target oil temperature threshold is between the oil temperature preheating threshold and a preset maximum oil temperature threshold, and the target oil temperature threshold is 55°C-65°C.

[0019] Beneficial Effects

[0020] The advantages of the present invention are:

[0021] 1. By setting a heater and an exhaust pipe section in the diesel tank, the diesel is preheated before entering the diesel engine combustion chamber from the tank, and the diesel is processed from a slurry into a liquid, which is conducive to more uniform spraying of the diesel, sufficient contact with the gas, easier ignition, and thus improving combustion efficiency.

[0022] 2. Through the design of the tailpipe section, the high-temperature exhaust gas that would otherwise be discharged as useless gas is heated through the fuel tank pipe wall. After the overall temperature of the diesel in the tank rises, the fuel tank motor can be turned off, thereby utilizing the waste heat and saving electricity.

[0023] 3. Multi-sensor fusion is used to monitor the oil temperature and oil level in real time, and a temperature control system is formed by controlling the gas flow valve. This not only ensures the safety of the fuel system but also helps the diesel engine to perform well. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the diesel preheating system of the present invention;

[0025] Figure 2 It is a schematic flow chart of the control method of the diesel preheating system of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the embodiments, but it does not constitute any limitation to the present invention. Any limited number of modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0027] See also Figure 1 A diesel preheating system using high-temperature exhaust gas of the present invention comprises a heater 3, an exhaust pipe section 4, a coolant tank 7 and a controller 14. The heater 3 is installed at the bottom of the diesel tank 2, the exhaust pipe section 4 is installed in the diesel tank 2 above the heater 3, one end of the exhaust pipe section 4 is connected to the exhaust pipe of the diesel engine 1, and the other end of the exhaust pipe section 4 penetrates and extends to the outside of the diesel tank 2, a gas flow valve 10 is installed in the exhaust pipe section 4, and a liquid level sensor 6 is provided in the diesel tank 2 above the exhaust pipe section 4. A circulation pipe 8 is provided between the inlet and outlet ends of the coolant tank 7, and the circulation pipe 8 has a pipe section located in the diesel tank 2, a flow pump 9 is installed in the circulation pipe 8, a temperature sensor 5 is installed in the diesel tank 2, and the liquid level sensor 6, the temperature sensor 5, the gas flow valve 10 and the flow pump 9 are connected to the controller 14 at the same time.

[0028] Diesel is added through the oil inlet of the diesel tank 2. In cold weather, within a certain period of time before and after the diesel engine is started, the diesel with high viscosity can be converted into a flowing liquid by starting the heater 3, and the diesel can be transported to the diesel engine 1 through the oil inlet pipe of the diesel tank 2 for combustion reaction. The high-temperature exhaust gas generated by the diesel engine 1 after operation can be directly discharged to the air through the exhaust pipe, or it can enter the tail pipe section 4. The high-temperature exhaust gas entering the tail pipe section 4 transfers heat to the pipe wall to heat the diesel in the tank. It can preheat the diesel together with the heater 3 or heat the diesel separately later, which can not only improve the viscosity of the diesel, improve the combustion efficiency of the diesel and the low-temperature operation ability of the diesel engine, but also save energy consumption. The temperature sensor installed in the diesel tank 2 can monitor the oil temperature in real time, and the oil level sensor above the tail pipe section 4 can monitor the oil level in real time. The diesel engine operating speed, load, temperature, oil temperature, and oil level are transmitted to the controller 14 for analysis and processing, and then a decision is made according to a preset program. Finally, the valves and pumps are adjusted to adapt to different working environments and conditions to ensure that the diesel can be maintained at an optimal viscosity.

[0029] For example, after the system has been running for a period of time, it is detected that the oil temperature is too high. At this time, the controller will control the opening of the gas flow valve 10 to reduce the flow of gas passing through the tail pipe section 4, and the gas flow valve 2 11 will increase the opening to increase the gas flow to meet the exhaust demand. If the oil temperature exceeds the maximum threshold, the flow pump 9 is controlled to start, and the coolant in the coolant tank 7 is extracted into the circulation pipe 8, thereby realizing the temperature reduction and temperature control of the diesel in the diesel tank 2.

[0030] For another example, if the oil level is too low, part of the exhaust pipe section 4 does not come into contact with the diesel and directly heats the air in the box, causing the internal environment of the box to be unstable. In this working condition, the gas flow valve 10 will be closed, the gas flow valve 2 11 will be fully opened, and then the heater 3 will be restarted to preheat the diesel.

[0031] In this embodiment, the exhaust pipe section 4 located in the diesel tank 2 is a spiral coil. Such a design can increase the exhaust gas passing time, while increasing the contact surface between the exhaust pipe section 4 and the diesel in the tank, achieving better heat transfer.

[0032] A three-way catalytic converter 12 is installed in the section of the tail gas pipe section 4 extending to the outside of the diesel tank 2. In addition, a gas flow valve 11 and a three-way catalytic converter 13 are installed on the exhaust pipe of the diesel engine 1, which realizes the branch discharge of the tail gas and satisfies the treatment of the tail gas. The two three-way catalytic converters are used for post-treatment of harmful exhaust gas.

[0033] Preferably, the pipe section of the circulation pipe 8 in the diesel tank 2 is located between the tail pipe section 4 and the heater 3. That is, the circulation pipe 8 is located between two heating sources, which can ensure rapid cooling of the diesel.

[0034] The top of the diesel tank 2 of this embodiment is provided with a pressure relief mechanism 15. The pressure relief mechanism 15 is used to prevent the formation of negative pressure in the tank, which leads to a decrease in the oil delivery pressure and a decrease in the oil supply, thereby reducing the power of the diesel engine.

[0035] In this embodiment, the controller 14 is electrically connected to an oil level warning light 16 for performing an alarm process when the diesel oil level is lower than the level sensor 6 .

[0036] like Figure 2 As shown, a control method based on the above diesel preheating system comprises:

[0037] The diesel engine is started, and the temperature of the diesel in the diesel tank 2 is obtained through the temperature sensor 5. If the diesel temperature is lower than the preset oil temperature preheating threshold, the heater 3 is started to heat the diesel. The liquid level of the diesel in the diesel tank 2 is obtained through the liquid level sensor 6. If the liquid level is detected to be higher than the liquid level sensor 6, the gas flow valve 10 is opened to allow the exhaust gas to enter the exhaust pipe section 4; if the liquid level is lower than the liquid level sensor 6, the gas flow valve 10 is closed. When the diesel temperature is higher than the oil temperature preheating threshold, the valve ratio of the gas flow valve 10 is calculated, and the opening of the gas flow valve 10 is controlled to keep the diesel temperature between the oil temperature preheating threshold and the preset maximum oil temperature threshold.

[0038] Since the exhaust gas directly passes through the interior of the diesel tank 2, and the contact area is large and the temperature rises quickly, the change has complex nonlinear characteristics, and it is difficult to meet the temperature control requirements using general single-loop control. The present invention establishes a closed-loop control model for the control of the gas flow valve 10 on the exhaust pipe section 4 according to different working conditions. In this example, the preheating target temperature of the diesel is set to 60°C. Correspondingly, the oil temperature preheating threshold is less than this temperature, and the maximum oil temperature threshold is greater than this temperature, so as to leave a buffer space for temperature rise to prevent the problem of excessive temperature caused by the exhaust pipe section 4 and the heater 3 continuously heating the diesel before cooling down.

[0039] Set the target temperature to T v , indicating that ideally the temperature will eventually stabilize at T v , from the start of system operation, the temperature sample data in the exhaust duct is collected at regular intervals, namely X1, X2, X3, X4...X k-2 , X k-1 , X k .

[0040] The difference between the sample and target temperature is E k , E k =T v -X k There are three situations: ① Ek >0, the current diesel temperature does not meet the standard; ②Ek =0, the current diesel temperature meets the requirements; ③E k <0, the current diesel temperature has exceeded the standard. The calculated OUT=P out +I out +D out , is the valve opening degree. k >0, it is necessary to increase P out Thus, increasing OUT can increase the opening degree of valve 1, E k <0, then reduce P out As a result, the opening degree of valve 1 is reduced. As for the control of gas flow valve 2 11, it can be designed to be reversely linked with gas flow valve 10, that is, it is only necessary to ensure that the sum of the valve degrees of the two is 100% valve degree, so as to ensure that when the gas flow valve 10 changes, an equivalent amount of gas can enter the tail gas pipe section 4. Among them, P out The calculation formula is as follows:

[0041] P out =K p (T v -X k )+out0=K p *E k +out0.

[0042] The above is a proportional control algorithm. out0 is a constant and can be set to 1 to avoid E k =0, OUT is also equal to 0, K p represents the proportional coefficient, and its size will directly affect the response speed of the system. p is very large, then a small difference E k You will also get a larger P out , then the system will be difficult to achieve stability. p Too small will cause the system to respond too slowly, although there may be a large difference E k Only a smaller value P can be obtained out , the system takes a long time to reach a stable state, so K p The setting should be adjusted according to the actual working conditions.

[0043] By the target value T v The difference E is obtained by subtracting the collected sample data k Due to the continuous temperature acquisition, there are a series of difference samples E1, E2, E3, ... E k-2 , E k-1 , E k . Adding up these differences, we get:

[0044] S E=E1+E2+E3+…+E k-2 +E k-1 +E k .

[0045] For a stable negative feedback system, S E > 0, because SE is the cumulative sum of errors. When the system tends to be stable, that is, when the temperature reaches the target temperature, E k =0, then P out With D out are all 0, at this time only I out Maintain system stability. out The calculation formula is as follows:

[0046]

[0047] Make an approximate transformation on it, namely:

[0048]

[0049] Where T represents the sampling time, from the above formula we can get I out Finally,

[0050]

[0051] When the value of Ti is large, it takes a long time for the temperature of the exhaust pipe section 4 to return to the set value, regardless of whether the current temperature of the exhaust pipe section 4 is greater than or less than the set value; when T i When it is smaller, the temperature fluctuation of the exhaust pipe section 4 will be larger, and the oscillation attenuation will be smaller.

[0052] According to the obtained difference sample E k , the difference between the two most recent sample differences can be expressed as:

[0053] D k =E k -E k-1

[0054] D k There are three situations: ①D k >0, the difference has an increasing trend; ②D k =0, the difference trend is stable; ③D k <0, the difference has a decreasing trend. D k It can reflect the state change trend of the temperature collected in the last two times. The larger the absolute value, the greater the temperature change rate. k From the formula, we can see that when the temperature increases, it is a negative number. The greater the growth rate, the smaller the value. When the temperature decreases, D k is a positive number, the greater the rate of decline, the greater the value. kIt has the function of suppressing temperature changes and making it stable. Its mathematical model can be expressed as:

[0055]

[0056] Make an approximate transformation on it, namely:

[0057]

[0058] From the above formula, we can get:

[0059]

[0060] T represents the sampling time, T d Denotes the differential time, T d The larger the differential effect, the stronger the suppression effect. The integrated OUT formula is as follows:

[0061]

[0062] The above closed-loop control algorithm can form a control closed loop when the system is running, regardless of whether the oil temperature is higher or lower than the target temperature, and continuously adjust the oil temperature to approach the target temperature.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A diesel preheating system using high temperature exhaust gas, characterized in that: The invention comprises a heater (3), an exhaust pipe section (4), a coolant tank (7) and a controller (14); the heater (3) is installed at the bottom of a diesel tank (2), the exhaust pipe section (4) is installed in the diesel tank (2) above the heater (3), one end of the exhaust pipe section (4) is connected to the exhaust pipe of the diesel engine (1), the other end of the exhaust pipe section (4) penetrates and extends to the outside of the diesel tank (2), a gas flow valve (10) is installed in the exhaust pipe section (4), and the exhaust pipe section (4) is connected to the exhaust pipe of the diesel engine (1). A liquid level sensor (6) is provided in the diesel tank (2) above the gas pipe section (4); a circulation pipe (8) is provided between the liquid inlet and outlet ends of the coolant tank (7), and the circulation pipe (8) has a pipe section located in the diesel tank (2); a flow pump (9) is installed in the circulation pipe (8); a temperature sensor (5) is installed in the diesel tank (2); the liquid level sensor (6), the temperature sensor (5), the gas flow valve (10) and the flow pump (9) are connected to a controller (14) at the same time.

2. A diesel preheating system using high temperature exhaust gas according to claim 1, characterized in that: The tail gas pipe section (4) located in the diesel tank (2) is a spiral coil.

3. A diesel preheating system using high temperature exhaust gas according to claim 1, characterized in that: A three-way catalytic converter (12) is installed in the section of the tail gas pipe section (4) extending to the outside of the diesel tank (2).

4. A diesel preheating system using high temperature exhaust gas according to claim 1, characterized in that: A second gas flow valve (11) and a second three-way catalytic converter (13) are installed on the exhaust pipe of the diesel engine (1).

5. A diesel preheating system using high temperature exhaust gas according to claim 1, characterized in that: The pipe section of the circulation pipe (8) located in the diesel tank (2) is located between the tail gas pipe section (4) and the heater (3).

6. A diesel preheating system using high temperature exhaust gas according to claim 1, characterized in that: A pressure relief mechanism (15) is provided on the top of the diesel tank (2).

7. A diesel preheating system using high temperature exhaust gas according to claim 1, characterized in that: The controller (14) is electrically connected to an oil level warning light (16).

8. A control method based on the diesel preheating system according to any one of claims 1 to 7, characterized in that: The method includes: The diesel engine is started, and the temperature of the diesel in the diesel tank (2) is obtained through the temperature sensor (5); if the diesel temperature is lower than a preset oil temperature preheating threshold, the heater (3) is started to heat the diesel; The liquid level of diesel in the diesel tank (2) is obtained by the liquid level sensor (6); if it is detected that the liquid level is higher than the liquid level sensor (6), the gas flow valve (10) is opened to allow the exhaust gas to enter the exhaust pipe section (4); if the liquid level is lower than the liquid level sensor (6), the gas flow valve (10) is closed; When the diesel temperature is higher than the oil temperature preheating threshold, the valve ratio of the gas flow valve 1 (10) is calculated, and the opening of the gas flow valve 1 (10) is controlled to keep the diesel temperature between the oil temperature preheating threshold and the preset maximum oil temperature threshold.

9. The control method according to claim 8, characterized in that: The valve ratio of the gas flow valve 1 (10) is calculated by the following formula: Where, OUT is the valve ratio of the gas flow valve (10); K p is the proportionality coefficient; E k is the difference sample, E k =T v -X k , T v is the target temperature, X k is the diesel temperature; T is the sampling time; T i is the integration time; T d is the differential time; out0 is the compensation constant.

10. The control method according to claim 8, characterized in that: The target oil temperature threshold is between the oil temperature preheating threshold and the preset maximum oil temperature threshold, and the target oil temperature threshold is 55°C-65°C.

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