Diesel preheating system using high-temperature exhaust gas and control method

Abstract

The application discloses a diesel preheating system utilizing high-temperature exhaust gas and relates to a mini-tiller, which comprises a heater, an exhaust pipe section, a cooling liquid tank and a controller; the heater is installed at the bottom of a diesel tank; the exhaust pipe section is installed in the diesel tank above the heater; one end of the exhaust pipe section is communicated with an exhaust pipe of a diesel engine; the other end of the exhaust pipe section penetrates through and extends to the outside of the diesel tank; a gas flow valve one is installed in the exhaust pipe section; a liquid level sensor is arranged in the diesel tank above the exhaust pipe section; a circulating pipe is arranged between the inlet and outlet of the cooling liquid tank, the circulating pipe has a pipe section in the diesel tank, a flow pump is installed in the circulating pipe, a temperature sensor is installed in the diesel tank, and the liquid level sensor, the temperature sensor, the gas flow valve one and the flow pump are connected with the controller simultaneously. The application further discloses a control method of the diesel preheating system utilizing high-temperature exhaust gas. The application is favorable for the more uniform spraying of diesel, the easier ignition and the improvement of the combustion efficiency.

Description

Technical Field

[0001] This invention relates to a micro-tiller, and more specifically, to a diesel preheating system and control method that utilizes high-temperature exhaust gas. Background Technology

[0002] Mini tillers offer significant advantages in operating in greenhouses, dry land, deep paddy fields, and small plots, making them one of the most popular and best-selling models in the agricultural machinery market. However, in areas with harder soil, such as mountainous or dry land areas, gasoline-powered mini tillers often lack sufficient horsepower, resulting in lower work efficiency. Therefore, diesel mini tillers with higher operating power are considered. In some low-temperature working environments, diesel fuel exhibits high viscosity due to its inherent properties. When the diesel engine is running, uneven spraying due to diesel condensation leads to incomplete combustion and low thermal efficiency. Therefore, improving the combustion efficiency of diesel engines in low-temperature environments is a pressing issue for current mini tillers. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a diesel preheating system and control method that utilizes high-temperature exhaust gas, thereby improving the uniformity of diesel injection and thus improving combustion efficiency.

[0004] The present invention discloses a diesel preheating system utilizing high-temperature exhaust gas, comprising a heater, an exhaust pipe section, a coolant tank, and a controller. The heater is installed at the bottom of the diesel tank, and 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, and the other end of the exhaust pipe section extends through and to the outside of the diesel tank. A gas flow valve 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 of the coolant tank, and the circulation pipe has a section located in the diesel tank. A flow pump is installed in the circulation pipe, and a temperature sensor is installed in the diesel tank. The liquid level sensor, temperature sensor, gas flow valve, and flow pump are all connected to the controller.

[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 section of the exhaust pipe that extends to the outside of the diesel tank.

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

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

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

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

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

[0012] Start the diesel engine and obtain the diesel temperature in the diesel tank through the temperature sensor. If the diesel temperature is lower than the preset oil temperature preheating threshold, start the heater to heat the diesel.

[0013] The diesel fuel level 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 is opened to allow exhaust gas to enter the exhaust pipe section; if the liquid level is lower than the liquid level sensor, the gas flow valve is closed.

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

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

[0016]

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

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

[0019] Beneficial effects

[0020] The advantages of this invention are:

[0021] 1. By installing a heater and exhaust pipe section in the diesel tank, the diesel fuel is preheated before entering the diesel engine combustion chamber from the tank, transforming it from a slurry into a liquid. This facilitates more uniform diesel fuel spraying, ensures full contact with the gas, and makes it easier to ignite, thereby improving combustion efficiency.

[0022] 2. By designing the exhaust pipe section, the high-temperature exhaust gas, which would otherwise be a useless gas, is heated by passing through the fuel tank pipe wall. Once the diesel fuel in the tank is heated to a whole, the fuel tank motor can be shut off, thus saving energy while utilizing the waste heat.

[0023] 3. By using multi-sensor fusion to monitor oil temperature and oil level in real time, and by controlling the gas flow valve, a temperature control system is formed, which not only ensures the safety of the fuel system, but also helps the diesel engine to perform well. Attached Figure Description

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

[0025] Figure 2 This is a schematic diagram of the control method for the diesel preheating system of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments, but this does not constitute any limitation on the present invention. Any limited modifications made by any person within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0027] See Figure 1 This invention discloses a diesel preheating system utilizing high-temperature exhaust gas, comprising 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 above the heater 3 within the diesel tank 2. One end of the exhaust pipe section 4 is connected to the exhaust pipe of a diesel engine 1, and the other end extends through and to the outside of the diesel tank 2. A gas flow valve 10 is installed in the exhaust pipe section 4. A liquid level sensor 6 is installed in the diesel tank 2 above the exhaust pipe section 4. A circulation pipe 8 is provided between the inlet and outlet of the coolant tank 7, and the circulation pipe 8 has a section located within 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, temperature sensor 5, gas flow valve 10, and flow pump 9 are all connected to the controller 14.

[0028] Diesel fuel is added through the inlet of diesel tank 2. In cold weather, for a certain period before and after starting the diesel engine, the heater 3 can be activated to convert the highly viscous diesel fuel into a flowing liquid state. The diesel fuel is then transported to diesel engine 1 through the fuel inlet pipe of diesel tank 2 for combustion. The high-temperature exhaust gas generated by diesel engine 1 after starting can be directly discharged into the air through the exhaust pipe or enter the exhaust manifold 4. The high-temperature exhaust gas entering the exhaust manifold 4 transfers heat to the pipe wall, thereby heating the diesel fuel in the tank. This can preheat the diesel fuel along with the heater 3 or heat the diesel fuel separately later. This not only improves the viscosity of the diesel fuel, increases its combustion efficiency and the low-temperature operating capability of the diesel engine, but also saves energy. The temperature sensor installed in diesel tank 2 can monitor the oil temperature in real time, while the oil level sensor above the exhaust manifold 4 can monitor the oil level in real time. The diesel engine's operating speed, load, temperature, oil temperature, and oil level are transmitted to the controller 14 for analysis and processing. Then, a decision is made according to the preset program, and finally, the valves and pumps are adjusted to adapt to different working environments and conditions, ensuring that the diesel fuel can be maintained at the optimal viscosity.

[0029] For example, after the system has been running for a period of time, if the oil temperature is detected to be too high, the controller will control the opening of gas flow valve 10 to reduce the flow of gas passing through exhaust pipe section 4, while gas flow valve 11 will increase its opening to increase the flow of gas to meet exhaust requirements. If the oil temperature exceeds the maximum threshold, the controller will start the flow pump 9 to draw coolant from the coolant tank 7 into the circulation pipe 8, thereby achieving temperature control and cooling of the diesel fuel in the diesel tank 2.

[0030] For example, if the oil level is too low, causing part of the exhaust pipe section 4 to not come into contact with diesel fuel and instead directly heat the air inside the tank, resulting in an unstable internal environment, then under this condition, the gas flow valve 10 will be closed, the gas flow valve 21 will be fully opened, and then the heater 3 will be restarted to preheat the diesel fuel.

[0031] In this embodiment, the exhaust pipe section 4 located in the diesel tank 2 is a spiral coil. This design increases the exhaust gas passage time and the contact area between the exhaust pipe section 4 and the diesel fuel in the tank, achieving better heat transfer.

[0032] A three-way catalytic converter 12 is installed in the section of the exhaust pipe 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, enabling separate exhaust gas emissions and meeting exhaust gas treatment requirements. The two three-way catalytic converters are used for the after-treatment of harmful exhaust gases.

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

[0034] In this embodiment, the diesel tank 2 is equipped with a pressure relief mechanism 15 on its top. The pressure relief mechanism 15 is used to prevent negative pressure from forming inside the tank, which would reduce the fuel supply pressure and thus reduce the diesel engine power.

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

[0036] like Figure 2 As shown, a control method based on the above-mentioned diesel preheating system is provided, the method comprising:

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

[0038] Because the exhaust gas passes directly through the interior of the diesel tank 2, and has a large contact area, it heats up rapidly, exhibiting complex nonlinear characteristics. General single-loop control is insufficient to meet temperature control requirements. This invention establishes a closed-loop control model for the gas flow valve 10 on the exhaust pipe section 4 under different operating conditions. In this example, the target preheating temperature of the diesel is set to 60℃. Correspondingly, the oil temperature preheating threshold is lower than this temperature, while the maximum oil temperature threshold is higher than this temperature, to allow for a temperature rise buffer space and prevent excessively high temperatures caused by continuous heating of the diesel by the exhaust pipe section 4 and heater 3 before cooling down.

[0039] Set the target temperature to T. v This indicates that, ideally, the temperature will eventually stabilize at T. v Temperature samples from the exhaust pipe are collected periodically from the start of system operation, numbered X1, X2, X3, X4...X. k-2 X k-1 X k .

[0040] The difference between the sample temperature and the target temperature is E. k E k =T v -X k There are three situations: ① Ek >0, current diesel fuel temperature not up to standard; ②Ek =0, the current diesel temperature meets the requirements; ③E k <0, the current diesel fuel temperature has exceeded the limit. The calculated OUT = P out +I out +D out This indicates the degree of valve opening. In E... k When P > 0, P needs to be increased. out This increases OUT to improve the opening degree of valve 1, E k When <0, P decreases. out This reduces the opening degree of valve 1. Regarding the control of gas flow valve 11, it can be designed to be in reverse linkage with gas flow valve 10; that is, it only needs to ensure that the sum of their valve degrees is 100% to ensure that a corresponding change in gas volume enters the exhaust pipe section 4 when gas flow valve 10 changes. Wherein, 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 the proportional control algorithm. out0 is a constant and can be set to 1 to avoid E k When K = 0, OUT also equals 0. p This represents the proportionality coefficient, the magnitude of which directly affects the system's response speed. If K p It's very large, so a small difference E k It will also result in a larger P. out If so, the system will find it difficult to achieve stability. Similarly, K... p If the value is too small, the system's response speed will be too slow, even though there may be a large difference in value E. k Only a small value P can be obtained. out The system takes a long time to reach a stable state, so K p The settings need to be adjusted according to the actual working conditions.

[0043] Through the target value T v The difference E was obtained by subtracting the collected sample data from the difference. k Due to continuous temperature data acquisition, a series of difference samples E1, E2, E3, ... E were obtained. k-2 E k-1 E k Summing 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 stabilize, that is, when the temperature reaches the target temperature, E k =0, then P out With D out All are 0, at this time only I out Maintain system stability. Among them, I out The calculation formula is as follows:

[0046]

[0047] We can approximate it by the following transformation:

[0048]

[0049] Where T represents the sampling time, I can be obtained from the above formula. out Ultimately;

[0050]

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

[0052] Based on 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 possibilities: ①D k >0, the difference tends to increase; ②D k =0, the difference trend is stable; ③D k <0, the difference shows a decreasing trend. D k It can reflect the trend of temperature change between the two most recent collections; the larger its absolute value, the greater the rate of temperature change. (D) k As can be seen from the formula, when the temperature increases, it is a negative number; the greater the rate of increase, the smaller the value. When the temperature decreases, D... k As a positive number, the greater the rate of descent, the larger the value of D. Therefore, we know that D... kIt has the function of suppressing temperature changes and stabilizing them. Its mathematical model can be expressed as:

[0055]

[0056] We can approximate it by the following transformation:

[0057]

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

[0059]

[0060] T represents the sampling time, T d T represents the differential time. d The larger the value, the stronger the differential effect, meaning the more pronounced the inhibition effect. The integrated OUT formula is as follows:

[0061]

[0062] The above closed-loop control algorithm enables the system to form a control closed loop regardless of whether the oil temperature is higher or lower than the target temperature during operation, continuously adjusting the oil temperature to approach the target temperature.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A diesel preheating system utilizing high-temperature exhaust gas, characterized in that, Includes 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) extends through and to the outside of the diesel tank (2). A gas flow valve (10) is installed in the exhaust pipe section (4). 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 inlet and outlet 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), and a temperature sensor (5) is installed in the diesel tank (2). The liquid level sensor (6), temperature sensor (5), gas flow valve (10) and flow pump (9) are all connected to the controller (14). The exhaust pipe section (4) located in the diesel tank (2) is a spiral coil; The exhaust pipe section (4) extends to the outside of the diesel tank (2) and is equipped with a three-way catalytic converter (12).

2. The diesel preheating system utilizing high-temperature exhaust gas according to claim 1, characterized in that, The exhaust pipe of the diesel engine (1) is equipped with a gas flow valve (11) and a three-way catalytic converter (13).

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

4. A diesel preheating system utilizing high-temperature exhaust gas according to claim 1, characterized in that, The diesel tank (2) is equipped with a pressure relief mechanism (15) on top.

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

6. A control method based on the diesel preheating system as described in any one of claims 1-5, characterized in that, The method includes: Start the diesel engine and obtain the diesel temperature in the diesel tank (2) through the temperature sensor (5). If the diesel temperature is lower than the preset oil temperature preheating threshold, start the heater (3) to heat the diesel. The diesel level in the diesel tank (2) is obtained by 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.

7. The control method according to claim 6, characterized in that, The valve ratio of the gas flow valve (10) is calculated by the following formula: ， In the formula, OUT is the valve ratio of gas flow valve 1 (10); K p E is the proportionality coefficient. k For the difference sample, E k =T v -X k T v For the target temperature, X k T represents the diesel fuel temperature; T represents the sampling time; T i T is the integration time; d is the differential time; out0 is the compensation constant.

8. The control method according to claim 6, characterized in that, The target oil temperature threshold is located between the oil temperature preheating threshold and the preset maximum oil temperature threshold, and the target oil temperature threshold is 55℃-65℃.

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