Diesel injection device and cyclic quantitative control method

Abstract

The invention discloses a diesel gasification device and a cyclic quantitative control method. The controller firstly preheats the heating piece and then controls the air inlet valve to be opened, so that air enters the mixing cavity through the air inlet pipe and the heating net, and the pressure in the cavity is adjusted to a preset pressure threshold upper limit Ptar1; the controller calculates the target fuel injection quantity of the liquid fuel injector according to the air state in the mixing cavity and the target equivalence ratio and controls the liquid fuel injector to complete fuel injection; the controller controls an oil and gas injection valve to be opened, an oil and gas mixture is injected till the lower limit Ptar2 of a preset pressure threshold value is reached, and after injection is finished, the controller calculates the residual air amount and the residual fuel oil amount in a mixing cavity based on the pressure, temperature and oxygen concentration detection signals after injection; and the controller opens the air inlet valve to supplement air to the mixing cavity until the pressure in the cavity reaches the pressure threshold upper limit Ptar1, then the air inlet valve is closed, the air supplement amount is determined according to the pressure difference before and after air supplement, and the needed oil supplement amount is calculated in combination with the target equivalence ratio. According to the invention, spray crushing and atomization are realized no longer depending on ultrahigh injection pressure.

Description

Technical Field

[0001] This invention belongs to the field of internal combustion engine fuel supply technology, specifically relating to a diesel injection device and a cyclic quantitative control method. Background Technology

[0002] In the fuel supply system of an internal combustion engine, the mixing state of fuel and air directly affects the stability and controllability of the combustion process. Currently, diesel engine fuel injection technologies mainly include high-pressure common rail injection, gas-injected direct injection (GDI), and air-assisted injection. Among them, the high-pressure common rail injection system establishes high-pressure conditions of 1000–2000 bar to form a high-speed jet of liquid fuel, relying on the jet breaking effect to achieve atomization; the GDI injection system is adapted to light liquid fuels and also breaks up droplets through the mechanical shearing action of the high-pressure jet; the air-assisted injection system introduces high-pressure air to impact the fuel jet, thereby enhancing the droplet breaking effect.

[0003] Since the aforementioned fuel injection technologies all rely on the mechanical atomization mechanism of liquid fuel, the fuel exists in droplet form throughout the injection and mixing process. Limited by the surface tension and viscosity of liquid fuel, certain technical limitations remain: firstly, droplets re-aggregate during injection and mixing, leading to locally higher fuel concentrations; secondly, the mixing process of fuel and air mainly depends on jet diffusion and droplet evaporation, and the uniformity of mixing is greatly affected by operating conditions and structure, making it difficult to maintain stability under different operating conditions. Furthermore, to achieve better atomization, the system typically needs to maintain a high injection pressure continuously, increasing the structural complexity and control difficulty of the injection system. Summary of the Invention

[0004] Purpose of the Invention: This invention aims to solve the problem that existing diesel injection supply technologies generally rely on high injection pressure to achieve mechanical atomization and fragmentation of liquid fuel. Since the fuel remains in droplet form during injection and mixing, the atomization and mixing effect is sensitive to changes in injection pressure and operating conditions, making it difficult to maintain stability under different conditions. Furthermore, high-pressure injection systems have complex structures and high control requirements. This invention provides a diesel vaporization device and a cyclic quantitative control method. By using a heating element installed in the mixing chamber, liquid diesel is injected in jet form and contacts the working surface of the heating element to achieve vaporization. Combining the diesel distillation range characteristics (180℃-360℃) and the safe threshold of diesel auto-ignition temperature (diesel flash point 220℃-250℃), the controller maintains the heating element's operating temperature within a preset range of 180-220℃ to meet the diesel vaporization requirements. Preheated air enters the mixing chamber through the intake pipe and diffuses and mixes with the gasified diesel to form a gaseous fuel-oil mixture. The controller coordinates the intake process and the fuel injection process based on temperature, pressure and oxygen concentration detection signals to keep the pressure and equivalence ratio in the mixing chamber stable within the target range, and injects the gaseous fuel-oil mixture out through the fuel injection valve.

[0005] The diesel vaporization injection device includes a liquid fuel injector, a mixing chamber, a heating element, a controller, an intake pipe, a heating grid, an intake valve, a fuel injection valve, a temperature sensor, a pressure sensor, and an oxygen concentration sensor.

[0006] The mixing chamber is a through-type cavity structure with a fuel injection hole on its upper end face and a fuel injection valve connected to the lower end face. The fuel injection valve is an electromagnetically controlled valve. The liquid fuel injector is an electromagnetically controlled injector, located at the fuel injection hole at the upper end of the mixing chamber. Its injection direction is perpendicular to the surface of the heating element. The heating element is a high-temperature resistant metal heat-conducting component, located inside the mixing chamber. The heating element is connected to a controller, which adjusts its operating temperature to maintain it at 180-220℃.

[0007] The radius of the projected area of ​​the conical fuel jet formed by the liquid fuel injector on the working surface of the heating element is: The effective working surface of the heating element is rectangular, with a length of L2 and a width of B, and should meet the following requirements. and This ensures that the effective working area of ​​the heating element completely covers the oil jet projection area.

[0008] One end of the air intake pipe is an air input end (compatible with a high-pressure air source, and the air input end can be set with an intake pressure), and the other end is connected to the side wall of the mixing chamber. A heating mesh is fixedly installed inside the air intake pipe along the airflow direction. The heating mesh is connected to the controller, and the controller synchronously regulates the temperature to achieve air preheating.

[0009] The intake valve is an electromagnetic control valve, which is installed in series on the connection path between the intake pipe and the mixing chamber, and is used to control the timing and flow rate of the preheated air.

[0010] The temperature sensor, pressure sensor, and oxygen concentration sensor are all installed on the side wall of the mixing chamber by threaded sealing, and the probe ends of the sensors all extend into the mixing chamber. The signal output ends of the temperature sensor, pressure sensor, and oxygen concentration sensor are respectively connected to the controller to collect and feed back the temperature, pressure, and oxygen concentration data inside the mixing chamber in real time.

[0011] A cyclic control method for a diesel vaporization device: based on the aforementioned diesel vaporization device, characterized in that the injection cycle sequentially includes a preheating stage, an air intake stage, a fuel-air mixing stage, an injection stage, and a fuel-air replenishment stage. In each stage, the controller controls the heating, air intake, fuel injection, and injection processes based on temperature, pressure, and oxygen concentration detection signals, thereby achieving adaptive adjustment of the multi-round injection process.

[0012] During the preheating stage, the controller initiates the preheating process of the heating element and heating grid, wherein the heating element is stably controlled within the preset operating temperature range T. h ∈[180℃, 220℃]; The heating grid is heated to the preset target temperature to preheat the air entering the mixing chamber. The controller controls the working state of the heating element according to the power supply, current or voltage parameters of the heating element to stabilize its temperature within the target range; at the same time, it initializes the oxygen concentration sensor to ensure that its output signal is in normal working condition.

[0013] During the intake phase, the controller opens the intake valve, allowing air to flow into the mixing chamber after passing through the heating mesh. In this phase, only air is introduced into the mixing chamber, and no fuel injection occurs. The controller controls the intake process based on the detection signal from the pressure sensor. When the pressure in the mixing chamber reaches the preset target pressure P... tar1 At this time, the controller closes the intake valve to stop air intake, and simultaneously, the controller adjusts the pressure within the mixing chamber accordingly. ,temperature Calculate the air quality before fuel injection Mixing chamber volume V, gas constant R, and air molar mass The formula is as follows:

[0014]

[0015] During the oil-gas mixing stage, the controller adjusts the air quality within the mixing chamber. Theoretical air-fuel ratio of diesel fuel and preset target equivalent ratio Calculate the mass of fuel to be injected in this cycle. The formula is as follows:

[0016]

[0017] Furthermore, the controller combines the equivalent flow area A of the liquid fuel injector and the injection pressure P. inj Fuel density and the pressure inside the mixing chamber Once the required injection pulse width t is determined inj The formula for controlling the liquid fuel injector to complete the injection is as follows:

[0018]

[0019] During the oil-gas injection phase, the controller controls the oil-gas injection valve to inject a gaseous oil-gas mixture. When the pressure sensor detects that the pressure inside the mixing chamber has dropped to a preset lower pressure threshold... When the injection stops, the controller adjusts the pressure in the mixing chamber after injection. ,temperature Oxygen concentration Oxygen concentration benchmark value Diesel molar mass Calculate the remaining air mass in the mixing chamber after injection. and remaining fuel mass The remaining mass is used as the initial state parameter for air and fuel replenishment control in the next injection cycle, as shown in the following formula:

[0020]

[0021]

[0022] During the oil and gas replenishment phase, the controller opens the intake valve to replenish air into the mixing chamber, and based on the detection signal from the pressure sensor, the pressure in the mixing chamber reaches the preset target pressure P. tar1 The intake valve is closed when the air replenishment is complete; after the air replenishment is finished, the controller adjusts the pressure P in the mixing chamber based on the pressure P after the air replenishment. tar1 Pressure P before replenishment tar2 Temperature after gas replenishment Calculate the air quality after replenishment. The required fuel replenishment amount for this injection cycle is determined by combining the target equivalence ratio λ. It controls the liquid fuel injector to inject fuel in order to prepare the mix ratio for the next injection cycle.

[0023]

[0024]

[0025] Furthermore, by repeating the process of air-fuel mixture injection and fuel replenishment, continuous injection control is achieved.

[0026] Beneficial Effects: This invention replaces the traditional technical path of relying on high injection pressure to achieve mechanical atomization and fragmentation of liquid fuel with a "liquid diesel jet-heated surface contact vaporization" method. This allows the fuel to participate in mixing and injection in gaseous form after entering the mixing chamber, thus reducing dependence on high-pressure atomization conditions. Simultaneously, the structural constraint of the fuel jet's projection area at the heating element being completely covered by the effective working area of ​​the heating element enhances the effective contact between the fuel jet and the hot surface, making the vaporization process more stable and helping to reduce droplet coalescence and uneven mixing. Furthermore, based on state detection signals such as temperature, pressure, and oxygen concentration, this invention coordinates and controls the preheating of the heating element, the pressure build-up in the mixing chamber, and the fuel injection process, achieving quantitative adjustment and cyclic recovery of the pressure and equivalence ratio within the mixing chamber. This results in a stable and repeatable gaseous fuel-oil mixture output, easily adaptable to different fuel supply requirements and operating conditions. In addition, this invention has a high degree of system integration, does not rely on complex mechanical transmissions and high-precision kinematic pairs, has a simple overall structure, few potential failure points, and high reliability, showing good prospects for engineering applications. Attached Figure Description

[0027] Figure 1 A schematic diagram of a diesel vaporization injection device.

[0028] Figure 2 Flowchart of a diesel vaporization injection method

[0029] Figure 3 Schematic diagram of the spatial coverage relationship between the oil jet and the heating element.

[0030] In the diagram: 1. Liquid fuel injector; 2. Mixing chamber; 3. Heating element; 4. Controller; 5. Intake pipe; 6. Heating mesh; 7. Intake valve; 8. Fuel injection valve; 9. Temperature sensor; 10. Pressure sensor; 11. Oxygen concentration sensor. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments.

[0032] In this embodiment, the component selection and assembly relationship of the diesel vaporization injection device are as follows:

[0033] The mixing chamber 2 is made of stainless steel, with an inner diameter of 50 mm, a length of 50 mm, and a volume of approximately 100 mL. The upper end face has a fuel injection hole with a diameter of 10 mm, and the lower end face is sealed to the fuel injection valve 8 through a flange. It can withstand a maximum working pressure of ≥10 bar.

[0034] The liquid fuel injector 1 is an electromagnetic injector with an injection pressure adjustment range of 10-20 MPa, an injection pulse width adjustment range of 0.2-5 ms, an injection flow rate of 15-30 mg / cycle, and an injection nozzle diameter of 0.12 mm. It is coaxially mounted at the fuel injection hole, and the vertical distance L1 between the jet centerline and the working surface of the heating element 3 is 6 mm. In this embodiment, the spray jet formed by the liquid fuel injector 1 is a conical jet with a full cone angle of 30° (θ=15°). The projected diameter of the jet on the working surface of the heating element 3 satisfies the following formula.

[0035] We obtained D=3.2mm.

[0036] The heating element 3 is made of nickel-chromium alloy and measures 10 mm × 10 mm × 2 mm, i.e., length L2 = 10 mm and B2 = 10 mm, which meets the requirements. , The surface is coated with a high-temperature resistant ceramic coating (high temperature resistance ≥ 600℃), and is fixed to the inner wall of the right side of the mixing chamber 2 by bolts, and connected to the controller 4. The heating power is 500 W.

[0037] The air intake pipe 5 is made of stainless steel with a diameter of 20 mm. The air input end is adapted to a high-pressure air source, and the air intake pressure is stable at 5 bar. The other end is connected to the side wall of the mixing chamber 2 (5 mm from the upper end face).

[0038] The heating mesh 6 is an 80-mesh platinum wire woven mesh with a heating power of 300 W. It is fixed inside the middle section of the air inlet pipe 5 and connected to the controller 4.

[0039] The intake valve 7 is an electromagnetic control valve with a diameter of 15mm and a response time of ≤1 ms. It is installed in series at the connection between the intake pipe 5 and the mixing chamber 2.

[0040] The sensors are as follows: temperature sensor 9 is a K-type thermocouple (measurement range 0-600 ℃, accuracy ±1 ℃), pressure sensor 10 is a piezoelectric pressure sensor (measurement range 0-10 bar, accuracy ±0.01 bar), and oxygen concentration sensor 11 is an electrochemical oxygen sensor (measurement range 0–25 %Vol, accuracy ±0.2 %Vol). All sensors are installed on the side wall of mixing chamber 2 via threaded seals (30 mm, 35 mm, and 40 mm from the upper end face, respectively), with the probe end extending 5 mm into the cavity.

[0041] The oil and gas injection valve 8 has an electromagnetically controlled injection structure with four injection holes, each with a diameter of 1.0 mm and an opening response time of ≤0.3 ms. It is sealed to the flange at the lower end of the mixing chamber 2.

[0042] The controller 4 is an STM32F407 microcontroller that integrates an AD acquisition module, a PWM output module, and a floating-point arithmetic unit. It can acquire temperature, pressure, and oxygen concentration signals and coordinate the control of various actuators. The control cycle is 1 ms. It can acquire temperature, pressure, and oxygen concentration signals, calculate equivalence ratio and injection pulse width, and coordinate the control of various actuators.

[0043] This embodiment uses a 2.0 L diesel engine operating at idle speed as the application object, with an engine speed of 800 r / min and a load of 20%. The target equivalent ratio of the mixture chamber 2 output is set to... = 1.0 ± 0.05, the specific execution process of the control method is divided into five stages: preheating stage, air intake stage, oil-air mixing stage, oil-air injection stage and oil-air replenishment stage.

[0044] During the preheating stage, the controller 4 initiates the preheating process of the heating element 3 and the heating mesh 6, wherein the target operating temperature of the heating element 3 is set to T. h =200℃, with an allowable fluctuation range of ±10℃. Controller 4 adjusts the power supply of heating element 3 (rated power 500 W) to bring heating element 3 into a stable heating state. Heating grid 6 is simultaneously powered on and heated, with its target temperature set at 150℃, to preheat the air subsequently entering the mixing chamber. During preheating, temperature sensor 9 detects the gas temperature inside mixing chamber 2. Based on a pre-established calibration relationship of "gas temperature in mixing chamber 2 - working temperature of heating element 3", controller 4 estimates the equivalent working temperature of heating element 3 and adjusts the power supply of heating element 3 accordingly to achieve T h The temperature is maintained stably within the preset range of 190–210 °C. When the controller 4 determines that the temperature of the heating element 3 has reached the target range and has remained stable for more than 2 seconds, the preheating stage is completed; at the same time, the oxygen concentration sensor 11 is initialized and sampled to confirm its normal operation, and the system enters the intake stage.

[0045] During the intake phase, controller 4 opens intake valve 7, allowing air to flow into mixing chamber 2 after preheating by heating mesh 6 at an intake pressure of 5 bar. During this phase, mixing chamber 2 is only filled with air and no fuel injection occurs. Controller 4 controls the intake process based on real-time pressure detection results from pressure sensor 10 within mixing chamber 2, setting the target pressure within mixing chamber 2 to P. tar1 =5 bar. During the intake process, controller 4 continuously acquires the pressure signal of mixing chamber 2 with a control cycle of 1 ms. When P is detected... tar1When the pressure reaches 5 bar and remains stable for more than 10 ms, the controller 4 immediately closes the intake valve 7 to stop air introduction, thereby creating a stable, air-only initial gas state in the mixing chamber 2. This provides consistent initial conditions for subsequent fuel injection and air-fuel mixing stages. The controller 4 adjusts the pressure in the mixing chamber 2 accordingly. ,temperature Calculate the air quality before fuel injection ,in, =473 K, R=8.314 J / (mol·K), V=100 ml, =28.97×10 -3 kg / mol from The mass of air in mixing chamber 2 is 368 mg.

[0046] During the oil-gas mixing stage, the controller 4 adjusts the air quality within the mixing chamber according to... and preset target equivalent ratio Calculate the mass of fuel to be injected in this cycle. Assuming the target equivalent ratio is 1, by Therefore, the injection quantity for this operation is 25.7 mg. Simultaneously, the controller 4, in conjunction with the equivalent flow area A and injection pressure P of the liquid fuel injector 1, calculates... inj and the pressure inside the mixing chamber Once the required injection pulse width t is determined inj ,in , =830kg / m 3 A = 1.13 × 10 -8 m 2 ,Depend on The injection pulse width is 1.7ms, which controls the liquid fuel injector 1 to complete the injection.

[0047] During the injection phase, the controller 4 controls the oil-gas injection valve 8 to inject a gaseous oil-gas mixture. When the pressure sensor 10 detects that the pressure in the mixing chamber 2 has dropped to a preset lower pressure threshold, the injection process continues. When the pressure reaches 2 bar, injection stops; simultaneously, controller 4 adjusts the pressure in the mixing chamber 2 after injection. ,temperature Oxygen concentration Calculate the remaining air mass in mixing chamber 2 after injection. and remaining fuel mass ,in, =463K =0.2、 =0.21、 =167×10 -3 kg / mol from , achievable =143mg =4.1mg, and the remaining mass is used as the initial state parameter for air and fuel replenishment control in the next injection cycle.

[0048] During the oil and gas replenishment phase, the controller 4 controls the intake valve 7 to open and replenish air to the mixing chamber 2, and based on the detection signal of the pressure sensor 10, the pressure in the mixing chamber 2 reaches the upper limit of the pressure threshold P. tar1 When the pressure reaches 5 bar, the intake valve 7 is closed; after the air replenishment is completed, the controller is based on the pressure P in the mixing chamber 2 after the air replenishment. tar1 Pressure P before replenishment tar2 ,temperature Calculate the air quality after replenishment. The required fuel replenishment amount for this injection cycle is determined by combining the target equivalence ratio λ. ,in, =473k, =14.3, from , achievable =221mg, =11.3mg, control the liquid fuel injector 1 to inject fuel to complete the preparation of the next injection cycle.

[0049] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A diesel vaporization device, characterized in that... include: Liquid fuel injector (1), mixing chamber (2), heating element (3), controller (4), intake pipe (5), heating mesh (6), intake valve (7), fuel injection valve (8), temperature sensor (9), pressure sensor (10) and oxygen concentration sensor (11); The mixing chamber (2) is a through-type cavity structure with a fuel injection hole on the upper end face and a sealed connection between the lower end face and the fuel injection valve (8). The fuel injection valve (8) is an electromagnetic control valve. The liquid fuel injector (1) is an electromagnetic control injector, which is located at the fuel injection hole on the upper end face of the mixing chamber (2) and its injection direction is perpendicular to the surface of the heating element (3). The heating element (3) is located inside the mixing chamber (2) and is connected to the controller (4). The air intake pipe (5) is connected to the mixing chamber (2). The air intake pipe (5) is equipped with a heating mesh (6) inside, and the heating mesh (6) is connected to the controller (4). The air intake valve (7) is an electromagnetic control valve, which is installed in series on the communication path between the air intake pipe (5) and the mixing chamber (2). The temperature sensor (9), pressure sensor (10) and oxygen concentration sensor (11) are sealed and installed on the side wall of the mixing chamber (2), with the probe end extending into the mixing chamber (2) and the signal output end connected to the controller (4) respectively.

2. The diesel gasification device as described in claim 1, characterized in that: The operating temperature of the heating element (3) is within a preset range of 180 to 220°C; the effective working surface of the heating element (3) is rectangular, and the effective working area of ​​the heating element (3) should completely cover the projection area of ​​the conical oil jet; the length L2 and width B of the heating element (3) should meet the following requirements. and ,in, This represents the oil jet penetration distance. The oil jet semi-cone angle.

3. The method for cyclic quantitative control of a diesel gasification device as described in claim 1, characterized in that, It can be divided into five stages: preheating stage, air intake stage, oil-air mixing stage, oil-air injection stage, and oil-air replenishment stage.

4. The method as described in claim 3, characterized in that, During the preheating stage, the controller (4) starts the preheating process of the heating element (3) and the heating grid (6). The controller (4) controls the working state of the heating element (3) according to the power supply, current or voltage parameters of the heating element (3) so that it is within the preset working temperature range of 180 to 220°C. At the same time, the heating grid (6) also reaches the target temperature.

5. The method as described in claim 3, characterized in that, During the intake phase, the controller (4) controls the intake valve (7) to open. At the same time, the intake process is controlled based on the detection signal of the pressure sensor (10). When the pressure in the mixing chamber (2) reaches the upper limit of the preset pressure threshold P, tar1 At that time, the controller (4) closes the air intake valve (7) to stop the air intake, and at the same time, the controller (4) adjusts the pressure in the mixing chamber (2) according to the pressure inside. ,temperature Mixing chamber (2) volume V, gas constant R, air molar mass Calculate the air quality before fuel injection ; Equation (1).

6. The method as described in claim 3, characterized in that, During the oil-gas mixing stage, the controller (4) adjusts the air mass in the mixing chamber according to the air mass. Theoretical air-fuel ratio of diesel fuel and preset target equivalent ratio Calculate the mass of fuel to be injected in this cycle. Meanwhile, the controller (4) combines the equivalent flow area A and injection pressure P of the liquid fuel injector (1). inj Diesel density and the pressure inside the mixing chamber Once the required injection pulse width t is determined inj Control the liquid fuel injector (1) to complete the injection; Equation (2) Equation (3).

7. The method as described in claim 3, characterized in that, During the oil-gas injection stage, the controller (4) controls the oil-gas injection valve (8) to inject a gaseous oil-gas mixture. When the pressure sensor (10) detects that the pressure in the mixing chamber (2) has dropped to the preset lower limit of the pressure threshold, When the injection stops, the controller (4) adjusts the pressure of the mixing chamber (2) after injection. ,temperature Oxygen concentration Oxygen concentration benchmark value Diesel molar mass Calculate the remaining air mass in the mixing chamber (2) after injection. and remaining fuel mass The remaining mass is used as the initial state parameter for air and fuel replenishment control in the next injection cycle; Equation (4) Equation (5).

8. The method as described in claim 3, characterized in that, During the oil and gas replenishment stage, the controller (4) controls the intake valve (7) to open and replenish air to the mixing chamber (2), and based on the detection signal of the pressure sensor (10), the pressure in the mixing chamber (2) reaches the preset target pressure P. tar1 When the intake valve (7) is closed, after the replenishment is completed, the controller determines the pressure P in the mixing chamber (2) after replenishment. tar1 Pressure P before replenishment tar2 Temperature after gas replenishment Calculate the air quality after replenishment. The required fuel replenishment amount for this injection cycle is determined by combining the target equivalence ratio λ. Control the liquid fuel injector (1) to inject fuel in order to complete the preparation of the next injection cycle; Equation (6) Equation (7).

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