A dual-stage supercharging intake system of a diesel engine based on a common rail structure and a control method thereof

Abstract

This invention discloses a dual-turbocharged intake system for a diesel engine based on a common rail structure and its control method. The dual-turbocharged intake system includes a series-connected exhaust gas turbocharger and a secondary turbocharger, a common rail intake manifold, a pressure-stabilized air reservoir, electronically controlled valves, sensors, and an electronic control unit. Air is pressurized in both stages and then stored in the common rail intake manifold and pressure-stabilized air reservoir. The electronic control unit, based on engine operating conditions and sensor signals, adjusts the secondary turbocharger speed and flow controller opening using a dual-pressure closed-loop control algorithm, and independently controls the opening of each electronically controlled valve, achieving precise control and uniform distribution of intake air to each cylinder. This invention overcomes insufficient boost at low speeds through dual-stage turbocharging and improves transient response through the common rail-air reservoir composite structure, solving the problems of slow response and uneven cylinder distribution in traditional intake systems, thus significantly improving diesel engine performance.

Description

Technical Field

[0001] This invention relates to the field of internal combustion engine technology, and in particular to a two-stage turbocharged intake system for a diesel engine based on a common rail structure and its control method. Background Technology

[0002] The diesel engine intake system is a critical system affecting engine performance, emissions, and fuel economy. Traditional diesel engine intake systems often employ mechanical control or simple electro-pneumatic valve control, which presents the following technical problems:

[0003] 1. Low control precision: The mechanical intake system has a slow response and cannot achieve precise intake volume control under various operating conditions, resulting in large fluctuations in the air-fuel ratio and affecting combustion efficiency;

[0004] 2. Uneven intake of each cylinder: Due to differences in intake pipe length, bends and other structural features, the actual intake volume of each cylinder deviates (usually >5%), resulting in uneven operation of each cylinder;

[0005] 3. Poor transient response: Under transient conditions such as engine acceleration and deceleration, the intake system responds slowly, affecting power and emissions;

[0006] 4. Inability to achieve flexible control: It is difficult to adjust parameters such as intake pressure and flow rate in real time according to operating conditions.

[0007] In existing technologies, high-pressure common rail technology has been successfully applied to diesel engine fuel systems, but research on applying the common rail concept to intake systems is still lacking. The main reasons are: the physical properties of air and fuel are very different (compressibility, density, viscosity, etc.), and there are technical obstacles to directly applying fuel common rail technology; the working pressure of the intake system is much lower than that of the fuel system, and the technical parameters need to be rematched; the air flow is large and pressure pulsation is difficult to suppress.

[0008] In view of this, this application aims to develop a diesel engine dual-turbocharged intake system based on a common rail structure, which aims to overcome insufficient boost pressure at low speeds through dual-stage turbocharging and improve transient response through a common rail-air tank composite structure, thereby solving the problems of slow response and uneven pressure distribution among cylinders in traditional intake systems. Summary of the Invention

[0009] The purpose of this invention is to provide a diesel engine dual-turbocharged intake system based on a common rail structure and its control method. This system uses a dual-stage turbocharger and a two-stage turbocharger connected in series to force air into the common rail intake manifold and pressure-stabilized air tank, creating high-pressure accumulator. An electronic control unit, dual-pressure closed-loop system, and independent electronically controlled valves for each cylinder enable precise pressure control under all operating conditions, uniform air intake for each cylinder, and rapid transient air replenishment, solving the problems of slow response, unevenness, and low control accuracy in traditional intake systems.

[0010] To achieve the above objectives, the present invention provides a two-stage turbocharged intake system for a diesel engine based on a common rail structure, comprising: an intake turbocharger unit, including an air filter, an exhaust gas turbocharger, and a second-stage turbocharger connected in series;

[0011] The common rail accumulator and distribution unit includes a pressure-stabilized air tank, a common rail intake pipe, and cylinders. The common rail intake pipe is connected to the outlet of the secondary turbocharger. The inlet of the pressure-stabilized air tank is connected to the outlet of the secondary turbocharger via a pipe equipped with an intake check valve to store a portion of the high-pressure air. The outlet of the pressure-stabilized air tank is connected to the common rail intake pipe via a bypass pipe. Multiple intake manifolds are connected to the common rail intake pipe, and each intake manifold is connected to the intake port of the corresponding cylinder. An electrically controlled air valve is installed on the intake manifold. Flow control is provided on the connection pipe between the pressure-stabilized air tank and the common rail intake pipe.

[0012] The exhaust energy recovery unit includes an exhaust manifold and an exhaust main pipe. The exhaust main pipe is equipped with multiple exhaust manifolds, which are connected to the exhaust ports of the corresponding cylinders. The exhaust main pipe is also equipped with a bypass branch that connects to a pressure-stabilized storage tank.

[0013] The sensor detection unit includes a temperature sensor, a first pressure sensor, and a second pressure sensor. The temperature sensor is installed on the common rail intake pipe to detect the air temperature inside the common rail pipe. The first pressure sensor is installed on the common rail intake pipe to detect the common rail pipe pressure. The second pressure sensor is installed on the pressure-stabilized gas storage tank to detect the gas storage tank pressure.

[0014] The electronic control unit receives sensor signals from the temperature sensor, the first pressure sensor, the second pressure sensor, and the electrically controlled pneumatic valve; the electronic control unit is also electrically connected to the electrically controlled pneumatic valve and the flow controller.

[0015] In this process, air passes through an air filter and enters the exhaust gas turbocharger for primary boost, then through a secondary turbocharger before entering the common rail intake manifold. The electronic control unit (ECU) calculates the target common rail pressure based on engine operating conditions, and a pressure sensor detects the actual pressure. The ECU adjusts the secondary turbocharger speed and the flow controller opening to stabilize the actual pressure at the target value. The ECU independently controls the electronically controlled valves of each cylinder according to their intake requirements, achieving a uniform distribution of intake air volume to each cylinder. During acceleration, the ECU quickly opens the flow controller, and high-pressure air from the air tank is supplied to the common rail, improving transient response.

[0016] According to an embodiment of this application, the common rail intake pipe and the pressure stabilizing storage tank constitute a common rail pressure accumulator structure, and the working pressure of the common rail intake pipe is 0.2-0.8 MPa.

[0017] According to an embodiment of this application, the common rail intake pipe is connected in parallel with the pressure-stabilizing air tank, and the volume of the air tank is 1.5-3 times the volume of the common rail intake pipe. It is used to store high-pressure air and quickly replenish pressure under transient conditions.

[0018] According to embodiments of this application, the secondary supercharger is a mechanical supercharger or an electric supercharger.

[0019] According to an embodiment of this application, the electro-pneumatic valve is a high-speed solenoid valve with a response time of less than 20ms.

[0020] According to an embodiment of this application, the bypass branch of the exhaust main is provided with an exhaust gas recirculation valve for regulating the amount of exhaust gas entering the pressure-stabilizing gas storage tank.

[0021] According to an embodiment of this application, the electronic control unit adopts a dual-pressure closed-loop control algorithm, including a target pressure calculation module, a pressure feedback control module, a cylinder coordination control module, and a transient compensation control module.

[0022] According to an embodiment of this application, an electronically controlled air valve is located near the cylinder in the intake manifold of each cylinder, independently controlling the intake of each cylinder, with an intake volume deviation of <2% for each cylinder.

[0023] Another aspect of this application discloses a dual-stage turbocharged intake control method for a diesel engine, based on a common rail-based dual-stage turbocharged intake system as described above, comprising the following steps:

[0024] S1: Signal Acquisition: Acquires engine operating condition signals, common rail pressure signals, stabilized air tank pressure signals, and temperature signals;

[0025] S2: Calculate the target intake pressure based on the operating condition signal: The electronic control unit queries and calculates the target common rail pressure from the preset pulse spectrum or control model based on the current engine speed and load;

[0026] S3: Dual pressure closed-loop regulation:

[0027] The electronic control unit compares the collected common rail pressure and gas tank pressure with the target pressure: if the actual pressure is lower than the target pressure, the speed of the secondary turbocharger is increased and the opening of the flow controller is adjusted to increase the intake boost; if the actual pressure is higher than the target pressure, the speed of the secondary turbocharger is reduced, or the bypass is opened appropriately to reduce the intake pressure.

[0028] S4: Intake Air Temperature Compensation Correction: Based on the temperature sensor signal, the electronic control unit performs real-time compensation on the air density and corrects the intake air volume calculation results to ensure consistent intake air control accuracy under different temperatures;

[0029] S5: Independent intake control for each cylinder: The electronic control unit independently controls the opening time, opening degree, and duration of the electronically controlled valve for each cylinder according to the working requirements of each cylinder, so as to achieve precise and uniform distribution of intake volume for each cylinder;

[0030] S6: Transient Condition Rapid Compensation: Under transient conditions, the electronic control unit quickly adjusts the flow controller opening to rapidly replenish the high-pressure air in the pressure-stabilized air tank to the common rail intake pipe;

[0031] S7: Smooth Control of Operating Condition Switching: When switching between operating conditions, the electronic control unit smoothly adjusts the boost pressure, the opening of the flow controller and the action of the electronically controlled air valve to ensure that the intake pressure is shock-free and the transition is smooth.

[0032] According to embodiments of this application, the operating conditions include idling, steady state, acceleration, high speed and high load, and deceleration.

[0033] The advantages of the present invention over the prior art are:

[0034] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0035] 1. Enhanced boosting capacity and significantly improved low-speed performance: The two-stage boosting structure, formed by connecting the exhaust gas turbocharger and the two-stage turbocharger in series, effectively overcomes the shortcomings of insufficient boosting and obvious turbo lag in traditional single-stage turbochargers at low speeds, resulting in a significant improvement in engine low-speed torque, starting performance and acceleration response.

[0036] 2. High intake pressure control accuracy and good stability: The common rail intake pipe and the pressure-stabilizing gas tank form a pressure storage structure. With the real-time feedback of dual pressure sensors and closed-loop control, high-precision and stable intake pressure control is achieved, resulting in higher combustion efficiency.

[0037] 3. Fast transient response and no lag in power response: The pressure-stabilized air tank can quickly release high-pressure air under transient conditions such as acceleration and sudden load increase, instantly replenishing the common rail pressure, reducing the intake system response time by more than 40%, and significantly improving the engine's transient power characteristics.

[0038] 4. Significantly improved intake uniformity of each cylinder: The use of independent high-speed electronically controlled valves for each cylinder, combined with a common rail pressure stabilization structure, can accurately distribute the intake volume of each cylinder, keeping the intake volume deviation of each cylinder within 2%, effectively improving problems such as uneven operation of each cylinder, knocking, and high exhaust temperature, and significantly improving engine smoothness, reliability and emission performance.

[0039] 5. Flexible and adjustable under all operating conditions, adaptable to high-power-density diesel engines and various harsh operating conditions, with strong adaptability.

[0040] 6. Superior starting performance and shorter starting time: The two-stage turbocharger and pressure-stabilizing air tank can provide sufficient intake pressure during the starting stage, significantly improving the engine's starting response speed and shortening the starting time, which is especially beneficial for reliable starting under harsh conditions such as low temperature and high altitude. Attached Figure Description

[0041] Figure 1 This is a schematic diagram illustrating the composition of a diesel engine dual-turbocharged intake system based on a common rail structure, as an example of the present invention.

[0042] The attached diagram is described below:

[0043] 1. Air filter, 2. Exhaust gas turbocharger, 3. Secondary turbocharger, 4. Common rail intake manifold, 5. Exhaust main manifold, 6. Intake manifold, 7. Cylinder, 8. Exhaust manifold, 9. Electronically controlled valve, 10. Pressure stabilizing tank, 11. Flow controller, 12. Temperature sensor, 13. First pressure sensor, 14. Second pressure sensor, 15. Electronic control unit, 16. Intake check valve. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0045] Please see Figure 1 The diagram illustrates a dual-turbocharged intake system for a diesel engine based on a common rail structure. It includes a series-connected exhaust gas turbocharger 2 and a secondary turbocharger 3, a common rail intake manifold 4, a pressure-stabilized air reservoir 10, electronically controlled valves 9, sensors, and an electronic control unit 15. Air, after being pressurized in both stages, enters the common rail intake manifold 4 and the pressure-stabilized air reservoir 10 for storage. The electronic control unit 15, based on engine operating conditions and sensor signals, adjusts the speed of the secondary turbocharger 3 and the opening of the flow controller 11 using a dual-pressure closed-loop control algorithm, and independently controls the opening of each electronically controlled valve 9, achieving precise control and uniform distribution of intake air to each cylinder. This invention overcomes insufficient boost pressure at low speeds through dual-stage turbocharging and improves transient response through the common rail-air reservoir composite structure, solving the problems of slow response and uneven distribution among cylinders in traditional intake systems, thus significantly improving diesel engine performance. It also improves intake response during startup, increasing starting speed and shortening starting time.

[0046] In this embodiment, a diesel engine dual-stage turbocharged intake system based on a common rail structure includes an intake turbocharger unit, a common rail accumulator and distribution unit, an exhaust energy recovery unit, a sensor detection unit, and an electronic control unit 15.

[0047] Specifically, the intake supercharging unit includes an air filter 1, an exhaust gas turbocharger 2, and a secondary supercharger 3 connected in series. The air filter 1 filters the air entering the system; the exhaust gas turbocharger 2 uses exhaust energy to perform primary supercharging of the air; the secondary supercharger 3 is connected in series after the exhaust gas turbocharger 2 to further supercharge the air after the primary supercharging. The exhaust gas turbocharger 2 and the secondary supercharger 3 are connected in series via piping to form a two-stage supercharging structure.

[0048] Specifically, the common rail accumulator and distribution unit includes a pressure-stabilizing air tank 10, a common rail intake pipe 4, and cylinders 7. The common rail intake pipe 4 is connected to the outlet of the secondary turbocharger 3 and is used to store and distribute high-pressure air. The inlet end of the pressure-stabilizing air tank 10 is connected to the outlet of the secondary turbocharger 3 through a pipeline with an intake check valve 16 and is used to store a portion of the high-pressure air. The outlet end of the pressure-stabilizing air tank 10 is connected to the common rail intake pipe 4 through a bypass pipeline and is used to store a portion of the high-pressure air for rapid pressure replenishment under transient conditions. Multiple intake manifolds 6 are connected to the common rail intake pipe 4, and the intake manifolds 6 are connected to the intake ports of the corresponding cylinders 7. An electrically controlled air valve 9 is installed on the intake manifolds 6. Flow control is provided on the connection pipeline between the pressure-stabilizing air tank 10 and the common rail intake pipe 4.

[0049] Specifically, the common rail intake pipe 4 and the pressure-stabilizing storage tank 10 constitute a common rail pressure accumulator structure. The working pressure of the common rail intake pipe 4 is 0.2-0.8MPa, and the volume is 0.5-2L.

[0050] Specifically, the common rail intake pipe 4 is connected in parallel with the pressure-stabilizing air storage tank 10. The volume of the air storage tank is 1.5-3 times that of the common rail intake pipe 4, and it is used to store high-pressure air to quickly replenish pressure under transient conditions.

[0051] Specifically, the exhaust energy recovery unit includes an exhaust manifold 8 and an exhaust main pipe 5. The exhaust main pipe 5 is provided with multiple exhaust manifolds 8, which are connected to the exhaust ports of the corresponding cylinders 7; the exhaust main pipe 5 is connected to the exhaust manifolds 8 and the turbine end of the exhaust gas turbocharger 2 to drive the turbocharger; the exhaust main pipe 5 is also provided with a bypass branch connected to the pressure-stabilized gas storage tank 10.

[0052] Specifically, the bypass branch of the exhaust main pipe 5 is equipped with an exhaust gas recirculation valve to regulate the amount of exhaust gas entering the pressure-stabilizing gas storage tank 10.

[0053] Specifically, the sensor detection unit includes a temperature sensor 12, a first pressure sensor 13, and a second pressure sensor 14. The temperature sensor 12 is disposed on the common rail intake pipe 4 and is used to detect the air temperature inside the common rail pipe; the first pressure sensor 13 is disposed on the common rail intake pipe 4 and is used to detect the pressure of the common rail pipe; the second pressure sensor 14 is disposed on the pressure-stabilized gas storage tank 10 and is used to detect the pressure of the gas storage tank.

[0054] Specifically, the electronic control unit 15 is connected to the temperature sensor 12, the first pressure sensor 13, the second pressure sensor 14, and the electrically controlled air valve 9 to receive sensor detection signals; the electronic control unit 15 is electrically connected to the electrically controlled air valve 9 and the flow controller 11.

[0055] Understandably, air enters the exhaust gas turbocharger 2 for primary boost after passing through the air filter 1, and then enters the common rail intake manifold 4 after being boosted by the secondary turbocharger 3. The electronic control unit 15 calculates the target common rail pressure based on the engine operating conditions, and the pressure sensor detects the actual pressure. The electronic control unit 15 stabilizes the actual pressure at the target value by adjusting the speed of the secondary turbocharger 3 and the opening of the flow controller 11. The electronic control unit 15 independently controls the electronically controlled air valves 9 of each cylinder according to the intake demand of each cylinder, so as to achieve a uniform distribution of intake volume to each cylinder. Under acceleration conditions, the electronic control unit 15 quickly opens the flow controller 11, and the high-pressure air in the air tank is replenished to the common rail, improving transient response.

[0056] Specifically, the secondary supercharger 3 is either a mechanical supercharger or an electric supercharger. During startup and idling, the exhaust energy is low, and the boosting capacity of the exhaust gas turbocharger 2 is limited. At this time, the secondary supercharger 3 is put into operation: if it is an electric secondary supercharger 3, the electronic control unit 15 directly drives it to quickly build up boost pressure; if it is a mechanical secondary supercharger 3, it rotates synchronously with the engine crankshaft to achieve forced intake boosting.

[0057] Specifically, the electronically controlled air valve 9 is a high-speed solenoid valve with a response time of less than 20ms. The electronically controlled air valve 9 is located in the intake manifold 6 of each cylinder near the cylinder 7, and independently controls the intake of each cylinder, with an intake volume deviation of less than 2% for each cylinder.

[0058] Specifically, the electronic control unit 15 adopts a dual-pressure closed-loop control algorithm, including a target pressure calculation module, a pressure feedback control module, a cylinder coordination control module, and a transient compensation control module.

[0059] Another aspect of this application discloses a dual-stage turbocharged intake control method for a diesel engine, based on the aforementioned dual-stage turbocharged intake system for a diesel engine with a common rail structure, comprising the following steps:

[0060] S1: Signal Acquisition: Acquires engine operating condition signals, common rail pressure signals, stabilized air tank pressure signals, and temperature signals;

[0061] S2: Calculate the target intake pressure based on the operating condition signal: The electronic control unit 15 queries and calculates the target common rail pressure from the preset pulse spectrum or control model based on the current engine speed and load;

[0062] S3: Dual pressure closed-loop regulation:

[0063] The electronic control unit 15 compares the collected common rail pressure and gas tank pressure with the target pressure: if the actual pressure is lower than the target pressure, the speed of the secondary turbocharger 3 is increased and the opening of the flow controller 11 is adjusted to increase the intake boost; if the actual pressure is higher than the target pressure, the speed of the secondary turbocharger 3 is reduced, or the bypass is opened appropriately to reduce the intake pressure.

[0064] S4: Intake air temperature compensation correction: Based on the signal from temperature sensor 12, electronic control unit 15 performs real-time compensation on air density and corrects the intake air volume calculation result to ensure consistent intake air control accuracy under different temperatures.

[0065] S5: Independent intake control for each cylinder: The electronic control unit 15 independently controls the opening time, opening degree and duration of the electronically controlled air valve 9 corresponding to each cylinder 7 according to the working requirements of each cylinder, so as to achieve precise and uniform distribution of intake volume for each cylinder.

[0066] S6: Transient condition rapid compensation: Under transient conditions, the electronic control unit 15 quickly adjusts the opening of the flow controller 11 to quickly replenish the high-pressure air in the pressure-stabilized air tank 10 to the common rail intake pipe 4.

[0067] S7: Smooth Control of Operating Condition Switching: When switching between operating conditions, the electronic control unit 15 smoothly adjusts the boost pressure, the opening of the flow controller 11 and the action of the electronically controlled air valve 9 to ensure that the intake pressure is not impacted and the transition is smooth.

[0068] Specifically, the operating conditions include idling, steady state, acceleration, high speed and high load, and deceleration.

[0069] In this embodiment, the working principle of a diesel engine dual-stage turbocharged intake system based on a common rail structure, as exemplified in this application, is based on a composite principle of dual-stage turbocharging, common rail pressure accumulation, and independent electronic control distribution, achieving high-precision, fast-response, and uniform control of the diesel engine's intake pressure and flow rate. Specifically:

[0070] 1. The two-stage supercharging principle employs an exhaust gas turbocharger 2 and a second-stage turbocharger 3 connected in series to form a two-stage supercharging structure. The exhaust gas turbocharger 2 utilizes the engine exhaust energy to achieve first-stage supercharging, meeting the supercharging requirements under medium and high-speed conditions; the second-stage turbocharger 3 actively intervenes under low-speed, starting, and transient conditions, compensating for the shortcomings of single-stage turbocharging, such as insufficient low-speed torque and significant turbo lag, to achieve stable supercharging pressure output across the entire operating range.

[0071] 2. Common Rail-Stabilized Air Storage Tank Pressure Accumulation Principle: High-pressure air, after being pressurized in two stages, enters the common rail intake pipe 4 and is then charged and pressurized to the stabilized air storage tank 10 through a bypass pipeline. The common rail intake pipe 4 is used to stabilize the pressure and distribute air to each cylinder; the stabilized air storage tank 10, as a high-pressure air energy storage unit, maintains stable system pressure under steady-state conditions and rapidly releases high-pressure air under transient conditions such as acceleration and sudden load increases, instantly replenishing the pressure in the common rail intake pipe 4, significantly improving the transient response speed of the intake system.

[0072] 3. Dual-pressure closed-loop control principle: The electronic control unit 15 collects pressure signals in real time through the pressure sensor on the common rail intake pipe 4 and the pressure sensor on the pressure stabilizing tank 10. Combined with the engine speed, load and intake air temperature signals, it adopts a dual-pressure closed-loop control algorithm to coordinately adjust the speed of the secondary turbocharger 3 and the opening of the flow controller 11, so that the common rail pressure and the tank pressure are stabilized at the target value, thereby achieving precise control of the intake pressure.

[0073] 4. Independent electronic control distribution principle for each cylinder: An independent electronically controlled air valve 9 is set at the position of each cylinder intake manifold 6 near the cylinder 7. The electronic control unit 15 independently controls the opening time, opening degree and duration of each electronically controlled air valve 9 according to the intake requirements of each cylinder, so as to eliminate the problem of uneven intake of each cylinder caused by the structural difference of the intake manifold 6 and realize the uniform distribution of intake volume of each cylinder.

[0074] 5. Principle of exhaust energy recovery and utilization: After the engine exhaust is collected by the exhaust manifold 8, part of it drives the exhaust gas turbocharger 2, and the other part can enter the pressure storage tank 10 through the bypass branch, so as to realize the recovery and reuse of exhaust energy and improve the overall energy utilization rate of the machine.

[0075] In this embodiment, the complete working process of the diesel engine twin-turbo intake system based on the common rail structure is as follows:

[0076] 1. Starting and Idling Conditions: When the engine starts, fresh air enters the intake system after being filtered by the air filter 1. Due to the low exhaust energy during starting and idling, the turbocharger 2 has limited boosting capacity. At this time, the secondary turbocharger 3 is activated: if it is an electric secondary turbocharger 3, the electronic control unit 15 directly drives it to quickly establish boost pressure; if it is a mechanical secondary turbocharger 3, it rotates synchronously with the engine crankshaft to achieve forced intake boosting. The boosted air enters the common rail intake manifold 4 and the pressure-stabilizing reservoir 10 sequentially, quickly establishing the basic intake pressure. The electronic control unit 15 regulates the flow controller 11 through dual-pressure closed-loop control based on the target idle pressure to keep the common rail pressure and reservoir pressure stable. The electronically controlled valves 9 of each cylinder operate with a small opening and short duration to ensure smooth idling and stable combustion. At the same time, a certain pressure reserve is maintained in the pressure-stabilizing reservoir 10 to shorten the engine start-up time and improve start-up response.

[0077] 2. Steady-state operation: When the engine is in a medium-speed, medium-load steady-state condition, the exhaust energy is sufficient, and the exhaust gas turbocharger 2 works efficiently, forming a two-stage synergistic supercharging with the secondary turbocharger 3. High-pressure air continuously fills the common rail intake manifold 4, and the pressure-stabilizing reservoir 10 maintains pressure reserves. The electronic control unit 15 calculates the target common rail pressure in real time according to the engine operating conditions, and collects the actual pressure through the first pressure sensor 13 and the second pressure sensor 14, and adjusts the speed of the secondary turbocharger 3 and the opening of the flow controller 11 in a closed loop to stabilize the intake pressure within the set range. The electronically controlled valves 9 corresponding to each cylinder are independently controlled according to the intake demand of that cylinder, realizing precise and uniform distribution of intake volume for each cylinder, effectively reducing the working difference between cylinders, improving combustion efficiency and engine smoothness.

[0078] 3. Transient acceleration / sudden load conditions: When the engine accelerates rapidly or is suddenly loaded, the electronic control unit 15 quickly identifies the change in operating conditions and enters the transient compensation control mode: 1) The electronic control unit 15 instantly opens the flow controller 11, and the high-pressure air stored in the pressure-stabilized air tank 10 is quickly replenished to the common rail intake pipe 4, increasing the intake pressure in a short time and eliminating the lag effect of the traditional turbocharger system; 2) At the same time, the electronic control unit 15 increases the speed of the secondary turbocharger 3, and works with the exhaust gas turbocharger 2 to increase the total boost pressure, achieving a dual response of "instantaneous air replenishment from the air tank + rapid pressure increase of the turbocharger"; 3) The electronically controlled air valves 9 of each cylinder synchronously increase their opening, so that the cylinder 7 can quickly obtain sufficient and uniform high-pressure air, and the power response is rapid and without delay.

[0079] 4. High-speed, high-load operation: When the engine operates at high speed and high load, the exhaust energy is sufficient, and the exhaust gas turbocharger 2 provides the main boost capacity. The secondary turbocharger 3 appropriately reduces its speed or partially bypasses the turbocharger to reduce drive losses. The common rail intake manifold 4 and the pressure-stabilizing reservoir 10 work together to maintain a high and stable intake pressure to meet the high power output requirements. The electronic control unit 15, through high-precision closed-loop control, ensures small intake pressure fluctuations and uniform intake for each cylinder, enabling the engine to maintain excellent power, economy, and emission levels even under high power density conditions.

[0080] 5. Deceleration, Fuel Cut-off, and Shutdown Conditions: When the engine decelerates or cuts off fuel, the electronic control unit 15 reduces the speed of the secondary turbocharger 3 and adjusts the flow controller 11 to gradually reduce the pressure in the common rail intake manifold 4 and the pressure stabilizing reservoir 10 to avoid pressure surges. The electronically controlled air valves 9 of each cylinder reduce their opening or close according to the operating conditions to ensure a smooth transition. After the engine stops, the intake check valve 16 closes, and the pressure stabilizing reservoir 10 retains a certain pressure to support the next rapid start-up.

[0081] Example 1: Application Case of a Six-Cylinder Diesel Engine

[0082] System Composition

[0083] 2. Exhaust gas turbocharger, 3. Mechanical two-stage turbocharger, 4. Common rail intake pipe (volume 1.5L, working pressure 0.5MPa), 10. Pressure stabilizing air tank (volume 3L), 9. 6 electronically controlled air valves (response time <15ms), pressure sensor a, pressure sensor b, temperature sensor 12, and electronic control unit 15.

[0084] Work process

[0085] Air enters the exhaust gas turbocharger 2 for primary boost after passing through air filter 1, and then enters the common rail intake manifold 4 after secondary boost through the supercharger. The ECU calculates the target common rail pressure as 0.5 MPa based on engine operating conditions (1800 rpm, 60% load). Pressure sensor a detects the actual pressure, and the ECU stabilizes the actual pressure at the target value by adjusting the speed of the secondary turbocharger 3 and the opening of the flow controller 11. The electronically controlled air valves 9 for each cylinder are independently controlled according to the intake demand of each cylinder, achieving uniform distribution of intake air volume to each cylinder. Under acceleration conditions, the ECU quickly opens the flow controller 11, and high-pressure air from the air tank is supplied to the common rail, improving transient response.

[0086] When the secondary turbocharger 3 is an electric turbocharger, the ECU reads the pressure in the pressure-stabilized air tank 10 when the diesel engine starts. If the pressure is sufficient, it starts directly. If the pressure is insufficient, the secondary turbocharger 3 is started simultaneously when the diesel engine starts to improve the starting speed. When the secondary turbocharger 3 is a mechanical turbocharger, the diesel engine starts and drives the turbocharger to run, which has the effect of boosting and replenishing air.

[0087] Control parameters

[0088] Common rail pressure control accuracy ±0.01MPa, intake volume deviation of each cylinder <2%, transient response time <40ms.

[0089] In summary, the technical solution of this application has the following beneficial effects:

[0090] 1. Enhanced boosting capacity and significantly improved low-speed performance: The two-stage boosting structure, formed by connecting the exhaust gas turbocharger and the two-stage turbocharger in series, effectively overcomes the shortcomings of insufficient boosting and obvious turbo lag in traditional single-stage turbochargers at low speeds, resulting in a significant improvement in engine low-speed torque, starting performance and acceleration response.

[0091] 2. High intake pressure control accuracy and good stability: The common rail intake pipe and the pressure-stabilizing gas tank form a pressure storage structure. With the real-time feedback of dual pressure sensors and closed-loop control, high-precision and stable intake pressure control is achieved, resulting in higher combustion efficiency.

[0092] 3. Fast transient response and no lag in power response: The pressure-stabilized air tank can quickly release high-pressure air under transient conditions such as acceleration and sudden load increase, instantly replenishing the common rail pressure, reducing the intake system response time by more than 40%, and significantly improving the engine's transient power characteristics.

[0093] 4. Significantly improved intake uniformity of each cylinder: The use of independent high-speed electronically controlled valves for each cylinder, combined with a common rail pressure stabilization structure, can accurately distribute the intake volume of each cylinder, keeping the intake volume deviation of each cylinder within 2%, effectively improving problems such as uneven operation of each cylinder, knocking, and high exhaust temperature, and significantly improving engine smoothness, reliability and emission performance.

[0094] 5. Flexible and adjustable under all operating conditions, adaptable to high-power-density diesel engines and various harsh operating conditions, with strong adaptability.

[0095] 6. Superior starting performance and shorter starting time: The two-stage turbocharger and pressure-stabilizing air tank can provide sufficient intake pressure during the starting stage, significantly improving the engine's starting response speed and shortening the starting time, which is especially beneficial for reliable starting under harsh conditions such as low temperature and high altitude.

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A two-stage turbocharged intake system for a diesel engine based on a common rail structure, characterized in that, include: The intake supercharging unit includes an air filter, an exhaust gas turbocharger, and a two-stage supercharger connected in series. The common rail accumulator and distribution unit includes a pressure-stabilizing storage tank, a common rail intake pipe, and cylinders. The common rail intake pipe is connected to the outlet of the secondary turbocharger; The inlet of the pressure-stabilizing gas storage tank is connected to the outlet of the secondary booster via a pipeline with an inlet check valve, for storing a portion of high-pressure air; The outlet end of the pressure-stabilized gas storage tank is connected to the common rail intake pipe through a bypass pipeline. Multiple intake manifolds are connected to the common rail intake pipe. Each intake manifold is connected to the intake port of the corresponding cylinder. An electronically controlled air valve is installed on the intake manifold. The connection between the pressure-stabilizing gas storage tank and the common rail inlet pipe is equipped with a flow control system. The exhaust energy recovery unit includes the exhaust manifold and the exhaust header. The exhaust main pipe is provided with a plurality of exhaust manifolds, and the exhaust manifolds are connected to the exhaust ports of the corresponding cylinders; the exhaust main pipe is also provided with a bypass branch connected to the pressure-stabilizing gas storage tank; The sensor detection unit includes a temperature sensor, a first pressure sensor, and a second pressure sensor. The temperature sensor is installed on the common rail intake pipe and is used to detect the air temperature inside the common rail pipe. The first pressure sensor is installed on the common rail intake pipe and is used to detect the common rail pressure; The second pressure sensor is installed on the pressure-stabilized gas storage tank and is used to detect the pressure of the gas storage tank; The electronic control unit is signal-connected to the temperature sensor, the first pressure sensor, the second pressure sensor, and the electrically controlled pneumatic valve to receive sensor detection signals; the electronic control unit is electrically connected to the electrically controlled pneumatic valve and the flow controller. Air enters the exhaust gas turbocharger for primary boost after passing through the air filter, and then enters the common rail intake manifold after being boosted by the secondary turbocharger. The electronic control unit (ECU) calculates the target common rail pressure based on engine operating conditions, and the pressure sensor detects the actual pressure. The ECU stabilizes the actual pressure at the target value by adjusting the speed of the secondary turbocharger and the opening of the flow controller. The ECU independently controls the electronically controlled air valves of each cylinder according to the intake demand of each cylinder, achieving uniform distribution of intake air volume to each cylinder. Under acceleration conditions, the ECU quickly opens the flow controller, and high-pressure air from the air tank is supplied to the common rail, improving transient response.

2. The diesel engine two-stage turbocharged intake system based on a common rail structure according to claim 1, characterized in that, The common rail intake pipe and the pressure-stabilizing storage tank constitute a common rail pressure accumulator structure, and the working pressure of the common rail intake pipe is 0.2-0.8MPa.

3. A two-stage turbocharged intake system for a diesel engine based on a common rail structure according to claim 1, characterized in that, The common rail intake pipe is connected in parallel with the pressure-stabilizing air storage tank. The volume of the air storage tank is 1.5-3 times that of the common rail intake pipe. It is used to store high-pressure air and quickly replenish pressure under transient conditions.

4. A two-stage turbocharged intake system for a diesel engine based on a common rail structure according to claim 1, characterized in that, The secondary supercharger is either a mechanical supercharger or an electric supercharger.

5. A two-stage turbocharged intake system for a diesel engine based on a common rail structure according to claim 1, characterized in that, The electrically controlled pneumatic valve is a high-speed solenoid valve with a response time of less than 20ms.

6. A two-stage turbocharged intake system for a diesel engine based on a common rail structure according to claim 1, characterized in that, The bypass branch of the exhaust main is equipped with an exhaust gas recirculation valve to regulate the amount of exhaust gas entering the pressure-stabilizing gas storage tank.

7. A two-stage turbocharged intake system for a diesel engine based on a common rail structure according to claim 1, characterized in that, The electronic control unit adopts a dual-pressure closed-loop control algorithm, including a target pressure calculation module, a pressure feedback control module, a cylinder coordination control module, and a transient compensation control module.

8. A two-stage turbocharged intake system for a diesel engine based on a common rail structure according to claim 1, characterized in that, The electronically controlled air valve is located near the cylinder in the intake manifold of each cylinder, and independently controls the air intake of each cylinder, with the air intake volume deviation of each cylinder being <2%.

9. A method for controlling the dual-stage turbocharged intake of a diesel engine, based on a common rail dual-stage turbocharged intake system for a diesel engine as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Signal Acquisition: Acquires engine operating condition signals, common rail pressure signals, stabilized air tank pressure signals, and temperature signals; S2: Calculate the target intake pressure based on the operating condition signal: The electronic control unit queries and calculates the target common rail pressure from the preset pulse spectrum or control model based on the current engine speed and load; S3: Dual pressure closed-loop regulation: The electronic control unit compares the collected common rail pressure and gas tank pressure with the target pressure: if the actual pressure is lower than the target pressure, the speed of the secondary turbocharger is increased and the opening of the flow controller is adjusted to increase the intake boost; if the actual pressure is higher than the target pressure, the speed of the secondary turbocharger is reduced, or the bypass is opened appropriately to reduce the intake pressure. S4: Intake Air Temperature Compensation Correction: Based on the temperature sensor signal, the electronic control unit performs real-time compensation on the air density and corrects the intake air volume calculation results to ensure consistent intake air control accuracy under different temperatures; S5: Independent intake control for each cylinder: The electronic control unit independently controls the opening time, opening degree, and duration of the electronically controlled valve for each cylinder according to the working requirements of each cylinder, so as to achieve precise and uniform distribution of intake volume for each cylinder; S6: Transient Condition Rapid Compensation: Under transient conditions, the electronic control unit quickly adjusts the flow controller opening to rapidly replenish the high-pressure air in the pressure-stabilized air tank to the common rail intake pipe; S7: Smooth Control for Operating Condition Switching: When switching between operating conditions, the electronic control unit smoothly adjusts the boost pressure, flow controller opening and electronically controlled air valve action to ensure that the intake pressure is shock-free and the transition is smooth.

10. A diesel engine dual-turbocharged intake control method according to claim 9, characterized in that, The operating conditions include idling, steady state, acceleration, high speed and high load, and deceleration.

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