A gasoline engine structure with multiple water injection in cylinder and a water injection control method

Abstract

The application relates to a gasoline engine structure and a water injection control method, which are characterized by comprising an engine cylinder body (1), an air intake manifold (2), an exhaust manifold (3), a spark plug (4), an oil injector (6) and a water injection mechanism which is connected with a controller (9), wherein the engine cylinder body (1) is provided with a piston (11), and the engine cylinder body (1) is provided with a cylinder pressure sensor and a water temperature sensor. The engine operation state is detected through the sensors arranged in the engine, the water injection amount, the water injection interval and the water injection time can be flexibly controlled, the water injection parameters are adjusted, the water injection amount is matched with the load of the engine, and the thermal efficiency of the engine is improved. Compared with the prior art, the strategy of multiple water injection is adopted to reduce the water injection penetration distance, the water injection atomization effect is strengthened, and the top of the piston is better covered with a liquid water film and water mist, so that the heat insulation effect is effectively achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of internal combustion engines, and relates to a gasoline engine structure with multiple water injection in a cylinder and a water injection control method. BACKGROUND

[0002] In order to reduce fuel consumption and emissions, automobile engines are developing towards supercharging and miniaturization. However, knock has also become a major problem restricting the thermal efficiency of the engine. At present, the method of reducing the in-cylinder temperature by retarding the ignition angle or enriching the fuel injection is generally used to control knock. The pollution emission problem of gasoline engines is becoming increasingly urgent, and energy saving and emission reduction has become one of the research directions of gasoline engines.

[0003] Engine direct water injection technology is used to inject circulating water into the cylinder during engine operation, which cools the cylinder components and working medium to some extent, controls the combustion process to suppress knock, optimizes the ignition time, widens the working boundary of the engine, improves the efficiency and fuel economy of the engine, and in addition, the reduction of combustion temperature is also conducive to reducing the generation of nitrogen oxides.

[0004] At present, the general in-cylinder water injection is single water injection, which is easy to cause incomplete atomization. At the same time, the water injection penetration distance is too large, which causes the liquid water to impact the cylinder wall and form a liquid water film on the cylinder wall. This part of water cannot absorb enough heat to vaporize into water vapor, and the liquid water film will continue to increase during engine operation. Eventually, it will mix with lubricating oil in the form of liquid water, causing oil-water mixing and other phenomena, affecting the normal operation of the engine. In addition, with the demand for improving the thermal efficiency of the engine, the adiabatic piston has become a hot spot. The general in-cylinder water injection has poor atomization effect, and it is difficult to uniformly distribute a layer of liquid water film / water mist on the top of the piston. During the movement of the piston, it cannot be completely adiabatic, thereby greatly reducing the thermal efficiency of the engine.

[0005] Patent CN108049990A discloses a method for controlling homogeneous compression ignition of an internal combustion engine by using cylinder outside water injection, which comprises an internal combustion engine body, an oil injector, an intake port water injector, a water injection common rail, a high-pressure water pump and a water tank. The intake port water injector is connected to the water injection common rail, the water injection pressure in the water injection common rail is established by the low-pressure water pump, the low-pressure water pump is driven by a 12V or 24V storage battery, and the water used in the control process of the homogeneous compression ignition of the internal combustion engine is stored in the water tank. However, the patent adopts the strategy of cylinder outside intake port water injection, which cannot guarantee that the injected liquid water is fully evaporated and enters the combustion chamber due to the low injection pressure. In addition, the patent cannot accurately control the water injection time and water injection quality according to the engine operation, and cannot guarantee that the top of the piston is uniformly covered with a heat-insulating water film. SUMMARY

[0006] The purpose of the present application is to overcome at least one of the defects of the prior art and provide a gasoline engine structure with multiple water injection in cylinder and a water injection control method.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] One of the technical solutions of the present application is to provide a gasoline engine structure with multiple water injection in cylinder, which comprises an engine cylinder body provided with an intake manifold, an exhaust manifold, a spark plug, an oil injector and a water injection mechanism, the water injection mechanism being connected to a controller, the engine cylinder body being provided with a piston, the engine cylinder body being provided with a cylinder pressure sensor and a water temperature sensor, the sensor arranged in the engine detecting the operation state of the engine, the water injection amount, water injection interval and water injection time being flexibly controlled, the water injection parameters being adjusted to adapt the water injection amount to the load of the engine, thereby improving the thermal efficiency of the engine.

[0009] Further, the water injection mechanism comprises a water tank, a high-pressure water pump unit and a water injector connected in sequence, the water injector being connected to the controller, under the control of the controller, the water in the water tank being injected into the engine cylinder body through the water injector.

[0010] Further, the high-pressure water pump unit comprises a high-pressure water pump arranged between the water tank and the water injector, the high-pressure water pump being connected to the controller, the water injection in cylinder being high-pressure water injection, the maximum pressure of the high-pressure water pump being 48 MPa, the water injection penetration distance being reduced, the water injection atomization effect being improved, and the water mist uniformly covering the top of the piston to achieve the heat insulation effect.

[0011] Further, the high-pressure water pump unit comprises a water injection common rail arranged between the high-pressure water pump and the water injector, the water pressure being controlled to be within a suitable range to ensure the stability of the work.

[0012] As a preferred technical solution, the water injection common rail and the water injector are connected through a high-pressure water pipe.

[0013] Further, the water tank is provided with a liquid level sensor connected to the controller, the liquid level sensor monitoring the liquid level in the water tank in real time, determining the remaining water amount and feeding back to the controller, and alarming when the liquid level in the water tank is lower than the preset value to avoid the situation of insufficient water amount.

[0014] As a preferred technical solution, the remaining water amount preset value is 10-15%.

[0015] Further, the spark plug and oil injector connection controller controls the engine spark plug ignition and oil injection through the controller.

[0016] The working principle of the present application comprises the following steps:

[0017] During the engine cold start stage, the water sprayer does not spray water into the engine cylinder, preventing the temperature in the cylinder from being too low, which leads to engine stall or excessive emission of pollutants;

[0018] When the engine enters a stable operating state, the in-cylinder water spraying mechanism begins to work, and the controller collects engine speed, intake pressure and temperature data in real time to detect the current operating condition of the engine;

[0019] If the engine is running stably and no knock occurs, no water spraying is performed;

[0020] If a knock occurs during abnormal operation, the controller automatically calculates the required water injection amount and water injection time, and then sends instructions to the water sprayer to spray the corresponding amount of water into the engine cylinder at the corresponding time; the water sprayer usually adopts a high-pressure multiple water injection strategy, i.e., a pre-injection and main injection water injection strategy, which can effectively reduce the water injection penetration distance and improve the water injection atomization effect; the controller adjusts the multiple water injection interval and water injection amount in real time based on the detected engine operating parameters (knock intensity).

[0021] Due to the multiple water injection strategy, the water injection atomization effect is improved, and when the water mist uniformly covers the top of the piston, a layer of liquid water film is formed, which absorbs heat transmitted through the piston as the liquid water evaporates, thereby forming a heat insulation layer on the top of the piston, achieving an effect similar to that of an adiabatic piston, while ensuring that the liquid water film gradually and completely evaporates during the power stroke of the piston.

[0022] One of the technical solutions of the present application is to provide a water injection control method, which uses the above-mentioned structure to control water injection, and the method comprises the following steps:

[0023] The controller detects the engine operating state to determine whether water injection is required;

[0024] If water injection is not required, the engine operating state of the next cycle is detected again;

[0025] If water injection is required, the controller calculates the required water injection amount based on the engine operating state (knock intensity), including the engine speed, intake pressure and temperature parameters;

[0026] and further calculates the water injection amount of pre-injection and main injection in multiple water injection, as well as the water injection interval;

[0027] Since the liquid water film and the water mist need to be uniformly covered on the piston top, the position of the piston from the top dead center at the current time needs to be determined according to the rotating speed of the engine, and the water injection time is accurately calculated;

[0028] The controller issues an instruction to the water injector, so that the water injector sprays water into the engine cylinder.

[0029] Further, the mass ratio of the total amount of water injection to the amount of fuel (water / fuel ratio, W / F) is 0.3-2.0, and the mass ratio of the water injection amount of the pre-injection to the water injection amount of the main injection in the multiple water injection is 0.3-4.0.

[0030] Further, the water injection interval is 30-90 CA.

[0031] Further, the water injection time is-180--90 CA.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) The present application can effectively improve the atomization effect of water injection, improve the wet wall of the cylinder wall caused by the excessive penetration distance of water injection, and improve the liquid water heat absorption and cooling effect;

[0034] (2) The present application controls the water injection time to ensure that the piston top can be covered with a liquid water film and a water mist, and uses the evaporation of liquid water to achieve a heat insulation effect and reduce heat transfer loss, thereby greatly improving the economy and power of the engine. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a structure diagram of the gasoline engine structure of the multiple water injection in the cylinder in the embodiment of the present application;

[0036] Figure 2 is a formation diagram of the liquid water film in the embodiment of the present application;

[0037] Figure 3 is a process diagram of the water injection control method in the embodiment of the present application.

[0038] MARKED DESCRIPTION IN THE FIGURE:

[0039] 1 - engine cylinder, 2 - intake manifold, 3 - exhaust manifold, 4 - spark plug, 5 - water injector, 6 - fuel injector, 7 - high-pressure water pump, 8 - water tank, 9 - controller, 10 - water injection common rail, 11 - piston. DETAILED DESCRIPTION

[0040] The present application will be described in detail below in combination with specific embodiments. The present embodiment is implemented on the premise of the technical scheme of the present application, and detailed implementation and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0041] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are used to describe common objects, only to indicate different instances of the same object, and are not intended to imply that the objects thus described must be in a given order, whether in time, space, order or any other manner.

[0042] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0043] Embodiment:

[0044] A gasoline engine structure with multiple water injection in cylinder, as shown in Figure 1 The engine cylinder body 1 is provided with an intake manifold 2, an exhaust manifold 3, a spark plug 4, an oil injector 6 and a water injection mechanism, the water injection mechanism is connected to a controller 9, and the engine cylinder body 1 is provided with a piston 11;

[0045] The controller 9 is an electronic controller (engine electronic control unit ECU);

[0046] The engine cylinder body 1 is provided with a cylinder pressure sensor and a water temperature sensor, and the engine operating state is detected through the sensor arranged in the engine;

[0047] The water injection mechanism includes a water tank 8, a high-pressure water pump unit and a water injector 5 connected in sequence, and the water injector 5 is connected to the controller 9, and under the control of the controller 9, the water in the water tank 8 is injected into the engine cylinder body 1 through the water injector 5;

[0048] The water injector 5 is arranged on the wall of the engine cylinder body 1, and the water injection amount, water injection interval and water injection time can be flexibly controlled, and by adjusting the water injection parameters, the water injection amount is adapted to the load of the engine, and the thermal efficiency of the engine is improved;

[0049] The high-pressure water pump unit comprises a high-pressure water pump 7 arranged between the water tank 8 and the water injector 5, and the high-pressure water pump 7 is connected to the controller 9; the water injection in the cylinder is high-pressure water injection, and the maximum pressure of the high-pressure water pump 7 is 48 MPa, and the pressure in the embodiment is preferably 35 MPa, so that the water injection penetration distance can be reduced, the water injection atomization effect is improved, and meanwhile, the water mist can uniformly cover the top of the piston 11, thereby achieving the heat insulation effect.

[0050] The high-pressure water pump unit comprises a water injection common rail 10 arranged between the high-pressure water pump 7 and the water injector 5, and the water injection common rail 10 can control the water pressure to be in a suitable range, thereby ensuring the working stability.

[0051] The water injection common rail 10 is in communication with the water injector 5 through a high-pressure water pipe.

[0052] The water tank 8 is provided with a liquid level sensor connected to the controller 9, and the liquid level sensor can monitor the liquid level in the water tank 8 in real time, determine the remaining water amount, and feed back to the controller 9 when the liquid level in the water tank 8 is lower than the preset value, so as to alarm and avoid the insufficient water amount.

[0053] The spark plug 4 and the fuel injector 6 are connected to the controller 9, and the controller 9 controls the ignition of the engine spark plug 4 and the fuel injection.

[0054] The working principle of the gasoline engine structure with multiple water injection in the cylinder is as follows:

[0055] In the cold start stage of the engine, the water injector 5 does not inject water into the engine cylinder 1, so as to prevent the temperature in the cylinder from being too low to cause misfire or too large emission pollutant concentration.

[0056] When the engine enters a stable running state, the water injection mechanism in the cylinder starts to work, and the controller 9 collects the speed, intake pressure and temperature data of the engine in real time to detect the current working condition of the engine.

[0057] If the engine runs stably without knock, no water injection is performed.

[0058] If the engine runs abnormally due to knock, the controller 9 automatically calculates the required water injection amount and water injection time, and then sends an instruction to the water injector 5, so that the water injector 5 injects the corresponding amount of water into the engine cylinder 1 at the corresponding time; the water injector 5 usually adopts a high-pressure multiple water injection strategy, i.e., a pre-injection and main injection water injection strategy, and the multiple water injection strategy can effectively reduce the water injection penetration distance and improve the water injection atomization effect; the controller 9 adjusts the multiple water injection interval and the water injection amount in real time according to the detected engine operating parameters (knock intensity).

[0059] As Figure 2As shown, due to the multiple water injection strategy, the water atomization effect is improved, when the water mist uniformly covers the top of the piston 11, forming a layer of liquid water film, with the evaporation of the liquid water, it will absorb the heat transmitted through the piston 11, thereby forming a layer of heat insulation layer on the top of the piston 11, similar to the effect of adiabatic piston, while ensuring that the liquid water film gradually and completely evaporates during the working stroke of the piston 11.

[0060] A water injection control method, using the above structure to control water injection, such as Figure 3 As shown, the specific steps are as follows:

[0061] The controller 9 detects the engine operating state to determine whether water injection is needed;

[0062] If water injection is not needed, the engine operating state of the next cycle is detected again;

[0063] If water injection is needed, the controller 9 calculates the required water injection amount according to the engine operating state (knock intensity), including the engine speed, intake pressure and temperature parameters;

[0064] And further calculate the water injection amount of pre-injection and main injection in multiple water injection, and the water injection interval;

[0065] Since it is necessary to uniformly cover the liquid water film and water mist on the top of the piston 11, it is necessary to determine the position of the piston 11 from the top dead center at the current time according to the engine speed, and to accurately calculate the water injection time;

[0066] The controller 9 issues an instruction to the water injector 5, so that the water injector 5 injects water into the engine cylinder 1.

[0067] For the water injection amount, the mass ratio of the total water injection amount to the fuel amount (water / fuel ratio, W / F) is controlled between 0.3 and 2.0, and in this embodiment, it is preferred to be 1.0. The water injection strategy in this embodiment is to detect whether knock occurs in the engine cylinder 1 to determine whether water injection is needed; if no knock occurs, water injection is stopped; if knock occurs, water injection is needed. In the cycle requiring water injection, the controller 9 adjusts the water injection amount in real time according to the knock intensity. The real-time adjusted parameters such as water injection amount and water injection time are obtained through multiple experiments during engine development, and are compiled into a map and written into the controller 9. In actual engine operation, according to different working conditions and different knock conditions, the controller 9 reads the relevant parameters from the map.

[0068] For the water injection interval, when the engine speed is low, the movement speed of the piston 11 is also low, at this time the evaporation time is relatively sufficient, and at the same time in the case of small water injection amount, a single injection strategy can be adopted; when the engine speed is increased or the water injection amount is large, then at this time a double injection strategy needs to be adopted. The double injection strategy is mainly to reduce the insufficient liquid water atomization, avoid the situation of liquid droplets hitting the wall and being unable to completely vaporize, and improve a series of problems such as cylinder wet wall and dilution of lubricating oil. At this time, the water injection interval needs to be adjusted in real time according to the engine speed and the determined water injection amount. The water injection interval is 30-90 CA, and in the embodiment it is preferably 30 CA.

[0069] The mass ratio of the water injection amount of the pre-injection to the main injection is 0.3-4.0, if the engine speed is higher, then the water injection amount of the pre-injection needs to be more, and the water injection amount of the main injection needs to be less, for example, the water injection amount of the pre-injection is 80% of the total mass, and the water injection amount of the main injection is 20% of the total mass.

[0070] Regarding the distribution of the water film on the top of the piston 11, since there are a large number of research results that can be referred to for the water injection penetration distance and the spray cone angle of the water injector 5 to change with the water injection interval, no matter the single water injection strategy or the double water injection strategy, the starting injection time can be determined according to the position of the piston 11, and the position of the piston 11 is the position of the maximum distance of the water injection penetration distance, at this time the injection can ensure that the water film is uniformly distributed on the top of the piston 11. Generally, the water injection time is controlled in the middle and early stage of the compression stroke (in the compression stroke, the piston 11 goes up), that is, -180- -90 CA, and in the embodiment it is preferably -180 CA, mainly to ensure that when the water is injected, the combustion chamber has enough space to envelope the water injection penetration distance and water mist diffusion, and at the same time to ensure sufficient heat absorption and evaporation of the liquid water.

[0071] The above description of the embodiments is to facilitate those of ordinary skill in the art to understand and use the application. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the present application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A water injection control method characterized by, The method uses the water injection structure of gasoline engine with multiple water injection in cylinder to control water injection, the structure includes engine cylinder (1), the engine cylinder (1) is provided with intake manifold (2), exhaust manifold (3), spark plug (4), fuel injector (6) and water injection mechanism, the water injection mechanism is connected with controller (9), the engine cylinder (1) is provided with piston (11), the engine cylinder (1) is provided with cylinder pressure sensor and water temperature sensor, the sensor arranged in the engine detects the engine operating state, flexibly controls the water injection amount, water injection interval and water injection time, adjusts the water injection parameters, so that the water injection amount is adapted to the load of the engine; The method comprises the following steps: The controller (9) detects the engine operating state and determines whether water injection is needed or not; If water injection is not needed, the engine operating state of the next cycle is detected again; If water injection is needed, the controller (9) calculates the required water injection amount according to the engine operating state, including the engine speed, intake pressure and temperature parameters; And further calculates the water injection amount of pre-injection and main injection in multiple water injection, and the water injection interval; According to the engine speed, the water injection time is accurately calculated; The controller (9) sends instructions to the water injector (5) to make the water injector (5) inject water into the engine cylinder (1); The mass ratio of the total water injection amount to the fuel amount is 0.3-2.0, and the mass ratio of the water injection amount of pre-injection to main injection in multiple water injection is 0.3-4.

0.

2. A water injection control method according to claim 1, characterized in that The water injection mechanism comprises water tank (8), high-pressure water pump unit and water injector (5) connected in sequence, and the water injector (5) is connected with the controller (9).

3. A water injection control method according to claim 2, characterized in that The high-pressure water pump unit comprises high-pressure water pump (7) arranged between the water tank (8) and the water injector (5), and the high-pressure water pump (7) is connected with the controller (9), and the maximum pressure of the high-pressure water pump (7) is 48 MPa.

4. A water injection control method according to claim 3, characterized in that The high-pressure water pump unit comprises water injection common rail (10) arranged between the high-pressure water pump (7) and the water injector (5).

5. The water injection control method of claim 2, wherein The water tank (8) is provided with liquid level sensor connected with the controller (9).

6. The water injection control method of claim 1, wherein The spark plug (4) and the fuel injector (6) are connected with the controller (9).

7. The water injection control method of claim 1, wherein The water injection interval is 30-90 CA.

8. The water injection control method of claim 1, wherein The water injection time is-180--90CA, corresponding to the middle and early stage of compression stroke.

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