Low-pressure multi-point injection efficient combustion system, engine and control method

Abstract

The invention discloses a low-pressure multi-point injection efficient combustion system, an engine and a control method. The system comprises an air inlet pipeline and a combustion chamber. The air inlet pipeline comprises a fuel gas channel and an air channel, and the fuel gas channel and the air channel are independently arranged and are respectively communicated with a combustion chamber in the air cylinder; the combustion chamber is located at the top of the piston to form a deep pit type structure, and a cambered surface protrusion is arranged in the center of the bottom of the combustion chamber. Fuel gas and air enter the combustion chamber through the fuel gas channel and the air channel respectively and are mixed and combusted in the combustion chamber. The problems of uneven mixing, high cost and poor emission of a traditional scheme are solved through independent gas inlet of the gas and air branch channels, turbulence enhancement of the combustion chamber and a low-pressure precise control technology, and the combustor is suitable for medium-high-power gas power equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of internal combustion engines, and particularly relates to a low-pressure multi-point injection high-efficiency combustion system and an engine. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Existing gas engine fuels include natural gas, gas, biogas, refinery tail gas, hydrogen, ammonia, etc. These gaseous fuels all have the characteristics of low emissions. Therefore, gas engines are gradually replacing diesel engines in fields such as stationary power generation, marine power, and oil and gas drilling. However, the existing gas engine technology still has the following bottlenecks:

[0004] Defects of premixed gas engines: In traditional premixing technologies, gas and air are mixed through a Venturi mixer before supercharging or after intercooling, and then the mixture is sent into each cylinder through the intake manifold for combustion. This form of gas premixing has problems such as a high risk of flashback, low control accuracy of the air-fuel ratio, and a tendency to knock. Since the intake manifold contains a mixture, when high-temperature gas flows back into the intake port during the scavenging process, it will ignite the mixed gas, causing a flashback phenomenon, which affects the safe and stable operation of the engine. The flashback phenomenon is particularly obvious when operating at a low load condition of less than 20%. In addition, the problem of low control accuracy of the air-fuel ratio is also relatively prominent. The main reason is that the density of the mixture fluctuates, resulting in a large deviation between the actual air-fuel ratio and the theoretical value. In transient conditions, the deviation value can reach ±12%, further causing low combustion efficiency of the engine and difficult control of NOx emissions. At low engine speeds and low load conditions, the premixed intake method is more likely to experience knocking.

[0005] Limitations of high-pressure direct injection technology: The gas in-cylinder high-pressure direct injection technology has advantages such as high combustion efficiency compared to the premixing technology. However, it also brings an increase in cost due to the addition of a high-pressure gas supply system. In addition, the reliability and lifespan of the high-pressure gas supply system also restrict the popularization of the gas in-cylinder high-pressure direct injection technology, and the failure rates of its high-pressure injection valves and seals are relatively high.

[0006] Deficiencies of in-cylinder injection mixing technology: The in-cylinder injection mixing technology refers to that after the gas is injected into the intake port, the gas and air start to mix in the intake port. However, due to the short mixing path between the two, the uniformity of the in-cylinder mixture concentration is poor, and the combustion efficiency decreases rapidly when the engine operates at low speeds. In addition, the emission level of the in-cylinder injection mixing technology route is difficult to meet the requirements of relevant regulations.

[0007] In summary, it is difficult for existing technologies to balance high combustion efficiency, low emissions, and low costs: the premixed scheme is limited by flashback and knocking, and cannot meet the reliability and transient requirements of high-power engines; the high-pressure direct injection technology is hindered in industrial applications due to cost and reliability issues; the existing sub-airway injection schemes have insufficient mixing effects, resulting in deteriorated fuel economy. Summary of the Invention

[0008] The object of the present invention is to provide a low-pressure multi-point injection high-efficiency combustion system, an engine, and a control method. By means of independent intake of gas and air through separate airways, enhanced turbulence in the combustion chamber, and low-pressure precise control technology, the problems of uneven mixing, high cost, and poor emissions in traditional schemes are solved, and it is applicable to medium- and high-power gas-powered equipment.

[0009] To achieve the above object, the present invention is implemented through the following technical solutions:

[0010] In a first aspect, an embodiment of the present invention provides a low-pressure multi-point injection high-efficiency combustion system, including an intake pipe and a combustion chamber; the intake pipe includes a gas passage and an air passage, the gas passage and the air passage are independently arranged and are respectively connected to the combustion chamber inside the cylinder; the combustion chamber is located at the top of the piston to form a deep-pit structure, and a curved surface protrusion is arranged at the central position of the bottom of the combustion chamber; gas and air enter the combustion chamber through the gas passage and the air passage respectively, and are mixed and burned in the combustion chamber.

[0011] As a further technical solution, the inlet of the gas passage is connected to the outlet of the gas injection valve, and the gas passage extends to a position within 30 mm of the valve face of the valve.

[0012] As a further technical solution, the cross-sectional area ratio of the gas passage to the air passage is 1:8 - 15.

[0013] As a further technical solution, the top inlet of the combustion chamber is in a constricted shape, so that the combustion chamber has a deep-pit structure with a constricted top and a large belly, and a flow guiding convex ring is formed by the gap between the top of the piston and the bottom of the cylinder head.

[0014] As a further technical solution, the ratio of the depth of the deep-pit structure to the cylinder diameter is 0.15 - 0.25.

[0015] As a further technical solution, the gas passage and the air passage are arranged opposite to each other.

[0016] As a further technical solution, the intake pressure of the gas is controlled by constant pressure, or is controlled in a follow-up manner according to the pressure difference between the gas and the air.

[0017] As a further technical solution, the volume of the gas chamber in the combustion chamber is less than or equal to 1 / 5 of the cylinder working volume.

[0018] In a second aspect, an embodiment of the present invention provides an engine, including the low-pressure multi-point injection high-efficiency combustion system described in the first aspect.

[0019] In a third aspect, an embodiment of the present invention provides a control method for a low-pressure multi-point injection high-efficiency combustion system, including the following steps:

[0020] Obtain the gas pressure and temperature, air pressure and temperature, and oxygen content in the exhaust gas, and calculate the current air-fuel ratio;

[0021] Judge whether the air-fuel ratio is the same as the set value. If so, maintain the current gas injection duration; if not, calculate the gas injection correction amount, adjust the gas injection duration so that the current air-fuel ratio after adjustment is equal to the set value;

[0022] The gas injection valve performs actions according to the gas injection duration, and the engine completes the speed regulation action.

[0023] The beneficial effects of the above embodiments of the present invention are as follows:

[0024] For the low-pressure multi-point injection high-efficiency combustion system provided by the present invention, the gas and air enter through separate airways at low pressure. This intake method, combined with a deep-pit type combustion chamber, enables the gas and air to be mixed and burned in the combustion chamber. Since there is no mixture gas in the intake airway and intake manifold, the situation of backfire and deflagration is completely eliminated, greatly improving safety; the combustion chamber is set in a deep-pit type structure, and the arc-shaped protrusion at the bottom of the deep-pit type structure can produce a tumbling effect on the gas and air. Through the tumbling effect, the mixing effect of the gas and air is enhanced, the uniformity of the gas and air mixture is improved, and the combustion effect is ensured.

[0025] For the low-pressure multi-point injection high-efficiency combustion system provided by the present invention, the inlet of the combustion passage is connected to the outlet of the gas injection valve, and the gas passage extends to a position within 30 mm of the valve face of the valve. The setting of the position of the gas passage and the gas injection valve can shorten the length of the gas passage, that is, shorten the length of the gas entering the cylinder, and further can greatly reduce the volume of the gas chamber, reduce the pressure loss during the gas flow process, and enable precise control of the air-fuel ratio.

[0026] For the low-pressure multi-point injection high-efficiency combustion system provided by the present invention, in order to improve the mixing effect when the gas and air enter independently, the inlet at the top of the combustion chamber with a deep-pit type structure is set in a necked shape, and a guiding convex ring is formed by the gap between the top of the piston and the bottom of the cylinder head. The guiding convex ring can produce a squeezing effect on the incoming gas and air. This necked and large-bellied structure can not only increase the squish effect of the mixture gas, but also enhance the in-cylinder tumbling effect, further improving the uniformity of the mixture gas, and thus improving the combustion effect.

[0027] The gas engine of the present invention adopts an efficient combustion system with low-pressure intake of gas and air through separate air passages, and is applicable to medium and large power gas engines such as stationary power generation, marine power, and drilling power. By means of low-pressure intake through separate air passages, the volume of the gas chamber is greatly reduced, the gas intake inertia is reduced, the turbulence in the combustion chamber is strengthened, and precise electronic control strategies are adopted to achieve efficient gas mixing under low pressure of 5 bar, providing an innovative solution for gas power equipment above 400 kW.

[0028] The control method provided by the present invention can achieve precise control of the air-fuel ratio, enable the response of the control system to be quickly realized, and can adjust the current air-fuel ratio to be the same as the set value only through one correction. Compared with the existing method that requires multiple corrections, the multiple feedback correction process is omitted, and the control accuracy is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The attached drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0030] Figure 1 is the front view of the intake pipe and the first combustion chamber of the present invention;

[0031] Figure 2 is the top view of the intake pipe and the first combustion chamber of the present invention;

[0032] Figure 3 is Figure 2 the sectional view taken along line A-A in

[0033] Figure 4 is the front view of the intake pipe and the second combustion chamber of the present invention;

[0034] Figure 5 is the top view of the intake pipe and the second combustion chamber of the present invention;

[0035] Figure 6 is Figure 5 the sectional view taken along line B-B in

[0036] Figure 7 is the flowchart of the control method of the present invention.

[0037] Wherein, 1, gas passage; 2, air passage; 3, combustion chamber; 301, arc-shaped protrusion; 302, guide convex ring; 4, outlet of gas injection valve; 5, exhaust passage; 6, cylinder head. DETAILED DESCRIPTION OF THE INVENTION

[0038] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0039] Embodiment 1

[0040] In a typical embodiment of the present invention, as Figure 1 shown, a low-pressure multi-point injection high-efficiency combustion system is provided, including an intake pipeline and a combustion chamber 3; the intake pipeline includes a gas pipeline 1 and an air pipeline 2, and the gas pipeline 1 and the air pipeline 2 are independently arranged and are respectively connected to the combustion chamber 3 inside the cylinder; the combustion chamber 3 is located at the top of the piston to form a deep-pit structure, and a curved surface protrusion 301 is arranged at the central position of the bottom of the combustion chamber; gas and air enter the combustion chamber 3 through the gas pipeline 1 and the air pipeline 2 respectively and are mixed and burned in the combustion chamber.

[0041] By independently arranging the gas pipeline and the air pipeline in the present invention, gas and air enter the cylinder through independent airways respectively, and gas and air are mixed and burned in the combustion chamber. Since there is no mixed gas in the intake airway and the intake manifold, the situation of backfire and deflagration is completely eliminated, greatly improving safety; the combustion chamber is set into a deep-pit structure, and the curved surface protrusion at the bottom of the deep-pit structure can produce a tumbling effect on gas and air, enhancing the mixing effect of gas and air through the tumbling effect and improving the uniformity of the mixing of gas and air.

[0042] In this embodiment, the inlet of the gas pipeline is connected to the outlet 4 of the gas injection valve, and the gas pipeline extends to a position within 30 mm of the valve face of the valve. The inlet of the gas injection valve is connected to the gas intake manifold, and the outlet of the gas pipeline is connected to the cylinder head. The arrangement of the gas pipeline and the gas injector can shorten the length of the gas pipeline, that is, shorten the length of the gas entering the cylinder, and further can greatly reduce the volume of the gas cavity. The volume of the gas cavity of the gas pipeline is less than or equal to 1 / 5 of the cylinder working volume, reducing the pressure loss during the gas flow process and enabling precise control of the air-fuel ratio.

[0043] In this embodiment, the number of gas channels and air channels is the same as that of the cylinders, and they correspond to the cylinders one by one. By adopting the low-pressure injection method, multi-point injection can be achieved. Further, the intake pressure of the gas is controlled by constant pressure or is controlled in a follow-up manner according to the pressure difference between the gas and the air. Specifically, the intake pressure of the gas can be set to 5 bar for constant pressure control, or the pressure difference between the gas and the air can be set to 100 - 150 kPa for follow-up control. The gas injection pressure can be achieved through a gas pressure regulating valve, and no additional supercharging device is required. For the existing high-pressure injection, the pressure needs to reach 300 bar. In contrast, this embodiment can achieve low-pressure injection of the gas, greatly reducing the gas injection pressure and simultaneously reducing the gas supply cost.

[0044] In this embodiment, the cross-sectional area ratio of the gas channel to the air channel is 1:8 - 15, resulting in a large volume difference between the gas channel and the air channel. The advantage is that it can reduce the local loss of the sudden expansion of the gas entering the gas chamber after the gas injection valve, making the gas control faster and more accurate.

[0045] The combustion chamber in this embodiment can be Figure 1 , Figure 2 the deep pit type structure in Figure 4 , Figure 5 In order to further improve the mixing effect of the gas and the air, it is also set as the deep pit type structure in

[0046] At this time, the top inlet of the deep pit type structure is in a constricted shape, and a guiding convex ring 302 is formed by the gap between the top of the piston and the bottom of the cylinder head 6. The guiding convex ring 302 can exert an extrusion effect on the incoming gas and air. This constricted and large-bellied structure can not only increase the squish effect of the mixture gas but also enhance the in-cylinder tumble effect, further improving the uniformity of the mixture gas. Further, an exhaust channel 5 is also provided on the cylinder head 6 for exhausting the cylinder.

[0046] In this embodiment, the ratio of the depth of the deep pit type structure to the cylinder diameter is 0.15 - 0.25, which can ensure the required compression ratio.

[0047] In this embodiment, the gas channel 1 and the air channel 2 are arranged oppositely, as shown in Figure 3 and Figure 6 . When the gas channel 1 and the air channel 2 are arranged oppositely, the gas and the air respectively enter the combustion chamber inside the cylinder through the gas channel and the air channel, flow along the wall surface of the combustion chamber, and then form a tumble effect through the arc-shaped protrusion 301 at the bottom for mixing, improving the mixing effect of the gas and the air.

[0048] The following provides specific data of the combustion systems of two engines:

[0049] 1. Marine engine:

[0050] Bore diameter: 200 mm, stroke: 275 mm, rated power: 1100 kW;

[0051] Cross-sectional area of gas passage: 200 mm 2 , cross-sectional area of air passage: 3500 mm 2 ;

[0052] The combustion chamber is of deep-pit type, the depth of the concave pit is 40 mm (bore diameter ratio 0.2), and the clearance height is 2 mm;

[0053] The gas injection pressure is a constant pressure of 5 bar, and the injection advance angle is 80°CA.

[0054] 2. Gas generator set:

[0055] Bore diameter: 200 mm, stroke: 255 mm, rated power: 2300 kW;

[0056] Cross-sectional area of gas passage: 200 mm 2 , cross-sectional area of air passage: 3500 mm 2 ;

[0057] The combustion chamber is of deep-pit type, the depth of the concave pit is 40 mm (bore diameter ratio 0.2), and the clearance height is 3 mm;

[0058] The gas injection pressure is a constant pressure of 5 bar, and the injection advance angle is 80°CA.

[0059] The injection quantity is adjusted in real time through the ECU, and the fluctuation range of air-fuel ratio is ±0.5%.

[0060] By comparing the combustion systems of the above two types of engines with that of the existing engine, the following effects of the combustion system provided by this application can be obtained:

[0061] Improved mixing efficiency: The combination of air intake through separate air passages and the enhanced turbulence and squish effects in the combustion chamber enables the gas and air to be fully mixed during the compression stroke, and the mixing uniformity is improved by ≥30%;

[0062] Increased thermal efficiency: The thermal efficiency is increased from 38% to over 41%;

[0063] Reduced emissions: The NOx emissions are reduced by over 50%, and the CO emissions are reduced by 40%-50%;

[0064] Cost optimization: The cost of the low-pressure gas supply system is reduced by 20%-30% compared with the high-pressure solution;

[0065] Combustion stability: In the load range of 5%-100%, the combustion cycle volatility <5%.

[0066] Example 2

[0067] In a typical embodiment of the present invention, an engine is provided, which includes the low-pressure multi-point injection high-efficiency combustion system described in Embodiment 1.

[0068] Embodiment 3

[0069] In a typical embodiment of the present invention, a control method for a low-pressure multi-point injection high-efficiency combustion system is provided. As Figure 7 shown, it includes the following steps:

[0070] Obtain the gas pressure and temperature, air pressure and temperature, and oxygen content in the exhaust gas, and calculate the current air-fuel ratio;

[0071] Judge whether the air-fuel ratio is the same as the set value. If so, maintain the current gas injection duration; if not, calculate the gas injection correction amount, adjust the gas injection duration, and make the current air-fuel ratio equal to the set value after adjustment;

[0072] The gas injection valve performs actions according to the gas injection duration, and the engine completes the speed regulation action.

[0073] Through the design of low-pressure intake through sub-airways and a deep-pit structure combustion chamber, precise control of the air-fuel ratio can be achieved, enabling the response of the control system to be quickly realized. In the control method of this embodiment, by only one correction, the current air-fuel ratio can be adjusted to be the same as the set value. Compared with the existing method that requires multiple corrections, the multiple feedback correction processes are omitted, improving the control accuracy.

[0074] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low-pressure multi-point injection high-efficiency combustion system, characterized in that, It includes an intake pipeline and a combustion chamber; the intake pipeline includes a gas passage and an air passage, the gas passage and the air passage are independently arranged and are respectively communicated with the combustion chamber inside the cylinder; the combustion chamber is located at the top of the piston to form a deep pit type structure, and an arc-shaped protrusion is arranged at the center position of the bottom of the combustion chamber; gas and air enter the combustion chamber through the gas passage and the air passage respectively and are mixed and burned in the combustion chamber.

2. The low-pressure multi-point injection high-efficiency combustion system according to claim 1, characterized in that The inlet of the gas passage is connected to the outlet of the gas injection valve, and the gas passage extends to a position within 30 mm of the valve face of the valve.

3. The low-pressure multi-point injection high-efficiency combustion system according to claim 1, characterized in that, The cross-sectional area ratio of the gas passage to the air passage is 1:8 - 15.

4. The low-pressure multi-point injection high-efficiency combustion system according to claim 1, wherein The top inlet of the combustion chamber is in a necking shape, so that the combustion chamber has a deep pit type structure with a necking and a large belly, and a flow guiding convex ring is formed by the gap between the top of the piston and the bottom of the cylinder head.

5. The low-pressure multi-point injection high-efficiency combustion system according to claim 1, characterized in that, The ratio of the depth of the deep pit type structure to the cylinder diameter is 0.15 - 0.

25.

6. The low-pressure multi-point injection high-efficiency combustion system according to claim 1, wherein The gas passage and the air passage are arranged opposite to each other.

7. The low-pressure multi-point injection high-efficiency combustion system according to claim 1, wherein The intake pressure of the gas is controlled by constant pressure or is controlled follow-up according to the pressure difference between the gas and the air.

8. The low-pressure multi-point injection high-efficiency combustion system according to claim 1, characterized in that, The volume of the gas chamber of the combustion chamber is less than or equal to 1 / 5 of the working volume of the cylinder.

9. An engine, characterized in that, It includes the low-pressure multi-point injection high-efficiency combustion system according to any one of claims 1 - 8.

10. A control method for a low-pressure multi-point injection high-efficiency combustion system according to any one of claims 1-8, characterized in that, It includes the following steps: Obtain the gas pressure and temperature, air pressure and temperature, and oxygen content in the exhaust gas, and calculate the current air-fuel ratio; Judge whether the air-fuel ratio is the same as the set value. If so, maintain the current gas injection duration; If not, calculate the gas injection correction amount, adjust the gas injection duration, and make the current air-fuel ratio equal to the set value after adjustment; The gas injection valve performs actions according to the gas injection duration, and the engine completes the speed regulation action.

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