WO2016169428A1 - 一种抑制直喷增压汽油发动机低速提前点火的方法 - Google Patents

一种抑制直喷增压汽油发动机低速提前点火的方法 Download PDF

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WO2016169428A1
WO2016169428A1 PCT/CN2016/079219 CN2016079219W WO2016169428A1 WO 2016169428 A1 WO2016169428 A1 WO 2016169428A1 CN 2016079219 W CN2016079219 W CN 2016079219W WO 2016169428 A1 WO2016169428 A1 WO 2016169428A1
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engine
ignition
direct
speed pre
egr
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PCT/CN2016/079219
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English (en)
French (fr)
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腾和
苗瑞刚
熊春英
骆旭薇
胡庭军
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江铃汽车股份有限公司
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Publication of WO2016169428A1 publication Critical patent/WO2016169428A1/zh
Priority to CONC2017/0010581A priority Critical patent/CO2017010581A2/es

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
    • F01P7/00—Controlling of coolant flow
    • F01P7/14—Controlling of coolant flow the coolant being liquid
    • F01P7/16—Controlling of coolant flow the coolant being liquid by thermostatic control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P5/00—Advancing or retarding ignition; Control therefor
    • F02P5/02—Advancing or retarding ignition; Control therefor non-automatically; dependent on position of personal controls of engine, e.g. throttle position

Definitions

  • the invention relates to the technical field of automobiles, and in particular to a method for suppressing low-speed pre-ignition of a direct-injection supercharged gasoline engine.
  • In-cylinder direct injection and supercharging technology is an effective method to miniaturize gasoline engines. Due to the homogeneous three-way catalytic post-treatment technology, the combustion mode can be widely applied to small direct injection. Pressure gasoline engine.
  • the engine adopting this combustion mode encounters a strong knocking phenomenon caused by pre-ignition caused by the lubricating oil entering the cylinder in the low-speed high-pressurization condition, and the peak value of the pressure oscillation can reach the cylinder burst pressure during normal combustion. It is of the order of magnitude and is therefore called a super shock.
  • LSPI low speed pre-ignition
  • LSPI mainly occurs in low-speed and high-boost conditions below 2,500 rpm and average effective pressure is higher than 16 bar. If frequent occurrences, engine components such as spark plugs, exhaust valves, pistons and connecting rods may fail. This self-cleaning action makes LSPI random and unsustainable due to the high frequency pressure waves generated by knocking that clean up residual lubricant adhering to the walls of the combustion chamber.
  • the area where LSPI occurs coincides with the scavenging area of the direct injection supercharged gasoline engine, that is, the LSPI operating condition is higher than the exhaust pressure.
  • the crankcase ventilation flow in this area is also close to the maximum operating range of the engine. Since direct injection increases the dilution of the engine crankcase oil and the increased volatility of the diluted oil, the crankcase ventilation recirculation carries considerable lubricant particles.
  • crankcase ventilation recirculation is introduced into the intake system before pressurization, which allows small particles of lubricating oil to be aggregated into large particles after cooling by the intercooler, and some large lubricating oil particles will Stay on the air intake wall and on the back of the intake valve disc.
  • the engine In low-speed and high-load conditions, the engine needs to use the air-scavenging to increase the boost pressure.
  • the lubricating oil particles stuck on the inlet wall and the back of the intake valve may short-circuit the cylinder into the exhaust passage. Part of the larger lubricating oil particles carried by the scavenging flow may remain on the wall of the combustion chamber located on the cylinder head. It is likely to evaporate and become an ignition source under the high temperature of the compression stroke, causing a large destructive LSPI. , as shown in Figure 4 and Figure 5.
  • the present invention provides a method for suppressing low-speed pre-ignition of a direct-injection supercharged gasoline engine, comprising the following steps:
  • step 3 2) comparing the current power of the engine at the full-speed power of the low-speed pre-ignition upper limit speed as the reference power, comparing the current power of the engine with the reference power of the engine, if the former is smaller than the latter, performing step 3); if the former is greater than The latter, perform step 4);
  • first water temperature is higher than the second water temperature.
  • the engine cooling water temperature is divided into two regions at low speed full load power: since LSPI occurs in a region smaller than the reference power, high temperature cooling is performed in the region using a higher first water temperature cooling water.
  • the intake port has a higher wall temperature, which improves the evaporability of the liquid lubricating oil particles retained on the wall surface of the intake port, thereby weakening the possibility of occurrence of low-speed pre-ignition and reducing the heat loss of the engine 100 in the region.
  • the lower second water temperature cooling water is used for lower temperature cooling in a region larger than the reference power, and the conventional explosion of the engine 100 can be suppressed.
  • the earthquake reduces the fuel consumption of the engine 100 caused by the control of knocking to enrich the in-cylinder mixture.
  • the above method prevents the super-knocking by preventing the liquid lubricating oil remaining on the wall surface of the intake port by high-temperature cooling in the region where the LSPI occurs.
  • the first water temperature ranges from 105 ° C to 108 ° C
  • the second water temperature ranges from 90 ° C to 95 ° C.
  • the cooling system of the engine is provided with an electronic thermostat on the water inlet side of the engine cooling water, and step 3) and step 4) are realized by calibrating the opening temperature of the electronic thermostat.
  • the method further comprises the steps of:
  • step 6) is specifically implemented by: presetting an EGR ejector and an on-off valve, and providing a compressed air inlet at an inlet end of the EGR ejector and an EGR inlet fitted inside the compressed air inlet, a discharge diffuser tube is disposed at an outlet end thereof, and the compressed air inlet is connected to the booster compressor outlet, the EGR inlet is connected to an exhaust manifold of the engine, and the outlet end is passed through The switching valve is coupled to the intake manifold.
  • the temperature of the gas entering the intake manifold in step 6) ranges from 120 ° C to 150 ° C.
  • the method further comprises the steps of:
  • step 10 comparing the current excess air coefficient, the maximum excess air ratio corresponding to the reference excess air coefficient; if the former is greater than the latter, step 10); if the former is equal to the latter, step 11);
  • step 11 increasing the fuel injection amount of the fuel injection system of the engine, adjusting the current excess air ratio to the reference excess air coefficient, and continuously running for a preset period of time, and then performing step 11).
  • Figure 1 shows the common engine speed and load zone where LSPI occurs
  • Figure 2 shows the relationship between the speed of the scavenging area and the LSPI area under full load conditions of the direct injection supercharged gasoline engine
  • Figure 3 shows the relationship between the crankcase ventilation and LSPI of a direct injection supercharged gasoline engine
  • Figure 4 shows the super-squeak phenomenon caused by LSPI of a high-pressure direct-injection gasoline engine
  • Figure 5 is the cylinder pressure oscillation measured by the engine knock sensor when a super shock occurs
  • FIG. 6 is a flow chart showing a specific embodiment of a method for suppressing low-speed pre-ignition of a direct injection supercharged gasoline engine according to the present invention
  • FIG. 7 is a schematic structural view of a direct injection supercharged gasoline engine cooling system according to the present invention.
  • FIG. 8 is a structural diagram of a specific implementation of introducing a part of high-temperature exhaust gas into an intake manifold according to the present invention
  • FIG. 9 is a schematic structural view of the EGR injection pump of FIG. 8.
  • Radiator 11 electronic thermostat 12; cooling water inlet pipe 13; cooling water pump 14; radiator main fan 15; radiator auxiliary fan 16; water temperature sensor 17;
  • Supercharger turbine 21 supercharger compressor 22; intercooler 23; throttle 24; check valve 25; intake manifold 26; EGR injection pump 27; compressed air inlet 271; EGR inlet 272; 273; diffuser 274; ejector nozzle 275; on-off valve 28; exhaust manifold 29; three-way catalyst 30; oxygen sensor 31;
  • the core of the present invention is to provide a method for suppressing low-speed pre-ignition of a direct-injection supercharged gasoline engine, which can reduce lubricating oil particles retained on the inlet or combustion chamber wall, thereby eliminating the phenomenon of low-speed pre-ignition.
  • FIG. 6 is a flow chart of a specific embodiment of a method for suppressing low-speed pre-ignition of a direct-injection supercharged gasoline engine according to the present invention.
  • the present invention provides a method for suppressing low-speed pre-ignition of a direct-injection supercharged gasoline engine 100, comprising the following steps:
  • Step S2 comparing the total power of the engine at the low-speed pre-ignition upper limit speed as the reference power, comparing the current power of the engine with the reference power of the engine, if the former Step S3 is performed, if the former is larger than the latter, step S4 is performed;
  • step S4 cooling the engine with a second water temperature; step S11 is performed;
  • first water temperature is higher than the second water temperature.
  • the engine cooling water temperature is divided into two regions at low speed full load power: since LSPI occurs in a region smaller than the reference power, high temperature cooling is performed in the region using a higher first water temperature cooling water.
  • the intake port has a higher wall temperature, which improves the evaporability of the liquid lubricating oil particles retained on the wall surface of the intake port, thereby weakening the possibility of occurrence of low-speed pre-ignition and reducing the heat loss of the engine 100 in the region.
  • the lower second water temperature cooling water is used for the low temperature cooling, which can suppress the conventional knocking of the engine 100 and reduce the fuel consumption increase of the engine 100 caused by the control of the knocking of the in-cylinder mixture.
  • the above method prevents the super-knocking by preventing the liquid lubricating oil remaining on the wall surface of the intake port by high-temperature cooling in the region where the LSPI occurs. It should be noted that the above-mentioned low-speed pre-ignition upper limit rotation speed is generally about 2,500 rpm, which is determined by the specific calibration of the engine.
  • the first water temperature may range from 105 ° C to 108 ° C
  • the second water temperature may range from 90 ° C to 95 ° C.
  • FIG. 7 is a schematic structural view of a direct injection supercharged gasoline engine cooling system according to the present invention.
  • the high-temperature cooling water in the engine 100 flows to the radiator 11 through the water outlet pipe, and the cooling water after the radiator 11 dissipates heat and cools down through the electronic thermostat. 12 flows to the cooling water inlet pipe 13, is extracted by the cooling water pump 14, and finally flows back to the inside of the engine 100 for cooling.
  • the high-temperature cooling water in the engine 100 flows through the electronic thermostat 12 (shown in the direction of the broken line in FIG. 7), flows to the cooling water intake pipe 13, is extracted by the cooling water pump 14, and finally flows back to the engine 100. Cool down.
  • the above method realizes the current by calibrating the opening temperature of the electronic thermostat 12 When the power is less than the full load power, the engine 100 is cooled by the first water temperature, and when the current power is greater than the full load power, the engine 100 is cooled with the second water temperature.
  • the above control method is not limited to the calibration of the electronic thermostat 12 to achieve different temperature cooling, and can also be realized by other means.
  • the water temperature sensor 17 can detect the water temperature, and the temperature of the cooling inlet pipe 13 can be independently controlled by the switch and the rotational speed control of the main cooling fan 15 and the auxiliary cooling fan 16 provided by the radiator, and the current power region is determined, and then the judgment is made.
  • the control signal is sent to the control unit of the radiator cooling fan, which compares the current temperature of the cooling inlet pipe with the required temperature, selects the switch or the rotation speed of the main and auxiliary cooling fans, and regulates the cooling through the radiator.
  • the air volume controls the water temperature of the cooling inlet pipe so that the current temperature of the inlet cooling water reaches the desired temperature.
  • the foregoing method further includes the following steps:
  • the above method is used to mix EGR with compressed air after detecting the occurrence of LSPI, thereby increasing the temperature of the overall intake air, which can be retained in the wall of the intake port.
  • the lubricating oil particles on the wall surface of the intake valve are rapidly evaporated, and the lubricating oil particles suspended in the intake air are accelerated to vaporize, thereby making it difficult to adhere to the wall surface of the combustion chamber in a liquid form when the engine 100 is scavenged.
  • the EGR is mixed into the intake air to dilute the intake oxygen concentration, and the dilution of the intake oxygen concentration enables the pre-ignition to occur, even if it occurs too late, it is difficult to cause super-knocking, and further suppresses the super-knocking effect.
  • the method can transiently increase the intake air temperature when LSPI occurs, thereby accelerating the evaporation of the liquid lubricating oil and reducing the effect of super-knocking.
  • the amount of EGR inhaled above can be selected according to actual needs, and it has been proved by experiments if When the EGR amount is 6% of the total intake air amount, the dilution of the intake oxygen concentration can be up to 10% under the metered combustion condition, which can better suppress the effect of super-knocking without greatly increasing the cylinder. Pressure. Of course, other values can also be used.
  • the above-mentioned EGR and compressed air mixed intake air temperature can also be selected according to actual needs. After a large number of experiments, when the intake air temperature reaches 120 ° C ⁇ 150 ° C, the crankcase ventilation can be recirculated into the intake system oil. The low boiling point and low ignition point components in the medium play a good role in evaporation and vaporization. Of course, other values can be used for the intake air temperature.
  • FIG. 8 is a structural diagram of a specific implementation of introducing EGR into an intake manifold according to the present invention
  • FIG. 9 is a schematic structural view of the EGR injection pump of FIG.
  • the above step S6 can be specifically implemented as follows: the intake system of the engine 100 can drive the turbocharger compressor 22 to rotate through the turbocharger turbine 21 , and output compressed air to the intercooler 23 .
  • the gas cooled by the intercooler 23 enters the interior of the engine 100 through the intake manifold 26 through the throttle valve 24 and the check valve 25, while the high temperature exhaust gas output from the engine 100 drives the turbocharger turbine 21 to rotate.
  • the above method may preset the EGR ejector 27 and the on-off valve 28, and at the inlet end of the EGR ejector 27, a compressed air inlet 271 and an EGR inlet 272 fitted inside the compressed air inlet 271 are provided at the outlet thereof.
  • the end is provided with a mixer 273, a conical diffuser 274, and a compressed air inlet 271 is connected to the outlet of the supercharger compressor 22, an EGR inlet 272 is connected to the exhaust manifold 29 of the engine 100, and an outlet end is passed through the on-off valve 28. Connected to the intake manifold 26.
  • opening and closing valve 28 is opened such that a portion of the uncooled compressed air enters EGR ejector 27 from compressed air inlet 271, expands and accelerates at ejector nozzle 275, and The outlet of the ejector nozzle 275 produces a low pressure at which a small amount of exhaust gas from the engine 100 is drawn into the interior of the EGR ejector 27 via the EGR inlet 272.
  • the compressed air entering from the compressed air inlet 271 and the EGR sucked in the EGR inlet 272 are mixed in the mixer 273, pressurized by the diffuser 274, mixed by the switching valve 28 and the compressed air from the intercooler 23, and then enter The intake manifold 26 of the engine 100 is within. If it is detected that LSPI does not occur in engine 100, switching on off valve 28, EGR cannot enter intake manifold 26 and engine 100 is operating without EGR conditions.
  • the EGR ejector pump 27 can automatically and automatically introduce EGR into the cylinder intake of the engine 100 using the ejector principle. It is conceivable that the above method can also be adopted by other parties.
  • the EGR is delivered to the intake manifold 26.
  • the EGR pump 27 can be replaced by a centrifugal or Roots type EGR pump.
  • the EGR pump is turned on, and the exhaust gas of part of the engine 100 is extracted by the EGR pump.
  • the switch valve 28 enters the intake pipe, mixes with the intercooled compressed air, and then enters the intake manifold 26 together.
  • the method for suppressing the low-speed pre-ignition of the direct-injection supercharged gasoline engine 100 may further include the following steps:
  • step S9 comparing the current excess air coefficient and the reference excess air coefficient corresponding to the maximum power mixture; if the former is greater than the latter, step S10 is performed; if the former is equal to the latter, step S11 is performed; and for obtaining stable combustion, engine 100 is not recommended.
  • step S10 increase the fuel injection amount of the fuel injection system of the engine, adjust the current excess air ratio to the reference excess air coefficient, and continue to run for a preset period of time, and then perform step S11.
  • step S10 increases the fuel injection amount, so that the current excess air ratio is adjusted to the reference excess air coefficient, so that the engine 100 corresponds to the maximum power mixture. Working at air-fuel ratio, this maximizes the transient power reduction and allows for rapid combustion, making up for the reduction in engine 100 transient power caused by the clean inlet method.
  • This enrichment increases the ignition energy and ignition lag period required for the mixture in the cylinder, further eliminating the conditions for pre-ignition; the flame speed approaches the maximum at the maximum power air-fuel ratio, so even if pre-ignition occurs, the flame It can propagate to the entire combustion chamber at near maximum speed, thus weakening the possibility of super knocking.
  • the enrichment control method can specifically detect the current oxygen concentration by the oxygen sensor 31 in front of the three-way catalyst 30, and increase the fuel injection amount by specifically increasing the injection time.
  • the preset time period may be specifically 30s or 500 working cycles, or may be other values, and may be specifically set as needed.

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  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
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Abstract

一种抑制直喷增压汽油发动机低速提前点火的方法，在当前功率小于参考功率时采用高水温冷却发动机，提高滞留在进气道壁面上的液体润滑油颗粒的蒸发性。并在发生提前点火时，将发动机的部分高温排气以废气再循环的方式与增压器压缩机输出的压缩空气一同输送至进气歧管，提高整体进气的瞬态温度，使滞留在进气道壁面和进气门盘壁面上的润滑油颗粒迅速蒸发，并使悬浮在进气中的润滑油颗粒加速汽化。此外，该方法在当前过量空气系数大于参考过量空气系数时增大发动机的喷油系统的喷油量，将当前过量空气系数调整至参考过量空气系数，减弱利用EGR对发动机的进气道清洁时产生的瞬态动力输出下降及高温进气对常规可控爆震强度的影响。

Description

一种抑制直喷增压汽油发动机低速提前点火的方法
本申请要求于2015年4月20日提交中国专利局、申请号为201510188177.3、发明名称为“一种抑制直喷增压汽油发动机低速提前点火的方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及汽车技术领域，尤其涉及一种抑制直喷增压汽油发动机低速提前点火的方法。
背景技术
缸内直喷和增压技术是使汽油机小型化的一种有效方法，由于均质计量混合气燃烧可以采用成熟的三元催化后处理技术，这种燃烧模式被广泛地应用于小型直喷增压汽油机。
采用这种燃烧模式的发动机在低速高增压工况会遇到一种由进入气缸的润滑油引发的提前点火导致的强烈爆震现象，其压力震荡的峰值可达正常燃烧时气缸爆发压力的数量级，因而被称为超级震爆。
鉴于这种不正常燃烧仅发生在直喷增压汽油机的低转速工况，称这种现象为低速提前点火或LSPI(low speed pre-ignition)。LSPI主要发生在2500转以下及平均有效压力高于16bar的低速高增压工况，如频繁发生可造成火花塞、排气门、活塞及连杆等发动机零部件失效。由于爆震产生的高频压力波会清理掉附着在燃烧室壁面上的残余润滑油，这种自清洁作用使LSPI具有随机性及不持续性。
如图1至图3所示，LSPI发生的区域和直喷增压汽油机的扫气区相吻合，即发生LSPI的工况进气压力高于排气压力。对直喷增压汽油机，在这个区域曲轴箱通风流量也接近发动机工作范围的最大值。由于直喷增加了燃油对发动机曲轴箱机油的稀释及被稀释的机油挥发性提高，曲轴箱通风再循环携带了可观的润滑油颗粒。发动机在增压模式工作时，曲轴箱通风再循环在增压前被引入进气系统，这使得小颗粒的润滑油得以在经中冷器冷却后聚合成大颗粒，有些大的润滑油颗粒会滞留在进气道壁面及进气门盘背面上。
在低速大负荷工况发动机需借助进气扫气来提高增压压力，滞留在进气道壁面及进气门盘背面上的润滑油颗粒可能会随扫气流短路气缸进入排气道。扫气流动携带的部分较大的润滑油颗粒可能会滞留在位于缸盖上的燃烧室壁面上，其很有可能在压缩冲程的高温条件下蒸发并成为点火源，引发破坏力较大的LSPI，如图4和图5所示。
鉴于上述LSPI的破坏力，如何抑制LSPI是开发高增压直喷汽油机必须考虑的问题，也是当前汽车小型化面临的一个挑战。
因此，亟待针对上述技术问题，开发一种抑制直喷增压汽油发动机低速提前点火的方法，从而通过减少滞留在进气道或燃烧室壁面上的润滑油颗粒，以实现消除低速提前点火的现象。
发明内容
本发明的目的为提供一种抑制直喷增压汽油发动机低速提前点火的方法，以减少滞留在进气道或燃烧室壁面上的润滑油颗粒，从而消除低速提前点火的现象。
为解决上述技术问题，本发明提供一种抑制直喷增压汽油发动机低速提前点火的方法，包括如下步骤：
1)检测发动机的当前功率；
2)把发动机在发生低速提前点火上限转速的全负荷功率作为参考功率，比较所述发动机的当前功率与所述发动机的参考功率的大小，若前者小于后者，执行步骤3)；若前者大于后者，执行步骤4)；
3)采用第一水温冷却所述发动机；
4)采用第二水温冷却所述发动机；再执行步骤11)；
11)保持发动机正常运行；
其中，所述第一水温高于第二水温。
采用这种方法，以低速全负荷功率把发动机100冷却水温分为两个区域：由于LSPI发生在小于参考功率的区域，因此在该区域采用较高的第一水温冷却水进行高温冷却，能使进气道具有较高的壁温，提高滞留在进气道壁面上的液体润滑油颗粒的蒸发性，从而消弱低速提前点火发生的可能性，并能够减少该区域发动机100的散热损失。而在大于参考功率的区域采用较低的第二水温冷却水进行低温冷却，能够抑制发动机100的常规爆 震，减少因控制爆震对缸内混合气的加浓而引起的发动机100油耗增加。
由此可见，上述方法通过在LSPI发生的区域通过高温冷却蒸发滞留在进气道壁面的液体润滑油，从而起到预防超级爆震的效果。
优选地，所述第一水温的范围为105℃～108℃，所述第二水温的范围为90℃～95℃。
优选地，所述发动机的冷却系统在发动机冷却水进水侧设有电子节温器，步骤3)、步骤4)通过对所述电子节温器的开启温度进行标定而实现。
优选地，在步骤3)之后，还包括如下步骤：
5)检测所述发动机是否发生低速提前点火；若是，执行步骤6)；若否，执行步骤7)；
6)将所述发动机的高温废气的一部分与增压器压缩机输出的压缩空气一同输送至所述发动机的进气歧管；
7)仅将所述增压器压缩机输出的压缩空气输送至所述进气歧管。
优选地，步骤6)具体通过如下方式实现：预设EGR引射器和开关阀，在所述EGR引射器的入口端设置压缩空气入口、套装于所述压缩空气入口内部的EGR入口，在其出口端设有锥形扩压管，并将所述压缩空气入口与所述增压器压缩机出口连接、所述EGR入口与所述发动机的排气歧管连接、所述出口端通过所述开关阀与所述进气歧管连接。
优选地，步骤6)中进入进气歧管的气体温度范围为120℃～150℃。
优选地，在所述步骤6)之后，还包括步骤：
8)检测缸内混合气的当前过量空气系数；
9)比较所述当前过量空气系数、最大功率混合气对应的参考过量空气系数；若前者大于后者，执行步骤10)；若前者等于后者，执行步骤11)；
10)增大所述发动机的喷油系统的喷油量，将所述当前过量空气系数调整至所述参考过量空气系数，并持续运行预设时间段，再执行步骤11)。
附图说明
图1为常见的发生LSPI的发动机转速及负荷区；
图2为直喷增压汽油机全负荷工况下扫气区转速和LSPI区的关系；
图3为直喷增压汽油机曲轴箱通风量和LSPI的关系；
图4为高增压直喷汽油发动机的LSPI引发的超级爆震现象；
图5为超级震爆发生时发动机爆震传感器测得的缸压震荡；
图6为本发明所提供抑制直喷增压汽油发动机低速提前点火的方法的一种具体实施方式的流程框图；
图7为本发明所涉及的直喷增压汽油机冷却系统的结构示意图；
图8为本发明所涉及将部分高温废气引入进气歧管的具体实施结构图；
图9为图8中EGR引射泵的结构示意图。
其中，图7和图8、图9中的附图标记与部件名称之间的对应关系为：
散热器11；电子节温器12；冷却水进水管13；冷却水泵14；散热器主风扇15；散热器辅助风扇16；水温传感器17；
增压器涡轮机21；增压器压缩机22；中冷器23；节气门24；单向阀25；进气歧管26；EGR引射泵27；压缩空气入口271；EGR入口272；混合器273；扩压器274；引射喷管275；开关阀28；排气歧管29；三元催化器30；氧传感器31；
喷油系统3；
发动机100。
具体实施方式
本发明的核心为提供一种抑制直喷增压汽油发动机低速提前点火的方法，该方法能减少滞留在进气道或燃烧室壁面上的润滑油颗粒，从而消除低速提前点火的现象。
为了使本领域的技术人员更好地理解本发明的技术方案，下面结合附图和具体实施例对本发明作进一步的详细说明。
请参考图6，图6为本发明所提供抑制直喷增压汽油发动机低速提前点火的方法的一种具体实施方式的流程框图。
在一种具体实施方式中，如图6所示，本发明提供一种抑制直喷增压汽油发动机100低速提前点火的方法，包括如下步骤：
S1：检测发动机100的当前功率；
S2：把发动机在发生低速提前点火上限转速的全负荷功率作为参考功率，比较所述发动机的当前功率与所述发动机的参考功率的大小，若前者 小于后者，执行步骤S3；若前者大于后者，执行步骤S4；
S3：采用第一水温冷却所述发动机；
S4：采用第二水温冷却所述发动机；再执行步骤S11；
S11：保持发动机正常运行；
其中，所述第一水温高于第二水温。
采用这种方法，以低速全负荷功率把发动机100冷却水温分为两个区域：由于LSPI发生在小于参考功率的区域，因此在该区域采用较高的第一水温冷却水进行高温冷却，能使进气道具有较高的壁温，提高滞留在进气道壁面上的液体润滑油颗粒的蒸发性，从而消弱了低速提前点火发生的可能性，并能够减少该区域发动机100的散热损失。而在大于参考功率的区域采用较低的第二水温冷却水进行低温冷却，能够抑制发动机100的常规爆震，减少因控制爆震对气缸内混合气的加浓而引起的发动机100油耗增加。
由此可见，上述方法通过在LSPI发生的区域通过高温冷却蒸发滞留在进气道壁面的液体润滑油，从而起到预防超级爆震的效果。需要说明的是，上述低速提前点火上限转速一般为2500转左右，由发动机具体标定决定。
上述第一水温的范围可以为105℃～108℃，上述第二水温的范围可以为90℃～95℃。
经大量实验证明，采用上述第一水温范围既能起到较好的蒸发作用，也由于气缸壁温的提高减少了发动机100的传热损失及降低了缸内燃料蒸汽在缸壁的冷凝，从而提高了燃料的利用效率。
请参考图7，图7为本发明所涉及的直喷增压汽油机冷却系统的结构示意图。
如图7所示，上述发动机100的冷却系统中，开启大循环时，发动机100内的高温冷却水经出水管路流向散热器11，散热器11散热、降温后的冷却水经电子节温器12流至冷却水进水管13，再经冷却水泵14抽取，最终流回发动机100内部进行冷却。小循环时，发动机100内的高温冷却水流经电子节温器12(如图7中虚线方向所示)，再流至冷却水进气管13，再经冷却水泵14抽取，最终流回发动机100内部进行冷却。
具体的方案中，上述方法通过标定电子节温器12的开启温度实现当前 功率小于全负荷功率时用第一水温冷却发动机100、当前功率大于全负荷功率时用第二水温冷却发动机100。
采用这种方法，通过对电子节温器12的打开温度进行标定，简单、方便地实现了不同功率情况下不同水温的冷却。具体对电子节温器12的标定过程需根据整车在不同车速及道路条件下散热器、水温控制同步进行。
可以想到，上述控制方法并不仅限对电子节温器12标定来实现不同温度的冷却，还可以通过其他方式来实现。例如，可以通过水温传感器17检测水温，并通过散热器设置的主冷却风扇15和辅助冷却风扇16的开关及转速控制独立地对冷却进水管13的温度控制，当判断当前功率所属区域、进而判断所需冷却水温度后，将控制信号发送给散热器冷却风扇的控制单元，该控制单元比较冷却进水管的当前温度与所需温度选择主辅冷却风扇的开关或转速，调节通过散热器的冷却风量，实现对冷却进水管水温的控制，以使进水冷却水的当前温度达到所需温度。
在一种具体实施方式中，上述方法在步骤S3之后，还包括如下步骤：
S5：检测发动机100是否发生低速提前点火；若是，执行步骤S6；若否，执行步骤S7；
S6：将发动机100的部分高温排气以废气再循环(Exhaust Gas Recirculation，即EGR)的方式与增压器压缩机22输出的压缩空气一同输送至发动机100的进气歧管26；
S7：仅将增压器压缩机22输出的压缩空气输送至进气歧管26。
由于发动机100的排气通常温度较高，采用上述方法，在检测到LSPI发生后将EGR与压缩空气混合，从而提高整体进气的温度，该瞬态高温进气能使滞留在进气道壁面和进气门盘壁面上的润滑油颗粒迅速蒸发，并能使悬浮在进气中的润滑油颗粒加速汽化，从而使其难以在发动机100扫气时以液体形式附着在燃烧室壁面上。同时，将EGR混入进气能对进气氧浓度进行稀释，对进气氧浓度的稀释能使提前点火即使发生也因时间太迟难以引发超级爆震，进一步起到抑制超级爆震的效果。
由此可见，该方法能够在LSPI发生时瞬态提高进气温度，从而加速液体润滑油的蒸发，起到减少超级爆震的效果。
上述吸入的EGR量可以根据实际需要自行选择，经试验证明，如果 EGR量为总进气量的6％时，在计量燃烧条件下对进气氧浓度的稀释可达10％，既能起到较好的抑制超级爆震的效果，又不会大幅度提高缸压。当然，也可以采用其他数值。
此外，上述EGR与压缩空气混合后的进气温度也可以根据实际需要自行选择，经大量实验证明，当进气温度达到120℃～150℃能够对曲轴箱通风再循环带入进气系统的机油中的低沸点、低燃点组分起到较好的蒸发、汽化作用。当然，该进气温度也可以选用其他数值。
请参考图8和图9，图8为本发明所涉及将EGR引入进气歧管的具体实施结构图，图9为图8中EGR引射泵的结构示意图。
如图8和图9所示，上述步骤S6可以具体通过如下方式实现：发动机100的进气系统可以通过增压器涡轮机21带动增压器压缩机22转动，输出压缩空气给中冷器23，经中冷器23冷却后的气体经节气门24、单向阀25通过进气歧管26进入发动机100内部，同时发动机100输出的高温废气又驱动增压器涡轮机21转动。具体的方案中，上述方法可以预设EGR引射器27和开关阀28，在EGR引射器27的入口端设置压缩空气入口271、套装于压缩空气入口271内部的EGR入口272，在其出口端设有混合器273、锥形扩压管274，并将压缩空气入口271与增压器压缩机22出口连接、EGR入口272与发动机100的排气歧管29连接、出口端通过开关阀28与进气歧管26连接。
工作过程中，如果检测到发动机100已经发生LSPI，打开开关阀28，使部分未冷却的压缩空气由压缩空气入口271进入EGR引射器27，在引射器喷管275处膨胀加速，并在引射器喷管275出口产生低压，在该低压作用下发动机100的少量排气经EGR入口272被吸入EGR引射器27内部。由压缩空气入口271进入的压缩空气和EGR入口272吸入的EGR在混合器273内混合，并经扩压管274增压后，经开关阀28和来自中冷器23的压缩空气混合，然后进入发动机100的进气歧管26内。如果检测到发动机100并未发生LSPI，关闭开关阀28，则EGR无法进入进气歧管26，发动机100在无EGR条件运行。
由此可见，利用EGR引射泵27能利用引射原理简单、方便地自动将EGR引入发动机100的气缸进气。可以想到，上述方法还可以通过其他方 式将EGR输送至进气歧管26，例如，可以用离心式或罗茨式EGR泵代替EGR引射泵27，当检测到LSPI已经发生，开启EGR泵，部分发动机100的废气被EGR泵抽取、经开关阀28进入进气管、与中冷后的压缩空气进行混合，再一同进入进气歧管26。
在另一种具体实施方式中，上述抑制直喷增压汽油发动机100低速提前点火的方法，在步骤S6之后，还可以包括步骤：
S8：检测缸内混合气的当前过量空气系数；
S9：比较所述当前过量空气系数、最大功率混合气对应的参考过量空气系数；若前者大于后者，执行步骤S10；若前者等于后者，执行步骤S11；为获取稳定燃烧，不建议发动机100在小于最大功率混合气对应的过量空气系数下工作；
S10：增大所述发动机的喷油系统的喷油量，将所述当前过量空气系数调整至所述参考过量空气系数，并持续运行预设时间段，再执行步骤S11。
由于EGR引入进气后会降低进入气缸的工质的密度，不可避免地会产生瞬态动力输出的降低，为尽可能减弱利用EGR对发动机100进气道清洁时产生的瞬态动力输出下降及可能的高温进气对常规可控爆震强度的影响，上述方法中步骤S10增大喷油量，使当前过量空气系数调整至所述参考过量空气系数，使发动机100在最大功率混合气对应的空燃比下工作，这样，最大程度地弥补瞬态功率下降、并使燃烧迅速，弥补了清洁进气道方法导致的发动机100瞬态功率的下降。这种加浓作用使气缸内混合气要求的点火能量和点火滞后期都增加，进一步消除了提前点火发生的条件；火焰速度在最大功率空燃比下接近最大值，因而即使发生提前点火，由于火焰可以在接近最大速度条件下向整个燃烧室传播，从而消弱了超级爆震发生的可能性。
该加浓的控制方法可以具体通过在三元催化器30前的氧传感器31检测当前氧浓度，并具体通过增加喷油时间来增加喷油量。上述预设时间段可以具体为30s或500个工作循环，也可以为其他数值，根据需要具体设定。
以上对本发明所提供的抑制直喷增压汽油发动机低速提前点火的方法进行了详细介绍。本文中应用了具体个例对本发明的原理及实施方式进行 了阐述，以上实施例的说明只是用于帮助理解本发明的方法及其核心思想。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以对本发明进行若干改进和修饰，这些改进和修饰也落入本发明权利要求的保护范围内。

Claims (7)

  1. 一种抑制直喷增压汽油发动机低速提前点火的方法，其特征在于，包括如下步骤：
    1)检测发动机的当前功率；
    2)把发动机在发生低速提前点火上限转速的全负荷功率作为参考功率，比较所述发动机的当前功率与所述发动机的参考功率的大小，若前者小于后者，执行步骤3)；若前者大于后者，执行步骤4)；
    3)采用第一水温冷却所述发动机；
    4)采用第二水温冷却所述发动机；再执行步骤11)；
    11)保持发动机正常运行；
    其中，所述第一水温高于第二水温。
  2. 根据权利要求1所述的抑制直喷增压汽油发动机低速提前点火的方法，其特征在于，所述第一水温的范围为105℃～108℃，所述第二水温的范围为90℃～95℃。
  3. 根据权利要求2所述的抑制直喷增压汽油发动机低速提前点火的方法，其特征在于，所述发动机的冷却系统在发动机冷却水进水侧设有电子节温器，步骤3)、步骤4)通过对所述电子节温器的开启温度进行标定而实现。
  4. 根据权利要求1-3任一项所述的抑制直喷增压汽油发动机低速提前点火的方法，其特征在于，在步骤3)之后，还包括如下步骤：
    5)检测所述发动机是否发生低速提前点火；若是，执行步骤6)；若否，执行步骤7)；
    6)将所述发动机的高温废气的一部分与增压器压缩机输出的压缩空气一同输送至所述发动机的进气歧管；
    7)仅将所述增压器压缩机输出的压缩空气输送至所述进气歧管。
  5. 根据权利要求4所述的抑制直喷增压汽油发动机低速提前点火的方法，其特征在于，步骤6)具体通过如下方式实现：预设EGR引射器和开关阀，在所述EGR引射器的入口端设置压缩空气入口、套装于所述压缩空气入口内部的EGR入口，在其出口端设有锥形扩压管，并将所述压缩空气入口与所述增压器压缩机出口连接、所述EGR入口与所述发动机的排气歧 管连接、所述出口端通过所述开关阀与所述进气歧管连接。
  6. 根据权利要求5所述的抑制直喷增压汽油发动机低速提前点火的方法，其特征在于，所述步骤6)中进入进气歧管的气体温度范围为120℃～150℃。
  7. 根据权利要求4所述的抑制直喷增压汽油发动机低速提前点火的方法，其特征在于，在所述步骤6)之后，还包括步骤：
    8)检测缸内混合气的当前过量空气系数；
    9)比较所述当前过量空气系数、最大功率混合气对应的参考过量空气系数；若前者大于后者，执行步骤10)；若前者等于后者，执行步骤11)；
    10)增大所述发动机的喷油系统的喷油量，将所述当前过量空气系数调整至所述参考过量空气系数，并持续运行预设时间段，再执行步骤11)。
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CN113624503A (zh) * 2021-08-12 2021-11-09 安徽江淮汽车集团股份有限公司 汽油机油低速早燃生成和抑制性的评价方法
CN113776998A (zh) * 2021-09-08 2021-12-10 安徽江淮汽车集团股份有限公司 一种增压器沉积物评价方法
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CN113624503B (zh) * 2021-08-12 2022-06-24 安徽江淮汽车集团股份有限公司 汽油机油低速早燃生成和抑制性的评价方法
CN113776998A (zh) * 2021-09-08 2021-12-10 安徽江淮汽车集团股份有限公司 一种增压器沉积物评价方法
CN113776998B (zh) * 2021-09-08 2022-06-24 安徽江淮汽车集团股份有限公司 一种增压器沉积物评价方法
WO2023247273A1 (fr) 2022-06-23 2023-12-28 Alter Oak Procédé de reconditionnement d'un contenant en bois comportant une étape d'imprégnation tannique et/ou aromatique du contenant en bois
FR3137010A1 (fr) 2022-06-23 2023-12-29 Alter Oak Procédé de reconditionnement d’un contenant en bois comportant une étape d’imprégnation tannique et/ou aromatique du contenant en bois

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