WO2021102680A1 - 一种柴油甲醇组合燃烧发动机及其控制方法 - Google Patents

一种柴油甲醇组合燃烧发动机及其控制方法 Download PDF

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Publication number
WO2021102680A1
WO2021102680A1 PCT/CN2019/120937 CN2019120937W WO2021102680A1 WO 2021102680 A1 WO2021102680 A1 WO 2021102680A1 CN 2019120937 W CN2019120937 W CN 2019120937W WO 2021102680 A1 WO2021102680 A1 WO 2021102680A1
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Prior art keywords
methanol
diesel
engine
alcohol
combined combustion
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PCT/CN2019/120937
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English (en)
French (fr)
Inventor
姚春德
姚安仁
王斌
吴涛阳
胡江涛
陈超
高健
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天津大学
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Application filed by 天津大学 filed Critical 天津大学
Priority to CN201980034534.7A priority Critical patent/CN112384689B/zh
Priority to PCT/CN2019/120937 priority patent/WO2021102680A1/zh
Priority to US17/163,550 priority patent/US20210156321A1/en
Publication of WO2021102680A1 publication Critical patent/WO2021102680A1/zh

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/08—Other arrangements or adaptations of exhaust conduits
    • 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
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
    • F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/30—Use of alternative fuels, e.g. biofuels

Definitions

  • the invention belongs to the field of engines, and particularly relates to a diesel-methanol combined combustion engine and a control method thereof.
  • Methanol vehicles are divided into ignited methanol passenger cars and commercial vehicles and compression-ignition methanol commercial vehicles.
  • the technical route adopted by ignited methanol passenger cars and commercial vehicles is similar to that of traditional gasoline engines, but the engine is cold due to the high latent heat of methanol vaporization. It is difficult to start, so gasoline needs to be used to start.
  • methanol fuel is completely used to form a homogeneous mixture in the intake port, and then the premixed mixture is ignited by a spark plug.
  • the technical route adopted by ignition-type methanol commercial vehicles is similar to that of methanol passenger vehicles.
  • the technical route of compression-ignition methanol commercial vehicles is mainly diesel-methanol combined combustion technology.
  • the diesel-methanol combined combustion engine adopts the pure diesel operating mode in the starting and idling conditions.
  • the diesel-methanol combined combustion mode referred to as DMCC mode, is adopted.
  • DOC diesel oxidation catalyst
  • SCR urea selective catalytic reduction system
  • DPF diesel particulate filter
  • Diesel-methanol combined combustion technology has the characteristics of high carbon monoxide and unburned hydrocarbon emissions, and nitrogen dioxide emissions account for a high proportion of nitrogen oxide emissions.
  • Nitrogen dioxide is the key group for passive regeneration of DPF.
  • the purpose of the present invention is to overcome the deficiencies in the prior art and provide a diesel-methanol combined combustion engine and a control method thereof.
  • a diesel-methanol combined combustion engine includes a diesel engine.
  • the diesel of the diesel engine adopts in-cylinder direct injection, and also includes a methanol injection system, a methanol electronic control unit, a methanol supply system, and a post-processor combination;
  • the methanol injection system is located in the engine On the intake port;
  • the methanol electronic control unit and the methanol supply system are connected to the methanol injection system;
  • the post-processor combination includes a methanol-specific selective catalytic reduction system, a diesel particulate filter, and a diesel oxidation catalyst, the methanol-specific option
  • the catalytic reduction system and the diesel particulate filter are controlled by the methanol electronic control unit.
  • the post-processor is assembled on the engine exhaust pipe, and the order of connection with the engine exhaust pipe is the methanol-specific selective catalytic reduction system and the diesel engine. Particulate filter and diesel oxidation catalyst.
  • the throttle position sensor is installed at the throttle lever shaft of the high-pressure oil pump, the water temperature sensor is installed on the cooling water pipeline, and the rotation speed sensor is installed.
  • the methanol level sensor is installed in the methanol tank of the methanol supply system.
  • the methanol electronic control unit is connected to the diesel engine ECU, and obtains the speed, accelerator pedal, cooling water temperature, and intake air temperature and pressure signals from the message.
  • the methanol injection system is composed of a methanol nozzle and a methanol sprayer.
  • a methanol injector is also arranged in the exhaust pipe of the diesel engine.
  • the reducing agent of the methanol-specific selective catalytic reduction system is methanol; the incomplete combustion products in the cylinder are used to reduce nitrogen dioxide and nitrogen monoxide.
  • the methanol supply system includes a methanol tank, a methanol pump coarse filter, a methanol level gauge, an electric methanol pump, a methanol filter, an alcohol pressure regulating valve, a methanol distribution pipe, an alcohol intake pipe and an alcohol return pipe;
  • the methanol pump coarse filter and the methanol level gauge are installed in the methanol tank.
  • the methanol flows through the methanol pump coarse filter, the electric methanol pump, the methanol filter, the alcohol pressure regulating valve, and then the alcohol inlet pipe to the methanol distribution pipe and the methanol nozzle.
  • the alcohol pressure regulating valve and the methanol tank are connected through the alcohol return pipe.
  • a method for controlling a diesel-methanol combined combustion engine, based on the above-mentioned diesel-methanol combined combustion engine, includes the following processes:
  • Step 1 The engine is started in pure diesel combustion mode
  • Step 2 The engine is burned in pure diesel mode
  • Step 3 Determine whether all the following conditions are met, namely:
  • Condition 1 Whether the methanol supply system has the conditions, that is, whether the methanol pressure reaches the set value and whether the methanol level is higher than the lower limit;
  • Condition 2 Whether the engine cooling water temperature is greater than or equal to the set threshold, that is, whether the engine cooling water temperature reaches 60°C;
  • Condition 3 Whether the engine has not reached the full load range, that is, whether the accelerator pedal is not at the 100% operating point;
  • Condition 4 Whether it is out of the part below the no-load throttle slash, that is, whether the engine and the gearbox are not disconnected;
  • step 4 If all the above conditions are met, go to step 4, otherwise go back to step 2;
  • Step 4 spray alcohol and implement combined combustion of diesel and methanol.
  • the method for determining the amount of alcohol sprayed by the methanol injection system is as follows:
  • Step 4-1 Firstly, by obtaining the operating conditions of the engine and combining the methanol injection map (MAP) based on the information of the engine operating conditions, the basic value of the target alcohol injection amount is determined;
  • MAP methanol injection map
  • Step 4-2 Revise the basic value of the target alcohol injection amount based on the influence of the cooling water temperature on the operating conditions of the diesel-methanol combined combustion engine;
  • Step 4-3 compare with the maximum alcohol injection volume at the current engine speed, and take the smaller value as the final alcohol injection volume
  • Step 4-4 query the alcohol injection volume and methanol MAP chart, determine the solenoid valve drive pulse width, and output it to the methanol nozzle.
  • the nozzle solenoid valve completes the alcohol injection volume control.
  • MAP methanol injection map
  • One dimension of the methanol MAP map is the engine speed n, and the other dimension is the accelerator pedal opening ⁇ ; there are 5 grid points in the MAP map, of which points 1 to 4 are two-dimensional data points determined in the bench calibration test. Point 5 represents the operating point.
  • Each point has a specific engine speed n and a methanol control injection volume m corresponding to the throttle opening ⁇ , that is, the engine speed at point 1 is n 1 , the throttle opening is ⁇ 1 , and methanol
  • the injection volume is m 1
  • the engine speed at point 2 is n 2
  • the throttle opening is ⁇ 2
  • the methanol injection volume is m 2
  • the engine speed at point 3 is n 3
  • the throttle opening is ⁇ 3
  • the methanol injection volume is m 3.
  • the engine speed at point 4 is n 4
  • the throttle opening is ⁇ 4
  • the methanol injection volume is m 4
  • the engine speed at point 5 is n 5
  • the throttle opening is ⁇ 5
  • the methanol injection volume is m 5
  • the methanol injection control amount m 5 corresponding to the engine operating condition point 5 (n 5 , ⁇ 5 ) is obtained.
  • the diesel particulate filter in the post-processor combination adopts a passive regeneration strategy, which relies on the higher concentration of nitrogen dioxide in the exhaust gas to oxidize the carbon particles in the diesel particulate filter.
  • a passive regeneration strategy which relies on the higher concentration of nitrogen dioxide in the exhaust gas to oxidize the carbon particles in the diesel particulate filter.
  • the in-cylinder working fuel will not only include direct-injected diesel but also methanol fuel. Since methanol fuel will do work, the engine output power will increase. This will enable the driver to passively reduce the depth of the accelerator pedal, thereby reducing the amount of diesel injection, and ultimately enable the engine to emit power to meet the needs of the vehicle, and achieve the purpose of reducing diesel consumption.
  • Diesel-methanol combined combustion engines have cleaner emissions than traditional diesel engines, and can reduce NOx and soot emissions at the same time.
  • the diesel-methanol combined combustion engine is equipped with a post-processor combination including methanol SCR, DPF and DOC.
  • the methanol SCR reductant is the incomplete combustion product (including methanol) formed by methanol at high temperature.
  • the urea SCR is eliminated, which can save urea. cost.
  • Diesel-methanol combined combustion engine can run in DMCC mode or in pure diesel mode. The working mode can be switched and the application scenarios are flexible.
  • Figure 1 is a comparison chart of the heat release rate between the pure diesel mode and the DMCC mode; in the figure, the abscissa represents the crankshaft angle in degrees, and the ordinate represents the cylinder pressure in megapascals.
  • Figure 2 is a comparison chart of the temperature equivalence ratio distribution in the main radiator cylinder of the pure diesel mode and the DMCC mode.
  • the abscissa represents the temperature in the cylinder
  • the ordinate represents the local equivalence ratio.
  • Figure 3 is a control flow chart of a diesel-methanol combined combustion engine.
  • Fig. 4 is a diagram of the partial connection relationship of the system in the embodiment.
  • Figure 5 is a schematic diagram of a methanol injection volume control strategy.
  • Figure 6 is a schematic diagram of the network structure of the methanol MAP diagram.
  • Fig. 7 is the control flow of methanol MAP correction in the embodiment.
  • Diesel-methanol combined combustion technology can achieve high-efficiency combustion of diesel engines, especially in medium and large load conditions, which can significantly improve the thermal efficiency of the engine, which is determined by the physical and chemical properties of methanol.
  • Methanol has a high latent heat of vaporization. When methanol is injected into the intake port to form a homogeneous mixture, the vaporization of methanol will absorb a large amount of heat, which will greatly reduce the temperature in the cylinder, thereby prolonging the stagnation period of diesel. The long flame retardation period of diesel will give the diesel a long enough time to fully atomize and form a highly active combustible mixture with methanol-air mixture.
  • FIG. 1 shows the comparison of cylinder pressure and heat release rate between pure diesel mode and DMCC mode. It can be seen from the figure that the in-cylinder pressure of DMCC mode during the compression stroke is significantly lower than that of pure diesel mode, which will greatly reduce the negative compression work.
  • the pure diesel mode begins to generate a combustion exothermic reaction, which causes the pressure in the cylinder to continue to rise, but according to the law of piston movement, it can be known that the volume change rate in the cylinder is small at this time, and the higher The pressure is transformed into effective output work.
  • DMCC mode combustion occurs at 10 degrees behind the above point, so when the piston starts to descend, the pressure in the cylinder decreases significantly, but after the combustion starts, the pressure in the cylinder rises rapidly. The maximum pressure in the cylinder is close to that of the pure diesel mode, but At this time, the rate of change of the in-cylinder volume is higher, which can convert higher pressure into effective output work.
  • the cylinder pressure of the DMCC mode is significantly higher than that of the pure diesel mode, but when the piston moves to 40 degrees after top dead center, the cylinder pressure of the DMCC mode is lower than that of the pure diesel mode.
  • the combustion duration of the DMCC mode is short .
  • the phenomenon of afterburning is less, the higher the proportion of afterburning increases, the heat loss will increase, and the energy taken away by the exhaust gas will also increase. Therefore, the high-efficiency combustion mechanism of diesel-methanol combined combustion technology is as follows: the high latent heat of methanol vaporization and the inhibition of low-temperature ignition of diesel prolongs the delay period of diesel, so that diesel and methanol-air mixture are fully mixed to achieve homogeneous compression ignition combustion.
  • Diesel-methanol combined combustion technology can simultaneously reduce NOx and soot emissions.
  • Figure 2 shows the comparison of the temperature equivalence ratio distribution in the main radiator cylinder between the pure diesel mode and the DMCC mode. It can be seen from the figure that the DMCC mode completely avoids the soot generation interval, and does not overlap with the area with a higher NO generation rate, which is also reduced. The key to NOx emissions.
  • the main reasons for the reduction of soot emissions in DMCC mode are as follows: the use of methanol premixing can effectively reduce the local equivalent ratio; the high oxygen content of methanol prevents methanol from generating soot during the combustion process; the extension of the diesel stagnation period reduces the diesel local equivalent ratio .
  • DMCC mode reduces NOx emissions for the following reasons: the high latent heat of methanol vaporization reduces the temperature in the cylinder and achieves low temperature combustion; the high proportion of methanol premix makes the heat release area more uniform, thereby reducing the local high temperature area; the fast methanol combustion speed makes the combustion high temperature duration Shorten, thereby reducing NOx emissions.
  • Diesel-methanol combined combustion engines include: diesel engines that can only use diesel fuel.
  • the diesel of diesel engines adopts in-cylinder direct injection. It also includes: a methanol injection system located on the intake of the diesel engine, and a methanol electricity connected to the methanol injection system.
  • methanol injection system includes: methanol nozzle and methanol injector ;
  • the methanol supply system is shown in Figure 8, which mainly includes a methanol tank, a methanol pump coarse filter, a methanol level gauge, an electric methanol pump, a methanol filter, an alcohol pressure regulating valve, a methanol distribution pipe, and an alcohol inlet pipe and an alcohol return pipe.
  • the methanol supply system includes a methanol tank 1, a methanol pump coarse filter 2, a methanol level gauge 3, an electric methanol pump 4, a methanol filter 5, an alcohol pressure regulating valve 6, a methanol distribution pipe 7, and an alcohol inlet pipe 9 and return.
  • Alcohol tube 10; methanol pump coarse filter 2 and methanol level gauge 3 are installed in methanol tank 1.
  • Methanol flows through methanol pump coarse filter 2, electric methanol pump 4, methanol filter 5, alcohol pressure regulating valve 6, and then Through the alcohol inlet pipe 9 to the methanol distribution pipe 7 and the methanol nozzle 8, the alcohol pressure regulating valve 6 and the methanol tank 1 are connected through an alcohol return pipe 10.
  • the methanol supply system should be designed for electro-liquid separation, and the alcohol-related parts should be made of stainless steel.
  • both the alcohol inlet pipe and the alcohol recovery pipe use rubber pipes, but the rubber is alcohol-resistant rubber, and ordinary rubber cannot be used. Instead, high fluorine rubber, nitrile rubber, silicone rubber, polytetrafluoroethylene or neoprene should be used. rubber.
  • the methanol level gauge should also be made of stainless steel.
  • FIG. 9 is a diagram of the ultra-low emission aftertreatment system of diesel-methanol combined combustion technology. It can be seen from the figure that the original engine is first connected to the methanol-specific selective catalytic reduction system (methanol SCR). The reductant of the system is methanol formed at high temperature. Of incomplete combustion products (including methanol). Then it is connected with a diesel particulate filter (DPF). Most of the DPF working conditions adopt a passive regeneration strategy. Nitrogen dioxide in the exhaust gas oxidizes the carbon particles trapped in the DPF. If a large pressure difference before and after the DPF is detected, It is necessary to inject methanol into the exhaust pipe to burn and oxidize the trapped carbon particles inside the DPF. Finally, it is connected to the diesel oxidation catalyst (DOC) to oxidize unburned hydrocarbons and carbon monoxide.
  • DOC diesel oxidation catalyst
  • the accelerator position sensor is the key to obtaining the driver's intention, and the engine output power can also be obtained through the accelerator position sensor.
  • the speed sensor is used to monitor the working speed of the engine.
  • the water temperature sensor is used to monitor the engine cooling water temperature.
  • the methanol level sensor is used to monitor the methanol level of the methanol tank.
  • the speed and accelerator pedal signals are used to interpolate methanol MAP, and the cooling water temperature signal and intake air temperature pressure signal are used to correct methanol MAP, as shown in Figure 7.
  • the methanol electronic control unit controls the on and off of the methanol pump and the power-on time of the methanol nozzle. .
  • MI MI1 ⁇ (1+f Tw )
  • MI is the target alcohol injection pulse width
  • MI1 is the basic alcohol injection pulse width
  • f Tw is the cooling water temperature correction coefficient
  • the formula of the cooling water temperature correction coefficient is:
  • T w is the current cooling water temperature value
  • T wh is the high value of the set cooling water temperature
  • T w0 is the set temperature threshold of the cooling water whether or not to spray alcohol.
  • FIG 3 shows the mode switching diagram of diesel-methanol combined combustion technology.
  • the working principle of diesel-methanol combined combustion technology is to start in pure diesel mode. When the engine reaches the set cooling water temperature, it starts to enter the DMCC mode, where the diesel fuel ignites the methanol premixed mixture. It can be seen from Figure 3 that when switching from the pure diesel mode to the DMCC mode, several conditions must be determined, including the methanol level, the cooling water temperature, the speed, and the accelerator pedal.
  • the cooling water temperature is set to 60°C. When the cooling water temperature reaches or exceeds 60°C, the engine can switch to the diesel-methanol combined fuel working mode.
  • methanol does not participate in the work under the no-load throttle oblique line and the full-throttle interval.
  • the part below the no-load throttle oblique line is the engine's low-load working area.
  • the combustion of methanol in this interval will reduce combustion efficiency
  • the injection of methanol will cause fuel waste.
  • Adding methanol in the full-load range will cause the maximum cylinder pressure and the maximum pressure rise rate to exceed the limit, which may cause damage to the engine. Therefore, methanol does not participate in combustion in the full-throttle range.
  • the method for controlling the above-mentioned engine includes the following processes:
  • Step 1 The diesel engine is started in pure diesel combustion mode
  • Step 2 Combustion in pure diesel mode
  • Step 3 Determine whether all the following conditions are met, namely:
  • Condition 1 Whether the methanol supply system has the conditions, that is, whether the methanol pressure reaches the set value (the normal working pressure of the methanol injection system is 0.4MPa), and whether the methanol level is higher than the lower limit;
  • Condition 2 Whether the cooling water temperature is greater than or equal to the set threshold, that is, whether the engine cooling water temperature reaches 60°C;
  • Condition 3 Whether the engine has not reached the full load range, that is, whether the accelerator pedal is not at the 100% operating point;
  • Condition 4 Whether it is out of the part below the no-load throttle slash, that is, whether the engine and the gearbox are not disconnected.
  • step 4 If all the above conditions are met, go to step 4, otherwise go back to step 2;
  • Step 4 Spray alcohol and implement combined combustion of diesel and methanol.
  • In-cylinder fuel for work will not only include direct-injection diesel fuel, but also methanol fuel. Because methanol fuel will do work, engine output will increase. This will enable the driver to passively reduce the depth of the accelerator pedal, thereby reducing the amount of diesel injection, and ultimately enable the engine to generate power to meet the needs of the vehicle.
  • the injection volume of methanol is the core of control.
  • the alcohol injection volume of the methanol injection system is the alcohol injection volume for each cylinder in each cycle when the diesel engine works in the diesel-methanol combined combustion mode.
  • the amount of alcohol injection is the most basic and most important parameter. It needs to realize effective control of the amount of alcohol injected each time under different working conditions, that is, diesel-methanol combined combustion vehicles under different working conditions and operating requirements. ,
  • the amount of alcohol spray mainly depends on two factors: one is the pressure of the alcohol spray; the other is the opening time of the methanol nozzle.
  • this system relies on the pressure regulating valve to control the alcohol injection pressure to a fixed value, and the amount of alcohol injection each time is basically proportional to the injection duration.
  • the method for determining the amount of alcohol sprayed by the methanol injection system is as follows:
  • Step 4-1 Firstly, by obtaining the operating conditions of the engine, and combining the methanol MAP diagram based on the information of the engine operating conditions, determine the basic value of the target alcohol injection amount;
  • Step 4-2 The correction of the basic value is to determine the corrected alcohol amount through the influence of the cooling water temperature on the operating conditions of the diesel-methanol combined combustion engine;
  • Step 4-3 Finally, compare with the maximum alcohol injection volume at the current engine speed, and take the smaller value as the final alcohol injection volume
  • Step 4-4 Then query the alcohol injection volume and methanol MAP chart, determine the solenoid valve drive pulse width, and output it to the methanol nozzle.
  • the nozzle solenoid valve completes the alcohol injection volume control.
  • the interpolation method of methanol MAP is as follows:
  • One dimension of the methanol MAP map is the engine speed n, and the other dimension is the accelerator pedal opening ⁇ .
  • the most important concept in this method is the grid; as shown in Figure 6, there are 5 points in the MAP map grid. Points 1 to 4 are two-dimensional data points determined in the bench calibration test. Point 5 represents the operating point. Each point is a methanol control injection volume m corresponding to a specific engine speed n and throttle opening ⁇ .
  • the engine speed at point 1 is n 1
  • the throttle opening is ⁇ 1
  • the methanol injection volume is m 1
  • the engine speed at point 2 is n 2
  • the throttle opening is ⁇ 2
  • the methanol injection volume is m 2
  • the point 3 The engine speed is n 3
  • the throttle opening is ⁇ 3
  • the methanol injection volume is m 3
  • the engine speed at point 4 is n 4
  • the throttle opening is ⁇ 4
  • the methanol injection volume is m 4
  • the engine speed at point 5 is n 5.
  • the throttle opening is ⁇ 5
  • the methanol injection volume is m 5.
  • the intermediate points 5'and 5′′ are introduced, and the corresponding methanol injection volumes are m 5 ′ and m 5 ′′, respectively. ;
  • the methanol injection control amount m 5 corresponding to the engine operating condition point 5 (n 5 , ⁇ 5 ) is obtained.
  • the DPF in the post-processor combination adopts a passive regeneration strategy, which relies on the higher concentration of nitrogen dioxide in the exhaust gas to oxidize the carbon particles in the DPF.
  • the methanol injector installed on the exhaust pipe is used to oxidize the carbon particles in the DPF.
  • Methanol is injected to burn and oxidize the trapped carbon particles inside the DPF, and finally connect with the DOC to oxidize unburned hydrocarbons and carbon monoxide.
  • an electronically controlled high-pressure common rail electronic control unit (ECU) is adopted, and the ECU supports Controllable Area Net---CAN communication.
  • ECU electronic control unit
  • the methanol electronic control unit obtains the speed, accelerator pedal, cooling water temperature, and intake air temperature and pressure signals from the diesel ECU CAN message.
  • the speed and accelerator pedal signals are used to interpolate the methanol MAP, and the cooling water temperature signal and intake air temperature pressure signal are used to correct the methanol MAP.
  • the methanol electronic control unit controls the on and off of the methanol pump and the power-on time of the methanol nozzle.

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Abstract

一种柴油甲醇组合燃烧发动机，包括柴油发动机、甲醇喷射***、甲醇电控单元、甲醇供给***和后处理器组合；甲醇喷射***位于发动机进气道上；甲醇电控单元、甲醇供给***与甲醇喷射***相连；后处理器组合包括甲醇专用选择性催化还原***、柴油机微粒过滤器以及柴油机氧化催化器，甲醇专用选择性催化还原***和柴油颗粒过滤器受控于甲醇电控单元，后处理器组合安装在发动机排气管上。通过柴油甲醇组合燃烧技术，能够实现柴油机高效燃烧，尤其在中大负荷工况能够显著提升发动机的热效率；柴油甲醇组合燃烧技术能够不需要尿素辅助同时降低NO x和soot排放。还涉及一种柴油甲醇组合燃烧发动机控制方法。

Description

一种柴油甲醇组合燃烧发动机及其控制方法 技术领域
本发明属于发动机领域，具体涉及一种柴油甲醇组合燃烧发动机及其控制方法。
背景技术
甲醇汽车分为点燃式甲醇乘用车和商用车以及压燃式甲醇商用车，其中点燃式甲醇乘用车和商用车采用的技术路线和传统的汽油机类似，但是由于甲醇高汽化潜热使得发动机冷启动困难，因此需要采用汽油来启动，当发动机充分热机后，完全使用甲醇燃料，在进气道形成均质混合气，然后由火花塞点燃预混混合气。点燃式甲醇商用车采用的技术路线与甲醇乘用车类似。压燃式甲醇商用车技术路线主要为柴油甲醇组合燃烧技术。这是因为甲醇的自燃温度较高，在压燃式发动机大部分运行工况点都无法实现压燃，因此需要柴油来引燃甲醇预混混合气。柴油甲醇组合燃烧发动机在启动和怠速工况采用纯柴油工作模式，当冷却水温度及其他条件达到要求后采用柴油甲醇组合燃烧模式，简称DMCC模式。
目前满足国五及其以上排放法规的重型柴油机大部分都采用以及柴油机氧化催化器(DOC)、尿素选择性催化还原***(尿素SCR)和柴油机微粒过滤器(DPF)后处理器组合。使用该后处理器组合需要持续在排气管内喷射尿素，这会增加用户的使用成本。与此同时为了使DPF再生需要在排气管内喷射柴油来氧化DPF内部收集的碳颗粒，这会出现DPF内部烧损的现象，同时也会增加用户的燃料成本。
柴油甲醇组合燃烧技术具有一氧化碳和未燃碳氢排放较高的特点，而且二氧化氮排放占氮氧化物排放的比例也较高，二氧化氮是DPF被动再生关键的基团。
基于上述原因，需要开发一种能够解决目前重型车烟度(PM)排放超限的问题，同时也能大幅降低车主燃料费用的技术方案。
发明内容
本发明的目的是为了克服现有技术中的不足，提供一种柴油甲醇组合燃烧发动机及其控制方法。
本发明的目的是通过以下技术方案实现的：
一种柴油甲醇组合燃烧发动机，包括柴油发动机，柴油发动机的柴油采取缸内直喷方 式，还包括甲醇喷射***、甲醇电控单元、甲醇供给***和后处理器组合；所述甲醇喷射***位于发动机进气道上；所述甲醇电控单元、甲醇供给***与甲醇喷射***相连；所述后处理器组合包括甲醇专用选择性催化还原***、柴油机微粒过滤器以及柴油机氧化催化器，所述甲醇专用选择性催化还原***和柴油颗粒过滤器受控于甲醇电控单元，所述后处理器组合安装在发动机排气管上，与发动机排气管连接的顺序依次为甲醇专用选择性催化还原***、柴油机微粒过滤器以及柴油机氧化催化器。
进一步的，还包括油门位置传感器、水温传感器、转速传感器和甲醇液位传感器，所述油门位置传感器安装在高压油泵的油门拉杆转轴处，所述水温传感器安装在冷却水管路上，所述转速传感器安装在飞轮盘外壳上，所述甲醇液位传感器安装在甲醇供给***的甲醇箱内。
进一步的，所述甲醇电控单元与柴油发动机ECU连接，从报文中获取转速、油门踏板、冷却水温度以及进气温度压力信号。
进一步的，所述甲醇喷射***由甲醇喷嘴和甲醇喷醇器组成。
进一步的，在柴油发动机的排气管中还布置有甲醇喷射器。
进一步的，所述甲醇专用选择性催化还原***的还原剂是甲醇；利用缸内不完全燃烧产物还原二氧化氮和一氧化氮。
进一步的，所述甲醇供给***包括甲醇箱、甲醇泵粗滤器、甲醇液位计、电动甲醇泵、甲醇滤清器、醇压调节阀、甲醇分配管以及进醇管和回醇管；所述甲醇泵粗滤器和甲醇液位计安装在甲醇箱中，甲醇依次流经甲醇泵粗滤器、电动甲醇泵、甲醇滤清器、醇压调节阀，再经进醇管到甲醇分配管和甲醇喷嘴，醇压调节阀与甲醇箱之间通过所述回醇管连接。
本发明提供的另一个技术方案如下：
一种柴油甲醇组合燃烧发动机的控制方法，基于上述柴油甲醇组合燃烧发动机，包括如下过程：
步骤1，发动机以纯柴油燃烧方式启动；
步骤2，发动机以纯柴油方式燃烧；
步骤3，判断是否满足下列全部条件，即：
条件一：甲醇供给***是否具备条件，即甲醇压力是否达到设定值、甲醇液位是否高于下限值；
条件二：发动机冷却水温度是否大于或等于设定的阈值，即发动机冷却水温度是否达到60℃；
条件三：发动机是否未达到满负荷区间，即油门踏板是否未处于100％工作点；
条件四：是否脱离空载油门斜线以下部分，即发动机与变速箱是否未脱开；
如满足上述全部条件，转步骤4，否则返回步骤2；
步骤4，喷醇，实施柴油甲醇组合燃烧。
进一步的，甲醇喷射***对喷醇量的确定方法如下：
步骤4-1，首先通过获得发动机的运行工况，在确知发动机工况信息的基础上结合甲醇喷射脉谱(MAP)，确定目标喷醇量基本值；
步骤4-2，通过冷却水温度对柴油甲醇组合燃烧发动机工况的影响，对目标喷醇量基本值进行修正；
步骤4-3，与发动机当前转速下的最大喷醇量进行比较，取较小值为最终喷醇量；
步骤4-4，查询喷醇量和甲醇MAP图，确定电磁阀驱动脉宽，输出到甲醇喷嘴，由喷嘴电磁阀完成喷醇量控制。
进一步的，步骤4-1中的甲醇喷射脉谱(MAP)采用插值的方法确定，具体如下：
甲醇MAP图一维是发动机转速n，另一维是油门踏板开度α；MAP图网格点共有5个点，其中点1～点4均为台架标定试验中确定的二维数据点，点5代表工况点，每一个点都是有具体的发动机转速n和油门开度α对应的一个甲醇控制喷射量m，即点1处发动机转速为n 1，油门开度为α 1，甲醇喷射量为m 1，点2处发动机转速为n 2，油门开度为α 2，甲醇喷射量为m 2，点3处发动机转速为n 3，油门开度为α 3，甲醇喷射量为m 3，点4处发动机转速为n 4，油门开度为α 4，甲醇喷射量为m 4，点5处发动机转速为n 5，油门开度为α 5，甲醇喷射量为m 5，为便于理解插值过程以及公式描述，引入中间点5＇和点5〞，对应的甲醇喷射量分别为m 5′和m 5″；
首先判断出发动机运行工况点5所处的MAP图网络区域，即确定与目前发动机转速n 5和油门开度α 5临近的四个标定MAP点；
之后，按照油门开度α 1和α 2方向进行插值，求出m 5′，具体的计算公式如下：
Figure PCTCN2019120937-appb-000001
进行完m 5′的插值后，再按照油门开度α 3和α 4方向上进行插值，求出m 5″，计算公式如下：
Figure PCTCN2019120937-appb-000002
求得m 5′和m 5″之后，还并没能得到发动机运行工况点5的甲醇控制量m 5值，还需要在发动机转速n 1和n 4方向上进行插值，最后求得m 5，计算公式如下：
Figure PCTCN2019120937-appb-000003
经过三次插值后得到了发动机运行工况点5(n 5，α 5)所对应的甲醇喷射控制量m 5。
进一步的，后处理器组合中的柴油颗粒过滤器采用被动再生的策略，依靠尾气中较高浓度的二氧化氮来氧化柴油颗粒过滤器中碳颗粒，当柴油颗粒过滤器前后压差较大时，通过排气管上安置的甲醇喷射器来喷射甲醇，在柴油颗粒过滤器内部进行燃烧氧化捕集的碳颗粒，最后与柴油氧化催化器相连，用于氧化未燃碳氢以及一氧化碳。
与现有技术相比，本发明的技术方案所带来的有益效果是：
一、本发明的发动机在柴油甲醇组合燃烧模式下，缸内做功燃料将不仅包括直喷的柴油，同时包括甲醇燃料，由于甲醇燃料会做功，发动机输出功率将增加。这会使驾驶员被动减少油门踏板深入，从而减少柴油喷射量，最终使发动机发出功率能够满足车辆行驶需要，并达到减少柴油消耗的目的。
二、柴油甲醇组合燃烧发动机相对于传统柴油机排放更清洁，能够同时降低NOx和soot排放。
三、柴油甲醇组合燃烧发动机配备包括甲醇SCR、DPF以及DOC的后处理器组合，甲醇SCR还原剂为甲醇在高温下形成的不完全燃烧产物(包括甲醇)，取消了尿素SCR，可节省尿素使用成本。
四、柴油甲醇组合燃烧发动机既可以运行在DMCC模式下，也可以工作在纯柴油模式下，工作模式可切换，应用场景灵活。
附图说明
图1是纯柴油模式与DMCC模式放热率对比图；图中，横坐标代表曲轴转角，单位为度，纵坐标代表缸压，单位为兆帕。
图2是纯柴油模式与DMCC模式主放热缸内温度当量比分布对比图，图中，横坐标代表缸内温度，纵坐标代表局部当量比。
图3是柴油甲醇组合燃烧发动机控制流程图。
图4是实施例中***局部连接关系图。
图5是甲醇喷射量控制策略示意图。
图6是甲醇MAP图网络结构示意图。
图7是实施例中甲醇MAP修正控制流程。
图8甲醇供给***图。
图9后处理***连接关系图。
具体实施方式
以下结合附图和具体实施例对本发明作进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
柴油甲醇组合燃烧技术能够实现柴油机高效燃烧，尤其在中大负荷工况能够显著提升发动机的热效率，这是由甲醇的物理和化学性质决定的。甲醇具有较高的汽化潜热，当甲醇喷入进气道形成均质混合气过程中，甲醇的汽化会吸收大量的热，这会使缸内的温度大幅降低，从而延长柴油的滞燃期。柴油较长的滞燃期会使柴油有足够长的时间进行充分雾化，与甲醇空气混合气形成高活性的可燃混合气。当缸内的边界条件达到这部分可燃混合气的着火条件时，这部分可燃混合气将以均质压燃的方式同时着火。该种燃烧方式会大幅提升定压燃烧的比例，同时该种燃烧方式的燃烧持续期较短。在做功冲程后期缸内温度明显降低，从而有效减少散热损失，提升发动机的热效率。图1为纯柴油模式与DMCC模式缸压和放热率对比，从图中可以看出，在压缩冲程中DMCC模式的缸内压力明显低于纯柴油模式，这会大幅减少压缩负功。活塞到达上止点时，纯柴油模式开始发生燃烧放热反应，从而使缸内的压力持续升高，但是依据活塞运动规律可知，此时缸内的容积变化率较小，没有将较高的压力转变为有效输出功。DMCC模式由于燃烧发生于上之点后10度，因此在当活塞开始下行时，缸内压力明显降低，但是开始燃烧以后，缸内压力迅速升高，最高缸内压力与纯柴油模式接近，但是此时缸内容积的变化率较高，能够将较高的压力转变为有效输出功。DMCC模式开始燃烧后缸内压力明显高于纯柴油模式，但是当活塞运动到上止点后40度以后，DMCC模式的缸内压力低于纯柴油模式，这是因为DMCC模式的燃烧持续期短，后燃现象较少，较高的后燃比例增加使散热损失增加，同时也会使排气带走的能量增加。因此，柴油甲醇组合燃烧技术高效燃烧机理如下：甲醇高汽化潜热以及对柴油低温着火的抑制作用使柴油滞燃期延长，从而使得柴油与甲醇空气混合气充分混合，实现均质压燃燃烧，这是柴油甲醇组合燃烧技术高效燃烧的机理。压缩冲程压力的降低、做功冲程后期散热损失减少、排气损失减少以及甲醇蒸发雾化余热回收是柴油甲醇组合燃 烧技术热效率高的关键。
柴油甲醇组合燃烧技术能够同时降低NOx和soot排放。图2为纯柴油模式与DMCC模式主放热缸内温度当量比分布对比，从图中可以看出DMCC模式彻底避开了soot生成区间，而与NO生成率较高的区域没有交集，也是降低NOx排放的关键。DMCC模式降低soot排放的主要原因如下：采用甲醇预混的方式能够有效降低局部当量比；甲醇高含氧比例使得甲醇在燃烧过程不会产生碳烟；延长柴油滞燃期使得柴油局部当量比降低。DMCC模式降低NOx排放原因如下：甲醇高汽化潜热降低了缸内温度，实现低温燃烧；甲醇高比例预混使放热区域更加均匀，从而使局部高温区域减少；甲醇燃烧速度快使得燃烧高温持续时间缩短，从而减少NOx排放。
实施例1：
针对机械泵发动机，该种应用场合主要是非道路发动机，包括船舶发动机、柴油发电机组、工程机械等，同时也包括国二及以下排放标准的道路车辆。
柴油甲醇组合燃烧发动机，包括：可单纯使用柴油燃料的柴油发动机，柴油发动机的柴油采取缸内直喷方式，还包括：位于柴油发动机进气道上的甲醇喷射***，与甲醇喷射***相连的甲醇电控单元以及甲醇供给***，后处理器组合，油门位置传感器、水温传感器、转速传感器、甲醇液位传感器，位于排气管中布置的甲醇喷射器；甲醇喷射***包括：甲醇喷嘴以及甲醇喷醇器；
甲醇供给***如图8所示，主要包括甲醇箱、甲醇泵粗滤器、甲醇液位计、电动甲醇泵、甲醇滤清器、醇压调节阀、甲醇分配管以及进醇管和回醇管。
所述甲醇供给***包括甲醇箱1、甲醇泵粗滤器2、甲醇液位计3、电动甲醇泵4、甲醇滤清器5、醇压调节阀6、甲醇分配管7以及进醇管9和回醇管10；甲醇泵粗滤器2和甲醇液位计3安装在甲醇箱1中，甲醇依次流经甲醇泵粗滤器2、电动甲醇泵4、甲醇滤清器5、醇压调节阀6，再经进醇管9到甲醇分配管7和甲醇喷嘴8，醇压调节阀6与甲醇箱1之间通过回醇管10连接。
由于甲醇对部分材料的腐蚀作用，因此涉醇部件的材料应该选用不锈钢材料。为了避免出现电化学腐蚀，在甲醇供给***中应该设计为电液分离，同时涉醇部件应该选用不锈钢材料。本***中进醇管以及回醇管都选用橡胶管，但是橡胶为耐醇橡胶，不能使用普通的橡胶，而应该采用高氟橡胶、丁腈胶、硅橡胶、聚四氟乙烯或者是氯丁橡胶。甲醇液位计也应该选用不锈钢材料。
图9为柴油甲醇组合燃烧技术超低排放后处理***图，从图中可以看出原始发动机先 与甲醇专用选择性催化还原***(甲醇SCR)相连，该***的还原剂为甲醇在高温下形成的不完全燃烧产物(包括甲醇)。然后与柴油机微粒过滤器(DPF)相连，该DPF大部分工况采用被动再生的策略，由尾气中的二氧化氮来氧化DPF中捕集的碳颗粒，如果检测到DPF前后压差较大，则需要在排气管内喷射甲醇，在DPF内部进行燃烧氧化捕集的碳颗粒。最后与柴油机氧化催化器(DOC)相连，用于氧化未燃碳氢以及一氧化碳。
油门位置传感器为获取驾驶员意图的关键，同时通过油门位置传感器也能获取发动机的输出功率。转速传感器用于监测发动机工作转速。水温传感器用于监测发动机冷却水温度。甲醇液位传感器用于监测甲醇箱甲醇液位。其中转速和油门踏板信号用于插值计算甲醇MAP，冷却水温度信号以及进气温度压力信号用于修正甲醇MAP，见图7，甲醇电控单元控制甲醇泵的通断以及甲醇喷嘴的加电时间。
冷却水温度对甲醇MAP修正公式如下：
MI＝MI1×(1+f Tw)
其中：MI为目标喷醇脉宽，MI1为基本喷醇脉宽，f Tw为冷却水温度修正系数。
冷却水温度修正系数公式为：
f Tw＝0.3×(T w-T w0)/(T wh-T w0)-0.3
其中：T w为当前冷却水温值，T wh为设定冷却水温度高值，T w0为设定的是否喷醇的冷却水温度阈值。
柴油甲醇组合燃烧技术模式切换图见图3。柴油甲醇组合燃烧技术工作原理为纯柴油模式启动，当发动机达到设定冷却水温度后开始进入DMCC模式，由柴油来引燃甲醇预混混合气。由图3可知，由纯柴油模式切换到DMCC模式时要进行若干条件判定，包括甲醇液位、冷却水温度、转速以及油门踏板。其中设定冷却水温度为60℃，当冷却水温度达到或超过60℃时，发动机可以切换为柴油甲醇组合燃料工作模式。为了实现DMCC模式高效安全燃烧，在空载油门斜线以下部分以及满油门区间甲醇不参与工作，其中空载油门斜线以下部分为发动机小负荷工作区间，该区间甲醇参与燃烧会使燃烧效率降低，同时该区间由于没有功率输出，甲醇的喷入会造成燃料浪费。满负荷区间加入甲醇会使最大缸压以及最大压力升高率超限，有可能对发动机造成损坏，因此在满油门区间甲醇也不参与燃烧。
如图3所示，对上述发动机进行控制的方法包括如下过程：
步骤1：柴油机以纯柴油燃烧方式启动；
步骤2：纯柴油方式燃烧；
步骤3：判断是否满足下列全部条件，即：
条件一：甲醇供给***是否具备条件，即甲醇压力是否达到设定值(甲醇喷射***正常工作压力为0.4MPa)，甲醇液位是否高于下限值；
条件二：冷却水温度是否大于或等于设定的阈值，即发动机冷却水温度是否达到60℃；
条件三：发动机是否未达到满负荷区间，即油门踏板是否未处于100％工作点；
条件四：是否脱离空载油门斜线以下部分，即发动机与变速箱是否未脱开。
如满足上述全部条件，转步骤4，否则返回步骤2；
步骤4：喷醇，实施柴油甲醇组合燃烧。
柴油甲醇组合燃烧模式下：
当全部满足设定条件时，甲醇将持续喷入进气道，然后随空气在进气道形成均质混合气，然后进入缸内。缸内做功燃料将不仅包括直喷的柴油，同时包括甲醇燃料，由于甲醇燃料会做功，发动机输出功率将增加。这会使驾驶员被动减少油门踏板深入，从而减少柴油喷射量，最终使发动机发出功率能够满足车辆行驶需要。
对于柴油甲醇组合燃烧技术而言，甲醇的喷射量是控制的核心。甲醇喷射***的喷醇量就是柴油机在柴油甲醇组合燃烧模式下工作时，针对每循环各气缸的喷醇量。对于柴油甲醇组合燃烧发动机，喷醇量是最基本和最重要的参数，需要实现在不同工况下，对每次喷醇量有效控制，即柴油甲醇组合燃烧车辆在不同工况和操作要求下，需求喷醇量的多少，以及如何实现目标值。喷醇量的大小主要取决于两个因素：其一为喷醇压力；其二为甲醇喷嘴开启时间。实际上，本***依靠调压阀控制喷醇压力为定值，每次喷醇量与喷射持续时间基本成正比。通过甲醇MAP图，查询基本喷醇量，确定喷嘴驱动脉宽，由喷嘴电磁阀实现。
如图5所示，甲醇喷射***喷醇量的确定方法如下：
步骤4-1：首先通过获得发动机的运行工况，在确知发动机工况信息的基础上结合甲醇MAP图，确定目标喷醇量基本值；
步骤4-2：对基本值的修正则通过冷却水温度对柴油甲醇组合燃烧发动机工况的影响，确定修正醇量；
步骤4-3：最后与发动机当前转速下的最大喷醇量进行比较，取较小值为最终喷醇量；
步骤4-4：然后查询喷醇量和甲醇MAP图，确定电磁阀驱动脉宽，输出到甲醇喷嘴，由喷嘴电磁阀完成喷醇量控制。
所述步骤4-1中，甲醇MAP的插值方法如下：
甲醇MAP图一维是发动机转速n，另一维是油门踏板开度α，该方法中最重要的一个概念就是网格；如图6所示，MAP图网格点共有5个点，其中点1～点4均为台架标定试验中确定的二维数据点，点5代表工况点，每一个点都是有具体的发动机转速n和油门开度α对应的一个甲醇控制喷射量m，即点1处发动机转速为n 1，油门开度为α 1，甲醇喷射量为m 1，点2处发动机转速为n 2，油门开度为α 2，甲醇喷射量为m 2，点3处发动机转速为n 3，油门开度为α 3，甲醇喷射量为m 3，点4处发动机转速为n 4，油门开度为α 4，甲醇喷射量为m 4，点5处发动机转速为n 5，油门开度为α 5，甲醇喷射量为m 5，为便于理解插值过程以及公式描述，引入中间点5＇和点5〞，对应的甲醇喷射量分别为m 5′和m 5″。；
首先判断出发动机运行工况点5所处的MAP图网络区域，即确定与目前发动机转速n5和油门开度α5临近的四个标定MAP点；
之后，按照油门开度α 1和α 2方向进行插值，求出m 5′，具体的计算公式如下：
Figure PCTCN2019120937-appb-000004
进行完m 5′的插值后，再按照油门开度α 3和α 4方向上进行插值，求出m 5″，计算公式如下：
Figure PCTCN2019120937-appb-000005
求得m 5′和m 5″之后，还并没能得到发动机运行工况点5的甲醇控制量m 5值，还需要在发动机转速n 1和n 4方向上进行插值，最后求得m 5，计算公式如下：
Figure PCTCN2019120937-appb-000006
经过三次插值后得到了发动机运行工况点5(n 5，α 5)所对应的甲醇喷射控制量m 5。
后处理器组合中的DPF采用被动再生的策略，依靠尾气中较高浓度的二氧化氮来氧化DPF中碳颗粒，当DPF前后压差较大时，通过排气管上安装的甲醇喷射器来喷射甲醇，在DPF内部进行燃烧氧化捕集的碳颗粒，最后与DOC相连，用于氧化未燃碳氢以及一氧化碳。
实施例2：
针对国四及其以上排放标准的柴油发动机，采用电控高压共轨电控单元(ECU)，ECU支持可控局域网(Controllable Area Net---CAN)通讯。对于这种发动机，在加装柴油甲醇 组合燃烧技术时不需要安装油门位置传感器、水温传感器和转速传感器，具体原理图见图4。从图中可以看出，甲醇电控单元从柴油ECU CAN报文中获取转速、油门踏板、冷却水温度以及进气温度压力信号。其中转速和油门踏板信号用于插值计算甲醇MAP，冷却水温度信号以及进气温度压力信号用于修正甲醇MAP。甲醇电控单元控制甲醇泵的通断以及甲醇喷嘴的加电时间。
其它内容与实施例1相同。
本发明并不限于上文描述的实施方式。以上对具体实施方式的描述旨在描述和说明本发明的技术方案，上述的具体实施方式仅仅是示意性的，并不是限制性的。在不脱离本发明宗旨和权利要求所保护的范围情况下，本领域的普通技术人员在本发明的启示下还可做出很多形式的具体变换，这些均属于本发明的保护范围之内。

Claims (11)

  1. 一种柴油甲醇组合燃烧发动机，包括柴油发动机，柴油发动机的柴油采取缸内直喷方式，其特征在于，还包括甲醇喷射***、甲醇电控单元、甲醇供给***和后处理器组合；所述甲醇喷射***位于发动机进气道上；所述甲醇电控单元、甲醇供给***与甲醇喷射***相连；所述后处理器组合包括甲醇专用选择性催化还原***、柴油机微粒过滤器以及柴油机氧化催化器，所述甲醇专用选择性催化还原***和柴油颗粒过滤器受控于甲醇电控单元，所述后处理器组合安装在发动机排气管上，与发动机排气管连接的顺序依次为甲醇专用选择性催化还原***、柴油机微粒过滤器以及柴油机氧化催化器。
  2. 根据权利要求1所述柴油甲醇组合燃烧发动机，其特征在于，还包括油门位置传感器、水温传感器、转速传感器和甲醇液位传感器，所述油门位置传感器安装在高压油泵的油门拉杆转轴处，所述水温传感器安装在冷却水管路上，所述转速传感器安装在飞轮盘外壳上，所述甲醇液位传感器安装在甲醇供给***的甲醇箱内。
  3. 根据权利要求1所述柴油甲醇组合燃烧发动机，其特征在于，所述甲醇电控单元与柴油发动机ECU连接，从报文中获取转速、油门踏板、冷却水温度以及进气温度压力信号。
  4. 根据权利要求1所述柴油甲醇组合燃烧发动机，其特征在于，所述甲醇喷射***由甲醇喷嘴和甲醇喷醇器组成。
  5. 根据权利要求1-4中任一权利要求所述柴油甲醇组合燃烧发动机，其特征在于，在柴油发动机的排气管中还布置有甲醇喷射器。
  6. 根据权利要求1-4中任一权利要求所述柴油甲醇组合燃烧发动机，其特征在于，所述甲醇专用选择性催化还原***的还原剂是甲醇；利用缸内不完全燃烧产物还原二氧化氮和一氧化氮。
  7. 根据权利要求1-4中任一权利要求所述柴油甲醇组合燃烧发动机，其特征在于，所述甲醇供给***包括甲醇箱、甲醇泵粗滤器、甲醇液位计、电动甲醇泵、甲醇滤清器、醇压调节阀、甲醇分配管以及进醇管和回醇管；所述甲醇泵粗滤器和甲醇液位计安装在甲醇箱中，甲醇依次流经甲醇泵粗滤器、电动甲醇泵、甲醇滤清器、醇压调节阀，再经进醇管到甲醇分配管和甲醇喷嘴，醇压调节阀与甲醇箱之间通过所述回醇管连接。
  8. 一种柴油甲醇组合燃烧发动机的控制方法，基于权利要求1所述柴油甲醇组合燃烧发动机，其特征在于，包括如下过程：
    步骤1，发动机以纯柴油燃烧方式启动；
    步骤2，发动机以纯柴油方式燃烧；
    步骤3，判断是否满足下列全部条件，即：
    条件一：甲醇供给***是否具备条件，即甲醇压力是否达到设定值、甲醇液位是否高于下限值；
    条件二：发动机冷却水的温度是否大于或等于设定的阈值，即发动机冷却水温度是否达到60℃；
    条件三：发动机是否未达到满负荷区间，即油门踏板是否未处于100％工作点；
    条件四：是否脱离空载油门斜线以下部分，即发动机与变速箱是否未脱开；
    如满足上述全部条件，转步骤4，否则返回步骤2；
    步骤4，喷醇，实施柴油甲醇组合燃烧。
  9. 根据权利要求8所述柴油甲醇组合燃烧发动机的控制方法，其特征在于，甲醇喷射***对喷醇量的确定方法如下：
    步骤4-1，首先通过获得发动机的运行工况，在确知发动机工况信息的基础上结合甲醇喷射脉谱(MAP)，确定目标喷醇量基本值；
    步骤4-2，通过冷却水温度对柴油甲醇组合燃烧发动机工况的影响，对目标喷醇量基本值进行修正；
    步骤4-3，与发动机当前转速下的最大喷醇量进行比较，取较小值为最终喷醇量；
    步骤4-4，查询喷醇量和甲醇MAP图，确定电磁阀驱动脉宽，输出到甲醇喷嘴，由喷嘴电磁阀完成喷醇量控制。
  10. 根据权利要求9所述柴油甲醇组合燃烧发动机的控制方法，其特征在于，步骤4-1中的甲醇喷射脉谱(MAP)采用插值的方法确定，具体如下：
    甲醇MAP图一维是发动机转速n，另一维是油门踏板开度α；MAP图网格点共有5个点，其中点1～点4均为台架标定试验中确定的二维数据点，点5代表工况点，每一个点都是有具体的发动机转速n和油门开度α对应的一个甲醇控制喷射量m，即点1处发动机转速为n 1，油门开度为α 1，甲醇喷射量为m 1，点2处发动机转速为n 2，油门开度为α 2，甲醇喷射量为m 2，点3处发动机转速为n 3，油门开度为α 3，甲醇喷射量为m 3，点4处发动机转速为n 4，油门开度为α 4，甲醇喷射量为m 4，点5处发动机转速为n 5，油门开度为α 5，甲醇喷射量为m 5，为便于理解插值过程以及公式描述，引入中间点5＇和点5〞，对应的甲醇喷射量分别为m 5′和m 5″；
    首先判断出发动机运行工况点5所处的MAP图网络区域，即确定与目前发动机转 速n 5和油门开度α 5临近的四个标定MAP点；
    之后，按照油门开度α 1和α 2方向进行插值，求出m 5′，具体的计算公式如下：
    Figure PCTCN2019120937-appb-100001
    进行完m 5′的插值后，再按照油门开度α 3和α 4方向上进行插值，求出m 5″，计算公式如下：
    Figure PCTCN2019120937-appb-100002
    求得m 5′和m 5″之后，还并没能得到发动机运行工况点5的甲醇控制量m 5值，还需要在发动机转速n 1和n 4方向上进行插值，最后求得m 5，计算公式如下：
    Figure PCTCN2019120937-appb-100003
    经过三次插值后得到了发动机运行工况点5(n 5，α 5)所对应的甲醇喷射控制量m 5。
  11. 根据权利要求8所述柴油甲醇组合燃烧发动机的控制方法，其特征在于，后处理器组合中的柴油颗粒过滤器采用被动再生的策略，依靠尾气中较高浓度的二氧化氮来氧化柴油颗粒过滤器中碳颗粒，当柴油颗粒过滤器前后压差较大时，通过排气管上安置的甲醇喷射器来喷射甲醇，在柴油颗粒过滤器内部进行燃烧氧化捕集的碳颗粒，最后与柴油氧化催化器相连，用于氧化未燃碳氢以及一氧化碳。
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