CN111520258B

CN111520258B - Compression ignition type methanol engine combustion system and control method

Info

Publication number: CN111520258B
Application number: CN202010365982.XA
Authority: CN
Inventors: 刘正白; 刘科
Original assignee: Southern University of Science and Technology
Current assignee: Southern University of Science and Technology
Priority date: 2020-04-30
Filing date: 2020-04-30
Publication date: 2023-08-18
Anticipated expiration: 2040-04-30
Also published as: CN111520258A

Abstract

The invention provides a compression ignition type methanol engine combustion system which comprises a methanol engine, a methanol storage and a fuel supply system for providing gasified methanol fuel for a mixer, wherein the ignition agent supply system is used for providing dimethyl ether ignition agent for the mixer, the gasified methanol fuel, the dimethyl ether ignition agent and air are mixed into mixed gas according to a proportion, and the mixed gas is input into the mixer in the methanol engine through an air inlet manifold. According to the compression ignition type methanol engine combustion system provided by the invention, the dimethyl ether primer is compression-ignited by compression combustion and then the gasified methanol fuel is ignited, so that the problem of difficult cold start of the methanol engine can be effectively solved; can replace the nozzle on the traditional cylinder to play the role of granulating the methanol fuel, and ensure the combustion effect and the utilization rate of the methanol fuel in the cylinder. The invention also provides a control method of the compression ignition type methanol engine combustion system.

Description

Compression ignition type methanol engine combustion system and control method

Technical Field

The invention relates to the technical field of methanol engines, in particular to a compression ignition type methanol engine combustion system and a control method.

Background

Along with the continuous improvement of the living standard of people, the environmental protection consciousness is gradually increased. With the increasing shortage of petroleum resources on earth, various new energy automobiles are also produced and matured with the development of technology. Methanol is a substance synthesized from raw materials such as coal, natural gas, wood, garbage and the like, and is considered as a preferred clean fuel for replacing petroleum fuels. Methanol has received widespread attention because of its broad methanol supply chain in China, and its low price and low emission from combustion on engines. However, the methanol engine is difficult to start in a low-temperature state, which is one of the main reasons that the methanol engine cannot be widely popularized on a large scale at present, and is one of the problems that the methanol engine is urgently needed to overcome at present.

Researchers have made a great deal of research on the aspects of dual-fuel combustion, such as adding methanol into diesel oil or gasoline, igniting the methanol by an ignition agent and the like, and the methanol engine is greatly limited in application in the automobile industry due to the fact that a methanol engine combustion system is complex, has high cost, is difficult to control, has poor reliability, is easy to cause a plurality of series of side effects and the like. A compression ignition methanol engine such as provided in publication No. CN101718224B includes an engine body, an EGR system, a methanol fuel supply system, and a DME catalytic synthesis system. The DME catalytic synthesis system starts to synthesize DME to participate in combustion only when the engine speed, the engine oil temperature and the cooling water temperature reach a certain value, and has no help to the cold start process of the engine. Therefore, the DME catalytic synthesis system included in the compression ignition methanol engine provided by the system cannot solve the technical problem of difficult cold start of the methanol engine.

In the existing methanol engine, the methanol fuel is required to be thinned into small particles through a nozzle to enter a cylinder so as to be ignited by ignition flame in the cylinder, so that the problem of insufficient combustion of the methanol fuel exists.

Disclosure of Invention

The invention aims to solve the defects that the existing compression ignition type methanol engine combustion system is difficult to start in a low-temperature state, namely, cold start is long and difficult, methanol fuel must enter a cylinder through a nozzle, and the methanol fuel is not combusted sufficiently.

The technical scheme adopted for solving the technical problems is as follows: a compression ignition methanol engine combustion system comprising a methanol engine and a methanol storage, the methanol engine comprising a housing and at least one cylinder disposed within the housing, further comprising:

a fuel supply system which is communicated with the methanol storage and provides gasified methanol fuel for the mixer, and comprises a first pipeline communicated with the methanol storage, an evaporator for gasifying the methanol fuel in the first pipeline and a fuel pipeline communicated with the evaporator and the mixer;

the ignition agent supply system is communicated with the methanol storage and provides a dimethyl ether ignition agent for the mixer, and comprises a second pipeline communicated with the methanol storage, a methanol cracker for converting methanol fuel in the second pipeline into the dimethyl ether ignition agent, a dimethyl ether storage which is communicated with the methanol cracker and pre-stores dimethyl ether gas, and an ignition agent pipeline for communicating the dimethyl ether storage with the mixer;

the mixer is characterized in that the gasified methanol fuel, the dimethyl ether ignition agent and air are mixed into mixed gas according to a proportion, the mixed gas is input into the methanol engine through an air inlet manifold, and the mixer comprises a mixing chamber, a first air inlet, a second air inlet, a third air inlet and an air outlet, wherein the first air inlet is arranged on the mixing chamber and communicated with a fuel pipeline, the second air inlet is communicated with an ignition agent pipeline, the third air inlet is communicated with outside air, and the air outlet is communicated with the air inlet manifold.

Further, the volume of the dimethyl ether ignition agent in the mixed gas in the mixer accounts for 2% -40% of the volume of the mixed gas.

Further, the methanol storage comprises a storage tank for storing methanol fuel and an air outlet pipeline for communicating the storage tank with the first pipeline and the second pipeline, and a low-pressure pump for increasing the output pressure of the methanol fuel in the air outlet pipeline is arranged on the air outlet pipeline.

Specifically, the air outlet pipeline is also provided with a methanol heater for performing first-stage heating on the methanol fuel in the air outlet pipeline.

Further, a first flow control valve for controlling the flow of the methanol fuel in the second pipeline is also arranged on the second pipeline.

Further, a secondary heater is arranged in the methanol cracker.

Further, the methanol cracker is communicated with the dimethyl ether storage through a third pipeline, and a first pressure control valve for regulating and controlling the third pipeline switch is arranged on the third pipeline.

Further, a second flow control valve for controlling the output quantity of dimethyl ether is arranged on the pilot agent pipeline.

Further, a methanol fuel flow valve for controlling the flow rate of the gasified methanol fuel into the mixing chamber is arranged on the fuel pipeline.

The compression ignition type methanol engine combustion system provided by the invention has the beneficial effects that: the fuel supply system can provide gasified methanol fuel for the mixer immediately when the methanol engine is started, the pilot agent supply system can provide dimethyl ether pilot agent for the mixer immediately when the methanol engine is started, the gasified methanol fuel, the dimethyl ether pilot agent and air are mixed in proportion by the mixer and then are input into the cylinder, and the gasified methanol fuel is ignited after the dimethyl ether pilot agent is compressed by compression combustion, so that the problem of difficult cold start of the methanol engine can be effectively solved; the fuel supply system provides gasified methanol fuel for the methanol engine, can replace a nozzle on a traditional cylinder to play a role in granulating the methanol fuel, and ensures the combustion effect and the utilization rate of the methanol fuel in the cylinder; meanwhile, the ignition agent supply system can participate in the whole process of cold start and normal operation of the methanol engine, and can greatly shorten the cold start time of the methanol engine; the methanol cracker is also provided, and can be used for generating dimethyl ether igniting agent from methanol fuel in the methanol storage through dehydration catalysis in the normal operation process of the methanol engine, storing the dimethyl ether igniting agent in the dimethyl ether storage and supplying dimethyl ether gas for the dimethyl ether storage; the dimethyl ether ignition agent adopted in the invention has the advantages of safety, reliability and stability, and is suitable for wide popularization and use in the automobile industry.

The invention also provides a control method of the compression ignition type methanol engine combustion system, which comprises the following steps:

starting a methanol engine, wherein methanol fuel in a methanol storage enters a fuel supply system and a pilot agent supply system respectively, the fuel supply system provides gasified methanol fuel for a mixer, the pilot agent supply system provides dimethyl ether pilot agent in a dimethyl ether storage for the mixer, the gasified methanol fuel, the dimethyl ether pilot agent and air are mixed according to a proportion and then enter a cylinder of the methanol engine through an intake manifold, the dimethyl ether pilot agent in the mixed gas is compression-ignited in the cylinder to form a pilot flame, and the rest of the mixed gas is ignited through the pilot flame to complete a normal combustion process;

and S2, starting a methanol cracker, and enabling the methanol fuel in the second pipeline to enter the methanol cracker to catalyze and produce dimethyl ether.

The control method of the compression ignition type methanol engine combustion system provided by the invention has the beneficial effects that: the mixed gas is formed by directly using the dimethyl ether ignition agent in the dimethyl ether storage to enter the mixer immediately when the methanol engine is cold started, the methanol engine is started by the mixed gas, and the dimethyl ether gas generated by catalyzing the methanol fuel in the operation process of the methanol engine is stored in the dimethyl ether storage to supply the dimethyl ether storage, so that the cold starting time of the methanol engine can be greatly shortened, and meanwhile, the normal operation of the methanol engine and the availability of enough ignition agent can be saved in the ignition agent supply system in the starting process are ensured.

Drawings

FIG. 1 is a schematic diagram of the operation of a compression ignition methanol engine combustion system provided by the invention.

In the figure: a 100-compression ignition methanol engine combustion system; 10-methanol engine, 11-shell and 12-cylinder; a 20-methanol storage, a 21-storage tank, a 22-air outlet pipeline, a 23-low pressure pump, a 24-methanol heater, a 30-fuel supply system, a 31-first pipeline, a 32-evaporator, a 33-fuel pipeline and a 34-methanol fuel flow valve; 40-pilot feed system, 41-second pipeline, 42-methanol cracker, 421-second heater, 43-dimethyl ether memory, 44-pilot pipeline, 45-first flow control valve, 46-first pressure control valve, 47-second flow control valve, 48-third pipeline; 50-mixer, 51-first inlet, 52-second inlet, 53-third inlet, 54-exhaust, 55-air duct, 60-intake manifold.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

Referring to fig. 1, a compression ignition methanol engine combustion system 100 is provided in accordance with the present invention. The compression ignition type methanol engine combustion system 100 takes gasified methanol as a basic fuel and dimethyl ether as a pilot agent, and mixes the gasified methanol fuel and the dimethyl ether pilot agent with air in the mixer 50 to form mixed gas, the dimethyl ether pilot agent in the mixed gas is compression-ignited in the cylinder 12 of the methanol engine 10 to form a pilot flame, and the rest mixed gas is ignited and combusted through the pilot flame, so that the piston in the methanol engine 10 is pushed to act reversely to realize the engine driving function. In the compression ignition type methanol engine combustion system 100 provided by the invention, during the operation of the methanol engine 10, a part of methanol fuel in the methanol storage 20 can be catalyzed to generate dimethyl ether gas serving as a pilot agent, and the dimethyl ether gas can be stored in the dimethyl ether storage 43 to provide enough dimethyl ether gas for the pilot agent supply system 40. The compression ignition type methanol engine combustion system 100 provided by the invention fully utilizes the effect that methanol fuel can be dehydrated and catalyzed by heating to generate dimethyl ether gas, and uses the dimethyl ether gas as a pilot agent to form a pilot flame by compression ignition, so that the problem of difficult cold start of the methanol engine 10 is solved. In the compression ignition type methanol engine combustion system 100, dimethyl ether gas is used as a primer, so that the compression ignition type methanol engine combustion system has the advantages of safety, reliability and stability, and is suitable for wide popularization and use in the automobile industry.

Specifically, as shown in fig. 1, the compression ignition type methanol engine combustion system 100 includes a methanol engine 10 and a methanol storage 20, a fuel supply system 30 which communicates with the methanol storage 20 and supplies vaporized methanol fuel to a mixer 50, a pilot agent supply system 40 which communicates with the methanol storage 20 and supplies dimethyl ether pilot agent to the mixer 50, and a mixture gas which is obtained by mixing the vaporized methanol fuel, the dimethyl ether pilot agent and air in proportion, and is inputted into the mixer 50 in the methanol engine 10 through an intake manifold 60. The methanol engine 10 is characterized in that dimethyl ether pilot agent in mixed gas provided by a mixer 50 forms pilot flame through compression ignition pilot agent, and gasified methanol fuel in the mixer 50 is ignited by the pilot flame. The methanol engine 10 performs a cold start process through the mixed gas, so that the technical problem of difficult start in the normal cold start process of the methanol engine 10 can be solved, normal combustion of methanol fuel in the cold start process is ensured, the utilization rate of the methanol fuel can be greatly improved, and the time required for cold start of the methanol engine 10 is greatly shortened. The ignition agent supply system 40 provides a basic material methanol fuel by the methanol storage 20, and the methanol fuel is dehydrated by the action of high temperature and a catalyst to prepare the dimethyl ether ignition agent which can be compressed and ignited by the methanol engine 10, so that the sufficient dimethyl ether gas is always maintained in the process of re-entering the cold start of the methanol engine 10 in the repeated use process of the methanol engine 10 for a long time.

Further, in a compression ignition methanol engine combustion system 100 provided by the present invention, a methanol engine 10 includes a housing 11 and at least one cylinder 12 disposed in the housing 11. In the present embodiment, three cylinders 12 are provided in the housing 11 in order. The cylinder 12 communicates with the mixer 50 through an intake manifold 60 to effect the supply of vaporized methanol fuel and dimethyl ether pilot. In this embodiment, the cylinder 12 in the methanol engine 10 does not need to be provided with an injection common rail and a nozzle for injecting the methanol fuel, but the methanol fuel is partially gasified by the fuel supply system 30 and then is input into the mixer 50, and then is mixed with the dimethyl ether ignition agent and air and then is input into the cylinder 12 to realize the combustion process of the mixed gas. The cost of the internal nozzles of the methanol engine 10 may be saved compared to the conventional methanol engine 10.

Further, the methanol storage 20 provided by the present invention includes a storage tank 21 for storing methanol fuel and an air outlet pipe 22 that communicates the storage tank 21 with the fuel supply system 30 and the pilot agent supply system 40, the air outlet pipe 22 being respectively communicated with a first pipe 31 in the fuel supply system 30 and a second pipe 41 in the pilot agent supply system 40. As shown in fig. 1, in the present embodiment, a low pressure pump 23 for increasing the output pressure of the methanol fuel in the gas outlet pipe 22 is provided in the gas outlet pipe 22 in the methanol storage 20. The low-pressure pump 23 is arranged so that the methanol fuel in the tank 21 can be fed to the mixer 50 while maintaining a certain pressure in each of the first pipe 31 and the second pipe 41. And the arrangement of low-pressure pump 23 can not only provide conveying power for the methanol fuel in the pipeline of fuel supply system 30, ensure that even the methanol fuel which is not completely gasified by fuel supply system 30 can be finally conveyed into methanol engine 10 for effective combustion, but also provide conveying power for the methanol fuel in the pipeline of pilot agent supply system 40, so that a part of the methanol fuel can be converted into pilot agent for storage and use.

Further, a methanol heater 24 for first-stage heating of the methanol fuel in the gas outlet pipe 22 is further provided on the gas outlet pipe 22. The methanol heater 24 is a first stage heater in the overall compression ignition methanol engine combustion system 100. The methanol heater 24 can raise the temperature of the methanol fuel in the two sets of pipelines of the fuel supply system 30 and the ignition agent supply system 40 as soon as possible, so that preliminary temperature rise can be performed on the methanol fuel to be gasified in the fuel supply system 30, and preparation can be made for heating, catalyzing and dehydrating the methanol fuel to be converted into the dimethyl ether ignition agent in the subsequent methanol cracker 42. By increasing the temperature of the methanol fuel after the first stage heating of the methanol heater 24, the time for gasifying the methanol fuel in the fuel supply system 30 can be shortened, and the utilization rate of the methanol fuel in the methanol cracker 42 can be improved. The methanol heater 24 provided in the gas outlet pipe 22 may be heated by circulating the exhaust gas generated by the methanol engine 10 thereto, or may heat the methanol fuel in the gas outlet pipe 22 by other electric heating methods. The heated methanol fuel enters the evaporator 32 for gasification mostly through the first pipeline 31, and enters the methanol cracker 42 for cracking to generate dimethyl ether gas through the action of the catalyst through the second pipeline 41.

Further, the fuel supply system 30 provided outside the methanol engine 10 includes a first pipe 31 communicating with the methanol reservoir 20, an evaporator 32 vaporizing the methanol fuel in the first pipe 31, and a fuel pipe 33 communicating the evaporator 32 with the mixer 50. The combustion supply system 30 delivers most of the methanol fuel in the methanol storage 20 to the evaporator 32 through the first pipe 31 for gasification. The evaporator 32 is provided to raise the temperature of the methanol fuel so that it can be gasified, and the gasified methanol fuel is introduced into the mixer 50 through the fuel pipe 33. The liquid methanol fuel in the first pipe 31 passes through the evaporator 32 to form vaporized methanol fuel, which is pushed to the fuel pipe 33 by the low-pressure pump 23 in the methanol storage 20.

In the compression ignition type methanol engine combustion system 100 provided by the invention, as the mixed gas is output from the methanol engine 10, the functions of cold start compression ignition and ignition of the methanol engine 10 can be realized only by ensuring that the mixed gas has gasified methanol fuel and dimethyl ether ignition agent at the same time.

Further, the pilot agent supply system 40 provided outside the methanol engine 10 includes a second pipe 41 communicating with the methanol storage 20, a methanol cracker 42 converting the methanol fuel in the second pipe 41 into a dimethyl ether pilot agent, a dimethyl ether storage 43 pre-storing a dimethyl ether gas communicating with the methanol cracker 42, and a pilot agent pipe 44 communicating the dimethyl ether storage 43 with the mixer 50.

In the ignition agent supply system 40 provided by the invention, the dimethyl ether gas pre-stored in the dimethyl ether storage 43 is used for ensuring that the mixed gas of the mixer 50 can be provided with enough dimethyl ether gas required for cold start as an ignition agent for a plurality of times when the methanol engine 10 is used for the first time. The dimethyl ether storage 43 is required to secure a certain capacity so that all the amount of the dimethyl ether gas in the dimethyl ether storage 43 can be used for ignition of the cold start methanol engine 10 a plurality of times.

Specifically, the capacity of the dimethyl ether gas stored in the dimethyl ether storage 43 is 10 times to 20 times, or even more, the amount of the dimethyl ether gas required for a single cold start of the methanol engine 10. During normal operation of the methanol engine 10, the dimethyl ether gas in the dimethyl ether storage 43 needs to continuously participate in the operation of the methanol engine 10 so as to ensure that each time the methanol engine 10 generates a pilot flame during compression ignition, and therefore the dimethyl ether gas in the dimethyl ether storage 43 needs to be replenished.

Further, in the compression ignition type methanol engine combustion system 100 provided by the present invention, the mixer 50 further includes a mixing chamber, the mixing chamber includes a first air inlet 51 provided on the mixing chamber and communicating with the fuel pipe 33, a second air inlet 52 communicating with the pilot agent pipe 44, a third air inlet 53 communicating with the outside air, and an air outlet 54 communicating with the intake manifold 60. The mixer 50 inputs the gasified methanol fuel supplied from the fuel supply system 30 into the mixing chamber of the mixer 50 through the first air inlet 51, inputs the dimethyl ether pilot supplied from the pilot supply system 40 into the mixing chamber of the mixer 50 through the second air inlet 52, inputs the external air into the mixing chamber of the mixer 50 through the third air inlet 53, and the air pipe 55 is provided on the third air inlet 53, inputs the external air into the third air inlet 53 through the air pipe 55, and mixes the fuel inputted from the respective air inlets in proportion into the mixing chamber of the mixer 50 to obtain the mixed gas which is favorable for compression ignition of the methanol engine, and inputs the mixed gas into the air inlet manifold 60 through the air outlet 54, and finally inputs the mixed gas into the cylinder 12 of the methanol engine 10 for compression ignition and combustion through the air inlet manifold 60.

Specifically, the mixer 50 is used to mix the vaporized methanol fuel supplied from the fuel supply system 30 with air and the dimethyl ether pilot supplied from the pilot agent supply system 40, and to obtain a desired mixed gas. Wherein, the volume of the dimethyl ether ignition agent in the mixed gas formed in the mixing chamber of the mixer 50 is 2-40% of the volume of the whole mixed gas, so that the mixed gas can be ignited by compression ignition in the cylinder 12 of the methanol engine 10, thereby ensuring the full combustion of the mixed gas in the cylinder 12. If the volume of the dimethyl ether pilot agent is less than 2% of the volume of the mixed gas, a compression ignition flame cannot be formed in the methanol engine 10, and the methanol engine 10 cannot be normally cold started. If the volume of the dimethyl ether pilot agent is greater than 40% of the volume of the mixed gas, it cannot be ensured that the pilot agent supply system 40 can always provide sufficient use of the dimethyl ether pilot agent, which would affect sufficient use of the dimethyl ether pilot agent required in the normal cold start process of the subsequent methanol engine 10. During a cold start of the methanol engine 10, the demand for the dimethyl ether pilot agent in the mixed gas is greater in the cylinder 12 at this time, because the temperature in the cylinder 12 is lower, and the proportion of the volume of the dimethyl ether pilot agent in the mixed gas is higher at this time. When the methanol engine 10 is operating normally, the demand for dimethyl ether gas in the mixture gas in the cylinder 12 is reduced, but combustion is still required from the dimethyl ether gas as the ignition agent, but at this time the proportion of the dimethyl ether ignition agent to the mixture gas is small. In the compression ignition methanol engine combustion system 100 provided by the invention, the dimethyl ether storage 43 is used for storing dimethyl ether gas for cold start and normal operation of the methanol engine 10, so that when the methanol cracker 42 does not generate dimethyl ether gas during the initial state of starting the methanol engine 10, a sufficient amount and a sufficient concentration of dimethyl ether gas can be provided to the interior of the mixer 50 immediately. The dimethyl ether gas in the dimethyl ether storage 43 in the pilot agent supply system 40 can immediately provide the dimethyl ether gas as the pilot agent for the mixer 50 when the methanol engine 10 is cold started, and form mixed gas in the mixer 50, and the dimethyl ether pilot agent in the mixed gas is ignited by compression in the cylinder 12, so that the methanol in the mixed gas is finally combusted, the technical problem that the methanol engine 10 is difficult to cold start and is difficult to burn is solved, the cold start time of the methanol engine 10 can be greatly shortened, and the cold start efficiency of the methanol engine 10 is improved; and the ignition agent supply system 40 provides enough ignition agent for compression of the internal cylinder 12 of the methanol engine 10 to improve the combustion efficiency of the methanol fuel in the internal cylinder 12 of the methanol engine 10, ensure the full combustion of the methanol fuel in the normal operation process of the methanol engine 10 and improve the utilization rate of the methanol fuel in the whole operation process of the methanol engine 10.

Further, a methanol cracker 42 for replenishing a dimethyl ether storage 43 with a pilot agent is further provided in the fuel supply system 40 in the compression ignition type methanol engine combustion system 100 according to the present invention. The methanol cracker 42 converts a portion of the methanol fuel provided in the methanol storage 20 to dimethyl ether gas, the pilot agent in the present invention. The methanol cracker 42 can realize self-production and self-sufficient of the dimethyl ether gas in the normal operation process of the whole compression ignition type methanol engine combustion system 100, and ensures that the dimethyl ether gas ignition agent is produced by the catalysis of the methanol fuel in the normal operation process of the methanol engine 10, thereby providing compression ignition for cold start and normal operation of the methanol engine 10 through the dimethyl ether gas ignition agent. The methanol cracker 42 is in communication with the methanol storage 20 via a second conduit 41 and with the dimethyl ether storage 43 via a third conduit 48. One end of the methanol cracker 42 is connected to the methanol storage 20, raw material methanol for producing dimethyl ether gas is obtained from the methanol storage 20, and the other end is connected to the dimethyl ether storage 43, and the dimethyl ether gas produced in the methanol cracker 42 is transferred to the dimethyl ether storage 43 for storage.

The methanol fuel heated by the methanol heater 24 in the methanol storage 20 enters the methanol cracker 42 through the second pipeline 41 and is cracked to generate dimethyl ether gas under the action of the catalyst, and the dimethyl ether gas generated by the cracking is input into the dimethyl ether storage 43 through the third pipeline 48 by the methanol cracker 42 for storage, so that sufficient and stable dimethyl ether gas is provided as an ignition agent for the normal operation of the methanol engine 10.

Specifically, the methanol cracker 42 provided by the present invention is provided with a secondary heater 421. The second heater 421 in the methanol cracker 42 further heats the methanol fuel that has been first-stage heated by the methanol heater 24. On the one hand, the working temperature inside the methanol cracker 42 can be ensured to meet the temperature required by the conversion of methanol, and on the other hand, the efficiency of converting the methanol fuel into the dimethyl ether ignition agent in the methanol cracker 42 can be improved, so that the efficient and effective conversion process of the methanol fuel in the methanol cracker 42 is ensured.

Specifically, a flow valve and a pressure valve are respectively disposed on the second pipe 41 and the third pipe 48 at both sides of the methanol cracker 42 to control the amount of methanol fuel entering the methanol cracker 42 and the opening and closing of the dimethyl ether gas on the third pipe 48. The second pipe 41 is provided with a first flow control valve 45 for controlling the flow rate of the methanol fuel in the second pipe 41. The amount of methanol fuel entering the methanol cracker 42 from the methanol storage 20 via the second conduit 41 can be regulated by means of this first flow control valve 45. After the dimethyl ether gas in the methanol cracker 42 is sufficiently saturated, the methanol fuel input can be closed by the first flow control valve 45. And a first pressure control valve 46 for controlling the output of dimethyl ether is provided on the third conduit 48. The dimethyl ether gas dehydrated and catalyzed by the methanol cracker 42 enters the dimethyl ether storage 43 for storage through the regulation and control of the first pressure control valve 46, when the pressure of the dimethyl ether gas in the dimethyl ether storage 43 is smaller than the preset pressure value on the first pressure control valve 46, the dimethyl ether gas in the dimethyl ether storage 43 is consumed to the extent that the dimethyl ether gas needs to be supplemented, at the moment, the first pressure control valve 46 is gradually opened along with the reduction of the internal pressure of the dimethyl ether storage 43, the third pipeline 48 and the dimethyl ether gas in the methanol cracker 42 are input into the dimethyl ether storage 43 for storage, and the quantity of the dimethyl ether gas stored in the dimethyl ether storage 43 is ensured to meet the normal operation requirement of the methanol engine 10, and the dimethyl ether gas supplemented for the dimethyl ether storage 43 at any time can be supplemented through regulating the first pressure control valve 46. After the dimethyl ether gas in the dimethyl ether storage 43 is fully stored or reaches the preset pressure value of the first pressure control valve 46, the first pressure control valve 46 closes the air outlet channel 42, and the dimethyl ether gas in the methanol cracker 42 is gradually saturated with the continuous replenishment of the methanol fuel, at this time, the first flow control valve 45 is closed, so that the methanol storage 20 stops supplying methanol to the methanol cracker 42, and further the operation of the methanol cracker 42 is stopped.

Specifically, as shown in fig. 1, the dimethyl ether storage 43 in the pilot agent supply system 40 is communicated with the mixer 50 through a pilot agent pipe 44, and a second flow control valve 47 for controlling the output of dimethyl ether is provided on the pilot agent pipe 44. The amount of dimethyl ether gas entering the mixer 50 is controlled by the second flow control valve 47. When the internal temperature of the methanol engine 10 satisfies the combustion temperature of the methanol fuel, the input amount of the dimethyl ether gas into the mixer 50 is regulated and reduced by the second flow control valve 47 to satisfy the requirement of the ignition agent required in normal operation in the internal cylinder 12 of the methanol engine 10. When the temperature in the methanol engine 10 is lowered or the methanol engine 10 needs to be started again, the flow rate of the dimethyl ether gas entering the mixer 50 is regulated through the second flow control valve 47 to increase the concentration of the dimethyl ether gas in the mixer 50, and the temperature in the cylinder 12 of the methanol engine 10 is increased and the methanol fuel is ignited by utilizing the compression ignition flame of the dimethyl ether gas stored in the dimethyl ether storage 43.

Further, in the fuel supply system 30 provided by the present invention, the fuel pipe 33 is provided with a methanol fuel flow valve 34 for controlling the flow rate of the vaporized methanol fuel into the mixer 50. The amount of the methanol fuel gasified in the fuel line 33 entering the mixer 50 is regulated by the methanol fuel flow valve 34.

The invention also provides a control method of the compression ignition type methanol engine combustion system 100, which comprises the following steps:

starting the methanol engine 10, enabling methanol fuel in the methanol storage 20 to enter a fuel supply system 30 and a pilot agent supply system 40 respectively, enabling the fuel supply system 30 to provide gasified methanol fuel for the mixer 50, enabling the pilot agent supply system 40 to provide dimethyl ether pilot agent in a dimethyl ether storage 43 for the mixer 50, enabling the gasified methanol fuel, the dimethyl ether pilot agent and air to enter a cylinder 12 of the methanol engine 10 through an air inlet manifold 60 after being mixed according to a proportion, enabling the dimethyl ether pilot agent in mixed gas to be compression-ignited in the cylinder 12 to form pilot flame, and igniting the mixed gas through the pilot flame to complete a normal combustion process;

specifically, the control method of the compression ignition type methanol engine combustion system 100, at S1: in the step of starting the methanol engine 10, the second flow control valve 47 on the pilot agent line 44 controls the amount of the dimethyl ether pilot agent input into the mixer 50 so that the amount of the dimethyl ether pilot agent input corresponds to the amount required for the mixed gas, at which time the dimethyl ether gas in the dimethyl ether storage 43 enters the mixer 50 through the pilot agent line 44. At the same time, vaporized methanol fuel output from vaporizer 32 enters mixer 50 through methanol fuel flow valve 34, and vaporizer 32 ensures that vaporized methanol fuel is formed into mixer 50. The dimethyl ether ignition agent, the gasified methanol fuel and the air are fully mixed in the mixer 50, and the proportion of various gases is controlled by the mixer 50, so that the mixed gas suitable for compression ignition in the methanol engine 10 is formed in the mixer 50. The mixture ratio of the mixer 50 is used for forming mixed gas, the ratio of the dimethyl ether ignition agent in the mixed gas is between 2 percent and 40 percent, and then the mixed gas enters the cylinder 12 of the methanol engine 10 through the air inlet manifold 60, and the dimethyl ether gas in the mixed gas is compressed in the cylinder 12 to form an ignition flame. The rest part of the mixed gas is ignited by the pilot flame to complete the normal combustion process, so that the pistons in the methanol engine 10 are pushed to act reversely to realize the engine driving function.

In step S1, a methanol fuel pretreatment step in the methanol storage 20 is further included, wherein the methanol fuel in the storage tank 21 in the methanol storage 20 is driven by the low-pressure pump 23 to enter the methanol heater 24 for first-stage heating. The first stage heating of the methanol heater 24 may provide a preliminary warm-up of the methanol fuel, which may increase the vaporization efficiency of the evaporator 32 in the fuel supply system 30, on the one hand, and may provide a preliminary heating of the methanol cracker 42 in the pilot agent supply system 40, on the other hand, increasing the catalytic rate of the methanol cracker 42.

And S2, starting the methanol cracker 42, and enabling the methanol fuel in the second pipeline 41 to enter the methanol cracker 42 for catalyzing and producing dimethyl ether.

At S2: in the step of starting the methanol cracker 42, the methanol fuel in the methanol storage 20 is mostly fed to the fuel supply system 30 via the first conduit 31 for gasification operation, and the small methanol fuel is fed to the methanol cracker 42 via the second conduit 41 for catalytic reaction. The secondary heater 421 in the methanol cracker 42 further heats the methanol fuel entering the methanol cracker 42 to a catalytic temperature and cracks the methanol fuel into dimethyl ether gas by the catalytic action of the internally disposed catalyst.

S3, replenishing the dimethyl ether storage 43 in the ignition agent supply system 40 with dimethyl ether gas: when the pressure value of the dimethyl ether gas in the dimethyl ether storage 43 is greater than or equal to the preset value of the first pressure control valve 46 on the third pipe 48, the third pipe 48 is closed, and the dimethyl ether gas generated in the methanol cracker 42 is stored in the methanol cracker 42. When the pressure value of the dimethyl ether gas in the dimethyl ether storage 43 is smaller than the preset value of the first pressure control valve 46 on the third pipeline 48, the third pipeline 48 is opened, and the dimethyl ether gas produced in the methanol cracker 42 is transported to the dimethyl ether storage 43 for storage through the third pipeline 48, so as to supplement the dimethyl ether gas consumed when the methanol engine 10 is started in the step S1.

S4: the methanol cracker 42 is shut down: when the first pressure control valve 46 closes the third pipe 48 and the dimethyl ether gas in the methanol cracker 42 is in a saturated state, the first flow control valve 45 provided on the second pipe 41 is closed, and the methanol storage 20 stops supplying the methanol fuel to the methanol cracker 42, so that the methanol cracker 42 stops working.

According to the control method of the compression ignition type methanol engine combustion system 100 provided by the invention, during cold start of the methanol engine 10, dimethyl ether gas in the dimethyl ether storage 43 can be directly used as an ignition agent to be conveyed into the mixer 50 for mixing to generate mixed gas, so that the methanol engine 10 is started by the mixed gas, and then the dimethyl ether gas generated by catalyzing methanol is stored in the dimethyl ether storage 43 by using the operation of the methanol engine 10 for preparing for next starting of the methanol engine 10, so that the cold start time of the methanol engine 10 can be greatly shortened, and meanwhile, enough ignition agent can be stored in the ignition agent supply system 40 for use during next starting of the methanol engine 10.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims

1. A compression ignition methanol engine combustion system comprising a methanol engine and a methanol storage, the methanol engine comprising a housing and at least one cylinder disposed in the housing, the compression ignition methanol engine combustion system further comprising:

the mixer is used for mixing the gasified methanol fuel, the dimethyl ether ignition agent and air according to a proportion to form mixed gas, and then inputting the mixed gas into the methanol engine through an air inlet manifold, and comprises a mixing chamber, a first air inlet, a second air inlet, a third air inlet and an air outlet, wherein the first air inlet is arranged on the mixing chamber and communicated with the fuel pipeline, the second air inlet is communicated with the ignition agent pipeline, the third air inlet is communicated with the outside air, and the air outlet is communicated with the air inlet manifold;

the second pipeline is also provided with a first flow control valve for controlling the flow of the methanol fuel in the second pipeline;

the methanol cracker is communicated with the dimethyl ether storage through a third pipeline, and a first pressure control valve for regulating and controlling the third pipeline switch is arranged on the third pipeline.

2. A compression ignition methanol engine combustion system as in claim 1 wherein the volume of said dimethyl ether pilot agent in said mixed gas in said mixer is 2% -40% of the volume of said mixed gas.

3. A compression ignition methanol engine combustion system as claimed in claim 1, wherein the methanol storage comprises a storage tank for storing methanol fuel and an outlet pipe connecting the storage tank with the first pipe and the second pipe, and a low pressure pump for increasing the output pressure of the methanol fuel in the outlet pipe is provided on the outlet pipe.

4. A compression ignition methanol engine combustion system as in claim 3 wherein said outlet conduit is further provided with a methanol heater for first stage heating of the methanol fuel in said outlet conduit.

5. A compression ignition methanol engine combustion system as in claim 1 wherein a secondary heater is provided in said methanol cracker.

6. A compression ignition methanol engine combustion system as set forth in claim 1 wherein said pilot conduit is provided with a second flow control valve for controlling the amount of dimethyl ether output.

7. A compression ignition methanol engine combustion system as in claim 1 wherein said fuel conduit is provided with a methanol fuel flow valve for controlling the flow of vaporized methanol fuel into said mixing chamber.

8. A method of controlling a compression ignition methanol engine combustion system as claimed in any one of claims 1 to 7, comprising the steps of: