CN111677592B - Control system and method for single-cylinder diesel engine co-combustion of gaseous methanol fuel - Google Patents
Control system and method for single-cylinder diesel engine co-combustion of gaseous methanol fuel Download PDFInfo
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- F02D41/14—Introducing closed-loop corrections
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- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/10—Parameters related to the engine output, e.g. engine torque or engine speed
- F02D2200/101—Engine speed
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Abstract
The invention discloses a control system and a method for blending and burning gaseous methanol fuel of a single cylinder diesel engine, which combines a plurality of parts divided by a rotating speed-exhaust temperature diagram and a power-rotating speed diagram of the single cylinder diesel engine and selects an optimal blending and burning ratio alpha according to the relationship between the rotating speed, the temperature and the power respectively w And the methanol control unit controls the opening and closing of the electric control double-opening semicircular valve according to the collected opening degree of the accelerator, the collected exhaust temperature, the collected rotating speed and the collected pressure of the diesel engine air inlet channel so as to adjust the mixed combustion ratio of the methanol. The invention realizes the optimal matching of the methanol co-combustion ratio and the operation condition of the single-cylinder diesel engine, and simultaneously considers the safety of the single-cylinder diesel engine co-combustion methanol and the dynamic property of the single-cylinder diesel engine co-combustion methanol.
Description
Technical Field
The invention belongs to the field of single-cylinder diesel engines, and relates to a control system and a control method for co-combustion of gaseous methanol fuel in a single-cylinder diesel engine.
Background
The diesel engine has the advantages of high compression ratio, good adaptability, high thermal efficiency and the like, and is a main power source in the fields of agriculture, transportation and the like, but pollutants such as NOx, HC, PM and the like generated when the diesel engine works can cause air pollution. In 2019, the dependence of petroleum in China on external environment exceeds 70%, and in order to reduce the dependence on petroleum resources, the application work for popularizing the methanol clean alternative fuel is developed in China. The methanol has the characteristics of high oxygen content, wide sources, low price and the like. The single-cylinder diesel engine is the main power of small agricultural machinery in China, and the methanol is doped in the single-cylinder diesel engine, so that the single-cylinder diesel engine has important significance for effectively reducing emission, reducing dependence on petroleum and protecting the environment.
At present, the main methods for blending and burning methanol in a diesel engine comprise: direct methanol/diesel fuel blending, port methanol injection. The direct blending method of diesel oil and methanol fuel is applied, a single-cylinder diesel engine is not required to be changed, but the problems that the mixed fuel formed by the methanol/diesel oil is easy to layer, the blending amount of the methanol is low, the cold start is poor, the proportion of the formed mixed fuel cannot be adjusted according to the working condition of the diesel engine and the like exist. The methanol injection method of the air inlet passage is suitable for a large-scale multi-cylinder diesel engine, and the methanol injection system of the air inlet passage has a complex structure and high accuracy requirement and is difficult to be applied to single-cylinder diesel.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a control system and a control method for co-combustion of gaseous methanol fuel in a single-cylinder diesel engine aiming at the characteristics of the single-cylinder diesel engine.
The technical scheme adopted by the invention is as follows:
the utility model provides a single cylinder diesel mixes control system who burns gaseous state methyl alcohol fuel, is including setting up methyl alcohol pipeline and the intake pipe differential pressure sensor in the intake pipe, the last automatically controlled two semicircle valves that open that are equipped with of methyl alcohol pipeline, automatically controlled two semicircle valves and intake pipe differential pressure sensor all with methyl alcohol the control unit between signal connection, intake pipe differential pressure sensor are arranged in measuring the pressure in the diesel engine intake duct, the methanol control unit still connects throttle position sensor, exhaust temperature sensor and speed sensor respectively, the methanol control unit is according to the throttle opening degree of collection, exhaust temperature, rotational speed and diesel engine intake duct pressure, and the automatically controlled opening and shutting of two semicircle valves of control and then adjust the mixing of methyl alcohol and burn than.
Furthermore, the electric control double-opening semicircular valve comprises 2 semicircular blocking pieces which are oppositely arranged, a gear is arranged at one end of the same side of each semicircular blocking piece, the gear and the corresponding semicircular blocking piece are welded into a whole and can rotate around the axis of the gear, and the two gears can be meshed with each other; one gear is meshed with a gear on an output shaft of the stepping motor, 2 semicircular retaining pieces can be controlled to rotate in the opposite direction or the reverse direction through the work of the stepping motor, and finally the opening of the electric control double-opening semicircular valve can be adjusted;
further, the air inlet pipe differential pressure sensor comprises a rubber diaphragm arranged along the side wall surface of the air inlet pipe 1, the upper surface of the rubber diaphragm is connected with the Hall element through a moving block, and the moving block has magnetism; the Hall element is connected with the methanol control unit through a data line; when the diesel engine runs, the rubber diaphragm is pressed by the pressure difference between the upper surface and the lower surface of the rubber diaphragmThe sheet is deformed to drive the motion block to move up and down, the Hall element converts the displacement signal of the motion block into potential difference and inputs the potential difference into the methanol control unit, and the methanol control unit calculates the pressure P in the air inlet passage of the diesel engine according to the potential difference j ；
Further, the relation between the blending combustion ratio alpha of the methanol and the opening degree of the electric control double-opening semicircular valve is expressed as follows:
wherein the flow rate of methanol
C is flow coefficient, theta is opening angle of the electric control double-opening semicircular valve, r is radius of the pipeline, P is j Is the pressure in the inlet duct of the diesel engine, T w Is the temperature in the methanol line, P x Is the pressure of gaseous methanol in the methanol line, M d Is the consumption of diesel oil.
A control method for blending combustion of gaseous methanol fuel in a single-cylinder diesel engine comprises the following steps:
step 1, judging whether a diesel engine is in a working area or not by a methanol control unit according to the opening degree of an accelerator, the rotating speed and the exhaust temperature; if the working area is within the working area, beginning to mix and burn methanol; if the diesel engine is not in the working area, methanol is not burnt, and the single-cylinder diesel engine only operates in a pure diesel mode;
Further, the drawing method of the rotation speed-exhaust temperature-methanol blending combustion ratio strategy diagram comprises the following steps:
s1.1, collecting working condition points of a normal operation range of the single-cylinder diesel through a single-cylinder diesel rack experiment, and recording the rotating speed and the temperature corresponding to the working condition points of the single-cylinder diesel under all normal operations; performing frame selection on the working condition points to form a rotating speed-exhaust temperature diagram of the single-cylinder diesel engine;
s1.2, carrying out region division on the rotating speed-exhaust temperature diagram of the single-cylinder diesel engine obtained in the step S1 according to the following steps:
when t is<t wmin Or n<n wmin That is, when the single-cylinder diesel engine is in idle speed and low-load working condition, the methanol alpha is not co-combusted at the moment max ＝0％；
When t is wmin <t<t 1 Or n wmin <n<n 1 At this time, α max ＝10％；
When t is 1 <t<t 2 Or n 1 <n<n 2 At this time, α max ＝20％；
When t is 2 <t<t 3 Or n 2 <n<n 3 At this time, α max ＝30％；
When t is 3 <t<t 4 Or n 3 <n<n 4 At this time, α max ＝20％；
When t is 4 <t<t wmax Or n 4 <n<n wmax At this time, α max ＝10％；
When t is wmax <t<t max Or n wmax <n<n max At this time, methanol alpha is not burnt max ＝0％；
Where t is exhaust temperature, n is rotational speed, n wmin The lowest rotating speed of the single-cylinder diesel engine for co-combustion of the methanol; t is t wmin Is the lowest exhaust temperature of the co-combustion methanol; n is wmax The maximum rotation speed of co-combustion of methanol, t wmax Is the maximum exhaust temperature of co-combustion of methanol, n max Is the maximum rotation speed of the single cylinder diesel engine, t max Is the highest exhaust temperature of the single cylinder diesel engine, n 1 、n 2 、n 3 、n 4 Are rotational speeds, respectively, and n3 is the maximum torque point rotational speed, n 2 ＝(n 3 +n wmin )/2、n 1 ＝(n 2 +n wmin )/2、n 4 ＝(n 3 +n wmax ) /2；t 1 、t 2 、t 3 、t 4 Are respectively temperature, and t 3 Is the maximum torque point temperature, t 1 ＝(t 2 +t wmin )/2、t 2 ＝(t 3 +t wmin ) /2、t 4 ＝(t 3 +t wmax )/2。。
Further, the drawing method of the rotation speed-power-methanol blending combustion ratio strategy diagram comprises the following steps:
s2.1, drawing a power-rotating speed diagram of the single-cylinder diesel according to the power and the rotating speed of the single-cylinder diesel;
s2.2, carrying out region division on the power-rotating speed diagram of the single-cylinder diesel engine obtained in the S2.1 according to the following steps:
when n is<n wmin Or p<p wmin At this time, α max ＝0％；
When n is wmin <n<n 1 Or p wmin <p<p 1 At this time, α max ＝10％；
When n is 1 <n<n 2 Or p 1 <p<p 1 At this time, α max ＝20％；
When n is 2 <n<n 3 Or p 2 <p<p 3 At this time, α max ＝30％；
When n is 3 <n<n 4 Or p 3 <p<p 4 At this time, α max ＝20％；
When n is 4 <n<n wmax Or p 4 <p<p wmax At this time, α max ＝10％；
When n is wmax <n<n max Or p wmax <p<p max At this time, α max ＝0％；
Wherein p is wmin Is the lowest power of co-combustion of methanol, p wmax Maximum power for co-combustion of methanol, p max The highest power of the single-cylinder diesel engine.
The invention has the beneficial effects that:
the maximum blending combustion ratio and the optimal blending combustion ratio of the single-cylinder diesel engine are determined according to parameters such as the position of an accelerator, the rotating speed, the exhaust temperature and the like of the single-cylinder diesel engine. The opening of the electric control double-open semicircular valve can be adjusted through the MSCU according to the operating condition characteristics of the diesel engine, the supply amount of methanol is adjusted, the co-combustion ratio of the methanol is changed, and the optimal matching of the methanol co-combustion ratio and the operating condition of the single-cylinder diesel engine is realized.
The methanol blending combustion ratio is selected by dividing a rotating speed-exhaust temperature diagram of a single-cylinder diesel engine and a power-rotating speed diagram of the single-cylinder diesel engine into a plurality of parts and then selecting the optimal blending combustion ratio alpha according to the relationship between the rotating speed, the temperature and the power w The safety of the single-cylinder diesel engine co-combustion of the methanol and the dynamic property of the single-cylinder diesel engine co-combustion of the methanol can be simultaneously considered.
Drawings
Fig. 1 is an overall view of a control device;
FIG. 2 is a view of a differential pressure sensor of the intake pipe;
FIG. 3 is a structural diagram of an electrically controlled double-open semicircular valve;
FIG. 4 is a parameter definition diagram of an electrically controlled double-open semicircular valve;
FIG. 5 is a plot of the rotation speed versus exhaust temperature for the methanol co-firing ratio;
FIG. 6 is a plot of the rotation speed-power methanol co-combustion ratio;
in the figure, 1, an air inlet channel, 2, an electric control double-opening semicircular valve, 3, a methanol pipeline, 4, an accelerator position sensor, 5, an exhaust temperature sensor, 6, a rotating speed sensor, 7, a methanol control unit, 8, an air inlet pipe differential pressure sensor, 9, a Hall element, 10, a motion block, 11, a rubber diaphragm, 12, a semicircular baffle, 13, a stepping motor, 14 and a gear.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The Control system for co-combustion of gaseous Methanol fuel by a single-cylinder diesel engine shown in fig. 1 comprises a Methanol pipeline 3 and an air inlet pipe differential pressure sensor 8 which are arranged on an air inlet pipe 1, wherein an electrically controlled double-open semicircular valve 2 is arranged on the Methanol pipeline 3, the electrically controlled double-open semicircular valve 2 and the air inlet pipe differential pressure sensor 8 are in signal connection with a Methanol Control Unit 7(Methanol Supply Control Unit), the air inlet pipe differential pressure sensor 8 is used for measuring the pressure in an air inlet passage of the diesel engine, the Methanol Control Unit 7 is also respectively connected with an accelerator position sensor 4, an exhaust temperature sensor 5 and a rotation speed sensor 6, wherein the accelerator position sensor 4 is used for measuring the opening degree of an accelerator, the exhaust temperature sensor 5 is used for measuring the exhaust temperature of the diesel engine, and the rotation speed sensor 6 is used for acquiring the rotation speed of the single-cylinder diesel engine; the methanol control unit 7 controls the electric control double-open semicircular valve 2 to open and close according to the collected throttle opening, the collected exhaust temperature, the collected rotating speed and the collected diesel engine air inlet pressure so as to adjust the mixed combustion ratio of the methanol.
In the present embodiment, the intake pipe differential pressure sensor 8 is composed of a hall element 9, a moving block 10, and a rubber diaphragm 11. As shown in fig. 2, a rubber diaphragm 11 is arranged along the side wall surface of the air inlet pipe 1, the lower part of the rubber diaphragm 11 is connected with the air inlet pipe 1, the upper part of the rubber diaphragm 11 is under atmospheric pressure, the upper surface of the rubber diaphragm 11 is connected with a hall element 9 through a moving block 10, and the moving block 10 has magnetism; the Hall element 9 is connected with the methanol control unit 7 through a data line; when the diesel engine runs, the rubber diaphragm 11 deforms due to the pressure difference between the upper surface and the lower surface of the rubber diaphragm 11, the moving block 10 is driven to move up and down, the Hall element 9 converts a displacement signal of the moving block 10 into a potential difference and inputs the potential difference into the methanol control unit 7, and the methanol control unit 7 calculates the pressure P in the air inlet channel of the diesel engine according to the potential difference j 。
In order to effectively control the co-combustion ratio of methanol, the invention optimally designs the electric control double-opening semicircular valve 2 on the methanol pipeline 3 as shown in figure 3, the electric control double-opening semicircular valve 2 comprises 2 semicircular baffle plates 12, the 2 semicircular baffle plates 12 are oppositely arranged, one end of the same side of each semicircular baffle plate 12 is provided with a gear 14, the gear 14 and the corresponding semicircular baffle plate 12 are welded into a whole and can rotate around the axis of the gear 14, and the two gears 14 can be mutually meshed; one gear 14 is meshed with a gear on an output shaft of the stepping motor 13, and the 2 semicircular baffles 12 can be controlled to rotate in the opposite direction or in the reverse direction through the work of the stepping motor 13, so that the opening of the electric control double-opening semicircular valve 2 can be adjusted finally.
As shown in figure 4, the included angle between 2 semicircular baffles 12 in the electric control double-opening semicircular valve 2 is an opening angle theta, the range of theta is 0-45 degrees, namely the maximum opening is 45 degrees, and the opening area is larger
r is the radius of the pipeline, and theta is the included angle between the edge of the semicircular baffle plate and the vertical line.
The principle of adjusting the mixed burning ratio of the methanol by the opening degree of the electric control double-opening semicircular valve 2 is as follows:
mass flow rate Q of methanol m (Kg/s) is expressed as:
ρ m is the density of the methanol gas and is,
P x is the pressure of the gaseous methanol in the methanol pipeline 3, and M is the molecular mass of methanol, namely 32; ideal gas constant R-8.314; the density of the methanol gas is substituted for formula (1) to obtain:
wherein C is the flow coefficient, A is the area of the electric control double-open semicircular valve 2, and P j Is the pressure in the inlet duct of the diesel engine, T w Is the temperature in the methanol line 3, generally constant;
methanol control unit 7(MSCU) according to the amount of fuel injectedAnd the rotating speed of the diesel engine, and calculating the consumption M of the diesel oil d (Kg/s), and the opening of the electric control double-open semicircular valve 2 is adjusted, the supply amount of the methanol is adjusted, so that the methanol blending combustion ratio reaches the required alpha,
wherein M is d Consumption of diesel oil, Q m The flow rate of methanol.
A control method for blending combustion of gaseous methanol fuel in a single-cylinder diesel engine comprises the following steps:
step 1, a methanol control unit 7 judges whether the diesel engine is in a working area or not (namely whether the diesel engine is in a medium load working condition or not) according to the opening degree of an accelerator, the rotating speed and the exhaust temperature; if the working area is within the medium load working condition, the methanol is started to be mixed and burnt; if the diesel engine is not in the working area (namely the diesel engine is in idle speed, low load working condition and high load working condition), the methanol is not blended, and the single-cylinder diesel engine only runs in a pure diesel mode;
The rotation speed-exhaust temperature-methanol co-combustion ratio strategy diagram is obtained by dividing a rotation speed-exhaust temperature diagram of a single-cylinder diesel engine into a plurality of state intervals; the method for drawing the rotation speed-exhaust temperature-methanol co-combustion ratio strategy diagram comprises the following steps:
s1.1, firstly, drawing a rotating speed-exhaust temperature graph of the single-cylinder diesel engine, specifically, collecting working condition points of a normal operation range of the single-cylinder diesel engine through a single-cylinder diesel engine bench test, and recording rotating speeds and temperatures corresponding to all the working condition points under normal operation; the recorded points are boxed to form a rotation speed-exhaust temperature diagram, i.e. the diamond area in fig. 5 is obtained.
S1.2, carrying out region division on the rotating speed-exhaust temperature diagram of the single-cylinder diesel engine obtained in the step S1 according to the following steps:
when t is<t wmin Or n<n wmin That is, when the single-cylinder diesel engine is in idle speed and low-load working condition, the methanol alpha is not co-combusted at the moment max 0 percent; i.e. area a in fig. 5.
When t is wmin <t<t 1 Or n wmin <n<n 1 At this time, α max 10%; i.e. region b in fig. 5.
When t is 1 <t<t 2 Or n 1 <n<n 2 At this time, α max 20 percent; i.e. region c in fig. 5.
When t is 2 <t<t 3 Or n 2 <n<n 3 At this time, α max 30 percent; i.e. the region d in fig. 5.
When t is 3 <t<t 4 Or n 3 <n<n 4 At this time, α max 20 percent; i.e. region c' in fig. 5.
When t is 4 <t<t wmax Or n 4 <n<n wmax At this time, α max 10 percent; i.e. region b' in fig. 5.
When t is wmax <t<t max Or n wmax <n<n max At this time, methanol alpha is not burnt max 0 percent; i.e., region a' in fig. 5.
Where t exhaust temperature, n is rotational speed, n wmin The lowest rotating speed of the single-cylinder diesel engine for co-combustion of the methanol; t is t wmin Is the lowest exhaust temperature of the co-combustion methanol; n is wmax Is the maximum rotation speed of co-burning methanol, t wmax Is the maximum exhaust temperature of co-combustion of methanol, n max Is the maximum rotation speed of the single cylinder diesel engine, t max Is the highest exhaust temperature of the single cylinder diesel engine, n 1 、n 2 、n 3 、n 4 Are rotational speeds, respectively, and n3 is the maximum torque point rotational speed, n 2 ＝(n 3 +n wmin )/2、n 1 ＝(n 2 +n wmin )/2、n 4 ＝(n 3 +n wmax ) /2；t 1 、t 2 、t 3 、t 4 Are respectively temperature, and t 3 Is the maximum torque point temperature, t 1 ＝(t 2 +t wmin )/2、t 2 ＝(t 3 +t wmin ) /2、t 4 ＝(t 3 +t wmax ) 2; the maximum co-combustion ratio is determined according to the rotating speed-exhaust temperature diagram of the single-cylinder diesel engine, and the safety of co-combustion of methanol in the single-cylinder diesel engine can be ensured.
The rotation speed-power-methanol co-combustion ratio strategy diagram is a method for dividing a single-cylinder diesel engine power-rotation speed diagram into a plurality of state intervals and drawing the rotation speed-power-methanol co-combustion ratio strategy diagram, and comprises the following steps:
s2.1, firstly, drawing a power-rotating speed diagram of the single-cylinder diesel according to the power and the rotating speed of the single-cylinder diesel;
s2.2, carrying out region division on the power-rotating speed diagram of the single-cylinder diesel engine obtained in the S2.1 according to the following steps:
when n is<n wmin Or p<p wmin At this time, α max 0 percent; i.e. region e in fig. 6.
When n is wmin <n<n 1 Or p wmin <p<p 1 At this time, α max 10 percent; i.e. region f in fig. 6.
When n is 1 <n<n 2 Or p 1 <p<p 1 At this time, α max 20%; i.e. the region g in fig. 6.
When n is 2 <n<n 3 Or p 2 <p<p 3 At this time, α max 30 percent; i.e. the region h in fig. 6.
When n is 3 <n<n 4 Or p 3 <p<p 4 At this time, α max 20%; i.e., region g' in fig. 6.
When n is 4 <n<n wmax Or p 4 <p<p wmax At this time, α max 10 percent; i.e., region f' in fig. 6.
When n is wmax <n<n max Or p wmax <p<p max At this time, α max 0 percent; i.e. the region e in fig. 6.
Wherein, pwmin is the lowest power of co-combustion methanol, pwmax is the highest power of co-combustion methanol, and pmax is the highest power of a single-cylinder diesel engine;
the maximum co-combustion ratio is determined according to the power-rotating speed diagram of the single-cylinder diesel engine, and the dynamic property of the single-cylinder diesel engine in co-combustion of methanol can be ensured.
The working process of the invention is further explained below:
1) after the power supply is switched on, the MSCU detects the working environment temperature of the single-cylinder diesel engine, determines the deformation rate of the rubber diaphragm and ensures the accuracy of the differential pressure sensor. Setting a correction coefficient A of the pressure sensor, and correcting to obtain a final pressure Pz equal to AP j . When the temperature is between-30 and-10 ℃, the correction coefficient is A1, and the range is 1-1.2; the correction coefficient is A2 at the temperature of minus 10 to 20 ℃, and the value is 1; the correction coefficient is A3 at 20-40 ℃, and the range of A3 is 0.9-1; the correction coefficient is A4 at 40-60 ℃, and the range is 0.8-0.9.
2) After the diesel engine is started, the MSCU detects the opening degree of an accelerator, detects the rotating speed and the exhaust temperature, and starts to mix and burn methanol if the MSCU is in a working area; if the condition is not met, the methanol is not blended, and the single-cylinder diesel engine runs in a pure diesel mode.
3) The MSCU determines the optimal methanol co-combustion ratio alpha under the working condition according to the rotating speed and the exhaust temperature, the methanol co-combustion ratio strategy diagram and the rotating speed-power co-combustion ratio strategy diagram on the basis of the rotating speed-exhaust temperature w And the maximum combustion ratio alpha max The MSCU calculates the supply amount of the methanol according to the stored fuel injection amount, and adjusts the opening of the electric control double-open semicircular valve to enable the co-combustion ratio of the methanol to reach the optimal co-combustion ratio alpha w 。
4) MS when the single cylinder diesel engine is in the co-combustion of methanolThe CU can monitor the accelerator position and the rotating speed change of the diesel engine in real time, compare the accelerator position and the rotating speed change with the data of the previous cycle, correct the mixed combustion ratio of the methanol, if the accelerator opening does not change and the rotating speed is increased, reduce the opening of the electric control double-open semicircular valve 2, the rotating speed increase amplitude is less than 50r/min, and reduce the methanol supply by 10 percent; the increase range is between 50 and 100r/min, the methanol supply amount is reduced by 20 percent, the increase range is between 100 and 150r/min, and the methanol supply amount is reduced by 30 percent; the increase range is between 150-200r/min, and the methanol supply amount is reduced by 40 percent; and when the increasing amplitude exceeds 200r/min, closing the electric control double-opening semicircular valve 2. If the rotating speed is reduced, the real-time load of the single-cylinder diesel engine is increased, the opening degree of the electric control double-opening semicircular valve 2 needs to be increased, and when the rotating speed reduction amplitude is less than 50r/min, the methanol supply amount is increased by 10%; when the rotating speed is reduced by 50r/min, the methanol supply amount of 10 percent is increased to enhance the dynamic property of the engine, but the increased methanol amount does not exceed a limit value, namely the modified co-combustion ratio does not exceed the maximum co-combustion ratio alpha max 。
The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.
Claims (5)
1. A control method for blending combustion of gaseous methanol fuel in a single-cylinder diesel engine is characterized by comprising the following steps:
step 1, judging whether a diesel engine is in a working area according to the opening degree of an accelerator, the rotating speed and the exhaust temperature by a methanol control unit (7), namely judging whether the diesel engine is in a medium-load working condition; if the methanol is in the working area, namely under the medium load working condition, the methanol is started to be co-burned; if the diesel engine is not in the working area, namely if the diesel engine is in idle speed, low-load working condition and high-load working condition, methanol is not burnt, and the single-cylinder diesel engine only runs in a pure diesel mode;
step 2, based on the rotation speed-exhaust temperature-methanol blending combustion ratio strategy diagram, according to the methodThe rotation speed and the exhaust temperature of the engine obtain the maximum co-combustion ratio alpha max1 (ii) a Based on the rotation speed-power-methanol blending combustion ratio strategy diagram, the maximum blending combustion ratio alpha is obtained according to the rotation speed and the power at the moment max2 Correcting the obtained twice maximum mixing combustion ratios to obtain the optimal mixing combustion ratio alpha w (ii) a The method of correction is alpha w ＝min(α max1 ，α max2 ) Wherein α is max1 Is the maximum co-combustion ratio, alpha, obtained according to the rotation speed-exhaust temperature methanol co-combustion ratio strategy diagram max2 The maximum mixing combustion ratio from the figure is planned according to the rotating speed-power mixing combustion ratio;
step 3, adjusting the opening of the electric control double-open semicircular valve (2) through a methanol control unit (7) to realize the optimal mixing combustion ratio alpha w ；
The drawing method of the rotation speed-exhaust temperature-methanol co-combustion ratio strategy diagram comprises the following steps:
s1.1, collecting working condition points of a normal operation range of the single-cylinder diesel through a single-cylinder diesel rack experiment, and recording the rotating speed and the temperature corresponding to the working condition points of the single-cylinder diesel under all normal operations; performing frame selection on the working condition points to form a rotating speed-exhaust temperature diagram of the single-cylinder diesel engine;
s1.2, carrying out region division on the rotating speed-exhaust temperature diagram of the single-cylinder diesel engine obtained in the S1.1 according to the following steps:
when t is<t wmin Or n<n wmin That is, when the single-cylinder diesel engine is in idle speed and low-load working condition, the methanol alpha is not co-combusted at the moment max ＝0％；
When t is wmin <t<t 1 Or n wmin <n<n 1 At this time, α max ＝10％；
When t is 1 <t<t 2 Or n 1 <n<n 2 At this time, α max ＝20％；
When t is 2 <t<t 3 Or n 2 <n<n 3 At this time, α max ＝30％；
When t is 3 <t<t 4 Or n 3 <n<n 4 At this time, α max ＝20％；
When t is 4 <t<t wmax Or n 4 <n<n wmax At this time, α max ＝10％；
When t is wmax <t<t max Or n wmax <n<n max At this time, methanol alpha is not burnt max ＝0％；
Where t is the exhaust temperature, n is the rotational speed, n wmin The lowest rotating speed of the single-cylinder diesel engine for co-combustion of the methanol; t is t wmin Is the lowest exhaust temperature of co-burning methanol; n is wmax Is the maximum rotation speed of co-burning methanol, t wmax Is the maximum exhaust temperature of co-combustion of methanol, n max The maximum rotation speed of the single cylinder diesel engine, t max The highest exhaust temperature, n, of the single cylinder diesel engine 1 、n 2 、n 3 、n 4 Are respectively the rotational speed, and n 3 Is the maximum torque point speed, n 2 ＝(n 3 +n wmin )/2、n 1 ＝(n 2 +n wmin )/2、n 4 ＝(n 3 +n wmax )/2；t 1 、t 2 、t 3 、t 4 Are respectively temperature, and t 3 Is the maximum torque point temperature, t 1 ＝(t 2 +t wmin )/2、t 2 ＝(t 3 +t wmin )/2、t 4 ＝(t 3 +t wmax ) /2；
The drawing method of the rotation speed-power-methanol blending combustion ratio map comprises the following steps:
s2.1, drawing a power-rotating speed diagram of the single-cylinder diesel according to the power and the rotating speed of the single-cylinder diesel;
s2.2, carrying out region division on the power-rotating speed diagram of the single-cylinder diesel engine obtained in the S2.1 according to the following steps:
when n is<n wmin Or p<p wmin At this time, α max ＝0％；
When n is wmin <n<n 1 Or p wmin <p<p 1 At this time, α max ＝10％；
When n is 1 <n<n 2 Or p 1 <p<p 2 At this time, α max ＝20％；
When n is 2 <n<n 3 Or p 2 <p<p 3 At this time, α max ＝30％；
When n is 3 <n<n 4 Or p 3 <p<p 4 At this time, α max ＝20％；
When n is 4 <n<n wmax Or p 4 <p<p wmax At this time, α max ＝10％；
When n is wmax <n<n max Or p wmax <p<p max At this time, α max ＝0％；
Wherein p is wmin Is the lowest power of co-firing methanol, p wmax The highest power for co-firing methanol, p max The highest power of the single-cylinder diesel engine.
2. A system for implementing the method for controlling the co-combustion of gaseous methanol fuel in a single cylinder diesel engine as claimed in claim 1, it is characterized by comprising a methanol pipeline (3) arranged on an air inlet pipe (1) and an air inlet pipe differential pressure sensor (8), the methanol pipeline (3) is provided with an electric control double-open semicircular valve (2), the electric control double-open semicircular valve (2) and an air inlet pipe differential pressure sensor (8) are in signal connection with the methanol control unit (7), the air inlet pipe differential pressure sensor (8) is used for measuring the pressure in an air inlet channel of the diesel engine, the methanol control unit (7) is also respectively connected with an accelerator position sensor (4), an exhaust temperature sensor (5) and a rotating speed sensor (6), the methanol control unit (7) controls the electric control double-open semicircular valve (2) to open and close according to the collected opening degree of the accelerator, the collected exhaust temperature, the collected rotating speed and the collected pressure of the diesel engine air inlet channel so as to adjust the co-combustion ratio alpha of the methanol.
3. The control system for co-combustion of gaseous methanol fuel in a single cylinder diesel engine according to claim 2, wherein the electrically controlled double-open semicircular valve (2) comprises 2 semicircular baffles (12) which are oppositely arranged, a gear (14) is fixedly arranged at the same side end of each semicircular baffle (12), and the two gears (14) are meshed with each other; one gear (14) is meshed with a gear on an output shaft of the stepping motor (13), and the stepping motor (13) drives 2 semicircular blocking pieces (12) to rotate in the opposite direction or in the reverse direction, so that the opening of the electric control double-opening semicircular valve (2) is finally adjusted.
4. The control system for the co-combustion of the gaseous methanol fuel in the single-cylinder diesel engine according to claim 2, wherein the air inlet pipe differential pressure sensor (8) comprises a rubber diaphragm (11) arranged along the side wall surface of the air inlet pipe (1), and the upper surface of the rubber diaphragm (11) is connected with the Hall element (9) through a moving block (10); the Hall element (9) is connected with the methanol control unit (7) through a data line; when a diesel engine runs, the rubber diaphragm (11) deforms due to the pressure difference between the upper surface and the lower surface of the rubber diaphragm (11) to drive the motion block (10) to move up and down, the Hall element (9) converts a displacement signal of the motion block (10) into a potential difference and inputs the potential difference into the methanol control unit (7), and the methanol control unit (7) calculates the pressure P in the diesel engine air inlet channel according to the potential difference j 。
5. The control system for co-combustion of gaseous methanol fuel in a single cylinder diesel engine as claimed in claim 2, wherein the relationship between the co-combustion ratio α of methanol and the opening degree of the electrically controlled double open semicircular valve (2) is expressed as follows:
wherein the flow rate of methanol
C is flow coefficient, theta is opening angle of the electric control double-open semicircular valve 2, r is the radius of the pipeline, P j Is the pressure in the inlet duct of the diesel engine, T w Is the temperature in the methanol line 3, P x Is the pressure of the gaseous methanol in the methanol line 3, M d Is the consumption of diesel oil.
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