CN114329829B - Automatic generation method and system for piston profile of marine diesel engine - Google Patents
Automatic generation method and system for piston profile of marine diesel engine Download PDFInfo
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Abstract
The invention discloses a method and a system for automatically generating a piston profile of a marine diesel engine, belonging to the technical field of design of combustion chambers of marine diesel engines, wherein the method comprises the following steps: presetting a target compression ratio, geometric parameters and an initial step length, and dividing the geometric parameters into independent variable parameters and dependent variable parameters, wherein the independent variable parameters comprise an aperture ratio, an open angle, a center boss depth, a piston bowl mouth rounding arc radius, a boss arc radius and a combustion chamber depth, and the dependent variable parameters comprise a piston bowl bottom arc radius and a center included angle; establishing a dependent variable adjusting algorithm, and automatically adjusting the dependent variable parameters by combining with a self-adaptive step length algorithm to enable the actual compression ratio to be equal to the target compression ratio; and inputting the independent variable parameters into a dependent variable adjusting algorithm to calculate actual dependent variable parameters, and generating the piston molded line. The method can rapidly and automatically generate one or more piston molded lines according to set parameters on the premise of ensuring that the compression ratio, the clearance height and the compensation volume are not changed, thereby greatly improving the efficiency.
Description
Technical Field
The invention relates to the technical field of design of combustion chambers of marine diesel engines, in particular to a method and a system for automatically generating piston profiles of a marine diesel engine.
Background
The marine diesel engine is the main power of the ship, and with the stricter emission regulations, the development of an efficient and clean combustion mode is receiving much attention. The piston is a component of the combustion chamber, and the geometry of the piston has a significant influence on the burn-through period, ignition, combustion, flame propagation, and emissions generation, thus greatly affecting the dynamics, economy, and emissions of the diesel engine, and the design of the piston profile is particularly important. The manual design of the piston profile needs to repeatedly adjust profile parameters to ensure that the compression ratio is unchanged, the process consumes time and power, and particularly under the DOE simulation condition, the number of the piston profiles needs to be large, and the manual design is unrealistic, so that the automatic generation of the piston profile by using software (according to set parameters) is a necessary means for designing the piston profile.
At present, commercial software such as DIESEL RK, AVL FIRE, CONVERGE and the like has a module for automatically generating a piston profile, the module automatically generates a piston profile according to input geometric characteristic parameters, but the generated piston profile cannot ensure the consistency of a bowl volume ratio (piston pit volume/combustion chamber volume when a piston is positioned at a top dead center) in a combustion chamber, so that the software automatically adjusts a clearance height or a compensation volume to ensure that a compression ratio is not changed. In the actual piston profile design process, the clearance height is determined by the safety height (the minimum distance between the piston and the air valve), and the compensation volume is determined by the structure of the cylinder cover, so that the clearance height cannot be changed. Therefore, the piston profile automatic generation module of the current commercial software needs to be further optimized.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, one object of the present invention is to provide an automatic piston profile generation method for a marine diesel engine, which can automatically generate one or more piston profiles rapidly and ensure consistent bowl volume ratio in a combustion chamber.
The invention also aims to provide an automatic generation system of the piston profile of the marine diesel engine.
In order to achieve the above object, an embodiment of the invention provides an automatic generation method for a piston profile of a marine diesel engine, which includes the following steps: step S1, presetting a target compression ratio, geometric parameters and an initial step length, and dividing the geometric parameters into independent variable parameters and dependent variable parameters, wherein the independent variable parameters comprise an aperture ratio, an open angle, a central boss depth, a piston bowl mouth rounding arc radius, a boss arc radius and a combustion chamber depth, and the dependent variable parameters comprise a piston bowl bottom arc radius and a central included angle; step S2, a dependent variable adjusting algorithm is established based on the independent variable parameters and the dependent variable parameters, and the dependent variable parameters are automatically adjusted by combining an adaptive step length algorithm, so that the actual compression ratio is equal to the target compression ratio; and step S3, inputting the independent variable parameters into the dependent variable adjusting algorithm to calculate actual dependent variable parameters so as to automatically generate the piston profile.
According to the automatic generation method of the piston profile of the marine diesel engine, the clearance height and the compensation volume are used as characteristic parameters, the compression ratio is used as a target parameter, the geometric characteristic parameters of the piston are divided into the independent variable and the dependent variable, the dependent variable adjustment algorithm is constructed, a plurality of piston profiles can be generated at one time according to the input characteristic parameters (the compression ratio, the clearance height and the compensation volume) and the geometric parameters (the geometric parameters of the piston profiles) by combining the self-adaptive step length algorithm, a CFD simulation software can be directly introduced to generate a combustion chamber geometric model for simulation optimization, the practicability is high, the compression ratio, the clearance height and the compensation volume are ensured to be unchanged, and the defect of an automatic generation module of the piston profiles of the current commercial software is overcome.
In addition, the automatic generation method of the marine diesel engine piston profile according to the above embodiment of the invention may further have the following additional technical features:
further, in an embodiment of the present invention, the dependent variable parameter in step S2 is adjusted according to the priority of the piston bowl bottom circular arc radius before the center included angle.
Further, in an embodiment of the present invention, the step S2 specifically includes: step S201, carrying out piston type parameterization on the independent variable parameters and the dependent variable parameters to establish a solved compression ratio equation set to obtain a current piston compression ratio; step S202, judging whether the current piston compression ratio is larger than the target compression ratio, if so, increasing the radius of the circular arc at the bottom of the piston bowl, and performing iteration until the radius of the circular arc at the bottom of the piston bowl and the first part of piston molded lines are not intersected any more; step S203, when the current piston compression ratio is larger than the target compression ratio, increasing the center included angle, namely adjusting the second part of piston molded lines, and when the current piston compression ratio is smaller than the target compression ratio, decreasing the center included angle, namely adjusting the second part of piston molded lines, wherein the steps S201 to S203 are executed in an iterative manner until the current piston compression ratio is equal to the target compression ratio after the center included angle changes once.
Optionally, in an embodiment of the present invention, the step S2 further includes: and step S204, when the initial step length cannot meet the requirement of calculating that the current piston compression ratio is equal to the target compression ratio, reducing the initial step length by half for recalculation, and iteratively executing the step S201 and the step S203 until the current piston compression ratio is equal to the target compression ratio.
Further, in an embodiment of the present invention, when the independent variable parameter is a single value, only one piston profile is generated, and when the independent variable parameter is an array, a plurality of piston profiles are generated.
In order to achieve the above object, an embodiment of the present invention provides an automatic generation system for piston profiles of marine diesel engines, including: the initialization module is used for presetting a target compression ratio, geometric parameters and an initial step length, and dividing the geometric parameters into independent variable parameters and dependent variable parameters, wherein the independent variable parameters comprise an aperture ratio, an open angle, a central boss depth, a piston bowl mouth rounding arc radius, a boss arc radius and a combustion chamber depth, and the dependent variable parameters comprise a piston bowl bottom arc radius and a central included angle; the construction and adjustment module is used for establishing a dependent variable adjustment algorithm based on the independent variable parameters and the dependent variable parameters, and automatically adjusting the dependent variable parameters by combining an adaptive step length algorithm to enable the actual compression ratio to be equal to the target compression ratio; and the generation module is used for inputting the independent variable parameters into the dependent variable adjustment algorithm to calculate actual dependent variable parameters so as to automatically generate the piston molded line.
According to the automatic generation system of the piston profile of the marine diesel engine, the clearance height and the compensation volume are used as characteristic parameters, the compression ratio is used as a target parameter, the geometric characteristic parameters of the piston are divided into the independent variable and the dependent variable, the dependent variable adjustment algorithm is constructed, a plurality of piston profiles can be generated at one time according to the input characteristic parameters (the compression ratio, the clearance height and the compensation volume) and the geometric parameters (the geometric parameters of the piston profiles) by combining the self-adaptive step length algorithm, a CFD simulation software can be directly introduced to generate a combustion chamber geometric model for simulation optimization, the practicability is high, the compression ratio, the clearance height and the compensation volume are ensured to be unchanged, and the defect of an automatic generation module of the piston profiles of the current commercial software is overcome.
In addition, the automatic generating system for the marine diesel engine piston profile according to the above embodiment of the invention may further have the following additional technical features:
further, in an embodiment of the present invention, the dependent variable parameter in the construction and adjustment module is adjusted according to the priority of the included angle between the circular arc radius of the bottom of the piston bowl and the center of the piston bowl.
Further, in an embodiment of the present invention, the building and adjusting module specifically includes: the construction unit is used for carrying out piston type parameterization on the independent variable parameters and the dependent variable parameters to establish a solved compression ratio equation set so as to obtain the current piston compression ratio; the piston bowl bottom arc radius adjusting unit is used for judging whether the current piston compression ratio is larger than the target compression ratio or not, and if so, increasing the piston bowl bottom arc radius until the piston bowl bottom arc radius is not intersected with the first part of piston molded lines; and the central included angle adjusting unit is used for increasing the central included angle to adjust the profile of the second part of the piston when the current piston compression ratio is larger than the target compression ratio, reducing the central included angle to adjust the profile of the second part of the piston when the current piston compression ratio is smaller than the target compression ratio, and iteratively executing the construction unit and the piston bowl bottom arc radius adjusting unit when the central included angle changes once until the current piston compression ratio is equal to the target compression ratio.
Optionally, in an embodiment of the present invention, the constructing and adjusting module further includes: and the step length adjusting module is used for reducing the initial step length by half for recalculation when the initial step length cannot meet the requirement of calculating that the current piston compression ratio is equal to the target compression ratio, and iteratively executing the building unit, the piston bowl bottom arc radius adjusting unit and the central included angle adjusting unit until the current piston compression ratio is equal to the target compression ratio.
Further, in an embodiment of the present invention, when the independent variable parameter is a single value, only one piston profile is generated, and when the independent variable parameter is an array, a plurality of piston profiles are generated.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a flow chart of a method for automatically generating a piston profile of a marine diesel engine according to an embodiment of the invention;
FIG. 2 is a schematic of a piston geometry according to one embodiment of the present invention;
FIG. 3 is a schematic diagram of the discretization of a piston in accordance with an embodiment of the present invention;
FIG. 4 is a schematic view of an automatically generated piston profile of one embodiment of the present invention;
fig. 5 is a schematic structural diagram of an automatic generation system for piston profiles of a marine diesel engine according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The method and the system for automatically generating the piston profile of the marine diesel engine according to the embodiment of the invention are described below with reference to the accompanying drawings, and firstly, the method for automatically generating the piston profile of the marine diesel engine according to the embodiment of the invention is described with reference to the accompanying drawings.
Fig. 1 is a flowchart of an automatic generation method of a marine diesel engine piston profile according to an embodiment of the present invention.
As shown in fig. 1, the automatic generation method of the piston profile of the marine diesel engine comprises the following steps:
in step S1, a target compression ratio, geometric parameters, and an initial step length are preset, and the geometric parameters are divided into independent variable parameters and dependent variable parameters, where the independent variable parameters include an aperture ratio, an open angle, a center boss depth, a piston bowl mouth radius arc radius, a boss arc radius, and a combustion chamber depth, and the dependent variable parameters include a piston bowl bottom arc radius and a center included angle.
It should be noted that the compression ratio is a geometric compression ratio of the diesel engine, the clearance height is a distance between the piston and the surface of the cylinder cover when the top dead center is reached, the compensation volume is a volume enclosed by the bottom planes of the cylinder cover and the cylinder cover, and the initial step length is a geometric parameter change step length, which is selected to be 0.5mm in the embodiment of the present invention.
Specifically, as shown in fig. 2, the geometric parameters are piston profile geometric parameters, including a diameter ratio, an open angle, a center boss depth, a boss arc radius, a piston bowl mouth rounding arc radius, a piston bowl bottom arc radius, a combustion chamber depth, and a center included angle; the aperture ratio, the opening angle, the depth of a central boss, the radius of a piston bowl opening rounding arc, the radius of a boss arc and the depth of a combustion chamber are set as independent variables, and the others are set as dependent variables.
Further, when the independent variable parameter is a singular value, only one piston profile is generated, and when the independent variable parameter is an array, a plurality of piston profiles are generated.
In step S2, a dependent variable adjustment algorithm is established based on the independent variable parameter and the dependent variable parameter, and the dependent variable parameter is automatically adjusted in combination with the adaptive step size algorithm, so that the actual compression ratio is equal to the target compression ratio.
Further, in an embodiment of the present invention, step S2 specifically includes:
step S201, carrying out piston type parameterization on the independent variable parameters and the dependent variable parameters to establish a solved compression ratio equation set to obtain the current piston compression ratio.
Specifically, as shown in fig. 3, the piston profile is parameterized, and a system of equations for solving the compression ratio is established, wherein the system of equations is composed of 6 linear equations and 3 circular equations as follows:
the expression for the line L1 is: h, wherein h h is the clearance height;
the expression for the line L2 is: x ═ r c Wherein r is c Is the piston radius;
the expression for the line L3 is: y is 0;
the expression for the line L4 is: k is 4 ×(x-p 1x )+p 1y Wherein k is 4 Is the slope of the line L4, p 1x 、p 1y The horizontal and vertical coordinates of the tangent point of the straight line L5 and the circle 1 are respectively, and the specific expression is as follows:
k 4 ＝tan((θ v + 90). times.pi/180, wherein θ v Is an open corner;
p 1x ＝r 1x -r 1 ×sin(θ v x π/180), wherein, r 1x Is the abscissa, r, of the circle C1 1 Is the radius of circle C1;
p 1y ＝r 1y -r 1 ×cos(θ v x pi/180), wherein r 1y Is the ordinate of circle C1;
the expression for the line L5 is: k is 5 ×(x-p 3x )+p 3y ；
Wherein k is 5 Is the slope of the line L5, p 3x 、p 3y The horizontal and vertical coordinates of the tangent point of the straight line L5 and the circle C3 are respectively, and the specific expressions are as follows:
k 5 ＝tan(θ m x π/180), wherein θ m Is a central included angle;
p 3x ＝r 3x +r 3 ×sin(θ m x pi/180), wherein r 3x Is the abscissa, r, of the circle C3 3 The radius of circle C3;
p 3y ＝r 3y +r 3 ×cos(θ m x pi/180), wherein r 3y Is the ordinate of circle C3;
the expression for the line L6 is: x is 0;
the expression for circle C1 is: (x-r) 1x ) 2 +(y-r 1y ) 2 ＝r 1 2 Wherein r is 1x 、r 1y 、r 1 The center of the circle C1 is respectively the horizontal coordinate, the vertical coordinate and the radius;
expression of circle C2The formula is as follows: (x-r) 2x ) 2 +(y-r 2y ) 2 ＝r 2 2 Wherein r is 2x 、r 2y 、r 2 The circle center of the circle C2 is respectively the horizontal coordinate, the vertical coordinate and the radius;
the expression for circle C3 is: (x-r) 3x ) 2 +(y-r 3y ) 2 ＝r 3 2 Wherein r is 3x 、r 3y 、r 3 The center of the circle C3 is abscissa, ordinate and radius.
Further, as shown in fig. 4, the bisector BL of L4 and L5 is solved by solving the perpendicular lines VL1 and VL2 of the lines L4 and L5, the center of the circular arc of the bottom of the piston bowl is located on BL, and the current piston compression ratio is solved by combining with the compression ratio equation set.
It should be noted that the dependent variable parameter in the embodiment of the present invention is adjusted according to the priority of the center included angle after the radius of the circular arc at the bottom of the piston bowl, which is specifically as follows.
Step S202, judging whether the current piston compression ratio is larger than the target compression ratio, if so, increasing the radius of the circular arc at the bottom of the piston bowl, and performing iteration until the radius of the circular arc at the bottom of the piston bowl is not intersected with the first part of piston molded lines.
Specifically, the current piston compression ratio is compared with a target compression ratio; if the current piston compression ratio is larger than the target compression ratio, the radius of the circular arc at the bottom of the piston bowl is increased, namely the circle C1 is changed into the circle C2, until the circular arc of C2 is not intersected with the line L4 any more; and vice versa.
Step S203, when the current piston compression ratio is larger than the target compression ratio, increasing the central included angle, namely adjusting the second part of piston molded lines, and when the current piston compression ratio is smaller than the target compression ratio, decreasing the central included angle, namely adjusting the second part of piston molded lines, wherein each time the central included angle changes by one degree, the steps S201 to S203 are executed in an iterative manner until the current piston compression ratio is equal to the target compression ratio.
Specifically, as shown in fig. 4, if the bottom arc of the piston bowl does not intersect with the line L4 and the target compression ratio is not achieved, the central included angle is adjusted, when the current piston compression ratio is smaller than the target compression ratio, the central included angle is reduced, that is, the L5 rotates in the up direction, and in order to ensure that the tangent point of the smooth transition L5 and the center boss arc automatically changes and moves from P2 to P1, the process of adjusting the radius of the bottom arc of the piston bowl is repeated when the central included angle changes once; and vice versa.
And (5) iterating the process, automatically adjusting the value of the factor variable, and iterating repeatedly until the actual compression ratio is equal to the target compression ratio.
Optionally, the embodiment of the present invention further includes:
and S204, when the initial step length cannot meet the requirement of calculating that the current piston compression ratio is equal to the target compression ratio, reducing the initial step length by half, recalculating, and iteratively executing the steps S201 to S203 until the current piston compression ratio is equal to the target compression ratio.
That is to say, when the step increment cannot meet the condition that the calculated compression ratio is equal to the target compression ratio, the step is reduced by half and calculation is carried out again, and the algorithm is the same as the conventional adaptive step algorithm so as to accelerate calculation convergence and reduce calculation time.
In step S3, the independent variable parameters are input into the dependent variable adjustment algorithm to calculate the actual dependent variable parameters, so as to automatically generate the piston profile.
Finally, the piston profile meeting the requirements can be generated by writing a program recognizable by MATLAB according to the method, and the result is shown in FIG. 5.
In summary, the method for automatically generating the profile of the marine diesel engine piston provided by the embodiment of the invention has the following beneficial effects: firstly, one or more piston molded lines (according to whether the independent variable is an array or not) can be quickly and automatically generated only according to preset parameters, so that the efficiency is greatly improved; secondly, the generated piston molded line can ensure that the compression ratio, the clearance height and the compensation volume are not changed, and the defects of the current commercial software are overcome; and finally, the generated piston molded line can ensure smooth transition of the joint of the straight line and the circular arc, and the piston molded line is close to the actual piston molded line, so that the simulation error is reduced.
Next, an automatic generation system of a piston profile of a marine diesel engine according to an embodiment of the present invention will be described with reference to the accompanying drawings.
Fig. 5 is a schematic structural diagram of an automatic generation system for piston profiles of a marine diesel engine according to an embodiment of the present invention.
As shown in fig. 5, the system 10 includes: an initialization module 100, a build and adjust module 200, and a generation module 300.
The initialization module 100 is configured to preset a target compression ratio, geometric parameters and an initial step length, and divide the geometric parameters into independent variable parameters and dependent variable parameters, where the independent variable parameters include an aperture ratio, an open angle, a center boss depth, a piston bowl mouth radius arc radius, a boss arc radius, and a combustion chamber depth, and the dependent variable parameters include a piston bowl bottom arc radius and a center included angle. The construction and adjustment module 200 is configured to establish a dependent variable adjustment algorithm based on the independent variable parameter and the dependent variable parameter, and automatically adjust the dependent variable parameter in combination with an adaptive step algorithm, so that the actual compression ratio is equal to the target compression ratio. The generating module 300 is configured to input the independent variable parameter into the dependent variable adjusting algorithm to calculate the actual dependent variable parameter, so as to automatically generate the piston profile.
Further, in one embodiment of the invention, the dependent variable parameter in the adjusting module is adjusted according to the priority of the included angle of the center after the radius of the circular arc at the bottom of the piston bowl.
Further, in an embodiment of the present invention, the building and adjusting module 200 specifically includes: the construction unit is used for carrying out piston type parameterization on the independent variable parameters and the dependent variable parameters to establish a solved compression ratio equation set so as to obtain the current piston compression ratio; the piston bowl bottom arc radius adjusting unit is used for judging whether the current piston compression ratio is larger than the target compression ratio or not, and if so, increasing the piston bowl bottom arc radius until the piston bowl bottom arc radius is not intersected with the first part of piston molded lines; and the central included angle adjusting unit is used for increasing the central included angle when the current piston compression ratio is greater than the target compression ratio, namely adjusting the molded lines of the second part of pistons, reducing the central included angle when the current piston compression ratio is less than the target compression ratio, namely adjusting the molded lines of the second part of pistons, and iteratively executing the constructing unit and the piston bowl bottom arc radius adjusting unit when the central included angle changes by one degree until the current piston compression ratio is equal to the target compression ratio.
Optionally, in an embodiment of the present invention, the constructing and adjusting module 200 further includes: and the step length adjusting module is used for reducing the initial step length by half for recalculation when the initial step length cannot meet the requirement of calculating that the current piston compression ratio is equal to the target compression ratio, and iteratively executing the building unit, the piston bowl bottom arc radius adjusting unit and the center included angle adjusting unit until the current piston compression ratio is equal to the target compression ratio.
Further, in one embodiment of the present invention, when the argument parameter is in the singular value, only one piston profile is generated, and when the argument parameter is in the array, a plurality of piston profiles are generated.
It should be noted that the foregoing explanation on the embodiment of the method for automatically generating a piston profile of a marine diesel engine is also applicable to the system of the embodiment, and is not repeated here.
In summary, the automatic generation system for the piston profile of the marine diesel engine provided by the embodiment of the invention has the following beneficial effects: firstly, one or more piston molded lines (according to whether the independent variable is an array or not) can be quickly and automatically generated only according to preset parameters, so that the efficiency is greatly improved; secondly, the generated piston molded line can ensure that the compression ratio, the clearance height and the compensation volume are not changed, and the defects of the current commercial software are overcome; and finally, the generated piston molded line can ensure smooth transition of the joint of the straight line and the circular arc, and the piston molded line is close to the actual piston molded line, so that the simulation error is reduced.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (8)
1. The automatic generation method of the piston profile of the marine diesel engine is characterized by comprising the following steps of:
step S1, presetting a target compression ratio, geometric parameters and an initial step length, and dividing the geometric parameters into independent variable parameters and dependent variable parameters, wherein the independent variable parameters comprise an aperture ratio, an open angle, a central boss depth, a piston bowl mouth rounding arc radius, a boss arc radius and a combustion chamber depth, and the dependent variable parameters comprise a piston bowl bottom arc radius and a central included angle;
step S2, establishing a dependent variable adjustment algorithm based on the independent variable parameter and the dependent variable parameter, and automatically adjusting the dependent variable parameter in combination with an adaptive step size algorithm to make the actual compression ratio equal to the target compression ratio, wherein the step S2 specifically includes:
step S201, carrying out piston type parameterization on the independent variable parameters and the dependent variable parameters to establish a solved compression ratio equation set to obtain a current piston compression ratio;
step S202, judging whether the current piston compression ratio is larger than the target compression ratio, if so, increasing the radius of the circular arc at the bottom of the piston bowl, and performing iteration until the radius of the circular arc at the bottom of the piston bowl and the molded line of the first part of the piston are not intersected any more;
step S203, when the current piston compression ratio is larger than the target compression ratio, increasing the center included angle, namely adjusting the second part of piston molded lines, and when the current piston compression ratio is smaller than the target compression ratio, decreasing the center included angle, namely adjusting the second part of piston molded lines, wherein the steps S201 to S203 are executed iteratively until the current piston compression ratio is equal to the target compression ratio after the center included angle changes once;
and step S3, inputting the independent variable parameters into the dependent variable adjusting algorithm to calculate actual dependent variable parameters so as to automatically generate the piston profile.
2. The method for automatically generating the piston profile of the marine diesel engine according to claim 1, wherein the dependent variable parameter in the step S2 is adjusted according to the priority of the piston bowl bottom circular arc radius before the center included angle.
3. The method for automatically generating a piston profile of a marine diesel engine according to claim 1, wherein the step S2 further comprises:
and S204, when the initial step length cannot meet the requirement of calculating that the current piston compression ratio is equal to the target compression ratio, reducing the initial step length by half for recalculation, and iteratively executing the steps S201 to S203 until the current piston compression ratio is equal to the target compression ratio.
4. The automatic generation method of marine diesel piston profiles according to claim 1, characterized in that when the argument parameter is a single value, only one piston profile is generated, and when the argument parameter is an array, a plurality of piston profiles are generated.
5. An automatic generating system for piston profiles of marine diesel engines, comprising:
the initialization module is used for presetting a target compression ratio, geometric parameters and an initial step length, and dividing the geometric parameters into independent variable parameters and dependent variable parameters, wherein the independent variable parameters comprise an aperture ratio, an open angle, a central boss depth, a piston bowl mouth rounding arc radius, a boss arc radius and a combustion chamber depth, and the dependent variable parameters comprise a piston bowl bottom arc radius and a central included angle;
a construction and adjustment module, configured to establish a dependent variable adjustment algorithm based on the independent variable parameter and the dependent variable parameter, and automatically adjust the dependent variable parameter in combination with an adaptive step size algorithm to make an actual compression ratio equal to the target compression ratio, where the construction and adjustment module specifically includes:
the construction unit is used for carrying out piston type parameterization on the independent variable parameters and the dependent variable parameters to establish a solved compression ratio equation set so as to obtain the current piston compression ratio;
the piston bowl bottom arc radius adjusting unit is used for judging whether the current piston compression ratio is larger than the target compression ratio or not, and if so, increasing the piston bowl bottom arc radius until the piston bowl bottom arc radius is not intersected with the first part of piston molded lines;
the center included angle adjusting unit is used for increasing the center included angle when the current piston compression ratio is larger than the target compression ratio, namely adjusting the molded lines of the second part of pistons, reducing the center included angle when the current piston compression ratio is smaller than the target compression ratio, namely adjusting the molded lines of the second part of pistons, and iteratively executing the constructing unit and the piston bowl bottom arc radius adjusting unit when the center included angle changes once until the current piston compression ratio is equal to the target compression ratio;
and the generating module is used for inputting the independent variable parameters into the dependent variable adjusting algorithm to calculate actual dependent variable parameters so as to automatically generate the piston molded line.
6. The automatic generation system of marine diesel piston profiles of claim 5, characterized in that the dependent variable parameters in the construction and adjustment module are adjusted according to the priority of the piston bowl bottom circular arc radius before the center included angle.
7. The marine diesel engine piston profile automatic generation system of claim 5, wherein the build and adjust module further comprises:
and the step length adjusting module is used for reducing the initial step length by half for recalculation when the initial step length cannot meet the requirement of calculating that the current piston compression ratio is equal to the target compression ratio, and iteratively executing the constructing unit, the piston bowl bottom arc radius adjusting unit and the central included angle adjusting unit until the current piston compression ratio is equal to the target compression ratio.
8. The automatic generation system for piston profiles of marine diesel engine according to claim 5, characterized in that when the independent variable parameter is a single value, only one piston profile is generated, and when the independent variable parameter is an array, a plurality of piston profiles are generated.
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| CN108446426A (en) * | 2018-02-05 | 2018-08-24 | 北京理工大学 | A kind of minimum basis boss wheel-type line design method based on parametrization plunger motion rule |
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