Combustion system control method, combustion system, and diesel engine

Abstract

A combustion system control method, a combustion system and a diesel engine, in which the combustion system control method can superimpose the spatial strength of the entrainment action of the two injected oil jets in the cylinder by injecting two main fuel jets, realize two-time organization of the oil jet for the flow field in the cylinder, strengthen the turbulence in the cylinder, improve the mixing speed of the oil and gas in the cylinder, and effectively increase the combustion rate in the middle and later stages of combustion and the air utilization rate in the cylinder; and by specifying the duration length of the first main fuel injection and the first injection pressure, ensure that the cylinder pressure can at least reach the cylinder pressure upper limit threshold; during the second main fuel injection, during the period in which the cylinder pressure decreases from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rates of the curve slope of the cylinder pressure change curve at each time point are all within a set slope change rate range, and the rotation angle of the crankshaft is equal to or greater than a first preset angle.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engines, and particularly to a control method of a combustion system, a combustion system, and a diesel engine.

[0002] This application claims the priority of a Chinese patent application filed with the China National Patent Office on June 17, 2021, with an application number of 202110669915.1 and an invention title of "Control Method of Combustion System, Combustion System and Diesel Engine", and all of its contents are incorporated into this application by being incorporated herein by reference.

Background Art

[0003] The conventional combustion organization method of diesel engines mainly uses diffusion combustion as the main method, and the combustion speed is greatly limited by the mixing speed of oil and gas. At present, all high-pressure common rail diesel engines adopt a single main fuel injection. The entrainment effect of a single high-pressure injection mainly occurs in the atomization region, and the entrainment effect weakens in the middle of the oil jet, resulting in a poor mixing effect of oil and gas. In addition, due to the high rotational speed of diesel engines, for four-stroke diesel engines, the time for organizing the mixing of oil and gas is very short. After the jets and droplets generated in a single injection are broken and atomized, it is difficult to diffuse in the combustion chamber in a timely manner to form a uniform mixture with air, which restricts the rapid progress of the combustion process and further restricts the power output of diesel engines.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present invention is to provide a control method of a combustion system, a combustion system, and a diesel engine so as to improve the uniformity of the mixture of fuel oil and air after fuel injection.

Means for Solving the Problems

[0005] On the one hand, the present invention relates to a control method for a combustion system including a piston, an injector, and a cylinder, wherein the piston is capable of reciprocating up and down within the cylinder. The injector sequentially executes at least a first main fuel injection and a second main fuel injection for each movement cycle of the piston. Moreover, the injector continues fuel injection during the process from the first main fuel injection to the second main fuel injection. The injection pressure corresponding to the time when the fuel injection speed is the highest during the process of the injector executing the first main fuel injection is the first injection pressure, and the injection pressure corresponding to the time when the fuel injection speed is the highest during the process of the injector executing the second main fuel injection is the second injection pressure. The control method of the combustion system is By specifying the duration of the first main fuel injection and the first injection pressure, enabling the cylinder pressure at at least some points during the process of the first main fuel injection to reach the cylinder pressure upper limit threshold. By repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure, during the process of the second main fuel injection, when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each point is within the set slope change rate range, and the rotation angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure is not less than the first preset angle. The control method of the combustion system includes the above steps.

[0006] As a preferred technical solution of the control method of the combustion system, the step of enabling the cylinder pressure at at least some points during the process of the first main fuel injection to reach the cylinder pressure upper limit threshold by specifying the duration of the first main fuel injection and the first injection pressure is If the cylinder pressure during the process of the first main fuel injection never reaches the cylinder pressure upper limit threshold value, then the cylinder pressure during the process of the first main fuel injection reaches the cylinder pressure upper limit threshold value at least at some points in time, and the crank angle corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value does not exceed the first angle, and the rotational angle of the crankshaft is not less than the second preset angle during the period when the cylinder pressure rises from the first cylinder pressure to the cylinder pressure upper limit threshold value, the step of repeatedly adjusting at least one of the start time, end time, and current first injection pressure of the first main fuel injection, wherein the cylinder volume corresponding to the time when the cylinder pressure becomes equal to the first cylinder pressure is the same as the cylinder volume corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value.

[0007] As a preferred technical solution of the combustion system control method, for each movement cycle of the piston, the time when the injector starts the first main fuel injection is the first time t 1 And the time when the fuel injection speed of the fuel injected by the injector is the lowest between the first main fuel injection and the second main fuel injection is the second time t 2 And the first injection pressure is P 1 And If the cylinder pressure during the process of the first main fuel injection never reaches the cylinder pressure upper limit threshold value, then the cylinder pressure during the process of the first main fuel injection reaches the cylinder pressure upper limit threshold value at least at some points in time, and the crank angle corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value does not exceed the first angle, and the rotational angle of the crankshaft is not less than the second preset angle during the period when the cylinder pressure rises from the first cylinder pressure to the cylinder pressure upper limit threshold value, the step of repeatedly adjusting at least one of the start time, end time, and current first injection pressure of the first main fuel injection is During the process of the first main fuel injection, the cylinder pressure P in the cylinder is collected in real time, and the angle of the crankshaft is collected in real time, and at the same time, the cylinder pressure P and the cylinder pressure upper limit threshold value P maxA step of comparing the above and determining whether the angle of the crankshaft exceeds the first angle, When the cylinder pressure P is less than the cylinder pressure upper limit threshold value P max and the angle of the crankshaft is located after the first angle, the numerical value of the first injection pressure P 1 is increased, and / or the difference between the second time t 2 and the first time t 1 is reduced as a whole.

[0008] As a preferred technical solution of the combustion system control method, the step of increasing the numerical value of the first injection pressure P 1 and / or reducing the difference between the second time t 2 and the first time t 1 as a whole includes: A step of obtaining the maximum value P x of the cylinder pressure in the process of the first main fuel injection, n = (P max - P x ) / P max is calculated, When n ≤ 5%, only the numerical value of the first injection pressure P 1 is increased by the first set value.

[0009] As a preferred technical solution of the combustion system control method, when n > 5%, the numerical value of the first injection pressure P1 is increased by the first set value, and the first time t 1 and / or the second time t 2 is adjusted so that the difference between the second time t 2 and the first time t 1 is reduced as a whole by the second set value.

[0010] As a preferred technical solution of the combustion system control method, when the cylinder pressure P is greater than or equal to the cylinder pressure upper limit threshold value P max and the angle of the crankshaft is located before the first angle, When the cylinder pressure P is equal to the cylinder pressure upper limit threshold value P max the real-time cylinder volume V in the cylinder is obtained, According to the relationship map between the cylinder volume and the crank angle, when the cylinder volume becomes equal to the real-time cylinder volume V, the crank angle φ during the upward movement of the cylinder corresponding thereto a and the crank angle φ during the downward movement of the cylinder b are obtained, φ 1 = φ b - φ a is calculated, φ 1 , the magnitude of the second preset angle φ n is judged, φ 1 < φ n If so, the numerical value of the first injection pressure P 1 is increased to the third set value, and / or the first time t 1 and / or the second time t 2 is adjusted so that the difference between the second time t 2 and the first time t 1 is reduced to the fourth set value as a whole.

[0011] As a preferred technical solution of the combustion system control method, the second injection pressure is P 2 , and by repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure, during the process of the second main fuel injection, when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each time point is within the set slope change rate range, and further, the rotation angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure is not less than the first preset angle, the step is φ 1 ≧ φ n If so, The step of obtaining the crank angle φ when the cylinder pressure P becomes equal to P n according to the map, where φ c > φ c > φ b and P n is the set cylinder pressure and P max > P n and the step that Crank angle φ b to crank angle φ c obtaining a relationship curve y between the cylinder pressure and the crank angle for the section from to k 1 = dy / dφ, k 2 = dk 1 / dφ, where the value of φ is φ c ~φ d in a step k 2 obtaining the maximum value k of the absolute value of max k max , comparing the magnitude of the preset parameter k a k max < k a if so, increasing the value of the second injection pressure P 2 by the fifth set value

[0012] As a preferred technical solution of the combustion system control method, the time when the injector finishes the second main fuel injection is the third time t 3 and if k max ≧ k a then the combustion system control method further includes φ 2 = φ c - φ b calculating φ 2 , determining the magnitude of the first preset angle φ m φ 2 < φ m if so, increasing the value of the third time t 3 by the sixth set value

[0013] As a preferred technical solution of the combustion system control method, if φ 2 ≧ φ m then the value of the third time t 3 is maintained as it is.

[0014] ​​​On the other hand, the present invention is a combustion system used to implement the control method of the combustion system described in any of the above aspects. The combustion system includes a piston, an injector, a cylinder, and a controller. The controller is configured to control the injector to sequentially perform at least a first main fuel injection and a second main fuel injection for each movement cycle of the piston, and further control the injector to continue fuel injection during the process from the first main fuel injection to the second main fuel injection. The controller is used to determine the duration and the first injection pressure of the first main fuel injection, so that the cylinder pressure at at least some time points during the process of the first main fuel injection can reach the cylinder pressure upper limit threshold. The controller is used to repeatedly adjust at least one of the duration of the second main fuel injection and the second injection pressure, so that during the process of the second main fuel injection, when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each time point is within the set slope change rate range, and further, the rotation angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure is greater than or equal to the first preset angle. The present invention provides a combustion system.

[0015] On the other hand, the present invention provides a diesel engine including the combustion system in the above aspect.

Advantages of the Invention

[0016] The beneficial effects of the present invention are as follows.

[0017] The present invention provides a control method for a combustion system, a combustion system, and a diesel engine. The control method for the combustion system enables the spatial intensity of the entrainment action of the high-speed oil jets injected twice by two main fuel injections to overlap within the cylinder, realizes two organizations of the oil jets with respect to the flow field within the cylinder, strengthens the turbulence within the cylinder, improves the mixing speed of the oil and gas within the cylinder, effectively increases the combustion speed in the middle and late stages of combustion and the air utilization rate within the cylinder. Moreover, by specifying the duration and the first injection pressure of the first main fuel injection to ensure the cylinder pressure, it is possible for the cylinder pressure at at least some time points during the process of the first main fuel injection to reach the cylinder pressure upper limit threshold value. By repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure, during the process of the second main fuel injection, when the cylinder pressure drops from the cylinder pressure upper limit threshold value to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each time point during this period is within the set slope change rate range. Additionally, the rotation angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold value to the set cylinder pressure is equal to or greater than the first preset angle, ensuring that the spatial entrainment overlap effect reaches the optimum and guaranteeing that the power output of the diesel engine is optimal.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. However, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative labor shall fall within the protection scope of the present invention.

[0020] Here, in the description of the present invention, the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is the orientation or positional relationship shown based on the drawings, and is only for the convenience of the description and simplification of the present invention. It is not intended to indicate or imply that the mentioned device or element must have a specific orientation and be configured and operated in a specific orientation. Therefore, it should not be understood as limiting the present invention. Furthermore, the terms "first" and "second" are only used for the purpose of description and should not be understood as meaning or suggesting relative importance. The terms "first position" and "second position" are two different positions. Here, the fact that the first feature is "above", "upward" and "top" of the second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the horizontal height of the first feature is higher than that of the second feature. The fact that the first feature is "below", "downward" and "bottom" of the second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the horizontal height of the first feature is lower than that of the second feature.

[0021] Here, in the description of the present invention, unless specifically defined or limited otherwise, the terms "mounting", "connecting", "connecting" should be interpreted broadly. For example, it may be a fixed connection, a detachable connection, or an integral connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection through an intermediate medium, or a communication inside two elements. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to specific situations.

[0022] Examples of the present invention will be described in detail below. An example of the above examples is shown in the drawings, and the same or similar reference numerals always represent the same or similar elements, or elements having the same or similar functions. The examples described below with reference to the drawings are exemplary and are used only for interpreting the present invention and should not be construed as limiting the present invention.

[0023] <Example 1> This embodiment provides a combustion control system, which includes a piston, an injector, and a cylinder. The piston can reciprocate up and down in the cylinder, and the injector is used to inject fuel oil into the combustion chamber provided on the piston. The combustion control system further includes a controller. The controller is used to control the injector to sequentially execute at least a first main fuel injection and a second main fuel injection for each movement cycle of the piston, and to control the injector to continue fuel injection in the process from the first main fuel injection to the second main fuel injection. Moreover, when the injector performs the first main fuel injection and when the injector performs the second main fuel injection, the speeds of the fuel oil injected are both not less than the set value, and the speed of the fuel oil injected by the injector between the first main fuel injection and the second main fuel injection is less than the set value. The controller can be connected to a control valve provided in the fuel supply pipeline for supplying fuel to the injector, and controls the magnitude of the current applied to the control valve to control the fuel injection pressure of the injector, and further adjusts the efficiency of the fuel oil ejected from the injector.

[0024] The controller is used to ensure that the cylinder pressure at least reaches the cylinder pressure upper limit threshold at some points during the process of the first main fuel injection by specifying the duration of the first main fuel injection and the first injection pressure. In addition, the controller repeatedly adjusts at least one of the duration of the second main fuel injection and the second injection pressure so that during the process of the second main fuel injection, when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each point is within the set slope change rate range, and the rotation angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure is equal to or greater than the first preset angle. The specific implementation process of the controller will be described in detail below.

[0025] In this embodiment, the injector is controlled to perform two main fuel injections during the piston movement cycle and continue the auxiliary injection during the process of the two main fuel injections, so that the spatial intensity of the entrainment action of the two high-speed oil jets injected with the main fuel in the cylinder can be superimposed, realizing the two organizations of the oil jets on the flow field in the cylinder, strengthening the turbulence in the cylinder, improving the mixing speed of the oil and gas in the cylinder, and effectively increasing the combustion speed in the middle and late stages of combustion and the air utilization rate in the cylinder. In addition, by specifying the duration of the first main fuel injection and the first injection pressure, it is ensured that the cylinder pressure can at least reach the cylinder pressure upper limit threshold. When the second main fuel injection is performed, when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each point is within the set slope change rate range, and the rotation angle of the crankshaft is equal to or greater than the first preset angle, ensuring that the spatial entrainment superposition effect is optimal and the power output of the diesel engine is optimal.

[0026] <Example 2> This embodiment provides a diesel engine, and the diesel engine includes the combustion system in Embodiment 1. Moreover, the diesel engine has the beneficial effects of the combustion system in Embodiment 1.

[0027] <Example 3> This embodiment provides a method for controlling a combustion system that can be implemented by the combustion system in Embodiment 1. The method for controlling the combustion system includes S100 to S200.

[0028] S100: By specifying the duration of the first main fuel injection and the first injection pressure, it is possible for the cylinder pressure at at least some points during the process of the first main fuel injection to reach the cylinder pressure upper limit threshold.

[0029] S200: By repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure, during the process of the second main fuel injection, when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each point is within the set slope change rate range, and moreover, the rotation angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure is greater than or equal to the first preset angle.

[0030] The method for controlling the combustion system controls the injector to perform two main fuel injections during the movement cycle of the piston and continue the auxiliary injection during the process of the two main fuel injections, so that the spatial intensity of the entrainment action of the high-speed oil jets injected twice in the cylinder can overlap, realizing the two-fold organization of the oil jets on the flow field in the cylinder, strengthening the turbulence in the cylinder, improving the mixing speed of the oil and gas in the cylinder, effectively increasing the combustion speed in the middle and late stages of combustion and the air utilization rate in the cylinder. At the same time, it can ensure that the spatial entrainment overlap effect reaches the optimum, and ensure that the power output of the diesel engine is optimal.

[0031] Also, in S100, if the cylinder pressure during the process of the first main fuel injection never reaches the cylinder pressure upper limit threshold value, then the cylinder pressure during the process of the first main fuel injection reaches the cylinder pressure upper limit threshold value at least at some points in time, and the crank angle corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value does not exceed the first angle, and the rotational angle of the crankshaft is not less than the second preset angle during the period when the cylinder pressure rises from the first cylinder pressure to the cylinder pressure upper limit threshold value. Until then, at least one of the start time, end time, and current first injection pressure of the first main fuel injection is repeatedly adjusted, and the cylinder volume corresponding to the time when the cylinder pressure becomes equal to the first cylinder pressure is the same as the cylinder volume corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value. In this way, closed-loop adjustment of the cylinder pressure during the process of the first main fuel injection can be realized, and finally the cylinder pressure during the process of the first main fuel injection reaches the cylinder pressure upper limit threshold value.

[0032] As shown in FIG. 1, for each motion cycle of the piston, the time when the injector starts the first main fuel injection is defined as the first time t 1 and the time when the speed of the fuel oil injected by the injector is the lowest between the first main fuel injection and the second main fuel injection is defined as the second time t 2 and the injection pressure corresponding to the time when the speed of the fuel oil injected during the process of the injector performing the first main fuel injection is the highest is defined as the first injection pressure P 1 .

[0033] Specifically, the method of "if the cylinder pressure during the process of the first main fuel injection never reaches the cylinder pressure upper limit threshold value, then the cylinder pressure during the process of the first main fuel injection reaches the cylinder pressure upper limit threshold value at least at some points in time, and the crank angle corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value does not exceed the first angle, and the rotational angle of the crankshaft is not less than the second preset angle during the period when the cylinder pressure rises from the first cylinder pressure to the cylinder pressure upper limit threshold value. Until then, at least one of the start time, end time, and current first injection pressure of the first main fuel injection is repeatedly adjusted" is as follows.

[0034] S10: In the process of the first main fuel injection, collect the cylinder pressure P in the cylinder in real time and collect the angle of the crankshaft in real time.

[0035] S20: Compare the cylinder pressure P with the upper limit threshold value P of the cylinder pressure max and determine whether the angle of the crankshaft exceeds the first angle.

[0036] If the cylinder pressure P is smaller than the upper limit threshold value P of the cylinder pressure max and the angle of the crankshaft is located after the first angle, execute S30.

[0037] S30: Increase the value of the first injection pressure P1 and / or make the difference between the second time t 2 and the first time t 1 as a whole smaller, and repeat S10.

[0038] By steps S10 to S30, after a limited number of piston movement cycles, when the angle of the crankshaft has not yet reached the first angle, ensure that the cylinder pressure can be equal to or higher than the upper limit threshold value P of the cylinder pressure max and further increase the combustion speed in the middle and late stages of combustion and the air utilization rate in the cylinder. As shown in Figure 2, in this embodiment, by setting the first angle as AI50, the control method of the combustion system can effectively shorten the time of AI50~AI90 and control the combustion speed to be stable at P during the period of AI50~AI90. max For the specific value of P max it can be set according to actual requirements.

[0039] Also, the method of increasing the value of the first injection pressure P 1 and / or making the difference between the second time t 2 and the first time t 1 as a whole smaller may be as follows.

[0040] The maximum value P of the cylinder pressure in the process of the first main fuel injection x is obtained.

[0041] n = (P max - P x ) / P max is calculated.

[0042] If n ≤ 5%, only the value of the first injection pressure P1 is increased to the first set value.

[0043] As can be understood, from all the collected cylinder pressure values during the movement cycle of the piston, the maximum value P of the cylinder pressure in the process of the first main fuel injection x can be obtained, and P max > P x is the case. Taking the example of increasing the value of the first injection pressure P 1 to the first set value, its meaning is to add the first set value to the first injection pressure P 1 during the current reciprocating up and down movement cycle of the piston to obtain a new first injection pressure P 1 and apply it to the next piston movement cycle.

[0044] If n > 5%, the value of the first injection pressure P 1 is increased to the first set value, and at the same time, the first time t 1 and / or the second time t 2 is adjusted so that the difference between the second time t 2 and the first time t 1 is reduced to the second set value as a whole.

[0045] Since the magnitude of the first injection pressure P 1 cannot increase infinitely, when n ≤ 5%, at this time, the difference between P max and the maximum value P of the cylinder pressure in the process of the first main fuel injection x is small, and by directly adjusting the first injection pressure P 1 , the injection speed of the oil jet is improved, and further, the mixing degree of oil and gas and the flow field in the cylinder are improved, and the cylinder pressure P in the cylinder, and the cylinder pressure P where P maxThe crankshaft angle can be adjusted when n>5%, P max and the maximum cylinder pressure P during the first main fuel injection x The difference between the first injection pressure and the second injection pressure is large. 1 At the same time, the second time t 2 and the first time t 1 It is necessary to adjust the difference between the cylinder pressure P and the cylinder pressure P. Similarly, the improvement of the injection speed of the oil jet, the cylinder pressure P in the cylinder, and the cylinder pressure P are P max The magnitude of the first set value and the second set value can be set as necessary, and the second time t 2 and the first time t 1 If necessary, adjust the difference between the second time t 2 or the first time t 1 It is also possible to adjust only the

[0046] In this embodiment, a method for adjusting the duration and the first injection pressure of the first main fuel injection based on experience is provided as an example, but in other embodiments, they can also be adjusted based on a model.

[0047] In addition, in S20, the cylinder pressure P is equal to or lower than the cylinder pressure upper limit threshold P max If the above is true and the crankshaft angle is before the first angle, the following steps may be included after S20.

[0048] S40: Cylinder pressure P is equal to the cylinder pressure upper limit threshold P max The real-time cylinder volume V in the cylinder is obtained when the volume becomes equal to

[0049] Specifically, obtaining the real-time volume in the cylinder is a conventional technique. For example, a combustion analysis device can be used to collect the cylinder pressure curve of each cycle of a diesel engine, and then the real-time volume in the cylinder can be obtained. The obtained real-time cylinder volume V is obtained when the cylinder pressure first reaches P during the first main fuel injection process. maxIt is the cylinder volume V when reaching

[0050] S50: According to the relationship map between the cylinder volume and the crank angle, obtain the crank angle φ when the cylinder volume becomes equal to the real-time cylinder volume V during the upward movement of the cylinder a and the crank angle φ during the downward movement of the cylinder b Obtain.

[0051] As can be understood, as the piston moves up and down, the volume in the cylinder first decreases and then increases, so that it corresponds to the same real-time volume, and the positions of the crank angle during the upward movement of the piston and the crank angle during the downward movement of the piston correspond. As shown in Figure 3, in this embodiment, the magnitude of the first cylinder pressure P corresponding to the crank angle φ during the upward movement of the cylinder is P a Equal to, and when the cylinder moves down, when the crank angle is φ 0 At this time, the cylinder pressure P is equal to the cylinder pressure upper limit threshold value P b Equal to. The relationship map between the cylinder volume and the crank angle can be obtained through a large number of initial experiments and can be stored in advance in the controller. max

[0052] S60: Calculate φ 1 = φ b - φ a Calculate.

[0053] S70: Determine the magnitude of φ 1 , the second preset angle φ n .

[0054] If φ 1 < φ n , execute S80.

[0055] S80: Increase the numerical value of the first injection pressure P 1 to the third set value, and / or adjust the first time t 1 and / or the second time t 2 so that the second time t 2 and the first time t 1 ​The difference from [the other value] is made smaller than the fourth set value as a whole, and step S10 is repeated.

[0056] Steps S40 to S80 can achieve closed-loop adjustment of the rotational angle of the crankshaft during the period when the cylinder pressure rises from the first cylinder pressure to the cylinder pressure upper limit threshold value. After a finite number of piston movement cycles, φ 1 The numerical value of n is guaranteed to be φ n or more, and furthermore, the economy of the entrainment superposition effect of the dual main injection can be guaranteed to be optimal. φ

[0057] Also, let the second injection pressure be P 2 and φ 1 ≧φ n In the case of, "By repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure, during the process of the second main fuel injection, when the cylinder pressure drops from the cylinder pressure upper limit threshold value to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each time point is within the set slope change rate range, and moreover, the rotational angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold value to the set cylinder pressure is the first preset angle or more" in S200 may specifically include the following steps located after S80.

[0058] S90: Obtain the crank angle φ n when the cylinder pressure P becomes equal to P c according to the map, φ c >φ b and P n is the set cylinder pressure and P max >P n is.

[0059] As can be understood, since φ c >φ b , the corresponding crank angle is φ b ~φ cThe cylinder pressure P during is at least P n or more, and it can be recognized that the cylinder pressure is within the peak fluctuation. P n For the value of, it can be provided as needed.

[0060] S100: Crank angle φ b From crank angle φ c To obtain the relationship curve y between the cylinder pressure and the crank angle in the section up to. Specifically, in the relationship curve y between the cylinder pressure and the crank angle, the independent variable is the crank angle and the dependent variable is the cylinder pressure.

[0061] S110: k 1 = dy / dφ, k 2 = dk 1 / dφ is calculated, and the value of φ is φ b ~φ c is.

[0062] k 1 Is the slope of curve y, k 2 Is the rate of change of the curve slope.

[0063] S120: k 2 The maximum value k of the absolute value of max Is obtained.

[0064] k 2 The maximum value of the absolute value of means the numerical value with the largest absolute value among the minimum negative value and the maximum positive value of k within the value range of φ which is φ b ~φ c Inside, k 2 Means the numerical value with the largest absolute value among the minimum negative value and the maximum positive value of.

[0065] S130: k max , Compare the magnitude of the preset parameter k a .

[0066] k max < k a If so, execute S140.

[0067] S140: Second injection pressure P 2Increase the value of

[0068] k a by the fifth set value and repeat step S10. The specific magnitude of a k and the fifth set value can be provided as necessary. In this embodiment, the value of 2 k is 0.05, and the corresponding set slope change rate range is -0.05 to 0.05. When the minimum value of a k is a or more, the value of 2 k is 0.05 or more. As can be understood, by increasing the second injection pressure P 2 the injection rail pressure can be increased and the cylinder pressure can be maintained near a certain value. Steps S90 to S140 realize closed-loop adjustment of the change rate of the curve slope at each time point of the cylinder pressure change curve during the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure. After the process of a finite number of piston movement cycles, it can be ensured that the minimum value of a k is

[0069] or more, and furthermore, it can be ensured that the economy of the entrainment superposition effect of dual main injection is optimal. 3 k max ≧k a If so, the following steps located after step S130 may further be included.

[0070] S150: Calculate 2 φ = c φ - b . S160: Determine the magnitude of 2 φ, the first preset angle m φ. If 2 φ m < 2 φ, execute S170. If m φ ≧ S170: Increase the value of 3 the third time S180: Third hour t 3 Maintain the numerical value as it is.

[0071] Regarding the magnitude of the sixth set value and the second preset angle φ m The magnitude can be set as needed. Through steps S150 to S180, a closed-loop adjustment of the corresponding crankshaft rotation angle during the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure is realized. After the process of a finite number of piston reciprocating motions, the numerical value of φ 2 can be guaranteed to be φ m or more, and further, the sum of φ 1 + φ 2 can be guaranteed to be sufficiently large, so that the economy of the entrainment superposition effect of dual main injection is optimized.

[0072] Obviously, the above embodiments of the present invention are not limitations to the embodiments of the present invention, but merely examples given for clearly explaining the present invention. For those skilled in the art, based on the above description, various other different forms of changes and modifications can be made. Here, it is not necessary and impossible to list all the embodiments one by one. Various modifications, equivalent alternations, and improvements in line with the gist and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling a combustion system including a piston, an injector, and a cylinder, wherein the piston is reciprocally movable up and down within the cylinder, the injector sequentially executes at least a first main fuel injection and a second main fuel injection for each movement cycle of the piston, the injector continues fuel injection during the process from the first main fuel injection to the second main fuel injection, the injection pressure corresponding to the time when the fuel injection speed is the highest during the process of the injector executing the first main fuel injection is the first injection pressure, and the injection pressure corresponding to the time when the fuel injection speed is the highest during the process of the injector executing the second main fuel injection is the second injection pressure, executing the first main fuel injection by increasing the injection pressure of the injector from zero to the first injection pressure and then decreasing it from the first injection pressure to a specific injection pressure, and then executing the second main fuel injection by increasing the injection pressure of the injector from the specific injection pressure to the second injection pressure and then decreasing it from the second injection pressure to zero, the method for controlling the combustion system is a step of making it possible for the cylinder pressure at at least some points during the execution of the first main fuel injection to reach the cylinder pressure upper limit threshold value by specifying the duration and the first injection pressure of the first main fuel injection; a step of repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure so that during the execution of the second main fuel injection, during the period when the cylinder pressure decreases from the cylinder pressure upper limit threshold value to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each point is within the set slope change rate range, and the rotation angle of the crankshaft corresponding to the period when the cylinder pressure decreases from the cylinder pressure upper limit threshold value to the set cylinder pressure is not less than the first preset angle, characterized in that it is a method for controlling a combustion system.

2. The step of making it possible for the cylinder pressure at at least some points during the execution of the first main fuel injection to reach the cylinder pressure upper limit threshold value by specifying the duration and the first injection pressure of the first main fuel injection is If the cylinder pressure during the execution of the first main fuel injection never reaches the cylinder pressure upper limit threshold value, the cylinder pressure during the execution of the first main fuel injection reaches the cylinder pressure upper limit threshold value at least at some points in time, and the crank angle corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value does not exceed the first angle, and the rotational angle of the crankshaft is not less than the second preset angle during the period in which the cylinder pressure rises from the first cylinder pressure to the cylinder pressure upper limit threshold value, a step of repeatedly adjusting at least one of the start time, end time, and current first injection pressure of the first main fuel injection, wherein the cylinder volume corresponding to the time when the cylinder pressure becomes equal to the first cylinder pressure is the same as the cylinder volume corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value. The method for controlling a combustion system according to claim 1, characterized in that.

3. For each motion cycle of the piston, the time when the injector starts the first main fuel injection is the first time t １ , and the time when the speed of the fuel oil injected by the injector is the lowest between the first main fuel injection and the second main fuel injection is the second time t ２ , and the first injection pressure is P １ , and If the cylinder pressure during the execution of the first main fuel injection never reaches the cylinder pressure upper limit threshold value, the cylinder pressure during the execution of the first main fuel injection reaches the cylinder pressure upper limit threshold value at least at some points in time, and the crank angle corresponding to the time when the cylinder pressure first reaches the cylinder pressure upper limit threshold value does not exceed the first angle, and the rotational angle of the crankshaft is not less than the second preset angle during the period in which the cylinder pressure rises from the first cylinder pressure to the cylinder pressure upper limit threshold value, the step of repeatedly adjusting at least one of the start time, end time, and current first injection pressure of the first main fuel injection is In the process of executing the first main fuel injection, the cylinder pressure P in the cylinder is collected in real time, the angle of the crankshaft is collected in real time, and the cylinder pressure P is compared with the upper limit threshold value P of the cylinder pressure ｍａｘ and a step of determining whether or not the angle of the crankshaft exceeds the first angle When the cylinder pressure P is less than the cylinder pressure upper limit threshold value P ｍａｘ and the angle of the crankshaft is located after the first angle, the numerical value of the first injection pressure P １ is increased, and / or the difference between the second time t ２ and the first time t １ is generally reduced, including the step of The method for controlling a combustion system according to claim 2, characterized in that.

4. The numerical value of the first injection pressure P １ is increased, and / or the step of making the difference between the second time t ２ and the first time t １ as a whole smaller is The step of obtaining the maximum value P of the cylinder pressure in the process of executing the first main fuel injection ｘ and n = (P ｍａｘ - P ｘ ) / P ｍａｘ and a step of calculating When n ≤ 5%, only increasing the numerical value of the first injection pressure P １ to the first set value, and including The method for controlling a combustion system according to claim 3, characterized in that.

5. When n > 5%, increase the numerical value of the first injection pressure P １ to the first set value, and by adjusting the first time t １ and / or the second time t ２ , make the difference between the second time t ２ and the first time t １ as a whole smaller than the second set value. The method for controlling a combustion system according to claim 4, characterized in that.

6. When the cylinder pressure P is equal to or higher than the cylinder pressure upper limit threshold value P ｍａｘ and the angle of the crankshaft is positioned before the first angle, Obtain the real-time cylinder volume V in the cylinder when the cylinder pressure P equals the cylinder pressure upper limit threshold value P ｍａｘ and According to the relationship map between the cylinder volume and the crank angle, the crank angle φ when the cylinder is ascending corresponding to the time when the cylinder volume becomes equal to the real-time cylinder volume V ａ and the crank angle φ when the cylinder is descending ｂ are obtained, φ １ = φ ｂ - φ ａ is calculated, φ １ and the second preset angle φ ｎ to determine their magnitudes, φ １ <φ ｎ If it is, the numerical value of the first injection pressure P １ is increased to the third set value, and / or the first time t １ and / or the second time t ２ By adjusting, the difference between the second time t ２ and the first time t １ is made smaller as a whole by the fourth set value. The method for controlling a combustion system according to claim 3, characterized in that.

7. Let the second injection pressure be P ２ and by repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure, in the process of performing the second main fuel injection, during the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each time point is within the set slope change rate range, and moreover, the rotation angle of the crankshaft corresponding to the period when the cylinder pressure drops from the cylinder pressure upper limit threshold to the set cylinder pressure is not less than the first preset angle, the step is φ １ ≧φ ｎ In the case of The crank angle φ ｎ when the cylinder pressure P becomes equal to P ｃ is obtained according to the map, where φ ｃ > φ ｂ and P ｎ is the set cylinder pressure and P ｍａｘ > P ｎ and the step Crank angle φ ｂ to the crank angle φ ｃ step of obtaining the relationship curve y between the cylinder pressure and the crank angle of the section from k １ = dy / dφ, k ２ = dk １ / dφ is a step of calculating, where the value of φ is φ ｂ ~ φ ｃ and is a step k ２ The maximum value k of the absolute value of ｍａｘ obtaining step, and k ｍａｘ and a step of comparing the magnitude of the preset parameter k ａ and, k ｍａｘ <k ａ If so, a step of increasing the numerical value of the second injection pressure P ２ to be greater than the fifth set value, and the like, The method for controlling a combustion system according to claim 6, characterized in that.

8. Let the time when the injector ends the second main fuel injection be the third time t ３ and k ｍａｘ ≥ k ａ If so, the combustion system control method further comprises φ ２ = φ ｃ - φ ｂ a step of calculating φ ２ and the first preset angle φ ｍ and a step of determining the magnitude of φ ２ <φ ｍ If it is, the step of increasing the numerical value of the third hour t ３ by the sixth set value, and the like The method for controlling a combustion system according to claim 7, characterized in that.

9. φ ２ ≧φ ｍ If so, the value of the third hour t ３ is retained as it is. The method for controlling a combustion system according to claim 8, characterized in that.

10. A combustion system that implements the control method of the combustion system according to any one of claims 1 to 9, the combustion system including a piston, an injector, a cylinder, and a controller, the controller controlling the injector to sequentially execute at least a first main fuel injection and a second main fuel injection for each movement cycle of the piston, and further controlling the injector to continue fuel injection in the process from the first main fuel injection to the second main fuel injection, the controller executing the first main fuel injection by increasing the injection pressure of the injector from zero to the first injection pressure and then decreasing it from the first injection pressure to a specific injection pressure, and then executing the second main fuel injection by increasing the injection pressure of the injector from the specific injection pressure to the second injection pressure and then decreasing it from the second injection pressure to zero, the controller being capable of causing the cylinder pressure at at least some points in the process of executing the first main fuel injection to reach the cylinder pressure upper limit threshold value by specifying the duration and the first injection pressure of the first main fuel injection, the controller repeatedly adjusting at least one of the duration of the second main fuel injection and the second injection pressure, so that in the process of executing the second main fuel injection, during the period when the cylinder pressure decreases from the cylinder pressure upper limit threshold value to the set cylinder pressure, the change rate of the curve slope of the cylinder pressure change curve at each point is within the set slope change rate range, and further, the rotation angle of the crankshaft corresponding to the period when the cylinder pressure decreases from the cylinder pressure upper limit threshold value to the set cylinder pressure is not less than the first preset angle A combustion system characterized by the above.

11. Including the combustion system according to claim 10, A diesel engine characterized by the above.

Images