A starting control method, device and engine system for a piston reciprocating engine

Abstract

The present invention discloses a starting control method, device and engine system for a reciprocating piston engine. The reciprocating piston engine includes an air storage tank, a main starting valve, at least two sub-starting valves and at least two cylinders; each cylinder corresponds to a sub-starting valve; each cylinder is connected to the main air delivery passage of the air storage tank through a sub-air delivery passage; the main starting valve is arranged on the main air delivery passage, and each sub-starting valve is arranged on the sub-air delivery passage connected to its corresponding cylinder; each cylinder includes a piston, and each piston is connected to the engine crankshaft through a transmission mechanism; a pressure sensor is installed on the air delivery passage, and an angle sensor is installed on the engine crankshaft; the starting control method includes: controlling the main starting valve to open; repeatedly executing the starting process until the engine starting condition is reached; closing the main starting valve and each sub-starting valve, which can reduce the usage amount of compressed air, and thus can reduce the volume of equipment such as the air storage tank and reduce the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of starting control, and particularly to a starting control method, device and engine system for a piston reciprocating engine. Background Art

[0002] Large engines are started by compressed air, which is usually referred to as starting air. The current starting process of large engines is as follows: During the starting process, the main starting valve is opened, and the compressed air reaches in front of the starting valves of each cylinder. According to the ignition sequence, when the piston reaches the top dead center, the starting valves of each cylinder are opened in turn. The compressed air enters the combustion chamber through the starting valve and pushes the piston downward to accelerate the engine. When the piston approaches the bottom dead center, the starting valve is closed. This process is repeated until the engine reaches the expected minimum speed, and then the starting valve and the main starting valve are closed, and the engine is successfully started.

[0003] Currently, the opening and closing of the starting valve are both determined based on the crankshaft rotation angle position. However, as the starting process continues, the starting air pressure will continue to decrease, and the normal opening time of the exhaust valve is inconsistent with the time when the piston moves up and down in a normally operating engine. Closing the exhaust valve during the compression process will increase the compression back pressure, which has an adverse effect on increasing the speed. Summary of the Invention

[0004] The present invention provides a starting control method, device and engine system for a piston reciprocating engine to reduce the usage amount of compressed air, thereby reducing the volume of equipment such as air storage tanks and lowering costs.

[0005] According to one aspect of the present invention, there is provided a starting control method for a piston reciprocating engine. The piston reciprocating engine includes an air storage tank, a main starting valve, at least two sub-starting valves and at least two cylinders; each cylinder corresponds to a sub-starting valve; each cylinder is connected to the main air supply passage of the air storage tank through a sub-air supply passage; the main starting valve is arranged on the main air supply passage, and each sub-starting valve is arranged on the sub-air supply passage connected to its corresponding cylinder; each cylinder includes a piston, and each piston is connected to the engine crankshaft through a transmission mechanism; a pressure sensor is installed on the air supply passage, and an angle sensor is installed on the engine crankshaft. The angle sensor is used to measure the crankshaft rotation angle, and the pressure sensor is used to measure the working medium pressure in front of the sub-starting valve.

[0006] The starting control method includes:

[0007] Controlling the main starting valve to open;

[0008] Repeatedly executing the starting process until the engine starting condition is reached;

[0009] Closing the main starting valve and each sub-starting valve;

[0010] Among them, each starting process includes: when the crankshaft angle of the engine crankshaft reaches the starting angle of the corresponding cylinder, controlling the opening of the sub-starting valve corresponding to the cylinder, so that the starting air in the air storage tank enters the cylinder, causing the piston in the cylinder to move downward, driving the engine crankshaft to rotate; when the crankshaft angle of the engine crankshaft reaches the ending angle of the corresponding cylinder, controlling the closing of the sub-starting valve corresponding to the cylinder;

[0011] Among them: the starting angle is the first fixed value, and the ending angle is the crankshaft angle corresponding to the maximum value of the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; or, the ending angle is the second fixed value, and the starting angle is the crankshaft angle corresponding to the maximum value of the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston is determined according to the working volume of the cylinder, the transmission mechanism parameters, the crankshaft angle, the working medium pressure in front of the sub-starting valve, and the working medium volume in front of the sub-starting valve.

[0012] Furthermore, the transmission mechanism includes a crank and a connecting rod; the first end of the crank is connected to the crankshaft, and the second end is connected to the first end of the connecting rod; the second end of the connecting rod is connected to the piston;

[0013] The transmission mechanism parameters include the stroke ratio of the crank and the connecting rod.

[0014] Furthermore, determining the starting angle and the ending angle includes:

[0015] Determining the pressure change formula of the cylinder according to the first formula, the second formula and the third formula;

[0016] Determining the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle according to the pressure change formula of the cylinder;

[0017] When the starting angle is the first fixed value, determining the relationship between the ending angle and the work done by unit mass of compressed air on the crankshaft according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle, and determining the crankshaft angle corresponding to the maximum value of the work done by unit mass of compressed air on the crankshaft as the ending angle;

[0018] When the ending angle is the second fixed value, determining the relationship between the starting angle and the work done by unit mass of compressed air on the crankshaft according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle, and determining the crankshaft angle corresponding to the maximum value of the work done by unit mass of compressed air on the crankshaft as the starting angle;

[0019] Among them: the pressure change formula of the cylinder is:

[0020]

[0021] Among them, C vm is the molar specific heat capacity at constant volume, Cv is the specific heat capacity at constant volume, k is the adiabatic index, h s is the specific enthalpy of starting air, P is the in-cylinder pressure in real time in the cylinder, m is the mass of the working fluid in real time in the cylinder, V is the volume in real time in the cylinder, is the instantaneous value of the crankshaft angle;

[0022] The first formula is:

[0023]

[0024] m s is the mass of the starting air entering the cylinder, ω is the angular velocity of the engine's crankshaft, μ is the flow coefficient, F is the instantaneous geometric flow area, ψ is the flow function, p1 is the pressure of the working fluid before the sub-starting valve, v1 is the volume of the working fluid before the sub-starting valve;

[0025] The second formula is:

[0026]

[0027] The third formula is:

[0028]

[0029] V h is the working volume of the cylinder, λ s is the stroke ratio of the crank and the connecting rod.

[0030] Furthermore, a speed sensor is installed on the engine crankshaft, and the speed sensor is used to measure the acceleration of the crankshaft;

[0031] The engine starting condition includes: the acceleration of the engine crankshaft reaches the minimum starting acceleration.

[0032] Furthermore, an exhaust valve is correspondingly arranged for each cylinder;

[0033] Each starting process further includes:

[0034] After closing the sub-starting valve, during the upward movement of the piston, the exhaust valve is opened.

[0035] According to another aspect of the present invention, a starting control device for a reciprocating piston engine is provided. The reciprocating piston engine includes an air storage tank, a main starting valve, at least two sub-starting valves, and at least two cylinders; each cylinder corresponds to a sub-starting valve; each cylinder is connected to the main air supply passage of the air storage tank through a sub-air supply passage; the main starting valve is arranged on the main air supply passage, and each sub-starting valve is arranged on the sub-air supply passage connected to its corresponding cylinder; each cylinder includes a piston, and each piston is connected to the engine crankshaft through a transmission mechanism; a pressure sensor is installed on the air supply passage, and an angle sensor is installed on the engine crankshaft. The angle sensor is used to measure the crankshaft angle, and the pressure sensor is used to measure the working medium pressure in front of the sub-starting valve.

[0036] The starting control device includes:

[0037] A first control module for controlling the opening of the main starting valve;

[0038] A starting process execution module for repeatedly executing the starting process until the engine starting condition is reached;

[0039] A second control module for closing the main starting valve and each sub-starting valve;

[0040] Wherein, each starting process includes: when the crankshaft angle of the engine crankshaft reaches the starting angle of the corresponding cylinder, controlling the opening of the sub-starting valve corresponding to the cylinder, so that the starting air in the air storage tank enters the cylinder, causing the piston in the cylinder to move downward, driving the engine crankshaft to rotate; when the crankshaft angle of the engine crankshaft reaches the termination angle of the corresponding cylinder, controlling the closing of the sub-starting valve corresponding to the cylinder.

[0041] Wherein: the starting angle is a first fixed value, and the termination angle is the crankshaft angle corresponding to the maximum value of the work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston; or, the termination angle is a second fixed value, and the starting angle is the crankshaft angle corresponding to the maximum value of the work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston; the work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston is determined according to the working volume of the cylinder, the transmission mechanism parameters, the crankshaft angle, the working medium pressure in front of the sub-starting valve, the real-time working medium temperature in the cylinder, and the working medium volume in front of the sub-starting valve.

[0042] Further, the transmission mechanism includes a crank and a connecting rod; the first end of the crank is connected to the crankshaft, and the second end is connected to the first end of the connecting rod; the second end of the connecting rod is connected to the piston.

[0043] The transmission mechanism parameters include the stroke ratio of the crank and the connecting rod.

[0044] Further, a speed sensor is installed on the engine crankshaft, and the speed sensor is used to measure the acceleration of the crankshaft.

[0045] The engine starting conditions include: the acceleration of the engine crankshaft reaches the minimum starting acceleration.

[0046] Furthermore, an exhaust valve is correspondingly provided for each cylinder;

[0047] Each starting process further includes:

[0048] After closing the sub-starting valve, during the upward movement of the piston, the exhaust valve is opened.

[0049] According to another aspect of the present invention, a piston reciprocating engine system is provided, which includes a piston reciprocating engine and a piston reciprocating engine starting control device.

[0050] A piston reciprocating engine starting control method designed in the embodiments of the present invention includes two solutions, namely, keeping the starting angle of the starting valve open and determining the maximum work done by the unit mass of compressed air on the crankshaft during the downward movement of the piston by changing the ending angle; keeping the ending angle of the starting valve closed unchanged and determining the maximum work done by the unit mass of compressed air on the crankshaft during the downward movement of the piston by changing the starting angle of the starting valve. During each downward movement of the piston, it can ensure the use of the unit mass of compressed air that does the most work on the crankshaft, improving the utilization rate of the compressed air. Therefore, the amount of compressed air used is reduced, and further, the volume of the air storage tank can be reduced and the cost can be lowered.

[0051] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0053] Figure 1 is a flowchart of a piston reciprocating engine starting control method provided by an embodiment of the present invention;

[0054] Figure 2 is a schematic structural diagram of a transmission mechanism of an engine piston provided by an embodiment of the present invention;

[0055] Figure 3 is a relationship diagram between the torque acting on the engine crankshaft and the crankshaft angle during the downward movement of the piston in the cylinder provided by an embodiment of the present invention;

[0056] Figure 4 It is a schematic structural diagram of a starting control device for a piston reciprocating engine provided by an embodiment of the present invention. Detailed implementation manners

[0057] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0058] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0059] An embodiment of the present invention provides a starting control method for a piston reciprocating engine. The piston reciprocating engine includes an air storage tank, a main starting valve, at least two sub-starting valves and at least two cylinders; each cylinder corresponds to a sub-starting valve; each cylinder is connected to the main air supply passage of the air storage tank through a sub-air supply passage; the main starting valve is arranged on the main air supply passage, and each sub-starting valve is arranged on the sub-air supply passage connected to its corresponding cylinder; each cylinder includes a piston, and each piston is connected to the engine crankshaft through a transmission mechanism; a pressure sensor is installed on the sub-air supply passage, and an angle sensor is installed on the engine crankshaft. The angle sensor is used to measure the crankshaft rotation angle, and the pressure sensor is used to measure the working medium pressure in front of the sub-starting valve. Figure 1 It is a flowchart of a starting control method for a piston reciprocating engine provided by an embodiment of the present invention. Refer to Figure 1 , and the starting control method includes:

[0060] S110. Control the main starting valve to open.

[0061] Specifically, during the starting process of a reciprocating piston engine, the engine controller controls the main starting valve to open. Compressed air reaches in front of each sub-starting valve corresponding to each cylinder from the air storage tank (air bottle) via the main starting valve. According to the ignition sequence preset by the engine controller, the starting valves of each cylinder are opened in sequence. Among them, at least two sub-starting valves and at least two cylinders can be understood that the number of sub-starting valves and cylinders is two or more. The embodiments of the present invention do not limit this and can be set according to actual needs. The ignition sequence of each cylinder can be set according to the actual situation. Exemplarily, each cylinder can be ignited in sequence, each cylinder can be ignited in reverse order, and each cylinder can be ignited in a disordered order. The embodiments of the present invention do not limit this. Among them, the air pipeline can be a sub-air pipeline or a main air pipeline. Since the pressure in the air storage tank (air bottle) is not the same at the beginning of each starting process, it is necessary to detect in real time the pressure of the working medium in front of the valve when the starting air enters the sub-starting valve from the air storage tank (air bottle) through a pressure sensor. The models of the pressure sensor and the angle sensor can be selected according to the actual situation. The embodiments of the present invention do not limit this.

[0062] S120. Repeat the starting process until the engine starting condition is reached.

[0063] Among them, each starting process includes: when the crank angle of the engine crankshaft reaches the starting angle of the corresponding cylinder, controlling the sub-starting valve corresponding to the cylinder to open, so that the starting air in the air storage tank enters the cylinder, causing the piston in the cylinder to move downward and driving the engine crankshaft to rotate; when the crank angle of the engine crankshaft reaches the termination angle of the corresponding cylinder, controlling the sub-starting valve corresponding to the cylinder to close;

[0064] Among them: the starting angle is a first fixed value, and the termination angle is the crank angle corresponding to the maximum work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; or, the termination angle is a second fixed value, and the starting angle is the crank angle corresponding to the maximum work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston is determined according to the working volume of the cylinder, the parameters of the transmission mechanism, the crank angle, the pressure of the working medium in front of the sub-starting valve, and the volume of the working medium in front of the sub-starting valve. Among them, the working volume of the cylinder can be determined according to the parameters of the engine, the parameters of the transmission mechanism can be determined according to the parameters of the engine crank and connecting rod, the crank angle is determined by real-time detection through an angle sensor, the pressure of the working medium in front of the sub-starting valve, that is, the pressure of the working medium in front of the valve, can be determined by real-time detection through a pressure sensor, the real-time pressure in the cylinder can be calculated based on the starting air quality, the mass conservation equation, and the volume change rate of the cylinder, and the volume of the working medium in front of the sub-starting valve can be determined according to the structural parameters of the engine.

[0065] According to the starting air quality, the mass conservation equation, and the volume change rate of the cylinder, the relationship between the pressure in the cylinder and the crankshaft angle when the sub-starting valve opens can be deduced. Furthermore, the relationship or graph between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle can be obtained. Since the starting angle and the ending angle of the starting valve affect the work done on the crankshaft during the downward movement of the piston in the cylinder, therefore, the embodiments of the present invention design two solutions, namely, keeping the starting angle of the starting valve opening as a first fixed value, and determining the maximum value of the work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston by changing the ending angle; keeping the ending angle of the starting valve closing as a second fixed value, and determining the maximum value of the work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston by changing the starting angle of the starting valve opening.

[0066] Among them, the first fixed value and the second fixed value can be set according to the actual situation, and the embodiments of the present invention do not limit this.

[0067] S130. Close the main starting valve and each sub-starting valve.

[0068] Specifically, set the minimum crankshaft starting acceleration in the engine controller. When the acceleration of the engine crankshaft is the minimum crankshaft starting acceleration set in the engine controller, close the main starting valve and each sub-starting valve, and the starting process ends.

[0069] A piston reciprocating engine starting control method designed by the embodiments of the present invention includes two solutions, namely, keeping the starting angle of the starting valve opening, and determining the maximum value of the work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston by changing the ending angle; keeping the ending angle of the starting valve closing unchanged, and determining the maximum value of the work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston by changing the starting angle of the starting valve opening. During each downward movement of the piston, it can ensure that the compressed air per unit mass that does the most work on the crankshaft is used, improving the utilization rate of the compressed air. Therefore, the amount of compressed air used is reduced, and further, the volume of the air storage tank can be reduced and the cost can be lowered.

[0070] Figure 2 It is a schematic structural diagram of a transmission mechanism of an engine piston provided by the embodiments of the present invention. Optionally, refer to Figure 2 , the transmission mechanism includes a crank 1 and a connecting rod 2; the first end of the crank 1 is connected to the crankshaft 3, and the second end is connected to the first end of the connecting rod 2; the second end of the connecting rod 2 is connected to the piston 4; the transmission mechanism parameters include the stroke ratio of the crank 1 and the connecting rod 2.

[0071] Specifically, according to the length data of the crank 1 and the connecting rod 2 in the transmission mechanism, the included angle data between the connecting rod and the piston, and the included angle data between the crank and the crankshaft, etc., the stroke ratio of the crank 1 and the connecting rod 2 in the transmission mechanism parameters can be obtained through calculation.

[0072] Optionally, determining the starting rotation angle and the ending rotation angle includes:

[0073] Determining the pressure change formula of the cylinder according to the first formula, the second formula and the third formula;

[0074] Determining the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft rotation angle according to the pressure change formula of the cylinder;

[0075] When the starting rotation angle is a first fixed value, determining the relationship between the ending rotation angle and the work done by the compressed air per unit mass on the crankshaft according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft rotation angle, and determining the crankshaft rotation angle corresponding to the maximum value of the work done by the compressed air per unit mass on the crankshaft as the ending rotation angle;

[0076] When the ending rotation angle is a second fixed value, determining the relationship between the starting rotation angle and the work done by the compressed air per unit mass on the crankshaft according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft rotation angle, and determining the crankshaft rotation angle corresponding to the maximum value of the work done by the compressed air per unit mass on the crankshaft as the starting rotation angle;

[0077] Wherein: the pressure change formula of the cylinder is:

[0078]

[0079] Where C vm is the molar specific heat at constant volume, C v is the specific heat at constant volume, k is the adiabatic index, h s is the starting air specific enthalpy, P is the real-time in-cylinder pressure in the cylinder, m is the real-time working medium mass in the cylinder, V is the real-time volume in the cylinder, is the instantaneous value of the crankshaft rotation angle;

[0080] The first formula is:

[0081]

[0082] m s is the starting air mass entering the cylinder, ω is the crankshaft angular velocity of the engine, μ is the flow coefficient, F is the instantaneous geometric flow cross-sectional area, ψ is the flow function, p1 is the working medium pressure before the sub-starting valve, v1 is the working medium volume before the sub-starting valve;

[0083] The second formula is:

[0084]

[0085] The third formula is:

[0086]

[0087] V h is the working volume of the cylinder, and λ s is the stroke ratio of the crank and the connecting rod.

[0088] Specifically, determine the pressure change formula of the cylinder according to the first formula, the second formula and the third formula; determine the relationship diagram between the torque acting on the engine crankshaft and the crankshaft angle during the downward movement of the piston in the cylinder according to the pressure change formula of the cylinder. Figure 3 is the relationship diagram between the torque acting on the engine crankshaft and the crankshaft angle during the downward movement of the piston in the cylinder provided by the embodiment of the present invention. Refer to Figure 3 , the abscissa is the crankshaft angle, and the ordinate is the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder. Figure 3 The shaded area in is the starting angle when the starting valve opens and the ending angle

[0089] when it closes, the magnitude of the work done by the piston on the crankshaft during the downward movement. When the starting angle is the first fixed value, adjusting different ending angles can obtain different values of the work done on the crankshaft. The specific adjustment frequency can be determined according to the actual situation.

[0090] According to the starting angle and ending angle of the starting valve adjusted according to the work done by the piston in the cylinder on the crankshaft, and the formula for the starting air quality entering the cylinder at different crankshaft angles, the gas flow mass corresponding to the starting angle and ending angle of the starting valve at this moment can be obtained. Dividing the work done on the crankshaft by the gas flow mass can obtain the magnitude of the work done by the compressed air per unit mass corresponding to the starting angle and ending angle of the starting valve at this moment.

[0090] According to the starting angle and ending angle of the starting valve adjusted according to the work done by the piston in the cylinder on the crankshaft, and the formula for the starting air quality entering the cylinder at different crankshaft angles, the gas flow mass corresponding to the starting angle and ending angle of the starting valve at this moment can be obtained. Dividing the work done on the crankshaft by the gas flow mass can obtain the magnitude of the work done by the compressed air per unit mass corresponding to the starting angle and ending angle of the starting valve at this moment.

[0091] When the ending angle is the second fixed value, adjusting different starting angles can obtain different values of the work done on the crankshaft. The specific adjustment frequency can be determined according to the actual situation.

[0092] According to the starting angle and ending angle of the starting valve adjusted according to the work done by the piston in the cylinder on the crankshaft, and the formula for the starting air quality entering the cylinder at different crankshaft angles, the gas flow mass corresponding to the starting angle and ending angle of the starting valve at this moment can be obtained. Dividing the work done on the crankshaft by the gas flow mass can obtain the magnitude of the work done by the compressed air per unit mass corresponding to the starting angle and ending angle of the starting valve at this moment.

[0093] According to this method, each time the starting rotation angle is adjusted, the work done by the compressed air per unit mass can be obtained. After multiple measurements, the relationship curve between the work done by the compressed air per unit mass and the starting rotation angle can be obtained. According to the maximum value of the work done by the compressed air per unit mass, the corresponding starting rotation angle can be selected, thus reducing the amount of compressed air used.

[0094] Optionally, a speed sensor is installed on the engine crankshaft, and the speed sensor is used to measure the acceleration of the crankshaft.

[0095] The engine starting conditions include: the acceleration of the engine crankshaft reaches the minimum starting acceleration.

[0096] Among them, the minimum starting acceleration can be the minimum crankshaft starting acceleration corresponding to the engine crankshaft. Specifically, the instantaneous speed value detected by the speed sensor installed on the engine crankshaft is calculated and processed by the engine controller to obtain the instantaneous acceleration value. When the instantaneous acceleration value reaches the minimum starting acceleration, the main starting valve and each sub-starting valve are closed, and the starting process ends. After the engine main starting valve is closed and before fuel injection starts, due to inertia, the engine speed will further increase. When the acceleration of the engine crankshaft reaches the set acceleration, the engine starting ends. The crankshaft speed of the engine can be stabilized before the minimum speed of engine starting. Driven by inertia, the crankshaft speed of the engine reaches the minimum speed of engine starting, which can reduce the amount of compressed air used, and thus can reduce the volume of equipment such as air storage tanks and lower the cost.

[0097] Optionally, each cylinder is also correspondingly provided with an exhaust valve.

[0098] Each starting process further includes:

[0099] After closing the sub-starting valve, during the upward movement of the piston, the exhaust valve is opened.

[0100] Specifically, after closing the sub-starting valve, during the upward movement of the piston, opening the exhaust valve can reduce the negative impact brought by the increase in the engine crankshaft speed. Exemplarily, during the upward movement of the piston, if the exhaust valve is closed, as the piston moves upward, during the process of compressing the gas in the combustion chamber, the reaction force of the combustion chamber wall on the piston will become larger and larger. Therefore, during the upward movement of the piston, opening the exhaust valve can reduce the reaction force of the combustion chamber wall on the piston, indirectly reducing the amount of compressed air used, and thus can reduce the volume of equipment such as air storage tanks and lower the cost.

[0101] Figure 4FIG. 0 is a schematic structural diagram of a starting control device for a piston reciprocating engine provided by an embodiment of the present invention. The piston reciprocating engine includes an air storage tank, a main starting valve, at least two sub-starting valves, and at least two cylinders; each cylinder corresponds to a sub-starting valve; each cylinder is connected to the main air supply passage of the air storage tank through a sub-air supply passage; the main starting valve is arranged on the main air supply passage, and each sub-starting valve is arranged on the sub-air supply passage connected to its corresponding cylinder; each cylinder includes a piston, and each piston is connected to the engine crankshaft through a transmission mechanism; a pressure sensor is installed on the sub-air supply passage, and an angle sensor is installed on the engine crankshaft. The angle sensor is used to measure the crankshaft angle, and the pressure sensor is used to measure the working medium pressure in front of the sub-starting valve; as Figure 4 shown, the starting control device 200 for the piston reciprocating engine includes:

[0102] A first control module 210, configured to control the opening of the main starting valve;

[0103] A starting process execution module 220, configured to repeatedly execute the starting process until the engine starting condition is reached;

[0104] A second control module 230, configured to close the main starting valve and each sub-starting valve;

[0105] Wherein, each starting process includes: when the crankshaft angle of the engine crankshaft reaches the starting angle of the corresponding cylinder, controlling the opening of the sub-starting valve corresponding to the cylinder, so that the starting air in the air storage tank enters the cylinder, causing the piston in the cylinder to move downward, driving the engine crankshaft to rotate; when the crankshaft angle of the engine crankshaft reaches the termination angle corresponding to the cylinder, controlling the closing of the sub-starting valve corresponding to the cylinder;

[0106] Wherein: the starting angle is a first fixed value,

[0107] The termination angle is the crankshaft angle corresponding to the maximum work done by the unit mass of compressed air on the crankshaft during the downward movement of the piston; or, the termination angle is a second fixed value, and the starting angle is the crankshaft angle corresponding to the maximum work done by the unit mass of compressed air on the crankshaft during the downward movement of the piston; the work done by the unit mass of compressed air on the crankshaft during the downward movement of the piston is determined according to the working volume of the cylinder, the transmission mechanism parameters, the crankshaft angle, the working medium pressure in front of the sub-starting valve, and the working medium volume in front of the sub-starting valve.

[0108] Further, the transmission mechanism includes a crank and a connecting rod; the first end of the crank is connected to the crankshaft, and the second end is connected to the first end of the connecting rod; the second end of the connecting rod is connected to the piston;

[0109] The transmission mechanism parameters include the stroke ratio of the crank and the connecting rod.

[0110] Further, the starting control device 200 for the piston reciprocating engine further includes:

[0111] The corner determination module is used to determine the starting corner and the ending corner:

[0112] Determine the pressure change formula of the cylinder according to the first formula, the second formula and the third formula;

[0113] Determine the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle according to the pressure change formula of the cylinder;

[0114] When the starting corner is the first fixed value, determine the relationship between the ending corner and the work done by the compressed air per unit mass on the crankshaft according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle, and determine the crankshaft angle corresponding to the maximum value of the work done by the compressed air per unit mass on the crankshaft as the ending corner;

[0115] When the ending corner is the second fixed value, determine the relationship between the starting corner and the work done by the compressed air per unit mass on the crankshaft according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle, and determine the crankshaft angle corresponding to the maximum value of the work done by the compressed air per unit mass on the crankshaft as the starting corner;

[0116] Among them: The pressure change formula of the cylinder is:

[0117]

[0118] Among them, C vm is the molar specific heat capacity at constant volume, C v is the specific heat capacity at constant volume, k is the adiabatic index, h s is the specific enthalpy of starting air, P is the real-time in-cylinder pressure in the cylinder, m is the real-time mass of the working fluid in the cylinder, V is the real-time volume in the cylinder, is the instantaneous value of the crankshaft angle;

[0119] The first formula is:

[0120]

[0121] m s is the mass of the starting air entering the cylinder, ω is the crankshaft angular velocity of the engine, μ is the flow coefficient, F is the instantaneous geometric flow area, ψ is the flow function, p1 is the working fluid pressure before the sub-starting valve, and v1 is the working fluid volume before the sub-starting valve;

[0122] The second formula is:

[0123]

[0124] The third formula is:

[0125]

[0126] Vh is the working volume of the cylinder, and λ s is the stroke ratio of the crank and the connecting rod.

[0127] Furthermore, a speed sensor is installed on the engine crankshaft, and the speed sensor is used to measure the acceleration of the crankshaft;

[0128] The engine starting conditions include: the acceleration of the engine crankshaft corresponding to each cylinder reaches the minimum starting acceleration.

[0129] Furthermore, an exhaust valve is correspondingly arranged for each cylinder. Specifically, the starting process execution module 220 is used for:

[0130] After closing the sub-starting valve, during the upward movement of the piston, open the exhaust valve.

[0131] The piston reciprocating engine starting control device provided by the embodiment of the present invention can execute the piston reciprocating engine starting control method provided by any embodiment of the present invention, and has the corresponding functional modules and beneficial effects for executing the method.

[0132] The embodiment of the present invention also provides a piston reciprocating engine system, which includes a piston reciprocating engine and the piston reciprocating engine starting control device described in the above embodiment.

[0133] A piston reciprocating engine system provided by the embodiment of the present invention includes two solutions, namely, keeping the starting angle of the starting valve open and determining the maximum work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston by changing the ending angle; keeping the ending angle of the starting valve closed unchanged and determining the maximum work done by the compressed air per unit mass on the crankshaft during the downward movement of the piston by changing the starting angle of the starting valve open, reducing the amount of compressed air used, and thus reducing the volume of the air storage tank and lowering the cost.

[0134] It should be understood that various forms of the processes shown above can be used, reordering, adding, or deleting steps. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitations are imposed herein.

[0135] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A starting control method for a reciprocating piston engine, characterized in that: The reciprocating piston engine includes an air storage tank, a main starting valve, at least two sub-starting valves and at least two cylinders; each of the cylinders corresponds to one of the sub-starting valves; each of the cylinders is connected to the main air supply passage of the air storage tank through a sub-air supply passage; the main starting valve is arranged on the main air supply passage, and each of the sub-starting valves is arranged on the sub-air supply passage connected to its corresponding cylinder; each of the cylinders includes a piston, and each of the pistons is connected to the engine crankshaft through a transmission mechanism; a pressure sensor is installed on the air supply passage, and an angle sensor is installed on the engine crankshaft. The angle sensor is used to measure the crankshaft angle, and the pressure sensor is used to measure the working medium pressure in front of the sub-starting valve. The starting control method includes: Controlling the opening of the main starting valve; Repeatedly executing the starting process until the engine starting condition is reached; Closing the main starting valve and each of the sub-starting valves; Wherein, each of the starting processes includes: when the crankshaft angle of the engine crankshaft reaches the starting angle of the corresponding cylinder, controlling the opening of the sub-starting valve corresponding to the cylinder, so that the starting air in the air storage tank enters the cylinder, causing the piston in the cylinder to move downward and driving the engine crankshaft to rotate; when the crankshaft angle of the engine crankshaft reaches the termination angle corresponding to the cylinder, controlling the closing of the sub-starting valve corresponding to the cylinder. Wherein: the starting angle is a first fixed value, and the termination angle is the crankshaft angle corresponding to the maximum work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; or, the termination angle is a second fixed value, and the starting angle is the crankshaft angle corresponding to the maximum work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston is determined according to the working volume of the cylinder, the parameters of the transmission mechanism, the crankshaft angle, the working medium pressure in front of the sub-starting valve, and the volume of the working medium in front of the sub-starting valve.

2. The method according to claim 1, characterized in that: The transmission mechanism includes a crank and a connecting rod; the first end of the crank is connected to the crankshaft, and the second end is connected to the first end of the connecting rod; the second end of the connecting rod is connected to the piston. The parameters of the transmission mechanism include the stroke ratio of the crank and the connecting rod.

3. The method according to claim 2, wherein Determining the starting angle and the termination angle includes: Determining the pressure change formula of the cylinder according to the first formula, the second formula and the third formula; Determining the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle according to the pressure change formula of the cylinder; When the starting angle is a first fixed value, determining the relationship between the termination angle and the work done by unit mass of compressed air on the crankshaft according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft angle, and determining the crankshaft angle corresponding to the maximum work done by unit mass of compressed air on the crankshaft as the termination angle; When the termination rotation angle is the second fixed value, the relationship between the starting rotation angle and the work done by unit mass of compressed air on the crankshaft is determined according to the relationship between the torque acting on the engine crankshaft during the downward movement of the piston in the cylinder and the crankshaft rotation angle, and the crankshaft rotation angle corresponding to the maximum value of the work done by unit mass of compressed air on the crankshaft is determined as the starting rotation angle; Wherein: the pressure change formula of the cylinder is: Among them, C vm is the molar heat capacity at constant volume, C v is the specific heat capacity at constant volume, k is the adiabatic index, h s is the specific enthalpy of starting air, P is the in-cylinder pressure in real time in the cylinder, m is the mass of the working fluid in real time in the cylinder, V is the volume in real time in the cylinder, is the instantaneous value of the crankshaft angle; The first formula is: m s where \(m\) is the starting air mass entering the cylinder, \(\omega\) is the angular velocity of the engine's crankshaft, \(\mu\) is the flow coefficient, \(F\) is the instantaneous geometric flow cross-sectional area, \(\psi\) is the flow function, \(p_1\) is the working medium pressure in front of the sub-starting valve, and \(v_1\) is the working medium volume in front of the sub-starting valve; The second formula is: The third formula is: V h is the working volume of the cylinder, and λ s is the stroke ratio of the crank and the connecting rod.

4. The method according to claim 1, characterized in that: A speed sensor is installed on the engine crankshaft, and the speed sensor is used to measure the acceleration of the crankshaft; The engine starting condition includes: the acceleration of the engine crankshaft reaches the minimum starting acceleration.

5. The method according to claim 1, characterized in that, Each of the cylinders is also correspondingly provided with an exhaust valve; Each of the starting processes further includes: After closing the sub-starting valve, during the upward movement of the piston, the exhaust valve is opened.

6. A piston reciprocating engine starting control device, characterized in that: The piston reciprocating engine includes an air storage tank, a main starting valve, at least two sub-starting valves and at least two cylinders; each of the cylinders corresponds to one of the sub-starting valves; each of the cylinders is connected to the main air supply passage of the air storage tank through a sub-air supply passage; the main starting valve is arranged on the main air supply passage, and each of the sub-starting valves is arranged on the sub-air supply passage connected to its corresponding cylinder; each of the cylinders includes a piston, and each of the pistons is connected to the engine crankshaft through a transmission mechanism; a pressure sensor is installed on the air supply passage, and an angle sensor is installed on the engine crankshaft, and the angle sensor is used to measure the crankshaft rotation angle, and the pressure sensor is used to measure the working medium pressure in front of the sub-starting valve; The starting control device includes: A first control module, used to control the opening of the main starting valve; A starting process execution module, used to repeatedly execute the starting process until the engine starting condition is reached; A second control module, used to close the main starting valve and each of the sub-starting valves; Wherein, each of the starting processes includes: when the crankshaft rotation angle of the engine crankshaft reaches the starting rotation angle of the corresponding cylinder, controlling the sub-starting valve corresponding to the cylinder to open, so that the starting air in the air storage tank enters the cylinder, causing the piston in the cylinder to move downward and driving the engine crankshaft to rotate; when the crankshaft rotation angle of the engine crankshaft reaches the termination rotation angle corresponding to the cylinder, controlling the sub-starting valve corresponding to the cylinder to close; Wherein: the starting rotation angle is the first fixed value, and the termination rotation angle is the crankshaft rotation angle corresponding to the maximum value of the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; or, the termination rotation angle is the second fixed value, and the starting rotation angle is the crankshaft rotation angle corresponding to the maximum value of the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston; the work done by unit mass of compressed air on the crankshaft during the downward movement of the piston is determined according to the working volume of the cylinder, the parameters of the transmission mechanism, the crankshaft rotation angle, the working medium pressure in front of the sub-starting valve, and the working medium volume in front of the sub-starting valve.

7. The device according to claim 6, characterized in that: The transmission mechanism includes a crank and a connecting rod; a first end of the crank is connected to the crankshaft, and a second end of the crank is connected to a first end of the connecting rod; a second end of the connecting rod is connected to the piston; The parameters of the transmission mechanism include the stroke ratio of the crank and the connecting rod.

8. The device according to claim 6, wherein: A speed sensor is installed on the engine crankshaft, and the speed sensor is used to measure the acceleration of the crankshaft; The engine starting conditions include: the acceleration of the engine crankshaft reaches the minimum starting acceleration.

9. The device according to claim 6, characterized in that An exhaust valve is correspondingly arranged for each cylinder; Each of the starting processes further includes: After closing the sub-starting valve, during the upward movement of the piston, the exhaust valve is opened.

10. A piston reciprocating engine system, characterized in that, It includes a piston reciprocating engine and the piston reciprocating engine starting control device according to any one of claims 6-9.

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