Eight-cylinder four-stroke turbocharged diesel engine MPC exhaust system

Abstract

The invention discloses an MPC exhaust system for an eight-cylinder four-stroke turbocharged diesel engine, comprising an exhaust pipe composed of several standard MPC devices, a reverse MPC device and an exhaust pressure fluctuation buffer, wherein one end of the exhaust pipe is connected to the turbocharger input port. One end of the reverse MPC device is closed, the inclination direction of the upper end of the ejector pipe of the reverse MPC device is opposite to the inclination direction of the ejector pipe of the standard MPC device, the lower end of the ejector pipe of the reverse MPC device is connected to the exhaust port of the first cylinder, the other end of the port is connected to one end of the exhaust pressure fluctuation buffer through a first reducer and an expansion joint in sequence, and the other end of the exhaust pressure fluctuation buffer is connected to one end of the standard MPC device at the upper end of the second cylinder through a second reducer and an expansion joint in sequence. The invention can reduce the influence of the exhaust pressure fluctuation between the two cylinders at the exhaust end of the eight-cylinder four-stroke turbocharged diesel engine on the scavenging, and avoid the phenomenon of excessive exhaust temperature caused by poor scavenging.

Description

Technical Field

[0001] The invention relates to a diesel engine exhaust system, in particular to an MPC (modular pulse converter) system suitable for an eight-cylinder four-stroke turbocharged diesel engine, belonging to the technical field of internal combustion engines. Background Art

[0002] The MPC system is widely used in eight-cylinder four-stroke turbocharged diesel engines. Its turbocharger has high efficiency, can utilize exhaust pulse energy, has large scavenging (both the cylinder's intake and exhaust valves are open), simple structure, and good low-operating performance. However, when the MPC system is actually used, it is found that the scavenging process of one of the two cylinders near the lower side of the closed end of the exhaust pipe of the eight-cylinder four-stroke turbocharged diesel engine is always disturbed, and the exhaust temperature is high, even exceeding the allowable value, which seriously affects the normal operation of the eight-cylinder four-stroke turbocharged diesel engine.

[0003] The main reason for uneven scavenging in the application of the MPC system of an eight-cylinder four-stroke turbocharged diesel engine is that the firing interval of each cylinder is 90°CA (crankshaft angle), and the exhaust of the firing cylinder one cylinder away just precedes the scavenging of the firing cylinder 180°CA, resulting in scavenging interference. The design of the cylinder firing sequence of an in-line eight-cylinder four-stroke turbocharged diesel engine mainly depends on the crank arrangement considering the crankshaft balance. Figure 1 As viewed from the end face of the crankshaft 30, the eight cranks 101 are in the same phase in groups of two, and the phase difference between two adjacent groups of cranks 301 is 90°. Figure 1 As shown in (a), (b) and (c), the eight cranks 301 corresponding to the first cylinder to the eighth cylinder are 1# to 8# respectively. Two cranks 301 of the same phase form a group, that is, 1# and 8#, 2# and 7#, 3# and 6#, 4# and 5# are each a group.

[0004] by Figure 1 Take (a) as an example, where the 2# and 7# cranks 301 are both at a phase angle of 0°, the 1# and 8# cranks 301 are both at a phase angle of 90°, the 4# and 5# cranks 301 are both at a phase angle of 180°, and the 3# and 6# cranks 301 are both at a phase angle of 270°. The fifth to eighth cylinders are downstream cylinders close to the turbocharger 10, and the exhaust flow rate is greater than that of the upstream cylinders far from the turbocharger 30, i.e., the 1st to 4th cylinders, and they are far away from the closed end of the upstream exhaust pipe. Therefore, the scavenging of these cylinders is less affected by the exhaust pressure fluctuations of the adjacent cylinders. Based on the above Figure 1 The crank phase arrangement in the common eight-cylinder four-stroke turbocharged diesel engine cylinder firing sequence is shown in Table 1 below.

[0005] Table 1. Common firing sequences for in-line eight-cylinder four-stroke turbocharged diesel engines

[0006] Serial number Firing order Serial number Firing order 1 1-4-2-6-8-5-7-3-1 6 1-6-2-4-8-3-7-5-1 2 1-3-7-5-8-6-2-4-1 7 1-3-2-4-8-6-7-5-1 3 1-6-7-4-8-3-2-5-1 8 1-6-2-5-8-3-7-4-1 4 1-5-2-3-8-4-7-6-1 9 1-3-2-5-8-6-7-4-1 5 1-5-7-3-8-4-2-6-1 10 1-4-7-6-8-5-2-3-1

[0007] Taking the ignition sequence of the cylinder No. 1 in Table 1 as an example, 180°CA after the exhaust of the first cylinder begins, the exhaust of the second cylinder coincides with the exhaust of the second cylinder during scavenging, and the pressure wave of the second cylinder interferes with the scavenging of the first cylinder. This causes poor scavenging of the first cylinder, resulting in the exhaust temperature of the first cylinder being about 50°C higher than that of other cylinders. Another example is the ignition sequence of No. 2, 180°CA after the exhaust of the second cylinder begins, the exhaust of the first cylinder coincides with the exhaust of the first cylinder during scavenging, and the scavenging stage of the second cylinder is disturbed by the exhaust pressure fluctuation of the first cylinder. In addition, the first cylinder is located in the upstream cylinder far away from the turbocharger and is the closed end of the exhaust pipe, which makes the pressure fluctuation greater and has a greater impact on the scavenging of the second cylinder, resulting in the exhaust temperature of the second cylinder being about 70 to 90°C higher than that of other cylinders. It can be seen that the scavenging of the first cylinder or the second cylinder is affected by the interference of the exhaust of the adjacent cylinders, resulting in excessively high exhaust temperature. In the long run, it seriously affects the normal operation of the eight-cylinder four-stroke turbocharged diesel engine. Summary of the invention

[0008] The purpose of the present invention is to provide an eight-cylinder four-stroke turbocharged diesel engine MPC exhaust system which has a simple structure, is easy to manufacture and can be easily arranged.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] An eight-cylinder four-stroke turbocharged diesel engine MPC exhaust system, comprising an exhaust pipe composed of several standard MPC devices connected in sequence through expansion joints, a reverse MPC device and an exhaust pressure fluctuation buffer, wherein the standard MPC device comprises a round pipe and an ejector pipe, wherein the vertical lower end of the ejector pipe is respectively connected to the exhaust port of the eighth cylinder to the exhaust port of the second cylinder arranged in descending order, the upper end of the ejector pipe is inclined toward the turbocharger direction and the pipe diameter is gradually contracted to form a nozzle, and the upper end of the nozzle is obliquely connected to the middle of the round pipe; the standard MPC device at the upper end of the exhaust port of the eighth cylinder at the end of the exhaust pipe One end of the circular tube of the reverse MPC device is connected to the turbocharger input port through an expansion joint; one end of the circular tube of the reverse MPC device is closed, the inclination direction of the upper end of the ejector tube of the reverse MPC device is opposite to the inclination direction of the ejector tube of the standard MPC device, the vertical lower end tube of the ejector tube of the reverse MPC device is connected to the exhaust port of the first cylinder, the other end of the circular tube of the reverse MPC device is connected to one end of the exhaust pressure fluctuation buffer through a first reducer and an expansion joint in sequence, and the other end of the exhaust pressure fluctuation buffer is connected to one end of the circular tube of the standard MPC device at the upper end of the second cylinder through a second reducer and an expansion joint in sequence.

[0011] The purpose of the present invention can be further achieved by the following technical measures.

[0012] Furthermore, the exhaust pressure fluctuation buffer is in an inverted asymmetric U-shape, and the length L1 of one end of the exhaust pressure fluctuation buffer is greater than the length L2 of the other end of the exhaust pressure fluctuation buffer; the diameter Φd2 of the circular tube of the reverse MPC device is equal to the diameter Φd1 of the circular tube of the standard MPC device.

[0013] Furthermore, the relationship between the tube diameter ΦD of the exhaust pressure fluctuation buffer and the circular tube diameter Φd1 of the standard MPC device, or the circular tube diameter Φd2 of the reverse MPC device is: ΦD=1.5Φd1=1.5Φd2; the relationship between the length L1 of one end of the exhaust pressure fluctuation buffer and the cylinder center distance L5 is: L1=2L5.

[0014] Furthermore, the reverse inclination angle of the ejector tube at the upper end of the reverse MPC device is 20°≤α≤25°.

[0015] An eight-cylinder four-stroke turbocharged diesel engine MPC exhaust system comprises an exhaust pipe consisting of several standard MPC devices connected in sequence via expansion joints, a terminal MPC device and a second exhaust pipe, wherein one end of the round tube of the standard MPC device at the upper end of the exhaust port of the eighth cylinder at the end of the exhaust pipe is connected to an input port of a turbocharger via an expansion joint; one end of the round tube of the standard MPC device on the upper side of the second cylinder is closed, and the terminal MPC device is the same as the standard MPC device except that the vertical tube length L3 of the terminal MPC device is greater than the vertical lower end tube length L4 of the ejector tube of the standard MPC device; one end of the round tube of the terminal MPC device is closed, and the other end of the round tube of the terminal MPC device is connected to one end of the second exhaust pipe via an expansion joint, and the other end of the second exhaust pipe is connected to another input port of the turbocharger via an expansion joint, and one end of the round tube of the standard MPC device adjacent to the terminal MPC device is closed.

[0016] Furthermore, the relationship between the diameter Φd3 of the second exhaust pipe and the diameter Φd1 of the circular pipe of the standard MPC device is: Φd3=0.7~0.8Φd1, the relationship between the vertical pipe length L3 of the terminal MPC device and the vertical lower end pipe length L4 of the ejector pipe of the standard MPC device is: L3=2~3L4; the relationship between the length L of the second exhaust pipe and the cylinder center distance L5 is: L=7L5.

[0017] The invention has the advantages of simple structure, convenient manufacture and easy maintenance, and can reduce the influence of exhaust pressure fluctuation between two cylinders at the exhaust end of an eight-cylinder four-stroke turbocharged diesel engine on scavenging, thereby avoiding the phenomenon of excessive exhaust temperature caused by poor scavenging.

[0018] When the eight-cylinder four-stroke turbocharged diesel engine MPC exhaust system of the first embodiment of the present invention is in operation, if the first cylinder near the closed end of the exhaust pipe in the cylinder ignites 180°CA before the second cylinder, then when the first cylinder is exhausted, the second cylinder is in the scavenging stage, at this time, the exhaust pressure wave of the first cylinder enters the exhaust pressure fluctuation buffer for buffering through the reverse MPC device, and its exhaust pressure fluctuation energy is attenuated, and then enters the exhaust pipe, which can effectively avoid the exhaust pressure from affecting the scavenging of the second cylinder. If the second cylinder near the closed end of the exhaust pipe in the cylinder ignites 180°CA before the first cylinder, then when the second cylinder is exhausted, the first cylinder is in the scavenging stage, at this time, most of the exhaust of the second cylinder flows to the downstream of the exhaust pipe under the ejection action of the standard MPC device on the upper side of the second cylinder, and a small part of the exhaust enters the exhaust pressure fluctuation buffer for buffering, and the exhaust pressure fluctuation energy is attenuated. Since the ejection angle of the reverse MPC device of the first cylinder is small, it can effectively avoid the exhaust pressure from affecting the scavenging of the first cylinder.

[0019] When the eight-cylinder four-stroke turbocharged diesel engine MPC exhaust system of the second embodiment of the present invention is in operation, if the first cylinder near the closed end of the exhaust pipe in the cylinder ignites 180°CA before the second cylinder, then when the first cylinder is exhausted, the second cylinder is in the scavenging stage. At this time, the exhaust pressure wave of the first cylinder enters the second exhaust pipe through the terminal MPC device, and its exhaust pressure fluctuation energy is attenuated before entering the other input port of the turbocharger, which can effectively avoid the exhaust gas from affecting the scavenging of the second cylinder. If the second cylinder near the closed end of the exhaust pipe in the cylinder ignites 180°CA before the first cylinder, then when the second cylinder is exhausted, the first cylinder is in the scavenging stage. At this time, the exhaust gas of the second cylinder flows to the downstream of the exhaust pipe under the ejection action of the ejector pipe of the corresponding standard MPC device, and almost does not enter the second exhaust pipe, which can effectively avoid its effect on the scavenging of the first cylinder.

[0020] Advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments thereof, which are given by way of example only with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a three-phase combination diagram of the crankshaft of the eight-cylinder four-stroke turbocharged diesel engine of the present invention;

[0022] Figure 2 is a schematic structural diagram of Embodiment 1 of the present invention;

[0023] Figure 3 It is a simplified structural diagram of the reverse MPC device.

[0024] Figure 4 is a structural diagram of Embodiment 2 of the present invention; DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] Embodiment 1:

[0027] like Figure 2 As shown, Figure 2 The marks ① to ⑧ in the middle refer to the first cylinder to the eighth cylinder.

[0028] This embodiment includes an exhaust pipe 20, a reverse MPC device 3 and an exhaust pressure fluctuation buffer 4 composed of 7 standard MPC devices 2 connected in sequence through expansion joints 1. The standard MPC device 2 includes a circular tube 21 and an ejector tube 22. The vertical lower end tube 221 of the ejector tube 22 is respectively connected to the exhaust port 681 of the eighth cylinder to the exhaust port 621 of the second cylinder arranged in descending order. The upper end of the ejector tube 22 is inclined toward the turbocharger 10 (i.e., to the left) and the pipe diameter is gradually reduced to form a nozzle. The upper end of the nozzle is obliquely connected to the middle of the circular tube 21. One end of the circular tube 21 of the standard MPC device 2 at the upper end of the exhaust port 681 of the eighth cylinder at the end of the exhaust pipe 20 is connected to the input port of the turbocharger 10 through an expansion joint 1. The left end port of the reverse MPC device circular tube 31 is closed, the inclination direction of the upper end of the reverse MPC device ejector tube 32 is opposite to the inclination direction of the ejector tube 22 of the standard MPC device 2, the vertical lower end tube 321 of the reverse MPC device ejector tube 32 is connected to the exhaust port 611 of the first cylinder 61, the right end port of the reverse MPC device circular tube 31 is connected to the lower left end of the exhaust pressure fluctuation buffer 4 through the first reducer 41 and the expansion joint 1 in sequence, and the upper left end of the exhaust pressure fluctuation buffer 4 is connected to the right end of the circular tube 21 of the standard MPC device 2 at the upper end of the second cylinder 62 through the second reducer 42 and the expansion joint 1 in sequence. The expansion joint 1 is a common metal expansion joint used to compensate for the thermal deformation of the standard MPC device 2 caused by the high exhaust temperature.

[0029] The exhaust pressure fluctuation buffer 4 is in an inverted asymmetric U shape, and the length L1 of one end of the exhaust pressure fluctuation buffer 4 is greater than the length L2 of the other end of the exhaust pressure fluctuation buffer. The diameter Φd2 of the reverse MPC device round tube 31 is equal to the diameter Φd1 of the standard MPC device round tube 21.

[0030] The relationship between the diameter ΦD of the exhaust pressure fluctuation buffer 4 and the diameter Φd1 of the round tube 21 of the standard MPC device 2, or the diameter Φd2 of the round tube 31 of the reverse MPC device is: ΦD = 1.5Φd1 = 1.5Φd2. The larger diameter of the exhaust pressure fluctuation buffer 4 can increase the volume of the exhaust pressure fluctuation buffer 4 to attenuate the exhaust pressure fluctuation. The relationship between the length L1 of one end of the exhaust pressure fluctuation buffer 4 and the cylinder center distance L5 is: L1 = 2L5.

[0031] like Figure 3As shown, the reverse inclination angle of the upper end of the ejector pipe 32 of the reverse MPC device is 20°≤α≤25°, which can reduce the interference of exhaust gas fluctuations on scavenging.

[0032] Embodiment 2:

[0033] like Figure 4 As shown, part of the structure of Example 2 is the same as that of Example 1. The same parts include an exhaust pipe 20 composed of 7 standard MPC devices 2 connected in sequence through expansion joints 1. The different parts include the terminal MPC device 5 and the second exhaust pipe 6, and the turbocharger 10 has two input ports. The left end of the round pipe 21 of the standard MPC device 2 at the upper end of the exhaust port of the eighth cylinder 68 at the end of the exhaust pipe 10 is connected to an input port 101 of the turbocharger 10 through an expansion joint 1. The right end of the round pipe 21 of the standard MPC device 2 on the upper side of the second cylinder 62 is closed. The terminal MPC device 5 is the same as the standard MPC device 2 except that the vertical pipe length L3 is greater than the vertical lower end pipe length L4 of the ejector pipe of the standard MPC device 2. The right end of the terminal MPC device round pipe 51 is closed, and the left end is connected to the right end of the second exhaust pipe 6 through an expansion joint 1. The left end of the second exhaust pipe 6 is connected to another input port 102 of the turbocharger 10 through an expansion joint 1.

[0034] The relationship between the pipe diameter Φd3 of the second exhaust pipe 6 and the pipe diameter Φd1 of the circular pipe of the standard MPC device 2 is: Φd3=0.7~0.8Φd1, the relationship between the vertical pipe length L3 of the terminal MPC device and the vertical lower end pipe length L4 of the ejector pipe 32 of the standard MPC device is: L3=2~3L4; the relationship between the length L of the second exhaust pipe and the cylinder center distance L5 is: L=7L5.

[0035] The present invention can effectively ensure that the first cylinder 61 and the second cylinder 62 at the end of the eight-cylinder four-stroke turbocharged diesel engine complete the scavenging process with high quality, avoid the first cylinder 61 and the second cylinder 62 affecting each other during the scavenging process and causing the exhaust temperature of a single cylinder to be too high, and can reduce the exhaust temperature from 50°C or 70-90°C to within 20°C, thereby improving the working reliability of the eight-cylinder four-stroke turbocharged diesel engine.

[0036] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. An eight-cylinder four-stroke turbocharged diesel engine MPC exhaust system, comprising an exhaust pipe composed of several standard MPC devices connected in sequence through expansion joints, wherein the standard MPC device comprises a round pipe and an ejector pipe, wherein the vertical lower end of the ejector pipe is respectively connected to the exhaust port of the eighth cylinder to the exhaust port of the second cylinder arranged in descending order, the upper end of the ejector pipe is inclined toward the turbocharger and the pipe diameter is gradually reduced to form a nozzle, and the upper end of the nozzle is obliquely connected to the middle of the round pipe; one end of the round pipe of the standard MPC device at the upper end of the exhaust port of the eighth cylinder at the end of the exhaust pipe is connected to the turbocharger input port through an expansion joint; Features: It also includes a reverse MPC device and an exhaust pressure fluctuation buffer, wherein one end of the reverse MPC device round tube has a closed port, the inclination direction of the upper end of the reverse MPC device ejector tube is opposite to that of the standard MPC device ejector tube, the vertical lower end tube of the reverse MPC device ejector tube is connected to the exhaust port of the first cylinder, the other end of the reverse MPC device round tube is connected to one end of the exhaust pressure fluctuation buffer through an expansion joint and a first reducer in sequence, and the other end of the exhaust pressure fluctuation buffer is connected to one end of the round tube of the standard MPC device at the upper end of the second cylinder through a second reducer and an expansion joint in sequence; The ignition interval between the first cylinder and the second cylinder is 180°CA; The exhaust pressure fluctuation buffer is in an inverted asymmetric U-shape, and the length L1 of one end of the exhaust pressure fluctuation buffer is greater than the length L2 of the other end of the exhaust pressure fluctuation buffer; the diameter Φd2 of the circular tube of the reverse MPC device is equal to the diameter Φd1 of the circular tube of the standard MPC device; The relationship between the diameter ΦD of the exhaust pressure fluctuation buffer and the diameter Φd1 of the round tube of the standard MPC device or the diameter Φd2 of the round tube of the reverse MPC device is: ΦD = 1.5Φd1 = 1.5Φd2; the relationship between the length L1 of one end of the exhaust pressure fluctuation buffer and the cylinder center distance L5 is: L1 = 2L5; The reverse inclination angle of the upper end of the ejector tube of the reverse MPC device is 20°≤α≤25°.

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