Diesel engine turbo variable supercharging system

Abstract

The present invention discloses a variable turbocharging system for a diesel engine, which includes a turbocharger, an exhaust pipe, and a plurality of cut-off valves. The outlets of each cylinder are respectively connected to a first exhaust pipe and a second exhaust pipe. The inlet x of the turbine end of the first turbocharger is divided into two paths. One path is connected to one end of the first exhaust pipe through a cut-off valve, and the other path is connected to one end of an additional exhaust pipe through a cut-off valve. The other ends of the first exhaust pipe and the additional exhaust pipe are merged into one path and then connected to the inlet a of the turbine end of the second turbocharger through a cut-off valve. The inlet y of the turbine end of the first turbocharger is connected to one end of the second exhaust pipe through a cut-off valve, and the other end of the second exhaust pipe is connected to the inlet b of the compressor end of the second turbocharger through a cut-off valve. The present invention realizes the functions of switching between two turbochargers and variable total volume of the exhaust pipe, makes the volume of the exhaust pipe match the working state of the turbocharger, and effectively improves the power performance and economic performance of the diesel engine.

Description

Technical Field

[0001] The present invention relates to an exhaust gas turbocharging system for a diesel engine, and particularly to an exhaust gas turbocharging system for a diesel engine that can change the matching characteristics between a turbocharger and a diesel engine, belonging to the technical field of internal combustion engines. Background Art

[0002] To improve the power performance and economy of a diesel engine, an exhaust gas turbocharging device is generally adopted. The energy in the exhaust gas is used to drive the turbine to rotate, and the rotation of the turbine drives the coaxial compressor to rotate, compressing the intake air of the diesel engine, increasing the excess air coefficient of the diesel engine, burning more diesel under the same fuel injection condition, increasing the output power of the diesel engine, and effectively improving the power performance and economy of the diesel engine.

[0003] However, a diesel engine is a reciprocating machine, and a turbocharger is a rotary machine. The different operating modes of the two machines result in the fact that the matching between the two machines cannot achieve full-load and full-condition optimization, and there can only be an optimal matching interval within a certain range (generally a 10% diesel engine load interval).

[0004] When the diesel engine is running, since each cylinder fires in sequence and drives the crankshaft to rotate through its respective connecting rod, the exhaust gas discharged from the diesel engine has pulse energy. When the diesel engine is running at a low load, the exhaust gas flow rate is small. The operation of the turbocharger using the pulse energy can effectively improve the matching effect between the diesel engine and the turbocharger, reduce the volume of the exhaust pipe, is conducive to using the pulse energy of the exhaust gas discharge, and can improve the working efficiency of the diesel engine low-load turbocharger. When the diesel engine is running at a high load, the exhaust gas flow rate is large and the energy is sufficient. Increasing the volume of the exhaust pipe can reduce the pulse energy in the exhaust pipe, is conducive to reducing the pressure fluctuation in front of the turbine inlet of the turbocharger, improving the operating stability of the turbocharger, and further improving the working efficiency of the turbocharger. The volume of the exhaust pipe is small at low load and large at high load, which is conducive to improving the working efficiency of the turbocharger. In other words, if the volume of the exhaust pipe can increase with the increase of the diesel engine load, the energy in the exhaust gas can be utilized more effectively.

[0005] The existing diesel engines generally determine the volume of the exhaust pipe according to the maximum exhaust gas volume of the diesel engine. The volume of the exhaust pipe is fixed, generally about 10 times the total displacement V of the diesel engine, and only a certain load interval can be determined as the matching point for the diesel engine and the turbocharger, and the different working conditions of high-load operation and low-load operation during the operation of the diesel engine cannot be taken into account. Summary of the Invention

[0006] The purpose of the present invention is to provide a variable turbocharging system for a diesel engine, which realizes the switching of the operation of two turbochargers and the combination of exhaust pipes with different volumes according to the different loads during the operation of the diesel engine, and effectively improves the matching effect between the diesel engine and the turbocharger.

[0007] The present invention is realized by the following technical solutions:

[0008] A variable supercharging system for a diesel engine, comprising a first turbocharger, a second turbocharger, a first exhaust pipe, a second exhaust pipe, an additional exhaust pipe, several three-way pipes and a plurality of stop valves. The first turbocharger is installed at one end of the diesel engine, and the second turbocharger is installed at the other end of the diesel engine; the compressor ends of the first turbocharger and the second turbocharger are respectively connected to both ends of the intake pipe, and the intake branch pipes connected in parallel on the intake pipe are respectively connected to the inlet ends of the corresponding cylinders. The first outlets of each cylinder are respectively connected to the first exhaust pipe through the first exhaust branch pipes, and the second outlets of each cylinder are respectively connected to the second exhaust pipe through the second exhaust branch pipes; the x inlet of the turbine end of the first turbocharger is divided into two paths through a three-way pipe. One path is connected to one end of the first exhaust pipe through the third stop valve, and the other path is connected to one end of the additional exhaust pipe through the second stop valve. The other end of the first exhaust pipe and the other end of the additional exhaust pipe are merged into one path through a three-way pipe and then connected to the a inlet of the turbine end of the second turbocharger through the first stop valve. The y inlet of the turbine end of the first turbocharger is connected to one end of the second exhaust pipe through the fourth stop valve, and the other end of the second exhaust pipe is connected to the b inlet of the compressor end of the second turbocharger through the fifth stop valve; the signal lines of the diesel engine CPU are respectively connected to the control ends of each stop valve.

[0009] Further, the exhaust gas flow rate of the second turbocharger is greater than that of the first turbocharger. The maximum exhaust gas flow rate Q1 of the first turbocharger = 0.55 times the exhaust gas flow rate of the diesel engine, and the maximum exhaust gas flow rate Q2 of the second turbocharger = 0.85 times the exhaust gas flow rate of the diesel engine.

[0010] Further, the volume v1 of the first exhaust pipe is equal to the total volume v3 of the additional exhaust pipe. The relationship between the volume v1 of the first exhaust pipe, the total volume v3 of the additional exhaust pipe and the total displacement V of the diesel engine is: v1 = v3 = (2.2 - 2.8)V; the relationship between the volume v2 of the second exhaust pipe and the total displacement V of the diesel engine is: v2 = (6.2 - 6.8)V;

[0011] Further, the stop valves are all electronically controlled pneumatic butterfly valves.

[0012] The structure of the present invention is relatively simple, convenient for manufacturing and installation, and easy to maintain. As the load of the diesel engine changes, the switching function of the first turbocharger and the second turbocharger is realized through the on-off combination of the corresponding stop valves, and the function of variable total volume of the exhaust pipe is realized, so that the volume of the exhaust pipe matches the working state of the turbocharger, and the turbocharger always works near the optimal matching point, effectively improving the power performance and economic performance of the diesel engine.

[0013] The advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments, which are given only by way of example with reference to the accompanying drawings. Description of the Drawings

[0014] Figure 1 is the schematic diagram of the present invention. Detailed Embodiments

[0015] The present invention will be further described below in conjunction with the accompanying drawings and an embodiment of a six-cylinder diesel engine.

[0016] In the description of the present invention, terms indicating orientation or order such as "left", "right", "first" to "fifth", etc. are based on the orientation or position relationship shown in the accompanying drawings, rather than indicating or implying that the device referred to must have a specific orientation.

[0017] As Figure 1 shown, the present invention includes a first turbocharger 1, a second turbocharger 2, a first exhaust pipe 3, a second exhaust pipe 4, an additional exhaust pipe 5, two three-way pipes 6, a first cut-off valve 71, a second cut-off valve 72, a third cut-off valve 73, a fourth cut-off valve 74 and a fifth cut-off valve 75. The first turbocharger 1 is installed at the right end of the diesel engine, and the second turbocharger 2 is installed at the left end of the diesel engine. The compressor ends 11 of the first turbocharger and 21 of the second turbocharger are respectively connected to both ends of the intake pipe 8. The intake branch pipes 81 connected in parallel on the intake pipe 8 are respectively connected to the inlet ends of the corresponding cylinders 10. The first outlets 101 of each cylinder 10 are respectively connected to the first exhaust pipe 3 through the first exhaust branch pipes 103, and the second outlets 102 of each cylinder 10 are respectively connected to the second exhaust pipe 4 through the second exhaust branch pipes 104. The inlet of the turbine end x of the first turbocharger is divided into two paths through the three-way pipe 6. One path is connected to the right end of the first exhaust pipe 3 through the third cut-off valve 73, and the other path is connected to the right end of the additional exhaust pipe 5 through the second cut-off valve 72. The left end of the first exhaust pipe 3 and the other left end of the additional exhaust pipe 5 are merged into one path through the three-way pipe 6 and then connected to the inlet a of the turbine end of the second turbocharger 2 through the first cut-off valve 71. The inlet y of the turbine end of the first turbocharger is connected to the right end of the second exhaust pipe 4 through the fourth cut-off valve 74, and the left end of the second exhaust pipe 4 is connected to the inlet b of the compressor end of the second turbocharger through the fifth cut-off valve 75. The respective signal lines 201 of the diesel engine CPU 20 are respectively connected to the control ends of the respective cut-off valves.

[0018] The exhaust gas flow rate of the second turbocharger 4 is greater than that of the first turbocharger 3. The maximum exhaust gas flow rate Q1 of the first turbocharger 1 = 0.55Q (diesel engine exhaust gas flow rate), and the optimal matching point is in the range of Q1 = 0.25 - 0.35Q at low load. The maximum exhaust gas flow rate Q2 of the second turbocharger = 0.85Q, and the optimal matching point is in the range of Q2 = 0.55 - 0.65Q at medium load.

[0019] The volume v1 of the first exhaust pipe 3 is equal to the volume v3 of the additional exhaust pipe 5. The relationship between the volumes v1 and v3 of the first exhaust pipe 3 and the total engine displacement V is: v1 = v3 = (2.2-2.8)V. The relationship between the volume v2 of the second exhaust pipe and the total engine displacement V is: v2 = (6.2-6.8)V. The exhaust pipe diameter d can be calculated based on the exhaust pipe volume v and the total exhaust pipe length L.

[0020] The first stop valve 71 to the fifth stop valve 75 all adopt electronically controlled pneumatic butterfly valves. After receiving the diesel engine load signal, the diesel engine CPU 20 sends an instruction to the solenoid valve of the corresponding electronically controlled pneumatic butterfly valve, and changes the valve core position of the solenoid valve to achieve the change of the on-off state of the stop valve by moving the cylinder piston rod, thereby realizing the switching of the first supercharger 3 and the second supercharger 4; changing the on-off state of the stop valve can also realize the function of variable total volume of the exhaust pipe, so that the exhaust pipe volume matches the working state of the supercharger, thereby improving the power performance of the diesel engine.

[0021] The control method of the diesel engine turbocharger system is shown in Table 1:

[0022] Table 1

[0023]

[0024]

[0025] During operation of a diesel engine equipped with the present invention, when the engine is operating at a load of 0-20%, all stop valves except third stop valve 73 are closed. Exhaust gas from the diesel engine enters the inlet of the turbine end x of the first turbocharger via first exhaust pipe 3, third stop valve 73, and tee pipe 6. At this time, the diesel engine load is near the optimal matching range of first turbocharger 1, i.e., Q1 = (-5% to -25%) Q. Furthermore, since the total volume of first exhaust pipe 3 is relatively small (2.5V), the pulse energy in the diesel engine exhaust can be effectively utilized, resulting in high operating efficiency of first turbocharger 1.

[0026] When the diesel engine operates at a load of 20%-40%, all shutoff valves except second shutoff valve 72 are closed. Diesel engine exhaust flows through first exhaust pipe 3, additional exhaust pipe 5, second shutoff valve 72, and tee pipe 6 and enters the inlet of turbine port x of the first turbocharger. At this point, the diesel engine load is within the optimal matching range of ±5% for first turbocharger 1, and the total exhaust pipe volume is 5V. This is larger than the diesel engine load of 0-20%, matching the diesel engine exhaust flow rate and improving the operating efficiency of first turbocharger 1.

[0027] When the diesel engine operates at 40%-50% load, except for the fourth cut-off valve 74 being opened, the rest of the cut-off valves are closed. The exhaust gas of the diesel engine enters the inlet y of the turbine end of the first turbocharger through the second exhaust pipe 4 and the cut-off valve 10. At this time, the load of the diesel engine is near the optimal matching range (+5% to +15% range), and the total volume of the second exhaust pipe 4 is 6.5V, which is slightly larger compared to the diesel engine load of 20%-40%, matching and being slightly larger than the diesel engine flow rate. And in this load range, the exhaust gas flow rate of the diesel engine has approached the maximum designed exhaust gas flow rate of the first supercharger 3. The relatively large exhaust volume is conducive to attenuating the pulse energy in the diesel engine exhaust gas, maintaining the stability of the inlet pressure of the first turbocharger 1, and improving the working efficiency of the first supercharger 3.

[0028] When the diesel engine operates at 50%-60% load, except for the fifth cut-off valve 75 being opened, the rest of the cut-off valves are closed. The exhaust gas of the diesel engine enters the inlet b of the turbine end of the second turbocharger through the second exhaust pipe 4 and the fifth cut-off valve 75. At this time, the load of the diesel engine is entirely within the optimal matching range of the second turbocharger 2. The total volume of 6.5V of the second exhaust pipe 4 matches the diesel engine flow rate, and the working efficiency of the second turbocharger 2 is relatively high.

[0029] When the diesel engine operates at 60%-80% load, except for the first cut-off valve 71 and the fifth cut-off valve 75 being opened, the rest of the cut-off valves are closed. The exhaust gas of the diesel engine enters the inlet a of the turbine end of the second turbocharger and the inlet b of the turbine end of the second turbocharger respectively through the first exhaust pipe 3, the first cut-off valve 71, the second exhaust pipe 4 and the fifth cut-off valve 75. At this time, the load of the diesel engine is near the optimal matching range of the second turbocharger 4 (+15% range), and the sum of the volumes of the first exhaust pipe 3 and the second exhaust pipe 4 is 9V, which is slightly larger compared to the 50%-60% load, matching the diesel engine exhaust gas flow rate, and the working efficiency of the second turbocharger 2 is relatively high.

[0030] When the diesel engine operates at 80%-110% load, except for the second cut-off valve 72 and the fifth cut-off valve 75 being opened, the rest of the cut-off valves are closed. The exhaust gas of the diesel engine enters the inlet x of the turbine of the first turbocharger through the first exhaust pipe 3, the additional exhaust pipe 5, the second cut-off valve 72 and the three-way pipe 6, and enters the inlet b of the turbine end of the second turbocharger through the large exhaust pipe 4 and the cut-off valve 11. At this time, the exhaust gas flow rate passing through the first turbocharger 1 is roughly equivalent to the flow rate of the diesel engine at 30%-40% load, and the exhaust gas flow rate passing through the second turbocharger 2 is roughly equivalent to the flow rate of the diesel engine at 50%-70% load, both being near the optimal matching load range of the first turbocharger 1 and the second turbocharger 2. At this time, the total flow rate of the first exhaust pipe 3, the second exhaust pipe 4 and the additional exhaust pipe 5 is 11.5V, matching the diesel engine exhaust gas flow rate, and the efficiencies of the first turbocharger 1 and the second turbocharger 2 are relatively high.

[0031] This embodiment can achieve the matching of the volume of the diesel engine exhaust pipe and the exhaust gas flow rate. On the one hand, the change in the exhaust pipe volume is beneficial for the two turbochargers to make full use of the exhaust energy. On the other hand, the switching between the first turbocharger and the second turbocharger is realized through the on-off combination of the corresponding cut-off valves, ensuring that the diesel engine load is always near the optimal matching load range of the turbocharger, effectively improving the matching characteristics of the diesel engine and the turbocharger, and enhancing the power performance and economy of the diesel engine. This embodiment can reduce the diesel fuel consumption by about 10 g / kWh in the low load range of 10%-30%, reduce the diesel fuel consumption by 4 g / kWh in the medium load range of 40%-65%, and reduce the diesel fuel consumption by about 2 g / kWh in the high load range of 80%-100%. The energy-saving effect is remarkable.

[0032] The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A variable supercharging system for a diesel engine, characterized in that, It includes a first turbocharger, a second turbocharger, a first exhaust pipe, a second exhaust pipe, an additional exhaust pipe, several three-way pipes and multiple stop valves. The first turbocharger is installed at one end of the diesel engine, and the second turbocharger is installed at the other end of the diesel engine; the compressor ends of the first turbocharger and the second turbocharger are respectively connected to both ends of the intake pipe, and the intake branch pipes connected in parallel on the intake pipe are respectively connected to the inlet ends of the corresponding cylinders. The first outlets of each cylinder are respectively connected to the first exhaust pipe through the first exhaust branch pipes, and the second outlets of each cylinder are respectively connected to the second exhaust pipe through the second exhaust branch pipes; the x inlet of the turbine end of the first turbocharger is divided into two paths through a three-way pipe. One path is connected to one end of the first exhaust pipe through the third stop valve, and the other path is connected to one end of the additional exhaust pipe through the second stop valve. The other end of the first exhaust pipe and the other end of the additional exhaust pipe are merged into one path through a three-way pipe and then connected to the a inlet of the turbine end of the second turbocharger through the first stop valve. The y inlet of the turbine end of the first turbocharger is connected to one end of the second exhaust pipe through the fourth stop valve, and the other end of the second exhaust pipe is connected to the b inlet of the compressor end of the second turbocharger through the fifth stop valve; each signal line of the diesel engine CPU is respectively connected to the control end of each stop valve; The exhaust gas flow of the second turbocharger is greater than that of the first turbocharger. The maximum exhaust gas flow of the first turbocharger Q1 = 0.55 times the exhaust gas flow of the diesel engine, and the maximum exhaust gas flow of the second turbocharger Q2 = 0.85 times the exhaust gas flow of the diesel engine; The volume v1 of the first exhaust pipe is equal to the total volume v3 of the additional exhaust pipe. The relationship between the volume v1 of the first exhaust pipe, the total volume v3 of the additional exhaust pipe and the total displacement V of the diesel engine is: v1 = v3 = (2.2 - 2.8)V; The relationship between the volume v2 of the second exhaust pipe and the total displacement V of the diesel engine is: v2 = (6.2 - 6.8)V.

2. The diesel engine turbo variable supercharging system according to claim 1, wherein The stop valves are all electronically controlled pneumatic butterfly valves.

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