Method for improving cavitation erosion of cylinder sleeve flange of locomotive diesel engine

Abstract

The invention belongs to the technical field of locomotive cooling. The invention discloses a method for improving cavitation erosion of a cylinder sleeve flange of a locomotive diesel engine to solve the problem of cavitation erosion of the cylinder sleeve flange of the locomotive diesel engine after long-term operation under a high-temperature working condition. The method includes increasing a high temperature water system pre-pump pressure in the diesel engine cooling system to a predetermined range to raise a boiling point of the high temperature water to a predetermined level. The boiling point of high-temperature water is increased by increasing the pre-pumping pressure in the water system to the preset range, boiling of the high-temperature water at the cylinder sleeve flange is restrained, cavitation erosion of bubbles generated by boiling to the cylinder sleeve flange is reduced, and powerful guarantee is provided for locomotive operation safety and reliability of diesel engine key components.

Description

Technical Field

[0001] The invention relates to the technical field of locomotive cooling, and in particular to a method for improving cavitation of a cylinder liner flange of a locomotive diesel engine. Background Art

[0002] Internal combustion locomotives usually use diesel engines as power equipment. When the diesel engine is working, the high temperature gas and friction heat will increase the temperature of parts such as pistons, piston rings, cylinders, cylinder heads, valves, etc., and reduce the strength of these parts. Overheating and overcooling of internal combustion engine parts will cause the performance of the internal combustion engine to deteriorate. Internal combustion locomotives must have a cooling system to cool the diesel engine parts to ensure the reliable operation of the diesel engine and achieve the best efficiency of the diesel engine. There are usually two cooling methods: water cooling and air cooling. Water cooling is widely used in most modern diesel engines.

[0003] The cooling water system of a locomotive diesel engine usually consists of a radiator, an expansion tank, a cooling fan, a charge air intercooler, a flow control valve, a pipeline, a water pump, a valve, etc. When the diesel engine is working, the crankshaft drives the water pump through the pump transmission device to send cooling water into the diesel engine cylinder liner, cylinder head and front and rear superchargers for circulation cooling. Its working water temperature reaches 80~95℃, which is generally called a high-temperature water system. In order to increase the air charge in the cylinder, the charge air is also cooled with water, and its working water temperature is 40~60℃, which is generally called a low-temperature water system or an intercooler water system. The cooling water from the water pump flows through the front cover assembly and is divided into two paths. One path enters the longitudinal cooling water cavity in the V-shaped angle of the engine body, and flows into the cylinder water jacket from the water outlet of each cylinder of the engine body through the reinforcement sleeve. After cooling the cylinder liner, it goes up to cool the cylinder head, and then the water outlet transition pipe on the upper part of each cylinder head is connected to the diesel engine water outlet main pipe. The other route enters the supercharger, cools the supercharger and then enters the diesel engine water outlet main pipe.

[0004] When a high-power high-speed diesel engine is running under the calibrated working condition, the temperature in the combustion chamber is about 1400℃. The high-temperature water circulation system is responsible for cooling the cylinder liner, and at the same time, it cools the oil cooler and three intercoolers. Therefore, the working temperature of high-temperature water is usually very high, close to the boiling point. When the diesel engine was disassembled and inspected after the endurance test, pitting was found at the flange of the cylinder liner. Pitting will destroy the sealing of the connection between the cylinder liner and the flange, resulting in insufficient pressure in the cylinder, which in turn affects the power output of the diesel engine. It may also cause mutual leakage of coolant, diesel, etc., affecting the normal operation of the diesel engine.

[0005] Therefore, how to prevent the cylinder liner flange of a locomotive diesel engine from cavitation after long-term operation under high temperature conditions is a problem that urgently needs to be solved in this field. Summary of the invention

[0006] In view of the above problems existing in the prior art, the present invention provides a method for improving the cavitation of the cylinder liner flange of a locomotive diesel engine.

[0007] According to one aspect of the present invention, a method for improving cavitation of a locomotive diesel engine cylinder liner flange is provided, wherein the high-temperature water system pump front pressure in the diesel engine cooling system is increased to a predetermined range to raise the boiling point of the high-temperature water to a predetermined level.

[0008] According to an embodiment of the present invention, the predetermined range of the pump front pressure is 70-200 kPa, and the predetermined level of the boiling point is not less than 120°C.

[0009] According to an embodiment of the present invention, the pump upstream pressure is increased to the predetermined range by pressurizing an expansion water tank.

[0010] According to one embodiment of the present invention, pressurizing the expansion water tank comprises the following steps: The pressurized gas is passed into the closed expansion tank through the air pipeline; detecting the pressure in the expansion water tank; Determine whether the pressure in the expansion water tank reaches a first pressure threshold, if it reaches the first pressure threshold, stop pressurizing, if it does not reach the first pressure threshold, continue pressurizing.

[0011] According to an embodiment of the present invention, the first pressure threshold is higher than 70 kPa.

[0012] According to one embodiment of the present invention, the method further comprises: The detected pressure in the expansion water tank is compared with a second pressure threshold, and if the second pressure threshold is reached, the expansion water tank is depressurized.

[0013] According to an embodiment of the present invention, the method further comprises: providing a pressure relief valve for the expansion water tank, and when the pressure in the expansion water tank reaches a second pressure threshold, the pressure relief valve automatically opens.

[0014] According to one embodiment of the present invention, the second pressure threshold is 170 kPa.

[0015] According to one embodiment of the present invention, the pump front pressure is increased to the predetermined range by adjusting the water replenishment position of the high-temperature water inlet pipeline.

[0016] According to one embodiment of the present invention, the water replenishment position is set as close as possible to the water pump inlet.

[0017] In the technical solution of the present invention, the boiling point of high-temperature water is increased by increasing the pre-pump pressure in the water system to a predetermined range, thereby suppressing the boiling of high-temperature water at the cylinder liner flange, reducing the cavitation of the cylinder liner flange caused by bubbles generated by boiling, and providing strong protection for the safety of locomotive operation and the reliability of key components of diesel engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a simulation diagram of the temperature state of the area near the diesel engine cylinder liner flange under working conditions; Figure 2 It is a partial structural diagram used to illustrate the principle of cooling water system; Figure 3 A flow chart of pressurizing an expansion water tank according to one embodiment of the present invention; Figure 4 The present invention is a simplified structural diagram of a device for pressurizing an expansion water tank according to an embodiment of the present invention.

[0020] In the attached picture: 10. Compressor; 20. Pressure sensor; 30. Pressure relief device; B. Expansion tank. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0023] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are only illustrative. Although only a few embodiments are described in detail in the present invention, it is easy for those skilled in the art to appreciate that multiple modifications are feasible without actually departing from the teaching of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, changes and deletions may be made to the design, operating conditions and parameters of the following exemplary embodiments.

[0024] The cooling water system of a locomotive diesel engine consists of a radiator, an expansion tank, a cooling fan, a charge air intercooler, a flow control valve, a pipeline, a water pump, a valve, etc. When the diesel engine is working, the crankshaft drives the water pump through the pump transmission device to send cooling water into the diesel engine cylinder liner, cylinder head and front and rear superchargers for circulation cooling. Its working water temperature is about 80~95℃, which is generally called a high-temperature water system. The high-temperature cooling water circulation device is used to cool the diesel engine cylinder liner, cylinder head and supercharger. In order to increase the air charge in the cylinder, the charge air is also cooled with water. Its working water temperature is about 40~60℃, which is generally called a low-temperature water system or an intercooler water system. The low-temperature cooling water circulation device is generally used to cool the engine oil and charge air.

[0025] When a high-power high-speed diesel engine is running at the rated operating conditions, the temperature in the combustion chamber is about 1400°C. The high-temperature water circulation system is responsible for cooling the cylinder liner, and at the same time, it cools the oil cooler and three intercoolers. Therefore, the operating temperature of high-temperature water is usually very high, close to the boiling point. When the diesel engine was disassembled and inspected after the endurance test, pitting was found at the flange of the cylinder liner. The inventor conducted a fluid analysis near the cylinder liner flange. Figure 1 The temperature state simulation diagram of the area near the cylinder liner flange of a diesel engine under working conditions is shown. Analysis shows that the water temperature here is about 120°C, and the water flow rate is very slow, about 1m / s. The inventors have discovered that due to the high water temperature here, the water boils, and the bubbles generated by boiling are the main cause of cavitation.

[0026] Therefore, in order to improve the cavitation problem, two approaches can be taken: first, increasing the flow rate of high-temperature water; second, increasing the absolute pressure of the water system to increase the boiling point of high-temperature water. The present invention inhibits cavitation by taking the second approach.

[0027] One aspect of the present invention provides a method for improving the cavitation of a cylinder liner flange of a locomotive diesel engine, the method comprising the following steps: increasing the high-temperature water system pump front pressure in the diesel engine cooling system to a predetermined range to raise the boiling point of the high-temperature water to a predetermined level.

[0028] Figure 2 A partial structural diagram is shown to illustrate the principle of the cooling water system. The high-temperature water pump is set in the high-temperature water system. Driven by the high-temperature water pump, the high-temperature water flows through the diesel engine cylinder liner, cylinder head and other components to absorb the heat of these components, and then flows to the radiator for heat dissipation. Usually, an expansion water tank is designed not far in front of the high-temperature water pump. The expansion water tank is connected to the inlet of the high-temperature water pump via a pipeline to replenish the high-temperature circulating water circuit.

[0029] In existing diesel locomotives, the expansion water tank and the diesel engine are arranged in the power room, and the height of the water tank is about 500~600mm from the high-temperature water pump inlet. The water replenishment point is located in the cooling room, which is only separated from the power room by a wall, and is about 500mm from the high-temperature water pump inlet.

[0030] According to the current installation height of the expansion water tank, it can be inferred that the pressure of the high-temperature water before the pump is about 60kPa, which only achieves the effect of air leakage in the water pipeline and cannot meet the diesel engine's pressurization requirement for the water system.

[0031] In some embodiments of the present invention, the pressure before the high-temperature water pump is increased to 70~200kPa. When the pressure before the pump is increased to this range, the boiling point of the high-temperature water rises to above 120°C, and it will not boil when circulating to the diesel engine cylinder liner flange, thereby reducing the cavitation caused by boiling water bubbles. For example, in the diesel engine calibration working condition, when the high-temperature water pump is not pressurized, the water pressure at the cylinder liner flange is 1.8bar, corresponding to the boiling point of water of 117°C. In order to ensure the reliability of key components, the water pressure needs to be increased at the inlet of the high-temperature water pump. When the water pressure before the pump is 70kPa, the corresponding water pressure at the cylinder liner flange is 2.5bar, and the boiling point of water is 126°C. When it is higher than 120°C, the boiling of water at the cylinder liner flange can be suppressed, thereby reducing the risk of cavitation. In order to ensure the reliability of key components during diesel engine operation, the water pressure needs to be increased at the outlet of the high-temperature water pump. When the water pressure before the pump is 70kPa, the corresponding water pressure at the cylinder liner flange is 2.5bar, and the boiling point of water is 126°C. However, it is understood that the method of the present invention is not limited to this scope, and the magnitude of the applied pressure can be determined according to the pressure requirement of the diesel engine on the water system and the installation height of the expansion water tank.

[0032] In some embodiments of the present invention, the pressure before the high temperature water pump is increased to a predetermined range by pressurizing the expansion water tank. Figure 3 As shown, pressurizing the expansion water tank may specifically include the following steps: Step S1: passing pressurized gas into a closed expansion water tank through an air pipeline; Step S2: Detecting the pressure in the expansion tank; Step S3: Determine whether the pressure in the expansion water tank reaches a first pressure threshold, if it reaches the first pressure threshold, stop pressurizing, if it does not reach the first pressure threshold, continue pressurizing.

[0033] In some embodiments, the first pressure threshold is not less than 70 kPa. The first pressure threshold is a value that increases the corresponding high-temperature water pump inlet pressure to a set range after the expansion water tank is pressurized, and is within the safe use range of the expansion water tank. In some embodiments, there is a certain range of pressure difference (mainly water pressure) between the expansion water tank and the high-temperature water pump inlet pressure. When the pressure in the expansion water tank is 70 kPa, the high-temperature water pump inlet pressure is not less than 70 kPa.

[0034] Figure 4 The structure diagram of the device for pressurizing the expansion water tank according to one embodiment of the present invention is shown. The pressurizing device may include, for example, an air compressor 10 and a pressure sensor 20. The air compressor 10 is connected to the body of the sealed expansion water tank B via an air pipeline so that pressurized gas (for example, compressed air) is passed into the expansion water tank B through the air pipeline. The gravity pressure of water is about 50 kPa. In order to achieve the pressurization requirement of 70~200 kPa before the pump of high-temperature water, the expansion water tank can be pressurized to, for example, 100 kPa. A pressure sensor 20 can be installed in the expansion water tank B to detect the pressure in the expansion water tank B. For example, a pressure sensor with a range of 0~6 bar can be used to feed back the pressure signal to the air compressor 10. When the pressure in the expansion water tank B is measured to be ≥100 kPa, the pressurization is stopped; when the pressure in the expansion water tank B is measured to be less than 100 kPa, the air compressor 10 is turned on to pressurize the expansion water tank B.

[0035] In some embodiments, the method of the present invention further comprises: comparing the detected pressure in the expansion water tank with a second pressure threshold, and if the second pressure threshold is reached, relieving the pressure of the expansion water tank. For example, a pressure relief valve may be provided for the expansion water tank, and when the pressure in the expansion water tank reaches the second pressure threshold, the pressure relief valve automatically opens. The second pressure threshold is a pressure threshold that ensures that the expansion water tank and its internal components can operate within a safe pressure range.

[0036] In a specific embodiment, for safety reasons, a pressure relief device 30 may also be provided for the expansion water tank B. For example, a closed expansion water tank B needs to be provided with a pressure relief valve. The opening pressure of the valve is, for example, 170 kPa. An active valve may be used, that is, in response to the pressure in the expansion water tank B detected by the pressure sensor 20 exceeding 170 kPa, a signal is provided to the pressure relief valve to open it. Optionally, in other embodiments, a passive valve may also be used. When any component of the pressure sensor, the pressure signal receiving element, or the air compressor fails, the pressure relief valve automatically opens when the pressure in the expansion water tank B exceeds 170 kPa, thereby controlling the gas pressure in the expansion water tank B to maintain the pressure before the high-temperature water pump.

[0037] In order to compare the pressure changes in front of the high-temperature water pump before and after the expansion water tank is pressurized, the following test is conducted. First, the high-temperature sealed expansion water tank is not pressurized, and the machine is started and operated to the calibrated working condition. After running for about 15 minutes, the high-temperature sealed expansion water tank is pressurized by about 20kPa, and then run for another 30 minutes to observe the pressure changes in front of the high-temperature water pump. The specific test results are shown in Table 1 below: Table 1 High temperature expansion tank pressurization test data

[0038] From the above data, it can be seen that when not pressurized, the pressure in front of the high-temperature water pump is 62.8kPa. After pressurizing by about 20kPa, the pressure in front of the high-temperature water pump is 80.1kPa, and in the following 30 minutes, the pressure in front of the high-temperature water pump did not drop, but increased slightly due to the increase in water temperature. From the above test results, it can be seen that pressurizing the high-temperature expansion water tank can increase the inlet pressure of the high-temperature water pump to above the target value of 70kPa and operate stably.

[0039] Optionally, in some embodiments, the pre-pump pressure of the high-temperature water is increased to a predetermined range by adjusting the water replenishment position of the high-temperature water inlet pipeline.

[0040] In order to test the influence of different water replenishment positions on the water pump inlet pressure, three water replenishment points were set on the high-temperature water inlet pipeline to verify the influence of the water replenishment position on the pressure before the high-temperature water pump. The distances between the three water replenishment points and the high-temperature water inlet flange of the diesel engine were 115mm (water replenishment point P1), 630mm (water replenishment point P2) and 1240mm (water replenishment point P3). The test was divided into two parts, respectively testing the relationship between the water pump flow and the water tank level at the same water replenishment position and the relationship between different water replenishment positions and the pressure before the pump.

[0041] A closed expansion water tank is used to replenish water in front of the high-temperature water pump. The water tank is not pressurized, and the water replenishment points are arranged at the above three locations. To repeat the verification, the diesel engine was operated under three working conditions during the test. The relevant parameters of the water pump under different working conditions are shown in Table 2 below.

[0042] Table 2 Related parameters of water pumps at different water replenishment points under different working conditions

[0043] From the test results in Table 2, it can be seen that under the same working condition, the water pump inlet pressure is the largest when the water is replenished at position P1, followed by position P2, and the smallest at position P3. Moreover, the conclusions are the same under the three working conditions. Moreover, at the same water replenishment position, the larger the water pump flow rate, the lower the water tank liquid level, and the smaller the water pump inlet pressure. Therefore, the closer the water replenishment position is to the water pump inlet, the greater the water pump inlet pressure, and the better the water replenishment effect.

[0044] In some embodiments, the water replenishment position can be arranged at a position as close as possible to the water pump inlet. For this reason, the water replenishment point in the cooling room can be changed to the power room to enhance the pressure before the high-temperature water pump.

[0045] Pressurizing the closed expansion water tank and setting the water replenishment point close to the pump inlet are both effective methods to increase the pressure before the high-temperature water pump. These two solutions can also be used in combination. Through the method of the present invention, the pressure before the pump in the water system can be increased to 70~200kPa. It can effectively prevent the boiling of high-temperature water in the pipeline and prevent the occurrence of cavitation, providing a strong guarantee for the safety of locomotive operation and the reliability of key components of diesel engines.

[0046] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention is limited to these examples; under the idea of ​​the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for improving the cavitation of the cylinder liner flange of a locomotive diesel engine, characterized in that: The high temperature water system pump inlet pressure in the diesel engine cooling system is increased to a predetermined range to raise the boiling point of the high temperature water to a predetermined level.

2. The method according to claim 1, characterized in that The predetermined range of the pump front pressure is 70-200 kPa, and the predetermined level of the boiling point is not less than 120°C.

3. The method according to claim 2, characterized in that The pump upstream pressure is increased to the predetermined range by pressurizing the expansion tank.

4. The method according to claim 3, characterized in that Pressurizing the expansion tank comprises the following steps: The pressurized gas is passed into the closed expansion tank through the air pipeline; detecting the pressure in the expansion water tank; Determine whether the pressure in the expansion water tank reaches a first pressure threshold, if it reaches the first pressure threshold, stop pressurizing, if it does not reach the first pressure threshold, continue pressurizing.

5. The method according to claim 4, characterized in that The first pressure threshold is higher than 70 kPa.

6. The method according to claim 4, characterized in that The method further comprises: The detected pressure in the expansion water tank is compared with a second pressure threshold, and if the second pressure threshold is reached, the expansion water tank is depressurized.

7. The method according to claim 3, characterized in that The method further comprises: providing a pressure relief valve for the expansion water tank, wherein the pressure relief valve automatically opens when the pressure in the expansion water tank reaches a second pressure threshold.

8. The method according to claim 6 or 7, characterized in that: The second pressure threshold is 170 kPa.

9. The method according to claim 2, characterized in that: The pump front pressure is increased to the predetermined range by adjusting the water replenishment position of the high-temperature water inlet pipeline.

10. The method according to claim 9, characterized in that The water replenishment position is set as close to the water pump inlet as possible.

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