Test method for judging cavitation erosion of engine cylinder sleeve by using water pressure fluctuation

Abstract

The invention relates to a test method for judging cavitation erosion of an engine cylinder sleeve by using water pressure fluctuation, which relates to the field of engines and comprises the following steps of: continuously and alternately circulating by using circulating cooling water on the outer wall of the engine cylinder sleeve; under the vibration of the cylinder sleeve and different water pressure changes, when the transient pressure of cooling water at a certain position of the cylinder sleeve is reduced to be lower than the liquid saturated steam pressure, bubbles are generated and separated out; along with the increase of bubbles, the bubbles are compressed to a certain degree under the vibration of the cylinder sleeve and the change of water pressure, and then the pressure rises to cause bursting; collecting and analyzing water pressure fluctuation data; and according to the collected data, whether the cavitation erosion phenomenon occurs in the cylinder sleeve is judged, and whether the cooling water channel needs to be redesigned is determined. The method is beneficial to quickly and accurately judging the cavitation erosion condition of the cylinder sleeve, timely discovering potential problems and taking preventive measures, prolonging the service life of the cylinder sleeve and reducing the maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of engines, and in particular to a test method for determining engine cylinder liner cavitation using water pressure fluctuations. Background Technology

[0002] In recent years, with increasingly stringent emission regulations, diesel engines have upgraded from the China V standard to the China VI standard, resulting in a significant increase in combustion pressure, reaching or exceeding 25 MPa. To enable engines to withstand higher loads and combustion pressures, the industry has widely adopted steel pistons. However, this change has also brought new problems: steel pistons lead to increased piston side impact force, a more concentrated knocking area, and a greater risk of cylinder liner cavitation. In this context, early detection of cylinder liner cavitation risk is crucial for accelerating engine project development cycles and saving costs.

[0003] Cavitation in diesel engine cylinder liners specifically refers to the phenomenon where, when the cooling water in the water jacket vibrates at high frequencies under piston-side pressure, bubbles form and burst, generating powerful pressure waves that violently impact the cylinder liner surface. This results in pitting, which gradually expands into foamy or sponge-like cavitation, a typical form of corrosion and wear. Given the severe impact of cavitation on engine performance and lifespan, capturing and analyzing cooling water pressure fluctuations to accurately determine the occurrence and extent of cavitation has become a critical issue in engine design and maintenance. However, currently, the industry lacks an effective method and system for quickly and accurately detecting the risk of cylinder liner cavitation.

[0004] Currently, the industry primarily relies on CAE analysis methods or by detecting cylinder liner vibration and using high-speed cameras to capture the number of air bubbles to determine whether cavitation has occurred in engine cylinder liners. While these methods provide effective analytical results to some extent, they also have significant limitations. On the one hand, the testing cost is relatively high, requiring substantial investment of manpower, resources, and time. On the other hand, the installation process of vibration sensors is complex and difficult, demanding a high level of expertise from both the operating environment and the personnel. Therefore, the industry urgently needs a simpler, faster, and more efficient testing and assessment method to address the shortcomings of existing technologies, improve testing efficiency, and reduce testing costs. Summary of the Invention

[0005] The purpose of this invention is to provide an efficient, accurate, adaptable and easy-to-operate method for detecting engine cylinder liner cavitation. It mainly establishes the ability to test and judge engine cylinder liner cavitation by capturing the changes in coolant pressure in a high-frequency range under different engine operating conditions and coolant temperatures. This allows for rapid and accurate judgment of cylinder liner cavitation, timely detection of potential problems and implementation of preventive measures, extension of cylinder liner service life and reduction of maintenance costs.

[0006] To achieve the above objectives, the present invention provides a test method for determining engine cylinder liner cavitation using water pressure fluctuations, comprising the following steps: The cooling water circulating on the outer wall of the engine cylinder liner is continuously and alternately circulated. Under cylinder liner vibration and different water pressure changes, when the transient pressure of the cooling water at a certain point of the cylinder liner drops below the liquid saturated vapor pressure, bubbles are generated and separated. As the number of bubbles increases, under the vibration of the cylinder liner and changes in water pressure, the bubbles are compressed to a certain extent, and the pressure rises, causing them to burst. Collect and analyze water pressure fluctuation data; Based on the collected data, determine whether cavitation erosion occurs in the cylinder liner and whether the cooling water passage needs to be redesigned.

[0007] Preferably, a pressure sensor is installed in the cavitation-prone area of ​​the engine cylinder liner cooling water passage. The pressure sensor is used to monitor the pressure fluctuation of the cooling water in real time.

[0008] Preferably, the sensor head does not protrude from the waterway surface to avoid affecting the accuracy of water flow and pressure fluctuations, while ensuring that the sensor is installed in a sealed manner.

[0009] Preferably, the pressure sensor sensitivity is set, and based on CAE and usage data evaluation, the data acquisition frequency of the data acquisition instrument is set to a value corresponding to the frequency of bubble bursting during engine cylinder liner cavitation.

[0010] Preferably, the engine coolant is pure water, and after 24 hours of break-in operation, the engine performance is checked and no problems are found before a transient impact pressure test is performed. At the same time, in order to eliminate gas in the water, the water needs to be boiled at 100°C for 5 minutes and then the auxiliary water tank pressure cap is opened for 10 minutes to release the gas.

[0011] Preferably, the water pressure fluctuations on the maximum thrust side of different cylinders and the corresponding engine speeds are tested under different operating conditions of the engine.

[0012] Preferably, the time-domain data of cooling water pressure collected under different operating conditions are filtered, and an appropriate high-pass filter frequency is selected to eliminate the influence of component vibration and engine combustion on water impact pressure.

[0013] Preferably, after filtering the time-domain cooling water pressure under the same operating conditions with a high-pass filter of 10KHz or higher, when the water pressure frequently experiences instantaneous impact pressure reaching a certain threshold, it is considered that the bubbles burst and the cylinder liner begins to show cavitation spots. As time accumulates, the number of cavitation spots increases, and the cylinder liner may be broken down. Therefore, it is determined that the cooling water passage needs to be redesigned.

[0014] Preferably, when frequent instantaneous water pressure impacts occur again under a certain operating condition and the pressure reaches a certain threshold, it is determined that the engine will definitely experience cavitation under the boundary conditions of that operating condition.

[0015] Preferably, the pressure sensor is positioned on the side of the engine cylinder liner where the lateral thrust is greatest.

[0016] In summary, the present invention has the following beneficial technical effects: This invention utilizes the method of collecting and analyzing high-frequency pressure changes in engine coolant (water) to determine whether the engine cylinder liner is cavitated. It can quickly detect the instantaneous impact pressure of water pressure. By monitoring the pressure fluctuations of coolant in real time and processing and analyzing the collected data in a timely manner, it can determine whether there is cavitation in the engine cylinder liner in a short time, without having to wait for obvious damage to the cylinder liner before inspection. This greatly improves the detection efficiency, helps to discover problems in time and take corresponding measures to prevent the cylinder liner cavitation from worsening.

[0017] This invention conducts comprehensive testing on engines under different operating conditions, including monitoring water pressure fluctuations under normal operating conditions such as different water temperatures, different engine oil temperatures, and different auxiliary water tank pressure cap pressures. It fully considers the various complex operating conditions that engines may face in actual operation, and can more comprehensively assess the risk of cavitation erosion of cylinder liners under different conditions. This provides a more reliable basis for engine design optimization and performance evaluation, making it more adaptable.

[0018] The entire testing system consists of conventional equipment and tools such as a data acquisition unit, pressure sensor, and testing software. It is simple to operate and easy to implement. Moreover, this method has minimal impact on the normal operation of the engine, requiring no large-scale modification or disassembly of the engine. It can be used to perform tests simultaneously during normal engine operation, demonstrating good practicality and operability, and is easy to promote and apply in actual production. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the water pressure fluctuations and corresponding engine speeds under three working conditions in step 6 of a test method for judging engine cylinder liner cavitation using water pressure fluctuations in this invention. Figure 2 This is a schematic diagram corresponding to step 8 in the test method for judging engine cylinder liner cavitation using water pressure fluctuations of the present invention; Figure 3 This is a schematic diagram of the device used in the test method for determining engine cylinder liner cavitation using water pressure fluctuations according to the present invention.

[0020] Reference numerals: 1. Engine under test; 2. Pressure sensor; 3. Data acquisition and control module; 4. PC. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention discloses a test method for determining engine cylinder liner cavitation using water pressure fluctuations. The core principle of this invention is the continuous alternating circulation of cooling water on the outer wall of the engine cylinder liner. Under cylinder liner vibration and varying water pressure, the transient pressure of the cooling water at a certain point in the cylinder liner is measured. ( The static pressure of the cooling water in the water chamber, Reduce to below the liquid saturated vapor pressure At that time, that is Bubbles are generated and separated. As the number of bubbles increases, under the influence of cylinder liner vibration and water pressure changes, the bubbles are compressed to a certain extent, and the increased pressure causes them to burst. Repeated action leads to the peeling of cylinder liner material and produces steep pressure fluctuations, with impact pressure generally exceeding 100 MPa. This invention aims to provide a method for rapidly detecting instantaneous water pressure impact and analyzing cavitation erosion.

[0023]

[0024] Instantaneous impact pressure (MPa); The initial value of the bubble radius (m); The transient value of the bubble radius (m); Cooling water density (kg / m3); The alternating pressure (MPa) caused by vibration; The static pressure of the cooling water in the water chamber (MPa); Speed ​​of sound (m / s); , Cooling water surface tension (N / m).

[0025] The implementation of this invention mainly includes a data acquisition device, a pressure sensor 2, testing software, a data acquisition cable, a LAN cable, and a PC 4. The specific steps are as follows: Step 1: Select a new engine and place a coolant pressure sensor 2 on the side of the engine with the greatest lateral thrust (exhaust side). The position and number of sensors are determined by CAE simulation analysis. At the same time, pure water is used for engine coolant during the test.

[0026] Step 2: Ensure that the sensor head does not protrude from the waterway surface to avoid affecting the accuracy of water flow and pressure fluctuations, and ensure that the sensor is installed in a sealed manner to prevent leakage.

[0027] Step 3: Connect the sensor to the data acquisition unit using a BNC data acquisition cable, and connect the data acquisition unit to the PC via a LAN cable to complete the test system setup.

[0028] Step 4 involves setting the sensitivity of pressure sensor 2. Based on CAE and usage data, the frequency of bubble bursting due to cavitation in engine cylinder liners reaches over 20kHz. Therefore, the data acquisition frequency of the data acquisition instrument is set to the corresponding value.

[0029] Step 5 requires using pure water for engine coolant and running the engine for 24 hours. After confirming that the engine performance is normal, a transient impact pressure test is then performed. Simultaneously, to eliminate air in the water, the water needs to be boiled at 100℃ for 5 minutes, and then the auxiliary water tank pressure cap should be opened for 10 minutes to release the air.

[0030] Step 6, based on the principle of cavitation, mainly tests the water pressure fluctuation on the maximum thrust side of different cylinders and the corresponding engine speed. Specifically, this includes three operating conditions: First, after the engine has fully warmed up and undergone a large circulation cycle, maintaining a water temperature of 80-90℃ and an oil temperature of 100-120℃, and controlling the water pressure within the engine's design target range under normal operating conditions, measuring the water pressure generated under universal characteristic conditions and the torque interval at different speeds; Second, under normal operating conditions, controlling the water pressure and oil temperature within the design target range, measuring the water pressure fluctuation on the maximum thrust side of different cylinders and the corresponding speed at coolant outlet temperatures of 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, and 105℃; Third, under common operating conditions, controlling the water pressure, outlet temperature, and oil temperature within the design target range, measuring the water pressure fluctuation on the maximum thrust side of different cylinders and the corresponding speed under different auxiliary water tank pressure cap pressures under the engine's external characteristic conditions.

[0031] Step 7 involves filtering the time-domain data of cooling water pressure collected under different operating conditions, selecting an appropriate high-pass filter frequency, and eliminating the influence of component vibration and engine combustion (vibration frequency mainly in the range of <10KHz) on water impact pressure. Unless otherwise specified, a high-pass filter above 10KHz is preferred to better visualize the cooling water pressure fluctuations and the impact pressure caused by bubble bursts.

[0032] Step 8 involves filtering the time-domain cooling water pressure under the same operating conditions using a high-pass filter above 10kHz. When the water pressure frequently experiences instantaneous impact pressure reaching a certain threshold (without special requirements, the threshold is set to 1 bar), it is considered that the bubbles have burst and cavitation spots have begun to appear on the cylinder liner. As time accumulates, the number of cavitation spots increases, and the cylinder liner may be broken down. Therefore, it is determined that the cooling water passage needs to be redesigned.

[0033] Step 9 is to repeat steps 3 to 6. When frequent instantaneous water pressure impacts occur again under a certain operating condition and the pressure reaches a certain threshold (no special requirements, the threshold is set to 1 bar), it is determined that the engine will definitely experience cavitation under the boundary conditions of this operating condition.

[0034] The sensor location should be selected through simulation to check the height of the inspection hole. It is typically located at the point of greatest impact from piston thrust, and the sensor assembly must not protrude from the water channel. Ideally, pure water should be used as the coolant, as only pure water can accurately transmit vibration signals to the high-frequency pressure sensor. To eliminate air bubbles in the water, it must be boiled at 100°C for 5 minutes, with the pressure cap open and partial load applied.

[0035] Through the detailed steps and conditions described above, this invention can effectively utilize water pressure fluctuations to determine engine cylinder liner cavitation, providing important technical support for engine design and performance evaluation.

[0036] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A test method for determining engine cylinder liner cavitation using water pressure fluctuations, characterized in that, Includes the following steps: The cooling water circulating on the outer wall of the engine cylinder liner is continuously and alternately circulated. Under cylinder liner vibration and different water pressure changes, when the transient pressure of the cooling water at a certain point of the cylinder liner drops below the liquid saturated vapor pressure, bubbles are generated and separated. As the number of bubbles increases, under the vibration of the cylinder liner and changes in water pressure, the bubbles are compressed to a certain extent, and the pressure rises, causing them to burst. Collect and analyze water pressure fluctuation data; Based on the collected data, determine whether cavitation erosion occurs in the cylinder liner and whether the cooling water passage needs to be redesigned.

2. The test method for judging engine cylinder liner cavitation using water pressure fluctuations according to claim 1, characterized in that, Pressure sensors are installed in the cavitation-prone areas of the engine cylinder liner cooling water passages. These pressure sensors are used to monitor the pressure fluctuations of the cooling water in real time.

3. The test method for judging engine cylinder liner cavitation using water pressure fluctuations according to claim 2, characterized in that, The sensor head does not protrude from the waterway surface to avoid affecting the accuracy of water flow and pressure fluctuations, while also ensuring a sealed sensor installation.

4. The test method for judging engine cylinder liner cavitation using water pressure fluctuations according to claim 3, characterized in that, The pressure sensor sensitivity was set, and based on CAE and usage data evaluation, the data acquisition frequency of the data acquisition instrument was set to a value corresponding to the frequency of bubble bursting during engine cylinder liner cavitation.

5. The test method for judging engine cylinder liner cavitation using water pressure fluctuations according to claim 4, characterized in that, The engine coolant is pure water, and after 24 hours of break-in operation, the engine performance is checked and no problems are found. Then, a transient impact pressure test is performed. At the same time, in order to eliminate the gas in the water, the water needs to be boiled at 100°C for 5 minutes and then the auxiliary water tank pressure cap is opened for 10 minutes to release the gas.

6. The test method for judging engine cylinder liner cavitation using water pressure fluctuations according to claim 5, characterized in that, Test the water pressure fluctuations on the maximum thrust side of different cylinders under different engine operating conditions and the corresponding engine speeds.

7. The test method for judging engine cylinder liner cavitation using water pressure fluctuations according to claim 6, characterized in that, The time-domain data of cooling water pressure collected under different operating conditions are filtered, and an appropriate high-pass filter frequency is selected to eliminate the influence of component vibration and engine combustion on water pressure.

8. The test method for judging engine cylinder liner cavitation using water pressure fluctuations according to claim 7, characterized in that, After filtering the time-domain cooling water pressure under the same operating conditions using a high-pass filter above 10kHz, when the water pressure frequently experiences instantaneous impact pressure reaching a certain threshold, it is considered that bubbles burst and cavitation spots begin to appear on the cylinder liner. As time accumulates, the number of cavitation spots increases, and the cylinder liner may be broken down. Therefore, it is determined that the cooling water passage needs to be redesigned.

9. A test method for determining engine cylinder liner cavitation using water pressure fluctuations according to claim 8, characterized in that, When frequent and instantaneous water pressure impacts occur again under a certain operating condition and the pressure reaches a certain threshold, it is determined that the engine will definitely experience cavitation under the boundary conditions of that operating condition.

10. A test method for determining engine cylinder liner cavitation using water pressure fluctuations according to claim 9, characterized in that, The pressure sensor is located on the side of the engine cylinder liner where the lateral thrust is greatest.

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