A knock threshold calibration strategy

Abstract

The present application relates to engine knock processing technical field, disclose a kind of knock threshold calibration strategy, comprising the following steps: step one: according to test requirement, confirm test boundary condition;Step two: establish knock threshold condition table;Step three: calibrate the first cylinder low temperature knock threshold;Step four: calibrate the second-6 cylinder low temperature knock threshold;Step five: calibrate the first cylinder high temperature knock threshold;Step six: calibrate the second-6 cylinder high temperature knock threshold;Step seven: select knock threshold, use two sets of knock threshold, in the environment condition with higher knock probability, use smaller knock threshold, timely trigger ignition advance angle knock delay function, effectively protect engine, reduce the probability of engine knock;In the environment condition with lower knock probability, use higher knock threshold, avoid early trigger ignition advance angle knock delay function, improve the power and economy of engine.

Description

Technical Field

[0001] This invention relates to the field of engine knock control technology, and more specifically to a knock threshold calibration strategy. Background Technology

[0002] The massive shockwaves generated by combustion in a gas turbine engine cause engine vibration, a phenomenon known as knocking. This is an abnormal combustion phenomenon caused by factors such as premature ignition timing, excessively high temperature, and low fuel octane rating. It can lead to severe knocking sounds and damage to the thermal boundary layer of the combustion chamber, increasing the mechanical and thermal loads on the engine, resulting in reduced engine output power, increased cylinder temperature, and increased fuel consumption.

[0003] Currently, the main method for detecting and calibrating knock is to use the signal from a knock sensor to determine whether knock has occurred, and then take measures such as retracting the ignition timing to reduce damage to the engine. However, engine knock is closely related to operating conditions, especially the intercooler intake temperature. The higher the intake temperature, the higher the probability of engine knock, and vice versa. In normal use, a single knock threshold is used. To avoid false alarms of knock events, the knock threshold is set too high, which may not protect the engine in time when knock occurs.

[0004] Therefore, the above-mentioned technologies have the problem that existing knock threshold calibration methods cannot completely and effectively protect the engine. Summary of the Invention

[0005] The technical problem to be solved by this invention is that existing threshold calibration methods cannot effectively protect the engine.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is to provide a knock threshold calibration strategy, comprising the following steps:

[0007] Step 1: Confirm the test boundary conditions according to the test requirements.

[0008] The test engine was installed on a performance test bench. During the test, the intercooler temperature of the engine was controlled at 45°C, the highest outlet water temperature of the engine was less than 106°C, the highest lubricating oil temperature (oil pan) was continuously less than or equal to 125°C, the relative humidity was controlled within 50%, and the highest exhaust temperature of the engine was controlled within 760°C. At the same time, cylinder pressure sensors were installed in each cylinder of the engine to test the cylinder pressure data during the engine operation, and a KBOX combustion analyzer was connected to record the actual knock pressure of the engine.

[0009] Step 2: Establish a knock threshold condition table

[0010] A knock threshold condition table is established with engine speed (rpm) as the x-axis and engine load (kPa) as the y-axis.

[0011] Step 3: Calibrate the low-temperature knock threshold of cylinder 1

[0012] Select the operating point in the knock threshold operating condition table, turn off the knock ignition retarding function (i.e., set the initial knock threshold value to infinity), increase the ignition advance angle of cylinder 1 until strong knocking occurs in cylinder 1, record the maximum knock ratio calculated by the ECU, and this maximum knock ratio is the starting point of the knock threshold. Gradually decrease the knock threshold of this operating condition, activate the knock ignition retarding function, until the actual knock pressure measured by the combustion analyzer of cylinder 1 is within the predetermined range, record the knock ratio at this time as the knock threshold of this operating condition, and fill it into the knock threshold operating condition table. Then select other operating points in the table and repeat the above steps until the low-temperature knock threshold of each operating condition of cylinder 1 is calibrated.

[0013] Step 4: Calibrate the low-temperature knock threshold for cylinders 2-6

[0014] Repeat step three to complete the calibration of the low-temperature knock threshold for cylinders 2-6 under various operating conditions;

[0015] Step 5: Calibrate the high-temperature knock threshold of cylinder 1

[0016] With the intercooler temperature controlled at 65℃ and other test conditions unchanged, select the first operating point in the knock threshold table, disable the knock ignition retarding function (i.e., set the initial knock threshold value to infinity), increase the ignition advance angle of cylinder 1 until strong knocking occurs in cylinder 1, and record the maximum knock ratio calculated by the ECU. This maximum knock ratio is the starting point of the knock threshold. Gradually decrease the knock threshold for this operating condition, activate the knock ignition retarding function, until the actual knock pressure measured by the combustion analyzer of cylinder 1 is within the predetermined range, and record the knock ratio at this time as the knock threshold for this operating condition. Then select other operating points in the table and repeat the above steps until the high-temperature knock threshold of cylinder 1 for each operating condition is calibrated.

[0017] Step Six: Calibrate the high-temperature knock threshold for cylinders 2-6

[0018] Select each operating point of cylinders 2-6 and repeat step five until the high temperature knock threshold of each operating point of cylinders 2-6 is calibrated.

[0019] Step 7: Select the knock threshold

[0020] The intercooler temperature is detected by the ECU. When the intercooler temperature is <45℃, the data in the low intercooler temperature knock threshold condition table is selected as the knock threshold. When the intercooler temperature is >65℃, the data in the high intercooler temperature knock threshold condition table is selected as the knock threshold. When the intercooler temperature is between 45-65℃, the knock threshold is calculated by interpolation.

[0021] Optionally, the method for determining strong detonation in steps three and five is that the detonation peak value displayed in the KBOX combustion analyzer is >10 bar, the predetermined range of actual detonation pressure in step three is detonation peak value <6 bar, and the predetermined range of actual detonation pressure in step five is detonation peak value <3 bar.

[0022] Optionally, the formula for calculating the detonation ratio in steps three and five is: Detonation ratio = integral value of detonation signal within the detonation window / integral value of detonation signal within the reference window.

[0023] Optionally, the principle for determining the knock threshold is as follows: when the knock ratio calculated by the ECU is greater than a certain set knock ratio, it is determined that a knock event has occurred, and the set knock ratio is the knock threshold.

[0024] In summary, this invention employs two sets of knock thresholds. A smaller knock threshold is used in environments with a high probability of knocking, promptly triggering the ignition advance angle knock retardation function to effectively protect the engine and reduce the likelihood of engine knocking. A higher knock threshold is used in environments with a low probability of knocking to avoid premature triggering of the ignition advance angle knock retardation function, thereby improving engine power and fuel economy. By selecting different knock threshold tables based on the knock probability, both timely protection and maximizing engine power can be achieved. Attached Figure Description

[0025] Figure 1 Flowchart for calibrating the temperature knock threshold of the low-temperature intercooler;

[0026] Figure 2 Flowchart for selecting the detonation threshold. Detailed Implementation

[0027] The following is in conjunction with the appendix Figure 1-2 The present invention will be described in further detail below.

[0028] Example 1

[0029] This invention discloses an engine knock threshold calibration strategy, comprising the following steps:

[0030] Step 1: Confirm the test boundary conditions according to the test requirements.

[0031] The test engine was installed on a performance test bench. The experimental conditions in this embodiment were as follows: the intercooler temperature of the engine was controlled at 45°C during the test, the highest outlet water temperature of the engine was adjusted to 106°C, the highest lubricating oil temperature (oil pan) was continuously set at 125°C, the relative humidity was controlled at 50%, and the highest exhaust temperature of the engine was controlled at 760°C. At the same time, cylinder pressure sensors were installed in each cylinder of the engine to test the cylinder pressure data during the engine operation, and a KBOX combustion analyzer was connected to record the actual knock pressure of the engine.

[0032] Step 2: Establish a knock threshold condition table

[0033] A knock threshold condition table is established with engine speed (rpm) as the x-axis and engine load (kPa) as the y-axis, as shown in Table 1.

[0034] Table 1: Knock Threshold Operating Conditions Table

[0035]

[0036] Step 3: Calibrate the low-temperature knock threshold of cylinder 1

[0037] Select the operating point in the knock threshold operating condition table, turn off the knock ignition retarding function (i.e., set the initial knock threshold value to infinity), increase the ignition advance angle of cylinder 1 until strong knock occurs in cylinder 1, record the maximum knock ratio calculated by the ECU, and this maximum knock ratio is the starting point of the knock threshold. Gradually decrease the knock threshold of this operating condition, activate the knock ignition retarding function, until the actual knock pressure measured by the combustion analyzer of cylinder 1 is within the predetermined range, record the knock ratio at this time as the knock threshold of this operating condition, and fill it into the knock threshold operating condition table. Then select other operating points in the table and repeat the above steps until the low-temperature knock threshold of each operating condition of cylinder 1 is calibrated, as shown in Table 2.

[0038] Table 2: Cylinder Knock Threshold Table (Low Intercooler Temperature)

[0039]

[0040] Step 4: Calibrate the low-temperature knock threshold for cylinders 2-6

[0041] Repeat step 3 to complete the calibration of the low-temperature knock threshold for each operating condition of cylinders 2-6, as shown in Tables 3 to 7.

[0042] Table 3: Second Cylinder Knock Threshold Table (Low Intercooler Temperature)

[0043]

[0044] Table 4: Third Cylinder Knock Threshold Table (Low Intercooler Temperature)

[0045]

[0046] Table 5: Knock Threshold Table for Cylinder 4 (Low Intercooler Temperature)

[0047]

[0048] Table 6: Cylinder 5 Knock Threshold Table (Low Intercooler Temperature)

[0049]

[0050] Table 7: Cylinder 6 Knock Threshold Table (Low Intercooler Temperature)

[0051]

[0052] Step 5: Calibrate the high-temperature knock threshold of cylinder 1

[0053] With the intercooler temperature controlled at 65℃ and other test conditions unchanged, select the first operating point in the knock threshold table, disable the knock ignition retarding function (i.e., set the initial knock threshold value to infinity), increase the ignition advance angle of cylinder 1 until strong knocking occurs in cylinder 1, and record the maximum knock ratio calculated by the ECU. This maximum knock ratio is the starting point of the knock threshold. Gradually decrease the knock threshold for this operating condition, activate the knock ignition retarding function, until the actual knock pressure measured by the combustion analyzer of cylinder 1 is within the predetermined range, and record the knock ratio at this time as the knock threshold for this operating condition. Then select other operating points in the table and repeat the above steps until the high-temperature knock threshold of cylinder 1 for each operating condition is calibrated, as shown in Table 8.

[0054] Table 8: Cylinder 1 Knock Threshold Table (High-Intensity Cooler Temperature)

[0055]

[0056] Step Six: Calibrate the high-temperature knock threshold for cylinders 2-6

[0057] Select each operating point of cylinders 2-6 and repeat step five until the high temperature knock threshold of each operating point of cylinders 2-6 is calibrated, as shown in Tables 9 to 13.

[0058] Table 9: Second Cylinder Knock Threshold Table (High and Low Cooler Temperatures)

[0059]

[0060] Table 10: Knock Threshold Table for Cylinder 3 (High and Low Cooler Temperatures)

[0061]

[0062] Table 11: Knock Threshold Table for Cylinder 4 (High and Low Cooler Temperatures)

[0063]

[0064] Table 12: Cylinder 5 Knock Threshold Table (High and Low Cooler Temperatures)

[0065]

[0066] Table 13: Cylinder 6 Knock Threshold Table (High and Low Cooler Temperatures)

[0067]

[0068] Step 7: Select the knock threshold

[0069] The intercooler temperature is detected by the ECU. When the intercooler temperature is <45℃, the data in the low intercooler temperature knock threshold condition table is selected as the knock threshold. When the intercooler temperature is >65℃, the data in the high intercooler temperature knock threshold condition table is selected as the knock threshold. When the intercooler temperature is between 45-65℃, the knock threshold is calculated by interpolation.

[0070] In a further embodiment, the method for determining strong detonation in steps three and five is that the detonation peak value displayed in the KBOX combustion analyzer is >10 bar, the predetermined range of actual detonation pressure in step three is the detonation peak value <6 bar, and the predetermined range of actual detonation pressure in step five is the detonation peak value <3 bar.

[0071] In a further embodiment, the formula for calculating the detonation ratio in steps three and five is: Detonation ratio = integral value of the detonation signal within the detonation window / integral value of the detonation signal within the reference window.

[0072] In a further implementation, the principle for determining the knock threshold is as follows: when the knock ratio calculated by the ECU is greater than a certain set knock ratio, it is determined that a knock event has occurred, and the set knock ratio is the knock threshold.

[0073] In summary, this invention proposes a knock threshold calibration strategy. It employs two sets of knock thresholds: a smaller threshold is used in environments with a high knock probability to promptly trigger the ignition advance angle knock retardation function, effectively protecting the engine and reducing the likelihood of engine knock; a higher threshold is used in environments with a low knock probability to avoid premature triggering of the ignition advance angle knock retardation function, thus improving engine power and fuel economy. By selecting different knock threshold tables based on the knock probability, the timely protection and maximum engine performance can be balanced, reducing the impact of knock sensor and engine consistency on the knock threshold.

[0074] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A knock threshold calibration strategy, characterized in that, Includes the following steps: Step 1: Confirm the test boundary conditions according to the test requirements. The test engine was installed on a performance test bench. During the test, the intercooler temperature of the engine was controlled at 45°C, the highest outlet water temperature of the engine was less than 106°C, the highest lubricating oil temperature was continuously less than or equal to 125°C, the relative humidity was controlled within 50%, and the highest exhaust temperature of the engine was controlled within 760°C. At the same time, cylinder pressure sensors were installed in each cylinder of the engine to test the cylinder pressure data during the engine operation, and a KBOX combustion analyzer was connected to record the actual knock pressure of the engine. Step 2: Establish a knock threshold condition table A knock threshold condition table is established with engine speed as the horizontal axis and engine load as the vertical axis. Step 3: Calibrate the low-temperature knock threshold of cylinder 1 Select the operating point in the knock threshold operating condition table, turn off the knock ignition retarding function (i.e., set the initial knock threshold value to infinity), increase the ignition advance angle of cylinder 1 until strong knocking occurs in cylinder 1, record the maximum knock ratio calculated by the ECU, and this maximum knock ratio is the starting point of the knock threshold. Gradually decrease the knock threshold of this operating condition, activate the knock ignition retarding function, until the actual knock pressure measured by the combustion analyzer of cylinder 1 is within the predetermined range, record the knock ratio at this time as the knock threshold of this operating condition, and fill it into the knock threshold operating condition table. Then select other operating points in the table and repeat the above steps until the low-temperature knock threshold of each operating condition of cylinder 1 is calibrated. Step 4: Calibrate the low-temperature knock threshold for cylinders 2-6 Repeat step three to complete the calibration of the low-temperature knock threshold for cylinders 2-6 under various operating conditions; Step 5: Calibrate the high-temperature knock threshold of cylinder 1 With the intercooler temperature controlled at 65℃ and other test conditions unchanged, select the first operating point in the knock threshold table, disable the knock ignition retarding function (i.e., set the initial knock threshold value to infinity), increase the ignition advance angle of cylinder 1 until strong knocking occurs in cylinder 1, and record the maximum knock ratio calculated by the ECU. This maximum knock ratio is the starting point of the knock threshold. Gradually decrease the knock threshold for this operating condition, activate the knock ignition retarding function, until the actual knock pressure measured by the combustion analyzer of cylinder 1 is within the predetermined range, and record the knock ratio at this time as the knock threshold for this operating condition. Then select other operating points in the table and repeat the above steps until the high-temperature knock threshold of cylinder 1 for each operating condition is calibrated. Step Six: Calibrate the high-temperature knock threshold for cylinders 2-6 Select each operating point of cylinders 2-6 and repeat step five until the high temperature knock threshold of each operating point of cylinders 2-6 is calibrated. Step 7: Select the knock threshold The intercooler temperature is detected by the ECU. When the intercooler temperature is <45℃, the data in the low intercooler temperature knock threshold condition table is selected as the knock threshold. When the intercooler temperature is >65℃, the data in the high intercooler temperature knock threshold condition table is selected as the knock threshold. When the intercooler temperature is between 45-65℃, the knock threshold is calculated by interpolation.

2. The detonation threshold calibration strategy according to claim 1, characterized in that, The method for determining strong detonation in steps three and five is that the detonation peak value displayed in the KBOX combustion analyzer is >10 bar. The predetermined range of actual detonation pressure in step three is detonation peak value <6 bar, and the predetermined range of actual detonation pressure in step five is detonation peak value <3 bar.

3. The detonation threshold calibration strategy according to claim 1, characterized in that, The formula for calculating the detonation ratio in steps three and five is: Detonation ratio = integral value of the detonation signal within the detonation window / integral value of the detonation signal within the reference window.

4. The detonation threshold calibration strategy according to claim 3, characterized in that, The principle for determining the knock threshold is as follows: when the knock ratio calculated by the ECU is greater than a certain set knock ratio, it is determined that a knock event has occurred. The set knock ratio is the knock threshold.

Images