GB/T 5487-1995 Determination of gasoline octane number (research method)
Some standard content:
National Standard of the People's Republic of China
Test method for knock characteristicsof motor fuels by the Research method1 Subject content and scope of application
GB/T 5487—1995
Replaces GB/T5487—85
This standard specifies the steps, operating conditions, test conditions and operating details for determining the octane number of gasoline (research method) using the American Society for Testing and Materials (ASTM) octane number tester. This standard is applicable to the determination of the anti-knock properties of gasoline for automobiles. Note: After other types of octane number machines are qualified according to the calibration value of toluene calibration fuel, refer to this method for the determination of gasoline octane number. 2 Reference standards
GB484 Motor gasoline
GB/T3144 Gas chromatography method for determination of hydrocarbon impurities in toluene GB/T4016 Terminology of petroleum products
GB/T4756 Sampling method for petroleum and liquid petroleum products (manual method) GB/T8170 Rules for rounding off values
GB/T11117.1 Reference fuel for knock test
Reference fuel isooctane
GB/T11117.2 Reference fuel for knock test Reference fuel n-heptane SH0041 Unleaded motor gasoline
SH 0112 Gasoline
3 Terminology
3.1 Verification fuel
A mixture of isooctane, n-heptane and ethyl liquid used to check the working condition of the engine. 3.2 Cylinder height
The relative position of the engine cylinder and the piston is indicated by the reading of a micrometer or a counter. 3.3 Knock sensor
The magnetostrictive sensor installed on the cylinder head is in direct contact with the combustion gas in the cylinder, generating a voltage proportional to the rate of change of the pressure in the cylinder. The more serious the detonation tendency in the cylinder, the greater the voltage value generated by the sensor. 3.4 Knock meter
Receives the signal sent by the detonation sensor, deletes the waves of other vibration frequencies, leaving only the detonation wave, and amplifies and integrates it. A stable voltage signal is obtained and then sent to the detonation meter. 3.5 Detonation meter
It is actually a millivolt meter that displays the detonation intensity with 0 to 100 divisions (working range 20 to 80 divisions). Approved by the State Administration of Technical Supervision on December 21, 1995, and implemented on August 1, 1996
3.6 Operation table
GB/T5487--1995
Specific relationship between octane number and cylinder height (compression ratio) of basic reference fuel blending oil at a pressure of 101.3kPa when producing standard knock intensity.
3.7 Knock intensity
Indicative value of knock intensity when the evaluation fuel is burned on the knock test device. 3.8 Maximum knock intensity oil-air ratio
The fuel-air mixture ratio when the fuel burns in the knock test device and produces the maximum knock intensity is called the maximum knock intensity oil-air ratio, which is achieved by adjusting the wave surface height in the carburetor glass sight glass. 3.9 The micrometer reading or the counter reading
is a digital indication of the cylinder height (the reference position indicating the cylinder height at the specified compression pressure when the engine is running). 3.10 Octane number
An agreed value indicating the anti-knock property of a spark-ignition engine fuel. In a standard engine test under specified conditions, it is determined by comparison with a standard fuel and is expressed as the volume percentage of isooctane in a standard fuel having the same anti-knock property as the fuel being measured. Different methods for determining the octane number give different values; therefore, the method used should be specified when quoting the octane number. 3.11 Benchmark reference fuel
Reference fuel isooctane, reference fuel n-heptane, a blend of reference fuel isooctane and reference fuel n-heptane in a volume ratio, or a blend of reference fuel isooctane with a known octane number and a standard dilution of ethyl liquid added to the reference fuel isooctane. 3.11.1 The reference fuel blend with an octane number greater than 100 is a blend with a specific octane number higher than 100 when a certain milliliter of standard diluted ethyl liquid is added to each liter of reference fuel isooctane according to the ratio determined by the test. The blending ratio is shown in Table 3. 3.11.2 The reference fuel blend with an octane number lower than 100 is a blend with an octane number of 100 for the reference fuel isooctane and a octane number of 0 for the reference fuel normal heptane. In the blend with the reference fuel isooctane and the reference fuel normal heptane, the volume percentage of the reference fuel isooctane is the octane number of the blend.
3.12 Broadening
The sensitivity of the knock meter, i.e., the division indicated on the knock meter for the unit octane number. 3.13 Standard knock intensity
In the blend with the maximum knock intensity, the volume percentage of the reference fuel isooctane is the octane number of the blend. Under the gas ratio, adjust the cylinder height to the specified value in the operation table, and make atmospheric pressure corrections according to Table 5. The degree of knock produced when the reference fuel blending oil with known octane number is burned in the knock test device is called the standard knock intensity. Generally, the "amplification" of the knock meter should be adjusted so that the knock meter reading at this time is 50. 3.14 Toluene calibration fuel
Toluene calibration fuel is a mixture of toluene, reference fuel n-heptane and reference fuel isooctane in different volume ratios. It is a highly sensitive fuel used to determine the allowable deviation and judge whether the test machine is suitable for the test. 4 Significance and application
4.1 Research octane number (RON) is related to the anti-knock performance of full-size spark ignition engines at low speeds. Motor octane number (MON) is related to the full 4.2 Establishment of the anti-knock index
The octane numbers of the above two methods are measured on a special single-cylinder engine under standard test conditions by comparing the knock inclination of the sample with that of the reference fuel. They cannot fully reflect the anti-knock performance of the fuel during vehicle operation. Therefore, an empirical relationship formula for calculating the anti-knock performance during vehicle operation is proposed:
Anti-knock index - K.·RON+K. ·MON+K
K, K, K: are coefficients, which are different for different types of vehicles. This is related to the operating characteristics and operating conditions of the engine. They are not determined through typical road tests. 194
GB/T5487..-1 995
General simplified formula, using the average anti-knock performance of the total number of vehicles. Usually K, = 0.5, K. 0.5, K, 0, that is, anti-knock index = RON + MON
4.3 Standard application
To ensure that the anti-knock performance of the fuel is correctly matched with the engine performance, this standard is used in engine manufacturers, oil refineries, and commercial delivery acceptance.
5 Method Overview
5.1 Octane number determination process
The research method of a fuel is to determine the knock tendency of the fuel under standard operating conditions by comparing it with the knock tendency of a reference fuel mixture with a known octane number. The specific method is to change the compression ratio and use an electronic knock meter to measure the knock intensity to obtain the standard knock intensity. At this time, the following two methods can be used for determination. 5.2 Interpolation method
Under the condition of a fixed compression ratio, the knock meter reading of the sample is between the knock meter readings of the two reference fuel blends, and the octane number of the sample is calculated by interpolation.
5.3 Compression ratio method
The cylinder height required for the sample to reach the standard knock intensity is read from Tables 1 and 2. When this method is used, the reference fuel instrument is used to determine the standard knock intensity, and the standard knock intensity should be checked frequently. 6 Equipment
The knock test arm
Includes a single-cylinder engine with a continuously variable compression ratio, with corresponding load equipment, auxiliary equipment and instruments, all of which are installed on a fixed base. The ASTM-CFR test machine made in the United States is defined as the test equipment for this standard. 7 Fuel
7.1 Reference fuel for knock test
7.1.1 Reference fuel is isooctane, which meets the requirements of GB/T11117.1. 7.1.2 Reference fuel is heptane, which meets the requirements of GB/T11117.2. 7.1.3 Reference fuel is a blended oil with an octane number of 80, which is a mixture of isooctane and reference fuel normal heptane. 7.1.4 Diluted ethyl liquid, reference fuel isooctane Ethyl liquid is blended with octane to make an octane number greater than 100, and is used as a reference fuel for measuring the octane number of the sample greater than 100.
7.2 Calibration fuel Toluene (specifications as specified in Table 8) is blended with reference fuel isooctane and reference fuel normal heptane to make the calibration fuel for the knock test device. The blending ratio and corresponding octane number are shown in Table 4. 8 Sampling
Sampling is carried out in accordance with the provisions of GB/T4756 method.
9 Engine operating conditions and test conditions
9.1 Engine speed
600±6r/min, and the maximum change in a test does not exceed 6r/min. 9.2 Ignition advance angle
Fixed at 13.0° before top dead center.
9.3 Spark plug gap
GB/T 5487-1995
0.51±0.13mm(0.020±0.005in). 9.4 For contactless ignition system, the gap between the bottom of the sensor and the end of the rotor (vane) is 0.08～0.013mm(0.003~0.005in).
9.5 Adjustment of rocker arm bracket
9.5.1 Adjustment of rocker arm bracket support screws: Each rocker arm bracket support screw is screwed into the cylinder body, and the distance between the machined surface on the cylinder body and the bottom surface of the fork body is 31mm(1 in). 9.5.2 Adjustment of rocker arm bracket: When the non-compensated counter reading is 722 (micrometer reading is 0.500in), the rocker arm bracket must be level. 9.5.3 The rocker arm should be set with the rocker arm bracket set and the intake and exhaust valves closed. The rocker arm bracket should be in a horizontal position. 9.6 Inlet and exhaust valve clearance
The inlet and exhaust valve clearances are both 0.20±0.03mm (0.008±0.001in). It is measured when the engine is running hot under standard operating conditions.
9.7 Crankcase lubricating oil
Use gasoline engine oil of L-EQE grade or above, and the viscosity grade is preferably 30. 9.8 Lubricating oil pressure
Under standard test conditions, the lubricating oil pressure is 172~207kPa (25~30lbf/in2). 9.9 Lubricating oil temperature
57±8.5℃ (135±15F), measured by immersing the thermistor in the crankcase lubricating oil. 9.10 Coolant temperature
100±1.5°C (212±3F), which should be kept constant within the range of ±0.5°C (±1F) during a test. 9.11 Intake air humidity
3.56~7.12g water/kg dry air (25~50gr water/b dry air). 9.12 Intake air temperature
Measured with a mercury thermometer inserted into the intake manifold, maintained within the range of ±1.1°C (±2F) according to the relationship between local atmospheric pressure and temperature in Table 5. Use this temperature as the setting value of the micrometer or counter to obtain the standard explosion intensity and make a preliminary check on the evaluation performance. Other temperatures may be used in subsequent tests as described in Article 12.3.2.2. However, the initial test must be carried out at the temperature specified in Table 5. 9.13 Carburetor throat diameter
The diameter at the throat is 14.3mm (i
in).
9.14 Setting of reference cylinder height
When the engine reaches the specified temperature, adjust the basic cylinder height according to the provisions of Appendix D. 9.15 Fuel-air ratio
For each test, whether it is the sample or the reference fuel, the fuel-air ratio should be adjusted to obtain the maximum detonation intensity. It is obtained by the height of the carburetor tank. The fuel level gauge should be within the scale range of 0.7 to 1.7, otherwise the nozzle hole should be cleaned or the size of the nozzle hole should be changed to meet the above requirements.
9.16 Detonation meter reading range
The detonation intensity is between 20 and 80 in the working range of the detonation meter. When it is less than 20, the detonation intensity is nonlinear, and when it is greater than 80, the potential change of the detonation meter is nonlinear.
9.17 Detonation meter width
When the octane number is 90, the width of the knock indication adjusted to each octane number is 10 to 18 divisions. The width of the spread will vary with the size of the octane number. For example, if the octane number is 90, it is not necessary to change the octane number in the range of 80 to 102 in most cases.
9.18 Interpolation reference fuel
When using the interpolation method for evaluation, the knock meter reading of the sample must be between the readings of two adjacent reference fuels, and the difference between the octane 196
GB/T 5487—1995
values of the two reference fuels cannot be greater than 2 units. Samples with an octane number below 100 can only be evaluated using reference fuels that do not contain ethyl liquid. When the octane number is between 100.0 and 103.5, only the following groups of reference fuels can be used: 100.0 and 100.7
100.7 and 101.3
101.3 and 102.5
102.5 and 103.5
9.19 Reference fuels for compression ratio method
The knock meter reading of the test sample must match the reference fuel mixture selected in the reference fuel system in Chapter 7. When the octane number is between 100.0 and 103.5, only 100.7, 101.3, 102.5, and 103.5 can be used. The difference between the test sample and the reference fuel shall not exceed the provisions in 14.3.
9.20 Sample treatment
The sample should be cooled to between 2 and 10℃ (35 and 50F) before being poured into the oil tank. 10 Starting and stopping the engine
10.1 Starting the engine
Preheat the crankcase lubricating oil to 57±8.5℃ (135±15F) before starting. Check whether the engine is normal and whether it lacks lubricating oil and coolant. Turn the engine 2 to 3 times, turn on the cooling water, add lubricating oil to each lubrication point, and then use the motor to drive the engine to run. Turn on the ignition, heat the switch, and the carburetor draws fuel from an oil tank to ignite the engine. 10.2 Engine shutdown
First close the fuel valve, then release all the fuel in the oil tank, turn off the heating and ignition switches, use the motor to run the engine for 1 minute, turn off the motor and the cooling water switch. In order to avoid corrosion and distortion of the engine's intake and exhaust valves and valve seats between two operations, turn the flywheel to the top dead center of the compression stroke so that both valves are in the closed position. 11 Adjustment of the knock meter
11.1 Zero adjustment of the knock meter
Under no power supply, adjust the adjustment screw on the knock meter so that the knock meter pointer is zero. Such adjustment should be checked at least once a month. 11.2 Zero adjustment of the knock meter
After the zero point of the knock meter is adjusted, power the knock meter, put the instrument zeroing switch at the "0" position, and the time constant at the "1" position, and check whether the knock meter pointer is zero. If it is not at zero, adjust the potentiometer under the knock meter, and tighten the protective cap after adjustment. Such adjustment should be adjusted once a day before the test.
11.3 Adjusting the time constant
To adjust the time constant is to adjust the integration time, that is, to adjust the sensitivity of the instrument response. Position "1" has the shortest integration time and the fastest response speed, but the instrument is also the most unstable. Position "6" has the longest integration time and the slowest response speed, but the instrument is the most stable. Usually, the time constant should be placed at "3" or "4".
11.4 Adjusting the spread
It is to adjust the instrument's discrimination ability. The appropriate instrument spread level shall comply with the requirements of Article 9.18. Taking the adjustment of the spread level when the octane number is 90 as an example, the specific adjustment is as follows:
11.4.1 Operate the engine with a reference fuel of 90 octane number so that the engine operating conditions meet the requirements of Chapter 9. 11.4.2 Turn the "Instrument Reading" and "Spread" knobs counterclockwise, adjust the coarse adjustment knob to the bottom, and adjust the fine adjustment knob to the middle position. 11.4.3 Adjust the "spread" coarse adjustment knob clockwise to the "3" position. 11.4.4 Adjust the "meter reading" coarse adjustment knob clockwise to make the knock meter pointer roughly point to the middle position. The fine adjustment knob can be used to adjust the precise reading.
11.4.5 Check the carburetor fuel level position to obtain the maximum knock intensity. If the maximum knock meter reading is difficult to obtain during adjustment, it means that the spread is too small. You can use methods 11.4.2 to 11.4.4 to increase the spread level. 11.4.6 Adjust the carburetor fuel level again to obtain the liquid level with the maximum knock reading. 11.4.7 Re-adjust the "Instrument Reading" fine adjustment knob to make the knock meter reading 50 ± 3. 11.4.8 Determine the actual instrument expansion level based on the reading of the knock meter of a unit octane number. The simplest way is to change the compression ratio without changing the fuel and observe the change of the knock meter pointer. For example, when working with a reference fuel with an octane number of 90, adjust the compression ratio to the micrometer and counter position of octane numbers of 89, 90, and 91 (according to the requirements of Tables 1 and 2). When it is stable, record the knock meter reading. The difference is the instrument expansion level. It can also be measured with two reference fuels with octane numbers above and below 90. Under the condition of unchanged compression ratio, the difference of the measurement results is the instrument expansion level.
11.4.9 Increase the width: Turn the "width" fine adjustment knob clockwise to make the knock meter pointer 100. Turn the "meter reading" fine adjustment knob counterclockwise to make the knock meter pointer return to 50±3. If the width is not enough, repeat the above steps. 11.4.10 Reduce the spread: Turn the "spread" fine adjustment knob counterclockwise to make the knock meter pointer 20 or lower, then turn the "meter reading" fine adjustment knob clockwise to raise the knock meter pointer to 50 ± 3. If the spread range needs to be reduced, repeat the above steps. 11.4.11 During the adjustment, if it is found that the adjustment range of the fine adjustment knob cannot meet the requirements, it should be used in conjunction with the coarse adjustment knob to meet the adjustment needs.
11.4.12 The spread range should be 10~~18 degrees per unit octane number. If the spread range per unit octane number is greater than 20 divisions, be more careful during operation.
12 Adjustment and inspection of the standard state of the test machine 12.1 Preliminary inspection of the standard knock intensity of the engine When the engine is under the standard test conditions of Chapter 9 and meets the maximum knock intensity requirements of Article 9.16, the engine should be shut down immediately when the ignition switch is turned off. If it does not shut down, it means that the mechanical condition of the engine is bad. At this time, the spark plug and the combustion chamber of the engine should be checked, and the carbon deposits should be removed and repaired before repeating the above operation.
12.2 The fuel-air mixture ratio of the maximum knock intensity and the standard knock intensity are obtained through a small series of steps:
12.2.1 Preliminary adjustment of the cylinder height: Pour the sample into the carburetor oil tank and adjust the liquid level to the position where the maximum knock intensity is estimated, rotate the selector valve, use the sample to operate, and after the engine is in the standard state, adjust the cylinder height so that the knock meter pointer is at 50 or a smaller position.
12.2.2 Adjust the fuel-air ratio: If the liquid level is 1.3 on the glass level gauge, let the knock meter pointer reach a balanced state, then increase the liquid level to 1.2, 1.1 in increments of 0.1 to obtain the knock meter reading under a richer fuel-air mixture ratio, until the knock meter reading is at least 5 divisions lower than the maximum value; then adjust the fuel liquid level to the position where the knock meter produces the maximum reading, such as 1.2. Then, in the same way, adjust the liquid level to 1.3, 1.4 in turn. Work under a lean fuel-air mixture ratio until the knock meter reading is at least 5 divisions lower than the maximum value, and then adjust the fuel liquid level back to the position where the knock meter produces the maximum reading, or to the middle position of the two liquid levels that produce the same knock meter reading, such as 1.25. This is the maximum knock intensity fuel liquid level. The method to check the correctness of the above adjustment is to adjust the liquid level to 0.1 position on both sides of the above position, such as 1.15 and 1.35. If the readings all drop, it means that the former adjustment is correct. If some readings increase, it means that the former adjustment is wrong and must be readjusted. 12.2.3 Carburetor cooling: If there is obvious evaporation of bubbles in the liquid level gauge, causing liquid level fluctuations or unstable combustion, the carburetor must be cooled.
12.2.4 Standard coolant: In the carburetor cooling equipment, the circulating coolant (water or water-based antifreeze) must not be lower than 0.5C (33F) during carburetor exchange. This coolant can be recycled when evaluating any sample fuel. 12.2.5 Further adjustment of the detonation degree: After determining the maximum knock intensity oil-gas ratio, the knock meter reading may not be within the range of 50 ± 3. At this time, the cylinder height should be adjusted to make the knock meter reading 50 ± 3. 12.3 Correction and evaluation characteristics
12.3.1 Under the standard test conditions, the engine is subjected to a calibration test of toluene standard fuel. If the test results can meet the requirements of Table 4, this 498
GB/T 5487—1995
indicates that the equipment is in good condition. If it exceeds the requirements of Table 4 but meets the requirements of Table 6, the method of changing the intake temperature tuning can be used to make the calibration test results meet the requirements of Table 4. If the test results exceed the requirements of Table 6, this indicates that the equipment is in a bad condition and further inspection and calibration of the technical status of the equipment is required.
12.3.2 Determination of intake temperature Follow the steps below: 12.3.2.1 During the initial calibration test with toluene-standardized fuel, the engine intake temperature shall be obtained from Table 5 based on the atmospheric pressure of the day.
12.3.2.2 If the results of the toluene-standardized fuel test meet the requirements of Table 4, the intake temperature shall be controlled at the value in 12.3.2.1 in the subsequent sample evaluation.
12.3.2.3 If the results of the A-standardized fuel test do not meet the requirements of Table 4, but meet the requirements of Table 6, the intake temperature shall be adjusted to make the test results meet the requirements of Table 4. In the subsequent sample evaluation, the temperature shall be controlled at the intake temperature when the toluene test results meet the requirements of Table 4.
12.3.3 Frequency of calibration test 12.3.3.1 Before each daily assessment test, the assessment characteristics shall be calibrated with toluene-standardized fuel. 12.3.3.2 The calibration test results shall be valid only within 7 hours thereafter. 12.3.3.3 When the operator is replaced, the machine is shut down for more than 2 hours, or the machine is shut down for major maintenance or replacement of parts, the evaluation characteristics should be recalibrated:
12.3.3.4 Only toluene-calibrated fuel with an octane number close to that of the sample is selected for testing every day. If the octane number of the sample cannot be estimated, it is also possible to first determine the octane number of the sample and then calibrate the evaluation characteristics. 13 Evaluation of the sample by interpolation method
13.1 When testing at the same compression ratio, the knock meter reading of the sample should be between the knock meter readings of the two reference fuels. 13.2 The reference fuel must be prepared in accordance with the requirements of Chapter 7 and 9.19. 13.3 The first interpolated reference fuel
According to the method in Chapter 12, determine the cylinder height at which the sample produces the standard knock intensity. According to the cylinder height at this time, use Table 1 or Table 2 to estimate the octane number of the sample. Prepare a reference fuel close to the estimated octane number and pour it into a tank of the carburetor. Adjust the fuel level to the position where the maximum knock intensity is estimated. Rotate the selector valve to operate the engine with this reference fuel. Then adjust the fuel level according to the method in 12.2.2 to obtain the maximum knock intensity level and the maximum knock reading, and make a record. 13.4 The interpolated reference fuel
After the interpolated reference fuel test, the second reference fuel can be prepared. It is expected that the knock meter readings of the above two reference fuels should include the knock meter readings of the sample. The difference in octane values of the two reference fuels should not exceed 2 octane numbers. Pour the adjusted second reference fuel into the third tank of the carburetor, and adjust the fuel level using the method of 12.2.2 to obtain the maximum knock intensity level and the maximum knock meter reading, and record them. If the knock meter readings of the two reference fuels include the sample readings, or one of the two is alternate with the sample readings, you can continue according to 13.7. 13.5 Check the consistency of the standard knock intensity If the knock meter readings of the first and second reference fuels do not meet the requirements of 13.4, use the knock meter readings that have been measured to estimate the octane number of the sample. If the relationship between the cylinder height and the octane number of the sample meets the requirements of Table 1 or Table 2, and the atmospheric pressure correction is made according to Table 5, the test described in 13.6 can be carried out. If not, make necessary adjustments to the cylinder height and knock meter, and repeat the operations of 13.2 and 13.3.
13.6 The first internal reference fuel
If the knock meter readings of the first and second reference fuels cannot include the readings of the sample, a third reference fuel should be selected based on the results of the measured data budget to replace one of the first two and cooperate with the other to achieve the goal of including the knock meter readings of the sample.
13.7 Reading rules
GB/T 5487 -
After obtaining the knock meter readings of a series of samples and reference fuels, check the fuel level again to see if it is the maximum detonation intensity level. Measure and record the knock meter readings of each fuel in the following order. a. Sample;
Second reference fuel;
First reference fuel.
When repeating the measurement, the order of the reference fuels should be changed. Each measurement must be made after the knock meter pointer is stable before recording. 13.8 To complete the test, at least the following number of test records are required: 13.8.1 In the following cases, two sets of data are required: a.
The difference in octane number calculated between the first set of data and the second set of data is not greater than 0.3 octane units; the average knock meter reading of the sample is within 50±5. 13.8.2
In the following cases, three sets of data are required: a.
The difference in octane number calculated between the first set of data and the second set of data is not greater than 0.5 octane units, and the calculation result of the third set of data is between the first two; the average knock meter reading of the sample is within 50±5. If the difference in octane number calculated between the first set of data and the second set of data is greater than 0.5 octane units, or the octane number calculated by the third set of data is not in the middle of the first two sets of data, these data cannot be used and must be retested according to Chapter 13 of this method. 13.9 Check the consistency of the standard knock intensity If the test results meet the requirements of 13.8. If the requirements of 13.8 are met, it shall be ensured that the compensated cylinder height for the octane number of the first reference fuel matched to the sample is within ±0.25 mm (0.010 in) micrometer reading or 14 counter units. If it is not within these limits, the standard knock intensity shall be adjusted to a reading of 50 and the sample shall be retested. 13.10 Final Test of the Sample
For the final test of the sample, first adjust the maximum knock intensity fuel level and, if necessary, adjust the cylinder height so that the knock meter reads 50. After each test, check the consistency of the standard knock intensity by the inspection method described in 13.9. 13.10.1 When the engine is operated at the intake air temperature listed in Table 5, if the atmospheric pressure changes during operation by more than 0.34 kPa (0.1 inHg), readjust the intake air temperature to the values listed in this table. If the atmospheric pressure still changes similarly after the engine has been standardized in accordance with 12.3.2, repeat the operation in 12.3.2. 13.11 Calculation of test results
13.11.1 If the test results meet the requirements of 13.8, calculations can be performed. First, calculate the average value of the knock meter readings of various fuels. 13.11.2 Substitute the average value calculated in 13.11.1 into the following formula to calculate the octane number of the sample. Accurate to two decimal places. X
Where: X-octane number of the sample;
A—octane number of a high-octane reference fuel; B—octane number of a low-octane reference fuel;
(A - B) + B
α—average knock meter reading of a high-octane reference fuel; 6—average knock meter reading of a low-octane reference fuel; C———average knock meter reading of the sample. 13.11.3 The results calculated in 13.11.2 shall be rounded to - decimal places according to GB/T8170 "Numerical Rounding Rules". 14 Determination of the sample by the compression ratio method
14.1 Determination of the standard knock intensity
GB/T5487-1995
14.1.1 Use the same range of reference fuel as the sample. 14.1.2 Adjust the compression ratio to a value that meets the requirements of Article 3.13. 14.1.3 Adjust the reference fuel level to obtain the maximum knock fuel-air ratio. 14.1.4 Adjust the knock meter to the position where the knock meter reads 50. 14.2 Evaluation of the sample fuel
Turn the carburetor fuel selector valve to the fuel tank containing the sample. 14.2.1 Adjust the compression ratio so that the knock meter reads 50. 14.2.2 Adjust the fuel tank level to obtain the maximum knock fuel-air ratio. 14.2.3 Re-adjust the compression ratio so that the knock meter reading is 50. 14.2.4 Read the counter reading (the reading compensated for atmospheric pressure), read the corresponding octane number value from Table 2, and complete each of the above steps to obtain an octane number measurement result.
14.3 Allowable difference between the octane number of the sample measurement result and the octane number of the reference fuel used to determine the standard knock intensity The maximum allowable difference between the octane number of the sample measurement result and the octane number of the reference fuel used to determine the standard knock intensity shall not exceed the following values.
Specimen octane rating range
Below 90.0
90.1～100.0
100.1～102.0
102.1～105.0
Above 105.1
Maximum permissible difference in octane rating between reference fuel and sample 2.0
14.4 When the difference between the reference fuel and the sample exceeds the above value, a reference fuel with an octane rating not exceeding the above value should be used, and the standard knock intensity should be re-determined as described in 14.1. Then turn the carburetor selector valve to the sample tank for fuel supply, and adjust the compression ratio so that the knock meter reads 50. Read the counter and read the corresponding octane rating from Table 2. 14.5 Frequency of checking standard detonation intensity
For samples with an octane number lower than 100, the standard detonation intensity shall be checked according to 14.1 after every four samples are evaluated. For samples with an octane number higher than 100, the standard detonation intensity shall be checked once after every two samples are evaluated. For "highly sensitive" high-octane gasoline, the frequency of checking shall be greater. 14.6 Calculation of sample results
The above repeated evaluation results shall be rounded to 1 decimal place according to GB/T8170 "Numerical Rounding Rules" 5 Presentation of measurement results
The octane number data obtained from 13.11 or 14.6 shall be reported as research octane number, abbreviated as XX·X/RON. 16 Precision
The following values shall be used to judge the reliability of the test results (95% confidence level). 16.1 Repeatability
In the same laboratory, by the same operator, using the same instrument and equipment, the same sample is tested twice in succession. When the sample is measured within the range of 90 to 95 average research octane number, the difference shall not exceed 0.2 octane number. 16.2 Reproducibility
In any two different laboratories, by different operators, using different instruments and equipment, at different or same time, the results of the same sample shall not exceed the following values: Average research octane number range
Octane number assessment allowable difference
GB/T 5487
For octane numbers between the above values, the reproducibility assessment difference limit is calculated by interpolation. Table 1 Comparison table of standard knock intensity micrometer readings and research octane numbers at various altitudes, with atmospheric pressure of 101.3 kPa (29.92 inHg) and throat diameter of 14.92
mm (9/16 in) Research method
Octane number
0. 703 1 0. 703
Micrometer reading
0.746 3 0. 7451 0
Research method
Octane number
Research method
Octane number
GB/T5487-1995
Continued Table 1
0.5580.558
0.5260.525
Micrometer reading
.0.604
0.5970.596
0.5540 .553
Research method
Octane number
Research method
Octane number
GB/T5487—1995
Continued Table 1
Micrometer reading
0.2720.271
Note: () The allowable difference is ±0.25mm±0.010inCounter reading = (0.012 micrometer reading) 1410. ② For correction values of other atmospheric pressures, see Table 5.
Research method
Octane number2 Evaluate the sample fuel
Turn the carburetor fuel selector valve to the fuel tank containing the sample. 14.2.1 Adjust the compression ratio so that the knock meter reads 50. 14.2.2 Adjust the fuel tank liquid level to obtain the fuel-air ratio for maximum knock. 14.2.3 Re-adjust the compression ratio so that the knock meter reads 50. 14.2.4 Read the counter reading (the reading compensated for atmospheric pressure), read the corresponding octane number value from Table 2, and complete each of the above steps to obtain an octane number measurement result.
14.3 Allowable difference between the octane number of the sample measurement result and the octane number of the reference fuel used to determine the standard knock intensity The maximum allowable difference between the octane number of the sample measurement result and the octane number of the reference fuel used to determine the standard knock intensity shall not exceed the following values.
Specimen octane rating range
Below 90.0
90.1～100.0
100.1～102.0
102.1～105.0
Above 105.1
Maximum permissible difference in octane rating between reference fuel and sample 2.0
14.4 When the difference between the reference fuel and the sample exceeds the above value, a reference fuel with an octane rating not exceeding the above value should be used, and the standard knock intensity should be re-determined as described in 14.1. Then turn the carburetor selector valve to the sample tank for fuel supply, and adjust the compression ratio so that the knock meter reads 50. Read the counter and read the corresponding octane rating from Table 2. 14.5 Frequency of checking standard detonation intensity
For samples with an octane number lower than 100, the standard detonation intensity shall be checked according to 14.1 after every four samples are evaluated. For samples with an octane number higher than 100, the standard detonation intensity shall be checked once after every two samples are evaluated. For "highly sensitive" high-octane gasoline, the frequency of checking shall be greater. 14.6 Calculation of sample results
The above repeated evaluation results shall be rounded to 1 decimal place according to GB/T8170 "Numerical Rounding Rules" 5 Presentation of measurement results
The octane number data obtained from 13.11 or 14.6 shall be reported as research octane number, abbreviated as XX·X/RON. 16 Precision
The following values shall be used to judge the reliability of the test results (95% confidence level). 16.1 Repeatability
In the same laboratory, by the same operator, using the same instrument and equipment, the same sample is tested twice in succession. When the sample is measured within the range of 90 to 95 average research octane number, the difference shall not exceed 0.2 octane number. 16.2 Reproducibility
In any two different laboratories, by different operators, using different instruments and equipment, at different or same time, the results of the same sample shall not exceed the following values: Average research octane number range
Octane number assessment allowable difference
GB/T 5487
For octane numbers between the above values, the reproducibility assessment difference limit is calculated by interpolation. Table 1 Comparison table of standard knock intensity micrometer readings and research octane numbers at various altitudes, with atmospheric pressure of 101.3 kPa (29.92 inHg) and throat diameter of 14.92
mm (9/16 in) Research method
Octane number
0. 703 1 0. 703
Micrometer reading
0.746 3 0. 7451 0
Research method
Octane number
Research method
Octane number
GB/T5487-1995
Continued Table 1
0.5580.558
0.5260.525
Micrometer reading
.0.604
0.5970.596
0.5540 .553
Research method
Octane number
Research method
Octane number
GB/T5487—1995
Continued Table 1
Micrometer reading
0.2720.271
Note: () The allowable difference is ±0.25mm±0.010inCounter reading = (0.012 micrometer reading) 1410. ② For correction values of other atmospheric pressures, see Table 5.
Research method
Octane number2 Evaluate the sample fuel
Turn the carburetor fuel selector valve to the fuel tank containing the sample. 14.2.1 Adjust the compression ratio so that the knock meter reads 50. 14.2.2 Adjust the fuel tank liquid level to obtain the fuel-air ratio for maximum knock. 14.2.3 Re-adjust the compression ratio so that the knock meter reads 50. 14.2.4 Read the counter reading (the reading compensated for atmospheric pressure), read the corresponding octane number value from Table 2, and complete each of the above steps to obtain an octane number measurement result.
14.3 Allowable difference between the octane number of the sample measurement result and the octane number of the reference fuel used to determine the standard knock intensity The maximum allowable difference between the octane number of the sample measurement result and the octane number of the reference fuel used to determine the standard knock intensity shall not exceed the following values.
Specimen octane rating range
Below 90.0
90.1～100.0
100.1～102.0
102.1～105.0
Above 105.1
Maximum permissible difference in octane rating between reference fuel and sample 2.0
14.4 When the difference between the reference fuel and the sample exceeds the above value, a reference fuel with an octane rating not exceeding the above value should be used, and the standard knock intensity should be re-determined as described in 14.1. Then turn the carburetor selector valve to the sample tank for fuel supply, and adjust the compression ratio so that the knock meter reads 50. Read the counter and read the corresponding octane rating from Table 2. 14.5 Frequency of checking standard detonation intensity
For samples with an octane number lower than 100, the standard detonation intensity shall be checked according to 14.1 after every four samples are evaluated. For samples with an octane number higher than 100, the standard detonation intensity shall be checked once after every two samples are evaluated. For "highly sensitive" high-octane gasoline, the frequency of checking shall be greater. 14.6 Calculation of sample results
The above repeated evaluation results shall be rounded to 1 decimal place according to GB/T8170 "Numerical Rounding Rules" 5 Presentation of measurement results
The octane number data obtained from 13.11 or 14.6 shall be reported as research octane number, abbreviated as XX·X/RON. 16 Precision
The following values shall be used to judge the reliability of the test results (95% confidence level). 16.1 Repeatability
In the same laboratory, by the same operator, using the same instrument and equipment, the same sample is tested twice in succession. When the sample is measured within the range of 90 to 95 average research octane number, the difference shall not exceed 0.2 octane number. 16.2 Reproducibility
In any two different laboratories, by different operators, using different instruments and equipment, at different or same time, the results of the same sample shall not exceed the following values: Average research octane number range
Octane number assessment allowable difference
GB/T 5487
For octane numbers between the above values, the reproducibility assessment difference limit is calculated by interpolation. Table 1 Comparison table of standard knock intensity micrometer readings and research octane numbers at various altitudes, with atmospheric pressure of 101.3 kPa (29.92 inHg) and throat diameter of 14.92
mm (9/16 in) Research method
Octane numberwwW.bzxz.Net
0. 703 1 0. 703
Micrometer reading
0.746 3 0. 7451 0
Research method
Octane number
Research method
Octane number
GB/T5487-1995
Continued Table 1
0.5580.558
0.5260.525
Micrometer reading
.0.604
0.5970.596
0.5540 .553
Research method
Octane number
Research method
Octane number
GB/T5487—1995
Continued Table 1
Micrometer reading
0.2720.271
Note: () The allowable difference is ±0.25mm±0.010inCounter reading = (0.012 micrometer reading) 1410. ② For correction values of other atmospheric pressures, see Table 5.
Research method
Octane number
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