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Octane Number Determination Methods

Octane Number Determination Methods

At present, there are many methods to test the explosion resistance of automobile gasoline. The octane number determination test methods are summarized as follows:

1. Motor and Research standard methods for octane number determination

The motor octane number of a fuel is determined by comparing the fuel reference with the detonation tendency of the reference fuel mixture with known octane number under standard operating conditions. The specific method is to obtain the standard detonation strength by changing the compression ratio and measuring the detonation strength with an electronic detonation meter.

octane engine for octane number determination
SINPAR Octane Engine used for octane number determination with Research and Motor test methods

At present, the national standards of octane number determination are the research octane test methods (ASTM D2699, GB/T 5487) and the motor octane test methods (ASTM D2700, GB/T 503). 

2. Interpolation method

When the compression ratio of a single cylinder engine remains unchanged. The detonation meter reading of the tested fuel is located between the detonation meter reading of two reference fuels with known octane number. (The difference between the octane number can not be greater than 2). Then the octane number of the tested fuel is calculated by the interpolation formula.

3. Compression Ratio Method

The standard detonation intensity of the engine is calibrated with reference fuel, then the measured fuel is replaced by the tested fuel. By adjusting the cylinder height (compression ratio), the detonation intensity of the tested fuel is the same as that of the reference fuel. The cylinder height at this time is recorded. And the octane number of the tested fuel is obtained by checking the table.

4. Infrared Spectrometry

At present, the methods of rapid detection of fuel octane number include infrared spectroscopy, meteorological chromatography and nuclear magnetic resonance spectroscopy. Because of the advantages of low cost, fast testing speed, no emission pollution and less fuel consumption. Infrared spectroscopy has gradually become the mainstream technology for the determination of octane number of automotive gasoline. The basic principle of infrared spectroscopy is to use infrared spectroscopy to determine the proportion of different components and components in automotive gasoline. Then, the octane number of automotive gasoline under test can be calculated and analyzed.

5. Driving method

Because the octane number measured by the laboratory method can not fully reflect the actual anti-explosion ability of gasoline while driving on the road. Some countries also use the driving method to evaluate the actual anti-explosion performance of gasoline. The octane number measured by this method is called Road octane number. Because of the complexity of the driving method, empirical formulas are often used in practical application.

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