octane (Octane Number) is the fuel (gasoline) used vehicle indicator Blast resistance. There are a variety of hydrocarbons in the gasoline, which readily initiated with n-heptane at elevated temperature and pressure than the spontaneous combustion, resulting blast phenomenon, reduce engine efficiency, but may lead to loss of the piston cylinder wall superheat even crack. Thus heptane octane number is set to zero, and isooctane which small blast phenomenon, which is defined as 100 octane. Other hydrocarbons have different octane, may be less than 0 (e.g., n-octane), there may be greater than 100 (e.g., toluene). Thus, octane gasoline directly dependent on the composition ratio of the various hydrocarbons in the gasoline.
1. Determination of octane number
The method of the current vehicle test gasoline antiknock many summarized are the following.
Motor method
of a motor octane number of a fuel under standard operating conditions, the fuel is compared with a reference knocking tendency of known octane reference fuel mixture ratio determined . Specific approach is by varying the compression ratio, and with an electronic meter to measure knock knock intensity obtained by standard knock intensitydegree.
Study Method
Motor Octane one fuel under normal operating conditions, the fuel is compared with a reference knocking tendency of known octane reference fuel mixture ratio determined . Specific approach is by varying the compression ratio, and with an electronic table to knock the knock intensity obtained by measuring a standard knock intensity.
At present national standard gasoline predetermined vehicle detection assays using research octane number (GB / T 5487-1995) a method antiknock gasoline and motor octane test method (GB / T 503- 1995). Different test standard conditions is the main difference between the research octane and motor octane tests test. Both test methods are operating at the respective standard conditions, the knock meter measuring the subject electronic fuel knock intensity and a known reference fuel and then the test fuel knock tendency as known octane ratio knock tendency compared to the reference fuel to determine the octane number of the test fuel. Specific practice may be employed and a compression ratio interpolation method.
The interpolation method
in the single-cylinder engine compression ratio is held unchanged under the knock meter readings of the test fuel octane number is located two known reference fuel (difference of not octane between greater than 2) of the knock meter readings, and then calculated by interpolation calculation test fuel octane number. Interpolation calculation formula is as follows:
where: X- measured octane gasoline vehicle;
A- parameter corresponding to the fuel octane ratio (high octane); [123 ] corresponding to the B-octane reference fuel ratio (low octane number);
a- reference fuel (high octane number) corresponding to the average knock meter readings;
b- reference fuel (lower octane) corresponding to the average knock meter readings;
c- vehicle measured average knock meter readings gasoline.
Compression ratio method
calibrated with a standard reference fuel engine knock intensity, and then switch to the test fuel, by adjusting the height of the cylinder (compression ratio), so that the measured knock intensity of the fuel with the reference fuel the same knock intensity record the height of the cylinder, then look-up table derived measured octane fuel.
IR Spectroscopy
test research octane and motor octane number of assays are unable to meet the test requirements of the manufacturing process line, while in the actual test fuel octane number, the two methods also has a slow test, test costs are very high and harmful emissions wait missingpoint. The method of rapid detection of the current fuel octane infrared spectroscopy, gas chromatography and nuclear magnetic resonance spectroscopy and the like. Due to low cost, test speed, test process does not produce pollution and emissions test measured less fuel consumption, etc., infrared spectroscopy technique has become the mainstream of the vehicle measured by gasoline octane. The basic principle is to use infrared spectroscopy IR spectroscopy gasoline car proportion of different components and each component, and contribution of each component according to the octane number of the test analysis calculated Gasoline octane.
Driving Law
As the octane measured by laboratory methods may not fully reflect the car is traveling on the road actual antiknock gasoline, some countries also adopted driving method to assess the actual anti-knock properties of gasoline, with the method of the measured octane number, referred to as the road octane number. Because the driving method is more complicated, the use of empirical formula calculated from practical application. Empirical formula is as follows:
United correction method road octane number
of the above equation was calculated according to the road octane number, its value is between the motor octane number and the research octane number. At present, China has not yet on the car to make the car-octane gasoline national standards for gasoline Road Act
different dielectric constant of the dielectric constant is different octane octane number
gasoline, octane large gasoline large dielectric constant, the dielectric constant can be measured if it can be calculated octane number, change in dielectric constant can be used to change the capacitance value of the capacitance measured. The method apparatus small size, low power consumption, low cost, with temperature compensation, facilitating field operations. Simple and reliable circuit is achieved, but there are not limitations of the measurement of organic solutes added to the gasoline.
2. The fuel octane octane
Fuel
Research Octane Number
Motor Octane Number
of the uprising
hexadecane
lt; -30
octane
-10 [ 123] heptane
0
diesel
15-25
iso-octane
100
90-92
95-96
E10 gasoline
87 -93
E85 gasoline
105
methane
107
vehicle in accordance with grade gasoline octane distinguished. There 66,70,76,80,85 equal sign. For example, number 70 indicates that the gasoline octane number of gasoline that is not less than 70. The measured results can be determined to belong octane grades of gasoline.