Fuel Octane Rating Procedure A-ASTM D2699 RON

Fuel Octane Rating Procedure A: Bracketing-Equilibrium Fuel Level according to ASTM D2699 RON follows the below brief operation steps:

1. Check that octane rating engine operating conditions are in compliance and equilibrated with the engine running on a typical fuel at approximately standard K.I.
2. Perform octane rating engine fit-for-use testing utilizing a TSF blend applicable for the O.N. range in which sample fuels are expected to rate. (Refer to “RON Test Engine TSF Blend Rating-ASTM D2699“)
3. Establish standard K.I. by octane rating engine calibration using a PRF blend having an O.N. close to that of the sample fuels to be rated.

• Set the cylinder height to the barometric pressure compensated value for the O.N. of the selected PRF.
• Determine the fuel level for maximum K.I. and then adjust the detonation meter, METER READING setting to produce a knock meter reading of 50 ± 2 divisions.
• Check that detonation meter spread is maximized commensurate with satisfactory knock meter stability.

Sample Fuel:

• Operate the engine on sample fuel.
• Make a preliminary adjustment to the cylinder height.
• Determine the fuel level for maximum K.I.
• Make a second adjustment of the cylinder height, so that the knock meter reading is 50 ± 2 divisions.
• Record the knock meter reading.
• Observe the cylinder height reading, compensated to standard barometric pressure. Using the appropriate guide table, determine the estimated O.N. of the fuel sample.

Reference Fuel No. 1:

• Prepare a PRF blend that has an O.N. estimated to be close to that of the sample fuel.
• Operate the engine on Reference Fuel No. 1 and determine the fuel level for maximum K.I.
• Record the equilibrium knock meter reading.

Reference Fuel No. 2:

• Select another PRF blend that can be expected to result in a knock meter reading that causes the readings for the two reference fuels to bracket that of the sample fuel.
• Operate the engine on Reference Fuel No. 2 and determine the fuel level for maximum K.I.
• If the knock meter reading for the sample fuel is bracketed by those of the two PRF blends, continue the test. Otherwise try another PRF blend(s) until the bracketing requirement is satisfied.
• Record the equilibrium knock meter reading.

Repeat Readings two or three times.

Fuel Octane Rating Calculation of O.N.:

• Calculate the average knock meter readings for the sample fuel and each of the PRF blends.
• Calculate the O.N. by interpolation of these average knock meter readings proportioned to the O.N. values of the bracketing PRF blends in accordance with the example shown in below Fig.