What is the difference between cetane number and cetane index

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How does PAT fit successfully into the overall concept of efficient petrochemical plant operation. New acoustic imaging camera models launched for partial discharge and compressed air leak detection. Request information. How to Achieve a Higher Cetane Index There are two principle ways in which cetane indexes can be improved. These are as follows: Hydro-treatment. Treating the fuel with hydrogen during the refinery process is one way of raising the cetane index — but is not without its drawbacks.

On the one hand, hydrogen is an expensive and increasingly rare commodity, making the process unattractive from a business point of view. Specifically, cetane is a measure of the tendency of diesel fuel to auto-ignite when injected into the combustion chamber of a diesel engine that has been heated by compression of the air in the chamber.

In a diesel engine, air is compressed in the engine's combustion chamber in the absence of any fuel, resulting in very hot compressed air. Fuel is then injected, using the heat of the compressed air to trigger combustion.

For efficient engine operation, it is important that the fuel ignites quickly and uniformly when injected. Some hydrocarbons will have a tendency to auto-ignite easily while others will resist ignition. Cetane is a measure of a hydrocarbons ability to readily ignite. So in diesel, a higher cetane number is more desirable. The index doesn't change when you add a cetane booster to it.

Cetane number is the actual measured ignition quality of the fuel, including the effect of additives. This is measured by running a reference engine on the final blend fuel and measuring where ignition actually hapens. At the refinery, the index and number are the same essentially. The refiner, distributor, retailer or end user may add a cetane improver to acheive a higher cetane number. Usually, there's a limit to how much a fuel can be boosted, usually in the range of cetane numbers. After that point, the effect of the additive becomes less.

VW specifies the cetane number of the fuel. North America literature says 45 cetane number, minimum. European literature says 49 cetane number for the ALH engine. I don't know why the discrepency exists. What discrepency? Two primary reference fuels hydrocarbons define the cetane number scale:. In , the low cetane number reference fuel was replaced with 2,2,4,4,6,8,8-heptamethylnonane also called isocetane or HMN , which had better oxidation stability and was easier to use in the CFR engine.

When measured against the two original standards, 2,2,4,4,6,8,8-heptamethylnonane has a cetane number of When a fuel has the same ignition delay period as a mixture of the two primary reference fuels, its cetane number is derived from the volume percent of cetane and heptamethylnonane, as follows:. In routine operations, the two primary reference fuels are replaced by two secondary reference fuels: T-fuel and U-fuel.