Cetane Number – What it is and Why it’s so Important

Cetane Number – What it is and Why it’s so Important

Cooperative Fuel Research Engine (CFR)

Cetane is a measurement of a diesel fuel ignition and or combustion quality. This Cetane Number or CN is one of several components that determine the quality of diesel and biodiesel fuels. This number is used for light and middle distillate fuels. For heavy (residual) fuels Calculated Ignition Index (CII) and Calculated Carbon Aromaticity Index (CCAI) are used.

In some ways this measurement is similar to the Octane Ratings given to gasoline. In its simplest terms Cetane Number measures the delay between the start of fuel injection into the combustion chamber and the beginning of compression ignition (Auto-ignition).

In medium and high speed diesel engines (this all automotive and truck engines) fuel needs to have a CN between 38 and 55 to operate. In general the higher the CN number, the better for the engine and for emissions. However raising CN above 55 currently offers little if any benefit.

In the US the group setting the standards for CN is the American Society for Testing of Materials (ASTM) and currently the minimum is 40. While diesel engines will start and run with 40 CN fuel, they do not run as efficiently as they will at a higher number.

In Europe the European Union (EU) has systematically over several years raised the minimum from 38 to the current 51. This has allowed engine manufacturers to produce more efficient engines with lower emissions and better economy. Most fuel in the EU has a CN of 55 or even better.

Cetane Number is measured using a very expensive and arcane Cooperative Fuel Research (CFR) engine and a process that very complex.

You can also measure CN using an Ignition Quality Tester (IQT) which is somewhat less complex, but still quite costly.

There is a third measurement called Cetane Index (CI) that measures density and distillation range of the fuel and through a calculation provides a measurement. This method will calculate a reasonably accurate number for the refined diesel.

The problem is that today most diesel fuel uses additives to reach the desired Cetane Number and additives do not affect the density, thus the CI of a fuel containing additives is not accurate.

Some of you may have seen a device that looks like a battery fluid tester (a hydrometer). These devices are not capable of determining CN or CI with any accuracy.

You can raise CN by altering the refining process or through the use of Alkyl nitrates or di-tert-butyl peroxide additives. NOTE: Remember that additives do not raise CI.

Also, biodiesel, depending on the base oil from which it is derived has a natural Cetane Rating of 46 to as high as 60.

With the advent of Pilot or Multiple Pulse fuel injection, Cetane Number becomes more important than ever. The delay in auto-ignition (CN) affects the combustion timing, which has a significant effect on power output, fuel economy, and emissions.

Raising Cetane Number together with Improving Fuel Atomization is the fastest way to improve fuel economy and reduce emissions through the use of correctly formulated additives.

Please post your comments, ideas, and suggestions

More information at: http://www.lcbamarketing.com/ - Click on Fuel School Articles.

Diesel Doctor

Copyright 2009© - William Richards

Biodiesel from Algae - The future of Biofuels

Biodiesel from Algae - The future of Biofuels

Biodiesel From Algae is likely a long term solution to the problems related to declining crude oil production and ever increasing prices.

Biofuels derived from Algae produce an Algae Oil are considered high quality and can be converted to an excellent biofuel. While all the technology is not yet in place to produce fuel on a mass scale, we are able to see that this is the direction we need to heading.

If you look at yield as a measure of viability, an acre of corn can produce approximately 20-30 gallons of Ethanol or 1,680,000 to 2,520,000 Btu's (84,000 Btu's per gallon) of energy; biodiesel derived from Soybean Oil produces approximately 70 gallons per acre or about 9,100,000 Btu's (130,000 Btu's per gallon), whereas biodiesel derived from Algae can produce up to 100,000 gallons or 13,000,000,000 (yes that's 13 Billion) Btu's (130,000 Btu's per gallon) from a single acre of non-arable desert.

As an oversimplified example if you converted 7,786,000 acres to the production of Algae Oil and converted that to biodiesel you could meet all of the fuel needs for transportation in the US. Note: This is about 10% of the size of New Mexico.

While this is likely a long way off, I believe our government and others in private industry should be investing in developing this technology as quickly as possible.

This technology can also be used to soak up huge amounts of CO2 and it leaves behind a biomass suitable for animal feed and many other possibilities.

Below, is a YouTube CNN video that shows some of this technology and how it can work.



We would appreciate your comments, questions, and ideas.

Diesel Doctor