key term - Cetane number

Definition

The cetane number is a measure of the quality of diesel fuel and its ignition properties, indicating how easily the fuel ignites in an engine. A higher cetane number suggests that the fuel ignites more readily, leading to better engine performance, reduced emissions, and smoother operation. Understanding cetane number is crucial for optimizing engine efficiency and exploring advanced fuel technologies.

5 Must Know Facts For Your Next Test

1. Cetane numbers typically range from 0 to 100, with higher numbers indicating better ignition quality; diesel fuels generally have cetane numbers between 40 and 55.
2. Improving cetane number can lead to reduced combustion noise and lower emissions of pollutants like nitrogen oxides (NOx) and particulate matter.
3. Certain additives can be mixed with diesel fuels to enhance cetane numbers, which may improve cold-start performance and reduce engine wear.
4. Cetane number can be tested using standardized methods, such as the ASTM D613 test, which measures the ignition delay time of a fuel.
5. Advanced biofuels and synthetic fuels are being developed with high cetane numbers to improve sustainability while maintaining engine performance.

Review Questions

• How does the cetane number affect the performance and efficiency of a diesel engine?
  • The cetane number directly influences how quickly and efficiently diesel fuel ignites in the combustion chamber. A higher cetane number results in shorter ignition delay times, leading to more complete combustion and improved power output. This enhanced performance translates into smoother engine operation, reduced emissions, and better overall efficiency.
• Compare and contrast cetane number with octane number in terms of their impact on fuel performance in engines.
  • Cetane number measures how readily diesel fuel ignites, while octane number measures gasoline's resistance to knocking during combustion. High cetane fuels lead to quicker ignition and smoother operation in diesel engines, whereas high octane fuels prevent premature ignition in gasoline engines. Both ratings are essential for optimizing engine performance but apply to different types of engines and combustion processes.
• Evaluate the implications of using biodiesel with varying cetane numbers on engine operation and emissions.
  • Using biodiesel with high cetane numbers generally leads to improved ignition quality, which can enhance engine operation by reducing combustion noise and emissions. However, biodiesel with low cetane numbers may cause longer ignition delays, resulting in incomplete combustion and increased emissions of pollutants. It's important to balance the cetane quality of biodiesel to maintain optimal engine performance while adhering to environmental standards.

Related terms

octane number: A rating that measures the performance of gasoline in engines, indicating its resistance to knocking or pre-ignition.

compression ratio:

The ratio of the maximum to minimum volume in the combustion chamber of an engine, influencing the engine's efficiency and power output.

diesel fuel: A type of fuel derived from crude oil that is used in diesel engines, characterized by its higher energy density and cetane number compared to gasoline.