Cetane number is one of the most important fuel performance metrics for mixing controlled compression ignition “diesel” engines, quantifying a fuel’s propensity for autoignition when injected into end-of-compression type temperature and pressure conditions. The historical default, and referee method is Cetane Number (CN) rating on a Cooperative Fuels Research (CFR) engine configured with indirect fuel injection and variable compression ratio. A subject fuel is evaluated against definition primary reference fuel blends with heptamethylnonane defining a low reactivity end-point of CN = 15 and hexadecane defining a high reactivity end-point of CN = 100. While the CN scale covers the range from zero (0) to 100 typical testing is in the range of 30 to 65 CN. Alternatively, several constant volume combustion chamber (CVCC) -based cetane rating devices have been developed to rate fuels with an equivalent Derived Cetane Number (DCN) or Indicated Cetane Number (ICN). These devices measure ignition delay for fuel injected into a fixed volume of high temperature and pressure air to simulate end-of-compression type conditions. In this study, a range of novel fuel compounds are evaluated across three CVCC methods, the Ignition Quality Tester (IQT), Fuel Ignition Tester (FIT), and Advanced Fuel Ignition Delay Analyzer (AFIDA). Resulting DCNs and ICNs are compared for fuels within the normal diesel fuel range of reactivity, as well as very high (\~100) and very low DCNs/ICNs (\~5). Distinct differences between results from various devices are discussed. This is important to consider as some new, high-efficiency engine combustion strategies, operate with more kinetically controlled distributed combustion as opposed to mixing controlled diffusion flames. These advanced combustion strategies may benefit from new fuel chemistries, but current rating methods of CN, DCN, and ICN may not fully describe their performance. In addition, recent evidence suggests ignition delay in modern on-road diesel engines with high-pressure common rail fuel injection systems may no longer directly correlate to traditional CN fuel ratings. Simulated end-of-compression conditions are compared for CN, DCN, and ICN, and discussed in the context of modern diesel engines to provide additional insight.  


Comparing Cetane Number Measurement Methods

Division / Sponsors: 
Internal Combustion Engine Division (ICED)

Paper Proceedings: https://asmedigitalcollection.asme.org/ICEF/ICEF2020/volume/84034

ICEF2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.