Session: 02-02: Alternative CI Fuels, Ignition, and Combustion Strategy

Paper Number: 191475

191475 - Empirically Characterizing Ignition Delay of Fuels With Varying Cetane Numbers Using a Compression-Ignition Engine 

Abstract: 

This study examines the ignition delay behavior of multiple fuels spanning a wide range of cetane numbers using measurements from a single-cylinder research engine (SCRE). The fuels tested include conventional diesel, biodiesel, renewable diesel, and selected aviation fuels, covering a broad spectrum of ignition quality. Experiments were conducted in a modern compression-ignition engine with a compression ratio of 17:1 and a high-pressure common-rail fuel injection system representative of current diesel engine technology.

Ignition delay was determined from in-cylinder pressure measurements and used to characterize fuel auto-ignition under realistic engine operating conditions. An empirical Arrhenius-type correlation was developed to relate ignition delay to key engine parameters, including intake pressure, injection pressure, intake oxygen concentration, and engine speed. The proposed correlation captures the ignition delay behavior of the tested fuels with reasonable accuracy across the range of operating conditions considered.

The results show that differences in ignition behavior among fuels can be effectively described using a relatively simple empirical formulation based on measurable engine parameters. The correlation also provides a basis for estimating fuel ignition quality metrics such as cetane number (CN). Predicted CN values derived from the ignition delay correlation are compared with measurements obtained using the ASTM D613 method, demonstrating the potential of this approach as a practical tool for characterizing ignition behavior and screening alternative fuels in modern compression-ignition engines.

Presenting Author: Khanh Cung Southwest Research Institute

Presenting Author Biography: Dr. Cung is a combustion and fuel researcher at SwRI. He has experience mostly with single-cylinder engine, CFD, and optical diagnostics. He used his experience to apply it to engine testing for validation and to understanding the combustion process for conventional and alternative fuels, in order to contribute to the global drive toward decarbonization.

Authors:

Khanh Cung Southwest Research Institute
Christopher Sharp Southwest Research Institute
Chris Bitsis Southwest Research Institute
Ryan Williams Southwest Research Institute
Edward Smith Southwest Research Institute