A Study of the Effect of Electronic Fuel Injection on the CFR F5 Cetane Rating Engine

At recent American Society for Testing and Materials (ASTM) Subcommittee D02.01 meetings, committee members and attendees from the petroleum industry have reiterated a longstanding desire to see precision improvements to the ASTM D613 Standard Test Method for Cetane Number of Diesel Fuel Oil. The existing ASTM D613 precision limits were calculated using ASTM National Exchange Group (NEG) monthly test data from the mid-1970s through the early 1990s. Over the past few decades, many detailed studies were performed to identify and better understand the shortcomings of the cetane method (both engine equipment and instrumentation). Many of these studies concluded that inconsistent combustion is the main contributing factor behind the lack of precision in the cetane number method, followed by shortcomings in the instrumentation used to measure ignition delay. The current study considered these prior works and expanded upon them by utilizing modern combustion analysis instrumentation and computer modeling that was not available at the time. A commercially available combustion analysis system (CAS) was utilized for recording baseline measurements to quantify cycle-to-cycle combustion variation of the existing engine equipment. Computational fluid dynamics (CFD) modeling was used to evaluate the level of improvement that may be achieved with a modern electronic fuel injection (EFI) system, and also to determine initial EFI operating parameters for the cetane engine. A prototype EFI system was installed onto a CFR cetane engine and baseline measurements were taken using CAS for comparison against the original mechanical fuel injection system. Early test results indicate that EFI combined with today’s CFR XCP engine instrumentation and controls will make it possible to reduce the current ASTM D613 precision limits by at least a factor of two.