Control-variable-based accommodation of biodiesel blends

Abstract

This paper introduces, and presents experimental validation for, an on-engine applicable control framework for fuel-flexible combustion of diesel–biodiesel blends. The approach is based on changing two of the closed-loop targeted control variables used by the engine control module (ECM): (1) replacing exhaust gas recirculation (EGR) fraction with combustible oxygen mass fraction (COMF); (2) replacing total injected fuel mass with total injected fuel energy, including replacing start of main injection timing with end of main injection timing. It is shown that the stock ECM control structure with pure biodiesel (B100) produces 38 per cent more brake-specific nitrogen oxides (NO x ) compared to pure conventional diesel (B0). However, new results presented here with the proposed control framework show that B100 can be made to produce lower brake-specific NO x , 2 per cent higher brake thermal efficiency, 50 per cent lower brake-specific particulate matter, and 1.2 dB lower combustion noise than B0. Benefits of, and novel contributions related to, this strategy are that it is generalizable to other engine systems, is physically based, does not require modified or additional engine calibration, and maintains the stock B0 performance. In essence, the approach presented defines the biodiesel blend control problem as closed-loop targeting of COMF and injected fuel energy, paving the way for future work in controller design to achieve these targets in real-time, on-engine situations.

Dieseline fueled flexible fuel compression ignition engine control based on in-cylinder pressure sensor

“…Snyder [17,18] did research on bio-diesel and diesel blend estimation based on wide-band oxygen sensor and did research on fuel accommodation control based on blend ratio detection. Guido [19] also carried out research on bio-diesel and diesel blends fueled flexible fuel vehicle, with also fuel detection and open-loop control method.…”

“…Former studies [17][18][19][20][21][22] on diesel/bio-diesel blends accommodation control tried to solve the problems mainly from the open-loop control point of view. Snyder [17,18] did research on bio-diesel and diesel blend estimation based on wide-band oxygen sensor and did research on fuel accommodation control based on blend ratio detection.…”

A robust fuel flexible combustion control strategy for biodiesel with variable fatty acid composition during mixing-controlled combustion

“…While differences in several of these fuel properties will cause changes in the fuel vaporization process, the key difference appears to be the oxygen content and the lower heating value of the fuel. 9–12…”

“…In order to overcome the combustion-related challenges of soy biodiesel, namely lower power output and higher NO x emissions, a blend fraction accommodation algorithm was developed in prior efforts by the authors 12 and demonstrated to be effective for different blend fractions of soy biodiesel. This algorithm adjusts the fuel mass with the objective of keeping fuel energy constant irrespective of changes in blend fraction in order to ensure the same power output for diesel as well as biodiesel blends.…”

“…These control strategies have been experimentally validated for any blend fraction of soybean-based biodiesel. 12,19 However, due to the variety of possible biodiesel feedstocks and differences in fuel processing, biodiesel composition (specifically, the fatty acid composition) can vary significantly from soy biodiesel. For a biodiesel blend accommodation algorithm to be used with a wide variety of biodiesel fuels, it is important to ensure robustness of the control strategy to variation in both the biodiesel blend fraction and the fatty acid composition.…”