The significance of octane numbers to hybrid electric vehicles with turbocharged direct injection engines. (15th February 2023)

• Record Type: Journal Article
• Authors: Zhou, Zhenbiao; Yang, Yi; Brear, Michael; Kar, Tanmay; Leone, Thomas; Anderson, James; Shelby, Michael; Lacey, Joshua
• Is Part Of: Fuel. Volume 334(2023)Part 1
• Publication Date: 2023-02-15
• Subjects: Octane number -- Hybrid electric vehicle -- Fuel efficiency -- Engine knock -- Drive cycle simulation; AER All-electric range -- CD Charge-depleting -- CR compression ratio -- CS Charge-sustaining -- EC Electricity consumption -- FC Fuel consumption -- GTDI Gasoline turbocharged direct-injection -- HEV Hybrid electric vehicle -- HWFET Highway fuel Highway fuel economy test -- KLFC Knock-limited fuel consumption -- KLFEL Knock-limited fuel efficiency loss -- KKLFEL KLFEL-weighted K -- MBT Maximum brake torque -- MON Motor octane number -- OI Octane index -- PHEV Plug-in hybrid electric vehicle -- RON Research octane number -- S Octane sensitivity -- SI Spark-ignition -- SUV Sports utility vehicle -- UDDS Urban dynamometer driving schedule; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.126604
• Languages: English
• ISSNs: 0016-2361

Abstract

Abstract: Hybrid powertrains reduce engine operation time at light loads where the engine is less efficient. For spark-ignition engines, this means that a larger fraction of operation time could be knock-limited, and the fuel octane quality could be more important for knock control and vehicle fuel efficiency. Built on our recent work on a conventional vehicle (Zhou et al., Fuel 302, 121, 095), this paper extends the investigation of fuel octane and vehicle fuel efficiency to hybrid electric vehicles using a same turbocharged, direct-injection engine with the number of cylinders reduced from 4 to 3. The impact of the Research Octane Number (RON) and the Motor Octane Number (MON) on knock-limited fuel efficiency loss (KLFEL) is investigated using the Octane Index model, OI = (1-K)·RON + K·MON, where K is the weighting factor of the two octane numbers. Vehicle modelling is conducted to investigate the K and KLFEL distributions in three EPA drive cycles and the impact of octane numbers on these distributions. With increasing hybridization, the K distribution is shifted to more negative range and is accompanied with larger knock-limited fuel losses (in both relative and absolute terms). Increasing the RON and decreasing the MON are found to both improve the fuel efficiency, but the former is significantly more effective than the latter for a given change in octane number. The increasing importance of octane specifications for drive cycle fuel economy is therefore demonstrated for hybrid vehicles with different degrees of electrification. Highlights: Knock-limited fuel efficiency is modelled for full hybrid and plug-in hybrid vehicles in three drive cycles. Hybrid vehicles have higher knock-limited fuel consumption and efficiency loss than a conventional vehicle. K-factor in the Octane Index model shifted to more negative value with increasing electrification. Fuel octane specifications have a larger impact on fuel economy of hybrid vehicles than that of convention vehicles.