An experimental study of uncertainty considerations associated with predicting auto-ignition timing using the Livengood-Wu integral method

Shah, Ashish; Cheng, Song; Longman, Douglas E.; Goldsborough, S. Scott; Rockstroh, Toby

doi:10.1016/j.fuel.2020.119025

Cited by 7 publications

(2 citation statements)

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“…A single cylinder gasoline direct injection research engine was utilized for this study. A brief description of the configuration and details relevant to the present investigation is provided here, and the reader is referred to previous publications 18–21 for more details about the experimental facility. A schematic of single cylinder research engine detailing the pre-chamber fueling system is shown in Figure 1.…”

Section: Experimental Configurationmentioning

confidence: 99%

Investigations into EGR dilution tolerance in a pre-chamber ignited GDI engine

Rohwer

Han

Shah

et al. 2022

International Journal of Engine Research

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EGR is a useful means to improve fuel economy in spark-ignited gasoline engines, especially under part-load conditions by means of reducing throttling losses. There is also a significant reduction in NOx emissions due to the reduced peak cylinder temperatures. However, the ability of conventional spark ignition systems to reliably ignite dilute mixtures limits the dilution tolerance due to the onset of combustion instability. In this study, an active pre-chamber system was evaluated at part load condition with various EGR rates using a regular grade full boiling range gasoline. A premixed air-fuel mixture was supplied to the pre-chamber, which assists in scavenging the residual mass fractions to enable reliable ignition of EGR dilute mixtures in the main combustion chamber. A range of pre-chamber injection, air-fuel mixture formulation, and ignition timing strategies were evaluated during the EGR sweeps. In addition, 0-D and 1-D simulations were conducted in GT-Power to assess the thermodynamic state and composition in the pre-chamber, as well as estimate the jet momentum at the various dilution rates. The active pre-chamber extended the EGR dilution limit from 20% for conventional SI to above 30%, with a higher pre-chamber flow rate (more scavenging) resulting in increased combustion stability. A tradeoff between the jet momentum and spark timing was observed when analyzing the GT-Power simulations and the pre-chamber jet momentum was found to decrease with increasing EGR rate. At unstable high EGR operation, no relation could be found between the pre-chamber indicated data and main chamber combustion stability.

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Section: Experimental Configurationmentioning

confidence: 99%

Investigations into EGR dilution tolerance in a pre-chamber ignited GDI engine

Rohwer

Han

Shah

et al. 2022

International Journal of Engine Research

Self Cite

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“…Lastly, 1-D engine simulations with 0-D combustion modeling were considered. Although 1-D simulation tools have the adequate throughput to address the problem scale, existing 0-D or quasi-dimensional combustion models (refs − ) were not found to have an appropriate balance of throughput and fidelity for prediction of fuel effects on end-gas autoignition under lean conditions, which is critical for MMC. Therefore, it was decided to create a dedicated 0-D combustion model relying on a 0-D chemical kinetics framework.…”

Section: Introductionmentioning

confidence: 99%

Octane Requirements of Lean Mixed-Mode Combustion in a Direct-Injection Spark-Ignition Engine

et al. 2022

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This study investigates the octane requirements of a hybrid flame propagation and controlled autoignition mode referred to as mixed-mode combustion (MMC), which allows for strong control over combustion parameters via a spark-initiated deflagration phase. Due to the throughput limitations associated with both experiments and 3-D computational fluid dynamics calculations, a hybrid 0-D and 1-D modeling methodology was developed, supported by experimental validation data. This modeling approach relied on 1-D, two-zone engine simulations to predict bulk in-cylinder thermodynamic conditions over a range of engine speeds, compression ratios, intake pressures, trapped residual levels, fueling rates, and spark timings. Those predictions were then transferred to a 0-D chemical kinetic model, which was used to evaluate the autoignition behavior of fuels when subjected to temperature–pressure trajectories of interest. Finally, the predicted autoignition phasings were screened relative to the progress of the modeled deflagration-based combustion in order to determine if an operating condition was feasible or infeasible due to knock or stability limits. The combined modeling and experimental results reveal that MMC has an octane requirement similar to modern stoichiometric spark-ignition engines in that fuels with high research octane number (RON) and high octane sensitivity (S) enable higher loads. Experimental trends with varying RON and S were well predicted by the model for 1000 and 1400 rpm, confirming its utility in identifying the compatibility of a fuel’s autoignition behavior with an engine configuration and operating strategy. However, the model was not effective in predicting (nor designed to predict) operability limits due to cycle-to-cycle variations, which experimentally inhibited operation of some fuels at 2000 rpm. Putting the operable limits and efficiency from MMC in the context of a state-of-the-art engine, the MMC showed superior efficiencies over the range investigated, demonstrating the potential to further improve fuel economy.

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