HCCI Heat Release Rate and Combustion Efficiency: A Coupled KIVA Multi-ZoneModeling Study.

HCCI;KIVA-MZ;Mechanical Engineering;Engineering;Mechanical Engineering

Mo, YanbinWooldridge, Margaret S. ;

University of Michigan

关键词: HCCI;    KIVA-MZ;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/60734/yanbinm_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Despite of the abundance of HCCI (Homogeneous Charged Compression Ignition) engine experiments, there are several unknown key characteristics, which are difficult to measure with a conventional test engine setup.First, the cylinder temperature distribution is not readily available from test measurements.Second, the instability and misfire mechanisms can not be easily analyzed by engine testing.Finally, the ability to isolate a particular variable is not always practical in testing.In this thesis, an analytical tool is used to explore HCCI combustion under more controlled conditions.A newly available KIVA-MZ model with a novel mapping scheme between CFD cells and thermodynamic zones, provides a virtual experimental environment to explore the combustion process with respect to various engine operating and design parameters. Nine engine operating and design parameters were investigated with respect to their effects on ignition timing.Equivalence ratio (0.2~0.4), EGR (5%, 20%, and 40%), Load (7~13 mg/cycle), RPM (750~3750), wall temperature (400K, 450K), swirl (0.93, 3.93), compression ratio (12.5, 16), piston geometry (bowl, pancake), and crevice volume (1%, 4%, and 8%) are those nine parameters.The effects of these parameters on combustion efficiency and burning rate were also investigated with controlled ignition timing.Based on the model results of cylinder temperature distribution information, the design parameters were found to influence the temperature distribution more than the operating parameters did.The ignition timing is not an independently controlled variable; however, the CFD results showed that ignition timing is the single most important variable for the whole combustion process.Besides ignition timing, equivalence ratio and engine speed are the second and third most important variables for burning rate.Fast burning rate normally results in higher combustion efficiency, but the peak combustion efficient is mainly determined by the crevice volume.In order to the knowledge from the CFD parametric study results, HCCI combustion correlations were developed.These correlations were implemented into GT-Power, a leading commercial 1D engine simulation software package handing general engine system simulation.This improved GT-Power model is a significant improvement over traditional HCCI engine control models with fixed combustion efficiency and burning duration.