Simulation and Model Development for Auto-Ignition and Reaction Front Propagation in Low-Temperature High-Pressure Lean-Burn Engines.

HCCI;Spark Assisted Compression Ignition;Knock;Low Temperature Combustion;Flamelet;Spark Ignited;Mechanical Engineering;Engineering;Mechanical Engineering

Martz, Jason BrianWooldridge, Margaret S. ;

University of Michigan

关键词: HCCI;    Spark Assisted Compression Ignition;    Knock;    Low Temperature Combustion;    Flamelet;    Spark Ignited;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/78870/jmartz_1.pdf?sequence=1&isAllowed=y

瑞士|英语

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

【 摘 要 】

While Homogeneous Charge Compression Ignition (HCCI) combustion is capable of highly efficient, ultra-low NOx operation, it lacks direct mechanisms for timing and burn rate control and suffers from marginal power densities.Concepts such as Spark-Assisted Compression Ignition (SACI) combustion have shown the ability to partially address these shortcomings, however detailed SACI models are currently lacking.To address the need for reaction front data within the ultra-dilute, high pressure and preheat temperature SACI regime, laminar premixed reaction front simulations were performed and correlations for burning velocity and front thickness were developed from the resulting dataset.Provided that preheat temperatures were elevated and that burned gas temperatures exceeded 1500 K, moderate burning velocities were observed at equivalence ratios typical of mid and high load HCCI operation.For a given burned gas temperature, burning velocities increased when moving from the SI to the SACI combustion regime, i.e. towards higher dilution and higher pre-heat temperatures.Given the proximity of SACI pre-heat temperatures to the ignition temperature, additional simulations examined the combustion regime, structure and general behavior of the reaction front as it propagated into an auto-igniting end-gas.While significant increases in burning velocity accompanied the transition from deflagrative to chemically dominated combustion, the reaction front contributed minimally to end-gas consumption once end-gas temperatures exceeded 1100 K.A model capable of capturing SI, SACI and HCCI combustion modes was formulated and implemented into KIVA-3V.Using the correlated laminar flame speed data, the model was capable of predicting trend-wise agreement with cylinder pressure and imaging data from an optical SACI engine.The simulated presence of flame surface density suggests that although the simulated reaction fronts are ultra-dilute, they are nevertheless within the flamelet regime during the deflagration portion of SACI combustion.End-gas auto-ignition occurred when the charge compression heating from boundary work and reaction front heat release combined to drive the end-gas to its ignition temperature, providing additional latitude for the execution and control of low temperature combustion processes.Additional simulations were performed to assess the ability of this additional deflagrative combustion mode to enable high efficiency operation with elevated work output relative to HCCI combustion.