HCCI Examination Questions with Answers

HCCI Examination Questions with
Answers
HCCI characteristics at light loads w/o throttling - Answer-fuel economy like a diesel
engine

HCCI characteristics at high loads - Answer-power density of a gasoline engine

Operating parameters - Answer-High EGR and high intake temps

Three ways to burn fuel in an engine - Answer-Deflagration (SI), diffusive (CI) and LTC

Potential of LTC - Answer-Low temperature through dilute combustion, lean
combustion, high effective expansion ratio

Requirements for HCCI - Answer-Sufficient temperature for autoignition and diluted
mixture

Rich limit of HCCI - Answer-Pressure rise rate and NOx

Lean limit of HCCI - Answer-CO emissions

Three key temperatures of HCCI - Answer-Autoignition temperature, minimum
temperature for CO, maximum temperature for NOx

Richer mixture means - Answer-more fuel in top glands

Faster rate of combustion allows - Answer-higher thermodynamic efficiency

Two challenges for moderating HCCI combustion - Answer-combustion speed and
combustion phasing

Combustion speed moderation - Answer-Dilution (eg EGR), Temp stratification (portion
heating), mixture stratification (portions phi), combined of mixture and temp strat

CA50 - Answer-Moderation of combustion phasing

Examples of combustion phasing - Answer-Variable octane number, variable valve
timing, variable compression ratio, fast thermal management, usage of spark to start
autoignition