Petrol engine

Engineering

Philosophy

Aerospace engineering

SPARK (programming language)

Materials science

Engine efficiency

Computer science

Internal combustion engine

Homogeneous charge compression ignition

Thermodynamics

Combustion chamber

Physics

Nuclear engineering

Organic chemistry

Ignition timing

Thermal

Thermal efficiency

Combustion

Epistemology

Automotive engineering

Environmental science

Computational fluid dynamics

Chemistry

Programming language

Ignition system

Octane rating

Property (philosophy)

Engine knocking

Spark-ignition engine

Applied Energy

Engine knock remains one of the major barriers to further improvement in thermal efficiency of Direct-Injection Spark-Ignition (DISI) engines. While Research Octane Number and Motor Octane Number are often used as standard rating methods for knock resistance of fuels, the impacts of other fuel properties on knock propensity in modern engines such as heat of vaporization (HoV) and laminar flame speed (LFS) require better understanding in order to co-optimize fuels and engine designs to achieve higher thermal efficiency and lower CO2 emission. In the present study, computational fluid dynamics (CFD) is used to model a boosted DISI engine with a focus on knock prediction and fuel property effects. A level-set G-equation model is employed to capture turbulent premixed combustion, and is coupled with a transported Livengood-Wu (L-W) integral approach to predict auto-ignition in the unburnt region. A criterion associated with the L-W integral is developed to accurately predict knock onset and knock-limited spark-advance. This model is then applied to a sensitivity analysis of HoV and LFS on knock tendency and thermal efficiency. The pressure-temperature trajectory framework is applied and extended to study the fuel effects on auto-ignition process in the engine. An existing efficiency-based merit function, which is derived from experiments for boosted SI engines, is evaluated and improved based on the current CFD results.

Fuel property effects on knock propensity and thermal efficiency in a direct-injection spark-ignition engine