An accelerated multi-zone model for engine cycle simulation of homogeneous charge compression ignition combustion

Abstract

We have developed an accelerated multi-zone model for engine cycle simulation (AMECS) of homogeneous charge compression ignition (HCCI) combustion. This model incorporates chemical kinetics and is intended for use in system-level simulation software. A novel methodology to capture thermal stratification in the multi-zone model is proposed. The methodology calculates thermal stratification inside the cylinder based on a single computational fluid dynamics (CFD) calculation for motored conditions. CFD results are used for tuning zone heat loss multipliers that characterize wall heat loss from each individual engine zone based on the assumption that these heat loss multipliers can then be used at operating conditions different from those used in the single CFD run because the functional form of thermal stratification is more dependent on engine geometry than on operating conditions. The model is benchmarked against detailed CFD calculations and fully coupled HCCI CFD chemical kinetics calculations. The results indicate that the heat loss multiplier approach accurately predicts thermal stratification during the compression stroke and (therefore) HCCI combustion. The AMECS model with the thermal stratification methodology and reduced gasoline chemical kinetics shows good agreement with boosted gasoline HCCI experiments over a range of operating conditions, in terms of in-cylinder pressure and heat release rate predictions. The computational advantage of this method derives from the need for only a single motoring CFD run for a given engine, which makes the method very well suited for rapid HCCI calculations in system-level codes such as GT-Power, where it is often desirable to evaluate consecutive engine cycles.

Computational Fluid Dynamics Simulation of Gasoline Compression Ignition

“…On the one hand, there are reduced order, phenomenological models ( [30][31][32]) for LTC combustion that are suited for strategy optimi zation using system-level simulation tools. However, to develop a fundamental understanding of the spray development and stratifi cation within the cylinder, and the effects of these on the combus tion process, a more detailed approach using CFD with chemical kinetics is adopted.…”

A Novel Fuel Performance Index for Low-Temperature Combustion Engines Based on Operating Envelopes in Light-Duty Driving Cycle Simulations

“…In order to deal with this limitation, a number of engine modeling approaches have been developed that-while avoiding the cost of a spatially resolved, multidimensional computational fluid dynamics simulation-consider multiple zones to represent different regions within an engine (e.g., core, piston crevice, boundary layer) [41][42][43][44][45]. While these multi-zone models can more closely match experimental results, particularly for heat release rate, peak pressure, and unburned hydrocarbon emissions, the single-zone model adequately predicts the point of ignition as a function of inlet properties [44].…”

Investigation of the LTC fuel performance index for oxygenated reference fuel blends

“…In order to deal with this limitation, a number of engine modeling approaches have been developed that-while avoiding the cost of a spatially resolved, multidimensional computational fluid dynamics simulation-consider multiple zones to represent different regions within an engine (e.g., core, piston crevice, boundary layer) [74,[81][82][83][84]. While these multi-zone models can more closely match experimental results, particularly for heat release rate, peak pressure, and unburned hydrocarbon emissions, the single-zone model adequately predicts the point of ignition as a function of inlet properties [83].…”