Development of a Computationally Efficient Tabulated Chemistry Solver for Internal Combustion Engine Optimization Using Stochastic Reactor Models

Abstract

The use of chemical kinetic mechanisms in computer aided engineering tools for internal combustion engine simulations is of high importance for studying and predicting pollutant formation of conventional and alternative fuels. However, usage of complex reaction schemes is accompanied by high computational cost in 0-D, 1-D and 3-D computational fluid dynamics frameworks. The present work aims to address this challenge and allow broader deployment of detailed chemistry-based simulations, such as in multi-objective engine optimization campaigns. A fast-running tabulated chemistry solver coupled to a 0-D probability density function-based approach for the modelling of compression and spark ignition engine combustion is proposed. A stochastic reactor engine model has been extended with a progress variable-based framework, allowing the use of pre-calculated auto-ignition tables instead of solving the chemical reactions on-the-fly. As a first validation step, the tabulated chemistry-based solver is assessed against the online chemistry solver under constant pressure reactor conditions. Secondly, performance and accuracy targets of the progress variable-based solver are verified using stochastic reactor models under compression and spark ignition engine conditions. Detailed multicomponent mechanisms comprising up to 475 species are employed in both the tabulated and online chemistry simulation campaigns. The proposed progress variable-based solver proved to be in good agreement with the detailed online chemistry one in terms of combustion performance as well as engine-out emission predictions (CO, CO2, NO and unburned hydrocarbons). Concerning computational performances, the newly proposed solver delivers remarkable speed-ups (up to four orders of magnitude) when compared to the online chemistry simulations. In turn, the new solver allows the stochastic reactor model to be computationally competitive with much lower order modeling approaches (i.e., Vibe-based models). It also makes the stochastic reactor model a feasible computer aided engineering framework of choice for multi-objective engine optimization campaigns.

Tabulated chemistry method for fast calculations of detailed chemical kinetics in system level simulations of internal combustion engines

“…The equivalence ratio for EGR refers to the equivalence ratio of the mixture from the previous cycle. Previous studies 16,17 have used a fixed composition for the EGR stream comprising of only CO 2 , H 2 O, and N 2 and at a fixed equivalence ratio of one. This assumption adds significant limitations in previous studies in literature for resolving the influence of EGR composition during transient cycle simulation.…”

“…Bozza et al 14 implemented tabulated kinetics of ignition (TKI) approach to better model the knock prediction in spark-ignited engines as compared to the traditional approach. 15 Combustion progress variable based on latent enthalpy has been used in various studies 16,17 to simulate compression and spark-ignited engines. Michel et al 18 used laminar diffusion flames as well as perfectly stirred reactor (PSR) calculations to generate tables within the FPI approach and applied the methodology to simulate diesel engines.…”

Combustion and Performance Evaluation of a Spark Ignition Engine Operating with Acetone–Butanol–Ethanol and Hydroxy

“…The escalation of the world population and the unprecedented trend of energy consumption represent significant challenges of the current century. The massive utilization of internal combustion engines (ICE) has led to worldwide modernization while supporting the current living standards; however, such high-scale utilization has also resulted in uncontrolled fossil fuel consumption and alarming environmental pollution [1][2][3]. The latter represents a complex problem since ICEs play a central role in different sectors such as transportation, agriculture, power generation, and industry, thus setting intensified pressure on pollution deceleration [4][5][6].…”

Advanced Technologies for the Optimization of Internal Combustion Engines

“…The last two papers published in this Special Issue [10,11] refer to the use of numerical methods to aid the engine development process.…”

“…In [10], a computationally efficient tabulated chemistry solver for internal combustion engine optimization using stochastic reactor models was developed. The use of chemical kinetic mechanisms in computer-aided engineering tools for internal combustion engine simulations is of high importance for studying and predicting pollutant formation of conventional and alternative fuels.…”