Emissions reduction through advanced engine models

  • 15-Mar-2010 02:52 EDT
Output from the srm suite provides results of chemical kinetics, turbulent mixing, and injection strategy analysis.

The engineers at cmcl innovations have exploited their mathematical modeling expertise to develop innovative fuel, combustion, and emissions software tools for the automotive market. As a result, the SAE 2010 World Congress will give cmcl innovations a chance to show its latest engine simulation technology.

The stochastic reactor modeling (srm) suite is an advanced in-cylinder combustion and emissions simulator for internal-combustion engine (ICE) applications. It is used to solve the complex interaction of thermo, chemical, and fluid dynamic processes that occur during the compression, power, and expansion strokes in the engine cylinder. The srm suite is able to provide solutions for these processes using sophisticated numerical methods to account for detailed chemical kinetics, turbulent mixing, heat loss, and injection strategies. This approach enables engineers to carry out more robust simulations of combustion and ensuing emissions without the heavy computational costs associated with conventional multidimensional CFD simulations.

Over the next decade, there will be four major challenges for the ICE community: firstly, to understand the formation and dynamics of soot, NOx, HCs, and CO emissions and to develop corresponding reduction strategies including aftertreatment; secondly, to develop advanced engine modes such as low-temperature combustion (LTC) or homogeneous charge compression ignition (HCCI) driven by chemical kinetics; thirdly, to understand conventional operating limitations such as knock, misfire, and ignition; and finally, to allow adoption of alternative fuels, exhaust gas recirculation, boosting, and injection strategies.These challenges will require the adoption of detailed chemistry within engine simulation.

The srm suite enables engineers to incorporate the state of the art in chemical kinetics for fuel oxidation and emissions models into their computations. The software can be employed for spark-ignition and compression-ignition direct-injection combustion modes as well as HCCI, LTC, controlled auto-ignition, and partially premixed compression-ignition. The srm suite also provides improved computation of crank-angle-resolved combustion and emissions characteristics such as heat release rate, combustion phasing and duration, in-cylinder pressure, chemical species including intermediates (radicals such as OH, formaldehyde, etc.) and emissions (CO, HC, NOx, and soot).

cmcl believes that its software is the first of its kind to contain an integrated comprehensive soot model, which yields the detailed soot particle size distributions and calculations of soot morphology and composition that are expected to be included in future emissions regulations.

Conventionally, in-cylinder combustion processes are modeled either using empirical or 1-D approaches, or with detailed 3-D CFD solutions, which are heavily weighted toward describing fluid dynamics (kinetics are approximated). cmcl innovations says the srm suite re-addresses this balance, firstly by accounting for in-cylinder mixture in-homogeneities in composition and temperature using high-dimensional probability density function representation. The model exploits statistical homogeneity, thus reducing the associated computational times relative to the equivalent 3-D CFD. Secondly, it re-addresses the balance by employing state-of-the-art detailed chemical kinetics that enable engineers to exploit the latest surrogate fuel oxidation models for improved combustion and emissions modeling.

The srm suite offers detailed fuel oxidation simulations using either state-of-the-art fuel models and/or user-provided fuel models such as conventional (diesel and gasoline) or alternative (CNG, hydrogen, ethanol, biodiesel) fuels.

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