A Fundamentally-Based Stochastic Mixing Model Method for Predicting NO and Soot Emissions from Direct Injection Diesel Engines

Abstract

A Two-step Approach for calculating slow and complex chemistry in inhomogeneous turbulent reactive flows, specifically in a direct injection (Dl) diesel engine, was evaluated. The first step in this approach is to complete a Multi-Dimensional Model (MDM) solution of the unsteady reactive flow. This was accomplished for a Dl diesel engine using the KIVA computer code developed at the Los Alamos National Laboratory. The output of this solution was used to define zones within the flow and to calculate zone processes and mass flow between zones. A Stochastic Mixing Model (SMM) computer code was developed to recalculate turbulent mixing and chemistry using the KIVA output. The SMM generates distributions of the turbulent properties within each zone which are required to calculate the slow emissions chemistry. This approach was evaluated by analyzing zone property distributions, the effect of changing zone boundaries, the effect of increasing the number of zones and the variance of SMM results over multiple stochastic runs. Predictions were compared to experimental results obtained under various engine operating conditions. This Two-step Approach is an efficient and accurate method for calculating slow and complex chemistry in turbulent reactive flows.

Key Words:

• Combustion
• emissions
• stochastic
• diesels