Optimized Kinetics Mechanism and Calculator for Natural Gas Combustion GRI-Mech 3.0

A reliable computer model of natural gas oxidation and pollutant formation requires sound elementary kinetics, successful prediction of basic flame properties, and a means for practical use by engineers without kinetics expertise. We describe the most recent version of an optimized kinetics mechanism for natural gas oxidation and NO formation and reburning. The accompanying on-line GRI-Mech Calculator allows non-experts to represent and solve combustion problems as combinations of well-mixed and plug flow reactors. Mechanism development begins with a critical literature evaluation of the elementary rate processes and parameters. Experimental measurements were selected to represent combustion properties that the mechanism is then optimized to predict. These targets include flame velocities, shock tube ignition delays, and species profiles in shock tubes, flow reactors and low pressure flames. New targets focusing on formaldehyde oxidation, the role of propane in natural gas, and the CH intermediate in prompt NO formation and reburn were added for this version. A rigorous optimization procedure adjusts a group of sensitive rate parameters (within evaluated kinetics error limits) to achieve the best simultaneous fit to the target database. The GRI-Mech Calculator 3.0 is a new on-line user-friendly modeling tool designed to simulate natural gas combustion chemistry scenarios using the GRI-Mech 3.0 mechanism. It provides graphical and numerical outputs of exhaust concentrations, temperatures, and pressures computed from user-selected input conditions, constraints, and reaction times for well-stirred or plug flow reactors. A new feature simulates processes by allowing users to assemble a flow diagram of their own reactor network. The Calculator will be made available on the GRI-Mech Website (and in a PC version). A hands-on demonstration is planned.