Effect of Asymmetric Mode on CO₂ State-to-State Vibrational-Chemical Kinetics

Area of Science:

• Chemical Kinetics
• Fluid Dynamics
• Thermodynamics

Background:

• Dissociation of carbon dioxide (CO2) is crucial in high-temperature environments.
• Understanding vibrational-chemical kinetics is key to accurately modeling CO2 dissociation.

Purpose of the Study:

• Investigate the impact of asymmetric vibrations on CO2 dissociation kinetics.
• Evaluate the accuracy of reduced kinetic models compared to a complete model.
• Analyze the influence of vibrational modes on fluid dynamics and heat transfer in hypersonic flows.

Main Methods:

• Employed a complete three-mode kinetic model for state-to-state vibrational-chemical kinetics.
• Utilized a reduced kinetic model focusing on the asymmetric vibrational mode.
• Simulated hypersonic flow along the stagnation line.

Main Results:

• Intermode vibrational energy transfer involving CO and CO2 asymmetric modes significantly reduces dissociation rates.
• The presence of CO depletes high vibrational states, inhibiting dissociation at lower temperatures.
• Reduced models overestimate asymmetric mode vibrational populations, potentially leading to overestimated dissociation rates.
• Asymmetric vibrations have minimal impact on fluid dynamics and heat transfer in hypersonic stagnation line flows.

Conclusions:

• While simplified models can be used for macroscopic variables and heat flux in hypersonic flows, they may inaccurately predict dissociation rates.
• Vibrational-chemical kinetics, particularly intermode energy transfer, plays a critical role in CO2 dissociation.
• VT transitions in the bending mode and chemical reactions dominate fluid dynamics and heat transfer in hypersonic flows.