This work investigates experimentally and numerically the kinetic effects of water vapor addition on the burning rates of H2, H2/CO mixtures, and C2H4 from 1 atm to 10 atm at flame temperatures between 1600 K and 1800 K. Burning rates were measured using outwardly propagating spherical flames in a nearly constant pressure chamber. Results show good agreement with newly updated kinetic models for H2 flames. However, there is considerable disagreement between simulations and measurements for H2/CO and C2H4 flames at high pressure and high water vapor dilution. Both experiments and simulations show that water vapor addition causes a monotonic decrease in mass burning rate and the inhibitory effect increases with pressure. For hydrogen flames, water vapor addition reduces the critical pressure above which a negative pressure dependence of the burning rate is observed. However, for C2H 4 flames, the burning rate always increases with pressure. The results also show that water vapor addition has the same effect as a pressure increase for H2 and H2/CO flames, shifting the reaction zone into a narrower window at higher temperatures. For all fuels, water vapor addition increases OH formation via H2O + O while reducing the overall active radical pool for hydrogen flames. For C2H4, the additional HO2 production pathway through HCO results in a dramatic difference in pressure dependence of the burning rate from that observed for hydrogen. The present work provides important additions to the experimental database for syngas and C0-C2 high pressure kinetic model validations.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Mechanical Engineering
- Physical and Theoretical Chemistry
- Elevated pressure
- Laminar burning rate
- Water dilution