Influence of Ozone on Ignition and Combustion Performance of a Lean Methane/Air Mixture

Abstract

The feasibility of improving ignition and combustion performance of methane by ozone addition has been studied in the present work. First, combustion of a lean methane/air mixture with ozone addition was conducted by using a constant volume combustion bomb. Results showed that ozone could extend the lean combustion limit and accelerate flame speed. Then, chemical reaction kinetic analysis was adopted to obtain ignition delay time and laminar flame speed which were used to analyze the influence of ozone on ignition and the combustion performance of the lean methane/air mixture, respectively. Analysis carried out with different equivalence ratio, initial temperature, and pressure showed that ignition delay time was shortened obviously with ozone addition. The peak concentration of CH2O increased and the time of peak concentration appearance advanced with ozone addition, which indicated that the beginning time of the low temperature reaction was advanced with ozone addition and thus improved ignition performance. Laminar flame speed could be accelerated obviously with ozone addition in different equivalence ratio, especially under the condition of research. Concentration of OH and other intermediate products with ozone addition was compared and results showed that ozone could increase the amount of OH and other products, thus improve combustion performance. The results obtained in this study showed that ozone could shorten ignition delay time and accelerate burning velocity of the lean methane/air mixture.

Investigation of Combustion Enhancement by Ozone in a Constant-Volume Combustion Bomb

“…In order to further investigate the influence of ozone on the methane/air mixture, a closed homogeneous batch reactor, which presented closed-state combustion simulation, was used to study the variation of the reaction path with ozone addition. The kinetic model was already verified in our previous study . The kinetic analysis also focused on an equivalence ratio of 0.6 and initial pressure of 500 kPa.…”

“…Chemical reaction kinetic analysis was conducted using the Chemkin software package to assist in the understanding of the mechanism of how ozone affected the combustion process. The chemical reaction mechanism and calculation model were verified in our previous study . The mechanism was composed of 342 steps of elementary reactions and 54 species.…”

“…The chemical reaction mechanism and calculation model were verified in our previous study. 26 The mechanism was composed of 342 steps of elementary reactions and 54 species. The CHEMKIN modules used in the study contained an external source for inlet gas, a premixed laminar flame-speed calculator, and an outlet flow (product) of the reactor.…”

“…To further explain the mechanism of how ozone affected the combustion performance of the methane/air mixture, chemical reaction kinetic analysis was conducted with the validated kinetic scheme. 26 In order to ensure the consistency between experiments and computation, initial conditions of the model, such as pressure, temperature, equivalence ratio, and ozone addition, were set to be the same as those in experiments. Chemical kinetic analysis was conducted in the following three steps.…”

“…The kinetic model was already verified in our previous study. 26 The kinetic analysis also focused on an equivalence ratio of 0.6 and initial pressure of 500 kPa. Calculation results showed that the dehydrogenation reaction path of CH 4 was the same as the analysis mentioned above, so the complete dehydrogenation process was no longer introduced.…”