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.
Combustion-related characteristic parameters, such as the start of combustion (SoC) and the timing of the peak pressure increase rate (PIR), can be used as the feedback signals for the closed-loop control of combustion. A dynamic Finite Element Method (FEM) model was firstly developed to confirm the closely related time period between combustion pressure and vibration. On this basis, a fast processing method was developed to estimate the timings of SoC and the peak PIR in the closely related time period. This method was verified on a twelve-cylinder heavy-duty diesel engine at various engine speed and load. Results showed that the maximum deviation of the two parameters were within 2 °CA and 1.5 °CA, respectively, which suggested that the proposed method had an adequate accuracy.
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