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An experimental study was carried out to characterize the exhaust flow structure inside the closed-coupled catalytic converter, which is installed on a firing four-cylinder 12-valve passenger car gasoline engine. Simultaneous velocity and pressure measurements were taken using cycle-resolved Laser Doppler anemometer (LDA) technique and pressure transducer. A small fraction of titanium (IV) iso-propoxide was dissolved in gasoline to generate titanium dioxide during combustion as seeding particles for the LDA measurements. It was found that the velocity is highly fluctuating due to the pulsating nature of the engine exhaust flow, which strongly depends on the engine operating conditions and the measuring locations. The pressure oscillation is correlated with the transient exhaust flow characteristics. The main exhaust flow event from each cylinder can only be observed at the certain region in front of the monolith brick.

Hybrid vehicles, which have a higher fuel economy and system efficiency than conventional gas only vehicles, has been attracting worldwide attention for its various advantages. These advantages include low emissions of greenhouse gases which mitigates direct or indirect effects on the ozone layer. LPI HEV recently developed by HMC performs with the same output level, torque and fuel economy as conventional gasoline hybrid vehicles by employing the world's first liquid-state-injection system for exclusive use of LPG. In particular, the improved fuel economy of the vehicle is expected to help cope with future regulations relating to environmental protection from exhaust fumes.