Abstract
Nowadays, we have many energy problems related to the depletion of natural resources and the environment. It is well known that the improvement of thermal efficiency in energy conversion systems is among the keys to the resolution of these problems. We have proposed a new gas-turbine system using of two-stage combustion (Chemical Gas Turbine: ChGT). In ChGT, fuel-rich combustion is employed at the first stage turbine. The exhaust gas from the first turbine still contains a considerable amount of combustible species, and is burned at the second-stage turbine as its fuel. Such combustion condition leads to improvement of thermal efficiency and decrease of NOX emission.In conventional gas turbine, some of air is introduced into combustion gas in combustor to cool and control turbine inlet temperature (TIT). In the first-stage of ChGT, however, air cannot be used for cooling because the combustion gas may ignite again. Therefore, we propose new combustion method for the first-stage that secondary-fuel is injected into the combustion gas instead of air. The equivalence ratio at the first-stage has been assumed about 1.9. In this method, the equivalence ratio at burner is set to less than 1.9, and the total equivalence ratio is 1.9 by injecting the secondary-fuel in the downstream of combustor. It is expected the combustion is more stable, and soot production could be suppress.In this study, we examined the advantage of this method. The temperature and species concentrations of the exhaust gas were measured with changing the flow rate and injected position of secondary-fuel. Moreover, the changes of flow pattern by introducing secondary-fuel were observed using PIV (Particle-Imaging Velocimetry) for the cold model of the combustor. From these measured results, we discussed the optimization of the secondary-fuel injection.
