Hyungmo Kim

Effects of CO2 dilution on combustion instabilities in dual premixed flames

There has been a rapid increase in the demand for biogas applications in recent years, and dry low NOx and dry low emission gas turbine combustors are promising platforms for such applications. Combustion instability is the most important drawback in dry low NOx gas turbine combustors and has, therefore, attracted considerable research interest lately. As a fundamental study towards the use of biogas in dry low NOx and dry low emission gas turbine combustors, this article investigates the influence of CO2 in surrogate biogas on combustion instability. Tests were conducted using a dry low NOx type, a dual lean premixed gas turbine combustor. For a dual flame with dual swirl, the pilot fuel mass fraction affects the flame structure, and the flame structure, in turn, determines the temperature distribution in the combustion chamber and the combustion instability. The effects of the pilot fuel mass fraction, which is an important parameter of the combustor, and the CO2 dilution rate, which is a major contributor of biogas combustion, on the combustion characteristics and instability are investigated through dynamic pressure signal and phase-resolved OH* images. Combustion instability decreases for higher CO2 dilution rates, whose effects depend on the pilot fuel mass fraction. The instability reaches its maximum at a pilot fuel mass fraction of 0.3. Tests confirm that combustion instability diminishes with CO2 dilution, as it reduces the perturbation in the heat emission, and the flame speed decreases resulting in a greater flame surface or volume. Further, investigation of the Rayleigh Index, which represents the coupling strength of the heat release fluctuation and the natural frequency, shows that CO2 dilution weakens the coupling strength, resulting in less combustion instability.

Performance Tests for Development of a Dry Low NOx Combustor

A 5MW-gas turbine engine (DGT-5) for power generation is currently under development by Doosan Heavy Industries, funded under a national RD NOx emissions<20ppm; PF<7.6%; Pressure pulsation amplitude <2kPa at low pressure (3bar, a), 100% load and FR 0.2 conditions.Copyright

Start-up Combustor Development for GT/FC Hybrid Power Generation System

Currently, 60kW class gas turbine fuel cell hybrid power generation system is being developed by Korea Aerospace Research Institute. In this system, gas turbine combustor acts as a component which supplies hot gas to the highly efficient power generating fuel cell as well. Because of connection problems between gas turbine and fuel cell, the combustor is necessarily to have flame stability and wide flamability range at the starting stages. Furthermore, in order to enhance the efficiency of the whole system, high combustion efficiency and low pressure loss are required. It also should satisfy the temperature limitations of turbine blade by supplying sufficiently low and uniform thermal energy. In the present study, for the optimization of the combustor, its stability characteristics are tested with change of various operating conditions such as injector shape, swirler air mass flow rate etc. For the basic performance factor survey, effects of combustor exit temperature, pressure loss, combustion efficiency and exhaust gas compositions are also investigated.