Experimental Investigations on NO_(x) Emission and Combustion Dynamics in an Axial Fuel Staging Combustor

Axial Fuel Staging(AFS)technology is an advanced low-emission combustion method in modem gas turbine,which divides the combustor into two axially arranged combustion zones.For revealing the characteristics of axial staged combustion,an industrial-grade combustor was designed and built.The distribution of temperature and velocity field in the combustor was presented with numerical simulation.And an Atmospheric Combustor Test Rig for axial staged combustion was built.The flow resistance characteristics of the combustor were measured at first.Then the effects of the equivalent ratio and the preheating temperature on the pollutant emission and combustion instability were investigated.The results show that the total pressure recovery coefficient in cold state is always above 98%;starting the secondary combustion at low load can reduce NO emissions by 50%,and can suppress the combustion oscillation amplitude of the combustor.At the design point with φ=0.62 and preheating temperature=400°C,NO emission and CO emission are 15.68 and 4.22 mg/m^(3)(@15%O_(2)).

Numerical and experimental investigation on emission performance of a fuel staged combustor

The low NOx emission technology has become an important feature of advanced aviation engine.A wide range of applications attempt to take advantage of the fact that staged combustion under lean-premixed-prevaporized(LPP)conditions can significantly cut down emission and improve combustion efficiency.This paper proposes a scheme with fuel centrally staged and multi-point injection.The mixing of fuel and air is improved,and the flame temperature is relative low in combustion zone,minimizing the formation of nitrogen oxides(NOx),especially thermal NOx.In terms of the field distribution of equivalence ratio and temperature obtained from Computational Fluid Dynamics(CFD),a chemical reactor network(CRN),including several different ideal reactor,namely perfectly stirred reactor(PSR)and plug flow reactor(PFR),is constructed to simulate the combustion process and predict pollution emission.The influences of the pilot equivalence ratio and percentage of pilot/main fuel on NOx and carbon monoxide(CO)emission were investigated by CRN model.The effects of the pilot fuel and primary fuel on pollution emission were investigated experimentally.Finally,the effects of pilot equivalence ratio and pilot fuel proportion on NOx emission were discussed in detail by comparing predict of CRN and experimental results.

Experimental Investigation on Ignition and Lean Blow-out Performance of a Multi-sector Centrally Staged Combustor

Improvement on extinction and pollution emission have become one of the most prominent research topics in gas turbine.It is widely recognized that the fuel/air mixture distribution in the recirculation zone is a critical factor in improving lean blow-out(LBO) and ignition.This paper proposed a new low emission scheme with fuel staged centrally and hybrid injector to improve flameout and emission.A relative small amount of fuel enters into central pilot airblast atomizer burner and then atomized by inner swirl air.The remaining majority of fuel is directly injected into vane channels of the primary swirler through a series of holes located on the sidewall of the main stage.Only pilot stage is fueled under ignition and lean flameout condition.The uniformity of fuel/air mixture distribution in the primary zone of the new design decreases NOX emission,meanwhile the fuel air mixture in pilot recirculation zone is locally rich to improve flameout and ignition.Experimental investigation was conducted to compare the new scheme with baseline design of dual-swirler in terms of LBO and ignition characteristics under the same condition in a multi-sector combustor.It is found that the fuel-air ratio of ignition limit and LBO decrease with the reference velocity increasing.The experimental results also show that the new scheme successfully improve lean blow-out and broaden the operation range of the combustor.The experimental results indicated that the centrally staged scheme can widen the operation boundary of the combustor and can provide guidance for design and optimization of combustion chamber.