Preliminary Study On Fuel Flexibility Of Aeroderivative Gas Turbine

Due to the high price of natural gas,gas-turbine units with natural gas as the main energy need to pay a high cost of power generation.Therefore,all countries in the world hope to use different types of fuel to broaden the flexibility of gas turbine fuel,so as to use more medium and low calorific value and other fuels,and reduce the cost of natural gas power generation.Therefore,how to modify the design of relevant gas turbine units so that they can burn a variety of fuels is the focus of attention.More and more attention has been paid to the air turbine due to its small size and strong fuel adaptability.In this paper,under the background of developing fuel flexibility of gas turbine and aiming at fuel flexibility of air turbine,the main contents and conclusions are as follows:In this paper,an improved design of the combustion chamber for the gas turbine is firstly carried out.Based on the index of prototype combustor,the index to be achieved in the design of the modified combustor was determined,and the gas quantity was distributed by gas turbine.The physical parameters of a typical coke oven gas were calculated,and the fuel mass flow of coke oven gas was determined according to the design index.The total equivalent ratio of the combustion chamber was calculated to be 0.3297.According to the characteristics of gas turbine and medium&low calorific value fuel,the structure of the burner with diffusion combustion mode is determined.Due to the fuel combustion instability and wide explosion limit under low working conditions,a dual-fuel dual-oil structure nozzle was adopted.The liquid path of the nozzle was designed according to the empirical formula coefficient method,the parameters such as nozzle radius and swirl size were determined,and the atomized particle size was verified by SMD.It is calculated that the SMD of auxiliary oil line is40μm at the design point of 2.5MPa,which is better than the test and meets the design requirements.The primary design of gas passage and swirl is carried out,and the reference structure parameters are determined.Then the aerodynamic and thermodynamic performance of the improved combustion chamber is calculated.Numerical simulation results show that the coke oven gas nozzles and cyclones can form a stable central reflux zone in the modified combustion chamber,which is conducive to the exchange of energy and components and the stable combustion of flame.The orifice Angle of fuel injection has obvious influence on the performance of the combustion chamber.When the radial Angle increases to,the reflow area of the combustion chamber shrinks,and the high temperature area at the head gradually shrinks to the axis of the nozzle.The structure design of axial swirl also has a significant effect on the flow field and temperature field of the combustion chamber,especially on the Angle of the swirl blade.When the number of swirls increases,the high temperature area at the head of the combustion chamber is closer to the wall surface,resulting in high wall temperature,which is easy to ablate the flame tube wall surface.OTDF and RTDF deteriorate rapidly.The calculation and analysis of the coke oven gas nozzles and swirl of the benchmark scheme under different load conditions are carried out.Finally,the key structural parameters of the swirl cup nozzle in the coke oven gas combustion chamber are as follows:the nozzle aperture is 2.5mm,the injection Angle of the nozzle aperture is 30°,the blade installation Angle of the axial swirl is 36.5°/38°,and the area ratio of the outer ring/inner ring of the venturi tube is 0.70.The final OTDF and RTDF of the combustion chamber were 0.21 and 0.15,with a total pressure loss of 94.6%and a combustion efficiency of 99.9%,which met the design requirements.Finally,the swirl cup nozzle at the head of the combustion chamber is tested.Flow field experiments show that the retrofit dual fuel nozzle and the center of the vortex cup formed stable backflow zone,cold and hot state conditions can assure the head of air and fuel combustion chamber relative to the mixing of cold flow field,combustion heat release to air ballooning,downstream axial lead nozzle bigger and smaller tangential momentum,momentum,in turn,make the length of recirculation region significantly shortened,reduce to 100 mm.At the same time,the combustion also increases the backflow strength and turbulence of the flow field.The temperature at each point increases linearly with the increase of the equivalent ratio.The flame center temperature is higher,the equivalent ratio is 0.45,the air flow rate is 10.41g/s,the flame center temperature is about 1200℃,the concentration of NO is 43ppm,and the content of CO is basically 0.According to the dual-fuel nozzle characteristics,the flame stability should be ensured during the fuel switching process,and the dynamic dual-fuel switching process should be divided into quasi-steady state processes,which are respectively the ignition condition S1 to the S6 condition where all coke oven gas is used.The experimental results show that the methane center path can ignite smoothly.With the switch of fuel inside and outside the nozzle,the flame shape changes,the color changes from light blue to gray,and the flame is concentrated at the bottom of the combustion chamber.Nitrogen blending fuel can effectively reduce the flame temperature,thus reducing NOx emissions.When the dilution of N₂ was 0%,the flame center temperature was 1025℃and NO emission was 24ppm.With the increase of N₂dilution,when the dilution was 60%,the flame center temperature decreased to 950℃,a decrease of about 75℃,and the NO emission was only 6ppm.