Numerical and Experimental Investigation on the Performance of Lean Burn Catalytic Combustion for Gas Turbine Application

This manuscript presents our numerical and experimental results regarding the performance characteristics of lean bum catalytic combustion for gas turbine application. The reactant transport was assumed to be controlled by both bulk diffusion as well as surface kinetics, implemented by means of an approximate reaction rate equation and empirical coefficients to incorporate reaction mechanism. Experimental and numerical results were compared to examine the effects of methane mole fraction, inlet temperature, operating pressure, velocity and hydrogen spe- cies on combustion intensity. The results indicate that inlet temperature is the most significant parameter that im- pacts operation of the catalytic combustor and the most effective methods for improving the methane conversion are increasing the inlet temperature and increasing the methane mole fraction. Simulations from ID heterogene- ous plug flow model can capture the trend of catalytic combustion and describe the behavior of the catalytic mo- nolith in detail. The addition of hydrogen will provide heat release by the exothermie combustion reaction so that the reactants reach a temperature at which methane oxidation can light-off.

Part-load Performance Characteristics of a Lean Burn Catalytic Combustion Gas Turbine System

The purpose of this study is to compare the part-load performance of a lean burn catalytic combustion gas turbine (LBCCGT) system in three different control modes: varying fuel, bleeding off the fuel mixture flow after the compressor and varying rotational speed. The conversions of methane species for chemical process are considered. A 1D heterogeneous plug flow model was utilized to analyze the system performance. The actual turbomachinery components were designed and predicted performance maps were applied to system performance research. The part-load characteristics under three control strategies were numerically investigated. The main results show that: the combustor inlet temperature is a significant factor that can significantly affect the part-load characteristics of the LBCCGT system; the rotational speed control mode can provide the best performance characteristics for part-load operations; the operation range of the bleed off mode is narrower than that of the speed control mode and wider than that of the fuel only mode; with reduced power, methane does not achieve full conversion over the reactor at the fuel only control mode, which will not warrant stable operation of the turbine system; the thermal efficiency of the LBCCGT system at fuel only control strategy is higher than that at bleed off control strategy within the operation range.

Numerical study on the combustion process in a gas turbine combustor with different reference velocities

The mixing and combustion processes under different reference velocities in a gas turbine combustor were numerically investigated using the Flamelet Generated Manifold(FGM)model based on the Reynolds Averaged Navier-Stokes(RANS)method.The flow and combustion fields show strong self-similarity except on the slow auto-ignition in the mixing layer between fuel-rich product and fresh air upstream of the flame stabilization position.The time-scale analysis was carried out to understand the combustion modes inside the combustor.In general,the residence time of the fuel-mixture is much longer than both the chemical time scale and the mixing time scale.Thus,the combustion properties in each sub-zone were dominated by the mean flow structures.Furthermore,the combustion process exhibits a mixing-controlled feature in total.However,partially premixed combustion still appears on the flame base.Most of the fuel was found to be oxidized in the primary zone and the intermediate zone;however,the slow oxidization reactions also play a non-negligible role on the whole combustion process.Finally,a sketch map on the space of mixture fraction and combustion efficiency was proposed to understand the mixing and oxidization experiences of the fuel mixture.

MILD Combustion for Hydrogen and Syngas at Elevated Pressures

As gas recirculation constitutes a fundamental condition for the realization of MILD combustion, it is necessary to determine gas recirculation ratio before designing MILD combustor. MILD combustion model with gas recirculation was used in this simulation work to evaluate the effect of fuel type and pressure on threshold gas recirculation ratio of MILD mode. Ignition delay time is also an important design parameter for gas turbine combustor, this parameter is kinetically studied to analyze the effect of pressure on MILD mixture ignition. Threshold gas recirculation ratio of hydrogen MILD combustion changes slightly and is nearly equal to that of 10 MJ/Nm3syngas in the pressure range of 1-19 atm, under the conditions of 298 K fresh reactant temperature and 1373 K exhaust gas temperature, indicating that MILD regime is fuel flexible. Ignition delay calculation results show that pressure has a negative effect on ignition delay time of 10 MJ/Nm3syngas MILD mixture, because OH mole fraction in MILD mixture drops down as pressure increases, resulting in the delay of the oxidation process.

N_(2)and Ar dilution on the premixed biogas jet flame under external acoustic enforcement

In this study,combustion instabilities and flue gas emission changes under different dilutions of N_(2)(nitrogen)and Ar(argon)of a promising biogas mixture(70%CH4-30%CO_(2))in the fight against greenhouse gas emissions were investigated.In the experiments,additions were made from 0%to 50%at intervals of 10%for both gases.In order to detect the instability of the flame,external acoustic enforcements at different frequencies was applied through the speakers placed in the combustion chamber arms.The dynamic pressure fluctuation values were recorded.The results showed that low dilution ratios were effective in reducing flame instability for both inert gases.However,as the dilution ratio increased,the fuel/air mixture became leaner and blowoff occurred.In the case of comparing two different gases,it has been observed that the effect of argon gas on reducing dynamic pressure fluctuation is higher.Burner outlet temperature and brightness values of the flame decreased in both Ar and N_(2)dilution.CO and NOx emissions increased with increasing diluent volume for all dilution conditions.When the emissions of the two diluent gases are compared,the CO emission,which was 3134 ppm in the undiluted condition,increased up to 4949 ppm in 50%Ar dilution,while it increased to 4521 ppm in 50%N_(2)dilution.

燃气轮机催化燃烧室的实验研究

:介绍了预混和催化燃烧相结合的燃烧室原理。对此种燃烧室进行实验研究 ,分析了影响催化燃烧的主要因素。预混与催化燃烧相结合能延长催化剂的使用寿命、改善燃烧室的可靠性。