Hongtao Zheng

Feature-Parameter-Criterion for Predicting Lean Blowout Limit of Gas Turbine Combustor and Bluff Body Burner

Lean blowout (LBO) limit is one of the most important combustor parameters. A new method named Feature-Parameter-Criterion (FPC) for predicting LBO limit has been put forward in the present work. A computational fluid dynamics (CFD) software FLUENT has been used to simulate the process of LBO of gas turbine combustor and bluff body burner. And “M” flame has been proposed as the portent for predicting lean blowout of gas turbine combustor. Effects of flow velocity, air temperature, droplet averaged-diameter, and flow distribution between swirlers and primary holes on the LBO limit of gas turbine combustor have been researched by use of Feature-Parameter-Criterion in this paper. The effects of fuel air mixture velocity and different structures on bluff body LBO limit have also been analyzed in the present work by use of FPC. The results show that the simulation of LBO limit based on FPC is in good agreement with the experiment data (the errors are about 5%) and this method is reliable for engineering applications.

Experimental study on chemical recuperation using hybrid dielectric barrier discharge-catalytic methane-steam reforming

Hybrid dielectric barrier discharge-catalytic steam reforming is proposed here for use in chemically recuperated gas turbines, so as to be compatible with the low-temperature exhaust heat from turbines. Four different types of reactor were designed for comparison, and extensive experiments were performed to evaluate the exhaust heat recovery in terms of effective carbon recovery rate, methane conversion, fuel heating value increase rate, and total enthalpy increase rate. The effect of methane space velocity and reactor wall temperature on methane conversion have been analyzed. The results showed that, for any reactor, there was an optimum methane space velocity for the most heat recovery. With increasing wall temperatures, the parallel synergistic reforming technology induced more methane conversion than the other reactors. Under the same input power, parallel synergistic reactors could recover more exhaust heat than the sum of catalyst-only and plasma-only reactors, with a relative total enthalpy increase as much as three times the sum of the latter two. Moreover, the parallel synergistic reforming technology resulted in a higher relative total enthalpy increase for reformed gas at low temperatures. These results demonstrate that parallel synergistic reforming technology is a promising technology to significantly recover exhaust heat under different working conditions.

Analysis of Turbulence Models in Numerical Simulation of Combustion Chamber

Several turbulence models were analyzed in this paper for the chemically recuperated gas turbine (CRGT) combustor and numerical simulation of the combustor’s flow fields using these turbulence models was carried out with the aid of CFD method and finally the contrastive analysis was made. Realizable k-e and RNG k-e turbulence models, PDF combustion model and the SIMPLE algorithm method were adopted in the numerical simulation. Through comparison of key influencing factors of the combustor such as flame length, position of the high temperature zone, wall temperature and evenness of exit temperature field, it could be concluded that the Realizable k-e turbulence model demonstrates better performance with high quality of convergence precision and evenly distributed parameters that meet the design requirements better.Copyright

Application of Eddy Dissipation Concept Model in Simulation of Gas Turbine Combustor

Non-premixed combustion flow with C16H29 fuel in gas turbine combustor was simulated by commercial software fluent. Under a design condition, the turbulence was solved by the RNG k - epsiv two-equation model, the physical nozzle was simulated by the discrete phase model (DPM) and discrete random walk (DRW) model, the reaction and NOx exhaust were analyzed by different reaction models as eddy dissipation concept (EDC)-2Step model, EDC-5Step model and thermal & prompt NOx models respectively. The result shows that there is a lower peak temperature, a better uniformity of temperature in outlet as 28%, a lower NOx exhaust as 728 ppm with EDC-5Step model including exothermic reactions.

Fuel prereforming and combustion characteristics study of chemically recuperated gas turbine

The chemically recuperated gas turbine cycle testing platform was designed and built based on theoretical research and experimental study, which included the dual-stage flash evaporation, the diesel steam reformer, and the dual-fuel combustion system. In this paper, an experimental study on the oil (C7H16) prereforming performance is analyzed and the relative increment of the equivalent calorific value is 46.2%. Combustion characteristics are calculated with oil and reformed gas and the results show that main combustion zone temperature drops from 2280 to 1910 K, which leads the ultra-low NO emissions of 1.8 ppm. The flame is stable using reformed gas and the wall temperature is low, but the nonuniformity of outlet is relatively high. Thermal efficiency of combustion is more than 99% even at low load condition.

Kinetic Effects of Non-Equilibrium Plasma-Assisted Methane Steam Reforming on Heat Recovery in Chemically Recuperated Gas Turbine

Plasma is proposed as a prospective tool for chemical heat recovery process without restriction from reaction temperature. The author designed DBD catalytic reactors and carried out extensive experiments to investigate methane conversion and products yield and analyze the effect laws of steam to methane ratio, resident time and reaction temperature on methane steam reforming (MSR). Based on extensive experimental studies of steam reforming, a detailed reaction mechanism for the plasma-assisted MSR was developed and evaluated by comparison of experimentally derived and numerically predicted conversion and products yield. The comparisons showed the kinetic model well predicted methane conversion and products yield in different operating conditions. By employing the kinetic model and path flux analysis module the kinetic effects of low temperature non-equilibrium plasma assisted CH4 steam reforming on the methane conversion was studied without catalyst. The results showed that CH3 recombination was the limiting reaction for CO production; meantime O was the critical species for CO production. By adding Ni catalyst can reduce methyl recombination and promote hydroxyl into oxygen, which is beneficial to heat recovery. The proposed research ensures the effect laws and characters of MSR by plasma, and contribute to improve the objective products concentration and furthermore the energy efficiency.Copyright

A New Method for Numerical Prediction of Lean Blowout in Aero-Engine Combustor

Lean blowout (LBO) is one of the most important parameters on combustor performance. A new method named Feature-Section-criterion (FSC) for predicting LBO of aero-engine annular combustor has been put forward in the present work. A CFD software FLUENT has been used to simulate the combustion flow field of an annular combustor. The prediction of LBO with FSC has been done in this paper and the effects of flow velocity, air temperature and droplet averaged-diameter on the LBO of aero-engine combustor have been discussed by using of FSC. The results show that the predictions of FSC are in agreement with corresponding experimental data. This showing that this method for predicting lean blowout is reliable and can be used for engineering applications.Copyright

Effect of Dual Fuel Nozzle Structures on Combustion Flow Field in CRGT Combustor

Three different structures of a new dual fuel nozzle design concept (inner swirl nozzle, double swirl nozzle, and outer swirl nozzle) were developed for the chemically recuperated gas turbine (CRGT) combustor. The combustion flow fields in the combustor with the three nozzles were investigated, respectively, based on the FLUENT simulation. The realizable - model and PDF model were adopted, respectively, for the turbulence flow and nonpremixed reformed gas combustion. The obtained results using these models showed good agreement with experimental results in original oil combustor. The effects of different dual fuel nozzle structures on the flow field, fuel concentration distribution, and temperature distribution in the combustor were simulated and analyzed. Results suggest that the double swirl nozzle and outer swirl nozzle can form a better flow field with obvious central recirculation zone (CRZ), shorten fuel and air mixing distance, and obtain a more uniform outlet temperature distribution, in comparison with the inner swirl nozzle. However, compared with double swirl nozzle, the outer swirl nozzle can result in a better combustion flow field with the high temperature region in the CRZ, which is important to stabilize the flame.

Numerical Simulation of Combustion Flows in Dual-fuel Combustor

In order to study the performance of dual-fuel combustor in gas turbine, combustion flows were simulated. The turbulence was solved by the RNG k - Â? two-equation model, the reaction was settled by the simple chemical reacting system (SCRC) of the infinitely fast chemical reaction assumption and the beta probability density function (PDF) without the intermediate reactions, and the use physical nozzle for oil-fuel was simulated by the atomizer model. The characteristic parameters of the non-premixed combustion flows between the oil fuel and the pyrolysis gas, such as pressure, temperature and velocity etc, were analysed with FLUENT. And the pollution of NOx was simulated in the combustion processes. The results show that: there is a lower peak temperature, a better uniformity of temperature in outlet, a lower NOx emission with pyrolysis gas fuel.

Numerical Simulation of Combustion Flows in Gas Generator

In order to enhance the performance of gas generators and optimize the structures, combustion flows were simulated. The turbulence was solved by the RNG two-equation model, the reaction was settled by the simple chemical reacting system (SCRC) of the infinitely fast chemical reaction assumption and the beta probability density function (PDF) without the intermediate reactions, the radiative heat transfer was calculated by P-l radiation model, the physical nozzle was simulated by the pressure-swirl atomizer model, and the emission of NOx was simulated as well. The characteristic parameters of the nonpremixed combustion flows between the air and the C 12 H 23 , such as pressure, temperature and velocity etc, were obtained with FLUENT program about different structures and air-inlet conditions. The follows were considered and demonstrated with simulation results: the resistance character of structures, the relationship between the mass of cooling-air and the temperature distribution on inner walls, the NOx emissions etc.