Combustor Outlet Temperature Research Articles

Thermodynamic analysis of natural gas/hydrogen-fueled compressed air energy storage system

In this paper, a diabatic compressed air energy storage system fueled by a natural gas/hydrogen mixture that integrates heating and power generation is proposed. A comprehensive thermodynamic analysis has been conducted to identify the key factors influencing system performance and elucidate the detailed formation and distribution patterns of irreversible losses when utilizing a hydrogen-natural gas blend as fuel in the proposed system. The research results indicate that increasing the hydrogen blending ratio from 0.5 to 1 lead to greater enhancements in roundtrip efficiency (∼1.08% vs. ∼0.33%), exergy efficiency (∼3.88% vs. ∼1.15%), and energy density (∼1.24% vs. ∼0.42%) compared to an increase from 0 to 0.5. The combustor suffers the largest exergy destruction proportion, with a notable reduction in exergy destruction achieved through increased hydrogen blending. System performance benefits significantly from higher combustor outlet temperatures and expansion ratios at various hydrogen blending ratios. The rate of change in exergy efficiency (∼42.76% vs. ∼83.17%) and energy density (∼58.83%) demonstrates an inverse correlation with the varied parameters (1100–1500K, 4–8), except for the rate of change in energy density (∼6.76%), which displays a positive relationship with the combustor outlet temperature. Notably, a significant decrease in the rate of change in roundtrip efficiency (∼1.87% vs. ∼6.64%) is observed within a specific parameter range (1400–1500K, 5–6). Sensitivity analysis identifies the combustor outlet temperature as the most influential factor in enhancing system performance, consistently showing positive effects of the hydrogen blending ratio.

Mode transition control law analysis of ammonia MIPCC aeroengine considering inlet–compressor safety matching

Inlet–Compressor (I–C) safety matching is a key technology for successfully implementing the mode transition of a turbine-based combined-cycle (TBCC) engine. To investigate the performance variation in Ammonia mass injection pre-compressor cooling (MIPCC) aeroengines (AMAs) during the mode transition, a model considering inlet–compressor engine safety matching was developed in this study. We provide a computation for the inlet unstart margin ξ which considers the positive shock wave assumption, I–C flow conservation equation, and combined inlet characteristics to assess the degree of I–C matching. Furthermore, the AMA characteristics indicate that the total pressure recovery coefficient of the hypersonic combined inlet has significantly affects the engine performance. The restraint ξ also ensures engine safety. A control law guided by ξ and the combustor outlet temperature (ξ–COT) was proposed to enhance the specific impulse and specific thrust of the AMA. Compared with the speed and COT control laws, the specific impulse and specific thrust were maximally improved by 2.93 % and 5.47 %, respectively, when ξ = 0.2. Both were further improved by 5.91 % and 10.49 %, respectively, when ξ = 0.1. Finally, the high-thrust performance results of the AMA, with the optimized control law ξ–COT during the mode transition process, were obtained.

Numerical and experimental study of combustion and emission characteristics of ammonia/methane fuel mixture in micro gas turbine combustor

Due to the increasing demand for low carbon fuels, ammonia is considered a viable option. Considering the problems associated with the combustion of ammonia, such as its narrow flammability range, it has been suggested to use it together with other fuels, such as methane. Following previous studies, which mainly focus on the emission of this fuel mixture in burners and simplified chambers, this research attempts to conduct an experimental and numerical study with a greater emphasis on performance parameters and pollution in an actual microturbine combustion chamber. The study investigates the effect of a mixture of ammonia with methane and its fraction on the combustion performance of the combustor and its emissions (NOx, CO) in two different thermal powers. The results showed that flame temperature decreased as the fraction of ammonia in the fuel increased, and the flame moves away from the injector. It also appeared that adding ammonia to the fuel increased the amount of NOx produced in the combustor without reducing CO significantly. Also, the combustor outlet temperature remained almost unchanged, but the combustion efficiency of the combustor decreased as the ammonia fraction increased.

Experimental study on the influence of inlet velocity and fuel/air ratio on outlet temperature profile performance in a turboshaft engine combustor

This paper presents an experimental study on the influence of inlet velocity and fuel/air ratio (FAR) on the outlet temperature profile in a mixed-flow trapped vortex combustor (MTVC) working with RP-3 liquid fuel. This new MTVC is using a single cavity to stabilize flames for turboshaft engine. Temperature profile performances, such as temperature non-uniformity, radial temperature profile, profile factor (RTDF) and pattern factor (OTDF), were examined at atmospheric pressure on a fan-shaped test rig at different inlet velocities and fuel/air ratios. By analyzing the temperature pattern in the cavity, the reason for the characteristic law of the outlet temperature profile is obtained. The results indicate that the MTVC has achieved a satisfactory temperature profile, which can meet the requirements of the turbine. The radial temperature profile at combustor outlet is not a flat straight line, showing a pattern of high temperature in the middle of combustor outlet and low temperature at both ends of combustor outlet. The peak temperature is 0.6 times the height of combustor outlet. The high temperature zone with a constant FAR lean towards the top of the outlet center, and the temperature non-uniformity, OTDF and RTDF increase with increasing velocity. However, the high temperature zone approaches the outlet axis at a constant velocity as FAR changes. The temperature non-uniformity decreases with an increases of FAR. There is an optimal velocity where OTDF and RTDF pass through a minimum value. A decrease or increase in velocity beyond this optimal velocity results in an increase in both OTDF and RTDF. This mainly depends on the fuel distribution, the air jet mixing, the local FAR in cavity, and the location of high-temperature products in combustor outlet.

Parametric optimization and exergy analysis of a high mach number aeroengine with an ammonia mass injection pre-compressor cooling cycle

The Ammonia mass injection pre-compressor cooling (Ammonia MIPCC) cycle provides a substantial potential for the development of a high Mach aeroengine. To evaluate performance and analyze exergy of Ammonia MIPCC aeroengine, the parameter matching modeling method and Sequential Quadratic Programming (SQP) optimization are applied. These proposed methods can realize the constraints of compressor outlet temperature, combustor outlet temperature, power balance and flow conservation, thereby optimizing the specific impulse performance. Results show that the optimal operating line (OOL) of the Ammonia MIPCC aeroengine can be divided into two paths: the temperature limit operating line and the maximum specific impulse operating line. Moreover, the OOL of the Ammonia MIPCC aeroengine is always in a high exergy utilization state. When the ammonia rate increases from 0 to 0.08, the changes in exergy reduction rate, specific impulse and specific thrust corresponding to OOL at Ma 3.0 are 18.89%–31.83%, 2347.47 to 1113.56s, 768.91–953.47 N/(kg/s), respectively. Additionally, results show that the cycle with lower inflow cooling requirements can improve economy. In summary, parameter optimization and exergy analysis help to determine the working characteristics of high Mach number Ammonia MIPCC aeroengines, enhance the engine thrust performance and extend the operating envelope.

Emission analysis for a new tubular aeroengine combustor in atmospheric test rig conditions

PurposeThe purpose of this study is to have semiempirical correlations for carbon monoxide (CO), unburned hydrocarbon (UHC) and nitrogen oxide (NOx) emissions that are collected and calibrated by using experimental data of a tubular-type combustor.Design/methodology/approachCombustor uses a coflow radial-type air-blast atomizer and is especially designed for the empirical correlation issues. Air mass flow rate, air inlet temperature and air-to-fuel ratio parameters have been changed and different inlet conditions have been created for combustor tests. Six different inlet temperatures from 475 to 350 K have been set for each air mass flow rate. Air mass flow rate values from 0.035 to 0.050 kg/s have been used to create varied combustor aerodynamic loadings.FindingsIncreasing combustor inlet temperature decreases the CO and UHC emissions. However, it has an adverse effect in NOx emissions. Moreover, CO and UHC emissions have an increasing trend by the mass flow rate rise that results an extra aerodynamic loading.Research limitations/implicationsIt is difficult to obtain real operating parameters for the combustor. Therefore, as a different approach in respect of the literature, rig test parameters have been used for thermodynamic calculations. Additionally, emission calculations of the combustor design point have been performed based on a conditioned test environment. Moreover, combustor outlet temperature and emission values have been scanned and mean values used for the analysis.Practical implicationsTo perform preliminary calculations for these pollutants, designers need experimentally calibrated correlations for the similar combustors.Social implicationsIf the application area of the designed engine is a civil aircraft, emissions are one of the most important issues because of the strict regulations of International Civil Aviation Organization. Therefore, aviation companies are continuously working on reducing of emissions.Originality/valueA comprehensive study for the preliminary emission calculation of newly designed gas turbine combustors was performed to investigate semiempirical correlations in the atmospheric test rig.

LES/flamelet/ANN of oxy-fuel combustion for a supercritical CO2 power cycle

Large eddy simulation (LES) employing a flamelet model coupled with an artificial neural network (ANN), namely the LES/flamelet/ANN is developed for supercritical oxy-fuel combustion and its validity is investigated in detail. An ANN is introduced to reduce the size of the flamelet library for non-adiabatic three gas-stream conditions of a real supercritical carbon dioxide (CO2) combustor. The fuel and oxidizer are methane (CH4) and a mixture of oxygen (O2) and CO2, respectively. To consider the real gas effect, the Soave-Redlich-Kwong (SRK) equation of state is solved to generate the flamelet library. The LES/flamelet/ANN is applied to two combustion fields in the combustor, namely the upstream and full fields of the combustor with low and high mesh sizes, respectively. The LES/flamelet/ANN for the upstream field is conducted to examine its applicability to the non-adiabatic three gas streams condition by varying the resolution of the flamelet library and by comparing it with the results obtained by the conventional LES/flamelet. The LES/flamelet/ANN for the full field is also conducted to validate the approach by comparing its results with those obtained from the experiment. The results show that the LES/flamelet/ANN of the upstream field properly reproduces the supercritical combustion behavior generated by the conventional LES/flamelet while maintaining the same level of computational cost. Furthermore, the LES/flamelet/ANN for the full field reasonably predicts the supercritical combustion behavior in the experiment, and the predicted combustor outlet temperature agrees well with the experimental results.

Investigation of a novel combustion stabilization mechanism and combustion characteristics of a multi-nozzle array model combustor

Short and uniformly dispersed flames in multi-nozzle array combustors allow for shorter flue gas residence time, resulting in less NOx emissions at high combustor outlet temperature. A new combustion stabilization mechanism based on high-speed jet induced flue gas recirculation has been utilized in an array model combustor. The stabilization mechanism allows for stable combustion at higher nozzle outlet velocity. The flame stabilization mechanism and combustion characteristics for the model combustor fueled methane have been investigated by using the combination of experiments and numerical simulations. The parameters studied include nozzle outlet velocity, inlet air temperature, and heat loss ratio. The combustion characteristics include NOx/CO emissions and reaction zone distribution. The results show that the flame stabilization mechanism is a result of the combined effects of the inner and outer recirculation zone. Under atmospheric conditions within the adiabatic temperature range from 1500 K to 2100 K, the NOx emissions are less than 20 ppm@15%O2 and the CO emissions are less than 30 ppm@15%O2. As the heat loss ratio decreases, the NOx emissions for the model combustor increase. When the nozzle outlet velocity increases, the lean blowout (LBO) for the model combustor increases. With increasing inlet air temperature, the equivalent ratio range of combustion stability expands. The downstream of the reaction zone is mostly affected by the nozzle outlet velocity and inlet air temperature, while the root of the reaction zone is essentially unaffected due to the role of inner recirculation zone. The unique stabilization mechanism of the multi-nozzle array combustion is beneficial for fuel flexibility.

Thermodynamic analysis of a comprehensive energy utilization system for natural gas pressure reduction stations based on Allam cycle

• A comprehensive energy utilization system for natural gas pressure reduction stations based on Allam cycle is proposed. • The effects of key parameters on the proposed system performance are clarified. • The proposed system and the pre-heating system are compared and analyzed. • Energy efficiency is 99.31% with turbine inlet parameters of 30 MPa/900 °C. In order to effectively utilize the pressure energy and cold energy of the natural gas pressure reduction stations, this paper proposes a comprehensive energy utilization system for natural gas pressure reduction stations based on Allam cycle. The low-grade waste heat during the Allam cycle and ambient heat are used to heat the decompressed natural gas to the temperature required by the user. Based on the established mathematical model, the effects of turbine inlet temperature, turbine inlet pressure, turbine outlet pressure, isentropic efficiency of power equipment, and natural gas expansion stages on the performance of the proposed system are studied. The proposed system and the pre-heating system are compared and analyzed. The results show that when the combustor outlet temperature is 900℃, the energy efficiency and incremental efficiency of the proposed system are 99.31% and 103.55%, respectively. Compared with pre-heating system based on gas turbine cycle, they have increased by 9.84 percentage points and 19.32 percentage points, respectively. Compared with the boiler-based post-heating system, the energy efficiency is increased by 3.5 percentage points.

Effects of inter-stage mixing on the NOx emission of staged ammonia combustion

Rich-lean staged combustion is a promising method to achieve low NOx emission for NH3 fuel. The NOx emission of the rich-lean staged combustion heavily relies on inter-stage mixing, which has not been explicitly explored for NH3 fuel. Therefore, this paper presents a modeling study concerning the effects of the inter-stage mixing on the NOx emission of NH3 fueled rich-lean staged combustion. The rich-lean staged combustor is modeled by chemical reactor networks. The non-uniform mixing is modeled by assuming Beta distribution, which is a suitable model for the random behavior of percentages and proportions that is featured in the jet-in-cross-flow mixing of the secondary air and the primary-stage combustion products. The NOx emission is obtained at different inter-stage mixedness, ηl, and rich-burn stage equivalence ratios, ∅r, with constant combustor outlet temperature (constant global equivalence ratio for lean stage, ∅g). The major impact of inter-stage mixing on NOx for staged NH3 combustion is strongly dependent on ∅r. The most significant NOx increase caused by poor inter-stage mixing occurs at around ∅r=1.25 and is due to the increase of thermal NOx, which is similar to hydrocarbon fuels. This finding has important implications for practical applications because the ∅r=1.25 point has the lowest NOx emission and is considered to be the desired operating point for staged gas turbine combustor. Therefore, complete mixing of the primary-stage combustion products and the secondary air needs to be done to ensure low NOx emission for rich-lean staged combustion of NH3. In contrast, at ∅r>1.4, poor mixing may lead to NOx reduction due to the reduction in fuel NOx. However, the NOx at this point is still high and should be avoided in practical operation.

Numerical Study of Radiation and Fuel–Air Unmixedness on the Performance of a Dry Low NOx Combustor

Abstract The development of gas turbine combustors is expected to consider the effects of radiation heat transfer in modeling. However, this is not always the case in many studies that neglect this for adiabatic conditions. The effect of radiation is substantiated here, concerning the impact on the performance, mainly the emissions. Also, the fuel–air unmixedness (mixing quality) influenced by the combustor design and operational settings has been investigated with regard to the emissions. The work was conducted with a Mitsubishi-type dry low NOx combustor developed and validated against experimental data. This 3D computational fluid dynamics study was implemented using Reynolds-averaged Navier Stokes simulation and the radiative transfer equation model. It shows that NO, CO, and combustor outlet temperature reduce when the radiative effect is considered. The reductions are 17.6% and below 1% for the others, respectively. Thus, indicating a significant effect on NO. For unmixedness across the combustor in a non-reacting simulation, the mixing quality shows a direct relationship with the turbulence kinetic energy (TKE) in the reacting case. The most significant improvements in unmixedness are shown around the main burner. Also, the baseload shows better mixing, higher TKE, and lower emissions (particularly NO) at the combustor outlet, compared to part-load.

Reacting Flow Characteristics and Multifuel Capabilities of a Multi-Nozzle Dry Low NOx Combustor: A Numerical Analysis

The fluctuating quality of natural gas (NG) in Peninsular Malaysia (PM) makes it challenging for the gas turbine (GT) combustor to meet the combustion performance requirements from the Original Equipment Manufacturer (OEM). Moreover, the gas quality sensitivity is more apparent in modern dry low NOx (DLN) combustors. Many of the prior combustion investigations were conducted on a modest scale in the laboratory. In actuality, combustion characterizations in complicated DLN combustors are more valuable to the power generation sector. Hence, the current numerical analysis utilized the RANS formulation and a detailed chemistry to examine the impact of ethane (C2H6), carbon dioxide (CO2), and nitrogen (N2) proportions in NG on combustion characteristics in a multi-nozzle DLN (MN-DLN) combustor, with the support of Modified Wobbe Index (MWI) calculations. Validations were performed using the combustor outlet temperature (COT) from the power plant where the actual MN-DLN combustor is operated, which revealed less than 10 % discrepancy. Qualitative validations were carried out by comparing the burn trace from the actual combustor wall to the predicted results, revealing an adequate Structural Similarity Index (SSIM) of 0.43. From numerical results of flame fronts and COTs, the addition of 20 % diluents (CO2 and N2) to NG demonstrated the blowoff risk. When MWIs of Kerteh and the JDA (major NG resources) were used as baselines, MWI ranges of all NG compositions under study surpassed the OEM’s ± 5 % limit. The increase in CO2 proportion results in a wide MWI range, especially when Kerteh is used as the baseline. Therefore, any GTs in PM that have previously been calibrated to use Kerteh's NG are more likely to have combustion instabilities if CO2 levels in NG suddenly increase. The higher MWI range backs up the current numerical results that showed the deleterious effects of a high CO2 composition throughout the combustor firing process. However, increasing the amount of C2H6 by up to 20 % is predicted to have minor effects on combustion characteristics. Overall, the validated numerical model of the MN-DLN combustor provided critical information about combustion characteristics and multifuel capabilities in respect to the NG quality in PM.

An Enhanced Solar Hybrid Brayton and Rankine Cycles with Integrated Magnetohydrodynamic Conversion System for Electrical Power Generation

In many developing countries,the use of conventional power plants to generate electricity is not meeting the increasing demands. Therefore, it has become important to find sustainable alternatives. In the present study, a solar hybrid combined cycle power plant consisting of a solar thermal plant, large-scale gas and steam turbines, and a magnetohydrodynamic generator has been investigated under oxy-fuel combustion. The performance analysis of this system under fuel pressure rate varying from 10 to 25 bar was conducted using Cycle Tempo software. The analysis of the gas and steam combined cycle shows that the net powers and the net efficiencies obtained ranged from 98 MWe to 134 MWe and 30.5% to 40%, respectively. In addition, the integration of the magnetohydrodynamic generator to the combined cycle led to an increase in the overall power from 169 MWe to 205 MWe. Moreover, it is seen that the fuel mass rate (2.81 kg/s) obtained in the gas turbine system under oxy-fuel combustion is significantly reduced when compared to conventional systems. The incorporation of solar energy and oxy-fuel combustion in the gas turbine system has increased the combustor inlet and outlet temperature and reduced the fuel consumption. From these observations, the solar hybrid system proposed in this study does not only generates electric power but also reduce the turbine exhaust fumes and CO2 emissions, which is a key factor in minimizing environment pollution.

A Comparative Study on Fault Detection Methods for Gas Turbine Combustion Systems

As one of the core components of gas turbines, the combustion system operates in a high-temperature and high-pressure adverse environment, which makes it extremely prone to faults and catastrophic accidents. Therefore, it is necessary to monitor the combustion system to detect in a timely way whether its performance has deteriorated, to improve the safety and economy of gas turbine operation. However, the combustor outlet temperature is so high that conventional sensors cannot work in such a harsh environment for a long time. In practical application, temperature thermocouples distributed at the turbine outlet are used to monitor the exhaust gas temperature (EGT) to indirectly monitor the performance of the combustion system, but, the EGT is not only affected by faults but also influenced by many interference factors, such as ambient conditions, operating conditions, rotation and mixing of uneven hot gas, performance degradation of compressor, etc., which will reduce the sensitivity and reliability of fault detection. For this reason, many scholars have devoted themselves to the research of combustion system fault detection and proposed many excellent methods. However, few studies have compared these methods. This paper will introduce the main methods of combustion system fault detection and select current mainstream methods for analysis. And a circumferential temperature distribution model of gas turbine is established to simulate the EGT profile when a fault is coupled with interference factors, then use the simulation data to compare the detection results of selected methods. Besides, the comparison results are verified by the actual operation data of a gas turbine. Finally, through comparative research and mechanism analysis, the study points out a more suitable method for gas turbine combustion system fault detection and proposes possible development directions.

Conceptual Approach to Combustor Nozzle and Reformer Characteristics for Micro-Gas Turbine with an On-Board Reforming System: A Novel Thermal and Low Emission Cycle

In order to implement moderate or intensive low oxygen dilution (MILD) combustion, it is necessary to extend the flame stability and operating range. In the present study, the conceptual designs of a combustor single nozzle and reformer were numerically suggested for a micro-gas turbine with an on-board reformer. The target micro-gas turbine achieved a thermal power of 150 kW and a turbine inlet temperature (TIT) of 1200 K. Studies on a nozzle and reformer applying an open-loop concept have been separately conducted. For the nozzle concept, a single down-scaled nozzle was applied based on a reference nozzle for a heavy-duty gas turbine. The nozzle can achieve a good mixture with a high swirl with a splined swirl curve lower NOx emissions and smaller pressure drop in the combustor. The concept of the non-catalytic partial-oxidation reforming reformate was designed using the combustor outlet temperature (COT) of the exhaust gas. Feasible hydrogen yields were mapped through the reformer. Based on the hydrogen yields from the reformer, hydrogen was added to the nozzle to investigate its combustion behavior. By increasing the hydrogen addition and decreasing the O2 fraction, the OH concentrations were decreased and widely distributed similar to the fundamental characteristics of MILD combustion.

Emission Characteristics and Visualization of an Axial-Fuel-Staged MILD Combustor

ABSTRACT Axial-fuel-staged combustion is a promising approach to control NOx emission at high combustor outlet temperatures by shortening the residence time of burnt gas in high-temperature region. In this paper, an axial-fuel-staged MILD combustor was studied experimentally. The combustor consists of a first MILD burner producing hot burnt gases and a secondary transverse jet nozzle injecting premixed fuel and air mixtures. By varying the secondary stage equivalence ratio (Φ2) at several constant overall equivalence ratios (Φt), NOx reduction (up to 35%) has been achieved at higher Φt but failed at lower Φt. And by increasing Φ2 at constant first stage equivalence ratios (Φ1), a continuous NOx emission increase was observed, which is insensitive to the variation of Φ1. Furthermore, the liftoff behavior of the reaction region was also studied and it was found to play important roles in the dilution of the jet mixtures, as well as OH* intensities and NOx emissions. With the decrease of Φ1, the OH* chemiluminescence images present a decreased OH* intensity when Φ2 is lean but an increased OH* intensity when Φ2 is rich. Finally, an opposed-flow flame calculation was performed and the experimental results were well-supported by this numerical study.

Optimal Design and Application of Gas Analysis System

To accurately measure the performance parameters of an aero-engine combustor under high-temperature and high-pressure environment, such as outlet temperature, combustion efficiency and pollutant emission, the optimal design of the existing gas sampling and analysis system was carried out, the data post-processing method was corrected, and the full-component enthalpy conservation method suitable for calculating combustor outlet temperature was established. A lean direct injection and low-pollution combustor was used to evaluate the performance and application of its gas analysis system and its data post-processing method. The investigation results indicate that the optimized gas analysis system meets the International Civil Aviation Organization's pollutant emission measurement requirements and that it has a fast response and a high data quality. The comparison of the measurement results of the gas analysis system with those of the traditional measurement methods shows that the gas analysis system has a more accurate measurement, a wider condition range and a better stability, thus accurately evaluating the outlet temperature, combustion efficiency and emission characteristics of a gas turbine combustor.

Experimental Study on the Emissions Characteristics of a Premixed Axial-Fuel-Staged Model Combustor

Abstract Axial-fuel-staged combustion is a promising technology to reduce NOx emission at high turbine inlet temperatures and provide extended gas turbine operational flexibility. To investigate the emissions characteristics of the axial-fuel-staged combustion, a staged model combustor was constructed and a parametric study was performed at atmospheric pressure. Fuel distribution, equivalence ratio, and jet velocity effects on the emissions characteristics have been studied in the present research. Results show that the influence of fuel distribution on emissions is depending on the combustor outlet temperature. The NOx emissions increase with secondary fuel fraction when the combustor outlet temperature is low but decrease when the combustor outlet temperature is high. Investigation of the equivalence ratio on each stage shows that a lower relative NOx increase in secondary combustion zone is achieved at higher first-stage equivalence ratio. Moreover, the secondary stage jet velocity was varied to study the jet mixing influence on the emissions. The results show that a higher jet velocity will enhance the mixing between the secondary jet and the upstream first-stage burnt gases, producing lower NOx emissions. Finally, a simplified axial-fuel-staged combustion chemical reactors network (CRN) model was established to study the mixing of the secondary fresh fuel/air mixture and the first-stage burnt gases. The CRN modeling results show that a poor mixing in the secondary stage will significantly increase the NOx emission, which means that the mixing enhancement at the secondary stage is important for the axial-fuel-staged combustor design.

Kinetics Modeling on NOx Emissions of a Syngas Turbine Combustor Using Rich-Burn, Quick-Mix, Lean-Burn Combustion Method

Abstract To avoid flashback issues of the high-H2 syngas fuel, current syngas turbines usually use nonpremixed combustors, which have high NOx emissions. A promising solution to this dilemma is rich-burn, quick-mix, lean-burn (RQL) combustion, which not only reduces NOx emissions but also mitigates flashback. This paper presents a kinetics modeling study on NOx emissions of a syngas–fueled gas turbine combustor using RQL architecture. The combustor was simulated with a chemical reactor network (CRN) model in chemkin-pro software. The combustion and NOx formation reactions were modeled using a detailed kinetics mechanism that was developed for syngas. Impacts of combustor design/operating parameters on NOx emissions were systematically investigated, including combustor outlet temperature, rich/lean air flow split, and residence time split. The mixing effects in both the rich-burn zone and the quick-mix zone were also investigated. Results show that for an RQL combustor, the NOx emissions initially decrease and then increase with combustor outlet temperature. The leading parameters for NOx control are temperature-dependent. At typical modern gas turbine combustor operating temperatures (e.g., <1890 K), the air flow split is the most effective parameter for NOx control, followed by the mixing at the rich-burn zone. However, as the combustor outlet temperature increases, the impacts of air flow split and mixing in the rich-burn zone on NOx reduction become less pronounced, whereas both the residence time split and the mixing in the quick-mix zone become important.

Comprehensive multivariable analysis of the possibility of an increase in the electrical efficiency of a modern combined cycle power plant with and without a CO2 capture and compression installations study

The main objective of the presentstudy is to determine whether the thermodynamic efficiency of a modern combined cycle power plant (CCPP) with steam reheating can be increased when using designs both with and without CO2 separation and compression installations. The relatively high costs of a steam cycle compared to a gas turbine (GT) have motivated the present direction of efficiency research in this area. Therefore, in all systems analyzed in this work, the same structure of heat recovery steam generator (HRSG) was assumed, producing fresh and secondary steam, with the parameters 600 °C/18 MPa and 600 °C/4 MPa, respectively, and a constant GT exhaust gas temperature of 630 °C. A methodology for modeling the operation of a GT within a wide range of compression ratios β (10 ≤ β ≤ 100) has been developed.Power plants that employ various types of open-air cooling (convective, film, or transpiration) in order to cool the air in a steam cycle (SC) were analyzed. These power plants were equipped with closed steam and closed air cooling, sequential combustion (reheat), and the ability to capture CO2from the flue gas.For all analyzed systems, a uniform methodology for determining the efficiency, the stream of coolant used in a GT, combustor outlet temperature (COT), and unitary CO2 emission was developed. These parameters were determined as a function of the pressure ratio, β.It is important to show the limitation of the efficiency increase that results from the COT, β level, the cooling method, and the structure of the CCPP. This paper shows that the power plant equipped with sequential combustion and steam cooling has the greatest potential for an increase in efficiency from ηel.n = 61.5% (β = 30) and ηel.n = 65.8% (β = 60) to ηel.n = 67.9% (β = 100), all at COT ≤ 1550 °C. Assuming COT = 1900 °C, the CCPP equipped with only closed-steam gas turbine cooling will reach the efficiency ηel.n = 65.5% at β = 76, and the system with film cooling will reach an efficiency ηel.n = 63.56% at β = 66. At β = 30, these CCPPs achieve efficiencies ηel.n = 61.7% (COT = 1550 °C) and ηel.n = 61.3% (COT = 1580 °C), respectively.