Gas Turbine Operating Conditions Research Articles

Modelling of JP-8 distributed combustion using a HyChem mechanism under gas turbine conditions

The critical advantages of liquid fuels in aviation over alternative energy carriers imply their dominance in the upcoming decades. The Mixture Temperature Controlled (MTC) combustion concept allows spatially homogeneous, efficient burning (distributed combustion) with low pollutant emission. MTC combustion of jet fuel JP-8 was investigated in an atmospheric burner, and the measured pollutant concentrations in the flue gas were reproduced using the Hybrid Chemistry (HyChem) approach employing Perfectly Stirred Reactor simulations. Using this robust approach comes with losing spatiotemporal characteristics if the mixture homogeneity assumption is globally valid. The effect of residence time and pressure under typical gas turbine operating conditions was investigated. Stable combustion was present above 3 ms residence time at pressures up the 60 bar, which was the upper limit of the investigated regime, while the lower residence time limit of stable combustion was 0.3 ms. The residence time interval of stable operation could be extended by applying flue gas recirculation. NO emission can be reduced by increasing the operating pressure, while the N2O production is dominant only up to 20 bar and in the 10–100 ms residence time range. CO emission vanishes above 10 ms residence time. Ultra-low emission operation requires >20 bar pressure and 10 ms residence time with distributed combustion, requiring larger combustion chambers for future jet engines.

Thermal Barrier Coatings in burner rig experiment analyzed through LAser Shock for DAmage Monitoring (LASDAM) method

This study investigates failure mechanisms in a typical thermal barrier coating (TBC) system comprising an EB-PVD columnar top coat, an aluminide bond coat, and a Ni-based single crystal superalloy substrate, simulating gas turbine operating conditions using a burner rig. TBC degradation, initiated by interfacial defects from the LASAT method, was studied during thermal gradient cycling under fast and slow cooling. In-situ optical and infrared imaging, along with ex-situ SEM cross-sectional analysis, monitored failure mechanisms. The Laser Shock for Damage Monitoring (LASDAM) technique provided insights into gradient and cooling rate impacts on columnar TBC damage. Results showed significant effects of cooling rate on delamination and localized failure at blister sites, with LASDAM revealing significant overheating at damage sites. Analysis included full-field temperature and damage assessment, emphasizing blister-driven delamination under severe thermal gradients. Discussion focused on elastic stored energy effects, noting that fast cooling induced transient conditions where reversed temperature gradients increased damage, limiting TBC lifespan.

Analysis of the influence of hydrogen co-firing on the operation and performance of the gas turbine and combined cycle

The effect of hydrogen co-firing on the performance and operating conditions of gas turbines (GTs) and gas turbine combined cycles (GTCCs) was investigated. Two operating scenarios were applied, and off-design analyses were conducted for three GTs with different turbine inlet temperatures (TITs). In the first scenario, the TIT was kept constant. As the hydrogen co-firing ratio increases, the pressure ratio of GT increased, and the power outputs of both GT and GTCC increased. With 100 % hydrogen in the 1650 °C GT, power output and efficiency improved by 5.36 % and 1.55 %p for GT, and 2.90 % and 0.72 %p for GTCC. In the second scenario, the power output was kept constant. The operating point moves toward lower pressure ratio and TIT regimes, and the efficiency of both GT and GTCC increased. With 100 % hydrogen in the 1650 °C GT, TIT decreased by 50.3K, and efficiency increased by 1.42 %p for GT, and 24.9K and 0.42 %p for GTCC. In both scenarios, the higher the TIT, the impact of hydrogen co-firing was more pronounced. It is expected that the second scenario might reduce NOx emissions while still increasing system efficiency in comparison to the NG fired case by operating the GT at a lower TIT and equivalence ratio.

Numerical study of the effect of NH3 addition on CH4/air combustion characteristics under gas turbine operating conditions

In this study, the effects of different NH3 additions on the laminar premix combustion characteristics of CH4/air flame were investigated, including laminar combustion velocity, ignition delay time, four important free radicals and NO emission.

Theoretical study on the inherent relationship between laminar burning velocity, ignition delay time, and NO emission of ammonia-syngas-air mixtures under gas turbine conditions

This study utilizes numerical methods with Chemkin 19.2 and Matlab R2020a to investigate the relationship between laminar burning velocity and free radical concentration, the relationship between laminar burning velocity and ignition delay time, and the relationship between NO emissions and free radical concentration for ammonia-syngas-air combustion. Additionally, it explores the mechanisms by which these three relationships change with variations in the initiate temperature and chamber pressure of the combustion chamber. Furthermore, to understand the theoretical foundation of these relationships, the study examines four global flame parameters: adiabatic flame temperature (Tad), activation energy (Ea), Zeldovich number (Ze), and Lewis number (Le). The results indicate that changes in initial temperature and pressure influence the laminar burning velocity by modifying the concentration of H + NH2 radicals. Simultaneously, alterations in initial temperature and pressure also adjust the quantitative relationship between laminar burning velocity and the concentration of H + NH2 radicals. Additionally, the results reveal that variations in initial temperature and pressure impact NO emissions by altering the concentration of H + NH2 radicals. Following a comprehensive examination of both the theoretical relationship between laminar burning velocity and ignition delay time and the empirical relationship between laminar burning velocity and ignition delay time, a relationship between the density-weighted collision rate BC in the laminar burning velocity expression and the pre-exponential factor A in the theoretical expression for ignition delay time was observed, where BC2A = C0∙Tuδ∙Pε (where C0, δ and ε are constants). This offers a potential methodology for investigating thermal effects, chemical effects, and transport effects in complex mixed fuel combustion processes. Further investigation demonstrates that an increase in the initial temperature within a gas turbine combustion chamber will, by promoting thermal effects, inhibiting transport effects, and altering chemical effects, affect the quantitative relationship between laminar burning velocity and ignition delay time. Further research reveals that an increase in the initiate temperature of the gas turbine combustion chamber affects the quantitative relationships between laminar burning velocity and ignition delay time by promoting thermal effects, suppressing transport effects, and chemical effects. An increase in chamber pressure influences these relationships by enhancing chemical and transport effects while inhibiting thermal effects. Moreover, the functions characterizing chemical effects, transport effects, and thermal effects can be reasonably approximated in this study as functions of initial temperature and pressure, especially under the specific F-class gas turbine conditions presented herein. This finding holds significance for the design of combustion chambers under actual gas turbine operating conditions.

Design and off-design performance analysis of supercritical carbon dioxide Brayton cycles for gas turbine waste heat recovery

The utilization of waste heat from marine gas turbines is an effective means of meeting future electric demands and achieving energy conservation and emission reduction. Meanwhile, the supercritical CO2 Brayton cycle, benefiting from its compact structure, is well-suited for power generation in limited spaces. Based on the reality that gas temperature and flow rate deviate from the design point with the variation of gas turbine operating conditions, this paper proposes a method for analyzing the off-design performance of supercritical CO2 cycles based on thermal source fluctuations rather than simply providing prescribed temperatures on the cycle side. This method allows for a clear understanding of the impact on the cycle when there are fluctuations in the thermal source. Firstly, the thermodynamic performance and economic viability of four types of supercritical CO2 cycles, namely simple regenerative, recompression, intercooling, and reheat, were optimized using a multi-objective genetic optimization algorithm. Subsequently, the off-design performance of these four cycles was investigated when the gas temperature and flow rate deviate from the design point. The results indicate that, compared to the decrease in gas temperature, the reduction in gas flow rate has a greater impact on the decline in cycle performance. Decreasing gas temperature enhances the exergy efficiency of all four cycles, while reducing gas flow rate initially increases and then decreases the exergy efficiency. The decrease in turbomachinery efficiency significantly contributes to the decline in cycle performance. When the gas flow rate exceeds 55% of the design value, it is recommended to adopt an intercooling cycle arrangement. Otherwise, a recompression cycle layout should be used.

Numerical study of the effect of pressure on the combustion characteristics of ammonia/coal-derived syngas mixture under gas turbine operating conditions

This study investigates the influence of pressure variation on combustion properties, including laminar burning velocity and ignition delay time, as well as emissions in gas turbine conditions. Based on numerical simulations and using Matlab, the impact of pressure on the relationship between laminar burning velocity and free radicals, as well as the relationship between ignition delay time and laminar burning velocity, were analyzed. The results of Matlab curve fitting suggest that the decrease in free radical concentration due to increased pressure is the main cause of the reduction in laminar burning velocity. The presence of reactions such as H + O2 = O + OH and all ammonia-related reactions results in a linear relationship between the laminar combustion velocity and max(H) or max(NH2 + H), which varies with pressure in mixed ammonia combustion. Moreover, the linear correlation coefficient between the laminar combustion velocity and free radicals is a function of pressure. Using a one-dimensional laminar premixed model and a zero-dimensional closed reactor model, this study has identified a power function relationship between the laminar combustion velocity and ignition delay time in synthetic gas mixed with ammonia combustion, where the coefficients and exponents of the power function are functions of pressure. Moreover, these two fitting relationships are independent of equivalence ratio and fuel ratio. Finally, the analysis of NO emissions indicates that the NO produced by chemical pathways affects the chemical equilibrium of NO produced by thermal pathways. Additionally, the reaction CO + OH = CO2 + H initially produces some NO in the thermal pathway·NH3 participates in reactions after H2 and CO have reacted. Lastly, it was found that the increase in pressure promotes the reaction NH + NO = N2O + H, which leads to a decrease in the molar fraction of NO with increasing pressure.

Premixed combustion and emission characteristics of methane diluted with ammonia under F-class gas turbine relevant operating condition

Ammonia has been used on a small scale in other industrial equipment, such as gas turbines, as a carbon-free fuel. However, ammonia fuel suffers disadvantages such as high ignition temperature, low flame velocity and high NOx emissions. Doping with ammonia using a more reactive fuel, such as methane, can solve the above problems. Therefore, under the relevant operating conditions of the gas turbine (T = 723 K, p = 16.5 atm), the effect of ammonia content on the combustion and emission characteristics of laminar premixed methane flames was numerically investigated. This research uses the PREMIX code from ANSYS CHEMKIN-PRO 2020 and Okafor chemical kinetic mechanisms and provides a reference for our subsequent analysis of gas turbine operating conditions. Firstly, the emission data of major pollutants under different ammonia content (XNH3 = 0–1.0) and equivalent ratio (Φ = .6–1.4) were calculated. Then, the laminar premixed flame structure is analyzed under the lean fuel conditions associated with gas turbines (Φ = .6, .8). Finally, the effect of ammonia addition on the chemical reaction path of NO and CO emission was studied. The results show that ammonia/methane mixture fuel is more suitable for combustion at .6 < Φ < .8 under high temperature and pressure. High ammonia content (XNH3 > .6) and low equivalent ratio can reduce NO and CO emissions. The molar fractions of H, O, and OH radicals and flame temperature decreased with the increase in ammonia content. In addition, high temperature and high pressure conditions and ammonia content greatly influence the reaction path of NO and CO production. The increase in pressure resulted in a change in the primary reaction that produced NO. In conclusion, this study guides reducing the emission of NO and CO from lean side of gas turbine plants.

A Probabilistic Model for Forging Flaw Crack Nucleation Processes for Heavy Duty Gas Turbine Rotor Operations

Abstract We present a probabilistic model for quantifying the number of load cycles for nucleation of forging flaws—for a 3.5NiCrMoV high strength low alloy rotor steel—into a crack under gas turbine operating conditions. The model correlates low cycle fatigue data, ultrasonic testing indication data, flaw morphology, and type with the nucleation process. This paper is the third of a series of publications presenting this modeling approach progressively. It focuses on the effect of temperature variation on the nucleation life of forging flaws. We quantified the number of cycles to crack nucleation was for specimens that included forging flaws at elevated temperatures. Flaws of different sizes and shapes are effectively described at respective temperature and stress levels by either an ellipsoidal finite element model or an analytical area-based model. A local probabilistic low-cycle fatigue model analyzes the resulting stress distributions accounting for statistical size effects. Via Maximum Likelihood Estimation of these probabilistic low cycle fatigue results, a probabilistic model for crack nucleation of forging flaws is obtained. This proposed probabilistic model is based on experimental data for realistic heavy duty gas turbine rotor temperature and stress conditions. It can be utilized in the energy sector for component life time quantification. Our suggested approach can support component assessment under flexible gas turbines operation conditions driven by increased availability of intermittent renewable energy sources.

Numerical study of the effect of flow nonuniformities on the low-pressure side of a Cooled Cooling Air heat exchanger

The Cooled Cooling Air (CCA) heat exchanger is a precooler that cools the bleed air from the compressor stages and is located inside the bypass duct of the aeroengine. Nonuniform flows enter the core of the heat exchanger because the cold side is the off-take from the fan flow, compromising its aerothermal performance. These aspects has been disregarded in the literature until now. In this study, the aerothermal performance of a CCA heat exchanger with flow nonuniformities on its Low-Pressure (LP) side is investigated. Three-wire meshes were designed using correlations from the literature, showing three off-design cases, namely, Cases 1, 2, and 3. The porous media and dual cell heat exchanger models were used in numerical simulations for the baseline and off-design cases. Experiments were performed at hot and cold conditions to validate the numerical simulations under actual gas turbine operating conditions. It has been found that heat transfer rate increases in Case 1 and 2 by 1.0% and 1.5%, as the flow non-uniformity is symmetric with respect to XZ plane. In contrast, in Case 3, the heat transfer rate reduces by 4.2% because the flow non-uniformity is asymmetric with respect to XZ plane, inducing cross-flows immediately upstream of the heat exchanger core. • Aerothermal performance with flow nonuniformities along LP side was investigated. • The porous media and dual cell heat exchanger models were used. • Experiments were performed under actual gas turbine operating conditions. • The overall heat transfer rates were improved by 1.0% and 1.5% in Cases 1 and 2. • The overall heat transfer rate declined by 4.2% in Case 3.

Effects of Upstream Step Geometries on Endwall Film Cooling and Phantom Cooling Performances of a Transonic Turbine Vane

Abstract In gas turbine engines, the endwall misalignment (step geometries with various step heights) commonly exists between the combustor exit and the first nozzle guide vane endwall, due to assembly error, metal corrosion, and thermal expansion. The step geometries affect the secondary flow field near the endwall and coolant flow behavior, thereby leading to a significant variation in endwall film cooling, vane surface phantom cooling, and vane passage aerodynamic performances. This paper presents a detailed experimental and numerical study on endwall film cooling and vane pressure side surface phantom cooling at simulated gas turbine operating conditions (high inlet freestream turbulence level of 16%, exit Mach number of 0.85, and exit Reynolds number of 1.7 × 106). The experimental measurements were conducted at Virginia Tech’s transonic blowdown wind tunnel for two configurations: baseline cascade (HR = 0) and forward-facing step geometry (HR = −0.1). The numerical predictions were performed by solving the steady-state Reynolds-averaged Navier Stokes (RANS) with realizable k–ɛ turbulence model. Based on a double coolant temperature model, a novel numerical method for the predictions of adiabatic wall film cooling effectiveness was proposed. The qualitative and quantitative comparisons between the numerical prediction results and experimental data are provided in this paper. The results indicate that this method can reliably predict endwall film cooling distributions and vane pressure side surface phantom cooling distributions, and significantly reduce (more than 50%) numerical prediction errors. The effects of upstream step geometries were numerically studied at the design flow conditions (BR = 2.5, DR = 1.2), by quantizing the endwall film cooling effectiveness, endwall net heat flux reduction (NHFR), vane pressure side surface phantom cooling effectiveness, and total pressure loss coefficients (TPLC) for various upstream step heights: three forward-facing step heights (HR = −0.16, −0.1, and −0.06), a baseline cascade (HR = 0), and four backward-facing step heights (HR = 0.06, 0.1, 0.136, and 0.2). Results show the upstream forward-facing step geometry is beneficial for enhancing endwall film cooling (maximum enhancement level of 15%), endwall net heat flux reduction (maximum enhancement level of 10%), and vane pressure side surface phantom cooling (maximum enhancement level of 66.7%). Nevertheless, the upstream backward-facing step geometry is pernicious to the endwall film cooling, endwall heat flux reduction, and phantom cooling, and these pernicious effects have sharply deteriorated when the upstream step height is larger than a critical value (HR > 0.136). To be specific, the film cooling effectiveness (from 30% to 80%), net heat flux reduction (up to 78%), and phantom cooling effectiveness (completely disappeared) significantly decrease by introducing an overlarge backward-facing step height HR = 0.2. The upstream step geometries lead to deteriorated aerodynamic performance, though the reduction level may be slight (0.36% at HR = 0.136). These suggest that the overlarge backward-facing misalignment will increase the risk of thermal failure and must be avoided during the component assembly and the operational processes of a gas turbine.

Lightweight methane-air gas turbine controller and simulator

• Lightweight CH4/air gas turbine simulator. • System identification, cycle, and sensitivity analyses CH4/air gas turbines. • Developing and calibrating a CH4/air gas turbine controller. • The potential of utilizing waste heat utilization mechanisms. • Control measures to eliminate turbine overheating. Due to the uncertainties of determining stable, efficient, and safe operating conditions of methane-air gas turbines and the complexity of involving multivariable parameters, the task of controlling and analyzing methane-gas turbines remains a challenge despite the existing methods of control and analyses in the literature. In fact, as far as the methane-air gas turbines are concerned, there is still much room for improvement within the criterion of (computation effort, settle time, its capacity to adjust with a variable range of set-points, as well as its stable, steady, and dynamic outputs can all be enhanced). Furthermore, an accurate system-identification phase has been adopted in this paper to initiate the process of advancing an efficient gas turbine controller by determining the system's sensitivities towards the involved multivariable parameters. Therefore, this paper presents a control and analysis tool for methane-air gas turbines. This tool is a ‘light code (the time to reach the desired set-point (i.e., settle period reaches 1 s)) to serve as a methane-air gas turbine controller that can be used for experimentation or applied on an industrial scale. Moreover, the code is designed with a user interface that enables the simulations and system identification for the methane-fueled gas turbine, thus; ensuring that the governing parameters are calibrated precisely. The code was created using LabVIEW and GASEQ and is driven by conventional gas turbine cycle assessments. A simulation case study has been utilized as a system identification phase to determine the system's sensitivity of temperatures and works at the three primary stages of a simple cycle methane-air gas turbine (compressor, combustion chamber, and turbine) toward the multivariable input parameters of the compression stage (compressor pressure ratio, efficiency, inlet pressure, and temperature), the combustion phase (methane, airflow rates) and the expansion phase (turbine ratio of pressures and isentropic efficiency). Based on the sensitivity analysis performed through the developed code, the turbine output temperature is shown to be very sensitive to the turbine's parameters ( P 04 / P 03 and ε t ). This essentially emphasizes the possibility of including waste heat utilization mechanisms (i.e., heat exchangers, combined cycles) for turbines with high P 04 / P 03 or/and low ε t , resulting in a high turbine outlet temperature. Based on the performed system identification phase and sensitivity analyses, the intervals of the Proportional controller gain ( K c ) , Integral time ( t i ) , and Derivative time ( t d ) have been identified to guarantee a settling period ( T s ) within [1 s-60 s] to achieve the desired temperature set-point which eliminates turbine overheating.

Turbine Vane Endwall Film Cooling and Pressure Side Phantom Cooling Performances With Upstream Coolant Flow at Various Injection Angles

Abstract In this paper, the endwall film cooling and vane pressure side surface phantom cooling performances of a first nozzle guide vane (NGV) with endwall contouring, similar to an industry gas turbine, were experimentally and numerically evaluated at the simulated realistic gas turbine operating conditions (high inlet freestream turbulence level of 16%, exit Mach number of 0.85, and exit Reynolds number of 1.7 × 106). A novel numerical method for the predictions of adiabatic wall film cooling effectiveness was proposed based on a double coolant temperature model. The credibility and accuracy of this numerical method were validated by comparing the predicted results with experimental data. Results indicate that the present numerical method can accurately predict endwall film cooling performance and vane surface phantom cooling performance for both the ideal low density ratio (DR = 1.2) and the typical high density ratio (DR = 2.0) conditions. The endwall film cooling effectiveness, vane surface phantom cooling effectiveness, and secondary flow field were compared and analyzed for the axisymmetric convergent contoured endwall at three coolant injection angles (small injection angle of θ = 40 deg, design injection angle of θ = 50 deg, large injection angle of θ = 60 deg), two density ratios (low density ratio of DR = 1.2 and typical high density ratio of DR = 2.0), and the design blowing ratio (M = 2.5), based on the commercial CFD solver ansys fluent. An analysis method of the coolant momentum flux φ (decomposed into the axial component φx and vertical component φz) was proposed to describe and explain the migration and mixing mechanisms of coolant flow. Results indicate that the proposed analysis method of the coolant momentum flux φ can accurately and reliably describe and explain the coolant flow physics, including the coolant lift-off, the interaction between the coolant and the mainstream, and the coolant migration in the vane passage. The increased coolant injection angles result in a deterioration of the endwall film cooling performance and vane pressure surface side phantom cooling performance. Nevertheless, the sensitivity of endwall film cooling effectiveness and phantom cooling effectiveness to coolant injection angles is variable, and is significantly affected by density ratio. This suggests that the coupling effects of the coolant injection angles and density ratio should be taken into account for the prediction of endwall film cooling and phantom cooling performances. It is very necessary for the optimized design of the coolant injection angles and the predictions of film cooling performance at the realistic density ratio.

Stresses within rare-earth doped yttria-stabilized zirconia thermal barrier coatings from in-situ synchrotron X-ray diffraction at high temperatures

There is a growing interest for smart coatings that can be integrated into turbine engines for in-situ temperature measurements or health monitoring. The addition of rare-earth dopants into standard thermal barrier ceramic top coat materials is used to obtain luminescent coatings that enable spectral measurements, for real-time temperature or health monitoring. The thermomechanical performance and durability of such novel coating compositions in extreme environments still remains to be evaluated. Consequently, the ability to manufacture sensor coatings which present suitable thermal properties needs to be demonstrated. For this study, highly luminescent erbium and europium doped yttria-stabilized zirconia and state-of-the-art yttria-stabilized zirconia coatings manufactured by air plasma spray were characterized to determine the effects of the embedded rare-earth dopants on coating internal strain and stress and to quantify and compare their high temperature response using synchrotron X-ray diffraction. In-situ depth-resolved strain measurements were performed at 15 μm intervals along the depth of the coatings to evaluate materials response at key locations, specifically at layer interfaces. In-plane stress was calculated for the coatings and a finite element model was implemented to supplement the results and enable further predictions. The results show that the sensor coatings that were manufactured in this work revealed only minor variations in the strain response of sensor coatings under a typical thermal cycle and especially at temperatures closer to that of gas turbine operating conditions, compared to state-of-the-art coatings. This work demonstrates the viability of manufacturing rare-earth doped yttria-stabilized zirconia coatings that provide beneficial spectroscopic monitoring capabilities while having minimal impact on the thermomechanical response of the thermal barrier coatings.

Leading edge impingement cooling analysis with separators of a real gas turbine blade

• Experiments of impingement cooling at real temperature conditions are conducted. • A new cooling design containing separators is suggested to prevent cross flow. • Deviation by using low temperature conditions of impingement cooling is presented. • Heat transfer data of impingement cooling are compared with published studies. This paper reports an analysis on leading edge impingement cooling of a turbine blade under real operation conditions of gas turbine. In the experiments, both mainstream and cooling air are heated to real high temperatures, and overall cooling effectiveness on the external blade mid-span surface is measured. Numerical strategy including RNG k-ε turbulence model is validated by the experimental data. Impingement cooling models with and without separators (Model A and Model B) are used as specimens, and the effects of high temperature conditions, separators and temperature ratios are discussed. The results indicate that: 1) When jet Reynolds number, mass flow ratio and temperature ratio are matched to the real conditions, the Nusselt numbers predicted by low temperature conditions can be generally matched, exclude the forepart of the internal surface at the blade leading edge. But the error of overall cooling effectiveness on the blade external surface is not neglected. 2) The application of separators can prevent the heat transfer deterioration caused by cross flow with extending the heat exchange area, thus the leading edge with separators can be further cooled over 30 K compared to the traditional design. 3) Under the real operating conditions of gas turbine, two new correlations between the surface averaged Nusselt number with jet Reynolds number and temperature ratio are suggested.

Flexible Fuel Operation of a Dry-Low-NOx Micromix Combustor with Variable Hydrogen Methane Mixtures

The role of hydrogen (H2) as a carbon-free energy carrier is discussed since decades for reducing greenhouse gas emissions. As bridge technology towards a hydrogen-based energy supply, fuel mixtures of natural gas or methane (CH4) and hydrogen are possible. The paper presents the first test results of a low-emission Micromix combustor designed for flexible-fuel operation with variable H2/CH4 mixtures. The numerical and experimental approach for considering variable fuel mixtures instead of recently investigated pure hydrogen is described. In the experimental studies, a first generation FuelFlex Micromix combustor geometry is tested at atmospheric pressure at gas turbine operating conditions corresponding to part- and full-load. The H2/CH4 fuel mixture composition is varied between 57 and 100 vol.% hydrogen content. Despite the challenges flexible-fuel operation poses onto the design of a combustion system, the evaluated FuelFlex Micromix prototype shows a significant low NOx performance and high combustion efficiency over a wide fuel range.

The Effects of Axisymmetric Convergent Contouring and Blowing Ratio on Endwall Film Cooling and Vane Pressure Side Surface Phantom Cooling Performance

Abstract To reduce the intensity of endwall secondary flow, the axisymmetric convergent contoured endwall is commonly designed in the first nozzle guide vane (NGV) passage of the real gas turbine engines. This endwall contouring can obviously alter flow field near endwall and affect the coolant flow through the upstream double-row discrete film holes. This leads to a significant influence on the endwall film cooling performance, vane surface phantom cooling, and vane passage aerodynamic performance. In this paper, a detailed numerical investigation on the endwall film cooling and vane pressure side surface phantom cooling was performed, at the simulated realistic gas turbine operating conditions (high inlet freestream turbulence level of 16%, exit Mach number of 0.85, and exit Reynolds number of 1.7 × 106). Based on a double coolant temperature model, a novel numerical method for the predictions of adiabatic wall film cooling effectiveness was proposed. This numerical method was validated by comparing the predicted results with experimental data of endwall Nusselt number, endwall film cooling effectiveness, and flow visualization near endwall. The results indicate that the present numerical method can accurately predict endwall thermal load distributions, endwall film cooling distributions, and vane surface phantom cooling distributions. The endwall heat transfer coefficient, endwall film cooling effectiveness, phantom cooling effectiveness of the vane pressure side surface, and total pressure loss coefficients (TPLC) were predicted and compared for two endwall contouring shapes (flat endwall and axisymmetric convergent contoured endwall) at three different blowing ratios (low blowing ratio of BR = 1.0, design blowing ratio of BR = 2.5, and high blowing ratio of BR = 3.5) with a constant density ratio of DR = 1.2, based on the present novel numerical method. Results show that the axisymmetric convergent endwall contouring leads to a slight enhancement (maximum enhancement level less than 20%) of endwall heat transfer in the entire vane passage (0 < x < 0.65Cx). The axisymmetric convergent endwall contouring has a significantly desired effect on endwall film cooling performance (maximum enhancement level of 67%), phantom cooling performance of the vane pressure side surface (maximum increase level approximately 100%), and aerodynamic loss (maximum reduction level of 1.45%) for all blowing ratio cases, but the benefit enhancement level is obviously affected by the blowing ratio values. This suggests that the optimum of endwall contouring shapes is an effective technical way to improve endwall film cooling performance and decrease the depletion of coolant; the coupled effects of the appropriate axisymmetric convergent endwall contouring and the optimum blowing ratio should be considered in the design process of advance endwall cooling schemes.

Comparative analysis and forecasting of isentropic efficiency of gas turbine compressor with ARIMA, VAR, NARNN and ANFIS approaches

It is extremely important to monitor the status of gas turbine to ensure its safe and reliable operation. In this work, the variation trend of isentropic efficiency of compressor is analysed based on the measured data of F-class heavy-duty gas turbine in practical industrial application. The actual measured data of F-class heavy-duty gas turbine includes the data under start-stop and unstable working conditions, which cannot be directly used for calculation and analysis. To solve this problem, the data selection rules are designed and determined according to the operating conditions of gas turbine to select the data under effective working state. The isentropic efficiency of compressor is calculated based on the selected data. Then the forecasting effects of four forecasting methods on the variation trend of isentropic efficiency of compressor are studied. Four indexes, namely, symmetric mean absolute percentage error (SMAPE), mean absolute percentage error (MAPE), root mean square error (RMSE), and similarity (SIM) values are utilized to evaluate the forecasting accuracy. The research results indicate that the Adaptive Neuro-Fuzzy Inference System (ANFIS) method has better forecasting effect than Autoregressive Integrated Moving Average (ARIMA), Vector Autoregression (VAR) and Nonlinear Autoregression Neural Network (NARNN) for this F-class heavy-duty gas turbine. Through the ANFIS method, the SIM up to 96.77%, the SMAPE and MAPE are less than 0.1, and the RMSE is only 0.1157. Therefore, the ANFIS method is suitable for forecasting the isentropic efficiency of this F-class heavy-duty gas turbine compressor.

Test-Rig Simulation on Hybrid Thermal Barrier Coating Assisted with Cooling Air System for Advanced Gas Turbine under Prolonged Exposures—A Review

Thermal barrier coating (TBC) and cooling air systems are among the technologies that have been introduced and applied in pursuing the extensive development of advanced gas turbine. TBC is used to protect the gas turbine components from the higher operating temperature of advanced gas turbine, whereas cooling air systems are applied to assist TBC in lowering the temperature exposure of protected surfaces. Generally, a gas turbine operates in three main operational modes, which are base load, peak load, and part peak load. TBC performance under these three operational modes has become essential to be studied, as it will provide the gas turbine owners not only with the behaviors and damage mechanism of TBC but also a TBC life prediction in a particular operating condition. For TBC under base load or so called steady-state condition, a number of studies have been reviewed and discussed. However, it has been found that most of the studies have been conducted without the assistance of a cooling air system, which does not simulate the TBC in advanced gas turbine completely. From this review, the studies on TBC-assisted cooling air system to simulate the advanced gas turbine operating conditions have also been summarized, which are limited to test rig simulations under thermal cyclic mode where thermal cyclic represents peak and part peak load conditions. The equipment used to simulate the gas turbine operating condition, test temperatures, and durations are parameters that have been taken into consideration under this review. Finally, a test rig that is capable of simulating both TBC and cooling air effects at a high operating temperature of advanced gas turbines for prolonged exposure under steady-state condition has been proposed to be developed.

Modeling and Analysis of a Micro Gas Turbine Fuelled with Hydrogen and Natural Gas Blends

This study deals with implementing an analytical model to simulate the energy performance associated with a Micro Gas Turbine when H2NG (Hydrogen Enriched Natural Gas) blends are used as fuel. The experimental campaign validated the simulation results at the actual operating conditions of the Micro Gas Turbine. The experimental campaign for model validation has been carried out over the spring and summer periods. Additionally, the MGT performance has been detected when fuelled H2NG with hydrogen fraction ranges between 0% vol. to 10% vol., with a 2% vol. Step., according to the main findings, the fuel consumption is reduced significantly. Also, heat recovery and electrical reliability improve slightly even though environmental factors influence the system. A numerical model was developed with MATLAB-Simulink to model the operation of the MGT. Thus, the relative standard errors affecting the main output parameters have been determined.