Heavy-duty Gas Turbine Engine Research Articles

Enhancing Turbine Performance Degradation Prediction with Atmospheric Factors

Heavy duty gas turbine engines are not only ingesting the air, but also eating a myriad of aerosol particles, which may have various negative effects on the turbine operation efficiency as well as the component failure. This paper attempts to develop predictive degradation models for gas turbines by integrating satellite collected atmospheric factors, on-site monitoring data, and physics-based calculated performance results. Multiple variables are analyzed and employed for predictive modeling. The vital variables are identified by using data exploratory correlation analysis and stepwise regression analysis. The performance degradation calculation is obtained from physics based thermodynamic heat balance of gas turbine. It requires balancing mass and energy of gas turbine to match measurement data through thermodynamic cycle matching. The performance degradation prior to the offline water wash is used as the predictor. Artificial neural network modeling is employed to establish the predictive models. A procedure is presented to explain the proposed methodology, and results are discussed. This paper provides an effective methodology and procedure to apply big data for the performance degradation prediction of gas turbines.

Provision of the required wear resistance criteria of heavy-duty gas turbine engine parts based on the control of the cutting conditions

A method for determining the wear resistance of parts has been presented based on the systematization of the modular source data bank, the evaluation of the surface layer quality parameters, the cutting accuracy, and the cutting conditions. As a result of the study, the calculated dependences have been obtained in terms of the determination of the optimal part cutting modes in relation to the provision of the target surface wear resistance parameters.

Uncharacteristic Circumferential TMF Cracking in a Heavy-duty Stationary Gas Turbine Engine Burner Outlet

Abstract Burners are key components of turbomachinery with internal combustion. They allow for a particularly lean combustion in heavy-duty stationary gas turbine engines for power stations and thus contribute significantly to economical operation. Depending on their design, burners are often subject to thermomechanical stress. This failure analysis is concerned with thermal cycling cracks at the burner outlet. Circumferential cracking, parallel to the component surface, is untypical for this damage mechanism. Thermal cycling and thermal-mechanical fatigue cracks usually spread in a radial direction. Possible causes could be the special kind of centrifugal casting structure or the high thermal tension, which might have built up during burner operation.

Transformation of Delta Ferrite Into Sigma Phase in Metastable Austenitic Stainless Steels After Long-Term High-Temperature Service Exposure

Abstract A service temperature increase of turbine exhaust casing liners of heavy-duty industrial gas turbines, driven by the need to raise thermal efficiencies, motivated a number of ageing trials. Casing liners are often made of metastable austenitic stainless steels, suitable for high temperature applications. Alloys such as 321SS and 347SS might contain, in the as-cast condition, rather large amounts of delta ferrite, if not further processed by rolling or forging, easily in excess of 15 %. Even rolled sheet and bar might contain significant volume fractions of that phase if welded, up to 15 % or so in the heat affected zone (HAZ) immediately adjacent to the fusion line, and in the weld metal. It is known from the literature and from field experience that delta ferrite might decompose into sigma phase after long-term service exposure at elevated temperatures. This may embrittle the material and can be detrimental to mechanical properties. It could also deleteriously affect creep strength. The main aim of ageing trials described in this paper was to study the phase stability of delta ferrite under simulated service conditions. The results are correlated to metallographic testing results, obtained from examining actual service components of heavy-duty gas turbine engines in the field.

Chloride-Induced Stress Corrosion Cracking in 316Ti Fuel Oil Pipes of a Gas Turbine Power Plant

Abstract Two bent pipe sections of the fuel oil system of a heavy-duty gas turbine engine had to be disassembled due to leakage. One of the two specimens received by the laboratory of the engine manufacturer featured a sub-standard weld repair performed by customer personnel. A metallurgical failure investigation was ordered to determine the root cause of the leakage and to verify the results of a laboratory investigation already performed by a third party at the customer's request. The repair-welded bent pipe section failed due to halide-induced pitting corrosion that propagated through-wall in a transgranular stress corrosion cracking (SCC) mode.

Characteristics of Lean Premixed Flame in Various Oxygen Concentrations Measured by Laser Imaging Techniques

For heavy-duty gas-turbine engines, one of the promising approaches to reducing NOX emissions is the adoption of lean premixed combustion. This technique could be combined with the conventional technique of exhaust gas recirculation (EGR). However, the reduction in the oxygen concentration will influence the burning velocity and reaction zone characteristics of the lean premixed flame. To elucidate this effect, in this study, we measured the lean premixed flame temperature and OH concentration distributions for various oxygen concentrations instantaneously and simultaneously using laser imaging techniques. Based on the results, we investigated the characteristics of a lean premixed flame under various oxygen concentrations and found that the OH laser-induced fluorescence (LIF) intensity in the reaction zone decreased with the oxygen concentration, as did the flame temperature at a given axial distance from the exit nozzle. The characteristics of the premixed flame changed from a small-scale convexo-concave surface to a smoother one, leading to a decrease in the ratio of turbulent to laminar burning velocity. In addition, local extinction of the premixed flame was observed under conditions with a high air ratio and low oxygen concentration.

Study of the Impact of Multiple Weld Repairs and Associated Stress-Relief Annealing on Mechanical Properties at Elevated Temperatures of Large Components Made of the Low-Alloy Steel 16Mo3

AbstractThis paper is related to 16Mo3, a low-alloy steel typical in the manufacture of large welded steel casings of heavy-duty gas turbine engines. The usual practice in manufacturing is to stress relieve these housings after fabrication welding. If, however, weld imperfections are detected by non-destructive testing, weld repairs are performed, followed by additional stress-relief heat treatments. The methods applied were used to detect possible embrittlement by secondary carbide precipitation and to finally draw conclusions on material changes. The critical area of a weld is the heat affected zone. In this area a worsening of the stress condition in connection with a change in carbide precipitation and thus a decrease in creep rupture strength occurs. A concrete alloy composition and heat treatment adapted to the precipitation behavior are important, because they determine the type, amount and distribution of the resulting carbides [1, 2].

발전용 소형가스터빈의 축류터빈 공력설계

본 논문은 두산중공업㈜에서 개발 중인 소형 가스터빈의 축류 터빈 설계 과정을 기술하였다. 축류 터빈의 설계 과정은 크게 유로설계, 익형설계, 3D 성능 계산의 세 단계로 구성되며. 최적의 유로를 설계하기 위해 자오면의 형상, 평균 반경, 블레이드간 간격, 유로 형상각 등 여러 형상 변수에 대해 통과유동계산 및 손실계산을 수행한다. 익형 설계는 유로 설계시 스팬 방향으로 계산된 입출구 유동각을 기준으로 실험상관식을 적용하여 최적의 블레이드 개수를 결정한 후 2D 익형 단면을 설계하며 2D NS 계산을 통해 캐스케이드 유동구조를 검토하여 설계한 단면의 설계적정성을 평가한다. 설계된 2D 익형 단면을 스팬 방향으로 적층하여 3D 익형을 생성하고, 다단 Euler 계산, 단익렬, 다단 NS 계산을 수행하여 3D 유동 특성을 고찰한다.

Development and Testing of a Low NOx Hydrogen Combustion System for Heavy-Duty Gas Turbines

Interest in hydrogen as a primary fuel stream in heavy-duty gas turbine engines has increased as precombustion carbon capture and sequestration (CCS) has become a viable option for integrated gasification combined cycle (IGCC) power plants. The U.S. Department of Energy has funded the Advanced IGCC/Hydrogen Gas Turbine Program since 2005 with an aggressive plant-level NOx target of 2 ppm at 15% O2 for an advanced gas turbine cycle. Approaching this NOx level with highly reactive hydrogen fuel at the conditions required is a formidable challenge that requires novel combustion technology. This study begins by measuring entitlement NOx emissions from perfectly premixed combustion of the high-hydrogen fuels of interest. A new premixing fuel injector for high-hydrogen fuels was designed to balance reliable flashback-free operation, reasonable pressure drop, and low emissions. The concept relies on small-scale jet-in-crossflow mixing that is a departure from traditional swirl-based premixing concepts. Single nozzle rig experiments were conducted at pressures of 10 atm and 17 atm, with air preheat temperatures of about 650 K. With nitrogen-diluted hydrogen fuel, characteristic of carbon-free syngas, stable operation without flashback was conducted up to flame temperatures of approximately 1850 K. In addition to the effects of pressure, the impacts of nitrogen dilution levels and amounts of minor constituents in the fuel—carbon monoxide, carbon dioxide, and methane—on flame holding in the premixer are presented. The new fuel injector concept has been incorporated into a full-scale, multinozzle combustor can with an energy conversion rate of more than 10 MW at F-class conditions. The full-can testing was conducted at full gas turbine conditions and various fuel compositions of hydrogen, natural gas, and nitrogen. This combustion system has accumulated over 100 h of fired testing at full load with hydrogen comprising over 90% of the reactants by volume. NOx emissions (ppm) have been measured in the single digits with hydrogen-nitrogen fuel at target gas turbine pressure and temperatures. Results of the testing show that small-scale fuel-air mixing can deliver a reliable, low-NOx solution to hydrogen combustion in advanced gas turbines.

E212 旋回流希薄予混合火炎のレーリー散乱・LIF同時計測(OS9 熱・流動(計測・試験))

In heavy-duty gas-turbine engines, one of the most promising approaches for gaseous fuel to reduce NOx emissions is the adoption of lean premixed combustion. But, practically, it burned before the perfect mixing is achieved because fuel and air are separately supplied to prevent flashback. This might cause inhomogeneous burning velocity distributions and induce instability of the flame position. So, it is necessary to mix fuel and air sufficiently and homogeneously before it burns. In this study, we presented the simultaneous measurements of 2-D mixing behavior and temperature distributions by combining acetone LIF and Rayleigh scattering methods, and investigated the relationship between fuel concentration and temperature in the flames. We clarified the flame characteristics by simultaneous measurements of OH-LIF and Rayleigh scattering

2123 希薄予混合燃焼器における燃料濃度分布と火炎温度分布計測に関する研究(J18-1 ガスタービンにおける熱流動問題(1),ジョイントセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

In heavy-duty gas turbine engines, the turbine inlet temperature increases year by year to improve thermal efficiency. But, at the same time, this leads to the increase of NOx emissions. One of the most promising approaches for gaseous fuel(natural gas) to reduce NOx emissions is the adoption of lean premixed combustion. With lean premixed combustion, locally high temperature regions which are attributed to mixture inhomogeneity are suppressed, and so it has large effect in reducing NOx. However, in the case that it is applied to combustor, since fuel and air are separately supplied because of preventing flashback, it is needed to burn the mixture after sufficient mixing. In this study, we examined the air-fuel mixing characteristics in the unburned region where is adjacent to flame zone in Lean Premix Combustor with Swirling Flow. The mixing characteristics were evaluated by measuring the instantaneous concentration of mixed gaseous fuel which contains acetone as a tracer, using planar laser-induced fluorescence(P-LIF). Simultaneously, we measured the instantaneous flame temperature by Rayleigh scattering method, and investigated correlation between mixing characteristics in the unburned side and temperature distribution in the burned side.

An Empirically Based Simulation Model for Heavy-Duty Gas Turbine Engines Using Treated Residual Fuel

An empirically based engine simulation model was developed to analyze the operation of a heavy-duty gas turbine on ash-bearing fuel. The effect of the ash in the combustion products on turbine efficiency was determined employing field data. The model was applied to the prediction of the performance of an advanced-cooled turbine engine with a water-cooled first-stage nozzle, when operated with ash-bearing fuels. Experimental data from a turbine simulator rig were used to estimate the expected rates of ash deposit formation in the advanced-cooled turbine engine, so that the results could be compared with those for current engines. The results of the simulations indicate that the rate of decrease in engine power would be 32 percent less in the advanced-cooled engine with water cooling. An improvement in predicted specific fuel consumption performance was also noted, with a rate of increase of 38 percent for the advanced-cooled engine.