Combustion Turbine Blades Research Articles

Experimental investigation on the effects of complex pressure gradients on the film cooling effectiveness of a serpentine nozzle

Serpentine nozzles more easily deform and damage due to high-temperature airflow because of their multi-bend channel configuration. Therefore, film cooling technologies should be applied to serpentine nozzles. Complex pressure gradients in serpentine nozzles lead to different film cooling characteristics from combustion chambers, turbine blades, and other exhaust systems. This study experimentally investigated the effects of complex pressure gradients and film hole inclination angles on a serpentine nozzle’s film cooling effectiveness (FCE) using pressure-sensitive paint (PSP). The flow mechanisms were obtained via numerical simulations. The experimental nozzle design needs to consider the needs of PSP observations and the normal flow of serpentine nozzles. However, the complex structure of serpentine nozzles makes those increasingly difficult. The studied pressure gradients include the pressure gradient mutation (PGM), strong adverse pressure gradient (SAPG), weak adverse pressure gradient (WAPG), and favorable pressure gradient (FPG). The results show that complex pressure gradients change the coolant coverage and adhesion and may induce a recirculation zone in the SAPG region. This affects the development of the vortex construction and leads to different FCE distributions. The FCE under the effects of the PGM is the largest, followed by the SAPG, WAPG, and FPG. A larger inclination angle weakens the coolant adhesion but may enhance its downstream and lateral flow treads. This is coupled with the effects of complex pressure gradients, where larger inclination angles bring better film cooling effects in some cases. After accounting for the four blowing ratios, the area-averaged FCEs under the effects of the SAPG, WAPG, and FPG are 28.9 %, 42.8 %, and 52.3 % lower than that under the PGM, respectively. The area-averaged FCEs under the conditions α = 45° and 60° are 6.6 % and 10 % lower than that under α = 30°.

Dissimilar Welding of Inconel Alloys With Austenitic Stainless-Steel: A Review

Abstract In this review paper, dissimilar welding between Inconel and austenitic stainless steel along with its application has been outlined for high-temperature applications. The mechanical and microstructural behavior of this dissimilar joint has been summarized thoroughly in this article. Dissimilar welding of Inconel alloys and stainless steel (SS) has massive demand in high temperature and high corrosive applications industries. Austenitic stainless steel contains 16–26% of Cr and 6–12% of Ni elements showing FCC structures have good weldability and high corrosion resistance. Austenitic stainless steel such as 304, 316 L, 304H, etc., containing austenite microstructure used in high-temperature applications like power plants, heat exchangers, heating elements, aircraft, and others. In addition, Ni-based Inconel alloys show high-temperature strength and corrosion resistance and are frequently used in high-temperature applications. Ni-based Inconel 718 alloy possesses excellent strength, corrosion resistance and creep resistance at high temperatures are frequently used in combustion chambers, power plants, and turbine blades applications. Inconel alloyed by elements Ti, Al and Nb attain strength by forming phases such as ɣ/-Ni3(-Ti, Al), ɣ//-Ni3Nb, and carbides such as MC and M23C6, nitrides, laves phase. The GTA dissimilar welding between expensive Inconel and cheaper stainless steel is successfully used in nuclear power plants. The dissimilarity in melting point, chemical composition, thermal, mechanical, and other properties between these materials make welding challengeable. This review paper focused on problems related to dissimilar welding like forming unmixed zone, elemental segregation, formation of laves phase, sensitization, microfissuring, and solidification cracking.

Experiment investigation of impingement/effusion cooling on overall cooling effectiveness and temperature gradients of afterburner heat shields in a high-performance aircraft engine

Considering that the jet impingement cooling method applied to the combustion chamber and turbine blade has a beneficial effect on the cooling performance, the impingement/effusion cooling was applied in the afterburner heat shield (DCH) to improve the reliability and durability of the afterburner cylinder. Although the impingement/effusion cooling scheme has been numerously investigated on the internal heat transfer, its investigation of conjugated heat transfer characteristics is limited as applying in the afterburner heat shield. This paper aims to investigate the effects of adding array impingement and area ratio on the conjugate heat transfer of afterburner heat shield. The surface temperatures on the mainstream side of DCH in the upstream (UR), midstream (MR), and downstream (DR) regions were measured using IR thermography under a high-temperature ratio between mainstream and coolant (Tg/Tc = 2). The overall cooling effectiveness (ϕ) and temperature uniformity (RSD) were plenty compared with the single-layer effusion cooling heat shield (ECH) at three momentum flux ratios (I = 0.02,0.22,0.50). Moreover, the area ratio of film to impingement holes (Af/Ai) was enlarged from 1 to 4 to obtain high cooling effectiveness and low-temperature gradient. The results indicate that when I is larger than 0.22, the area-averaged ϕ of DCH compared with ECH can be improved by about 16% over the whole measured regions, and 20% in the UR with the lowest ϕ. In addition, the drop coefficient of the RSD of DCH can reach 18%. In comparison with the DCH at Af/Ai = 1, the DCH with an area ratio of 4 can achieve gains of 80% and 45% on ϕ and RSD, respectively. Therefore, adding array impingement on the coolant side of DCH and increasing Af/Ai cannot only effectively reduce the surface temperature of the heat shield and form efficient cooling in the UR, but also increase the temperature uniformity over the entire heat shield, thereby improving the reliability and durability of the afterburner cylinder. Furthermore, the comprehensive and new database can be used to evaluate the computational fluid dynamics simulations in related coupled and decoupled research.

Characterization of a Newly Designed Test Bench for Investigations of Flame–Wall Interaction

Abstract For the thermal design of combustion chambers and turbine blades in jet engines, a detailed knowledge of the combustion and of the heat loads to the walls is necessary. In general, high operating temperatures and reduced combustor size are striven for in order to increase engine efficiency and reduce weight. Consequently, the components are exposed to temperatures above the melting point of the materials and there is a growing risk of incomplete combustion within the combustion chambers. To study these effects, we setup a new test bench for fundamental investigation of chemical near-wall reactions at atmospheric pressure. First results of gaseous, nonpremixed near-wall CH4/air and H2/air flames are presented. Optical methods such as two-line laser-induced fluorescence thermometry and OH* chemiluminescence were applied. Further, the heat release to the wall was determined by means of inverse heat conduction calculation using the data of implemented thermocouples.

In-situ temperature monitoring directly from cathode surface of an operating solid oxide fuel cell

The electrode temperature distribution of a solid oxide fuel cell is an important parameter to consider for gaining better insight into the cell performance and its temperature-related degradations. The present efforts of measuring gas channel temperatures do not accurately reveal the cell surface temperature distribution. Therefore, the authors propose a cell-integrated multi-junction thermocouple array to measure the electrode temperature distribution from a working solid oxide fuel cell. In this work, the authors deposited a thin film/wire multi-channel thermal array on the cathode of a commercially-sourced solid oxide fuel cell. The temperature of the cell was measured under varying fuel compositions of hydrogen and nitrogen. The multi-channel array showed excellent temperature correlation with the fuel flow rate and with the cell’s performance whilst commercial thermocouples showed a very dull response (10 ~ 20 °C discrepancy between thermocouples and the multi-channel array). Furthermore, cell temperature measurements via the multi-channel array enabled detecting potential fuel crossover. This diagnostic approach is applied to a working solid oxide fuel cell, yielding insights into key degradation modes including gas-leakage induced temperature instability, its relation to the theoretical open circuit voltage and current output, and propagation of structural degradation. It is envisaged that the use of the multi-thermocouple array techniques could lead to significant improvements in the design of electrochemical energy devices, like fuel cells and batteries and their safety features, and other hard-to-reach devices such as inside an internal combustion engine or turbine blades.

High Chrome Steel Modified by High-Current Pulsed Electron Beam

The paper presents the results of the structure and properties modification of 20Cr23Ni18 (AISI 310) high chrome austenitic stainless steel after the exposure to the low energy high current pulsed electron beam (LEHCPEB) irradiation. The AISI 310 is used to manufacture machine components and mechanisms operating at 1000–1050°С such as combustion chambers, turbine blades, and others. The SOLO plasma-ionassisted electron-beam setup (Institute of High Current Electronics SB RAS, Tomsk, Russia) is used for the steel treatment. The SOLO provides a low-pressure arc discharge with a grid-stabilized cathode plasma boundary and the open-boundary anode plasma. The electron-beam parameters include 18 keV energy; 20, 30 and 40 J/cm2 energy density; 50 and 200 μs pulse duration; the number of pulses – 3; 0.3 s–1 pulse frequency; ~0.02 Pa gas (argon) pressure in the process chamber. Scanning and transmission electron microscopies and the X-ray diffraction analysis are used to investigate the structure and phase composition of the steel, microhardness and wear resistance being regarded as the steel properties. It is shown that the exposure of the AISI 310 to high-current pulsed electron beam results in a high-speed melting of the surface layer, creates the crystallized cellular structure of submicron size, and enhances the wear resistance by 8 times.

Heat transfer and flow structure of an impinging jet with upstream flow

In the present study, Particle Image Velocimetry and infrared thermography are used to investigate a jet issuing from a perforation with a crossflow on both sides of the perforated plate. This type of injection is typical of industrial applications such as combustion chamber or turbine blade cooling. The influence of five different parameters (Reu, e/D, Rej, Rec, H/D) has been considered. Due to the upstream flow influence, the injection flow is not axisymmetric: the highest mean velocity values are present in the lower part of the injection and on its sides forming a crescent shape jet with high velocity fluctuations in the jet core. The jet has global upward movement and its velocity rapidly decreases. Heat transfer rates resulting from its impingement are relatively low, compared to those of an academic jet issuing from a long tube. Moreover, Nusselt number distribution is not axisymmetric for low injection-to-plate spacing H/D. The injection Reynolds number and the injection-to-plate distance are the parameters with the greatest influence on heat transfer rates. Finally, correlations are deduced from heat transfer measurements.

Feasibility of manufacturing combustion chambers for aeronautical use in Mexico

The aeronautical sector is strategically important for the economic development of Mexico and has grown steadily over the last 10 years. Furthermore, it generates high added value for its products. In Mexico, the aircraft manufacturing sector mainly focuses on the fabrication of heat exchangers, seals, fuel ducts, and engine support rings. Currently, this sector is not involved in the manufacture of engine hot section components such as combustion chambers and turbine blades. Estimation of the associated costs enables assessment of the feasibility of fabricating such components. This study investigates the feasibility of establishing production lines for aeronautical combustion chamber fabrication in factories dedicated to the manufacture of aeronautical gas turbine engines.

Technological assessment of high temperature sensing systems under extreme environment

PurposePresently there exists no way to directly measure strain at high temperatures in engine components such as the combustion chamber, exhaust nozzle, propellant lines, and turbine blades and shaft. The purpose of this paper is to address this issue.Design/methodology/approachThermomechanical fatigue (TMF) prediction, which is a critical element for a blade design, is a strong function of the temperature and strain profiles. Major uncertainties arise from the inability of current instrumentation to measure temperature and strain at critical locations. This prevents the structural designer from optimizing the blade design for high temperature environments, which is a significantly challenging problem in engine design.FindingsBeing able to directly measure strains in different high temperature zones would deeply enhance the effectiveness of aircraft propulsion systems for fatigue damage assessment and life prediction. The state of the art for harsh environment, high temperature sensors has improved considerably over the past few years.Originality/valueThis paper lays down specifications for high temperature sensors and provides a technological assessment of these new sensing technologies. The paper also reviews recent advances made in harsh environment sensing systems and takes a peek at the future of such technologies.

Eddy-Current Modeling of a Continous Conductivity Profile Resulting From a Diffusion Process

This paper deals with the modelization of eddy-current measurements over combustion turbine blade coatings affected by depletion of aluminum. First, we model the response of an eddy-current coil over a layered metallic structure with a top over-aluminized coating by extending the analytical Uzal-Rose's model for one hyperbolic tangent conductivity profile to a conductivity profile using two hyperbolic tangents for taking inward and outward depletion of aluminum inside the coating into account. Results obtained with this model are similar to those obtained with a numerical multilayer model but with a reduced computing time.

Effect of the Unit Pressure on the Selection Parameters of Intermetallic Coatings NiAl and Ni<sub>3</sub>Al after Plastic Working

Modern materials on intermetallic matrix are in the scope of research of many scientific – research centers in Poland [1]. Intermetallic systematic alloys containing aluminium have high resistance to oxidation, abrasive corrosion and fatigue as well as heat resistance. That is why they are applied in the production of machine parts used in hard service conditions (internal combustion turbine blades, exhaust valves, turbo-blower rotors) [2]. Intermetallic coatings can be obtained by means of plasma spraying. Thermal spraying technology is widely used due to the possibility of increasing the service properties in surface layers (strength property, tribological, anti-corrosive and decorative property) as well as coating application on machine parts elements, on tools for plastic working (forging moulds busters, piston rods, gear wheels teeth, crank journals, valve seats, and combustion engine cylinders) [3, 4]. NiAl and Ni3Al coatings are characterized by high fatigue resistance, heat resistance and considerable corrosion resistance [5]. Coatings obtained by thermal spraying have high surface roughness. Thus, subsequent plastic treatment is advisable for plasma-sprayed intermetallic coatings. Therefore it is vital to define to what extent the change of unit pressure will influence reduction of surface roughness of intermetallic coatings. For this purpose experimental upsetting research was carried out on C45 steel samples having NiAl and Ni3Al coatings for the following unit pressures p = 500 MPa, p = 800 MPa, p = 1100 MPa.

Pre-combustion, post-combustion and oxy-combustion in thermal power plant for CO 2 capture

This paper presents a summary of technical-economic studies. It allows evaluating, in the French context, the production cost of electricity derived from coal and gas power plants with the capture of CO 2, and the cost per tonne of CO 2 avoided. Three systems were studied: an Integrated Gasification Combined Cycle (IGCC), a conventional combustion of Pulverized Coal (PC) and a Natural Gas Combined Cycle (NGCC). Three main methods were envisaged for the capture of CO 2: pre-combustion, post-combustion and oxy-combustion. For the IGCC, two gasification types have been studied: a current technology based on gasification of dry coal at 27 bars (Shell or GE/Texaco radiant type) integrated into a classical combined cycle providing 320 MWe, and a future technology (planned for about 2015–2020) based on gasification of a coal–water mixture (slurry) that can be compressed to 64 bars (GE/Texaco slurry type) integrated into an advanced combined cycle (type H with steam cooling of the combustion turbine blades) producing a gross power output of 1200 MWe.

Advances in effusive cooling techniques of gas turbines

Gas turbine combustion chambers and turbine blades require better cooling techniques to cope with the increase in operating temperatures with each new engine model. Current gas turbine inlet temperatures are approaching 2000 K. Transpiration-cooled components have proved an effective way to achieve high temperatures and erosion resistance for gas turbines operating in aggressive environments, though there is a shortage of durable and proven technical solutions. Effusion cooling, on the other hand, is a relatively simple and more reliable technique offering a continuous coverage of cooling air over the component’s hot surfaces. This paper presents a numerical model suitable to design the geometric features of effusive cooling systems of gas turbine hot components, and to evaluate their thermo-fluid-dynamic characteristics. The model has been developed specifically with the aim to show the potential advantages deriving from the adoption of the new Poroform ® technology. According to this technology the design of the distributions of the diameter and density of holes on the cooled surface allows complete freedom for the thermo-mechanical optimization of the cooled component, with a view to reducing the metal’s working temperature and achieving isothermal conditions for large blade areas. In this paper the diameter, density and spacing of the holes, the adiabatic film efficiency and the coolant air consumption of a first stage gas turbine effusion cooled blade are extensively discussed to highlight the system cooling capacity. The results of two cooling solutions for a first-stage gas turbine blade are presented, i.e. the thermo-fluid-dynamic optimized design and one possible manufacturing-oriented optimized design of the cooled component.

Coating Life Prediction for Combustion Turbine Blades

A life prediction method for combustion turbine blade coatings has been developed by modeling coating degradation mechanisms including oxidation, spallation, and aluminum loss due to inward diffusion. Using this model, the influence of cycle time on coating life is predicted for GTD-111 coated with an MCrAlY, PtAl, or aluminide coating. The results are used to construct a coating life diagram that depicts failure and safe regions for the coating in a log-log Plot of number of startup cycles versus cycle time. The regime where failure by oxidation, spallation, and inward diffusion dominates is identified and delineated from that dominated by oxidation and inward diffusion only. A procedure for predicting the remaining life of a coating is developed. The utility of the coating life diagram for predicting the failure and useful life of MCrAlY, aluminide, or PtAl coatings on the GTD-111 substrate is illustrated and compared against experimental data.

Inhibition of Interdiffusion From MCrAlY Overlay Coatings by Application of a Ni-Re Interlayer

The durability of protective coatings on combustion turbine blades and vanes is a critical issue in the power generation industry. Coating life usually dictates the refurbishment intervals for these components, and these intervals have generally been of shorter duration than desired by the operators of the equipment. Both MCrAlY and aluminide type coatings protect against oxidation and hot corrosion by forming a protective Al2O3 surface layer. Degradation of the coatings occurs by depletion of the aluminum content of the coating through interdiffusion with the substrate and through the formation and spallation of an external Al2O3 scale. The results obtained in this study clearly show that the application of a thin interlayer of Ni-Re beneath the MCrAlY coating can significantly decrease the growth rate of the inner β-NiAl depletion zone. Order of magnitude reductions in the inner depletion zone thickness formed at 1000 h were obtained with both the Ni-32 wt.% Re and the Ni-47 wt.% Re interlayer coatings. Since formation of the inner depletion zone is believed to result from interdiffusion with the substrate, these results suggest that the Ni-Re interlayer provided a significant impediment to the inward diffusion of Al into the substrate.

High-Cycle Fatigue Design Evolution and Experience of Free-Standing Combustion Turbine Blades

Combustion turbine blade design criteria can generally be classified as either temperature or fatigue related. Since less is usually known about the factors influencing the fatigue phenomenon, it is considered the more challenging. In addition, as analytical and experimental techniques became more sophisticated and more accurate, the natural tendency was to replace archaic “guidelines” or “rules” with less conservative approaches that at times led to the discovery of new high-cycle fatigue “thresholds.” This paper presents the evolution of the combustion turbine blade high cycle fatigue design criteria for free-standing blades. It also presents the analysis and corrective actions taken to resolve several unique combustion turbine blade fatigue problems, all encountered over a 35-year period while the author has been employed at Westinghouse Electric Corporation. Included are high-cycle fatigue problems due to cooling air leakage, seal pin friction, and combustion temperature maldistribution, as well as flow-induced nonsynchronous vibration.

Vapor Deposition and Condensate Flow on Combustion Turbine Blades: Theoretical Model to Predict/ Understand Some Corrosion Rate Consequences of Molten Alkali Sulfate Deposition in the Field or Laboratory

Article Vapor Deposition and Condensate Flow on Combustion Turbine Blades: Theoretical Model to Predict/ Understand Some Corrosion Rate Consequences of Molten Alkali Sulfate Deposition in the Field or Laboratory was published on December 1, 1987 in the journal International Journal of Turbo & Jet-Engines (volume 4, issue 3-4).

Life Assessment Technology for Combustion Turbine Blades

Combustion turbine blades operating in the hot gas path are subject to degradation by embrittlement, creep, thermal fatigue, hot corrosion, and synergistic effects among the above. Development of techniques to assess the extent of degradation of the blades under these conditions can have a significant and favorable economic impact for the utility industry. The Electric Power Research Institute (EPRI) is currently engaged in a number of research activities aimed at the development of such techniques. This paper is an overview of the present and planned activities relating to life assessment technology for blades.

Small Diameter Film Cooling Holes: Wall Convective Heat Transfer

The wall heat transfer resulting from small diameter holes drilled at 90 deg through gas turbine combustion chamber and turbine blade walls is considered. Available information is briefly reviewed and shown to generally omit the hole approach surface heat transfer and to relate only to the internal hole heat transfer. Experimental techniques are described for the determination of the overall heat transfer in a metal plate with a large number of coolant holes drilled at 90 deg. The results are compared with conventional short-tube internal heat transfer measurements and shown to involve much higher heat transfer rates and this mainly resulted from the additional hole approach flow heat transfer.

Viscous dissipation effects on thermophoretically augmented aerosol particle transport across laminar boundary layers

The sensitivity of aerosol particle motion to local temperature gradients has motivated this investigation of viscous dissipation effects on mass transport rates across nonisthermal, low mass-loading ‘dusty gas’ laminar boundary layers (lbl). From numerical lbl transfer calculations, including ‘ash’ particle thermophoresis and variable thermophysical properties, it has been found that for a specified wall temperature, T w , and mainstream static temperature, T e cous dissipation within the boundary layer increases total particle deposition rates, its relative importance being dependent on T w /T e . For combustion turbine blades which operate at near-unity Mach number, neglect of viscous dissipation is found to cause about a 25% underestimate of the fouling rate at T w /T e = 0.8 for particle diameters between 0.6 × 10 −2 μ m and 0.3 μm. Alternatively, for conditions of fixed adiabatic wall temperature, T aw , or fixed stagnation (reservoir) temperature, T 0 , dusty gas acceleration to appreciable Mach numbers is associated with reduced particle arrival rates due, in part, to the associated reduction in mainstream gas temperature. Recently developed mass transfer rate correlations are extended and found to be successful when tested against the present numerical calculations.