Turbine Entry Research Articles

Nickel base alloy with metal matrix composite zirconium boride with inorganic coatings for high temperature environments

Gas turbine engines designers strive to achieve high performance levels through various means and increasing turbine entry temperature is among the most used operational features to achieve this functionality. Advances in materials as well as developments in thermal barrier coating technology have significantly contributed in achieving this functionality. This dissertation work presents a thin film sensor based approach for experimental evaluation of temperatures on hot section aero gas turbine engine components made of nickel chromium based alloy with- coating (Zirconium boride). Develop a thin film sensor based approach for experimental evaluation of temperatures on hot section aero gas turbine engine components made of nickel based alloy with coating zirconium boride. Coating characterization is carried out from the point of view of metallurgical and mechanical properties. During metallurgical evaluation, coated samples are characterized by optical and electron microscopy (SEM and TEM). Studying the microstructure and mechanical properties hardness, tensile etc of nickel chromium alloys. Understanding the corrosion behaviour of nickel chromium plate, with ZrB2 coating alloys and relating with structures.

Simulación de condiciones de operación y fluidos de trabajo para ciclos Rankine orgánicos

En el presente trabajo se comparan condiciones de operación para diferentes fluidos en ciclos de Rankine orgánicos, que utilicen energías de bajo grado. Los fluidos estudiados fueron: R152a (1,1-difluroetano), R-290 (propano), R-600a (2-metilpropano o isobutano), R-744 (dióxido de carbono), y R-1270 (propileno). Se realizó la simulación del ciclo de Rankine orgánico y de sus modificaciones: ciclo con recalentamiento intermedio, ciclo de regeneración y ciclo con recalentamiento y regeneración. Se usó el simulador de procesos HYSYS v3.2. Los mejores resultados se alcanzaron para el ciclo con regeneración, aunque los rendimientos térmicos fueron inferiores al 10%. Se simularon condiciones de operación que permitieran superar este valor, lo cual se logró con el refrigerante R-600a en el ciclo Rankine con regeneración, que opere entre 3 500 kPa y 150 ºC a la entrada de la turbina, y 700 kPa en el condensador. Con ello se obtiene un rendimiento térmico de 15,33% y se producen 7,11 kW de potencia eléctrica.

Surface quality improvement and adjustment of SLM-processed CM247LC samples by modulated laser parameters

Nickel-base alloys, such as “CM247LC”, are usually used in the aviation field to manufacture high-pressure turbine blades with cooling channels, to increase the turbine entry temperature and the efficiency. Since there are many different cooling strategies for turbine blades, the requirements for the surface parameters (e.g. surface roughness) vary highly. In this study, five different surface parameters, such as root mean square height, skewness, kurtosis, developed interfacial area ratio and texture aspect ratio with different modulated laser parameters, have been measured, analyzed, plotted as diagrams and compared with reference continuous wave SLM-produced samples. Process maps with an overall surface parameter (including all five parameters) are also presented. Results show a wide range of surface parameter values, as needed for the varying surface requirements of different blade cooling systems.

FEA optimization of injection parameters in ceramic core development for investment casting of a gas turbine blade

Turbine blade/vane castings for aero-engine applications are produced through the investment casting process. In order to increase the turbine entry temperature and also to reduce the weight of individual blades, ceramic cores are used in the investment casting process to generate complex internal cooling passages. The wall thickness of hollow blades produced are critical, as a minimum wall thickness of 0.5 mm must be maintained ensuring desired strength of the high speed rotating turbine blades. The dimensional deviations in the ceramic cores due to shrinkage & warpage must be quantified before designing the tooling for the Ceramic Injection moulding. In present study, an attempt is made to quantify the shrinkage and warpage during injection molding. The quality of ceramic cores depends on the injection parameters. Predicting the shrinkage and warpage associated with the ceramic injection process helps in avoiding costly and time consuming iterations involved in die design and development. The flow process during filling, packing and cooling stages and the effect of injection molding parameters such as holding time, injection pressure (packing pressure) and flow rate on shrinkage, warpage and Von-Mises stresses on green core is studied using Moldex3D injection molding flow software. In the present study, a Taguchi based partial factorial experiment for optimization of ceramic injection parameters for injection molding of ceramic core is presented. The effect of individual parameters and their interaction is also presented.

Thermodynamic performance assessment of solar-based combined power and absorption refrigeration cycle

Concentrated solar power technology has gained rapid pace in the area of sustainable energy. In recent years concentrated solar power is being appreciated worldwide as they effectively convert available solar energy to its true potential resultant energy. In this context, the principal objective of this research is to develop a model driven on solar thermal integrated with a cogeneration cycle. The effect on power generation was noted by varying parameters such as DNI, turbine inlet pressure, mass flow rate of molten salt and turbine entrance temperature was ascertained on energy and exergy efficiencies of cogenerated driven cycle. From the results it was observed, a gradual growth at turbine entry pressure ranging between 180 bar to 220 bar causes an eventual rise in first law related efficiency and exergy related efficiency of Rankine and cogeneration cycle from (31.115% to 31.44%; 42.05% to 42.56%) and (42.03% to 42.14%; 56.04% to 56.55%).

Determination of Thermal Barrier Coatings Layers Optimum Thickness via PSO-SA Hybrid Optimization Method concerning Thermal Stress

Turbine entry temperature of turbo-engines has been increased to improve proficiency. Consequently, protecting the hot section elements experiencing aggressive service conditions necessitates the applying of thermal barrier coatings (TBC). Developing TBC systems and improving performance is an ongoing endeavour to prolong the lifetime. Thus, various studies have been conducted to find the optimum properties and dimensions. In this paper, the optimum thickness of intermediate bond coat (BC) and top coat (TC) have been determined via a novel hybrid particle swarm and simulated annealing stochastic optimization method. The optimum thicknesses have been achieved under the constraint of thermal stress induced by thermal fatigue, creep, and oxidation in the TC while minimizing the weight during twenty cycles. The solutions for BC and TC thicknesses are respectively 50 μm and 450 μm. Plane stress condition has been adopted for theoretical and finite element stress analysis, and the results are successfully compared.

Development of an ultra-low head siphon hydro turbine using computational fluid dynamics

Structural simplification and efficient hydraulic performance are key to effectively utilizing ultra-low head water power resources and reducing hydroelectric unit costs. In this study, a computational fluid dynamics (CFD) method was used to predict hydraulic performance of an axial turbine at the Gaoliangjian power station. CFD results agreed well with field test data. Using the same numerical method, a new siphon turbine was then designed based on the original distributor and turbine runner equipment. This study investigated the effect of different siphon outlet passage geometry parameters, runner blade shapes, and distributors on the hydraulic performance of the siphon turbine. The maximum hydraulic efficiency increased to 87.9% under a head of 2.87 m. Finally, the hydraulic performance of the turbine was compared for four different distributor designs after adding an intake sump at the turbine entrance. The bell-shaped distributor with four guide vanes resulted in the highest power output at the lowest head. Therefore, the siphon turbine is a good option for energy conversion in ultra-low water head settings.

Entropy and Vorticity Wave Generation in Realistic Gas Turbine Combustors

Understanding the nature of the unsteady flow at the combustor exit is required to accurately simulate time-dependent phenomena in the turbine entry, such as indirect noise generation. Using large-eddy simulations of the combustion process in a realistic geometry, the flow at its exit is analyzes. Two realistic near-ground certification operating conditions are considered. Different mechanisms for large-scale flow and thermal structure generation are described, which are ejected into the turbine. Modal decomposition methods are used to extract the spatial and temporal scales at the turbine entry. It is found that, depending on the operating condition, the entropy waves convect as elongated streaks in the core of the combustor annulus or the proximity of the walls. The dominant unsteady character of the fluctuations exhibits different spectral properties: that is, low frequency in the core and high frequency toward walls. At the combustor exit, the vortical field is dominated by the swirl in the air inlet, which is found to have little influence on the entropy perturbations. Furthermore, the importance of considering the interaction of multiple fuel injectors and combustion zones in an annular combustor is investigated. It is shown that pulsating circumferential vorticity modes can occur in multisector annular combustors, but these do not affect the entropy wave distribution.

EVALUATION OF DEGRADATION EFFECT ON INTERCOOLED GAS TURBINE PERFORMANCE OPERATED IN FLEXIBLE MODE

This paper investigates the effect of type and level of degradation in industrial gas turbine components on its performance under flexible operation due to working as a back-up to renewable energy sources (RES). This investigation was carried out for a 2-shaft 100MW aero-derivative gas turbine with intercooler. Due to the influence of unpredictable nature of power produced by RES, power plants are now operating in a flexible manner, which will require the operator to either stop operation during high feed-in from renewables or reducing the power output from the power plant to a certain percentage. This in turn has an impact on the gas turbine performance and thermal efficiency, which is also affected by the type and level of degradation of their components compared to the non-degraded gas turbines. In-House performance simulation software (TURBOMATCH), which was developed in Cranfield University, was used to carry out gas turbine performance modelling according to daily flexible operation scenarios for all seasons. These daily operating scenarios, which describe the power settings and ambient conditions for a period of 24 hours, were developed from data obtained from the UK national grid and the meteorology office data base. Different levels of degradation in mass flow and efficiency for low-pressure compressor and high-pressure turbine were applied in this study. Results illustrate an obvious impact of degradation type and level on fuel flow, turbine entry temperature, blade cooling temperature, shaft rotational speed and thermal efficiency for different seasons. This study has resulted in a tool which may be useful to power plant operators in understanding the various operating scenarios according to the criteria they wish to choose.

Heat balancing of direct reforming fuel cells in MGT-SOFC hybrid systems

Solid oxide fuel cells convert chemical energy in electrical energy and are highly suitable for the conversion of hydrocarbon based fuels and products from PowerToGas conversions. Embedded in a micro gas turbine-cycle instead of the combustion chamber the heat energy of the injected fuel, released in the SOFC-Stack, can additionally converted into work and by a turbine-generator into electricity. In a compact system, SOFC stacks are designed to realize a direct steam-reforming process inside. In such direct-reforming fuel cell systems the SOFC operating temperature due to the heat demand for reforming, can be reduced to a value in the range of the outlet temperature of the downstream flow (650°C). If the cycle uses a recuperating system, the operating conditions of the SOFC can be realized without additional high-temperature heat exchanger systems. The system with an uncooled turbine, described in [1], just can reach the operating temperature with an additional high-temperature heat exchange. The system described in this publication does not require an additional high-temperature heat exchanger, because the X-value, as the ratio between the exchanged heat quantity and the required amount of heat to complete the MGT-cycle [2] due to the referring process, is nearly zero and can be realized via the inner container wall (of the MLC). The cycle is completed (between the SOFC and the turbine entry) by the heat input of an afterburner. Here the unreacted fuel of the SOFC fuel-stream is used to provide the necessary heat energy for the downstream turbo-generator-system.

Development of a Steady-State Experimental Facility for the Analysis of Double-Wall Effusion Cooling Geometries

The continuous drive for ever higher turbine entry temperatures is leading to considerable interest in high performance cooling systems which offer high cooling effectiveness with low coolant utilization. The double-wall system is an optimized amalgamation of more conventional cooling methods including impingement cooling, pedestals, and film cooling holes in closely packed arrays characteristic of effusion cooling. The system comprises two walls, one with impingement holes, and the other with film holes. These are mechanically connected via pedestals allowing conduction between the walls while increasing coolant-wetted area and turbulent flow. However, in the open literature, experimental data on such systems are sparse. This study presents a new experimental heat transfer facility designed for investigating double-wall systems. Key features of the facility are discussed, including the use of infrared thermography to obtain overall cooling effectiveness measurements. The facility is designed to achieve Reynolds and Biot (to within 10%) number similarity to those seen at engine conditions. The facility is used to obtain overall cooling effectiveness measurements for a circular pedestal, double-wall test piece at three coolant mass-flows. A conjugate computational fluid dynamics (CFD) model of the facility was developed providing insight into the internal flow features. Additionally, a computationally efficient, decoupled conjugate method developed by the authors for analyzing double-wall systems is run at the experimental conditions. The results of the simulations are encouraging, particularly given how computationally efficient the method is, with area-weighted, averaged overall effectiveness within a small margin of those obtained from the experimental facility.

Industrial gas turbine engine response and combustion performance to fuel changeovers in compositions and heating values

Extension of gaseous fuel flexibility for an industrial gas turbine engine is reported in this paper. A Siemens SGT-400 engine with 13.4 MW rating with hybrid combustion system configuration was string tested to operate on and switch between three different gaseous fuels with temperature corrected Wobbe Index varying between 45 MJ/m3, 38 MJ/m3 and 30 MJ/m3. The alteration of fuel heating value was achieved by injection or withdrawal of N2 into or from the fuel system. The results show that NOx decreases for fuels with lower heating value at the same engine output power and most importantly the engine can maintain stable operation on, and switching between these three different fuels with heating values changeover rate faster than 10% per minute without shutdown or change in load condition. The effect of gaseous fuels with different compositions and heating values on turbine entry temperature, NOx emission and combustion was further investigated in a high pressure combustion testing rig and it is found that the peak temperature and temperature gradient of turbine entry temperature are reduced by application of lower heating value of fuels. It is also noted that for the fuels having the same heating value different diluent, either CO2 or N2, has insignificant effect on hot gas temperature profile, however, different diluent does have impact on NOx emission and NOx emissions is lower by up to 5 ppm if CO2 is selected as diluent compared to N2 as diluent. The physical and chemical mechanisms for NOx reduction for gas turbine engines operating on lower heating value fuels have been identified: improving fuel and air mixing by stronger fuel to air momentum ratio and enhanced turbulence level, slowing chemical reaction by decreasing laminar flame speed and reduction of thermal NOx due to decrease in adiabatic flame temperature and flame shifted to downstream.

Analyses of the Costs Associated With Very High Turbine Entry Temperatures in Helium Recuperated Gas Turbine Cycles for Generation IV Nuclear Power Plants

Previous analyses of generation IV (GEN IV) helium gas turbine cycles indicated the possibility for high turbine entry temperatures (TETs) up to 1200 °C in order to improve cycle efficiency, using improved turbine blade material and optimum turbine cooling fractions. The purpose of this paper is to understand the effect on the levelized unit electricity cost (LUEC) of the nuclear power plant (NPP), when the TET is increased to 1200 °C from an original TET of 950 °C and when an improved turbine blade material is used to reduce the turbine cooling fraction. The analyses focus on the simple cycle recuperated (SCR) and the intercooled cycle recuperated (ICR). The baseline LUECs of the NPPs were calculated as $61.84/MWh (SCR) and $62.16/MWh for a TET of 950 °C. The effect of changing the turbine blades improved the allowable blade metal temperature by 15% with a reduction in the LUEC by 0.6% (SCR) and 0.7% (ICR). Furthermore, increasing the TET to 1200 °C has a significant effect on the power output but more importantly it reduces the LUECs by 22.7% (SCR) and 19.8% (ICR). The analyses intend to aid development of the SCR and ICR including improving the decision making process on choice of cycles applicable to the gas-cooled fast reactors (GFRs) and very high-temperature reactors (VHTRs), where helium is the coolant.

Impact of Predicted Combustor Outlet Conditions on the Aerothermal Performance of Film-Cooled High Pressure Turbine Vanes

Turbine inlet conditions in lean-burn aeroengine combustors are highly swirled and present nonuniform temperature distributions. Uncertainty and lack of confidence associated with combustor-turbine interaction affect significantly engine performance and efficiency. It is well known that only Large-eddy and scale-adaptive simulations (SAS) can overcome the limitations of Reynolds-averaged Navier–Stokes (RANS) in predicting the combustor outlet conditions. However, it is worth investigating the impact of such improvements on the predicted aerothermal performance of the nozzle guide vanes (NGVs), usually studied with RANS-generated boundary conditions. Three numerical modelling strategies were used to investigate a combustor-turbine module designed within the EU Project FACTOR: (i) RANS model of the NGVs with RANS-generated inlet conditions; (ii) RANS model of the NGVs with scale-adaptive simulation (SAS)-generated inlet conditions; (iii) SAS model inclusive of both combustor and NGVs. It was shown that estimating the aerodynamics through the NGVs does not demand particularly complex approaches, in contrast to situations where turbulent mixing is key. High-fidelity predictions of the turbine entrance conditions proved very beneficial to reduce the discrepancies in the estimation of adiabatic temperature distributions. However, a further leap forward can be achieved with an integrated simulation, capable of reproducing the transport of unsteady fluctuations generated from the combustor through the turbine, which play a key role in presence of film cooling. This work, therefore, shows how separate analysis of combustor and NGVs can lead to a poor estimation of the thermal loads and ultimately to a wrong thermal design of the cooling system.

Evaluation of ultra-high bypass ratio engines for an over-wing aircraft configuration

Today, main hub airports are already at their capacity limit and hence, smaller airports have become more interesting for providing point-to-point connections. Unfortunately, the use of regional airports induces an increased environmental footprint for the population living around it. In an attempt to solve the related problems, the research project Coordinated Research Centre 880 aims to examine the fundamentals of a single-aisle aircraft with active high-lift configuration powered by two geared ultra-high bypass turbofan engines mounted over the wing. Low direct operating costs, noise shielding due to the over-wing configuration, and short runway lengths are the main advantages. Highlighting the performance, economical and noise benefits of a geared ultra-high bypass engine is the key aim of this paper. This assessment includes a correspondingly adjusted aircraft. Open literature values are applied to design the two investigated bypass ratios; a reference engine with a bypass ratio of 5 and 17 respectively. This study shows that a careful selection of engine mass flow, turbine entry temperature and overall pressure ratio determines the desirable bypass ratio. The aircraft direct operating costs drop by 5.7% when comparing the designed conventional with a future ultra-high bypass ratio engine. Furthermore, the sound at source for a selected mission and operating condition can be reduced by 7 dB. A variable bypass nozzle area for the ultra-high bypass ratio engine is analysed in terms of performance and operability. An increase of safety margin is shown for the turbofan engine with a variable bypass nozzle. It is concluded that this unconventional aircraft configuration with ultra-high bypass ratio engines mounted over the wing has the potential to relieve main hub airports and reduce the environmental impact.

Erosion behavior of EB-PVD 7YSZ coatings under corrosion/erosion regime: Effect of TBC microstructure and the CMAS chemistry

Aero-engines operating in dust-laden environments often encounter a lot of dust/sand that causes a severe problem to the TBCs by means of erosion. As the turbine entry temperatures are rising, molten sand is also a big concern to the life-time of TBCs.This paper deals with the TBC behavior under the combined influence of erosion and corrosion attack. Variations in TBC morphology, CMAS infiltration time and CMAS composition and their influence on the erosion resistance at room temperature were investigated. Two different EB-PVD 7YSZ morphologies consisting of a different porosity arrangement were tested in the erosion/corrosion regime. The more ‘Feathery’ structure has a better resistance to erosion compared to a more columnar ‘Normal’ structure, which leads to less degradation of the TBC. However, under the influence of CMAS infiltration the effect was found to be reversed. In general, CMAS-infiltrated EB-PVD TBCs exhibit a higher erosion resistance than the non-infiltrated ones.

High Resolution Experimental and Computational Methods for Modelling Multiple Row Effusion Cooling Performance

The continuing rise in turbine entry temperatures has necessitated the development of ever-more advanced cooling techniques. Effusion cooling is an example of such a system and is characterised by a high density of film cooling holes that operate at low blowing ratios, thereby achieving high overall cooling effectiveness. This paper presents both an experimental and computational investigation into the cooling performance of effusion systems. Two flat-plate geometries (with primary hole pitches of 3.0D and 5.75D) are experimentally investigated via a pressure sensitive paint technique yielding high resolution film effectiveness distributions via heat-mass transfer analogy. A computational fluid dynamics (CFD) scalar tracking method was used to model the setup computationally with the results comparing favourably to those obtained from the experiments. The CFD domain was modified to assess the cooling performance from a single film hole ejection. A superposition method was developed and applied to the resulting two-dimensional film effectiveness distribution that quickly yielded data for an array of closely-packed holes, allowing a rapid assessment of a multi-hole effusion type setup. The method produced satisfactory results at higher pitches, but at lower pitches, high levels of jet interactions reduced the performance of the superposition method.

Low-Emission combustion of fuel in aeroderivative gas turbines

The paper is the first of a planned set of papers devoted to the world experience in development of Low Emission combustors (LEC) for industrial Gas Turbines (GT). The purpose of the article is to summarize and analyze the most successful experience of introducing the principles of low-emission combustion of the so-called “poor” (low fuel concentration in air when the excess air ratio is about 1.9–2.1) well mixed fuelair mixtures in the LEC for GTs and ways to reduce the instability of combustion. The consideration examples are the most successful and widely used aero-derivative GT. The GT development meets problems related to the difference in requirements and operation conditions between the aero, industrial, and power production GT. One of the main problems to be solved is the LEC development to mitigate emissions of the harmful products first of all the Nitrogen oxides NOx. The ways to modify or convert the initial combustors to the LEC are shown. This development may follow location of multiburner mixers within the initial axial envelope dimensions or conversion of circular combustor to the can type one. The most interesting are Natural Gas firing GT without water injection into the operating process or Dry Low emission (DLE) combustors. The current GT efficiency requirement may be satisfied at compressor exit pressure above 3 MPa and Turbine Entry temperature (TET) above 1500°C. The paper describes LEC examples based on the concept of preliminary prepared air–fuel mixtures' combustion. Each combustor employs its own fuel supply control concept based on the fuel flow–power output relation. In the case of multiburner combustors, the burners are started subsequently under a specific scheme. The can type combustors have combustion zones gradually ignited following the GT power change. The combustion noise problem experienced in lean mixtures' combustion is also considered, and the problem solutions are described. The GT test results show wide ranges of stable operation at needed levels of NOx and CO emissions. The world experience analysis and generalization and investigation of the further development directions for the high performance GT will assist development of domestic LEC for prospective GTs.

Thermodynamic investigation of parameters affecting the execution of steam injected cooled gas turbine based combined cycle power plant with vapor absorption inlet air cooling

Present paper deals with the thermodynamic investigation of influence of different parameters in steam injected cooled gas turbine based combined cycle power plant employing vapor absorption cooling of inlet air and two pressure heat recovery steam generator. Vapor absorption cooling scheme is run by utilizing the heat energy of the exhaust gas at the exit of HRSG. Gas turbine blades are cooled using film cooling technique. A study of the influence of ambient conditions, cycle pressure ratio, and turbine entry temperature on plant performance has been carried out. It has been noted that the efficiency of gas turbine improves by up to 6.91% and specific work output enhances by 16.42% with the integration of vapor absorption inlet air cooling to the simple cycle. The CCPP specific work output advances 17.34% at given turbine entry temperature as the steam to air ratio increases from 3% to 7% at the cycle pressure ratio of 24. Similarly thermal efficiency of CCPP increases by 6.78% for same cycle pressure ratio of 24 and the constant increment in steam to air ratio from 3 to 7%.

Thermodynamic Analysis of Organic Rankine Cycle with Hydrofluoroethers as Working Fluids

Abstract This paper presents an analysis of organic Rankine cycle (ORC) using hydrofluoroethers including HFE7000, HFE7100 and HFE7500 as working fluids under constant external conditions. A computer program has been developed to parametrically compare the first and second law efficiencies, power output, turbine size factor with increase in turbine entry temperature. The results show that HFE7000 produces the maximum thermodynamic efficiencies and performs better in view of the net power output under the given working conditions. Moreover, HFE7000 has the lowest turbine size factor comparing with HFE7100 and HFE7500. Therefore, HFE7000 can be recommended to be used as working fluid in ORC to convert low-grade heat into power.