Turbine Section Research Articles

Root cause analysis of failure of bolts in the low pressure section of a gas turbine in an oil and gas production plant

This research establishes the cause of a severe failure in bolts in the low pressure (LP) section of a gas turbine in an oil and gas production plant. The failure in bolts was reported together with massive failures of turbine blades in the second stage in the hot section of the turbine. The failure was categorized as an unexpected premature failure, given that it was reported to take place after 20 k of service and that the expected service life for this turbine is beyond 100 k. This research had a two-fold purpose; i) to analyse the cause of failure in both components (failed bolts and blades) and ii) to come up with a scenario for the chain of events. Standard microscopic examination techniques (optical metallography and electron microscopy) were used to correlate microstructure of failed components with possible failure mechanisms. Results showed a clear corrosion-fatigue-induced failure in blades. Hardly is there any evidence of fatigue failure in bolts. Bolts appeared to have experienced an excessive load and have consequently been heavily deformed and broken. The failure scenario was proposed, based on the service history, observations, and microstructural examinations.

Increasing Efficiency in an Aeronautical Engine through Maintenance Evaluation and Upgrades: Analysis of the Reliability and Performance Improvements under Financial Issues

This paper defines a methodology for the evaluation of the technical and economic performance of aeronautical engines through the upgrades introduced during its life. The CFM56 is a high-bypass turbofan engine. The variants share a common design, but the details are different. The fan and booster evolved over the different iterations of the engine, as did the compressor, combustor, and turbine sections. Maintenance consists of the activities carried out during the life cycle of an engine to ensure safe, reliable, and economic operation. Maintenance costs represent 20–25% of an airline’s operating costs, of which 35–40% refer to the engine. The changes in the performance parameters indicate the state of the engine in the medium to long term: for example, it is possible to detect blade fouling or data on vibrations, and highlight changes in the characteristic behavior of an engine. This work investigates the behavior of the performance parameters in the period prior to an engine development event: a comparison is made with the monitoring of engine vibrations. In the conclusions, a final expressive graph makes us aware of the significant progress, over the years, achieved with the methodology here presented.

Creep behavior identification of an environmental barrier coating using full-field measurements

For the use of thermal and environmental barrier coating (T/EBC) with ceramic matrix composites, it is crucial to master the behavior under (extreme) environments representative of the hot section of engine turbines. An experimental setup to simulate such thermal loading has been developed with various diagnostics enabling for kinematic and thermal field measurements, which are used to drive a finite element model and estimate thermomechanical properties such as creep parameters of the coating.

Magnetron Sputtered Silicon Coatings as Oxidation Protection for Mo‐Based Alloys

Mo‐based alloys with solidus temperatures around and above 2000 °C are attractive high‐temperature structural materials for future applications in the hot section of gas turbines. However, their oxidation behavior is poor due to pesting starting at 600 °C and nonprotective oxide growth at temperatures above 1000 °C. To ensure a sufficient oxidation resistance over a wide temperature range, protective coatings become inevitable. Herein, silicon coatings have been applied by magnetron sputtering on Mo‐9Si‐8B and on titan–zirconium–molybdenum alloy (TZM). The coating architecture is designed to minimize the intercolumnar gaps and porosity, thereby increasing the density. Specimens are tested at 800 and 1200 °C in air isothermally for up to 300 h. The focus is put on the chemical reactions at the coating–substrate interface, the phase formation, and the evolution of the thermally grown oxide. An initially globular SiO2 evolves into a uniform SiO2 layer providing excellent oxidation protection. The investigations reveal a rather slow interdiffusion between the coating and the alloys when tested in air. At the coating–substrate interface exclusively, the Mo3Si phase develops. Finally, the phase formation at the coating–substrate interface is studied in detail for various heat treatments in air and vacuum.

Reliability Based Maintenance in Hydropower: A Case Study of Bijaypur-I Small Hydropower Plant

Reliability engineering is emerging field which provides a tools to ensure the system is capable to deliver reliable product and service to the customer. Electricity is one of the most important human needs in this modern age. So reliability of such facilities plays important role in the quality of life and the economy of the county. Hydropower is one of the main source of energy in Nepal, whose reliability plays important role to successful transaction of traditional fuel to electricity to ensure the targeted energy consumption by government of Nepal in fifteenth five year plan. So this paper foster the way of improving the reliability of hydropower plant to ensure the reliability of power supply in National grid. As the study carried out in Bijayapur-I small Hydropower plant, the reliability and availability found as 0.876 and 0.793 only and insufficient flow seems the major contribution to decrease reliability as scheduled outage, whereby problem in turbine section plays important role to reduce the reliability in the electromechanical system of the plant whose contribution in reliability and availability is 79% so any failure in turbine section adversely affects the performance of plant. Due to this the maintenance strategy should be focused on turbine section. And the study recommended to increase the frequency of flushing of radial filter of cooling system, redundancy in filter system can increase the reliability, use of cyclone separator to separate the dissolved limestone and dissolved sand is the another option, and to use close loop cooling system instead of open system.

Blade synchronous vibration measurements of a new upgraded heavy duty gas turbine MGT-70(3) by using tip-timing method

The work described in this paper is part of a comprehensive prototype test conducted on a heavy duty power generation gas turbine recently upgraded by MAPNA Turbine Engineering and Manufacturing Company (TUGA). A Blade tip-Timing system is proposed to determine the synchronous vibration characteristics of the rotor blades and to validate the design calculations. The last three stages of turbine section are equipped with tip-timing sensors. Six probes are positioned along the circumferential direction for each stage. The locations of sensors are accurately chosen based on the values of the natural frequencies and the number of necessary modes needed to be captured. The vibration parameters of the blades are obtained by post-processing and analyzing of the acquired data. The resonance frequencies are plotted against rotating speed during transient acceleration of the machine and the damping and amplitude of vibration in resonance condition are also determined. The obtained results meet the designer expectations and confirm a safe operation from vibrational point of view.

Pengaruh rasio diameter terhadap parameter-parameter energi turbin arus laut horizontal

The ducted tidal turbine models have been developed to utilize convertion of the kinetic energy on ocean currents. The research on refining the turbine characteristics has been carried out by modifying the turbine’s shape and size. The study of the duct diameter ratio effect on the energy characteristics of the turbine was done in this work. This study was conducted by modifying the duct diameter ratio ( ) with the constant inlet diameter D 0 and outlet D 2 . The flow conditions are analyzed for five cases of turbines with different shapes and diameters to determine the optimum conditions. The optimum value of the diameter ratio could be obtained at the maximum value of power coefficient C P . Flow velocity in the ducted turbine was measured at three turbine sections, namely; the inlet section, the impeller housing section, and the outlet section. The measurement of flow in turbines was carried out at the free stream velocity U 0 = 1,5 m/s. The power coefficient C P and thrust coefficient C T were calculated based on flow velocity data on the turbine cVennell sections for each case. The power coefficient C P reaches the maximum value (Betz limit) at the resistance coefficient K = 2 and the value of axial induction factor a = 0,37. These values were founded at diameter ratio d=0,66. The value of thrust coefficient C T reaches the maximum value at K = 3,9, a = 0,53 and . The optimum value of the diameter ratio was founded at d=0,69.

Effect of microstructure on fatigue crack propagation in a titanium-aluminide alloy under thermomechanical fatigue conditions - Current activities in the subcommittee of Titanium-Aluminide alloys in the Society of Materials Science, Japan (JSMS) -

Titanium aluminide (TiAl) alloys have attracted to considerable interest as a material of blade in the low-pressure turbine section of aero engines since their superior specific strength. The mechanical properties and strengths of TiAl alloys are strongly sensitive to their microstructure controlled with thermo-mechanical processing. The collaborative research has been started from 2017 by the subcommittee on Titanium-Aluminide alloys, JSMS Committee on High Temperature Strength of Materials, in order to get basic information about the influence of microstructure on the high-temperature strength. This paper is a part of the collaborative research. The crack propagation tests were carried out under the load controlled out-of-phase type TMF (OP-TMF) loading condition with temperature range 400 ℃ -760 ℃ . The effect of microstructure on fatigue crack propagation behavior in was discussed.

Study of the pressure distribution over the cross section of the steam pipe turbine T-185-130

Study of the pressure distribution over the cross section of the steam pipe turbine T-185-130

The SEM Metallography Analysis of Vacuum Cast ZhS6K Superalloy Turbine Blade after Various Working Hours

A vacuum cast Ni-base superalloy ZhS6K is used for the production of turbine blades whose are working in the hot section of turbine in former USSR DV-2 jet engine. The usual working temperature for this kind of alloy is designed for 800/1050°C. Turbine blades with protective alitized layer made from this alloy were evaluated at the starting stage, then after 600, 1000, 1500 and 2000 hours of regular working. The SEM methods of quantitative metallography were used for structural characteristics evaluation. The microstructural analysis shows increasing of the medium distance of secondary dendrite arms D, what is related to chemical changes in dendritic structure, and the intermetallic strengthening gamma prime phase coarse and turn into spherical shape what leads to decreasing of dislocation and precipitation strengthening mechanism and further decreasing of hot temperature properties of the alloy. The method used at quantitative evaluation and techniques of colour optical microscopy and SEM is useful when microstructure degradation of superalloys has occurred.

A phenomenological base semi-physical thermodynamic model for the cylinder and exhaust manifold of a natural gas 2-megawatt four-stroke internal combustion engine

This paper presents the application of a systematic methodology to obtain a semi-physical model of phenomenological base for a 2 MW internal combustion engine to generate electric power operating with natural gas, as a function of the average thermodynamic value normally measured in industrial applications. Specifically, the application of the methodology is focused on the cylinders, exhaust manifold, and turbocharger turbine sections. The proposed model was validated with actual operating data, obtaining an error rate not exceeding 5%, which allow a thermal characterization of the Jenbacher JMS 612 GS-N based on the model. A parametric analysis is conducted; considering the volumetric efficiency, the output electric power, the effective efficiency, the exhaust gas temperature, the turbine mass flow, the specific fuel consumption under the nominal operation conditions, which is 1.16 bar in the gas pressure, 65 °C in the cooling water temperature, 35 °C in the average ambient temperature, and 1500 rpm. The results of this model can be used to evaluate the thermodynamic performance parameters of waste heat recovery systems. On the other hand, new control strategies and the implementation of state observers for the detection and diagnosis of failures can be developed based on the proposed model.

Simulative Investigation of the Radar Cross Section of Wind Turbines

Wind-power generation is one of the fundamental sources of renewable energy. However, due to the increasing size of wind turbines, they cause unwanted interference with radar systems for civic protection, especially for on-shore locations. This paper presents parameter studies performed on different wind-turbine models, with a focus on differences of the aerodynamical shape of the rotor blades. Numerical simulation is employed to estimate the influence of different wind-turbine design parameters, with the aim of deriving strategies to minimize wind-turbine influence on radar systems for civic protection. Due to the complex nature of the aerodynamic shape of the blade, a general model cannot be derived from the studies. However, further steps to eventually achieve this goal are outlined.

Linear friction welding of AD730™ Ni-base superalloy: Process-microstructure-property interactions

Linear friction welding (LFW) is a near net shape solid state joining technology for aerospace applications. In this study LFW of a recently introduced Ni-based superalloy, AD730™, with superior properties for use in the hot section of gas turbines was studied. In order to minimize the number of experiments for achieving sound welds, an analytical method was developed that allowed to determine the optimum process parameters with a limited number of experiments. The predictions of the method were validated by LFW experiments, and sound samples without defects were produced. Microstructure evolution of the as-welded samples from the weld center to the base metal was investigated using laser confocal and field emission scanning electron microscopy (SEM) including electron back scatter diffraction (EBSD), energy dispersive spectrometer (EDS) and backscattered imaging (BSE). Post-weld heat treatment (PWHT), consisting of a γ′ sub-solvus solutionizing followed by aging, was conducted on LFWed blocks. Then, microstructure evolution and mechanical testing were conducted on PWHTed samples and compared with the as welded blocks. The obtained results were correlated with microhardness as well as tensile testing at room temperature and 650 °C, and interpreted in terms of fundamental metallurgical processes. Macroscopic examination of the PWHTed joints revealed that the samples failed out of the weld zone, further demonstrating the appropriate selection of LFW processing parameters using the proposed analytical method. PWHTed samples exhibited better room and high temperature tensile properties compared to those of the as-welded samples. Microscopic examination of the fracture zones of the samples showed that the higher levels of reprecipitation of γ′ particles in the thermomechanically-affected zone (TMAZ) of the PWHT samples were associated to their higher tensile properties compared to the as welded ones.

Divergent instability control of aeroelastic system driven by aerodynamic forces under disturbance based on discrete sliding mode control algorithms

Divergent instability control of 2D pretwisted blade section of wind turbine driven by aerodynamic forces under disturbance is investigated. Realization of divergent instability control is based on two types of discrete sliding mode control algorithms. The structure is modeled as 2D pretwisted blade section integrated with structural damping, which is driven by aerodynamic model with perturbed disturbance. Discrete sliding mode control algorithm suitable for disturbance control is investigated to control divergent flap/lead-lag vibrations of blade section. To increase convergence performance and reduce the chattering phenomenon, discrete sliding mode control based on disturbance observer is applied. Convergence of disturbance observer is analyzed, and stability of closed-loop system is discussed. The simulation results show that not only the convergence accuracy can be improved by sliding mode control based on disturbance observer controller, but also the displacement chattering and the control input chattering can be effectively eliminated. Compared with conventional discrete sliding mode control, it has more advantages in the control of divergent instability. To facilitate the real-time realization and automation and at the same time to ensure accuracy, a design of quadratic feedback to build the performance control matrix in sliding mode control based on disturbance observer is developed in present study.

The characteristics and divergence of fan-shaped and cylindrical holes on the suction side of a turbine blade under rotating conditions

Detailed film cooling effectiveness for fan-shaped and cylindrical holes on the suction side of a turbine blade under rotating conditions was obtained by experimental measurements. The experiments were conducted using a 1-stage turbine installed in a closed-loop, low-speed, thermal wind tunnel. The turbine section was designed to rotate at different settled speeds, and the velocity of the mainstream was adjusted to achieve a zero-incidence angle. In the experiments, a steady-state thermochromic liquid crystal (TLC) technique was used to evaluate the film cooling performance. The row hole was situated at an axial location of 8% with an injection angle of 45°. The diameter of the cylindrical hole was 0.8 mm, and the length-to-diameter ratio was 6. For the fan-shaped hole, the forward expansion angle and the lateral diffusion angle were 12° and 10°, respectively. The effects of blowing ratio (M), rotation speed (Ω) and density ratio (DR) on the film cooling performance were analyzed. The blowing ratio was varied from 0.5 to 2.0 with three rotation speeds, 300 rpm, 450 rpm and 600 rpm. CO2 and N2 acted as coolants to achieve the two density ratios of 1.47 and 0.98, respectively. The results showed that the row of fan-shaped holes had better film cooling performance under most operating conditions and especially at low blowing ratios. The length of the coolant trace first increases and then decreases along the spanwise direction, from hub to tip, at all operating conditions. With an increase in the rotation speed, the lateral averaged film cooling effectiveness of both hole geometries decreases. However, fan-shaped holes have better film cooling performance at low rotation speed. In addition, the results for the density ratio showed that CO2, which has a higher density ratio, achieves higher film cooling performance for fan-shaped holes, while the length of the coolant trace is almost constant between the two density ratios.

Annihilation of non-stationary vibration of a gas turbine rotor system under rub-impact effect using a nonlinear absorber

In this study, the effects of a smooth nonlinear energy sink (NES) on a continuously rotating system is investigated by considering its non-stationary motion and rub in disks positions. This rotary system is modeled based on a gas generation (GG) section of an industrial gas turbine. The contact between the rotor and stator is considered to be elastic with Coulomb-type frictional forces. It is considered that the NES's damping and stiffness are linear and cubic, respectively. The shaft is modeled using Rayleigh beam theory and the extended Hamilton principle is employed to obtain the equations of motion. In order to fully model the dynamics of the system, in the Galerkin method, the first three bending modes of the system are used. The genetic algorithm is used to obtain the optimized parameters of the NES and minimize the Root Mean Square (RMS) near to operating speed and the peak amplitudes of the rotor vibrations in the working range. It is demonstrated that the NES can considerably decrease the vibration level and possibility of rub phenomenon in the non-stationary motion of rotating system within a wide range of rotational speed and also can make the motion of the system smoother.

Power generation enhancement in a biomass-based combined cycle using solar energy: Thermodynamic and environmental analysis

Renewable energy sources are one of the promising solutions to deal with the problems and environmental issues arising from fossil fuels. Among the various types of thermodynamic cycles, combined systems are one of the most efficient power generation systems. In this regard, in the present work, a combined cycle is proposed based on new configuration of hybrid biomass-solar energies for production of 13.4 MW power in three sections (Biomass section, Solar section and Steam turbine section). Initially, the proposed cycle is extensively analyzed in energetic, exergetic, and environmental terms and LCOE costs are calculated to estimate the economy of the proposed cycle. Then, for having a clear insight on the effect of adding each of the solar and steam turbine sections to biomass section, the generated power and CO2 emission of each biomass, biomass/solar, and combined cycles are compared and examined. In the end, during the parametric study, the effect of prime thermodynamic parameters on the share of each of the cycle sections on the entire proposed cycle is studied and evaluated. The results showed that, adding the solar section to the biomass-based system brings about an increase of around 25% in power production and a reduction of about 31% in CO2 emission. Also, the amount of CO2 emissions from the proposed combined cycle is about 49% lower than that of the standalone biomass-based system.

Vibration Control of Blade Section Based on Sliding Mode PI Tracking Method and OPC Technology

Vibration control of the blade section of a wind turbine is investigated based on the sliding mode proportional‐integral (SM‐PI) method, i.e., sliding mode control (SMC) based on a PI controller. The structure is modeled as a 2D pretwisted blade section integrated with calculation of structural damping, which is subjected to flap/lead‐lag vibrations of instability. To facilitate the hardware implementation of the control algorithm, the SM‐PI method is applied to realize tracking for limited displacements and velocities. The SM‐PI algorithm is a novel SMC algorithm based on the nominal model. It combines the effectiveness of the sliding mode algorithm for disturbance control and the stability of PID control for practical engineering application. The SM‐PI design and stability analysis are discussed, with superiority and robustness and convergency control demonstrated. An experimental platform based on human‐computer interaction using OPC technology is implemented, with position tracking for displacement and control input signal illustrated. The platform verifies the feasibility and effectiveness of the SM‐PI algorithm in solving practical engineering problems, with online tuning of PI parameters realized by applying OPC technology.

An Efficiency Methodology for Unsteady Full-engine simulation

When carrying out numerical analysis for the entire gas turbine engine, it is necessary to numerically model the flow field, heat conduction, and combustion in the compressor, combustor, and exhaust turbine section, which are its components. The calculation cost tends to increase because it is necessary to consider the complexity of shape, non-stationaryness, and the time scale of each physical phenomenon being largely different. In this paper, we apply approximate solution method of unsteady calculation with using nonlinear harmonic method, and introduce the analysis result of the whole engine including combustion analysis with comparison with the steady calculation result.

HIGH TEMPERATURE CYCLIC TEST RIG – A NEW RIG FOR HOT GAS PARTS LIFETIME VALIDATION

Flexible gas turbine operation requires adapted hot gas parts design and lifetime assessment methods. The High Temperature Cyclic Test Rig (HTCTR) is developed to cyclically test internally cooled components from combustor and turbine sections of gas turbines in close-to-engine conditions for a wide range of operating conditions in order to improve component lifetime management. These advanced tests should serve as basis for new model development and validation for conditions that are more representative of those in an engine than the standard material specimen tests.