Experience With Large Gas Turbine Combustion Chambers

Equipment in which an assembly of in-line cylindrical components rotated in water at 1040 rpm displayed excessive vibration after less than one hour of operation. The malfunction was traced to an aluminum alloy 6061-T6 combustion chamber that was part of the rotating assembly. Analysis (visual inspection, 100x/500x/800x micrographic examination, spectrographic analysis, and hardness testing) supported the conclusions that, as a result of improper heat treatment, the combustion-chamber material was too soft for successful use in this application. Misalignment of the combustion chamber and one or both of the mating parts resulted in eccentric rotation and the excessive vibration that caused malfunction of the assembly. Irregularities in the housing around the combustion chamber and temperature variation relating to the combustion pattern in the chamber were considered to be possible contributing factors to localization of the cavitation erosion. Recommendations included adopting inspection procedures to ensure that the specified properties of aluminum alloy 6061-T6 were obtained and that the combustion chamber and adjacent components were aligned within specified tolerances. In a similar situation, consideration should also be given to raising the pressure in the coolant in order to suppress the formation of cavitation bubbles.

Combustion chamber components (cylinder head-cylinder liner-piston assembly-fuel film) were treated as a coupled body. Based on the three-dimensional numerical simulation of heat transfer of the coupled body, the multi-dimensional simulation computation coupling flow and solid on working process and combustion chamber components of internal combustion engine was performed using Discrete Transfer Radiation Model (DTRM) radiation heat transfer model, zoning solution method and boundary coupling method. The simulation was applied to the influence investigation of the space non-uniformity in radiation heat transfer among combustion chamber components on the generation of in-cylinder soot emissions. The results show that the space non-uniformity in heat transfer among the combustion chamber components has great influence on the generation of in-cylinder NOx emissions. The difference value of total soot in cylinder when exhaust valves are opened is 1.3% (no radiation), 0.8% (radiation). So the effect of radiation heat transfer space non-uniformity of combustion chamber components on total soot production can be ignored. While in local area radiation heat transfer space non-uniformity has certain effect on soot production inside whole combustion chamber space, and has less effect on soot production in the area near the wall of combustion chamber components.

Conversion and modernization of a gas turbine engine involves solving a number of tasks, one of which is the development of a combustion chamber for operation on various gaseous fuels. The complexity of solving this problem is associated with a variety of interrelated processes occurring in the CC, which are complex and insufficiently studied. The work on the small-size gas turbine engine CC is even more complicated by the lack of a generally accepted and well-developed finishing technique typical of large gas turbine engines, which is emphasized both in domestic and foreign works. The report considers the main approaches to classifying the dimensions of combustion chambers of gas turbine engines [1] according to various criteria, namely: to the power type size (according to CIAM)Classification based on the reduced air flow through the compressor. The criteria included in the classification are analysed, in relation to the implemented designs, the most objective classification is selected for further consideration of the design of the combustion chamber of a small-sized gas turbine engine when converting it to gaseous fuel. The features and technical limitations of converting the combustion chamber from liquid to gaseous fuel are considered, which is an urgent task against the background of gasification programs of the fuel and energy complex in the Russian Federation. Attention is paid to the factors that have the greatest impact on the environmental characteristics of the converted combustion chambers.

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

Combustion is now considered as a non-negligible contributor to gas turbine noise. Combustion noise can be divided into two types: direct combustion noise directly caused by flame surface fluctuations and indirect combustion noise caused by non-homogeneities in the burnt gases, which radiate sound when interacting with the first turbine stages. The aim of the present project is to obtain an extensive experimental database as well as a better understanding of the physical phenomena inside a pressurized combustion chamber with a choked exhaust nozzle. To do so, a pressurized model scale combustor has been developed, containing a tangential admission injector creating a swirling premixed flow. Satisfactory premixing is obtained in the injection device by a porous media. The combustion chamber shows large optical accesses and various ports for pressure and temperature sensors. On the upstream side, an impedance control device is installed while, downstream, the exhaust nozzle can be easily varied to study its influence on noise generation. A mean chamber pressure higher than 2 bar can be reached for the targeted operating points. The present analysis of the flame behaviour is a first step towards the study of combustion noise. The flame dynamics are characterized by spectral analysis of the dynamic pressure in the combustion chamber. The aim of this work is to determine the dominating acoustic modes during combustion operation. With the help of analytical calculations, the test bench is first modelled as a two cavity system, and later as a five cavity system, taking into account the feeding lines. The nozzle can be assumed as choked due to the pressurization of the chamber. With this method, the majority of the acoustic modes can be identified and explained. The study shows that these modes are linked to the geometry of the whole combustor including the injection tube, the combustion chamber and the feeding lines.

This article shows the effect that biogases obtained from crop residuals from the Andean region have on the performance of a whole medium-sized electrical-generating gas turbine. This technology could be used to supply electricity in energy-depressed areas where biogas is the only accessible resource. The gas turbine worked with higher efficiencies when the obtained biogases were used compared to natural gas. The biofuel that presented the highest efficiencies was the one obtained from wheat residuals alone. Despite this fact, this biofuel would be the most prone to create aerodynamic problems in the stages of the gas turbine. In this work, it was found that the addition of guinea pig manure to different crop residuals created biofuels less prone to create aerodynamic problems in the compression and expansion stages. In particular, the studied biofuel that had the most similar aerodynamic behavior to the design natural gas case was the one obtained from guinea pig manure and quinoa residuals. On the other hand, this biogas presented the lowest efficiencies of the studied biofuels. Despite this fact, this biofuel showed higher efficiencies than the natural gas case. In the gas turbine combustion chamber, all the studied biofuels operated at lower temperatures than the ones with natural gas, even in the high-power range. This would be an important feature for the running of the combustion chamber and the high-pressure turbine superalloys.

The demand for flexible operation of stationary gas turbines, especially at part load, requires the simultaneous design for sufficient efficiency and life time. Both can be addressed by the secondary air system. The here applied concept modulates cooling air supply in off-design. Typically, a reduction of cooling air leads to higher efficiency but shorter turbine life time. This paper presents investigations on such concepts, aiming for trade-offs between fuel burn and turbine blade life. The considered life time mechanisms are creep, which is dominant in rotor blades, and oxidation. In addition, the effects on emissions from the combustion are outlined. The reference gas turbine is a literature-based, generic gas turbine in the 300 MWpower output segment. Regarding cooling air control, the focus is on the first two stages of the four-stage turbine. All simulations are performed by application of component zooming with an appropriate in-house tool: a previously introduced coupled model of the reference gas turbine that essentially connects gas turbine performance with a secondary air system network model. This coupled model is now extended with blade life evaluation and emission models. The results contain trade-offs for different operating points at base and part load. For example, the combined cooling air control of stage 1 rotor blade and stage 2 vane offers several benefits regarding fuel consumption: saving up to Δwfuel,rel = 0.5% in the heat recovery’s kink point operation at 60 % of base load of a combined cycle application. This saving is at the expense of creep life. However, some operating points could even operate at higher blade temperatures in order to improve life regarding hot corrosion. Furthermore, generic sensitivities of controlled secondary air supply to cooling layers and hot gas ingestion at rim seals are discussed. Overall, the presented trades mark promising potentials of modulated secondary air system concepts from a technical point of view.

This study presents comprehensive thermoeconomic and thermoenvironomic modeling and analysis of selected gas turbine power plants in Nigeria using the first and second laws of thermodynamics (exergy) concept. Exergetic analysis was conducted using operating data obtained from the power plants to determine the exergy destruction and exergy efficiency of each major component of the gas turbine in each power plant. The results of the study showed that the combustion chamber (CC) is the most exergy destructive component compared to other cycle components. The percentage of exergy destruction in CC varies between 86.05% and 94.6%. By increasing the gas turbine inlet temperature (GTIT), the exergy destruction of this component can be reduced. The total exergy improvement potential of the selected plants varies from 54.04 to 159.88 MW. The component with the highest exergy improvement potential is the CC, which has the value that varies from 30.21 to 88.86 MW. Thermoeconomic analysis showed that the cost of exergy destruction is high in the CC, and an increase in the GTIT effectively decreases this cost. The exergy costing analysis revealed that the unit cost of electricity produced in the plants ranged from cents 1.99/kWh (N3.16/kWh) to cents 5.65 /kWh (N8.98/kWh). Thermoenvironomic analysis showed that the CO2 emissions varied between 100.18 and 408.78 kg CO2/MWh, while cost rate of environmental impact varied from 40.18 $/h (6, 388.62 N/h) to 276.97 $/h (44, 038. 23 N/h). The results further showed that CO2 emissions and cost of environmental impact decrease with increasing GTIT. The sustainability index increase with increasing GTIT. Finally, this study will assist efforts to understand the thermodynamic losses in the gas turbine cycle, and to improve efficiency as well as provide future recommendations for better performance, sustainability, and lessening environmental impact of power plant.

Turbojet engine can be divided into three major sections including the compressor, combustion chamber and the gas turbine section. The relatively high temperature gas that passes through the high pressure turbine stages of a turbojet engine from the combustion chamber has a direct effect on the performance and efficiency of the gas turbine, which may hamper its longevity in the long run, particularly the turbine blades. The turbine blades extract energy from the high temperature gas and transfer the kinetic energy of the flowing gas to the compressor stages where it provides forward thrust and rotates the turbine shaft which drives the high pressure and low Pressure compressor fan blades. However, the ability of materials to withstand this high temperature is based on properties of such materials which can be attributed to advances in material selection, improvement techniques in terms of surface protection and cooling as well as manufacturing processes which this paper is based on. Material indices were derived for High Pressure (HP) turbine blades to determine materials that can resist yielding and creep condition when exposed to high temperature above 700°C in a turbojet engine gas turbine. Based on the material indices derived, CES software 2014 was used to generate graphs showing materials with adequate fracture toughness, fatigue strength, stiffness and yield strength property that can withstand the in-service condition of HP turbine blade. Considering all these properties in terms of relatively high temperature, Nickel based super alloys dominated the graphs but in terms of density, titanium alloys dominated as CES software gave the minimum density of nickel alloy (8150 kg/m3) as twice that of titanium alloy (4410 kg/m3). Although both alloys are very expensive, nickel based alloy particularly Nickel-Cr-Co-Mo Super alloy also known as Rene 41 was chosen because of its excellent corrosion property and high strength at elevated temperature (About 1000°C) which makes it suitable for conventional HP turbine blade application.

The gas turbines are generally used for large scale power generation. The basic gas turbine cycle has low thermal efficiency, which decreases in the hard climatic conditions of operation, so the cycles with thermodynamic improvement is found to be necessary. Among several methods shown their success in increasing the performances, the steam injected gas turbine cycle (STIG) consists of introducing a high amount of steam at various points in the cycle. The main purpose of the present work is to improve the principal characteristics of gas turbine used under hard condition of temperature in Algerian Sahara by injecting steam in the combustion chamber. The suggested method has been studied and compared to a simple cycle. Efficiency, however, is held constant when the ambient temperature increases from ISO conditions to 50°C. Computer program has been developed for various gas turbine processes including the effects of ambient temperature, pressure ratio, injection parameters, standard temperature, and combustion chamber temperature with and without steam injection. Data from the performance testing of an industrial gas turbine, computer model, and theoretical study are used to check the validity of the proposed model. The comparison of the predicted results to the test data is in good agreement. Starting from the advantages, we recommend the use of this method in the industry of hydrocarbons. This study can be contributed for experimental tests.

Chapter Thirty One - Gas Turbines

Using mixtures of hydrogen and natural gas as primary energy sources in current power generation systems with gas turbines is one of the worldwide trends for global decarbonization goals. However, despite the problems of adaptation of the existing assets for the use of hydrogen, little has been studied about its effects on gas turbine generation systems that operate in tropical climatic conditions where temperatures are higher than 30 °C, and relative humidity reaches values higher than 80%.The gas turbine generator plant with steam injection and cooled air inlet studied consisted of a General Electric LM5000 gas turbogenerator composed of a low-pressure compressor, high-pressure compressor, combustion chambers, turbine, and generator. The steam injection system comprises a heat recovery steam generator and two MUP pumps. The air-cooling system comprises two electric coolers, a cooling tower, two pumps, a cooling coil, two evaporators in series, and two condensers in parallel. The air-cooling system allows for reaching the minimum temperature of 8.8 °C. Plant with Stig cycle in ISO conditions (15°C and 60% RH) produces 52 MW with a thermal efficiency of 43%. The atmospheric conditions in the geographical location of the power plant are, on average, 32°C and 80% relative humidity at sea level. Therefore, the plant with the Stig cycle under local operating conditions produces a power of 44.4 MW with a thermal energy efficiency of 41.6 %. A simulation was conducted in a Stig cycle generation system with a gas turbine, steam injection in the combustion chamber, and cooling air at 8.8°C at the compressor inlet. The system is set to produce 44.4 MW for fuel mix ranges between 0–50% hydrogen. The study results showed that for every 5% by volume of hydrogen added to the H2-natural gas mixture, 5.6% kJ/m3 of energy is lost. Thermal efficiency decreases an average of 2.67% for every 10% increase in hydrogen, which forces an increase in the volume of the fuel mixture to generate the same power. For a percentage of 20% by volume of H2 in the fuel mixture, there are increases in global exergy destruction, avoidable exergy destruction, and unavoidable exergy destruction of 21.5%, 16%, and 31%, respectively. In comparison, the exergetic efficiency decreases by 13.7%. The component most affected by the use of the fuel mixture is the combustion chamber, in which exergy destruction increases by 17.8 MW compared to using 100% natural gas. In addition, the combustion chamber suffers an increase in exergy destruction of 29,2% for every 10% increase in the percentage of hydrogen injection in the fuel mixture. For every 10% increase in H2 volume, there is an average increase in the NOx concentration of 0.4% and a 5% decrease in the CO2 concentration.

Gas turbines are one type of internal combustion drive, the initial mover utilizes gas combustion as a fluid to rotate the turbine with internal combustion. Gas turbines at private companies producing electricity use the initial movers, namely gas turbines and steam turbines. Therefore, it is also called the "Steam Gas Power Plant/PLTGU.”Private company especially in Block 2, uses two gas turbine units with Mitsubishi GT 2.1 specifications which are used as the initial drive of the generator. Types of overhauls in gas turbines are divided into three, including turbine inspection, combustor inspection, and major inspection. In maintaining the reliability of the GT 2.1 Gas Turbine, an overhaul combustion inspection was carried out in the combustion chamber because there was an increase in heat rate of 17,9% which caused a decrease in thermal efficiency and net turbine power of the GT 2.1 Gas Turbine by 17% and 2,1%. So that steps are taken to optimize the GT 2.1 Gas Turbine with the combustion inspection method by repairing and cleaning the combustion bucket nozzle. Increased thermal efficiency by 27,8% or 27,13% to 36,01% from data before overhaul. This was also followed by an increase in compressor power and turbine power so that the net turbine power increased by 38% or 141339,35 hp to 195246,54 hp.

Steam injection is a well-known principle for increasing gas turbine efficiency by taking advantage of the relatively high gas turbine exhaust temperatures. Unfortunately, performance is not sufficiently improved compared with alternative bottoming cycles. However, previously investigated supplements to the STIG-principle — such as sequential combustion and consideration of a back pressure steam turbine — led to a remarkable increase in efficiency. The cycle presented in this paper includes a further improvement: The steam, which exits from the back pressure steam turbine at a rather low temperature, is no longer led directly into the combustion chamber. Instead, it reenters the boiler to be further superheated. This modification yields additional improvement of the thermal efficiency due to a significant reduction of fuel consumption. Taking into account the simpler design compared with combined-cycle power plants, the described type of an advanced STIG-cycle (A-STIG) could represent an interesting alternative regarding peak and medium load power plants.

Due to enormous material losses in the case of emergency, it is vital to ensure the operation reliability of the natural gas pipeline compressor stations (CS). The risk of breakdown is rather high for gas turbines (GT) with total operation time approaching the design-estimated life and particularly for those in which the actual period of operation exceeds this value. Over 25% of turbine drives working on natural gas transportation net in Russia have exceeded their design life [1]. For instance, around 600 gas turbines of the GTC-10-4 type (10MW power) are still in service despite their 120,000–160,000 hours of operation (more than 1,000 gas turbines GTC-10 type have been made and installed at natural gas pumping stations in the seventies in Russia). These gas turbines contain several critical components. Most of them are related to the high temperature parts, including inner high-temperature turbine casing (ITC). This ITC is a kind of a collector (duct) connecting a combustion chamber outlet and the turbine’s entry. Combined with an insulation layer, it serves as a protective shield for outer (main) turbine casing against the effect of hot gases. Notwithstanding the fact that the GTC-10-4 turbine has a modest inlet gas temperature (TIT∼800°C), there are various problems with the ITC shape and state during the turbine’s operation. The ITC operates under conditions of dramatic temperature changes, pressure drops, extended periods of high temperature. All these factors can cause the ITC shell deformations, which results in poor turbine performances. Regular maintenance inspections including opening a turbine do not permit to establish reasons for dramatic changes in the ITC shape. A detailed numerical analysis has been performed to better understand the ITC dynamics over its service period of operation. Moreover, it should be observed that ITC forms a flow prior to entering a turbine. Then, gas flow is directed to the first stage nozzles of the turbine. Advanced numerical flow investigation methods were applied to improve hot gas distribution in front of the turbine. A considerable decrease in velocity nonuniformity was achieved both radially and circumferentially through the ITC shape optimization. Great need in this component stimulated introduction of a new manufacturing technology aimed at production of new ITCs and replacement of numerous defective ones still used at natural gas pumping stations across Russia. Results of thermo-deformation analysis and numerical flow investigation for various ITC configurations are presented in the paper. It also contains proposals for improving the state of the ITC and outer turbine casing (OTC) in the result of the fixing unit development and applying a new insulation material.