Combustor Outlet Temperature Research Articles

Gas Turbine Fouling: A Comparison Among 100 Heavy-Duty Frames

Over recent decades, the variability and high costs of the traditional gas turbine fuels (e.g., natural gas) have pushed operators to consider low-grade fuels for running heavy-duty frames. Synfuels, obtained from coal, petroleum, or biomass gasification, could represent valid alternatives in this sense. Although these alternatives match the reduction of costs and, in the case of biomass sources, would potentially provide a CO2 emission benefit (reduction of the CO2 capture and sequestration costs), these low-grade fuels have a higher content of contaminants. Synfuels are filtered before the combustor stage, but the contaminants are not removed completely. This fact leads to a considerable amount of deposition on the nozzle vanes due to the high temperature value. In addition to this, the continuous demand for increasing gas turbine efficiency determines a higher combustor outlet temperature. Current advanced gas turbine engines operate at a turbine inlet temperature (TIT) of (1400–1500) °C, which is high enough to melt a high proportion of the contaminants introduced by low-grade fuels. Particle deposition can increase surface roughness, modify the airfoil shape, and clog the coolant passages. At the same time, land-based power units experience compressor fouling, due to the air contaminants able to pass through the filtration barriers. Hot sections and compressor fouling work together to determine performance degradation. This paper proposes an analysis of the contaminant deposition on hot gas turbine sections based on machine nameplate data. Hot section and compressor fouling are estimated using a fouling susceptibility criterion. The combination of gas turbine net power, efficiency, and TIT with different types of synfuel contaminants highlights how each gas turbine is subjected to particle deposition. The simulation of particle deposition on 100 gas turbines ranging from 1.2 MW to 420 MW was conducted following the fouling susceptibility criterion. Using a simplified particle deposition calculation based on TIT and contaminant viscosity estimation, the analysis shows how the correlation between type of contaminant and gas turbine performance plays a key role. The results allow the choice of the best heavy-duty frame as a function of the fuel. Low-efficiency frames (characterized by lower values of TIT) show the best compromise in order to reduce the effects of particle deposition in the presence of high-temperature melting contaminants. A high-efficiency frame is suitable when the contaminants are characterized by a low-melting point thanks to their lower fuel consumption.

Emission characteristics of aviation kerosene combustion in aero-engine annular combustor with low temperature plasma assistance

A plasma-assisted combustion test platform for annular combustor was developed to validate the feasibility of using plasma-assisted combustion actuation to reduce emission levels. Combustor outlet temperature and emission levels of O2, CO2, H2, CO, and NOx were measured by using a thermocouple and a Testo 350-Pro Flue Gas Analyzer, respectively. Combustor combustion efficiency was also calculated. The effects of duty ratio, feedstock air-flow rate, and actuator position on combustion efficiency and emission performance have been analyzed. The results show that the target of CO and NOx emissions reduction in plasma-assisted combustion could not be fully achieved for kerosene/air mixture with different combustor excessive air coefficients. It is also shown that plasma-assisted combustion with dilution air hole actuation is superior to that of secondary air hole actuation for the combustion of liquid-kerosene fuel. Besides, plasma-assisted combustion effect is more obvious with an increase of duty ratio or feedstock air-flow rate. These results are valuable for the future optimization of kerosene-fueled aero-engine when using plasma-assisted combustion devices to improve emission performance of annular combustor.

Feasibility study of ultra-low NOx Gas turbine combustor using the RML combustion concept

A new combustion concept, the so called RML, was investigated to validate its application as a gas turbine combustor for combustor outlet temperatures over 1973 K. The feasibility study of the RML combustor was conducted with zero dimensional combustion calculations. The emission characteristics of RQL, LEAN, EGR and RML combustors were compared. The calculation results showed that the RQL combustor has lower NOx emissions than the LEAN at high outlet temperature. NOx emissions of the RML combustor at equivalence ratio of the rich chamber of 2.0 can be reduced by 30 % compared with the EGR combustor, and lower than the RQL combustor at a combustor outlet temperature over 1973 K. However, the CO emissions of the RML combustor were higher than those of the LEAN and EGR combustors. Also, the possibility of applying the RML combustor to gas turbines was discussed considering residence time, equivalence ratio of the rich chamber and recirculation rate. Although further research to design and realize the proposed RML combustor is needed, this study verified that the RML concept can be successfully used in a gas turbine combustor.

Performance analysis of a partial oxidation steam injected gas turbine cycle

Partial oxidation gas turbine (POGT) has great potential in improving efficiency because of staged releasing of the chemical energy of fuel. Several researchers have studied the applications of POGT in repowering of different existing power plants. In this study, the POGT is integrated with a steam injected gas turbine (STIG) cycle. This research evaluated the overall thermodynamic performance of a partial oxidation steam injected gas turbine (POSTIG) cycle and investigated the influences of key variables. In addition, comparisons with the STIG cycle were conducted based on exergy analysis. Results show that the combustor outlet temperature of the bottoming gas turbine cycle, the pressure ratio of the bottoming gas turbine cycle compressor, and the temperature of partial oxidation affected the efficiency and specific work output of the POSTIG cycle obviously. Compared with the simple gas turbine cycle, the oxygen concentration in the combustor outlet gas of the POSTIG cycle decreases significantly, and the cooling flow rate increases. Efficiency of the POSTIG cycle is at least two percentage points higher than that of the STIG cycle because of the production and utilization of higher quality steam, along with lower exergy destruction during the graded release of the fuel's chemical energy.

Concept for a Combustion System in Oxyfuel Gas Turbine Combined Cycles

Abstract A promising candidate for CO2 neutral power production is semiclosed oxyfuel combustion combined cycles (SCOC-CC). Two alternative SCOC-CCs have been investigated both with recirculation of the working fluid (WF) (CO2 and H2O) but with different H2O content due to different conditions for condensation of water from the working fluid. The alternative with low moisture content in the recirculated working fluid has shown the highest thermodynamic potential and has been selected for further study. The necessity to use recirculated exhaust gas as the working fluid will make the design of the gas turbine quite different from a conventional gas turbine. For a combined cycle using a steam Rankine cycle as a bottoming cycle, it is vital that the temperature of the exhaust gas from the Brayton cycle is well-suited for steam generation that fits steam turbine live steam conditions. For oxyfuel gas turbines with a combustor outlet temperature of the same magnitude as conventional gas turbines, a much higher pressure ratio is required (close to twice the ratio as for a conventional gas turbine) in order to achieve a turbine outlet temperature suitable for combined cycle. Based on input from the optimized cycle calculations, a conceptual combustion system has been developed, where three different combustor feed streams can be controlled independently: the natural gas fuel, the oxidizer consisting mainly of oxygen plus some impurities, and the recirculated working fluid. This gives more flexibility compared to air-based gas turbines, but also introduces some design challenges. A key issue is how to maintain high combustion efficiency over the entire load range using as little oxidizer as possible and with emissions (NOx, CO, unburnt hydrocarbons (UHC)) within given constraints. Other important challenges are related to combustion stability, heat transfer and cooling, and material integrity, all of which are much affected when going from air-based to oxygen-based gas turbine combustion. Matching with existing air-based burner and combustor designs has been done in order to use as much as possible of what is proven technology today. The selected stabilization concept, heat transfer evaluation, burner, and combustion chamber layout will be described. As a next step, the pilot burner will be tested both at atmospheric and high pressure conditions.

Experimental Study on Combustor Outlet Temperature Field of Gas Turbine

Experimental study on combustor outlet temperature field of heavy-duty gas turbine had been finished on high-pressure test system. Experimental results indicate: The OTDF is sensitive to diameter of dilution holes, and the RTDF is sensitive to location of dilution holes. The test results have important guiding significance and reference value to design, commission and working about the similar combustor.

Heating and Efficiency Comparison of a Fischer-Tropsch (FT) Fuel, JP-8+100, and Blends in a Three-Cup Combustor Sector

In order to realize alternative fueling for military and commercial use, industry guidelines be met. These aviation fueling requirements are outlined in MIL-DTL-83133F(2008) or ASTM D 7566-Annex standards and are classified as “drop-in” fuel replacements. This paper provides combustor performance data for synthetic-paraffinic-kerosene- (SPK-) type (Fisher-Tropsch (FT)) fuel and blends with JP8+100, relative to JP-8+100 as baseline fueling. Data were taken at various nominal inlet conditions: 75psia (0.52 MPa) at 500°F (533 K), 125 psia (0.86 MPa) at 625°F (603 K), 175 psia (1.21 MPa) at 725°F (658 K), and 225 psia (1.55 MPa) at 790 F (694 K). Combustor performance analysis assessments were made for the change in flame temperatures, combustor efficiency, wall temperatures, and exhaust plane temperatures at 3%, 4%, and 5% combustor pressure drop (%P) for fuel:air ratios (F/A) ranging from 0.010 to 0.025. Significant general trends show lower liner temperatures and higher flame and combustor outlet temperatures with increases in FT fueling relative to JP8+100 fueling. The latter affects both turbine efficiency and blade/vane life. In general, 100% SPK-FT fuel and blends with JP-8+100 produce less particulates and less smoke and have lower thermal impact on combustor hardware.

Leading Edge Shielding Concept in Gas Turbines With Can Combustors

The remarkable developments in gas turbine materials and cooling technologies have allowed a steady increase in combustor outlet temperature and, hence, in gas turbine efficiency over the last half century. However, the efficiency benefits of higher gas temperature, even at the current levels, are significantly offset by the increased losses associated with the required cooling. Additionally, the advancements in gas turbine cooling technology have introduced considerable complexities into turbine design and manufacture. Therefore, a reduction in coolant requirements for the current gas temperature levels is one possible way for gas turbine designers to achieve even higher efficiency levels. The leading edges of the first turbine vane row are exposed to high heat loads. The high coolant requirements and geometry constraints limit the possible arrangement of the multiple rows of film cooling holes in the so-called showerhead region. In the past, investigators have tested many different showerhead configurations by varying the number of rows, inclination angle, and shape of the cooling holes. However, the current leading edge cooling strategies using showerheads have not been shown to allow a further increase in turbine temperature without the excessive use of coolant air. Therefore, new cooling strategies for the first vane have to be explored. In gas turbines with multiple combustor chambers around the annulus, the transition duct walls can be used to shield, i.e., to protect, the first vane leading edges from the high heat loads. In this way, the stagnation region at the leading edge and the showerhead of film cooling holes can be completely removed, resulting in a significant reduction in the total amount of cooling air that is otherwise required. By eliminating the showerhead the shielding concept significantly simplifies the design and lowers the manufacturing costs. This paper numerically analyzes the potential of the leading edge shielding concept for cooling air reduction. The vane shape was modified to allow for the implementation of the concept and nonrestrictive relative movement between the combustor and the vane. It has been demonstrated that the coolant flow that was originally used for cooling the combustor wall trailing edge and a fraction of the coolant air used for the vane showerhead cooling can be used to effectively cool both the suction and the pressure surfaces of the vane.

Effect of jet noise reduction on gas turbine engine efficiency

This article introduces a method for gas-turbine preliminary design, featuring jet-noise reduction as one of the main design objectives, or as the main objective. Selected methods have been implemented in an integrated systemic approach tool that includes gas turbine performance, aircraft performance and noise prediction. This tool enables the optimisation of the thermodynamic cycle for low noise, low fuel consumption, or a compromise between the two. Two case studies have been carried out for a 4000 nautical mile, 216-passenger aircraft: one targeting at minimum noise; and one for minimum fuel consumption. The parametric analysis approach enables the visualisation of the effect of cycle choices (overall pressure ratio, bypass ratio, combustor outlet temperature) on parameters such as engine size, weight, specific thrust, specific fuel consumption, noise and mission fuel. It is shown that noise reduction comes at the expense of fuel consumption, reducing the energy conversion efficiency of the system. Nevertheless the proposed tool allows the performance engineer to make appropriate choices for given design targets.

Basic Research of the Intercooled Turbofan Aero-Engine

In conventional turbofan aero-engine designs, the effective way of improvement of engine efficiency is through the increasing of overall pressure ratio and improving of combustor inlet gas temperature, but the further incresement of compressor overall pressor ratio is constricted by high pressure compressor outlet allowed temperature. The improvement of combustor outlet temperature is limited by turbine allowed inlet temperature during take-off and climbing. An intercooled core can be designed with a significantly higher overall pressure ratio also with reduced cooling air requirements, providing a higher thermal efficiency compared with a conventional core. Through the basic analysis of performance of intercooler aeroengines. It indicated that the intercooled aero-engines can decrese the feul consume clearly and have a further potential in future civil aircraft application.

Study on Combustor Outlet Temperature Field of Gas Turbine

Experimental study on combustor outlet temperature field of heavy-duty gas turbine had been finished on high-pressure test system. Experimental results indicate: The OTDF is sensitive to diameter of dilution holes, and the RTDF is sensitive to location of dilution holes. The test results have important guiding significance and reference value to design, commission and working about the similar combustor.

3D Numerical Combustion Simulation of Designed Low Heating Value Fuel Combustor for Further Detail Modulation

This study applied three-dimension numerical combustion simulation method to design the specifications of a low heating value (LHV) fuel combustor. According to the discussion on design parameter system, quantity of main jets is the governing factor for flame stabilization of the primary combustor zone. Combustor outlet temperature factor improves with increase of load, and can be reduced to 0.33 under full load. However, load increase may slightly change recirculation flow structure and weaken flame stabilization. The findings showed that the combustion strength of near-field area greatly increased, and the recirculation flow structure center moved to the liner well when combustor used propane as fuel. This also caused deterioration of temperature factor.

Analysis of main gaseous emissions of heavy duty gas turbines burning several syngas fuels

This work presents the development of a simple analytical model of performance for heavy duty gas turbine combustors and its use for the analysis of main emissions for a set of syngas fuels. This set of syngas fuels has been selected as a wide representation of different compositions of syngas fuels, from fossil or vegetal origins. Their combustion processes have been modelled as a set of chemical reactors in serial and a detailed kinetic model, simulating a conventional diffusion flame combustor. In each slice, the thermodynamics and the kinetics have been modelled using perfect stirred reactor models. The combustor model has been validated with the GE MS7001F gas turbine experimental data. From this validation the model applicability range has been established for combustor outlet temperatures above 1200 K. Finally the combustor model has been applied to the comparison of different syngas fuels emissions in three new generation gas turbines.

Experimental Study of Heat Transfer Augmentation Near the Entrance to a Film Cooling Hole in a Turbine Blade Cooling Passage

Film cooling is extensively used by modern gas turbine blade designers as a means of limiting the blade temperature when exposed to extreme combustor outlet temperatures. The following paper describes an experimental study of heat transfer near the entrance to a film cooling hole in a turbine blade cooling passage. Steady state heat transfer results were acquired by using a transient measurement technique in a 40 times actual rectangular channel, representative of an internal cooling channel of a turbine blade. Platinum thin film gauges were used to measure the inner surface heat transfer augmentation as a result of thermal boundary layer renewal and impingement near the entrance of a film cooling hole. Measurements were taken at various suction ratios, extraction angles, and wall temperature ratios with a main duct Reynolds number of 25,000. A numerical technique based on the resolution of the unsteady conduction equation, using a Crank–Nicholson scheme, is used to obtain the surface heat flux from the measured surface temperature history. Computational fluid dynamics predictions were also made to provide better understanding of the near-hole flow. The results show extensive heat transfer enhancement as a function of extraction angle and suction ratio in the near-hole region and demonstrate good agreement with a corresponding study. Furthermore it was shown that the effect of a wall-to-coolant ratio is of a second order and can therefore be considered negligible compared with the primary variables such as the suction ratio and extraction angle.o

Potential of reducing the environmental impact of aviation by using hydrogen Part II: Aero gas turbine design

AbstractThe main objective of the paper is to evaluate the potential of reducing the environmental impact of civil subsonic aviation by using hydrogen fuel. The paper is divided into three parts of which this is Part II. In Part I the background, prospects and challenges of introducing an alternative fuel in aviation were outlined. In this paper, Part II, the aero engine design when using hydrogen is covered. The subjects of optimum cruising altitude and airport implications of introducing liquid hydrogen-fuelled aircraft are raised in Part III.The study shows that burning hydrogen in an aero gas turbine seems to be feasible from a technical point of view. If the priority is to lower the mission fuel consumption, the results indicate that an engine employing increased combustor outlet temperature, overall pressure ratio and by-pass ratio, seems to be the most attractive choice. The mission NOxemissions, on the other hand, seem to be reduced by using engines with a weak core and lowered by-pass ratio.

The Effect of Turbine Blade Cooling on the Cycle Efficiency of Gas Turbine Power Cycles

A thermodynamic cycle analysis computer code for the performance prediction of cooled gas turbines has been used to calculate the efficiency of plants with varying combustor outlet temperature, compressor pressure ratio, and turbomachinery polytropic efficiency. It is shown that the polytropic efficiency exerts a major influence on the optimum operating point of cooled gas turbines: for moderate turbomachinery efficiency the search for enhanced combustor outlet temperature is shown to be logical, but for high turbomachinery efficiency this is not necessarily so. The sensitivity of the cycle efficiency to variation in the parameters determining the cooling flow rates is also examined. While increases in allowable blade metal temperature and film cooling effectiveness are more beneficial than improvements in other parameters, neither is as important as increase in turbomachinery aerodynamic efficiency.

Aspects of Cooled Gas Turbine Modeling for the Semi-Closed O2/CO2 Cycle With CO2 Capture

In order to capture the behavior of the oxyfuel cycle operating with high combustor-outlet temperature, the impact of blade and vane cooling on cycle performance must be included in the thermodynamic model. As a basis for a future transient model, three thermodynamic models for the cooled gas turbine are described and compared. The first model, known previously from the literature, models expansion as a continuous process with simultaneous heat and work extraction. The second model is a simple stage-by-stage model and the third is a more detailed stage-by-stage model that includes velocity triangles and enables the use of advanced loss correlations. An airbreathing aeroderivative gas turbine is modeled, and the same gas turbine operating in an oxyfuel cycle is studied. The two simple models show very similar performance trends in terms of variation of pressure ratio and turbine inlet temperature in both cases. With the more detailed model, it was found that, without any change of geometry, the turbine rotational speed increases significantly and performance drops for the maintained geometry and pressure ratio. A tentative increase of blade angles or compressor pressure ratio is found to increase turbine performance and decrease rotational speed. This indicates that a turbine will require redesign for operation in the oxyfuel cycle.

Kawasaki goes online with low-NOX gas turbine

The operating requirements for practical catalytic combustion systems are presented. Catalytic materials for methane combustion are then reviewed in light of these operating requirements. Measured catalytic rates for methane oxidization for a number of active metal and oxide catalyst systems are reported and compared. The precious metals, particularly Pd, are most active. The oxides can exhibit high surface areas but in all cases have a much lower areal activity resulting in a substantially lower weight specific activity. Data on the thermal stability and volatility of both support and active components are presented and discussed in terms of the required operating temperatures. It is concluded that at the required operating temperature for modern gas turbines, most catalyst systems would not have sufficient stability and life. An alternative approach is to limit the catalyst temperature and to react a portion of the fuel after the catalyst. This process has substantial advantages. This latter system will be described and the important catalyst performance characteristics discussed. Test results demonstrate NOx levels below 2 ppm even at combustor outlet temperatures as high as 1500°C.

Modeling the Air-Cooled Gas Turbine: Part 2—Coolant Flows and Losses

Abstract This paper is Part II of a study concerned with developing a formal framework for modeling air-cooled gas turbine cycles. It deals with the detailed specification of coolant flowrates and losses. For accurate performance assessment, it is necessary to divide the turbine expansion into individual stages with stator and rotor rows being treated separately. Particular care is needed when deriving the equations for the rotor, and it is shown how all required flow variables can be estimated from minimal data if design values are unavailable. Specification of the cooling flowrates is based on a modified Holland and Thake procedure, which can be formalized in terms of averaged parameters. Thermal barrier coatings can be included if present. The importance of allowing for fluctuations in combustor outlet temperature is stressed and procedures for dealing with end-wall and disk cooling are suggested. There is confusion in the literature concerning cooling losses, and it is shown how these may be defined and subdivided in a consistent way. The importance of representing losses in terms of irreversible entropy creation rather than total pressure loss is stressed. A set of models for the components of the cooling loss are presented and sample calculations are used to illustrate the division and magnitude of the loss.

High Pressure Test Results of a Catalytically Assisted Ceramic Combustor for a Gas Turbine

A catalytically assisted ceramic combustor for a gas turbine was designed to achieve low NOx emission under 5 ppm at a combustor outlet temperature over 1300°C. This combustor is composed of a burner system and a ceramic liner behind the burner system. The burner system consists of 6 catalytic combustor segments and 6 premixing nozzles, which are arranged in parallel and alternately. The ceramic liner is made up of the layer of outer metal wall, ceramic fiber, and inner ceramic tiles. Fuel flow rates for the catalysts and the premixing nozzles are controlled independently. Catalytic combustion temperature is controlled under 1000°C, premixed gas is injected from the premixing nozzles to the catalytic combustion gas and lean premixed combustion over 1300°C is carried out in the ceramic liner. This system was designed to avoid catalytic deactivation at high temperature and thermal and mechanical shock fracture of the honeycomb monolith of the catalyst. A combustor for a 10 MW class, multican type gas turbine was tested under high pressure conditions using LNG fuel. Measurements of emission, temperature, etc. were made to evaluate combustor performance under various combustion temperatures and pressures. This paper presents the design features and the test results of this combustor.