MW Class Gas Turbine Research Articles

Effect of Refrigerated Inlet Cooling on Greenhouse Gas Emissions for a 250 MW Class Gas Turbine Engine

In this study, the effect of inlet air cooling on greenhouse gas (GHG) emissions and engine performance for a land-based gas turbine engine was investigated under varying ambient temperatures (15–55 °C). The study aimed to reduce GHG emissions while improving output power and fuel efficiency during hot weather operating conditions. For illustrative purposes, a representative gas turbine engine model, approximating the 250 MW class General Electric (GE) engine, was analyzed in a simple cycle. A refrigeration process was integrated with a turboshaft gas turbine engine to chill the incoming air, and the power required for cooling was extracted from the gas turbine’s output power. This mechanical chiller was assumed to provide a 15 °C inlet air temperature. Without inlet air cooling, at 55 °C ambient temperature, the engine’s power output was calculated to decrease by 15.06%, while power-specific fuel consumption and GHG emissions increased by 6.09% and 5.84%, respectively. However, activating the refrigeration or cooling system in the inlet made it possible to mitigate most of the adverse effects of hot weather on the engine’s performance and GHG emissions. Therefore, with inlet air cooling, the power output loss reduces to 3.28%, indicating an 11.78% recovery compared to the 15.06% loss without cooling. Similarly, the rise in power-specific fuel consumption caused by high ambient temperature decreases from 6.09% to 3.43%, reflecting a 2.66% improvement. An important finding of the study is that with inlet air cooling, the increase in GHG emissions reduces from 5.84% to 3.41%, signifying a 2.43% improvement on a hot day with a temperature of 55 °C.

A case study of cascade supercritical CO2 power cycle for waste heat recovery from a small gas turbine

• A single heated cascade sCO 2 cycle is studied as bottomer of a 4.7 MW gas turbine. • Around 1500 kW of net electric power can be recovered by the sCO 2 -based technology. • The specific cost of the considered sCO 2 -based technology is around 2000 $/kW. • Performance of the investigated cycle is similar to the one of the partial heating cycle. • Driving the compressor at the same rotational speed of the turbines is not possible. Among the technological solutions that can be applied to waste heat recovery, the supercritical CO 2 (sCO 2 ) cycle represents an innovative option. This work studies the performance of the single heated cascade sCO 2 cycle as the bottomer power system of a 5 MW-class gas turbine and follows a former study of the authors about the partial heating cycle. A number of parametric analyses has been carried out with attention paid to the selection of (i) minimum and maximum CO 2 pressures, based on a compressor Mach number selected to avoid highly loaded turbomachinery, (ii) maximum CO 2 temperature, and (iii) specific design parameters such as temperature difference at the cold side of the primary heater, recuperator effectiveness and single-stage radial-type turbine efficiency, the latter calculated according to Aungier’s correlations by taking actual size and running conditions into account. The results of this study suggest that around 1500 kW of net electric power can be recovered by the single heated cascade sCO 2 cycle. This figure is not so different from the power output previously calculated for the partial heating cycle as well as the specific cost of the technology, which is around 2000 $/kW, lower than a possible competing technology for waste heat recovery applications as the organic Rankine cycle. Nevertheless, the architecture investigated in this study needs two turbines which can rotate on the same shaft, but driving the compressor at the same rotational speed of the two turbines is not possible, as emerges from preliminary considerations about the size of the turbomachinery impellers.

Techno-economic investigations of supercritical CO2-based partial heating cycle as bottoming system of a small gas turbine

Supercritical CO2 (sCO2) cycles represent an innovative technology especially if applied for waste heat recovery from gas turbines. This work investigates the performance of the partial heating sCO2 cycle as the bottoming cycle of a 5 MW-class gas turbine. Particular attention is paid to the selection of both minimum CO2 pressure and temperature and use of the non-dimensional criterion named Acceleration Margin to Condensation is made to prevent the formation of liquid CO2 droplets at the inlet of the compressor. Moreover, in order to avoid heavily loaded turbomachinery, considerations about the machine Mach numbers result in possible limits for the maximum cycle pressure. Single-stage radial turbomachines are selected and their efficiency calculated according to Aungier's correlations by taking actual size and running conditions into account. Focusing on the net electric power produced by the bottoming cycle and on the corresponding specific cost, a number of investigations has been carried out. After setting a limit for the compressor Mach number, around 1600 kW can be recovered by the sCO2 bottoming cycle, though a techno-economic optimization would guide towards an optimum point with slightly more than 1500 kW of power output and a specific cost for the technology of around 2000 $/kW.

Performance Improvement of a 43 MW Class Gas Turbine Engine with Inlet Air Cooling

In this study, a process of inlet air cooling was implemented in the intake of a land-based gas turbine engine for electricity generation. The motivation behind the study is to improve the performance of the gas turbine engine in hot climate conditions,which causes a significant decrease in the output power and an increase in specific fuel consumption. For inlet air cooling, a refrigeration cycle was attached to the turbo-shaft gas turbine engine,and power required by the refrigeration is extracted from the mechanical engine power output of the gas turbine. A 43 MWclass gas turbine engine which is similar totheGeneral Electric LM6000 engine was modeled in this study. Considering an average coefficient of performance of 3.0 for a refrigeration system, the inlet cooling provided (by supplying cooled inlet air at 15oC) a 22.21% net power increase anda5.2% power specific fuel consumption improvement at 55oCambient conditions.

30 Years of Dry-Low-NOx Micromix Combustor Research for Hydrogen-Rich Fuels—An Overview of Past and Present Activities

Abstract This paper presents an overview of the past and present of low-emission combustor research with hydrogen-rich fuels at Aachen University of Applied Sciences (AcUAS). In 1990, AcUAS started developing the dry-low-NOx Micromix combustion technology. Micromix reduces NOx emissions using jet-in-crossflow mixing of multiple miniaturized fuel jets and combustor air with an inherent safety against flashback. At first, pure hydrogen as fuel was investigated with lab-scale applications. Later, Micromix combustor prototypes were developed for the use in an industrial gas turbine Honeywell/Garrett GTCP-36-300, proving low NOx characteristics during real gas turbine operation, accompanied by the successful definition of safety laws and control system modifications. Further, the Micromix was optimized for the use in annular and can-combustors as well as for fuel-flexibility with hydrogen-methane-mixtures and hydrogen-rich syngas qualities by means of extensive experimental and numerical simulations. In 2020, the latest Micromix application is demonstrated in a commercial 2 MW-class gas turbine can-combustor with full-scale engine operation. This paper discusses the advances in Micromix research over the last three decades.

Performance Degradation of a 43 MW Class Gas Turbine Engine in Kuwait Climate

Performance Degradation of a 43 MW Class Gas Turbine Engine in Kuwait Climate

Demonstration Test of Ammonia/Natural Gas Co-Firing Power Generation with 2 MW Class Gas Turbine

Demonstration Test of Ammonia/Natural Gas Co-Firing Power Generation with 2 MW Class Gas Turbine

Model-based performance diagnostics of heavy-duty gas turbines using compressor map adaptation

The major cause of the performance degradation of industrial gas turbines is compressor fouling due to airborne contaminants. Performance diagnostics is required to evaluate degradation precisely. In general, the measured performance in the fully opened inlet guide vane (IGV) condition is regarded as full-load performance and used for diagnostics. A new diagnostic method is proposed in this study. A scheme to determine whether the measured performance is at full-load operation is suggested. If operation is not at full-load, a virtual gas turbine state corresponding to the measured data is modeled using adaptive modeling. Then, the virtual full-load performance and the corrected performance are predicted using a reference firing temperature. This calculation methodology is applied to almost two-years of data of a 150 MW class gas turbine. The analysis revealed that the maximum reduction of power output and efficiency are 14.8 MW and 0.8 percentage points compared with the rated performance. In addition, it was shown that if the measured performance is used directly, the maximum deviation in the predicted power degradation was as much as 4.9 MW (2.8%) compared with the rated performance. This paper demonstrates the necessity of a model-based analysis for enhancing the accuracy of performance diagnostics.

Evaluation of Degradation Characteristics of Thermal Barrier Coating on Gas Turbine Blades

In order to evaluate the lifespan of high-temperature parts with thermal barrier coating in gas turbines used for power generation, this study was performed on an 80 MW-class gas turbine exceeding 24 k equivalent operating hours. Degradation characteristics were evaluated by analyzing the YSZ (Yttria Stabilized Zirconia) top coat, which serves as the thermal barrier coating layer, the NiCrAlY bond coat, and interface layers. Microstructural analysis of the top, middle, and bottom sections showed that Thermal Growth Oxide (TGO) growth, Cr precipitate growth within the bond coat layer, and formation of diffusion layer occur actively in high-temperature sections. These microstructural changes were consistent with damaged areas of the thermal barrier coating layer observed at the surface of the used blade. The distribution of Cr precipitates within the bond coat layer, in addition to the thickness of TGO, is regarded as a key indicator in the evaluation of degradation characteristics.

Dynamic test and fatigue life evaluation of compressor blades

High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. To verify the reliability of the high cycle fatigue fracture of the 5 MW gas turbine engine blade being developed by Doosan Heavy Industries & Construction Co., Ltd., dynamic tests were conducted using real size compressor rigs according to previous studies. The dynamic safety margin of the 5MW gas turbine engine blade was calculated on the basis of the ratio between the dynamic stress and endurance limit stress respectively determined through the compressor rig and fatigue tests. The HCF characteristics and the fatigue life stability of the DGT-5 compressor blades were verified through these processes. A fatigue life design procedure for the gas turbine compressor blade was established on the basis of the design, analysis, and test processes implemented in a previous study. In sum, the 5 MW class gas turbine compressor blades were found to be well designed in terms of resonance stability and fatigue life.

Modal characteristics and fatigue strength of compressor blades

High-cycle fatigue (HCF) has been identified as one of the primary causes of gas turbine engine failure. The modal characteristics and endurance strength of a 5 MW gas turbine engine blade developed by Doosan Heavy Industries & Construction Co., Ltd. in HCF fracture were verified through analysis and tests to determine the reliability of the compressor blade. A compressor blade design procedure that considers HCF life was performed in the following order: airfoil and blade profile design, modal analysis, stress distribution test, stress endurance limit test, and fatigue life verification. This study analyzed the Campbell diagram and estimated resonance risk on the basis of the natural frequency analysis and modal test of the compressor blade to guarantee safe and operational reliability. In addition, the maximum stress point of the compressor blade was determined through stress distribution analysis and test. The bonding point of the strain gage was determined by using fatigue test. Stress endurance limit test was performed based on the results of these tests. This research compared and verified the modal characteristics and endurance strengths of the compressor blades to prevent HCF fracture, which is among the major causes of gas turbine engine damage. A fatigue life design procedure of compressor blades was established. The 5 MW class gas turbine compressor blade is well designed in terms of resonance stability and fatigue endurance limit.

Comparative economic analysis of gas turbine-based power generation and combined heat and power systems using biogas fuel

We evaluated the economic feasibility of small CHP (combined heat and power) and CC (combined cycle) systems using a 5 MW-class gas turbine fueled with biogas. The significance of this study is that we used practical hourly and seasonal variations of the CHP and CC performance based on detailed performance analysis. Using the investment and running costs of the entire facilities and the prices of electricity and heat, economic indices such as the annual gross margin, the net present value of the cash flow and the payback period were estimated. Two kinds of heat demand patterns were compared in the CHP system. Major findings are as follows. A strong dependence of the project economics on heat sales was observed. Both of the CHP cases showed an economic benefit over both the CC system and the gas turbine-only system. Another important finding is that the CHP system would be more beneficial than the CC system in terms of the total net present value after twenty years as long as the annual heat demand is over thirty percent of the annual electricity supply. The effect of increasing prices and costs was also simulated, and improvements in project economics were estimated.

Crack Growth Behavior and Evaluation of Material Degradation for Serviced First-Stage Nozzles of Gas Turbine.

Crack growth behavior in serviced first-stage nozzles of an 80 MW class gas turbine was studied. Crack growths in the outer wall and trailing edge were mainly observed in the nozzles inspected in this research. Cracks propagated along the dendrite or grain boundary. Precipitation of chromic carbides was also observed, and it seemed to affect crack growth. The small punch method which is a destructive test using a small 10 mm square and 0.5 mm thick specimen, was suitable for evaluating the degradation of the gas turbine nozzle. Crack growth behavior was also analyzed from inspection data. Crack growth in nozzles operated in DSS mode was more severe than that in WSS mode. These cracks were identified as the thermal fatigue cracks that propagate by temperature variations at start-up and shut-down of the turbines. The crack propagation in the outer wall has a tendency to arrest when the crack length reaches about half width of the wall. This crack arrest will be caused by thermal stress releasing with crack growths. A statistical trend analysis based on 3σ gave a conservative assessment result and was found to be a reasonable assessment method for the gas turbine nozzle cracking.