The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform

Hyuck Jun Jang - One of the best experts on this subject based on the ideXlab platform.

  • using Compressor Discharge Air bypass to enhance power generation of a steam injected gas turbine for combined heat and power
    Energy, 2014
    Co-Authors: Do Won Kang, Hyuck Jun Jang
    Abstract:

    In gas turbine combined heat and power systems, steam injection is a good way to cope with seasonal variations in electricity and heat demands. However, even though thermal energy demand decreases considerably in cooling seasons, the surplus exhaust heat cannot be fully utilized for steam injection in conventional operation because of a reduction in Compressor surge margin. This study suggests a modified operation to increase power output without damaging the minimum allowable surge margin. This can be realized by extracting some of the Compressor Discharge Air and supplying it to the turbine exhaust side. This paper shows that the modified operation allows for more steam to be injected in comparison to conventional steam-injected operation while maintaining the same Compressor surge margin. The modified operation provides another merit of modulating the heat-to-power-generation ratio by controlling both the amount of Air bypass and the steam injection rate. In particular, pure power generating operation, where generated steam is fully injected such that no heat output is available, is possible without decreasing the surge margin below a desired minimum value. The impact of the Air bypass is demonstrated for a sample ambient temperature condition and the trend with ambient temperature variation is also illustrated.

  • A Study on Power Uprating of a Steam Injected Gas Turbine Cogeneration System by Compressor Discharge Air Bypass
    Volume 6A: Energy, 2013
    Co-Authors: Won Kang, Hyuck Jun Jang
    Abstract:

    Gas turbines are widely used for cogeneration systems. In general, electricity and heat demands are not constant throughout the year. In cooling seasons, generally, heat demand decreases but electricity demand increases. In small gas turbine cogeneration systems, steam injection is a good way to respond to the demand variation. However, steam injection causes Compressor Discharge pressure to rise. This means a reduction in Compressor surge margin, which is a critical operational parameter. Hence, even though thermal energy demand decreases considerably as is the case in cooling seasons, the surplus exhaust heat cannot be utilized for the steam injection in the conventional operation. In this study, a modified steam injected operation is suggested, which uprates electric power output without damaging a minimum allowable surge margin. This can be realized by extracting some of Compressor Discharge Air and supplying it to the turbine exhaust side. The modified operation allows more steam to be injected into the combustor in comparison to the conventional steam injected operation while it guarantees the same Compressor surge margin. The modified operation concept provides another merit of modulating the heat to power generation ratio by controlling both the amount of Air bypass and the steam injection rate. In particular, pure power generating operation, where full amount of generated steam is injected and thus no heat output is available, is possible without decreasing the surge margin below a desired minimum value.Copyright © 2013 by ASME

A. Robertson - One of the best experts on this subject based on the ideXlab platform.

  • Second generation PFBC systems R and D - Phase 2 and Phase 3. Monthly technical report, 08/01/1999--08/31/1999
    1999
    Co-Authors: A. Robertson
    Abstract:

    When DOE funds were exhausted in March 1995, all Phase 2 activities were placed on hold. In February 1996 a detailed cost estimate was submitted to the DOE for completing the two remaining Phase 2 Multi Annular Swirl Burner (MASB) topping combustor test campaigns; in August 1996 release was received from FETC to proceed with the two campaigns to: (1) test the MASB at proposed demonstration plant full to minimum load operating conditions; (2) identify the lower oxygen limit of the MASB; (3) demonstrate natural gas to carbonizer fuel gas switching; and (4) demonstrate operation with low temperature Compressor Discharge Air rather than high temperature ({approx} 1,600 F) vitiated Air. The 18 in. MASB was last tested at the University of Tennessee Space Institute (UTSI) in a high-oxygen configuration and must be redesigned/modified for low oxygen operation. A second-generation PFB combustion plant incorporating an MASB based topping combustor will be constructed at the City of Lakeland's McIntosh Power Plant under the US DOE Clean Coal V Demonstration Plant Program. This plant will require the MASB to operate at oxygen levels that are lower than those previously tested. Preliminary calculations aimed at defining the operating envelope of the demonstration plant MASB have been completed. Phase 3--Commercial plant design update: The Second-Generation PFB Combustion Plant conceptual design prepared in 1987 is being updated to reflect the benefit of pilot plant test data and the latest advances in gas turbine technology. The updated plant is being designed to operate with 95% sulfur capture and a single Westinghouse 501G gas turbine. The 1987 study investigated two coal feeding arrangements, e.g., dry and paste feed. Paste feeding resulted in a lower cost of electricity. Paste, however, increases the water content of the carbonizer generated syngas; this increases the equilibrium partial pressure of hydrogen sulfide gas over calcium oxide/calcium carbonate and thereby reduces the carbonizer sulfur capture efficiency. Recognizing that the carbonizer and the CPFBC work together to control the plant overall sulfur capture efficiency, the higher CPFBC efficiency can compensate for the carbonizer's lower sulfur capture efficiency depending upon the amount of coal and/or char being fed to each unit. Since the latter are determined by the overall plant heat and material balance, they prepared a balance for each feed case to enable selection of the plant coal feed system.

  • Second generation PFBC systems R and D Phase 2 and Phase 3. Monthly technical report, July 1--July 31, 1999
    1999
    Co-Authors: A. Robertson
    Abstract:

    When DOE funds were exhausted in March 1995, all Phase 2 activities were placed on hold. In February 1996 a detailed cost estimate was submitted to the DOE for completing the two remaining Phase 2 Multi Annular Swirl Burner (MASB) topping combustor test campaigns; in August 1996 release was received from FETC to proceed with the two campaigns to: (1) test the MASB at proposed demonstration plant full to minimum load operating conditions; (2) identify the lower oxygen limit of the MASB; (3) demonstrate natural gas to carbonizer fuel gas switching; and (4) demonstrate operation with low temperature Compressor Discharge Air rather than high temperature ({approx} 1,600 F) vitiated Air. The 18 in. MASB was last tested at the University of Tennessee Space Institute (UTSI) in a high-oxygen configuration and must be redesigned/modified for low oxygen operation. A second-generation PFB combustion plant incorporating an MASB based topping combustor will be constructed at the City of Lakeland's McIntosh Power Plant under the US DOE Clean Coal V Demonstration Plant Program. This plant will require the MASB to operate at oxygen levels that are lower than those previously tested. Preliminary calculations aimed at defining the operating envelope of the demonstration plant MASB have been completed. Phase 3--Commercial plant design update: The Second-Generation PFB Combustion Plant conceptual design prepared in 1987 is being updated to reflect the benefit of pilot plant test data and the latest advances in gas turbine technology. The updated plant is being designed to operate with 95% sulfur capture and a single Westinghouse 501G gas turbine. The 1987 study investigated two coal feeding arrangements, e.g., dry and paste feed. Paste feeding resulted in a lower cost of electricity. Paste, however, increases the water content of the carbonizer generated syngas; this increases the equilibrium partial pressure of hydrogen sulfide gas over calcium oxide/calcium carbonate and thereby reduces the carbonizer sulfur capture efficiency. Recognizing that the carbonizer and the CPFBC work together to control the plant overall sulfur capture efficiency, the higher CPFBC efficiency can compensate for the carbonizer's lower sulfur capture efficiency depending upon the amount of coal and/or char being fed to each unit. Since the latter are determined by the overall plant heat and material balance, they prepared a balance for each feed case to enable selection of the plant coal feed system.

  • SECOND GENERATION PFBC SYSTEMS R AND D - PHASE 2 AND 3
    1999
    Co-Authors: A. Robertson
    Abstract:

    When DOE funds were exhausted in March 1995, all Phase 2 activities were placed on hold. In February 1996 a detailed cost estimate was submitted to the DOE for completing the two remaining Phase 2 Multi Annular Swirl Burner (MASB) topping combustor test campaigns; in August 1996 release was received from FETC to proceed with the two campaigns to: (1) test the MASB at proposed demonstration plant full to minimum load operating conditions; (2) identify the lower oxygen limit of the MASB; (3) demonstrate natural gas to carbonizer fuel gas switching; and (4) demonstrate operation with ''low temperature'' Compressor Discharge Air rather than high temperature ({approx}1600 F) vitiated Air.

Tong Seop Kim - One of the best experts on this subject based on the ideXlab platform.

  • Simulation of Optimizing the Partial Load Performance of a Gas Turbine Combined Cycle Using Exhaust Heat Recuperation and Inlet Bleed Heating
    Journal of Engineering for Gas Turbines and Power, 2021
    Co-Authors: Seong Won Moon, Tong Seop Kim
    Abstract:

    Abstract This paper proposes a novel method to extend the operating range and improve the partial load efficiency of the gas turbine combined cycle (GTCC). The combination of exhaust heat recuperation and inlet bleed heating (IBH) was evaluated through a cycle simulation. The degree of heat recuperation was modulated during partial load operation to enhance the cycle efficiency. The recuperation ratio was modulated before control of the variable inlet guide vane (VIGV) began. This means that the recuperation control covers the high partial load regime. The gas turbine power remained almost constant in this regime because the inlet flow rate and turbine inlet temperature (TIT) were kept constant. In contrast, the power of the bottoming cycle decreased with increasing recuperation ratio due to the decrease in exhaust gas energy. After the recuperation ratio reached a limit, the load control was the same, as in conventional plants: VIGV control followed by fuel only control. The purpose of using IBH was to reduce CO emissions in the low load regime. Some of the Compressor Discharge Air was recirculated to the Compressor inlet, and the combustion temperature was maintained at a high level. Both IBH and recuperation were effective in extending the operating range. The turndown ratio was predicted to decrease by approximately 10%p. The efficiency remained higher than the full load efficiency over a wide partial load range. The efficiency of the recuperated GTCC was 4.1%p higher at 50% power than that of the conventional GTCC.

  • Simulation of Optimizing the Partial Load Performance of a Gas Turbine Combined Cycle Using Exhaust Heat Recuperation and Inlet Bleed Heating
    Volume 5: Controls Diagnostics and Instrumentation; Cycle Innovations; Cycle Innovations: Energy Storage, 2020
    Co-Authors: Seong Won Moon, Tong Seop Kim
    Abstract:

    Abstract Extending the operating range and improving the partial load efficiency of the gas turbine combined cycle (GTCC) is becoming increasingly important. This paper proposes a novel method to achieve the two goals simultaneously. To fulfill the research objective, the combination of exhaust heat recuperation and inlet bleed heating (IBH) was adopted and evaluated. A cycle simulation was conducted to confirm whether the research goal could be achieved. A recuperator was installed between the Compressor and combustor of the gas turbine, and the degree of heat recuperation was modulated during partial load operation to enhance the cycle efficiency compared to the conventional GTCC plant. In contrast to the conventional GTCC plant, the recuperation ratio was modulated before control of the variable inlet guide vane (VIGV) began. This means that the recuperation control covers the high partial load regime. The gas turbine power remained almost constant in this regime because the inlet flow rate and turbine inlet temperature were kept constant. In contrast, the power of the bottoming cycle decreased with increasing recuperation ratio due to the decrease in exhaust gas energy. After the recuperation ratio reached a limit, the load control was the same, as in conventional plants: VIGV control followed by fuel only control. The purpose of using IBH was to reduce CO emissions in the low load regime. Some of the Compressor Discharge Air was recirculated to the Compressor inlet, and the combustion temperature was maintained at a high level. The simulation showed that both IBH and recuperation are effective in extending the operating range. The predicted reduction in the turndown ratio was approximately 10%p. The partial load efficiency improvement by the recuperation was sensible. The efficiency remained higher than the full load efficiency over a wide partial load range. The efficiency of the recuperated GTCC was 4.1%p higher at 50% power than that of the conventional GTCC.

James M. Rakowski - One of the best experts on this subject based on the ideXlab platform.

  • metallic alloys for primary surface recuperators
    Volume 5: Marine; Microturbines and Small Turbomachinery; Oil and Gas Applications; Structures and Dynamics Parts A and B, 2006
    Co-Authors: James M. Rakowski, Mark Lipschutz, Charles P Stinner, Preston J Montague
    Abstract:

    The efficiency of small and intermediate-size gas turbine engines can be significantly increased by the use of a primary surface recuperator, which uses waste heat from the exhaust gas to preheat the Compressor Discharge Air before it enters the combustor. The result is lower fuel consumption to reach a particular firing temperature. The construction and operation of a primary surface recuperator present numerous challenges in the area of materials selection. Experiences with stainless steels and nickel-base alloys in construction and application in Solar Turbines’ Mercury 50 gas turbine will be presented, along with the results of extensive laboratory creep and oxidation testing and post-test evaluation. Oxidation testing in humidified Air has been carried out on a variety of commercially available stainless steel and nickel-base alloy thin foils considered as materials of construction for primary surface recuperators. Two predominant degradation modes have been identified. The active mode generally depends on the exposure conditions and the alloy composition. Alloys which are rich in iron tend to suffer from accelerated oxidation, while alloys with higher chromium and nickel contents tend to exhibit oxide scale evaporation via the formation of volatile chromium-bearing species. The active mechanism is evident in the oxidation kinetics, the oxide scale morphology and composition, and in observations of compositional changes in the metal alloy substrate.Copyright © 2006 by ASME

  • the use and performance of wrought 625 alloy in primary surface recuperators for gas turbine engines
    Corrosion, 2005
    Co-Authors: James M. Rakowski, Mark Lipschutz, Charles P Stinner, Preston J Montague
    Abstract:

    Recuperation increases the efficiency of a gas turbine engine by extracting heat from the exhaust gas stream and using it to pre-heat the Compressor Discharge Air. High temperature oxidation and creep are major concerns, necessitating the use of heat-resistant alloys for the recuperator panels. Most current recuperator designs specify austenitic stainless steel foil as the material of construction. Water vapor, present in the exhaust gas as a by-product of combustion, has been shown to be detrimental to elevated temperature oxidation resistance, particularly for ferrous alloys. The protective chromium oxide scale breaks down rapidly in the presence of water vapor due to the formation of fast-growing iron oxide nodules. Increasing the amount of chromium and nickel appears to alleviate the risk of breakaway oxidation. Alloy 625, a common wrought Ni-Cr-Mo superalloy, is a candidate material for recuperator Air cells. Long–term oxidation testing of 100 micron thick samples performed at 704–815oC (1300–1500oF) did not result in breakaway oxidation but indicated a tendency towards weight loss. The observed oxidation kinetics can be explained by a model combining the simultaneous growth and evaporation of an oxide layer. Evaporation of chromia appears to be accelerated in the presence of water vapor by the formation of volatile species such as chromium oxyhydroxide. Comparing these results to those of other nickel-base superalloys and high-alloy content stainless steels revealed that minor element chemistry can be modified to mitigate evaporation by the formation of an external spinel oxide layer.

  • The Use and Performance of Oxidation and Creep-Resistant Stainless Steels in an Exhaust Gas Primary Surface Recuperator Application
    Volume 6: Turbo Expo 2004, 2004
    Co-Authors: James M. Rakowski, Mark Lipschutz, Charles P Stinner, J. Preston Montague
    Abstract:

    Recuperation increases the efficiency of a gas turbine engine by extracting heat from the exhaust gas stream and using it to pre-heat the Compressor Discharge Air. Oxidation of the thin metal foil recuperator walls is a major concern, necessitating the use of heat-resistant alloys. Water vapor, present in the exhaust gas as a by-product of combustion, has been shown to be detrimental to the elevated temperature oxidation resistance of some ferrous alloys currently used for recuperators, e.g., Type 347 stainless steel. The walls of the primary surface recuperator are also subjected to a complex state of stress. Creep deformation can cause the Compressor Discharge Air passages to expand, thus restricting exhaust gas flow and increasing the turbine backpressure. The material of construction must, therefore, be resistant to both oxidation and creep deformation. Long-term oxidation, stress-rupture, and creep test results and analysis will be presented for both commercially available and developmental austenitic stainless steel foil materials. A 20Cr-25Ni austenitic stainless steel containing a small addition of Nb was found to exhibit good creep strength when compared to current alloys of construction. This alloy also possesses excellent resistance to attack in environments containing high levels of water vapor. Oxide volatility and breakaway oxidation were not observed after 10,000 hours of exposure at temperatures as high as 760°C (1400°F).Copyright © 2004 by ASME

Mojtaba Tahani - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of gas turbine operating parameters with inlet fogging and wet compression processes
    Applied Thermal Engineering, 2009
    Co-Authors: Sepehr Sanaye, Mojtaba Tahani
    Abstract:

    Abstract Inlet fogging has been widely noticed in recent years as a method of gas turbine Air inlet cooling for increasing the power output in gas turbines and combined cycle power plants. The effects of evaporative cooling on gas turbine performance were studied in this paper. Evaporative cooling process occurs in both Compressor inlet duct (inlet fogging) and inside the Compressor (wet compression). By predicting the reduction in Compressor Discharge Air temperature, the modeling results were compared with the corresponding results reported in literature and an acceptable difference percent point was found in this comparison. Then, the effects of both evaporative cooling in inlet duct, and wet compression in Compressor, on the power output, turbine exhaust temperature, and cycle efficiency of 16 models of gas turbines categorized in four A–D classes of power output, were investigated. The results of this analysis for saturated inlet fogging as well as 1% and 2% overspray are reported and the prediction equations for the amount of actual increased net power output of various gas turbine nominal power output are proposed. Furthermore the change in values of physical parameters and moving the Compressor operating point towards the surge line in Compressor map was investigated in inlet fogging and wet compression processes.