A Gas Turbine Cycle Selection Issue: Recuperated or ICR

2007 ◽  
Author(s):  
Colin Rodgers ◽  
Aubrey Stone ◽  
David White
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Heat Dissipation ◽  
Cycle Performance ◽  
Specific Power ◽  
Exhaust Emission ◽  
Inlet Temperature ◽  
Part Load ◽  
Pressure Losses ◽  
Exhaust Temperature

The intercooled recuperative gas turbine (ICR) potentially offers the advantages of higher specific power, and improved thermal efficiency compared to the recuperative gas turbine, such advantages are however contingent upon the additional parasitic encumbrances of the intercooler heat dissipation or recovery apparatus and pressure losses, plus flowpath ducting and complexity. The thermodynamic performances, relative sizing and relative costs of both an ICR and recuperative gas turbine engine, with a thermal efficiency goal approaching 40%, combined with low exhaust emission requirements were studied. The study encompassed primary candidate engine flowpath configurations comprising of single shaft, two shaft, and two spool designs, with both recuperation (R), and combined Intercooling and Recuperation (ICR). In conducting the study all engine flowpaths were sized for 300kW with a maximum turbine inlet temperature of 1837F (1000C), representative of conservative life limits for conventional un-cooled superalloy turbine rotors. Heat exchanger effectivenesses of the intercooler and recuperator were selected at 80 and 85%, as a compromise between cost, weight, and thermal efficiency considerations. The study confirmed that the simple recuperated cycle is capable of comparable peak thermal efficiency levels to the ICR provided that ICR intercooling parasitic losses are duly accounted, and furthermore has intrinsically lower manufacturing and development costs than the ICR. The cycle performance code used for the studies included prediction of engine exhaust emissions, part load characteristics, and compressor operating lines. The emissions assessment slightly favored the ICR as a consequence of its higher specific power. Assuming part load operation at variable speed and constant turbine exhaust temperature, the two spool ICR showed slightly better part load fuel economy than a recuperated engine.

Gas Turbine Airflow Control for Optimum Heat Recovery

1983 ◽  
Vol 105 (1) ◽  
pp. 72-79 ◽  
Author(s):  
W. I. Rowen ◽  
R. L. Van Housen
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Guide Vane ◽  
Control Mode ◽  
Cycle Performance ◽  
Inlet Guide Vane ◽  
Part Load ◽  
Exhaust Temperature ◽  
Cycle Efficiency

Gas turbines furnished with heat recovery equipment generally have maximum cycle efficiency when the gas turbine is operated at its ambient capability. At reduced gas turbine output the cycle performance can fall off rapidly as gas turbine exhaust temperature drops, which reduces the heat recovery equipment performance. This paper reviews the economic gains which can be realized through use of several control modes which are currently available to optimize the cycle efficiency at part load operation. These include variable inlet guide vane (VIGV) control for single-shaft units, and combined VIGV and variable high-pressure set (compressor) speed control for two-shaft units. In addition to the normal control optimization mode to maintain the maximum exhaust temperature, a new control mode is discussed which allows airflow to be modulated in response to a process signal while at constant part load. This control feature is desirable for gas turbines which supply preheated combustion air to fired process heaters.

Semi-Closed Recuperated Cycle With Wet Compression

2017 ◽  
Author(s):  
Hans E. Wettstein
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Specific Power ◽  
Efficiency Gain ◽  
Lower Efficiency ◽  
Part Load ◽  
Thermal Transients ◽  
Wet Compression ◽  
Main Compressor

The semi-closed recuperated cycle (SCRC) has been suggested earlier by the author in several versions. The best of them used two compressors with one intercooling stage each. In this paper the intercooled main compressor has been replaced by a compressor with high fogging and no intercooling anymore. It is assumed that the system and the main compressor have its design points in the middle of the intended fogging water injection range. This turns out to allow another thermal efficiency gain by 2 to 3 percent points to clearly above 60% also combined with increased specific power related to the consumed combustion air and with no bottoming cycle. This paper demonstrates the technical feasibility based on Turbomachinery technologies, which have already proven commercial viability. The thermodynamic assumptions have been derived from existing gas turbine (GT) technology and are used within already confirmed operating ranges. With the same firing temperature also the thermal efficiency level of current Combined Cycles (GTCC) can be achieved. A special feature of the SCRC is the opportunity for inventory control of part load operation. This means that part load operation can be made by pressure reduction instead of temperature reduction as in open gas turbines. Thermal transients leading to hot part life consumption can therefore be avoided to a large extent and the combustor can operate at nearly constant temperature also at low part load with corresponding low emissions. Low part load operation achieves the same efficiency as base load. The result is more flexibility than in current GTCC technology associated with less complexity due to the needlessness of an extra bottoming cycle. Realizing this type of cycle aiming at its best efficiency potential however needs the development capability of a highly skilled gas turbine manufacturer. But it could also be developed for a lower efficiency range by using existing components with conservative data. The SCRC concept could also be aimed at combined heat and power applications or at naval propulsion by replacing CODOG’s. Due to its specific features the SCRC in general or with wet compression could be developed in the micro turbine power output size as well as up to above 1000MW single block size. Its inherent water condensation at elevated pressure makes an external source of make-up water obsolete.

Gas Turbine Airflow Control for Optimum Heat Recovery

1982 ◽  
Author(s):  
W. I. Rowen ◽  
R. L. Van Housen
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Guide Vane ◽  
Control Mode ◽  
Cycle Performance ◽  
Inlet Guide Vane ◽  
Part Load ◽  
Exhaust Temperature ◽  
Cycle Efficiency

Gas turbines furnished with heat recovery equipment generally have maximum cycle efficiency when the gas turbine is operated at its ambient capability. At reduced gas turbine output the cycle performance can fall off rapidly as gas turbine exhaust temperature drops, which reduces the heat recovery equipment performance. This paper reviews the economic gains which can be realized through use of several control modes which are currently available to optimize the cycle efficiency at part load operation. These include variable inlet guide vane (VIGV) control for single-shaft units, and combined VIGV and variable high pressure set (compressor) speed control for two-shaft units. In addition to the normal control optimization mode to maintain the maximum exhaust temperature, a new control mode is discussed which allows airflow to be modulated in response to a process signal while at constant part load. This control feature is desirable for gas turbines which supply preheated combustion air to fired process heaters.

scholarly journals A gas turbine cooled-stage expansion model for the simulation of blade cooling effects on cycle performance

2019 ◽  
Author(s):  
Roberta Masci ◽  
Enrico Sciubba
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Numerical Procedure ◽  
Expansion Ratio ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Cooling Effects ◽  
Cooling Air ◽  
Cycle Efficiency

Modern gas turbines firing temperatures (1500-2000K) are well beyond the maximum allowable blade material temperatures. Continuous safe operation is made possible by cooling the HP turbine first stages -nozzle vanes and rotor blades- with a portion of the compressor discharge air, a practice that induces a penalty on the cycle thermal efficiency. Therefore, a current issue is to investigate the real advantage, technical and economical, of raising maximum temperatures much further beyond current values. In this paper, process simulations of a gas turbine are performed to assess HP turbine first-stage cooling effects on cycle performance. A new simplified and properly streamlined model is proposed for the non-adiabatic expansion of the hot gas mixed with the cooling air within the blade passage, which allows for a comparison of several cycle configurations at different TIT (turbine inlet temperature) and max (total turbine expansion ratio) with a realistically acceptable degree of approximation.. The calculations suggest that, at a given max, the TIT can be increased in order to reach higher cycle efficiency up to a limit imposed by the required amount and temperature of the cooling air. Beyond this limit, no significant gains in thermal efficiency are obtained by adopting higher max and/or increasing the TIT, so that it is convenient in terms of cycle performance to design at lower rather than higher max. The small penalty on cycle efficiency is compensated by lower plant cost. The results of our model agree with those of some previous much more complex and computationally expensive studies, so that the novelty of this paper lies in the original method adopted on which the proposed model is based, and in the fast, accurate and low resource intensity of the corresponding numerical procedure: all advantages that can be crucial for industry needs. The presented analysis is purely thermodynamic, with no investigation on the effects of the different configurations on plant costs, so that future work addressing a thermo-economic analysis of the air-cooled gas turbine power plant is the next logical step.

scholarly journals Performance Benefits for Wave Rotor-Topped Gas Turbine Engines

1996 ◽  
Author(s):  
Scott M. Jones ◽  
Gerard E. Welch
Keyword(s):  
Steady State ◽  
Gas Turbine ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Cycle Performance ◽  
Specific Power ◽  
Inlet Temperature ◽  
Wave Rotor ◽  
Turbine Engine ◽  
One Dimensional

The benefits of wave rotor-topping in turboshaft engines, subsonic high-bypass turbofan engines, auxiliary power units, and ground power units are evaluated. The thermodynamic cycle performance is modeled using a one-dimensional steady-state code; wave rotor performance is modeled using one-dimensional design/analysis codes. Design and off-design engine performance is calculated for baseline engines and wave rotor-topped engines, where the wave rotor acts as a high pressure spool. The wave rotor-enhanced engines are shown to have benefits in specific power and specific fuel flow over the baseline engines without increasing turbine inlet temperature. The off-design steady-state behavior of a wave rotor-topped engine is shown to be similar to a conventional engine. Mission studies are performed to quantify aircraft performance benefits for various wave rotor cycle and weight parameters. Gas turbine engine cycles most likely to benefit from wave rotor-topping are identified. Issues of practical integration and the corresponding technical challenges with various engine types are discussed.

scholarly journals Effect of Various Control Modes on the Steady-State Full and Part Load Performance of a Direct-Cycle Nuclear Gas Turbine Power Plant

1974 ◽  
Author(s):  
R. E. Covert ◽  
J. M. Krase ◽  
D. C. Morse
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Plant Performance ◽  
Control Mode ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Operating Characteristics ◽  
Reactor Outlet ◽  
Part Load

The performance and principal operating characteristics of the Gas Turbine HTGR power plant are reported. The reference design of the dry cooled 1100-MW(e) power plant incorporates four helium gas turbine power conversion loops integrated into the prestressed concrete reactor vessel, which also contains the reactor and the entire primary coolant system. The reactor core is virtually the same as that for the comparable HTGR steam cycle and is operated with similar maximum fuel temperatures, resulting in a turbine inlet temperature of 1500 F (816 C). An overall plant efficiency of about 37 percent is realized with a design point cycle pressure ratio of 2.35 and with a high-effectiveness recuperator in each loop. Component performance and cycle performance calculations are discussed. The variation of plant performance with ambient temperature is described. Three distinct control modes are described which are, in order of decreasing part-load efficiency, helium inventory control, reactor outlet temperature control, and bypass flow (compressor outlet to turbine outlet) control. The latter offers the most rapid control of plant output. Also described is the standard operating control mode which combines reactor outlet temperature and bypass controls to facilitate both ramp and step load changes.

scholarly journals Current Status of Ceramic Gas Turbine (CGT302)

1998 ◽  
Author(s):  
Hirotake Kobayashi ◽  
Tetsuo Tatsumi ◽  
Takashi Nakashima ◽  
Isashi Takehara ◽  
Yoshihiro Ichikawa
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Technology Development ◽  
Development Program ◽  
Point Of View ◽  
Current Status ◽  
Fiscal Year ◽  
Inlet Temperature ◽  
Development Organization ◽  
New Energy

In Japan, from the point of view of energy saving and environmental protection, a 300kW Ceramic Gas Turbine (CGT) Research and Development program started in 1988 and is still continuing as a part of “the New Sunshine Project” promoted by the Ministry of International Trade and Industry (MITT). The final target of the program is to achieve 42% thermal efficiency at 1350°C of turbine inlet temperature (TIT) and to keep NOx emissions below present national regulations. Under contract to the New Energy and Industrial Technology Development Organization (NEDO), Kawasaki Heavy Industries, Ltd. (KHI) has been developing the CGT302 with Kyocera Corporation and Sumitomo Precision Products Co., Ltd. By the end of the fiscal year 1996, the CGT302 achieved 37.0% thermal efficiency at 1280°C of TIT. In 1997, TIT reached 1350°C and a durability operation for 20 hours at 1350°C was conducted successfully. Also fairly low NOx was proved at 1300°C of TIT. In January 1998, the CGT302 has achieved 37.4% thermal efficiency at 1250°C TIT. In this paper, we will describe our approaches to the target performance of the CGT302 and current status.

Thermodynamic Performance of Complex Gas Turbine Cycles

2002 ◽  
Author(s):  
Sanjay ◽  
Onkar Singh ◽  
B. N. Prasad
Keyword(s):  
Gas Turbine ◽  
Specific Power ◽  
Turbine Engines ◽  
Inlet Temperature ◽  
Air Cooling ◽  
Gas Turbine Engines ◽  
Current State ◽  
Thermodynamic Performance ◽  
Internal Convection ◽  
Plant Efficiency

This paper deals with the thermodynamic performance of complex gas turbine cycles involving inter-cooling, re-heating and regeneration. The performance has been evaluated based on the mathematical modeling of various elements of gas turbine for the real situation. The fuel selected happens to be natural gas and the internal convection / film / transpiration air cooling of turbine bladings have been assumed. The analysis has been applied to the current state-of-the-art gas turbine technology and cycle parameters in four classes: Large industrial, Medium industrial, Aero-derivative and Small industrial. The results conform with the performance of actual gas turbine engines. It has been observed that the plant efficiency is higher at lower inter-cooling (surface), reheating and regeneration yields much higher efficiency and specific power as compared to simple cycle. There exists an optimum overall compression ratio and turbine inlet temperature in all types of complex configuration. The advanced turbine blade materials and coating withstand high blade temperature, yields higher efficiency as compared to lower blade temperature materials.

scholarly journals Comparison of Various Fluidized Bed Combustor-Gas Turbine Systems

1985 ◽  
Author(s):  
Arthur P. Fraas
Keyword(s):  
Gas Turbine ◽  
Fluidized Bed ◽  
Thermal Efficiency ◽  
Combustion Efficiency ◽  
Capital Cost ◽  
Inlet Temperature ◽  
Extensive Experience ◽  
Helium Gas ◽  
Steam Plant ◽  
Fluidized Bed Combustor

Pressurizing a fluidized bed combustor with a gas turbine greatly improves both sulfur retention and combustion efficiency. Operating the gas turbine with a high inlet temperature (e.g. 900°C) would yield a thermal efficiency about four points higher than for an atmospheric furnace, but 40 y of experience have failed to solve problems with flyash erosion and deposits. Extensive experience such as that with fluidized bed catalytic cracking units indicates that the gas turbine blade erosion and deposit problems can be handled by dropping the turbine inlet temperature below 400°C where the turbine delivers just enough power to drive the compressor. The resulting thermal efficiency is about half a point higher than for an atmospheric bed, and the capital cost of the FBC-related components is about 40% lower. While a closed-cycle helium gas turbine might be used rather than a steam cycle, the thermal efficiency would be about four points lower and the capital cost of the FBC-related components would be roughly twice that for the corresponding steam plant.

Modelling the Effect of External Flue Gas Recirculation on NOx and CO Emissions in a Premixed Gas Turbine Combustor With Chemical Reactor Networks

2018 ◽  
Author(s):  
V. Prakash ◽  
J. Steimes ◽  
D. J. E. M. Roekaerts ◽  
S. A. Klein
Keyword(s):  
Gas Turbine ◽  
Flue Gas ◽  
Recirculation Zone ◽  
Chemical Reactor ◽  
Inlet Temperature ◽  
Part Load ◽  
Flue Gas Recirculation ◽  
Reactor Networks ◽  
Gas Recirculation ◽  
The Impact

The increasing amount of renewable energy and emission norms challenge gas turbine power plants to operate at part-load with high efficiency, while reducing NOx and CO emissions. A novel solution to this dilemma is external Flue Gas Recirculation (FGR), in which flue gases are recirculated to the gas turbine inlet, increasing compressor inlet temperature and enabling higher part load efficiencies. FGR also alters the oxidizer composition, potentially leading to reduced NOx levels. This paper presents a kinetic model using chemical reactor networks in a lean premixed combustor to study the impact of FGR on emissions. The flame zone is split in two perfectly stirred reactors modelling the flame front and the recirculation zone. The flame reactor is determined based on a chemical time scale approach, accounting for different reaction kinetics due to FGR oxidizers. The recirculation zone is determined through empirical correlations. It is followed by a plug flow reactor. This method requires less details of the flow field, has been validated with literature data and is generally applicable for modelling premixed flames. Results show that due to less O2 concentration, NOx formation is inhibited down to 10–40% and CO levels are escalated up to 50%, for identical flame temperatures. Increasing combustor pressure leads to a rise in NOx due to thermal effects beyond 1800 K, and a drop in CO levels, due to the reduced chemical dissociation of CO2. Wet FGR reduces NOx by 5–10% and increases CO by 10–20%.

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