A New Calculation Approach to the Energy Balance of a Gas Turbine Including a Study of the Impact of the Uncertainty of Measured Parameters

2005 ◽  
Author(s):  
Helmer G. Andersen ◽  
Pen-Chung Chen
Keyword(s):  
Energy Balance ◽  
Gas Turbine ◽  
Control Volume ◽  
Ambient Air ◽  
Energy Balance Equation ◽  
Inlet Temperature ◽  
Exhaust Gas ◽  
Gas Composition ◽  
Intake Flow ◽  
The Impact

Computing the solution to the energy balance around a gas turbine in order to calculate the intake mass flow and the turbine inlet temperature requires several iterations. This makes hand calculations very difficult and, depending on the software used, even causes significant calculation times on PCs. While this may not seem all that important considering the power of today’s personal computers, the approach described in this paper presents a new way of looking at the gas turbine process and the resulting simplifications in the calculations. This paper offers a new approach to compute the energy balance around a gas turbine. The energy balance requires that all energy flows going into and out of the control volume be accounted for. The difficulty of the energy balance equation around a gas turbine lies in the fact that the exhaust gas composition is unknown as long as the intake flow is unknown. Thus, a composition needs to be assumed when computing the exhaust gas enthalpy. This allows the calculation of the intake flow, which in turn provides a new exhaust gas composition, and so forth. By viewing the exhaust gas as a flow consisting of ambient air and combusted fuel, the described iteration can be avoided. The study presents the formulation of the energy balance applying this approach and looks at the accuracy of the result as a function of the inaccuracy of the input parameters. Furthermore, solutions of the energy balance are presented for various process scenarios, and the impact of the uncertainty of key process parameter is analyzed.

Modeling of Natural Gas Composition Effect on Low NOx Burners Operation in Heavy Duty Gas Turbine

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Serena Romano ◽  
Roberto Meloni ◽  
Giovanni Riccio ◽  
Pier Carlo Nassini ◽  
Antonio Andreini
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Deep Understanding ◽  
Combustion Efficiency ◽  
Gas Composition ◽  
Gas Combustion ◽  
Annular Combustor ◽  
Heavy Duty Gas Turbine ◽  
Minimal Environmental Impact ◽  
The Impact

Abstract This paper addresses the impact of natural gas composition on both the operability and emissions of lean premixed gas turbine combustion system. This is an issue of growing interest due to the challenge for gas turbine manufacturers in developing fuel-flexible combustors capable of operating with variable fuel gases while producing very low emissions at the same time. Natural gas contains primarily methane (CH4) but also notable quantities of higher order hydrocarbons such as ethane (C2H6) can also be present. A deep understanding of natural gas combustion is important to obtain the highest combustion efficiency with minimal environmental impact. For this purpose, Large Eddy Simulations of an annular combustor sector equipped with a partially premixed burner are carried out for two different natural gas compositions with and without including the effect of flame strain rate and heat loss resulting in a more adequate description of flame shape, thermal field, and extinction phenomena. Promising results, in terms of NOx, compared against available experimental data, are obtained including these effects on the flame brush modeling, enhancing the fuel-dependency under nonadiabatic condition.

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%.

Through Flow Calculations for Convective Cooling Turbines

2014 ◽  
Author(s):  
Li Haibo ◽  
Chunwei Gu
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Calculation Method ◽  
Conjugate Heat Transfer ◽  
High Efficiency ◽  
Thermodynamic Efficiency ◽  
Inlet Temperature ◽  
Flow Calculation ◽  
Through Flow ◽  
The Impact

Conjugate heat transfer is a key feature of modern gas turbine, as cooling technology is widely applied to improve the turbine inlet temperature for high efficiency. Impact of conjugate heat transfer on heat loads and thermodynamic efficiency is a key issue in gas turbine design. This paper presented a through flow calculation method to predict the impact of heat transfer on the design process of a convective cooled turbine. A cooling model was applied in the through flow calculations to predict the coolant requirements, as well as a one-dimensional mixing model to evaluate some key parameters such as pressure losses, deviation angles and velocity triangles because of the injection cooling air. Numerical simulations were performed for verification of the method and investigation on conjugate heat transfer within the blades. By comparing these two calculations, it is shown that the through flow calculation method is a useful tool for the blade design of convective cooled turbines because of its simplicity and flexibility.

Off-Design Performance Investigation of a Low Calorific Value Gas Fired Generic-Type Single-Shaft Gas Turbine

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Raik C. Orbay ◽  
Magnus Genrup ◽  
Pontus Eriksson ◽  
Jens Klingmann
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Calorific Value ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Flammability Limits ◽  
Generic Type ◽  
Wobbe Index ◽  
The Impact

When low calorific value gases are fired, the performance and stability of gas turbines may deteriorate due to a large amount of inertballast and changes in working fluid properties. Since it is rather rare to have custom-built gas turbines for low lower heating value (LHV) operation, the engine will be forced to operate outside its design envelope. This, in turn, poses limitations to usable fuel choices. Typical restraints are decrease in Wobbe index and surge and flutter margins for turbomachinery. In this study, an advanced performance deck has been used to quantify the impact of firing low-LHV gases in a generic-type recuperated as well as unrecuperated gas turbine. A single-shaft gas turbine characterized by a compressor and an expander map is considered. Emphasis has been put on predicting the off-design behavior. The combustor is discussed and related to previous experiments that include investigation of flammability limits, Wobbe index, flame position, etc. The computations show that at constant turbine inlet temperature, the shaft power and the pressure ratio will increase; however, the surge margin will decrease. Possible design changes in the component level are also discussed. Aerodynamic issues (and necessary modifications) that can pose severe limitations on the gas turbine compressor and turbine sections are discussed. Typical methods for axial turbine capacity adjustment are presented and discussed.

Fuel Cell Temperature Control With a Pre-Combustor in SOFC Gas Turbine Hybrids During Load Changes

2016 ◽  
Author(s):  
Valentina Zaccaria ◽  
Zachary Branum ◽  
David Tucker
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Inlet Temperature ◽  
System Efficiency ◽  
Temperature Deviation ◽  
Conservation Of Energy ◽  
The Impact

The use of high temperature fuel cells, such as Solid Oxide Fuel Cells (SOFCs), for power generation, is considered a very efficient and clean solution to conservation of energy resources. Especially when the SOFC is coupled with a gas turbine, the global system efficiency can go beyond 70% on natural gas LHV. However, the durability of the ceramic material and the system operability can be significantly penalized by thermal stresses due to temperature fluctuations and non-even temperature distributions. Thermal management of the cell during load following is therefore very critical. The purpose of this work was to develop and test a pre-combustor model for real-time applications in hardware-based simulations, and to implement a control strategy in order to keep cathode inlet temperature as constant as possible during different operative conditions of the system. The real-time model of the pre-combustor was incorporated into the existing SOFC model and tested in a hybrid system facility, where a physical gas turbine and hardware components were coupled with a cyber-physical fuel cell for flexible, accurate, and cost-reduced simulations. The control of the fuel flow to the pre-combustor was proven to be very effective in maintaining a constant cathode inlet temperature during a step change in fuel cell load. After imposing a 20 A load variation to the fuel cell, the controller managed to keep the temperature deviation from the nominal value below 0.3% (2 K). Temperature gradients along the cell were maintained below 10 K/cm. An efficiency analysis was performed in order to evaluate the impact of the pre-combustor on the overall system efficiency.

Impact of Blade Cooling on Gas Turbine Performance Under Different Operation Conditions and Design Aspects

2015 ◽  
Author(s):  
Maryam Besharati-Givi ◽  
Xianchang Li
Keyword(s):  
Gas Turbine ◽  
Power Output ◽  
Combustion Process ◽  
Inlet Temperature ◽  
Blade Cooling ◽  
Operation Conditions ◽  
Turbine Performance ◽  
Cooling Air ◽  
The Impact ◽  
The Relationship

The increase of power need raises the awareness of producing energy more efficiently. Gas turbine has been one of the important workhorses for power generation. The effects of parameters in design and operation on the power output and efficiency have been extensively studied. It is well-known that the gas turbine inlet temperature (TIT) needs to be high for high efficiency as well as power production. However, there are some material restrictions with high-temperature gas especially for the first row of blades. As a result blade cooling is needed to help balance between the high TIT and the material limitations. The increase of TIT is also limited by restriction of emissions. While the blade cooling can allow a higher TIT and better turbine performance, there is also a penalty since the compressed air used for cooling is removed from the combustion process. Therefore, an optimal cooling flow may exist for the overall efficiency and net power output. In this paper the relationship between the TIT and amount of cooling air is studied. The TIT increase due to blade cooling is considered as a function of cooling air flow as well as cooling effectiveness. In another word, the increase of the TIT is limited while the cooling air can be increased continuously. Based on the relationship proposed the impact of blade cooling on the gas turbine performance is investigated. Compared to the simple cycle case without cooling, the blade cooling can increase the efficiency from 28.8 to 34.0% and the net power from 105 to 208 MW. Cases with different operation conditions such as pressure ratios as well as design aspects with regeneration are considered. Aspen plus software is used to simulate the cycles.

The Impact of Atmospheric Conditions on Gas Turbine Performance

1990 ◽  
Vol 112 (4) ◽  
pp. 590-596 ◽  
Author(s):  
A. A. El Hadik
Keyword(s):  
Relative Humidity ◽  
Ambient Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Arabian Gulf ◽  
Inlet Temperature ◽  
Atmospheric Conditions ◽  
Design Factor ◽  
Turbine Performance ◽  
The Impact

In a hot summer climate, as in Kuwait and other Arabian Gulf countries, the performance of a gas turbine deteriorates drastically during the high-temperature hours (up to 60°C in Kuwait). Power demand is the highest at these times. This necessitates an increase in installed gas turbine capacities to balance this deterioration. Gas turbines users are becoming aware of this problem as they depend more on gas turbines to satisfy their power needs and process heat for desalination due to the recent technical and economical development of gas turbines. This paper is devoted to studying the impact of atmospheric conditions, such as ambient temperature, pressure, and relative humidity on gas turbine performance. The reason for considering air pressures different from standard atmospheric pressure at the compressor inlet is the variation of this pressure with altitude. The results of this study can be generalized to include the cases of flights at high altitudes. A fully interactive computer program based on the derived governing equations is developed. The effects of typical variations of atmospheric conditions on power output and efficiency are considered. These include ambient temperature (range from −20 to 60°C), altitude (range from zero to 2000 m above sea level), and relative humidity (range from zero to 100 percent). The thermal efficiency and specific net work of a gas turbine were calculated at different values of maximum turbine inlet temperature (TIT) and variable environmental conditions. The value of TIT is a design factor that depends on the material specifications and the fuel/air ratio. Typical operating values of TIT in modern gas turbines were chosen for this study: 1000, 1200, 1400, and 1600 K. Both partial and full loads were considered in the analysis. Finally the calculated results were compared with actual gas turbine data supplied by manufacturers.

Regeneration Analysis Under Different Exhaust Gas Thermal Conditions

1990 ◽  
Vol 112 (3) ◽  
pp. 431-437
Author(s):  
G. Bella ◽  
V. Rocco
Keyword(s):  
Wall Temperature ◽  
Initial Conditions ◽  
Control Volume ◽  
Thermal Conditions ◽  
Soot Oxidation ◽  
Channel Length ◽  
Temperature History ◽  
Inlet Temperature ◽  
Exhaust Gas ◽  
Regeneration Period

A refinement of the honeycomb trap model developed by the authors for analyzing the temperature history of the trap channels during the regeneration period is presented. The first results obtained, shown in previous papers [1, 2], encouraged the authors to improve the model in order to account for the heat transfer not only along the channel length, but also in the radial direction. In order to achieve this objective, a control volume approach was used to simulate the soot regeneration in all contiguous channels along the axial and radial directions of the monolith, and to determine the wall temperature and soot oxidation as a function of time. Different thermodynamic conditions of the exhaust gas at the trap inlet were considered in order to examine the effects of cold regeneration. For the same soot amount accumulated in the trap, the soot burnup time and temperature history depend on the inlet temperature. In addition to varying the gas initial conditions, the effects of the amount of soot collected and its radial distribution in the channels, before the regeneration process takes place, were also considered in order to predict the wall temperature rise and the soot oxidation rate. The results show the temperature peak values and their location inside the trap, and permit estimation of the conditions under which the trap temperature can reach unbearable values.

CCPP Operational Flexibility Extension Below 30% Load Using Reheat Burner Switch-Off Concept

2015 ◽  
Author(s):  
Dirk Therkorn ◽  
Martin Gassner ◽  
Vincent Lonneux ◽  
Mengbin Zhang ◽  
Stefano Bernero
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Fast Response ◽  
Combined Cycle ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Operational Flexibility ◽  
Part Load ◽  
Combustion Technology ◽  
The Impact

Highly competitive and volatile energy markets are currently observed, as resulting from the increased use of intermittent renewable sources. Gas turbine combined cycle power plants (CCPP) owners therefore require reliable, flexible capacity with fast response time to the grid, while being compliant with environmental limitations. In response to these requirements, a new operation concept was developed to extend the operational flexibility by reducing the achievable Minimum Environmental Load (MEL), usually limited by increasing pollutant emissions. The developed concept exploits the unique feature of the GT24/26 sequential combustion architecture, where low part load operation is only limited by CO emissions produced by the reheat (SEV) burners. A significant reduction of CO below the legal limits in the Low Part Load (LPL) range is thereby achieved by individually switching the SEV burners with a new operation concept that allows to reduce load without needing to significantly reduce both local hot gas temperatures and CCPP efficiency. Comprehensive assessments of the impact on operation, emissions and lifetime were performed and accompanied by extensive testing with additional validation instrumentation. This has confirmed moderate temperature spreads in the downstream components, which is a benefit of sequential combustion technology due to the high inlet temperature into the SEV combustor. The following commercial implementation in the field has proven a reduction of MEL down to 26% plant load, corresponding to 18% gas turbine load. The extended operation range is emission compliant and provides frequency response capability at high plant efficiency. The experience accumulated over more than one year of successful commercial operation confirms the potential and reliability of the concept, which the customers are exploiting by regularly operating in the LPL range.

Sign in / Sign up

Export Citation Format

Share Document