scholarly journals Parametric Study of Various Thermodynamic Cycles for the Use of Unconventional Blends

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4656
Author(s):  
Odi Fawwaz Alrebei ◽  
Philip Bowen ◽  
Agustin Valera Medina
Keyword(s):  
Working Conditions ◽  
Parametric Study ◽  
Gas Turbines ◽  
Carbon Capture ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Simple Cycle ◽  
Working Fluid ◽  
Specific Work ◽  
Cycle Efficiency

This paper aims to conduct a parametric study for five gas turbine cycles (namely, simple, heat exchanged, free turbine and simple cycle, evaporative, and humidified) using a CO2-argon-steam-oxyfuel (CARSOXY) mixture as a working fluid to identify their optimal working conditions with respect to cycle efficiency and specific work output. The performance of the five cycles using CARSOXY is estimated for wet and dry compression, and a cycle is suggested for each range of working conditions. The results of this paper are based on MATLAB codes, which have been developed to conduct the cycle analysis for CARSOXY gas turbines, assuming a stoichiometric condition with an equivalence ratio of 1.0. Analyses are based on the higher heating value (HHV) of methane as fuel. This paper also identifies domains of operating conditions for each cycle, where the efficiency of CARSOXY cycles can be increased by up to 12% compared to air-driven cycles. The CARSOXY heat exchanged cycle has the highest efficiency among the other CARSOXY cycles in the compressor pressure ratio domain of 2–3 and 6–10, whereas, at 3–6, the humidified cycle has the highest efficiency. The evaporative cycle has intermediate efficiency values, while the simple cycle and the free turbine-simple cycle have the lowest efficiencies amongst the five cycles. Additionally, a 10% increase in the cycle efficiency can be theoretically achieved by using the newly suggested CARSOXY blend that has the molar fractions of 47% argon, 10% carbon dioxide, 10% H2O, and 33% oxyfuel at low compressor inlet temperatures, thus theoretically enabling the use of carbon capture technologies.

Systems Level Performance Estimations for a Pulse Detonation Combustor Based Hybrid Engine

2008 ◽  
Author(s):  
Venkat E. Tangirala ◽  
Narendra D. Joshi
Keyword(s):  
Gas Turbine ◽  
Compression Ratio ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Entire Range ◽  
Operating Conditions ◽  
Simple Cycle ◽  
Inlet Temperature ◽  
Specific Work ◽  
Pulse Detonation

The Pulse Detonation Combustor (PDC) has recently evoked much interest as a pressure-gain combustor for use in gas turbines. A key application for a Pulse Detonation Engine (PDE) concept has been envisioned as a hybrid power generation engine, which would replace the combustor in a conventional gas turbine with a PDC. Estimations of performance parameters, namely, thermal efficiency (ηth) and specific work (Wnet) are reported for a PDC based hybrid engine for various configurations of the engine. The performance enhancing configurations of the PDC-based hybrid engine, considered in the present study, include simple cycle, intercooling, regeneration and reheat, similar to the configurations for a conventional gas turbine (GT) engine in the literature. The performance estimations for a conventional gas turbine engine and a PDC based hybrid engine are compared for the same operating conditions (such as inlet pressure, inlet temperature, compression ratio, overall equivalence ratio) and for various configurations. The thermal efficiency of an intercooled PDC hybrid engine with regeneration has the highest value for the entire range of turbine pressure ratios, from 1.2 to 40 (corresponding to a compression ratio range of 1 to 30). An intercooled PDC based hybrid engine with reheat produces the highest specific work (Wnet) when compared to all other configurations. Among simple-cycle /regeneration /reheat configurations of a PDC based hybrid engine, ητh for the intercooled PDC based hybrid engines has the highest estimated value (0.47) at a turbine pressure ratio of 30. The intercooled PDC based hybrid engine also produces the highest specific work (Wnet) when compared to simple-cycle/regeneration/reheat hybrid engine configurations over the entire range of turbine pressure ratios.

Gas Properties as a Limit to Gas Turbine Performance

2002 ◽  
Author(s):  
R. C. Wilcock ◽  
J. B. Young ◽  
J. H. Horlock
Keyword(s):  
Gas Turbines ◽  
Industrial Development ◽  
Pressure Ratio ◽  
Cycle Performance ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Cycle Efficiency ◽  
Gas Properties

Although increasing the turbine inlet temperature has traditionally proved the surest way to increase cycle efficiency, recent work suggests that the performance of future gas turbines may be limited by increased cooling flows and losses. Another limiting scenario concerns the effect on cycle performance of real gas properties at high temperatures. Cycle calculations of uncooled gas turbines show that when gas properties are modelled accurately, the variation of cycle efficiency with turbine inlet temperature at constant pressure ratio exhibits a maximum at temperatures well below the stoichiometric limit. Furthermore, the temperature at the maximum decreases with increasing compressor and turbine polytropic efficiency. This behaviour is examined in the context of a two-component model of the working fluid. The dominant influences come from the change of composition of the combustion products with varying air/fuel ratio (particularly the contribution from the water vapour) together with the temperature variation of the specific heat capacity of air. There are implications for future industrial development programmes, particularly in the context of advanced mixed gas-steam cycles.

Thermodynamic Analysis of Part-Flow Cycle Supercritical CO2 Gas Turbines

2008 ◽  
Author(s):  
Motoaki Utamura
Keyword(s):  
Heat Exchanger ◽  
Gas Turbines ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pinch Point ◽  
Regenerative Heat ◽  
Regenerative Heat Exchanger ◽  
Flow Cycle ◽  
Cycle Efficiency

Cycle characteristics of closed gas turbines using super critical carbon dioxide as a working fluid are investigated. It is found an anomalous behavior of physical properties of CO2 at pseudo-critical point may limit heat exchange rate of a regenerative heat exchanger due to the presence of pinch point inside the regenerative heat exchanger. Taking such pinch problem into consideration, the cycle efficiency of Brayton cycle is assessed. Its value is found limited to 39% degraded by 8% compared with the case without the pinch present inside. As an alternative a part flow cycle is investigated and its operable range has been identified. It is revealed that the part flow cycle is effective to recover heat transfer capability and may achieve the cycle thermal efficiency of 45% under maximum operating conditions of 20MPa and 800K. Optimal combination of turbine expansion ratio and a part flow ratio is 2.5 and 0.68 respectively. Parametric study is carried out. In neither compressor nor turbine, deteriorated adiabatic efficiency may affect cycle efficiency significantly. However, pressure drop characteristics of heat exchangers govern the cycle efficiency.

Thermodynamic Analysis of Part-Flow Cycle Supercritical CO2 Gas Turbines

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Motoaki Utamura
Keyword(s):  
Heat Exchanger ◽  
Gas Turbines ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pinch Point ◽  
Regenerative Heat ◽  
Regenerative Heat Exchanger ◽  
Flow Cycle ◽  
Cycle Efficiency

Cycle characteristics of closed gas turbines using supercritical carbon dioxide as a working fluid are investigated. It is found that an anomalous behavior of the physical properties of CO2 at the pseudocritical point may limit the heat exchange rate of a regenerative heat exchanger due to the presence of a pinch point inside the regenerative heat exchanger. Taking such a pinch problem into consideration, the cycle efficiency of the Brayton cycle is assessed. Its value is found to be limited to 39% degraded by 8% compared with the case without the pinch present inside. As an alternative, a part-flow cycle is investigated and its operable range has been identified. It is revealed that the part-flow cycle is effective to recover heat transfer capability and may achieve the cycle thermal efficiency of 45% under maximum operating conditions of 20 MPa and 800 K. Optimal combination of turbine expansion ratio and a part-flow ratio is 2.5 and 0.68, respectively. Parametric study is carried out. In neither compressor nor turbine, deteriorated adiabatic efficiency may affect cycle efficiency significantly. However, pressure drop characteristics of heat exchangers govern the cycle efficiency.

scholarly journals Performance Optimization of Closed Cycle Gas Turbines

1984 ◽  
Author(s):  
W. Hilary Lee
Keyword(s):  
Performance Optimization ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Performance Model ◽  
Specific Work ◽  
Closed Cycle ◽  
Temperature Ratio ◽  
Working Media ◽  
Cycle Efficiency ◽  
Cycle Temperature

Criteria for optimal cycle pressure ratio with respect to maximum cycle efficiency and maximum net specific work as functions of cycle temperature ratio were developed based on a non-dimensionalized performance model for closed cycle gas turbines. The effects of total specific pressure drop, the component efficiencies, and cycle working media properties on the optimal pressure ratio are discussed.

scholarly journals Large Eddy Simulations of Strongly Non-Ideal Compressible Flows through a Transonic Cascade

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 772
Author(s):  
Jean-Christophe Hoarau ◽  
Paola Cinnella ◽  
Xavier Gloerfelt
Keyword(s):  
Compressible Flows ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Working Fluid ◽  
Viscous Effects ◽  
Large Eddy

Transonic flows of a molecularly complex organic fluid through a stator cascade were investigated by means of large eddy simulations (LESs). The selected configuration was considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non-ideal gas effects. A heavy fluorocarbon, perhydrophenanthrene (PP11), was selected as the working fluid to exacerbate deviations from the ideal flow behavior. The LESs were carried out at various operating conditions (pressure ratio and total conditions at inlet), and their influence on compressibility and viscous effects is discussed. The complex thermodynamic behavior of the fluid generates highly non-ideal shock systems at the blade trailing edge. These are shown to undergo complex interactions with the transitional viscous boundary layers and wakes, with an impact on the loss mechanisms and predicted loss coefficients compared to lower-fidelity models relying on the Reynolds-averaged Navier–Stokes (RANS) equations.

scholarly journals Industrial Gas Turbine Uprates: Tips, Tricks and Traps

1997 ◽  
Author(s):  
T. L. Ragland
Keyword(s):  
Gas Turbine ◽  
Output Power ◽  
Gas Turbines ◽  
Customer Value ◽  
Low Cost ◽  
Pressure Ratio ◽  
Original Design ◽  
Advantages And Disadvantages ◽  
Industrial Gas Turbine ◽  
Cycle Efficiency

After industrial gas turbines have been in production for some amount of time, there is often an opportunity to improve or “uprate” the engine’s output power or cycle efficiency or both. In most cases, the manufacturer would like to provide these uprates without compromising the proven reliability and durability of the product. Further, the manufacturer would like the development of this “Uprate” to be low cost, low risk and result in an improvement in “customer value” over that of the original design. This paper describes several options available for enhancing the performance of an existing industrial gas turbine engine and discusses the implications for each option. Advantages and disadvantages of each option are given along with considerations that should be taken into account in selecting one option over another. Specific options discussed include dimensional scaling, improving component efficiencies, increasing massflow, compressor zero staging, increasing firing temperature (thermal uprate), adding a recuperator, increasing cycle pressure ratio, and converting to a single shaft design. The implications on output power, cycle efficiency, off-design performance engine life or time between overhaul (TBO), engine cost, development time and cost, auxiliary requirements and product support issues are discussed. Several examples are provided where these options have been successfully implemented in industrial gas turbine engines.

Optimisation of CO Turndown for an Axially Staged Gas Turbine Combustor

2020 ◽  
Author(s):  
Jacob E. Rivera ◽  
Robert L. Gordon ◽  
Mohsen Talei ◽  
Gilles Bourque
Keyword(s):  
Residence Time ◽  
Parametric Study ◽  
Gas Turbines ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Independent Effect ◽  
Inlet Temperature ◽  
Operating Characteristics ◽  
Two Stage ◽  
The Impact

Abstract This paper reports on an optimisation study of the CO turndown behaviour of an axially staged combustor, in the context of industrial gas turbines (GT). The aim of this work is to assess the optimally achievable CO turndown behaviour limit given system and operating characteristics, without considering flow-induced behaviours such as mixing quality and flame spatial characteristics. To that end, chemical reactor network modelling is used to investigate the impact of various system and operating conditions on the exhaust CO emissions of each combustion stage, as well as at the combustor exit. Different combustor residence time combinations are explored to determine their contribution to the exhaust CO emissions. The two-stage combustor modelled in this study consists of a primary (Py) and a secondary (Sy) combustion stage, followed by a discharge nozzle (DN), which distributes the exhaust to the turbines. The Py is modelled using a freely propagating flame (FPF), with the exhaust gas extracted downstream of the flame front at a specific location corresponding to a specified residence time (tr). These exhaust gases are then mixed and combusted with fresh gases in the Sy, modelled by a perfectly stirred reactor (PSR) operating within a set tr. These combined gases then flow into the DN, which is modelled by a plug flow reactor (PFR) that cools the gas to varying combustor exit temperatures within a constrained tr. Together, these form a simplified CRN model of a two-stage, dry-low emissions (DLE) combustion system. Using this CRN model, the impact of the tr distribution between the Py, Sy and DN is explored. A parametric study is conducted to determine how inlet pressure (Pin), inlet temperature (Tin), equivalence ratio (ϕ) and Py-Sy fuel split (FS), individually impact indicative CO turndown behaviour. Their coupling throughout engine load is then investigated using a model combustor, and its effect on CO turndown is explored. Thus, this aims to deduce the fundamental, chemically-driven parameters considered to be most important for identifying the optimal CO turndown of GT combustors. In this work, a parametric study and a model combustor study are presented. The parametric study consists of changing a single parameter at a time, to observe the independent effect of this change and determine its contribution to CO turndown behaviour. The model combustor study uses the same CRN, and varies the parameters simultaneously to mimic their change as an engine moves through its steady-state power curve. The latter study thus elucidates the difference in CO turndown behaviour when all operating conditions are coupled, as they are in practical engines. The results of this study aim to demonstrate the parameters that are key for optimising and improving CO turndown.

A Nitrogen Oxides Emission Prediction Model for Gas Turbines Based on Interpretable Multilayer Perceptron Neural Networks

2020 ◽  
Author(s):  
Dawen Huang ◽  
Shanhua Tang ◽  
Dengji Zhou
Keyword(s):  
Neural Networks ◽  
Nitrogen Oxides ◽  
Prediction Model ◽  
Working Conditions ◽  
Gas Turbines ◽  
Middle Layer ◽  
Operating Conditions ◽  
Nox Emission ◽  
Outlet Temperature ◽  
Output Layer

Abstract Gas turbines, an important energy conversion equipment, produce Nitrogen Oxides (NOx) emissions, endangering human health and forming air pollution. With the increasingly stringent NOx emission standards, it is more significant to ascertain NOx emission characteristics to reduce pollutant emissions. Establishing an emission prediction model is an effective way for real-time and accurate monitoring of the NOx discharge amount. Based on the multi-layer perceptron neural networks, an interpretable emission prediction model with a monitorable middle layer is designed to monitor NOx emission by taking the ambient parameters and boundary parameters as the network inputs. The outlet temperature of the compressor is selected as the monitorable measuring parameters of the middle layer. The emission prediction model is trained by historical operation data under different working conditions. According to the errors between the predicted values and measured values of the middle layer and output layer, the weights of the emission prediction model are optimized by the back-propagation algorithm, and the optimal NOx emission prediction model is established for gas turbines under the various working conditions. Furthermore, the mechanism of predicting NOx emission value is explained based on known parameter influence laws between the input layer, middle layer and output layer, which helps to reveal the main measurement parameters affecting NOx emission value, adjust the model parameters and obtain more accurate prediction results. Compared with the traditional emission monitoring methods, the emission prediction model has higher accuracy and faster calculation efficiency and can obtain believable NOx emission prediction results for various operating conditions of gas turbines.

Correlations Hidden in Compressor Maps

2011 ◽  
Author(s):  
Joachim Kurzke
Keyword(s):  
High Speed ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Operating Conditions ◽  
Specific Work ◽  
Gas Generator ◽  
High Pressure Ratio ◽  
Map Adaptation ◽  
Physical Phenomena ◽  
Corrected Flow

Realistic compressor maps are the key to high quality gas turbine performance calculations. When modeling the performance of an existing engine then these maps are usually not known and must be approximated by adapting maps from literature to either measured data or to other available information. There are many publications describing map adaptation processes, simple ones and more sophisticated physically based scaling rules. There are also reports about using statistics, genetic algorithms, neural networks and even morphing techniques for re-engineering compressor maps. This type of methods does not consider the laws of physics and consequently the generated maps are valid at best in the region in which they have been calibrated. This region is frequently very narrow, especially in case of gas generator compressors which run in steady state always on a single operating line. This paper describes which physical phenomena influence the shape of speed and efficiency lines in compressor maps. For machines operating at comparatively low speeds (so that the flow into each stage is subsonic), there is usually considerable range between choke and stall corrected flow. As the speed of the machine is increased the range narrows. For high-speed stages with supersonic relative flow into the rotor the efficiency maximum is where the speed line turns over from vertical to lower than maximum corrected flow. At this operating condition the shock is about to detach from the leading edge of the blades. The flow at a certain speed can also be limited by choking in the compressor exit guide vanes. For high pressure ratio single stage centrifugal compressors this is a normal case, but it can also happen with low pressure ratio multistage boosters of turbofan engines, for example. If the compressor chokes at the exit, then the specific work remains constant along the speed line while the overall pressure ratio varies and that generates a very specific shape of the efficiency contour lines in the map. Also in other parts of the map, the efficiency varies along speed lines in a systematic manner. Peculiar shapes of specific work and corrected torque lines can reveal physically impossibilities that are difficult to see in the standard compressor map pictures. Compressor maps generated without considering the inherent physical phenomena can easily result in misleading performance calculations if used at operating conditions outside of the region where they have been calibrated. Whatever map adaptation method is used: the maps created in such a way should be checked thoroughly for violations of the underlying laws of compressor physics.

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