scholarly journals Effects of Variable Liquid Properties on Multicomponent Droplet Vaporization

1992 ◽  
Author(s):  
R. Kneer ◽  
M. Schneider ◽  
B. Noll ◽  
S. Wittig
Keyword(s):  
Volatile Component ◽  
Lewis Number ◽  
Single Component ◽  
Vapor Concentration ◽  
Large Temperature ◽  
Diffusion Limit ◽  
Gas Temperature ◽  
Droplet Vaporization ◽  
Limit Model ◽  
Vaporization Process

A multicomponent droplet vaporization model, the Diffusion-Limit Model, is modified to account for the variation of liquid properties due to large temperature gradients as well as considerable concentration gradients within the droplet. The effects on the vaporization behavior are analysed for an isolated bicomponent droplet consisting of heptane and dodecane. The results are presented for both moderate and high gas temperatures excluding combustion. During the vaporization process the liquid phase properties vary considerably. For example, the Lewis number changes approximately one order of magnitude. The mass ratio of the liquid components seems to be rather sensitive to the variation of thermophysical property values, especially during the second half of the droplet lifetime, where about 50% of the droplet mass will still evaporate. The gas phase behavior is less affected by the use of constant liquid properties. For both gas temperature levels tested it was found that single component models cannot describe satisfactorily the whole vaporization process of multicomponent droplets. With regard to ignition the sharp rise of the vapor concentration in the beginning of the droplet vaporization is important. This behavior is caused by the more volatile component and cannot be achieved by the single component substitute.

Effects of Variable Liquid Properties on Multicomponent Droplet Vaporization

1993 ◽  
Vol 115 (3) ◽  
pp. 467-472 ◽  
Author(s):  
R. Kneer ◽  
M. Schneider ◽  
B. Noll ◽  
S. Wittig
Keyword(s):  
Volatile Component ◽  
Lewis Number ◽  
Single Component ◽  
Vapor Concentration ◽  
Large Temperature ◽  
Diffusion Limit ◽  
Gas Temperature ◽  
Droplet Vaporization ◽  
Limit Model ◽  
Vaporization Process

A multicomponent droplet vaporization model, the Diffusion-Limit Model, is modified to account for the variation of liquid properties due to large temperature gradients as well as considerable concentration gradients within the droplet. The effects on the vaporization behavior are analyzed for an isolated biocomponent droplet consisting of heptane and dodecane. The results are presented for both moderate and high gas temperatures excluding combustion. During the vaporization process the liquid phase properties vary considerably. For example, the Lewis number changes by approximately one order of magnitude. The mass ratio of the liquid components seems to be rather sensitive to the variation of thermophysical property values, especially during the second half of the droplet lifetime, where about 50 percent of the droplet mass will still evaporate. The gas phase behavior is less affected by the use of constant liquid properties. For both gas temperature levels tested it was found that single component models cannot describe satisfactorily the whole vaporization process of multicomponent droplets. With regard to ignition the sharp rise of the vapor concentration in the beginning of the droplet vaporization is important. This behavior is caused by the more volatile component and cannot be achieved by the single component substitute.

Numerical Study of Bicomponent Droplet Vaporization in a High Pressure Environment

1996 ◽  
Author(s):  
J. Stengele ◽  
H.-J. Bauer ◽  
S. Wittig
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Gas Phase ◽  
Numerical Study ◽  
Droplet Evaporation ◽  
Single Component ◽  
Vapor Concentration ◽  
Diffusion Limit ◽  
Evaporation Process ◽  
Droplet Vaporization

The understanding of multicomponent droplet evaporation in a high pressure and high temperature gas is of great importance for the design of modern gas turbine combustors, since the different volatilities of the droplet components affect strongly the vapor concentration and, therefore, the ignition and combustion process in the gas phase. Plenty of experimental and numerical research is already done to understand the droplet evaporation process. Until now, most numerical studies were carried out for single component droplets, but there is still lack of knowledge concerning evaporation of multicomponent droplets under supercritical pressures. In the study presented, the Diffusion Limit Model is applied to predict bicomponent droplet vaporization. The calculations are carried out for a stagnant droplet consisting of heptane and dodecane evaporating in a stagnant high pressure and high temperature nitrogen environment. Different temperature and pressure levels are analyzed in order to characterize their influence on the vaporization behavior. The model employed is fully transient in the liquid and the gas phase. It accounts for real gas effects, ambient gas solubility in the liquid phase, high pressure phase equilibrium and variable properties in the droplet and surrounding gas. It is found that for high gas temperatures (T = 2000 K) the evaporation time of the bicomponent droplet decreases with higher pressures, whereas for moderate gas temperatures (T = 800 K) the lifetime of the droplet first increases and then decreases when elevating the pressure. This is comparable to numerical results conducted with single component droplets. Generally, the droplet temperature increases with higher pressures reaching finally the critical mixture temperature of the fuel components. The numerical study shows also that the same tendencies of vapor concentration at the droplet surface and vapor mass flow are observed for different pressures. Additionally, there is almost no influence of the ambient pressure on fuel composition inside the droplet during the evaporation process.

Multicomponent and High-Pressure Effects on Droplet Vaporization

2002 ◽  
Vol 124 (2) ◽  
pp. 248-255 ◽  
Author(s):  
S. K. Aggarwal ◽  
H. C. Mongia
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Single Component ◽  
Pressure Effects ◽  
Diffusion Limit ◽  
Fuel Droplet ◽  
Droplet Model ◽  
Droplet Vaporization ◽  
Wide Range ◽  
High Pressure Effects

This paper deals with the multicomponent nature of gas turbine fuels under high-pressure conditions. The study is motivated by the consideration that the droplet submodels that are currently employed in spray codes for predicting gas turbine combustor flows do not adequately incorporate the multicomponent fuel and high-pressure effects. The quasi-steady multicomponent droplet model has been employed to investigate conditions under which the vaporization behavior of a multicomponent fuel droplet can be represented by a surrogate pure fuel droplet. The physical system considered is that of a multicomponent fuel droplet undergoing quasi-steady vaporization in an environment characterized by its temperature, pressure, and composition. Using different vaporization models, such as infinite-diffusion and diffusion-limit models, the predicted vaporization history and other relevant properties of a bicomponent droplet are compared with those of a surrogate single-component fuel droplet over a range of parameters relevant to gas turbine combustors. Results indicate that for moderate and high-power operation, a suitably selected single-component (50 percent boiling point) fuel can be used to represent the vaporization behavior of a bicomponent fuel, provided one employs the diffusion-limit or effective-diffusivity model. Simulation of the bicomponent fuel by a surrogate fuel becomes increasingly better at higher pressures. In fact, the droplet vaporization behavior at higher pressures is observed to be more sensitive to droplet heating models rather than to liquid fuel composition. This can be attributed to increase in the droplet heatup time and reduction in the volatility differential between the constituent fuels at higher pressures. For ignition, lean blowout and idle operations, characterized by low pressure and temperature ambient, the multicomponent fuel evaporation cannot be simulated by a single-component fuel. The validity of a quasi-steady high-pressure droplet vaporization model has also been examined. The model includes the nonideal gas behavior, liquid-phase solubility of gases, and variable thermo-transport properties including their dependence on pressure. Predictions of the high-pressure droplet model show good agreement with the available experimental data over a wide range of pressures, implying that quasi-steady vaporization model can be used at pressures up to the fuel critical pressure.

Numerical investigation of non-uniform flow in twin-silo combustors and impact on axial turbine stage performance

2021 ◽  
pp. 095765092199394
Author(s):  
Hafiz M Hassan ◽  
Adeel Javed ◽  
Asif H Khoja ◽  
Majid Ali ◽  
Muhammad B Sajid
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Internal Flow ◽  
Large Temperature ◽  
Clear Understanding ◽  
Gas Temperature ◽  
Turbine Stage ◽  
Flow Angle ◽  
Axial Turbine ◽  
Stage Performance

A clear understanding of the flow characteristics in the older generation of industrial gas turbines operating with silo combustors is important for potential upgrades. Non-uniformities in the form of circumferential and radial variations in internal flow properties can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the advent of non-uniformities from twin-silo combustors and their propagation through a single axial turbine stage of the Siemens v94.2 industrial gas turbine. Results indicate the formation of strong vortical structures alongside large temperature, pressure, velocity, and flow angle deviations that are mostly located in the top and bottom sections of the turbine stage caused by the excessive flow turning in the upstream tandem silo combustors. A favorable validation of the simulated exhaust gas temperature (EGT) profile is also achieved via comparison with the measured data. A drop in isentropic efficiency and power output equivalent to 2.28% points and 2.1 MW, respectively is observed at baseload compared to an ideal straight hot gas path reference case. Furthermore, the analysis of internal flow topography identifies the underperforming turbine blading due to the upstream non-uniformities. The findings not only have implications for the turbine aerothermodynamic design, but also the combustor layout from a repowering perspective.

Modeling of Gas Turbine Fuel Nozzle Spray

1997 ◽  
Vol 119 (1) ◽  
pp. 34-44 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the airassist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The presents investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

Modeling of Gas Turbine Fuel Nozzle Spray

1995 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A 2-D fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the air-assist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near critical evaporation. The present investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

Axisymmetric Unsteady Droplet Vaporization and Gas Temperature Distribution

1989 ◽  
Vol 111 (2) ◽  
pp. 487-494 ◽  
Author(s):  
S. K. Lee ◽  
T. J. Chung
Keyword(s):  
Gas Phase ◽  
Gas Temperature ◽  
The Finite Element Method ◽  
Grid Spacing ◽  
Droplet Model ◽  
Time Step ◽  
Two Phase ◽  
Droplet Vaporization ◽  
Droplet Liquid ◽  
Injection Pulse

Droplet vaporization and temperature distributions of axisymmetric unsteady sprays are investigated. The so-called discrete droplet model of two-phase flows, often known as the Eulerian–Lagrangian method, is used. Calculations are carried out with Eulerian coordinates using finite elements for the gas phase and the method of characteristics using the second-order Runge–Kutta scheme for the droplet liquid phase. The sensitivity of the numerical results to changes in time step, injection pulse time, grid spacing, and number of droplet characteristics is examined. Through a simple example, it is shown that applications of the finite element method to more complicated problems appear to be promising.

scholarly journals Fault Detection for Gas Turbine Hot Components Based on a Convolutional Neural Network

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2149 ◽  
Author(s):  
Jiao Liu ◽  
Jinfu Liu ◽  
Daren Yu ◽  
Myeongsu Kang ◽  
Weizhong Yan ◽  
...  
Keyword(s):  
Neural Network ◽  
Fault Detection ◽  
Convolutional Neural Network ◽  
Gas Turbine ◽  
Detection Sensitivity ◽  
Large Temperature ◽  
Gas Temperature ◽  
Ambient Conditions ◽  
Real World Data ◽  
The Impact

Gas turbine hot component failures often cause catastrophic consequences. Fault detection can improve the availability and economy of hot components. The exhaust gas temperature (EGT) profile is usually used to monitor the performance of the hot components. The EGT profile is uniform when the hot component is healthy, whereas hot component faults lead to large temperature differences between different EGT values. The EGT profile swirl under different operating and ambient conditions also cause temperature differences. Therefore, the influence of EGT profile swirl on EGT values must be eliminated. To improve the detection sensitivity, this paper develops a fault detection method for hot components based on a convolutional neural network (CNN). This paper demonstrates that a CNN can extract the information between adjacent EGT values and consider the impact of the EGT profile swirl. This paper reveals, in principle, that a CNN is a viable solution for dealing with fault detection for hot components. Based on the distribution characteristics of EGT thermocouples, the circular padding method is developed in the CNN. The sensitivity of the developed method is verified by real-world data. Moreover, the developed method is visualized in detail. The visualization results reveal that the CNN effectively considers the influence of the EGT profile swirl.

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