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.

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.

scholarly journals Improved High-Pressure, High-Temperature (HPHT) Materials Qualification using Dissolved H<sub>2</sub>S Concentration as the Sour Service Scalable Metric

CORROSION ◽  
10.5006/3867 ◽  
2021 ◽  
Author(s):  
BRENT SHERAR ◽  
Peter Ellis II ◽  
Jing Ning
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Gas Phase ◽  
Stress Cracking ◽  
High Pressure High Temperature ◽  
Sulfide Stress ◽  
Sulfide Stress Cracking ◽  
Sour Service ◽  
The Relationship ◽  
Severity Parameter

Gas phase H&lt;sub&gt;2&lt;/sub&gt;S partial pressure (P&lt;sub&gt;H2S&lt;/sub&gt;) is associated with sulfide stress cracking (SSC) and is routinely used as the ‘scalable’ parameter to qualify materials for high-pressure, high-temperature (HPHT) wells. Candidate materials for HPHT wells routinely require ANSI/NACE MR0175/ISO 15156 compliance because a few mole ppm of H&lt;sub&gt;2&lt;/sub&gt;S at high pressure may place the well beyond the 0.05 psia (0.3 kPa) sour service threshold. P&lt;sub&gt;H2S&lt;/sub&gt; has been accepted historically as the scalable sour severity parameter. However, as the total pressure increases, the relationship between P&lt;sub&gt;H2S&lt;/sub&gt; and the dissolved H&lt;sub&gt;2&lt;/sub&gt;S concentration becomes non-linear. This limits the robustness of P&lt;sub&gt;H2S&lt;/sub&gt; as the sour severity metric. Thus, ISO 15156-1:2020 now permits the use of H2S fugacity (f&lt;sub&gt;H2S&lt;/sub&gt;), H&lt;sub&gt;2&lt;/sub&gt;S activity (a&lt;sub&gt;H2S&lt;/sub&gt;), and H&lt;sub&gt;2&lt;/sub&gt;S aqueous concentration (C&lt;sub&gt;H2S&lt;/sub&gt;) as alternatives for sour testing. This recent revision is based on evidence that f&lt;sub&gt;H2S&lt;/sub&gt; and C&lt;sub&gt;H2S&lt;/sub&gt; each provide better correlations to SSC at elevated total pressures than P&lt;sub&gt;H2S&lt;/sub&gt;. This paper will address the merits and challenges of using f&lt;sub&gt;H2S&lt;/sub&gt; or C&lt;sub&gt;H2S&lt;/sub&gt; to define sour severity: We argue that C&lt;sub&gt;H2S&lt;/sub&gt; is a practical, experimentally verifiable approach, which can be used to validate ionic-equation of state (EOS) frameworks used to characterize mildly sour HPHT environments.

scholarly journals Vaporizable endoskeletal droplets via tunable interfacial melting transitions

2020 ◽  
Vol 6 (14) ◽  
pp. eaaz7188 ◽  
Author(s):  
Gazendra Shakya ◽  
Samuel E. Hoff ◽  
Shiyi Wang ◽  
Hendrik Heinz ◽  
Xiaoyun Ding ◽  
...  
Keyword(s):  
Gas Phase ◽  
Liquid Core ◽  
Secondary Phase ◽  
Intermolecular Forces ◽  
Droplet Evaporation ◽  
Melting Transition ◽  
Emulsion Droplet ◽  
Droplet Vaporization ◽  
Liquid Emulsion ◽  
Droplet Phase

Liquid emulsion droplet evaporation is of importance for various sensing and imaging applications. The liquid-to-gas phase transformation is typically triggered thermally or acoustically by low–boiling point liquids, or by inclusion of solid structures that pin the vapor/liquid contact line to facilitate heterogeneous nucleation. However, these approaches lack precise tunability in vaporization behavior. Here, we describe a previously unused approach to control vaporization behavior through an endoskeleton that can melt and blend into the liquid core to either enhance or disrupt cohesive intermolecular forces. This effect is demonstrated using perfluoropentane (C5F12) droplets encapsulating a fluorocarbon (FC) or hydrocarbon (HC) endoskeleton. FC skeletons inhibit vaporization, whereas HC skeletons trigger vaporization near the rotator melting transition. Our findings highlight the importance of skeletal interfacial mixing for initiating droplet vaporization. Tuning molecular interactions between the endoskeleton and droplet phase is generalizable for achieving emulsion or other secondary phase transitions, in emulsions.

scholarly journals Experimental and Theoretical Study of Droplet Vaporization in a High Pressure Environment

1997 ◽  
Author(s):  
Jörg Stengele ◽  
Michael Willmann ◽  
Sigmar Wittig
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Droplet Diameter ◽  
Droplet Evaporation ◽  
Pressure Effects ◽  
Evaporation Process ◽  
Temperature Model ◽  
Uniform Temperature ◽  
Continuous Increase ◽  
Limit Model

Due to the continuous increase of pressure ratios in modern gas turbine engines the understanding of high pressure effects on the droplet evaporation process gained significant importance. The precise prediction of the evaporation time and the movement of the droplets is crucial for optimum design and performance of modern gas turbine combustion chambers. Numerous experimental and numerical investigations have been done already in order to understand the evaporation process of droplets in high pressure environments. But until now, all high pressure experiments were carried out with droplets attached to a thin fiber resulting in the impairment of the droplet evaporation process due to the suspension unit. In the present study, a new experimental set up is introduced where the evaporation of free falling droplets is investigated. Monodisperse droplets are generated in the upper part of the test rig and fall through the stagnant high pressure gas inside the pressure chamber. Due to the relative velocity between droplet and gas, convective effects have to be considered in this study which are taken into account by experimental correlations. The droplet diameter and the droplet velocity are measured simultaneously by means of video technique and a stroboscope lamp. Detailed measurements with heptane droplets are presented for different pressures (p = 20 bar, 30 bar and 40 bar), gas temperatures (T = 550 K and 650 K) and initial diameters (d0 = 680 μm, 780 μm and 840 μm). The experiments were carried out with single component droplets. The experimental results are compared with numerical calculations. For this a theoretical model was developed based on the Conduction Limit model and the Uniform Temperature model. Good agreement for all conditions investigated is observed when using the Conduction Limit model. The Uniform Temperature model predicts incorrectly the evaporation process of the droplet.

scholarly journals Experimental and Numerical Study on Pressure Distribution of 90° Elbow for Flow Measurement

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Beibei Feng ◽  
Shiming Wang ◽  
Shengqiang Li ◽  
Xingtuan Yang ◽  
Shengyao Jiang
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Pressure Distribution ◽  
Flow Measurement ◽  
Static Pressure ◽  
Numerical Study ◽  
Numerical Approach ◽  
Test System ◽  
Numerical Results ◽  
Helium Gas

Numerical simulation is performed to investigate the pressure distribution of helium gas under high pressure and high temperature for 10 MW High Temperature Gas-Cooled Reactor (HTGR-10). Experimental studies are first conducted on a self-built test system to investigate the static pressure distribution of a 90° elbow and validate the credibility of the computational approach. The 90° elbow is designed and manufactured geometrically the same as HTGR-10. Based on the experimental data, comparison of static pressure of inner wall and outer wall of 90° elbow with numerical results is carried out to verify the numerical approach. With high agreement between experimental results and numerical results of water flowing through 90° elbow, flow characteristics of helium gas under high pressure and high temperature are investigated on the confirmed numerical approach for flow measurement. And wall pressure distribution of eight cross sections of 90° elbow is given in detail to represent the entire region of the elbow.

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