scholarly journals Brush Seal Leakage Performance With Gaseous Working Fluids at Static and Low Rotor Speed Conditions

1993 ◽  
Vol 115 (2) ◽  
pp. 397-403 ◽  
Author(s):  
J. A. Carlile ◽  
R. C. Hendricks ◽  
D. A. Yoder
Keyword(s):  
Carbon Dioxide ◽  
Pressure Drop ◽  
State Theory ◽  
Operating Conditions ◽  
Rotor Speed ◽  
Working Fluids ◽  
Brush Seal ◽  
Annular Seal

The leakage performance of a brush seal with gaseous working fluids at static and low rotor speed conditions was investigated. This report includes the leakage results for air, helium, and carbon dioxide at several bristle/rotor interferences. In addition, the effects of packing a lubricant into the bristles and also of reversing the pressure drop across the seal were investigated. Results were compared to that of an annular seal at similar operating conditions. In order to generalize the results, they were correlated using corresponding state theory. The brush seal tested had a bore diameter of 3.792 cm (1.4930 in.), a fence height of 0.0635 cm (0.025 in.), and 1800 bristles/cm-circumference (4500 bristles/in.-circumference). Various bristle/rotor radial interferences were achieved by using a tapered rotor. The brush seal reduced the leakage in comparison with the annular seal, up to 9.5 times. Reversing the pressure drop across the brush seal produced leakage rates approximately the same as that of the annular seal. Addition of a lubricant reduced the leakage by 2.5 times when compared to a nonlubricated brush seal. The air and carbon dioxide data were successfully correlated using the corresponding state theory. However, the helium data followed a different curve from the air and carbon dioxide data.

scholarly journals Brush Seal Leakage Performance With Gaseous Working Fluids at Static and Low Rotor Speed Conditions

1992 ◽  
Author(s):  
Julie A. Carlile ◽  
Robert C. Hendricks ◽  
Dennis A. Yoder
Keyword(s):  
Carbon Dioxide ◽  
Pressure Drop ◽  
State Theory ◽  
Operating Conditions ◽  
Rotor Speed ◽  
Working Fluids ◽  
Brush Seal ◽  
Annular Seal

The leakage performance of a brush seal with gaseous working fluids at static and low rotor speed conditions was investigated. This report includes the leakage results for air, helium, and carbon dioxide at several bristle/rotor interferences. In addition, the effects of packing a lubricant into the bristles and also of reversing the pressure drop across the seal were investigated. Results were compared to that of an annular seal at similar operating conditions. In order to generalize the results, they were correlated using corresponding state theory. The brush seal tested had a bore diameter of 3.792 cm (1.4930 in.), a fence height of 0.0635 cm (0.025 in.), and 1800 bristles/cm-circumference (4500 bristles/in.-circumference). Various bristle/rotor radial interferences were achieved by using a tapered rotor. The brush seal reduced the leakage in comparison to the annular seal, up to 9.5 times. Reversing the pressure drop across the brush seal produced leakage rates approximately the same as that of the annular seal. Addition of a lubricant reduced the leakage by 2.5 times when compared to a non-lubricated brush seal. The air and carbon dioxide data were successfully correlated using corresponding state theory. However, the helium data followed a different curve than the air and carbon dioxide data.

Analysis of Advanced Supercritical Carbon Dioxide Power Cycles With a Bottoming Cycle for Concentrating Solar Power Applications

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Saeb M. Besarati ◽  
D. Yogi Goswami
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Solar Power ◽  
Waste Heat ◽  
Operating Conditions ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Working Fluids ◽  
Supercritical Carbon

A number of studies have been performed to assess the potential of using supercritical carbon dioxide (S-CO2) in closed-loop Brayton cycles for power generation. Different configurations have been examined among which recompression and partial cooling configurations have been found very promising, especially for concentrating solar power (CSP) applications. It has been demonstrated that the S-CO2 Brayton cycle using these configurations is capable of achieving more than 50% efficiency at operating conditions that could be achieved in central receiver tower type CSP systems. Although this efficiency is high, it might be further improved by considering an appropriate bottoming cycle utilizing waste heat from the top S-CO2 Brayton cycle. The organic Rankine cycle (ORC) is one alternative proposed for this purpose; however, its performance is substantially affected by the selection of the working fluid. In this paper, a simple S-CO2 Brayton cycle, a recompression S-CO2 Brayton cycle, and a partial cooling S-CO2 Brayton cycle are first simulated and compared with the available data in the literature. Then, an ORC is added to each configuration for utilizing the waste heat. Different working fluids are examined for the bottoming cycles and the operating conditions are optimized. The combined cycle efficiencies and turbine expansion ratios are compared to find the appropriate working fluids for each configuration. It is also shown that combined recompression-ORC cycle achieves higher efficiency compared with other configurations.

Analysis of Advanced Supercritical Carbon Dioxide Power Cycles With a Bottoming Cycle for Concentrating Solar Power Applications

2013 ◽  
Author(s):  
Saeb M. Besarati ◽  
D. Yogi Goswami
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Solar Power ◽  
Waste Heat ◽  
Operating Conditions ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Working Fluids ◽  
Supercritical Carbon

A number of studies have been performed to assess the potential of using supercritical carbon dioxide (S-CO2) in closed-loop Brayton cycles for power generation. Different configurations have been examined among which recompression and partial cooling configurations have been found very promising, especially for concentrating solar power (CSP) applications. It has been demonstrated that the S-CO2 Brayton cycle using these configurations is capable of achieving more than 50% efficiency at operating conditions that could be achieved in central receiver tower type CSP systems. Although this efficiency is high, it might be further improved by considering an appropriate bottoming cycle utilizing waste heat from the top S-CO2 Brayton cycle. The organic Rankine cycle (ORC) is one alternative proposed for this purpose, however, its performance is substantially affected by the selection of the working fluid. In this paper, a simple S-CO2 Brayton cycle, a recompression S-CO2 Brayton cycle, and a partial cooling S-CO2 Brayton cycle are first simulated and compared with the available data in the literature. Then, an ORC is added to each configuration for utilizing the waste heat. Different working fluids are examined for the bottoming cycles and the operating conditions are optimized. The combined cycle efficiencies and turbine expansion ratios are compared to find the appropriate working fluids for each configuration. It is also shown that combined recompression-ORC cycle achieves higher efficiency compared with other configurations.

Analysis of Thermophysical Properties for Selected Supercritical Fluids

2014 ◽  
Author(s):  
Juan Carlos Jouvin ◽  
Jeffrey Samuel ◽  
Igor Pioro
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Fluids ◽  
Supercritical Water ◽  
Fast Reactor ◽  
Thermophysical Properties ◽  
Power Plants ◽  
Operating Conditions ◽  
Effect Of Temperature ◽  
Working Fluids ◽  
R 134A

Currently, there are six Generation IV reactor systems under development worldwide: 1) Very-High-Temperature Reactor (VHTR); 2) Sodium-cooled Fast Reactor (SFR); 3) SuperCritical Water-cooled Reactor (SCWR), 4) Gas-cooled Fast Reactor (GFR), 5) Lead-cooled Fast Reactor (LFR); and 6) Molten Salt Reactor (MSR). Of these six systems, Canada has decided to pursue the SCWR as its choice for a Generation IV reactor, with some research being conducted on the VHTR. One main objective of SCWRs is to increase the thermal efficiency of current nuclear power plants from the 30–35% range to approximately 45–50%. In order to accomplish this, SCWRs are being designed to operate well above the critical point of water at pressures of 25 MPa and reactor outlet temperatures up to 625°C. These operating conditions also make the SCWR, along with the VHTR and other Generation IV systems, suitable candidates to support thermochemical hydrogen cogeneration. The design and operation of a facility capable of accurately and safely conducting experiments in supercritical water is a very expensive task. In order to facilitate our understanding of supercritical heat-transfer phenomena, modeling fluids such as carbon dioxide, refrigerants, ammonia and helium can be used to complement our knowledge of supercritical fluids. Some of these fluids, namely helium and carbon dioxide, have also been considered as potential working fluids in some special designs of reactors and power cycles. The objective of this paper is to investigate the feasibility of using alternative working fluids such as helium and Refrigerant-134a (R-134a) by comparing the fluid and transport properties with those of water. Operating conditions of SCWRs are scaled into those of the modeling fluid, R-134a, in order to provide proper SCWR-equivalent conditions. The equivalent properties for helium, which is one possible coolant for the VHTR, are also discussed. The thermophysical properties for selected working fluids are obtained from NIST REFPROP software. The results indicate that the thermophysical properties of the fluids undergo significant changes within the critical and pseudocritical regions similar to that of supercritical water. A sensitivity analysis for the effect of temperature on selected thermophysical properties at various supercritical pressures was performed.

Nonlinear Characteristics Analysis of a Rotor-Bearing-Brush Seal System

2018 ◽  
Vol 18 (05) ◽  
pp. 1850063 ◽  
Author(s):  
Yuan Wei ◽  
Zhaobo Chen ◽  
Earl H. Dowell
Keyword(s):  
Periodic Motion ◽  
Nonlinear Dynamic ◽  
Operating Conditions ◽  
Design Parameters ◽  
Force Model ◽  
Rotor Speed ◽  
Nonlinear Characteristics ◽  
Disk Mass ◽  
Brush Seal ◽  
Rotor Bearing

The vibration response and nonlinear dynamic behavior of a rotor-bearing-brush seal system were investigated with a new seal force model of the brush seal. The nonlinear oil–film force model was adopted based on a short bearing assumption. The dimensionless equation of motion was solved using the fourth order Runge–Kutta method. The effects of key parameters including rotor speed, installation spacing of the brush seal, disk eccentricity, disk mass, and journal mass on the nonlinear dynamic characteristics of rotor-bearing-brush seal system were determined and compared under different operating conditions with a bifurcation diagram, time history, axis orbit, poincaré map, frequency spectrum, and spectrum cascade. The results showed that the system response contained various nonlinear phenomena, such as periodic motion, multi-periodic motion, and quasi-periodic motion. The interaction of the rotor speed, installation spacing of the brush seal, disk eccentricity, disk mass, and journal mass could seriously affect the stability and working condition of the system. This study provides a theoretical support for the selection of key design parameters and further understanding of the nonlinear characteristics of rotor-bearing-seal systems with a brush seal.

A Computational Fluid Dynamics Modified Bulk Flow Analysis for Circumferentially Shallow Grooved Liquid Seals

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Luis San Andrés ◽  
Tingcheng Wu ◽  
Hideaki Maeda ◽  
Ono Tomoki
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Friction Factor ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Bulk Flow ◽  
Rotor Speed ◽  
Force Coefficients ◽  
Annular Seal ◽  
Direct Stiffness

In straight-through centrifugal pumps, a grooved seal acts as a balance piston to equilibrate the full pressure rise across the pump. As the groove pattern breaks the development of fluid swirl, this seal type offers lesser leakage and lower cross-coupled stiffnesses than a similar size and clearance annular seal. Bulk-flow models (BFMs) predict expediently the static and dynamic force characteristics of annular seals; however they lack accuracy for grooved seals. Computational fluid dynamics (CFD) methods give more accurate results, but are not computationally efficient. This paper presents a modified BFM to predict the rotordynamic force coefficients of shallow depth, circumferentially grooved liquid seals with an accuracy comparable to a CFD solution but with a simulation time of bulk-flow analyses. The procedure utilizes the results of CFD to evaluate the bulk flow velocity field and the friction factors for a 73 grooves annular seal (depth/clearance dg/Cr = 0.98 and length/diameter L/D = 0.9) operating under various sets of axial pressure drop and rotor speed. In a groove, the flow divides into a jet through the film land and a strong recirculation zone. The penetration angle (α), specifying the streamline separation in the groove cavity, is a function of the operating conditions; an increase in rotor speed or a lower pressure difference increases α. This angle plays a prominent role to evaluate the stator friction factor and has a marked influence on the seal direct stiffness. In the bulk-flow code, the friction factor model (f = nRem) is modified with the CFD extracted penetration angle (α) to account for the flow separation in the groove cavity. The flow rate predicted by the modified bulk-flow code shows good agreement with the measured result (6% difference). A perturbation of the flow field is performed on the bulk-flow equations to evaluate the reaction forces on the rotor surface. Compared to the rotordynamic force coefficients derived from the CFD results, the modified bulk-flow code predicts rotordynamic force coefficients within 10%, except that the cross-coupled damping coefficient is over-predicted up to 14%. An example test seal with a few grooves (L/D = 0.5, dg/Cr = 2.5) serves to further validate the predictions of the modified BFM. Compared to the original bulk-flow analysis, the current method shows a significant improvement in the predicted rotordynamic force coefficients, the direct stiffness and damping coefficients, in particular.

Flow Coefficient Evaluation of Poppet Valves Used in Reciprocating Compressors for LDPE

2008 ◽  
Author(s):  
Enzo Giacomelli ◽  
Massimo Schiavone ◽  
Fabio Manfrone ◽  
Andrea Raggi
Keyword(s):  
Pressure Drop ◽  
Time Pressure ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Operating Life ◽  
High Fatigue ◽  
Strongly Connected ◽  
And Performance ◽  
Poppet Valves

Poppet valves have been used for a long time for very high pressure reciprocating compressors, as for example in the case of Low Density Polyethylene. These applications are very critical because the final pressure can reach 350 MPa and the evaluation of the performance of the machines is strongly connected to the proper operation and performance of the valve itself. The arrangement of cylinders requires generally a certain compactness of valve to withstand high fatigue stresses, but at the same time pressure drop and operating life are very important. In recent years the reliability of the machines has been improving over and over and the customers’ needs are very stringent. Therefore the use of poppet valves has been extended to other cases. In general the mentioned applications are heavy duty services and the simulation of the valves require some coefficients to be used in the differential equations, able to describe the movement of plate/disk or poppet and the flow and related pressure drop through the valves. Such coefficients are often determined in an experimental way in order to have a simulation closer to the real operating conditions. For the flow coefficients it is also possible today to use theoretical programs capable of determining the needed values in a quick and economical way. Some investigations have been carried out to determine the values for certain geometries of poppet valves. The results of the theory have been compared with some experimental tests. The good agreement between the various methods indicates the most suitable procedure to be applied in order to have reliable data. The advantage is evident as the time necessary for the theoretical procedure is faster and less expensive. This is of significant importance at the time of the design and also in case of a need to provide timely technical support for the operating behavior of the valves. Particularly for LDPE, the optimization of all the parameters is strongly necessary. The fatigue stresses of cylinder heads and valve bodies have to match in fact with gas passage turbulence and pressure drop, added to the mechanical behavior of the poppet valve components.

Simultaneous Measuring Method for Both Volumetric Flow Rates of Air-Water Mixture Using a Turbine Flowmeter

1996 ◽  
Vol 118 (1) ◽  
pp. 29-35 ◽  
Author(s):  
K. Minemura ◽  
K. Egashira ◽  
K. Ihara ◽  
H. Furuta ◽  
K. Yamamoto
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Volumetric Flow Rate ◽  
Oil Field ◽  
Liquid Density ◽  
Water Mixture ◽  
Rotor Speed ◽  
Flow Rates ◽  
Field Development ◽  
Turbine Flowmeter

A turbine flowmeter is employed in this study in connection with offshore oil field development, in order to measure simultaneously both the volumetric flow rates of air-water two-phase mixture. Though a conventional turbine flowmeter is generally used to measure the single-phase volumetric flow rate by obtaining the rotational rotor speed, the method proposed additionally reads the pressure drop across the meter. After the pressure drop and rotor speed measured are correlated as functions of the volumetric flow ratio of the air to the whole fluid and the total volumetric flow rate, both the flow rates are iteratively evaluated with the functions on the premise that the liquid density is known. The evaluated flow rates are confirmed to have adequate accuracy, and thus the applicability of the method to oil fields.

Understanding Carbon Dioxide Transfer in Direct Methanol Fuel Cells Using a Pore-Scale Model

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Nathaniel Metzger ◽  
Archana Sekar ◽  
Jun Li ◽  
Xianglin Li
Keyword(s):  
Carbon Dioxide ◽  
Pressure Drop ◽  
Gas Flow ◽  
Direct Methanol Fuel Cells ◽  
Gas Pressure ◽  
Mass Transfer Resistance ◽  
Transfer Resistance ◽  
Cell Components ◽  
Direct Methanol ◽  
Methanol Fuel Cells

Abstract The gas flow of carbon dioxide from the catalyst layer (CL) through the microporous layer (MPL) and gas diffusion layer (GDL) has great impacts on the water and fuel management in direct methanol fuel cells (DMFCs). This work has developed a liquid–vapor two-phase model considering the counter flow of carbon dioxide gas, methanol, and water liquid solution in porous electrodes of DMFC. The model simulation includes the capillary pressure as well as the pressure drop due to flow resistance through the fuel cell components. The pressure drop of carbon dioxide flow is found to be about two to three orders of magnitude higher than the pressure drop of the liquid flow. The big difference between liquid and gas pressure drops can be explained by two reasons: volume flowrate of gas is three orders of magnitude higher than that of liquid; only a small fraction of pores (<5%) in hydrophilic fuel cell components are available for gas flow. Model results indicate that the gas pressure and the mass transfer resistance of liquid and gas are more sensitive to the pore size distribution than the thickness of porous components. To buildup high gas pressure and high mass transfer resistance of liquid, the MPL and CL should avoid micro-cracks during manufacture. Distributions of pore size and wettability of the GDL and MPL have been designed to reduce the methanol crossover and improve fuel efficiency. The model results provide design guidance to obtain superior DMFC performance using highly concentrated methanol solutions or even pure methanol.

Transport Characteristics of a Multi-Species Slurry in a Horizontal Pipeline

2001 ◽  
Author(s):  
P. V. Skudarnov ◽  
H. J. Kang ◽  
C. X. Lin ◽  
M. A. Ebadian ◽  
P. W. Gibbons ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Deposition Velocity ◽  
Single Species ◽  
Operating Conditions ◽  
High Level Waste ◽  
Slurry Flow ◽  
Flow Loop ◽  
Waste Transfer ◽  
High Level ◽  
Slurry Transport

Abstract In the course of the U.S. Department of Energy’s (DOE) tank waste retrieval, immobilization, and disposal activities, high-level waste transfer lines have the potential to become plugged. In response to DOE’s needs, Florida International University’s Hemispheric Center for Environmental Technology (FIU-HCET) is studying the mechanism and behavior of pipeline plugging to determine the pipeline operating conditions for safe slurry transport. Transport behavior of multi-species slurry has been studied in a 1-in O.D. pipeline flow loop. The slurry was a five-species mixture of Fe2O3, Al2O3, MnO2, Ni2O3, and SiO2, which simulated actual waste at the Savannah River DOE site. The relationship between the pressure drop in the straight horizontal sections of the flow loop and the mean slurry flow velocity was determined for two solids volume concentrations of 5.2 and 7.8%. Critical deposition velocity was measured from visual observations. An existing empirical model that predicts the pressure gradient for a single-species slurry flow in a horizontal pipeline was used to describe the pressure drop data.

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