Leakage and Rotordynamic Characteristics for Three Types of Annular Gas Seals Operating in Supercritical CO2 Turbomachinery

2021 ◽  
Author(s):  
Zhigang LI ◽  
Zhuocong Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Supercritical Co2 ◽  
High Speed ◽  
Dynamic Pressure ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Real Gas Effect ◽  
Nist Database ◽  
Swirl Velocity ◽  
Fluid Properties ◽  
Gas Seals

Abstract This paper presents a comprehensive assessment and comparison on the leakage and rotordynamic performance of three types of annular gas seals for application in a 14 MW supercritical CO2 turbine. These three seals represent the main seal types used in high-speed rotating machines at the balance piston location in efforts to limit internal leakage flow and achieve rotordynamic stability, including a labyrinth seal (LABY), a fully-partitioned pocket damper seal (FPDS), and a hole-pattern seal (HPS). These three seals were designed to have the same sealing clearance and similar axial lengths. To enhance the seal net damping capability at high inlet preswirl condition, a straight swirl brake also was designed and employed at seal entrance for each type seal to reduce the seal inlet pre-swirl velocity. Numerical results of leakage flow rates, rotordynamic force coefficients, cavity dynamic pressure and swirl velocity developments were analyzed and compared for three seal designs at high positive inlet preswirl (in the direction of shaft rotation), using a proposed transient CFD-based perturbation method based on the multiple-frequency elliptical-orbit rotor whirling model and the mesh deformation technique. To take into account of real gas effect with high accuracy, a table look-up procedure based on the NIST database was implemented, using an in-house code, for the fluid properties of CO2 in both supercritical and subcritical conditions.

A CFD Study on the Dynamic Coefficients of Labyrinth Seals

2012 ◽  
Author(s):  
Donghui Zhang ◽  
Chester Lee ◽  
Michael Cave
Keyword(s):  
High Speed ◽  
Fluid Dynamic ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Dynamic Coefficients ◽  
Rotating Impeller ◽  
Coupling Stiffness ◽  
Direct Stiffness ◽  
Compressor Efficiency

Labyrinth seals are widely used in gas compressors to reduce internal leakage and increase the compressor efficiency. Due to the eccentricity between the rotating impeller and the stationary part as *well as the shaft whirling motion, forces are generated when the leakage flow passing through the cavities and the seals. For a lot of applications with high speed and pressure, these forces can drive the system unstable. Thus, predicting the forces accurately become a very important for compressor rotordynamic designs. A lot of research and studies has been done to the seals itself, including bulk flow method, computational fluid dynamic (CFD) and test measurement. The seal and leakage flow interaction forces can be predicted relatively accurate. But very few research treat the seal and cavities as one component interacting with the leakage flow and produce the forces. This paper presents results of CFD investigations on the dynamic coefficients of one typical impeller eye seal and front cavity. The CFD results show that large forces are generated in the front cavity due to circumferential uniform pressure distribution, which caused by the downstream labyrinth seal. The forces generated in the front cavity are more than in the front seal. It was found that the inertia, damping, and stiffness are proportional to average pressure. The cross-coupling stiffness increases with speed with power of 2 while the direct stiffness increases with speed with power of about 1.7.

Numerical Investigation of an Improved Gas and Steam Turbine Seal

1996 ◽  
Vol 210 (6) ◽  
pp. 477-479 ◽  
Author(s):  
M H Gordon ◽  
U M Kelkar ◽  
M C Johnson
Keyword(s):  
High Temperature ◽  
Numerical Investigation ◽  
High Speed ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Labyrinth Seal ◽  
Optimal Shape ◽  
Steam Turbines ◽  
Brush Seal ◽  
Sealing Mechanism

A numerical study has been conducted to assess the viability of a new sealing mechanism for gas and steam turbines. This new static-to-rotating sealing mechanism is mounted on flexible legs which permit radial movement and is designed to take advantage of the hydro-dynamic pressure forces, which result from fluid leaking around the seal, to maintain an ideally small and constant clearance. Relatively simple seal geometries have been numerically tested to find an optimal shape. These results indicate that a substantial sealing improvement (between two and four times less leakage) relative to a labyrinth seal is possible. Although these results show that a brush seal is more effective than the present seal, the present seal is designed to operate in high-speed and high-temperature environments in which the brush seal would degrade.

Effects of Pressure Ratio and Sealing Clearance on Leakage Flow Characteristics in the Rotating Honeycomb Labyrinth Seal

2007 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Guojun Li ◽  
Zhenping Feng
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Aerodynamic Efficiency ◽  
Flow Losses ◽  
Leakage Flow Rate ◽  
Swirl Velocity

Honeycomb stepped labyrinth seals in turbomachinery enhance aerodynamic efficiency by reducing leakage flow losses through the clearance between rotating and stationary components. The influence of pressure ratio and sealing clearance on the leakage flow characteristics in the honeycomb stepped labyrinth seal is numerically determined. The geometries investigated represent designs of the honeycomb labyrinth seal typical for modern turbomachinery. The leakage flow fields in the honeycomb and smooth stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT. Numerical simulations covered a range of pressure ratio and three sizes of sealing clearance for the honeycomb and smooth stepped labyrinth seals. The numerical discharge coefficients of the non-rotating honeycomb and smooth stepped labyrinth seals are in good agreement with previous experimental data. In addition rotational effects are also taken into account in numerical computations. The numerical results show that the leakage flow rate increases with the increasing pressure ratio at the fixed sealing clearance for the rotating and non-rotating honeycomb labyrinth seal. The influence of the sealing clearance on the leakage flow pattern for the rotating and non-rotating honeycomb labyrinth seal are observed. Moreover, the similar leakage flow rates are obtained at the same flow condition between the rotating and non-rotating honeycomb labyrinth seal due to the honeycomb acts to kill swirl velocity development for the rotating honeycomb labyrinth seal.

Leakage Flow of Labyrinth Seals in Hydraulic Components

Volume 3 ◽  
2004 ◽  
Author(s):  
Minter Cheng
Keyword(s):  
Reynolds Number ◽  
High Speed ◽  
Labyrinth Seal ◽  
Industrial Applications ◽  
Width Ratio ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Cavity Depth ◽  
Analysis Technique ◽  
Cavity Width

Leakage flow plays an important role on the performance evaluation of hydraulic components. Leakage flow induces adverse influences on many practical industrial applications. For the sake of reducing friction and/or abrasion, most of the high-speed hydraulic components install some kind of non-contact seals to minimize leakage flow, the labyrinth seal is the most popular one. This research is to investigate the leakage flow of labyrinth seals in hydraulic components by using numerical analysis technique. The parameters investigated in this study are cavity number, cavity width, cavity depth, cavity gap, and Reynolds number. The traditional rectangular cavity is considered in this research. It shows that cavity width is about 20∼30 times of clearance, cavity depth is about 3∼5 times of clearance, cavity gap is greater than 50 times of clearance, cavity depth to width ratio is about 0.15∼0.25, and cavity gap to width ratio is greater than 2.5 have better sealing capability.

Numerical Investigation on the Leakage and Rotordynamic Characteristics for Three Types of Annular Gas Seals in Wet Gas Conditions

2018 ◽  
Author(s):  
Zhigang Li ◽  
Zhi Fang ◽  
Jun Li
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Flow Rates ◽  
Force Coefficients ◽  
Wet Gas ◽  
Annular Seal ◽  
Direct Stiffness ◽  
Gas Seals

The modern compressor operation is challenged by the liquid presence in wet gas operating conditions. The liquid phase may affect the compressor stability by partially flooding the internal annular gas seals and inducing subsynchronous vibration. To improve the annular seal behavior and increase rotor stability, high-precision results of leakage flow rates and rotordynamic force coefficients are needed for annular gas seals in wet gas conditions. In order to better understand the leakage and rotordynamic characteristics of the annular gas seal in wet gas conditions, a 3D transient CFD-based perturbation method was proposed for computations of leakage flow rates and rotordynamic force coefficients of annular gas seals with liquid phase in main gas phase, based on inhomogeneous Eulerian-Eulerian multiphase flow model, mesh deformation technique and the multi-frequency rotor whirling orbit model. Numerical results of frequency-dependent rotordynamic force coefficients and leakage flow rates were presented and compared for three types of non-contact annular gas seals, which include a smooth plain annular seal (SPAS), a labyrinth seal (LABY) and a fully-partitioned pocket damper seal (FPDS). These three seals were designed to have the identical rotor diameter, sealing clearance and axial length. The accuracy and availability of the present transient CFD numerical method were demonstrated with the experiment data of leakage flow rates and frequency-dependent rotordynamic force coefficients of the smooth plain seal with four inlet liquid volume fractions (LVF) of 0%, 2%, 5% and 8%. Steady and transient numerical simulations were conducted at inlet air pressure of 62.1 bar, pressure ratio of 0.5, rotational speed of 15 000 rpm and inlet preswirl ratio of 0.3 for four inlet LVFs varying from 0% to 8% and fourteen subsynchronous and synchronous whirling frequencies up to 280 Hz. The numerical results show that inlet liquid phase has a significant influence on the leakage and rotordynamic coefficients for all three types of annular gas seals. The mixture leakage flow rate increases with the increasing inlet LVF, combining the decreasing gas-phase and linearly increasing liquid-phase leakage flow rates. The smooth plain seal leaks the most gas phase and liquid phase, followed by the pocket damper seal and then the labyrinth seal. Increasing inlet LVF significantly decreases the direct stiffness and slightly increases the effective damping of the smooth plain seal. The labyrinth seal possesses evident negative direct stiffness and shows a noticeable decreasing effective damping with the increasing inlet LVF at the subsynchronous frequency range. Increasing inlet LVF obviously increases all the force coefficients of the pocket damper seal including the positive effective damping. From a rotordynamic viewpoint, the FPDS possesses a better liquid tolerant capability and so is a better sealing scheme for the balance piston seals and center seals of the centrifugal compressor in wet gas operating condition.

Numerical Investigation on the Leakage and Rotordynamic Characteristics for Three Types of Annular Gas Seals in Wet Gas Conditions

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Zhigang Li ◽  
Zhi Fang ◽  
Jun Li
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Flow Rates ◽  
Force Coefficients ◽  
Wet Gas ◽  
Annular Seal ◽  
Direct Stiffness ◽  
Gas Seals

The modern compressor operation is challenged by the liquid presence in wet gas operating conditions. The liquid phase may affect the compressor stability by partially flooding the internal annular gas seals and inducing subsynchronous vibration (SSV). To improve the annular seal behavior and increase the rotor stability, high-precision results of leakage flow rates and rotordynamic force coefficients are needed for annular gas seals in wet gas conditions. In order to better understand the leakage and rotordynamic characteristics of the annular gas seal in wet gas conditions, a 3D transient CFD-based perturbation method was proposed for computations of leakage flow rates and rotordynamic force coefficients of annular gas seals with liquid phase in main gas phase, based on inhomogeneous Eulerian-Eulerian multiphase flow model, mesh deformation technique, and the multifrequency rotor whirling orbit model. Numerical results of frequency-dependent rotordynamic force coefficients and leakage flow rates were presented and compared for three types of noncontact annular gas seals, which include a smooth plain annular seal (SPAS), a labyrinth (LABY) seal, and a fully partitioned pocket damper seal (FPDS). These three seals were designed to have the identical rotor diameter, sealing clearance, and axial length. The accuracy and the availability of the present transient CFD numerical method were demonstrated with the experiment data of leakage flow rates and frequency-dependent rotordynamic force coefficients of the smooth plain seal with four inlet liquid volume fractions (LVFs) of 0%, 2%, 5%, and 8%. Steady and transient numerical simulations were conducted at inlet air pressure of 62.1 bar, pressure ratio of 0.5, rotational speed of 15,000 rpm, and inlet preswirl ratio of 0.3 for four inlet LVFs varying from 0% to 8% and 14 subsynchronous and synchronous whirling frequencies up to 280 Hz. The numerical results show that the inlet liquid phase has a significant influence on the leakage and rotordynamic coefficients for all three types of annular gas seals. The mixture leakage flow rate increases with the increasing inlet LVF, combining the decreasing gas-phase and linearly increasing liquid-phase leakage flow rates. The smooth plain seal leaks the most gas phase and liquid phase, followed by the pocket damper seal (PDS) and then the labyrinth seal. Increasing inlet LVF significantly decreases the direct stiffness and slightly increases the effective damping of the smooth plain seal. The labyrinth seal possesses evident negative direct stiffness and shows a noticeable decreasing effective damping with the increasing inlet LVF at the subsynchronous frequency range. Increasing inlet LVF obviously increases all the force coefficients of the pocket damper seal including the positive effective damping. From a rotordynamic viewpoint, the FPDS possesses a better liquid tolerant capability and so is a better sealing scheme for the balance piston seals and center seals of the centrifugal compressor in wet gas operating condition.

Power Dissipation in Smooth and Honeycomb Labyrinth Seals

1989 ◽  
Author(s):  
W. F. McGreehan ◽  
S. H. Ko
Keyword(s):  
Power Dissipation ◽  
High Speed ◽  
Material Design ◽  
Labyrinth Seal ◽  
General Assumption ◽  
Design Parameters ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Wide Range

The surface frictional characteristics of a labyrinth seal can result in significant windage power dissipation for high speed seals. Recent advances in seal design have produced high speed, high pressure labyrinth seals which operate at very low leakage rates. The reduced leakage is beneficial to gas turbine efficiency, but seal discharge temperatures can approach material design limits with high windage power dissipation. Also, a high air temperature rise can influence seal leakage flow. Consequently, the general assumption of negligible rotational effect on leakage is not always valid. A method is presented for the prediction of seal power dissipation and leakage flow over a wide range of design parameters. Results are compared to available test data and several approaches examined for the reduction of seal windage.

scholarly journals Is ink heating a relevant concern in the High Speed Sintering process?

2021 ◽  
Author(s):  
Rhys J. Williams ◽  
Patrick J. Smith ◽  
Candice Majewski
Keyword(s):  
Cross Sections ◽  
Inkjet Printing ◽  
High Speed ◽  
Sintering Process ◽  
Significant Drop ◽  
Powder Bed ◽  
Consistent Manner ◽  
Fluid Properties ◽  
Different Temperatures ◽  
Accuracy And Repeatability

AbstractHigh Speed Sintering (HSS) is a novel polymer additive manufacturing process which utilises inkjet printing of an infrared-absorbing pigment onto a heated polymer powder bed to create 2D cross-sections which can be selectively sintered using an infrared lamp. Understanding and improving the accuracy and repeatability of part manufacture by HSS are important, ongoing areas of research. In particular, the role of the ink is poorly understood; the inks typically used in HSS have not been optimised for it, and it is unknown whether they perform in a consistent manner in the process. Notably, the ambient temperature inside a HSS machine increases as a side effect of the sintering process, and the unintentional heating to which the ink is exposed is expected to cause changes in its fluid properties. However, neither the extent of ink heating during the HSS process nor the subsequent changes in its fluid properties have ever been investigated. Such investigation is important, since significant changes in ink properties at different temperatures would be expected to lead to inconsistent printing and subsequently variations in part accuracy and even the degree of sintering during a single build. For the first time, we have quantified the ink temperature rise caused by unintentional, ambient heating during the HSS process, and subsequently measured several of the ink’s fluid properties across the ink temperature range which is expected to be encountered in normal machine operation (25 to 45 ∘C). We observed only small changes in the ink’s density and surface tension due to this heating, but a significant drop (36%) in its viscosity was seen. By inspection of the ink’s Z number throughout printing, it is concluded that these changes would not be expected to change the manner in which droplets are delivered to the powder bed surface. In contrast, the viscosity decrease during printing is such that it is expected that the printed droplet sizes do change in a single build, which may indeed be a cause for concern with regard to the accuracy and repeatability of the inkjet printing used in HSS, and subsequently to the properties of the polymer parts obtained from the process.

Numerical investigation on the performance of impeller back seal configuration in a supercritical CO2 radial-inflow turbine

2021 ◽  
pp. 095440622110095
Author(s):  
Qiuwan Du ◽  
Yuqi Wang ◽  
Di Zhang ◽  
Yonghui Xie
Keyword(s):  
Numerical Investigation ◽  
Supercritical Co2 ◽  
Labyrinth Seal ◽  
Brayton Cycle ◽  
Mechanical Seal ◽  
Nozzle Outlet ◽  
Excellent Performance ◽  
Core Component ◽  
Comprehensive Performance ◽  
Radial Inflow Turbine

Radial-inflow turbine is a core component in supercritical CO2 (SCO2) Brayton cycle. The leakage from the nozzle outlet towards the impeller back brings a great challenge to the efficiency and security of the power system. In this paper, the labyrinth seal (LS) and dry gas seal (DGS) are arranged on the impeller back of a SCO2 radial-inflow turbine and the influence on the comprehensive performance is investigated. Results demonstrate that both LS and DGS configurations can significantly reduce leakage of the impeller back and DGS configuration performs better. Compared with the configuration without leakage, the power and efficiency of DGS configuration are only reduced by 0.27% and 0.35% respectively. The seal clearance and the inlet width have a greater effect on LS configuration. The thermo-mechanical seal deformation values of DGS configurations are all less than 8 μm, which verifies the feasibility. Finally, a novel combined seal configuration with both LS and DGS is proposed and excellent performance is achieved, providing a potential approach for the sealing problem of SCO2 radial-inflow turbine.

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

Sign in / Sign up

Export Citation Format

Share Document