Investigation of the Influence of Different Rim Seal Geometries in a Low-Pressure Turbine

2011 ◽  
Author(s):  
P. Schuler ◽  
K. Dullenkopf ◽  
H.-J. Bauer
Keyword(s):  
Mass Flow ◽  
Total Pressure ◽  
Gas Flow ◽  
Low Pressure ◽  
Flow Rates ◽  
Low Pressure Turbine ◽  
Hot Gas ◽  
Seal Design ◽  
Compound Design ◽  
Mass Flow Rates

The sealing of the machine’s inside against hot-gas ingestion is commonly provided by blowing relative cold compressor air radially out through the turbine wheelspace. Rim-seals located inside the wheelspace are primarily designed to keep the required amount of sealing at a minimum. A further possible function of the rim-seal follows from the desire to reduce the aerodynamic losses contributed by the interaction of the emerging sealing flow with the boundary layer of the incoming main flow. Investigations performend in the EU project MAGPI concentrate on the interaction between the sealing flow and the main gas flow and in particular on the effect of different rim seal designs regarding the loss-mechanism in a low-pressure turbine passage. Two different rim seal designs inside a linear low-pressure turbine cascade rig have been analysed in detail. Both, the simple axial gap and the more complex compound design were investigated under the influence of different sealing mass flow rates. Furthermore, a configuration without any cavity in the main gas flow served as a reference case. Extensive measurements of the total pressure loss over the turbine blade have been conducted by means of a five-hole probe. Additionally, the blade loading has been measured at several blade heights. A considerable increase of total pressure losses was observed due to the presence of a cavity with any rim seal design, even for no sealing flow. Higher sealing mass flow rates intensified this effect which becomes manifested in a strengthening of the secondary flows downstream the cascade. Experiments revealed also significant differences in loss-increment depending on the rim seal design used. Deeper insight into the interaction of the flows close to the rim seal is given by results of Laser-Doppler-Velocimetry measurements. The rounded shape of the compound design, which implies an axial overlapping, represents a promising prevention against hot-gas ingestion. While the axial gap design is characterized by higher losses, it also suffers considerable hot-gas ingestion in front of the blade leading edge. A parametric study regarding a possible optimization of the axial gap design is presented in this work.

The Influence of Different Rim Seal Geometries on Hot-Gas Ingestion and Total Pressure Loss in a Low-Pressure Turbine

2010 ◽  
Author(s):  
P. Schuler ◽  
W. Kurz ◽  
K. Dullenkopf ◽  
H.-J. Bauer
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Gas Flow ◽  
Low Pressure ◽  
Total Pressure Loss ◽  
Pressure Loss Coefficient ◽  
Low Pressure Turbine ◽  
Hot Gas ◽  
Flow Through ◽  
Total Pressure Loss Coefficient

In order to prevent hot-gas ingestion into the rotating turbo machine’s inside, rim seals are used in the cavities located between stator- and rotor-disc. The sealing flow ejected through the rim seal interacts with the boundary layer of the main gas flow, thus playing a significant role in the formation of secondary flows which are a major contributor to aerodynamic losses in turbine passages. Investigations performed in the EU project MAGPI concentrate on the interaction between the sealing flow and the main gas flow and in particular on the influence of different rim seal geometries regarding the loss-mechanism in a low-pressure turbine passage. Within the CFD work reported in this paper static simulations of one typical low-pressure turbine passage were conducted containing two different rim seal geometries, respectively. The sealing flow through the rim seal had an azimuthal velocity component and its rate has been varied between 0–1% of the main gas flow. The modular design of the computational domain provided the easy exchange of the rim seal geometry without remeshing the main gas flow. This allowed assessing the appearing effects only to the change of rim seal geometry. The results of this work agree with well-known secondary flow phenomena inside a turbine passage and reveal the impact of the different rim seal geometries on hot-gas ingestion and aerodynamic losses quantified by a total pressure loss coefficient along the turbine blade. While the simple axial gap geometry suffers considerable hot-gas ingestion upstream the blade leading edge, the compound geometry implying an axial overlapping presents a more promising prevention against hot-gas ingestion. Furthermore, the effect of rim seals on the turbine passage flow field has been identified applying adequate flow visualisation techniques. As a result of the favourable conduction of sealing flow through the compound geometry, the boundary layer is less lifted by the ejected sealing flow, thus resulting in a comparatively reduced total pressure loss coefficient over the turbine blade.

Under-Expanded Gas Flow at a Straight Mini-Tube Exit

2013 ◽  
Author(s):  
Takahiro Yoshimaru ◽  
Yutaka Asako ◽  
Toru Yamada
Keyword(s):  
Mass Flow ◽  
Total Pressure ◽  
Gas Flow ◽  
Pitot Tube ◽  
Outer Diameter ◽  
Flow Rates ◽  
Numerical Result ◽  
Mass Flow Rates ◽  
Tube Exit ◽  
Slight Discrepancy

This paper focuses on under-expanded gas flow at a straight mini-tube exit. Pitot total pressure of gas flow (jet) in downstream region from a straight mini-tube exit was measured to give data for validation of numerical results. A mini-tube of 495μm in diameter & 56.3 mm in length and a pitot tube of 100 μm in outer diameter were used. The pitot total pressure was measured every 0.1 mm interval in the flow and radial directions. The measurement was done for the mass flow rates of 9.71×10−5 kg/s and 1.46×10−4 kg/s. The data were accumulated for validation of the numerical result to reveal the characteristics of the under-expanded gas flow at the exit of a mini-tube. Comparisons were conducted for sample computations and a slight discrepancy can be seen between numerical and experimentally measured pitot total pressures.

scholarly journals Simulation and Modeling of Flow in a Gas Compressor

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Anna Avramenko ◽  
Alexey Frolov ◽  
Jari Hämäläinen
Keyword(s):  
Steady State ◽  
Mass Flow ◽  
Gas Flow ◽  
Simulation Method ◽  
High Mass ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Flow Through

The presented research demonstrates the results of a series of numerical simulations of gas flow through a single-stage centrifugal compressor with a vaneless diffuser. Numerical results were validated with experiments consisting of eight regimes with different mass flow rates. The steady-state and unsteady simulations were done in ANSYS FLUENT 13.0 and NUMECA FINE/TURBO 8.9.1 for one-period geometry due to periodicity of the problem. First-order discretization is insufficient due to strong dissipation effects. Results obtained with second-order discretization agree with the experiments for the steady-state case in the region of high mass flow rates. In the area of low mass flow rates, nonstationary effects significantly influence the flow leading stationary model to poor prediction. Therefore, the unsteady simulations were performed in the region of low mass flow rates. Results of calculation were compared with experimental data. The numerical simulation method in this paper can be used to predict compressor performance.

Investigation of Flow Instabilities Near the Rim Cavity of a 1.5 Stage Gas Turbine

2009 ◽  
Author(s):  
M. Rabs ◽  
F.-K. Benra ◽  
H. J. Dohmen ◽  
O. Schneider
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Gas Turbines ◽  
Flow Instabilities ◽  
Navier Stokes ◽  
Flow Rates ◽  
Air Mass ◽  
Hot Gas ◽  
Path Modelling ◽  
Mass Flow Rates

The present paper gives a contribution to a better understanding of the flow at the rim and in the wheel space of gas turbines. Steady state and time-accurate numerical simulations with a commercial Navier-Stokes solver for a 1.5 stage turbine similar to the model treated in the European Research Project ICAS-GT were conducted. In the framework of a numerical analysis, a validation with experimental results of the test rig at the Technical University of Aachen will be given. In preceding numerical investigations of realistic gas turbine rim cavities with a simplified treatment of the hot gas path (modelling of the main flow path without blades and vanes), so called Kelvin-Helmholtz vortices were found in the area of the gap when using appropriate boundary conditions. The present work shows that these flow instabilities also occur in a 1.5 stage gas turbine model with consideration of the blades and vanes. Therefore, several simulations with different sealing air mass flow rates (CW 7000, 20000, 30000) have been conducted. The results show, that for high sealing air mass flow rates Kelvin-Helmholtz Instabilities are developing. These vortices significantly coin the flow at the rim.

Under-Expanded Gaseous Flow at a Straight Micro-Tube Exit

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Takahiro Yoshimaru ◽  
Yutaka Asako ◽  
Toru Yamada
Keyword(s):  
Total Pressure ◽  
Gas Flow ◽  
Numerical Results ◽  
Pitot Tube ◽  
Outer Diameter ◽  
Flow Rates ◽  
Gaseous Flow ◽  
Mass Flow Rates ◽  
Tube Exit ◽  
Slight Discrepancy

This paper focuses on under-expanded gaseous flow at a straight micro-tube exit. The pitot total pressure of gas flow (jet) in the downstream region from a straight micro-tube exit was measured by a total pressure pitot tube to accumulate data for validation of numerical results. A micro-tube of 495μm in diameter and 56.3 mm in length and a total pressure pitot tube of 100 μm in outer diameter were used. The pitot total pressure was measured at intervals of 0.1 mm in both the flow and radial directions. The measurement was done for the mass flow rates of 9.71 × 10−5 kg/s and 1.46 × 10−4 kg/s. The data were accumulated for validation of the numerical results to reveal the characteristics of the under-expanded gas flow at the exit of a micro-tube. Comparisons were conducted for numerical results of corresponding cases and a slight discrepancy can be seen between numerical and experimentally measured pitot total pressures.

Review of Critical Flowmeters for Gas Flow Measurements

1962 ◽  
Vol 84 (4) ◽  
pp. 447-457 ◽  
Author(s):  
B. T. Arnberg
Keyword(s):  
Mass Flow ◽  
Flow Measurement ◽  
Gas Flow ◽  
Flow Measurements ◽  
Flow Rates ◽  
Real Gas ◽  
Discharge Coefficients ◽  
Critical Nozzles ◽  
Mass Flow Rates ◽  
Flow Functions

Critical flowmeters for accurately measuring the mass flow rates of nonreacting real gases were reviewed. Discussions were presented on theoretical flow functions, on parameters for correlating discharge coefficients, and on the importance of real gas properties. The performance characteristics of critical nozzles and orifices of several designs were reviewed. Approaches were discussed to problems which must be researched before the fullest potential of this type of flow measurement can be realized.

Experimental Investigation of Turbine Leakage Flows on the Three-Dimensional Flow Field and Endwall Heat Transfer

2006 ◽  
Vol 129 (3) ◽  
pp. 608-618 ◽  
Author(s):  
Hans-Jürgen Rehder ◽  
Axel Dannhauer
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Secondary Flow ◽  
Mass Flow ◽  
Test Section ◽  
Flow Behavior ◽  
Leakage Flow ◽  
Flow Rates ◽  
Low Pressure Turbine ◽  
Mass Flow Rates

Within a European research project, the tip endwall region of low pressure turbine guide vanes with leakage ejection was investigated at DLR in Göttingen. For this purpose a new cascade wind tunnel with three large profiles in the test section and a contoured endwall was designed and built, representing 50% height of a real low pressure turbine stator and simulating the casing flow field of shrouded vanes. The effect of tip leakage flow was simulated by blowing air through a small leakage gap in the endwall just upstream of the vane leading edges. Engine relevant turbulence intensities were adjusted by an active turbulence generator mounted in the test section inlet plane. The experiments were performed with tangential and perpendicular leakage ejection and varying leakage mass flow rates up to 2%. Aerodynamic and thermodynamic measurement techniques were employed. Pressure distribution measurements provided information about the endwall and vane surface pressure field and its variation with leakage flow. Additionally streamline patterns (local shear stress directions) on the walls were detected by oil flow visualization. Downstream traverses with five-hole pyramid type probes allow a survey of the secondary flow behavior in the cascade exit plane. The flow field in the near endwall area downstream of the leakage gap and around the vane leading edges was investigated using a 2D particle image velocimetry system. In order to determine endwall heat transfer distributions, the wall temperatures were measured by an infrared camera system, while heat fluxes at the surfaces were generated with electric operating heating foils. It turned out from the experiments that distinct changes in the secondary flow behavior and endwall heat transfer occur mainly when the leakage mass flow rate is increased from 1% to 2%. Leakage ejection perpendicular to the main flow direction amplifies the secondary flow, in particular the horseshoe vortex, whereas tangential leakage ejection causes a significant reduction of this vortex system. For high leakage mass flow rates the boundary layer flow at the endwall is strongly affected and seems to be highly turbulent, resulting in entirely different heat transfer distributions.

scholarly journals Inert Gas and Refrigerating Vapor Mass Flow Rates Ratio: A Much Promising Parameter for Diffusion-Absorption-Refrigeration Systems Performances Evaluation

2021 ◽  
Vol 8 (2) ◽  
pp. 253-258
Author(s):  
Djallel Zebbar ◽  
Souhila Zebbar ◽  
Sahraoui Kherris ◽  
Kouider Mostefa
Keyword(s):  
Mass Flow ◽  
Gas Flow ◽  
Inert Gas ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Absorption Refrigeration ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Diffusion Absorption ◽  
Vapor Mass

This paper is consecrated to the thermodynamic study and analysis of diffusion-absorption-refrigeration (DAR) plants. The mass and energy balances analysis at the evaporator has allowed to highlight a new and original parameter, which can be used to analyze DAR system performances. It is the ratio of inert gas to refrigerant vapor mass flow rates at the evaporator inlets. This coefficient, which expression has been for the first time deduced mathematically, informs about the quality of the cycle and its performance, which are deeply affected by the growth of the inert gas flow energy expended to drive the refrigerant through the evaporator. The study shows that the coefficient of performance is decreasing with the increase of the mass flow rates ratio. The latter can be also used to find the optimal operating mode for the DAR machine with a specified working fluid.

Investigation of Effects of Radial Distortion on Transonic Fan Behavior

2010 ◽  
Author(s):  
Dmytro M. Voytovych ◽  
Guoping Xia ◽  
Chenzhou Lian ◽  
Charles L. Merkle
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Tip Vortex ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Transonic Fan ◽  
Total Pressure Ratio

The flow analysis around blades of a transonic fan is presented for both clean and radially distorted inlets. Computations are shown for four-blade passages that are accomplished with a second order accurate code using a k-ω turbulence model. The mass flow rate along a speed line is controlled by varying a choked nozzle downstream of the fan. The results show good agreement with data for three speed lines. In the near-stall region, the flow first becomes unsteady and then unstable with the unsteadiness increasing at lower speeds. The four-blade simulations remained stable to lower mass flow rates than the single-blade simulations. In the near-stall vicinity, tip vortex breakdown occurred creating a low momentum zone near the blade tip on the pressure side that grew as the mass flow was decreased until it eventually blocked the passage. The presence of distortion reduced the operational range and moved the stall line to higher mass flow rates. At high speeds distortion reduced both the mass flow rate and total pressure ratio while at lower speeds, the choking mass flow rate was reduced, but the total pressure ratio was slightly improved. The flow separation near the hub on the suction side was caused by the distortion. Its size was decreasing with rotational speed.

Sheath Flow Focusing in Supersonic Jet Spectroscopy

1987 ◽  
Vol 41 (8) ◽  
pp. 1351-1357 ◽  
Author(s):  
Steven W. Stiller ◽  
Murray V. Johnston
Keyword(s):  
Mass Flow ◽  
Gas Flow ◽  
Supersonic Jet ◽  
Nozzle Geometry ◽  
Spectral Broadening ◽  
Flow Rates ◽  
Sheath Flow ◽  
Focusing Effect ◽  
Sample Stream ◽  
Mass Flow Rates

The mechanism of cooling in sheath-flow-focused supersonic jet expansions is examined. Cooling is found to be strongly influenced by the sheath gas flow properties but independent of the carrier gas in the sample stream. These results indicate that considerable turbulence and mixing between the sheath and sample gases occur downstream from the orifice. However, mixing cannot be complete, since, relative to results with a conventional jet expansion, a substantial enhancement of analyte is obtained along the centerline of a sheath-flow-focused jet expansion. Spectral broadening at “high” analyte mass flow rates within the sample stream is found to arise from inefficient cooling. There are limits to both how large and how small the nozzle orifice can be. Small orifices result in spectral broadening, even at very low analyte mass flow rates. Large orifices may have Reynolds numbers sufficient to cause turbulent flow, which degrades the focusing effect. The optimum nozzle geometry and gas flow conditions for sheath-flow-focused jet expansions are discussed.

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