Numerical Study of Aerodynamic Losses of Effusion Cooling Holes in Aero-Engine Combustor Liners

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
A. Andreini ◽  
A. Bonini ◽  
G. Caciolli ◽  
B. Facchini ◽  
S. Taddei
Keyword(s):  
Mass Flow ◽  
Cooling System ◽  
Numerical Study ◽  
Numerical Data ◽  
Good Reliability ◽  
Data Set ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Depth Analysis ◽  
Aero Engine

Due to the stringent cooling requirements of novel aero-engines combustor liners, a comprehensive understanding of the phenomena concerning the interaction of hot gases with typical coolant jets plays a major role in the design of efficient cooling systems. In this work, an aerodynamic analysis of the effusion cooling system of an aero-engine combustor liner was performed; the aim was the definition of a correlation for the discharge coefficient (CD) of the single effusion hole. The data were taken from a set of CFD RANS (Reynolds-averaged Navier-Stokes) simulations, in which the behavior of the effusion cooling system was investigated over a wide range of thermo/fluid-dynamics conditions. In some of these tests, the influence on the effusion flow of an additional air bleeding port was taken into account, making it possible to analyze its effects on effusion holes CD. An in depth analysis of the numerical data set has pointed out the opportunity of an efficient reduction through the ratio of the annulus and the hole Reynolds numbers: The dependence of the discharge coefficients from this parameter is roughly linear. The correlation was included in an in-house one-dimensional thermo/fluid network solver, and its results were compared with CFD data. An overall good agreement of pressure and mass flow rate distributions was observed. The main source of inaccuracy was observed in the case of relevant air bleed mass flow rates due to the inherent three-dimensional behavior of the flow close to bleed opening. An additional comparison with experimental data was performed in order to improve the confidence in the accuracy of the correlation: Within the validity range of pressure ratios in which the correlation is defined (>1.02), this comparison pointed out a good reliability in the prediction of discharge coefficients. An approach to model air bleeding was then proposed, with the assessment of its impact on liner wall temperature prediction.

Numerical Study of Aerodynamic Losses of Effusion Cooling Holes in Aero-Engine Combustor Liners

2010 ◽  
Author(s):  
A. Andreini ◽  
A. Bonini ◽  
G. Caciolli ◽  
B. Facchini ◽  
S. Taddei
Keyword(s):  
Mass Flow ◽  
Cooling System ◽  
Numerical Study ◽  
Data Set ◽  
Flow Rates ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Depth Analysis ◽  
Aero Engine ◽  
Mass Flow Rates

Due to the stringent cooling requirements of novel aeroengines combustor liners, a comprehensive understanding of the phenomena concerning the interaction of hot gases with typical coolant jets plays a major role in the design of efficient cooling systems. In this work an aerodynamic analysis of the effusion cooling system of an aero-engine combustor liner was performed; the aim was the definition of a correlation for the discharge coefficient (CD) of the single effusion hole. The data was taken from a set of CFD RANS simulations, in which the behavior of the effusion cooling system was investigated over a wide range of thermo fluid-dynamics conditions. In some of these tests, the influence on the effusion flow of an additional air bleeding port was taken in account, making possible to analyze its effects on effusion holes CD. An in depth analysis of the numerical data set has pointed out the opportunity of an efficient reduction through the ratio of the annulus and the hole Reynolds numbers: the dependence of the discharge coefficients from this parameter is roughly linear. The correlation was included in an in-house one dimensional thermo-fluid network solver and its results were compared with CFD data. An overall good agreement of pressure and mass flow rates distributions was observed. The main source of inaccuracy was observed in the case of relevant air bleed mass flow rates, due to the inherent three-dimensional behavior of the flow close to bleed opening. An additional comparison with experimental data was performed in order to improve the confidence in the accuracy of the correlation: within the validity range of pressure ratio in which the correlation is defined (> 1.02), this comparison pointed out a good reliability in the prediction of discharge coefficients. An approach to model air bleeding was then proposed, with the assessment of its impact on liner wall temperature prediction.

Numerical Characterization of Aerodynamic Losses of Jet Arrays for Gas Turbine Applications

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Da Soghe
Keyword(s):  
Gas Turbine ◽  
Discharge Coefficient ◽  
Cooling System ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Department Of Energy ◽  
Data Set ◽  
Wide Range ◽  
Depth Analysis

Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In this work, an aerodynamic analysis of jet arrays for active clearance control was performed; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The data were taken from a set of CFD RANS simulations, in which the behavior of the cooling system was investigated over a wide range of fluid-dynamics conditions. Furthermore, several different holes arrangements were investigated in significant detail, with the aim of evaluating the influence of the hole spacing on the discharge coefficient distribution. Tests were conducted by varying the jet Reynolds number in a wide range of effective engine operative conditions (Re = 2000-12,000, Pressure- Ratio = 1.01-1.6). To point out the reliability of the CFD analysis, some comparisons with experimental data, measured at the Department of Energy Engineering of the University of Florence, were drawn. An in-depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the mass velocity ratio of hole and feeding pipe: the dependence of the discharge coefficients from this parameter is roughly logarithmic.

scholarly journals Numerical Characterization of Pressure Drop Across the Manifold of Turbine Casing Cooling System

2012 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Antonio Andreini
Keyword(s):  
Discharge Coefficient ◽  
Cooling System ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Diameter Ratio ◽  
Data Set ◽  
Wide Range ◽  
Depth Analysis ◽  
Length To Diameter Ratio

Array of jets is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooling systems of turbine blades and vanes or in the turbine blade tip clearances control of large aeroengines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In a previous work the authors have performed an aerodynamic analysis of different arrays of jets for active clearance control; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The developed empirical correlation expresses the Cd of each hole as a function of the ratio between the hole and the manifold mass velocity and the local value of the pressure ratio. In its original form, the correlation does not take in to account the effect of the hole length to diameter ratio (t/d) so, in the present contribution, the authors report a study with the aim of evaluating the influence of such parameter on the discharge coefficient distribution. The data were taken from a set of CFD RANS simulations, in which the behaviour of the cooling system was investigated over a wide range of fluid-dynamics conditions (Pressure-Ratio = 1.01–1.6, t/d = 0.25–3). To point out the reliability of the CFD analysis, some comparisons with experimental data were drawn. An in depth analysis of the numerical data set has led to an improved correlation with a new term function of the hole length to diameter ratio.

Numerical Characterization of Aerodynamic Losses of Jet Arrays for Gas Turbine Applications

2011 ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Da Soghe
Keyword(s):  
Gas Turbine ◽  
Discharge Coefficient ◽  
Cooling System ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Department Of Energy ◽  
Data Set ◽  
Wide Range ◽  
Depth Analysis

Jet array is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooled region of gas turbine airfoils or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In this work an aerodynamic analysis of jet arrays for active clearance control was performed; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The data were taken from a set of CFD RANS simulations, in which the behaviour of the cooling system was investigated over a wide range of fluid-dynamics conditions. More in detail, several different holes arrangements were investigated with the aim of evaluating the influence of the hole spacing on the discharge coefficient distribution. Tests were conducted by varying the jet Reynolds number in a wide range of effective engine operative conditions (Re = 2000–12000, Pressure-Ratio = 1.01–1.6). To point out the reliability of the CFD analysis, some comparisons with experimental data, measured at the “Department of Energy Engineering” of the University of Florence, were drawn. An in depth analysis of the numerical data set has underlined the opportunity of an efficient reduction through the mass velocity ratio of hole and feeding pipe: the dependence of the discharge coefficients from this parameter is roughly logarithmic.

scholarly journals Numerical Characterization of Pressure Drop Across the Manifold of Turbine Casing Cooling System

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Riccardo Da Soghe ◽  
Antonio Andreini
Keyword(s):  
Discharge Coefficient ◽  
Cooling System ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Diameter Ratio ◽  
Data Set ◽  
Wide Range ◽  
Depth Analysis ◽  
Length To Diameter Ratio

An array of jets is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooling systems of turbine blades and vanes or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In a previous work, the authors have performed an aerodynamic analysis of different arrays of jets for active clearance control; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The developed empirical correlation expresses the (Cd) of each hole as a function of the ratio between the hole and the manifold mass velocity and the local value of the pressure ratio. In its original form, the correlation does not take in to account the effect of the hole length to diameter ratio (t/d) so, in the present contribution, the authors report a study with the aim of evaluating the influence of such parameter on the discharge coefficient distribution. The data were taken from a set of CFD RANS simulations, in which the behavior of the cooling system was investigated over a wide range of fluid-dynamics conditions (pressure-ratio = 1.01–1.6, t/d = 0.25–3). To point out the reliability of the CFD analysis, some comparisons with experimental data were drawn. An in depth analysis of the numerical data set has led to an improved correlation with a new term function of the hole length to diameter ratio.

Numerical Method for Studying Bearing Gap Pressure Wave Development and Subsequent Performance Mapping of Externally Pressurized Gas Journal Bearings

2019 ◽  
Author(s):  
Tom M. Lawrence ◽  
Marvin D. Kemple
Keyword(s):  
Numerical Method ◽  
Cross Section ◽  
Mass Flow ◽  
Pressure Wave ◽  
Design Space ◽  
Numerical Study ◽  
Pressure Waves ◽  
Wide Range ◽  
Wave Development ◽  
Static Instability

Abstract In previous work, numerical methods were developed to determine the pressure waves (pressure distribution) in the bearing gap of round externally pressurized gas bearings (EPB’s) that were pressurized through porous liners (PL bearings) or through liners with rows of feedholes (FH bearings). When integrated and differentiated these pressure portraits yield the net hydrodynamic force (FH) between the shaft and the bushing and the mass flow rates through the bearing gap. These results successfully replicated force-deflection curves and mass flow rate data for experimentally tested prototype FH and PL bearings over a wide range of mass flow constriction and clearances. Subsequently the numerical study was expanded to a broader design space of clearance and mass flow compensation. Also, a bearing performance mapping method of mapping the normalized bearing load over the clearance-eccentric deflection plane was developed for different levels of mass compensation. These performance maps produced a very interesting result as they indicated certain areas in the design space of FH bearings where static instability (negative stiffness) would be encountered. This static instability was not observed in the experimental data but is noted in references as known to occur in practice. Because this numerical method is based on the development of pressure wave portraits, the FH pressure wave could then be “dissected” in the areas of the onset of static instability which gave much insight as to the possible causes of static instability. This initial work, then, was perhaps the first to predict where in design space static instability would occur and yield some insight via examination of the corresponding pressure waves as to the cause. The numeric techniques developed, however are in no way limited to non-rotating bearings but are extensible to rotating bearings. The method is also easily extensible to examination of any configuration of feedholes or orifices. Nor is it limited to parallel deflections but can yield results for unbalanced loads. The method is also not limited to round bearings but can be applied to any cross-section configuration of bearing gap cross section such as a 3 lobed bearing or a slotted 3 lobed bearing. Examination of the resulting pressure wave development patterns for different scenarios can be examined to garner insight as to the causes of differing performance that can be applied to alterations towards optimization. Thus sharing in detail the developed numerical method underlying these studies seems worthwhile.

Experimental Validation and Design Simulations of a Passive Two-Phase Cooling System for Datacenters

2020 ◽  
Author(s):  
Jackson B. Marcinichen ◽  
John R. Thome ◽  
Raffaele L. Amalfi ◽  
Filippo Cataldo
Keyword(s):  
Thermal Performance ◽  
Experimental Validation ◽  
Cooling System ◽  
Electronics Cooling ◽  
Operating Conditions ◽  
Two Phase ◽  
Data Set ◽  
Pressure Drops ◽  
Wide Range ◽  
Important Challenge

Abstract Thermosyphon cooling systems represent the future of datacenter cooling, and electronics cooling in general, as they provide high thermal performance, reliability and energy efficiency, as well as capture the heat at high temperatures suitable for many heat reuse applications. On the other hand, the design of passive two-phase thermosyphons is extremely challenging because of the complex physics involved in the boiling and condensation processes; in particular, the most important challenge is to accurately predict the flow rate in the thermosyphon and thus the thermal performance. This paper presents an experimental validation to assess the predictive capabilities of JJ Cooling Innovation’s thermosyphon simulator against one independent data set that includes a wide range of operating conditions and system sizes, i.e. thermosyphon data for server-level cooling gathered at Nokia Bell Labs. Comparison between test data and simulated results show good agreement, confirming that the simulator accurately predicts heat transfer performance and pressure drops in each individual component of a thermosyphon cooling system (cold plate, riser, evaporator, downcomer (with no fitting parameters), and eventually a liquid accumulator) coupled with operational characteristics and flow regimes. In addition, the simulator is able to design a single loop thermosyphon (e.g. for cooling a single server’s processor), as shown in this study, but also able to model more complex cooling architectures, where many thermosyphons at server-level and rack-level have to operate in parallel (e.g. for cooling an entire server rack). This task will be performed as future work.

Theoretical, Numerical, and Experimental Study of the Time of Flight Flowmeter

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Ian Gaskin ◽  
Evgeniy Shapiro ◽  
Dimitris Drikakis
Keyword(s):  
Experimental Data ◽  
Response Time ◽  
Flow Rate ◽  
Dynamic Range ◽  
Time Of Flight ◽  
Numerical Data ◽  
Working Fluid ◽  
Independent Function ◽  
Data Set ◽  
Wide Range

Time-of-flight flowmeters offer advantages over other flowmeter types since these are less sensitive to the physical properties of the fluid. However, calibration of the flowmeter for a particular working fluid is still required. A flowmeter that does not require re-calibration with different fluids is desirable in many applications. This paper investigates the performance of a device that measures the time of flight of a heat pulse in a gas stream to determine the flow rate in a pipe. A fusion of the theoretical, experimental, and numerical data is used to suggest a gas-independent correlation function between the response time and flow rate. In particular, the numerical data augmented by the theoretical analysis to account for the wire response time is validated against experimental data and used to further enhance the experimental data set. Nitrogen, helium, and tetrafluoroethane (R134a) are investigated, as these gases provide a wide range of physical and thermodynamic properties. Simulated results match the trends of experimental data well and allow good qualitative analysis. The results also show that using detected pulse width information together with the time of flight can yield a 20% reduction in the errors due to gas type than by using time of flight data alone. This gives a relatively gas-independent function over a dynamic range of 1:400.

Numerical Study of the Effect of Multiple Tightly-Wound Vortices on a Transonic Fan Stage Performance

2014 ◽  
Author(s):  
Alejandro Castillo Pardo ◽  
Ahad Mehdi ◽  
Vassilios Pachidis ◽  
David G. MacManus
Keyword(s):  
Mass Flow ◽  
Vortex Flow ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Close Relation ◽  
Critical Value ◽  
Engine Design ◽  
Wide Range ◽  
Inlet Conditions ◽  
Transonic Fan

As a result of the new engine design trends, the likelihood of tightly-wound vortices being ingested by the engine rises. Therefore, the risk associated with the ingestion of swirl distortion becomes a major concern. A numerical analysis of the response of a transonic fan stage to the ingestion of different distorted flow patterns is carried out using steady-state CFD. The CFD approach is generated and validated against experimental data for undistorted inlet conditions. Following the validation, a wide range of configurations with vortex flow distortions are analysed and evaluated. The change in global performance is quantified and the flow field is extensively analysed. Consequently, the parameters that have the most critical impact on the performance of the fan stage are identified. The study identifies a close relation between the number of vortices ingested and the change in rotor performance. However, the deviation from the clean rotor performance has been found to be independent of the circumferential distance between vortices. Additionally, the effects of the radial location, polarity and vortex magnitude have been assessed. Ingested co-rotating vortices cause a significant reduction in pressure ratio and corrected mass flow. In contrast, counter-rotating vortices are associated with an increase in the pressure ratio and corrected mass flow. The change in rotor performance increases with the strength. However, a dramatical drop in pressure ratio is observed for counter-rotating vortices when the vortex strength exceeds a critical value.

Numerical study of secondary mass flow modulation in a Bypass Dual-Throat Nozzle

2020 ◽  
pp. 095441002094792
Author(s):  
MH Hamedi-Estakhrsar ◽  
M Ferlauto ◽  
H Mahdavy-Moghaddam
Keyword(s):  
Mass Flow ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Numerical Data ◽  
Thrust Vectoring ◽  
Flow Modulation ◽  
Contraction Ratio ◽  
Turbulent Airflow ◽  
Thrust Vector ◽  
Set Up

The fluidic thrust-vectoring modulation on a Bypass Dual-Throat Nozzle (BDTN) is studied numerically. The thrust vectoring modulation is obtained by varying the secondary mass flow, introducing different area contraction ratios of the bypass duct. The scope of present study is twofold: (i) to set up a model for the control of the secondary mass flow that is consistent with the resolution of the nozzle main flow and (ii) to derive a simplified representation of a valve system embedded in the bypass channel. The simulations of the turbulent airflow inside the BDTN and its efflux in the external ambient have been simulated by using RANS approach with RNG [Formula: see text] turbulence modeling. The numerical results have been validated with experimental and numerical data available in the open literature. The nozzle performance and thrust vector angle are computed for different values of the bypass area contraction ratio. The effects of different secondary mass flow rates on the system resultant thrust ratio and discharge coefficient of the bypass dual-throat nozzle have been investigated. By using the proposed approach to the secondary mass flow modulation, the thrust pitch angle has been controlled up to 27°.

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