A Numerical Study of Buoyant Plane Parallel Jets

2002 ◽  
Vol 124 (6) ◽  
pp. 1210-1213 ◽  
Author(s):  
Robert E. Spall
Keyword(s):  
Numerical Study ◽  
Symmetry Plane ◽  
Inlet Temperature ◽  
Plane Parallel ◽  
Archimedes Number ◽  
Merge Point ◽  
Two Jets ◽  
Heated Jet ◽  
Vertical Symmetry Plane

A numerical study was performed to assess the influence of buoyancy on plane, parallel jets. Results indicate that, relative to isothermal jets, the location along the vertical symmetry plane at which the two jets merge (the merge point) decreases with increasing jet inlet temperature. This decrease is attributed to higher entrainment rates for the heated jet relative to the isothermal jet. It was also found that for sufficiently high values of the Archimedes number, the merge point becomes nearly independent of the initial jet spacing.

Investigation of a Rotor Blade With Tip Cooling Subject to a Nonuniform Temperature Profile

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Harika S. Kahveci
Keyword(s):  
Temperature Profile ◽  
Turbine Blade ◽  
Numerical Study ◽  
Turbine Rotor ◽  
Inlet Temperature ◽  
Pressure Side ◽  
Engine Operation ◽  
Pressure Losses ◽  
Blade Tip ◽  
Temperature Levels

Abstract One of the challenges in the design of a high-pressure turbine blade is that a considerable amount of cooling is required so that the blade can survive high temperature levels during engine operation. Another challenge is that the addition of cooling should not adversely affect blade aerodynamic performance. The typical flat tips used in designs have evolved into squealer form that implements rims on the tip, which has been reported in several studies to achieve better heat transfer characteristics as well as to decrease pressure losses at the tip. This paper demonstrates a numerical study focusing on a squealer turbine blade tip that is operating in a turbine environment matching the typical design ratios of pressure, temperature, and coolant blowing. The blades rotate at a realistic rpm and are subjected to a turbine rotor inlet temperature profile that has a nonuniform shape. For comparison, a uniform profile is also considered as it is typically used in computational studies for simplicity. The effect of tip cooling is investigated by implementing seven holes on the tip near the blade pressure side. Results confirm that the temperature profile nonuniformity and the addition of cooling are the drivers for loss generation, and they further increase losses when combined. Temperature profile migration is not pronounced with a uniform profile but shows distinct features with a nonuniform profile for which hot gas migration toward the blade pressure side is observed. The blade tip also receives higher coolant coverage when subject to the nonuniform profile.

The Effect of Hot-Streaks on HP Vane Surface and Endwall Heat Transfer: An Experimental and Numerical Study

2005 ◽  
Author(s):  
T. Povey ◽  
K. S. Chana ◽  
T. V. Jones ◽  
J. Hurrion
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling System ◽  
Numerical Study ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
Wall Heat Transfer ◽  
Hot Streak ◽  
End Wall

Pronounced non-uniformities in combustor exit flow temperature (hot-streaks), which arise because of discrete injection of fuel and dilution air jets within the combustor and because of end-wall cooling flows, affect both component life and aerodynamics. Because it is very difficult to quantitatively predict the affects of these temperature non-uniformities on the heat transfer rates, designers are forced to budget for hot-streaks in the cooling system design process. Consequently, components are designed for higher working temperatures than the mass-mean gas temperature, and this imposes a significant overall performance penalty. An inadequate cooling budget can lead to reduced component life. An improved understanding of hot-streak migration physics, or robust correlations based on reliable experimental data, would help designers minimise the overhead on cooling flow that is currently a necessity. A number of recent research projects sponsored by a range of industrial gas turbine and aero-engine manufacturers attest to the growing interest in hot-streak physics. This paper presents measurements of surface and end-wall heat transfer rate for an HP nozzle guide vane (NGV) operating as part of a full HP turbine stage in an annular transonic rotating turbine facility. Measurements were conducted with both uniform stage inlet temperature and with two non-uniform temperature profiles. The temperature profiles were non-dimensionally similar to profiles measured in an engine. A difference of one half of an NGV pitch in the circumferential (clocking) position of the hot-streak with respect to the NGV was used to investigate the affect of clocking on the vane surface and end-wall heat transfer rate. The vane surface pressure distributions, and the results of a flow-visualisation study, which are also given, are used to aid interpretation of the results. The results are compared to two-dimensional predictions conducted using two different boundary layer methods. Experiments were conducted in the Isentropic Light Piston Facility (ILPF) at QinetiQ Farnborough, a short duration engine-size turbine facility. Mach number, Reynolds number and gas-to-wall temperature ratios were correctly modelled. It is believed that the heat transfer measurements presented in this paper are the first of their kind.

scholarly journals Numerical Study on Optimal Scheme of the Geothermally Heated Bridge Deck System

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6633
Author(s):  
Weidong Lyu ◽  
Hefu Pu ◽  
Jiannan (Nick) Chen ◽  
Zelei Gao
Keyword(s):  
Ambient Temperature ◽  
Bridge Deck ◽  
Numerical Study ◽  
Concrete Cover ◽  
Evaluation Index ◽  
Inlet Temperature ◽  
Evaluation Indexes ◽  
Ground Source ◽  
Absorption Power ◽  
Synthetic Evaluation

Ground source deicing system application in bridge decks is an alternative to salt use, which reduces corrosion and extends the deck service life. Herein, a preliminary parametric numerical analysis is performed to investigate the effects of several important parameters (tube spacing, inlet temperature, flow rate, and concrete cover) on heat transfer performance. Three evaluation indexes (average top surface temperature, snow melting proportion, and heat absorption power) are introduced, and a synthetic evaluation index is proposed to comprehensively consider factors. Mainly referring to the synthetic evaluation index, the optimal design scheme of a geothermally heated bridge deck system under various conditions (layout, lane number, ambient temperature, and tube spacing) is obtained and analyzed to determine the optimal inlet temperature and guide heated bridge deck design. Finally, the influence of wind speed and two adjustment methods are studied. The results indicate that the horizontal layout is the recommended circulating tube layout. The established empirical equations reveal that the optimal inlet temperature is linearly related to ambient temperature and exhibits a quadratic relationship with tube spacing. There is no need to add a heat insulation layer at the bridge deck bottom, and only tubes arranged near the wheels in lanes are recommended.

The Effect of Hot-Streaks on HP Vane Surface and Endwall Heat Transfer: An Experimental and Numerical Study

2005 ◽  
Vol 129 (1) ◽  
pp. 32-43 ◽  
Author(s):  
T. Povey ◽  
K. S. Chana ◽  
T. V. Jones ◽  
J. Hurrion
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling System ◽  
Numerical Study ◽  
Guide Vane ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
Gas Temperature ◽  
Hot Streak

Pronounced nonuniformities in combustor exit flow temperature (hot-streaks), which arise because of discrete injection of fuel and dilution air jets within the combustor and because of endwall cooling flows, affect both component life and aerodynamics. Because it is very difficult to quantitatively predict the effects of these temperature nonuniformities on the heat transfer rates, designers are forced to budget for hot-streaks in the cooling system design process. Consequently, components are designed for higher working temperatures than the mass-mean gas temperature, and this imposes a significant overall performance penalty. An inadequate cooling budget can lead to reduced component life. An improved understanding of hot-streak migration physics, or robust correlations based on reliable experimental data, would help designers minimize the overhead on cooling flow that is currently a necessity. A number of recent research projects sponsored by a range of industrial gas turbine and aero-engine manufacturers attest to the growing interest in hot-streak physics. This paper presents measurements of surface and endwall heat transfer rate for a high-pressure (HP) nozzle guide vane (NGV) operating as part of a full HP turbine stage in an annular transonic rotating turbine facility. Measurements were conducted with both uniform stage inlet temperature and with two nonuniform temperature profiles. The temperature profiles were nondimensionally similar to profiles measured in an engine. A difference of one-half of an NGV pitch in the circumferential (clocking) position of the hot-streak with respect to the NGV was used to investigate the affect of clocking on the vane surface and endwall heat transfer rate. The vane surface pressure distributions, and the results of a flow-visualization study, which are also given, are used to aid interpretation of the results. The results are compared to two-dimensional predictions conducted using two different boundary layer methods. Experiments were conducted in the Isentropic Light Piston Facility (ILPF) at QinetiQ Farnborough, a short-duration engine-sized turbine facility. Mach number, Reynolds number, and gas-to-wall temperature ratios were correctly modeled. It is believed that the heat transfer measurements presented in this paper are the first of their kind.

Numerical Analysis of Fluid Flow in an Internal Turbine Blade Cooling Passage

1995 ◽  
Author(s):  
Marc L. Babich ◽  
Song-Lin Yang ◽  
Donna J. Michalek ◽  
Oner Arici
Keyword(s):  
Turbine Blade ◽  
High Efficiency ◽  
Stokes Equations ◽  
Numerical Study ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Grid Turbulence ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Cooling Passage

The need to develop ultra-high efficiency turbines demands the exploration of methods which will improve the thermal efficiency and the specific thrust of the engine. One means of achieving these goals is to increase the turbine inlet temperature. In order to accomplish this, further advances in turbine blade cooling technology will have to be realized. A technique which has only recently been used in the analysis of turbine blade cooling is computational fluid dynamics. The purpose of this paper is to present a numerical study of the flowfield inside of the internal cooling passage of a radial turbine blade. The passage is modeled as two-dimensional and non-rotating. The flowfield solutions are obtained using a pseudo-compressible formulation of the Navier-Stokes equations. The spatial discretization is performed using a symmetric second-order accurate TVD (Total Variational Diminishing) scheme. Calculations are performed on a multi-block-structured grid. Turbulence is modeled using a modified κ-ω model. In the absence of experimental data, results appear to be realistic based on common experiences with fluid mechanics.

Numerical Study of Heat Transfer in Novel Wavy Trailing Edge Design for Gas Turbine Airfoils

2019 ◽  
Author(s):  
Sarwesh Parbat ◽  
Li Yang ◽  
Minking Chyu ◽  
Sin Chien Siw ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Gas Turbine ◽  
Numerical Study ◽  
Turbine Blades ◽  
Suction Side ◽  
Inlet Temperature ◽  
Protective Film ◽  
Pressure Side ◽  
Trailing Edge

Abstract The strive to achieve increasingly higher efficiencies in gas turbine power generation has led to a continued rise in the turbine inlet temperature. As a result, novel cooling approaches for gas turbine blades are necessary to maintain them within the material’s thermal mechanical performance envelope. Various internal and external cooling technologies are used in different parts of the blade airfoil to provide the desired levels of cooling. Among the different regions of the blade profile, the trailing edge (TE) presents additional cooling challenges due to the thin cross section and high thermal loads. In this study, a new wavy geometry for the TE has been proposed and analyzed using steady state numerical simulations. The wavy TE structure resembled a sinusoidal wave running along the span of the blade. The troughs on both pressure side and suction side contained the coolant exit slots. As a result, consecutive coolant exit slots provided an alternating discharge between the suction side and the pressure side of the blade. Steady state conjugate heat transfer simulations were carried out using CFX solver for four coolant to mainstream mass flow ratios of 0.45%, 1%, 1.5% and 3%. The temperature distribution and film cooling effectiveness in the TE region were compared to two conventional geometries, pressure side cutback and centerline ejection which are widely used in vanes and blades for both land-based and aviation gas turbine engines. Unstructured mesh was generated for both fluid and solid domains and interfaces were defined between the two domains. For turbulence closer, SST-kω model was used. The wall y+ was maintained < 1 by using inflation layers at all the solid fluid interfaces. The numerical results depicted that the alternating discharge from the wavy TE was able to form protective film coverage on both the pressure and suction side of the blade. As a result, significant reduction in the TE metal was observed which was up to 14% lower in volume averaged temperature in the TE region when compared to the two baseline conventional configurations.

A Numerical Study on Integral Solar Air Collector

2013 ◽  
Vol 860-863 ◽  
pp. 146-150
Author(s):  
Fu Sheng Dong ◽  
Ming Fu Hu ◽  
Xiao Chun Huang
Keyword(s):  
Mathematical Model ◽  
Solar Radiation ◽  
Thermal Efficiency ◽  
Radiation Intensity ◽  
Numerical Study ◽  
One Dimension ◽  
Inlet Temperature ◽  
Solar Radiation Intensity ◽  
Solar Air Collector ◽  
Matlab Programming

A mathematical modeling method was devoted to study the thermal performance of integral solar air collector. A mathematical model of heat transfer was set up based on one-dimension assumptions at first, and then numerical solution was brought out by using finite-difference method under one-dimension steady heat exchange. Through the MATLAB programming, the approximate solutions for the local air temperature and thermal efficiency were obtained at the quasi-steady state. After calculation, the influence of air inlet velocity, inlet temperature, solar radiation intensity and height of flow channel on the performance of collector was analyzed. It is discovered that the mathematical model is reasonable, the thermal efficiency decreases with temperature of inlet air increasing and increases with air velocity increasing, on which the solar radiation intensity have little influence. Depth of the channel and optimum flow both have a best value.

A Numerical Study of Inlet Geometry for a Low Inertia Mixed Flow Turbocharger Turbine

2014 ◽  
Author(s):  
Thomas M. Leonard ◽  
Stephen Spence ◽  
Juliana Early ◽  
Dietmar Filsinger
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Velocity Ratio ◽  
Cone Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Transient Performance ◽  
Blade Angle ◽  
Low Velocity ◽  
Mixed Flow

Mixed flow turbines can offer improvements over typical radial turbines used in automotive turbochargers, with regards to transient performance and low velocity ratio efficiency. Turbine rotor mass dominates the rotating inertia of the turbocharger, and any reductions of mass in the outer radii of the wheel, including the rotor back-disk, can significantly reduce this inertia and improve the acceleration of the assembly. Off-design, low velocity ratio conditions are typified by highly tangential flow at the rotor inlet and a non-zero inlet blade angle is preferred for such operating conditions. This is achievable in a Mixed Flow Turbine without increasing bending stresses within the rotor blade, which is beneficial in high speed and high inlet temperature turbine design. A range of mixed flow turbine rotors was designed with varying cone angle and inlet blade angle and each was assessed at a number of operating points. These rotors were based on an existing radial flow turbine, and both the hub and shroud contours and exducer geometry were maintained. The inertia of each rotor was also considered. The results indicated that there was a trade-off between efficiency and inertia for the rotors and certain designs may be beneficial for the transient performance of downsized, turbocharged engines.

scholarly journals Numerical Investigation on Supercritical Heat Transfer of RP3 Kerosene Flowing inside a Cooling Channel of Scramjet

2014 ◽  
Vol 6 ◽  
pp. 213438 ◽  
Author(s):  
Ning Wang ◽  
Yu Pan ◽  
Heng Bao ◽  
Jin Zhou
Keyword(s):  
Heat Transfer ◽  
Specific Heat ◽  
Wall Temperature ◽  
Numerical Study ◽  
Hydrocarbon Fuel ◽  
Inlet Temperature ◽  
Good Prediction ◽  
Cooling Channels ◽  
Commercial Code ◽  
Cooling Technology

Supercritical convective heat transfer characteristics of hydrocarbon fuel play a fundamental role in the active cooling technology of scramjet. In this paper, a 2D-axisymmetric numerical study of supercritical heat transfer of RP3 flowing inside the cooling channels of scramjet has been conducted. The main thermophysical properties of RP3, including density, specific heat, and thermal conductivity, are obtained from experimental data, while viscosity is evaluated from a commercial code with a ten-species surrogate. Effects of heat flux, mass flow rate, and inlet temperature on supercritical heat transfer processes have been investigated. Results indicate that when the wall temperature rises above the pseudocritical temperature of RP3, heat transfer coefficient decreases as a result of drastic decrease of the specific heat. The conventional heat transfer correlations, that is, Gnielinski formula, are no longer proper for the supercritical heat transfer of RP3. The modified Jackson and Hall formula, which was proposed for supercritical CO2 and water, gives good prediction except when the wall temperature is near or higher than the pseudocritical temperature.

Transition in Homogeneously Heated Inclined Plane Parallel Shear Flows

2003 ◽  
Vol 125 (5) ◽  
pp. 795-803 ◽  
Author(s):  
S. Generalis ◽  
M. Nagata
Keyword(s):  
Shear Flows ◽  
Numerical Study ◽  
Fluid Layer ◽  
Travelling Wave ◽  
Inclined Plane ◽  
Vertical Orientation ◽  
Plane Parallel ◽  
Wide Range ◽  
Parallel Shear Flows ◽  
Roll Type

The transition of internally heated inclined plane parallel shear flows is examined numerically for the case of finite values of the Prandtl number Pr. We show that as the strength of the homogeneously distributed heat source is increased the basic flow loses stability to two-dimensional perturbations of the transverse roll type in a Hopf bifurcation for the vertical orientation of the fluid layer, whereas perturbations of the longitudinal roll type are most dangerous for a wide range of the value of the angle of inclination. In the case of the horizontal inclination transverse roll and longitudinal roll perturbations share the responsibility for the prime instability. Following the linear stability analysis for the general inclination of the fluid layer our attention is focused on a numerical study of the finite amplitude secondary travelling-wave solutions (TW) that develop from the perturbations of the transverse roll type for the vertical inclination of the fluid layer. The stability of the secondary TW against three-dimensional perturbations is also examined and our study shows that for Pr=0.71 the secondary instability sets in as a quasi-periodic mode, while for Pr=7 it is phase-locked to the secondary TW. The present study complements and extends the recent study by Nagata and Generalis (2002) in the case of vertical inclination for Pr=0.

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