Development of Experimental and Numerical Methods for the Analysis of Active Clearance Control Systems

2020 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Lorenzo Mazzei ◽  
Lorenzo Tarchi ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Current Trend ◽  
Turbulence Models ◽  
Pressure Head ◽  
Test Sample ◽  
Low Pressure ◽  
Numerical Approach ◽  
Impingement Heat Transfer ◽  
Aero Engines ◽  
Clearance Control

Abstract To increase the performance of modern aero-engines, the control of blade tip leakages in mandatory. In the last decades, this task was performed by Active Clearance Control (ACC) systems, which manage the casing thermal deformations and the associated losses via cooling jets impinging on the casing outer surface. The current trend of increasing the engine by-pass ratio pushes the limits of ACC traditional design, since a lower pressure head is available for the generation of the jets. Therefore, denser jet patterns and lower jet-to-target distances are required to compensate the reduction of the jets' Reynolds number. Literature correlations for the estimation of impingement heat transfer are then out of their confidence range, and also RANS numerical approaches appear not to be suitable. In this work, methodologies for the development of accurate and reliable tools to determine the heat transfer characteristics of low pressure ACC systems are presented. More precisely, this paper describes a custom designed finite difference procedure capable of solving the inverse conduction problem on the target plate of a test sample. The methodology was successfully applied to an experimental setup for the measurement of the heat transfer features of a representative low pressure ACC system. The experimental data was then used to validate a suitable numerical approach. Results show that RANS is not able to mimic the experimental trends, while scale-resolving turbulence models provide a good reconstruction of the experimental evidences, thus allowing to obtain a correct interpretation of flow and thermal phenomena.

Development of Experimental and Numerical Methods for the Analysis of Active Clearance Control Systems

2020 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Lorenzo Mazzei ◽  
Lorenzo Tarchi ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Current Trend ◽  
Turbulence Models ◽  
Pressure Head ◽  
Test Sample ◽  
Low Pressure ◽  
Numerical Approach ◽  
Tip Clearance ◽  
Target Plate ◽  
Clearance Control

Abstract The ever increasing performance requirements of modern aero-engines necessitate the development of effective ways to improve efficiency and reduce losses. Casing temperature control is particularly critical from this point of view, since thermal expansion directly affects the blade tip clearance and thus the associated leakages. To limit the turbine tip flows, Active Clearance Control (ACC) systems have been implemented over the last decades. These systems are usually based upon impingement cooling, generated by a series of perforated manifolds enclosing the turbine casing. When dealing with aeroengine low pressure turbines, the current trend in increasing the engine by-pass ratio, so as to enhance the system propulsive efficiency, pushes the limits of ACC traditional design performance. The reduction of the pressure head at the ACC system inlet requires lower nozzle-to-target distances as well as denser impingement arrays to compensate the reduction of the jets’ Reynolds number. Literature correlations for the impingement heat transfer coefficient estimation are then out of their confidence range and also RANS numerical approaches appear not suitable for future ACC designs. In this work, methodologies for the development of accurate and reliable tools to determine the heat transfer characteristics of low pressure ACC systems are presented. More precisely, this paper describes a custom designed finite difference procedure capable of solving the inverse conduction problem on the target plate of a test sample. The methodology was successfully applied to an experimental setup for the measurement of the thermal loads on a target plate of a representative low pressure ACC impinging system. The experimental data is then used to validate a suitable numerical approach. Results show that RANS model is not able to mimic the experimental trends, while scale-resolving turbulence models provide a good reconstruction of the experimental evidences, thus allowing to obtain a correct interpretation of flow and thermal phenomena for ACC systems.

Technique for Adequate CFD-Modeling of the Pump With Hydro-Drive of the Low-Pressure Stage

2016 ◽  
Author(s):  
Vasilii M. Zubanov ◽  
Leonid S. Shabliy ◽  
Alexander V. Krivcov ◽  
Valeriy N. Matveev
Keyword(s):  
Rotational Speed ◽  
Cfd Simulation ◽  
Turbulence Models ◽  
Pressure Head ◽  
Low Pressure ◽  
Inlet Pressure ◽  
Cfd Modeling ◽  
Future Research ◽  
Rotor Speed ◽  
Pressure Stage

This article describes the technique for CFD-modeling of a powerful two-stage pump with the following main parameters: main rotor speed is 13,300 rpm, inlet pressure is 0.2 MPa, pressure head is more than 3,000 meters with mass flow of 250 kg/s. The main feature of investigated pump is the hydro-drive of the low-pressure stage of turbine with variable rotational speed. There are two highlights in this work in comparison with the previous ones. The first one is how to choose the rotating speed of hydro-turbine. The second one is the CFD-modeling of cavitation processes. The core part of proposed technique is the determination of rotational speed during CFD-simulation by special methodology. Another feature is the cavitation modeling to be sure that there is no cavitation in pre-pump at quite low inlet pressure and variable rotor speed. Also, recommendations about program tools (ANSYS CFX, NUMECA AutoGrid5, ANSYS ICEM CFD) are a significant part of the discussed technique, as well as modeling features (fluid domain restriction, meshing, turbulence models choosing, convergence checking, post-processing). The adequacy of CFD-model was evaluated by comparing predicted characteristics of the pump with the experimental ones derived from the test rig. The differences amounted to less than 10%. The obtained technique can be used in the future research for performance improving and efficiency increasing of pumps with hydro-drive of the low-pressure stage by CFD-tools.

Multi-Jet Impingement Heat Transfer With a Dimple-Pimple Patterned Jet Plate

2020 ◽  
Author(s):  
Husam Zawati ◽  
Gaurav Gupta ◽  
Yakym Khlyapov ◽  
Erik Fernandez ◽  
Jayanta Kapat ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Underlying Mechanism ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Air Jets ◽  
Impingement Heat Transfer ◽  
Definition Of

Abstract The objective of the present study is the evaluation of the heat transfer difference between a novel jet plate configuration and a conventional flat jet orifice plate. Physical mechanisms that lead to a change in Nusselt number when comparing both configurations are discussed in two regions: impingement and crossflow. In the presented work, both plates with identical inline arrays of (20 × 26) circular air jets impinging orthogonally on a flat target comprised of 20 segments parallel to the jet orifice plates, are studied. The first is a staggered configuration of a pimple-dimple (convex-concave) plate. This plate features two jet diameters: (a) 4.63 mm emanating from negative sphere of 14.63 mm in radius inward imprint; (b) 2.19 mm emanating from a positive sphere of 17.07 mm in radius, protruding from the base of the plate. The second jet plate is flat, which serves as a baseline for the heat transfer study. This plate has a constant jet orifice diameters of 3.49 mm, found based on the definition of total average open area of the first plate (NPR configuration). Heat transfer characteristics and turbulent flow structures are investigated over jet-averaged Reynolds numbers (Reav,j) of 5,000, 7,000, and 9,000. Jet-to-plate distance (Z/Dj) is varied between (2.4 – 6.0) jet diameters. A numerical study is carried out to compare various turbulence models (κε-EB, κε-Lag EB, κε-v2f, κω-SST, RST). Numerical simulations are analyzed in detail to explain the underlying mechanism of heat transfer enhancement, related to such geometries. The convex-concaved plate yields lower globally-averaged heat transfer coefficients when compared to a flat jet plate in the impingement region. However, enhancement up to 23% is seen in the crossflow region, where the crossflow effects are dominant in a maximum-crossflow configuration.

CFD Prediction for Multi-Jet Impingement Heat Transfer

2009 ◽  
Author(s):  
Y. Q. Zu ◽  
Y. Y. Yan ◽  
J. D. Maltson
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Computational Cost ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Reynolds Stress Model ◽  
Large Eddy Simulation Model ◽  
Flow And Heat Transfer ◽  
Shear Stress Transport ◽  
Impingement Heat Transfer

In this paper, the flow and heat transfer characteristics of two lines of staggered or inline round jets impinging on a flat plate are numerically analyzed using the CFD commercial code FLUENT. Firstly, the relative performance of seven versions of turbulence models, including the standard k-ε model, the renormalization group k-ε model, the realizable k-ε model, the standard k-ω model, the Shear-Stress Transport k-ω model, the Reynolds stress model and the Large Eddy Simulation model, for numerically predicting single jet impingement heat transfer is investigated by comparing the numerical results with available benchmark experimental data. As a result, the Shear-Stress Transport k-ω model is recommended as the best compromise between the computational cost and accuracy. Using the Shear-Stress Transport k-ω model, the impingement flow and heat transfer under multi-jets with different jet distributions and attack angles are simulated and studied. The effect of hole distribution and angle of attack, etc. on the heat transfer coefficient of the target plate are examined.

Unsteady Work Processes Within a Low Pressure Turbine Vane Passage

2013 ◽  
Author(s):  
Martin Marx ◽  
Martin Lipfert ◽  
Martin G. Rose ◽  
Stephan Staudacher ◽  
Detlef Korte
Keyword(s):  
Pressure Fluctuations ◽  
Low Pressure ◽  
Numerical Approach ◽  
Test Facility ◽  
Work Processes ◽  
Unsteady Pressure ◽  
Low Pressure Turbine ◽  
Stator Vane ◽  
Aero Engines ◽  
Work Done

A two-stage low pressure turbine is tested within the co-operation project between the Institute of Aircraft Propulsion Systems (ILA) and MTU Aero Engines GmbH. With experimental data taken in the altitude test facility this study aims to analyze the origin and effect of unsteady pressure fluctuations causing unsteady work in the second stator vane. Measurements at aerodynamic design conditions cover steady and unsteady surface pressure data on the mid span streamline position. Unsteady pressure fluctuations are identified close to the throat plane area, which are influenced by both upstream and downstream events such as wake and potential field interaction. Upstream moving static pressure waves can be identified. To support the experimental results, URANS CFD predictions of the whole turbine configuration were performed. The numerical approach is suitable to reproduce the observed phenomena and allows a deeper investigation. The observed pressure pulsations influence the local unsteady work done to and by the fluid. An evaluation of particle paths in the second stator vane indicates an isentropic energy transfer from free stream to wake fluid. Due to this unsteady energy exchange the momentum deficit of the wake gets reduced, resulting in a potential benefit on the mixing loss.

Reynolds Averaged and Large Eddy Computations of Flow and Heat Transfer Under Round Jet Impingement

2014 ◽  
Author(s):  
Thangam Natarajan ◽  
James Jewkes ◽  
Ramesh Narayanaswamy ◽  
Yongmann M. Chung ◽  
Anthony D. Lucey
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Navier Stokes ◽  
Round Jet ◽  
Eddy Simulation ◽  
Impingement Heat Transfer ◽  
Turbulent Statistics ◽  
Large Eddy

The fluid dynamics and heat transfer characteristics of a turbulent round jet are modelled numerically using Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES). Meshes with varying degrees of coarseness, with both radial and axial refinements are investigated. Discretization is carried out using the finite volume method. The jet configurations are chosen to enable validation against well-established experimental jet-impingement heat-transfer studies, particularly that of Cooper et al. [1]. The Reynolds number studied is 23000. The height of discharge from the impingement wall is fixed at twice the jet diameter. The work critically examines the effect of Reynolds number, standoff distance and helps to ascertain the relative merits of various turbulence models, by comparing turbulent statistics and the Nusselt number distributions. The present work is carried out as a preliminary validation, in a wider study intended to determine the thermofluidic behaviour of jets impinging upon an oscillating surface.

Aero-Thermal Investigation of Convective and Radiative Heat Transfer on Active Clearance Control Manifolds

2019 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Operating Conditions ◽  
Impingement Heat Transfer ◽  
Blade Tip ◽  
Clearance Control

Abstract The present paper deals with the characterization of heat transfer on blade tip Active Clearance Control manifolds. Real engine geometries and operating conditions were considered in validated CFD computations to understand the impacts of both manifold surfaces convective and radiative heat transfer on the aero-thermal performance of the system. Different manifold geometries were accounted for also. The study sorted out that both the radiation and the convective heat transfer on the manifold surfaces are responsible of performance deteriorations as the impingement heat transfer on the casing is considered. The last evidence is motivated by the fresh fluid heat up along the feeding pipe. Radiative heat transfer from the casing to the manifold is found to be relevant, especially in case of high casing temperature or low undercowl flow rates. As a result of the study, is remarked that ACC manifold radiative and convective heat transfer should be considered for a proper system design.

Experimental and Numerical Analysis of Multiple Impingement Jet Arrays for an Active Clearance Control System

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Antonio Andreini ◽  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Francesco Maiuolo ◽  
Lorenzo Tarchi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Internal Diameter ◽  
Impingement Jet ◽  
Blade Tip ◽  
Typical Shape ◽  
Aero Engines ◽  
D 12 ◽  
Clearance Control ◽  
The Heat Transfer Coefficient

The turbine blade tip clearances control in large aero-engines is currently performed by means of impinging fan air on the outer case flanges. The aim of the present study is to evaluate both the heat transfer coefficient and the adiabatic thermal effectiveness characteristics of an enginelike ACC system, and in particular, to comprehend the effects of the undercowl flow on the impingement jets. The considered geometry replicates the impingement tubes and the by-pass duct used in active control clearance systems. The tube's internal diameter is D = 12 mm, the cooling hole's diameter is d = 1 mm, and the span-wise pitch is Sy/d=12. In order to simulate the undercowl flow, the impingement arrays are inserted inside a tunnel that replicates the typical shape of a real engine by-pass duct. Tests were conducted varying both the mainstream Reynolds number and the jets Reynolds number in a range typical of real-engine operative conditions (Rej=2000-10000, β=1.05-1.15). Numerical calculations are finally proposed to point out if CFD is able to confidently reproduce the experimental evidences.

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