Developing an Application for Refractory Open Cell Metal Foams in Jet Engines

2004 ◽  
Vol 851 ◽  
Author(s):  
Wassim E. Azzi ◽  
William L. Roberts ◽  
Afsaneh Rabiei
Keyword(s):  
Pressure Drop ◽  
Gas Turbines ◽  
High Speed ◽  
Infrared Imaging ◽  
Metal Foam ◽  
Turbine Blades ◽  
Metal Foams ◽  
Thermodynamic Efficiency ◽  
Open Cell ◽  
The Difference

ABSTRACTThe thermodynamic efficiency of the Brayton cycle, upon which all gas turbines (aeropropulsion and power generation) are based on scales with the peak operating temperature. However, the peak temperature is limited by the turbine blades and the temperature they can withstand. The highest temperatures in the gas turbine occur in the combustor region but these temperatures are often too high for turbine blades. As a result, the combustion products must be diluted with relatively cooler air from the compressor to reduce the temperature to tolerable levels for the turbine blades. This research suggests placing a ring of high temperature open cell metal foam between the combustors and turbine sections of the jet engine to mix and average the difference in temperatures resulting from the cooling schemes in combustor cans. Temperature mixing effect was tested using a special setup with the application of an infrared camera and streams of hot and cold air passing through the foam. High speed flow pressure drop around Mach 1 (340 m/s) was done on the same foam samples to understand pressure drop in the compressible regime of air. Infrared imaging showed that open cell metal foams successfully mixed and averaged the difference in temperatures of the hot and cold gasses thus creating a more uniform temperature profile while pressure drop testing revealed that open cell metal foams result in minimal pressure drop at high flows especially when the increase in temperature in taken into consideration.

Pore-Level Numerical Simulation of Open-Cell Metal Foams With Application to Aero Engine Separators

2014 ◽  
Author(s):  
Thiago Piazera de Carvalho ◽  
Hervé P. Morvan ◽  
David Hargreaves
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Porous Medium ◽  
Pressure Drop ◽  
Metal Foam ◽  
Metal Foams ◽  
Open Cell ◽  
X Ray ◽  
Pore Level ◽  
Aero Engines

In aero engines, the oil and air interaction within bearing chambers creates a complex two-phase flow. Since most aero engines use a close-loop oil system and releasing oil out is not acceptable, oil-air separation is essential. The oil originates from the engine transmission, the majority of which is scavenged out from the oil pump. The remainder exits via the air vents, where it goes to an air oil separator called a breather. In metal-foam-style breathers separation occurs by two physical processes. Firstly the largest droplets are centrifuged against the separator walls. Secondly, smaller droplets, which tend to follow the main air path, pass through the metal foam where they ideally should impact and coalesce on the material filaments and drift radially outwards, by the action of centrifugal forces. Although these devices have high separation efficiency, it is important to understand how these systems work to continue to improve separation and droplet capture. One approach to evaluate separation effectiveness is by means of Computational Fluid Dynamics. Numerical studies on breathers are quite scarce and have always employed simplified porous media approaches where a momentum sink is added into the momentum equations in order to account for the viscous and/or inertial losses due to the porous zone [1]. Furthermore, there have been no attempts that the authors know of to model the oil flow inside the porous medium of such devices. Normally, breathers employ a high porosity open-cell metal foam as the porous medium. The aim of this study is to perform a pore-level numerical simulation on a representative elementary volume (REV) of the metal foam with the purpose of determining its transport properties. The pore scale topology is represented firstly by an idealized geometry, namely the Weaire-Phelan cell [2]. The pressure drop and permeability are determined by the solution of the Navier-Stokes equations. Additionally, structural properties such as porosity, specific surface area and pore diameter are calculated. The same procedure is then applied to a 3D digital representation of a metallic foam sample generated by X-ray tomography scans [3]. Both geometries are compared against each other and experimental data for validation. Preliminary simulations with the X-ray scanned model have tended to under predict the pressure drop when compared to in-house experimental data. Additionally, the few existing studies on flow in metal foams have tended to consider laminar flow; this is not the case here and this also raises the question that Reynolds-averaged turbulence models might not be well suited to flows at such small scales, which this paper considers.

scholarly journals Review and a Theoretical Approach on Pressure Drop Correlations of Flow through Open-Cell Metal Foam

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3153
Author(s):  
Huizhu Yang ◽  
Yongyao Li ◽  
Binjian Ma ◽  
Yonggang Zhu
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Metal Foam ◽  
Flow Characteristics ◽  
Metal Foams ◽  
High Porosity ◽  
Open Cell ◽  
Wide Range ◽  
Flow Through

Due to their high porosity, high stiffness, light weight, large surface area-to-volume ratio, and excellent thermal properties, open-cell metal foams have been applied in a wide range of sectors and industries, including the energy, transportation, aviation, biomedical, and defense industries. Understanding the flow characteristics and pressure drop of the fluid flow in open-cell metal foams is critical for applying such materials in these scenarios. However, the state-of-the-art pressure drop correlations for open-cell foams show large deviations from experimental data. In this paper, the fundamental governing equations of fluid flow through open-cell metal foams and the determination of different foam geometry structures are first presented. A variety of published models for predicting the pressure drop through open-cell metal foams are then summarized and validated against experimental data. Finally, two empirical correlations of permeability are developed and recommended based on the model of Calmidi. Moreover, Calmidi’s model is proposed to calculate the Forchheimer coefficient. These three equations together allow calculating the pressure drop through open-cell metal foam as a function of porosity and pore diameter (or strut diameter) in a wide range of porosities ε = 85.7–97.8% and pore densities of 10–100 PPI. The findings of this study greatly advance our understanding of the flow characteristics through open-cell metal foam and provide important guidance for the design of open-cell metal foam materials for different engineering applications.

An Optimization Design Platform for Fir-Tree Root and Groove for Steam Turbine

2018 ◽  
Author(s):  
Deqi Yu ◽  
Xiaojun Zhang ◽  
Jiandao Yang ◽  
Kai Cheng ◽  
Weilin Shu ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Steam Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Optimization Design ◽  
Turbine Blades ◽  
Local Stress ◽  
Optimization Method ◽  
Steam Turbines ◽  
Geometry Configuration

Fir-tree root and groove profiles are widely used in gas turbine and steam turbine. Normally, the fir-tree root and groove are characterized with straight line, arc or even elliptic fillet and splines, then the parameters of these features were defined as design variables to perform root profile optimization. In ultra-long blades of CCPP and nuclear steam turbines and high-speed blades of industrial steam turbine blades, both the root and groove strength are the key challenges during the design process. Especially, in industrial steam turbines, the geometry of blade is very small but the operation velocity is very high and the blade suffers stress concentration severely. In this paper, two methods for geometry configuration and relevant optimization programs are described. The first one is feature-based using straight lines and arcs to configure the fir-tree root and groove geometry and genetic algorithm for optimization. This method is quite fit for wholly new root and groove design. And the second local optimization method is based on B-splines to configure the geometry where the local stress concentration occurs and the relevant optimization algorithm is used for optimization. Also, several cases are studied as comparison by using the optimization design platform. It can be used not only in steam turbines but also in gas turbines.

Experimental and numerical thermal analysis of open-cell metal foams developed through a topological optimization and 3D printing process

2018 ◽  
Vol 83 (1) ◽  
pp. 10904 ◽  
Author(s):  
Abdelatif Merabtine ◽  
Nicolas Gardan ◽  
Julien Gardan ◽  
Houssem Badreddine ◽  
Chuan Zhang ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
3D Printing ◽  
Numerical Simulations ◽  
Lattice Model ◽  
Metal Foam ◽  
Complex Geometry ◽  
Metal Foams ◽  
Topological Optimization ◽  
Plaster Mold ◽  
Open Cell

This study focuses on the thermal analysis and comparing a lattice model and an optimized model of open-cell metal foams manufactured thanks to a metal casting process. The topological optimization defines the complex geometry through thermal criteria and a plaster mold reproduces it in 3D printing to be used in casting. The study of the thermal behavior conducted on the two open foam metal structures is performed based on several measurements, as well as numerical simulations. It is observed that the optimized metal foam presented less and non-homogenous local temperature than the lattice model with the gap of about 10 °C between both models. The pore size and porosity significantly affect the heat transfer through the metal foam. The comparison between numerical simulations and experimental results regarding the temperature fields shows a good agreement allowing the validation of the developed three-dimensional model based on the finite element method.

Development and Evaluation of Silicon Nitride Components for Ceramic Gas Turbine

1998 ◽  
Author(s):  
Yasushi Hara ◽  
Katsura Matsubara ◽  
Ken-ichi Mizuno ◽  
Toru Shimamori ◽  
Hiro Yoshida
Keyword(s):  
Silicon Nitride ◽  
Gas Turbines ◽  
High Speed ◽  
Gas Flow ◽  
Impact Damage ◽  
Turbine Blades ◽  
Impact Testing ◽  
Particle Impact ◽  
Inlet Temperature ◽  
Power Turbine

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles. In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1350 °C in accordance with the project goals, we developed two silicon nitride materials with further improved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles. On applying these silicon nitride ceramics to CGT engine, we evaluated various properties of silicon nitride materials considering the environment in CGT engine. Particle impact testing is one of those evaluations. Materials used in CGT engine are exposed in high speed gas flow, and impact damage of these materials is considered to be a concern. We tested ST-1 in the particle impact test. In this test, we observed fracture modes, and estimated the critical impact velocity. This paper summarizes the development of silicon nitride components, and the result of evaluations of these silicon nitride materials.

Microtomography-Based Analysis of Pressure Drop and Heat Transfer Through Open Cell Metal Foams

2013 ◽  
Author(s):  
M. Oliviero ◽  
S. Cunsolo ◽  
W. M. Harris ◽  
M. Iasiello ◽  
W. K. S. Chiu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Metal Foam ◽  
High Surface ◽  
Thermal Characteristics ◽  
Industrial Applications ◽  
Metal Foams ◽  
Surface Evolver ◽  
Periodic Cell ◽  
Numerical Predictions

Their light weight, open porosity, high surface area per unit volume and thermal characteristics make metal foams a promising material for many industrial applications involving fluid flow and heat transfer. Pressure drop and heat transfer of porous media have inspired a number of experimental and numerical studies. Many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models. Most studies are based on idealized periodic cell structures. In this study, the true 3-D micro-structure of the metal foam is obtained by employing x-ray computed microtomography (XCT). For comparison, ideal Kelvin foam structures are developed in the free-to-use software “Surface Evolver” surface energy minimization program. Pressure drop and heat transfer are then investigated using the CFD Module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out.

Preliminary NVH Characterization of Metal Foam-Polymer Interpenetrating Phase Composites

2009 ◽  
Author(s):  
Satish Sharma ◽  
Nassif E. Rayess ◽  
Nihad Dukhan
Keyword(s):  
Mathematical Model ◽  
Thermal Stability ◽  
Hybrid Material ◽  
Aluminum Foam ◽  
Metal Foam ◽  
Dynamic Properties ◽  
Metal Foams ◽  
Thermoplastic Polymer ◽  
Open Cell

The damping and basic dynamic properties of a novel type of multifunctional hybrid material known as Metal Foam-Polymer Composite are investigated. This material is obtained by injection molding a thermoplastic polymer through an open cell Aluminum Foam, in essence creating two contiguous morphologies; an Aluminum Foam interconnected “skeleton” with the open pores filled with a similarly interconnected polymer substructure. This coexistence of both materials allows each to contribute its salient properties (e.g. the plastics contributing surface toughness and the metal foams contributing thermal stability). Basic damping testing results are presented for various Aluminum Foam porosities and pore sizes as well as for three types of polymers. A basic mathematical model of the damping is also presented. The integrity of the interface between the Aluminum Foam and the Polymer is discussed in terms of its effect on the overall material damping.

scholarly journals The effect of open-cell metal foams strut shape on convection heat transfer and pressure drop

2016 ◽  
Vol 103 ◽  
pp. 333-343 ◽  
Author(s):  
Giuseppe Ambrosio ◽  
Nicola Bianco ◽  
Wilson K.S. Chiu ◽  
Marcello Iasiello ◽  
Vincenzo Naso ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Convection Heat Transfer ◽  
Metal Foams ◽  
Convection Heat ◽  
Open Cell
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