A Path Toward Effective Piston/Cylinder Interface Scaling Approach

2017 ◽  
Author(s):  
L. Shang ◽  
M. Ivantysynova
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Design Parameters ◽  
Simulation Tool ◽  
Scaling Method ◽  
Plate Interface ◽  
Piston Cylinder ◽  
Swash Plate ◽  
Solid Part

Scaling three main lubricating interfaces (piston/cylinder interface, cylinder block/valve plate interface, and slipper/swash plate interface) of swash plate type axial piston machine while remaining the pump performance is a rewarding but challenging task. Instead of designing a new unit for the desired displacement, scaling a well-designed existing unit to the desired size requires much less computational and experimental cost. However, scaling all the components linearly is far from enough to remain the original sized unit’s performance due to the unscalable fluid properties and material properties. This paper proposes a novel scaling method for the piston/cylinder interface which is able to achieve the baseline performance at some of the operating conditions, and closing the gap between the scaled unit performance and the baseline performance at the rest of the operating conditions. The authors use a special in-house developed simulation tool to study the design parameters of the piston/cylinder interface impacts on the performance in terms of leakage flow rate, and the energy dissipation. This in-house developed tool is able to model the lubricating fluid film behavior considering the complex fluid and structure interaction, the macro and micro motion of the piston, the three-dimensional fluid heat-transfer, the three-dimensional solid part heat-transfer, and the solid part deformation due to both the pressure and the thermal load. This paper includes a brief introduction of the simulation tool, the results of the design parameters investigation, the proposed scaling method, and the simulation results comparison between the baseline unit and the scaled unit using the proposed method.

Numerical Simulation of Gas Flow and Heat Transfer in Cross-Wavy Primary Surface Channel for Microtubine Recuperators

2005 ◽  
Author(s):  
H. X. Liang ◽  
Q. W. Wang ◽  
L. Q. Luo ◽  
Z. P. Feng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Gas Turbine ◽  
Numerical Study ◽  
High Reliability ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
The Cross

Three-dimensional numerical simulation was conducted to investigate the flow field and heat transfer performance of the Cross-Wavy Primary Surface (CWPS) recuperators for microturbines. Using high-effective compact recuperators to achieve high thermal efficiency is one of the key techniques in the development of microturbine in recent years. Recuperators need to have minimum volume and weight, high reliability and durability. Most important of all, they need to have high thermal-effectiveness and low pressure-losses so that the gas turbine system can achieve high thermal performances. These requirements have attracted some research efforts in designing and implementing low-cost and compact recuperators for gas turbine engines recently. One of the promising techniques to achieve this goal is the so-called primary surface channels with small hydraulic dimensions. In this paper, we conducted a three-dimensional numerical study of flow and heat transfer for the Cross-Wavy Primary Surface (CWPS) channels with two different geometries. In the CWPS configurations the secondary flow is created by means of curved and interrupted surfaces, which may disturb the thermal boundary layers and thus improve the thermal performances of the channels. To facilitate comparison, we chose the identical hydraulic diameters for the above four CWPS channels. Since our experiments on real recuperators showed that the Reynolds number ranges from 150 to 500 under the operating conditions, we implemented all the simulations under laminar flow situations. By analyzing the correlations of Nusselt numbers and friction factors vs. Reynolds numbers of the four CWPS channels, we found that the CWPS channels have superior and comprehensive thermal performance with high compactness, i.e., high heat transfer area to volume ratio, indicating excellent commercialized application in the compact recuperators.

scholarly journals Fast three-dimensional heat transfer model for computing internal temperatures in the bearing housing of automotive turbochargers

2018 ◽  
Vol 21 (8) ◽  
pp. 1286-1297 ◽  
Author(s):  
Antonio Gil ◽  
Andrés Omar Tiseira ◽  
Luis Miguel García-Cuevas ◽  
Tatiana Rodríguez Usaquén ◽  
Guillaume Mijotte
Keyword(s):  
Heat Transfer ◽  
Coke Formation ◽  
Three Dimensional ◽  
Heat Transfer Model ◽  
Operating Conditions ◽  
Thermal Design ◽  
Working Fluid ◽  
Transfer Model ◽  
Lumped Model ◽  
Bearing System

Each of the elements that make up the turbocharger has been gradually improved. In order to ensure that the system does not experience any mechanical failures or loss of efficiency, it is important to study which engine-operating conditions could produce the highest failing rate. Common failing conditions in turbochargers are mostly achieved due to oil contamination and high temperatures in the bearing system. Thermal management becomes increasingly important for the required engine performance. Therefore, it has become necessary to have accurate temperature and heat transfer models. Most thermal design and analysis codes need data for validation; often the data available fall outside the range of conditions the engine experiences in reality leading to the need to interpolate and extrapolate disproportionately. This article presents a fast three-dimensional heat transfer model for computing internal temperatures in the central housing for non-water cooled turbochargers and its direct validation with experimental data at different engine-operating conditions of speed and load. The presented model allows a detailed study of the temperature rise of the central housing, lubrication channels, and maximum level of temperature at different points of the bearing system of an automotive turbocharger. It will let to evaluate thermal damage done to the system itself and influences on the working fluid temperatures, which leads to oil coke formation that can affect the performance of the engine. Thermal heat transfer properties obtained from this model can be used to feed and improve a radial lumped model of heat transfer that predicts only local internal temperatures. Model validation is illustrated, and finally, the main results are discussed.

Heat Transfer and Thermal Elastic Deformation Analysis on the Piston/Cylinder Interface of Axial Piston Machines

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Matteo Pelosi ◽  
Monika Ivantysynova
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Elastic Deformation ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Fluid Film ◽  
Design Elements ◽  
Piston Cylinder ◽  
Viscous Shear ◽  
Axial Piston

The piston/cylinder interface of swash plate–type axial piston machines represents one of the most critical design elements for this type of pump and motor. Oscillating pressures and inertia forces acting on the piston lead to its micro-motion, which generates an oscillating fluid film with a dynamically changing pressure distribution. Operating under oscillating high load conditions, the fluid film between the piston and cylinder has simultaneously to bear the external load and to seal the high pressure regions of the machine. The fluid film interface physical behavior is characterized by an elasto-hydrodynamic lubrication regime. Additionally, the piston reciprocating motion causes fluid film viscous shear, which contributes to a significant heat generation. Therefore, to fully comprehend the piston/cylinder interface fluid film behavior, the influences of heat transfer to the solid boundaries and the consequent solid boundaries’ thermal elastic deformation cannot be neglected. In fact, the mechanical bodies’ complex temperature distribution represents the boundary for nonisothermal fluid film flow calculations. Furthermore, the solids-induced thermal elastic deformation directly affects the fluid film thickness. To analyze the piston/cylinder interface behavior, considering the fluid-structure interaction and thermal problems, the authors developed a fully coupled simulation model. The algorithm couples different numerical domains and techniques to consider all the described physical phenomena. In this paper, the authors present in detail the computational approach implemented to study the heat transfer and thermal elastic deformation phenomena. Simulation results for the piston/cylinder interface of an existing hydrostatic unit are discussed, considering different operating conditions and focusing on the influence of the thermal aspect. Model validation is provided, comparing fluid film boundary temperature distribution predictions with measurements taken on a special test bench.

scholarly journals A Three-Dimensional Coupled Internal/External Simulation of a Film-Cooled Turbine Vane

1999 ◽  
Author(s):  
James D. Heidmann ◽  
David L. Rigby ◽  
Ali A. Ameri
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Three Dimensional ◽  
High Heat ◽  
Operating Conditions ◽  
High Heat Flux ◽  
Nasa Lewis Research ◽  
Turbine Vane ◽  
Film Cooling Holes

A three-dimensional Navier-Stokes simulation has been performed for a realistic film-cooled turbine vane using the LeRC-HT code. The simulation includes the flow regions inside the coolant plena and film cooling holes in addition to the external flow. The vane is the subject of an upcoming NASA Lewis Research Center experiment and has both circular cross-section and shaped film cooling holes. This complex geometry is modeled using a multi-block grid which accurately discretizes the actual vane geometry including shaped holes. The simulation matches operating conditions for the planned experiment and assumes periodicity in the spanwise direction on the scale of one pitch of the film cooling hole pattern. Two computations were performed for different isothermal wall temperatures, allowing independent determination of heat transfer coefficients and film effectiveness values. The results indicate separate localized regions of high heat flux in the showerhead region due to low film effectiveness and high heat transfer coefficient values, while the shaped holes provide a reduction in heat flux through both parameters. Hole exit data indicate rather simple skewed profiles for the round holes, but complex profiles for the shaped holes with mass fluxes skewed strongly toward their leading edges.

Development and validation of a novel quasi-dimensional combustion model for un-scavenged prechamber gas engines with numerical simulations and engine experiments

2020 ◽  
pp. 146808742095133 ◽  
Author(s):  
Konstantinos Bardis ◽  
Panagiotis Kyrtatos ◽  
Guoqing Xu ◽  
Christophe Barro ◽  
Yuri Martin Wright ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Design Parameters ◽  
Combustion Model ◽  
Experimental Investigations ◽  
Computationally Efficient ◽  
Lean Burn ◽  
Dimensional Models ◽  
Three Dimensional Models

Lean-burn gas engines equipped with an un-scavenged prechamber have proven to reduce nitrogen oxides (NOx) emissions and fuel consumption, while mitigating combustion cycle-to-cycle fluctuations and unburned hydrocarbon (UHC) emissions. However, the performance of a prechamber gas engine is largely dependent on the prechamber design, which has to be optimised for the particular main chamber geometry and the foreseen engine operating conditions. Optimisation of such complex engine components relies partly on computationally efficient simulation tools, such as quasi and zero-dimensional models, since extensive experimental investigations can be costly and time-consuming. This article presents a newly developed quasi-dimensional (Q-D) combustion model for un-scavenged prechamber gas engines, which is motivated by the need for reliable low order models to optimise the principle design parameters of the prechamber. Our fundamental aim is to enhance the predictability and robustness of the proposed model with the inclusion of the following: (i) Formal derivation of the combustion and flow submodels via reduction of the corresponding three-dimensional models. (ii) Individual validation of the various submodels. (iii) Combined use of numerical simulations and experiments for the model validation. The resulting model shows very good agreement with the numerical simulations and the experiments from two different engines with various prechamber geometries using a set of fixed calibration parameters.

Parametric Study of Vortex Generator Effects in an Additive Manufactured Minichannel Heat Exchanger

2019 ◽  
Author(s):  
Hamidreza Rastan ◽  
Tim Ameel ◽  
Björn Palm
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Additive Manufacturing ◽  
Heat Exchanger ◽  
Angle Of Attack ◽  
Three Dimensional ◽  
High Energy ◽  
Vortex Generators ◽  
Design Parameters ◽  
Minichannel Heat Exchanger

Abstract Heat exchangers with mini- and micro-channel components are capable of high energy exchange due to their incumbent large surface area to volume ratio. Concurrently, recent advances in additive manufacturing simplify the creation of metallic minichannels that incorporate turbulators for heat transfer enhancement. As part of the development of a minichannel heat exchanger with turbulators, this study analyzes the three-dimensional conjugate heat transfer and laminar flow in a minichannel heat exchanger equipped with rectangular winglet vortex generators (VGs) through numerical simulation. The minichannels have a hydraulic diameter of 2.86 mm and are assumed to be made from aluminum alloy AlSi10Mg. This material is one of the popular alloys in the additive manufacturing industry (three-dimensional (3D) printing) because of its light weight and beneficial mechanical and thermal properties. The working fluid is distilled water with temperature-dependent thermal properties. The minichannel is heated by a constant heat flux of 5 W cm−2 and the Reynolds number is varied from 230 to 950. The simulations are performed using the COMSOL® platform, which solves the governing mass, momentum, and energy equations based on the finite element method. The effect of the VG design parameters, which include VG angle of attack, height, length, thickness, longitudinal pitch, and distance from the sidewalls, is investigated. It is found that the generation of three-dimensional vortices caused by the presence of the vortex generators can notably boost the convective heat transfer, at the cost of increased pressure drop, potentially reducing the heat exchanger size for a given heat duty. A sensitivity analysis indicates that the angle of attack, VG height, VG length, and longitudinal pitch have the most significant effects on the heat transfer and flow friction characteristics. In contrast, the VG thickness and distance from the sidewalls only had minor influences on the heat exchanger performance over the studied range of design parameters.

A Parametric Study on Fluid Flow and Heat Transfer in a Printed Circuit Heat Exchanger

2011 ◽  
Author(s):  
Sang-Moon Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Transport Model ◽  
Three Dimensional ◽  
Design Parameters ◽  
Printed Circuit ◽  
Reference Shape ◽  
Shear Stress Transport Model

Numerical analyses for pressure drop and heat transfer in the flow channels of a printed circuit heat exchanger have been performed numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations have been solved in conjunction with the shear stress transport model as a turbulence closure. The numerical solutions are validated with the available experimental results of the reference shape. The effects of two design parameters, namely, the channel angle and the ellipse aspect ratio of the cold channel, on the heat transfer and the friction performance have been evaluated.

Numerical Simulations of the Fluid Flow and Heat Transfer during a Solidification Phase Change of a Polymer in a Die

2010 ◽  
Vol 97-101 ◽  
pp. 2736-2743
Author(s):  
Shi Xiong Ren ◽  
Sha Sha Dang ◽  
Tao Lu ◽  
Kui Sheng Wang
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Liquid Volume ◽  
Liquid Volume Fraction ◽  
Three Dimensional Models ◽  
Lower Temperature ◽  
Thermal Oil

Three-dimensional models of heat transfer have been established and numerically solved using a commercial software package, Fluent, in order to obtain distributions of temperature, velocity, pressure, and liquid volume fraction of the polymer. The influences of the boundary conditions on the phase change of the polymer and the temperature distribution in the die have been evaluated. The results show that the temperature of the region close to the pelletizing surface is relatively low due to the cooling effect of the cool water, while the temperature deeper inside the die is higher, with a lower temperature gradient, as a result of the heating effect of the hot thermal oil and the polymer. A solidification phase change of the polymer occurs near the polymer outlet due to heat loss from the polymer to the water, while deeper inside the hole the polymer remains fluid without solidification, due to heating by the thermal oil. Numerical simulation provides a reliable method to optimize the design of the die, the choice of metallic material for the die, and the operating conditions of the polymer pelletizing under water.

On the Coupling of Inverse Design and Optimization Techniques for Turbomachinery Blade Design

2006 ◽  
Author(s):  
Duccio Bonaiuti ◽  
Mehrdad Zangeneh
Keyword(s):  
Mechanical Design ◽  
Design Method ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Optimization Techniques ◽  
Operating Conditions ◽  
Inverse Design ◽  
Design Parameters ◽  
Optimization Strategy ◽  
Design And Optimization

Optimization strategies have been used in recent years for the aerodynamic and mechanical design of turbomachine components. One crucial aspect in the use of such methodologies is the choice of the geometrical parameterization, which determines the complexity of the objective function to be optimized. In the present paper, an optimization strategy for the aerodynamic design of turbomachines is presented, where the blade parameterization is based on the use of a three-dimensional inverse design method. The blade geometry is described by means of aerodynamic parameters, like the blade loading, which are closely related to the aerodynamic performance to be optimized, thus leading to a simple shape of the optimization function. On the basis of this consideration, it is possible to use simple approximation functions for describing the correlations between the input design parameters and the performance ones. The Response Surface Methodology coupled with the Design of Experiments (DOE) technique was used for this purpose. CFD analyses were run to evaluate the configurations required by the DOE to generate the database. Optimization algorithms were then applied to the approximated functions in order to determine the optimal configuration or the set of optimal ones (Pareto front). The method was applied for the aerodynamic redesign of two different turbomachine components: a centrifugal compressor stage and a single-stage axial compressor. In both cases, both design and off-design operating conditions were analyzed and optimized.

The Role of Forward Sweep in Subsonic Axial Fan Rotor Aerodynamics at Design and Off-Design Operating Conditions

2003 ◽  
Author(s):  
A. Corsini ◽  
F. Rispoli
Keyword(s):  
Three Dimensional ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Design Parameters ◽  
Axial Fan ◽  
Suction Surface ◽  
Free Vortex ◽  
Application Range ◽  
Rotor Aerodynamics ◽  
Work Distribution

The role that forward sweep plays in the aerodynamics of subsonic axial fan rotor is herein discussed, with emphasis on the combined effects of non-uniform three-dimensional work distribution and modified stacking lines. To study blade forward sweep effects numerical investigations have been undertaken on highly loaded fans of non-free vortex design, with ideal total head rise coefficient typical of industrial application range. The results of two rotors with identical overall design parameters and, respectively, with 35-deg forward swept blades and unswept blades have been compared. The investigation has been carried-out using an accurate in-house developed multi-level parallel finite element RANS solver, with the adoption of a non-isotropic two-equation turbulence closure. The pay-off derived from the sweep technology has been assessed with respect to the operating range improvement. To this end the flow structure developing through the blade passages and downstream of the rotors as well as loss distributions have been analysed at three different operating conditions. The studies showed that the forward swept blade operates more efficiently in particular at low volume flows, with a delayed onset of stall. The analyses of three-dimensional flow structures showed that, sweeping forward the blade, the flow centrifugation on blade suction surface is reduced and non-free vortex spanwise secondary flows is attenuated. Moreover, reduced fluid mechanical losses have been also pointed out in rotor with swept blades.

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