Analysis of the Oil Squeezing Power Losses of a Spur Gear Pair by Mean of CFD Simulations

2012 ◽  
Author(s):  
Franco Concli ◽  
Carlo Gorla
Keyword(s):  
High Efficiency ◽  
Fluid Dynamic ◽  
Axial Direction ◽  
Spur Gear ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Main Concern ◽  
Power Losses ◽  
Dynamic Simulations ◽  
Gear Mesh

Efficiency is becoming more and more a main concern in the design of power transmissions and the demand for high efficiency gearboxes is continuously increasing. Also the new restrictive euro standards for the reduction of pollutant emissions from light vehicles impose to improve the efficiency of the engines but also of the gear transmissions. For this reason the resources dedicated to this goal are continuously increasing. The first step to improve efficiency is to have appropriate models to compare different design solutions. Even if the efficiency of transmissions is quit high if compared to the efficiency of the engines and appropriate models to predict the power losses due to gear meshing, to bearings and to seals already exist, in order to have a further improvement, some aspects like the power losses related to the oil churning, oil squeezing and windage are still to be investigated. These losses rise from the interaction between the moving or rotating elements of the transmission and the lubricant. In previous papers [39, 40, 41 43, 44], the authors have investigated the churning losses of planetary speed reducers (in which there is a relative motion between the “planets + planet carrier” and the lubricant). This report is focused on the oil squeezing power losses. This kind of losses is associated with the pumping of the oil at the gear mesh, where there is a contraction of the volume between the mating gears due to the rotation of them and a consequent overpressure. This overpressure implies a fluid flow primarily in the axial direction and this, for viscous fluids, means additional power losses and a decrease of the efficiency. In this work this phenomena has been studied by means of some CFD (computational fluid dynamic) simulations with a VOF (volume of fluid) approach. The influence of some operating conditions like the rotational speed and the lubricant temperature have been studied. The results of this study have been included in a model to predict the efficiency of the whole transmission.

Load-Independent Spin Power Losses of a Spur Gear Pair: Model Formulation

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
S. Seetharaman ◽  
A. Kahraman
Keyword(s):  
Power Loss ◽  
Spur Gear ◽  
Companion Paper ◽  
Total Spin ◽  
Operating Conditions ◽  
Gear Pair ◽  
Power Losses ◽  
Gear Mesh ◽  
Drag Forces ◽  
Mechanics Model

A physics-based fluid mechanics model is proposed to predict spin power losses of gear pairs due to oil churning and windage. While the model is intended to simulate oil churning losses in dip-lubricated conditions, certain components of it apply to air windage losses as well. The total spin power loss is defined as the sum of (i) power losses associated with the interactions of individual gears with the fluid, and (ii) power losses due to pumping of the oil at the gear mesh. The power losses in the first group are modeled through individual formulations for drag forces induced by the fluid on a rotating gear body along its periphery and faces, as well as for eddies formed in the cavities between adjacent teeth. Gear mesh pumping losses will be predicted analytically as the power loss due to squeezing of the lubricant, as a consequence of volume contraction of the mesh space between mating gears as they rotate. The model is applied to a unity-ratio spur gear pair to quantify the individual contributions of each power loss component to the total spin power loss. The influence of operating conditions, gear geometry parameters, and lubricant properties on spin power loss are also quantified at the end. A companion paper (Seetharaman et al., 2009, “Oil Churning Power Losses of a Gear Pair: Experiments and Model Validation,” ASME J. Tribol., 131, p. 022202) provides comparisons to experiments for validation of the proposed model.

Numerical Simulation for the Preliminary Design of Fuel Flexible Stationary Gas Turbine Combustors Using Conventional and Alternative Fuels

2012 ◽  
Author(s):  
Washington Orlando Irrazabal Bohorquez ◽  
João Roberto Barbosa ◽  
Rob Johan Maria Bastiaans ◽  
Philip de Goey
Keyword(s):  
Numerical Simulation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
High Efficiency ◽  
Numerical Study ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Gas Turbine Combustor ◽  
Primary Zone

Currently, high efficiency and low emissions are most important requisites for the design of modern gas turbines due to the strong environmental restrictions around the world. In the past years, alternative fuels have been considered for application in industrial gas turbines. Therefore, combustor performance, pollutant emissions and the ability to burn several fuels became of much concern and high priority has been given to the combustor design. This paper describes a methodology focused on the design of stationary gas turbines combustion chambers with the ability to efficiently burn conventional and alternative fuels. A simplified methodology is used for the calculations of the equilibrium temperature and chemical species in the primary zone of a gas turbine combustor. Direct fuel injection and diffusion flames, together with numerical methods like Newton-Raphson, LU Factorization and Lagrange Polynomials, are used for the calculations. Diesel, ethanol and methanol fuels were chosen for the numerical study. A computer code sequentially calculates the main geometry of the combustor. From the numerical simulation it is concluded that the basic gas turbine combustor geometry, for some operating conditions and burning diesel, ethanol or methanol, are of similar sizes, because the development of aerodynamic characteristics predominate over the thermochemical properties. It is worth to note that the type of fuel has a marked effect on the stability and combustion advancement in the combustor. This can be seen when the primary zone is analyzed under a steady-state operating condition. At full power, the pressure is 1.8 MPa and the temperature 1,000 K at the combustor inlet. Then, the equivalence ratios in the primary zone are 1.3933 (diesel), 1.4352 (ethanol) and 1.3977 (methanol) and the equilibrium temperatures for the same operating conditions are 2,809 K (diesel), 2,754 K (ethanol) and 2,702 K (methanol). This means that the combustor can reach similar flame stability conditions, whereas the combustion efficiency will require richer fuel/air mixtures of ethanol or methanol are burnt instead of diesel. Another important result from the numerical study is that the concentration of the main pollutants (CO, CO2, NO, NO2) is reduced when ethanol or methanol are burnt, in place of diesel.

scholarly journals Fluid-dynamic study of the behavior of the air inside a textile Stenter

2021 ◽  
Vol 2118 (1) ◽  
pp. 012006
Author(s):  
J W Parra ◽  
M B Quadri ◽  
D C Rodríguez
Keyword(s):  
Finite Element Method ◽  
Turbulence Model ◽  
Textile Industry ◽  
Fluid Dynamic ◽  
High Energy ◽  
Operating Conditions ◽  
The Finite Element Method ◽  
Dynamic Simulations ◽  
3D Geometry ◽  
High Energy Consumption

Abstract In the textile industry, drying is one of the most important processes. This process requires large investments and high energy consumption, which generates high costs for companies in this sector. In this work, a modeling of the behavior of the air was carried out in a textile Stenter, under real operating conditions through the development of fluid-dynamic simulations. For the computational modeling of the problem, a 3D geometry was constructed based on measurements taken from an injector of a textile Stenter. The standard k-ε turbulence model was used in the turbulent flow solution. The equations of the model were solved numerically using the finite element method. The standard k-ϵ turbulence model proved to be a model capable of reproducing the behavior of the air in the injectors of the textile Stenter.

Frictional dynamic model predictions of FZG-A10 spur gear pairs considering profile errors

2020 ◽  
pp. 135065012096297
Author(s):  
Nabih Feki ◽  
Maroua Hammami ◽  
Olfa Ksentini ◽  
Mohamed Slim Abbes ◽  
Mohamed Haddar
Keyword(s):  
Dynamic Model ◽  
Coefficient Of Friction ◽  
Power Loss ◽  
Spur Gear ◽  
Operating Conditions ◽  
Time Dependent ◽  
Nonlinear Dynamic Model ◽  
Gear Mesh ◽  
Proposed Model ◽  
Profile Errors

In this work, a nonlinear dynamic model of an FZG-A10 spur gear was investigated by taking into account for the actual time-varying gear mesh stiffness and the frictional effects between meshing gear teeth to evaluate the influence of the dynamic effects on frictional gear power loss predictions. The equations of motion of the generalized translational-torsional coupled dynamic system derived from Lagrange principle was extended compared to authors’ previous work in order to account for time dependent coefficient of friction and profile errors. The dynamic response of spur gears, computed by an iterative implicit scheme of Newmark, is changed due to the presence of coefficient of friction and profile errors. A dynamic analysis was performed and the influence of frictional effect including tooth shape deviations, in particular, was scrutinized since a time-dependent coefficient of friction is deeply related to the gear surface roughness and all parameters dependent on gears error profiles are introduced in the proposed model. The predicted meshing gear power losses with constant and local friction coefficient were compared. The influence of constant and variable profile errors considered in the local coefficient of friction formulation was also studied and their corresponding root mean square (RMS) power loss was compared to the experimental results. The results using FZG A10 spur gear pairs running under several operating conditions (different loads and speeds) validate the superiority of the proposed model against previous similar models.

Partial EHL friction coefficient model to predict power losses in cylindrical gears

2018 ◽  
Vol 233 (2) ◽  
pp. 303-316 ◽  
Author(s):  
Aitor Arana ◽  
Jon Larrañaga ◽  
Ibai Ulacia
Keyword(s):  
Friction Coefficient ◽  
Operating Conditions ◽  
Power Losses ◽  
Gear Mesh ◽  
Numerical Predictions ◽  
Reference Stress ◽  
Fluid Load ◽  
Stress Behaviour ◽  
Good Agreement ◽  
Ehl Friction

The accurate prediction of friction coefficient and power losses in the gear mesh is a key subject to several gear-related fields of study. However, there is still not a unified method for large ranges of operating conditions, different gear geometries and lubricant types. The current paper meets this demand by modelling partial EHL friction with an asperity-fluid load sharing approach where fluid traction is calculated with the Ree-Eyring equation and the reference stress behaviour is predicted from piezoviscosity coefficient. It will be shown that only an accurate description of the lubricant’s viscosity behaviour is required to compute friction in gears. Finally, mesh power losses are predicted considering thermal effects and numerical predictions are compared to experimental results showing good agreement.

scholarly journals An Accelerated Thrombosis Model for Computational Fluid Dynamics Simulations in Rotary Blood Pumps

2022 ◽  
Author(s):  
Christopher Blum ◽  
Sascha Groß-Hardt ◽  
Ulrich Steinseifer ◽  
Michael Neidlin
Keyword(s):  
Clinical Data ◽  
Computational Models ◽  
Thrombus Formation ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Model Parameters ◽  
Dynamic Simulations ◽  
Heartmate Ii ◽  
Blood Pumps ◽  
Rotary Blood Pumps

Abstract Purpose Thrombosis ranks among the major complications in blood-carrying medical devices and a better understanding to influence the design related contribution to thrombosis is desirable. Over the past years many computational models of thrombosis have been developed. However, numerically cheap models able to predict localized thrombus risk in complex geometries are still lacking. The aim of the study was to develop and test a computationally efficient model for thrombus risk prediction in rotary blood pumps. Methods We used a two-stage approach to calculate thrombus risk. The first stage involves the computation of velocity and pressure fields by computational fluid dynamic simulations. At the second stage, platelet activation by mechanical and chemical stimuli was determined through species transport with an Eulerian approach. The model was compared with existing clinical data on thrombus deposition within the HeartMate II. Furthermore, an operating point and model parameter sensitivity analysis was performed. Results Our model shows good correlation (R2 > 0.93) with clinical data and identifies the bearing and outlet stator region of the HeartMate II as the location most prone to thrombus formation. The calculation of thrombus risk requires an additional 10–20 core hours of computation time. Conclusion The concentration of activated platelets can be used as a surrogate and computationally low-cost marker to determine potential risk regions of thrombus deposition in a blood pump. Relative comparisons of thrombus risk are possible even considering the intrinsic uncertainty in model parameters and operating conditions.

Experimental and Numerical Investigation on Windage Power Losses in High Speed Gears

2017 ◽  
Author(s):  
D. Massini ◽  
T. Fondelli ◽  
A. Andreini ◽  
B. Facchini ◽  
L. Tarchi ◽  
...  
Keyword(s):  
High Speed ◽  
Power Transmission ◽  
Fluid Dynamic ◽  
Spur Gear ◽  
Cooling Capacity ◽  
Relative Magnitude ◽  
Power Losses ◽  
Test Rig ◽  
Aero Engines ◽  
Cooling And Lubrication

Enhancing the efficiency of gearing systems is an important topic for the development of future aero-engines with low specific fuel consumption. The transmission system in fact has a direct impact on the engine overall efficiency by means of its weight contribution, internal power losses and lubrication requirements. Thus, an evaluation of its structure and performance is mandatory in order to optimize the design as well as maximize its efficiency. Gears are among the most efficient power transmission systems, whose efficiencies can exceed 99 %, nevertheless in high speed applications power losses are anything but negligible. All power dissipated through losses is converted into heat that must be dissipated by the lubrication system. More heat leads to a larger cooling capacity, which results in more oil, larger heat exchangers which finally means more weight. Mechanical power losses are usually distinguished in two main categories: load-dependent and load-independent losses. The former are all those associated with the transmission of torque, while the latter are tied to the fluid-dynamics of the environment which surrounds the gears, namely windage, fluid trapping and squeezing between meshing gear teeth and inertial losses resulting by the impinging oil jets, usually adopted in high speed transmission for cooling and lubrication purposes. The relative magnitude of these phenomena is strongly dependent on the operative conditions of the transmission. While load-dependent losses are predominant at slow speeds and high torque conditions, load-independent mechanisms become prevailing in high speed applications, like in turbomachinery. Among fluid-dynamic losses, windage is extremely important and can dominate the other mechanisms. In this context, a new test rig was designed for investigating windage power losses resulting by a single spur gear rotating in a free oil environment. The test rig allows the gear to rotate at high speed within a box where pressure and temperature conditions can be set and monitored. An electric spindle, which drives the system, is connected to the gear through a high accuracy torque meter, equipped with a speedometer providing the rotating velocity. The test box is fitted with optical accesses in order to perform particle image velocimetry measurements for investigating the flow-field surrounding the rotating gear. The experiment has been computationally replicated, performing RANS simulations in the context of conventional eddy viscosity models. The numerical results were compared with experimental data in terms of resistant torque as well as PIV measurements, achieving a good agreement for all of the speed of rotations.

scholarly journals Theoretical and experimental control strategies assessment of a Sliding Vane Oil Pump

2020 ◽  
Vol 197 ◽  
pp. 06022
Author(s):  
Fabio Fatigati ◽  
Marco Di Bartolomeo ◽  
Giuseppe Lo Biundo ◽  
Francesco Pallante ◽  
Roberto Cipollone
Keyword(s):  
High Efficiency ◽  
Combustion Engine ◽  
Control Strategies ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Rate Variation ◽  
Vane Pump ◽  
Oil Flow ◽  
Pros And Cons ◽  
Virtual Platform

To date, Sliding Vane Pump (SVP) technology is one of the most attractive solution in different technical applications thanks to its reliability and compactness and capability to keep a high efficiency even when it is working far from rated condition. In particular, this feature makes the SVP suitable to be employed for the oil circulation (SVOP) in Internal Combustion Engine (ICE) which is characterized by a wide oil flow rates variation, delivered pressure and temperature variation which causes operating conditions of the pump far from the design point. Flow delivered changes in these machines are produced by varying the eccentricity for a mechanical connection with the engine - or by varying the speed of revolution. The mild hybridization of the powertrains calls for a strong development of electrically assisted engine auxiliaries which undoubtedly makes the flow variations easier to be done, but the presence of an electric motor requires some technological choices not fully assessed, a cost increase and a reliability decrease. The paper presents a mathematical model of a SVOP for oil circulation in ICE, suitably validated by a wide experimental activity. The model integrates a mono and zero-dimensional fluid-dynamic analysis and allows to represent the intimate behaviour of the machine. Moreover, it was employed as virtual platform to discuss pros and cons of different flow rate variation strategies and their effect on the efficiency of the SVOP.

scholarly journals The Importance of Detailed Chemical Mechanisms in Gas Turbine Combustion Simulations

2014 ◽  
Vol 16 (2-3) ◽  
pp. 179 ◽  
Author(s):  
M. Braun-Unkhoff ◽  
E. Goos ◽  
T. Kathrotia ◽  
T. Kick ◽  
C. Naumann ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Reaction Mechanisms ◽  
Fluid Dynamic ◽  
Pollutant Emissions ◽  
Dynamic Simulations ◽  
Gas Turbine Combustion ◽  
Combustion Systems ◽  
German Aerospace ◽  
Combustion Processes ◽  
Detailed Chemical

<p>This paper – in memory of Jürgen Warnatz – summarizes selected recent papers of the Chemical Kinetics Group at the German Aerospace Center in Stuttgart. It shows the need for detailed chemical reaction mechanisms to understand practical combustion systems. A comprehensive description of combustion processes based on detailed mechanisms is especially important in the design of new gas turbine combustion chambers and in the optimization of existing ones to improve efficiency and to reduce pollutant emissions, with fuel-flexibility and load-flexibility ever becoming more important. Different aspects of combustion processes where detailed reaction mechanisms provide useful insights will be covered in this paper: Fuels (alternative jet fuels, biomass based fuels), pollutants (soot), diagnostics (chemiluminescence), and thermochemistry. Furthermore, the underlying thermodynamics inevitably connected with detailed reaction schemes will be addressed. Exemplified results will be presented clearly demonstrating the predictive capabilities of detailed reaction mechanisms to be explored in computational fluid dynamic simulations to further optimize technical combustion systems.</p>

scholarly journals Evaluation of Reaction Between 2,4-Thiazolidinedione and P-Methoxybenzaldehyde in Microreactors for Production of Drugs for Treatment of Diabetes Mellitus Type 2

2020 ◽  
Author(s):  
Rodrigo Vieira ◽  
Harrson Santana ◽  
João Silva Jr. ◽  
Paula Meira ◽  
Gabriel Bressan ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Fluid Dynamic ◽  
Batch Reactor ◽  
Biological Action ◽  
Operating Conditions ◽  
Diabetes Mellitus Type ◽  
Reaction Yield ◽  
Dynamic Simulations ◽  
Diabetes Mellitus Type Ii ◽  
Pharmaceutical Industries

The use of microreactors in chemical and pharmaceutical industries allow a series of advantages due to their reduced sizes regarding conventional batch reactors. In the present paper the transposition of the reaction between 2,4-Thiazolidinedione with p-Methoxybenzaldehyde, generating the compound with potential biological action against diabetes mellitus type II, from batch to a continuous capillary microreactor was carried out. The microdevice performance was evaluated experimentally and numerically by Computational Fluid Dynamics. The efficiency and viability of microreactors usage for the intermediate pharmaceutical active production was assessed. The optimized operating conditions were obtained for the batch reactor (processing time) and microreactor (residence time), the promoter base selection and optimal concentration was also performed, in order to maximize reactants conversion and reaction yield. Considering the acquired data, computational fluid dynamic simulations were carried out, allowing obtaining a computational methodology to be used for a fast increment of production from microreactor to industrial demand.

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