Elasto-Hydrodynamic Model of Hybrid Journal Bearings for Aero-Engine Gear Fuel Pump Applications

2021 ◽  
pp. 1-32
Author(s):  
Jacopo Tacconi ◽  
Shahrokh Shahpar ◽  
Andrew King ◽  
Johannes Paulus Olufeagba ◽  
Raymarn Khan ◽  
...  
Keyword(s):  
Numerical Model ◽  
Pressure Distribution ◽  
Pressure Rise ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Aviation Fuel ◽  
Engine Fuel ◽  
Fuel Pump ◽  
Trade Offs ◽  
Aero Engine

Abstract Gear pumps are largely employed in aero-engine fuel systems to provide the combustor with fuel at adequate pressure and flow rate. The radial load applied on the gears, as a consequence of the pump pressure rise, is entirely supported by the hybrid journal bearings. Lubrication of these is accomplished using low viscosity aviation fuel, which makes the design and analysis of journal bearings particularly challenging. A numerical model has been developed to support the analysis and future design of hybrid journal bearings for fuel pump applications. The primary objective of the tool is to characterise the equilibrium position of the journal during steady-state operation at part and full load, where the resultant elastic displacements are more significantly affecting the pressure distribution of the lubrication film. The developed method effectively combines Elrod's cavitation algorithm with the dimensionless pressure definition known as the Vogelpohl parameter, resulting in a simple and robust methodology to characterise the pressure distribution within the lubricant for different bearing designs and operating conditions. Six different multidimensional root-finding solvers have been implemented and their performance evaluated against robustness, accuracy and computational speed requirements. Newton-Raphson based methods have shown promising trade-offs for the problem at hand. Validation of the tool has been made comparing experimental film thickness measurements, performed on a fuel pump from a modern turbofan engine, with predicted data from the numerical model.

scholarly journals Influence of different types of volutes on centrifugal aviation fuel pump

2021 ◽  
Vol 13 (3) ◽  
pp. 168781402110052
Author(s):  
Weijun Wang ◽  
Zhenggui Li
Keyword(s):  
High Efficiency ◽  
Pressure Pulsation ◽  
Stokes Equations ◽  
Radial Force ◽  
Operating Conditions ◽  
Aviation Fuel ◽  
Monitoring Point ◽  
Fuel Pump ◽  
Axial Forces ◽  
Frequency Area

High efficiency and low vibration are two hot topics in the field of fluid mechanics. In this paper, different spiral volutes are designed for centrifugal aviation fuel pump based on Velocity Coefficient Method. Physical fields under different operating conditions are simulated by computational fluid dynamics (CFD) software that solved the Navier–Stokes equations for three-dimensional flow (3D-RANS). And theoretical and simulation values of radial and axial forces are analyzed. The unsteady pressure fluctuation based on the steady results at the monitoring point is solved and Fast Fourier Transform (FFT) is used to obtain the influence of different volutes on pressure pulsation. The influence of three volutes on is analyzed and compared with the simulation. The results show that the double volutes improve significantly the large flow efficiency of the aviation fuel pump, 20%–30% higher than that of the single volute. The doubles volute can also optimize the radial force under the off-design condition. The radial force of the single volute fuel pump is 100 N. The radial force of the two types of double volute fuel pump is between 10 and 20 N. The three types of volute have no obvious influence on the axial force. Two types of double volutes provide excellent suppression of fuel pump pulsation spikes over the full frequency range. The peak value of single volute is mainly concentrated in the low frequency area below 2000 Hz. The blade frequency (170 Hz) and frequency multiplication are the main frequencies of the pulsation and the pulsation decreases rapidly in the high frequency area. The research results provide theoretical support for the design of aviation fuel pump with low pressure pulsation.

The Effect of Elastic Distortions on Journal Bearing Performance

1967 ◽  
Vol 89 (4) ◽  
pp. 409-415 ◽  
Author(s):  
J. O’Donoghue ◽  
D. K. Brighton ◽  
C. J. K. Hooke
Keyword(s):  
Exact Solution ◽  
Pressure Distribution ◽  
Elastic Deformation ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Wide Range ◽  
Constant Viscosity ◽  
Outside Diameter

This paper presents a solution to the problem of hydrodynamic lubrication of journal bearings taking into account the elastic distortions of the shaft and the bearing. The exact solution for determining the elastic deformation for a given pressure distribution around a bearing is given, together with the reiterative procedure adopted to find the pressure distribution which satisfies both the hydrodynamic and elastic requirements of the system. Results are given which have been derived for a material with a Poisson’s ratio of 0.28, but other values such as 0.33 do not incur substantial errors. The results can be applied to a wide range of operating conditions using the nondimensional group of terms suggested in the paper. The bearing is assumed to be infinite in length, and infinite in thickness. The latter assumption is shown to be valid for a particular case where the outside diameter of the bearing shell is 3.5 times the shaft diameter. A further assumption in the calculation is a condition of constant viscosity of the lubricant existing around the bearing.

scholarly journals Three-dimensional imaging of swirled spray injection in a generic aero engine burner under realistic operating conditions

2021 ◽  
Vol 63 (1) ◽  
Author(s):  
Joachim Klinner ◽  
Christian E. Willert
Keyword(s):  
High Speed ◽  
Cross Correlation ◽  
Droplet Diameter ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Field Analysis ◽  
Calibration Data ◽  
Engine Fuel ◽  
Fuel Injector ◽  
Aero Engine

AbstractTomographic shadowgraph imaging is applied to reconstruct the instantaneous three-dimensional spray field immediately downstream of a generic aero engine fuel injector. Within the swirl passage of the injector model, a single kerosene jet undergoes air-blast atomization in a cross-flow configuration at Weber numbers of $$\text {We}=360-770$$ We = 360 - 770 , air pressures of $$p_a=4-7\,\text{ bar }$$ p a = 4 - 7 bar and air temperatures of $$T_a=440-570\,\text{ K }$$ T a = 440 - 570 K . High-speed, high magnification shadowgraphy is used to visualize the initial fuel atomization stages within the fuel injector before the spray enters the spray chamber. The 4-camera tomographic measurement setup is described in detail and includes a depth-of-field analysis with respect to droplet size based on Mie simulations and calibration data of the point-spread function. For a volume size of $$16\times 13\times 10\,\text{ mm}^3$$ 16 × 13 × 10 mm 3 , the smallest resolvable droplet diameter is estimated to be $$d=10\,\mu \text{ m }$$ d = 10 μ m within the focal plane and increases to $$d \approx 20\,\mu \text{ m }$$ d ≈ 20 μ m toward the edges of the volume. Droplet velocities above the resolution limit were retrieved by 3-d cross-correlation of two volumetric reconstructions recorded at two consecutive time-steps. This is accompanied by an error analysis on the random error dependency on the camera viewing geometry. The results indicate increasing motion and fluctuations of the spray tail with increasing temperature and Weber number. Validation against PDA data further downstream of the burner plate revealed consistency for size classes $$d=10\,\mu \text{ m }$$ d = 10 μ m and $$d=15\,\mu \text{ m }$$ d = 15 μ m . Deviations from PDA occur in regions with strong velocity gradients due to different spatial resolutions, the presence of reconstruction ambiguities (ghost particles), uncertainties inherent to the two-frame cross-correlation of spray volumes and the finite LED pulse duration. Graphical Abstract

Design and Performance Evaluation of an Aero Engine Booster Pump

2015 ◽  
Author(s):  
Ashfaq C. Mohammed ◽  
Shivakumar Ulaganathan ◽  
Lingamoorthy Kannan ◽  
Anbuchezhian Singaravelu ◽  
Girish K. Degaonkar
Keyword(s):  
Performance Evaluation ◽  
Centrifugal Pump ◽  
Flow Analysis ◽  
Simulation Method ◽  
Operating Conditions ◽  
Engine Fuel ◽  
Fuel System ◽  
Pump Impeller ◽  
Aero Engine ◽  
And Performance

The primary function of an aero engine fuel system is to supply metered fuel to the combustion chamber at all operating conditions based on the flow demand set by the engine controller. Centrifugal pump is one of the components in fuel system that feeds fuel to the HP pump. Impeller design is a critical one which dictates the overall performance of centrifugal pump. This paper discusses about design and performance evaluation of impeller with twisted blade configuration. Impeller design is performed based on Euler’s one dimensional theory. Steady state performance of the impeller at design and off-design operating conditions is analyzed by using commercial CFD code ANSYS-CFX with a standard SST turbulence model. The governing mathematical model for flow analysis is a three dimensional incompressible Reynolds Averaged Navier-Stokes (RANS) equation. Cavitation phenomenon is simulated in the CFD multiphase analysis to assess the pump impeller performance under cavitation at different NPSH values. Rayleigh-Plesset cavitation model is used along with RANS equation to perform cavitation analysis. From this study, the simulation method and technique adapted is appropriate for predicting the performance of impeller of centrifugal pump with or without cavitation. Performance of the impeller reduces drastically as there is decrease in NPSH. The prediction of critical NPSH is vital for safer operation of the pump, specifically at high altitude the pump inlet pressure falls which may result in cavitation during operation.

Unsteady simulations of migration and deposition of fly-ash particles in the first-stage turbine of an aero-engine

2021 ◽  
pp. 1-21
Author(s):  
Z. Hao ◽  
X. Yang ◽  
Z. Feng
Keyword(s):  
Fly Ash ◽  
Film Cooling ◽  
Particle Deposition ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Velocity Model ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Aero Engine

Abstract Particulate deposits in aero-engine turbines change the profile of blades, increase the blade surface roughness and block internal cooling channels and film cooling holes, which generally leads to the degradation of aerodynamic and cooling performance. To reveal particle deposition effects in the turbine, unsteady simulations were performed by investigating the migration patterns and deposition characteristics of the particle contaminant in a one-stage, high-pressure turbine of an aero-engine. Two typical operating conditions of the aero-engine, i.e. high-temperature take-off and economic cruise, were discussed, and the effects of particle size on the migration and deposition of fly-ash particles were demonstrated. A critical velocity model was applied to predict particle deposition. Comparisons between the stator and rotor were made by presenting the concentration and trajectory of the particles and the resulting deposition patterns on the aerofoil surfaces. Results show that the migration and deposition of the particles in the stator passage is dominated by the flow characteristics of fluid and the property of particles. In the subsequential rotor passage, in addition to these factors, particles are also affected by the stator–rotor interaction and the interference between rotors. With higher inlet temperature and larger diameter of the particle, the quantity of deposits increases and the deposition is distributed mainly on the Pressure Side (PS) and the Leading Edge (LE) of the aerofoil.

scholarly journals Fundamental limits of electron and nuclear spin qubit lifetimes in an isolated self-assembled quantum dot

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
George Gillard ◽  
Ian M. Griffiths ◽  
Gautham Ragunathan ◽  
Ata Ulhaq ◽  
Callum McEwan ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Spin Relaxation ◽  
Nuclear Spin ◽  
Operating Conditions ◽  
External Control ◽  
Spin Qubits ◽  
Fundamental Limits ◽  
Trade Offs ◽  
Wide Range ◽  
Spin Qubit

AbstractCombining external control with long spin lifetime and coherence is a key challenge for solid state spin qubits. Tunnel coupling with electron Fermi reservoir provides robust charge state control in semiconductor quantum dots, but results in undesired relaxation of electron and nuclear spins through mechanisms that lack complete understanding. Here, we unravel the contributions of tunnelling-assisted and phonon-assisted spin relaxation mechanisms by systematically adjusting the tunnelling coupling in a wide range, including the limit of an isolated quantum dot. These experiments reveal fundamental limits and trade-offs of quantum dot spin dynamics: while reduced tunnelling can be used to achieve electron spin qubit lifetimes exceeding 1 s, the optical spin initialisation fidelity is reduced below 80%, limited by Auger recombination. Comprehensive understanding of electron-nuclear spin relaxation attained here provides a roadmap for design of the optimal operating conditions in quantum dot spin qubits.

Bifurcation Analysis of Self-Acting Gas Journal Bearings

2001 ◽  
Vol 123 (4) ◽  
pp. 755-767 ◽  
Author(s):  
Cheng-Chi Wang ◽  
Cha’o-Ku`ang Chen
Keyword(s):  
Dynamic Behavior ◽  
Reynolds Equation ◽  
Rotational Velocity ◽  
Power Spectra ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Finite Differences Method ◽  
Subharmonic Response ◽  
Rotor Center ◽  
Rotor Mass

This paper studies the bifurcation of a rigid rotor supported by a gas film bearing. A time-dependent mathematical model for gas journal bearings is presented. The finite differences method and the Successive Over Relation (S.O.R) method are employed to solve the Reynolds’ equation. The system state trajectory, Poincare´ maps, power spectra, and bifurcation diagrams are used to analyze the dynamic behavior of the rotor center in the horizontal and vertical directions under different operating conditions. The analysis shows how the existence of a complex dynamic behavior comprising periodic and subharmonic response of the rotor center. This paper shows how the dynamic behavior of this type of system varies with changes in rotor mass and rotational velocity. The results of this study contribute to a further understanding of the nonlinear dynamics of gas film rotor-bearing systems.

Investigations on Aerodynamic Loading Limits of Subsonic Compressor Tandem Cascades: Midspan Flow

2013 ◽  
Author(s):  
Charlotte Hertel ◽  
Christoph Bode ◽  
Dragan Kožulović ◽  
Tim Schneider
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Numerical Simulations ◽  
Pressure Distribution ◽  
Large Range ◽  
Pressure Rise ◽  
Transition Model ◽  
Diffusion Factor ◽  
Aerodynamic Loading ◽  
Tandem Cascades

An optimized subsonic compressor tandem cascade was investigated experimentally and numerically. Since the design aims at incompressible applications, a low inlet Mach number of 0.175 was used. The experiments were carried out at the low speed cascade wind tunnel at the Technische Universität Braunschweig. For the numerical simulations, the CFD-solver TRACE of DLR Cologne was used, together with a curvature corrected k-ω turbulence model and the γ-Reθ transition model. Besides the incidence variation, the aerodynamic loading has also been varied by contracting endwalls. Results are presented and discussed for different inlet angles and endwall contractions: pressure distribution, loss coefficient, turning, pressure rise, AVDR and Mach number. The comparison of experimental and numerical results is always adequate for a large range of incidence. In addition, a comparison is made to an existing high subsonic tandem cascade and conventional cascades. For the latter the Lieblein diffusion factor has been employed as a measure of aerodynamic loading to complete the Lieblein Chart of McGlumphy [1].

scholarly journals Influence of Thermodynamic Effect on Blade Load in a Cavitating Inducer

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Kengo Kikuta ◽  
Noriyuki Shimiya ◽  
Tomoyuki Hashimoto ◽  
Mitsuru Shimagaki ◽  
Hideaki Nanri ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Pressure Rise ◽  
Cavitation Number ◽  
Design Parameters ◽  
Trailing Edge ◽  
Thermodynamic Effect ◽  
Blade Tip

Distribution of the blade load is one of the design parameters for a cavitating inducer. For experimental investigation of the thermodynamic effect on the blade load, we conducted experiments in both cold water and liquid nitrogen. The thermodynamic effect on cavitation notably appears in this cryogenic fluid although it can be disregarded in cold water. In these experiments, the pressure rise along the blade tip was measured. In water, the pressure increased almost linearly from the leading edge to the trailing edge at higher cavitation number. After that, with a decrease of cavitation number, pressure rise occurred only near the trailing edge. On the other hand, in liquid nitrogen, the pressure distribution was similar to that in water at a higher cavitation number, even if the cavitation number as a cavitation parameter decreased. Because the cavitation growth is suppressed by the thermodynamic effect, the distribution of the blade load does not change even at lower cavitation number. By contrast, the pressure distribution in liquid nitrogen has the same tendency as that in water if the cavity length at the blade tip is taken as a cavitation indication. From these results, it was found that the shift of the blade load to the trailing edge depended on the increase of cavity length, and that the distribution of blade load was indicated only by the cavity length independent of the thermodynamic effect.

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