Experimental Analysis of the Two-Phase Unsteady Flow in an Aero-Engine LPP Burner

The present paper reports the results of an experimental investigation on the unsteady flow in a Lean Premixed Prevaporized (LPP) burner for aeronautical applications. The experiments were focused on two main aspects: understanding the effect of the fuel spray on the unsteady air flow field and characterizing the fuel spray under unsteady flow conditions in terms of velocity and spatial distribution of the fuel droplets. The experimental campaign was performed with laser-based instrumentation (LDV, PDA and PIV) on a large-scale model of the LPP burner with air preheating and fuel injection in order to allow detailed measurements of the two-phase unsteady flow. The gas flow field is dominated by a spiral vortex breakdown phenomenon, which results in a complex unsteady flow configuration and an extended recirculation zone near the axis of the burner. The fuel droplets flow field is strongly correlated to the gas flow field. By comparing the results of the present experimental campaign with results obtained without fuel spray, there is evidence of a positive effect of the spray on the air flow field. The spray effect results in a reduction of the recirculation phenomenon in the exit section of the LPP burner. At the LPP burner exit a general satisfactory degree of vaporization is obtained. However, at the periphery of the premixing duct outlet section, a significant concentration of larger droplets of not yet vaporized fuel is present, due to the secondary air blast disintegration of the liquid film formed on the internal surface of the premixer tube. This phenomenon is responsible for lack of homogeneity of the fuel distribution in time and space at the premixer duct exit.

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Enhanced Computational Fluid Dynamics Modeling and Laser Doppler Anemometer Measurements for the Air-Flow in an Aero-engine Front Bearing Chamber—Part I

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4029272 ◽

2015 ◽

Vol 137 (8) ◽

Cited By ~ 2

Author(s):

J. Aidarinis ◽

A. Goulas

Keyword(s):

Flow Field ◽

Ball Bearing ◽

Air Flow ◽

Laser Doppler Anemometer ◽

Laser Doppler ◽

Scale Model ◽

Type I ◽

Two Phase ◽

Aero Engine ◽

Lubrication Oil

Modern aero-engine development requires also a gradual increase in the overall effectiveness of lubrication systems. This particularly applies to bearing chambers where a complex two-phase flow is formed by the interaction of the sealing air and the lubrication oil. It is important to increase the level of understanding of the flow field inside the bearing chamber and to develop engineering tools in order to optimize its design and improve its performance. To achieve this, an experimental and a computational study of the whole front bearing chamber were carried out for a range of shaft rotational speeds and sealing air mass flow. The experimental measurements of the air velocity inside the chamber were carried out using a laser Doppler anemometer (LDA) in two-phase air/oil-flow conditions. The experimental facility is a 1:1 scale model of the front bearing chamber of an aero-engine. Computational 3D modeling of the bearing chamber was performed. The bearing gap and the presence of lubrication oil were modeled as an anisotropic porous medium with functions relating the pressure loss of the air coming through the gap and the tangential component of velocity of the air exiting the gap of the ball bearing with the air-flow rate through the gap and the rotational speed of the shaft. The methodology to obtain the above mentioned functions and the results of the detailed study are given (Aidarinis, J., and Goulas, A., 2014, “Enhanced CFD Modeling and LDA Measurements for the Air-Flow in an Aero Engine Front Bearing Chamber: Part II,” ASME Paper No. GT2014-26062). The enhanced computational model of the chamber implementing the law of pressure drop of the “lubricated” bearing and the function of modeling the tangential velocity of the air exiting the bearing was used to calculate the flow field for the full range of the measurements. A limiting curve dividing the operational map of the bearing chamber into two areas was predicted. Large vortical and swirling structures dominate the flow and they vary in size according to the position of the operation point relative to the limiting curve. Operation above the limiting curve leads to flow classified as type I with air going through the ball bearing while for operation below the limiting curve line the flow is classified as type II, there is no air-flow through the bearing gap.

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Enhanced CFD Modelling and LDA Measurements for the Air-Flow in an Aero-Engine Front Bearing Chamber: Part I

Volume 5C: Heat Transfer ◽

10.1115/gt2014-26060 ◽

2014 ◽

Author(s):

J. Aidarinis ◽

A. Goulas

Keyword(s):

Flow Field ◽

Ball Bearing ◽

Computational Study ◽

Air Flow ◽

Full Range ◽

Scale Model ◽

Type I ◽

Two Phase ◽

Aero Engine ◽

Lubrication Oil

Modern aero-engine development requires also a gradual increase in the overall effectiveness of lubrication systems. This particularly applies to bearing chambers where a complex two-phase flow is formed by the interaction of the sealing air and the lubrication oil. It is important to increase the level of understanding of the flow field inside the bearing chamber and to develop engineering tools in order to optimize its design and improve its performance. To achieve this an experimental and a computational study of the whole front bearing chamber were carried out for a range of shaft rotational speeds and sealing air mass flow. The experimental measurements of the air velocity inside the chamber were carried out using a Laser Doppler Anemometer (LDA) in two-phase air/oil flow conditions. The experimental facility is a 1:1 scale model of the front bearing chamber of an aero-engine. Computational 3D modeling of the bearing chamber was performed. The bearing gap and the presence of lubrication oil was modeled as an anisotropic porous medium with functions relating the pressure loss of the air coming through the gap and the tangential component of velocity of the air exiting the gap of the ball bearing with the air-flow rate through the gap and the rotational speed of the shaft. The methodology to obtain the above mentioned functions and the results of the detailed study are given in [1]. The enhanced computational model of the chamber implementing the law of pressure drop of the ‘lubricated’ bearing and the function of modeling the tangential velocity of the air exiting the bearing, was used to calculate the flow field for the full range of the measurements. A limiting curve dividing the operational map of the bearing chamber into two areas was predicted. Large vortical and swirling structures dominate the flow and they vary in size according to the position of the operation point relative to the limiting curve. Operation above the limiting curve leads to flow classified as type I with air going through the ball bearing while for operation below the limiting curve line the flow is classified as type II, there is no air-flow through the bearing gap.

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EXPERIMENTAL STUDY ON AIR FLOW FIELD CHARACTERISTICS OF SUCTION METERING DEVICE

INMATEH Agricultural Engineering ◽

10.35633/inmateh-65-06 ◽

2021 ◽

pp. 57-66

Author(s):

Meng Zhang ◽

Zeqi Liu ◽

Yajun Zhuang ◽

Jie Han ◽

Yin Xiang ◽

...

Keyword(s):

Flow Field ◽

Negative Pressure ◽

Gas Flow ◽

Vacuum Chamber ◽

Air Flow ◽

Test Bed ◽

Seed Metering Device ◽

Suction Hole ◽

Hole Structure ◽

Gas Flow Field

The vacuum seed metering device absorbs seeds by using the negative pressure generated by vacuum air flow. Therefore, it is of great significance to study the variation law of pyrolysis gas flow field to improve its seed metering performance. In this paper, the common disc and composite disc were selected as the research objects and tested on the indoor test-bed. The negative pressure was measured by U-type barometer, and the effects of fan speed, suction hole size, seed hole structure and air chamber thickness on the air flow field were studied. Firstly, the influence of fan rotation frequency on vacuum chamber negative pressure is studied, and the variation law of negative pressure in vacuum chamber and fan port of common disc and composite disc under the same frequency is compared. Secondly, the suction holes in the vacuum chamber were numbered, the negative pressure distribution of the suction holes was measured, and the influence of the number and diameter of the suction holes on the negative pressure of the vacuum chamber was studied. Finally, the negative pressure was measured at the distance of 0 to 10 mm from the suction hole to study the effect of seed hole structure on the air flow field. Moreover, increase the additional thickness of the vacuum chamber from 0 to 40 mm to study the influence of the chamber thickness on the distribution of the gas flow field. This paper makes a comprehensive experimental analysis on the influencing factors of air flow field of air suction seed metering device, necessary for future design of air suction seed metering device.

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Experimental Investigation of the Turbulent Flow Field of Vaporizing Diesel-Sprays

Design, Application, Performance and Emissions of Modern Internal Combustion Engine Systems and Components ◽

10.1115/icef2002-509 ◽

2002 ◽

Cited By ~ 2

Author(s):

Michael Staudt ◽

Ulrich Meingast ◽

Ulrich Renz

Keyword(s):

Flow Field ◽

Gas Flow ◽

Elevated Temperatures ◽

Laser Doppler Anemometry ◽

Air Flow ◽

Injection System ◽

Penetration Length ◽

Fuel Droplets ◽

Fuel Jet ◽

Dimensional Measurements

In this work investigations of the flow-field inside and around a heated, vaporizing diesel-fuel-jet are presented. The experiments are carried out in a high-pressure-chamber at elevated temperatures using a commercial Bosch-Common-Rail Diesel-injection system. The pressure and temperature inside the chamber are chosen according to the conditions in a real engine cylinder after compression. Droplet diameters and velocities inside the fuel jet are measured by means of Phase-Doppler-Anemometry (PDA). In order to obtain the velocities of the gas phase very close to the free penetrating fuel jet by Laser-Doppler-Anemometry (LDA), the air inside the chamber is seeded with Titan-Dioxide (TiO2)-particles. Turbulence values like RMS and length scales are derived from these measurements. In addition to these spatially limited measurements the global flow-field around the penetrating fuel-jet is observed by two-dimensional measurements with Particle-Image-Velocimetry (PIV). From the nozzle exit up to 2/3 of the whole penetration length an air flow perpendicular to the spray axis can be detected. This air-flow into the spray provides the heat transfer and vaporization of the fuel-droplets. The fuel jet contains a high droplet concentration which leads to high intensities in the resulting PIV-images from which discrete spray contours can be calculated. By means of the gas-flow velocity components at this contour the total mass of the absorbed air is calculated. This mass is compared at three injection pressures: 80, 100 and 135 MPa. Further experiments concentrate on a spray impinging straight onto a flat wall. The wall jet leads to additional contributions of air absorption into regions with high droplet concentrations.

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