Measurements in a Motored Four-Stroke Reciprocating Model Engine

1982 ◽  
Vol 104 (2) ◽  
pp. 235-241 ◽  
Author(s):  
C. Arcoumanis ◽  
A. F. Bicen ◽  
J. H. Whitelaw
Keyword(s):  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Swirl Flow ◽  
Inlet Valve ◽  
Piston Bowl ◽  
Compression Stroke ◽  
Piston Head ◽  
The Mean ◽  
Model Engine ◽  
Comparison Of The Results

Measurements of ensemble-averaged axial and swirl velocities and the rms of the corresponding fluctuations obtained by laser-Doppler anemometry, are reported for the axisymmetric swirling flow in a four-stroke model engine motored at 200 rpm with a compression ratio of 3.5. A centrally located valve, incorporating a 60 degree seat angle and 30 degree swirl vanes resulting in a swirl number of 1.2, was used to draw in and exhaust seeded air. The piston-head configurations included a flat surface and a cylindrical bowl with and without a lip. Comparison of the results with those obtained previously, with a flat piston in the absence of compression, shows that the mean and rms profiles during the intake stroke are similar. In the axial plane a system of vortices is created which has almost disappeared by the time the inlet valve closes with a small vortex existing near the cylinder head at the early part of compression; later on this vortex breaks up and the mean velocities tend to become uniform. The intake generated turbulence decays gradually until the inlet valve closes; it then becomes uniform and remains constant in magnitude for the rest of the compression stroke. The mean swirl flow has a spiralling nature during intake but tends towards solid body rotation during compression with associated turbulence levels of similar magnitude to the axial ones. During the expansion stroke the rms velocities decrease further until the exhaust valve opens and new turbulence is generated. The influence of the piston bowl is generally small but the addition of a lip results, during the compression stroke, in inward movement of the air towards the bowl as the piston approaches TDC. The reverse squish effect, observed during the expansion stroke and due to the outgoing motion of the entrapped air inside the bowl, results in significant reversed velocities near the axis and increase in the turbulence levels close to the piston.

Intake Valve and In-Cylinder Flow Development in a Reciprocating Model Engine

1986 ◽  
Vol 200 (2) ◽  
pp. 143-152 ◽  
Author(s):  
C Vafidis ◽  
J H Whitelaw
Keyword(s):  
Flow Field ◽  
Laser Doppler Anemometry ◽  
Axial Flow ◽  
Normal Stresses ◽  
Intake Valve ◽  
Inlet Valve ◽  
Piston Bowl ◽  
Flow Development ◽  
Model Engine ◽  
Cylinder Flow

Measurements of three velocity components have been obtained by laser Doppler anemometry at the exit plane of the intake valve and inside the cylinder of a model engine motored at 200 r/min with a compression ratio of 7.7 and both axisymmetric and off-centre valves with flat and bowl-in-piston configurations. The results indicate that during early intake the valve flow is influenced by piston geometry and its proximity to the cylinder head. With the flat piston the TDC flow field is influenced by the intake-generated axial flow pattern but not by the tangential motion, induced by the off-centre valve, which decays around inlet valve closure. The breakdown of the intake-generated vortices is accompanied by redistribution of the normal stresses which, during compression, tend towards homogeneity. Inside the piston bowl, a vortex is induced during early intake and decays later in the induction stroke to a uniform flow field which is transformed during late compression by the squish effect.

Influence of Induction Swirl and Piston Configuration on Air Flow in a Four-Stroke Model Engine

1984 ◽  
Vol 198 (2) ◽  
pp. 71-79 ◽  
Author(s):  
C Vafidis
Keyword(s):  
Velocity Distribution ◽  
Laser Doppler Anemometry ◽  
Stroke Model ◽  
Piston Bowl ◽  
Vortex Pattern ◽  
Swirl Velocity ◽  
Cyclic Variations ◽  
Model Engine ◽  
Cylinder Flow ◽  
Dead Centre

Measurements of ensemble-averaged mean, r.m.s. and cycle resolved instantaneous swirl velocities, obtained by laser—Doppler anemometry, are reported for the in-cylinder flow in a four-stroke model engine motored at 200 r/min. Variable induction swirl was created by 30° and 60° vanes located in axisymmetric and off-centre intake ports with flat and re-entrant bowl piston configurations. The results showed that the main features of the initial swirl velocity distribution, which are determined by the intake port/valve geometry, persist through the compression stroke. The swirl centre performed in all cases a helical motion whose development was a function of the clearance volume at top dead centre; the weakness of this motion made it susceptible to cyclic variations which were significantly reduced with the re-entrant piston bowl. High induction swirl resulted in lower turbulence intensity at top dead centre of compression, in the flat piston case, and more complex vortex pattern inside the re-entrant piston bowl. The angular momentum decay from inlet valve closure to top dead centre of compression was shown to depend on initial swirl ratio and velocity distribution and calculated to be about 30 and 45 per cent for the flat and re-entrant bowl piston, respectively.

Valve and In-Cylinder Flow Generated by a Helical Port in a Production Diesel Engine

1987 ◽  
Vol 109 (4) ◽  
pp. 368-375 ◽  
Author(s):  
C. Arcoumanis ◽  
C. Vafidis ◽  
J. H. Whitelaw
Keyword(s):  
Diesel Engine ◽  
Laser Doppler Anemometry ◽  
Operating Conditions ◽  
Valve Lift ◽  
Valve Closure ◽  
Rapid Decay ◽  
Inlet Valve ◽  
Compression Stroke ◽  
Axial Velocity Distribution ◽  
Cylinder Flow

The flow generated by the helical port of a production Diesel engine has been investigated by laser Doppler anemometry under steady flow and operating conditions at ∼ 900 rpm and compression ratio of 8. The flow around the valve periphery was found to be non-uniform with the axial velocity distribution being more sensitive to valve lift. The in-cylinder swirl distribution at inlet valve closure exhibited an axial stratification in the disc-chamber while turbulence intensity remained constant in the clearance volume during the rest of the compression stroke with levels of 0.5 vp and a minimum of about 0.4 vp at top-dead-center following a rapid decay at θ=340°.

Prediction of the in-piston-bowl swirl ratio of diesel engines

2018 ◽  
Vol 233 (10) ◽  
pp. 2381-2389
Author(s):  
Yanzhe Sun ◽  
Tianyou Wang ◽  
Ming Wen ◽  
Yufeng Li ◽  
Fuquan Tian ◽  
...  
Keyword(s):  
Steady Flow ◽  
Test Data ◽  
Diesel Engines ◽  
Volume Ratio ◽  
Swirl Flow ◽  
Intake Valve ◽  
Swirl Ratio ◽  
Piston Bowl ◽  
Compression Stroke ◽  
Key Steps

Steady flow tests are widely used to evaluate the performance of intake ports in generating swirl flow in diesel engines. Such test data, however, may deviate largely from the real in-piston-bowl swirl ratio due to the complex unsteady air motion in the compression stroke. In this study, a new method is proposed to predict the unsteady in-piston-bowl swirl ratio of diesel engines from steady flow test data by focusing on three key steps, including the swirl field at intake valve close timing, swirl enhancement due to squish flow, and swirl decay during the compression stroke. Experimental results on an optically accessible diesel engine under non-firing conditions show that, at intake valve close, the relationship between the swirl ratio and the vertical location was approximately linear and the mean swirl ratio could be fitted by a Bessel function; the correlation between the swirl decay coefficient and surface-to-volume ratio was built by fitting the experiment data. Furthermore, the in-piston-bowl swirl ratio during the compression stroke could then be derived according to the conservation of angular momentum.

Numerical Simulation of the Fluid Flow and Heat Transfer Processes During Scavenging in a Two-Stroke Engine Under Steady-State Conditions

1992 ◽  
Vol 114 (2) ◽  
pp. 383-393 ◽  
Author(s):  
M. de Castro Gouveia ◽  
J. A. dos Reis Parise ◽  
A. O. Nieckele
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Steady State ◽  
Swirling Flow ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Uniform Wall Temperature ◽  
Piston Head ◽  
Bottom Dead Center ◽  
Comparison Of The Results

A numerical simulation of the scavenging process in a two-stroke flat-piston model engine has been developed. Air enters the cylinder circumferentially, inducing a three-dimensional turbulent swirling flow. The problem was modeled as a steady-state axisymmetric flow through a cylinder with uniform wall temperature. The steady-state regime was simulated by assuming the piston head fixed at the bottom dead center. The calculation was performed employing the k–ε model of turbulence. A comparison of the results obtained for the flow field with available experimental data showed very good agreement, and a comparison with an available numerical solution revealed superior results. The effects of the Reynolds number, inlet port angles, and engine geometry on the flow and in-cylinder heat transfer characteristics were investigated. The Nusselt number substantially increases with larger Reynolds numbers and a smaller bore-to-stroke ratio. It is shown that the positioning of the exhaust valve(s) is the main parameter to control the scavenging process.

scholarly journals Noise radiation from a ducted rotor in a swirling-translating flow

2009 ◽  
Vol 641 ◽  
pp. 463-473 ◽  
Author(s):  
ERIKA QUARANTA ◽  
DIMITRIS DRIKAKIS
Keyword(s):  
Mach Number ◽  
Swirling Flow ◽  
Source Model ◽  
Swirl Flow ◽  
Mean Flow ◽  
Scattering Problems ◽  
Noise Radiation ◽  
Directivity Patterns ◽  
The Mean ◽  
Ducted Rotor

This paper investigates the noise radiation produced by a rotor inside a duct, which is convected by a swirling-translating mean flow. The study is based on an extension of Gennaretti's and Morino's boundary element method to the frequency domain for scattering problems in conjunction with a spinning rotor source model in the presence of a swirl flow. The proposed formulation is validated against exact solutions and is further used to investigate the effects of the translating flow Mach number and swirling flow angular velocity on noise radiation to the far field. The scattered sound is highly affected by the convecting mean flow. The modal content of the scattered field increases when increasing the translating flow Mach number, while a swirling flow leads to a reduction of the mode propagation, if co-rotating with respect to the azimuthal order of the spinning source, or an increase of the modal content, if counter-rotating with respect to the source. In general, the mean translating flow moves the main lobes of the directivity patterns downstream, while in some cases the mean swirling flow neglects this effect and the downstream lobe is completely shifted.

Numerical simulation of swirling flow effect on the first stage vane film cooling distribution

2016 ◽  
Vol 07 (03) ◽  
pp. 1650031
Author(s):  
Hong Yin
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Swirling Flow ◽  
Cooling System ◽  
Leading Edge ◽  
Suction Side ◽  
Local Area ◽  
Swirl Flow ◽  
Flow Effect ◽  
Recirculation Flow

In advanced gas turbine technology, lean premixed combustion is an effective strategy to reduce peak temperature and thus, NO[Formula: see text] emissions. The swirler is adopted to establish recirculation flow zone, enhancing mixing and stabilizing the flame. Therefore, the swirling flow is dominant in the combustor flow field and has impact on the vane. This paper mainly investigates the swirling flow effect on the turbine first stage vane cooling system by conducting a group of numerical simulations. Firstly, the numerical methods of turbulence modeling using RANS and LES are compared. The computational model of one single swirl flow field is considered. Both the RANS and LES results give reasonable recirculation zone shape. When comparing the velocity distribution, the RANS results generally match the experimental data but fail to at some local area. The LES modeling gives better results and more detailed unsteady flow field. In the second step, the RANS modeling is incorporated to investigate the vane film cooling performance under the swirling inflow boundary condition. According to the numerical results, the leading edge film cooling is largely altered by the swirling flow, especially for the swirl core-leading edge aligned case. Compared to the pressure side, the suction side film cooling is more sensitive to the swirling flow. Locally, the film cooling jet is lifted and turned by the strong swirling flow.

A Study of Three-Dimensional Mixed Convective Heat Transfer From Short Vertical Cylinders in a Horizontal Forced Flow

2000 ◽  
Author(s):  
David A. Scott ◽  
P. H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Three Dimensional ◽  
Forced Flow ◽  
Low Velocity ◽  
Buoyancy Forces ◽  
The Mean ◽  
Mixed Convective Flow ◽  
Comparison Of The Results

Abstract Heat transfer from relatively short vertical isothermal cylinders in a horizontal forced fluid flow has been considered. The flow conditions are such that the buoyancy forces resulting from the temperature differences in the flow are in general significant despite of the presence of a horizontal forced flow of air, that is, mixed convective flow exists. Because the cylinders are short and the buoyancy forces act normal to the forced flow, three-dimensional flow exists. The experiments were performed in a low velocity, open jet wind tunnel. The study involved the experimental determination of the mean heat transfer coefficient and a comparison of the results with a previous numerical analysis. Mean heat transfer rates were determined using the ‘lumped capacity’ method. The mean Nusselt number has the Reynolds number, Grashof number and the height to diameter ratio of the cylinders as parameters. The results have been used to determine the conditions under which the flow departs from purely forced convection and enters the mixed convection regime, i.e., determining the conditions for which the buoyancy effects should be included in convective heat transfer calculations for short cylinders.

Feature Extraction From Time Resolved Reacting Flow Data Sets

2018 ◽  
Author(s):  
H. Ek ◽  
I. Chterev ◽  
N. Rock ◽  
B. Emerson ◽  
J. Seitzman ◽  
...  
Keyword(s):  
Swirling Flow ◽  
Azimuthal Velocity ◽  
Flow Fields ◽  
Swirl Flow ◽  
Reacting Flow ◽  
Data Sets ◽  
Time Resolved ◽  
Recirculating Flow ◽  
Flow Features ◽  
Dynamical Flow

This paper presents measurements of the simultaneous fuel distribution, flame position and flow velocity in a high pressure, liquid fueled combustor. Its objective is to develop methods to process, display and compare large quantities of instantaneous data with computations. However, time-averaged flow fields rarely represent the instantaneous, dynamical flow fields in combustion systems. It is therefore important to develop methods that can algorithmically extract dynamical flow features and be directly compared between measurements and computations. While a number of data-driven approaches have been previously presented in the literature, the purpose of this paper is to propose several approaches that are based on understanding of key physical features of the flow — for this reacting swirl flow, these include the annular jet, the swirling flow which may be precessing, the recirculating flow between the annular jets, and the helical flow structures in the shear layers. This paper demonstrates nonlinear averaging of axial and azimuthal velocity profiles, which provide insights into the structure of the recirculation zone and degree of flow precession. It also presents probability fields for the location of vortex cores that enables a convenient method for comparison of their trajectory and phasing with computations. Taken together, these methods illustrate the structure and relative locations of the annular fluid jet, recirculating flow zone, spray location, flame location, and trajectory of the helical vortices.

Liquid Sheet Disintegration and Atomization Process on a Simplified Airblast Atomizer

1993 ◽  
Vol 115 (3) ◽  
pp. 461-466 ◽  
Author(s):  
G. Lavergne ◽  
P. Trichet ◽  
P. Hebrard ◽  
Y. Biscos
Keyword(s):  
High Speed ◽  
Swirling Flow ◽  
Video Camera ◽  
Frequency Instability ◽  
Liquid Sheet ◽  
Processing Unit ◽  
Spray Formation ◽  
High Speed Video Camera ◽  
The Mean ◽  
Component Phase

Liquid sheet break-up in coflowing shear flow is the mean by which liquids are atomized in practical injectors for gas turbine combustors. The present study explores experimentally the mechanisms of liquid sheet instabilities and spray formation. Experiments are conducted on four airblast geometries. A high-speed video camera associated with an image processing unit was used to study the liquid sheet instabilities. A microphone and a frequency analyzer were used to track the disintegration frequency. Instability amplitude and disintegration length of the liquid sheet were measured. A two-component Phase Doppler Particle Analyzer was used to characterize the resultant spray. The spatial distribution of the particle size is influenced by the swirling flow field. These experimental results will be used to assess models of fuel sheet instabilities and disintegration.

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