Steady and Unsteady Airflow Through the Intake Valve of a Reciprocating Engine

1985 ◽  
Vol 107 (3) ◽  
pp. 413-420 ◽  
Author(s):  
A. F. Bicen ◽  
C. Vafidis ◽  
J. H. Whitelaw
Keyword(s):  
Flow Pattern ◽  
Steady Flow ◽  
Laser Doppler Anemometry ◽  
Flow Regimes ◽  
Residual Effects ◽  
Mean Flow ◽  
Flow Angle ◽  
Flow Unsteadiness ◽  
Reciprocating Engine ◽  
Valve Operation

An experimental investigation of the airflow through various axisymmetric intake ports of a motored reciprocating engine is reported. Detailed velocity field measurements obtained by laser Doppler anemometry and for steady and various unsteady flow conditions are presented together with valve discharge coefficients from steady flow tests. The results showed that over the lift range investigated the valve flow exhibited various regimes indicated by the changes in the flow pattern at the valve exit. With a 45-deg seat angle, four regimes were identified compared to three in the case of a 60-deg valve. The overall behavior of the 45-deg valve, however, was found to be generally better. Rounding of the edges of the 45-deg valve reduced the number of flow regimes to two with marked improvements on discharge coefficient. The flow angle at the valve exit depended less on the flow regimes and more on the cylinder confinement, in the absence of which the transition from one regime to another was delayed. The mean flow pattern at the valve exit was found to be insensitive to flow unsteadiness, piston confinement and valve operation and thus could be predicted with reasonable accuracy from steady flow tests. The in-cylinder flow characteristics were also insensitive to valve operation, but strongly depended on piston interaction, flow unsteadiness and residual effects from the previous cycle.

Short Helical Combustor: Dynamic Flow Analysis in a Combustion System With Angular Air Supply

2016 ◽  
Author(s):  
Behdad Ariatabar ◽  
Rainer Koch ◽  
Hans-Jörg Bauer
Keyword(s):  
Angular Momentum ◽  
Flow Pattern ◽  
Transient Flow ◽  
Vortex Breakdown ◽  
Flow Analysis ◽  
Design Parameters ◽  
Mean Flow ◽  
Dynamic Flow ◽  
Flow Angle ◽  
Rotational Direction

A novel gas turbine combustor which features a helical arrangement of the burners around the turbine shaft has been subject of a detailed flow analysis. A fundamental investigation of the combustor concept has been conducted in the authors previous work [1]. The main design parameters for such a combustor were identified based on kinematic assessments of the flow fields predicted by CFD. In particular, it has been shown in the previous work that the swirl rotational direction of adjacent burners determines the overall flow pattern in such a staggered design of the combustor dome. However, for the optimal configuration the exit mean flow angle was lower than the half of its initial value at the combustor inlet. The reason for this unwanted decay of the initial high angular momentum flux was not clear. In the present work a comprehensive global flow analysis of such a short helical combustor is performed. The underlying physics of large changes of the flow pattern and exit flow angle are elucidated by the analysis of the different terms (momentum, pressure and friction) in the integral balance equation of angular momentum. The term “dynamic flow analysis” is used in contrast to the “kinematic flow analysis” in our previous work and does not refer to transient flow phenomena. It is shown that the flow in the vicinity of the burners is governed by inertial forces associated to an asymmetric pressure distribution on the sidewall and the combustor dome. Downstream the sidewalls, the swirl rotational direction of circumferentially adjacent burners determines the structure of vortex-breakdown and the flow pattern in the primary combustion zone. It is shown that the turbulent mixing phenomena have minor effects on the flow structure at the combustor exit. To compare mean flow quantities of different combustor designs, a consistent averaging method is introduced which is based on the work of the Pinako and Wazelt [2]. This analysis can also be applied to conventional combustors to assess different swirl configurations regarding the resulting flow pattern, mixing performance and total pressure loss.

Short Helical Combustor: Dynamic Flow Analysis in a Combustion System With Angular Air Supply

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
B. Ariatabar ◽  
R. Koch ◽  
H.-J. Bauer
Keyword(s):  
Angular Momentum ◽  
Flow Pattern ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Flow Analysis ◽  
Mean Flow ◽  
Gas Turbine Combustor ◽  
Flow Angle ◽  
High Angular Momentum ◽  
Air Supply

A novel gas turbine combustor is investigated by means of a global flow analysis. Its main feature is the helical arrangement of the burners, which allows the utilization of the high angular momentum of the flow from compressor, so that the length of the flame tube and the number of NGV can be reduced. The concept was studied in Ariatabar et al. (2016, “Short Helical Combustor: Concept Study of an Innovative Gas Turbine Combustor With Angular Air Supply,” ASME J. Eng. Gas Turbines Power, 138(3), p. 031503) based on similarity considerations and a kinematic assessment of the simulated flow in various combustor models. For the best configuration found in the previous work, the exit mean flow angle was lower than the half of its initial value at the combustor inlet. The reason for this unwanted decay of the initial high angular momentum flux was not clear. In the present work, the underlying physics of the strong reduction of the mean flow angle is elucidated by analysis of the integral balance equation of angular momentum. It is shown that the flow in the vicinity of the burners is governed by inertial forces associated with an asymmetric pressure distribution on the sidewall and the combustor dome. The friction and turbulent mixing phenomena are found to have marginal effects on the flow pattern. To compare mean flow quantities of different combustor designs, a physically consistent averaging method is introduced, which can also be applied to a conventional combustor to assess different swirl configurations regarding the resulting flow pattern, mixing performance, and total pressure loss.

Mathematical modeling of Couette flow in anomalous thermoviscous liquid

2011 ◽  
Vol 8 (1) ◽  
pp. 143-152
Author(s):  
S.F. Khizbullina
Keyword(s):  
Mathematical Modeling ◽  
Angular Velocity ◽  
Numerical Experiment ◽  
Temperature Dependence ◽  
Steady Flow ◽  
Couette Flow ◽  
Outer Cylinder ◽  
Flow Regimes ◽  
Constant Angular Velocity ◽  
Coaxial Cylinders

The steady flow of anomalous thermoviscous liquid between the coaxial cylinders is considered. The inner cylinder rotates at a constant angular velocity while the outer cylinder is at rest. On the basis of numerical experiment various flow regimes depending on the parameter of viscosity temperature dependence are found.

The Sears problem for a lifting airfoil revisited - new results

1984 ◽  
Vol 141 ◽  
pp. 109-122 ◽  
Author(s):  
H. M. Atassi
Keyword(s):  
Small Angle ◽  
Potential Flow ◽  
Angle Of Attack ◽  
Nonlinear Dependence ◽  
Mean Flow ◽  
Linear Superposition ◽  
Flow Angle ◽  
Independent Components ◽  
The Mean ◽  
Gust Response

It is shown that for a thin airfoil with small camber and small angle of attack moving in a periodic gust pattern, the unsteady lift caused by the gust can be constructed by linear superposition to the Sears lift of three independent components accounting separately for the effects of airfoil thickness, airfoil camber and non-zero angle of attack to the mean flow. This is true in spite of the nonlinear dependence of the unsteady flow on the mean potential flow of the airfoil. Specific lift formulas are derived and analysed to assess the importance of mean flow angle of attack and airfoil camber on the gust response.

Comparison of Experimental and Numerical Simulations of Flow Within an Arterio-Venous Graft

2000 ◽  
Author(s):  
Paul F. Fischer ◽  
Seung Lee ◽  
Francis Loth ◽  
Hisham S. Bassiouny ◽  
Nurullah Arslan
Keyword(s):  
Flow Field ◽  
Steady Flow ◽  
Laser Doppler Anemometry ◽  
Transition To Turbulence ◽  
Flow Conditions ◽  
Venous Graft ◽  
Venous Anastomosis ◽  
Av Graft ◽  
Good Agreement

Abstract This was a study to compare computational and experimental results of flow field inside the venous anastomosis of an arteriovenous (AV) graft. Laser Doppler anemometry (LDA) measurements were conducted inside an upscaled end-to-side graft model under steady flow conditions at Reynolds number 1820 which is representative of the in vivo flow conditions inside a human AV graft. The distribution of the velocity and turbulence intensity was measured at several locations in the plane of the bifurcation. This flow field was simulated using computation fluid dynamics (CFD) and shown to be in good agreement. Under steady flow conditions, the flow field demonstrated an unsteady character (transition to turbulence).

scholarly journals CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Fabio Nardecchia ◽  
Annalisa Di Bernardino ◽  
Francesca Pagliaro ◽  
Paolo Monti ◽  
Giovanni Leuzzi ◽  
...  
Keyword(s):  
Flow Field ◽  
Water Channel ◽  
Flow Regimes ◽  
Two Dimensional ◽  
Mean Flow ◽  
Ansys Fluent ◽  
Practical Applications ◽  
Aspect Ratios ◽  
Starting Point ◽  
Step Down

Computational fluid dynamics (CFD) is currently used in the environmental field to simulate flow and dispersion of pollutants around buildings. However, the closure assumptions of the turbulence usually employed in CFD codes are not always physically based and adequate for all the flow regimes relating to practical applications. The starting point of this work is the performance assessment of the V2F (i.e., v2¯ − f) model implemented in Ansys Fluent for simulating the flow field in an idealized array of two-dimensional canyons. The V2F model has been used in the past to predict low-speed and wall-bounded flows, but it has never been used to simulate airflows in urban street canyons. The numerical results are validated against experimental data collected in the water channel and compared with other turbulence models incorporated in Ansys Fluent (i.e., variations of both k-ε and k-ω models and the Reynolds stress model). The results show that the V2F model provides the best prediction of the flow field for two flow regimes commonly found in urban canopies. The V2F model is also employed to quantify the air-exchange rate (ACH) for a series of two-dimensional building arrangements, such as step-up and step-down configurations, having different aspect ratios and relative heights of the buildings. The results show a clear dependence of the ACH on the latter two parameters and highlight the role played by the turbulence in the exchange of air mass, particularly important for the step-down configurations, when the ventilation associated with the mean flow is generally poor.

Extraction Techniques and Analysis of Turbulence Quantities From In-Cylinder Velocity Data

1989 ◽  
Vol 111 (3) ◽  
pp. 466-478 ◽  
Author(s):  
A. E. Catania ◽  
A. Mittica
Keyword(s):  
Direct Injection ◽  
Detailed Comparison ◽  
Ensemble Average ◽  
Small Scale ◽  
Velocity Data ◽  
Mean Flow ◽  
Reciprocating Engine ◽  
Reduction Methods ◽  
The Mean ◽  
Correlation And Spectral Analysis

In addition to the frequently used statistical ensemble-average, non-Reynolds filtering operators have long been proposed for nonstationary turbulent quantities. Several techniques for the reduction of velocity data acquired in the cylinder of internal combustion reciprocating engines have been developed by various researchers in order to separate the “mean flow” from the “fluctuating motion,” cycle by cycle, and to analyze small-scale engine turbulence by statistical methods. Therefore a thorough examination of these techniques and a detailed comparison between them would seem to be a preliminary step in attempting a general study of unconventional averaging procedures for reciprocating engine flow application. To that end, in the present work, five different cycle-resolved data reduction methods and the conventional ensemble-average were applied to the same in-cylinder velocity data, so as to review and compare them. One of the methods was developed by the authors. The data were acquired in the cylinder of a direct-injection automotive diesel engine, during induction and compression strokes, using an advanced hot-wire anemometry technique. Correlation and spectral analysis of the engine turbulence, as determined from the data with the different procedures, were also performed.

scholarly journals LDA Study of the Flow Development Through an Orthogonally Rotating U-Bend of Strong Curvature and Rib Roughened Walls

1996 ◽  
Author(s):  
H. Iacovides ◽  
D. C. Jackson ◽  
H. Ji ◽  
G. Kelemenis ◽  
B. E. Launder ◽  
...  
Keyword(s):  
Laser Doppler Anemometry ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Symmetry Plane ◽  
Suction Side ◽  
Outer Wall ◽  
Outer Side ◽  
Pressure Side ◽  
Mean Flow ◽  
Flow Development

This paper reports laser Doppler anemometry (LDA) and wall pressure measurements of turbulent flow in a square-sectioned, rotating U-bend typical of coolant passages employed in modern gas turbine blades. In the upstream and downstream tangents, the pressure and suction (inner and outer) surfaces are roughened with discrete square-sectioned ribs in a staggered arrangement for a rib-height to duct-diameter ratio of 0.1. Three cases have been examined at a passage Reynolds number of 105: a stationary case; a case of positive rotation (the pressure side coinciding with the outer side of the U-bend) at a rotation number (Ro=ΩD/Um) of 0.2; and a case of negative rotation at Ro=−0.2. Measurements have been obtained along the symmetry plane of the duct. In the upstream section, the separation bubble behind each rib is about 2.5 rib-heights long. Rotation displaces the high momentum fluid towards the pressure side, enhances turbulence along the pressure side and suppresses turbulence along the suction side. The introduction of ribs in the straight sections reduces the size of the separation bubble along the inner wall of the U-bend, by raising turbulence levels at the bend entry; it also causes the formation of an additional separation bubble over the first rib interval along the outer wall, downstream of the bend exit. Rotation also modifies the mean flow development within the U-bend, with negative rotation speeding up the flow along the inner wall and causing a wider inner-wall separation bubble at exit. Turbulence levels within the bend are generally increased by rotation and, over the first two diameters downstream of the bend, negative rotation increases turbulence while positive rotation on the whole has the opposite effect.

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