Flow field development and energy evolution in road tunnels with unidirectional uniform traffic

2015 ◽  
Vol 147 ◽  
pp. 66-76 ◽  
Author(s):  
Jin Sike ◽  
Gong Yanfeng ◽  
Zhang Guangli
Keyword(s):  
Flow Field ◽  
Energy Evolution ◽  
Field Development ◽  
Road Tunnels

The Effect of Four Part Gap Geometry Configurations for Variable Stator Vanes in a Compressor Cascade

2012 ◽  
Author(s):  
Marcel Gottschall ◽  
Konrad Vogeler ◽  
Ronald Mailach
Keyword(s):  
Flow Field ◽  
Separated Flow ◽  
Reynolds Numbers ◽  
Compressor Cascade ◽  
Field Development ◽  
Operating Range ◽  
Rear Part ◽  
Axis Position ◽  
Stagger Angle ◽  
Variable Stator

The article describes numerical investigations on the influence of four different endwall clearance topologies for variable stator vanes to secondary flow field development and the performance of high pressure compressors. The aim of this work is to quantify the characteristics of different clearance configurations depending on the penny-axis position and the penny diameter for a typical operating range. All clearance configurations were implemented to a linear cascade of modern stator profiles. The analysis was introduced using a relative clearance size of 1.3% chord at three stagger angles and two characteristic Reynolds numbers to model the operating range on aircraft engines. 3D numerical calculations were carried out to gain information about the flow field inside the cascade. They were compared with measurements of a 5-hole-probe as well as pressure tappings on the airfoil and the endwall. The CFD shows the clearance characteristics in good agreement with the measurements for the lower and the nominal stagger angle. Small gaps in the rear part of the vane have a beneficial effect on the flow field. In contrast, a clearance in the higher loaded front part of the vane always resulted in increased losses. Otherwise, the significant enhanced performance of a rear part gap, which was measured at the higher stagger angle, was not reflected by the CFD. The reduced mixing losses and the higher averaged flow turning even compared to a configuration without a clearance are not verified with the calculations. Large flow separations at the high stagger angle result in a two to four times higher underturning of the CFD in comparison to the experiments. The clearance effects to the characteristic radial loss distribution up to 40 % bladeheight also deviate from the measurements due to heavy mixing of clearance and reversed separated flow.

Polymer electrolyte membrane fuel cell flow field designs and approaches for performance enhancement

2019 ◽  
Vol 234 (8) ◽  
pp. 1189-1214 ◽  
Author(s):  
Erman Çelik ◽  
İrfan Karagöz
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Flow Field ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
High Energy ◽  
Cell Performance ◽  
High Energy Density ◽  
Field Development ◽  
Electrolyte Membrane

Polymer electrolyte membrane fuel cells are carbon-free electrochemical energy conversion devices that are appropriate for use as a power source on vehicles and mobile devices emerging with their high energy density, lightweight structure, quick startup and lower operating temperature capabilities. However, they need more developments in the aspects of reactant distribution, less pressure drops, precisely balanced water content and heat management to achieve more reliable and higher overall cell performance. Flow field development is one of the most important fields of study to increase cell performance since it has decisive effects on performance parameters, including bipolar plate, and thus fuel cell weight. In this study, recent developments on conventional flow field designs to eliminate their weaknesses and innovative design approaches and flow field architectures are obtained from patent databases, and both numerical and experimental scientific studies. Fundamental designs that create differences are introduced, and their effects on the performance are discussed with regard to origin, objective, innovation strategy of design besides their strength and probable open development ways. As a result, significant enhancements and design strategies on flow field designs in polymer electrolyte membrane fuel cells are summarized systematically to guide prospective flow field development studies.

The Impact of Compressor Exit Conditions on Fuel Injector Flows

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
C. L. Ford ◽  
J. F. Carrotte ◽  
A. D. Walker
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Numerical Data ◽  
Flow Fields ◽  
Main Reaction ◽  
Fuel Injector ◽  
Lean Burn ◽  
Field Development ◽  
Inlet Conditions ◽  
The Impact

This paper examines the effect of compressor generated inlet conditions on the air flow uniformity through lean burn fuel injectors. Any resulting nonuniformity in the injector flow field can impact on local fuel air ratios and hence emissions performance. The geometry considered is typical of the lean burn systems currently being proposed for future, low emission aero engines. Initially, Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) predictions were used to examine the flow field development between compressor exit and the inlet to the fuel injector. This enabled the main flow field features in this region to be characterized along with identification of the various stream-tubes captured by the fuel injector passages. The predictions indicate the resulting flow fields entering the injector passages are not uniform. This is particularly evident in the annular passages furthest away from the injector centerline which pass the majority of the flow which subsequently forms the main reaction zone within the flame tube. Detailed experimental measurements were also undertaken on a fully annular facility incorporating an axial compressor and lean burn combustion system. The measurements were obtained at near atmospheric pressure/temperatures and under nonreacting conditions. Time-resolved and time-averaged data were obtained at various locations and included measurements of the flow field issuing from the various fuel injector passages. In this way any nonuniformity in these flow fields could be quantified. In conjunction with the numerical data, the sources of nonuniformities in the injector exit plane were identified. For example, a large scale bulk variation (+/−10%) of the injector flow field was attributed to the development of the flow field upstream of the injector, compared with localized variations (+/−5%) that were generated by the injector swirl vane wakes. Using this data the potential effects on fuel injector emissions performance can be assessed.

scholarly journals Influence of Control Mechanism on the Flow field of Duct at Mach 1.2 for Area Ratio 2.56

2019 ◽  
Vol 8 (6S4) ◽  
pp. 1135-1138 ◽  
Keyword(s):  
Experimental Investigation ◽  
Mach Number ◽  
Flow Field ◽  
Recirculation Zone ◽  
Control Mechanism ◽  
Area Ratio ◽  
Central Axis ◽  
Orifice Diameter ◽  
Field Development

In this paper, the outcome of the experimental investigation and the flow field development in the duct at supersonic Mach number of 1.2 is presented. The experiments were conducted at various NPR which covers the condition of correct expansion and under expansion. A Convergent-divergent (C-D) nozzle which is connected with the suddenly expanded duct of the diameter of 16 mm of area ratio 2.56. The recirculation zone is controlled by using the microjets of 1 mm of orifice diameter which are placed at 90 degrees interval at 6.5 mm from the central axis of the main jet. The L/D of the duct was used in the investigation was from 1 to 10, and the NPR at which the experiments were conducted considered are in the range from 3, 5, 7, 9 and 11.

The Impact of Compressor Exit Conditions on Fuel Injector Flows

2012 ◽  
Author(s):  
C. L. Ford ◽  
J. F. Carrotte ◽  
A. D. Walker
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Numerical Data ◽  
Flow Fields ◽  
Main Reaction ◽  
Fuel Injector ◽  
Lean Burn ◽  
Field Development ◽  
Inlet Conditions ◽  
The Impact

This paper examines the effect of compressor generated inlet conditions on the air flow uniformity through lean burn fuel injectors. Any resulting non-uniformity in the injector flow field can impact on local fuel air ratios and hence emissions performance. The geometry considered is typical of the lean burn systems currently being proposed for future, low emission aero engines. Initially, RANS CFD predictions were used to examine the flow field development between compressor exit and the inlet to the fuel injector. This enabled the main flow field features in this region to be characterized along with identification of the various stream-tubes captured by the fuel injector passages. The predictions indicate the resulting flow fields entering the injector passages are not uniform. This is particularly evident in the annular passages furthest away from the injector center-line which pass the majority of the flow which subsequently forms the main reaction zone within the flame tube. Detailed experimental measurements were also undertaken on a fully annular facility incorporating an axial compressor and lean burn combustion system. The measurements were obtained at near atmospheric pressure/temperatures and under non-reacting conditions. Time-resolved and time-averaged data were obtained at various locations and included measurements of the flow field issuing from the various fuel injector passages. In this way any non-uniformity in these flow fields could be quantified. In conjunction with the numerical data, the sources of non-uniformities in the injector exit plane were identified. For example, a large scale bulk variation (+/−10%) of the injector flow field was attributed to the development of the flow field upstream of the injector, compared with localized variations (+/−5%) that were generated by the injector swirl vane wakes. Using this data the potential effects on fuel injector emissions performance can be assessed.

Study of Turbulence Models in Flows Through Adverse Pressure Gradient System

2005 ◽  
Author(s):  
E. Karunakaran ◽  
V. Ganesan
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Pressure Gradient ◽  
Numerical Simulations ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Reynolds Stress Model ◽  
Gradient System ◽  
Field Development

This paper is concerned with the study of performance of popular turbulence models used in the CFD analysis. Turbulence models considered for evaluation include the eddy viscosity models and the Reynolds stress model. The recent k-ε-v2-f model recommended for a flow with separation is also studied. Evaluation of the turbulence models in the present study focuses on a three-dimensional flow field development with adverse pressure gradient and flows that simulate wall-bounded turbulence. Numerical calculations are performed using SIMPLE based algorithm. Nowadays, decelerating flow in a diffuser is assessed by numerical simulations and the validation is done with experimental results. A comparison of the numerical results and the experimental data are presented. The main objective of the comparison is to obtain information on how well the numerical simulations representing the flow field with the standard turbulence models, are able to reproduce the experimental data.

scholarly journals Isothermal Flow Fields in a Research Combustor for Lean Blowout Studies

1991 ◽  
Author(s):  
G. J. Sturgess ◽  
S. P. Heneghan ◽  
M. D. Vangsness ◽  
D. R. Ballal ◽  
A. L. Lesmerises
Keyword(s):  
Flow Field ◽  
Laser Doppler Anemometry ◽  
Constant Density ◽  
Undue Influence ◽  
Optical Access ◽  
Field Development ◽  
Lean Blowout ◽  
Primary Zone ◽  
Density Flow ◽  
Jet Behavior

A propane-fueled research combustor has been designed and developed to investigate lean blowouts in a simulated primary zone of the combustors for aircraft gas turbine engines. To better understand the flow development and to ensure that the special provisions in the combustor for optical access did not introduce undue influence, measurements of the velocity fields inside the combustor were made using laser Döppler anemometry. These measurements were made in isothermal, constant density flow to relate the combustor flow field development to known jet behavior and to backward-facing step experimental data in the literature. The major features of the flow field appear to be consistent with the expected behavior, and there is no evidence that the provision of optical access adversely affected the flows measured.

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

2010 ◽  
Author(s):  
J. Aidarinis ◽  
D. Missirlis ◽  
K. Yakinthos ◽  
A. Goulas
Keyword(s):  
Flow Field ◽  
Cooling System ◽  
Air Flow ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Experimental Measurements ◽  
Field Development ◽  
Lubricant Oil ◽  
Aero Engine ◽  
Engine Bearing

The constant development of aero engines towards lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increased demands of the lubrication systems, such as the bearing chambers of the aero engine. For this reason, it is of particular importance to increase our level of understanding of the flow field inside the bearing chambers in order to optimize its design and performance. The flow field in such cases is of a complicated nature since there is a strong interaction between air-flow and lubricant oil together with the geometrical configurations and the shaft rotational speed inside the bearing chamber. The behavior of this interaction must be investigated in order to understand the flow field development inside the aero engine bearing and, at a next step, optimize its performance in relation to the lubrication and heat transfer capabilities. Such an effort is presented in this work where an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided in two separate smaller sections where the flow passes from the first section partially through the bearing and the holding structure, to the second one where the vent and the scavenge are placed. The investigation was performed with the combined use of experimental measurements and Computational Fluid Dynamics (CFD) modeling. The experimental measurements were carried out with the use of a Laser Doppler Anemometry (LDA) system in an experimental rig modeling the front bearing chamber of an aero engine for real operating conditions taking into account both air-flow and lubricant oil-flow and for a varying number of shaft rotating speeds. The CFD modeling was performed with the use of a commercial CFD package. The air-flow inside the bearing was modeled with the adoption of a porous medium assumption. The experimental measurements and the CFD computations presented similar flow patterns and satisfactory quantitative agreement. At the same time the effect of the important parameters such as the air and oil mass flow together with the shaft rotation speed and the effect of the chamber inside geometry were identified. These conclusions can be exploited in future attempts in combination with the developed CFD model, in order to optimize the efficiency of the lubricant and cooling system. The latter forms the main target of this work which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing so as to be used for optimization efforts.

Shock Wave and Flow Field Development in Hypersonic Re-Entry

ARS Journal ◽  
1961 ◽  
Vol 31 (2) ◽  
pp. 185-194 ◽  
Author(s):  
RONALD F. PROBSTEIN
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Field Development
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