Measurement of Compressible Flow Pressure Losses in Wye-Junctions

1994 ◽  
Vol 116 (3) ◽  
pp. 535-541 ◽  
Author(s):  
N. I. Abou-Haidar ◽  
S. L. Dixon
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Incompressible Flows ◽  
Separate Flow ◽  
Working Fluid ◽  
Vena Contracta ◽  
Pressure Losses ◽  
Flow Loss ◽  
Flow Pressure ◽  
Limiting Condition

This paper considers the compressible flow pressure losses in sharp-cornered wye-junctions with symmetric branches under dividing and combining flow conditions. Determination of the additional total pressure losses occurring in flow through several three-leg junctions, using dry air as the working fluid, has been made experimentally. Results covering a wide speed range up to choking are presented for 30, 60, and 90 deg wye-junctions. Separate flow visualization schlieren tests detected the presence of normal shock waves, located at up to one duct diameter downstream of the junction, and therefore confirmed the choking of the flow at the vena contracta. The highest attainable Mach number (M3) of the averaged whole flow was 0.9 for one of the dividing flow geometries and 0.65 for several of the combining flow cases. These values of M3 were the maximum possible and hence represent a limiting condition dictated by choking. In general, the compressible flow loss coefficients, caused by the presence of the wye-junctions, can be expected to be higher for dividing flows and lower for combining flows than would be the case for incompressible flows because of the influence of Mach number, M3.

scholarly journals Compressible Flow Pressure Losses in Wye-Junctions

1992 ◽  
Author(s):  
N. I. Abou-Haidar ◽  
S. L. Dixon
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Incompressible Flows ◽  
Separate Flow ◽  
Working Fluid ◽  
Flow Visualisation ◽  
Vena Contracta ◽  
Pressure Losses ◽  
Flow Pressure ◽  
Limiting Condition

This paper considers the compressible flow pressure losses in sharp cornered wye-junctions with symmetrical branches under dividing and combining flow conditions. Determination of the additional total pressure losses occurring in flow through several three-leg junctions, using dry air as the working fluid, has been made experimentally. Results covering a wide speed range up to choking are presented for three different wye-junction geometries. Separate flow visualisation Schlieren tests detected the presence of normal shock waves, located at up to one duct diameter downstream of the junction, and therefore confirmed the choking of the flow at the vena contracta. The highest attainable Mach number (M3) of the averaged whole flow was 0.9 for one of the dividing flow geometries and 0.65 for several of the combining flow cases. These values of M3 were the maximum possible and hence represent a limiting condition dictated by choking. In general, the compressible flow loss coefficients, caused by the presence of the wye-junctions, can be expected to be higher for dividing flows and lower for combining flows than would be the case for incompressible flows because of the influence of Mach number (M3) on the magnitude of the denominator.

Prediction of Compressible Flow Pressure Losses in 30–150 Deg Sharp-Cornered Bends

1995 ◽  
Vol 117 (4) ◽  
pp. 589-592 ◽  
Author(s):  
Nia Haidar
Keyword(s):  
Compressible Flow ◽  
Turbine Engines ◽  
Air Cooling ◽  
Gas Turbine Engines ◽  
Pressure Losses ◽  
Flow Pressure ◽  
Secondary Air ◽  
Limiting Condition ◽  
Experimental Findings ◽  
Wide Speed Range

This paper considers the measurement and prediction of the additional total pressure losses of subsonic steady air flow in sharp-cornered bends, similar to those present in the secondary air cooling systems of gas turbine engines. The bends examined ranged between 30 to 150 in 30 deg increments and were circular in cross section. Experimental results covering a wide speed range up to choking are presented for five different bend geometries. An analytical flow model provided results in fairly good agreement with the measurements obtained and equally compared favourably with the experimental findings of other researchers at low Mach numbers. The highest attainable upstream Mach number (MU) of the average upstream flow was 0.57 for the 30 deg bend. The maximum possible values of MU represent a limiting condition dictated by downstream choking of the flow. The compressible flow coefficients, caused by the presence of the bends, can be expected to be between 10 to 20 percent higher than those for incompressible flow.

Radial Impeller Forces Using CFD: Part II — A Comparison Between Compressible and Incompressible Flows

2002 ◽  
Author(s):  
Daniel O. Baun ◽  
Ronald D. Flack
Keyword(s):  
Mach Number ◽  
Flow Rate ◽  
Incompressible Flows ◽  
Lateral Force ◽  
Magnetic Bearing ◽  
Flow Coefficient ◽  
Low Flow ◽  
Working Fluid ◽  
Centrifugal Impeller ◽  
Cfd Model

Lateral centrifugal impeller forces are calculated using the CFD model developed in Part I of this paper. The impeller forces are evaluated by integrating the pressure and momentum profiles at both the impeller inlet and exit planes. Direct impeller lateral force measurements were made using a magnetic bearing supported pump rotor. Comparisons between the simulated and measured forces are first made for both average and transient impeller forces with water as the working fluid. Air was then substituted as the working fluid in the validated CFD model and the effect of impeller Mach number and Reynolds number on the static impeller lateral forces was investigated. The non-dimensional lateral impeller force characteristics as a function of normalized flow coefficient are similar in character between the incompressible and compressible case. At the matching point flow coefficient the non-dimensional impeller force magnitude was the same for all compressible and incompressible simulations. For any normalized flow rate other than the matching point flow rate, the magnitude of the non-dimensional impeller force increased as the Mach number increased. As the choke condition was approached the magnitude of the impeller force increased exponentially. As the Mach number increased the transition of the force orientation vector from the low flow asymptote to the high flow asymptote occurred over a progressively smaller range of flows.

A Weakly Compressible Flow Model and Rapid Convergence Methods

1988 ◽  
Vol 110 (4) ◽  
pp. 441-445 ◽  
Author(s):  
Charles C. S. Song ◽  
Mingshun Yuan
Keyword(s):  
Mach Number ◽  
Steady Flow ◽  
Compressible Flow ◽  
Flow Model ◽  
Incompressible Flows ◽  
Acoustic Noise ◽  
Hydraulic Transients ◽  
Flow Solution ◽  
Weakly Compressible ◽  
Speed Up

A weakly compressible flow model for small Mach number flows is applied to the computation of steady and unsteady inviscid flows. The equations of continuity and motion are decoupled from the energy equation, but, unlike the equations for incompressible fluids, these equations retain the ability to represent rapidly changing flows such as hydraulic transients and hydroacoustics. Two methods to speed up the process of convergence when an explicit method is used to calculate steady incompressible flows are proposed. The first method which is quite similar to the artificial compressiblity method is to assume an arbitrarily small sound speed (equivalent to large Mach number) to speed up the convergence. Any positive finite number may be used for M. One disadvantage of this method is the contamination of the steady flow solution by acoustic noise that may reverberate in the flow field for some time after the steady flow has been essentially established. The second method is based on the concept of valve stroking or boundary control. Certain boundary stroking functions that will unify the hydroacoustic and hydrodynamic processes can be found by using the inverse method of classical hydraulic transients. This method yields uncontaminated steady flow solution very rapidly independent of the Mach number.

Numerical Modeling of Heat Transfer and Pressure Losses for Uncooled Gas Turbine Blade Tip: Effect of Tip Clearance and Tip Geometry

2007 ◽  
Author(s):  
Lamyaa A. El-Gabry
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Gas Turbine ◽  
Computational Study ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Pressure Losses ◽  
Blade Tip ◽  
Exit Mach Number

A computational study has been performed to predict the heat transfer distribution on the blade tip surface for a representative gas turbine first stage blade. CFD predictions of blade tip heat transfer are compared to test measurements taken in a linear cascade, when available. The blade geometry has an inlet Mach number of 0.3 and an exit Mach number of 0.75, pressure ratio of 1.5, exit Reynolds number based on axial chord of 2.57×106, and total turning of 110 deg. Three blade tip configurations were considered; they are flat tip, a full perimeter squealer, and an offset squealer where the rim is offset to the interior of the tip perimeter. These three tip geometries were modeled at three tip clearances of 1.25, 2.0, and 2.75% of blade span. The tip heat transfer results of the numerical models agree fairly well with the data and are comparable to other CFD predictions in the open literature.

scholarly journals Aerodynamic Losses in Turbines with and without Film Cooling, as Influenced by Mainstream Turbulence, Surface Roughness, Airfoil Shape, and Mach Number

2012 ◽  
Vol 2012 ◽  
pp. 1-28 ◽  
Author(s):  
Phil Ligrani
Keyword(s):  
Surface Roughness ◽  
Mach Number ◽  
Film Cooling ◽  
Total Pressure ◽  
High Speed ◽  
Density Ratio ◽  
Aerodynamic Loss ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Exit Mach Number

The influences of a variety of different physical phenomena are described as they affect the aerodynamic performance of turbine airfoils in compressible, high-speed flows with either subsonic or transonic Mach number distributions. The presented experimental and numerically predicted results are from a series of investigations which have taken place over the past 32 years. Considered are (i) symmetric airfoils with no film cooling, (ii) symmetric airfoils with film cooling, (iii) cambered vanes with no film cooling, and (iv) cambered vanes with film cooling. When no film cooling is employed on the symmetric airfoils and cambered vanes, experimentally measured and numerically predicted variations of freestream turbulence intensity, surface roughness, exit Mach number, and airfoil camber are considered as they influence local and integrated total pressure losses, deficits of local kinetic energy, Mach number deficits, area-averaged loss coefficients, mass-averaged total pressure loss coefficients, omega loss coefficients, second law loss parameters, and distributions of integrated aerodynamic loss. Similar quantities are measured, and similar parameters are considered when film-cooling is employed on airfoil suction surfaces, along with film cooling density ratio, blowing ratio, Mach number ratio, hole orientation, hole shape, and number of rows of holes.

Heat Transfer in Rotating Serpentine Coolant Passage With Ribbed Walls at Low Mach Numbers

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Shang-Feng Yang ◽  
Je-Chin Han ◽  
Salam Azad ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Low Mach Number ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers ◽  
Wide Range ◽  
Mach Numbers

This paper experimentally investigates the effect of rotation on heat transfer in typical turbine blade serpentine coolant passage with ribbed walls at low Mach numbers. To achieve the low Mach number (around 0.01) condition, pressurized Freon R-134a vapor is utilized as the working fluid. The flow in the first passage is radial outward, after the 180 deg tip turn the flow is radial inward to the second passage, and after the 180 deg hub turn the flow is radial outward to the third passage. The effects of rotation on the heat transfer coefficients were investigated at rotation numbers up to 0.6 and Reynolds numbers from 30,000 to 70,000. Heat transfer coefficients were measured using the thermocouples-copper-plate-heater regional average method. Heat transfer results are obtained over a wide range of Reynolds numbers and rotation numbers. An increase in heat transfer rates due to rotation is observed in radially outward passes; a reduction in heat transfer rate is observed in the radially inward pass. Regional heat transfer coefficients are correlated with Reynolds numbers for nonrotation and with rotation numbers for rotating condition, respectively. The results can be useful for understanding real rotor blade coolant passage heat transfer under low Mach number, medium–high Reynolds number, and high rotation number conditions.

INFLUENCE OF GAS-DYNAMIC TESTING RIG PIPELINES MATERIAL ON THEIR DYNAMIC CHARACTERISTICS

2021 ◽  
pp. 118-125
Author(s):  
А.В. Саврико ◽  
С.Н. Лымич ◽  
К.В. Кружаев ◽  
В.С. Левин ◽  
А.В. Москвичев
Keyword(s):  
Flow Rate ◽  
Dynamic Characteristics ◽  
Dynamic Testing ◽  
Analytical Calculation ◽  
Working Fluid ◽  
Factors Affecting ◽  
Pressure Losses ◽  
Steel Pipes ◽  
Gas Dynamic ◽  
Friction Pressure

Приведено исследование зависимости газодинамических характеристик стенда от применяемого материала трубопровода. Oсновополагающими факторами, влияющими на работоспособность стенда, являются выходные параметры - давление и расход рабочего тела, которые напрямую зависят от потерь давления на трение, создаваемого элементами стенда. Для оценки степени влияния материалов на потери стенда выбраны два вида труб: полипропиленовые и металлические. Аналитические расчёты потери давления рассматриваемых трубопроводов из различного материала показали, что трубопроводы из полипропилена предпочтительнее. Однако при проведении эксперимента получены противоположные данные, которые показали, что в полипропиленовых магистралях возможно присутствие значительного количества диафрагм: в местах пайки труб, образовавшихся в процессе изготовления. Именно этот факт способствует существенному повышению значений сопротивлений в полипропиленовых трубопроводах на 20 % по сравнению со стальными трубами, где диафрагмы отсутствуют. В результате проведения исследования был введен коэффициент, учитывающий влияние диафрагм полипропиленового трубопровода при аналитическом расчете на сопротивление. Для сохранения более точных снимаемых значений с газодинамических стендов целесообразнее использовать трубопроводы из металла, в которых рассчитать потери возможно с отклонениями до 3 % Here we give the study of the dependence of the gas-dynamic characteristics of the stand on the pipeline material used. The fundamental factors affecting the performance of the stand are the output parameters-the pressure and flow rate of the working fluid, which directly depend on the friction pressure losses created by the elements of the stand. To assess the degree of influence of materials on the losses of the stand, we selected two types of pipes: polypropylene and metal. Analytical calculations of the pressure loss of the considered pipelines made of various materials have shown that pipelines made of polypropylene are preferable. However, during the experiment, we obtained the opposite data, which showed that a significant number of diaphragms may be present in polypropylene pipelines: in the places of soldering of pipes formed during the manufacturing process. This fact contributes to a significant increase in the resistance values in polypropylene pipelines by 20 % compared to steel pipes, where there are no diaphragms. As a result of the study, we introduced a coefficient that takes into account the influence of polypropylene pipeline diaphragms in the analytical calculation of resistance. To preserve more accurate values taken from gas-dynamic stands, it is more expedient to use metal pipelines in which it is possible to calculate losses with deviations of up to 3 %

On the unsteady inviscid force on cylinders and spheres in subcritical compressible flow

2008 ◽  
Vol 366 (1873) ◽  
pp. 2161-2175 ◽  
Author(s):  
M Parmar ◽  
A Haselbacher ◽  
S Balachandar
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Propagation Speed ◽  
Added Mass ◽  
The Body ◽  
Mass Force ◽  
Unsteady Force ◽  
Mass Coefficient ◽  
Added Mass Coefficient ◽  
Cylinders And Spheres

The unsteady inviscid force on cylinders and spheres in subcritical compressible flow is investigated. In the limit of incompressible flow, the unsteady inviscid force on a cylinder or sphere is the so-called added-mass force that is proportional to the product of the mass displaced by the body and the instantaneous acceleration. In compressible flow, the finite acoustic propagation speed means that the unsteady inviscid force arising from an instantaneously applied constant acceleration develops gradually and reaches steady values only for non-dimensional times c ∞ t / R ≳10, where c ∞ is the freestream speed of sound and R is the radius of the cylinder or sphere. In this limit, an effective added-mass coefficient may be defined. The main conclusion of our study is that the freestream Mach number has a pronounced effect on both the peak value of the unsteady force and the effective added-mass coefficient. At a freestream Mach number of 0.5, the effective added-mass coefficient is about twice as large as the incompressible value for the sphere. Coupled with an impulsive acceleration, the unsteady inviscid force in compressible flow can be more than four times larger than that predicted from incompressible theory. Furthermore, the effect of the ratio of specific heats on the unsteady force becomes more pronounced as the Mach number increases.

CFD Aided Design of Heat Transfer Plates for Gasketed Plate Heat Exchangers

2014 ◽  
Author(s):  
Ece Özkaya ◽  
Selin Aradag ◽  
Sadik Kakac
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Separate Flow ◽  
Working Fluid ◽  
Number Range ◽  
Plate Heat ◽  
Pressure Distributions ◽  
Cfd Analyses

In this study, three-dimensional computational fluid dynamics (CFD) analyses are performed to assess the thermal-hydraulic characteristics of a commercial Gasketed Plate Heat Exchangers (GPHEx) with 30 degrees of chevron angle (Plate1). The results of CFD analyses are compared with a computer program (ETU HEX) previously developed based on experimental results. Heat transfer plate is scanned using photogrammetric scan method to model GPHEx. CFD model is created as two separate flow zones, one for each of hot and cold domains with a virtual plate. Mass flow inlet and pressure outlet boundary conditions are applied. The working fluid is water. Temperature and pressure distributions are obtained for a Reynolds number range of 700–3400 and total temperature difference and pressure drop values are compared with ETU HEX. A new plate (Plate2) with corrugation pattern using smaller amplitude is designed and analyzed. The thermal properties are in good agreement with experimental data for the commercial plate. For the new plate, the decrease of the amplitude leads to a smaller enlargement factor which causes a low heat transfer rate while the pressure drop remains almost constant.

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