An Investigation On the Discharge Coefficient of Compound Orifices in Rotating Disks

2021 ◽  
Author(s):  
Jiaxi Yan ◽  
Junkui Mao ◽  
Song Wei ◽  
Zhaolin Sun ◽  
Ranran Tian
Keyword(s):  
Discharge Coefficient ◽  
Positive Impact ◽  
Incidence Angle ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Static Condition ◽  
Operating Conditions ◽  
Confined Space ◽  
Empirical Formulas ◽  
Significant Difference

Abstract In the modern multi-shaft gas turbine engines, orifice is an important throttling element and the discharge coefficient of rotating orifices may vary considerably depending on the operating conditions, the geometry and surrounding environment. The influences of the rotating number and the pressure ratio on the rotating orifices flow characteristics are investigated in the present study. Besides, the effects of confined space, wall inclination angle (a) and the angle between the axis of orifice and the disk wall normal (ß) are also analyzed statistically. It is found that the rotating number has a significant effect on the discharge coefficient. As the rotating number increases from 0 to 0.6, the discharge coefficient reduces by about 47.88%. When rotating number is 0.74 and pressure ratio is 1.10, the discharge coefficient can be improved by 16.88% with a changes from 90° to 180°. The parameter, ß, affects discharge coefficient slightly in rotating condition. However, the maximum discharge coefficient is achieved with ß=0° in the static condition. The results also show that, a confined space weakens the effect of rotation, and changes the air flow direction in the inlet chamber, which also has a positive impact on the discharge coefficient. In the current research, it is found that there is a significant difference between the traditional empirical formulas used in the literature and the fitting result. By modifying the incidence angle and taking account of the influence of the angle of inclination, the maximum error was reduced from 56.79% to 3.16%

Impact of the Expansion Ratio on the Unsteady Aerodynamics and Performance of a HP Axial Turbine

2016 ◽  
Author(s):  
P. Gaetani ◽  
G. Persico ◽  
A. Spinelli ◽  
A. Mora
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Flow Direction ◽  
Axial Flow ◽  
Unsteady Aerodynamics ◽  
Fast Response ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
And Performance

In the frame of the European research project RECORD, the flow field within a HP axial-flow turbine model was investigated experimentally for several operating conditions. A number of studies on stator-rotor interaction in HP turbines for subsonic as well as transonic/supersonic conditions were proposed in the last decades, but none of them compared different conditions for the same geometry. In this paper, the transonic condition is investigated and compared to three subsonic ones, in the frame of an entirely new experimental campaign. The research was performed at the Laboratorio di Fluidodinamica delle Macchine of the Politecnico di Milano (Italy), where a cold-flow, closed-loop test rig is available for detailed studies on turbines and compressors. The boundary conditions resulted in keeping constant both the turbine inlet temperature and the stage outlet absolute flow direction; so far, while the expansion ratio was varied, the rotational speed was also modified accordingly. The analysis was performed by means of a conventional five hole probe in the stator – rotor axial gap and by a fast response aerodynamic probe downstream of the rotor. The local time-averaged and phase-resolved flow field was then derived and used to analyze the stage aerodynamics and performance. Results show that the stage expansion ratio has a dramatic impact on both the rotor aerodynamics and stage performance. In particular, Mach number effects are recognized in the stator cascade that passes from transonic to low subsonic conditions. On the rotor cascade the reduction of expansion ratio reduces significantly the Mach and Reynolds numbers and increases the incidence angle as well; the rotor loss mechanics as well as the vane-rotor interaction are greatly amplified. Correspondingly a significant variation of stage overall efficiency is recorded.

An Impact of Various Shroud Bleed Slot Configurations and Cavity Vanes on Compressor Map Width and the Inducer Flow Field

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Subenuka Sivagnanasundaram ◽  
Stephen Spence ◽  
Juliana Early ◽  
Bahram Nikpour
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Operating Conditions ◽  
Choked Flow ◽  
Recirculating Flow ◽  
Heavy Duty Diesel ◽  
Compressor Map ◽  
The Impact

This paper describes an investigation of map width enhancement and a detailed analysis of the inducer flow field due to various bleed slot configurations and vanes in the annular cavity of a turbocharger centrifugal compressor. The compressor under investigation is used in a turbocharger application for a heavy duty diesel engine of approximately 400 hp. This investigation has been undertaken using a computational fluid dynamics (CFD) model of the full compressor stage, which includes a manual multiblock-structured grid generation method. The influence of the bleed slot flow on the inducer flow field at a range of operating conditions has been analyzed, highlighting the improvement in surge and choked flow capability. The impact of the bleed slot geometry variations and the inclusion of cavity vanes on the inlet incidence angle have been studied in detail by considering the swirl component introduced at the leading edge by the recirculating flow through the slot. Further, the overall stage efficiency and the nonuniform flow field at the inducer inlet have been also analyzed. The analysis revealed that increasing the slot width has increased the map width by about 17%. However, it has a small impact on the efficiency, due to the frictional and mixing losses. Moreover, adding vanes in the cavity improved the pressure ratio and compressor performance noticeably. A detail analysis of the compressor with cavity vanes has also been presented.

Variable Inlet Guide Vane Effect on Centrifugal Compressor Performance in Wet Gas Flow

2016 ◽  
Author(s):  
Levi André B. Vigdal ◽  
Lars E. Bakken
Keyword(s):  
Centrifugal Compressor ◽  
Guide Vane ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Compressor Stage ◽  
Guide Vanes ◽  
Wet Gas ◽  
Compressor Performance

The introduction of variable inlet guide vanes (VIGVs) upfront of a compressor stage affects performance and permits tuning for off-design conditions. This is of great interest for emerging technology related to subsea compression. Unprocessed gas from the wellhead will contain liquid condensate, which affects the operational condition of the compressor. To investigate the effect of guide vanes on volume flow and pressure ratio in a wet gas compressor, VIGVs are implemented upfront of a centrifugal compressor stage to control the inlet flow direction. The guide vane geometry and test rig setup have previous been presented. This paper documents how changing the VIGV setting affects compressor performance under dry and wet operating conditions. The reduced performance effect and operating range at increased liquid content are of specific interest. Also documented is the change in the VIGV effect relative to the setting angle.

An Impact of Various Shroud Bleed Slot Configurations and Cavity Vanes on Compressor Map Width and the Inducer Flow Field

2011 ◽  
Author(s):  
Subenuka Sivagnanasundaram ◽  
Stephen Spence ◽  
Juliana Early ◽  
Bahram Nikpour
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Operating Conditions ◽  
Choked Flow ◽  
Recirculating Flow ◽  
Heavy Duty Diesel ◽  
Compressor Map ◽  
The Impact

This paper describes an investigation of map width enhancement and a detailed analysis of the inducer flow field due to various bleed slot configurations and vanes in the annular cavity of a turbocharger centrifugal compressor. The compressor under investigation is used in a turbocharger application for a heavy duty diesel engine of approximately 400hp. This investigation has been undertaken using a CFD model of the full compressor stage which includes a manual multi-block structured grid generation method. The influence of the bleed slot flow on the inducer flow field at a range of operating conditions has been analysed, highlighting the improvement in surge and choked flow capability. The impact of the bleed slot geometry variations and the inclusion of cavity vanes on the inlet incidence angle have been studied in detail by considering the swirl component introduced at the leading edge by the recirculating flow through the slot. Further, the overall stage efficiency and the non-uniform flow field at the inducer inlet have been also analysed. The analysis revealed that increasing the slot width has increased the map width by about 17%. However, it has a small impact on the efficiency due to the frictional and mixing losses. Moreover, adding vanes in the cavity improved the pressure ratio and compressor performance noticeably. A detail analysis of the compressor with cavity vanes has also been presented.

A High Performance Low Pressure Ratio Turbine for Engine Electric Turbocompounding

2011 ◽  
Author(s):  
Aman M. I. Mamat ◽  
Muhamad H. Padzillah ◽  
Alessandro Romagnoli ◽  
Ricardo F. Martinez-Botas
Keyword(s):  
High Performance ◽  
Gasoline Engine ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Design Procedure ◽  
Low Pressure ◽  
Operating Conditions ◽  
Exhaust Gases ◽  
Electric Generator ◽  
Turbine Design

In order to enhance energy extraction from the exhaust gases of a highly boosted downsized engine, an electric turbo-compounding unit can be fitted downstream of the main turbocharger. The extra energy made available to the vehicle can be used to feed batteries which can supply energy to electric units like superchargers, start and stop systems or other electric units. The current research focuses on the design of a turbine for a 1.0 litre gasoline engine which aims to reduce the CO2 emissions of a “cost-effective, ultra-efficient gasoline engine in small and large family car segment”. A 1-D engine simulation showed that a 3% improvement in brake specific fuel consumption (BSFC) can be expected with the use of an electric turbocompounding. However, the low pressure available to the exhaust gases expanded in the main turbocharger and the constant rotational speed required by the electric motor, motivated to design a new turbine which gives a high performance at lower pressures. Accordingly, a new turbine design was developed to recover energy of discharged exhaust gases at low pressure ratios (1.05–1.3) and to drive a small electric generator with a maximum power output of 1.0 kW. The design operating conditions were fixed at 50,000 rpm with a pressure ratio of 1.1. Commercially available turbines are not suitable for this purpose due to the very low efficiencies experienced when operating in these pressure ranges. The low pressure turbine design was carried out through a conventional non-dimensional mixed-flow turbine design method. The design procedure started with the establishment of 2-D configurations and was followed by the 3-D radial fibre blade design. A vane-less turbine volute was designed based on the knowledge of the rotor inlet flow direction and the magnitude of the absolute speed. The overall dimensions of the volute design were defined by the area-to-radius ratios at each respective volute circumferential azimuth angle. Subsequently, a comprehensive steady-state turbine performance analysis was performed by mean of Computational Fluid Dynamics (CFD) and it was found that a maximum of 76% of total-static efficiency ηt-s can be achieved at design speed.

Film Cooling Discharge Coefficient Measurements in a Turbulated Passage With Internal Crossflow

2001 ◽  
Vol 123 (4) ◽  
pp. 774-780 ◽  
Author(s):  
Ronald S. Bunker ◽  
Jeremy C. Bailey
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Substantial Effect ◽  
Internal Cooling ◽  
Gas Turbine Blades ◽  
Discharge Coefficients ◽  
Cooling Enhancement

Gas turbine blades utilize internal geometry such as turbulator ribs for improved cooling. In some designs it may be desirable to benefit from the internal cooling enhancement of ribs as well as external film cooling. An experimental study has been performed to investigate the effect of turbulator rib placement on film hole discharge coefficient. In the study, a square passage having a hydraulic diameter of 1.27 cm is used to feed a single angled film jet. The film hole angle to the surface is 30 deg and the hole length-to-diameter ratio is 4. Turbulators were placed in one of three positions: upstream of film hole inlet, downstream of film hole inlet, and with the film hole inlet centered between turbulators. For each case 90 deg turbulators with a passage blockage of 15 percent and a pitch to height ratio of 10 were used. Tests were run varying film hole-to-crossflow orientation as 30, 90, and 180 deg, pressure ratio from 1.02 to 1.8, and channel crossflow velocity from Mach 0 to 0.3. Film hole flow is captured in a static plenum with no external crossflow. Experimental results of film discharge coefficients for the turbulated cases and for a baseline smooth passage are presented. Alignment of the film hole entry with respect to the turbulator is shown to have a substantial effect on the resulting discharge coefficients. Depending on the relative alignment and flow direction discharge coefficients can be increased or decreased 5–20 percent from the nonturbulated case, and in the worst instance experience a decrease of as much as 50 percent.

Effect of Shaft Rotation, Hole and Annulus Geometry on the Discharge Behavior Through Rotating Radial Holes

2015 ◽  
Author(s):  
Daniel Riedmüller ◽  
Jan Sousek ◽  
Michael Pfitzner
Keyword(s):  
Discharge Coefficient ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Flow Phenomena ◽  
Flow Through ◽  
Discharge Behavior ◽  
Set Up ◽  
The One

This paper reports on various effects on the flow through rotating radial holes (centrifugal, centripetal) in conjunction with the geometries of hole and surrounding annuli. The aerodynamic behavior of radial rotating holes is different from the one of axial and stationary holes due to the presence of centrifugal and Coriolis forces acting in the main flow direction. Furthermore, the geometry of the inlet and outlet region is often influencing the separation behavior of the flow at the holes. To investigate the flow phenomena and the discharge behavior of these radial holes in detail, an existing test rig containing two independently rotating shafts (co- and counter rotating) was used. Experimental and numerical investigations have been performed for both flow directions through the radial holes (centripetal and centrifugal), for different hole geometries (oblong holes and round holes), inlet types (rounded and sharp), length to diameter ratios (variation of either length or diameter) and gap widths between inner and outer shaft. For each of these geometrical variations flow properties have been varied such as pressure ratio across the holes, incident Mach number and rotational speed of both shafts. To enable large parametric studies and grid independency studies an optimization model with completely automatic grid generation, CFD simulation and post-processing has been set up. As a main result of the current studies it was found, that the shaft to hole diameter is another parameter of interest for the flow behavior through shaft holes. For a centripetal flow through the shaft holes and a decreasing inner gap width, the discharge coefficient was observed to increase initially before it drops significantly. In addition, measurements of centripetal flow though oblong holes revealed higher discharge coefficient in comparison with round holes and equal length to diameter ratio.

Unsteady Rotor-Stator Interaction of a Radial-Inflow Turbine With Variable Nozzle Vanes

2010 ◽  
Author(s):  
Tomoki Kawakubo
Keyword(s):  
Shock Wave ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Mode Analysis ◽  
Turbine Stage ◽  
Impeller Blade ◽  
Blade Loading ◽  
Clearance Flow ◽  
Rotor Stator Interaction

For radial turbines used in automotive turbochargers, the importance of variable flow capacity by means of a variable geometry system is getting higher under the growing demands for improved engine performance and reduced engine emissions. To realize a high-performance and aeromechanically-reliable turbine stage, the unsteady flow phenomena caused by the rotor-stator interaction and their impact on the mechanical integrity must be understood deeply. In the present paper, the periodic disturbance generated by the rotor-stator interaction of a research turbine stage is investigated. The research purposes are (i) to extract the flow phenomenon which is responsible for the blade excitation, (ii) to identify the operating condition at which the influence of the extracted phenomenon becomes stronger, and (iii) to clarify how and where the disturbance energy is fed into the blades. Three dimensional unsteady stage CFD simulations are conducted to investigate the unsteady stage interaction. Two parameters are mainly focused: the nozzle vane angle and the stage pressure ratio. By changing the former, the effect of different degrees of reaction can be examined, while by changing the latter, the effect of different Mach number levels can be evaluated. The unsteady blade loading is extracted from the CFD result and coupled with the blade displacement obtained from the eigen vibratory mode analysis to examine the aeromechanical influence of the unsteady loading on the impeller blade excitation at various operating conditions. The nozzle shock wave and nozzle clearance flow are identified as the principal phenomena for the impeller blade excitation. At the mean section of the impeller blade the nozzle shock wave impinges on the S/S and diffracts on the P/S periodically, these two processes constitute high unsteady blade loading at the impeller L/E. At the shroud section the nozzle clearance flow generates high fluctuation in the relative flow direction to the impeller which results in high unsteadiness in the blade loading. These two phenomena are more important at vane closed conditions due to the higher nozzle loading. The higher the pressure ratio, the higher the normalized loading, though once the nozzle shock wave is established the normalized loading does not increase appreciably. Most of the excitation energy enters the blade at the impeller L/E at the closed condition, while it enters the blade both at the L/E and T/E at the open condition.

Characterization of Brush Seal Permeability

2016 ◽  
Author(s):  
Thomas G. Gresham ◽  
Brian K. Weaver ◽  
Houston G. Wood ◽  
Alexandrina Untaroiu
Keyword(s):  
Porous Media ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Backing Plate ◽  
Physical Mechanisms ◽  
Brush Seal ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through

A basis for the study of flow through a brush seal is established by applying the fundamentals of porous media fluid mechanics. Permeability, the measure of a medium’s ability to transmit flow, is one of the most important factors needed to characterize a brush seal’s ability to reduce leakage. Previous studies have indicated that the performance of a brush seal is highly dependent on operating conditions. By investigating how the permeability is affected by the operating conditions (pressure ratio specifically), further understanding of the performance of this type of seal is developed. Experimental data in the literature was used in tandem with computational fluid dynamics (CFD) simulation results in order to characterize how the permeability of a single-stage brush seal changes as the pressure ratio changes. For each value of pressure ratio, the permeability of the CFD model was adjusted until the leakage calculated from the model matched experimentally measured values. The physical mechanisms behind the observed variations in permeability are discussed. Explanations are proposed based on flutter and deformation of the bristles and how these phenomena can affect the internal tortuosity of the bristle pack. As pressure across the bristles increases, it is expected that they will bend under the backing plate to align with the flow direction in the clearance region, but the increase in pressure will also act to compress the bristle pack in the flow direction, decreasing the spacing between bristles and reducing their ability to move relative to each other, thereby reducing the effective permeability of the bristle pack. By demonstrating the dependence of permeability on operating conditions, it is shown that the common assumption of constant permeability coefficients can often result in an insufficient model. Assumptions regarding the model of a bristle pack as an isotropic porous media are discussed, and the validity and utility of this model are assessed. This paper provides important insight into what a reasonable value of permeability of a typical brush seal is, and how that value may change as a function of operating conditions.

Film Cooling Discharge Coefficient Measurments in a Turbulated Passage With Internal Cross Flow

2001 ◽  
Author(s):  
Ronald S. Bunker ◽  
Jeremy C. Bailey
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Cross Flow ◽  
Substantial Effect ◽  
Internal Cooling ◽  
Discharge Coefficients ◽  
Cooling Enhancement

Gas turbine blades utilize internal geometry such as turbulator ribs for improved cooling. In some designs it may be desirable to benefit from the internal cooling enhancement of ribs as well as external film cooling. An experimental study has been performed to investigate the effect of turbulator rib placement on film hole discharge coefficient. In the study a square passage having a hydraulic diameter of 1.27 cm is used to feed a single angled film jet. The film hole angle to the surface is 30° and the hole length-to-diameter ratio is 4. Turbulators were placed in one of three positions: upstream of film hole inlet, downstream of film hole inlet, and with the film hole inlet centered between turbulators. For each case 90° turbulators with a passage blockage of 15% and a pitch to height ratio of 10 were used. Tests were run varying film hole-to-cross flow orientation as 30°, 90°, and 180°, pressure ratio from 1.02 to 1.8, and channel cross flow velocity from Mach 0 to 0.3. Film hole flow is captured in a static plenum with no external cross flow. Experimental results of film discharge coefficients for the turbulated cases and for a baseline smooth passage are presented. Alignment of the film hole entry with respect to the turbulator is shown to have a substantial effect on the resulting discharge coefficients. Depending on the relative alignment and flow direction, discharge coefficients can be increased or decreased 5 to 20% from the non-turbulated case, and in the worst instance experience a decrease of as much as 50%.

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