On the Optimum Pressure Drop of Axial Kinetic Turbines Operating Within Nozzles

2018 ◽  
Author(s):  
Jaime Moreu ◽  
Ricardo García-Morato ◽  
Jesús Valle ◽  
Santiago de Guzmán ◽  
Miriam Terceño
Keyword(s):  
Pressure Drop ◽  
Turbine Blades ◽  
Radial Component ◽  
Optimum Pressure ◽  
Cost Of Energy ◽  
Actuator Disc ◽  
Points Of View ◽  
Ultimate Objective ◽  
Induced Velocity ◽  
Energy Harnessing

Kinetic turbines harnessing tidal and ocean currents make use, in some designs, of nozzles and/or diffusers. Nozzles come at a cost, but they can help from the structural, hydrodynamic or positioning points of view. In those cases, they might make sense as long as they drive the LCoE (Levelized Cost of Energy) down, which is the ultimate objective of energy-harnessing devices. The design must then optimize the combined performance of both blades and nozzle. However, the interaction between turbine blades and nozzle is not always fully clear, and even less its optimization. A relevant amount of efficiency can be lost if the design spiral is not appropriate. The authors have suggested in [1] an approach for the optimization of turbines within nozzles. This approach was followed in [2] and validated with model tests. In the approach, the turbine is initially substituted by an actuator disc that applies a radially constant pressure drop. But in these references, the optimum pressure drop in the actuator disc was the same as if there was no nozzle at all, i.e., 4/9ρv2. This is equivalent to considering the nozzle coefficient does not depend on the pressure drop, and thus, on the induced velocity field. Hence it is a somewhat arbitrary assumption. This paper describes, using actuator disc theory, how nozzles affect the disc optimum pressure drop in uniform flow conditions. The effect of a hub is also analyzed. Then, using a viscous FVM CFD code, the variation of the pressure drop is quantified for two different acceleration nozzles, one suffering flow separation and the other one not. As the pressure drop increases, so does the flow expansion downstream. This rises the average radial component of velocity at the nozzle, increasing the thrust and nozzle coefficient. Therefore the optimum pressure drop goes up compared to that without nozzle. The increment in efficiency that can be obtained with this approach is quantified for the studied nozzles. Finally, the integration of this effect into the blade design is discussed.

Research of the Nonlinear Wake Model of HAWT

2013 ◽  
Vol 448-453 ◽  
pp. 1747-1753
Author(s):  
Rui Yang ◽  
Sheng Long Zhang ◽  
Jiu Xin Wang
Keyword(s):  
Radial Component ◽  
Wake Vortex ◽  
Surface Model ◽  
Trailing Edge ◽  
Vortex Sheets ◽  
Central Vortex ◽  
Actuator Disc ◽  
Horizontal Axis Wind Turbines ◽  
Wake Model ◽  
Induced Velocity

In the existing linear wake (cylindrical surface) model of horizontal axis wind turbines, the rotor was taken as the actuator-disc composed of infinite blades with infinitesimal chords. The distribution of variable circulation along blade was not taken into account and the span-wise (or radial) component of induced velocity is totally ignored. And assumed that the all trailing vortex filament shed from blade trailing edge would locate on their own cylindrical stream-surface. This aerodynamic model for determination of wake configuration is obviously different from that actually observed wake in wind tunnel experiment. Therefore, a "nonlinear" wake model was proposed, in this model the wake vortex system was divided into the central vortex along rotor axis, the bound vortex along blade axis, the wake vortex sheets shed from blade trailing edge and extent into infinity behind the rotor. Then, on the basis of potential theory in fluid mechanics a set of integral equations for evaluation of induced velocity in wake were derived with Biot-Savarts formula.

High Speed Flow through Perforated Plates

1960 ◽  
Vol 64 (590) ◽  
pp. 103-105
Author(s):  
P. G. Morgan
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Perforated Plate ◽  
Wire Mesh ◽  
Flow Conditions ◽  
High Speed Flow ◽  
Perforated Plates ◽  
Speed Flow ◽  
Flow Through ◽  
Points Of View

The flow through porous screens has been widely studied from both the theoretical and experimental points of view. The most widely used types of screen are the wire mesh and the perforated plate, and the majority of the literature has been concerned with the former. Several attempts have been made to correlate the parameters governing the flow through such screens, i.e. the pressure drop, the flow conditions and the geometry of the mesh.

Optimum Performance of a Regenerative Gas Turbine Power Plant Operating With/Without a Solid Oxide Fuel Cell

2011 ◽  
Vol 8 (5) ◽  
Author(s):  
Y. Haseli
Keyword(s):  
Fuel Cell ◽  
Pressure Drop ◽  
Solid Oxide Fuel Cell ◽  
Hybrid System ◽  
Thermal Efficiency ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Work Output ◽  
Oxide Fuel ◽  
Optimum Pressure

Optimum pressure ratios of a regenerative gas turbine (RGT) power plant with and without a solid oxide fuel cell are investigated. It is shown that assuming a constant specific heat ratio throughout the RGT plant, explicit expressions can be derived for the optimum pressure ratios leading to maximum thermal efficiency and maximum net work output. It would be analytically complicated to apply the same method for the hybrid system due to the dependence of electrochemical parameters such as cell voltage on thermodynamic parameters like pressure and temperature. So, the thermodynamic optimization of this system is numerically studied using models of RGT plant and solid oxide fuel cell. Irreversibilities in terms of component efficiencies and total pressure drop within each configuration are taken into account. The main results for the RGT plant include maximization of the work output at the expenses of 2–4% lower thermal efficiency and higher capital costs of turbo-compressor compared to a design based on maximum thermal efficiency. On the other hand, the hybrid system is studied for a turbine inlet temperature (TIT) of 1 250–1 450 K and 10–20% total pressure drop in the system. The maximum thermal efficiency is found to be at a pressure ratio of 3–4, which is consistent with past studies. A higher TIT leads to a higher pressure ratio; however, no significant effect of pressure drop on the optimum pressure ratio is observed. The maximum work output of the hybrid system may take place at a pressure ratio at which the compressor outlet temperature is equal to the turbine downstream temperature. The work output increases with increasing the pressure ratio up to a point after which it starts to vary slightly. The pressure ratio at this point is suggested to be the optimal because the work output is very close to its maximum and the thermal efficiency is as high as a littler less than 60%.

Heat Transfer and Pressure Drop in Pin-Fin Trapezoidal Ducts

1999 ◽  
Vol 121 (2) ◽  
pp. 264-271 ◽  
Author(s):  
J.-J. Hwang ◽  
D.-Y. Lai ◽  
Y.-P. Tsia
Keyword(s):  
Nusselt Number ◽  
Pressure Drop ◽  
Turbine Blades ◽  
Total Flow ◽  
Gas Turbine Blades ◽  
Pin Fin ◽  
Flow Reynolds Number ◽  
Outlet Flow ◽  
Pin Configuration ◽  
Flow Duct

Experiments are conducted to determine the log-mean averaged Nusselt number and overall pressure-drop coefficient in a pin-fin trapezoidal duct that models the cooling passages in modern gas turbine blades. The effects of pin arrangement (in-line and staggered), flow Reynolds number (6,000 ≦ Re ≦ 40,000) and ratio of lateral-to-total flow rate (0 ≦ ε ≦ 1.0) are examined. The results of smooth trapezoidal ducts without pin arrays are also obtained for comparison. It is found that, for the single-outlet-flow duct, the log-mean averaged Nusselt number in the pin-fin trapezoidal duct with lateral outlet is insensitive to the pin arrangement, which is higher than that in straight-outlet-flow duct with the corresponding pin array. As for the trapezoidal ducts having both outlets, the log-mean averaged Nusselt number has a local minimum value at about ε = 0.3. After about ε ≧ 0.8, the log-mean averaged Nusselt number is nearly independent of the pin configuration. Moreover, the staggered pin array pays more pressure-drop penalty as compared with the in-line pin array in the straight-outlet-flow duct; however, in the lateral-outlet-flow duct, the in-line and staggered pin arrays yield almost the same overall pressure drop.

Analysis of Compression Ignition Engine Cycle Based on Irreversible Thermodynamics

2013 ◽  
Vol 837 ◽  
pp. 446-451
Author(s):  
Ion Omocea
Keyword(s):  
Pressure Drop ◽  
Irreversible Thermodynamics ◽  
Pressure Variation ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Fuel Flow ◽  
Marine Propulsion ◽  
Complex Optimization ◽  
Points Of View ◽  
Engine Cycle

We use a model that is based on the cycle behavior inlet pressure variation. This analysis revealed the two main regimes of operation marine propulsion engines. Pressure drop in the suction process can be seen from two points of view: this pressure drop is an active dissipation and at the same time is a passive dissipation, contributing to the deterioration of cycle infrastructure. Interference of the two effects is reflected by the appearance of a ψaopt=0,3...0,35, for which indicated power Pi becomes maximum in terms of given geometric and gazodynamic configurations. Respectively for a weighting of conductance gazodynamic imposed. When fuel flow is imposed, the analysis revealed that the share of shall be amended to variation of ψa, which involves the geometric and gazodynamic configuration variable. In this numerical analysis showed the existence of ψaopt=0,1...0,15, for which indicated efficiency ηi is maximum. These findings are the basis for the complex optimization cycle program for four-stroke compression ignition engine.

Topology Optimization of Serpentine Channels for Minimization of Pressure Loss and Maximization of Heat Transfer Performance As Applied for Additive Manufacturing

2019 ◽  
Author(s):  
Shinjan Ghosh ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Topology Optimization ◽  
Additive Manufacturing ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Blade Cooling

Abstract Gas Turbine blade cooling is an important topic of research, as a high turbine inlet temperature (TIT) essentially means an increase in efficiency of gas turbine cycles. Internal cooling channels in gas turbine blades are key to the cooling and prevention of thermal failure of the material. Serpentine channels are a common feature in internal blade cooling. Optimization methods are often employed in the design of blade internal cooling channels to improve heat-transfer and reduce pressure drop. Topology optimization uses a variable porosity approach to manipulate flow geometries by adding or removing material. Such a method has been employed in the current work to modify the geometric configuration of a serpentine channel to improve total heat transferred and reduce the pressure drop. An in-house OpenFOAM solver has been used to create non-traditional geometries from two generic designs. Geometry-1 is a 2-D serpentine passage with an inlet and 4 bleeding holes as outlets for ejection into the trailing edge. Geometry-2 is a 3-D serpentine passage with an aspect ratio of 3:1 and consists of two 180-degree bends. The inlet velocity for both the geometries was used as 20 m/s. The governing equations employ a “Brinkman porosity parameter” to account for the porous cells in the flow domain. Results have shown a change in shape of the channel walls to enhance heat-transfer in the passage. Additive manufacturing can be employed to make such unconventional shapes.

Experimental Investigation of Crossflow Diverters in Jet Impingement Cooling

2019 ◽  
Author(s):  
Srivatsan Madhavan ◽  
Kishore Ranganath Ramakrishnan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Target Surface ◽  
Pumping Power ◽  
Detailed Measurement ◽  
To Come

Abstract Jet impingement is a cooling technique commonly employed in combustor liner cooling and high-pressure gas turbine blades. However, jets from upstream impingement holes reduce the effectiveness of downstream jets due to jet deflection in the direction of crossflow. In order to avoid this phenomenon and provide an enhanced cooling on the target surface, we have attempted to come up with a novel design called “crossflow diverters”. Crossflow diverters are U-shaped ribs that are placed between jets in the crossflow direction (under maximum crossflow condition). In this study, the baseline case is jet impingement onto a smooth surface with 10 rows of jet impingement holes, jet-to-jet spacing of X/D = Y/D = 6 and jet-to-target spacing of Z/D = 2. Crossflow diverters with thickness ‘t’ of 1.5875 mm, height ‘h’ of 2D placed in the streamwise direction at a distance of X = 2D from center of the jet have been investigated experimentally. Transient liquid crystal thermography technique has been used to obtain detailed measurement of heat transfer coefficient for four jet diameter based Reynolds numbers of 3500, 5000, 7500, 12000. It has been observed that crossflow diverters protect the downstream jets from upstream jet deflection thereby maximizing their stagnation cooling potential. An average of 15–30% enhancement in Nusselt number is obtained over the flow range tested. However, this comes at the expense of increase in pumping power. Pressure drop for the enhanced geometry is 1–1.5 times the pressure drop for baseline impingement case. At a constant pumping power, crossflow diverters produce 9–15% enhancement in heat transfer coefficient as compared to baseline smooth case.

The Edge Singularity of an Actuator Disc With a Constant Normal Load

2003 ◽  
Author(s):  
Gijs A. M. van Kuik
Keyword(s):  
Normal Load ◽  
Leading Edge ◽  
Radial Component ◽  
Pressure Jump ◽  
Axial Component ◽  
Field Calculation ◽  
Edge Singularity ◽  
Momentum Theory ◽  
Actuator Disc ◽  
Constant Normal Load

All rotor and propeller design methods using momentum theory are based on the concept of the actuator disc, formulated by Froude. In this concept, the rotor load is represented by a uniform pressure jump. This pressure jump generates infinite pressure gradients at the edge of the disc, leading to a velocity singularity. The subject of this paper is the characterization of this velocity singularity assuming inviscid flow. The edge singularity is also the singular leading edge of the vortex sheet emanating from the edge. The singularity is determined as a simple bound vortex of order O(1), carrying an edge force Fedge = −ρ Vedge × Γ. The order of Fedge equals the order of Vedge. This order is determined by a radial momentum analysis. The classical momentum theory for actuators with a constant, normal load Δp appears to be inconsistent: the axial balance provides a value for the velocity at the actuator, with which the radial balance cannot be satisfied. The only way to obtain consistency is to allow the radial component of Fedge to enter the radial balance. The analysis does not resolve on the axial component of Fedge. A quantitative analysis by a full flow field calculation has to assess the value of Fedge for the various actuator disc flow states. Two other solutions for the edge singularity have been published. It is shown that both solutions do not comply with the governing boundary conditions.

Isolated and Coupled Effects of Rotating and Buoyancy Number on Heat Transfer and Pressure Drop in a Rotating Two-Pass Parallelogram Channel With Transverse Ribs

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Tong-Miin Liou ◽  
Shyy Woei Chang ◽  
Yi-An Lan ◽  
Shu-Po Chan
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Pressure Drop ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Cross Sectional ◽  
Gas Turbine Blades ◽  
Performance Factors ◽  
Heat Transfer Efficiency ◽  
Rotating Channel

Detailed Nusselt number (Nu) distributions over the leading (LE) and trailing (TE) endwalls and the pressure drop coefficients (f) of a rotating transverse-ribbed two-pass parallelogram channel were measured. The impacts of Reynolds (Re), rotation (Ro), and buoyancy (Bu) numbers upon local and regionally averaged Nu over the endwall of two ribbed legs and the turn are explored for Re = 5000–20,000, Ro = 0–0.3, and Bu = 0.0015–0.122. The present work aims to study the combined buoyancy and Coriolis effects on thermal performances as the first attempt. A set of selected experimental data illustrates the isolated and interdependent Ro and Bu influences upon Nu with the impacts of Re and Ro on f disclosed. Moreover, thermal performance factors (TPF) for the tested channel are evaluated and compared with those collected from the channels with different cross-sectional shapes and endwall configurations to enlighten the relative heat transfer efficiency under rotating condition. Empirical Nu and f correlations are acquired to govern the entire Nu and f data generated. These correlations allow one to evaluate both isolated and combined Re, Ro and/or Bu impacts upon the thermal performances of the present rotating channel for internal cooling of gas turbine blades.

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