Aerodynamic Performance of Tip Injections for a Winglet-Shrouded Linear Turbine Cascade

2017 ◽  
Author(s):  
Min Zhang ◽  
Yan Liu ◽  
Meng-Chao Zhang ◽  
Bao-Xi Mo ◽  
Jing-Guang Yang
Keyword(s):  
Energy Loss ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Aerodynamic Performance ◽  
Loss Coefficient ◽  
Entropy Generation Rate ◽  
Turbine Cascade ◽  
Tip Injection

Tip injection is applied in high pressure gas turbine blades to improve the tip surface heat transfer, while it also alters the flow fields in the tip gap and near the tip regions. This paper evaluates the aerodynamic performance of tip injections for a linear turbine cascade. A previously investigated winglet shroud tip without (WS) and with seals (WSS) and a flat tip are considered as datum cases. Five jet holes are distributed on the winglet shroud tips but they are not constructed on the flat tip geometry. Four injection mass flow ratios, Mr,d, of the injection mass flow rate to the mainstream mass flow rate being 0.1%, 0.2%, 0.3% and 0.5% are examined using both experiments and CFD, while three additional Mr,d including 0.7%, 0.9% and 1.0% are further numerically studied. Influences of tip injections on loss changes under various jet mass flow ratios are pinpointed via analyzing the entropy generation rate and energy loss coefficient. For Mr,d being 0.3%, the jet fluid penetrates into the near-tip region and enhances the upper passage vortex, especially for the WSS case due to the blockage effect of the seals. More severe velocity gradients and larger entropy generation rates are observed in the cascade for the WS and WSS tips with the tip jet (simply named by WSJ and WSSJ respectively). Compared with the flat tip, the WS and WSS tips reduce the energy loss coefficient by 18.98% and 33.86% respectively, while the WSJ and WSSJ bring smaller decrements of 15.89% and 27.08% separately. Contrast to the energy loss changes, tip injection can help prevent the over-tip leakage (OTL) flow from entering into the tip gap. For Mr,d being 0.3%, the WSJ and WSSJ decrease the OTL mass flow rates at a gap inlet plane by 16.97% and 65.37% respectively relative to the flat tip. When compared to the corresponding non-injection WS and WSS cases, the WSJ and WSSJ achieve further reductions of 11.43% and 29.00% separately. However, in the WSJ and WSSJ cases, the OTL mass flow rate at a tip exit plane is not noticeably lessened as it also includes the increased injection mass flow apart from the leakage main fluid. With the increase in jet mass flow ratio (Mr,d), the aerodynamic performance of the cascade with WSJ and WSSJ is gradually deteriorated. Particularly, the energy loss coefficient of the injection cases even becomes larger than that of the flat tip when Mr,d exceeds 0.7%. This change trend of the energy loss is also confirmed by an one-dimensional loss model analysis for the mixing process between the injected and the main streams.

Selecting the cooling water mass flow rate for a power plant under variable load with entropy generation rate minimization

Energy ◽  
2016 ◽  
Vol 107 ◽  
pp. 725-733 ◽  
Author(s):  
Rafał Laskowski ◽  
Adam Smyk ◽  
Janusz Lewandowski ◽  
Artur Rusowicz ◽  
Andrzej Grzebielec
Keyword(s):  
Power Plant ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Water Mass ◽  
Cooling Water ◽  
Entropy Generation Rate ◽  
Variable Load ◽  
Water Mass Flow Rate

Numerical and Experimental Investigation of Aerodynamic Performance for a Straight Turbine Cascade With a Novel Partial Shroud

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Yan Liu ◽  
Tian-Long Zhang ◽  
Min Zhang ◽  
Meng-Chao Zhang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cross Sections ◽  
Total Pressure ◽  
Pressure Coefficient ◽  
Aerodynamic Performance ◽  
Turbine Cascade ◽  
Tip Leakage ◽  
Partial Shroud

A comparative experimental and numerical analysis is carried out to assess the aerodynamic performance of a novel partial shroud in a straight turbine cascade. This partial shroud is designed as a combination of winglet and shroud. A plain tip is employed as a baseline case. A pure winglet tip is also studied for comparison. Both experiments and predictions demonstrate that this novel partial shroud configuration has aerodynamic advantages over the pure winglet arrangement. Predicted results show that, relative to the baseline blade with a plain tip, using the partial shroud can lead to a reduction of 20.89% in the mass-averaged total pressure coefficient on the upper half-span of a plane downstream of the cascade trailing edge and 16.53% in the tip leakage mass flow rate, whereas the pure winglet only decreases these two performance parameters by 11.36% and 1.32%, respectively. The flow physics is explored in detail to explain these results via topological analyses. The use of this new partial shroud significantly affects the topological structures and total pressure loss coefficients on various axial cross sections, particularly at the rear part of the blade passage. The partial shroud not only weakens the tip leakage vortex (TLV) but also reduces the strength of passage vortex near the casing (PVC) endwall. Furthermore, three partial shrouds with width-to-pitch ratios of 3%, 5%, and 7% are considered. With an increase in the width of the winglet part, improvements in aerodynamics and the tip leakage mass flow rate are limited.

Single-phase natural circulation loop using oils and ternary hybrid nanofluids: Steady-state and transient thermo-hydraulics

2020 ◽  
pp. 1-32
Author(s):  
Mayaram Sahu ◽  
Jahar Sarkar ◽  
Laltu Chandra
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Width Ratio ◽  
Total Entropy ◽  
Hybrid Nanofluids

Abstract Steady-state and transient behaviours of single-phase natural circulation loop (SPNCL) are investigated using four thermal oils (Therminol VP1, Paratherm CR, Dowtherm A and Dowtherm Q) and water-based ternary hybrid (various combinations of different nature and shaped nanoparticles: Al2O3, Cu, CNT and Graphene) nanofluids as loop fluid. The influences of nanoparticle volume concentration and loop height to width ratio on the mass flow rate and total entropy generation rate of SPNCL are investigated. Results disclose that ternary hybrid nanofluids enhance flow initiation, reduce fluctuation and are expected to attain a steady-state faster than water. Steady-state mass flow rate increases/decreases for ternary hybrid nanofluid depending on the shape of the nanoparticle and total entropy generation rate decreases as compared to water. Thermal oil shows a higher mass flow rate and total entropy generation rate as compared to water. Al2O3-Cu-CNT-water and paratherm CR show the best result among all ternary hybrid nanofluids and thermal oils, respectively. The nanoparticle shape decides the optimum nanoparticle volume fraction. Increasing the height to width ratio decreases the total entropy generation and upsurges the mass flow rate at specified input power. The optimum height to width ratio depends on fluid.

Experimental and Numerical Investigations on the Aerodynamic Performance of the Three-Stage Turbine With Consideration of the Leakage Flow Effect

2016 ◽  
Author(s):  
Yang Chen ◽  
Jun Li ◽  
Chaoyang Tian ◽  
Gangyun Zhong ◽  
Xiaoping Fan ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Leakage Flows ◽  
Wheel Disk

The aerodynamic performance of three-stage turbine with different types of leakage flows was experimentally and numerically studied in this paper. The leakage flows of three-stage turbine included the shroud seal leakage flow between the rotor blade tip and case, the diaphragm seal leakage flow between the stator blade diaphragm and shaft, as well as the shaft packing leakage flow and the gap leakage flow between the rotor blade curved fir-tree root and wheel disk. The total aerodynamic performance of three-stage turbine including leakage flows was firstly experimentally measured. The detailed flow field and aerodynamic performance were also numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and S-A turbulence model. The numerical mass flow rate and efficiency showed well agreement with experimental data. The effects of leakage flows between the fir-tree root and the wheel disk were studied. All leakage mass flow fractions, including the mass flow rate in each hole for all sets of root gaps were given for comparison. The effect of leakage flow on the aerodynamic performance of three-stage was illustrated and discussed.

Analytical and Experimental Investigation to Determine the Variation of Hottel–Whillier–Bliss Constants for a Scaled Forced Circulation Flat-Plate Solar Water Heater

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
U. C. Arunachala ◽  
M. Siddhartha Bhatt ◽  
L. K. Sreepathi
Keyword(s):  
Mass Flow Rate ◽  
Heat Loss ◽  
Mass Flow ◽  
Flow Rate ◽  
Loss Coefficient ◽  
Absorber Plate ◽  
Forced Circulation ◽  
Solar Water ◽  
Scale Thickness ◽  
Overall Heat Loss Coefficient

Fixed tilt flat-plate solar thermal collectors, popularly known as solar water heaters, still remain as one of the most interesting technologies for utilization of solar energy. The system performance deteriorates due to scaling because of the continuous use of hard water as feed water. The present study deals with the experimental and analytical approach to determine the variation of Hottel–Whillier–Bliss (H–W–B) constants (which compactly represent the efficiency characteristics of a solar water heater) due to variation in solar power input and degree of scaling in case of forced circulation system (FCS) without considering the variation of input power to the circulating pump. Indoor tests are performed with a copper tube to investigate the flow characteristics. This forms a part of conventional FCS, in place of the usual nine-fin tube array in a full-fledged collector. In indoor tests, electrical heating is favored to simulate solar radiation level. Various energy parameters are determined and compared by incorporating the developed numerical code FLATSCALE. Variation between experimental and analytical mass flow rate, overall heat loss coefficient, and H–W–B constants with simulated solar radiation level is plotted. In scaled condition, the drop in instantaneous efficiency is due to both scale thickness and reduced water flow rate. Scale thickness acts as an additional thermal conductive resistance between absorber plate and flowing water. Overall heat loss coefficient increases as absorber plate temperature is high during reduced flow rate. The maximum deviation observed is 21.68% in mass flow rate, 14.64% in absorber plate mean temperature, 7.86% in overall heat loss coefficient, and 12.04% in instantaneous efficiency. Compared to a clean tube, a highly scaled tube of 3.7 mm scale thickness indicates a drop of 4.76% in instantaneous efficiency and 40.28% in mass flow rate. It is concluded that the growth of scale in FCS does not affect the instantaneous efficiency significantly because of the margin in heat carrying capacity of water in spite of high drop in the flow rate.

On the Impact of Passive Tip-Injection on the Downstream Flow Field of a Shrouded LP-Turbine: CFD and Experimental Results

2016 ◽  
Author(s):  
Pouya Ghaffari ◽  
Reinhard Willinger
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Tip Leakage ◽  
Air Turbine ◽  
Tip Injection ◽  
Lp Turbine ◽  
Downstream Flow ◽  
The Impact ◽  
Discharge Behaviour

Using shrouded blades with fins is a common method to reduce the leakage mass flow rate through the clearance between rotor and stator. A variety of methods have been developed improving the discharge behaviour of this sealing application. The leakage mass flow rate and its interaction with the main flow resulting in mixing losses and deviations in turning is also an important issue and has to be taken into consideration. The objective of this paper is to present a method aiming at reduction of tip-leakage mass flow rate and its high angular momentum by means of passive tip-injection. The results include analytical study followed by CFD calculations for compressible flow in a rotational frame of reference as well as experimental data. An uncooled low pressure air turbine with shrouded blades is considered for the CFD and the measurements. Three passive tip-injection configurations are investigated numerically out of which one configuration is also examined experimentally in the framework of this study.

Optimal Analysis of Entropy Generation and Heat Transfer in Parabolic Trough Collector Using Green-Synthesized TiO2/Water Nanofluids

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Eric C. Okonkwo ◽  
Muhammad Abid ◽  
Tahir A. H. Ratlamwala ◽  
Serkan Abbasoglu ◽  
Mustafa Dagbasi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Entropy Generation Rate ◽  
Convection Coefficient ◽  
Parabolic Trough ◽  
Volumetric Concentration ◽  
Flow Rates

This study presents an experimental nanoparticle synthesis and the numerical analysis of a parabolic trough collector (PTC) operating with olive leaf synthesized TiO2/water nanofluid. The PTC is modeled after the LS-2 collector for various operating conditions. An analysis of the heat transfer and entropy generation in the PTC is carried out based on the first and second laws of thermodynamics for various parameters of nanoparticle volumetric concentration (0 ≤ φ ≤ 8%), mass flow rate (0.1 ≤ m˙ ≤ 1.1 kg/s), and inlet temperatures (350–450 K) under turbulent flow regime. The effect of these parameters is evaluated on the Nusselt number, thermal losses, heat convection coefficient, outlet temperature, pressure drop, entropy generation rate, and Bejan number. The results show that the values of the Nusselt number decrease with higher concentrations of the nanoparticles. Also, the addition of nanoparticles increases the heat convection coefficient of the nanofluid compared to water. The thermal efficiency of the system is improved with the use of the new nanofluid by 0.27% at flow rates of 0.1 kg/s. The entropy generation study shows that increasing the concentration of nanoparticles considerably decreases the rate of entropy generation in the system. It is also observed that increasing the volumetric concentration of nanoparticles at low mass flow rates has minimal effect on the rate of entropy generation. Finally, a correlation that provides a value of mass flow rate that minimizes the entropy generation rate is also presented for each values of inlet temperature and nanoparticle volumetric concentration.

Impact Investigation on the Aerodynamic Performance for Seal Leakage at the Stator Root of Multistage Axial Compressor

2020 ◽  
Author(s):  
Qi Wang ◽  
Lanxue Ren ◽  
Zhou Zhang ◽  
Ting Wang ◽  
Mingcong Luo
Keyword(s):  
Numerical Model ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Flow Distribution ◽  
Numerical Approach ◽  
Aerodynamic Performance ◽  
The Impact ◽  
Multistage Axial Compressor

Abstract This paper presents a numerical model based on the mass flow rate of seal leakage. This numerical model is considered as a correct method for 3-D numerical simulation. It can be used to simulate the effect of seal leakage at the stator root of a multistage axial compressor. Implementation of the correct method is using a numerical model based on the flux conservation which can control the mass flow rate of seal leakage accurately at the seal cavity of compressor. The mass flow rate of seal leakage is chosen as the key research parameter on the aerodynamic performance effect of the seal engineering application in a multistage axial compressor. Combined with the 3-D numerical simulation methods, an engineering numerical approach is set up in this study. A nine-stage axial compressor is taken as the research object in this paper and its aerodynamic performance is tested for proving the applicability of the numerical model for seal leakage. In the cases of several operating rotation speeds, numerical results of the nine-stage axial compressor performance characteristic curves are in good agreement with the experimental data. It is considered that the numerical approach based on the simplified numerical model in this paper can predict the performance of multistage axial compressor accurately. Then, comparisons are made against different cases of seal leakage mass flow rate for analyzing the impact of seal leakage increasing on the aerodynamic performance of the nine-stage axial compressor. The main point of comparisons is focused on the changes of the overall performance and the flow distribution in the compressor with the seal leakage changing. The results indicate that performance of multistage axial compressor is degenerated faster and faster with seal leakage increasing in all operating working points. An overall decline is appeared in the flow capacity, working capacity, efficiency and surge margin of the compressor. For the impact investigation on the changes of flow distribution, the total pressure loss coefficient, the relative Mach number contours and the movement of streamlines are studied in different seal leakage cases under several operating working points. The result also shows that stators located in front stages of multistage axial compressor are affected more seriously with the increasing mass flow rate of seal leakage. Under the influence of seal leakage, degradation of flow condition in stators located in front stages is more severely than that in back stages, the total pressure loss coefficient and entropy are increased, and the flow separations at the root of stators in front stages are developed faster with seal leakage increasing. So it can be confirmed that relatively larger flow losses in front stages bring significant impact on the decay of aerodynamic performance for a multistage axial compressor.

Performance Evaluation of the Flow in Micro Junctions: Head Change Versus Head Loss Coefficients

2013 ◽  
Author(s):  
Bastian Schmandt ◽  
Heinz Herwig
Keyword(s):  
Energy Transfer ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Head Loss ◽  
Total Head ◽  
Single Mass ◽  
Flow Through ◽  
Loss Coefficients

Losses due to the flow through conduit components in a pipe system can be characterised by head loss coefficients. They basically account for the dissipation in the flow field or, in a more general sense, for the entropy generation due to the conduit component under consideration. When only one single mass flow rate is involved, an entropy based approach is straight forward and ṁ can be used as a general reference quantity. If, however, the mass flow rate is split or united like in junctions, some new aspects appear. In our study the general approach for these kind of conduit components is discussed. Like for single mass flow rates losses are accounted for by determining the entropy generation rates. New aspects for the branched flows are an additional parameter, the splitting ratio, and the fact that there is an energy transfer between the single branches that has to be accounted for appropriately. It turns out that this energy transfer changes the total head in each flow brach in addition to a sole loss of total head. Therefore, the coefficients should be named head change coefficients when this effect occurs. As an example the flow through a T-shaped junction is considered, for which head loss coefficients are determined for both branches and discussed with respect to their physical meaning.

Steady-State Energetic and Exergetic Performances of Single-Phase Natural Circulation Loop With Hybrid Nanofluids

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Mayaram Sahu ◽  
Jahar Sarkar
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Hybrid Nanofluid ◽  
Natural Circulation Loop ◽  
Hybrid Nanofluids

Energy and exergy performances of natural circulation loop (NCL) with various water-based hybrid nanofluids (Al2O3 + TiO2, Al2O3 + CNT, Al2O3 + Ag, Al2O3 + Cu, Al2O3 + CuO, Al2O3 + graphene) with 1% volumetric concentration are compared in this study. New thermophysical property models have been proposed for hybrid nanofluids with different particle shapes and mixture ratio. Effects of power input, loop diameter, loop height, loop inclination and heater/cooler inclination on steady-state mass flow rate, effectiveness, and entropy generation are discussed as well. Results show that both the steady-state mass flow rate and energy–exergy performance are enhanced by using the hybrid nanofluids, except Al2O3 + graphene, which shows the performance decrement within the studied power range. Al2O3 + Ag hybrid nanofluid shows highest enhancement in mass flow rate of 4.8% compared to water. The shape of nanoparticle has shown a significant effect on steady-state performance; hybrid nanofluid having cylindrical and platelet shape nanoparticles yields lower mass flow rate than that of spherical shape. Mass flow rate increases with the increasing loop diameter and height, whereas decreases with the increasing loop and heater/cooler inclinations. Both effectiveness and entropy generation increase with the decreasing loop diameter and height, whereas increasing the loop and heater/cooler inclinations. This study reveals that the particle shape has a significant effect on the performance of hybrid nanofluids in NCL, and the use of hybrid nanofluid is more effective for higher power.

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