Blade Lean and Shroud Leakage Flows in Low Aspect Ratio Turbines

Rosic, Budimir; Xu, Li

doi:10.1115/1.3106002

Cited by 21 publications

(15 citation statements)

References 14 publications

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“…The experiments were carried out by Rosic [28] using a low speed multistage air turbine that was designed to represent the first few stages of a high pressure steam turbine (Fig.1). Atmospheric air enters the inlet section radially and passes through a flow straightener before entering the turbine.…”

Section: The Model Turbine and Experimental Methodsmentioning

confidence: 99%

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Uncertainty Quantification of Leakages in a Multistage Simulation and Comparison With Experiments

Mazzoni

Ahlfeld

Rosic

et al. 2017

Journal of Fluids Engineering

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The present paper presents a numerical study of the impact of tip gap uncertainties in a multistage turbine. It is well known that the rotor gap can change the gas turbine efficiency but the impact of the random variation of the clearance height has not been investigated before. In this paper the radial seals clearance of a datum shroud geometry, representative of steam turbine industrial practice, was systematically varied and numerically tested. By using a Non-Intrusive Uncertainty Quantification simulation based on a Sparse Arbitrary Moment Based Approach, it is possible to predict the radial distribution of uncertainty in stagnation pressure and yaw angle at the exit of the turbine blades. This work shows that the impact of gap uncertainties propagates radially from the tip towards the hub of the turbine and the complete span is affected by a variation of the rotor tip gap. This amplification of the uncertainty is mainly due to the low aspect ratio of the turbine and a similar behavior is expected in high pressure turbines..

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Section: The Model Turbine and Experimental Methodsmentioning

confidence: 99%

“…The traverse grid was 37 x 37 uniformly spaced points in both radial and pitch-wise directions. A detailed description of the experimental setup is reported in [28].…”

Section: The Model Turbine and Experimental Methodsmentioning

confidence: 99%

Uncertainty Quantification of Leakages in a Multistage Simulation and Comparison With Experiments

Mazzoni

Ahlfeld

Rosic

et al. 2017

Journal of Fluids Engineering

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“…The facility was success fully used in the past, and there are several publications describing results obtained using this model turbine [11,12], The key turbine geometrical and operational parameters and key blade parameters are presented in Table 1. More details about the turbine opera tional parameters can be found in Rosie [10].…”

Section: The Modeled Turbine Stagementioning

confidence: 99%

“…The turbine stage geometry used in this study is the same as the experimental multistage air turbine, described in Rosie [10], The low speed, three-stage air turbine, was designed to represent the first few stages of an HP steam turbine. The facility was success fully used in the past, and there are several publications describing results obtained using this model turbine [11,12], The key turbine geometrical and operational parameters and key blade parameters are presented in Table 1.…”

Section: The Modeled Turbine Stagementioning

confidence: 99%

Aerodynamic Analysis of Steam Turbine Feed-Heating Steam Extractions

Rosic

Mazzoni

Bignell³

2014

Journal of Engineering for Gas Turbines and Power

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Feed-heating in steam turbines, the use o f steam extracted from the turbine to heat the feed-water, is known to raise the plant efficiency and so is included in most steam turbine power plant designs. The steam is extracted through an extraction slot that runs around the casing downstream o f a rotor blade row. The slot is connected to a plenum, which runs around the outside o f the turbine annulus. Steam flows to the feed-heaters through a pipe connected usually to the bottom o f the plenum. The steam extraction is driven by a circumferentially nonuniform pressure gradient in the plenum. This causes the mass flow rate o f steam extracted to vary circumferentially, which affects the main passage flow downstream o f the extraction point. The flow in the extraction plenum and the influence o f the steam extraction on the mainstream aerodynamics is analyzed numerically in this paper. A complete annulus with the extraction slot and plenum together with the down stream stator and rotor blade rows is modeled in this study. The results reveal a highly nonuniform steam extraction around the annulus with the highest extraction rates from the bottom nearest the extraction pipe and the lowest at the top o f the annulus. This dif ference in extraction rates modifies the flow angle and loss circumferential distribution downstream o f the stator blade row. This study finds out that the distribution o f steam extraction around the annulus and its influence on the main passage flow could be greatly improved by changing the shape and increasing the volume o f the extraction slot and plenum

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“…For the compound lean stator blade, the midspan section move into a region of low pressure. As a consequence, the loading of blade increase [24].…”

Section: Simple and Compound Axial Leanmentioning

confidence: 99%

3D shape optimisation of a low-pressure turbine stage

Witanowski¹,

Klonowicz²,

Lampart³

2018

Int. J. EQ

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The possibility of reducing the flow losses in low-pressure turbine stage has been investigated in an iterative process using a novel hybrid optimisation algorithm. Values of the maximised objective function that is isentropic efficiency are found from 3D RANS computation of the flowpath geometry, which was being changed during the optimisation process. To secure the global flow conditions, the constraints have been imposed on the mass flow rate and reaction. Among the optimised parameters are stator and rotor twist angles, stator sweep and lean, both straight and compound. Blade profiles remained unchanged during the optimisation. A new hybrid stochastic-deterministic algorithm was used for the optimisation of the flowpath. In the proposed algorithm, the bat algorithm was combined with the direct search method of Nelder-Mead in order to refine the best obtained solution from the standard bat algorithm. The method was tested on a wide variety of well-known test functions. Also, the results of the optimisation of the other stochastic and deterministic methods were compared and discussed. The optimisation gives new 3D-stage designs with increased efficiency comparing to the original design. Keywords: CFD, efficiency, hybrid method, low pressure steam turbine, optimisation, swarm intelligence. INTRODUCTIONThe performance and profitability of energetic systems depend fundamentally on turbine characteristics -the lower the turbine efficiency, the lower the system efficiency e.g. steam power plant efficiency [1, 2], ORC efficiency [3], energy storage efficiency [4]. Consequently, system efficiency basically depends on the expander design. The computational fluid dynamics (CFD) tools are extremely useful in the design of high-efficiency turbines because of inaccuracy of empirical loss correlation models [5]. The most important component of the total loss is usually connected with the losses within the blade passages -mainly profile loss and secondary (endwall) loss. Despite the significant amount of models, none of them by far has proven to be really general [6]. This leads to the use of computational fluid dynamics in an intensive way for turbomachinery blade design, but this higher performance must be achieved with fast prototyping and lower cost. The largest computational power cost during efficiency optimisation of turbine is connected with the calculation of values of the objective function, which is obtained from a RANS solver.Novel methods must be used in order to obtain the global minimum with lower number of calls of the objective function. Among these methods are neural network metamodels [7,8], Kriging and co-Kriging methods [9] and hybrid stochastic-deterministic algorithms [2,[10][11][12][13][14].In this work, the new hybrid stochastic-deterministic optimisation method was used. The method is a combination of Bat algorithm [15] and Nelder-Mead method [16]. Also, a parametric stator and rotor geometry model has been developed. As shown in this paper, these methods allow one for efficient optimisatio...

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Blade Lean and Shroud Leakage Flows in Low Aspect Ratio Turbines

Cited by 21 publications

References 14 publications

Uncertainty Quantification of Leakages in a Multistage Simulation and Comparison With Experiments

Uncertainty Quantification of Leakages in a Multistage Simulation and Comparison With Experiments

Aerodynamic Analysis of Steam Turbine Feed-Heating Steam Extractions

3D shape optimisation of a low-pressure turbine stage

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