Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential

Leggett, John C.; Richardson, E.S.; Priebe, Stephan; Shabbir, Aamir; Michelassi, Vittorio; Sandberg, Richard D.

doi:10.1115/gt2019-91253

Cited by 4 publications

(4 citation statements)

References 17 publications

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“…In the case of averaging without using common parameters before the cascade, the "history" of the flow is not taken into account, and only the parameters of the initial non-uniform flow are averaged in different ways [1][2][3][4][5][6]. In [2] determines axisymmetric flow, which is averaged through surfaces and meridian streamlines, [3] performs averaging based on mechanical work potential, [4] uses Favre-averaged Fourier-based methods with application to gas turbines, [5,6] also uses averaging techniques to evaluate turbomachine efficiency. A significant variety of gas flow averaging methods raises the question of their effectiveness and allows you to combine different approaches to improve their performance.…”

Section: Literature Reviewmentioning

confidence: 99%

Improved Hybrid Methods for Determining the Integral Characteristics of Turbomachine Nozzle Cascades

Lapuzin

Subotovich

Yudin

et al. 2021

Lecture Notes in Mechanical Engineering

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To determine the integral gas-dynamic characteristics of nozzle cascades of turbomachines, it is necessary to average the parameters of the threedimensional flow behind the cascade that is non-uniform along with the pitch and along with the height of the cascade. Two types of averaging methods are used. For the first type of methods, the flow parameters at the entrance to the cascade are not taken into account when averaging the parameters of a nonuniform flow behind the cascade. For the second type of methods (hybrid), the pressure behind the cascade is found from the condition of maintaining the enthalpy drop in the initial non-uniform three-dimensional and averaged flows. In a cylindrical flow, the hybrid method is usually used to determine the velocity coefficient. The main disadvantage of this method is the significantly overestimated mass flow mass rate and component onto the axial direction of the angular momentum. To improve the methods of the second type, it is proposed to replace the ratio of the components of the momentum with two parameters, namely: mass flow rate and the component of the moment of momentum on the axial direction. It allows determining the velocity coefficient and two angles for the averaged flow. It is shown that the second kinetic energy of the flow can be replaced by entropy and, thus, the velocity coefficient can be adjusted provided the complex quality criterion is kept constant.

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Section: Literature Reviewmentioning

confidence: 99%

Improved Hybrid Methods for Determining the Integral Characteristics of Turbomachine Nozzle Cascades

Lapuzin

Subotovich

Yudin

et al. 2021

Lecture Notes in Mechanical Engineering

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“…Consequently, euergy appears well-suited to examining turbomachinery flow as it has been derived from the same thermodynamic process to which turbomachines aspire -a reversible adiabatic expansion. To the author's knowledge, this method has only previously been applied by Blackburn & Miller 2.3 Modelling loss mechanisms in turbomachinery (2017) to examine pressure gain combustion and Leggett et al (2019) to examine unsteady compressor flow.…”

Section: Literature Reviewmentioning

confidence: 99%

The Effect of Heat Transfer on Turbine Performance

Jardine

Miller

2021

Journal of Turbomachinery

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For over 50 years, high-pressure gas turbine blades have been cooled using air bled from the compressor. This cooling results in very high rates of heat transfer, both within the fluid and within the blade. The heat transfer often occurs across large differences in temperature and thus is highly irreversible. It is therefore surprising that little is understood about the effect of this heat transfer on turbine performance. This paper solves this problem by applying a new method known as mechanical work potential, or euergy, analysis. The key consequence of the analysis is that the value placed on all heat, relative to work, becomes set by the Joule (Brayton) cycle efficiency. This means that when heat is transferred locally within a flow, or when viscous reheat occurs, the value of this heat should be set by the Joule cycle efficiency. This paper demonstrates how the new method can be implemented both in the preliminary design systems and in the analysis of conjugate CFD solutions of complex engine representative components. The new method provides the cooling designer with a new way of raising turbine efficiency, a form of recuperation locally in the flow. This method offers the exciting potential to design cooling systems that, when added to a blade profile, actually reduces profile loss by up to 7.3%.

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“…In the companion paper, the comparison against experiments showed that the RANS simulation is well able to recover the flow physics due to the strong influence of free-stream turbulence. However, several recent papers have shown that a detailed discussion of losses (entropy generation) can be better performed by LES [18,20,21,24] . In addition, the SLES turb.inj.…”

Section: Exergy Analysis In the Simulation Domainmentioning

confidence: 99%

“…Lower levels of turbulence modelling are obtained for LES approach compared to RANS [38,39] that may expect a better resolution of the flow field at the interface between cavity and main annulus flow. From a loss perspective, recent studies have shown that the assessment of loss in a gas turbine can be obtained more accurately by LES compared to RANS [18,20] , this being due to a better resolution of turbulent field that drives the mixing process of momentum and enthalpy which in turns controls the level of losses generated in the flow field [35] . This paper uses the exergy formalism to draw the loss generated in a low-speed linear cascade with an upstream cavity including a parametric study of the purge flow rate supplied to the cavity and the rim seal geometry.…”

Section: Introductionmentioning

confidence: 99%

Description of the flow in a linear cascade with an upstream cavity part 2: Assessing the loss generated using an exergy formulation (draft)

et al. 2020

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Purge air is injected in cavities at hub of axial turbines to prevent hot mainstream gas ingestion into interstage gaps. This process induces additional losses for the turbine due to an interaction between purge and mainstream flow. To deal with this issue, this paper is devoted to the study of a low speed linear cascade with an upstream cavity at a Reynolds number representative of a low-pressure turbine using RANS and LES with inlet turbulence injection. Different rim seal geometries and purge flow rates are studied. Details about numerical methods and comparison with experiments can be found in a companion paper. The analysis here focuses on the loss generation based on the description of the flow and influence of the turbulence introduced in the companion paper. The measure of loss is based on an exergy analysis (i.e. energy in the purpose to generate work) that extends a more common measure of loss in gas turbines, entropy. The loss analysis is led for a baseline case by splitting the simulation domain in the contributions related to the boundary layers over the wetted surfaces and the remaining domain (i.e. the complementary of boundary layers domains) where secondary flows and related loss are likely to occur. The analysis shows the strong contribution of the blade suction side boundary layer, secondary vortices in the passage and wake at the trailing edge on the loss generation. The study of different pur ge flow rates shows increased secondary vortices energy and subsequent loss for higher purge flow rates. The rim seal geometry with axial overlapping promotes a delayed development of secondary vortices in the passage compared to simple axial gap promoting lower levels of loss.

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Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential

Cited by 4 publications

References 17 publications

Improved Hybrid Methods for Determining the Integral Characteristics of Turbomachine Nozzle Cascades

Improved Hybrid Methods for Determining the Integral Characteristics of Turbomachine Nozzle Cascades

The Effect of Heat Transfer on Turbine Performance

Description of the flow in a linear cascade with an upstream cavity part 2: Assessing the loss generated using an exergy formulation (draft)

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