Gas Turbine Engine Internal Air Systems: A Review of the Requirements and the Problems

Moore, Alastair

doi:10.1115/75-wa/gt-1

Cited by 15 publications

(13 citation statements)

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“…To achieve clearance control improvements, we must know more about the relative displacement of the case and rotor, particularly under I l l l l l l I I l l i f i K l I I i [1][2][3][4][5][6][7][8][9][10][11][12][13] transient conditions, in modern engines. In advanced engines more attention must be given to engine stiffness, case roundness, case bending and to case/rotor dynamics of the total assembly.…”

Section: Discussionmentioning

confidence: 99%

“…However, an additional factor which favors the cantilevered construction is the significantly lower boundary-layer temperature (at the inner gas path) than with the shrouded stator vanes (Ref. 10). …”

Section: Sealing Clearance Sensitivitymentioning

confidence: 99%

“…But in the high-pressure compressor, the higher temperatures require metal systems such as sprayed nickel/graphite. The high-pressure turbine [1][2][3][4][5][6][7][8][9][10][11] requires very high temperature oxidation resistant materials which, in general, are not abradable and do not provide low energy rubs. Finally, the low-pressure turbine can use some of the materials suitable for the high pressure compressor but honeycomb shrouds are the most popular.…”

Section: Gas Path Sealing Materialsmentioning

confidence: 99%

“…46). Thus, the heat input is highly localized, and a local thermal bump is generated which expands, [1][2][3][4][5][6][7][8][9][10][11][12] rubs harder, and finally wears away. This is then followed by rubbing over a second small segment which grows and then wears, etc.…”

Section: Gas Path Sealing Materialsmentioning

confidence: 99%

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Gas Path Sealing in Turbine Engines

Ludwig

Bill

1980

A S L E Transactions

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SUMMARYA survey of gas path seals is presented with particular attention given to sealing clearance effects on engine component efficiency. The effects on compressor pressure ratio and stall margin are pointed out. Various caserotor relative displacements, which affect gas path seal clearances, are identified. Forces produced by nonuniform sealing clearances and their effect on rotor stability are discussed qualitatively, and recent work on turbine-bladetip sealing for high temperatures is described. The need for active clearance control and for engine structural analysis is discussed. The functions of the internal-flow system and its seals are reviewed.

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Section: Discussionmentioning

confidence: 99%

Section: Sealing Clearance Sensitivitymentioning

confidence: 99%

Section: Gas Path Sealing Materialsmentioning

confidence: 99%

Section: Gas Path Sealing Materialsmentioning

confidence: 99%

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Gas Path Sealing in Turbine Engines

Ludwig

Bill

1980

A S L E Transactions

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“…Seal leakage reduction directly improves the specific fuel consumption and the thrust-to-weight ratio. More specifically, it has been demonstrated by Moore (1) that for a turbofan engine with an overall pressure ratio of 35 and a bypass ratio of 6, reducing the bleed air flow of 1% leads to reduce the SFC of 0.4%. The equivalent annual fuel savings would then rise to 55 m gallons.…”

Section: Introductionmentioning

confidence: 99%

Experimental characterisation of carbon fibre brush seal leakage performance as a function of bristle pack geometrical parameters under dry conditions

Outirba

Hendrick

Nicolas³

2017

Aeronaut. j.

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Over the last decades, it has been progressively acknowledged that reducing the specific fuel consumption and the emission of pollutants, as well as improving the thrust-to-weight ratio involves extensive research on advanced sealing technologies. Amongst these, brush seals are particularly well considered for their excellent leakage performance, their low friction properties, and their ability to cope with inevitable rotor excursions during flights. This paper presents the experimental work that has been carried on in order to characterise carbon fibre brush seals leakage rate in function of the bristle pack geometry, under different pressure loads and rotational speeds. The analysed parameters are the bristle-free length, the density and the inter-plate distance. The work, performed by the ULB (Université Libre de Bruxelles) in collaboration with French engine manufacturer Safran Aircraft Engines, highlights specific behaviour of carbon fibre brush seals under differential pressure, proposes a leakage prediction model developed through empirical equations, and discusses over the most influential parameters that influence the air consumption of a brush seal.

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Transient modelling and simulation of gas turbine secondary air system

Nikolaidis

Wang

Laskaridis

2020

Applied Thermal Engineering

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The behaviour of the jet engine during transient operation and specifically its secondary air system (SAS) is the point of this work. This paper presents a methodological approach to develop a fast, one-dimensional transient platform for preliminary analysis of the flow behaviour in gas turbine engines secondary air system. For this purpose, different elements of the system including rotating chamber, pipe, turbine blade cooling, orifice, and labyrinth seal are modelled in a modular form. The validity of the developed models for each component is checked against experimental/publicly available data. Then, using a flow network simulation approach, the secondary air system of a two-spool turbofan engine is modelled and simulated in transient mode. The coupling effect between volume packing and swirl are considered in the simulation, under two pre-defined scenarios for step and scheduled boundary condition variations. In the step-change scenario, the boundary conditions are changed instantly to represent the flow behaviour of the SAS under extreme operating conditions (i.e. shaft fracture, flameout, etc.). In the scheduled scenario, the boundary conditions vary linearly with time to represent the performance of the SAS under normal operating conditions (i.e. acceleration and deceleration). The key findings include the fact that, under normal engine operation, the flow in the SAS varies smoothly and converges much faster than the primary flow by around one magnitude. Thus, it is reasonable to use steady-state SAS model to simulate SAS flow behaviour under these conditions. However, under extreme conditions (e.g. flameout), which could induce an abrupt change in the primary airflow properties (pressure, temperature), reverse airflow or choking conditions in SAS may be observed. This could result in a malfunction of the SAS, inducing further damages to the engine.

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Gas Turbine Engine Internal Air Systems: A Review of the Requirements and the Problems

Cited by 15 publications

References 0 publications

Gas Path Sealing in Turbine Engines

Gas Path Sealing in Turbine Engines

Experimental characterisation of carbon fibre brush seal leakage performance as a function of bristle pack geometrical parameters under dry conditions

Transient modelling and simulation of gas turbine secondary air system

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