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Influence of Axial Compressor Model Simplification and Mesh Density on Surge Margin Evaluation

Muchowski Rafał, Gubernat Sławomir Maciej

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 3

243--253

EN

The menace of surge occurrence in the compressors is taken very seriously and its avoidance became a fundamental for the design of any modern jet engines. Nowadays, a problem with appropriate evaluation of the compressor surge margin while considering different simplifications of three-dimensional CFD model is still present. For that purpose, this article presents a comparison between the measurement data and several variants of 3D CFD models characterized by a specific mesh density. To calculate all the results on which the comparisons and conclusions are based, an 8-stage axial compressor is taken into account. Flow conditions of the machine are computed for three part load speeds: The low, the mid and the high one respecting the variable guide vanes schedule fitted to the specific load. For each of speed variants a four mesh configurations were generated: coarse, medium, fine and extra-fine. All speed configurations were treated with two different turbulence models – Wilcox k-ω and Menter’s SST k-ω, giving ultimately 15 CFD models, calculated with the TRACE solver using an initialization based on a circumferentially averaged flow solution delivered by the Streamline Curvature Method. During the study an additional assessment of reference grid independence was performed and the mesh convergence has been achieved. A comparison between turbulence models and the measurement proves that SST turbulence model is not well distributed through the speeds in compare to the measurement data and the Wilcox turbulence model. Inconsistency of sensitivity in the mesh coarsening for different rotational speeds was found. Increasing the mesh roughness level has to be executed for each speed separately. Overall compressor map shows that shift of the Pressure Ratio and the Mass Flow decreases with lower rotational speed. Neglecting the system add-ons like labyrinth sealing volumes, bleed-ports and other leakages has a visible influence on deviations from the measurements. Because of intended future use in design and optimization the “Medium” grid with Wilcox k-ω turbulence model was chosen, being a good representation of the Rig characteristics with reduction of the computing time.

2

Investigation of inlet distortion effects on axial compressor performance based on streamline curvature method

Abbasi S., Pirnia A., Taghavi-Zenouz R.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 4

1005--1015

EN

In this paper, the effects of inlet flow distortion on performance maps and details of the flow field are investigated using the Streamline Curvature Method. The results are presented for both design and off-design conditions and compared with experimental data, which shows good agreement. The effects of inlet flow distortion are investigated by inlet total pressure variation in three different cases in the way that the average total pressure remains constant and equal to the design value. The results show that a relative increase in the total pressure at tip causes an increase in the pressure ratio and efficiency as well as a better performance in the choking region. Alternatively, a relative increase in the total pressure in hub causes opposite behavior and a better performance at the surging region.

3

Surge margin value controling factors selection of the turbojet engine compressor

Antas S., Ćwik A.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2008

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nr 133

25--38

EN

Article presents conditions analysis of compressor turbine matching for aircraft turbojet engine and theoretical research of factors affecting this matching. Recommendations are presented for rational design actions to enable change of the steady state operating line position for compressor and gasifier turbine on the full compressor map. Influence of the throat area change of gasifier turbine nozzle guide vanes (FGV)CT and the throat area change of exhaust nozzle F5 on the parameters and engine compressor surge margin were measured at manufacturing conditions with the value of Πc*/G1cor ratio. Results obtained from experimental tests for exhaust nozzle throat area changes verified this theoretical research.

4

An anlytical and numerical method of calculating the surge margin of compressor of turboshaft engine with free power turbine.

Antas Stanisław

Archive of Mechanical Engineering

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2001

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Vol. 48, nr 4

373-397

EN

The paper presents a description of the comprehensive computational analysis aimed at providing compressor stable operation range. In this article author presents the computational predictions of compressor surge margin value, derived by means of originally elaborated analytical and numerical method. One has defined, in both analytical and numerical way, the influence of change of throat area of gasifier turbine nozzle guide vanes, and change of throat area of power turbine nozzle guide vanes on engine compressor surge margin measured in manufacturing conditions. The results of computational analysis are compared with measured parameters obtained from experimental tests of turbohalt engine. Conclusions from the computational analyses are then presented.

PL

Praca obejmuje opis wszechstronnej analizy teoretycznej prowadzonej w celu zapewnienia zakresu statecznej pracy sprężarki. W artykule przedstawiono obliczenia wartości zapasu statecznej pracy sprężarki, wykonane przy użyciu opracowanych przez autora oryginalnych metod analitycznej i numerycznaj. Metodą anlityczną i numeryczną określono wpływ zmian przekroju minimalnego wieńca dyszowego turbiny wytwornicowej i turbiny napędowej na zapas statecznej pracy sprężarki mierzony w warunkach produkcyjnych. Rezultaty badań teoretycznych zweryfikowano parametrami zmierzonymi, uzyskanymi podczas badań eksperymentalnych silnika śmigłowego z wolną turbiną napędową. W zakończeniu pracy przedstawiono wnioski wynikające z porównania wyników badań teoretycznych i eksperymentalnych.