Computational Investigation of Effect of Axial Spacing on Blade Row Interaction in a 1½ Stage Axial Flow Turbine

Ummiti, Muneeswara Babu; Sitaram, N.; Prasad, B. V. S. S. S.

doi:10.1080/19942060.2009.11015254

Cited by 7 publications

(9 citation statements)

References 1 publication

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“…Finally, validation-calibration of CFD codes for predicting the extremely challenging areas of separated flows can be also carried out (Pachidis et al, 2006). The increased computational power available nowadays throughout the research community has increased the application of high-fidelity numerical approaches on every kind of flow prediction, starting from pure aerodynamic phenomena occurring at inlets or compressors and extending them in combustion or turbine cooling research, employing multidisciplinary tools of chemical or heat transfer nature (Chaluvadi et al, 2003;Ramakrishna et al, 2009;Ummiti et al, 2009). In case of far off-design turbomachinery performance studies such as the above-described ones, the availability of experimental datasets is the only aspect that prevents the numerical tools from being further validated and at a second stage further improved.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation of a Compressor Cascade at Highly Negative Incidence

Zachos

Grech

Charnley

et al. 2011

Engineering Applications of Computational Fluid Mechanics

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ABSTRACT:The performance prediction of axial flow compressors and turbines still relies on the stationary testing of blade cascades. Most of the blade testing studies are done for operating conditions close to the design point or in off-design areas not too far from it. However, blade-and consequently engine-performance remain unexplored at relatively far off-design conditions, such as windmilling or sub-idle. Such regimes are dominated by blade operation under extremely low mass flows and rotational speeds that imply highly negative values of incidence angle, thus totally separated flows on the pressure side of the blades. Those flow patterns are difficult to be measured and even more difficult to be numerically predicted as the current modelling capability of separated internal flows is of limited reliability. In this paper, the performance of a 3-dimensional linear compressor cascade at highly negative incidence angle is initially experimentally investigated. The main objective of the study is to derive the total pressure loss and outlet flow angle through the blades and use the data for the validation-calibration of a numerical solver enhancing its capability to predict highly separated flows. The development of the CFD model and the simulation strategy followedare also presented.The numerical results are compared against the derived test data demonstrating a good agreement. In addition, most trends of the properties of interest have been captured sufficiently, therefore the physical phenomena are considered to be well captured, allowing the numerical tool to be used for further studies on similar test cases.

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Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation of a Compressor Cascade at Highly Negative Incidence

Zachos

Grech

Charnley

et al. 2011

Engineering Applications of Computational Fluid Mechanics

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“…The flow unsteadiness has been shown to be influenced by the axial clearance variation by many authors. 8,19–21 Figure 7 illustrates how the magnitude of unsteadiness influences the shape of the efficiency curves. As can be seen, there is no clear correlation between the reduced blade passing frequency and the slope of efficiency for the studied turbine geometries.…”

Section: Correlations Of Stator Outlet Mach Number and Reduced Blade mentioning

confidence: 99%

“…Several studies have found the rotor pressure fluctuation to be smaller when the clearance is increased, and this behaviour does not seem to require the presence of shock waves. 8,19–21 Due to changes in pressure fluctuation, also unsteady work 22,23 and the enthalpy change at the rotor inlet are influenced when the axial clearance changes.…”

Section: Introductionmentioning

confidence: 99%

Importance of the vane exit Mach number on the axial clearance-related losses

Grönman

Biester

Turunen-Saaresti

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part A:

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More efficient and physically smaller axial turbine designs are promoted to lower emissions and increase revenue. The physical size and the weight of the axial turbine can be minimised by adjusting the distance between successive stator and rotor rows. The influence of changing stator-rotor axial clearance can usually have either a positive or a negative influence on the turbine performance, and the reasons for this varying behaviour are not currently fully understood. A previous study revealed several design parameters that correlate with the efficiency curve shape. However, the effects of two parameters, namely the stator outlet Mach number and the reduced blade passing frequency, still remained unclear. Therefore, a novel approach is taken to analyse the correlations between the two design parameters and the axial clearance efficiency curve shape. Several different turbines are analysed using data available in the literature, and also new data are presented. The study suggests that the stator outlet Mach number correlates reasonably well with the efficiency curve shape, and it was further linked to five loss mechanisms and the rotational speed. Although the unsteady interaction plays an important role in the loss share, the level of unsteadiness did not correlate with the efficiency curve shape.

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“…Also, Ummiti et al. 21 found a decrease of pressure fluctuation coefficients in the rotor-blade surfaces when the axial clearance increased.…”

Section: Introductionmentioning

confidence: 98%

Influence of the axial turbine design parameters on the stator–rotor axial clearance losses

Grönman

Turunen-Saaresti

Röyttä

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part A:

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The drive towards lower emissions in aerospace engines promotes more efficient and physically smaller engines. One way to decrease the size of the axial turbine is to minimize the distance between successive stator and rotor rows. This can usually have either a positive or negative influence on the turbine performance. The reasons for this behaviour are not currently fully understood. In this study, a novel approach is taken to find new insights into this design question by analysing the influence of different design parameters on the turbine efficiency behaviour. Several different turbines are analysed using the literature. For the first time, the performed analysis reveals the design parameters, which correlate with the different efficiency curve shapes. The correlating parameters are the stator–rotor axial clearance, stator pitch to axial chord ratio, turning velocity Mach number and rotor aspect ratio. The mechanisms behind the found correlations are further analysed to connect the physical phenomena with the design parameters.

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Computational Investigation of Effect of Axial Spacing on Blade Row Interaction in a 1½ Stage Axial Flow Turbine

Cited by 7 publications

References 1 publication

Experimental and Numerical Investigation of a Compressor Cascade at Highly Negative Incidence

Experimental and Numerical Investigation of a Compressor Cascade at Highly Negative Incidence

Importance of the vane exit Mach number on the axial clearance-related losses

Influence of the axial turbine design parameters on the stator–rotor axial clearance losses

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