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- Baagherzadeh Hushmandi, Narmin, et al.
(författare)
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Numerical investigation of partial admission phenomena at midspan of an axial steam turbine
- 2007
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Ingår i: Proceedings of the 7th European Conference on Turbomachinery: Fluid Dynamics and Thermodynamics, ETC 2007. - : European Conference on Turbomachinery (ETC).
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Konferensbidrag (refereegranskat)abstract
- This paper presents unsteady Navier-Stokes analysis to investigate partial admission phenomena in an axial two-stage steam turbine. The computations are performed in two-dimensional flow conditions at the midspan of the turbine with CFD software Fluent. Unlike some previous numerical work published in open literature, the partial admission in the present study is introduced into the model by blocking only one segmental arc (85.7°) of the guide vanes at the first stage. It is therefore necessary to model the whole annulus of the turbine in the numerical simulations. Results of the analysis show that the peak static pressure drop occurs downstream of the blockage at the entrance to the blocked region where emptying of the rotor channel occurs. The first stage rotor blades experience large static pressure changes on their surfaces and large tangential and axial forces. The magnitude of the tangential and axial forces is twice as large at the entrance to the cavity behind the blockage than at the exit of the blocked region. Entropy concentration downstream of the blockage is considerably high due to the nonuniformities in the flow field. The present results show good agreement between experiments and computations, in tendency of the circumferential static pressure at different axial cross sections. The difference between the numerical and experimental absolute values of the circumferential static pressure drop in the blocked region indicates that the three-dimensional effects are very important to the flow field behind the blockage.
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| 3. |
- Fridh, Jens, et al.
(författare)
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DYNAMIC FEATURES OF PARTIAL ADMISSION : OUTCOMES FROM ROTATING MEASUREMENTS
- 2007
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Ingår i: Euroturbo 7. - Athens : Local Conference Organising Committee. ; , s. 451-462
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Konferensbidrag (refereegranskat)abstract
- A system for rotating measurements has been designed and commissioned for a two-stage axial turbine of impulse design. Relative total pressure and strain gauge measurements in the rotating frame of reference have been performed during partial admission tests in this turbine. The overall project objectives are to determine unsteady aerodynamic losses related to admission sector-ends and rotor forcing functions. Some outcomes are presented and discussed herein. The unsteadiness in the measured relative total pressure is observed to be largest downstream of the suction side of the partial admission blockage where the high momentum fluid vividly interacts with the rotor. Strain gauge results show a high strain peak downstream of the suction side of the blockage. When reducing the shaft speed at constant pressure ratio, the dip in relative total pressure and the peak in tensile strain, that occur when a blade enters the blocked region, are shifted in the counter rotational direction. This is believed to reflect earlier emptying of the rotor blade channel. Furthermore, an increase of the flow capacity coefficient with a decrease of admission degree has been observed.
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| 7. |
- Salomon Popa, Marianne, 1976-, et al.
(författare)
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Distant Master Program in Sustainable Energy Engineering : Self-assessment of the intake autumn 2004
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Since 1997 the Department of Energy Technology (EGI) has offered the Sustainable Energy Engineering (SEE) MSc Program to over 200 students from around 50 different countries. In June 2004, it was decided by the KTH President to offer the International Master Program on Sustainable Energy Engineering (SEE) as a distance program. Based on this, EGI offered a distance version of the Sustainable Energy Engineering Program (identified as DSEE) for the academic years (2004/2005 and 2005/2006) on a trial basis to a selected group of qualified students. This is a complete e-learning program that is held in conjunction with the regular SEE-program, offering an alternative for those students who could be accepted for the regular SEE-program but who can not afford to participate in the on-campus courses. All mandatory courses are offered on-line and lectures can be followed either synchronously or asynchronously via internet.This report contains the status of the first students that started the program in autumn 2004 and highlights the experience gained during the first year of the distance program as well as the challenges and opportunities associated with offereing a distance program in energy technology.
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| 9. |
- Vogt, Damian M., et al.
(författare)
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Experimental investigation of mode shape sensitivity of an oscillating low-pressure turbine cascade at design and off-design conditions
- 2007
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 129:2, s. 530-541
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Tidskriftsartikel (refereegranskat)abstract
- The effect of negative incidence operation on mode shape sensitivity of an oscillating low-pressure turbine rotor blade row has been studied experimentally. An annular sector cascade has been employed in which the middle blade has been made oscillating in controlled three-dimensional rigid-body modes. Unsteady blade surface pressure data were acquired at midspan on the oscillating blade and two pairs of nonoscillating neighbor blades and reduced to aeroelastic stability data. The test program covered variations in reduced frequency, flow velocity, and inflow incidence; at each operating point, a set Of three orthogonal modes was tested such as to allow for generation of stability plots by mode recombination. At nominal incidence, it has been found that increasing reduced frequency has a stabilizing effect on all modes. The analysis of mode shape sensitivity yielded that the most stable modes are of bending type with axial to chordwise character whereas high sensitivity has been found for torsion-dominated modes. Negative incidence operation caused the flow to separate on the fore pressure side. This separation was found to have a destabilizing effect on bending modes of chordwise character, whereas an increase in stability could be noted for bending modes of edgewise character Variations of stability parameter with inflow incidence have hereby found being largely linear within the range of conditions tested. For torsion-dominated modes, the influence on aeroelastic stability was close to neutral.
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