PCA will be manning Booth #806 at the ASME Turbo Expo in Charlotte, North Carolina, June 26th to 30th 2017. Chris Robinson, Graham Cox, Hamid Hazby and Jason Wu will be attending the conference and will be pleased to welcome visitors to the booth.
Dr Hazby and Dr Wu will present the following papers:
OPTIMIZATION DESIGNS OF FRONT STAGE NOZZLES IN A LP STEAM TURBINE
J. Wu, G. L. Deng, X. Q. Du, P.F. Zhang
This paper presents the findings of the original nozzle of the fourth stage in a 7 stage LP steam turbine where an obvious geometric feature is the extremely thick leading edge (LE). A cascade test was carried out to investigate the mechanism of loss reduction. A detailed comparison study was carried out using a conventional thinner leading edge design and the original thicker LE profile. The studies reveal that the overall loss in the original design is significantly lower than the counterpart of the thinner LE option together with a much wider range of incidence for which the vane is of low loss. This design philosophy is then successfully cloned to the first stage and third stage nozzles in a seven stage LP steam turbine. The analysis indicates that the obvious advantages of the new designs over the conventional thinner option are on not only the reduction of the profile loss, but the reduction of the blade count which has a significant implication on manufacturing cost. The numerical studies reveal that the idea behind this thick LE design philosophy is to minimise the profile loss without incurring a significant penalty on diffusion loss or at the worst separation. A detail investigation on the stage 2 nozzle indicates that this concept only works for a reasonably high aspect ratio blading where the secondary loss is limited.
FREE-FORM VERSUS RULED INDUCER DESIGN IN A TRANSONIC CENTRIFUGAL IMPELLER
Hamid Hazby, Mick Casey, Chris Robinson, Daniel Rusch and Rene Hunziker
The detailed design of the inducer of a high pressure ratio transonic radial compressor impeller with a design inlet tip relative Mach number of 1.4 is considered. Numerical analysis has been used to compare a datum impeller with ruled inducer design with a number of different free-form design concepts, generated following the same aerodynamic design philosophy. The datum stage and one with a free-form inducer, referred to as ‘barrelled forward swept', with forward swept leading edge near the tip and increased chord at mid-span, have been manufactured and tested. The tests were performed with the same stationary components, including the casing, vaned diffuser and the volute. The design with a barrelled forward sweep of the inducer allows the designer more control of the strength and position of the passage shock at the inlet while meeting mechanical constraints. Interestingly, the performance is also enhanced at off-design points at lower tip-speeds. The measurements show that the stage tested with the swept impeller achieves higher efficiency of between 0.5% and 1.6% compared to the datum design, depending on the operating speed. The CFD simulations are used to further study the flow at part speeds, in order to explain the causes of the observed performance differences at off design conditions.