To develop a non-equilibrium wet steam throughflow calculation method, including modelling of all the loss-generating two-phase phenomena

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

The proposed project will build on recent work supported by Alstom (now General Electric) at Cambridge and integrate with the ongoing Future Conventional Power Research Consortium project, which also has a wet steam component based in Cambridge. The objectives of the project are as follows:
(a) To develop a non-equilibrium wet steam throughflow calculation method, including modelling of all the loss-generating two-phase phenomena. The basis for this work will be provided by a current Alstom-supported PhD project at Cambridge that is now nearing completion. The current status is that non-equilibrium routines and wake-chopping models have been included within a streamline curvature code, enabling the global effects of condensation within turbines to be predicted, together with droplet size spectra. However, for this method to be of value both at the design stage and as a research tool, a host of additional two-phase phenomena need to be modelled. These include: contributions from heterogeneous condensation; deposition of droplets onto turbine blades by inertial impact and turbulent transport; migration of films under the action of shear and centrifugal forces; coarse water formation at blade trailing edges; computation of losses and their distribution between different phenomena such as thermal relaxation, fog-droplet drag, the braking effect of coarse water impaction etc. Models exist for many of these phenomena (notably due to the pioneering work of Gyarmathy [1]), but some are based on one-dimensional assumptions and require extension and adaption for inclusion into the (two-dimensional) streamline curvature code. Cambridge has considerable experience in this area, including the modelling of similar phenomena in water-injected compressors [2].
(b) Application of the throughflow code to provide a comprehensive study of how machine geometry, operating conditions and model assumptions influence the overall magnitude of losses and their distribution between the different phenomena. For example, changes to the LP turbine inlet temperature are likely to change the location of condensation such that it occurs with a very different expansion rate history. This may have a significant effect on the droplet size distribution, which in turn will affect all the other two-phase processes listed in (a) above. Such a study will require significant interaction with our industrial partners, and the CASE studentship thus provides an ideal framework for this undertaking.
In addition to (a) and (b) it is intended that there should be an additional component to the work, the precise nature of which should depend on the preferences and background of the PhD student.
Possibilities include (i) inclusion of velocity slip modelling within STEAMBLOCK (the 3D unsteady wet steam code recently developed at Cambridge) and application to study inertial relaxation effects in a variety of configurations (e.g., interpretation of Pitot tube measurements); (ii) a comprehensive study of the role of heterogeneous effects; (iii) fundamental phase-change modelling (i.e., nucleation and droplet growth studies).
References

[1] Gyarmathy, G., 1962. "Grundlagen einer Theorie der Nassdampfturbine". PhD Thesis (also
CEGB translation : "Bases for a Theory for Wet Steam Rurbines", T. 781).

[2] White, A.J., and Meacock, A. J., 2011. "Wet Compression Analysis Including Velocity Slip Effects", J. Eng. Gas Turbines Power 133(8), 081701

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510440/1 01/10/2016 30/09/2021
1759560 Studentship EP/P510440/1 01/10/2016 30/09/2020 Andrej Vasilj
 
Description This project is directed towards developing a comprehensive throughflow method that can be used for turbine design and development. Current state of the project consists of the throughflow code that is capable of non-equilibrium condensation with nucleation and droplet growth based on Lagrangian particle tracking. Accuracy of the calculated droplet spectrum prediction is improved by adding a stochastic wake segmentation code that captures unsteady effects of wake chopping and its influence on condensation process. Underlying droplet spectrum plays a role on both turbulent and inertial depostion processes that are captured in the code.
All of this enables fast analysis of turbine design while including the effects of wetness.
Exploitation Route This is a crucial tool for any turbine designer since it allows for inclusion of much broader spectrum of physical phenomena that might affect turbine performance.
Sectors Aerospace, Defence and Marine,Chemicals,Energy,Transport

 
Description The findings are to be used by one of the world's largest turbine manufacturers in order to improve their turbine design process. Since wetness in turbines accounts for up to 5% of energy losses, turbine optimisation leads to more eco-friendly use of fossil fuel as well as global energy savings. For this particular manufacturer, potential 10 year impact reaches $23.2Bn in global energy savings (present value).
Sector Aerospace, Defence and Marine,Chemicals,Energy,Transport
Impact Types Economic

 
Description  
IP Reference  
Protection Copyrighted (e.g. software)
Year Protection Granted
Licensed Yes
Impact Project still under development.
 
Title Droplet deposition software 
Description Software capable of determining droplet deposition in turbine passages. 
Type Of Technology Software 
Year Produced 2019 
Impact To be determined. 
 
Title Stochastic wake segmentation 
Description Software capable of determining effects of wake segmentation on non-equilibrium condensation. 
Type Of Technology Software 
Year Produced 2018 
Impact To be determined. 
 
Description TED talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Gave a TED talk to a group of approx. 300 on the two phase flow in turbomachinery and its global impact. The talk was selected as the best TED talk out of 33 by an anonymous survey.
Year(s) Of Engagement Activity 2018
 
Description Talk at Bellerbys College 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Gave a presentation to Bellerbys College students and staff about two phase flow in turbomachinery that increased interest in engineering and engineering related subjects.
Year(s) Of Engagement Activity 2019