Achieving high power heat-recovery systems using molecularly-complex fluids

Lead Research Organisation: University of Southampton
Department Name: Faculty of Engineering & the Environment

Abstract

Achieving UK and EU emissions targets requires a transformation in the power generation and manufacturing industries. In the UK we consume 350TWhr of electricity every year, but with modern power-stations which are typically around 50% efficient a large proportion of energy is wasted as rejected heat. Recovering just 10% of this heat would save the equivalent power output of 22 power stations. This is not to mention the heat which could be recovered from manufacturing industries where large quantities of energy are wasted through the heating and cooling during metal-forming processes. In order to make heat-recovery economically viable, low-temperature Organic Rankine Cycles (ORC) can be deployed using fluids with boiling-points close to ambient temperatures, such as many 'molecularly-complex' fluids. The power is extracted in an ORC across a turbine, where these 'molecularly-complex' fluids exist in a gaseous state, and pass through the turbine at high speeds. Increasing the power extracted from the turbine makes heat-recovery systems much more economically favourable and can be achieved by raising the pressure ratio across the turbine. In order to do this efficiently requires a better understanding of molecular-complex gas flows because there is very little known about these complex flows in turbines. The lack of an in-depth understanding of the molecular complex gas-dynamics in ORC turbines means that it is unlikely that optimum power levels are being achieved with present-day design methods.

Therefore this proposal aims to determine methods of significantly increasing heat-recovery system power outputs by exploiting the effects of molecular complexity in Organic Rankine Cycle turbines. A target is set of doubling current turbine power levels. In order to determine methodologies to achieve this, a combination of experimental and computational tests are planned. Experiments of molecularly complex gas flows will be studied using a specially designed experimental test-rig which will be able to mimic the flow conditions found in the ORC turbine. The computational simulations will involve the use of a research flow-solver, which will be modified to account for molecular-complex gas properties. The experimental data will aid the development of an accurate computational model, which will then be used to determine novel turbine blade designs to operate at high pressure ratios.

This research will directly benefit both the fluid-mechanics research community and the power-generation industry. The research will improve our fundamental understanding of the fluid mechanics of molecularly complex fluids, and will also aid the development of sustainable power generation technologies. An improved understanding of molecular-complex gas flows in turbines has the potential to substantially reduce the UK's fossil fuel dependence and improve our ability to recover currently otherwise 'wasted' heat from power stations and manufacturing processes as well as solar and geothermal radiation. This has a large societal benefit both in-terms of aiding the fight against climate-change and improving the UK's energy security. This work will help towards meeting the targets of the UK Climate Change Act 2008 to reduce by 34 percent our greenhouse gas emissions by 2020 and 80 percent by 2050, against the 1990 baseline.

Planned Impact

By determining methods of significantly increasing heat-recovery system power outputs, this proposal has the potential to have a transformative impact on large and small scale electrical power production, metal forming industries, and renewable power systems such as solar and geothermal. If the average power station within the UK recovered the waste heat it rejected at an efficiency of just 10%, we would save about 42TWhr per year, which is 12% of the UK electrical energy consumption. This can be achieved using Organic Rankine Cycles (ORC) operating with molecular complex working fluids. The economic incentive for using a heat-recovery ORC is very dependent on installation and operating costs since the heat input to the cycle tends to come at little cost. Capital costs and operational costs are thus directly related to the plant's size, and therefore for a given power requirement, the costs will be inversely proportional to the specific-power output from the ORC turbine. Increasing turbine specific-power outputs makes the implementation of heat-recovery systems economically favourable and thus facilitates a transformative reduction in man-made emissions levels. This has a large societal benefit both in-terms of aiding the fight against climate-change and improving the UK's energy security.

This research has an impact on the power-generation and turbomachinery industry both within the UK and worldwide.This proposal is being supported by GE Global Research, who are providing financial backing for this work. GE are global leaders in power generation and supply Organic Rankine Cycles (ORC) throughout the world. GE are in a position to implement the outcomes of this work internationally, which gives this proposal a truly global impact. GE recognize the requirement for research in this area because the modern turbine design methods and principles used in industry, which up to now have been based largely on classical gas dynamics and simple real-gas relations, may be grossly inappropriate for the case of the ORC turbine. Indeed several recent computational studies have highlighted the need for experimental data to establish the veracity of modern computational methods for ORC turbine flows because of the inherent uncertainties in the simulating flows with complex equations of state. By combining experimental testing with computational modelling, this project will determine how turbine designers can accurately simulate the flows in ORC turbines, which will be crucial to determining new high performance turbine designs.

As well as the benefits to the production of more sustainable power this has an important impact to the wider turbomachinery and fluid mechanics research community. Currently, there is a lack of experimental work of molecularly complex gas flows, especially within turbomachinery environments. In particular, it is not well known how shock waves develop in these flows, and hence how shock losses will differ from more conventional working fluids, such as steam or air. This is important because raising turbine power levels will require raising the turbine Mach numbers, which normally leads to increases in shock-wave related loss. Recent computational work indicates that molecular complexity effects can reduce or even eliminate shock-waves. This can be exploited to increase turbine power, efficiency, and operability, although has yet to be proven experimentally. The proposed experimental and computational work will determine variations in shock loss at a range of ORC typical conditions so that this can be potentially exploited in the turbine design process. In particular, this could lead to practical shock-free blade designs methods to be determined. This will have a significant impact on turbine performance both in terms of efficiency and operability.

Publications

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Wheeler, Andrew P. S. (2014) A STUDY OF THE THREE-DIMENSIONAL UNSTEADY REAL-GAS FLOWS WITHIN A TRANSONIC ORC TURBINE in Proceedings of the Asme Turbo Expo: Turbine Technical Conference and Exposition, 2014, Vol 3b

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Galiana, Francisco J. Dura (2015) A STUDY OF TRAILING-EDGE LOSSES IN ORGANIC RANKINE CYCLE TURBINES in Asme Turbo Expo: Turbine Technical Conference and Exposition, 2015, Vol 2a

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Durá Galiana F (2016) A Study of Trailing-Edge Losses in Organic Rankine Cycle Turbines in Journal of Turbomachinery

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Baumgärtner D (2020) The Effect of Isentropic Exponent on Transonic Turbine Performance in Journal of Turbomachinery

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Wheeler, Andrew P. S. (2013) THE ROLE OF DENSE GAS DYNAMICS ON ORC TURBINE PERFORMANCE in Proceedings of the Asme Turbo Expo: Turbine Technical Conference and Exposition, 2013, Vol 2

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Wheeler A (2013) The Role of Dense Gas Dynamics on Organic Rankine Cycle Turbine Performance in Journal of Engineering for Gas Turbines and Power

 
Description Our experimental and computational work to-date reveal the behaviour of complex gas flows in turbines used for waste heat recovery. The so-called 'dense gases' behave very differently from gases used in conventional turbines (such as gas turbines and steam turbines), and can be exploited for recovering low-grade heat. This project discovered the first experimental measurements of how trailing-edge (base) flows in these types of turbines. These flows contribute a significant amount to the overall performance of the turbine. By setting-up a unique experiment of the flow in the stator vane of the turbine we showed that the flow in the trailing edge is greatly modified by 'dense-gas' effects which occur in these types of turbines. We were also able to model these effects using high-fidelity computational simulations validated by the experimental data. The results are important to turbine designers who can make use of this information to improve turbine performance.
Exploitation Route The data is important in terms of Organic Rankine Cycle Turbine design, and we are working with GE (global leaders in this technology) to implement to results of this work into their design methods.
Sectors Aerospace, Defence and Marine,Energy

URL https://whittle.eng.cam.ac.uk/research-areas/transonic-turbines-for-low-carbon-power-cycles/
 
Description The research findings are aiding the development of high performance heat recovery systems. The project was co-funded by GE Global Research, who will incorporate the research findings into their design methods.
First Year Of Impact 2013
Sector Energy
Impact Types Economic

 
Description Centre for Defence Enterprise
Amount £48,000 (GBP)
Organisation Defence Science & Technology Laboratory (DSTL) 
Sector Public
Country United Kingdom
Start 11/2011 
End 02/2012
 
Description EPSRC Early Career Fellowship
Amount £801,334 (GBP)
Funding ID EP/L027437/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 12/2014 
End 12/2019
 
Title Method of simulating Organic Rankine Cycle turbine flows 
Description We have developed a new transient wind tunnel which simulates the flows found in Organic Rankine Cycle turbines. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact We have recently published results from this facility showing how the flow behaviour in an Organic Rankine Cycle turbine is greatly dependent on the choice of working fluid. 
URL http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2427865
 
Description Industrial Collaboration with Rolls Royce 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
PI Contribution We are applying our research of multi-component and molecularly complex fluids, to a thermal management system design project. The details are commercially sensitive at this stage
Collaborator Contribution This is commercially sensitive at this stage
Impact This is commercially sensitive at this stage
Start Year 2019
 
Description Industrial collaboration with GE Global Research 
Organisation General Electric
Department GE Global Research
Country India 
Sector Private 
PI Contribution GE are a global leader in turbomachinery, and in waste heat recovery systems such as ORC turbines. We are working closely with GE who will make use of the results of our work within theire design systems
Collaborator Contribution GE are profividing valuable guidance on turbine design which aids us in the development of our experimental and computational simulations to ensure they represent correctly the true turbine environment. They are providing financial support and in-kind support for my EPSRC Fellowship and also supported my earlier EPSRC First Grant Proposal.
Impact The collaboration as led to the following publications: https://gasturbinespower.asmedigitalcollection.asme.org/article.aspx?articleID=1735630 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2427865 http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1907813&resultClick=1
Start Year 2010
 
Description Co-organizer of the first NICFD 2016 Conference 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact The aim of this event was to gather together a new international cross-disciplenary community of people that are interested in discussing the fluid dynamics of non-ideal compressible flows (NICFD). The growing interest towards NICFD in the last decade, especially for its advanced applications in the field of propulsion and power, has determined an impulse in research. This conference is intended to promote the exchange of information among the quite diverse community, whose interests span from the fundamentals to the industrial application.
Year(s) Of Engagement Activity 2016
URL http://www.kcorc.org/en/news-and-events/nicfd-2016-1st-international-seminar-non-ideal-com/
 
Description Invited seminar: "Exploiting unsteady & transonic flows in turbomachines to improve performance" Dept Aeronautics, Imperial College,16/03/2011 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact At his invited seminar at Imperial College, I presented my research work on turbine used for waste heat recovery and transonic turbines. it was attended by a several acacemic staff as well as students from the Department of Aeronautics.
Year(s) Of Engagement Activity 2011
 
Description Southampton Heat Recovery Systems Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Type Of Presentation keynote/invited speaker
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This workshop, organized and run by Dr Andy Wheeler brought together academics, research students and people involved in the heat recovery industry to discuss the technological and research challenges for modern and future heat recovery systems.


.

A network of academics and industrialists was developed with shared research objectives related to heat recovery systems were discussed.
Year(s) Of Engagement Activity 2013
URL https://www.ocs.soton.ac.uk/index.php/orcworkshop/2013