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Distributed aircraft propulsion has renewed the interest in power-dense, high-efficiency power packs. Ceramic turbomachinery could be a major enabler, although no successful design has been achieve...

[Restricted], Rolls-Royce plc.

Unmanned Aerial Vehicles (UAVs) are commonly propeller-driven and low-speed. The concept of cost-efficient, much higher speed and longer range applications of micro jet engines was previously addressed such that an existing basic turbojet engine was converted into a single spool turbofan without using additional components of booster and low pressure turbine. Normally, this situation emerges matching problems since two spools are required to adjust the fan speed independently. A simple solution was to use a Continuously Variable Transmission (CVT) gearbox to adjust optimal speed for the fan. As a result, missing of the positive functionality of the booster would lump into the fan root to form a unified low pressure compression system (unified-LPC). Such a unified-LPC demands unique characteristics of having an extreme twist, very high pressure ratio and mass flux at the root section than at the tip section, despite the exact opposite is being enforced due to the wheel speed rise with radius. In light of these challenges, this work aims to investigate detailed aerodynamics of an existing design previously made and reported by the authors. It is shown that, despite the aerodynamic loading contrast throughout the span, the unified-LPC can still have a wide operating range and acceptable off-design aerodynamics. Complementing the previous design-oriented work, this paper aims to provide guidelines for such unified compression systems., İnsansız Hava Araçları (İHA'lar) genellikle pervaneli ve düşük hızlıdır. Mikro jet motorlarının düşük maliyetli, çok daha yüksek hızlı ve daha uzun menzilli bir konsepti, daha önceki çalışmalarda, mevcut bir temel turbojet motorunun, ek güçlendirici kompresör (“booster”) ve düşük basınçlı türbin kullanılmadan tek milli bir turbofana dönüştürüleceği şekilde ele alınmıştı. Normalde bu durum, fan hızını bağımsız olarak ayarlamak için iki mil gerektirdiğinden eşleşme sorunları ortaya çıkarır. Bir çözüm, fan için optimum hızı ayarlamak üzere Sürekli Değişken Şanzıman (CVT) dişli kutusu kullanmaktır. Sonuç olarak, güçlendirici kompresörün olumlu işlevselliğinin eksikligi, tek fan kademesi içerisinde fiili bir birleşik bir düşük basınçlı sıkıştırma sistemi (birleşik DBK) oluşturmak için fan köküne eklenecektir ve bu da fana ek yük bindirecektir. Böyle bir birleşik DBK, yarıçapla birlikte çark hız artışı nedeniyle tam tersinin fiziksel olarak dikte edilmesine rağmen, kökte uca kıyasla çok yüksek basınç oranı ve kütle akışına sahip olma ve aşırı bir bükülme gibi benzersiz özellikler gerektirir. Bu zorlukların ışığında, bu çalışma, yazarlar tarafından daha önce yapılmış ve rapor edilmiş mevcut bir tasarımın ayrıntılı aerodinamiğini araştırmayı amaçlamaktadır. Kanat uzunluğu boyunca aerodinamik yükleme kontrastına rağmen, birleşik DBK'nın hala geniş bir çalışma aralığına ve kabul edilebilir tasarım dışı aerodinamiğe sahip olabileceğini gösterilmiştir. Önceki tasarım odaklı çalışmayı tamamlayan bu makale, bu tür birleşik sıkıştırma sistemleri için tasarımcılara kılavuz sağlamayı amaçlamaktadır.

A gas turbine is a turbomachine composed of a compressor part, a part with heat supply to the compressed gas and a turbine part in which the hot gas expands. The present chapter discusses gas turbines for mechanical power ­generation. These are machines with an outgoing shaft, meant to drive a load. The largest market sector of such machines is electrical power generation, but machines for driving compressors and pumps in industrial plants and for driving large vehicles and ships also are examples. We discuss the working principles of the components of power gas turbines in the present chapter. As electric power generation is the largest sector of application, we choose components of such machines for illustrations. The main purpose of the chapter is the discussion of the overall performance of power gas turbines. Performance analysis is a matter of thermodynamic modelling and is not strongly linked to a particular application.

The Covid-19 pandemic has changed the university education, with most teaching moved off campus and students learning online or remote at home, but a cornerstone of undergraduate engineering education has been a big challenge, namely the laboratory classes. As the engineering and education communities continue to adapt to the realities of a global pandemic, it is important to recognize the importance of the laboratory-based courses. In order to address to this situation, an ambitious approach is taken to recreate the laboratory experience entirely online with the help of the digital twins of the fluid mechanics, thermodynamics, and turbomachinery laboratory experiments. Laboratory based undergraduate courses such as EFPLAB1, EFPLAB2 (Energy; Fluid and Process Laboratory 1 & 2) and EFPENG (Energy; Fluid and Process Engineering) are important parts of the “mechanical engineering” and “energy systems engineering” curricula of the Lucerne University of Applied Sciences (HSLU) in Switzerland. Each course mentioned above include six different laboratory experiments about fluid mechanics, thermodynamics, turbomachinery, energy efficiency, and energy systems, including mass- and energy flow balances in energy systems. During the Covid-19 pandemic, it was necessary to adapt to the new environment of remote learning courses and modify the laboratory experiments so that they can be carried out online. The approach was developing digital twins of each laboratory experiment with web applications and providing an environment together with supporting videos and interactive problems so that the laboratory experiments can be carried out remotely. A digital twin is a digital representation of a physical system, e.g., the test rig. It may contain a collection of various digital models with related physical equations and solutions, information related to the operation of the test rig, including 2D or 3D models, process models, sensor data records, and documentation. Ideally, all quantities and attributes that could be measured or observed from the real experiment should be accessible from its digital twin. The digital twin not only reproduces the experimental setup in the laboratory but also helps to improve the knowledge related to the theory and concepts of the laboratory experiments. One major advantage of the digital twin is that the number and range of the parameters, which can be manipulated or varied, is larger in comparison to the actual testing in the laboratory. This paper explains the development of the digital twins (web applications) of the laboratory experiments and provides information about the selected experiments such as potential vortex, linear momentum equation, diffuser flow, radial compressor, fuel cell, and pump test rig with the measurement of pump characteristics. A remote or distance learning has many hurdles, one of the largest being how to teach hands-on laboratory courses outside of an actual laboratory. The experience at the Lucerne University of Applied Sciences showed that teaching online labs using the digital twins of the laboratory experiments can work and the students can take part in remote laboratories that meet the learning outcomes and objectives as well as engage in scientific inquiry from a distance.

The field of turbomachinery is undergoing major advances in aeroelasticity and this chapter provides an overview of these new developments in the key enabling methodology of unsteady aerodynamic modeling. Also see the earlier discussions in chapters “Aeroelasticity in Turbomachines” and “Modeling of Fluid-Structure Interaction.”

Μεγάλη προσπάθεια γίνεται τα τελευταία χρόνια για την ανάπτυξη αποδοτικών μηχανών μετατροπής ενέργειας. Τα κίνητρα για αυτή την προσπάθεια είναι κυρίως η ολοένα αυξανόμενη ζήτηση για ηλεκτρική ενέργεια, η εξάντληση των κοιτασμάτων ορυκτών καυσίμων καθώς και η μόλυνση του περιβάλλοντος από εκπομπές αέριων ρύπων. Μια τεχνολογία που φαίνεται ότι θα συμβάλει σημαντικά στην διαμόρφωση του ενεργειακού τομέα στο μέλλον, είναι οι μικροστρόβιλοι. Οι μικροστρόβιλοι λόγω των πλεονεκτημάτων που παρουσιάζουν μπορούν να χρησιμοποιηθούν σε εφαρμογές κατανεμημένης παραγωγής ηλεκτρικής ενέργειας, smart grids, υβριδικά συστήματα και συστήματα συμπαραγωγής.Αντικείμενο της παρούσας διατριβής είναι η μελέτη εφαρμογών μικροστροβίλων, τόσο υπολογιστικά όσο και πειραματικά. Οι υπολογιστικές δραστηριότητες περιλαμβάνουν κυρίως την μελέτη υβριδικών συστημάτων τύπου SOFC-GT (Solid Oxide Fuel Cell – Gas Turbine). Στα συστήματα αυτά γίνεται συνδυασμός ενός μικροστροβίλου και μιας γεννήτριας τύπου SOFC, η οποία λειτουργεί σε συνθήκες υπερπίεσης (υπετροφοδοτείται). Το καύσιμο αντιδρά ηλεκτροχημικά στις κυψέλες καυσίμου SOFC (που υποκαθιστούν το θάλαμο καύσης του μικροστροβίλου) και παράγει ηλεκτρική ενέργεια μαζί με θερμότητα. Η θερμότητα χρησιμοποιείται από το μικροστρόβιλο για την παραγωγή επιπλέον ηλεκτρικής ενέργειας. Τα συστήματα αυτά έχουν υψηλούς βαθμούς απόδοσης και θεωρούνται ως μια εναλλακτική επιλογή των συμβατικών συστημάτων ηλεκτροπαραγωγής.Για την μοντελοποίηση των υβριδικών συστημάτων χρησιμοποιήθηκε ένα λογισμικό γενικής χρήσης (AspenPlus). Ξεκινώντας με μια προτεινόμενη μέθοδο από την διαθέσιμη βιβλιογραφία, έγιναν προσθήκες νέων στοιχείων με σκοπό την δημιουργία ενός βελτιωμένου μοντέλου. Επιπλέον, αναπτύχθηκαν μοντέλα για την προσομοίωση των στροβιλομηχανών στο λογισμικό γενικής χρήσης, ιδιαίτερα σε μερικό φορτίο, για πρώτη φορά σε αυτό το περιβάλλον. Στην παρούσα διατριβή εξετάζονται σχεδιασμοί υβριδικών συστημάτων βασιζόμενοι σε εμπορικά διαθέσιμους μικροστροβίλους και σε μια επιτυχημένη γεννήτρια τύπου SOFC η οποία δοκιμάστηκε σε αρκετά πιλοτικά προγράμματα διεθνώς. Αναπτύχθηκαν μοντέλα και βαθμονομήθηκαν με βάση πειραματικά δεδομένα από την βιβλιογραφία. Μελετήθηκε η συμπεριφορά σε συνθήκες πλήρους και μερικού φορτίου καθώς και η επίδραση σημαντικών λειτουργικών παραμέτρων στις επιδόσεις των υβριδικών συστημάτων. Τα αποτελέσματα έδειξαν ότι τα συστήματα αυτά μπορεί να οδηγήσουν σε υψηλούς βαθμούς απόδοσης, εφόσον γίνει κατάλληλη βελτιστοποίηση στο σχεδιασμό του συστήματος καθώς και στο μέγεθος του μικροστροβίλου. Η προηγούμενη εμπειρία που αποκτήθηκε οδήγησε σε μια μεθοδολογία για την βελτιστοποίηση των στροβιλομηχανών σε υβριδικά συστήματα SOFC-GT. Η μεθοδολογία περιλαμβάνει δυο βήματα. Στο πρώτο γίνεται μια παραμετρική ανάλυση για να αποτιμηθεί το λειτουργικό πεδίο του συστήματος και στο δεύτερο, λαμβάνοντας υπόψη τις πληροφορίες του πρώτου βήματος, υπολογίζονται οι βέλτιστες γεωμετρίες για τον συμπιεστή και τον στρόβιλο χρησιμοποιώντας in-house κώδικες που αναπτύχθηκαν για αυτό τον σκοπό. Τα αποτελέσματα έδειξαν σημαντική βελτίωση των επιδόσεων του συστήματος σε όλο το εύρος λειτουργίας του. Η υποδομή που δημιουργήθηκε επιτρέπει τη μελέτη επιπλέον σχεδιαστικών επιλογών, με χωριστή επιλογή συμπιεστή και στροβίλου, διαφορετικού τύπου συμπιεστή κτλ, όπως και διαφορετικών επιλογών στο σύστημα ελέγχου. Οι πειραματικές δραστηριότητες που έγιναν στα πλαίσια αυτής της διατριβής, αφορούν ένα μικροστρόβιλο τύπου turbojet. Παρουσιάζεται η εμπειρία που αποκτήθηκε από την ανάπτυξη ενός μοντέλου για την προσομοίωση της συμπεριφοράς του σε μόνιμες συνθήκες λειτουργίας. Τα αποτελέσματα έδειξαν ότι κάποιες μετρήσεις που λαμβάνονται από την λειτουργία της μηχανής δεν είναι αντιπροσωπευτικές της μέσης τιμής που επικρατεί σε κάθε διατομή. Ωστόσο η απόκλιση είναι συστηματική και επαναλήψιμη με αποτέλεσμα να μπορούν να υιοθετηθούν διαδικασίες διόρθωσης των μετρήσεων. Εκτός από την μελέτη σε μόνιμες συνθήκες λειτουργίας, μελετήθηκε και η μεταβατική λειτουργίας της μηχανής μέσω ενός μοντέλου που αναπτύχθηκε για αυτό το σκοπό. Τα αποτελέσματα των προσομοιώσεων είναι σε αρκετά καλή συμφωνία με τα πειραματικά δεδομένα. Η εμπειρία που αποκτήθηκε από το μεταβατικό μοντέλο λειτουργίας αναμένεται να αξιοποιηθεί για την ανάπτυξη μεταβατικού μοντέλου λειτουργίας για τα συστήματα SOFC-GT, προκειμένου να μελετηθεί καλύτερα το σύστημα ελέγχου για προστασία της συστοιχίας SOFC από αιχμές πίεσης, surge, αποσυσμπίεση κτλ.

This paper was erroneously published in ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition, Vol. 2D and removed on October 13, 2021. Copyright © 2021 by ASME

This paper was removed from publication at the author’s request. February 18, 2021. Copyright © 2021 by ASME

PT XYZ is one of the companies in Indonesia focusing on heavy rotating equipment, repair and manufacture Not only domestically, the company also plans to expand the business internationally to other countries in South East Asia. By increasing the company’s sales revenue and expanding the market share, PT XYZ might be able to achieve the goal. However, in the sales it is found that the current operational management strategy can no longer sustain profitable and it makes the sales revenue drops for the last two years. The purpose of this research is to find and identify the strategy of the turbomachinery equipment service business to keep on growing in Indonesia. The conceptual framework used this strategy begins with analyzing the external environment by using PESTLE, Porter’s Five Forces, and competitor analysis. After external analysis, internal analysis is done by analyzing the resources and the value chain. Later on, all of the results will be summarized with a SWOT analysis. The results reveal that the company does not have a coherent business strategy. Thus, it evokes several problems in some internal parts of the company, such as an ineffective marketing strategy and improper resource allocation. The applied strategy in this research is the differentiation strategy. This differentiation strategy expansion will be the key to support the company’s development in the turbomachinery equipment service market in Indonesia. Meanwhile, the outcome is expected to extend PT XYZ’s market share, product development, and service development later in the future.

Turbomachinery technology and mechanical systems provide a strategic advantage by enabling oil and gas industry exploration and production companies to acquire, transport and refine hydrocarbons efficiently, productively and safely, with a smaller environmental footprint and at lower cost per barrel of hydrocarbons. However, this advantage is underscored by the process safety risks associated with failures of these large and complex mechanical systems such as gas turbines, liquid natural gas (LNG) trains, reciprocating, and centrifugal gas compressor systems, etc. Catastrophic failures of these mechanical systems result in the unintended release of energy with severe consequences and devastating impact on HSE, assets, and commercial penalties. After data mining, reviewing, and analyzing historical incidents, several questions arise: Are we doing enough to minimize the likelihood of an unplanned release of explosive energy resulting in fires and projectiles? Are current measures sufficient to manage the risk of loss of pressure or loss of vacuum containment? Even though turbomachinery original equipment manufacturers (OEM) utilize existing engineering tools (HAZOPS, FMEA, etc.), incident data demonstrates that the challenge remains. How do we drive better financial results while managing operational performance and process safety risks? Moreover, how do we learn from what has happened to innovate our approach to process safety risk management?

This paper outlines a practical intervention aiming to collect the effects of introducing flexible learning in engineering higher education. The work dis- cusses the implementation of the flipped classroom method and the threshold concepts in the Turbomachinery section of Fluid Engineering course in the third year of Mechanical Engineering (Bachelor's degree) at the Universitat Politècnica de Catalunya. Fluid Engineering is traditionally one of the hardest courses involving a complex interaction between understanding concepts and using those concepts in the solution of cases, which also require the devel- opment of a set of skills. This case study is centred on two student cohorts, and the research spans over two consecutive Fall semesters. The study is based on sound pedagogy of educational technologies, in practice, frequent student-to-instructor interaction, academic results, and statistical and survey analyses. A principal conclusion is that overall class performance is much higher than that of the previous courses. The results indicate that learners gained under- standing from semester to semester and no statistical significance was ob- served between group and exam format. Students were satisfied with the level of suitability and the degree of compliance of the new implementation and found it constructive in their learning process, an important educational benefit. This positive experience, in terms of benefit-cost and outcomes, en- courages the intervention without sacrificing any curriculum syllabus, but taking advantage and bringing the benefits of interactivity distance learning technologies and traditional face-to-face lectures. This scholarly research aims to contribute to this area, by abandoning traditional lecturing in favour of active learning

The mechanisms of blade row interaction affecting rotor film cooling are identified in order to make recommendations for the design of film cooling in the real, unsteady turbine environment. Present design practice makes the simplifying assumption of steady boundary conditions, despite intrinsic unsteadiness due to blade row interaction; we argue that if film cooling responds non-linearly to unsteadiness, the time-averaged performance will then be in error. Non-linear behaviour is confirmed using experimental measurements of flat-plate cylindrical film cooling holes, main-stream unsteadiness causing a reduction in film effectiveness of up to 31% at constant time-averaged boundary condition. Unsteady computations are used to identify the blade row interaction mechanisms in a high-pressure turbine rotor: a ‘negative jet’ associated with the upstream vane wake, and frozen and propagating vane potential field interactions. A quasi-steady model is used to predict unsteady excursions in momentum flux ratio of rotor cooling holes, with fluctuations of at least ±30% observed for all hole locations. Computations with modified upstream vanes are used to vary the relative strength of wake and potential field interactions. In general, both mechanisms contribute to rotor film cooling unsteadiness. It is recommended that the designer should choose a cooling configuration which behaves linearly over the expected unsteady excursions in momentum flux ratio as predicted by a quasi-steady hole model.

Whilst the automotive industry has made progress with electrified turbomachinery at the passenger vehicle scale, progress has been slower for heavy duty, on and off-highway, and industrial scale engines. But, the numbers of these engines, and their contribution to carbon emissions and general pollution, are still significant.

In the current design of turbomachines, engine performance is improved by reducing the clearances between the rotating components and the stator, which allows for loss decrease. Due to these clearance reductions, contact events may occur between the rotor and the stator. An abradable coating is deposited along the stator circumference as a sacrificial material to lower the contact severity. However, experiments highlighted the occurrence of rotor/stator interactions with high wear depth on the abradable coating as well as high temperature increases within the abradable coating following contacts. This work focuses on the sensitivity analysis of rotor/stator interactions with respect to the rotor angular speed and the initial clearances between the rotor and the stator, taking into account thermal effects within the abradable coating. Convergence analyses are first conducted to validate the numerical model. Then, after a calibration of the thermal model of the abradable coating based on two experimental test cases, the numerical model is used to investigate the cross effects of the angular speed and the initial clearances on the obtained rotor/stator interactions.

This article highlights the introduction of digital and maintenance, repair, and overhaul (MRO) at ASME Turbo Expo 2018. The Digital impact begins at the OEM where analytical experiments assess the impact of geometry and boundary conditions on part life/performance. Performance characteristics taken from operational data are integrated with physical characteristics taken from the MRO environment to model and predict new part performance in existing turbomachinery and applied to the design and development of new turbomachinery. Most OEMs today offer an asset monitoring solution based on predictive analytics for their products. Operators and MROs looking for a more universal solution are reaching out to third parties or developing their own asset monitoring systems. Maintenance actions and shop findings are fed back to the asset monitoring solution to provide real time troubleshooting and repair work-scoping, saving valuable time in the operational and MRO environments.

In the field of turbomachinery, vibration amplitude is often reduced by dissipating the kinetic energy of the blades with devices that utilize dry friction. Under-platform dampers, for example, are often placed in the underside of two consecutive turbine blades. Dampers are kept in contact with the under-platform of the respective blades by means of the centrifugal force. If the damper is well designed, vibration of blades instigate a relative motion between the under-platform and the damper. A friction force, that is a non-conservative force, arises in the contact and partly dissipates the vibration energy. Several contact models are available in the literature to simulate the contact between the damper and the under-platform. However, the actual dynamics of the blade-damper interaction have not fully understood yet. Several test rigs have been previously developed to experimentally investigate the performance of under-platform dampers. The majority of these experimental setups aim to evaluate the overall damper efficiency in terms of reduction in response amplitude of the blade for a given exciting force that simulates the aerodynamic loads. Unfortunately, the experimental data acquired on the blade dynamics do not provide enough information to understand the damper dynamics. Therefore, the uncertainty on the damper behavior remains a big issue. In this work, a novel experimental test rig has been developed to extensively investigate the damper dynamic behavior. A single replaceable blade is clamped in the rig with a specific clamping device. With this device the blade root is pressed against a groove machined in the test rig. The pushing force is controllable and measurable, to better simulate the actual centrifugal load acting on the blade. Two dampers, one on each side of the blade, are in contact with the blade under-platforms and with platforms on force measuring supports. These supports have been specifically designed to measure the contact forces on the damper. The contact forces on the blade are computed by post processing the measured forces and assuming the static equilibrium of the damper. The damper kinematics is rebuilt by using the relative displacement, measured with a differential laser, between the damper and the blade under-platform. This article describes the main concepts behind this new approach and explains the design and working of this novel test rig. Moreover, the influence of the damper contact forces on the dynamic behavior of the blade is discussed in the result section.

The support structure of an offshore wind turbine (OWT) accounts for up to 25% of the capital cost; therefore, investigations into reliable and efficient foundations are critical for the offshore wind turbine industry. This paper describes an innovative hybrid monopile foundation for OWTs, which is an optimization of the original monopile foundation with broader applications. The behavior of OWTs with the hybrid monopile foundation in service conditions are investigated under lateral cyclic loadings, by considering the effects of wind, waves, and ice. A series of centrifuge tests are conducted in order to analyze these behaviors in detail, and OWT models with the original single-pile as well as wheel-only foundations are tested for comparison. Based on these tests, the accumulated lateral displacement and stiffness during cyclic loadings are presented, and the results indicate that the hybrid foundation exhibits a larger cyclic capacity than the other foundations. The influence of the cycle numbers, cyclic loading characteristics, and soil properties is examined during the tests; furthermore, the effects of these factors on the model deformation responses are illustrated. This study proposes the first analytical method for quantitatively estimating the cyclic lateral displacement of the new hybrid foundation in service conditions, and a degradation coefficient is recommended based on the test results. This method aims to provide a simple approach to predicting responses of OWTs with hybrid monopile foundations in service conditions.

In this work we study experimentally the flow dynamics inside the rotor of a three straight-bladed Cross-Flow Turbine (CFT). The CFT model used in the experiments is based on symmetric NACA-0015 profiles, with a chord to rotor diameter ratio of 0.16. The turbine model was designed in order to quantify the flow inside and around the rotor using planar Digital Particle Image Velocimetry (DPIV). Tests were made by forcing the rotation of the turbine with a DC motor, which provided precise control of the Tip Speed Ratio (TSR), while being towed in a still-water tank at a constant turbine diameter Reynolds number of 6.1 × 104. The range of TSRs covered in the experiments went from 0.7 to 2.3. The focus is given to the analysis of the blade-wake interactions inside the rotor. The investigation has allowed us to relate the interactions with the performance differences in this type of turbines, as a function of the operational tip speed ratio.

The preliminary fluid dynamic design of turbomachinery operating with non-standard working fluids and unusual operating conditions and specifications can be very challenging because of the lack of know-how and guidelines. Examples are the design of turbomachinery for small-capacity organic Rankine cycle and supercritical CO2 cycle power plants, whereby the efficiency of turbomachinery components has also a strong influence on the net conversion efficiency of the system. These machines operate with the fluid in thermodynamic states which, for part of the process, largely deviate from those obeying to the ideal gas law. This in turn implies the presence of so-called non-ideal compressible fluid dynamics effects. Active subspaces, a model reduction technique, is at the basis of the methodology presented here, which is aimed at the optimal meanline design of unconventional turbomachinery. The resulting surrogate model depends on a very small set of non-physical variables, called active variables. The procedure integrates into a single constrained optimization framework the selection of the working fluid, the thermodynamic cycle calculation and the preliminary sizing of the turbomachinery component. As a demonstration of the advantages of the proposed approach, the design of a 10kW mini organic Rankine cycle turbine with a turbine inlet temperature of 240°C is illustrated. In this case, approximately the same maximum efficiency is estimated for three dissimilar turbines operating with different working fluids and rather different thermodynamic cycles. The use of active subspaces allows the seamless evaluation of the sensitivity of results to input parameters, both those related to the machine and the working fluid. The novel design procedure is compared in terms of computational efficiency to a conventional approach based on the coupling of a genetic algorithm directly with a meanline code. Results show that the calculation based on the use of surrogate models is more than two orders of magnitude faster. The surrogate can be used to solve any design problem within the specified boundaries of the design envelope. Results are affected by uncertainty on the estimation of losses and of non-ideal compressible fluid dynamics effects, which, in turn, do not affect the applicability of the method, which will become quantitatively accurate once this information will be available. Work to this end is underway in various laboratories.

Gas foil bearing has been widely used in high-speed turbo machinery due to its oil-free, wide temperature range, low cost, high adaptability, high stability and environmental friendliness. In this paper, state-of-the-art investigations of gas foil bearings are reviewed, mainly on the development of the high-speed turbo machinery in China. After decades of development, progress has been achieved in the field of gas foil bearing in China. Small-scale applications of gas foil bearing have been realized in a variety of high-speed turbo machinery. The prospects and markets of high-speed turbo machinery are very broad. Various high-speed turbomachines with gas foil bearings have been developed. Due to the different application occasions, higher reliability requirements are imposed on the foil bearing technology. Therefore, its design principle, theory, and manufacturing technology should be adaptive to new application occasions before mass production. Thus, there are still a number of inherent challenges that must be addressed, for example, thermal management, rotor-dynamic stability and wear-resistant coatings.

As compared to the conventional large scale gas turbines, the aerothermodynamics design of a micro gas turbine will be quite different not only due to the small scale effects, but also due to the constraints associated with many considerations. As a major component and main work unit of the micro gas turbine, the design flow and the design results of the micro radial turbine directly determine the physical realization of the micro gas turbine. This paper mainly presents the investigation and discussion on scaling considerations and the design flow through a micro radial turbine which with diameter of 10 mm for a 50 W-class micro gas turbine. Firstly, theoretical analysis of scaling effects, thermodynamics, fluid mechanics, turbomachinery aerothermodynamics, heat transfer and rotor dynamics are described. Secondly, four sub-modules of different design considerations are constructed and the periodical design results are presented. Finally, the design flow of millimeter-scale radial turbine is proposed. The results indicate that the distinctive design principles and design challenges are not negligible and the discussions and definitions of the design flow for the micro turbine are essential. These works not only methodize the design details, but also define the basic design flow as the reference for the new designer.

Performance prediction in preliminary design stages of several turbomachinery components is a critical task in order to bring the design processes of these devices to a successful conclusion. In this paper, a review and analysis of the major loss mechanisms and loss models, used to determine the efficiency of a single stage centrifugal compressor, and a subsequent examination to determine an appropriate loss correlation set for estimating the isentropic efficiency in preliminary design stages of centrifugal compressors, were developed. Several semi-empirical correlations, commonly used to predict the efficiency of centrifugal compressors, were implemented in FORTRAN code and then were compared with experimental results in order to establish a loss correlation set to determine, with good approximation, the isentropic efficiency of single stage compressor. The aim of this study is to provide a suitable loss correlation set for determining the isentropic efficiency of a single stage centrifugal compressor, because, with a large amount of loss mechanisms and correlations available in the literature, it is difficult to ascertain how many and which correlations to employ for the correct prediction of the efficiency in the preliminary stage design of a centrifugal compressor. As a result of this study, a set of correlations composed by nine loss mechanisms for single stage centrifugal compressors, conformed by a rotor and a diffuser, are specified.

The effect of poor soil condition and unbalanced weight of the turbo machineries can lead to increased amplitudes of vibration which are further multiplied if subjected to seismic loading. In the current work, a computational model for the turbo machinery foundation was developed in SAP 2000 software to analyze the effect of Kathmandu earthquake (2015) in five different soil conditions i.e. very hard generic rock, generic rock, generic soil, NEHRP C class and NEHRP D class. The results reveal that turbo machinery foundation with barrettes can be used in seismic areas as barrettes safeguard the foundation by absorbing/reducing the seismic load due to high specific surface and side resistance. However for poor soil conditions like NEHRP D (clay soil), it was found that barrettes alone are not sufficient to limit the vibrations induced by either dynamic loading due to rotating motion of the machineries or seismic loading. Applications of geosynthetics along with barrettes considerably reduce the vibrations at top deck for poor soil conditions.

This study presented a hybrid model method based on proper orthogonal decomposition (POD) for flow field reconstructions and aerodynamic design optimization. The POD basis modes have better description performance in a system space compared to the widely used semi-empirical basis functions because they are obtained through singular value decomposition of the system. Instead of the widely used linear regression, nonlinear regression methods are used in the function response of the coefficients of POD basis modes. Moreover, an adaptive Latin hypercube design method with improved space filling and correlation based on a multi-objective optimization approach was employed to supply the necessary samples. Prior to design optimization, the response performance of POD-based hybrid models was first investigated and validated through flow reconstructions of both single- and multiple blade rows. Then, an inverse design was performed to approach a given spanwise flow turning distribution at the outlet of a turbine blade by changing the spanwise stagger angle, based on the hybrid model method. Finally, the spanwise blade sweep of a transonic compressor rotor and the spanwise stagger angle of the stator blade of a single low-speed compressor stage were modified to reduce the flow losses with the constraints of mass flow rate, total pressure ratio, and outlet flow turning. The results are presented in detail, demonstrating the good response performance of POD-based hybrid models on missing data reconstructions and the effectiveness of POD-based hybrid model method in aerodynamic design optimization.

In advanced gas turbines, the turbine blade operated temperature is above the melting point of blade material. A sophisticated cooling scheme must be developed for continuous safe operation of gas turbines with high performance. This report describes the development and application of a validated Computational Fluid Dynamics modelling approach for internal cooling passages in rotating turbomachinery which analyze change in pressure, velocity, temperature and pressure of fluid in the passage. Velocity changes in the passage help to determine turbulence created in the passage. The CFD analysis is conducted with smooth passage, straight turbulator passage, skewed turbulator passage with different inlet conditions and best model is finalized with high turbulence output. The analysis is carried out using commercial CFD software on k-e model. On evaluating results of different velocity and temperatures, it is found that straight turbulator has more turbulence when compared to smooth and skewed turbulators.

The predominant advantage of a supercritical CO2 (SCO2) Brayton cycle is it’s diminished compression work when compared to an ideal working fluid such as helium, due to low compressibility factor. For flows where the density approaches the critical density, molecular interactions get stronger and the ideal gas assumption is no longer appropriate. As a means to investigate the accuracy of real gas models and sensitivity of the performance of a turbomachine on the numerical accuracy in the supercritical region, numerous unsteady simulations of a radial turbine have been performed. Real Gas Properties (RGP) table has been generated to overcome difficulties of instabilities in simulations in the supercritical region. Four Equation of States (EOS) models with different RGP table resolutions have been studied and results are compared with the experimental measurement performed at the Sandia National Laboratory. The studied unshrouded radial impeller has 11 blades while the nozzle has 10 vanes. The unsteady simulation results show the dependency of the predicted radial turbine performance on the RGP table resolution as well as on the implemented EOS models. In general, the results indicate that by using appropriate EOS model and a look up table with high resolution, the CFD can predict turbine performance with high accuracy while the use of some EOS and low resolution look up tables lead to significant deviations between the simulated and measured results. As a result of this study, an appropriate EOS model and sufficient resolution of the look-up table for turbines operating at supercritical region are suggested.

Non-equilibrium condensation of steam occurs in many jet and turbomachinery devices, such as supersonic nozzles, ejectors and across the last stages of steam turbines. Wet steam models are available in many commercial CFD codes and can represent the metastable behaviour of the flow with reasonable accuracy. Unfortunately, the use of built-in models does not allow freedom in the choice of model parameters and settings. In the present paper, a numerical model for the simulation of wet steam flow has been developed and implemented within a commercial CFD code (ANSYS Fluent) via user defined functions. The scheme is based on a single-fluid approach and solves the transport equation for a homogeneous mixture flow coupled with conservation equations for the number of droplets and liquid mass fraction. The model is compared against a well-known steam nozzle test-case.

This paper presents the results of the application of a shape-optimization technique to the design of the stator and the rotor of a centrifugal turbine conceived for Organic Rankine Cycle (ORC) applications. Centrifugal turbines have the potential to compete with axial or radial-inflow turbines in a relevant range of applications, and are now receiving scientific as well as industrial recognition. However, the non-conventional character of the centrifugal turbine layout, combined with the typical effects induced by the use of organic fluids, leads to challenging design difficulties. For this reason, the design of optimal blades for centrifugal ORC turbines demands the application of high-fidelity computational tools. In this work, the optimal aerodynamic design is achieved by applying a non-intrusive, gradient-free, CFD-based method implemented in the in-house software FORMA (Fluid-dynamic Opti-mizeR for turboMachinery Aerofoils), specifically developed for the shape optimization of turbomachinery profiles. FORMA was applied to optimize the shape of the stator and the rotor of a transonic centrifugal turbine stage, which exhibits a significant radial effect, high aerodynamic loading, and severe non-ideal gas effects. The optimization of the single blade rows allows improving considerably the stage performance, with respect to a baseline geometric configuration constructed with classical aerodynamic methods. Furthermore, time-resolved simulations of the coupled stator-rotor configuration shows that the optimization allows to reduce considerably the unsteady stator-rotor interaction and, thus, the aerodynamic forcing acting on the blades.

The dynamic response of line-cavity systems in ideal and non-ideal compressible-fluid conditions is investigated numerically using the SU2 open-source suite for multi-physics simulations. The response of the system is studied for small but finite pressure perturbations, to predict the behaviour of fast-response pressure probes in turbomachinery for gas and ORC power systems. The probe step-response is found to present significant damping due to non-linear wave propagation. Non-idealities in the close proximity of the liquid-vapour curve increase the signal damping due to non-monotone variations of the speed of sound. A simplified approach is proposed to predict the probe dynamic characteristics in ideal regime. The estimation of the probe dynamics in non-ideal regime is found to be very critical and to strongly depend on the thermodynamic state of the fluid. The present results provides a guideline for the design of fast-response pressure probes to be used e.g. past the rotor stage of ORC turbine vanes.

In today's competitive environment, new turbomachinery designs need to be not only more efficient, quieter, and “greener” but also need to be developed at on much shorter time scales and at lower costs. A number of advanced optimization strategies have been developed to achieve these requirements. This paper reviews recent progress in turbomachinery design optimization to solve real-world aerodynamic problems, especially for compressors and turbines. This review covers the following topics that are important for optimizing turbomachinery designs. (1) optimization methods, (2) stochastic optimization combined with blade parameterization methods and the design of experiment methods, (3) gradient-based optimization methods for compressors and turbines and (4) data mining techniques for Pareto Fronts. We also present our own insights regarding the current research trends and the future optimization of turbomachinery designs.

Hydraulic turbines include stationary and rotating components. The interaction of the components, mainly between the runner blades and distributor vanes, is critical when the frequency of the rotor-stator interaction (RSI) approaches the runner natural frequency. This causes resonance in the turbine runner and the premature failure of the blades. Several turbines have experienced such problems in the last few years. The studies indicated that the added mass effect causes change in natural frequency of the runner. In the critical conditions, when the runner natural frequency is close to the RSI frequency, hydrodynamic damping is an important parameter in controlling turbomachinery blade-forced response. A reliable technique that can predict/estimate the change in the runner natural frequency due to added mass has yet to be developed. This paper reviews the investigations conducted on fluid structure interaction (FSI) focusing on the role of hydrodynamic damping during resonance, RSI and added mass effect. In specific, the review includes: (1) role of boundary layer to improve the damping effect, (2) how nearby structure and submergence level changes the damping effect, (3) dependency on mode-shape, (4) how freestream velocity and vortex shedding helps to increase damping, (5) damping during cavitation, (6) damping variation with respect to a dimensionless β parameter and (7) damping effect during rotation. In the summary, need for the future study of FSI within the field of hydropower and how damping is important in avoiding the catastrophic failures in the early life of hydraulic turbines is discussed. This is the authors' accepted and refereed manuscript to the article. Locked until 31 July 2019 due to copyright restrictions

The use of brush seals in turbomachinery has increased steadily in recent years because they reduce leakage and improve operating stability. This study evaluates the performance enhancement of a 500 MW-class steam turbine plant that results from replacing conventional seals with brush add-up seals for the inter-stage packing seal locations. Leakage flow rates of all seal locations in high- and intermediate-pressure turbines were estimated, and the brush add-up seal was found to reduce leakage by 50–68%. The entire power plant was simulated using a stage-by-stage turbine model and stage efficiency correction. With the advanced seals in all inter-stage locations of the high- and intermediate-pressure turbines, 0.44% and 0.33% increases in power output and efficiency were predicted. A larger performance benefit was observed with the installation in the high-pressure turbine. An economic analysis shows that the seal replacement is quite cost-effective. The predicted net present value was quite large compared to the initial cost, and the estimated payback period was less than a year. The replacement in all the high-pressure turbine stages and in the front stages of the intermediate-pressure turbine stages has the highest business value.

Large-scale dynamics of high Reynolds industrial rotor/stator cavities is poorly understood today, although it remains critical in determining operating margins for many devices. For space applicat...

Mistuning can dangerously increase the vibration amplitude of the forced response of a turbomachinery rotor. In the case of damping coming from aerodynamic effects the situation is more complicated because the magnitude of the damping changes for the different travelling wave modes of the system. This damping variability modifies the effect of mistuning, and it can even result in a reduction of the mistuned forced response amplitude below that of the tuned case (this is not possible in the usual case of constant material damping). In this paper the Asymptotic Mistuning Model (AMM) methodology is used to analyze this situation. The AMM is a reduced order model that is systematically derived from the mistuned bladed disk full model using a perturbative procedure based on the small size of the mistuning and the damping. The AMM allows to derive a very simple expression for an upper bound of the maximum amplification factor of the vibration amplitude that the system can experience (an extension of the well known Whitehead 1966 result to include the effect of non-uniform aerodamping). This new upper bound gives information on the mechanisms involved in the amplification/reduction of the mistuned response: (i) the number of modes participating in the response, and (ii) the ratio between the aerodamping of the directly forced mode and that of the of the rest of the modes. A FEM of a mistuned bladed disk is also used to verify the AMM predictions for several different forcing configurations, and both results show a very good quantitative agreement.

Combined cycles using Solid oxide fuel cells (SOFCs) are expected to provide very high efficiency. The SOFCs are combined with a Gas turbine (GT) or a Gas turbine combined cycle (GTCC). The major SOFC design parameters greatly impact the combined cycle efficiency because the SOFC still produces a majority of the electricity in the combined cycles. In this paper, the influence of the SOFC’s fuel utilization on the efficiency of the combined cycles is carried out using parametric analysis. It is demonstrated and validated that an optimal fuel utilization exists. Four types of SOFC/GT and SOFC/GTCC combined cycles are analyzed. Each combined cycle is found to have an optimal fuel utilization, which is always lower than that of the SOFC-alone system. The main reason is that the turbine inlet temperature rises and thus GT or GTCC power increases with decreasing fuel utilization because of the increased remaining fuel after the cell stack. The value decreases as the power share of the turbomachinery part increases. The peak efficiencies of the SOFC/GT and SOFC/GTCC were predicted to be over 72 % and 76 %. The optimal fuel utilization corresponding to peak efficiency was 0.8 for the SOFC-alone system, 0.7 for the SOFC/GT system, and 0.6 for the SOFC/GTCC system.