bluuebunny/crossref_metadata_2025 huggingface dataset:
Student Research Projects With Industrial Impact
Authors: Grimshaw S. D. , Clark C. J. , Taylor J. V. , Spataro R.
Published: September 2021

This paper describes six final year undergraduate research projects supported by a collaboration between the Whittle Laboratory at the University of Cambridge and Reaction Engines (RE), a UK aerospace company. The collaboration is now in its fourth year of projects relating to RE’s Synergetic Air Breathing Rocket Engine (SABRE).

The approach taken in these projects combines modern teaching pedagogy with a best practice methodology for industrial-academic collaboration and a well established framework for structuring research problems. This paper explains how the three methodologies are tailored and adapted for use with final year undergraduate research projects.

The approach is mapped on to an annual project cycle which begins with the industry and academic partners deciding which topics to investigate and proceeds through student selection, the project work itself and concludes with student assessment and end-of-year reporting. The projects combine analytical, computational and experimental work and have covered counter-rotating turbomachinery, S-ducts in compressors and Helium Turbine design, all of which are topics of primary importance to the design of SABRE.

Following descriptions of each of the six completed projects, the impact of the work and lessons learned are considered from the point of view of the students, the industrial partner and the academic supervisors. Overall, the students found the work extremely engaging and have all been encouraged to pursue careers in engineering, either in industry or through post-graduate study. For the industry partner the collaboration provides expertise and an approach which is not available in-house as well providing a ‘second look’ at key technical questions. For the academics involved, the opportunity to lead research on a ‘real’ problem with an industrial partner has proved highly motivating as well as providing opportunities for personal and career development.
An Analytical Two-Phase Flow Model for Prediction of Leakage in Wet Gas Labyrinth Seals and Pocket Damper Seals. Is Simplicity Still Desired?
Authors: Yang Jing , San Andrés Luis
Published: September 2021

Current and upcoming two-phase pump and compression systems in subsea production facilities must demonstrate long-term operation and continuous availability. Annular pressure seals, limiting secondary flow, also influence the dynamic stability of turbomachinery. Hence, it becomes paramount to quantify the leakage and dynamic force coefficients of annular seals operating with two-phase flow, a liquid in gas mixture or wet gas. Until now, a simple model for labyrinth seals (LSs) and the more modern pocket damper seals (PDSs) is not available, though these seal types find wide applications in subsea machinery. The paper develops a simple analytical model predicting the leakage and cavity pressures for LSs and PDSs operating with two-phase flow. The model adapts Neumann’s leakage equation for use with the physical properties of a homogeneous two-phase flow mixture. Predictions of leakage for a four-blade, eight-pocket, fully partitioned PDS operating under a low supply pressure (PS = 2.3 bar and 3.2 bar) and a low rotor speed equal to 5,250 rpm (surface speed = 35 m/s) agree well with experimental results procured for both a pure gas and a wet gas conditions (2.2% in liquid volume). Predicted leakage and cavity pressures also agree with those found by a multi-million node computational fluid dynamics (CFD) model. For an eight-blade, sixteen-pocket PDS supplied with air at PS = 62.1 bar, discharge pressure Pa = 31.1 bar and rotor speed of 15 krpm (surface speed = 91 m/s), the analytical model predicts leakage that is just 2% larger than a published CFD prediction. For the PDS supplied with an oil in gas mixture having gas volume fraction βS = 0.92 ∼ 0.98, the simple model delivers leakage that is up to ∼ 6% lower than published CFD results. An analysis of the two-phase leakage predictions via a modified flow factor reveals a loss coefficient (cd) impervious to the range of supply and discharge pressures considered and growing in proportion to the liquid volume fraction. Throughout the life of an oil well that sees radical changes in gas and liquid composition as well as pressure conditions, the expedient model, quick and accurate to estimate leakage in wet gases seals, can be readily integrated into an engineering routine or practice.
Preliminary Design Tool for Centrifugal Compressors
Authors: Baye-Wallace Lily , Musgrove Grant O.
Published: September 2021

Commonly, compressor designs rely on previous machines that can be slightly modified to achieve new operating requirements. In some cases, however, a completely new design is needed because no previous designs are available for the specific operating range of interest. Without a previous design, it is difficult to make initial trade studies of an appropriate impeller diameter, speed, and number of compression stages. While new compressor designs are a common occurrence in applied research applications, conceptual design typically require a point-by-point process to balance the requirements with acceptable design parameters. This can be done manually or through automation to optimize for a specific operating parameter, such as efficiency. The authors are unaware of any tool available that bounds the range of design parameters for a centrifugal compressor stage without applying a point-by-point method. In this work, two common references for conceptual compressor design were cross-checked to develop an Excel-based tool to quickly determine the design space for a given set of compressor requirements.

The tool relies on design experience presented by Aungier and Baljé as well as other experience drawn from available literature [1],[2]. The sheet functions from a series of assumptions based within the design experience and requires inputs regarding the desired power, fluid flow rate, and total-to-total pressure ratio, as well as inlet conditions. While the tool currently assumes an ideal gas, future revisions can include calls to REFPROP for a real gas.
Numerical Simulation on the Vortex Shedding From Airfoils of a Swirl Distortion Generator
Authors: Hayden Andrew , Hefner Cole , Untaroiu Alexandrina , Gillespie John , Lowe K. Todd
Published: September 2021

The StreamVane™ swirl distortion generator, developed by Virginia Tech, can efficiently reproduce the boundary layer of an airframe or duct found in boundary layer ingesting (BLI) aircraft. Due to manufacturing limitations, the vanes within StreamVanes induce unsteady, vortical wakes, commonly known as a von Karman vortex street. This paper investigates the use of a commercial URANS code and SST turbulence model to predict the vortex shedding frequency from the vanes. The objective was accomplished in two main tasks. First, the CFD methodology was validated by modeling the fluid dynamics of a linear cascade experiment done by the von Karman Institute. Second, the same methodology was applied to airfoils used in StreamVane design to calculate the shedding frequency as a function of turning angle and TE thickness. It was predicted that an increase in turning angle exponentially increased the shedding frequency while an increase in TE thickness exponentially decreased the shedding frequency. The results provided a correlation between the shedding frequency and airfoil characteristics in StreamVanes as well as various turbomachinery components.
Extending a Van der Pol Based Reduced-Order Model for Fluid-Structure Interaction Applied to Non-Synchronous Vibrations in Turbomachinery
Authors: Hollenbach Richard , Kielb Robert , Hall Kenneth
Published: September 2021

This paper expands upon a multi-degree-of-freedom, Van der Pol oscillator used to model buffet and Nonsynchronous Vibrations (NSV) in turbines. Two degrees-of-freedom are used, a fluid tracking variable incorporating a Van der Pol oscillator and a classic spring, mass, damper mounted cylinder variable; thus, this model is one of fluid-structure interaction. This model has been previously shown to exhibit the two main aspects of NSV. The first is the lock-in or entrainment phenomenon of the fluid shedding frequency jumping onto the natural frequency of the oscillator, while the second is a stable limit cycle oscillation (LCO) once the transient solution disappears. Improvements are made to the previous model to better understand this aeroelastic phenomenon. First, an error minimizing technique through a system identification method is used to tune the coefficients in the Reduced Order Model (ROM) to improve the accuracy in comparison to experimental data. Secondly, a cubic stiffness term is added to the fluid equation; this term is often seen in the Duffing Oscillator equation, which allows this ROM to capture the experimental behavior more accurately, seen in previous literature. The finalized model captures the experimental cylinder data found in literature much better than the previous model. These improvements also open the door for future models, such as that of a pitching airfoil or a turbomachinery blade, to create a preliminary design tool for studying NSV in turbomachinery.
The STEP 10 MWe sCO2 Pilot Demonstration Status Update
Authors: Marion John , Lariviere Brian , McClung Aaron , Mortzheim Jason
Published: September 2021

The Gas Technology Institute (GTI®), Southwest Research Institute® (SwRI®) and General Electric Global Research (GEGR) are executing the “STEP” [Supercritical Transformational Electric Power] project, to design, construct, commission, and operate an integrated and reconfigurable 10 MWe sCO2 [supercritical CO2] pilot plant test facility. The $122* million project is funded $84 million by the US DOE’s National Energy Technology Laboratory (NETL Award Number DE-FE0028979) and $38* million (*including building investment) by the team members, component suppliers and others interested in sCO2 technology. This paper provides an update on the project’s progress. The pilot facility is currently under construction at SwRI’s San Antonio, Texas, USA campus. Now well into Phase 2, a ground-breaking was held in October of 2018, and civil work and the construction of a dedicated 22,000 ft2 building is complete. Most major equipment is in fabrication or delivered to site. Efforts have already provided valuable project learnings for technology commercialization. This project is a significant step toward sCO2 cycle based power generation commercialization and is informing the performance, operability, and scale-up to commercial plants.
High-Fidelity Simulations of a High-Pressure Turbine Stage: Effects of Reynolds Number and Inlet Turbulence
Authors: Zhao Yaomin , Sandberg Richard D.
Published: September 2021

We present the first wall-resolved high-fidelity simulations of high-pressure turbine (HPT) stages at engine-relevant conditions. A series of cases have been performed to investigate the effects of varying Reynolds numbers and inlet turbulence on the aerothermal behavior of the stage. While all of the cases have similar mean pressure distribution, the cases with higher Reynolds number show larger amplitude wall shear stress and enhanced heat fluxes around the vane and rotor blades. Moreover, higher-amplitude turbulence fluctuations at the inlet enhance heat transfer on the pressure-side and induce early transition on the suction-side of the vane, although the rotor blade boundary layers are not significantly affected. In addition to the time-averaged results, phase-lock averaged statistics are also collected to characterize the evolution of the stator wakes in the rotor passages. It is shown that the stretching and deformation of the stator wakes is dominated by the mean flow shear, and their interactions with the rotor blades can significantly intensify the heat transfer on the suction side. For the first time, the recently proposed entropy analysis has been applied to phase-lock averaged flow fields, which enables a quantitative characterization of the different mechanisms responsible for the unsteady losses of the stages. The results indicate that the losses related to the evolution of the stator wakes is mainly caused by the turbulence production, i.e. the direct interaction between the wake fluctuations and the mean flow shear through the rotor passages.
Turbine Inlet Temperature Measurements in a T 8200 kW Gas Turbine Using Water Vapor Emission
Authors: Tree Dale R. , Badger Dustin , Zeltner Darrel , Rezasoltani Mohsen
Published: September 2021

The measurement of turbine inlet temperature is challenging because of high temperatures and complicated physical access, but continuous measurement of the turbine inlet temperature is very important for maximizing turbine efficiency and increasing durability. This paper provides in-situ turbine rotor inlet temperature (TRIT) measurements in an 8200 kW operating gas turbine engine. The measurements were obtained using integrated spectral infrared (ISIR) emission from the water vapor of the combustion gases entering the turbine rotor. The method utilizes a sapphire optical fiber to convey the signal from the turbine wall to outside the turbine casing. All components are capable of long-term exposure to the turbine operating conditions. The temperature measurements were obtained at 6 operating conditions between 50% and full load. The TRIT temperature was also determined using more than 20 test cell inputs and Solar Turbine’s commercial test cell engine model. The two temperatures (measured and modeled) were within 11 K (less than 1%) across the load sweep. Uncertainty calculations suggest that the uncertainty of the measurement can be expected to be ±2.9% within a confidence interval of 95%. The method also yields the nozzle guide vane surface temperature which was found to increase monotonically with increasing load.
Optimization of Fuel Nozzle Diameter in a Novel Cross Flow Lean Direct Injection Burner
Authors: Chakraborty Kingshuk , Chakravarthy S. R.
Published: September 2021

Lean Direct Injection (LDI) concept proves to be an ultra-low NOx combustion scheme for future gas turbine combustors because of its ability to operate at very lean conditions. For LDI burners, the Fuel Nozzle Diameters (FND) play a vital role in deciding a balance between the various performance criteria demanded by the gas turbine industry like efficient usage of fuel, a wide range of flame stability, uniform exit temperature distribution and very low overall emissions. This paper attempts to find the optimum FND in terms of some key combustion parameters, for a novel multi-swirl LDI burner having a cross-flow mixing between fuel jets and swirling air. At first, lean blow out limits were detected from experiments with different FND using two different fuels, methane and liquefied petroleum gas, within a range of air flow rates. It was observed that with the decrease in FND the flame extinguished at a higher equivalence-ratio. Then their performances were compared through CFD simulations with two different combustion models, namely, Eddy Dissipation and PDF Flamelet. The combined results of cold and hot flow simulations showed that with the decrease in FND the fuel jet was able to penetrate deeper into the air swirl by overcoming the air momentum, which resulted in enhanced mixing leading to more efficient utilization of fuel and also uniform exit temperature distribution resulting in lower pattern factor. Thus the findings of this research work should be resourceful in the development of modern cross-flow LDI combustors.
Film Cooling Effectiveness Measurement of Fan-Shaped Holes Manufactured Using EDM Technique
Authors: Rouina S. , Abdeh H. , Barigozzi G. , Odemondo V. , Abba L. , Iannone M.
Published: September 2021

In this study, the influence of geometric factors such as hole diameter (D), length-to-diameter ratio (L/D), injection angle (α), and lateral expansion angle (β) on film cooling effectiveness of holes made using EDM is experimentally investigated. Nine different cooling configurations were tested on a flat plate wind tunnel at various coolant Reynolds number (Rec) and coolant to mainstream blowing ratio (M). The considered flat plate model incorporates engine sized V-shaped holes. EDM reliability is assessed through a hole qualification process, while effectiveness was measured by the Pressure Sensitive Paint (PSP) technique. Results confirm the suitability of EDM for V-shaped hole manufacturing as long as a correct tolerance on β is prescribed. An accurate qualification of hole morphology is also recommended.
Practical Method for Burner Staging Turbine Forced Response Evaluation
Authors: Kafedzhiyski Nikola , Mayorca Maria
Published: September 2021

Decarbonization and sustainability efforts challenge gas turbine engineers to come up with creative strategies for reduction of emissions and efficiency increase over the whole operating range. Burner staging at part loads presents a flexible solution to achieve these goals through selective burner deactivation. Shutting off burners could also be required for combustion of increased H2 content at some conditions. Burner staging will create circumferential unevenness with patterns of hot and cold streaks that could excite blade rows through the entire turbine. This paper presents a parametric method for annular combustor staging patterns profile generation intended for use for forced response predictions from a limited number of combustor CFD calculations while keeping the key phenomenological features. Two cases with burner staging turbine inlet temperature distributions are considered and compared to a base case with uniform temperature distribution. The unsteady aerodynamic forcing was obtained from full wheel time marching unsteady computational fluid dynamics calculations. The results show that the hot streaks generate important and noticeable excitation sources. Additionally, the results show that the pattern generator could be used extensively before and after the unsteady calculations phase to minimize the excitation levels and the computational load.
Flow Fields, Emission and Stabilization in Premixed Centrally-Staged Swirl Flames With Different Air Split Ratios
Authors: Su Tong , Lin Yuzhen , Zhang Chi , Han Xiao
Published: September 2021

The flow fields, emission levels, and static stability characteristics were investigated experimentally under various air split ratios (ASR, the ratio of the pilot stage air mass flow rate to the total air mass flow rate) at a fixed equivalence ratio of 0.8 of both main and pilot stages in a premixed centrally-staged swirl flame. The flame structures were captured by a CH* chemiluminescence high-speed camera and the corresponding results were processed by Abel deconvolution. Besides, the flow fields obtained by using planar Particle Image Velocimetry (PIV) technique were combined with flame structures to make a better study on the aerodynamic structures of the centrally-staged swirl flames. The emission levels of NOx and CO were measured by a gas analyzer. The stability boundaries and flame structures at different equivalence ratios under three ASRs were also studied.

It is found that the size of the reacting primary recirculation zone (PRZ) becomes larger as more air is distributed to the pilot stage. This can be explained by the fact that the majority of the pilot fluid participates in the formation of the PRZ and also as a result of a stronger penetrability of the pilot jet. Moreover, the NOx emission levels increase while CO levels decrease, which is because of the longer residence time of the radicals within a larger PRZ and less impingement of the main flame on the combustor liner. Finally, the stability boundary is extended, and the total blowout equivalence ratio was decreased as the air split ratio increases, which demonstrates the flame stabilization effect of the pilot flame. In brief, the above findings can be a help to choose the appropriate air split ratio in the early design stage of the centrally-staged aero-engine combustors.
Development of a Robust Scrubber Level Controller
Authors: Day Carolyn M. , Beck Griffin C. , Schubring Scott A.
Published: September 2021

Gas-liquid scrubbers rely on level control systems (generally consisting of a level indicator, a level controller, and a pneumatic control valve for liquid release) to maintain an appropriate liquid level within the vessel. Scrubbers are often upstream of turbomachinery and failures at the scrubber can cause liquid ingestion or downtime. In natural gas service, these control systems are subject to harsh environments due to the influx of liquid slugs, high-velocity gases, corrosive fluids, vibrations, and a chaotic gas-liquid interface. In these severe conditions, level control system failures are commonplace and lead to safety and environmental hazards, equipment damage, and lost production. A need exists to augment or replace the typical liquid level control system with an alternative solution that is cost-effective, robust, and can operate reliably in the harsh natural gas environment. A project investigated failures related to scrubber level control systems, identified improvements to these systems, developed a prototype level controller, and tested the prototype controller and a variety of commercially available controllers at various conditions that emulated certain field conditions. The results of these tests gave insight into what type of controller may be best suited to the tested conditions and what controller options should be pursued further.
Unsteady Pressure Measurements in a Heated Rotating Cavity
Authors: Jackson Richard W. , Tang Hui , Scobie James A. , Pountney Oliver J. , Sangan Carl M. , Owen J. Michael , Lock Gary D.
Published: September 2021

The flow in the heated rotating cavity of an aero-engine compressor is driven by buoyancy forces, which result in pairs of cyclonic and anticyclonic vortices. The resultant cavity flow field is three-dimensional, unsteady and unstable, which makes it challenging to model the flow and heat transfer. In this paper, properties of the vortex structures are determined from novel unsteady pressure measurements collected on the rotating disc surface over a range of engine-representative parameters. These measurements are the first of their kind with practical significance to the engine designer and for validation of computational fluid dynamics. One cyclonic/anticyclonic vortex pair was detected over the experimental range, despite the measurement of harmonic modes in the frequency spectra at low Rossby numbers. It is shown that these modes were caused by unequal size vortices, with the cyclonic vortex the larger of the pair. The structures slipped relative to the discs at a speed typically around 10% to 15% of that of the rotor, but the speed of precession was often unsteady. The coherency, strength and slip of the vortex pair increased with the buoyancy parameter, due to the stronger buoyancy forces, but they were largely independent of the rotational Reynolds number.
Improved Prediction of Losses With Large Eddy Simulation in a Low-Pressure Turbine
Authors: Miki Kenji , Ameri Ali
Published: September 2021

There is a need to improve predictions of losses resulting from large eddy simulations (LES) of low-pressure turbines (LPT) in gas turbines. This may be done by assessing the accuracy of predictions against validation data and understanding the source of any inaccuracies. LES is a promising approach for capturing the laminar/turbulent transition process in a LPT. In previous studies, the authors utilized LES to model the flow field over a Variable Speed Power Turbine (VSPT) blade and successfully captured characteristic features of separation/reattachment and transition on the suction side at both the cruise (positive incidence) and take-off conditions (negative incidence) and as well, simulated the effect of free-stream turbulence (FST) on those phenomena. The predicted pressure loading profiles agreed well with the experimental data for both a high and a low FST case at a Reynolds number of Reex = 220,000. In this paper, we present wake profiles resulting from computations for a range of FST values. Although the predicted wake profiles for the lowest FST case (Tu = 0.5%) matched the experimental data, at higher FST (Tu = 10–15%,) the wake was wider than the experimentally measured wake and for both cases were displaced laterally when compared to the experimental measurements. In our investigation of the causes of the said discrepancies we have identified important effects which could strongly influence the predicted wake profile. Predicted losses were improved by assuring the validity of the flow solution. This was done by utilizing spectral analysis to scrutinize the dynamic behavior of the wake and determine solution accuracy resulting from low mesh density and low accuracy of convective modeling.
Numerical Methods for Calculating Component Modes for Geometric Mistuning Reduced-Order Models
Authors: Beck Joseph A. , Brown Jeffrey M. , Kaszynski Alex A. , Gillaugh Daniel L.
Published: September 2021

Geometric mistuning models formulated from a component mode synthesis methods often require the calculation of component modes, particularly constraint and fixed interface normal modes, during substructuring. For Integrally Bladed Rotors, these calculations are required for each sector. This paper proposes methods that reuse information garnered from solving the constraint modes of a single sector on the remaining sectors to reduce memory requirements and solution times. A mesh metamorphosis tool is used to ensure finite element models match geometry obtained from a 3D optical scanner. This tool also produces a common mesh pattern from sector-to-sector. This is exploited to produce common permutation matrices and symbolic factorizations of sector stiffness matrices that are proposed for reuse in solving subsequent constraint modes. Furthermore, a drop tolerance is introduced to remove small values during constraint mode calculation to reduce memory requirements. It is proposed to reuse this dropping pattern produced from a single sector on the remaining sectors. Approaches are then extended to a parallel processing scheme to propose effective matrix partitioning methods. Finally, information gathered during the constraint mode calculations are reused during the solution of the fixed interface normal modes to improve solution time. Results show reusing permutation matrices and symbolic factorizations from sector-to-sector improves solution time and introduces no error. Using a drop tolerance is shown to reduce storage requirements of a constraint mode matrix. Additionally, it is shown that reusing the same dropping pattern introduces minimal error without degradation in solution times. Similarly, reusing the information from constraint modes for calculating fixed interface normal modes greatly improves the performance in a shift-and-invert technique for solving eigenvalue problems.
Measurements of Static and Dynamic Load Performance of a 102 mm Carbon-Graphite Porous Surface Tilting-Pad Gas Journal Bearing
Authors: San Andrés Luis , Bolen Rachel , Yang Jing , McGowan Ryan
Published: September 2021

Aerostatic journal bearings with porous tilting pads enable shaft support with minute drag power losses. To date archival information on the static and dynamic load performance of this bearing type is scant. Thus, the paper presents measurements conducted with an air lubricated bearing with diameter d = 102 mm and comprising four tilting pads made of porous carbon-graphite, each with length L = 76 mm. Two nested Belleville washers resting on spherical pivots support each pad. At ambient temperature of ∼ 21°C, as the air supply pressure into the bearing pads increases, so does the bearing aerostatic specific load (F/(L·d)) that reaches 58% of the pressure difference, supply minus ambient. With an air supply pressure of 7.8 bar(a), the test bearing static stiffness KS = 13.1 MN/m, is independent of both shaft speed and static load. KS is just 63% of the washers’ stiffness KP = 20.6 MN/m (during loading). While operating with shaft speeds equal to 6 krpm and 9 krpm (150 Hz) and under specific loads to 115 kPa and 101 kPa respectively, dynamic load experiments with excitation frequencies up to 342 Hz show the test bearing supplied with air at 7.8 bar(a) has frequency independent stiffness (K) and damping (C) coefficients. For rotor speeds equaling 0, 6 and 9 krpm, the bearing direct stiffnesses KXX ∼ KYY range from 13.6 MN/m to 32.7 MN/m as the specific load increases from 0 kPa to 115 kPa. The direct damping coefficients CXX ∼ CYY are as large as 5.8 kN·s/m, though having a large experimental uncertainty. Bearing cross-coupled force coefficients are insignificant. The test porous gas bearing reached its intended load capacity, demonstrated a dynamically stable operation and produced force coefficients mainly affected by the pads’ pivot supports and the magnitude of air supply pressurization.
Aeroderivative Gas Turbine Enclosure Ventilation System
Authors: Yerram Ravinder , Watkins Richard , Ponnuraj Balakrishnan
Published: September 2021

GE Aeroderivative Gas Turbines are derived from GE’s Aircraft engine family and converted to Land and Marine applications. As these Aeroderivative Gas Turbines are relatively smaller in size for similar power capacity in comparison to Heavy Duty Gas Turbines, there is a great need of developing efficient and compact turbine enclosure ventilation system for proper cooling and ventilation. Ineffective ventilation flow distribution inside the gas turbine enclosure causes engine circumferential nonuniform temperature distribution and it allows the formation of explosive fuel gas pockets inside the enclosure in the unlikely event of fuel leaks. Also, the engine nonuniform circumferential temperature gradient has an adverse impact on the operational efficiency and/or the mechanical integrity of the turbine. Proper cooling and ventilation system will also protect the sensitive equipment, like fuel valve actuators or any other instruments inside the turbine enclosure due to excessive radiation heat from engine hot surfaces, mainly near combustor and power turbine region. All the expected but significant engine leakages into the enclosure are estimated and considered for selection of right size, type, placing of ventilation fan at different operating conditions like full load, part load, elevation and ambient conditions. For first step, a 3D Computational Fluid Dynamics (CFD) analyses were done for turbine enclosure with mass/volumetric flow rate, temperature, and pressure boundary conditions to understand the flow/temperature distribution inside the enclosure. Radiation boundary conditions are applied on the engine casing external surfaces, enclosure walls and roof. The convective heat transfer from the hot surfaces are computed by CFD model based on the velocity and temperature predictions. In next step, from CFD analysis, identified the poor ventilation/stagnation zones using low velocity and recirculation areas close to the gas fuel components. After identifying the poor ventilation regions, a gas leak was introduced to see whether gas cloud volume is within the ISO 21789 – 2009 limits. From gas leak analysis results, enclosure outlet IR detector settings were decided and implemented to monitor the gas leak amount and feedback to control system in the form of ALARM/SHUTDOWN so that Gas Turbine operates safely.
Experimental Investigation and Optimal Design on the Film Cooling Performance of Fan-Shaped Hole With Vortex Generator Fed by Crossflow
Authors: Wang Jie , Zhang Chao , Liu Xuebin , Song Liming , Li Jun , Feng Zhenping
Published: September 2021

Aiming at investigating the effects of crossflow and vortex generator on film cooling characteristics of fan-shaped hole, the film cooling performance was measured experimentally by infrared camera. The blowing ratio is fixed at 0.5 and 1.5. The Reynolds number of the mainstream based on the hole diameter remains at 7000 and the inlet Reynolds number of crossflow is 40000. The experimental results show that the film cooling performance becomes better when the blowing ratio increases from 0.5 to 1.5 for each model, and the film cooling performance becomes worse under the influence of crossflow. When the blowing ratio is 1.5, the area-averaged film cooling effectiveness of the fan-shaped hole model with vortex generator decreases by 16.6% because of the influence of crossflow. The combined model always performs better compared with the model without vortex generator under all working conditions. When the blowing ratio becomes 1.5, under the influence of crossflow, the area-averaged film cooling effectiveness of the combined model could increase by 14.8%, compared with the model without vortex generator. To further improve the film cooling performance, the global optimization algorithm based on the Kriging method and the CFD technology are coupled to optimize the combined model under crossflow condition at the high blowing ratio, and the optimized design is verified by experiments. The experimental results show that the area-averaged film cooling effectiveness of the optimized design increases by 17.8% compared with the reference model.
Forced Response Excitation of a Compressor Stator Owing to Shock Wave Induced by Adjacent Rotor Blade
Authors: Miura Toshimasa , Sakai Naoto , Kanazawa Naoki , Nakayama Kentaro
Published: September 2021

The accurate prediction of high cycle fatigue (HCF) is becoming one of the key technologies in the design process of state-of-the-art axial compressors. If they are not properly designed, both rotor blades and stator vanes can be damaged. There are two main factors to cause HCF. One is low engine order (LEO) and the other is high engine order (HEO) excitation by fluid force associated with adjacent rotor-stator interaction. For the front stages of axial compressors for power generations and aero engines, the inlet Mach number of a rotor tip typically exceeds the speed of sound and strong shock waves tend to be induced. This can be the source of HEO excitation fluid force, and adjacent stator vanes are sometimes severely damaged. Thus, the aim of this study is to establish an efficient method for predicting the vibration response in this type of problem with high accuracy. To achieve this, numerical investigations are carried out by one-way fluid structure interaction (FSI) simulation. To validate the accuracy of FSI simulation, experiments are also conducted using a gas turbine engine for power generation. In the experiment, the vibration level is measured with strain gauges mounted on the surface of stator vanes and the data are compared with the predicted results.

In the first part of the study, efficient prediction methods of excitation fluid force on the stator vane are investigated by time transformation (TT) and harmonic balance (HB) methods. Their accuracies are evaluated by comparing the results with those calculated by transient rotor stator (TRS) simulation whose pitch ratio is one between rotor and stator computational domains. It is found that the TT method can accurately predict the excitation fluid force with lower computation load even when there are pitch differences between rotor and stator regions.

In the second part of the study, forced response analyses are carried out using the excitation fluid force obtained in the unsteady flow simulation. To obtain the total damping of the system, both hammering test and flutter simulations are carried out. Computed results are validated with experimental data and it is found that the predicted vibration level is in good agreement with experimental results.

Through this study, the effectiveness of one-way FSI simulation is confirmed for this type of forced response prediction. By utilizing the combination of efficient unsteady computational fluid dynamics (CFD) methods and harmonic response analysis, vibration amplitude can be predicted accurately and efficiently.
Forced Response Excitation due to the Stator Vanes of Two and Three Compressor Stages Away
Authors: Miura Toshimasa , Sakai Naoto , Kanazawa Naoki , Nakayama Kentaro
Published: September 2021

State-of-the-art axial compressors of gas turbines employed in power generation plants and aero engines should have both high efficiency and small footprint. Thus, in many cases, axial compressors are designed to have thin rotor blades and stator vanes with short axial distances, and are driven at high rotational speed. Recently, problems of high cycle fatigue (HCF) associated with forced response excitation have gradually increased as a result of these trends. Rotor blade fatigue can be caused not only by the wake and potential effect of the adjacent stator vane, but also by the stator vanes of two, three or four compressor stages away. Thus, accurate prediction and suppression method of them under the resonance condition are necessary in the design process. Concerning the forced response excitation associated with the adjacent stator vanes, there are many previous studies on simulating the vibration by fluid structure interaction (FSI) simulation. In these studies, the aerodynamic force acting on the blade is simulated by an efficient unsteady computational fluid dynamics (CFD) method such as the nonlinear harmonic (NLH) method. These methods can be available in commercial CFD solvers and can significantly reduce computational cost. However, there are few examples of the problems associated with the stator vanes from two and three compressor stages away and no efficient simulation method is available. In this study, the problem of rotor blade vibration caused by the stator vanes of two and three compressor stages away is studied. Ways to accurately predict and effectively control the vibration are also investigated.

In the first part of the study, one-way FSI simulation is carried out using a full annulus CFD model. To validate the accuracy of the simulation, experiments are also conducted using a gas turbine test facility. The vibration level of the blade is measured using a blade tip timing (BTT) measurement system and the obtained results are compared with the simulated data. It is found that one-way FSI simulation can accurately predict the order of the vibration level.

In the second part of the study, a method of controlling the forced response excitation is investigated by optimizing the clocking of the stator vanes. It is confirmed that by controlling the clocking of the stator vanes, the vibration amplitude can be effectively suppressed without reducing the compressor performance.

Through this study, ways to evaluate and control the unsteady pressure force and vibration response of the rotor blade are validated. By optimizing the clocking of stator vanes, the blade vibration level can be effectively reduced.
Rotor-Blade Interaction During Blade Resonance Drive-Through
Authors: Grein Roland , Ehehalt Ulrich , Siewert Christian , Kill Norbert
Published: September 2021

In the future energy landscape, combined cycle power plants will increasingly take the role of providing balancing power for fluctuating renewable energy sources due to their high availability and fast start-up times. This implies more frequent cycling, a larger number of speed cycles and thus new challenges for plant design and operation. One of these challenges is a potential increase of cyclic fatigue incurred by last-stage blades during start-up and coast-down. Blade vibrations might be induced by synchronous shaft vibrations when the blade resonance is excited by lateral shaft vibrations. In this paper, we report measurement results of shaft and blade vibrations observed at some Siemens Energy steam turbines. Apart from the expected increase of blade vibrations when the double rotating speed crosses the blade resonance, a distinctive dip of shaft vibrations at the low-pressure turbine bearings is observed. We argue that this phenomenon is likely related to the aforementioned interaction between blade and shaft vibrations and present a theoretical framework to describe this interaction and the observed effect.
Development and Integration of the Dual Fuel Combustion System for the MGT Gas Turbine Family
Authors: Ćosić Bernhard , Reiß Frank , Blümer Marc , Frekers Christian , Genin Franklin , Pähr Judith , Waßmer Dominik
Published: September 2021

Industrial gas turbines like the MGT6000 are often operated as power supply or as mechanical drives for pumps and compressors at remote locations on islands and in deserts. Moreover, small gas turbines are used in CHP applications with a high need for availability. In these applications, liquid fuels like ‘Diesel Fuel No. 2’ can be used either as main fuel or as backup fuel if natural gas is not reliably available. The MAN Gas Turbines (MGT) operate with the Advanced Can Combustion (ACC) system, which is already capable of ultra-low NOx emissions for a variety of gaseous fuels. This system has been further developed to provide dry dual fuel capability to the MGT family. In the present paper, we describe the design and detailed experimental validation process of the liquid fuel injection, and its integration into the gas turbine package.

A central lance with an integrated two-stage nozzle is employed as a liquid pilot stage, enabling ignition and start-up of the engine on liquid fuel only, without the need for any additional atomizing air. The pilot stage is continuously operated to support further the flame stabilization across the load range, whereas the bulk of the liquid fuel is injected through the premixed combustor stage. The premixed stage comprises a set of four decentralized nozzles placed at the exit of the main air swirler. These premixed nozzles are based on fluidic oscillator atomizers, wherein a rapid and effective atomization of the liquid fuel is achieved through self-induced oscillations of the liquid fuel stream.

We present results of numerical and experimental investigations performed in the course of the development process illustrating the spray, hydrodynamic, and thermal performance of the pilot injectors. Extensive testing of the burner at atmospheric and full load high-pressure conditions has been performed, before verification of the whole combustion system within full engine tests. The burner shows excellent emission performance (NOx, CO, UHC, soot) without additional water injection, while maintaining the overall natural gas performance. Soot and particle emissions, quantified via several methods, are well below legal restrictions. Furthermore, when not in liquid fuel operation, a continuous purge of the injectors based on compressor outlet (p2) air has been laid out. Generic atmospheric coking tests were conducted before verifying the purge system in full engine tests. Thereby we completely avoid the need for an additional high-pressure auxiliary compressor or demineralized water. We show the design of the fuel supply and distribution system. We designed it to allow for rapid fuel switchovers from gaseous fuel to liquid fuel, and for sharp load jumps. Finally, we discuss the integration of the dual fuel system into the standard gas turbine package of the MGT6000 in detail.
Intercooler Parametric Analysis for the IRA Engine Cycle Performance Augmentation
Authors: Alexiou Emmanouil , Vlahostergios Zinon , Salpingidou Christina , Donus Fabian , Misirlis Dimitrios , Yakinthos Kyros
Published: September 2021

Aiming in the direction of designing high efficiency aircraft engines, various concepts have been developed in recent years, among which is the concept of the intercooled and recuperative aero engine (IRA engine). This concept is based on the use of a system of heat exchangers (recuperator) mounted inside the hot-gas exhaust nozzle, as well as a system of heat exchangers (intercooler) mounted between the intermittent-pressure compressor (IPC) and the high-pressure compressor (HPC) compressor modules. Through the operation of the system of recuperator module, the heat from the exhaust gas, downstream the LP turbine of the aero engine is driven back to the combustion chamber. Thus, the preheated air enters the engine combustion chamber with increased enthalpy, providing higher combustion efficiency and consequently reduced thrust specific fuel consumption (TSFC) and low-level emissions. Additionally, by integrating the intercooler module between the compressor stages of the aero engine, the compressed air is cooled, leading to less required compression work to reach the compressor target pressure and significant improvements can be achieved in the overall engine efficiency and the specific fuel consumption hence, contributing to the reduction of CO2 and NOx emissions.

The present work is focused on the optimization of the performance characteristics of an intercooler specifically designed for aero engine applications, working cooperatively with a novel design recuperator module targeting the reduction of specific fuel consumption and taking into consideration aero engine geometrical constraints and limitations for two separate operating scenarios. The intercooler design was based on the elliptically profiled tubular heat exchanger which was developed and invented by MTU Aero Engines AG. For the specific fuel consumption investigations, the Intercooled Recuperated Aero engine cycle that combines both intercooling and recuperation was considered. The optimization was performed with the development of an intercooler surrogate model, capable to incorporate major geometrical features. A large number of intercooler design scenarios was assessed, in which additional design criteria and constraints were applied. Thus, a significantly large intercooler design space was covered resulting to the identification of feasible designs providing beneficial effect on the Intercooled Recuperated Aero engine performance leading to reduced specific fuel consumption, reduced weight and extended aircraft range.
An Approach to Measure Total-Head in Wakes and Near End Walls at High Fogging Conditions
Authors: Harbeck Janneck , Geist Silvio , Schatz Markus
Published: September 2021

Evaporation cooling increases gas turbine power output. Experimental results suggest an 8% increase of power when 1% of the overall mass flow is added via water droplets injected upstream of the compressor. However, water injection has an impact on the flow field, which requires experimental research involving probe measurements in the droplet-laden flow as well as reliable monitoring during operation, as the volumetric flow rate throughout the stages changes notably and deviates from (dry) design parameters. Measuring with a conventional pressure probe in two-phase flows is challenging because the droplet-laden flow can clog the pressure taps, thus effectively separating the sensor from the measurement location. This paper presents a consistent approach to measure stagnation pressure in a droplet-laden flow field. The probe was purged constantly to prevent droplets from clogging the tubing. The recorded pressure is then corrected using a transfer function to account for the purging pressure offset. A detailed description of how to obtain this function is given within the paper. With this setup, the flow field downstream of a blade cascade was measured at several water mass fractions and spray characteristics. The pressure measurements are compared with the usual LDA/PDA measurements in the wake of the cascade. Based on the test results, an evaluation of the change of total-head loss due to water injection and evaporation compared to dry operation can be performed.