bluuebunny/crossref_metadata_2025 huggingface dataset:
The Teaching Value of Defining Iterative Design Projects in Serving Capstone Engineering Undergraduate Education
Authors: Mirzamoghadam Alexander V. , Harding Jacob C.
Published: November 2013

In the past several years, the traditional fourth year “hands-on” requirement for engineering programs in the US is being satisfied by what is now called Capstone Senior Design Project (herein referred to as CSDP). The engineering CSDP program director sends a call to the local industries within the State for solicitation of project proposals that will be worked on by the interdisciplinary engineering student team. Each industrial participant will have to contribute a preset budget defined by the program to the engineering school for each submitted proposal that has been selected by the student team. Honeywell has been an avid participant in the University of Arizona CSDP program for the past several years. Rather than define a simple CSDP that can be fully completed in the first attempt, the author has sought the value of teaching iterative design to the student team by defining a multi-year CSDP scope, in that after the first year, each successive team learns from the past design and implements its own improvement to the design it inherits. This paper gives an overview of Honeywell’s CSDP titled “Measuring Heat Transfer in Annular Flow Between Co-Rotating or Counter-Rotating Cylinders”. Now in its fourth iteration, each wave of student team has been able to understand the complexity of the design, the challenge of testing for structural integrity, the controllability of implementing a balanced system of heat gain and loss to reach steady state operation, the evolution of starting with slip ring temperature measurements and ending at wireless telemetry, DOE testing to rank influencing variables, and heat transfer correlation of the data relating Nusselt versus Reynolds number. Beginning with the first year CSDP team, this paper covers the design approach selected by that team, its results, and the lessons learned as a result of failure in meeting the full requirements, which is then taken on by the next group of students the following year.
A New Procedure for Predicting NOx Emission in Preliminary Gas Turbine Combustor Design
Authors: Xu Kang , Shen Suhua , Li Chenkai , Zheng Lipeng
Published: November 2013

A novel method has been developed for predicting flow field by a set of physics-based and empirical equations which provide inputs to a chemical reactor networks (CRN) composed of Perfectly Stirred Reactors (PSR) and Plug Flow Reactors (PFR), allowing rapid and reasonable analysis of NOx emissions. The method is applied to a rectangular section of a gas turbine combustor and the simulation results are compared with experimental results. The CRN has been established and successfully validated for baseline operating conditions. This methodology has shown to be efficient for estimating NOx emissions with a short simulation time (few minutes) and small CPU requirements.
Study on Zero CO2 Emission Atmospheric Pressure SOFC Hybrid Power System Integrated With OTM
Authors: Duan Liqiang , Huang Kexin , Yang Yongping , Chen Xinming , Song Xiaohui , Pan Xiang
Published: November 2013

Based on a benchmark SOFC hybrid power system without CO2 capture, a zero CO2 emission atmospheric pressure SOFC hybrid power system integrated with oxygen ion transport membrane (OTM) is proposed. The oxygen is produced by the OTM for the oxy-fuel combustion afterburner, and the anode outlet gas of the SOFC is injected into the afterburner and then burns with the oxygen from OTM. So the combustion products of the afterburner are only composed of CO2 and H2O, CO2 in the flue gas can be separated and captured by a simple condensation method. After the recovery of heat and work by the heat recovery steam generator (HRSG) and steam turbine, part of the outlet flue gas from the HRSG is injected into the afterburner to reduce the outlet flue gas temperature of the afterburner to about 1100°C, 200°C higher than the operating temperature of OTM. The rest exits the system and CO2 is captured. The fuel utilization factor of SOFC and the pressure ratio (π) between two sides of OTM membrane as the key factors which greatly influence the overall system performance are analyzed and optimized. The research results show that the efficiency of the zero CO2 emission atmospheric pressure SOFC hybrid power system integrated with OTM is around 58.36%, only 2.48% lower than that of the benchmark system (60.84%) but 0.96% higher than that of the zero CO2 emission atmospheric pressure SOFC hybrid system integrated with the cryogenic air separation unit. The research achievements from this paper will help for further study on zero CO2 emissions SOFC hybrid power system with higher efficiency.
Soot Formation and Flame Characterization of an Aero-Engine Model Combustor Burning Ethylene at Elevated Pressure
Authors: Geigle Klaus Peter , Hadef Redjem , Meier Wolfgang
Published: November 2013

Swirl-stabilized, non-premixed ethylene/air flames were investigated at pressures up to 5 bars to study the effect of different operating parameters on soot formation and oxidation. Focus of the experiments was the establishment of a data base describing well defined flames, serving for validation of numerical simulation. Good optical access via pressure chamber windows and combustion chamber windows enables application of laser-induced incandescence to derive soot volume fractions after suitable calibration. This results in ensemble averaged as well as instantaneous soot distributions. Beyond pressure, parameters under study were the equivalence ratio, thermal power and amount of oxidation air. Latter could be injected radially into the combustor downstream of the main reaction zone through holes in the combustion chamber posts. Combustion air was introduced through a dual swirl injector whose two flow rates were controlled separately. The split of those air flows provided an additional parameter variation. Nominal power of the operating points was approximately 10 kW/bar leading to a maximum power of roughly 50 kW, not including oxidation air.
Heat Transfer and Pressure Loss Characteristics of Zig-Zag Channel With Rib-Turbulators
Authors: Siw Sin Chien , Chyu Minking K. , Alvin Mary Anne
Published: November 2013

This paper describes a detailed experimental study of rib-turbulators in a novel four-pass channel with 110 degree turns that exhibits a “zig-zag” pattern, and hence the name. The rectangular cross-sectional channel has the cross-section of 63.5mm by 25.4mm, corresponding to the aspect ratio of 2.5:1. This specific design with several turns will generate additional secondary vortices, while providing longer flow path that allows coolant to remove a greater heat load before being discharged downstream. Heat transfer is further enhanced by the presence of rib-turbulators. Four test cases with different rib-configurations are explored and compared to the baseline case, the smooth zig-zag channel. For the first three cases, the rib pitch-to-height (p/e) ratio is 10 and height-to-hydraulic diameter (e/Dh) of 0.044. Larger ribs are used in the fourth case, giving the p/e ratio of 5, and e/Dh of 0.088. The local heat transfer coefficient of the entire zig-zag channel is determined using the transient liquid crystal technique. The Reynolds number is based on the hydraulic diameter of the channel and bulk mean velocity ranges from 15,000 up to 30,000. The heat transfer in the zig-zag channel is enhanced due to the additional vortices and bulk flow mixing induced by the presence of turns and ribs in the entire channel. The highest heat transfer is observed along each rib-turbulator, followed by the region immediately behind the rib-turbulators. However, the heat transfer at the corner of each turn remains low and unaffected by the presence of rib-turbulators. The zigzag channel with larger rib-turbulators exhibits the highest heat transfer enhancement at approximately 4.0–4.8 times higher than that of the smooth channel, followed by the other test cases with the heat transfer enhancement ranging from 2.5–3.5. In each zig-zag channel test case, although rib-turbulators have profound impact toward the heat transfer enhancement, with rather minimal increment in pressure loss within the tested Reynolds number.
Three-Dimensional Mass Fraction Distribution of a Spray Measured by X-Ray Computed Tomography
Authors: Coletti Filippo , Benson Michael J. , Sagues Alexander L. , Miller Benjamin H. , Fahrig Rebecca , Eaton John K.
Published: November 2013

In order to design a spraying system with the desired characteristics, the atomization process has to be understood in detail, including the primary break-up of the liquid core. Accurate prediction of primary break-up is a major barrier to computer-based analysis of spray combustion. The development of models is hindered by the lack of validation data in a region where the fluid is dense, and optical access is therefore limited.

The present experimental study is aimed at probing the spray structure by means of X-ray computed tomography (CT). A full-cone atomizer (0.79 mm orifice diameter) spraying in air at ambient pressure is investigated as a proof of concept. A mixture of water and iodine is used as the working fluid, providing elevated X-ray absorption and therefore improved signal-to-noise ratio. Several hundreds of X-ray projections are acquired as the spraying atomizer is rotated in front of the detector. Standard software for medical imaging is used to reconstruct the three-dimensional time-averaged distribution of liquid mass fraction in the full field of view, from the intact liquid core to the dilute spray region. A spatial resolution of 0.6 mm is obtained along the spraying direction, while the resolution is 0.3 mm in the other two directions. Significant asymmetries in the structure of the spray are revealed.
Operating Performance and Wear Investigations of Brush Seals for Steam Turbine Applications
Authors: Raben M. , Schwarz H. , Friedrichs J.
Published: November 2013

In recent years brush seals have become more and more an established alternative to existing labyrinth seals due to their increased pressure difference capability per stage in combination with a radial adaptive characteristic. In general brush seal and shaft should be in a concentric position. To utilize the special advantages of a brush seal system the radial adaptive capability of the seal’s bristle pack has to be achieved and guaranteed for the entire operation time. Every mechanism leading to a contact between the rotor and the seal will potentially cause an abrasive wear on both sides. In order to reduce this wear and to improve the operating performance of the brush seal, the influencing parameters resulting from the rotor eccentricity, the thermal gradient and the blown down characteristic of the bristle pack itself have to be understood. For this purpose the TU Braunschweig developed a unique steam test rig for brush seal investigations which allows live steam operations of single and multi stage brush seals up to 50 bar and 450 °C. Equipped with a 300 mm motor driven shaft, long time endurance tests under varying, transient operating conditions can be carried out. In addition to the steam test rig a second cold air test facility with an optical access and a force-displacement measurement unit is used. To analyse the operating bristle pack the brush seal packages and their characteristics were tested in detail under pressure gradients up to 8 bar. The paper shows the results of different seal designs with regards to the blow-down characteristics during a live steam endurance test. Based on these results especially the axial design of the brush seal was found to be an important parameter, since it has a significant influence on potential vibration behaviour of the bristle pack under specific load conditions. In contrast, the transient live steam measurements have shown that a limited amount of movement and vibrations enables an improved radial adaptiveness, leading to reduced leakages during transient operations. Finally the paper introduces a new rotor concept for the steam test rig for further investigations of the brush seal - rotor interaction. It enables the utilization of new and especially varying rotor materials for increased steam parameters as well as the detection of the heat introduction into the rotor during the operating time by rotor-integrated temperature probes.
Numerical Simulation on Ice Accretion Phenomena in Rotor-Stator Interaction Field
Authors: Hayashi Ryosuke , Yamamoto Makoto
Published: November 2013

Ice accretion is a phenomenon where super-cooled water droplets impinge and accrete on a body. On a jet engine, ice accretion disturbs the inlet flow, and separated ice pieces can damage to the turbine component, which leads to the severe performance degradation. We simulated icing phenomena in a fan rotor-stator interaction field [1]. This study mainly focused on the icing property at the rotor blade, because the maximum ice thickness of the rotor blade is about seven times larger than that of the stator vane. Moreover, in the study, the effect of the tip clearance was neglected because of the computational simplicity. Therefore, in the present study, we simulate icing phenomena in a rotor-stator interaction field, considering the tip clearance, to clarify the effect of the tip clearance on the ice accretion of the stator vane. The numerical results indicate the tip leakage vortex affect the icing phenomenon at the stator vane.
Siemens SGT-800 Industrial Gas Turbine Enhanced to 50MW: Combustor Design Modifications, Validation and Operation Experience
Authors: Lörstad Daniel , Lindholm Annika , Pettersson Jan , Björkman Mats , Hultmark Ingvar
Published: November 2013

Siemens Oil & Gas introduced an enhanced SGT-800 gas turbine during 2010. The new power rating is 50.5MW at a 38.3% electrical efficiency in simple cycle (ISO) and best in class combined-cycle performance of more than 55%, for improved fuel flexibility at low emissions. The updated components in the gas turbine are interchangeable from the existing 47MW rating. The increased power and improved efficiency are mainly obtained by improved compressor airfoil profiles and improved turbine aerodynamics and cooling air layout. The current paper is focused on the design modifications of the combustor parts and the combustion validation and operation experience.

The serial cooling system of the annular combustion chamber is improved using aerodynamically shaped liner cooling air inlet and reduced liner rib height to minimize the pressure drop and optimize the cooling layout to improve the life due to engine operation hours. The cold parts of the combustion chamber were redesigned using cast cooling struts where the variable thickness was optimized to maximize the cycle life. Due to fewer thicker vanes of the turbine stage #1, the combustor-turbine interface is accordingly updated to maintain the life requirements due to the upstream effect of the stronger pressure gradient.

Minor burner tuning is used which in combination with the previously introduced combustor passive damping results in low emissions for >50% load, which is insensitive to ambient conditions. The combustion system has shown excellent combustion stability properties, such as to rapid load changes and large flame temperature range at high loads, which leads to the possibility of single digit Dry Low Emission (DLE) NOx. The combustion system has also shown insensitivity to fuels of large content of hydrogen, different hydrocarbons, inerts and CO. Also DLE liquid operation shows low emissions for 50–100% load.

The first SGT-800 with 50.5MW rating was successfully tested during the Spring 2010 and the expected performance figures were confirmed. The fleet leader has, up to January 2013, accumulated >16000 Equivalent Operation Hours (EOH) and a planned follow up inspection made after 10000 EOH by boroscope of the hot section showed that the combustor was in good condition. This paper presents some details of the design work carried out during the development of the combustor design enhancement and the combustion operation experience from the first units.
PM Characteristics of Low NOx Combustor Burning Biodiesel and its Blends With Kerosene
Authors: Altaher Mohamed A. , Andrews Gordon E. , Li Hu
Published: November 2013

Particulate matter (PM) emissions from gas turbine engines have increasing attention due to their impact on global climate change, human health and local air quality. Most of the existing data for particle size distribution in aero engines is for diffusion or rich/lean type combustors where the rich zones generate solid nano particle carbon emissions. This work investigates well mixed lean low NOx combustion where mixing is good and generation of solid carbon particulate emissions should be very low. This work investigated the particulate number concentrations and size distributions of exhaust gases emitted from a radial swirler based low NOx gas turbine combustor. The tests were conducted using a radial swirler industrial low NOx gas turbine combustor under atmospheric pressure and 600K at reference Mach number of 0.017 and 0.023. A baseline of natural gas combustion was compared with a waste rape seed cooking oil methyl ester biodiesel (WME), its blend with kerosene B20, B50 and pure kerosene. The particulate emissions were compared as a function of the lean well mixed primary zone equivalence ratio. A SMPS with a Nano-Differential Mobility Analyzer (NDMA) was used to determine the number and concentration and size distribution of aerosols. The results showed that all WME particulates showed unimodal distribution characteristics with peak particle number at around 20nm. Conversion of the number distribution to mass showed very low mass emissions of around 1 mg/kgfuel. Modern low NOx engines such as the Trent 970-84 has carbon mass emissions of 9 mg/kgfuel based on the ICAO FOA-3 procedures. Thus, it is not unreasonable that in much lower NOx combustor designs the solid mass emissions will be lower than in current low NOx engines. Comparison is also made with particulate emissions from a diffusion flame APU gas turbine and much higher particle number emissions were demonstrated.
Simulation of Solarized Combined Cycles: Comparison Between Hybrid GT and ISCC Plants
Authors: Barigozzi G. , Franchini G. , Perdichizzi A. , Ravelli S.
Published: November 2013

The present paper investigates two different Solarized Combined Cycle layout configurations. In the first scheme, a solarized gas turbine is coupled to a solar tower. Pressurized air at compressor exit is sent to the solar tower receiver before entering the GT combustor. Here temperature is increased up to the nominal turbine inlet value through natural gas combustion. In the second CC layout, solar energy is collected by line focusing parabolic trough collectors and used to produce superheated steam in addition to the one generated in the heat recovery boiler. The goal of the paper is to compare the thermodynamic performance of these CSP technologies when working under realistic operating conditions. Commercial software and in-house computer codes were combined together to predict CSP plant performance both on design and off-design conditions. Plant simulations have shown the beneficial effect of introducing solar energy at high temperature in the Joule-Brayton cycle and the drawback in terms of GT performance penalization due to solarization. Results of yearly simulations on a one hour basis for the two considered plant configurations are presented and discussed. Main thermodynamic parameters such temperatures, pressure levels, air and steam flow rates are reported for two representative days.
Techno-Economic Evaluation of an IGCC Power Plant With Carbon Capture
Authors: Majoumerd Mohammad Mansouri , Assadi Mohsen , Breuhaus Peter
Published: November 2013

Most of the scenarios presented by different actors and organizations in the energy sector predict an increasing power demand in the coming years mainly due to the world’s population growth. Meanwhile, global warming is still one of the planet’s main concerns and carbon capture and sequestration is considered one of the key alternatives to mitigate greenhouse gas emissions. The integrated gasification combined cycle (IGCC) power plant is a coal-derived power production technology which facilitates the pre-combustion capture of CO2 emissions.

After the establishment of the baseline configuration of the IGCC plant with CO2 capture (reported in GT2011-45701), a techno-economic evaluation of the whole IGCC system is presented in this paper. Based on publicly available literature, a database was established to evaluate the cost of electricity (COE) for the plant using relevant cost scaling factors for the existing sub-systems, cost index, and financial parameters (such as discount rate and inflation rate). Moreover, an economic comparison has been carried out between the baseline IGCC plant, a natural gas combined cycle (NGCC), and a supercritical pulverized coal (SCPC) plant.

The calculation results confirm that an IGCC plant is 180% more expensive than the NGCC. The overall efficiency of the IGCC plant with CO2 capture is 35.7% (LHV basis), the total plant cost (TPC) is 3,786 US$/kW, and the COE is 160 US$/MWh.
Effect of Leading Edge Roughness and Reynolds Number on Compressor Profile Loss
Authors: Im Ju Hyun , Shin Ju Hyun , Hobson Garth V. , Song Seung Jin , Millsaps Knox T.
Published: November 2013

An experimental investigation has been conducted to characterize the influence of leading edge roughness and Reynolds number on compressor cascade profile loss. Tests have been conducted in a low-speed linear compressor cascade at Reynolds numbers between 210,000 and 640,000. Blade loading and loss have been measured with pressure taps and pneumatic probes. In addition, a two-component laser-doppler velocimeter (LDV) has been used to measure the boundary layer velocity profiles and turbulence levels at various chordwise locations near the blade suction surface. The “smooth” blade has a centerline-averaged roughness (Ra) of 0.62 μm. The “rough” blade is roughened by covering the leading edge of the “smooth” blade, including 2% of the pressure side and 2% of the suction side, with a 100 μm-thick tape with a roughness Ra of 4.97 μm. At Reynolds numbers ranging from 210,000 to 380,000, the leading edge roughness decreases loss slightly. At Reynolds number of 210,000, the leading edge roughness reduces the size of the suction side laminar separation bubble and turbulence level in the turbulent boundary layer after reattachment. Thus, the leading edge roughness reduces displacement and momentum thicknesses as well as profile loss at Reynolds number of 210,000. However, the same leading edge roughness increases loss significantly for Re = 450,000 ∼ 640,000. At Reynolds number of 640,000, the leading edge roughness decreases the magnitude of the favorable pressure gradient for axial chordwise locations less than 0.41 and induces turbulent separation for axial chordwise locations greater than 0.63, drastically increasing loss. Thus, roughness limited to the leading edge still has a profound effect on the compressor flow field.
On the Performance of Porous Sound Absorbent Ceramic Lining in a Combustion Chamber Test Rig
Authors: Ries Hans-Christoph , Carlesso Mateus Vieira , Eigenbrod Christian , Kroll Stephen , Rezwan Kurosch
Published: November 2013

This paper discusses the potential of using porous ceramic lining as insulating material in combustion chambers with respect to their sound absorbent ability to suppress thermoacoustic instabilities. For this purpose a combustion chamber test rig was developed and different types of ceramic linings were tested. The examined range of power was between 40 and 250 kW and the air-propane equivalence ratio was between 1.2 and 2.0. The overall sound pressure level and frequency domain of a lean premixed swirl stabilized and piloted burner are presented. The resonance frequencies and sound pressure levels are obtained and compared for the different combustion chamber linings. The results show a significant decrease in overall sound pressure level by up to 23.5 dB for sound absorbent lining in comparison to the common sound reflecting combustion chamber lining. In summary, sound absorbent ceramic combustion chamber lining can contribute to improve the stability of lean premixed gas turbines.
First and Second Law Analysis of Future Aircraft Engines
Authors: Grönstedt Tomas , Irannezhad Mohammad , Lei Xu , Thulin Oskar , Lundbladh Anders
Published: November 2013

An optimal baseline turbofan cycle designed for a performance level expected to be available around year 2050 is established. Detailed performance data are given in take-off, top of climb and cruise to support the analysis. Losses are analyzed based on a combined use of the first and second law of thermodynamics, to establish a basis for discussion on future radical engine concepts and to quantify loss levels of very high performance engines. In the light of the performance of the future baseline engine, three radical cycles designed to reduce the observed major loss sources are introduced. The combined use of a first and second law analysis of an open rotor engine, an intercooled recuperated engine and an engine working with a pulse detonation combustion core is presented. In the past, virtually no attention has been paid to the systematic quantification of the irreversibility rates of such radical concepts. Previous research on this topic has concentrated on the analysis of the turbojet and the turbofan engine. In the framework developed, the irreversibility rates are quantified through the calculation of the exergy destruction per unit time. A striking strength of the analysis is that it establishes a common currency for comparing losses originating from very different physical sources of irreversibility. This substantially reduces the complexity of analyzing and comparing losses in aero engines. In particular, the analysis sheds new light on how the intercooled recuperated engine establishes its performance benefits.
Turbulent Flame Speed as an Indicator for Flashback Propensity of Hydrogen-Rich Fuel Gases
Authors: Lin Y.-C. , Daniele S. , Jansohn P. , Boulouchos K.
Published: November 2013

The turbulent flame speed (ST) is proposed to be an indicator of flashback propensity for hydrogen-rich fuel gases at gas turbine relevant conditions. Flashback is an inevitable issue to be concerned about when introducing fuel gases containing high hydrogen content to gas turbine engines, which are conventionally fueled with natural gas. These hydrogen-containing fuel gases are present in the process of the integrated gasification combined cycle (IGCC) with and without pre-combustion carbon capture, and both syngas (H2 + CO) and hydrogen with various degree of inert dilution fall in this category. More understanding on the flashback phenomenon for these mixtures is thus necessary in order to evolve the IGCC concept (either with or without carbon capture) into a promising candidate for clean power generation.

Compared to syngas, the hydrogen-rich fuel mixtures exhibit an even narrower operational envelope between the occurrence of lean blow out and flashback. When flashback occurs, the flame propagation is found to happen exclusively in the boundary layer of the pipe supplying the premixed fuel/air mixture to the combustor. This finding is based on the experimental investigation of turbulent, lean-premixed, non-swirled, confined jet flames for three fuel mixtures with H2 > 70 Vol. %. Measurements were performed up to 10 bar at fixed bulk velocity at the combustor inlet (u0 = 40 m/s) and preheat temperature (T0 = 623 K). Flame front characteristics were retrieved via OH-PLIF diagnostics, and turbulent flame speed (ST) was derived accordingly from the perspective of a global consumption rate.

Concerning the flashback limit, the operational range of the hydrogen-rich mixtures is found to be well represented by the velocity gradients prescribed respectively by the flame (gc) and the flow (gf). The former (gc) is determined as ST/(Le × δL0), where Le is the Lewis number and δL0 is the calculated thermal thickness of the one-dimensional laminar flame. The latter (gf) is predicted by the Blasius correlation for fully developed turbulent pipe flow, and it indicates the capability with which the flow can counteract the opposed flame propagation. Our results show that the equivalence ratios at which the two velocity gradients reach similar levels correspond well to the flashback limits observed at various pressures. The methodology is also found to be capable of predicting the aforementioned difference in the operational range between syngas and hydrogen-rich mixtures.
Evaluation of Reduced Kinetics in Simulation of Gasified Biomass Gas Combustion
Authors: Zhang Xiaoxiang , Munjat Nur Farizan , Jayasuriya Jeevan , Fakhrai Reza , Fransson Torsten
Published: November 2013

It is essentially important to use appropriate chemical kinetic models in the simulation process of gas turbine combustion. To integrate the detailed kinetics into complex combustion simulations has proven to be a computationally expensive task with tens to thousands of elementary reaction steps. It has been suggested that an appropriate simplified kinetics which are computationally efficient could be used instead. Therefore reduced kinetics are often used in CFD simulation of gas turbine combustion. At the same time, simplified kinetics for specific fuels and operation conditions need to be carefully selected to fulfill the accuracy requirements. The applicability of several simplified kinetics for premixed Gasified Biomass Gas (GBG) and air combustion are evaluated in this paper.

The current work is motivated by the growing demand of gasified biomass gas (GBG) fueled combustion. Even though simplified kinetic schemes developed for hydrocarbon combustions are published by various researchers, there is little research has been found in literature to evaluate the ability of the simplified chemical kinetics for the GBG combustion. The numerical Simulation tool “CANTERA” is used in the current study for the comparison of both detailed and simplified chemical kinetics. A simulated gas mixture of CO/H2/CH4/CO2/N2 is used for the current evaluation, since the fluctuation of GBG components may have an unpredictable influence on the simulation results. The laminar flame speed has an important influence with flame stability, extinction limits and turbulent flame speed, here it is chosen as an indicator for validation. The simulation results are compared with the experimental data from the previous study [1] which is done by our colleagues. Water vapour which has shown a dilution effect in the experimental study are also put into concern for further validation. As the results indicate, the reduced kinetics which are developed for hydrocarbon or hydrogen combustion need to be highly optimized before using them for GBG combustion. Further optimization of the reduced kinetics is done for GBG and moderate results are achieved using the optimized kinetics compared with the detailed combustion kinetics.
Numerical Investigation of Improving Turbine Sealing Effectiveness Through Slot Width Modification of the Rim Seal
Authors: Zhang Jinghui , Ma Hongwei
Published: November 2013

The hot gas in the main annulus of a gas turbine can ingest into the rotor-stator cavities through the rim seal clearance as a result of the interaction of the rotor and the stator disks and the external flow in the hot gas annulus. To prevent the turbine root region from being heated up, this ingestion has to be avoided almost completely. This paper introduces a new idea to improve turbine sealing effectiveness through slot width modification of the rim seal. Unsteady numerical simulations are performed with two different rim seal geometries at the design condition with different cooling flow rates. Both of the rim seal geometries are simple axial seal configurations. One is uniform slot rim seal geometry and is taken as the reference case. The other is a new kind of rim seal geometry with slot width modification. The clearance is bigger in the main flow path and smaller in the stator wake region keeping the area of the two kinds of rim seal surfaces equivalent.

The sealing air egress happens in the main path flow region and the ingestion happens in the stator wake region. Through comparing the results of the two kinds of rim seal geometries, it is found out that the contoured slot rim seal geometry can reduce the pressure in the cavity which leads to the decrease of the gas turbine loss. The inward radial velocity of the ingestion increases in the stator wake region and hence the axial seal gap has been reduced in this region. The time-averaged outward radial velocity decreases in the main flow region and becomes more uniform. Unsteady flow patterns in the rim seal region are compared for the two seal configurations. The sealing effectiveness is rapidly improved by using the contoured seal configuration. This work provides an idea to increase the sealing effectiveness and decrease the pressure in the cavity.
A Novel Gas Generator Concept for Jet Engines Using a Rotating Combustion Chamber
Authors: Jeschke Peter , Penkner Andreas
Published: November 2013

A gas generator — consisting of a single-stage shrouded mixed-flow compressor without a diffusor, a rotating combustion chamber, and a vaneless single-stage shrouded centripetal turbine — is presented and analyzed here. All components comprise a coherent rotating device, which avoids most of the problems usually associated with small gas generators. In other words, the concept avoids all radial clearances, it is vaneless, shortens the combustion chamber, minimizes the wetted area and enables ceramic materials to be used, due to compressive blade stresses. However, the concept faces severe structural, thermal and chemical reaction challenges. All these features and their implications are discussed and their benefits for several jet engines are quantified, mainly by means of thermodynamic cycle calculations. An upfront CFD analysis identifies a polytropic compressor efficiency of around 95%. It is then demonstrated that the concept offers a thrust-to-weight ratio which is several times higher than the standard when incorporated into small UAV-type jet engines. It also enables an attractive multistage and dual-flow, but fully vaneless design option. Lastly, a thermal efficiency increase of several percentage points would be achieved, if the concept were to be realized in the (small) core of turbofans with highest overall pressure ratios and high bypass ratios.

In summary, the paper presents a gas generator approach which may be considered by designers of small jet engines like those used in UAV applications and it might even be a (challenging) long-term option for the small core engines encountered in future turbofans and turboprops.
Numerical Analysis of Three-Dimensional Corner Separation in a Linear Compressor Cascade
Authors: Gao Feng , Ma Wei , Boudet Jérôme , Ottavy Xavier , Lu Lipeng , Lebœuf Francis
Published: November 2013

Nowadays, the internal flow in aircraft engine compressors can be quite accurately reproduced at design condition by the CFD tools. However, CFD generally fails to simulate some singular 3D phenomena, near off-design conditions, such as the corner separation. Studies have pointed out that the separation regions are often over-estimated when the flow state is far from design condition, owing to the turbulence model. Much work is devoted to improving the capability of the turbulence model in capturing the onset and the extent of the corner separation, which is desired in the designing procedures.

In this paper, steady RANS simulations are carried out in the same configuration as an experiment of Ma et al. These simulations are obtained with a high-precision in-house Navier-Stokes solver (Turb’Flow). With the same mesh, an unsteady simulation (URANS) is subsequently presented, in order to investigate the influence of a fluctuating inflow.

Attention is focused on a specific angle of attack of 4 degrees, for which the three-dimensional corner separation is clearly observed. For the unsteady simulation, unsteadiness is imposed through perturbations of the angle of attack at the inlet. The results of the steady and unsteady computations are analyzed and compared with those of the experiment. The time-averaged URANS results agree well with the RANS results. The fluctuating inflow does not show much influence on the mean performance of the compressor cascade. The onset of the corner separation occurs earlier in the simulations than in the experiment, considering the blade surface pressure and the passage velocity profiles. However, the cross-stream extent of the corner separation appears slightly under-estimated by CFD, according to the outlet total pressure losses and the passage velocity profiles. Finally, the URANS simulation allows to recover bi-modal PDFs, as observed in the experiment.
Hydrodynamic Air-Riding in Leaf Seals
Authors: Jahn Ingo H. J. , Gillespie David , Cooper Paul
Published: November 2013

Leaf seals are filament seals for use at static to rotating interfaces in rotating machinery. They are capable of withstanding significant pressure differences while minimising leakage. One of their advantages over comparable filament seals is the ability of the leaves to generate significant hydrodynamic lift at their tips. If this force is sufficient to lift the leaf tip away from the rotor, leaf wear is eliminated and an infinite life seal is created. In order to design seals that are capable of operating in this mode, a good understanding of the hydrodynamic effect and how it interacts with the seal is required. This paper presents a detailed theoretical and experimental investigation into hydrodynamic air-riding in leaf seals. First the hydrodynamic lift is investigated by analysing the flow field and forces generated between a static structure resembling the leaf tip geometry and a moving surface resembling the rotor. This allows the fundamental effects behind air-riding to be identified and quantified. Next a coupled model is presented, which captures the interactions between the lift force and the leaf tip movements. This gives a full picture of the steady-state fluid-structure interactions controlling air-riding in leaf seals. Based on these results several guidelines for obtaining air-riding are extracted. Finally the predictions from the coupled model are compared to results from a high speed test campaign using a prototype leaf seal. Good agreement is found, confirming the presence of hydrodynamic air-riding in leaf seals and demonstrating the accuracy of the presented coupled model.
CFD Best Practices to Predict NOx, CO and Lean Blowout for Combustor Design
Authors: Ajmani Kumud , Mongia Hukam , Lee Phil
Published: November 2013

An effort was undertaken to identify best practices for CFD analysis of fluid flow in Lean-Direct Injection (LDI) combustors with swirl-venturi swirlers for next-generation LDI design. The National Combustion Code (NCC) was used to perform non-reacting and reacting computations on several LDI injector configurations in a 3×3 element array with different vane angles. Non-reacting and reacting computations were performed with single and multi-element LDI configurations, with a consistent approach to mesh-optimization, spray-modeling and kinetics-modeling with the NCC. Computational predictions of NOx emissions index were compared with experimental data. CFD values of CO were used to assess lean blow-out predictive capability for two different multi-element, LDI configurations and compared to experimental data.
Effects of Simplified Platform Overlap and Cavity Geometry on the Endwall Flow: Measurements and Computations in a Low-Speed Linear Turbine Cascade
Authors: MacIsaac G. D. , Sjolander S. A. , Praisner T. J. , Grover E. A. , Jurek R.
Published: November 2013

Incorporating the platform overlap and endwall cavity into the early stages of turbine CFD analyses is desirable from the perspective of accurately capturing the near endwall flow features. However, the overlap and cavity geometry increase the complexity of the computational domain making CFD meshes more difficult to generate and the CFD solutions more resource intensive. Thus, geometric approximations are often made to simplify the CFD analysis. This paper examines, experimentally, the secondary flows of a linear turbine cascade with three different platform overlap geometries, two of which incorporate geometric simplifications. These are then compared with the corresponding computations.

Experimental measurements were collected using a seven-hole pressure probe at a plane located 40% of the axial chord downstream of the trailing edge. Steady-state computational predictions were performed using ANSYS CFX 12.0 and employed the SST transition turbulence model.

The experimental results show that the presence of an upstream rim-seal creates a stronger passage vortex, relative to a flat endwall, resulting in larger integrated losses as well as higher levels of secondary kinetic energy and streamwise vorticity. Subtle differences in the strength of the passage vortex and the associated losses are observed for the simplified geometries in both the measured and predicted results. By examining the details of the cavity flow, a recirculation zone is identified which energizes the formation of the passage vortex. The effect of the recirculation zone may be attenuated or intensified by the rim-seal geometry. The paper concludes by addressing the validity and usefulness of the proposed platform overlap simplifications in design-oriented computations.
Response of Liquid Jet to Modulated Crossflow
Authors: Song Jinkwan , Ramasubramanian Chandrasekar , Lee Jong Guen
Published: November 2013

Experimental results on the response of spray formed by the liquid (Jet-A) jet injection into a crossflow (Air) is presented with a special emphasis on its response to the modulating crossflow. The pressure of the chamber is up to 3.5 atm and the corresponding Weber number is up to 510. The spray of a liquid jet for steady and oscillating crossflow is characterized. The flow field at the injector location in the crossflow direction is determined using PIV (Particle Image Velocimetry) for oscillating as well as steady crossflow case. Planar Mie-scattering measurement is used to characterize the response of spray formed under oscillating crossflow and supplementary phase-averaged PDPA measurements are used to understand the response behavior. The global response of spray to the oscillating crossflow is characterized using the planar Mie-scattering imaging. It shows that there exist very little differences in the heights of the maximum-pixel intensity trajectory for the non-oscillating and oscillating crossflow conditions and the trajectory under oscillating crossflow is lower than that of steady crossflow, suggesting the oscillating crossflow affects the atomization (i.e. the oscillating crossflow enhances atomization process, results in smaller droplets and penetrates less transversely). The response of spray to the oscillating crossflow characterized in terms of the spray transfer function (STF) shows that the gain of the STF increases linearly (at least monotonically) as the liquid-air momentum flux ratio increases but does not change as much with respect to the change of the Weber number for a fixed liquid-air momentum flux ratio. This also indicates that the liquid jet atomization under oscillating crossflow is enhanced much more with the increase of liquid-air momentum flux ratio than with the increase of Weber number. The phase-averaged PDPA measurements confirm that the oscillating crossflow indeed enhances the atomization process in that the oscillating crossflow results in relatively greater number of smaller droplets and the mean droplet size.
Fault Tolerant Supervision of an Industrial Gas Turbine
Authors: Larsson Emil , Åslund Jan , Frisk Erik , Eriksson Lars
Published: November 2013

Supervision of the performance of an industrial gas turbine is important since it gives valuable information of the process health and makes efficient determination of compressor wash intervals possible. Slowly varying sensor faults can easily be misinterpreted as performance degradations and result in an unnecessary compressor wash. Here, a diagnostic algorithm is carefully combined with non-linear state observers to achieve fault tolerant performance estimation. The proposed approach is evaluated in an experimental case study with six months of measurement data from a gas turbine site. The investigation shows that faults in all gas path instrumentation sensors are detectable and isolable. A key result of the case study is the ability to detect and isolate a slowly varying sensor fault in the discharge temperature sensor after the compressor. The fault is detected and isolated before the wash condition of the compressor is triggered, resulting in fault tolerant estimation of compressor health parameters.
Evaluation of the Shortcomings of Current Engine Technology Stack-Up Methods and Suggestions for Improvement
Authors: Perullo Christopher A. , Kestner Brian K. , Tai Jimmy C. M. , Schutte Jeff S. , Mavris Dimitri N.
Published: November 2013

There are currently numerous government and industry entities engaging in aviation technology development programs [1,2,3]. Due to the number of technologies being investigated there exists an understandable desire to rank technologies in order to identify the most beneficial ones. Historically, this has been done through the use of “waterfall” or technology stack-up charts [4].One purpose of such waterfall charts is to show the amount of benefit each technology provides to the integrated system. This approach is valid, and extremely useful, for verifying the modeling of such technologies; however, there are shortcomings in using a waterfall chart to assess the relative contribution of individual technologies to the overall system level benefit. This is due to several considerations that are not taken into account when developing conventional technology ranking charts. For example, the relative impact of each technology can be highly dependent on the order in which technologies are applied, the system the technology is applied to, the relative design changes that occur either before or after the technology is applied, and other technologies that are present on the system. In order to explore these characteristics this paper uses propulsion technologies since there are strong interactions between the various components of an engine. Engine technologies also commonly rely upon enabling technologies which provide less benefit, but without them the larger “bigger hitting” technologies are not feasible.

This research explores and quantifies the issues associated with several conventional methods of creating technology ranking charts. Propulsion technologies targeting both thermal and propulsive efficiency are applied to a baseline aircraft and engine configuration. Several conventional technology ranking and stack-up techniques are applied in order to evaluate how the relative impacts of individual technologies vary greatly depending on the assessment method. In all cases the same technology packages are applied such that the final benefit is the same, regardless of ranking method. It is suggested that a range of currently used ranking techniques all used to determine a more robust estimate of the impact.