bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Injection Evaporation in Frame 7EA Gas Turbine Wrapper
Authors: Bianchi Michele , De Pascale Andrea , Melino Francesco , Peretto Antonio , Savic Sasha
Published: August 2017

A Southern California cogeneration plant is comprised of four GE-made Frame No 7, Model EA, heavy duty gas turbines driving Electrical Generators. Turbine exhaust gases are routed into the heat recovery steam generators (HRSG) of the split level. The HRSG are furnished with supplemental firing in order to boost the production of the steam.

The produced NOX abatement is realized by the continuous steam injection and selective catalyst reduction (SCR).

In order to reduce the steam consumption for NOX abatement, water injection in combustion chamber can be taken into account. Unfortunately, available gas turbine combustor cannot be used to inject water directly into the liner (and thus maximize the impact of water injection compared to steam injection); for this reason, an alternative solution was investigated which consists on water injection into the combustor wrapper. By doing this, effects on NOX abatement are similar to those of steam injection for power augmentation, namely only about 30% of water injected this way will actually quench the NOX, the rest flowing through the dilution holes. To ensure no impact of water injection on the combustor hardware’s integrity, any liquid droplets injected into the wrapper shall evaporate prior to reaching the liner.

In order to estimate the behavior of liquid water droplets injected into the wrapper, a calculation code was developed by University of Bologna. This calculation code is able to estimate the evaporation rate of a spray of liquid water by calculating the droplets diameter reduction, the air temperature drop, etc. as function of boundary conditions.

More in details, the aim of this study is to estimate the maximum droplet sizes to ensure the full evaporation of the water and to eliminate negative effects on the combustor life. In order to achieve this goal, a parametric study has been developed, changing the droplet size to calculate the time needed for full evaporation and compare this with the time of droplet travel from the injection point to the first dilution holes of the combustor liner. More in details, it was calculated, under various gas turbine operating conditions, what would be the maximal droplet size needed to evaporate within the available residence time into the wrapper.
Numerical Study of Counter Jet Formed by Impinging Jets in Cross-Flow and its Effect on Mixing
Authors: Epalle Thomas A. , Gaugain Fabien , Melot Vincent , Darabiha Nasser , Gicquel Olivier
Published: August 2017

In this paper we will numerically analyse flow mixing in multiple jets in a crossflow. The system comprises a row of six radially-distributed injectors around the main pipe. The configuration represents mixing zones in industrial systems where a counter jet can be formed in the injection plane. Flow mixing can be modified as a result of geometry and injection velocities. We propose a simple model to describe the counter jet length as a function of injection flow characteristics. We also develop empirical laws to help engineers design practical test facilities.

We then vary the velocity ratio to obtain both impinging and non-impinging jets in the injection plane. The focus is mainly on flow characteristics around the radial injection plane in the case of impinging jets, examining the mixing quality and efficiency by introducing a passive scalar discharge in a nitrogen flow. The mean velocity and width of the counter jet are finally analyzed by changing the injection velocities. These results are compared to those of non-impinging jets. It is found that the non-impinging jet configurations are convenient for short length mixing chambers, while the impinging ones should be considered in the case of longer mixing chambers.
Numerical Research of Aerodynamic Sweep on Leading Edge in the Ram-Rotor
Authors: Guan Jian , Han Ji-ang , Zhong Jingjun , Yuan Chenguang
Published: August 2017

In order to diminish the flow loss in the ram-rotor and improve its aerodynamic performance, the effect of forward and backward swept leading edge on flow field and shock pattern in the ram-rotor was investigated using 3-dimensional steady CFD. Ram-rotors with sweeping angles of −60°, −30°, −15°, 0°, 15°, 30°, 60° were modeled, and ram-rotor performance, shock pattern and leakage flow in different swept schemes were the main focuses of attention. The effect of sweeping angle was also discussed in this paper. It has been found that forward sweep makes performance curves move to high mass flow rate zone in the performance map. Meanwhile, strake tip loading decreases, and maximum adiabatic efficiency increases by 0.31% compared to baseline ram-rotor. Contrary to the forward swept scheme, performance curves of backward sweep schemes shift to small mass flow rate zone, and the tip leakage near front part of strake is enhanced. Backward sweep plays a positive role in improving pressure ratio with a maximum increment of 0.46% at peak efficiency point, but causes a high flow loss. As sweeping angle changes, there is an optimum angle value to get a high performance.
The Influences of Unbalance Mass, Mesh Density, and Bearing Clearance on Unbalance Response: Measurements and Analysis on a Rigid Rotor Supported by Hybrid Bump-Metal Mesh Foil Bearings
Authors: Zhao Xueyuan , Zhang Tao , Feng Kai
Published: August 2017

Hybrid bump-metal mesh foil bearings (HB-MFBs) are novel gas foil bearings (GFBs) that comprise foil strips and metal mesh blocks in bearing substructure. HB-MFBs have several advantages over previous GFBs, such as high structural damping, more precise size, dimensional stability, and highly efficient cooling management. This study designed and manufactured HB-MFBs and bump-type foil bearings (BFBs) with identical diameters and bearing clearances to compare their rotordynamic performance in a test rig with a rigid rotor supported by two GFBs and driven by an impulse turbine. The rotordynamic performance of the bearings in terms of mesh density, unbalance mass, and bearing clearance were measured and discussed by comparing the experimental results of the two types of test bearings. Experimental results show that the HB-MFBs can efficiently suppress the motion amplitude of subsynchronous vibrations of a rotor-bearing system at high rotational speed, although the added unbalance mass and bearing clearance vary in a large region.
Experimental and Numerical Verification of Effect of Using Curvilinear Element Blades for Low-Solidity Cascade Diffuser in Centrifugal Compressor
Authors: Tsukamoto Kazuhiro , Hiradate Kiyotaka , Sakamoto Kiyohide , Shinkawa Yasushi
Published: August 2017

The effect of using curvilinear element blades (CEBs) on a low-solidity cascade diffuser (LSD) in a centrifugal compressor was investigated both experimentally and numerically.

Centrifugal compressors require a higher efficiency and wider operating range to reduce the lifecycle costs of plants in which they are used and the effects their users have on the environment. A LSD has a wider operating range than a common vaned diffuser that has high solidity, but worse efficiency at the design point. For this reason, this research aims to improve the efficiency of the LSD and keep its operating range wide without changing the blade setting angle or two-dimensional geometry.

As a first step, LSDs with three different curvilinear element profiles were compared with a conventional LSD, and the mechanism of the performance improvement was investigated by using a numerical simulation. These diffusers have the same two-dimensional geometry, blade setting angle, and number of blades but different blade stacking geometry in the span-wise direction. Unsteady Reynolds Averaged Navier-Stokes (RANS) simulations were conducted using a one-blade path model with an inlet, impeller, and LSD diffuser passages.

The LSD using the CEBs improved the efficiency by 1.9% over that of the conventional LSD at the design point while maintaining the same operating range. The calculation results reveal that the recirculation region decreased at the suction surface of the diffuser vane in the CEB case and the diffuser efficiency improved. The concaved suction surface increased the blade loading and induced higher velocity on the suction surface. The higher velocity prevented reverse flow on the suction surface at the hub side, and the secondary flow removed the thick boundary layer at the trailing edge to the downstream of the diffuser.

Experimental verification was also conducted using a single-stage compressor with an impeller, diffuser, and scroll casing to verify the prediction. The experimental results showed the LSD using the CEB has a higher pressure rise at the stator region than the conventional LSD and verified the performance improvement due to using the CEBs.
Plausibility Study of Hecto Pressure Ratio Concepts in Large Civil Aero Engines
Authors: Klein Felix , Staudacher Stephan
Published: August 2017

Enabling high overall pressure ratios, wave rotors and piston concepts seem to be solutions surpassing gas turbine efficiency. Therefore, a comparison of a wave rotor and three piston concepts relative to a reference gas turbine is offered. The piston concepts include a Wankel, a 2-stroke reciprocating engine and a free-piston. All concepts are investigated with and without intercooling. An additional combustion chamber downstream the piston engine is investigated, too. The shaft power chosen corresponds to large civil turbofans. Relative to the reference gas turbine a maximum efficiency increase of 11.2 percent for the piston concepts and 9.8 percent for the intercooled wave rotor is demonstrated. These improvements are contrasted by a 5.8 percent increase in the intercooled reference gas turbine and a 4.2 percent increase due to improved gas turbine component efficiencies. Intercooling the higher component efficiency gas turbine leads to a 9.8 percent efficiency increase. Furthermore, the study demonstrates the high difference between intercooler and piston engine weight and a conflict between piston concept efficiency and chamber volume, highlighting the need for extreme lightweight design in any piston engine solution. Improving piston engine technology parameters is demonstrated to lead to higher efficiency, but not to a chamber volume reduction. Heat loss in the piston engines is identified as the major efficiency limiter.
Impact of Damper Parameters on the Stability Margin of an Annular Combustor Test Rig
Authors: Betz Michael , Wagner Michael , Zahn Max , Stadlmair Nicolai V. , Schulze Moritz , Hirsch Christoph , Sattelmayer Thomas
Published: August 2017

An experimental investigation of the influence of dampers on the stability margin of an atmospheric lab-scale annular combustor is presented. The rig allows the comparison of different damper configurations regarding the number of dampers, their spatial distribution and the amount of purge air used for temperature control. The porosity of the perforated plates at the damper exits as well as the influence of the purge air are systematically investigated. Eigenfrequencies and damping rates are computed from the acoustic pressures measured in the combustor with three different methods: The first method is based on the analysis of the decay of the pulsating pressures after sudden shut-down of sirens providing single frequency acoustic excitation. The second method employs Lorentzian fitting to the pressure spectra resulting from turbulent combustion noise and the third method consists of the analysis of the autocorrelation of the acoustic pressures. Since with all three methods very similar eigenfrequencies and damping rates are obtained for the reference configuration without dampers the more complicated first method with forcing does not exhibit advantages over the simpler two other methods, which analyze the acoustic response of the combustor to turbulent combustion noise. As expected, adding dampers leads to a significant increase of the damping rate, but surprisingly the magnitude of this increase depends on the evaluation method employed. Because of the deterioration of the quality of Lorentzian fitting it cannot be applied in cases with strong damper influence. Furthermore, the forcing needed for the decay method induces hot gas ingestion in the dampers leading to detuning. This means that this method modifies the system to be diagnosed and that the results obtained characterize the case with over-temperature in the dampers, which is not representative for normal combustor operation. In conclusion, best results are obtained with the simple autocorrelation method. Pressure data analysis reveals that combustor damping increases with porosity and purge air mass flow rate.
Large Eddy Simulations of Static and Rotating Ribbed Channels in Adiabatic and Isothermal Conditions
Authors: Grosnickel Thomas , Duchaine Florent , Gicquel Laurent Y. M. , Koupper Charlie
Published: August 2017

In an attempt to better understand spatially developing rotating cooling flows, the present study focuses on a computational investigation of a straight, rotating rib roughened cooling channel initially numerically studied by Fransen et al. [1]. The configuration consists of a squared channel equipped with 8 rib turbulators placed with an angle of 90 degrees with respect to the flow direction. The rib pitch-to-height (p/h) ratio is 10 and the height-to-hydraulic diameter (h/Dh) ratio is 0.1. The simulations are based on a case where time resolved two-dimensional Particle Image Velocimetry (PIV) measurements have been performed at the Von Karman Institute (VKI) in a near gas turbine operating condition: the Reynolds number (Re) and the rotation number (Ro) are around 15000 and ± 0.38 respectively. Adiabatic as well as anisothermal conditions have been investigated to evaluate the impact of the wall temperature on the flow, especially in the rotating configurations. Static as well as both positive and negative rotating channels are compared with experimental data. In each case, either an adiabatic or an isothermal wall boundary condition can be computed. In this work, Large Eddy Simulation (LES) results show that the high fidelity CFD model manages very well the turbulence increase (decrease) around the rib in destabilizing (stabilizing) rotation of the ribbed channels. Thanks to the full spatial and temporal description produced by LES, the spatial development of secondary flows are found to be at the origine of observed differences with experimental measurements. Finally, the model is also able to reproduce the differences induced by buoyancy on the flow topology in the near rib region and resulting from an anisothermal flow in rotation.
Effect of Holes Array on Effusion Cooling Characteristics of a Three-Nozzle Model Combustor Liner
Authors: Ji Yongbin , Ge Bing , Zang Shusheng , Xin Jianhua , Ye Chun , Song Huafen
Published: August 2017

Effusion cooling performance for a simulated three-nozzle annular combustor under both non-reacting and reacting flow conditions is experimentally investigated. Under this realistic swirling flow, cooling behavior shows the remarkable difference with that under uniform flow case. Mainstream air is electrically heated to a certain temperature level (180 °C) under non-reacting conditions, while methane-air premixed combustion is performed under reacting conditions at the equivalence ratio of 0.7. Especially, the effect of effusion holes array is discussed for the in-line and staggered layouts. Infrared thermography is used to record the temperature distribution on the two bent cooling test panels equipped with the outer and inner liners respectively after individual in-situ calibration process. Local and average overall cooling effectiveness results are then analyzed as a vital parameter to weigh the cooling performance.

Results show that no matter under non-reacting or reacting flow conditions, the temperature distribution is skewed, which is closely related to the multi-nozzle swirling flow structure inside the combustor. In addition, an elliptic region area of relatively low cooling effectiveness appears at the downstream the injector outlet due to swirling jets impingement effect when the reaction is activated, however, this is not observed under cold flow cases. The impinging swirling flame on the combustor wall also leads to the local blowing ratio declining, so the effusion film will be not easy to issue through the holes. Influence of holes layout on the cooling characteristics are also different on the outer and inner liners. It is assumed to be caused by the interaction of effusion jets and main swirling flow. This reminds us that in the annular combustor, effusion cooling optimization should be considered according to the curvature. Generally, staggered effusion cooling holes arrangement presents better cooling performance than the in-line arrangement.
Operation and Flame Observation of Micro Gas Turbine Firing Ammonia
Authors: Iki Norihiko , Kurata Osamu , Matsunuma Takayuki , Inoue Takahiro , Tsujimura Taku , Furutani Hirohide , Kobayashi Hideaki , Hayakawa Akihiro
Published: August 2017

A demonstration test with the aim to show the potential of ammonia-fired power plant is planned using a micro gas turbine. 50kW class turbine system firing kerosene is selected as a base model. Over 40kW of power generation was achieved by firing ammonia gas only. Over 40kW of power generation was also achieved by firing mixture of ammonia and methane. However ammonia gas supply increases NOx in the exhaust gas dramatically. NOx concentration in the exhaust gas of gas turbine reached at over 600ppm. In the case of the gas turbine operation firing kerosene-ammonia with 31kW of power generation at 75,000rpm of rotating speed, the LHV (Lower Heating Value) ratio of ammonia to the total supplied fuel was changed from 0% to 100% in detail. NO emission increases rapidly to around 400ppm with ammonia at 7% of LHV ratio of ammonia. Then NO emission increases gradually to 600ppm with ammonia at 27% of LHV ratio of ammonia. NO emission has the peak around 60% of LHV ratio of ammonia. NO emission decreases below 500ppm at 100% of LHV ratio of ammonia. The gas turbine operation firing methane-ammonia with 31kW of power generation at 75,000rpm of rotating speed was also tried. NO emission increases rapidly to around 470ppm with ammonia at 7% of LHV ratio of ammonia. Then NO emission increases gradually to 600ppm with ammonia around 30% of LHV ratio of ammonia. NO emission has the peak at 65% of LHV ratio of ammonia. NO emission decreases below 500ppm at 100% of LHV ratio of ammonia. Since the ammonia flame in the prototype combustor seems to be inhomogeneous, ammonia combustion in the prototype combustor may have high NOx region and low NOx region. Therefore there is a possibility of low-NOx combustion.

Flame observation was planned to know combustion state for improvement toward the low NOx combustor. Flame observation from the combustor exit was available by extending the combustor exit with the adaptor of the bent coaxial tubes and the quartz window. Swirling flames of ammonia, methane and methane-ammonia were observed near the center axis of the combustor. Flame observation at 39.1kW of power generation was succeeded. In the case of the flame observation, fuel consumption increased due to increase of the heat loss from the combustor. The emissions of NO and NH3 clearly depend on the combustion inlet temperature at 75,000rpm of rotating speed. The emissions of NO and NH3 in the case of the flame observation setting corresponds to the emission in the case of the normal setting at the condition that the power output is 11.2kW lower.
Improved Prediction of Labyrinth Seal Performance Through Scale Adaptive Simulation and Stream Aligned Grids
Authors: Wein Lars , Seume Joerg R. , Herbst Florian
Published: August 2017

The accurate prediction of cavity flows is of importance to the turbomachinery design process. However, cavity flows are complex. It is known, that RANS models tend to struggle with the prediction of cavity flows and the flow phenomena associated with them. At the same time, scale-resolving methods are more accurate and give a more detailed view on the turbulent structure of the flow. This is accompanied by an inherent dependency on the computational grid, the timestep, and the size of the domain. Therefore, an experimentally validated comparison of RANS, URANS and SAS simulations for a stepped labyrinth seal is given in the paper at hand to demonstrate the individual methods capabilities, limitations, and requirements.

It was shown that an alignment of the grid with the local flow direction can save about 40% of computational resources, while simultaneously reducing the discretization error by 25%. RANS and time averaged URANS results in comparison to measurements showed that the swirl development in the cavity is overpredicted and the cavity vortex is underpredicted. A distinct grid dependency was noticed for the SAS-SST turbulence model. The intermediate grid enhances the results in comparison to RANS and URANS. URANS-SST and SAS-SST simulations capture the same dominant frequencies of the velocity spectra, when the same sector size is used. Furthermore, the prediction of dominant frequencies depends strongly on the circumferential size of the domain. The time-averaged results are more sensitive to the grid refinement and turbulence model than to the size of the domain.
Investigation of the Reacting Flow Field of a Lean Burn Injector With Varying Degree of Swirl at Elevated Pressure Condition
Authors: Hassa Christoph , Meier Ulrich , Heinze Johannes , Magens Eggert , Schroll Michael , Bagchi I.
Published: August 2017

Two RR Lean Direct Injection (LDI) injector versions with different amounts of pilot swirl were investigated. Experiments, performed at elevated pressure and temperature, corresponding to engine conditions at idle include Mie scattering. LII and absorption measurements are used for soot concentration within the primary zone. The soot emission at the outlet is measured by an SMPS instrument. These experimental studies are complemented with PIV measurements. The acquired data allows evaluation of the combustion process from the liquid phase, followed by evaporation, reaction and finally soot production with high spatial resolution.

The change of swirl produced rather moderate changes in the flow field, nevertheless qualitative changes in the fuel placement were observed. Starting from there, differences in heat release and soot formation can be explained, which lead to larger changes of soot emission.

These observations show that a good knowledge of the interaction of gas and liquid phase is necessary to predict the occurrence of behavioral changes in the operating regime.
Modeling of Acoustic Damping of Perforations on the Combustion Instability of Annular Aeroengine Combustors
Authors: Tao Wenjie , Zhang Man , Li Lei
Published: August 2017

Combustors running at lean conditions are prone to combustion instability. It occurs when the unsteady heat release interacts constructively with the acoustic waves in the combustor. Acoustic dampers such as perforated liners are commonly used to suppress the instabilities. For analyzing the damping effects of perforations on the combustion instability in an annular combustion chamber, a linear acoustic model has been developed in this work. This model comprises 1D straight injection ducts, a 2D thin annular chamber and an annular cavity that feeds flow to the chamber through perforations. The analytical model is constructed as an acoustic network and the solution of the system’s dispersion equation gives the frequencies and growth rates of the instability modes.

The proposed method is used firstly to calculate the acoustic modes in an annular combustion chamber with four injectors deprived of perforations, and the results correspond well with the Large Eddy Simulation of the same combustor. With perforations, the model yields reduced growth rates for three acoustic modes including the first azimuthal mode, the first axial mode and the first mixed mode. Key parameters critical to the damping effect of perforations are then studied and the lowest growth rates are found for perforations at a common Strouhal number near 0.3.
Unsteady Measurement of Core Penetration Flow in a Turbine Rotor-Stator Disc Cavity
Authors: Kim You Il , Song Seung Jin
Published: August 2017

The existence and causes of the deep ingress of the annulus flow into the core region of a turbine rotor-stator disc cavity, or core penetration flow, have been investigated experimentally. In addition, the effects of annulus flow coefficient, rotational Reynolds number, and non-dimensional purge air flow rate on the core penetration flow have been examined. Using the low–speed, low expansion ratio single-stage cold turbine test facility at Seoul National University (SNU), time-resolved tangential and radial velocities in the cavity have been measured with 2-D hot-wire anemometers. In addition, time-resolved static pressures on the stator disc have been measured with fast response pressure transducers, and the unsteady cavity velocity field in the absolute frame has been measured using Particle Image Velocimetry (PIV). Geometric non-axisymmetry (e.g. eccentricity of a rotor disc cover in this study) can change the cavity exit pressure, and thus the radial pressure gradient in the cavity. A time lag in the tangential velocity adjustment to the variation in the radial pressure gradient results in a net radial force, leading to core penetration flow. The core penetration flow occurs twice when the cavity exit pressure increases, and once when the cavity exit pressure decreases. In this study, with a once per revolution geometric non-axisymmetry, the core penetration flow occurs three times per revolution, revolving at the disc’s rotational speed. Variations in the annulus flow coefficient or rotational Reynolds number do not affect the core penetration flow, but increasing the purge air flow rate weakens the core penetration flow.
Prediction of Combustion Noise in a Model Combustor Using a Network Model and a LNSE Approach
Authors: Ullrich Wolfram C. , Hirsch Christoph , Sattelmayer Thomas , Mahmoudi Yasser , Dowling Ann P. , Swaminathan Nedunchezhian , Lackhove Kilian , Sadiki Amsini , Fischer André , Staufer Max
Published: August 2017

The reduction of pollution and noise emissions of modern aero engines represents a key concept to meet the requirements of the future air traffic. This requires an improvement in the understanding of combustion noise and its sources, as well as the development of accurate predictive tools. This is the major goal of the current study where the LOTAN network solver and a hybrid CFD/CAA approach are applied on a generic pre-mixed and pressurized combustor to evaluate their capabilities for combustion noise predictions. LOTAN solves the linearized Euler equations (LEE) whereas the hybrid approach consists of RANS mean flow and frequency-domain simulations based on linearized Navier-Stokes equations (LNSE). Both solvers are fed in turn by three different combustion noise source terms which are obtained from the application of a statistical noise model on the RANS simulations and a postprocessing of an incompressible and compressible LES. In this way the influence of the source model and acoustic solver is identified. The numerical results are compared with experimental data. In general good agreement with the experiment is found for both the LOTAN and LNSE solvers. The LES source models deliver better results than the statistical noise model with respect to the amplitude and shape of the heat release spectrum. Beyond this it is demonstrated that the phase relation of the source term does not affect the noise spectrum. Finally, a second simulation based on the inhomogeneous Helmholtz equation indicates the minor importance of the aerodynamic mean flow on the broadband noise spectrum.
Analysis of a Large-Scale Cooling System Fan Gearbox Loads
Authors: Lombard Charles H. O. , Els Daniel N. J. , Muiyser Jacques , Zapke Albert
Published: August 2017

South Africa’s coal-fired power stations use super heated steam to drive generator turbines. In arid regions, air-cooled condensers (ACCs) are used to condense the process steam. These ACCs consists of an array of over 200 axial flow fans, each driven by a motor via a reduction gearbox. Distorted fan inlet air flow conditions cause transient blade loading, which results in variations in output shaft bending and torque. A measurement project was conducted where the input and output shaft of such a gearbox were instrumented with strain gauges and wireless bridge amplifiers. Gearbox shaft speed and vibration were also measured. Torsional and bending strains were measured for a variety of operational conditions, where correlations were seen between gearbox loading and wind conditions. The input side experienced no unexpected loads from the motor or changing wind conditions, whereas output shaft loading was influenced by the latter. Digital filters were applied to identify specific bending components, such as the influence of fan hub misalignment and dynamic blade loading. Reverse loading of the gearbox was measured during the fan stop period, and vibration analysis revealed torsional and gearbox vibrations. This investigation documented reliable full scale ACC gearbox loads.
Parallel Between Rankine and Combined-Cycle Power Plants Configurations Burning Blast Furnace Gas
Authors: Bonolo de Campos Gustavo , Bringhenti Cleverson , Cavalca Diogo F. , Tomita Jesuíno T. , Riederer Werner , L. Pinto Raphael
Published: August 2017

The increasing fuel prices and stringent environmental legislation compel industries worldwide to pursue means to increase their processes efficiency. A higher efficiency relates to a reduction in fuel consumption, which results in a lower operational cost and emissions. When considering a steel mill, processes encountered in the blast furnace and in the coke oven, for example, generate gases that can be availed as low-grade fuels to return some sort of energy back to the process. This practice reduces the amount of high-grade fuel required and increases the global efficiency of the industrial site; however, demands higher investments and increase the management complexity. A thorough evaluation of such power cycles is important to assess their application.

This paper is based on a currently operational combined-cycle power plant composed by two gas turbines that are adapted to use blast furnace gas as main fuel and one steam turbine with a total power rating of 490 MWe. This power plant configuration is compared to another one in which the topping cycle — composed by two gas turbines — is eliminated, and the same amount of blast furnace gas is burnt in a conventional steam generator, operating as a Rankine-cycle. The software Gate Cycle™ was used to model and simulate both cycles and provide the main parameters to analyze their performance. Parameters such as power rating, efficiency, emissions, and expected capital expenditure provided means to assess both options and evaluate their application.

The combined-cycle provided higher efficiency and power rating when compared with the Rankine-cycle. However, the expected values for capital expenditure showed to be also higher. A major difference between both cycles is the higher flexibility of the combined-cycle power plant, which is essential to guarantee an electric energy source within the industrial site. As a counterpart, the operational complexity is significantly higher when compared with the Rankine-cycle. Overall, the present work provides valuable information to assess both solutions.
Analysis of the Vortex Series Around Tabs in the Bent Marine Exhaust Ejector
Authors: Ren Aoyu , Sun Hai’ou , Wang Zhongyi , Chen Xudong
Published: August 2017

In order to facilitate the application of special structural ejectors, which improve the ability of pumping the secondary flow without additional power consumption, reducing the flue gas temperature at the export and enhancing the ship viability under the threat of infrared guided weapons, this paper regardes the 90 ° bend tabs ejector as the research object according to the actual situation of our country’s ships, focuses on the inner effect of the existence of tabs on the flow field in the bent channel, and mainly revealed the transformation of the vortex around the tabs, for providing an explanation to a certain extent about how the tabs affect the macro performance of ejector. With ANSYS software, ring 8 equilateral triangles tabs were designed with 120 ° wall surface mounting angle. With adjusting the blocking ratio of the main outlet area based on the similar zoom, setting inlet swirl angle, and building a hybrid grid to compute, the vortex structure distribution and the development around tabs were observed. The maximum vorticity of vortex at different distances in the mixing tube to the mix tube exit had been calculated to reflect the change of vortex intensity. The final results show that although the streamwise vortices are still located in an axial symmetrical distribution, the swirl angle leads to an uneven distribution of the flow on both sides of a single tab. The inlet swirl angle can make the symmetry of the steamwise vortex vaguer, but the effect of the convection to the vortex is enhanced. The blocking area ratio of the nozzle cross-sectional surface has a large effect on the vorticity of the streamwise vortex. The calculation results show that the larger the blocking area is, the greater the vorticity of streamwise vortex is, which also shows that when the tab shape is fixed, the tab surface area will increase the streamwise vorticity. Through the above research, the shape and the change of the streamwise vortex generated by the tabs in the bent ejector are clearly demonstrated, which can be a reference for the design of high performance bent ejector.
Probabilistic LCF Risk Evaluation of a Turbine Vane by Combined Size Effect and Notch Support Modeling
Authors: Mäde Lucas , Gottschalk Hanno , Schmitz Sebastian , Beck Tilmann , Rollmann Georg
Published: August 2017

A probabilistic risk assessment for low cycle fatigue (LCF) based on the so-called size effect has been applied on gas-turbine design in recent years. In contrast, notch support modeling for LCF which intends to consider the change in stress below the surface of critical LCF regions is known and applied for decades. Turbomachinery components often show sharp stress gradients and very localized critical regions for LCF crack initiations so that a life prediction should also consider notch and size effects. The basic concept of a combined probabilistic model that includes both, size effect and notch support, is presented. In many cases it can improve LCF life predictions significantly, in particular compared to E-N curve predictions of standard specimens where no notch support and size effect is considered. Here, an application of such a combined model is shown for a turbine vane.
Next Generation Turbine Testing at DLR
Authors: Rehder Hans-Jürgen , Pahs Andreas , Bittner Martin , Kocian Frank
Published: August 2017

Axial turbines for aircraft engines and power plants have reached a very high level of development. Further improvements, in particular in terms of higher efficiency and reduced number of blades and stages, resulting in higher loads, are possible, but can only be achieved through a better understanding of the flow parameters and a closer connection between experiment and numerical design and simulation. An analysis of future demands from the industry and existing turbine research rigs shows that there appears a need for a powerful turbine test rig for aerodynamic experiments.

This paper deals with the development and built up of a new so called Next Generation Turbine Test Facility (NG-Turb) at the German Aerospace Center (DLR) in Göttingen. The NG-Turb is a closed-circuit, continuously running facility for aerodynamic turbine investigations, allowing independent variation of engine relevant Mach and Reynolds numbers. The flow medium (dry air) is driven by a 4-stage radial gear compressor with a high pressure ratio and a wide inlet volume flow range. In a first stage the NG-Turb test section will allow investigations on single shaft turbines up to 2½ stages. In a further expansion stage the NG-Turb will be equipped with a second independent shaft system, then enabling experiments with configurations of high and low (or intermediate) pressure turbines and in particular offering the possibility for investigations at counter rotating turbines. Secondary air for cooling investigations can be provided by auxiliary screw compressors. Mass flow through the Turbine is determined redundantly with an uncertainty of about ±0.3%, using well calibrated Venturi nozzles upstream and downstream of the test section.

The operation concept and main design features of the NG-Turb will be described and an overview of the applied standard measurement and data acquisition technics capturing efficiency, traverse data etc. will be given. Thermodynamic cycle calculations have been performed in order to simulate the flow circuit of the NG-Turb and to access whether turbine operating points can be driven within the performance map of the compressor system. Finally the calibration procedure for the Venturi nozzles, which has been conducted during the commissioning phase of the NG-Turb by applying a special calibration test section, is explained and some results will be shown.
A Generalized FGM Progress Variable Weight Optimization Using HEEDS
Authors: Goldin Graham , Zhang Yongzhe
Published: August 2017

The Flamelet Generated Manifold (FGM) model requires a reaction progress variable which is usually defined as a weighted sum of species mass fractions. This progress variable should increase monotonically as flamelet states progress from unburnt to chemical equilibrium. A favorable attribute of the progress variable is that the flamelet species should change gradually with the progress variable, which reduces sensitivity of these species to any predicted errors in the progress variable. Previous publications have presented optimization algorithms for specific flamelet operating conditions, including fuel and oxidizer compositions and temperatures, and pressures. This work applies the HEEDS optimization software to find optimal species weights for a range of fuels and operating conditions. The fuels included are methane, methane-hydrogen, n-dodecane and n-heptane, at fuel-oxidizer temperatures of 293K and 1000K, and pressures of 1 and 30 atmospheres. For manifolds modeled by constant pressure ignition reactors, the optimal progress variable weights using four species weights are {αCO2 = 1, αCO = 0.91, αH2O = 0.52, αH2 = 1}, and for eight species weights are {αCO2 = 1, αCO = 0.91, αH2O = 0.51, αH2 = 1, αC2H2 = 0.16, αOH = −0.66, αH = −0.38, αO = 0.4}.
Experimental Based Empirical Model of the Initial Onset of Sand Deposits on Hastelloy-X From 1000°C to 1100°C Using Particle Tracking
Authors: Boulanger Andrew , Hutchinson John , Ng Wing F. , Ekkad Srinath V. , Keefe Matthew J. , Xu Weibin , Barker Brett J. , Hsu Kwen
Published: August 2017

Deposition experiments are performed on a Hastelloy-X coupon using Arizona Road Test Dust (ARD). A statistical empirical model of the initial onset of ARD deposits is developed from the experimental data. The initial onset of deposits are a quadratic function of local surface temperature and impact velocity components (normal and tangential). A prominent observation is that tangential impact velocity has a significant non-linear, independent effect on deposits relative to normal impact velocity and local surface temperatures. All experiments use 20–40 μm ARD on a bare metal surface over a 1000–1100°C range. Unlike prior mass-based deposit studies, initial deposits for this study are quantified using a Coverage Ratio (CR), which is the area covered by deposits relative to the total area available. The empirical CR model has a strong correlation to coupon surface temperature and impact velocity vectors and is a foundation for future numerical or experimental model comparisons.
Experimental Investigation With Optical Diagnostics of a Lean-Premixed Aero-Engine Injection System Under Relevant Operating Conditions
Authors: Malbois P. , Salaun E. , Frindt F. , Cabot G. , Renou B. , Grisch F. , Bouheraoua L. , Verdier H. , Richard S.
Published: August 2017

A Lean-Premixed (LP) aero-engine injection system was experimentally studied using optically-based measurements. Experiments were conducted under relevant operating conditions up to 1.38 MPa and using commercial kerosene as fuel.

First of all, the structure of the reaction zone and the flame length into the combustion chamber have been studied with CH* chemiluminescence. It is observed from the data measurements that combustion can produce two types of flames, a V-shaped flame in which combustion is stabilized a few mm downstream from the injector and a tulip flame in which combustion is developing inside the injection system. The flame is found to be shorter and more confined when increasing the pressure. To complement this study, experiments were also performed using the OH-PLIF measurement technique. Data processing of the absorption of OH fluorescence signals along the laser propagation allowed the determination of the absolute distribution of OH concentration without any calibration of the OH fluorescence signals. The obtained values are in agreement with estimated premixed adiabatic chemical equilibrium results. Furthermore, the flame front location and its structure were captured from gradient-based filtering operations on OH-PLIF signals. Finally, pollutant emissions were also measured with an exhaust gas sampling probe positioned downstream from the combustor outlet. It has been found that NOx emission increases with Fuel Air Ratio (FAR) and pressure whereas CO exhibits an inverse trend.
Stall Inception in a High Speed Centrifugal Compressor During Speed Transients
Authors: Lou Fangyuan , Fabian John C. , Key Nicole L.
Published: August 2017

The inception and evolution of rotating stall in a high-speed centrifugal compressor are characterized during speed transients. Experiments were performed in the Single Stage Centrifugal Compressor (SSCC) facility at Purdue University and include speed transients from sub-idle to full speed at different throttle settings while collecting transient performance data. Results show a substantial difference in the compressor transient performance for accelerations versus decelerations. This difference is associated with the heat transfer between the flow and the hardware. The heat transfer from the hardware to the flow during the decelerations locates the compressor operating condition closer to the surge line and results in a significant reduction in surge margin during decelerations. Additionally, data were acquired from fast-response pressure transducers along the impeller shroud, in the vaneless space, and along the diffuser passages. Two different patterns of flow instabilities, including mild surge and short-length-scale rotating stall, are observed during the decelerations. The instability starts with a small pressure perturbation at the impeller leading edge and quickly develops into a single-lobe rotating stall burst. The stall cell propagates in the direction opposite of impeller rotation at approximately one third of the rotor speed. The rotating stall bursts are observed in both the impeller and diffuser, with the largest magnitudes near the diffuser throat. Furthermore, the flow instability develops into a continuous high frequency stall and remains in the fully developed stall condition.
Wet Gas Compression: Characterizing Two-Phase Flow Inside a Compressor With Flow Visualization
Authors: Poerner Melissa , Cater Ryan , Nolen Craig , Musgrove Grant , Ransom David
Published: August 2017

Wet Gas Compression (WGC) continues to be an important topic as oil and gas production is driven further out into the ocean and moves critical equipment to the ocean floor. In the last year, significant milestones have been reached for WGC by the installation of the first wet gas compressor off the coast of Norway. Even with this achievement, there is a lack of understanding of the physics behind WGC and there are deficiencies in the ability to predict the compressor performance. Understanding the two phase flow structure inside the compressor is important for validating WGC simulations and being able to predict compressor performance. This paper reviews the results from a test program focused on characterizing the flow inside the compressor by using flow visualization. An open impeller centrifugal compressor was outfitted with windows to view the flow inside the compressor at the inlet, inside the impeller and in the diffuser section. Testing was conducted with an ambient suction pressure at various compressor speeds, flow rates, and liquid volume fractions. Images and videos were captured at the different conditions in order to observe the two phase flow structure. The general patterns and trends that characterize wet gas flow are discussed in this paper.
An Investigation of Combustion Properties of Butanol and its Potential for Power Generation
Authors: Methling Torsten , Richter Sandra , Kathrotia Trupti , Braun-Unkhoff Marina , Naumann Clemens , Riedel Uwe
Published: August 2017

Over the last years, global concerns about energy security and climate change have resulted in many efforts focusing on the potential utilization of non-petroleum-based, i.e. bio-derived, fuels. In this context, n-butanol has recently received high attention because it can be produced sustainably. A comprehensive knowledge about its combustion properties is inevitable to ensure an efficient and smart use of n-butanol if selected as a future energy carrier.

In the present work, two major combustion characteristics, here laminar flame speeds applying the cone-angle method and ignition delay times applying the shock tube technique, have been studied, experimentally and by modeling exploiting detailed chemical kinetic reaction models, at ambient and elevated pressures. The in-house reaction model was constructed applying the RMG-method. A linear transformation method recently developed, linTM, was exploited to generate a reduced reaction model needed for an efficient, comprehensive parametric study of the combustion behavior of n-butanol/hydrocarbon mixtures.

All experimental data were found to agree with the model predictions of the in-house reaction model, for all temperatures, pressures, and fuel-air ratios. On the other hand, calculations using reaction models from the open literature mostly overpredict the measured ignition delay times by about a factor of two. The results are compared to those of ethanol, with ignition delay times very similar and laminar flame speeds of n-butanol slightly lower, at atmospheric pressure.