bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation on the Effect of Surface Wettability on a Two-Phase Flow in a Compressor Cascade
Authors: Neupert Niklas , Harbeck Janneck Christoph , Joos Franz 
Published: August 2017

In recent years overspray fogging has become a powerful means for power augmentation of industrial gas turbines. Despite the positive thermodynamic effect on the cycle droplets entering the compressor increase the risk of water droplet erosion. Further deposited water leads to a higher sensitivity towards fouling due to an increased stickiness of the blades. Therefore erosion resistant hydrophobic coatings are applied to the first stages of compressors. Although some patents claim the use of such coatings the aerodynamic impact of a different wettability is not regarded so far. This issue was addressed in the field of aerodynamic efficiency of wings in heavy rain showing higher penalty for hydrophobic coatings.
In this study the issue of a different blade surface wettability in a linear transonic compressor cascade is addressed. Different coatings are applied resulting in contact angles of 51–95°. The inflow Mach number was fixed at design inflow Mach number and the inflow angle was varied over a broad range. The effect on the water film pattern is analyzed in terms of position of film breakup, rivulet width and totally wetted surface.
The performance of the cascade under two-phase flow was analyzed using LDA/PDA measurement technique in terms of loss coefficient based on wake momentum thickness and flow turning. It is shown that the wettability of the surface has significant effects on the film structure leading to a lower fraction of wetted surface with increasing contact angle. The influence on performance is limited to effects in the proximity of the surface and is dependent on operation point. While in design conditions hydrophilic coating show lower losses the trend is vice-versa for off-design conditions.
The data represent first experimental work on the influence of surface wettability in a droplet-laden flow supporting positive features for hydrophobic coatings in gas turbine compressors.
On the Importance of Engine-Representative Models for Fan Flutter Predictions
Authors: Stapelfeldt Sina , Vahdati Mehdi 
Published: August 2017

This paper examines the factors which can result in discrepancies between rig tests and numerical predictions of the flutter boundary for fan blades. Differences are usually attributed to the deficiency of CFD models for resolving the flow at off-design conditions. This work was initiated as a result of inconsistencies between the flutter prediction of two rig fan blades, called here Fan F1 and Fan F2. The numerical results agreed well with the test data in terms of flutter speed and nodal diameter for both fans. However, they predicted a significantly higher flutter margin for F2 than for Fan F1, while rig tests showed that the two blades had similar flutter margins. A new set of flutter computations for both blades using the whole LP domain (intake, fan, OGV and ESS) was therefore performed. The new set of computations considered the effects of the acoustic liner and mistuning for both blades. The results of this work indicate that the previous discrepancies between CFD and tests were due to:
1. Differences in the effectiveness of the acoustic liner in attenuating the pressure wave created by the blade vibration as a result of differences in flutter frequencies between the two fan blades.
2. Differences in the level of unintentional mistuning of the two fan blades due to manufacturing tolerances.
In the second part of this research, the effects of blade misstaggering and inlet temperature on aerodynamic damping were investigated.
The data presented in this paper clearly show that manufacturing and environmental uncertainties can play an important role in the flutter stability of a fan blade. They demonstrate that aeroelastic similarity is not necessarily achieved if only aerodynamic properties and the traditional aeroelastic parameters, reduced frequency and mass ratio, are maintained. This emphasises the importance of engine-representative models, in addition to an accurate and validated CFD code, for the reliable prediction of the flutter boundary.
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.
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.
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.
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.