Flow-Field Investigation of Two Gas-Sampling Probes

2006 ◽  
Author(s):  
Leiyong Jiang ◽  
Shaji Manipurath ◽  
Gilles Bourque ◽  
Michel Houde
Keyword(s):  
Cooling Water ◽  
Elevated Pressure ◽  
Field Investigation ◽  
Complex Conjugate ◽  
Probe Design ◽  
Wall Region ◽  
Original Design ◽  
Gas Sampling ◽  
Heat Transfers

The flow fields in and around two versions of a water-cooled gas-sampling probe, situated downstream of a gas turbine combustor, were numerically studied in an elevated pressure and temperature environment. The probes are of triple-walled stainless steel assembly, where the gas sample is transported through a centre tube, while preheated and pressurized cooling water flows through two surrounding annuli. Complex conjugate heat transfers amongst the exhaust mixture, cooling water and probe walls were modelled at a selected operating condition. The numerical results indicate over-heating and possible vaporization of water or cavitation in the upstream tip region of the probe with the original design. This is consistent with the evidence of damage observed in these probes from prolonged testing under similar conditions. For the modified probe, the effectiveness of cooling water is much improved, which is confirmed by long-term combustor rig testing. From this investigation, some recommendations for probe design and operation are provided. Moreover, the present study has proved that the numerical simulation is a valuable tool for probe design and trouble-shooting, and to accurately predict conjugate heat transfers in such flows, the laminar sub-layer in the near-wall region should be adequately resolved.

scholarly journals RAPELD: a modification of the Gentry method for biodiversity surveys in long-term ecological research sites

2005 ◽  
Vol 5 (2) ◽  
pp. 19-24 ◽  
Author(s):  
William E. Magnusson ◽  
Albertina P. Lima ◽  
Regina Luizão ◽  
Flávio Luizão ◽  
Flávia R. C. Costa ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Planning ◽  
Amazon Basin ◽  
Local People ◽  
Ecological Research ◽  
Original Design ◽  
Biological Surveys ◽  
Incomplete Coverage ◽  
Long Term Ecological Research

Our objectives were to develop a method that would be appropriate for long-term ecological studies, but that would permit rapid surveys to evaluate biotic complementarity and land-use planning in Amazonia. The Amazon basin covers about 7 million km². Therefore, even a sparse coverage, with one sample site per 10.000 km², would require about 700 sampling sites. Financial considerations limit the number of sites and investment at each site, but incomplete coverage makes evaluation of biotic complementarity difficult or impossible (Reddy & Dávalos 2003). Our next challenge is to install similar systems throughout Amazonia. The cost, based on modification of Al Gentry's original design is moderate (less than US$ 50.000 per site if it is not necessary to immediately identify all vascular plants in plots) and we can obtain RAP results for most taxa in the short term at much lower cost. However, biological surveys will only be relevant if the local people participate and the surveys serve as much to teach the local communities about the value of their natural resources as they serve to teach the international community about biodiversity. Therefore, we want to see each site run as a long-term ecological research project by local people and institutions. Biological surveys are an important tool in land-use planning, but only the local people can implement those plans.

Monitoring and Calibration of Long Term Mooring System Design Assumptions Through Use of AIS and Weather Data

2021 ◽  
Author(s):  
Dag Børre Lillestøl ◽  
Odd Torbjørn Kårvand ◽  
Are Torstensen
Keyword(s):  
Low Cost ◽  
Environmental Data ◽  
Weather Data ◽  
Mooring System ◽  
System Behavior ◽  
Original Design ◽  
Actual System ◽  
Early Failures ◽  
And Performance

Abstract This paper outlines an approach on how to improve the mooring integrity of existing long term mooring systems by using existing and commercially available data. It will be demonstrated how the use of AIS and hindcast weather data can be used to increase understanding of mooring systems and to monitor and quantify gaps between "as-designed", "as-installed" and "as-is" of a long term mooring system. Long term moored units have traditionally suffered from many early failures, caused by damages and errors introduced in the installation phase, and costly and unnecessary "late in life" failures. A fact rated high on the agenda of the underwriters. Numerous papers have been written on this topic, but it is only in recent years the industry have started to ensure that systems are inspected to a sufficient degree with respect to the physical condition, taking these learnings into account. However, the second important element, the calibration of the mooring analysis vs. actual vessel and mooring system behavior/performance, have not yet gotten the attention required. Deviations from the intended design are introduced in the installation phase of a mooring system. In addition, the design assumptions will never be fully accurate. The gap between the design assumptions and the actual system will increase over time, and the industry today do not focus on mapping and quantifying the effect of this gap sufficiently. The described method explains how one can introduce a pro-active approach, without installing onboard equipment, but rather utilizing algorithms on existing data and design documentation. This paper focuses on the use of AIS data in combination with historic weather/environmental data and seek to demonstrate how this low-cost method can provide useful information with respect to the mooring system. To emphasize the mapped importance of such calibrations, the July 2021 Edition of the in-service DNV Class Rules, DNVGL-OS-0300, formally introduces requirements to calibration of design assumptions of long term mooring units through use of survey data, service history and actual mooring system behavior in order to ensure a unit's mooring system condition and performance is known in light of the original design assumptions.

Comprehensive Evaluation of Rutting of Warm-Mix Asphalt Utilizing Long-Term Pavement Performance Specific Pavement Studies

2020 ◽  
Vol 2674 (7) ◽  
pp. 272-283 ◽  
Author(s):  
Biswajit K. Bairgi ◽  
A.S.M. Asifur Rahman ◽  
Rafiqul A. Tarefder ◽  
Matias M. Mendez Larrain
Keyword(s):  
Comprehensive Evaluation ◽  
Field Investigation ◽  
Warm Mix Asphalt ◽  
Pavement Performance ◽  
Laboratory Evaluation ◽  
Production Temperature ◽  
Wheel Tracking Test ◽  
Modified Binder ◽  
Wheel Tracking

Warm-mix asphalt (WMA) technologies allow binder softening for compaction benefits. Lower production temperature also causes reduced short-term aging in WMA. Considering the long-term implication of the reduced aging and binder softening, WMA is being questioned about its rutting characteristics. As such, this study evaluates different WMA technologies for rutting characteristics in comparison to traditional hot-mix asphalt (HMA) through laboratory and field investigation. The study utilized the long-term pavement performance (LTPP) project in the state of New Mexico called Specific Pavement Study-10 (SPS-10), which was designed to evaluate the WMA performances. The LTPP SPS-10 section includes: (i) control HMA, (ii) foaming, (iii) Evotherm, (iv) Cecabase 1, and (v) Cecabase 2 mixtures. Cecabase 2 mixture consists of a polymer-modified binder (PG 70-28+), whereas other mixtures consist of PG 70-28 binder. The aggregate type, properties, and gradations are the same in all the sections. Laboratory evaluation of rutting was conducted through the Hamburg wheel tracking test. Long-term field rutting was evaluated through Mandli’s pavement profile scanner, a laser-based distress evaluation technology. The study found that WMA with foaming, Evotherm, or Cecabase shows slightly higher rutting compared with the control HMA; however, all the sections satisfied laboratory and field rutting criteria. The use of a polymer-modified binder in WMA significantly improves the rutting characteristics.

scholarly journals Pressure-Induced Geopolymerization in Alkali-Activated Fly Ash

2018 ◽  
Vol 10 (10) ◽  
pp. 3538 ◽  
Author(s):  
Sol Park ◽  
Hammad Khalid ◽  
Joon Seo ◽  
Hyun Yoon ◽  
Hyeong Son ◽  
...  
Keyword(s):  
Fly Ash ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Elevated Pressure ◽  
X Ray Diffraction ◽  
27Al Mas Nmr ◽  
Alkali Activated

The present study investigated geopolymerization in alkali-activated fly ash under elevated pressure conditions. The fly ash was activated using either sodium hydroxide or a combination of sodium silicate solution and sodium hydroxide, and was cured at 120 °C at a pressure of 0.22 MPa for the first 24 h. The pressure-induced evolution of the binder gel in the alkali-activated fly ash was investigated by employing synchrotron X-ray diffraction and solid-state 29Si and 27Al MAS NMR spectroscopy. The results showed that the reactivity of the raw fly ash and the growth of the zeolite crystals were significantly enhanced in the samples activated with sodium hydroxide. In contrast, the effects of the elevated pressure conditions were found to be less apparent in the samples activated with the sodium silicate solution. These results may have important implications for the binder design of geopolymers, since the crystallization of geopolymers relates highly to its long-term properties and functionality.

Preparation of Long Term Operation in Dukovany NPP, Czech Republic

2009 ◽  
Author(s):  
Robert Krivanek
Keyword(s):  
Czech Republic ◽  
Risk Analysis ◽  
Feasibility Study ◽  
Regulatory Body ◽  
Original Design ◽  
Term Operation ◽  
Safety Aspects ◽  
Program Strategy ◽  
The Status

Dukovany NPP has 4 units with VVER440/213 type reactors and is in its 24th year of operation. Operational permission is valid for 30 years. Since 2004, NPP has started to prepare a LTO program which includes: • a detailed feasibility study, • an evaluation of safety aspects of LTO, • the preparation of a long-term modernization plan, • risk analysis etc. This program is now approved by company management and by the Czech regulatory body. It should enable operation up to 60 years. The article gives information about the status of the NPP Dukovany long-term operation (LTO) preparation. It gives an overview of results of the prepared LTO Assurance Program, Strategy of the NPP Dukovany LTO, along with risk analysis. The article details the procedure for the NPP Dukovany preparation for operation beyond the limits of original design lifetime, and ensuing planned stages.

Towards Improved Boundary Layer Flashback Resistance of a 65 kW Gas Turbine With a Retrofittable Injector Concept

2018 ◽  
Author(s):  
Alireza Kalantari ◽  
Vincent McDonell ◽  
Scott Samuelsen ◽  
Shahram Farhangi ◽  
Don Ayers
Keyword(s):  
Boundary Layer ◽  
Gas Turbine ◽  
Elevated Pressure ◽  
Current Data ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Pollutant Emissions ◽  
Wall Region ◽  
Lean Premixed Combustion ◽  
High Hydrogen

Lean premixed combustion is extensively used in gas turbine industry to reduce pollutant emissions. However, combustion stability still remains as a primary challenge associated with high hydrogen content fuels. Flashback is a crucial concern for designing gas turbine combustors in terms of operability limits. The current experimental study addresses the boundary layer flashback of hydrogen-air premixed jet flames at gas turbine premixer conditions (i.e. elevated pressure and temperature). Flashback propensity of a commercially available injector, originally designed for natural gas, is studied at different operating conditions and corresponding measurements are presented. The pressure dependence of flashback propensity is consistent with previous studies. The previously developed flashback model is successfully applied to the current data, verifying its utilization for various test conditions/setups. In addition, the model is used to predict flashback propensity of the injector at the actual engine preheat temperature. The injector is then modified to increase boundary layer flashback resistance and the corresponding data are collected at the same operating conditions. To avoid the boundary layer flashback, the mixture is leaned out in the near-wall region, where the flame can potentially propagate upstream. The comparison of gathered data shows a clear improvement in flashback resistance. This improvement is further elaborated by numerically studying fuel/air mixing characteristics for the two injectors.

Effects of food texture change on metabolic parameters: short- and long-term feeding patterns and body weight

2001 ◽  
Vol 280 (3) ◽  
pp. R780-R789 ◽  
Author(s):  
Hélène Labouré ◽  
Sandrine Saux ◽  
Stylianos Nicolaidis
Keyword(s):  
Body Weight ◽  
Insulin Response ◽  
Human Consumption ◽  
Original Design ◽  
Complete Diet ◽  
Texture Change ◽  
Texture Modification ◽  
Short And Long Term ◽  
Metabolic Management

A complete diet was prepared with cooked pieces of meat, beans, cream starch, and water and presented to the rats in two different textures: a blended purée and a rough mixture that required a lot of chewing. We hypothesized that this texture modification might change both anticipatory reflexes and feeding behavior. Feeding rate, meal size, intermeal intervals, and their correlation were monitored in response to each texture. The long-term (6 wk) effect on body weight was assessed. Periprandial plasma glucose, insulin, glucagon, and lipid concentrations were assayed. Whole and background metabolism, respiratory quotient, and locomotion were measured using a computerized calorimeter of original design. In the short term, rats preferred the mixture. However, after 3 wk, they ingested more purée than mixture and gained more body weight per gram of food ingested as purée. Insulin response declined earlier with the mixture. During meals, glycerol and free fatty acid increased earlier with purée, whereas in the postprandial period, glycerol increased earlier with mixture. The metabolic rate, however, was not significantly affected. We concluded that texture, an everyday manipulation performed on food for human consumption, affects not only palatability of ingestants but also their metabolic management in the short and long term.

Resistance Mechanism of Microbial Fouling in Circulating Water to Bactericide

2011 ◽  
Vol 347-353 ◽  
pp. 931-936
Author(s):  
Mo Jie Sun ◽  
Hong Dan Shi ◽  
Sheng Zheng
Keyword(s):  
Resistance Mechanism ◽  
Water System ◽  
Cooling Water ◽  
Resistance Mechanisms ◽  
Sulfate Reducing ◽  
Circulating Water ◽  
Plant Uses ◽  
Reducing Bacteria ◽  
Great Harm

Microorganisms in circulating water of power plant bring great harm to cooling water system. It not only affects the effect of heat transfer, but also would lead to corrosion of heat exchanger, in seriously would result in shutdown. Now the plant uses the bactericide to treat with the microbial fouling generally, and a variety of fungicides have been developed. However, the long-term usage of fungicide will make the bacteria appear resistance, which greatly limits the application of such measures. This paper overviewed different resistance mechanisms of Pseudomonas, sulfate-reducing bacteria, iron bacteria and slime forming bacteria in the microbial fouling to bactericide and put forward some solutions.

scholarly journals Assessment of Long-Term Gas Sampling Design at Two Commercial Manure-Belt Layer Barns

2010 ◽  
Vol 60 (6) ◽  
pp. 702-710 ◽  
Author(s):  
Li-Long Chai ◽  
Ji-Qin Ni ◽  
Yan Chen ◽  
Claude A. Diehl ◽  
Albert J. Heber ◽  
...  
Keyword(s):  
Sampling Design ◽  
Gas Sampling
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