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Feasibility of Pulse Combustion in Micro Gas Turbines

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Journal of Thermal Science 2012年第5期21卷 466-473页

作者： juha honkatukia Esa Saari Timo Knuuttila Jaakko Larjola Jari Backman Lappeenranta University of Technology P.O. Box 2053851 Lappeenranta Finland T-Turbine Oy Rakentajainkuja 4 B02330 Espoo Finland

In gas turbines, a fast decrease of efficiency appears when the output decreases; the efficiency of a large gas tur-bine （20...30 MW） is in the order of 40 %, the efficiency of a 30 kW gas turbine with a recuperator is in the order of 25 %, but the efficiency of a very small gas turbine （2...6 kW） in the order of 4...6 % （or 8... 12 % with an op- timal recuperator）. This is mainly a result of the efficiency decrease in kinetic compressors, due to the Reynolds number effect. Losses in decelerating flow in a flow passage are sensitive to the Reynolds number effects. In con- trary to the compression, the efficiency of expansion in turbines is not so sensitive to the Reynolds number; very small turbines are made with rather good efficiency because the flow acceleration stabilizes the boundary layer. This study presents a system where the kinetic compressor of a gas turbine is replaced with a pulse combustor. The combustor is filled with a combustible gas mixture, ignited, and the generated high pressure gas is expanded in the turbine. The process is repeated frequently, thus producing a pulsating flow to the turbine; or almost a uni- form flow, if several parallel combustors are used and triggered a/ternately in a proper way. Almost all the com- pression work is made by the temperature increase from the combustion. This gas turbine type is investigated theoretically and its combustor also experimentally with the conclusion that in a 2 kW power size, the pulse flow gas turbine is not as attractive as expected due to the big size and weight of parallel combustors and due to the ef- ficiency being in the order of 8 % to 10 %. However, in special applications having a very low power demand, below 1000 W, this solution has better properties when compared to the conventional gas turbine and it could be worth of a more detailed investigation.

关键词： Gas turbine pulse combustion micro size low Reynolds number

为了有效地控制波罗的海的污染:对当前一些污染减排政策失败的剖析及建议

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AMBIO－人类环境杂志 2001年第4期30卷 245-253页

作者： Markku Ollikainen juha honkatukia 秦莉赫尔辛基大学芬兰经济研究所环境经济部

我们应用生态-经济学模型,研究了波罗的海国家关于将每一个国家的营养物质排放总量减少一半的宣言。这一模型包括以国家为基础的减排污染物费用函数和描述磷和氮如何从一国流动到另一国的转移系数(由波罗的海水文学模型估算而得)。结果... 详细信息

我们应用生态-经济学模型,研究了波罗的海国家关于将每一个国家的营养物质排放总量减少一半的宣言。这一模型包括以国家为基础的减排污染物费用函数和描述磷和氮如何从一国流动到另一国的转移系数(由波罗的海水文学模型估算而得)。结果表明,就氮而言,目前的减排政策和成本-效益政策相比,减排费用非常高,而且各国受益不平衡。可以预料,那些减排边际成本高的国家,其执行上述减排协定以及对氮的减排投资的兴趣不会太大,这一结论已被我们的数据所证实。因此,我们建议并概要地提出一种联合执行政策,以使减排具有成本效益并鼓励进行减排投资。

关键词：波罗的海海洋污染污染物减排政策污染控制

From Finnish Assortment Pricing to Market Economy Using Prices for Sawn Wood and Chips in Reference Bucking

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Open Journal of Forestry 2024年第3期14卷 233-280页

作者： juha Lappi Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life Sciences s Norway

Dominant Finnish assortment pricing gives prices for sawlog and pulp wood volumes. Buyers buck stems to sawlogs using secret price matrices. Agreed dimensions allow wide range of sawlog volumes. Forest owners cannot objectively compare biddings: timber trade is a lottery game. Bucking is analyzed in terms of sawlog, pulp wood, log cylinder, sawn wood, value-weighted sawn wood, and chips. Sawn wood and its value are computed from top diameter of the sawlog. Profit maximization requires buyers to buck logs producing smaller than maximal value, causing dead weight loss. Nominal assortment prices have unpredictable relation to effective stumpage price. Assortment pricing does not meet requirements of market economy. If sawmills linked to pulp mills buck smaller sawlog percentages than independent sawmills, as generally believed, they use higher price for chips in their own harvests than they pay for independent sawmills, indicating imperfect competition for chips. Sawn wood potential pricing is suggested which gives prices for sawn wood and chips coming both from sawlogs and pulp wood in reference bucking which maximizes sawn wood for given minimum and maximum log length and minimum top diameter. Simple algorithm generates feasible bucking schedules from which optimum can be selected using any objective. Pricing produces unit price for all commercial wood utilizing ratio of theoretical sawn wood and commercial volume in stand. Unit price can be compared to stem pricing and could be compared to assortment pricing if assortment pricing would produce predictable sawlog percentages. Sawn wood potential pricing is concrete, transparent, easy to compute, considers stem size and tapering, reduces trading cost and is less risky to buyers than stem pricing. It meets requirements of market economy. Readers can repeat computations using open-source software Jlp22.

关键词： Sawmill Pulp Mill Jlp22 Dead Weight Loss Stem Price

Estimation of drag forces caused by natural woody vegetation of different scales

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Journal of Hydrodynamics 2014年第4期26卷 608-623页

作者： JALONEN Johanna JRVEL juha Department of Civil and Environmental Engineering Aalto University

To reliably estimate water levels and velocities in vegetated rivers and floodplains, flow resistance models based on physical plant properties are advantageous. The purpose of this study is （1） to assess the suitable parameterization of woody riparian vegetation in estimating the drag forces, （2） to address the effect of plant scale on the drag estimates and reconfiguration, and （3） to evaluate the applicability of three recently developed flow resistance models. Experiments on four tree species in a towing tank together with detailed characterization of tree properties were carried out to establish a novel dataset. Despite the variability in the tree height （0.9 m-3.4 m）, the stem, leaf and total areas proved to be suitable characteristic dimensions for estimating the flow resistance at different scales. Evaluations with independent data revealed that the tested models produced reasonable results. The performance of the models was controlled by the parameter values used rather than the model structure or the plant scale.

关键词： drag force flow resistance woody vegetation modelling

The comparison of design airflow rates with dynamic and steady-state displacement models in varied dynamic conditions

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Building Simulation 2021年第4期14卷 1201-1219页

作者： Natalia Lastovets Risto Kosonen juha Jokisalo Department of Mechanical Engineering Aalto UniversityEspooFinland College of Urban Construction Nanjing Tech UniversityNanjingChina

A temperature-based method is usually applied in displacement ventilation (DV) design when overheating is the primary indoor climate concern. Different steady-state models have been developed and implemented to calculate airflow rate in rooms with DV. However, in practical applications, the performance of DV depends on potentially dynamic parameters, such as strength, type and location of heat gains and changing heat gain schedule. In addition, thermal mass affects dynamically changing room air temperature. The selected steady-state and dynamic models were validated with the experimental results of a lecture room and an orchestra rehearsal room. Among the presented models, dynamic DV model demonstrated a capability to take into account the combination of dynamic parameters in typical applications of DV. The design airflow rate is calculated for the case studies of dynamic DV design in the modelled lecture room in both dynamic and steady-state conditions. In dynamic conditions of heavy construction in 2–4 hours occupancy periods, the actual airflow rate required could be 50% lower than the airflow rate calculated with the steady-state models. The difference between steady-state and dynamic multi-nodal model is most significant with heavyweight construction and short occupancy period (17%–28%). In cases with light construction, the dynamic DV model provides roughly the same airflow rates for four-hour occupancy period than the Mund’s model calculates. The dynamic model can significantly decrease the design airflow rate of DV, which can result in a reduction of investment costs and electrical consumption of fans.

关键词： displacement ventilation design airflow rate temperature gradient dynamic model simplified building energy models

Geometrically modeling 2D scattered points: a review of the potential for methodologically improving mobile laser scanning in data processing

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International Journal of Digital Earth 2014年第6期7卷 432-449页

作者： Yi Lin juha Hyyppa Department of Remote Sensing and Photogrammetry Finnish Geodetic Institute MasalaFinland

As a state-of-the-art mapping technology,mobile laser scanning(MLS)is increasingly applied to fields such as digital presentations of city ***,its application has recently met a bottleneck in data *** has been found that conventional methods for geometrically modeling 3D scattered points are inadequate when dealing with large volumes of MLS *** fact,this is a challenge that has already been noted in the MLS-relevant fields,*** sensing,robot perception,and pattern recognition.A variety of algorithms under the schematic frame of analysis,modeling and synthesis(AMS)have been developed in these *** AMS paradigm is to first extract the implicit geometric primitives within each scan profile by geometrically modeling its 2D scattered points(GM2P).The resultant 2D geometric primitives are then integrated to restore the real 3D geometrical *** this process,GM2P is a kernel procedure whereby a review of the GM2P algorithms is assumed to be of significance for developing new efficient algorithms for geometrically modeling 3D scattered *** idea is supported by MLS sampling often being executed via parallel scan ***,the results of the literature review indicate an avenue for methodologically improving MLS in data processing.

关键词： MLS geometrically modeling scattered points GM2P AMS scan profile

Ion emission from warm dense matter produced by irradiation with a soft x-ray free-electron laser

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Matter and Radiation at Extremes 2024年第1期9卷 71-84页

作者： Josef Krása Tomás Burian Vera Hájková Jaromír Chalupský Šimon Jelínek Katerina Frantálová Michal Krupka Zuzana Kuglerová Sushil Kumar Singh Vojtech Vozda Ludek Vysín MichalŠmíd Pablo Perez-Martin Marion Kühlman Juan Pintor Jakub Cikhardt Matthias Dreimann Dennis Eckermann Felix Rosenthal Sam M.Vinko Alessandro Forte Thomas Gawne Thomas Campbell Shenyuan Ren YuanFeng Shi Trevor Hutchinson Oliver Humphries Thomas Preston Mikako Makita Motoaki Nakatsutsumi Xiayun Pan Alexander Köhler Marion Harmand Sven Toleikis Katerina Falk Libor juha Department of Radiation and Chemical Physics Institute of PhysicsCzech Academy of SciencesNa Slovance 218221 Prague 8Czech Republic Laser Plasma Department Institute of Plasma PhysicsCzech Academy of SciencesZa Slovankou 318200 Prague 8Czech Republic Department of Surface and Plasma Science Faculty of Mathematics and PhysicsCharles University in PragueV Holesovi ckách 218000 Prague 8Czech Republic Department of Physical Electronics Faculty of Nuclear Science and Engineering PhysicsCzech Technical University in PragueV Holesovi ckách 218000 Prague 8Czech Republic Helmholtz-Zentrum Dresden-Rossendorf Bautzner Landstraße 40001328 DresdenGermany DESY Photon Science Notkestraße 85D-22607 HamburgGermany Institut de Minéralogie de Physique des Matériaux et de CosmochimieUMR 7590–UPMC/CNRS/IRD/MNHNSorbonne Université4 place Jussieu75005 ParisFrance Department of Physics Faculty of Electrical EngineeringCzech Technical University in PragueTechnická216627 Prague 6Czech Republic Center for Soft Nanoscience University of MünsterBusso-Peus-Straße 10D-48149 MünsterGermany Department of Physics Clarendon LaboratoryUniversity of OxfordParks RoadOxford OX13PUUnited Kingdom Central Laser Facility STFC Rutherford Appleton LaboratoryDidcot OX110QXUnited Kingdom Lawrence Livermore National Laboratory 7000 East AvenueLivermoreCalifornia 94550USA European XFEL GmbH Holzkoppel 4D-22869 SchenefeldGermany Technische Universität Dresden 01062 DresdenGermany

We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric *** the experiment,we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution *** find that most emitted ions are thermal,but that some impurities chemisorbed on the target surface,such as protons,are accelerated by the electrostatic field created in the plasma by escaped *** morphology of the complex crater structure indicates the presence of several ion groups with varying *** find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.

关键词： electrostatic emitted chemi

Variation in the timing of river entry of Atlantic salmon (Salmo salar L.) in the Baltic

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Current Zoology 2009年第5期55卷 342-349页

作者： Anna KUPARINEN juha MERIL Department of Biological and Environmental Sciences

The timing of river entry in the Atlantic salmon is known to depend on genetic, demographic and environmental factors, but little is known about the relative magnitude of among population and among year variation and covariation in this respect in natural state Atlantic salmon rives. To investigate this, variability in the timing of river entry in three historical Finnish Atlantic salmon populations were analyzed using salmon trap data collected during 1870- 1902. The analyses reveled that 1 ） the timing of river entry differed substantially and consistently among the rivers, and that 2） variation among the rivers was much larger than variation among years. Annual variations were not explained by regional environmental conditions, whereas in one river the timing of the local flood peak was a significant predictor of the timing of river entry. Differences in the timing of salmon entry to geographically closely situated rivers suggests that a regionally fixed opening date for coastal fisheries might not be the best management strategy as it may lead to uneven exploitation of salmon populations from different rivers [ Current Zoology 55 （5）： 342 - 349, 2009] .

关键词： Atlantic salmon Coastal fisheries Fisheries management Freshwater entry Migration River entry

From Finnish Assortment Pricing to Market Economy Using Prices for Sawn Wood and Chips in Reference Bucking

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