Modelling and validation of wet steam flow in a low pressure steam turbine

Results of numerical investigations of the wet steam flow in a three stage low pressure steam turbine test rig are presented. The test rig is a scale model of a modern steam turbine design and provides flow measurements over a range of operating conditions which are used for detailed comparisons with the numerical results. For the numerical analysis a modern CFD code with user defined models for specific wet steam modelling is used. The effect of different theoretical models for nucleation and droplet growth are examined. It is shown that heterogeneous condensation is highly dependent on steam quality and, in this model turbine with high quality steam, a homogeneous theory appears to be the best choice. The homogeneous theory gives good agreement between the test rig traverse measurements and the numerical results. The differences in the droplet size distribution of the three stage turbine are shown for different loads and modelling assumptions. The different droplet growth models can influence the droplet size by a factor of two. An estimate of the influence of unsteady effects is made by means of an unsteady two-dimensional simulation. The unsteady modelling leads to a shift of nucleation into the next blade row. For the investigated three stage turbine the influence due to wake chopping on the condensation process is weak but to confirm this conclusion further investigations are needed in complete three dimensions and on turbines with more stages. Copyright © 2011 by ASME.

Induction and preliminary characterization of a novel halophage SNJ1 from lysogenic Natrinema sp F5

Halophage SNJ1 was induced with mitomycin C from Natrinema sp. strain F5. The phage produces plaques on Natrinema sp. strain J7 only. The phage has a head of about 67 nm in diameter and a tail of 570 nm in length and belongs morphologically to the family Siphoviridae. The phage is strongly salt dependent; NaCl concentration affects the integrity of SNJ1, phage adsorption, and plaque formation. The optimal NaCl concentration for phage adsorption and plaque formation is 30% and 25%, respectively.

A preliminary study on methods for retaining data quality problems in automatically generated test data

Data in an organisation often contains business secrets that organisations do not want to release. However, there are occasions when it is necessary for an organisation to release its data such as when outsourcing work or using the cloud for Data Quality (DQ) related tasks like data cleansing. Currently, there is no mechanism that allows organisations to release their data for DQ tasks while ensuring that it is suitably protected from releasing business related secrets. The aim of this paper is therefore to present our current progress on determining which methods are able to modify secret data and retain DQ problems. So far we have identified the ways in which data swapping and the SHA-2 hash function alterations methods can be used to preserve missing data, incorrectly formatted values, and domain violations DQ problems while minimising the risk of disclosing secrets. © (2012) by the AIS/ICIS Administrative Office All rights reserved.

Modelling of turbulent lifted jet flames using flamelets: A priori assessment and a posteriori validation

This study focuses on the modelling of turbulent lifted jet flames using flamelets and a presumed Probability Density Function (PDF) approach with interest in both flame lift-off height and flame brush structure. First, flamelet models used to capture contributions from premixed and non-premixed modes of the partially premixed combustion in the lifted jet flame are assessed using a Direct Numerical Simulation (DNS) data for a turbulent lifted hydrogen jet flame. The joint PDFs of mixture fraction Z and progress variable c, including their statistical correlation, are obtained using a copula method, which is also validated using the DNS data. The statistically independent PDFs are found to be generally inadequate to represent the joint PDFs from the DNS data. The effects of Z-c correlation and the contribution from the non-premixed combustion mode on the flame lift-off height are studied systematically by including one effect at a time in the simulations used for a posteriori validation. A simple model including the effects of chemical kinetics and scalar dissipation rate is suggested and used for non-premixed combustion contributions. The results clearly show that both Z-c correlation and non-premixed combustion effects are required in the premixed flamelets approach to get good agreement with the measured flame lift-off heights as a function of jet velocity. The flame brush structure reported in earlier experimental studies is also captured reasonably well for various axial positions. It seems that flame stabilisation is influenced by both premixed and non-premixed combustion modes, and their mutual influences. © 2014 Taylor & Francis.

Preliminary study on the photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high-pressure mercury lamp irradiation

Under a high-pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals ((OH)-O-.) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high-performance liquid chromatography using benzene as a probe. The results showed that (OH)-O-. photoproduction increased from 1.80 to 2.74 muM by increasing the HA concentration from 10 to 40 mg L-1 at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of (OH)-O-. in the HA solution with Fe(111) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of (OH)-O-. in HA solution with algae with or without Fe(111) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of (OH)-O-. in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4-8 pH range led to the highest (OH)-O-. photoproduction at pH 4.0.

Application and validation of a new biotic index using data from several water systems

Protozoans of Lake Donghu were collected from five stations using the PFU method. The sampling was conducted for one year and two times a month. The aim of this research was to test the applicability of a new protozoa biotic index, species pollution value (SPV) and community pollution value (CPV), established by the authors using data from the River Hanjiang. Each station's CPV was calculated from the SPV and the correlation analysis between the CPV and the comprehensive chemical index of stations I, II, III showed a significant correlation between them. The pollution status of the five stations was correctly evaluated by the CPV. These results suggested that the biotic index could be applied in water systems other than the River Hanjiang. The SPV of some protozoa species in Lake Donghu, not observed in the River Hanjiang were established. In order to further test the applicability of the biotic index, protozoan and chemistry data from the Rivers Torrente Stirone and Parma of Italy were used. The results showed that the CPV for the two rivers had a close relationship with the chemical water quality, which indicated that the biotic index could be applied in other parts of the world for the monitoring and estimating of water quality. Since the results of testing and verifying the biotic index in some other water systems in China were also satisfactory, this indicated that the biotic index has an extensive suitability for freshwater ecosystems. As long as more than 50% of the species in a sample have a SPV, the CPV calculated from the SPV is reliable for monitoring and evaluating water quality.

A preliminary phylogenetic analysis of Metapenaeopsis (Decapoda : Penaeidae) based on mitochondrial dna sequences of selected species from the Indo-West Pacific

Phylogenetic relationships within Metapenaeopsis remain largely unknown. The modern revision of the genus suggests that the shape of the petasma, followed by the presence of a stidulating organ, are the most important distinguishing taxonomic features. In the present study, phylogenetic relationships were studied among seven Metapenaeopsis species from the Indo-West Pacific based on partial sequences of mitochondrial 16S rRNA and cytochrome c oxidase I (COI) genes. Mean sequence divergence was 6.4% for 16S and 15.8% for COI. A strikingly large nucleotide distance (10.0% for 16S and 16.9% for COI) was recorded between M. commensalis, the only Indo-West Pacific species with a one-valved petasma, and the other species with a two-valved petasma. Phylogenetic analyses using neighbor-joining, maximum parsimony, and maximum likelihood generated mostly identical tree topologies in which M. commensalis is distantly related to the other species. Two clades were resolved for the remaining species, one with and the other without a stridulating organ, supporting the main groupings of the recent taxonomic revision. Results of the present study also indicate that the deep-water forms represent a relatively recent radiation in Metapenaeopsis.

Preliminary design of a tensile-strained p-type Si/SiGe quantum well infrared photodetector

Considering tensile-strained p-type Si/Si1-yGey quantum wells grown on a relaxed Si1-xGex ( 0 0 1) virtual substrate ( y < x), the hole subband structure and the effective masses of the first bound hole state in the quantum wells are calculated by using the 6 x 6 k center dot p method. Designs for tensile-strained p-type quantum well infrared photodetectors ( QWIPs) based on the bound-to-quasi-bound transitions are discussed, which are expected to retain the ability of coupling normally incident infrared radiation without any grating couplers, have lower dark current than n-type QWIPs and also have a larger absorption coefficient and better transport characteristics than normal unstrained or compressive-strained p-type QWIPs.

In situ hydrate dissociation using microwave heating: Preliminary study

In this work, we investigate the dissociation behavior of natural gas hydrate in a closed system with microwave (MW) heating and hot water heating. The hydrate was formed at temperatures of 1-4 degrees C and pressures of 4.5-5.5 MPa. It was found that the gas hydrate dissociated more rapidly with microwave than with hot water heating. The rate of hydrate dissociation increased with increasing microwave power, and it was a function of microwave power. Furthermore, the temperature of the hydrate increased linearly with time during the microwave radiation.