Startup analysis of an H2‐O2‐fired gas turbine cycle

A new thermodynamic cycle using artificial energy is now under investigation. The Japanese World Energy Network research program (WE‐NET) is one of the artificial energy technology programs which will use hydrogen energy. One of the targets of the program is the development of a high‐thermal‐efficiency, emission‐free power plant. The H₂‐O₂‐fired gas turbine is the key technology of the program and the advanced Rankine cycle is suggested as one of the most effective cycles. The advanced Rankine cycle is based on the direct steam expansion cycle. Mass and heat balance calculations were performed to determine the optimal operating point and the component design was carried out to develop the cycle. Further investigations necessary to realize the cycle include such topics as operational ability and cost performance. This paper considers operational ability, especially startup performance. In this analysis, the algorithm and process flow configuration for startup are developed. The investigation finds that the advanced Rankine cycle has good potential for practical use. © 1999 Scripta Technica, Electr Eng Jpn, 128(1): 9–16, 1999     

Numerical study of twin-screw extruders by three-dimensional flow analysis—development of analysis technique and evaluation of mixing performance for full flight screws

We have developed a method for predicting the three-dimensional flow field in the melt conveying zone in counter-rotating and co-rotating twin-screw extruders. We applied this technique to the full flight screws with thin flight width and open C-shaped channels in both rotating type extruders having the same screw configurations. We compared the details of velocity and stress fields, the flow rates of transportation, and various kinds of leakage flows for both rotating type extruders. Also, we obtained the spatial distribution of tracer particles and residence time distribution using a numerical tracer experiment. The flow rate in the transport direction in the co-rotating twin-screw was larger than that in the counter-rotating twin-screw, and this suggested that the latter has higher transport performance when the screws have thin flight width and open C-shaped channels as used in this study. As for the distributive mixing, it was found that the co-rotating twin-screw excels in the area of fluid rearrangement between the two screws and distribution in the rotational direction, while the counter-rotating twin-screw has the desirable characteristic of wide distribution in the axial direction. With regard to dispersive mixing, there was no considerable difference between calculated stress fields in both rotating type extruders.     

POROSITY AND RESIDUAL EQUILIBRIUM SATURATION OF SINTERED SPHERES OF GLASS BEADS

Sintered spheres(made of glass beads) were simply produced with a definite diameter, with a precision of ±0·5 mm in diameter, for a wide range of sintered angles (0–27°). The experimental values of the porosity of the sintered spheres were consistent with the calculated results for the coordination number N ≠ 8. The residual equilibrium saturation, as one of the basic physical properties of sintered glass beads was investigated experimentally and theoretically, resulting in the presence of a distribution in the angle of pendular ring.     

Numerical simulations of annular extrudate swell using various types of viscoelastic models

In this study, numerical simulations of annular extrudate swell of high density polyethylene (HDPE) were carried out. Some important viscoelastic models, such as the Larson, the PTT and the K-BKZ model, were employed for the swell calculation through various types of dies. These numerical results were compared with the experimental ones. The numerical results of the swell behaviors were very different in each viscoelastic model, while their simple shear flow characteristics were almost the same. As a result, the uniaxial elongational viscosity for large deformation as the steady state region is not important, but the property for relatively small deformation has remarkable effects on the numerical results for the die that have a uniaxial contraction region. Both reversible and irreversible types were tried for the Larson model. It was found that there was a difference between the irreversibility assumption of the K-BKZ model and the Larson model. While there was a serious difference in the response for reversing strain among these viscoelastic models, the response was very important to predict annular extudate swell behavior.     

A new process variable and dynamics selection method based on a genetic algorithm‐based wavelength selection method

Soft sensors have been used in industrial plants to estimate process variables that are difficult to measure online. Soft sensor models predicting an objective variable should be constructed with only important explanatory variables in terms of predictive ability, better interpretation of models and lower measurement costs. Besides, some process variables can affect an objective variable with time‐delays. Therefore, we have proposed the methods for selecting important process variables and optimal time‐delays of each variable simultaneously, by modifying the genetic algorithm‐based wavelength selection method that is one of the wavelength selection methods in spectrum analysis. The proposed methods can select time‐regions of process variables as a unit by using process data that includes process variables that are delayed in the range from zero to a set/given maximum value. The case study with simulation data and real industrial data confirmed that predictive, easy‐to‐interpret, and appropriate models were constructed using the proposed methods. © 2012 American Institute of Chemical Engineers AIChE J, 58: 1829–1840, 2012     

Integration of pillar array columns into a gradient elution system for pressure-driven liquid chromatography

A gradient elution system for pressure-driven liquid chromatography (LC) on a chip was developed for carrying out faster and more efficient chemical analyses. Through computational fluid dynamics simulations and an experimental study, we found that the use of a cross-Tesla structure with a 3 mm mixing length was effective for mixing two liquids. A gradient elution system using a cross-Tesla mixer was fabricated on a 20 mm × 20 mm silicon chip with a separation channel of pillar array columns and a sample injection channel. A mixed solution of water and fluorescein in methanol was delivered to the separation channel 7 s after the gradient program had been started. Then, the fluorescence intensity increased gradually with the increasing ratio of fluorescein, which showed that the gradient elution worked well. Under the gradient elution condition, the retention times of two coumarin dyes decreased with the gradient time. When the gradient time was 30 s, the analysis could be completed in 30 s, which was only half the time required compared to that required for an isocratic elution. Fluorescent derivatives of aliphatic amines were successfully separated within 110 s. The results show that the proposed system is promising for the analyses of complex biological samples.     

Maintenance-free soft sensor models with time difference of process variables

In industrial plants, soft sensors are widely used to estimate process variables that are difficult to measure online. However, their predictive accuracy gradually decreases with changes in the state of the plants. Although regression models are reconstructed with database which includes newest data to solve this problem, some problems remain in practice. Therefore, we have attempted to reduce the effects of deterioration with age on soft sensor models without maintenance of the models. By constructing models based upon the time difference of an objective variable and that of explanatory variables, the effects of drift and gradual changes can be handled. We verified the superiority of the proposed method over traditional ones with simulation data and applied this method to actual industrial data. It was confirmed that the proposed method could achieve almost the same predictive accuracy as the updating model for 3 years without reconstruction of the model.     

Structure and electrical properties of ITO thin films deposited at high rate by facing target sputtering

High rate deposition of ITO thin films at a low substrate temperature was attempted by using a facing target sputtering (FTS) system. Deposition rate as high as 53 nm/min was realized on polycarbonate film substrate of 80-μm thickness. When the film was deposited at a deposition rate above 80 nm/min, polycarbonate film substrate was thermally damaged. The film deposited by FTS has much smaller compressive film stress than the film deposited by conventional magnetron sputtering. The film stress was reduced significantly by increasing the sputtering gas pressure and stress-free films can be obtained by adjusting the sputtering gas pressure. This may be mainly caused by the fact that bombardment by high energy negative oxygen ions to substrate surface during deposition can be completely suppressed in the FTS. Film structure and electrical properties changed little with substrate position, and uniform films were obtained by the FTS.     

Isolation and amino acid sequence of a protein-synthesis inhibitor from the seeds of rye (Secale cereale)

A protein-synthesis inhibitor, designated RPSI, was isolated from the seeds of rye (Secale cereale) using gel filtration and S-Sepharose column chromatography. RPSI is a basic protein with an isoelectric point of over 10, and the concentration of protein required for 50% inhibition of protein synthesis (IC50) of purified RPSI was about ten-fold the concentration of ricin A-chain. The complete amino acid sequence of RPSI was discovered by analyzing the peptides and fragments obtained from the proteolytic digests and by the cyanogen bromide- and hydroxylamine-cleavages of RPSI. RPSI consists of 280 amino acid residues and has a molecular weight of 30,171. RPSI has only 21% sequence identity with that of ricin A-chain, but all five amino acid residues involved in the active site of ricin A-chain are conserved in RPSI.     

Identification of the aspartic acid residue located at or near substrate-binding site of rye seed chitinase-c

Two children with acquired immunodeficiency syndrome (AIDS) and progressive encephalopathy underwent MR spectroscopy before and after antiretroviral therapy. Initial MR spectroscopy of the basal ganglia region showed decreased N-acetylaspartate (NAA)/creatine (Cr) and a lactate peak. After therapy, there was improvement in NAA/Cr and an absence of the abnormal lactate peak. We suggest that decreased NAA/Cr in AIDS is reversible, that brain lactate might correlate with inflammation, and that MR spectroscopy can be useful in treatment trials.