Numerical investigation on multi-stage swirl cooling at mid-chord region of gas turbine blades

Compared with the single-stage one, the multi-stage swirl cooling technique has great potential at the mid-chord region of gas turbine blades. Currently, the effect of the chamber structure at the mid-chord region of the blades on the multi-stage swirl cooling is still unknown. In this study, four kinds of the multi-stage swirl chamber models are built: Case 1 has two swirl nozzles and three chambers, and cases 2-4 have six swirl nozzles and seven chambers. Fluid flow and heat transfer characteristics of the coolant in the swirl cooling configurations are numerically investigated. The standard k-epsilon turbulent model is adopted in current study and the Reynolds number of the coolant varies from 12,000 to 52000. The results show that the long swirl chamber in case 1 has negative effect on the performance of the swirl cooling this is because the swirl velocity along the axial direction is gradually reduced and the Nusselt number is decreased remarkably. For cases 2-4, the chambers are separated into several short ones. Therefore, the swirl velocity could keep high value and so is the Nusselt number. Although more swirl chambers could lead to higher pressure loss coefficient, cases 2-4 show better comprehensive thermal performance as compared to case 1. Among the current cases, the swirl chamber structure in case 4 shows the highest cooling effectiveness and obtains more uniform temperature distributions on the external surface of the blade

Based on Total Variation Regularization Iterative Blind Image Restoration Algorithm

In the process of image formation, transmission and recording, because of the imaging system, transmission medium and the equipment is not perfect, it makes the quality of image declined, the key of blurred image restoration is to estimate the Point Spread Function. Because Point Spread Function can’t be obtained, we can’t get the precise of fuzzy model. In this paper, we study a kind of blind image restoration method, the total variation regularization and iterative blind deconvolution is combined, we use Total Variation regularization algorithm in fuzzy identification stage, and use the combined of Total Variation regularization and iterative blind deconvolution algorithm in image restoration stage. In order to obtain the only solution of the algorithm, we also use the image and Point Spread Function constraints in the iterative process. The simulation results show that the proposed algorithm is more effective than some of the existing algorithms

Green Production Technology of the Monomer of Nylon-6: Caprolactam

After two decades’ endeavor, the Research Institute of Petroleum Processing (RIPP) has successfully developed a green caprolactam (CPL) production technology. This technology is based on the integration of titanium silicate (TS)-1 zeolite with the slurry-bed reactor for the ammoximation of cyclohexanone, the integration of silicalite-1 zeolite with the moving-bed reactor for the gas-phase rearrangement of cyclohexanone oxime, and the integration of an amorphous nickel (Ni) catalyst with the magnetically stabilized bed reactor for the purification of caprolactam. The world’s first industrial plant based on this green CPL production technology has been built and possesses a capacity of 200 kt·a−1. Compared with existing technologies, the plant investment is pronouncedly reduced, and the nitrogen (N) atom utilization is drastically improved. The waste emission is reduced significantly; for example, no ammonium sulfate byproduct is produced. As a result, the price difference between CPL and benzene drops. In 2015, the capacity of the green CPL production technology reached 3 × 106 t·a−1, making China the world’s largest CPL producer, with a global market share exceeding 50%

Serum-Based Culture Conditions Provoke Gene Expression Variability in Mouse Embryonic Stem Cells as Revealed by Single-Cell Analysis

Variation in gene expression is an important feature of mouse embryonic stem cells (ESCs). However, the mechanisms responsible for global gene expression variation in ESCs are not fully understood. We performed single-cell mRNA-seq analysis of mouse ESCs and uncovered significant heterogeneity in ESCs cultured in serum. We define highly variable gene clusters with distinct chromatin states and show that bivalent genes are prone to expression variation. At the same time, we identify an ESC-priming pathway that initiates the exit from the naive ESC state. Finally, we provide evidence that a large proportion of intracellular network variability is due to the extracellular culture environment. Serum-free culture reduces cellular heterogeneity and transcriptome variation in ESCs

Fast Switching of CO₃^–(H₂O)_<i>n</i> and O₂^–(H₂O)_<i>n</i> Reactant Ions in Dopant-Assisted Negative Photoionization Ion Mobility Spectrometry for Explosives Detection

Ion mobility spectrometry (IMS) has become the most deployed technique for on-site detection of trace explosives, and the reactant ions generated in the ionization source are tightly related to the performances of IMS. Combination of multiform reactant ions would provide more information and is in favor of correct identification of explosives. Fast switchable CO₃^–(H₂O)_<i>n</i> and O₂^–(H₂O)_<i>n</i> reactant ions were realized in a dopant-assisted negative photoionization ion mobility spectrometer (DANP-IMS). The switching could be achieved in less than 2 s by simply changing the gas flow direction. Up to 88% of the total reactant ions were CO₃^–(H₂O)_<i>n</i> in the bidirectional mode, and 89% of that were O₂^–(H₂O)_<i>n</i> in the unidirectional mode. The characteristics of combination of CO₃^–(H₂O)_<i>n</i> and O₂^–(H₂O)_<i>n</i> were demonstrated by the detection of explosives, including 2,4,6-trinitrotoluene (TNT), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), ammonium nitrate fuel oil (ANFO), and black powder (BP). For TNT, RDX, and BP, product ions with different reduced mobility values (<i>K</i>₀) were observed with CO₃^–(H₂O)_<i>n</i> and O₂^–(H₂O)_<i>n</i>, respectively, which is a benefit for the accurate identification. For ANFO, the same product ions with <i>K</i>₀ of 2.07 cm² V^–1 s^–1 were generated, but improved peak-to-peak resolution as well as sensitivity were achieved with CO₃^–(H₂O)_<i>n</i>. Moreover, an improved peak-to-peak resolution was also obtained for BP with CO₃^–(H₂O)_<i>n</i>, while the better sensitivity was obtained with O₂^–(H₂O)_<i>n</i>

Dopant-Assisted Negative Photoionization Ion Mobility Spectrometry for Sensitive Detection of Explosives

Ion mobility spectrometry (IMS) is a key trace detection technique for explosives and the development of a simple, stable, and efficient nonradioactive ionization source is highly demanded. A dopant-assisted negative photoionization (DANP) source has been developed for IMS, which uses a commercial VUV krypton lamp to ionize acetone as the source of electrons to produce negative reactant ions in air. With 20 ppm of acetone as the dopant, a stable current of reactant ions of 1.35 nA was achieved. The reactant ions were identified to be CO₃^–(H₂O)_<i>n</i> (<i>K</i>₀ = 2.44 cm² V^–1 s^–1) by atmospheric pressure time-of-flight mass spectrometry, while the reactant ions in ⁶³Ni source were O₂^–(H₂O)_<i>n</i> (<i>K</i>₀ = 2.30 cm² V^–1 s^–1). Finally, its capabilities for detection of common explosives including ammonium nitrate fuel oil (ANFO), 2,4,6-trinitrotoluene (TNT), <i>N</i>-nitrobis­(2-hydroxyethyl)­amine dinitrate (DINA), and pentaerythritol tetranitrate (PETN) were evaluated, and the limits of detection of 10 pg (ANFO), 80 pg (TNT), and 100 pg (DINA) with a linear range of 2 orders of magnitude were achieved. The time-of-flight mass spectra obtained with use of DANP source clearly indicated that PETN and DINA can be directly ionized by the ion-association reaction of CO₃^– to form PETN·CO₃^– and DINA·CO₃^– adduct ions, which result in good sensitivity for the DANP source. The excellent stability, good sensitivity, and especially the better separation between the reactant and product ion peaks make the DANP a potential nonradioactive ionization source for IMS