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Continuous flow technologies have become increasingly important for biocatalytic processes. In this study, we present the application and modelling of covalently immobilised N-acetylglucosamine 2-epimerase and N-acetylneuraminic acid lyase in packed bed reactors for the synthesis of N-acetylneuraminic acid. The immobilised enzymes were stable under continuous flow process conditions with half-life times of >28 d (epimerase immobilised on hexamethylamino methacrylate HA403/M) or 58 d (lyase immobilised on dimenthylamino methacrylate ECR8309M), suitable for continuous flow applications. Kinetic studies revealed Michaelis–Menten kinetic behaviour for both enzymes. The kinetic parameters and the inhibitions were analysed under continuous flow conditions and were integrated into a process model using Python. The model was validated by varying flow rates, the mass of immobilised enzymes and the reactor dimensions and shows a low error compared to the measured data. An error accuracy of 6% (epimerase) or 9% (lyase) was achieved. The product concentrations of the enzyme cascade at the end of the packed bed reactor can be predicted with an accuracy of 9% for the calculation of a large column (84.5 mL) or of 24% if several small columns (2.5 mL, 0.8 mL) are connected in series. The developed model has proved to be valid and will be used to optimise the process with respect to substrate concentrations, reactor dimensions and flow rate. [ABSTRACT FROM AUTHOR]

The impact of supercooled water droplets is the cause of aircraft icing, and the acquisition of impingement characteristics is the key to icing prediction and the design of ice protection systems. The introduction of water droplet collection efficiency is required to obtain the characteristics for the Lagrangian method. In this work, a traditional flow tube method, a local flow tube method, and a statistical method are established to calculate the local collection efficiency, based on Lagrangian droplet trajectories. Through the numerical simulations of the air–droplet flow field around an NACA 0012 airfoil, the accuracies of the three methods in regard to collection efficiency are verified. Then, these three methods are applied to obtain the results for water droplet trajectories and the collection efficiency of an S-shaped duct, a 2D engine cone section and an icing wind tunnel. The results show that the distributions of water droplet collection efficiency obtained by the three methods are consistent and the three methods are all feasible when the water droplets do not overlap or cross before hitting the aircraft surfaces. When the water droplets are shadowed by upstream surfaces or blown by air injection, the droplet trajectories might overlap or even cross, and the local collection efficiencies obtained by the traditional flow tube method, local flow tube method, and statistical method might differ. The statistical method is relatively accurate. However, not all the droplet impingement characteristics obtained by the three methods are different due to these effects, and the non-crossing of the droplet trajectories is not a necessary condition for the use of the flow tube method. The effects of trajectory crossings are analyzed and discussed in detail in different situations for the three methods. This work is helpful for understanding and accurately calculating the droplet impingement characteristics and is of great significance for simulations of the aircraft icing process and anti/de-icing range. [ABSTRACT FROM AUTHOR]

The impact of supercooled water droplets is the cause of aircraft icing, and the acquisition of impingement characteristics is the key to icing prediction and the design of ice protection systems. The introduction of water droplet collection efficiency is required to obtain the characteristics for the Lagrangian method. In this work, a traditional flow tube method, a local flow tube method, and a statistical method are established to calculate the local collection efficiency, based on Lagrangian droplet trajectories. Through the numerical simulations of the air–droplet flow field around an NACA 0012 airfoil, the accuracies of the three methods in regard to collection efficiency are verified. Then, these three methods are applied to obtain the results for water droplet trajectories and the collection efficiency of an S-shaped duct, a 2D engine cone section and an icing wind tunnel. The results show that the distributions of water droplet collection efficiency obtained by the three methods are consistent and the three methods are all feasible when the water droplets do not overlap or cross before hitting the aircraft surfaces. When the water droplets are shadowed by upstream surfaces or blown by air injection, the droplet trajectories might overlap or even cross, and the local collection efficiencies obtained by the traditional flow tube method, local flow tube method, and statistical method might differ. The statistical method is relatively accurate. However, not all the droplet impingement characteristics obtained by the three methods are different due to these effects, and the non-crossing of the droplet trajectories is not a necessary condition for the use of the flow tube method. The effects of trajectory crossings are analyzed and discussed in detail in different situations for the three methods. This work is helpful for understanding and accurately calculating the droplet impingement characteristics and is of great significance for simulations of the aircraft icing process and anti/de-icing range.

A compilation of new advances made in the research field of laboratory reaction kinetics in China's Key Development Project for Air Pollution Formation Mechanism and Control Technologies was presented. These advances are grouped into six broad, interrelated categories, including volatile organic compound (VOC) oxidation, secondary organic aerosol (SOA) formation, new particle formation (NPF) and gas-particle partitioning, ozone chemistry, model parameters, and secondary inorganic aerosol (SIA) formation, highlighting the laboratory work done by Chinese researchers. For smog chamber applications, the current knowledge gained from laboratory studies is reviewed, with emphasis on summarizing the oxidation mechanisms of long-chain alkanes, aromatics, alkenes, aldehydes/ketones in the atmosphere, SOA formation from anthropogenic emission sources, and oxidation of aromatics, isoprene, and limonene, as well as SIA formation. For flow tube applications, atmospheric oxidation mechanisms of toluene and methacrolein, SOA formation from limonene oxidation by ozone, gas-particle partitioning of peroxides, and sulfuric acid-water (H 2 SO 4 -H 2 O) binary nucleation, methanesulfonic acid-water (MSA-H 2 O) binary nucleation, and sulfuric acid-ammonia-water (H 2 SO 4 -NH 3 -H 2 O) ternary nucleation are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

The near-surface ozone concentration in China has been increasing annually, making ozone pollution a focal point for air quality improvement. Reactions between peroxy radicals (HO 2 and RO 2) and nitric oxide (NO) are the primary photochemical source of ozone, thus the real-time monitoring of peroxy radicals can provide accurate insights into ozone production. In this study, a high-sensitive, low-interference instrument (ROxLIF) was developed by integrating chemical conversion with laser-induced fluorescence technique, ultimately enabling the distinct detection of HO 2 and RO 2 radicals. A conditional and stability optimization method was established to isolate intrinsic factors such as chemical loss, wall loss, and reaction pathways. Following optimization, the high detection capacity proved suitable for various RO 2 species derived from typical volatile organic compounds (VOCs) in ambient air, with normalized sensitivities ranging from 0.856 to 1.083 compared to CH 3 O 2. Specialized cell design ensured the near-zero NO interference in the fluorescence detection process, further enhancing the accuracy of ozone production qualification. Real-time P(Ox) quantification by ROxLIF is in good agreement with a direct measurement result during different scenarios. With a 60 s integration time, the detection limit for RO 2 radical was 1.08 × 106 cm−3 (2σ). The ROxLIF instrument operated reliably during a month-long measurement, generating high-quality timeseries on the concentrations of HO 2 and RO 2 radicals, which demonstrates the promising potential for accurate diagnosis of ozone formation. • A high-sensitive, low-interference system (ROxLIF) for peroxy radical detection was developed. • Consistency in high-sensitivity for various RO 2 are normalized by stability optimization method. • The quantification of P(Ox) in real time by means of ROxLIF is found to be in good agreement with direct measurement. [ABSTRACT FROM AUTHOR]

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The ignition, oxidation, and pyrolysis chemistry of methyl propyl ether (MPE) was probed experimentally at several different conditions, and a comprehensive chemical kinetic model was constructed to help understand the observations, with many of the key parameters computed using quantum chemistry and transition state theory. Experiments were carried out in a shock tube measuring time variation of CO concentrations, in a flow tube measuring product concentrations, and in a rapid compression machine (RCM) measuring ignition delay times. The detailed reaction mechanism was constructed using the Reaction Mechanism Generator software. Sensitivity and flux analyses were used to identify key rate and thermochemical parameters, which were then computed using quantum chemistry to improve the mechanism. Validation of the final model against the 1–20 bar 600–1500 K experimental data is presented with a discussion of the kinetics. The model is in excellent agreement with most of the shock tube and RCM data. Strong non‐monotonic variation in conversion and product distribution is observed in the flow‐tube experiments as the temperature is increased, and unusually strong pressure dependence and significant heat release during the compression stroke is observed in the RCM experiments. These observations are largely explained by a close competition between radical decomposition and addition to O2 at different sites in MPE; this causes small shifts in conditions to lead to big shifts in the dominant reaction pathways. The validated mechanism was used to study the chemistry occurring during ignition in a diesel engine, simulated using Ignition Quality Test (IQT) conditions. At the IQT conditions, where the MPE concentration is higher, bimolecular reactions of peroxy radicals are much more important than in the RCM. [ABSTRACT FROM AUTHOR]

A connecting structure between the ignitor and the BOP stack is proposed, and a three-dimensional model and a finite element model are established. Taking the 11" pilot tube with the corresponding ram BOP as an example, the impact force and wind load effect on the field operation are analyzed by ANSYS finite element simulation, and the mechanical properties of the weak points when the 13-3/8" pilot tube is suspended at high temperature (800 °C). The simulation results show that: the maximum equivalent stress of 11" BOP structure is about 65 MPa under the condition of only bearing its own gravity, and 64 MPa under the impact force of wellhead, all of which are located at the branch of ignition tube; under the condition of level 6 wind load, the influence is very small and can be ignored; the maximum stress of 13-3/8" BOP structure at high temperature appears at the opening on both sides, which is 58. 4 MPa, with deformation 27 mm more than that at room temperature, which has little effect on the overall structure. The connection structure between the pilot tube and the BOP group can meet the field operation conditions, which has guiding significance for the next step of well control rescue operation and tool design. [ABSTRACT FROM AUTHOR]

The paper shows the possibility of improving gas-dynamic characteristics of a submerged air intake and presents a technology of developing design solutions according to the principle of conformity to the flow lines. The gas-dynamic principle of shaping is provided by means of computer-aided integrated technologies of design and application of numerical visualization methods as design tools. The revealed regularity of the working process of the external streamline of the preceding airframe surfaces unambiguously defines the fundamental design distinctions of the conformal air intake in the form of the converging side edges on the stream and determines its advantages over the analogs.

Photoionization mass spectrometry as a powerful analytical method has been widely utilized and provided valuable insight in the field of gas‐phase reactions. Here, a highly sensitive vacuum ultraviolet (VUV) photoionization time‐of‐flight mass spectrometer combined with a microwave discharge generator and a fast flow tube reactor has been developed to study radical reactions of atmospheric and combustion interests. Two kinds of continuous light sources, the tunable VUV synchrotron radiation at Hefei, China for isomer‐specific product detection and a commercial krypton discharge lamp for time‐consuming kinetic measurements, are employed as photoionization sources in the apparatus. A multiplexed detection with high sensitivity (the limit of detection ∼0.8 ppb) and high mass resolution (M/ΔM ∼ 2100) has been approached. As representative examples, the self‐reaction of the methyl radical, CH3, and the reaction of the methyl radical with molecular oxygen are studied and multiple species including reactive radicals and isomeric/isobaric products are detected and identified. In addition, some preliminary results related to the reaction kinetics are also presented. [ABSTRACT FROM AUTHOR]

This paper presents results obtained between 2010 and 2014 in the field of fan aerodynamics at the Department of Composite Technology at the VZLÚ aerospace research and experimental institute in Prague – Letnany. The need for rapid and accurate methods for the preliminary design of blade machinery led to the creation of a mathematical model based on the basic laws of turbomachine aerodynamics. The mathematical model, the derivation of which is briefly described below, has been encoded in a computer programme, which enables the theoretical characteristics of a fan of the designed geometry to be determined rapidly. The validity of the mathematical model is assessed continuously by measuring model fans in the measuring unit, which was developed and manufactured specifically for this purpose. The paper also presents a comparison between measured characteristics and characteristics determined by the mathematical model as the basis for a discussion on possible causes of measured deviations and calculation deviations.