In order to achieve a more stable spiral annular flow with lower pressure drop, this paper develops a novel winglet-type arc-vane swirler. Four swirler structures based on a winglet and introduced perforation and their effects on gas-liquid two-phase flow characteristics are studied and analyzed. The stability of liquid film in the spiral annular flow under inlet flow patterns of bubble, slug, and annular flow is evaluated using the Probability Density Function method. In combination with numerical simulations, the flow characteristics within each swirler are examined, revealing the influence of swirler structures on the formation of spiral annular flow. The results demonstrate that all four swirler structures generate more stable spiral annular flow than the arc-vane swirler under various flow patterns. Specifically, the winglet-type arc-vane swirler exhibits a more axisymmetric pressure distribution and higher tangential velocity, resulting in the most stable spiral annular flow and the longest stable distance. The flow-guiding effect promotes bubble migration toward the swirler center, with noticeable coalescence observed at the outlets of both the winglet-type arc-vane swirler and the fully perforated winglet-type arc-vane swirler. Although the fully perforated winglet-type arc-vane swirler improves the circumferential gas-liquid distribution at the inlet, it also complicates bubble re-coalescence after breakup. In the partially perforated winglet-type arc-vane swirler, bubbles are destabilized by turbulent disturbances downstream of the perforations, resulting in lower stability than in the fully perforated winglet-type arc-vane swirler. In the winglet-type arc-vane swirler without hub, the fluid undergoes intense turbulence, causing the bubbles to rupture and disperse, resulting in the poorest stability of the liquid film.

The spreading behavior of a liquid film formed by oblique jet impingement directly influences the efficiency and uniformity of film cooling in liquid rocket engines. In this study, numerical simulations based on the volume of fluid (VOF) model were conducted, and an experimental system was established to measure film morphology and thickness for validation. The results show good agreement between the simulation and experiment, with relative deviations in film width and thickness of 20% and 10%, respectively, confirming the model's accuracy and applicability. On this basis, the effects of jet velocity, jet angle, jet orifice diameter, and wall contact angle on film spreading characteristics were systematically investigated. The results indicate that the increasing jet velocity and jet orifice diameter significantly increase the liquid film width and length. Increasing the jet angle increases the overall spreading area while reducing its streamwise length and increasing its width. Increasing the contact angle reduces the spreading area. Further sensitivity analysis reveals that the liquid film width is primarily influenced by the jet velocity and jet angle; the liquid film length is jointly determined by the jet velocity and jet orifice diameter; the jet orifice diameter predominantly governs the thickness in the thin-layer zone; and the thickness in the rise zone is jointly controlled by the jet angle and jet orifice diameter. These findings elucidate the key factors governing liquid film spreading characteristics, thereby providing theoretical guidance for the design and optimization of liquid-film cooling in liquid rocket engines.

Herein, four MgCo2Oz catalysts were fabricated via the co-precipitation method by using NH3 & sdot;H2O, NaOH, (NH4)2CO3 and Na2CO3 as the precipitants to regulate their catalytic performance for the thermal decomposition of ammonium per-chlorate (AP). The results indicated that carbonate precipitants helped to fabricate finer particles of Mg/Co species compared to hydroxide precipitants, while ammonia ions enlarged the as-fabricated particles more easily than Na+ precipitants. Furthermore, compared to NaOH precipitant, NH3 & sdot;H2O contributed to fabricating higher crystalline spinel-structured MgCo2O4 crystals, but the use of Na2CO3 precipitant was unfavorable for the interaction of Co/Mg species and also decreased the formation and crystallinity of spinelstructured MgCo2O4 crystals. Different from the other catalysts, the MC-NH3 & sdot;H2O-200 catalyst exhibited a uniform nanosheet structure with distinct polygonal features and many complex tiny pores, which presented smaller average pore size and larger BET surface area. Notably, there existed relatively stronger charge transfer between Mg and Co species on the surface of the MC-NH3 & sdot;H2O-200 catalyst. As a whole, MC-NH3 & sdot;H2O-200 presented the best catalytic activity for the thermal decomposition of AP, and reduced its HTD temperature to 274.4 degrees C by 150.1 degrees C, but the as-fabricated MgCo2Oz catalysts via Na +-based precipitants showed better activity in promoting the heat release of AP thermal decomposition than those catalysts via NH4+ precipitant agents, and the MC-NaOH-200 catalyst increased the heat release of AP thermal decomposition from 428.30 J g-1 to 2005.48 J g-1. Finally, the effect of precipitant types on the structure-activity relationship and catalytic mechanism of the as-fabricated MgCo2Oz catalyst on AP thermal decomposition was proposed.

To realize particle parameters measurements of condensed phase products in a solid rocket motor (SRM) plume under the rarefied atmospheric environment, a laser diffraction-based particle parameter measurement system was established based on the principle of laser diffraction particle sizing. Static particle size measurements were validated by using standard particles with diameters of 0.8 & micro;m, 1.5 & micro;m, 20 & micro;m, 100 & micro;m and 240 & micro;m. The results indicate that the maximum relative deviation of particle size measurement is 6.7%. On this basis, the measurement system was applied to measure particle parameters of condensed phase products in the SRM plume under the normal and rarefied atmospheric environments. The results show that the volume-weighted mean particle size (D43) of condensed phase products in SRM plume under the rarefied atmospheric environment is approximately 10 & micro;m, which is much smaller than the normal atmospheric environment. The light transmittance of SRM plume under the rarefied atmospheric environment during stable working stage ranges from 96.0% to 98.5%, while that under the normal atmospheric environment is below 30.0%. Furthermore, when distance from the nozzle exit increases, the particle size distribution broadens firstly and then narrows. The above measurement results of particle parameters of condensed phase products in the SRM plume can provide direct data support for the evaluation of plume characteristic signals, plume simulation modeling, and optimization design of SRM.

A multispectral reconstruction method for flame color images based on K-means clustering and backpropagation neural networks (BPNN) is proposed to overcome the low spectral resolution of temperature measurement using color RGB three-band radiation images. A synchronized imaging system with an RGB camera and a 25-band multispectral camera was built to capture candle flame images. Image partitioning created a training set linking the three-band RGB and 25-band multi-spectral responses. Neural network training established a mapping between them. Spectral reconstruction of the candle flame images achieved an average relative error below 5%. The temperature inversion yielded an average error of 31.5 K, with a mean error of 1.79% in the error distribution, respectively, with test set R2 values of 0.97-0.99, confirming high model accuracy. This work demonstrates the feasibility of merging the spatial advantages of RGB images with the spectral advantages of multispectral data, offering a new approach for dynamic flame temperature field monitoring.

Herein, the influence of calcination temperature on the evolutionary process of Mg/Co species interaction in the MgCo2Oz catalyst was studied for AP thermal decomposition. The results indicated that the as-fabricated MC-Na2CO3 catalyst by microwave irradiation assisting sodium carbonate co-precipitation method exhibited a typical flaky structure with non-uniform and coarse particle morphology, and the species of Co or/and Mg presented in an amorphous structure or/and a highly dispersed state. However, the calcination brought about the evolution of CO2 due to the decomposition of carbonate, and the treatment of calcination at 200 °C resulted in the formation of both MgCo2O4 and MgO crystals, which also promoted the interaction of Co and Mg species. Furthermore, the further enhancement of calcination temperature not only enlarged the growth up of spinel-structured MgCo2O4 crystals, but also decreased the diffraction peaks of MgO crystals through its proposed chemical reaction with Co species. This evolutionary process under the action of calcination at gradually increased temperatures regulated the chemical composition and states of elements on the surface of MC-Na2CO3 catalyst, and the surface Mg/Co molar ratio gradually decreased and then rebounded to 0.82 when the calcination temperature increases from 200 to 450 °C. The as-fabricated MC-Na2CO3-350 catalyst presented the largest surface Co2+/Co3+ molar ratio and the best catalytic performance of AP thermal decomposition, which reduced the HTD temperature of AP by 150.8 °C and increased its heat release to1685.48 J g−1. Finally, the influence of MC-Na2CO3-350 catalyst on AP thermal decomposition mechanism was discussed and proposed.

This paper proposes a measurement method integrating ultrasonic reflection and cross-correlation techniques to achieve accurate characterization of Taylor bubble velocity and length in vertical gas-liquid slug flows. The optimal sensor spacing was determined through rigorous cross-correlation analysis of the experimental data. By employing two ultrasonic sensors in an upstream-downstream configuration, ultrasonic reflection signals were captured to extract the gas-liquid interfacial information of Taylor bubbles under various flow conditions. Validation against simultaneous image-based measurements demonstrates that the relative errors for both velocity and length are within +/- 8%. This research provides a robust, non-invasive approach for measuring key parameters associated with Taylor bubble dynamics.

For the thermometry of ablation testing on insulation materials in solid rocket motors using oxygen–kerosene flames, multispectral imaging technology was employed to obtain radiative multispectral images of the oxygen–kerosene flame and the ablation surface of the insulation materials. Based on the differences in radiative characteristics between the flame and the ablated surface, the particle swarm optimization [Formula: see text]-means algorithm was applied for image clustering and segmentation. Parametric fitting of the spectral data for pixel points in different segments was performed, allowing for the simultaneous acquisition of combustion parameters for both the high-temperature tail flame and the ablation surface of the insulation specimens. In testing with different jet conditions, the temperature in the core region of the high-temperature tail flame under high-speed conditions is 300 K higher than that under low-speed conditions, with emissivity ranging from 0.05 to 0.15; the emissivity distribution is essentially consistent across both conditions. The temperature distribution of the ablation surface of the insulation materials ranges from 1560 to 1780 K, showing similar distribution. The more severe ablation of the insulation materials under high-speed jet conditions is the reason for the higher emissivity.

To investigate the structural integrity of solid propellant under low temperature ignition impulsion conditions, this paper employs the generalized nonlinear Zhu-Wang-Tang (ZWT) constitutive model with four Maxwell elements, where the parameters of the constitutive model are obtained combining the tensile test data and slime mold algorithm (SMA). Based on the secondary development function of UMAT of the ABAQUS finite element analysis software, this constitutive model is then adopted to numerically simulate the propellant uniaxial tensile test under constant strain. The simulation results were compared with experimental data to validate the reliability of the numerical simulation method. Finally, this numerical simulation method is used to study the structural integrity of 5-pointed star HTPB solid propellant under curing cooling and ignition impulsion conditions at -30 degrees C. The results show that the SMA has faster convergence and higher accuracy than commonly used ant colony optimization. The uniaxial tensile simulation results of the propellant under constant strain are consistent with the experimental results, which verifies the dependability of the constitutive model and the numerical simulation method. The HTPB solid propellant under the conditions of curing cooling and ignition impact at different ignition pressures (10, 12, 15, and 20 MPa) is also applicable to the HTPB solid propellant under different ignition pressures. The maximum equivalent stress and equivalent strain values of HTPB solid propellant under curing cooling and different ignition impulsion pressures (10, 12, 15, and 20 MPa) all appeared at the transition arc of the grain. The structural integrity of the grain is not damaged within 20 MPa ignition pressure at a low temperature of -30 degrees C.

To investigate the individual and combined influences of vibration and misalignment on the atomization characteristics of the impingement, this study employs the polyhedral mesh adaptive refinement algorithm and volume of fluid to discrete phase model (VOF-to-DPM) method to simulate impinging jet atomization. The numerical simulation results are validated through comparison with experimental data, ensuring calculation accuracy. The findings indicate that increased vibration frequency deteriorates atomization performance, with the back-splash phenomenon becoming particularly pronounced at a vibration frequency of 1000 Hz. In contrast to previous research, which typically addresses vibration and misalignment independently, this research concurrently evaluates their combined effects in a single numerical framework, and the results demonstrate that when the misaligned degree is small, low-frequency vibrations can mitigate the adverse effects of misaligned impingement, enhancing atomization performance. However, when the degree of misalignment is large, low-frequency vibrations amplify the deflection angle of the liquid film, shortening breakup length and degrading atomization performance. Consequently, this research provides novel insights into the dynamics of impinging jet atomization and contributes valuable implications for propulsion system design.

This paper investigates the influencing factors of the colorimetric radiation image temperature measurement method, including the representative wavelength, the calibration method, and the camera exposure time. A relatively high-precision method is next obtained for selecting a representative wavelength and calibration method. Then it is applied to the measurement of the combustion temperature of the solid propellant specimen. Finally, the temperature variation regularity of a different propellant was analyzed in the process of combustion. The results show that selecting the maximum response of each channel of the camera as the representative wavelength and the function construction method is more accurate for calibration and calculation. In the range of the photoelectric response of the camera, the exposure time has little effect on the temperature measurement accuracy. Compared with thermocouple temperature measurement results, the relative deviation of radiation image thermometry is -1.2%, which verifies the accuracy of radiation image thermometry.

Electromagnetic flowmeter has advantages such as non-invasiveness, no moving parts and high reliability. And they are not affected by physical parameters like fluid density, temperature, pressure, and viscosity. However, they can be influenced by non-uniform distribution of medium conductivity. In this paper, the theoretical model of electromagnetic flowmeter under annular conductivity distribution was established based on the fundamental control equation and the annular domain weight function. To verify the effectiveness of the theoretical model, COMSOL Multiphysics numerical simulation and experimental validation study were both conducted. The relative deviations between the theoretical value and the numerical simulation, as well as the experimental result, are +/- 4 % and +/- 1 %, respectively. This study provides a theoretical basis for expanding the application of electromagnetic flowmeter to annular conductivity distribution.

This paper investigates the weight function distribution in the electromagnetic flowmeter with conductive pipe wall by combining the virtual current density method and COMSOL Multiphysics simulation software. It was found that the average weight function values were identical in any arbitrarily small annular domain in the pipe wall or fluid. Additionally, the ratio of the average weight function of the fluid domain to the pipe wall domain was only related to the ratio of their conductivity. Then a correlation for the average weight function ratio of the fluid and pipe wall was derived for the first time. The weight function correlation of the fluid domain was subsequently obtained by combining the physical meaning of the weight function. Finally, a theoretical model was derived based on the weight function correlation and the control equation of the electromagnetic flowmeter. The deviation between this model and the calculation results of the electromagnetic flowmeter model established by COMSOL Multiphysics was less than 4%.

The Solid Rocket Motor (SRM) is widely used as the power source of weapon systems because of its high reliability, good performance and simple structure [1]. With the development of power demand and technology of weapon systems, the energy density of SRM continues to increase. As the weapon system's largest quality initiating explosive device, the safety and stability of its transportation, storage and utilization are critical [2]. The U.S. put forward the concept of Low Vulnerability Ammunitions after the explosion of ammunition caused by the fire of the aircraft carrier “Forrest” in 1967. Low vulnerability means that when the ammunition is excited by external factors such as thermal, mechanical, shock wave, and so on, the ammunition has a little reaction and causes less secondary damage [3]. During transportation, storage, maintenance, and use of SRM, they may encounter dangerous conditions such as falling, impact, overturning vehicles, and drop impact. These dangerous drop impacts often occur in a transient state, which is sudden and random, and it is difficult to monitor and evaluate the damage response in real-time [4].

The accurate oil prediction of wells is essential for making informed decisions regarding the extension of the well lifespan and the enhancement of oil recovery rates. However, the prediction of oil well production is highly challenging due to the complex, nonlinear, and non-stationary data influenced by reservoir geological characteristics and operational adjustments. To address this, a novel prediction method for oil well production is proposed in this study. Firstly, the data-cleaning approach designed in this study is utilized to eliminate outliers from the raw dataset and impute missing values. Subsequently, relevant features are identified through analysis to form a usable dataset. The proposed deep learning neural network, namely the self-attention mechanism integrated with long short-term memory, is trained and learned on this dataset. Finally, the predictive performance of the model is validated using a set of actual oil production data. Through data experiments, the proposed model effectively predicts oil well production with superior accuracy compared to baseline models, achieving an R-squared of 0.872. This method provides reliable decision support for optimizing oil field development and management.

This study investigates the combustion of a single aluminum droplet in a high-temperature convective setting, focusing on the interplay between the environment and droplet evaporation combustion. Using the VOF numerical method, a two-dimensional multiphase flow combustion model for micron-sized aluminum droplets is developed. Experimental validation compares predicted droplet diameter with experimental data. The combustion behavior of aluminum droplets in high-temperature convective environments is analyzed, emphasizing gas-phase combustion during stable stages. Parametric variations in flow velocity and oxygen concentration reveal the formation of vortices around the droplet, influencing aluminum vapor accumulation and evaporation rates. Combustion primarily occurs at the droplet's windward side, with reaction rates decreasing downstream. Increasing gas velocity from 1.5 m/s to 3 m/s thins the aluminum vapor concentration boundary layer, boosting combustion rates by 35%. Elevating oxygen concentration from 20% to 50% brings the flame closer to the droplet, accelerating combustion rates by 2.7 times, suggesting oxygen concentration's role in reaction acceleration and combustion duration reduction. This research offers insights for simulating aluminum droplets in propellant applications.

The characteristics of phase-isolation of annular flow caused by axial flow swirler are very critical for separation efficiency of axial inlet separator and accuracy of phase-isolation based measurement method. However, there are lack of comparative study among different types of swirlers and research focusing on characteristics of phase-isolation. In this paper, the phase-isolation characteristics caused by four different classic axial flow swirlers with the same main structural parameters were firstly experimentally studied in upward vertical gas-liquid two-phase flow. Five flow patterns were proposed after obvious evolution in phase distribution at downstream of the swirler, including gas-column flow, swirling annular flow, central bubble flow, central bubble-column flow, and variable diameter gas-column flow. According to the different phase-isolation characteristics, flow patterns downstream of the swirler were divided into stable phase-isolation, quasi-phase-isolation, and non-effective phase-isolation. The corresponding flow pattern maps were also obtained respectively. The experimental results also show that the swirler with good phase-isolation performance generally requires a larger pressure drop as the cost. Finally, the flow in the swirlers was studied numerically. It is found that although the outlet angle of the swirlers is the same, different types of swirlers will result in flow with different deflection angle, and eventually cause the different phase-isolation performance.

The light transmittance measurement method, which is used to characterize smoke characteristic signal of solid rocket motor plume, can provide important reference for development and design of low smoke characteristic signal solid propellants and motors. The light transmittance measurement method of solid rocket motor plume based on laser modulation spectrum analysis is proposed in this paper. By using a 405 nm laser as the light source and a narrow-band filter detection method, the influence of plume radiation on the measurement of light transmittance of solid rocket motor plume smoke can be minimized. Additionally, combined with the laser modulation spectrum analysis technology, the signal amplitude is selected by the laser modulation frequency to improve the signal-to-noise ratio of the signal. Compared with the laser constant current measuring mode, laser high-frequency modulation measuring mode with spectrum analysis effectively improves the optical transmittance measurement accuracy. Based on this, a solid rocket motor plume smoke transmittance test system is developed to measure the plume smoke of standard test motors with different propellants and combustion chamber pressures. The results demonstrate that the system can effectively measure the light transmittance of the plume smoke. The light transmittance of solid rocket motor plume can be increased by reducing the aluminum content of solid propellant or increasing the pressure of the combustion chamber. Thus, this research provides an effective measuring tool for evaluating smoke concentration of solid rocket motor plume, which is beneficial to develop low smoke characteristic signal solid propellants and motors. image

Spiral annular flow within ducts is widely utilized in modern industry, with the swirler serving as a critical component in generating such flow patterns. The structure of the swirler significantly influences the generation and stability of the spiral annular flow. This study selected four different swirler structures with outstanding performance from previous research and analyzed their characteristics through visual image processing combined with numerical simulations. By analyzing the amplitude information of the wave fluctuations in the annular swirling flow liquid film under different operating conditions using probability density functions, it was found that the swirler A(Flat-vane swirler) and swirler B(Flat-vane swirler with hub) produced smaller fluctuations in the annular swirling flow liquid film, indicating better stability compared to the swirler C(Arc-vane swirler) and swirler D(Spiral-vane swirler), which exhibited poor performance. Combining the numerical simulation results with the analysis of the internal mechanism of the swirlers, it was discovered that within the swirler A and swirler B, the fluid between the swirler vanes experienced a larger pressure gradient, resulting in phenomena such as “jump” and “pull” under this pressure gradient. This, in turn, contributed to the generation of greater tangential velocity and radial pressure gradient after the fluid exited the swirler. Due to the influence of the swirler structure, the swirler A and swirler B did not completely separate the fluid region into four independent spaces. Instead, in the central connection area of the rear section of the swirler, the gas phase components aggregated earlier, greatly promoting the downstream generation of spiral annular flow. This study analyzed the two-phase flow process and mechanism inside the swirler, filling a gap in previous research and providing important references for the optimization and selection of swirlers.