Suppression Characteristics Research Articles

Dust suppression analysis of a new conveying channel using CFD-DEM simulation and experiment test

Dust pollution related to channel discharge has drawn the attention of industries dealing with bulk mate-rial handling. However, this mode of transportation is a complex phenomenon that requires low particle velocity and high airflow control to suppress dust. Thus, it is necessary to develop an accurate double guide plates system to verify the characteristics of the conveying channel. Therefore, in this investigation, the inclination angle of the guide plate (55°, 60°, 65°, 70°) and the spacing from the upper outlet (170 mm, 180 mm, 190 mm, 200 mm, 210 mm) are calculated. The dust suppression characteristics of different guide plate spacing and inclination angles are studied. The fluid medium is air, and viscosity and density of the flow field are 1.8 × 10-5 Pa·s and 1.225 kg/m3, respectively. The calculation results are also synchronized with experimental data of the conveying channel. The results show that the dust suppression effect is the best when the inclination angle of the guide plate is 65° and the spacing is 170 mm. The particle velocity and airflow velocity are further discussed in detail. The particle velocity change and airflow velocity are the smallest with the inclination angle of the guide plate is 65° ∼ 70° and the spacing is 170 mm.

Investigation on Influence of Transverse Jet Incidence Angle on Radiation of Plume

To study the effects of different incidence angles on the flow mixing and infrared suppression characteristics of the jet, the transverse jets were introduced on the basis of the axisymmetric convergent nozzle model, and the effects of five different transverse jets on the flow mixing and infrared suppression characteristics of the jet were studied. The flowfield and temperature field are obtained by solving the N-S (Navier-Stokes equation is the momentum conservation equation of viscous fluid) equation with the finite volume method. The infrared radiation intensity of the jet is obtained by using Reverse Monte Carlo method and narrowband model. The results showed that the transverse jet induces pair vortex structures that gradually increase in the direction of the flow. In addition, the vorticity increases with the increase of jet incidence angle, and the mixing ability of the cold flow and the high-temperature core region becomes stronger. The length of the high-temperature core region decreases continuously with the increase of the transverse jet incidence angle θ and reaches a minimum when θ=150°. Compared to the condition without the transverse jet, the length of the high-temperature core region is shortened by 38.9%. The intensity of radiation decreases with the increase of the transverse jet incidence angle. When the incidence angle θ is 150 deg, the radiation intensity of the plume decreases by 34.9%.

On low-frequency vibration suppression characteristics of corrugated metamaterial beams

On low-frequency vibration suppression characteristics of corrugated metamaterial beams

A Novel Balanced‐to‐Balanced Filtering Crossover With Wideband Isolation and Common‐Mode Suppression

ABSTRACTIn this paper, a novel balanced‐to‐balanced (BTB) filtering crossover is proposed, which is co‐designed to integrate the bandpass response and common‐mode (CM) suppression characteristics without cascading the filtering networks and Baluns. Even‐ and odd‐mode analysis is adopted to verify that the proposed BTB filtering crossover can achieve the differential‐mode (DM) cross‐transmission while maintaining high isolation and CM suppression. For verification of the design theory, a microstrip prototype with the center frequency f0 of 2.45 GHz is fabricated and measured. The measured DM return loss, insertion loss, and isolation are 28.7, 0.54, and 43.6 dB, respectively. For CM excitation, the measured CM suppression and isolation at f0 are 45.4 and 45.6 dB, respectively. More importantly, the proposed crossover features wideband isolation (over 20 dB) and CM suppression (over 45 dB) covering all measured frequencies from 1.0 to 4.0 GHz.

Numerical Investigation of Raman-Assisted Four-Wave Mixing in Tapered Fiber Raman Fiber Amplifier

The generation of unwanted higher-order Raman effects is the main factor restricting the power scaling of Raman fiber amplifiers (RFAs). This phenomenon arises from an interplay of physical processes, including stimulated Raman scattering (SRS), four-wave mixing (FWM), and the intricate temporal and spectral dynamics. Tapered fibers have demonstrated excellent nonlinear effects suppression characteristics due to the varying core diameter along the fiber, which is widely used in ytterbium-doped fiber lasers. In this paper, a comprehensive numerical investigation is conducted on the core-pumping tapered fiber RFAs considering Raman-assisted FWM. The higher-order Raman power in the tapered fiber is always kept at a low level, showing a weak Raman-assisted FWM effect. A numerical investigation is conducted to study the impact of the tapering ratio, the lengths of the thin part, tapered region, and thick part on the higher-order Raman threshold of RFAs. Furthermore, the impact of phase mismatch variations caused by changes in the seed wavelength, on the output signal power and nonlinear effects is analyzed. This paper presents, for the first time, a study on core-pumped RFAs using tapered fibers, providing a novel perspective on enhancing the power of RFAs.

Torsional vibration suppression and electromechanical coupling characteristics of electric drive system considering misalignment

Torsional vibration suppression and electromechanical coupling characteristics of electric drive system considering misalignment

Suppression characteristic of three inhibitors on the flame propagation of titanium dust layer

The suppression effect of three inhibitors (TiO2, NaHCO3, and NH4H2PO4) on the flame propagation of titanium dust layer is investigated in the self-made experimental system. Both camera and infrared images are used to record the effect of the inhibitor on the flame propagation process of titanium/inhibitors powder. The combustion products of three inhibitor/Ti dusts are analyzed to suppression mechanism of inhibitors. The effect of three inhibitors on the ignition induction time of the titanium powder is studied. The decomposition process of NaHCO3 and NH4H2PO4 and the production of gas under high temperature conditions may be the main reason for accelerating the flame propagation. The multiple high temperature regions in the dust layer can accelerate the flame propagation rate. Suppression mechanisms of three inhibitors are explained in detail. The inhibition mechanism of TiO2 mainly lies in its strong thermal stability. The inhibition effects of NaHCO3 and NH4H2PO4 include the dilution process and the decomposition process.

Investigation of motion response suppression characteristics in floating platforms equipped with novel spiral side plates

AbstractTo enhance the stability of floating wind turbine platforms, this study combines the structural characteristics of helical side plates and proposes the installation of serrated helical side plates on Spar wind turbine platforms. Based on potential flow theory, the present study employs blade element momentum theory and radiation‐diffraction theory. Upon establishing a dynamic data link library, wind‐wave coupling was implemented, and the dynamic response characteristics of platforms with different helical side plates were compared. The results indicate that in the frequency domain analysis, the platform with serrated helical side plates demonstrates reduced sensitivity to waves, with a particularly notable increase in added mass in the heave direction, suggesting excellent hydrodynamic performance. In the time domain analysis, improvements in the platform's surge and heave stability performances were observed, measuring 10.99% and 10.64%, respectively, in extreme conditions. Owing to the unique features of the serrated structure, the tension in the mooring chains on the wave‐facing side is reduced, thereby effectively lowering the fatigue load on the mooring chains.

Multi‐component coupling synergistic effect of resourced gold tailings on intumescent flame‐retardant polypropylene

AbstractAddressing the challenge of resource utilization of gold tailings. A high performance flame‐retardant fillers (K‐GTF) were prepared from gold tailings (GTF) by coupling and condensation for application to intumescent flame‐retardant polypropylene (PP). K‐GTF enhances the flame‐retardant, thermal stability, smoke suppression and mechanical properties of flame‐retardant PP through synergistic approach. The results show that K‐GTF demonstrates good flame‐retardant synergism, with PP composites containing 3% additive (PP/G3) exhibiting substantial flame‐retardant and smoke suppression characteristics. Notably, PP/G3 boasts a limiting oxygen index (LOI) of 36.1%, which is substantially higher than the 33.6% LOI of the flame‐retardant PP without added K‐GTF (PP/G0). Furthermore, the peak heat release rate (PHRR), peak smoke production rate (PSPR), total heat release rate (THR), and total smoke production (TSP) of PP/G3 were decreased by 32.5%, 26.9%, 31.6%, and 21.5%, respectively, as compared to PP/G0. According to the synergistic mechanism analysis, K‐GTF exerts a multi‐component coupling synergistic effect, which promotes the production of phosphorus‐rich cross‐linking structures in flame‐retardant PP materials during the combustion, thereby promotes the formation of stable, dense and intumescent char to further enhances the flame‐retardant performance of the PP materials. In terms of mechanical effects, the introduction of K‐GTF alleviates the issue of a substantial decline in mechanical properties typically caused by flame retardants in PP materials. This indicates that K‐GTF improves the compatibility between the flame retardants and the PP matrix, thereby enhancing the mechanical properties of the flame‐retardant PP materials.Highlights Successfully synthesis a flame‐retardant synergist (K‐GTF). K‐GTF has good synergistic flame‐retardant effect. K‐GTF substantially enhances char formation and thermal stability of flame‐retardant PP. K‐GTF exerts a multi‐component coupling synergistic effect. K‐GTF enhances the compatibility between the PP matrix and the flame retardants.

Miniaturized filter with harmonic suppression characteristics by embedding microstrip resonators in half‐mode substrate‐integrated waveguide resonant cavities

AbstractA novel filter design is proposed that employs harmonic rejection characteristics based on half‐mode substrate‐integrated waveguide resonance cavities and microstrip resonators. The objective is to expand the filter's blocking bandwidth and reduce the filter's size. The filter employs two half‐mode substrate‐integrated waveguide resonant cavities, which serve to effectively reduce the size of the filter. Moreover, the higher‐order modes TE201 and TE202 are unable to propagate within the resonant cavities. The suppression of the TE102 mode is achieved by setting the coupling window between the resonant cavities at the weakest field strength of this mode. Concurrently, two microstrip resonators are integrated into the coupling window, thereby enabling the realization of a fourth‐order filter response with only two resonant cavities. The filter was processed and measured, and the results were found to be in good agreement with the simulation. It is proved that the design method proposed in this paper is feasible.

Suppression characteristics of water mist containing alkali metal compounds in natural gas explosions

The natural gas explosion in semi-constrained spaces seriously jeopardize public safety. Water mist containing additive is an important method to reduce the disaster intensity. However, in actual scenarios, the explosion usually propagates for a certain distance before entering the mist area, which is more difficult to suppress the explosion. Therefore, the self-designed experimental system was used to recognize the suppression effect of water mist containing alkali metal compounds under the simulated scenario. The results show that the flame propagation distance was significantly reduced, the shortest overfire range was decreased by 40.0 % compared with the water mist condition. The peak overpressure and pressure rise rate also showed a significant decrease, the maximum pressure drop rate reached 72.3 %. When the explosion flame entered the atomized region, the turbulent disturbance generated by the atomization accelerated the mixture of combustion zone and the unburned area, which increases the possibility of consuming free radicals. Compared with the KCl and NaCl, the mist containing K2CO3 and Na2CO3 share higher suppression capacity. This study provides scientific guidance for the practical application of water mist explosion suppression.

Study on temperature noise suppression characteristics of passive thermal control materials in gravitational wave detection

Study on temperature noise suppression characteristics of passive thermal control materials in gravitational wave detection

High-dimensional nonlinear flutter suppression of variable thickness porous sandwich conical shells based on nonlinear energy sink

Nonlinear energy sink (NES) is widely applied in engineering field due to the advantages of light weight, high robustness, unidirectional energy transfer, rapid and broadband vibration isolation. In this paper, nonlinear energy sink is utilized to suppress vibration of the variable thickness porous sandwich conical shells for the first time, and the high-dimensional nonlinear flutter suppression characteristics of the system of simply supported variable stiffness truncated porous sandwich conical shell coupled NES under aerodynamic force and thermal stress are investigated. By applying the first-order shear deformation theory (FSDT), Hamilton's principle and Galerkin technique, the high-dimensional nonlinear ordinary differential flutter suppression equations of the system appended with NES are established. The accuracy of the theoretical approach is ensured by the comparison of frequency results, while the NES dissipated kinetic energy ratio and the comparison of NES performance with other suppression systems are presented to prove the effectiveness of NES on nonlinear flutter suppression. The time history diagrams and limit cycle oscillation (LCO) amplitude curves, which reflect the high-dimensional nonlinear flutter suppression effect of NES, are obtained by employing the Runge-Kutta method. The effects of aerodynamic pressure, the parameters and positions of single NES, and the positions of parallel NES and series NES on the high-dimensional nonlinear flutter suppression characteristics of the system attached with NES are discussed in depth. Finally, the optimal high-dimensional nonlinear flutter suppression scheme is arrived.

Effect of diammonium hydrogen phosphate coated with silica on flame retardancy of epoxy resin.

Epoxy resin has become one of the most widely used polymers owing to their excellent comprehensive properties. However, the inherent inflammability of epoxy resin (EP) has seriously limited its application in a range of fields with high fire safety requirements. Herein, a novel shell-core hierarchy architecture (DAP@SiO2) was prepared, composed of diammonium hydrogen phosphate (DAP) and in situ grown silica, and its structure and morphology were characterized by electron microscopy and infrared spectroscopy. The results indicated that silica particles were uniformly coated onto the surface of DAP. The modified DAP was used to reinforce the epoxy resin. The thermal stability of the EP blends was studied with the use of thermogravimetric analysis. The diammonium phosphate in DAP@SiO2 flame retardant produces pyrolysis gases such as NH3 and N2 during decomposition, diluting the concentration of oxygen and flammable volatile products around the flame. Secondly, silica migrates to the surface of epoxy resin to form a shielding layer, forming compounds containing Si-O-Si and O-Si-C structures, which can be cross-linked with other condensed phase products, greatly improving the thermal stability of the carbon layer. Fire behavior was evaluated using the limiting oxygen index (LOI), vertical burning test, and the cone calorimetry, and the flame retardancy mode of action was explained. With 12% of DAP@SiO2 involved, the EP blend passes UL-94 V-0 level, and its limiting oxygen index (LOI) reaches 33.2%. The incorporation of DAP@SiO2 in an EP matrix showed a slight reduction in the heat release and smoke production. The flame retardant mode of the EP polymer shows that its flame retardant and smoke suppression characteristics are related to the interaction of flame retardants in the gas phase and condensed phase. The mechanical properties test results illustrated that the tensile strength, elastic modulus and impact strength of EP/3%DAP@SiO2 are improved compared with pure EP. This is due to the crosslinking reaction between a large number of amino groups on the surface of DAP@SiO2 and the epoxy group on the epoxy resin, which significantly enhances the interfacial compatibility between DAP@SiO2 and epoxy resin, making the combination of DAP@SiO2 and epoxy resin closer.

Numerical investigation of air entrainment and outlet temperature characteristics of an infrared suppression device with obstacles

Infrared suppression devices (IRS) are crucial for stealth capabilities of modern naval ships and fighter jets. This study numerically investigates the air entrainment and outlet temperature characteristics of an IRS device with conical and spherical obstacles using finite volume method, to solve continuity, momentum, energy, and eddy viscosity-based k-ε equations. We vary Reynolds number (Ren), blockage volume ratio (Vob/Vmf), funnel-overlap height (Hov/Dn), and the nozzle inlet temperature (Tin/Tinf) within the ranges of 3.23×105 to 1.914×106, 0 to 0.106, 0 to 0.653, and 1.243 to 2.577, respectively, to analyze their impacts on enhancement in air entrainment and attenuation in outlet temperature. We observed that the dimensional air entrainment rate monotonously increases with the Reynolds number, and the obstacles further improve air ingestion. The conical obstacle entrains 28.96% more air than the spherical obstacle at a same Reynolds number (Ren=3.225×105) and blockage ratio. The blockage ratio positively impacts on the air ingress; and the maximum air ingestion occurs at a blockage ratio of 0.0266. An IRS with the higher positive overlap-height of funnels promotes air ingress to suppress the outlet temperature. Within the studied overlap height range (0–0.49), air ingress is enhanced by 50% and 85.9%, respectively at Ren=3.225×105 and 1.914×106. At Ren=1.914×106, the IRS exhibits 1.67 times more air entrainment rate at Tin/Tinf=1.91 than at Tin/Tinf=1.2438.

Experimental and simulation studies on suppressing gas explosions with diverse atomized liquid droplets: Insights for improved safety in mining

Gas explosions represent a prevalent thermodynamic hazard in coal mining, significantly endangering worker safety and the operation's overall safety. Water mist stands out among various explosion suppression techniques due to its high heat absorption capacity and environmental sustainability, offering a promising avenue for application. This study introduces a custom-built pipeline gas explosion testing apparatus to investigate the suppression effects of different atomized liquid droplets on gas explosions. By collecting and analyzing experimental data from pressure sensors under varying conditions within the pipeline, we conduct a thorough comparison of the explosion suppression characteristics attributed to different atomized droplets. Based on this foundation, the Fluent software was used for numerical simulation research to further analyze the explosion suppression effects of different atomized droplets. Additionally, numerical simulations were conducted to optimize the nozzle arrangement. Our findings reveal that an increase in atomization pressure, leading to smaller droplet sizes, significantly mitigates the impulse of the gas explosion shock wave. This indicates a marked inhibitory effect of atomized droplets on gas explosions, with finer droplets showing enhanced suppression capabilities. The simulation results from the optimized nozzle arrangement can provide valuable guidance for on-site deployment. Through a combination of experimental and simulation data, this study conducts a qualitative and quantitative analysis of the suppression mechanisms offered by different atomized droplets, considering parameters such as explosion impulse, blast energy, and explosion indices. The insights gained provide a theoretical foundation for reducing the ring-breaking effect of gas explosions and enhancing explosion suppression strategies, which are crucial for ensuring the safety of coal mining operations.

Experimental Study on Explosion Characteristics of LPG/Air Mixtures Suppressed by CO2 Synergistic Inert Powder

In order to study the explosion suppression characteristics of LPG/air mixture by CO2 synergistic inert powder, explosion suppression experiments were conducted in a 20 L explosion device. The results show that the explosion suppression effect of NaHCO3 powder is prior to Al(OH)3 powder under the condition of no CO2 synergy. As the mass concentration of inert powder increases, the peak value of explosion pressure Pex and the peak value of the pressure rise rate (dP/dt)ex decrease, and the explosion suppression effect gradually enhances. Gas–solid two-phase inhibitors exhibit more significant inhibitory effects than single-phase inhibitors. Increasing the volume fraction of CO2 or the mass concentration of inert powder can improve the explosion suppression effect. The explosion suppression effect of CO2/NaHCO3 is significantly better than that of CO2/Al(OH)3. The research results have certain significance for the prevention and control of LPG explosion accidents.

Beam-steerable filtering patch antenna with wide-stopband suppression and stable radiation characteristics

A method of designing beam-steerable patch antennas with wide stopband suppression is proposed in this article. The wide stopband suppression characteristic is realized by designing suitable parallel coupled lines and open-circuited stubs. The beam steering characteristic is achieved by using a driven patch and two pairs of metal walls vertically placed on both sides of the driven antenna. By controlling the different states of the switching PIN diodes loaded between metal walls, the stable beam steering characteristic can be obtained over the entire operating bandwidth. An experimental antenna is designed and manufactured to validate the approach. The beam steering angles of the simulation and measurement results are ±30°. Moreover, in the three proposed operating states, the out-of-band suppression from 2.6 GHz to 10 GHz is more than 16 dB. The proposed antenna can achieve the characteristic of both wide stopband suppression and beam steering. In addition, the proposed antenna is able to maintain good impedance characteristics during beam steering and maintain stable beam over the entire operating bandwidth.

Development of a Zr-Based Metal-Organic Framework (UiO-66) for a Cooperative Flame Retardant in the PC/ABS.

Polycarbonate/acrylonitrile butadiene styrene (PC/ABS) blends are widely used as engineering plastic alloys; however, they have a low fire safety level. To improve the flame-retardant property of PC/ABS, a zirconium-based metal-organic framework material (UiO-66) was synthesized with zirconium chloride and terephthalic acid and used as a flame-retardant cooperative agent. Its flame-retardant performance and mode of action in the PC/ABS blends were carefully investigated. The results showed that UiO-66 had good thermal stability and delayed the pyrolysis of the materials, thus significantly enhancing the efficiency of intumescent flame retardants. By compounding 7.0 wt% hexaphenyloxy-cyclotri-phosphazene (HPCTP) with 3.0 wt% UiO-66, the PC/ABS blends reached a limiting oxygen index value of 27.0% and V0 rating in the UL-94 test, showing significantly improved resistance to combustion dripping. In addition, UiO-66 enhanced the smoke and heat suppression characteristics of the intumescent flame-retardant materials. Finally, the flame-retardant mode of action in the blends was indicative of UiO-66 having a cooperative effect on the flame-retardant performance of PC/ABS/HPCTP materials. This work provides good ideas for further development of the flame-retardant ABS/PC.

Suppression characteristics and mechanisms of solid inhibitors on sawdust explosions in dust transportation systems

The explosion characteristics of pine sawdust mixed with typical inhibitors (calcium carbonate, calcium phosphate, ammonium phosphate) were investigated under different inerting ratios in a vertical flame propagation device. Different analytical analyses by TG-DTG-DSC and FTIR analysis were also coupled to understand the physical and chemical mechanisms of the treated samples. The results show that the flame propagation velocity and the peak pressure decreased by more than 50% for an inerting ratio of 60 wt%.This work clarifies the suppression characteristics and mechanism of different inhibitors in the flame propagation of biomass dust and yields some insights into the prevention and mitigation of biomass dust explosions in industrial applications.