In the precision cutting of difficult-to-process metals,surface thermal damage to a workpiece is a significant technical challenge.Although clean minimum quantity lubrication(MQL)technology,which replaces traditional ...In the precision cutting of difficult-to-process metals,surface thermal damage to a workpiece is a significant technical challenge.Although clean minimum quantity lubrication(MQL)technology,which replaces traditional pouring cooling,is used,inadequate heat dissipation remains an issue.Cryogenic air MQL(CAMQL),an eco-friendly technology,can enhance the heat transfer performance of the lubricating film in the cutting zone,offering excellent cooling and lubrication effects.However,the influence of jet and temperature parameters on the average particle size and distribution characteristics of atomized droplets is not well understood.This study first analyzes the evolution of lubricant physical properties and establishes a quantitative mapping relationship between cryogenic air temperature and physical parameters of lubricant.Next,the unstable fluctuation in the annular liquid film at the two-phase flow nozzle exit is observed and analyzed.A thickness model of annular liquid film is developed,revealing the effect of airflow field on the annular liquid film.Finally,a model for the average particle size of atomized droplets under CAMQL is established.Numerical analysis and validation experiments under different working conditions show that the measured values align with the theoretical values.Under an air pressure of 0.4 MPa and an air flow temperature of−50℃,the droplet particle size is 133.5μm,with an error of 8.2%.The effect of air pressure on particle size is greater than that of air flow temperature.Additionally,the distribution spans of droplet size under different conditions are analyzed,and the results demonstrated that low temperatures help shorten the interval between particle sizes and improve the relative uniformity of particle size distribution.This research provides a theoretical basis for the application of CAMQL technology in the cutting process.展开更多
The aluminum hydroxide adjuvant possesses a poorly crystalline boehmite (PCB) structure, the stability of which is significantly affected by storage conditions. In the present study, we conducted a comprehensive inves...The aluminum hydroxide adjuvant possesses a poorly crystalline boehmite (PCB) structure, the stability of which is significantly affected by storage conditions. In the present study, we conducted a comprehensive investigation into the structural and quality alterations of aluminum hydroxide adjuvants under varying temperature conditions over time. Three batches of the adjuvant were stored at 2–8℃, 18–25℃, and 37℃, respectively, for 6 months. Key parameters, including X-ray diffraction patterns, pH, isoelectric point (pI), adsorption capacity, and average particle size, were analyzed to assess the impact of storage temperatures. X-ray diffraction analysis confirmed the PCB structure of the aluminum hydroxide adjuvant. Notably, after 1 month of storage at 37℃, new diffraction peaks emerged at 18.2 °2θ, with their intensity increasing progressively over time. Concurrently, the largest decreases in pI and pH were observed, measuring 0.78 and 1.33, respectively. In contrast, adjuvants stored at 2–8℃ for 6 months exhibited only faint diffraction peaks at 18.2 °2θ, indicating minor structural changes. Under these conditions, the reductions in pI and pH were comparatively smaller, at 0.43 and 0.80, respectively. The average particle size of the adjuvants remained within 110–140 nm across all storage conditions. Additionally, the aluminum hydroxide adjuvant consistently demonstrated a high protein adsorption capacity, approximately 8 mg BSA/mg Al^(3+), with no statistically significant differences in adsorption rates observed among the different temperature conditions (P > 0.05). These findings highlighted the remarkable adsorption efficiency of nanoparticle aluminum hydroxide adjuvants throughout storage, reinforcing their potential as superior vaccine adsorbents. However, elevated storage temperatures were shown to accelerate structural aging, promoting the formation of highly crystalline phases such as gibbsite or bayerite, which could compromise the stability and quality of the adjuvant.展开更多
In order to deal with the disadvantages of excessive grinding and non-uniformity in finished particle under high-pressure grinding rolls （HPGR） finished grinding system, four aspects were investigated, including eva...In order to deal with the disadvantages of excessive grinding and non-uniformity in finished particle under high-pressure grinding rolls （HPGR） finished grinding system, four aspects were investigated, including evaluating indicators, effects of operating factors, effect of particle uniformity on the flotation and formation mechanism of particle uniformity. Experiment of HPGR finished grinding system, cationic reverse flotation experiment and simulation test of particle bed comminution under the condition of quasi-static were carried out. Theoretical analyses indicated that both of uniformity coefficient and average particle size should be included in the uniformity analysis of the mineral particles. The results show that the effect of circulation fan impeller speed on particle uniformity is the most evident, HPGR working pressure and roll gap are second and HPGR roller speed is the last. Average particle size has a more obvious effect on the grade of flotation concentrate while uniformity coefficient has a more obvious effect on the flotation recovery. Considering the two aspects of grade and recovery, the optimal uniformity coefficient for flotation is 1.1-1.2 and the optimal average particle size for flotation is 50-55 μm. The operating factors which promote the shielding effect and compact effect in the HPGR finished grinding system should be strengthened based on the uniformity of particles.展开更多
The velocity distribution of sinter and gas in vertical cooling furnace(VCF)has an important influence on gas-solid heat transfer.Based on the slot model of single hopper in the VCF of Meishan Iron and Steel Co.,Ltd.,...The velocity distribution of sinter and gas in vertical cooling furnace(VCF)has an important influence on gas-solid heat transfer.Based on the slot model of single hopper in the VCF of Meishan Iron and Steel Co.,Ltd.,the velocity and particle size distribution of sinter and the velocity and pressure distribution of gas were studied using a computational fluid dynamics-discrete element method model to obtain the gas-solid flow rule in the VCF.The results showed that the velocity of sinter near the wall and the edge of vent cowl was lower than that in the rest of the same plane.Therefore,the rectangular section of the vertical cooling furnace can be divided into a quasi-static zone,a plug flow zone and a convergent flow zone according to the flow velocity of the sinter.The average particle size and the void fraction of sinter bed were distributed in"W"and"V"shape along the width direction,respectively.The distribution of gas velocity in the furnace cavity was uneven,and the high-velocity area gradually changed from the center to the edge of the furnace cavity with the rise of gas.Reducing the ratio of edge to center gas flow from 2.7∶1 to 0.7∶1 could improve the gas velocity,but could not change the gas velocity distribution.The gas velocity distribution was more affected by the average particle size distribution of the sinter bed.It was suggested that measures need be taken to adjust it to improve the gas velocity distribution in the VCF.展开更多
基金supported by the following foundation items:the National Natural Science Foundation of China(Nos.52375447 and 52205481)the Shandong Provincial Natural Science Foundation of General Program(No.ZR2024ME205)+1 种基金the Special Fund of Taishan Scholars Project(No.tsqn202408220)the Shandong Provincial Natural Science Foundation of Youth Fund(No.ZR2021QE116).
文摘In the precision cutting of difficult-to-process metals,surface thermal damage to a workpiece is a significant technical challenge.Although clean minimum quantity lubrication(MQL)technology,which replaces traditional pouring cooling,is used,inadequate heat dissipation remains an issue.Cryogenic air MQL(CAMQL),an eco-friendly technology,can enhance the heat transfer performance of the lubricating film in the cutting zone,offering excellent cooling and lubrication effects.However,the influence of jet and temperature parameters on the average particle size and distribution characteristics of atomized droplets is not well understood.This study first analyzes the evolution of lubricant physical properties and establishes a quantitative mapping relationship between cryogenic air temperature and physical parameters of lubricant.Next,the unstable fluctuation in the annular liquid film at the two-phase flow nozzle exit is observed and analyzed.A thickness model of annular liquid film is developed,revealing the effect of airflow field on the annular liquid film.Finally,a model for the average particle size of atomized droplets under CAMQL is established.Numerical analysis and validation experiments under different working conditions show that the measured values align with the theoretical values.Under an air pressure of 0.4 MPa and an air flow temperature of−50℃,the droplet particle size is 133.5μm,with an error of 8.2%.The effect of air pressure on particle size is greater than that of air flow temperature.Additionally,the distribution spans of droplet size under different conditions are analyzed,and the results demonstrated that low temperatures help shorten the interval between particle sizes and improve the relative uniformity of particle size distribution.This research provides a theoretical basis for the application of CAMQL technology in the cutting process.
文摘The aluminum hydroxide adjuvant possesses a poorly crystalline boehmite (PCB) structure, the stability of which is significantly affected by storage conditions. In the present study, we conducted a comprehensive investigation into the structural and quality alterations of aluminum hydroxide adjuvants under varying temperature conditions over time. Three batches of the adjuvant were stored at 2–8℃, 18–25℃, and 37℃, respectively, for 6 months. Key parameters, including X-ray diffraction patterns, pH, isoelectric point (pI), adsorption capacity, and average particle size, were analyzed to assess the impact of storage temperatures. X-ray diffraction analysis confirmed the PCB structure of the aluminum hydroxide adjuvant. Notably, after 1 month of storage at 37℃, new diffraction peaks emerged at 18.2 °2θ, with their intensity increasing progressively over time. Concurrently, the largest decreases in pI and pH were observed, measuring 0.78 and 1.33, respectively. In contrast, adjuvants stored at 2–8℃ for 6 months exhibited only faint diffraction peaks at 18.2 °2θ, indicating minor structural changes. Under these conditions, the reductions in pI and pH were comparatively smaller, at 0.43 and 0.80, respectively. The average particle size of the adjuvants remained within 110–140 nm across all storage conditions. Additionally, the aluminum hydroxide adjuvant consistently demonstrated a high protein adsorption capacity, approximately 8 mg BSA/mg Al^(3+), with no statistically significant differences in adsorption rates observed among the different temperature conditions (P > 0.05). These findings highlighted the remarkable adsorption efficiency of nanoparticle aluminum hydroxide adjuvants throughout storage, reinforcing their potential as superior vaccine adsorbents. However, elevated storage temperatures were shown to accelerate structural aging, promoting the formation of highly crystalline phases such as gibbsite or bayerite, which could compromise the stability and quality of the adjuvant.
基金Project(2013EG132088)supported by Special Program for Research Institutes of the Ministry of Science and Technology,ChinaProject(12010402c187)supported by Key Science and Technology Program of Anhui Province,China
文摘In order to deal with the disadvantages of excessive grinding and non-uniformity in finished particle under high-pressure grinding rolls （HPGR） finished grinding system, four aspects were investigated, including evaluating indicators, effects of operating factors, effect of particle uniformity on the flotation and formation mechanism of particle uniformity. Experiment of HPGR finished grinding system, cationic reverse flotation experiment and simulation test of particle bed comminution under the condition of quasi-static were carried out. Theoretical analyses indicated that both of uniformity coefficient and average particle size should be included in the uniformity analysis of the mineral particles. The results show that the effect of circulation fan impeller speed on particle uniformity is the most evident, HPGR working pressure and roll gap are second and HPGR roller speed is the last. Average particle size has a more obvious effect on the grade of flotation concentrate while uniformity coefficient has a more obvious effect on the flotation recovery. Considering the two aspects of grade and recovery, the optimal uniformity coefficient for flotation is 1.1-1.2 and the optimal average particle size for flotation is 50-55 μm. The operating factors which promote the shielding effect and compact effect in the HPGR finished grinding system should be strengthened based on the uniformity of particles.
基金Financial support provided by the Fundamental Research Funds for the Central Universities of China(N2225022)is gratefully acknowledged.
文摘The velocity distribution of sinter and gas in vertical cooling furnace(VCF)has an important influence on gas-solid heat transfer.Based on the slot model of single hopper in the VCF of Meishan Iron and Steel Co.,Ltd.,the velocity and particle size distribution of sinter and the velocity and pressure distribution of gas were studied using a computational fluid dynamics-discrete element method model to obtain the gas-solid flow rule in the VCF.The results showed that the velocity of sinter near the wall and the edge of vent cowl was lower than that in the rest of the same plane.Therefore,the rectangular section of the vertical cooling furnace can be divided into a quasi-static zone,a plug flow zone and a convergent flow zone according to the flow velocity of the sinter.The average particle size and the void fraction of sinter bed were distributed in"W"and"V"shape along the width direction,respectively.The distribution of gas velocity in the furnace cavity was uneven,and the high-velocity area gradually changed from the center to the edge of the furnace cavity with the rise of gas.Reducing the ratio of edge to center gas flow from 2.7∶1 to 0.7∶1 could improve the gas velocity,but could not change the gas velocity distribution.The gas velocity distribution was more affected by the average particle size distribution of the sinter bed.It was suggested that measures need be taken to adjust it to improve the gas velocity distribution in the VCF.
