Different compression sutures combined with intracameral air injection for acute corneal hydrops

·AIM:To evaluate the efficacy and safety of full-thickness sutures combined with intracameral air injection(FTS-AI)versus pre-Descemet’s membrane sutures combined with intracameral air injection(PDS-AI)in the management of acute corneal hydrops in keratoconus.·METHODS:The research included 8 patients(8 eyes)suffering from acute corneal hydrops caused by keratoconus.Four patients were randomly assigned to FTS-AI.And the other four were randomly assigned to PDS-AI.Corneal oedema,visual acuity,corneal thickness were assessed during follow-up.·RESULTS:The demographics,preoperative duration of symptoms and severity of corneal hydrops between the two groups were not significantly different.The mean corneal oedema resolution time after FTS-AI and PDSAI were 11±1.15 and 15±1.41 d,respectively(P=0.005).The maximum corneal thickness of the scarred region decreased in both groups at one week postoperatively(P<0.05).No obvious difference was found in the mean maximal corneal thickness between the two groups postoperatively.The BCVA improved significantly after FTS-AI and PDS-AI at three months postoperatively.No obvious difference was found in the BCVA after FTS-AI and PDS-AI at three months postoperatively.·CONCLUSION:FTS-AI and PDS-AI are safe and effective therapies to accelerate the resolution of corneal oedema in acute corneal hydrops secondary to keratoconus.Despite faster resolution of corneal oedema in the FTS-AI group,we recommend PDS-AI to avoid potential endothelium cell damage.

Steady air injection flow control for increasing the surge margin of radial flow compressor

Steady air injection upstream of the leading edge was used to increase the surge margin of a centrifugal compressor.To reveal the mechanism,steady numerical simulations were performed on a high pressure ratio centrifugal compressor rotor operated with a rotor tip speed of 586 m/s.Eight different injection yaw angle with four different injection mass flow was performed to determine the configuration that provide the best results for the compression system studied in this work.The injection angle,α,was fifteen degree and the injectors were placed at short distance（ten percent of the inlet tip radius upstream of the compressor face） to achieve maximum control over the leading edge flow by varying individual injection parameters.The results show that at design speed（n=50 000 r/min） with injection flow rate more than 2% of the main flow rate and yaw angle between 20° and 30°,the mass flow rate at stall decreases for approximately 8%.But with higher injection rate,other compressor parameters were affected such as compressor efficiency and compressor total pressure ratio.

Oil oxidation in the whole temperature regions during oil reservoir air injection and development methods

The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.

Simulation of Air Source Heat Pump with Refrigerant Injection for Heating Operation

An air source heat pump(ASHP)with refrigerant injection is proposed for the air conditioning system of electric vehicles(EVs),especially for efficient heating in cold winter,when there is no wasted heat of engines.The simulation model is built with the framework of two-phase fluid network,where the compressor is separated as two compressors and the economizer is treated as two heat exchangers in the injection path and the main refrigerant path.With the validated simulation model,the heating performance is analyzed,and the results show that the coefficient of performance(COP)of ASHP with refrigerant injection is higher than 1.4 and the discharge temperature is less than 100℃ when the outdoor temperature is-20℃.The above performance ensures that the air conditioning system and EVs can operate normally with high efficiency even in the cold winter,which is much helpful for the practicability of EVs.

Lag times in toe-to-heel air injection(THAI)operations explain underlying heavy oil production mechanisms

From a time value of revenue point of view,it is preferred that the time between reservoir stimulation and oil production response is small.Heavy oil combustion processes have a lag time between air injection and liquid production,but the common practice in production data analysis uses simultaneous injection and production data when seeking a relationship between them.In this research,the time scales of production for the Kerrobert toe-to-heel air injection(THAI)heavy oil project in Saskatchewan,Canada,is analyzed by using cross correlation analysis,i.e.time delay analysis between air injection and oil production.The results reveal two time scales with respect to production response with two distinctive recovery mechanisms:(1)a short time scale response(nearly instantaneous)where oil production peaks right after air injection(directly after opening production well)reflecting cold heavy oil production mechanisms,and(2)a longer time scale(of order of 100-300 days)response where peak production occurs associated with the collective phenomena of air injection,heat generating reactions,heat transfer,and finally,heated mobilized heavy oil drainage to the production well.This understanding of the two time scales and associated production mechanisms provides a basis for improving the performance of THAI.

Resistance of Air Injection Transportation in a Cutter-suction Dredger

Cutter-suction dredger transports slurry through pipeline. But the pipeline is easy to be jammed and frayed because of huge resistance, resulting in limited exertion of dredger and high energy consumption. One of the solutions is air injection transporting, which can reduce the resistance in pipeline. This paper makes research on the relations between pipeline distance and other factors such as slurry concentration, pressure of air injection and transportation distance, by making use of Prof. Aluf Orell＇ s slug model. The test data prove that the key factors are slurry concentration and air volume fraction, and that high slurry concentration and low air volume fraction can reduce more resistance, and such reducing effect becomes weaker with the increase of transportation distance.

Experimental study on secondary air mixing along the bed height in a circulating fluidized bed with a multitracer-gas method

A multitracer-gas method was proposed to study the secondary air(SA)mixing along the bed height in a circulating fluidized bed(CFB)using carbon monoxide(CO),oxygen(O_(2)),and carbon dioxide(CO_(2))as tracer gases.Experiments were carried out on a cold CFB test rig with a cross-section of 0.42 m×0.73 m and a height of 5.50 m.The effects of superficial velocity,SA ratio,bed inventory,and particle diameter on the SA mixing were investigated.The results indicate that there are some differences in the measurement results obtained using different tracer gases,wherein the deviation between CO and CO_(2) ranges from 42%to 66%and that between O_(2) and CO_(2) ranges from 45%to 71%in the lower part of the fluidized bed.However,these differences became less pronounced as the bed height increased.Besides,the high solid concentration and fine particle diameter in the CFB may weaken the difference.The measurement results of different tracer gases show the same trends under the variation of operating parameters.Increasing superficial velocity and SA ratio and decreasing particle diameter result in better mixing of the SA.The effect of bed inventory on SA mixing is not monotonic.

Heat Transfer and Flow Characteristics of Water Flow with Air Injection in Polyethylene Tube Placed over Metal Rods: Influence of Pitch Length and Tube Width

A polyethylene tube can be used as a heat exchanger for a low-running-cost?temperature control system. In this system, the flow of temperature-controlled?water in the tube is used as the heat source, and the tube is placed on the ceiling of a temperature-controlled space using a metal net. Owing to this structure, the tube is deformed by its weight. This deformation has a significant influence on heat transfer and flow characteristics. Therefore, an air injection method, in which air and water are injected simultaneously into the tube, is developed for preventing the deformation of the tube. In this study, bedding metal rods were used instead of a metal net. The influence of the pitch length of the metal rods (5 - 15 cm) and the width of the polyethylene tube 15, 20, 25, 30, and 35 cm was examined experimentally. The length of the polyethylene tube was 178 cm. The air flow rate was 9.5 × 10-5 m3/s. The water flow rates were 60, 80, 100, 120, and 140 mL/min. Results show that the thermal response improved because of air injection. In particular, the temperature at steady state increased, and steady state was attained approximately 1.2 - 3 times faster with air injection than without air injection. The optimum pitch length of the metal rods and the range of the optimum width of the polyethylene tube were 8 cm and 20 - 25 cm, respectively, with and without air injection.

H_2/Air连续旋转爆震波的起爆及传播过程试验

在环缝-喷孔对撞式喷注模型发动机上,采用H2/O2热射流切向喷注的起爆方式,进行了H2/Air组合的连续旋转爆震试验,试验成功起爆并实现了爆震波的持续旋转传播。切向喷注的热射流并没有直接诱导形成旋转爆震波,从点火到形成稳定传播的旋转爆震波之间存在时间间隔。对高频信号的时频分析结果表明,在该试验工况下,旋转爆震波的传播过程非常稳定,其传播频率为5.5～5.95 kHz,平均传播频率为5.75 kHz,对应的平均传播速度为1716.4m/s,为理论预测值的91.14%。在没有测量高频压力的情况下开展了长程试验,结果表明,连续旋转爆震波也可以在更长的时间范围内稳定工作。

Heat front propagation in shale oil reservoirs during air injection:Experimental and numerical studies

Air injection technique for developing shale oil has gained significant attention. However, the ability of the heat front to consistently propagate within the shale during air injection remains uncertain. To address this, we investigated the heat front propagation within oil-detritus mixtures, shale cores, and fractured shale cores using a self-designed combustion tube(CT) and experimental schemes. By integrating the results obtained from high-pressure differential scanning calorimetry and CT, we developed a comprehensive reaction kinetics model to accurately analyze the main factors influencing the heat front propagation within fractured shale. The findings revealed that in the absence of additional fractures, the heat front failed to propagate within the tight shale. The flow of gases and liquids towards the shale core was impeded, resulting in the formation of a high-pressure zone at the front region of the shale. This pressure buildup significantly hindered air injection, leading to inadequate oxygen supply and the extinguishment of the heat front. However, the study demonstrated the stable propagation of the heat front within the oil-detritus mixtures, indicating the good combustion activity of the shale oil.Furthermore, the heat front successfully propagated within the fractured shale, generating a substantial amount of heat that facilitated the creation of fractures and enhanced gas injection and shale oil flow. It was important to note that after the heat front passed through the shale, the combustion intensity decreased. The simulation results indicated that injecting air into the main fracturing layers of the shale oil reservoir enabled the establishment of a stable heat front. Increasing the reservoir temperature(from 63 to 143℃) and oxygen concentration in the injected gas(from 11% to 21%) promoted notable heat front propagation and increased the average temperature of the heat front. It was concluded that temperature and oxygen concentration had the most important influence on the heat front propagation, followed by pressure and oil saturation.

Air-SAGD technology for super-heavy oil reservoirs

The air oxidation of super-heavy oil at low temperature was studied in laboratory and its influences on oil viscosity, component and steam sweep efficiency before and after air-injection were analyzed. The feasibility, operation mode and air flooding effect at the late stage of steam assisted gravity drainage(SAGD) were investigated by numerical simulation. The experimental results show for vertical-horizontal well pair SAGD test area of Xing VI Formation in Block Du 84 of Liaohe Oilfield, the low temperature oxidation occurred between 150-250 ?C(steam chamber temperature), the oil viscosity increased greatly after low temperature oxidation, consequently, the oil displacement efficiency dropped sharply. Three development methods in the late stage of SAGD were simulated, i.e., steam + air low temperature oxidation, only air low temperature oxidation and only air high temperature oxidation. By comparing production dynamic curves and residual oil distribution etc., high temperature oxidation reduced the heat loss in late stage of SAGD, recovered the residual oil effectively, and prolonged reservoir development time.

大尺度自航模气层减阻试验研究

[目的]旨在研究气流量、航行倾角对船底凹槽内气层保持和节能效果的影响。[方法]以一艘肥大型散货船的较大尺度缩比模型为研究对象,通过设计气层减阻自航模系统和船底凹槽方案,开展开阔水域条件下自航模气层减阻试验,研究模型正浮状态下喷气减阻效果,以及模型一定纵倾角状态下对航速和轴功率的影响。[结果]结果表明:在主机转速一定时,喷气可以明显提高自航模的航速,停止喷气后,船底凹槽内的气体仍能维持较长时间;船体艉倾角为0°~0.25°时的气层减阻效果较好,较大艉倾角时气体从自航模艏部两侧溢出,气层无法对船底实现有效覆盖,减阻效果不佳。[结论]研究结果可对气层减阻技术在肥大型船舶上的工程应用提供一定参考。

壁挂空调底盘模具结构设计

根据空调底盘的结构和外观要求,设计了一种含有多种脱模结构的热流道塑料模具。模具中,产品两端的扣位采用“斜导柱+滑块”机构脱模;出水管采用“油缸+滑块+斜抽芯”机构脱模;排风口、排风口旁边的V形槽、排风口内部的筋位采用组合滑块机构脱模;排风口中间的筋位采用由排风口滑块驱动的,先横向脱模、再纵向移动的滑块机构脱模;产品右上角的圆柱孔采用“斜导柱+斜抽芯”机构脱模;产品内表面的扣位采用定模斜顶结构脱模;在滑块上设置避空孔,防止滑块与顶杆发生干涉;根据产品结构设计的冷却系统,有利于模温均匀。

Experimental Study on the Skin Friction Reduction of Flat Plate by Formation of Air Cavity

The effects on the local skin friction of smooth flat plate by formation of air cavity are investigated experimentally,under the conditions of several variations of air injection angle,pore size,porous surface area and transverse step.The experimental results show that local skin friction of downstream of the porous section could be reduced at extent ranging from 50% to 90%,by injection air through pore or slot,with free stream velocities from 2 to 6 m/s.The pore size and area of air injection surface have small effect on skin friction reduction,step has significant effect on skin friction reduction.The mechanism of the skin friction reduction is due to the formation of air cavity,mixed with air and water,between the flat plate and its water boundary layer.

无人机用点燃式二冲程柴油机燃烧特性研究

针对柴油燃料雾化蒸发困难导致的发动机燃烧效果差、易爆震的问题,本文采用空气辅助缸内直喷方案,对一台点燃式二冲程柴油发动机开展燃烧特性研究。建立了点燃式二冲程柴油发动机的三维仿真模型,对混合气特性和燃烧特性进行仿真研究,并通过台架试验进行了验证。研究结果表明:点燃式二冲程柴油发动机在热机工况下,点火时刻有58%的燃油蒸发,缸内平均当量比由冷起动工况下的0.2提升至0.8,混合气品质较高,缸内燃烧情况良好。通过燃用汽油、柴油两种燃料进行发动机整机性能对比试验发现,在高转速大负荷工况下,两种燃料的燃烧特性曲线十分接近,柴油燃烧的指示平均有效压力(IMEP)的分布均值仅比汽油低1.2%。总体而言,柴油燃料应用于点燃式二冲程发动机的燃烧性能与汽油燃料相似,且使用柴油燃料时缸内压力最大震荡幅值仅为0.02 MPa,远小于爆震阈值,不会出现爆震现象。

补气增焓准二级压缩空气源热泵理论最佳除霜量研究

为解决能源浪费的问题,通过引入相关结霜模型进行理论分析,结合实验数据得出“理论最佳除霜量”的半经验公式。为验证该公式有效性,针对某厂家的补气增焓准二级压缩空气源热泵进行不同工况下:空气相对湿度65%、70%、80%,对应的空气干球温度-4~4℃的温度区间的实验测试。通过测试不同状态下的实际除霜量与“理论最佳除霜量”的半经验公式计算的理论除霜量进行比较,发现两者相对误差较小,保持在±10%以内,该公式对霜层后期的预测值较为准确,可作为设计补气增焓准二级压缩能够空气源热泵融霜时间控制的基准。

发酵罐内通入空气去除H_(2)S同步提升产甲烷效率研究

餐厨垃圾高温厌氧消化沼气中含有高浓度的H_(2)S,在使用前需要将其去除。对连续运行了230d的高温厌氧消化反应器进行研究,考察了不同有机负荷、通入空气量和沼气顶空循环对H_(2)S去除效果的影响,并分析了向反应器顶空通入空气后厌氧消化性能的提升效果。实验发现,在水力停留时间15d和沼气顶空停留时间2.8h的条件下,恒流量连续通入3倍理论空气量可去除78%的H_(2)S。进一步采用沼气顶空循环,H_(2)S体积分数从平均0.2%下降至0.01%以下,去除率达到95%。在通入空气的工况下,餐厨垃圾高温厌氧消化的甲烷产率提高了8.5%,达到310mL/g(以COD质量计);沼气容积产气率提高了10.5%,达到4.2L/(L∙d)。乙酸和丙酸的浓度与对照反应器相比没有显著变化,均维持在较低浓度水平。总体而言,在反应器内脱除H_(2)S的工艺方法操作简便,成本低廉,具有广阔的工程应用前景。

基于空气辅助喷射不同温度航空煤油喷雾特性可视化研究

为了探明燃油温度和喷油脉宽对空气辅助航空煤油喷雾特性的影响,在定容燃烧弹上搭建空气辅助燃油喷射系统,利用高速阴影成像技术探究了不同燃油温度和不同喷油脉宽下航空煤油的喷雾特性。研究表明,当喷油脉宽为12 ms时,高温燃油液滴更倾向于沿着喷嘴径向运动,低温燃油液滴更倾向于沿着喷嘴轴向运动,燃油温度从40℃降低到-40℃时,平均索特平均直径增大了14.7%,小粒径的占比大幅度减少;燃油温度为-40℃时大喷油脉宽下出现的“两段喷雾”对喷雾前后期的贯穿距和面积有不同的影响,喷雾卷吸幅度和宽度增大,喷油脉宽从5 ms增加到14 ms时,平均索特平均直径增加了22.2%。因此低温冷起动大喷油脉宽时,适当提高燃油温度可有效促进发动机顺利起动。

延长低渗透油藏CO_(2)驱油参数优化数值模拟研究

CO_(2)驱油在特低渗油藏中具有较好的应用效果,是提高采收率的重要方法。以延长油田H区块为研究对象,分析目前注水开发存在的问题,根据动静态参数将井组分成2类,应用数值模拟方法,分别对2类井组CO_(2)驱油的开发方式、注气时机、注气速度、井底流压及气水交替周期进行了优化。结果表明,以气水比1∶1且气水交替的方式在油井含水40%~60%时注气效果最佳。第1类注气井组的最优注气速度为10~15 t/d,井底流压1 MPa,气水交替周期60天;第2类注气井组最优注气速度为5~10 t/d,井底流压2 MPa,气水交替周期30天。该研究结果对H区块低渗油藏现场注CO_(2)驱油设计具有重要的指导作用。