In view of the problems of high injection pressure and low water injection rate in water injection wells of low permeability reservoirs featuring high temperature and high salinity,two new surfactants were synthesized...In view of the problems of high injection pressure and low water injection rate in water injection wells of low permeability reservoirs featuring high temperature and high salinity,two new surfactants were synthesized,including a quaternary ammonium surfactant and a betaine amphoteric surfactant.The composite surfactant system BYJ-1 was formed by mixing two kinds of surfactants.The minimum interfacial tension between BYJ-1 solution and the crude oil could reach 1.4×10^(-3) mN/m.The temperature resistance was up to 140℃,and the salt resistance could reach up to 120 g/L.For the low permeability core fully saturated with water phase,BYJ-1 could obviously reduce the starting pressure gradient of low permeability core.While for the core with residual oil,BYJ-1 could obviously reduce the injection pressure and improve the oil recovery.Moreover,the field test showed that BYJ-1 could effectively reduce the injection pressure of the water injection well,increase the injection volume,and increase the liquid production and oil production of the corresponding production well.展开更多
A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditiona...A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.展开更多
Biodiesel fuel is a potential alternative energy source for diesel engines due to its physiochemical characteristics relatively similar to those of traditional diesel fuel.In this study,the performance,emission,and co...Biodiesel fuel is a potential alternative energy source for diesel engines due to its physiochemical characteristics relatively similar to those of traditional diesel fuel.In this study,the performance,emission,and combustion features of a mono cylinder DI diesel engine are assessed using 20%Pumpkin seed methyl ester(PSOME20)and considering varying injection pressures(200,220,240,and 260 bar).The considered Pumpkin seed oil is converted into pumpkin biodiesel by transesterification and then used as fuel.The findings demonstrate that the Brake Thermal Efficiency(BTE)of PSOME20 can be raised by 1.68%,and the carbon monoxide(CO),hydrocarbon(HC),and smoke emanations can be lowered,while oxides of nitrogen(NOx)emissions are increased at an injection pressure(IP)of 240 bar compared to the standard IP of 200 bar.The cylinder pressure and the Heat Release Rate(HRR)become higher at 240 bar,whereas the ignition delay is shortened with respect to PSOME20 at a normal IP of 200 bar.展开更多
Injection pressure is one of the key parameters used in the design of shale gas reservoir stimulation.Higher injection pressure helps to initiate fractures,inject fracturing fluid and proppant smoothly and maximize th...Injection pressure is one of the key parameters used in the design of shale gas reservoir stimulation.Higher injection pressure helps to initiate fractures,inject fracturing fluid and proppant smoothly and maximize the stimulated reservoir volume as soon as possible.If the injection pressure is too high,however,the risk of casing deformation is increased significantly.In this paper,the numerical calculation format of the injection pressure safety window while ensuring casing integrity(i.e.,the maximum safety injection pressure)was proposed based on an example of an actual engineering project.Then,it was verified based on the actual situation of one shale gas well in Weiyuan.The numerical calculation format is as follows.First,a 3D finite element model of initial fine geostress field is established in the scale of block.Second,a primary submodel for introducing the asymmetric characteristics of reservoir stiffness to simulate the asymmetry of fracture distribution.Third,a secondary submodel containing the attributes of casing,cement sheath and reservoir material properties.Fourth,submodels are used to calculate the casing deformation generated by different injection loads and estimate the maximum allowable fracturing injection pressure(pj)while the safety requirement of casing deformation is satisfied.The calculation result of the case well shows that when the cementing quality is poor and fractures are distributed asymmetrically,the lateral and vertical displacements at the maximum displacement point of the casing under the injection pressure of 80 MPa are obviously lower than those under 90 MPa.According to the yield limit criterion of P-110 casing steel,the casing deformation in this case is elastic strain,so the injection pressure of 80 MPa is safe.In conclusion,this method has rational precision and accuracy,for its numerical result is consistent with the actual engineering phenomenon.展开更多
In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-b...In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-based alloy(typically pure lead or lead-bismuth eutectic(LBE))is used as the coolant.To clarify the pressure build-up characteristics under water-jet injection,this study conducted several experiments by injecting pressurized water into a molten LBE pool at Sun Yat-sen University.To obtain a further understanding,several new experimental parameters were adopted,including the melt temperature,water subcooling,injection pressure,injection duration,and nozzle diameter.Through detailed analyses,it was found that the pressure and temperature during the water-melt interaction exhibited a consistent variation trend with our previous water-droplet injection mode LBE experiment.Similarly,the existence of a steam explosion was confirmed,which typically results in a much stronger pressure build-up.For the non-explosion cases,increasing the injection pressure,melt-pool temperature,nozzle diameter,and water subcooling promoted pressure build-up in the melt pool.However,a limited enhancement effect was observed when increasing the injection duration,which may be owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steam cavity.Regardless of whether a steam explosion occurred,the calculated mechanical and kinetic energy conversion efficiencies of the melt were relatively small(not exceeding 4.1%and 0.7%,respectively).Moreover,the range of the conversion efficiency was similar to that of previous water-droplet experiments,although the upper limit of the jet mode was slightly lower.展开更多
Using natural gas(NG)as the primary fuel helps alleviate the fossil fuel crisis while reducing engine soot and nitrogen oxide(NO_(X))emissions.In this paper,the influences of a novel split injection concept on an NG h...Using natural gas(NG)as the primary fuel helps alleviate the fossil fuel crisis while reducing engine soot and nitrogen oxide(NO_(X))emissions.In this paper,the influences of a novel split injection concept on an NG high pressure direct injection(HPDI)engine are examined.Four typical split injection strategies,namely split pre-injection of pilot diesel(PD)and NG,split post-injection of PD and NG,split pre-injection of NG,and split post-injection of PD,were developed to investigate the influences on combustion and emissions.Results revealed that split pre injection of NG enhanced the atomization of PD,whereas the split post-injection of NG lowered the temperature in the core region of the PD spray,resulting in the deterioration of combustion.The effect of the split injection strategy on indicated thermal efficiency exceeded 7.5%.Split pre-injection was favorable to enhancing thermal efficiency,whereas split post-injection was not.Ignition delay,combustion duration,and premixed combustion time proportion were affected by injection strategies by 3.8%,50%,and 19.7%,respectively.Split pre-injection increased CH_(4) emission in the exhaust.Split post-injection,especially split post-injection of PD and NG,reduced the unburned CH_(4) emission by approximately 30%.When the split post-injection ratio was less than 30%,the trade-off between NO_(X) and soot was interrupted.The distribution range of hydroxyl radicals was expanded by pre-injection,and NO_(X) was generated in the region where the NG jet hit the wall.This paper provides valuable insights into the optimization of HPDI injection parameters.展开更多
Oxygenated fuels can reduce harmful emissions without affecting engine performance,meeting the big challenge in the transportation industry,which keeps the environment safe and reduces global warming.This study invest...Oxygenated fuels can reduce harmful emissions without affecting engine performance,meeting the big challenge in the transportation industry,which keeps the environment safe and reduces global warming.This study investigates the impact of biodiesel injection strategies and fuel injection pressures(FIP)on diesel engine exhaust emission characteristics.The engine is fuelled with 20%Jatropha biodiesel(JB)and 80%diesel,named JB20D.The ratios of fuel injection pressures started with injecting the fuel(diesel and JB20D)from 200 bar to 500 bar.The experimental outcomes indicate that the engine performance of brake-specific fuel consumption increased by 21.36%from the burning of JB20D compared with diesel,while brake thermal efficiency improved by 6.54%for low and high FIP compared to the diesel.The high fuel injection pressures slightly decrease the nitrogen oxide(NOX)emissions for both diesel and biodiesel.The emissions of NOX decreased from the combustion of JB20D by 18.7%under high fuel injection pressures compared to diesel.The concentration of soot particulate decreased by 20.4%form JB20D combustion than those combusted from diesel fuel.展开更多
The purpose of this study was to analyze the influence of the injection pressure and orifice diameter on the spray characteristics of soybean biodiesel.The macroscopic spray characteristics of the spray tip penetratio...The purpose of this study was to analyze the influence of the injection pressure and orifice diameter on the spray characteristics of soybean biodiesel.The macroscopic spray characteristics of the spray tip penetration(STP)and spray cone angle(SCA)were tested with a high-speed camera system.The microscopic spray characteristics,such as the statistical size distribution,Sauter mean diameter(SMD),representative diameters and dispersion boundary,were obtained using a Malvern laser particle size analyzer(PSA).The test results showed that with an increasing injection pressure,the STP and the SCA of the biodiesel increased,but the curves of size-volume distribution and cumulative volume distribution of the atomized droplets shifted to smaller diameters.The SMD and representative diameters decreased,and the dispersion boundary was reduced.Moreover,with a decreasing orifice diameter,longer STP and smaller SCA values were observed.Similarly,the size distribution curves of the atomized biodiesel droplets shifted to smaller diameters.The SMD and representative diameters were reduced,and the relative size range of the atomized biodiesel droplets was enlarged.Higher injection pressures and smaller orifice diameters improved the biodiesel atomization;however,the smaller orifice diameters caused an inhomogeneous size distribution of the atomized biodiesel droplets.展开更多
Carbon dots(CDs)show great potential as a new type of oil-displacing agent for unconventional oil and gas development.However,the instability and easy aggregation epitomize the challenges that accompany the applicatio...Carbon dots(CDs)show great potential as a new type of oil-displacing agent for unconventional oil and gas development.However,the instability and easy aggregation epitomize the challenges that accompany the application of CDs in high temperature and high salinity(HT/HS)reservoirs.In this research,novel benzene sulfonate-modified carbon dots(BS-CDs)with remarkable thermal stability and salt resistance were fabricated through an in-situ electrochemical exfoliation method.Molecular simulation verifies that the introduction of benzene sulfonate groups substantially strengthens the electrostatic repulsion between BS-CDs,leading to outstanding dispersibility and stability even at a temperature of 100℃ and salinity of 14×10^(4) mg/L.Core flooding tests show that 0.05 wt.%BS-CDs nanofluid can significantly reduce the water injection pressure by 50.00%and enhanced oil recovery(EOR)to 68.39%under HT/HS conditions.According to the atomic force microscopy(AFM)scanning results,the adhesion force between the core(after BS-CDs treatment)and oil decreased by 11.94 times,indicating that the hydrophilicity of the core surface was increased.In addition,the distribution of the adhesion force curve is more concentrated,which means that the micro-scale wettability of the core changes from oil-wet to more homogeneous water-wet.This study provides a feasible way for the development and application of good thermal stability and salt resistance CDs in unconventional reservoir development.展开更多
In this study,maintaining a constant fuel rate,injection pressure of 275 bar to1000 bar(275 × 10^(2) kPa to 1000× 10^(2) kPa),has been changed.Effect of injection pressure,the pressure inside the cylinder on...In this study,maintaining a constant fuel rate,injection pressure of 275 bar to1000 bar(275 × 10^(2) kPa to 1000× 10^(2) kPa),has been changed.Effect of injection pressure,the pressure inside the cylinder on the free energy,power,engine indicators,particularlyindicators of fuel consumption,pollutants and their effects on parameters affecting the outputof the engine combustion chamber have been studied in droplet diameter.Finally,the effects offuel mixture equivalence,Cantor temperature,soot and NO_(x),due to the increase of injectionpressure,engine efficiency and emissions have been examined.展开更多
Isotactic polypropylene（i PP） samples obtained by pressure vibration injection molding（PVIM） and conventional injection molding（CIM） were studied by polarized-light microscopy（PLM）, respectively. It was found ...Isotactic polypropylene（i PP） samples obtained by pressure vibration injection molding（PVIM） and conventional injection molding（CIM） were studied by polarized-light microscopy（PLM）, respectively. It was found that the alternating bright and dark banded spherulites were generated in the transitional region of PVIM parts. It is the first time that the banded spherulites of isotactic polypropylene were observed in polymer processing. What＇s more, the banded spherulites were proved to be constituted of α-form crystal by hot stage polarized-light microscopy（HT-PLM） and wide angle X-ray diffraction（WAXD）. Morphology of the banded spherulites was also studied by scaning electronical microscopy（SEM）.展开更多
For the question of applying high-pressure water injection to increase gas extraction efficiency by increasing the permeability of water to drive gas action, an independently designed gas desorption experimental measu...For the question of applying high-pressure water injection to increase gas extraction efficiency by increasing the permeability of water to drive gas action, an independently designed gas desorption experimental measuring device was used under the condition of external solution invasion. The law of water effect on gas desorption was obtained after water invasion through experiment for the first time. The results show that water＇s later invasion not only can make the quantity of gas dcsorp- tion greatly reduced, but also can make gas desorption end early. Therefore, when evaluating the applications of high-pressure water injection to increase gas extraction efficiency, we should take water damaging effects on gas desorption into account.展开更多
A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different inject...A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.展开更多
Dear Sir,Ifound the article by Sobac1etal[1]very interesting.The authors concluded that repeated intravitreal injection(IVI)of ranibizumab or bevacizumab didn’t seem have adverse effects on retinal nerve fiber layer(...Dear Sir,Ifound the article by Sobac1etal[1]very interesting.The authors concluded that repeated intravitreal injection(IVI)of ranibizumab or bevacizumab didn’t seem have adverse effects on retinal nerve fiber layer(RNFL)thickness in wet age-related macular degeneration(AMD)patients.展开更多
One of the most important of these emissions is fine particulate matter,which is a harmful emission of diesel engines,leading to the imposition of strict regulations.Biodiesel,with its high oxygen content,is an effect...One of the most important of these emissions is fine particulate matter,which is a harmful emission of diesel engines,leading to the imposition of strict regulations.Biodiesel,with its high oxygen content,is an effective alternative to significantly reduce these emissions.In this study,rapeseed methyl ester(RME)was used as a diesel engine fuel and the emitted particulate matter was comparedwith ultra-lowsulfur diesel(ULSD).Inmost experimental studies,the emission of soot wasmeasured.In this work,the effects of injection timing,injection pressure(IP),and engine load on fine particulate matter in both nucleation and accumulation modes were studied.The results show that IP increases the number of particles in the accumulation mode while the number of particles in the crystallization mode is higher for rapeseed methyl ester(RME)than for ultra-low sulfur diesel(ULSD).Conversely,the formation rates of particles in the accumulationmode are higher for ULSD.Cumulative concentration numbers(CCN)are generally higher for RME in crystallization mode but higher for ULSD in accumulation mode.Increasing the IP reduces the CCN values.The particle size in crystallizationmode reaches a maximum of 22 nm at IPs of 800 and 1000 bar but decreases to 15 nm at 1200 bar.Most fine particles fall in the 5–100 nm diameter range.High engine loads reduce the particle size distribution in nucleationmode for both fuels,with a slight increase in particle size in nucleationmode.Thestudy concluded that the use of rapeseed methyl ester as an engine fuel benefits the environment and improves air quality due to the significant reduction in the size,number,and concentration of nano-soot particles and total particles emitted from the engine.展开更多
For internal combustion engines,engines installed for transport ships,cargo ships,and fishing vessels are mainly diesel engines.The number of engines is increasing due to the development of the maritime and seafood ex...For internal combustion engines,engines installed for transport ships,cargo ships,and fishing vessels are mainly diesel engines.The number of engines is increasing due to the development of the maritime and seafood exploitation sectors.Therefore,the high demand for petroleum fuels increases environmental pollution due to engine emissions.Reducing environmental pollution from the combustion of petroleum fuels has become a concern worldwide,especially for internal combustion engines.The exhaust gases from the engine contain harmful substances such as soot and nitrogen oxides(NO_(x)).Fuels with higher carbon content generate more soot when burned.In contrast,biofuels have low carbon and sulfur content and supply ample oxygen,which helps to reduce soot formation.For these reasons,biofuels are encouraged as alternative fuels to petroleum.Vegetable oil is one of the primary raw materials for biofuel production.This study presents a mixture of diesel and vegetable oil utilized as fuel for fishing vessels’diesel engines.The results of experimental research on a fishing vessel’s 4CHE Yanmar diesel engine when using diesel fuel mixed with coconut oil(B15,15%coconut oil,and 85%diesel)show that increasing B15 fuel injection pressure by about 10–15%compared with diesel fuel injection pressure reduces the engine’s soot emissions and increases power compared to unadjusted.This solution contributes to reducing environmental pollution from engine emissions.展开更多
Objective:To investigate the correlation between the peak pressure of contrast agent injection and tubal patency during real-time three-dimensional hysterosalpingo-contrast sonography.Methods:Seventy female patients w...Objective:To investigate the correlation between the peak pressure of contrast agent injection and tubal patency during real-time three-dimensional hysterosalpingo-contrast sonography.Methods:Seventy female patients who underwent real-time three-dimensional hysterosalpingo-contrast sonography of uterine and oviduct in the department of ultrasound medicine in our hospital were selected to measure the peak pressure in the examination process through the pressure injection device of contrast agent,to compare the pressure differences of different obturability patency degree of oviduct,and to draw a ROC curve to determine the optimal cut-off value of the peak pressure.Results:According to the different patency degree of fallopian tubes,the contrast results were divided into three groups:bilateral tubes unobstructed group,unilateral tube lesioned group and bilateral tubes lesioned group.The peak pressures of the three groups were(34.69±9.30)KPa,(52.71±18.55)KPa and(73.88±11.01)KPa,respectively.The area under the peak pressure ROC curve(AUC)of the"unilateral tube lesioned group"and"bilateral tubes lesioned group"was 0.785,the optimal cut-off value of the peak pressure was 51.90KPa,the area under the peak pressure ROC curve(AUC)of the"unilateral tube lesioned group"and"bilateral tubes lesioned group"was 0.851,and the optimal cut-off value of the peak pressure was 73.50KPa.Conclusion:The peak pressure of contrast agent injection in RT-3D-HyCoSy can be used as a quantitative index to deduce the patency degree of oviduct.There is a correlation between the peak pressure and the tubal patency.展开更多
The first way to identify the needle in relation to the peripheral nerve W. Halsted and R. Hall in 1884 performed the first regional blockade (using direct visualization). However, Vassily von Anrep was a few months e...The first way to identify the needle in relation to the peripheral nerve W. Halsted and R. Hall in 1884 performed the first regional blockade (using direct visualization). However, Vassily von Anrep was a few months earlier described the blockade of the peripheral nerve by anatomical landmarks. In 1912, the blockade of the brachial plexus was first performed using electrical stimulation, but this technique has been widely used only since 1962. The most popular way to identify the needle relative to the nerve at the moment remains US guidance. A promising direction may be optical coherence tomography. But this method is under development. In the last decade, a method for determining the pressure of a local anesthetic has been introduced into practice to determine the position of the needle relative to the nerve.展开更多
Trajectory analysis of fuel injection into supersonic cross flow is studied in this paper. A directly-connected wind tunnel is constructed to provide stable supersonic freestream. Based on the test rig, the schlieren ...Trajectory analysis of fuel injection into supersonic cross flow is studied in this paper. A directly-connected wind tunnel is constructed to provide stable supersonic freestream. Based on the test rig, the schlieren system is established to reveal the fuel injection process visually. Subsequently, the method of quantitative schlieren is adopted to obtain data of both fuel/air interface and bow shock with the aid of Photoshop and Origin. Finally, the mechanism based on two influential factors of fuel injection angle and fuel injection driven pressure, is researched by vector analysis. A dimensionless model is deduced and analyzed. The curve fitting result is achieved. The relationship between the data and the two influential factors is established. The results provide not only the quantitative characteristics of the fuel injection in supersonic cross flow but also the valuable reference for the future computational simulation.展开更多
Based on the numerical simulation analysis, structure parameters of the high pressure fuel pump and common rail as well as flow limiter are designed and the GD-1 high pressure common rail fuel injection system is self...Based on the numerical simulation analysis, structure parameters of the high pressure fuel pump and common rail as well as flow limiter are designed and the GD-1 high pressure common rail fuel injection system is self-developed. Fuel injection characteristics experiment is performed on the GD-1 system. And double-factor variance analysis is applied to investigate the influence of the rail pressure and injection pulse width on the consistency of fuel injection quantity, thus to test whether the design of structure parameters is sound accordingly. The results of experiment and test show that rail pressure and injection pulse width as well as their mutual-effect have no influence on the injection quantity consistency, which proves that the structure parameters design is successful and performance of GD-1 system is sound.展开更多
文摘In view of the problems of high injection pressure and low water injection rate in water injection wells of low permeability reservoirs featuring high temperature and high salinity,two new surfactants were synthesized,including a quaternary ammonium surfactant and a betaine amphoteric surfactant.The composite surfactant system BYJ-1 was formed by mixing two kinds of surfactants.The minimum interfacial tension between BYJ-1 solution and the crude oil could reach 1.4×10^(-3) mN/m.The temperature resistance was up to 140℃,and the salt resistance could reach up to 120 g/L.For the low permeability core fully saturated with water phase,BYJ-1 could obviously reduce the starting pressure gradient of low permeability core.While for the core with residual oil,BYJ-1 could obviously reduce the injection pressure and improve the oil recovery.Moreover,the field test showed that BYJ-1 could effectively reduce the injection pressure of the water injection well,increase the injection volume,and increase the liquid production and oil production of the corresponding production well.
基金Project(Z110803)supported by the State Key Laboratory of Geomechanics and Geotechnical Engineering,ChinaProject(2008AA062303)supported by the National High Technology Research and Development Program of China
文摘A fast explicit finite difference method (FEFDM),derived from the differential equations of one-dimensional steady pipe flow,was presented for calculation of wellhead injection pressure.Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM.Moreover,a flow rate estimate method was developed for the project whose injection rate has not been clearly determined.A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project,which is a good practice verification of FEFDM.At last,this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure.The result shows that for deep wellbore,the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted.It is also shown that with flow rate increasing,the friction term can no longer be neglected.
文摘Biodiesel fuel is a potential alternative energy source for diesel engines due to its physiochemical characteristics relatively similar to those of traditional diesel fuel.In this study,the performance,emission,and combustion features of a mono cylinder DI diesel engine are assessed using 20%Pumpkin seed methyl ester(PSOME20)and considering varying injection pressures(200,220,240,and 260 bar).The considered Pumpkin seed oil is converted into pumpkin biodiesel by transesterification and then used as fuel.The findings demonstrate that the Brake Thermal Efficiency(BTE)of PSOME20 can be raised by 1.68%,and the carbon monoxide(CO),hydrocarbon(HC),and smoke emanations can be lowered,while oxides of nitrogen(NOx)emissions are increased at an injection pressure(IP)of 240 bar compared to the standard IP of 200 bar.The cylinder pressure and the Heat Release Rate(HRR)become higher at 240 bar,whereas the ignition delay is shortened with respect to PSOME20 at a normal IP of 200 bar.
基金supported by the General Program of National Natural Science Foundation of China“Theoretical and Experimental Study on Key Mechanical Problems in Unconventional Natural Gas Exploitation”(No.:11272216).
文摘Injection pressure is one of the key parameters used in the design of shale gas reservoir stimulation.Higher injection pressure helps to initiate fractures,inject fracturing fluid and proppant smoothly and maximize the stimulated reservoir volume as soon as possible.If the injection pressure is too high,however,the risk of casing deformation is increased significantly.In this paper,the numerical calculation format of the injection pressure safety window while ensuring casing integrity(i.e.,the maximum safety injection pressure)was proposed based on an example of an actual engineering project.Then,it was verified based on the actual situation of one shale gas well in Weiyuan.The numerical calculation format is as follows.First,a 3D finite element model of initial fine geostress field is established in the scale of block.Second,a primary submodel for introducing the asymmetric characteristics of reservoir stiffness to simulate the asymmetry of fracture distribution.Third,a secondary submodel containing the attributes of casing,cement sheath and reservoir material properties.Fourth,submodels are used to calculate the casing deformation generated by different injection loads and estimate the maximum allowable fracturing injection pressure(pj)while the safety requirement of casing deformation is satisfied.The calculation result of the case well shows that when the cementing quality is poor and fractures are distributed asymmetrically,the lateral and vertical displacements at the maximum displacement point of the casing under the injection pressure of 80 MPa are obviously lower than those under 90 MPa.According to the yield limit criterion of P-110 casing steel,the casing deformation in this case is elastic strain,so the injection pressure of 80 MPa is safe.In conclusion,this method has rational precision and accuracy,for its numerical result is consistent with the actual engineering phenomenon.
基金supported by Basic and Applied Basic research foundation of Guangdong province(Nos.2021A1515010343 and 2022A1515011582)the Science and Technology Program of Guangdong Province(Nos.2021A0505030026 and 2022A0505050029).
文摘In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor,secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel,where a molten lead-based alloy(typically pure lead or lead-bismuth eutectic(LBE))is used as the coolant.To clarify the pressure build-up characteristics under water-jet injection,this study conducted several experiments by injecting pressurized water into a molten LBE pool at Sun Yat-sen University.To obtain a further understanding,several new experimental parameters were adopted,including the melt temperature,water subcooling,injection pressure,injection duration,and nozzle diameter.Through detailed analyses,it was found that the pressure and temperature during the water-melt interaction exhibited a consistent variation trend with our previous water-droplet injection mode LBE experiment.Similarly,the existence of a steam explosion was confirmed,which typically results in a much stronger pressure build-up.For the non-explosion cases,increasing the injection pressure,melt-pool temperature,nozzle diameter,and water subcooling promoted pressure build-up in the melt pool.However,a limited enhancement effect was observed when increasing the injection duration,which may be owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steam cavity.Regardless of whether a steam explosion occurred,the calculated mechanical and kinetic energy conversion efficiencies of the melt were relatively small(not exceeding 4.1%and 0.7%,respectively).Moreover,the range of the conversion efficiency was similar to that of previous water-droplet experiments,although the upper limit of the jet mode was slightly lower.
基金Supported by the National Natural Science Foundation of China(No.51909154)Shanghai Engineering Research Center of Ship Intelligent Maintenance and Energy Efficiency(No.20DZ2252300).
文摘Using natural gas(NG)as the primary fuel helps alleviate the fossil fuel crisis while reducing engine soot and nitrogen oxide(NO_(X))emissions.In this paper,the influences of a novel split injection concept on an NG high pressure direct injection(HPDI)engine are examined.Four typical split injection strategies,namely split pre-injection of pilot diesel(PD)and NG,split post-injection of PD and NG,split pre-injection of NG,and split post-injection of PD,were developed to investigate the influences on combustion and emissions.Results revealed that split pre injection of NG enhanced the atomization of PD,whereas the split post-injection of NG lowered the temperature in the core region of the PD spray,resulting in the deterioration of combustion.The effect of the split injection strategy on indicated thermal efficiency exceeded 7.5%.Split pre-injection was favorable to enhancing thermal efficiency,whereas split post-injection was not.Ignition delay,combustion duration,and premixed combustion time proportion were affected by injection strategies by 3.8%,50%,and 19.7%,respectively.Split pre-injection increased CH_(4) emission in the exhaust.Split post-injection,especially split post-injection of PD and NG,reduced the unburned CH_(4) emission by approximately 30%.When the split post-injection ratio was less than 30%,the trade-off between NO_(X) and soot was interrupted.The distribution range of hydroxyl radicals was expanded by pre-injection,and NO_(X) was generated in the region where the NG jet hit the wall.This paper provides valuable insights into the optimization of HPDI injection parameters.
文摘Oxygenated fuels can reduce harmful emissions without affecting engine performance,meeting the big challenge in the transportation industry,which keeps the environment safe and reduces global warming.This study investigates the impact of biodiesel injection strategies and fuel injection pressures(FIP)on diesel engine exhaust emission characteristics.The engine is fuelled with 20%Jatropha biodiesel(JB)and 80%diesel,named JB20D.The ratios of fuel injection pressures started with injecting the fuel(diesel and JB20D)from 200 bar to 500 bar.The experimental outcomes indicate that the engine performance of brake-specific fuel consumption increased by 21.36%from the burning of JB20D compared with diesel,while brake thermal efficiency improved by 6.54%for low and high FIP compared to the diesel.The high fuel injection pressures slightly decrease the nitrogen oxide(NOX)emissions for both diesel and biodiesel.The emissions of NOX decreased from the combustion of JB20D by 18.7%under high fuel injection pressures compared to diesel.The concentration of soot particulate decreased by 20.4%form JB20D combustion than those combusted from diesel fuel.
基金financially supported by the National Natural Science Foundation of China(51806020)the Youth Innovation Team of Shaanxi Universities(Energy Saving and New Energy Vehicles)the Special Funds for Basic Scientific Research of Central Colleges,Chang’an University(310822172203 and 300102228403)。
文摘The purpose of this study was to analyze the influence of the injection pressure and orifice diameter on the spray characteristics of soybean biodiesel.The macroscopic spray characteristics of the spray tip penetration(STP)and spray cone angle(SCA)were tested with a high-speed camera system.The microscopic spray characteristics,such as the statistical size distribution,Sauter mean diameter(SMD),representative diameters and dispersion boundary,were obtained using a Malvern laser particle size analyzer(PSA).The test results showed that with an increasing injection pressure,the STP and the SCA of the biodiesel increased,but the curves of size-volume distribution and cumulative volume distribution of the atomized droplets shifted to smaller diameters.The SMD and representative diameters decreased,and the dispersion boundary was reduced.Moreover,with a decreasing orifice diameter,longer STP and smaller SCA values were observed.Similarly,the size distribution curves of the atomized biodiesel droplets shifted to smaller diameters.The SMD and representative diameters were reduced,and the relative size range of the atomized biodiesel droplets was enlarged.Higher injection pressures and smaller orifice diameters improved the biodiesel atomization;however,the smaller orifice diameters caused an inhomogeneous size distribution of the atomized biodiesel droplets.
基金the National Key Research and Development Program of China(No.2019YFA0708700)the Innovation fund project for graduate student of China University of Petroleum(East China)(No.22CX04050A)the Fundamental Research Funds for the Central Universities,the China National Petroleum Corporation Innovation Found(No.2021DQ02-0205).
文摘Carbon dots(CDs)show great potential as a new type of oil-displacing agent for unconventional oil and gas development.However,the instability and easy aggregation epitomize the challenges that accompany the application of CDs in high temperature and high salinity(HT/HS)reservoirs.In this research,novel benzene sulfonate-modified carbon dots(BS-CDs)with remarkable thermal stability and salt resistance were fabricated through an in-situ electrochemical exfoliation method.Molecular simulation verifies that the introduction of benzene sulfonate groups substantially strengthens the electrostatic repulsion between BS-CDs,leading to outstanding dispersibility and stability even at a temperature of 100℃ and salinity of 14×10^(4) mg/L.Core flooding tests show that 0.05 wt.%BS-CDs nanofluid can significantly reduce the water injection pressure by 50.00%and enhanced oil recovery(EOR)to 68.39%under HT/HS conditions.According to the atomic force microscopy(AFM)scanning results,the adhesion force between the core(after BS-CDs treatment)and oil decreased by 11.94 times,indicating that the hydrophilicity of the core surface was increased.In addition,the distribution of the adhesion force curve is more concentrated,which means that the micro-scale wettability of the core changes from oil-wet to more homogeneous water-wet.This study provides a feasible way for the development and application of good thermal stability and salt resistance CDs in unconventional reservoir development.
文摘In this study,maintaining a constant fuel rate,injection pressure of 275 bar to1000 bar(275 × 10^(2) kPa to 1000× 10^(2) kPa),has been changed.Effect of injection pressure,the pressure inside the cylinder on the free energy,power,engine indicators,particularlyindicators of fuel consumption,pollutants and their effects on parameters affecting the outputof the engine combustion chamber have been studied in droplet diameter.Finally,the effects offuel mixture equivalence,Cantor temperature,soot and NO_(x),due to the increase of injectionpressure,engine efficiency and emissions have been examined.
文摘Isotactic polypropylene（i PP） samples obtained by pressure vibration injection molding（PVIM） and conventional injection molding（CIM） were studied by polarized-light microscopy（PLM）, respectively. It was found that the alternating bright and dark banded spherulites were generated in the transitional region of PVIM parts. It is the first time that the banded spherulites of isotactic polypropylene were observed in polymer processing. What＇s more, the banded spherulites were proved to be constituted of α-form crystal by hot stage polarized-light microscopy（HT-PLM） and wide angle X-ray diffraction（WAXD）. Morphology of the banded spherulites was also studied by scaning electronical microscopy（SEM）.
文摘For the question of applying high-pressure water injection to increase gas extraction efficiency by increasing the permeability of water to drive gas action, an independently designed gas desorption experimental measuring device was used under the condition of external solution invasion. The law of water effect on gas desorption was obtained after water invasion through experiment for the first time. The results show that water＇s later invasion not only can make the quantity of gas dcsorp- tion greatly reduced, but also can make gas desorption end early. Therefore, when evaluating the applications of high-pressure water injection to increase gas extraction efficiency, we should take water damaging effects on gas desorption into account.
基金Supported by National High Technology Research and Development Program ("863" Program) of China (No.2008AA11A114)
文摘A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.
文摘Dear Sir,Ifound the article by Sobac1etal[1]very interesting.The authors concluded that repeated intravitreal injection(IVI)of ranibizumab or bevacizumab didn’t seem have adverse effects on retinal nerve fiber layer(RNFL)thickness in wet age-related macular degeneration(AMD)patients.
文摘One of the most important of these emissions is fine particulate matter,which is a harmful emission of diesel engines,leading to the imposition of strict regulations.Biodiesel,with its high oxygen content,is an effective alternative to significantly reduce these emissions.In this study,rapeseed methyl ester(RME)was used as a diesel engine fuel and the emitted particulate matter was comparedwith ultra-lowsulfur diesel(ULSD).Inmost experimental studies,the emission of soot wasmeasured.In this work,the effects of injection timing,injection pressure(IP),and engine load on fine particulate matter in both nucleation and accumulation modes were studied.The results show that IP increases the number of particles in the accumulation mode while the number of particles in the crystallization mode is higher for rapeseed methyl ester(RME)than for ultra-low sulfur diesel(ULSD).Conversely,the formation rates of particles in the accumulationmode are higher for ULSD.Cumulative concentration numbers(CCN)are generally higher for RME in crystallization mode but higher for ULSD in accumulation mode.Increasing the IP reduces the CCN values.The particle size in crystallizationmode reaches a maximum of 22 nm at IPs of 800 and 1000 bar but decreases to 15 nm at 1200 bar.Most fine particles fall in the 5–100 nm diameter range.High engine loads reduce the particle size distribution in nucleationmode for both fuels,with a slight increase in particle size in nucleationmode.Thestudy concluded that the use of rapeseed methyl ester as an engine fuel benefits the environment and improves air quality due to the significant reduction in the size,number,and concentration of nano-soot particles and total particles emitted from the engine.
文摘For internal combustion engines,engines installed for transport ships,cargo ships,and fishing vessels are mainly diesel engines.The number of engines is increasing due to the development of the maritime and seafood exploitation sectors.Therefore,the high demand for petroleum fuels increases environmental pollution due to engine emissions.Reducing environmental pollution from the combustion of petroleum fuels has become a concern worldwide,especially for internal combustion engines.The exhaust gases from the engine contain harmful substances such as soot and nitrogen oxides(NO_(x)).Fuels with higher carbon content generate more soot when burned.In contrast,biofuels have low carbon and sulfur content and supply ample oxygen,which helps to reduce soot formation.For these reasons,biofuels are encouraged as alternative fuels to petroleum.Vegetable oil is one of the primary raw materials for biofuel production.This study presents a mixture of diesel and vegetable oil utilized as fuel for fishing vessels’diesel engines.The results of experimental research on a fishing vessel’s 4CHE Yanmar diesel engine when using diesel fuel mixed with coconut oil(B15,15%coconut oil,and 85%diesel)show that increasing B15 fuel injection pressure by about 10–15%compared with diesel fuel injection pressure reduces the engine’s soot emissions and increases power compared to unadjusted.This solution contributes to reducing environmental pollution from engine emissions.
基金Anhui province 2018 key research and opening plan project(No.1804h08020248)。
文摘Objective:To investigate the correlation between the peak pressure of contrast agent injection and tubal patency during real-time three-dimensional hysterosalpingo-contrast sonography.Methods:Seventy female patients who underwent real-time three-dimensional hysterosalpingo-contrast sonography of uterine and oviduct in the department of ultrasound medicine in our hospital were selected to measure the peak pressure in the examination process through the pressure injection device of contrast agent,to compare the pressure differences of different obturability patency degree of oviduct,and to draw a ROC curve to determine the optimal cut-off value of the peak pressure.Results:According to the different patency degree of fallopian tubes,the contrast results were divided into three groups:bilateral tubes unobstructed group,unilateral tube lesioned group and bilateral tubes lesioned group.The peak pressures of the three groups were(34.69±9.30)KPa,(52.71±18.55)KPa and(73.88±11.01)KPa,respectively.The area under the peak pressure ROC curve(AUC)of the"unilateral tube lesioned group"and"bilateral tubes lesioned group"was 0.785,the optimal cut-off value of the peak pressure was 51.90KPa,the area under the peak pressure ROC curve(AUC)of the"unilateral tube lesioned group"and"bilateral tubes lesioned group"was 0.851,and the optimal cut-off value of the peak pressure was 73.50KPa.Conclusion:The peak pressure of contrast agent injection in RT-3D-HyCoSy can be used as a quantitative index to deduce the patency degree of oviduct.There is a correlation between the peak pressure and the tubal patency.
文摘The first way to identify the needle in relation to the peripheral nerve W. Halsted and R. Hall in 1884 performed the first regional blockade (using direct visualization). However, Vassily von Anrep was a few months earlier described the blockade of the peripheral nerve by anatomical landmarks. In 1912, the blockade of the brachial plexus was first performed using electrical stimulation, but this technique has been widely used only since 1962. The most popular way to identify the needle relative to the nerve at the moment remains US guidance. A promising direction may be optical coherence tomography. But this method is under development. In the last decade, a method for determining the pressure of a local anesthetic has been introduced into practice to determine the position of the needle relative to the nerve.
文摘Trajectory analysis of fuel injection into supersonic cross flow is studied in this paper. A directly-connected wind tunnel is constructed to provide stable supersonic freestream. Based on the test rig, the schlieren system is established to reveal the fuel injection process visually. Subsequently, the method of quantitative schlieren is adopted to obtain data of both fuel/air interface and bow shock with the aid of Photoshop and Origin. Finally, the mechanism based on two influential factors of fuel injection angle and fuel injection driven pressure, is researched by vector analysis. A dimensionless model is deduced and analyzed. The curve fitting result is achieved. The relationship between the data and the two influential factors is established. The results provide not only the quantitative characteristics of the fuel injection in supersonic cross flow but also the valuable reference for the future computational simulation.
文摘Based on the numerical simulation analysis, structure parameters of the high pressure fuel pump and common rail as well as flow limiter are designed and the GD-1 high pressure common rail fuel injection system is self-developed. Fuel injection characteristics experiment is performed on the GD-1 system. And double-factor variance analysis is applied to investigate the influence of the rail pressure and injection pulse width on the consistency of fuel injection quantity, thus to test whether the design of structure parameters is sound accordingly. The results of experiment and test show that rail pressure and injection pulse width as well as their mutual-effect have no influence on the injection quantity consistency, which proves that the structure parameters design is successful and performance of GD-1 system is sound.
