Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carrie...Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carried out. And the improved attenuation curves were obtained, by which the engine noise was predicted. The effect of fuel injection parameters in combustion noise was investigated during the combustion process. At last, the method combining single variable optimization and multivariate combination was introduced to online optimize the combustion noise. The results show that injection parameters can affect the cylinder pressure rise rate and heat release rate, and consequently affect the cylinder pressure load and pressure oscillation to influence the combustion noise. Among these parameters, main injection advance angle has the greatest influence on the combustion noise, while the pilot injection interval time takes the second place, and the pilot injection quantity is of minimal impact. After the optimal design of the combustion noise, the average sound pressure level of the engine is distinctly reduced by 1.0 d B(A) generally. Meanwhile, the power, emission and economy performances are ensured.展开更多
UWS （optimized Urea-Water Solution） injection system is required to increase the NH3 conversion efficiency of urea-based SCR （Selective Catalytic Reduction） system of modem automobiles. The focus of the current st...UWS （optimized Urea-Water Solution） injection system is required to increase the NH3 conversion efficiency of urea-based SCR （Selective Catalytic Reduction） system of modem automobiles. The focus of the current study is to do parametric studies by simulation in a three-dimensional model using CFD （Computational Fluid Dynamics） code AVL FIRE. Simulations were carried out to study the characteristics of evaporation and thermolysis UWS considering the effect of injection velocity, duration of injection, injection angle and for different types of injection. In the case of the injection velocities up to 20-50 m/sec, the ammonia concentration continues to increase. It is found that as the duration injection decreases, the concentration of ammonia increases. In case of continuous injection, the flow rate is less which results in lower velocity of injection, lesser atomization and slower evaporation resulting lesser conversion of UWS into NH3. Shorter duration of injection leads better atomization with increased velocity of injection which results in faster evaporation and thermolysis.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
Gas channeling in fractures during CO_(2) injection into the deep coal seam seriously reduces the CO_(2) storage efficiency after the development of coalbed methane.The generation and migration of coal fines causes bl...Gas channeling in fractures during CO_(2) injection into the deep coal seam seriously reduces the CO_(2) storage efficiency after the development of coalbed methane.The generation and migration of coal fines causes blockages in the fractures in the stage of drainage and gas production,reducing the gas channeling effect of injected CO_(2) caused by the heterogeneity of the coal seam.To explore the impact of coal fines within coal seam fractures on the efficacy of CO_(2) storage,experiments on the production stage and CO_(2) injection for storage were conducted on coal combinations containing propped fractures,fractures,and matrix.The CO_(2) storage characteristics of coal at the constraint of coal fines,as well as the influence of multiple rounds of intermittent CO_(2) injection and different injection parameters on the CO_(2) storage effect,were analyzed.The research results show that blockage by coal fines increases the resistance to fluid flow in the fractures by 71.2%.The CO_(2) storage capacity and storage potential of coal with coal fines are 6.5 cm^(3)/g and 8.8%higher than those of coal without coal fines,while the CO_(2) storage capacity of fractured coal under the influence of coal fines has the largest increase of 9.4 cm^(3)/g.The CO_(2) storage of coal containing coal fines is significantly higher(6.6%)than that of the coal without coal fines.The CO_(2) storage effect of the coal with coal fines is improved with the increase in injection rate,whereas the CO_(2) storage effect of the coal without coal fines decreases significantly(by 7.8%).Multiple rounds of intermittent injection increases the CO_(2) storage volume of coal by 20.4%(with coal fines)and 17.1%(without coal fines).The presence of coal fines in fractures also slows down the downward trend of CO_(2) storage fraction after multiple rounds of CO_(2) injection.The blockage in fractures significantly increases the CO_(2) injection time and difficulty,but can increase the CO_(2) storage fraction by 4.7%-17.1%,and the storage volume by 1.9%-14%,increasing the feasibility of CO_(2) storage in fractured coal seams that have previously been exploited for methane production.The multiple rounds of intermittent CO_(2) injection and shut-in periods has shown potential for greater CO_(2) storage and injection efficiency.展开更多
Lead has been recognized as a high risk toxic for most organisms including human. The effects of Pb in non-mammalian vertebrates are oprly known, particularly in anuran amphibians. The purpose of this study was to det...Lead has been recognized as a high risk toxic for most organisms including human. The effects of Pb in non-mammalian vertebrates are oprly known, particularly in anuran amphibians. The purpose of this study was to determine the effect of this metal on some hematological parameters of adult Bufo arenarum. It was found that all parameters remained unaltered within normal ranges, with the exception of reticulocyte counts which was significantly increased compared to the in controls (3. 7% vs. 0. 2 % ). It is suggested that the selective change found in reticulocyte count might be considered as an early response of a biomarker to sublethal exposition of Bufo arenarum to lead.展开更多
On the basis of heat transfer and chemical kinetics theory, both connections coal self ignite with oxygen concentration and range of oxidation zone with air leak intensity are analyzed, and calculating method is deduc...On the basis of heat transfer and chemical kinetics theory, both connections coal self ignite with oxygen concentration and range of oxidation zone with air leak intensity are analyzed, and calculating method is deduced to gain the lower limit of oxygen concentration and the range of oxidation zone. The change rule of correlative parameter is quantitatively researched between before nitrogen injection and after nitrogen injection in gob, such as oxygen concentration, oxidation zone width, etc. According to theoretical calculation, the relation position and flow of nitrogen injection with oxidation zone width is conformed, and computational formulas of the best flow and position of nitrogen injection are obtained. It offers a theoretic criterion for preventing and controlling float coal self ignite by nitrogen injection in gob.展开更多
The China Spallation Neutron Source （CSNS） uses H- stripping and phase space painting metnocl co fill a large ring acceptance with a small emittance linac beam. The dependence of the painting beam on the injection b...The China Spallation Neutron Source （CSNS） uses H- stripping and phase space painting metnocl co fill a large ring acceptance with a small emittance linac beam. The dependence of the painting beam on the injection beam parameters was studied for the Rapid Cycling Synchrotron （RCS）. The simulation study was done for injection with different momentum spreads, different rms emittances of the injection beam, and different matching conditions. Then, the beam loss, 99% and rms emittances were obtained, and the optimized injection beam parameters were given. The interaction between H- beam and stripping foil was studied, and the effect of foil scattering was simulated. The stripping efficiency was calculated and the suitable thickness of stripping foil was obtained. In addition, the energy deposition on the foil and the beam loss due to the foil scattering were also studied.展开更多
Advanced water injection has become an effective method for developing low-permeability reservoirs.However,after a period of high yield from fracturing,the injected waterflows rapidly along high-capacity channels,which...Advanced water injection has become an effective method for developing low-permeability reservoirs.However,after a period of high yield from fracturing,the injected waterflows rapidly along high-capacity channels,which greatly reduces the sweep efficiency of reservoirs.In this work,the plugging process by microspheres and nanospheres from the fracture to the matrix was simulated through core experiments.The plugging performance of multi-scale microspheres(microspheres and nanospheres)on the core matrix was evaluated by measuring the plugging rate and other parameters.Enhanced oil recovery after synergistic plugging with multi-scale microspheres was used as the evaluation index,a sensitivity analysis of injection parameters was performed,and the best combination of injection parameters was optimized by orthogonal experiments.The experimental results showed that the plugging performance of nanospheres is mainly reflected in thefilling of the core matrix,while the plugging performance of microspheres is mainly reflected by retention at the injection end of the core(as opposed to the fractured end face).The plugging rate of nanospheres reached 78.83%,which is much higher than the 30.28%rate achieved with microspheres.The maximum oil recovery after plugging was 19.12%,which corresponds to the following combination of injection parameters:total injection of 0.6 pore volume(PV),injection ratio between nanospheres and microspheres of 2:1,injection rate of 1.5 mL$min 1,and aging time of 6 days.Among the injection parameters,the injection ratio between nanospheres and microspheres had the greatest influence on the recovery of waterflooding after plugging,followed by the total injection of multi-scale microspheres.The injection rate and aging time had little effect.展开更多
Geothermal energy,a kind of clean and environmentally friendly energy source,is an important object of future natural resource development and utilization,among which,hot dry rock is one of the important deep geotherm...Geothermal energy,a kind of clean and environmentally friendly energy source,is an important object of future natural resource development and utilization,among which,hot dry rock is one of the important deep geothermal resources.In the current multi-objective optimization of heat extraction performance,reservoir production models are less considered and the effects of different optimization ideas are not compared comprehensively.To improve the heat extraction efficiency and prolong the exploitation life of geothermal reservoirs,this paper determines the appropriate operating parameters of geothermal system(injection temperature,injection rate,production pressure and injection-production well spacing)based on the coupled thermal-hydraulic-mechanical model of hot dry rock exploitation in the Gonghe area of Qinghai and three heat extraction optimization methods.In addition,the heat extraction performances of different schemes are comparatively evaluated.And the following research results are obtained.First,the sensitivity analysis of injection and production parameters shows that power generation and recovery factor are in a reverse relation with injection-production pressure difference,which is the direct reason for the adoption of multiobjective optimization.Second,the optimization scheme prepared on the basis of parametric study indicates that the shortest life of a geothermal reservoir is 10 years,the injection-production pressure difference is up to 67 MPa,there is a significant thermal breakthrough phenomenon and the reservoir safety faces challenges.Third,by virtue of multi-objective optimization and decision making integration,the optimal operation parameter combination of hot dry rock system is determined,the life of geothermal reservoirs can exceed 20 years and balanced optimization is achieved.In conclusion,the idea of multi-objective optimization is feasible and applicable to geothermal energy exploitation and this method provides a reference for the efficient geothermal energy development and utilization and is helpful to the realization of“double carbon”goal in China.展开更多
We propose a novel method to compute globally injective parameterizations with arbitrary positional constraints on disk topology meshes.Central to this method is the use of a scaffold mesh that reduces the globally in...We propose a novel method to compute globally injective parameterizations with arbitrary positional constraints on disk topology meshes.Central to this method is the use of a scaffold mesh that reduces the globally injective constraint to a locally flipfree condition.Hence,given an initial parameterized mesh containing flipped triangles and satisfying the positional constraints,we only need to remove the flips of a overall mesh consisting of the parameterized mesh and the scaffold mesh while always meeting positional constraints.To successfully apply this idea,we develop two key techniques.Firstly,an initialization method is used to generate a valid scaffold mesh and mitigate difficulties in eliminating flips.Secondly,edgebased remeshing is used to optimize the regularity of the scaffold mesh containing flips,thereby improving practical robustness.Compared to state-of-the-art methods,our method is much more robust.We demonstrate the capability and feasibility of our method on a large number of complex meshes.展开更多
With increasingly stringent emission regulations and demand for fuel economy by the public,the combustion and emission problems of automotive diesel engines during transient operation have become vital and urgent issu...With increasingly stringent emission regulations and demand for fuel economy by the public,the combustion and emission problems of automotive diesel engines during transient operation have become vital and urgent issues.In this study,combustion deterioration has been experimentally analyzed using a heavy-duty turbocharged diesel engine running under transient conditions(constant speed and increasing torque).Optimization of the transient combustion process was performed by adjusting the fuel injection parameters.The results indicated that the notable combustion deterioration relative to steady state operation while transient was a function of the delay in the air-supply to the turbocharged engine,and took the form of combustion phasing delay,resulting in rapidly increasing smoke emission and fuel consumption.However,the delay in combustion phasing can be controlled by advancing the fuel injection timing,effectively increasing thermal efficiency.Unfortunately,smoke and NO x emissions increased at the same time.The deterioration in combustion phasing can also be improved by increasing injection pressure,resulting in decreased smoke emission while NO x emission increased.It is worth noting that the effective thermal efficiency first increased and then decreased as fuel injection pressure increased during transient operation.展开更多
In this paper effects of various injection molding parameters on tribological properties of ultra-high molecular weight polyethylene （UHMWPE） were investigated. The tribological properties like coefficient of fricti...In this paper effects of various injection molding parameters on tribological properties of ultra-high molecular weight polyethylene （UHMWPE） were investigated. The tribological properties like coefficient of friction and wear rate were obtained from the experimental results of hip simulator which was designed and fabricated in the laboratory. Bovine serum was used as a lubricant in this study. In addition, the hardness of the specimen was also investigated as well. The injection molding parameters that varied for this study are melt temperature, injection velocity and compaction time. The results show that contact loads and melt temperature were mostly influenced the tribological behavior of UHMWPE. A wear mechanism map was developed to study the dominant wear mechanism that influences the wear behavior of UHMWPE. SEM was employed to study the worn out morphologies of UHMWPE. The dominant wear mechanisms that are dominated through our study are ironing, scratching, ploughing, plastic deformation, and fatigue wear.展开更多
基金Project(2011BAE22B05)supported by the National Science and Technology Pillar Program during the 12th Five-year Plan of China
文摘Combustion noise takes large proportion in diesel engine noise and the studies of its influence factors play an important role in noise reduction. Engine noise and cylinder pressure measurement experiments were carried out. And the improved attenuation curves were obtained, by which the engine noise was predicted. The effect of fuel injection parameters in combustion noise was investigated during the combustion process. At last, the method combining single variable optimization and multivariate combination was introduced to online optimize the combustion noise. The results show that injection parameters can affect the cylinder pressure rise rate and heat release rate, and consequently affect the cylinder pressure load and pressure oscillation to influence the combustion noise. Among these parameters, main injection advance angle has the greatest influence on the combustion noise, while the pilot injection interval time takes the second place, and the pilot injection quantity is of minimal impact. After the optimal design of the combustion noise, the average sound pressure level of the engine is distinctly reduced by 1.0 d B(A) generally. Meanwhile, the power, emission and economy performances are ensured.
文摘UWS （optimized Urea-Water Solution） injection system is required to increase the NH3 conversion efficiency of urea-based SCR （Selective Catalytic Reduction） system of modem automobiles. The focus of the current study is to do parametric studies by simulation in a three-dimensional model using CFD （Computational Fluid Dynamics） code AVL FIRE. Simulations were carried out to study the characteristics of evaporation and thermolysis UWS considering the effect of injection velocity, duration of injection, injection angle and for different types of injection. In the case of the injection velocities up to 20-50 m/sec, the ammonia concentration continues to increase. It is found that as the duration injection decreases, the concentration of ammonia increases. In case of continuous injection, the flow rate is less which results in lower velocity of injection, lesser atomization and slower evaporation resulting lesser conversion of UWS into NH3. Shorter duration of injection leads better atomization with increased velocity of injection which results in faster evaporation and thermolysis.
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.
基金supported by National Natural Science Foundation of China(52104048,42272198)。
文摘Gas channeling in fractures during CO_(2) injection into the deep coal seam seriously reduces the CO_(2) storage efficiency after the development of coalbed methane.The generation and migration of coal fines causes blockages in the fractures in the stage of drainage and gas production,reducing the gas channeling effect of injected CO_(2) caused by the heterogeneity of the coal seam.To explore the impact of coal fines within coal seam fractures on the efficacy of CO_(2) storage,experiments on the production stage and CO_(2) injection for storage were conducted on coal combinations containing propped fractures,fractures,and matrix.The CO_(2) storage characteristics of coal at the constraint of coal fines,as well as the influence of multiple rounds of intermittent CO_(2) injection and different injection parameters on the CO_(2) storage effect,were analyzed.The research results show that blockage by coal fines increases the resistance to fluid flow in the fractures by 71.2%.The CO_(2) storage capacity and storage potential of coal with coal fines are 6.5 cm^(3)/g and 8.8%higher than those of coal without coal fines,while the CO_(2) storage capacity of fractured coal under the influence of coal fines has the largest increase of 9.4 cm^(3)/g.The CO_(2) storage of coal containing coal fines is significantly higher(6.6%)than that of the coal without coal fines.The CO_(2) storage effect of the coal with coal fines is improved with the increase in injection rate,whereas the CO_(2) storage effect of the coal without coal fines decreases significantly(by 7.8%).Multiple rounds of intermittent injection increases the CO_(2) storage volume of coal by 20.4%(with coal fines)and 17.1%(without coal fines).The presence of coal fines in fractures also slows down the downward trend of CO_(2) storage fraction after multiple rounds of CO_(2) injection.The blockage in fractures significantly increases the CO_(2) injection time and difficulty,but can increase the CO_(2) storage fraction by 4.7%-17.1%,and the storage volume by 1.9%-14%,increasing the feasibility of CO_(2) storage in fractured coal seams that have previously been exploited for methane production.The multiple rounds of intermittent CO_(2) injection and shut-in periods has shown potential for greater CO_(2) storage and injection efficiency.
文摘Lead has been recognized as a high risk toxic for most organisms including human. The effects of Pb in non-mammalian vertebrates are oprly known, particularly in anuran amphibians. The purpose of this study was to determine the effect of this metal on some hematological parameters of adult Bufo arenarum. It was found that all parameters remained unaltered within normal ranges, with the exception of reticulocyte counts which was significantly increased compared to the in controls (3. 7% vs. 0. 2 % ). It is suggested that the selective change found in reticulocyte count might be considered as an early response of a biomarker to sublethal exposition of Bufo arenarum to lead.
基金NationalNaturalScienceFoundationofChina! (No .5 99740 2 0 )
文摘On the basis of heat transfer and chemical kinetics theory, both connections coal self ignite with oxygen concentration and range of oxidation zone with air leak intensity are analyzed, and calculating method is deduced to gain the lower limit of oxygen concentration and the range of oxidation zone. The change rule of correlative parameter is quantitatively researched between before nitrogen injection and after nitrogen injection in gob, such as oxygen concentration, oxidation zone width, etc. According to theoretical calculation, the relation position and flow of nitrogen injection with oxidation zone width is conformed, and computational formulas of the best flow and position of nitrogen injection are obtained. It offers a theoretic criterion for preventing and controlling float coal self ignite by nitrogen injection in gob.
基金Supported by National Natural Science Foundation of China(11205185,11175020,11175193)
文摘The China Spallation Neutron Source （CSNS） uses H- stripping and phase space painting metnocl co fill a large ring acceptance with a small emittance linac beam. The dependence of the painting beam on the injection beam parameters was studied for the Rapid Cycling Synchrotron （RCS）. The simulation study was done for injection with different momentum spreads, different rms emittances of the injection beam, and different matching conditions. Then, the beam loss, 99% and rms emittances were obtained, and the optimized injection beam parameters were given. The interaction between H- beam and stripping foil was studied, and the effect of foil scattering was simulated. The stripping efficiency was calculated and the suitable thickness of stripping foil was obtained. In addition, the energy deposition on the foil and the beam loss due to the foil scattering were also studied.
基金funded by the NationalNatural Science Foundation of China(52274056,51974348).
文摘Advanced water injection has become an effective method for developing low-permeability reservoirs.However,after a period of high yield from fracturing,the injected waterflows rapidly along high-capacity channels,which greatly reduces the sweep efficiency of reservoirs.In this work,the plugging process by microspheres and nanospheres from the fracture to the matrix was simulated through core experiments.The plugging performance of multi-scale microspheres(microspheres and nanospheres)on the core matrix was evaluated by measuring the plugging rate and other parameters.Enhanced oil recovery after synergistic plugging with multi-scale microspheres was used as the evaluation index,a sensitivity analysis of injection parameters was performed,and the best combination of injection parameters was optimized by orthogonal experiments.The experimental results showed that the plugging performance of nanospheres is mainly reflected in thefilling of the core matrix,while the plugging performance of microspheres is mainly reflected by retention at the injection end of the core(as opposed to the fractured end face).The plugging rate of nanospheres reached 78.83%,which is much higher than the 30.28%rate achieved with microspheres.The maximum oil recovery after plugging was 19.12%,which corresponds to the following combination of injection parameters:total injection of 0.6 pore volume(PV),injection ratio between nanospheres and microspheres of 2:1,injection rate of 1.5 mL$min 1,and aging time of 6 days.Among the injection parameters,the injection ratio between nanospheres and microspheres had the greatest influence on the recovery of waterflooding after plugging,followed by the total injection of multi-scale microspheres.The injection rate and aging time had little effect.
基金National Natural Science Foundation of China(NSFC)“Theory and Technology of Complex Seam Network in High Temperature Rock for Storage”(No.52192621)National Key Research and Development Program(No.2018YFB1501804)+2 种基金Sichuan Science and Technology Program Project“Research on the Mechanism of Enhanced Heat Transfer between Geothermal Well Completion Structure and Downhole Heat Exchanger”(No.2021Ya1.389)National Key Research and Development Program(No.2021YJ0389)“Research on the Mechanism of Fracture Damage in Dry Hot Rock Extraction”(PRP/open-2110)of the State Key Laboratory of Oil and Gas Resources and Exploration,China University of Petroleum(Beijing).
文摘Geothermal energy,a kind of clean and environmentally friendly energy source,is an important object of future natural resource development and utilization,among which,hot dry rock is one of the important deep geothermal resources.In the current multi-objective optimization of heat extraction performance,reservoir production models are less considered and the effects of different optimization ideas are not compared comprehensively.To improve the heat extraction efficiency and prolong the exploitation life of geothermal reservoirs,this paper determines the appropriate operating parameters of geothermal system(injection temperature,injection rate,production pressure and injection-production well spacing)based on the coupled thermal-hydraulic-mechanical model of hot dry rock exploitation in the Gonghe area of Qinghai and three heat extraction optimization methods.In addition,the heat extraction performances of different schemes are comparatively evaluated.And the following research results are obtained.First,the sensitivity analysis of injection and production parameters shows that power generation and recovery factor are in a reverse relation with injection-production pressure difference,which is the direct reason for the adoption of multiobjective optimization.Second,the optimization scheme prepared on the basis of parametric study indicates that the shortest life of a geothermal reservoir is 10 years,the injection-production pressure difference is up to 67 MPa,there is a significant thermal breakthrough phenomenon and the reservoir safety faces challenges.Third,by virtue of multi-objective optimization and decision making integration,the optimal operation parameter combination of hot dry rock system is determined,the life of geothermal reservoirs can exceed 20 years and balanced optimization is achieved.In conclusion,the idea of multi-objective optimization is feasible and applicable to geothermal energy exploitation and this method provides a reference for the efficient geothermal energy development and utilization and is helpful to the realization of“double carbon”goal in China.
基金supported by the National Natural Science Foundation of China(61802359,62025207)USTC Research Funds of the Double First-Class Initiative(YD0010002003).
文摘We propose a novel method to compute globally injective parameterizations with arbitrary positional constraints on disk topology meshes.Central to this method is the use of a scaffold mesh that reduces the globally injective constraint to a locally flipfree condition.Hence,given an initial parameterized mesh containing flipped triangles and satisfying the positional constraints,we only need to remove the flips of a overall mesh consisting of the parameterized mesh and the scaffold mesh while always meeting positional constraints.To successfully apply this idea,we develop two key techniques.Firstly,an initialization method is used to generate a valid scaffold mesh and mitigate difficulties in eliminating flips.Secondly,edgebased remeshing is used to optimize the regularity of the scaffold mesh containing flips,thereby improving practical robustness.Compared to state-of-the-art methods,our method is much more robust.We demonstrate the capability and feasibility of our method on a large number of complex meshes.
基金supported by the National Natural Science Foundation of China(Grant No.51206060)the National Basic Research Program of China("973"Program)(Grant No.2013CB228402)
文摘With increasingly stringent emission regulations and demand for fuel economy by the public,the combustion and emission problems of automotive diesel engines during transient operation have become vital and urgent issues.In this study,combustion deterioration has been experimentally analyzed using a heavy-duty turbocharged diesel engine running under transient conditions(constant speed and increasing torque).Optimization of the transient combustion process was performed by adjusting the fuel injection parameters.The results indicated that the notable combustion deterioration relative to steady state operation while transient was a function of the delay in the air-supply to the turbocharged engine,and took the form of combustion phasing delay,resulting in rapidly increasing smoke emission and fuel consumption.However,the delay in combustion phasing can be controlled by advancing the fuel injection timing,effectively increasing thermal efficiency.Unfortunately,smoke and NO x emissions increased at the same time.The deterioration in combustion phasing can also be improved by increasing injection pressure,resulting in decreased smoke emission while NO x emission increased.It is worth noting that the effective thermal efficiency first increased and then decreased as fuel injection pressure increased during transient operation.
文摘In this paper effects of various injection molding parameters on tribological properties of ultra-high molecular weight polyethylene （UHMWPE） were investigated. The tribological properties like coefficient of friction and wear rate were obtained from the experimental results of hip simulator which was designed and fabricated in the laboratory. Bovine serum was used as a lubricant in this study. In addition, the hardness of the specimen was also investigated as well. The injection molding parameters that varied for this study are melt temperature, injection velocity and compaction time. The results show that contact loads and melt temperature were mostly influenced the tribological behavior of UHMWPE. A wear mechanism map was developed to study the dominant wear mechanism that influences the wear behavior of UHMWPE. SEM was employed to study the worn out morphologies of UHMWPE. The dominant wear mechanisms that are dominated through our study are ironing, scratching, ploughing, plastic deformation, and fatigue wear.
