The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type...The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system（HPCRS）including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.展开更多
In recent years,shale gas production horizontal well types mainly include conventional horizontal well,highly deviated well and scoop-shape horizontal well.For the sake of construction decision making,it is necessary ...In recent years,shale gas production horizontal well types mainly include conventional horizontal well,highly deviated well and scoop-shape horizontal well.For the sake of construction decision making,it is necessary to study these three types of wells from the aspects of drag and torque characteristic,weight on bit transferring efficiency,key hole sections or links and extreme penetration length.In this paper,these three types of horizontal wells were taken as the study objects.Their drag and torque,load transfer and extended reach drilling were explored based on the dynamic model of full hole drilling string and the simulation calculation of dynamic characteristics of full hole drilling string system.And the results were applied and tested on site in three shale gas wells(a conventional horizontal well,a highly deviated well and a scoop-shape horizontal well)in the Changning area,Sichuan Basin.And the following research results were obtained.First,the contact friction strength of the deeper part of the buildup section in the scoop-shape horizontal well is very high,and it is 1.67 times that of the hold section.The total contact force of buildup section in the scoop-shape horizontal well is 1.62 times that in the highly deviated well.Second,the contact friction strength of the hold section in highly deviated well is not only higher than that of its buildup section,but also higher than any characteristic section in the three well types of the same depth.Third,the operating stress of drilling strings during the drilling of three well types is not high,but during the extended reach drilling in the curved section of the scoop-shape horizontal well,it is necessary to focus on the twist off of drilling string in the hold section.Fourth,the weight on bit transferring efficiency of scoop-shape horizontal well is lower than that of conventional horizontal well and highly deviated well.In conclusion,the research results preliminarily reveal the drag and torque characteristics and active load transferring mechanisms of conventional horizontal well,highly deviated well and scoop-shape horizontal well for shale gas production,and present important hole sections for safety assessment.They can be used as references for efficient and safe construction of shale gas horizontal wells.展开更多
Heterogeneous computing (HC) environment utilizes diverse resources with different computational capabilities to solve computing-intensive applications having diverse computational requirements and constraints. The ta...Heterogeneous computing (HC) environment utilizes diverse resources with different computational capabilities to solve computing-intensive applications having diverse computational requirements and constraints. The task assignment problem in HC environment can be formally defined as for a given set of tasks and machines, assigning tasks to machines to achieve the minimum makespan. In this paper we propose a new task scheduling heuristic, high standard deviation first (HSTDF), which considers the standard deviation of the expected execution time of a task as a selection criterion. Standard deviation of the ex- pected execution time of a task represents the amount of variation in task execution time on different machines. Our conclusion is that tasks having high standard deviation must be assigned first for scheduling. A large number of experiments were carried out to check the effectiveness of the proposed heuristic in different scenarios, and the comparison with the existing heuristics (Max-min, Sufferage, Segmented Min-average, Segmented Min-min, and Segmented Max-min) clearly reveals that the proposed heuristic outperforms all existing heuristics in terms of average makespan.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51076014)Research Fund for the Doctoral Program of Higher Education of China(Grant No.20101101110011)
文摘The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system（HPCRS）including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.
基金supported by Sichuan Youth Science and Technology Innovation Team Project“Drilling Speed Increase”(No.:2017TD0014)Sichuan Science and Technology Plan International Cooperation Program“Non-linear Vibration Characteristics of Reaming while Drilling System and Optimization of Reaming Parameters”(No.:2016HH0008).
文摘In recent years,shale gas production horizontal well types mainly include conventional horizontal well,highly deviated well and scoop-shape horizontal well.For the sake of construction decision making,it is necessary to study these three types of wells from the aspects of drag and torque characteristic,weight on bit transferring efficiency,key hole sections or links and extreme penetration length.In this paper,these three types of horizontal wells were taken as the study objects.Their drag and torque,load transfer and extended reach drilling were explored based on the dynamic model of full hole drilling string and the simulation calculation of dynamic characteristics of full hole drilling string system.And the results were applied and tested on site in three shale gas wells(a conventional horizontal well,a highly deviated well and a scoop-shape horizontal well)in the Changning area,Sichuan Basin.And the following research results were obtained.First,the contact friction strength of the deeper part of the buildup section in the scoop-shape horizontal well is very high,and it is 1.67 times that of the hold section.The total contact force of buildup section in the scoop-shape horizontal well is 1.62 times that in the highly deviated well.Second,the contact friction strength of the hold section in highly deviated well is not only higher than that of its buildup section,but also higher than any characteristic section in the three well types of the same depth.Third,the operating stress of drilling strings during the drilling of three well types is not high,but during the extended reach drilling in the curved section of the scoop-shape horizontal well,it is necessary to focus on the twist off of drilling string in the hold section.Fourth,the weight on bit transferring efficiency of scoop-shape horizontal well is lower than that of conventional horizontal well and highly deviated well.In conclusion,the research results preliminarily reveal the drag and torque characteristics and active load transferring mechanisms of conventional horizontal well,highly deviated well and scoop-shape horizontal well for shale gas production,and present important hole sections for safety assessment.They can be used as references for efficient and safe construction of shale gas horizontal wells.
基金Project supported by the National Natural Science Foundation of China (No. 60703012)the National Basic Research Program (973) of China (No. 2006CB303000)the Heilongjiang Provincial Scientific and Technological Special Fund for Young Scholars (No. QC06C033),China
文摘Heterogeneous computing (HC) environment utilizes diverse resources with different computational capabilities to solve computing-intensive applications having diverse computational requirements and constraints. The task assignment problem in HC environment can be formally defined as for a given set of tasks and machines, assigning tasks to machines to achieve the minimum makespan. In this paper we propose a new task scheduling heuristic, high standard deviation first (HSTDF), which considers the standard deviation of the expected execution time of a task as a selection criterion. Standard deviation of the ex- pected execution time of a task represents the amount of variation in task execution time on different machines. Our conclusion is that tasks having high standard deviation must be assigned first for scheduling. A large number of experiments were carried out to check the effectiveness of the proposed heuristic in different scenarios, and the comparison with the existing heuristics (Max-min, Sufferage, Segmented Min-average, Segmented Min-min, and Segmented Max-min) clearly reveals that the proposed heuristic outperforms all existing heuristics in terms of average makespan.
