液压机械式压差伺服系统的差分进化H_(∞)优化设计方法

针对液压机械式压差伺服系统正向设计的难点,提出压差伺服系统的差分进化H∞优化设计方法。通过建立状态空间模型,并设计差分进化H_∞频域优化指标,提出一种压差伺服系统的动态设计方法;在此基础上,完成了压差伺服系统镇定、伺服控制规律的优化设计,并进行系统级仿真。仿真结果表明,压差伺服系统稳态特性满足0.92±0.01 MPa,静态误差小于1%,动态调节时间小于0.01 s,超调量小于10%,相角裕度大于70°,20 Hz正弦波动输入信号的干扰下具有鲁棒抗干扰性能。

Formation damage mechanism and control strategy of the compound function of drilling fluid and fracturing fluid in shale reservoirs

For the analysis of the formation damage caused by the compound function of drilling fluid and fracturing fluid,the prediction method for dynamic invasion depth of drilling fluid is developed considering the fracture extension due to shale minerals erosion by oil-based drilling fluid.With the evaluation for the damage of natural and hydraulic fractures caused by mechanical properties weakening of shale fracture surface,fracture closure and rock powder blocking,the formation damage pattern is proposed with consideration of the compound effect of drilling fluid and fracturing fluid.The formation damage mechanism during drilling and completion process in shale reservoir is revealed,and the protection measures are raised.The drilling fluid can deeply invade into the shale formation through natural and induced fractures,erode shale minerals and weaken the mechanical properties of shale during the drilling process.In the process of hydraulic fracturing,the compound effect of drilling fluid and fracturing fluid further weakens the mechanical properties of shale,results in fracture closure and rock powder shedding,and thus induces stress-sensitive damage and solid blocking damage of natural/hydraulic fractures.The damage can yield significant conductivity decrease of fractures,and restrict the high and stable production of shale oil and gas wells.The measures of anti-collapse and anti-blocking to accelerate the drilling of reservoir section,forming chemical membrane to prevent the weakening of the mechanical properties of shale fracture surface,strengthening the plugging of shale fracture and reducing the invasion range of drilling fluid,optimizing fracturing fluid system to protect fracture conductivity are put forward for reservoir protection.

航空发动机燃油伺服系统可控流路设计方法

针对液压机械伺服系统正向设计的难点,提出了液压机械伺服系统可控流路的基本概念和理论。通过建立状态空间模型,采用闭环系统分析法及液压机械伺服系统可控流路概念,提出了单腔和串联式双腔两种基本结构的可控流路设计方法;在此基础上,以燃油伺服等压差控制系统的正向设计为典型算例,应用提出的可控流路设计方法进行了系统性设计。仿真结果表明,燃油伺服等压差控制系统静态误差为0,动态调节时间不大于0.01 s,超调量不大于10%,相角裕度大于45°,正弦波动输入信号的干扰下具有鲁棒抗干扰性能。

航空发动机燃油伺服系统定压活门正向频域设计方法

定压活门是为航空发动机燃油伺服系统提供伺服参考压力的关键部件,其性能直接影响燃油伺服系统的性能。本文提出一种定压活门的正向频域设计方法,内容包括:基于线性系统理论,推导了定压活门系统的状态空间模型;基于频域设计理论,提出了一种定压活门的动态设计方法,完成了镇定控制增益的设计;为了便于工程应用,提出了基于图谱的型孔设计、组合设计方法,指导规则型孔、组合型孔结构参数的设计。仿真结果表明,在幅值为1 MPa的进口油源压力阶跃扰动和大幅值的变负载出口型孔流通面积阶跃扰动下,设计的定压活门稳态特性满足1.5±0.01 MPa,稳态误差小于0.7%,动态调节时间小于5 ms,相角裕度基本大于45°。