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1.
《International Journal of Hydrogen Energy》2022,47(12):8130-8144
Compared to liquid/gas hydrogen tank, the pipeline is an economical way for hydrogen transportation. With the quick development of utility tunnel in China, hydrogen pipeline enters the gas compartment can be expected soon. However, all the safety requirements of the gas compartment in the current standards are designed for natural gas, and the applicability for hydrogen is unknown. Therefore, a series of studies were started to investigate the safety of hydrogen in utility tunnel. In this work, a real utility tunnel locates at Shanghai was selected as the physical object. A 3D numerical model was built and successfully validated by a scaled tunnel test. The model has the maximum deviation of +9.5%. After that, a comparatively study of the dispersion behavior of CH4 and H2 was conducted. The assumed scenario was a 20 mm small-hole leaks with gauge pressure of 1.0 MPa in the middle of the tunnel. Numerical results shown that, H2 has a larger dispersion velocity and higher concentration, and is more dangerous compared to CH4. The current emergency ventilation strategy of air change rate of 12 times/h is not effective enough to dilute the H2 flammable cloud. The alarm time of the testing points shown strong linear law. There was a sharp variation in the range of 20%–100% LFL (Lower Flammable Limit), so the alarm strategy in the tunnel standards is too ideal for both CH4 and H2. The numerical results in the present study could provide a guidance for the design and safety management of the hydrogen tunnel. 相似文献
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In this paper, we present an aero‐structural model of a tethered swept wing for airborne wind energy generation. The carbon composite wing has neither fuselage nor actuated aerodynamic control surfaces and is controlled entirely from the ground using three separate tethers. The computational model is efficient enough to be used for weight optimisation at the initial design stage. The main load‐bearing wing component is a nontypical “D”‐shaped wing‐box, which is represented as a slender carbon composite shell and further idealised as a stack of two‐dimensional cross section models arranged along an anisotropic one‐dimensional beam model. This reduced 2+1D finite element model is then combined with a nonlinear vortex step method that determines the aerodynamic load. A bridle model is utilised to calculate the individual forces as a function of the aerodynamic load in the bridle lines that connect the main tether to the wing. The entire computational model is used to explore the influence of the bride on the D‐box structure. Considering a reference D‐box design along with a reference aerodynamic load case, the structural response is analysed for typical bridle configurations. Subsequently, an optimisation of the internal geometry and laminate fibre orientations is carried out using the structural computation models, for a fixed aerodynamic and bridle configuration. Aiming at a minimal weight of the wing structure, we find that for the typical load case of the system, an overall weight savings of approximately 20% can be achieved compared with the initial reference design. 相似文献
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以重庆市甄子岩29号危岩体为研究对象,基于现场调查和分析解剖,建立UDEC离散元数值计算模型,对其演化变形过程进行模拟分析。研究表明,在巨大的自重作用下,由于基座岩体岩质软,岩体较破碎,且基座外侧为直立的陡崖,具有完整的临空面,从而使基座岩体易发生压缩流变及剪切流变,进而使危岩体存在滑移垮塌的危险。 相似文献
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This paper presents the stability improvement results of hybrid doubly fed induction generator (DFIG)-based and permanent magnet generator (PMG)-based offshore wind farms (OWFs) using a static synchronous series compensator (SSSC). An adaptive-network-based fuzzy inference system (ANFIS) controller of the proposed SSSC is designed to render adequate damping characteristics to the studied system. A frequency-domain approach based on a linearized system model using eigenvalue technique analysis is performed. A time-domain scheme based on a nonlinear system model subject to a three-phase short circuit fault at infinite bus with variations in the signal transmission delays has also been investigated to compare the damping of the studied system in cases of with and without controller. The simulation results with MATLAB/SIMULINK toolbox have been presented. It can be concluded from the simulation results that the proposed SSSC joined with the designed ANFIS damping controller can offer adequate damping performance to the studied hybrid DFIG-based and PMG-based OWFs under severe disturbance. 相似文献
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水平井压裂技术在低渗透及非常规储层中得到了广泛应用,压裂后水平井的产能预测关系到油田开发方案的制定,因此,国内外学者对压后渗流模型的建立和求解方法做出了不懈的努力。本文详细回顾了国内外学者所建压裂水平井产能预测模型及求解方法,指出了不同模型和求解方法的优缺点,并展望了压裂水平井产能模型的发展方向。 相似文献
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常规的冲击钻井工具不能满足井眼轨迹控制要求、使用寿命有限、缓解脱压不显著等问题,影响了在定向井钻井中的推广应用。建立248;215.9 mm PDC钻头和岩石的有限元模型,分析钻井参数对破岩效率的影响规律,结果表明:冲击频率为17.5 Hz和35 Hz时,破岩效率最优; 破岩效率随钻压增大而增加,而后变化逐渐平缓; 破岩效率随钻头转速增大而增加; 破岩效率随冲击载荷的增加变化平缓。据此研制了新型水力旋冲钻井工具。现场试验表明,该工具符合定向水平井“一趟钻”工艺要求,使机械钻速提高56%,使用寿命达150 h,MWD信号正常。 相似文献
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本文按结冰风洞制冷方式、试验对象、用途性质和试验段尺寸归纳总结了结冰风洞的类型,指出校准标准主要针对的结冰风洞类型;阐述结冰风洞空气动力流场校准可以依据的3个国内外标准;介绍SAE结冰风洞校准标准中云雾场校准的主要内容;分析研究相关标准的特点和存在的不足;提出未来我国制定结冰风洞校准标准的建议。 相似文献
10.
This paper describes algorithms that use demand-side management to address large-scale integration of wind power. In particular, demand response (DR) is used to manage wind power intermittency by shifting the time that electrical power system loads occur in response to real-time prices and wind availability. An economic dispatch with transmission, DR capacity and operational constraints is used to model the operation of a transmission constrained system with a high penetration of wind power. This optimization model is used to determine the optimal sizing and distribution of DR given a fixed budget for customer incentives and the installation of enabling technology. We demonstrate the effectiveness of the operational model based on a simple PJM 5-bus system and an IEEE 118-bus system. Simulation results show that transmission constraints have a greater effect on sizing of DR capacity than the location of wind power, which means that buses electrically close to congested lines tend to have higher incentives to deploy DR resources than other buses. The second part of the work examines optimal siting of technology that enables DR based on the frequency of DR based load changes, which are generally a function of the network location. 相似文献