Comprehensive numerical investigations on the thermal performance of heat recirculating micro combustor with pin fins for micro-thermal voltaic system applications

Aiming at improving the relatively low energy output and energy conversion efficiency of the micro-thermal voltaic (MTPV) system, an innovative heat recirculating micro combustor with pin fins is designed. The effects of pin fins arrangement, hydrogen/air equivalent ratio on the energy output and performance of CHMC, HMCP and HMCI are compared and investigated. The result shows that when the V_in is 6 m/s and Φ is 1.0, the emitter power of CHMC is 72.76W, and that of HCMP and HCMI micro combustor are 75.99W and 76.35W. and the emitter efficiency of CHMC, HCMP and HCMI is 41.93%, 43.26% and 44.01%. HMCI has better energy output capability compared with CHMC and HMCP. Even though, HMCI brings a higher pressure drop, it is within the acceptable range. When the V_in is 6 m/s, the pressure drop from the pin fins only accounts for 26.4% of the total pressure drop for HMCI. Through the study of equivalent ratio, it is found that HMCI has good adaptability in different equivalent ratio range. This work provides new ideas for the development of MTPV system in the future.     

Experimental research on combined effect of obstacle and local spraying water fog on hydrogen/air premixed explosion

In order to reveal the mechanism of water fog explosion suppression and research the combined effect of water fog and obstacle on hydrogen/air deflagration, multiple sets of experiments were set up. The results show that the instability of thermal diffusion under lean combustion conditions is the main influencing factor of hydrogen/air flame surface instability, and the existence of water fog will aggravate the hydrogen/air flame surface instability. When obstacle is not considered, 8 μm, 15 μm, 30 μm water fog can significantly reduce the flame velocity and explosion overpressure of hydrogen/air, 45 μm fine water fog plays the opposite role. When considering the relative position of the water fog release position and the obstacle, the 8 μm, 15 μm, 30 μm water fog has almost no suppression effect when released near the obstacle, but a significant suppression effect occur, when using the 45 μm water fog. In the field of theoretical research, the research results not only provide an experimental basis for the fine water fog to reduce the consequences of hydrogen explosion accidents, and the optimal diameter range used by the water fog, but also provide experimental reference for the numerical simulation of hydrogen/air explosion suppression in semi-open space, and promote the development of hydrogen explosion suppression theory. In terms of engineering applications, this study can provide a theoretical basis for the layout of fire fighting equipment in the engine room of nuclear power plants or hydrogen-powered ships.     

Evaluation of cut cell cartesian method for simulation of a hook and claw type hydrogen pump

Hook and claw pumps are used for recirculation of excess hydrogen in fuel cells. Optimization of the pump design is essential. Computational Fluid Dynamic (CFD) is an effective method for performance optimization. However, it is difficult to conduct CFD simulation because of the sharp cusp of the rotor profile. Cut cell Cartesian mesh could be the solution to handle this complex and moving geometries. The aim of this paper is to evaluate ANSYS Forte for hook and claw pumps. Firstly, the conservation accuracy of the cut cell cartesian mesh is verified using an adiabatic piston cylinder case. Then, simulation results of hook and claw type pump are compared with experimental data. Finally, simulation results of air and hydrogen are compared. The results show that the CFD simulation of hook and claw pumps using cut cell cartesian mesh could provide an efficient and effective approach for the optimization of the system.     

Novel TiC-based composites with enhanced mechanical properties

Novel TiC-based composites were synthesized by reactive hot-pressing at 1800 °C for 1 h with ZrB₂ addition as a sintering aid for the first time. The effects of ZrB₂ contents on the phase composition, microstructure evolution, and mechanical properties were reported. Based on the reaction and solid solution coupling effects between ZrB₂ and TiC, the product ZrC may be partially or completely dissolved into the TiC matrix, and then phase separation within the miscibility gap is observed to form lamellar nanostructured ZrC-rich (Zr, Ti)C. The TiC-10 mol.% ZrB₂ (starting batch composition) exhibits good comprehensive mechanical properties of hardness 27.7 ± 1.3 GPa, flexural strength 659 ± 48 MPa, and fracture toughness of 6.5 ± 0.6 MPa m^1/2, respectively, which reach or exceed most TiC-based composites using ceramics as sintering aids in the previous reports.     

高等级生物安全实验室通风空调系统冗余设计原则探讨

对比分析了国内外标准有关高等级生物安全实验室通风空调系统冗余设计的要求。结合我国已有高等级生物安全实验室,重点分析了送风机、排风机、排风高效过滤器冗余设计的具体实施形式和存在的问题,给出了冗余设计原则建议。     

热处理对挤压态Mg-6Gd-5Y-1Zn合金组织与性能的影响

通过对Mg-6Gd-5Y-1Zn(质量分数,%)合金在固溶和时效处理状态下显微组织和力学性能的研究发现,α-Mg基体、沿挤压方向分布的条状18R-LPSO相、少量的Mg₂₄(GdYZn)₅ 相以及细层片状的14H-LPSO相构成了挤压态合金的组成相。挤压态合金经固溶(T4)处理后,一部分18R-LPSO相溶入基体,并且基体中的14H-LPSO相伸长同时粗化。挤压态合金经过固溶加时效(T6)处理后,大量β′相从α-Mg基体中析出。T6态合金的室温力学性能最好,其屈服强度、抗拉强度及伸长率分别为272 MPa、406 MPa和6.1%。β′相沉淀也发生在挤压态合金的直接人工时效(T5)处理过程,但相比于T6处理,14H-LPSO相和β′相在基体中的体积分数均偏低。     

油藏中后期减氧空气驱提高采收率机理研究

尕斯库勒油田E¹₃油藏已经进入高含水时期，储采失衡加剧，综合含水率达到了80%以上，原油产量下降，经济效益变差。为了提高油藏原油采出程度、改善油藏开发效果，调研了国内外减氧空气驱的机理研究以及现场试验的资料，建立了以油藏真实孔渗饱数据为基础的一维条形地层机理模型，并选取该油藏Y12-27井组进行了减氧空气驱可行性验证。研究表明:纵向顶部减氧空气驱驱油效果优于水驱和氮气驱；驱替压力对原油采出程度影响不大；注水转注气可以提高原油采出程度；对于减氧空气驱，由于低温氧化反应的作用，氧气浓度对原油采出程度有一定影响，但比较微弱，其中，氧气浓度为10%时，驱替结束采出程度最高；尕斯库勒油田E¹₃油藏属于注水开发“双高”油藏，适用于减氧空气驱；对于该油藏Y12-27井组，顶部减氧空气驱驱油效果好于水驱和氮气驱，建议氧气浓度超过10%时采取关井等措施。     

锂-二氧化碳电池阴极催化剂的研究进展

锂-二氧化碳电池通过捕获、转化二氧化碳为储能物质，既可以减少二氧化碳排放量又可以作为创新的储能装置，引起了研究者们的广泛关注。本文简单介绍了锂-二氧化碳电池的工作机理、发展历程和目前研究存在的难题，通过对研究工作的总结、电池性能的对比，将不同类型的催化剂进行了系统的分类和简单的概括，综述了催化剂的设计理念和研究现状，提出了催化剂目前存在的难题与挑战，并展望了催化剂未来的发展方向。本文主要针对锂-二氧化碳电池阴极催化剂的最新研究进展进行了详细的阐述，指出高效的阴极催化剂是促进锂-二氧化碳电池电化学反应动力学、降低充电平台和过电势的关键所在。     

基于压缩机-支架系统的异常噪声研究

针对某乘用车发动机转速在1 573 r/min，压缩机开启时车内噪声异常的问题，对样车进行试验分析与诊断，对压缩机-支架系统进行仿真分析，提出改进方案并验证改进效果。利用LMS声振信号采集系统采集振动噪声数据，采用频谱分析、阶次追踪等方法，并结合压缩机-支架系统模态仿真结果，确定车内异常噪声是压缩机轴频21阶与压缩机-支架系统3阶模态频率接近发生共振造成的。通过优化支架结构来提高压缩机-支架系统3阶模态频率以此来避免共振，并换装橡胶驱动盘缓和压缩机输入扭矩波动。将改进结构进行整车试验，结果表明：匀速工况空调开启时问题转速下，车内噪声降低了2.5 dB(A)；匀加速工况空调开启时发动机转速1 500~1 650 r/min区间，车内噪声无峰值，其余转速空调开启时改进前/后车内噪声基本不变，噪声波动趋势平缓。     

亲子乐园空调送风方式的数值模拟研究

大型综合室内亲子乐园属于高大空间,设有游乐设施和游戏的特殊性使得对空间的舒适性要求一致,但是送风气流遇阻严重,室内存在较多气流死角,影响室内空气质量和儿童健康。因此其空调设计不仅需要考虑温度、风速的空间均匀度,还要考虑各点的空气龄和PMV-PPD指标。以天津某亲子乐园为研究对象,利用scSTREAM软件对适用于该房间的辐射供冷加新风、置换通风、混合通风三种空调方式的送风效果进行数值模拟分析,从流场的均匀性、人员的热舒适性等方面对模拟结果进行探讨,研究结果表明辐射供冷加新风方式的空间均匀性和PMV指标最佳,混合通风方式的空气龄最小。