电控柴油机分缸均衡控制算法及试验

柴油机各个气缸的进气量、喷油量、燃烧等存在差异,导致气缸间存在做功差异,直接影响柴油机转速的平稳性以及排放性能等。针对位置式电控柴油机,采用PI闭环控制,通过瞬时转速信号识别并计算各缸的工作差异,利用分缸均衡控制算法对油量进行补偿修正。试验结果显示低转速稳态工况转速波动由7 r/min降至3 r/min,各缸工作不均匀度由±5 r/min降至±2 r/min,在瞬态过程和高转速3 400 r/min时该算法仍然适用有效。     

MOF-199固载过氧化磷钨酸盐催化剂的制备及其在柴油脱硫中的应用

采用简易的原位合成法合成了过氧化磷钨酸盐(TBA)₃PW₄封装于MOF-199孔道内的固载型催化剂(TBA)₃PW₄@MOF-199,借助电感耦合等离子体(ICP)、傅里叶红外光谱(FT-IR)、X射线衍射(XRD)、热重分析(TG)、场发射扫描电子显微镜(SEM)及N₂吸附-脱附等温曲线(BET)等分析手段对催化剂样品(TBA)₃PW₄@MOF-199的组成、稳定性及形貌进行了表征。采用含苯并噻吩(BT)、二苯并噻吩(DBT)、4-甲基二苯并噻吩(4-MDBT)和4,6-二甲基二苯并噻吩(4,6-DMDBT) 4种硫源的多组分模拟柴油与萃取剂组成的液-液双相系统,以双氧水为氧化剂,对催化剂的脱硫活性进行了探究,并探讨了催化剂用量、氧化剂用量及反应温度对脱硫效率的影响。结果表明：在最佳反应条件(反应温度70 ℃、催化剂(TBA)₃PW₄@MOF-199用量40 mg、H₂O₂用量0.26 mmol、模拟柴油体积0.75 mL及萃取剂［Bmim］PF₆体积0.75 mL)下,催化剂(TBA)₃PW₄@MOF-199的脱硫效率可以在80 min内达到99.9%,同时重复使用8次,脱硫效率仍保持在91%以上。该催化剂优异的催化脱硫活性及稳定性使其在工业应用上具有一定的前景。     

Extended Reflexive Ontologies for the Generation of Clinical Recommendations

Decision recommendations are a set of alternative options for clinical decisions (e.g., diagnosis, prognosis, treatment selection, follow-up, and prevention) that are provided to decision makers by knowledge-based Clinical Decision Support Systems (k-CDSS) as aids. We propose to follow a “reasoning over domain” approach for the generation of decision recommendations by gathering and inferring conclusions from production rules. In order to rationalize our approach, we present a specification that will sustain the logic models supported in the knowledge bases we use for persistence. We introduce first the underlying knowledge model and then the necessary extensions that will convey toward the solution of the reported needs. The starting point of our approach is the proposition of Reflexive Ontologies (RO). Here, we go a step further, proposing an extension of RO that includes the handling and reasoning that production rules provide. Our approach speeds up the recommendation generation process.     

Nonlinear model predictive control of an internal combustion engine exposed to measured disturbances

This work presents the design procedure of a speed controller for a large, lean burn, natural gas engine in island mode operation. This is a disturbance rejection problem with a measured, large disturbance. The core element is a nonlinear model predictive control (NMPC) algorithm that serves as outer loop controller in a cascaded control structure and generates set-points for low level control loops. The NMPC relies on a control oriented model that includes the physics based equations, assumptions on underlying control loops and constraints given by the control requirements. It is shown how to design the running cost such that the stability of the NMPC without terminal cost and constraints can be guaranteed for the nominal system and for the perturbed system exposed to parametric uncertainties and un-modeled dynamics. The functionality of the control strategy is demonstrated in simulation and by experimental results derived at the engine-testbed.     

Semi-physical mean-value NOx model for diesel engine control

A semi-physical model has been developed to predict nitrogen oxide (NO_x) emissions produced by diesel engines. This model is suitable for online NO_x estimation and for model-based engine control. It is derived from a zero-dimensional thermodynamic model which was simplified by only retaining main phenomena contributing to NO_x formation. The crank angle evolution of the burned gas temperature, which has a strong impact on NO_x formation rate, is described by a semi-empirical model whose key variable is the maximum burned gas temperature. This variable presents a good correlation with the molar fraction of NO_x at the end of combustion and can be expressed as a function of the intake burned gas ratio and the start of combustion. The maximum burned gas temperature sub-model is then coupled to an averaged NO_x formation kinetic model (based on the Zeldovich mechanism) to form a mean-value model for NO_x computation. This latter model was validated using data sets recorded in two diesel engines for steady-state operating conditions as well as for several driving cycles including parametric variations of the engine calibration.     

催化柴油管式液相加氢脱硫数值模拟

采用计算流体力学(CFD)软件FLUENT,以用户自定义函数(UDF)添加化学反应和反应热,对实验室带有陶瓷膜管分散器的催化柴油管式液相加氢脱硫反应器进行模拟计算,得出反应床层不同部位的硫化物含量分布和温度分布状况。从反应床层的入口到出口,催化柴油的硫化物含量逐渐下降,且下降速度趋缓。在压力6.5 MPa、混氢量0.84%(m)、空速2 h~(-1)、进口温度633 K的条件下,位于床层高度0.15 m处出现最高温度点643.8 K,径向温差最大2.1 K,表明催化柴油管式液相加氢脱硫反应器催化剂装填合适的高径比为4~6。工艺条件的模拟结果表明:随着进口温度上升、混氢量增加、空速减小脱硫率提高,与实验数据吻合程度较好,说明模拟研究过程中采用的模型和控制方程准确性较高。     

PR状态方程二元相互作用参数的拟合及对柴油中氢气溶解度的预测

通过Aspen Hysys模拟计算了温度(323~623)K和压力(4~10)MPa条件下,氢气在0~#柴油、直馏柴油、催化柴油和焦化柴油中的溶解度。计算结果对比实验数据,得到氢气在4种柴油中溶解度的平均误差分别为17.49%、11.48%、20.09%和14.00%。因二元相互作用参数与柴油性质以及温度之间存在着一定的关联,为了得到更加准确的溶解度数据,提出了计算PR状态方程中二元相互作用参数的关联式,并用Matlab进行关联式参数的拟合和氢气溶解度的计算,得到溶解度数据的平均误差分别为8.12%、7.51%、5.73%和6.10%,有效地提高了数据的准确性。因此,提出的二元相互作用参数的计算关联式可以为更加准确地预测氢气在柴油中的溶解度提供有效的方法。     

Zipf定律与网络信息计量学

作为文献计量学重要定律的Zipf定律已在许多领域得到较广泛的应用,网络信息计量学伴随着网络信息的激增而受到人们越来越大的关注。该文结合搜索结果数量的分布情况,提出了在网络信息计量学中仍然存在Zipf定律的猜想,并采用公开的词语集在几个代表性的搜索引擎中进行实验验证,证实了搜索结果数目近似服从Zipf定律的结论,其中Baidu与So搜索结果的Zipf指数为0.003。     

节目传输机房接地系统浅析

根据无线局发射台节目传输机房具有的功能,分析了机房设备安全、人员操作安全和设备稳定运行所需的接地要求,并根据这些要求重点分析了电磁适应接地。