Backfire control and power enhancement of a hydrogen internal combustion engine

Frequent backfire can occur in inlet port fuel injection hydrogen internal combustion engines (HICEs) when the equivalence fuel–air ratio is larger than 0.56, thus limiting further enhancement of engine power. Thus, to control backfire, an inlet port fuel injection HICE test system and a computational fluid dynamics model are established to explore the factors that cause backfire under high loads. The temperature and the concentration of the gas mixture near the intake valves are among the essential factors that result in backfire. Optimizing the timing and pressure of hydrogen injection reduces the concentration distribution of the intake mixture and the temperature of the high-concentration mixture through the inlet valve, thus allowing control of backfire. Controlling backfire enables a HICE to work normally at high equivalence fuel–air ratio (even beyond 1.0). A HICE with optimized hydrogen injection timing and pressure demonstrates significant enhancement of the power output.     

Resistance Analyses for Ultrafiltration in Tubular Membrane Module

Abstract

The resistance analyses for ultrafiltration of macromolecular solutions by the resistances-in-series model and the modified gel-polarization model, respectively, have been extended to the turbulent ultrafiltration system in this study. The experiments are carried out by ultrafiltrating dextran T500 solutions in a tubular membrane module with membrane material of ZrO₂-TiO₂/carbon. It is found that the permeate fluxes are predicted very well by these models for both laminar and turbulent systems, and the resistance caused by the concentration polarization/gel layer (R _p) can be reduced by increasing the crossflow velocity on the membrane surface. Analysis by the resistances-in-series model showed that, R _p decreases with flow velocity with exponents of 0.49 and 0.99 for the laminar system and the turbulent system, respectively.     

磁选厂选矿比与精矿品位经济关系的研究

通过研究同一选矿厂不同选矿流程精矿品位与选矿比的数学关系,探索了铁精矿粉不同品位的合理价格     

Provenance and temporal variations in selected flavonoids in leaves of Cyclocarya paliurus

Cyclocarya paliurus is a well-known multiple function plant in China. To reveal the provenance variation of selected flavonoids in leaves of C. paliurus and changes of their level during the growing season, twelve provenances were grown in a field trial and sampled five times at approximately 1 month intervals. The levels of flavonoids varied significantly in leaves of C. paliurus from different provenances, and isoquercitrin represented the largest component of the selected compounds, followed by kaempferol and quercetin. The growing season also significantly affected the concentration of total flavonoids and its composition. In most cases, the greatest concentration was observed in July and October, showing a bimodal temporal variation pattern. Results not only demonstrated that leaves of C. paliurus exhibited commendably higher levels of quercetin, kaempferol and isoquercitrin, but also provided a basis for breeding strategies, selecting superior provenances, and choosing harvesting time for producing specific flavonoids for the food industry.     

Investigation of Ozone Concentration Measurement by Visible Photo Absorption Method

The measurement of ozone concentration based on the visible photo absorption method is investigated. An LED having an emission peak at 609 nm and a photo diode sensitive at visible light frequencies are used as the light source and the photo detector, respectively. The transmittance is measured as a function of ozone concentration, which is in reasonable agreement with the Beer–Lambert relationship. The effective absorption cross-section can therefore be estimated from the fitting procedure. The concentrations determined by both the UV and visible photo absorptions agree well with each other in the range from 7.1 to 68.4 g/m³(N). The relative error in these concentrations is discussed on the basis of the Twyman–Lothian curve. The ozone measurement for the air-fed ozone generation is also investigated. The effect of photo absorption due to NOx species is unavoidable. The present results provide useful data if the ozone measurement based on the visible photo absorption method is applied to ozone monitoring instruments or used for laboratory experiments.     

Potenzial des IR Micro‐Imaging zur In‐situ‐Untersuchung chemischer Reaktionen in nanoporösen Katalysatoren

The in‐situ study of chemical reactions is an intensively studied research topic. A suitable method for this investigation is the IR micro‐imaging technique, which allows to record space‐ and time‐resolved IR spectra. The preparation of a suitable model system with a 3D pore system for the in‐situ recording of concentration profiles using IR micro‐imaging is described, enabling the space‐ and time‐resolved monitoring of catalytic reactions in nanoporous catalysts for the first time. The model system consists of a nanoporous glass monolith with gas‐tight sealed outer surface, therefore, enabling the recording of concentration profiles of cyclohexane and cyclohexane‐benzene mixtures as a function of time.     

空气中氡浓度日变化对平均浓度测量的影响

本文分析和估计了氡浓度的日变化对准累积型仪测量平均氡浓度的影响,指出了适当选择采样终了时间,可以减小这种影响。文中对采集浓度不变又不衰变的气体时,收集最比于 t~(1/2)。或 t(t 为采样时间)的准累积型测氡仪,在氡浓度日变化为矩形波和正弦波情况下,分别给出了其测量值与平均浓度相对偏差随采样终了时间之相位的变化曲线。     

轻水堆一迥路中放射性核素浓度的计算方法及计算机程序

本文分别对轻水堆一回路两种不同的布置方式,推导了一回路中放射性核素浓度的计算方法,并编制了计算机程序。其一是一体化布置方式,即主换热器位于压力壳内,在运行期间一回路水始终处于中子辐照之下;对此又分为在压力壳顶部有气空间和无气空间两种情况。其二是分置式布置,即主换热器位于压力壳之外,在一回路水循环期间仅部分时间处于中子辐照之下。本程序由 FORTRAN 语言编制,在 PDP-11/34 机上运行(程序介绍未写入本文)。     

选矿厂破碎设备工况参数优化研究

选矿是采矿和冶炼的一个中间环节。它在提高矿石品位使之符合冶炼要求以及合理利用国家资源方面，成为国民经济中一个不可缺少的组成部分。我国大多数大型选矿厂都是上世纪五六十年代建成投产，设计规模一般为30～40万t／a。随着我国能源的需求量越来越大，这些选矿厂在1980年～1990年间都进行了生产规模的扩建。与此同时由于最初开采的矿源已经开始枯竭，各矿山企业都寻找了新矿源，破碎处理的矿石性质也发生了改变。