高锰酸盐指数在线自动监测仪的现状与问题

高锰酸盐指数在线自动监测仪已在中国水质自动监测系统中得到广泛应用,其生产厂家日趋成熟、相关标准逐步出台、仪器性能基本达标.但在实际应用过程中.该仪器仍有许多问题需要进一步认识与改进.从标准溶液的选择、滴定终点判定方法的选择、国家标准、干扰排除问题、受TOC在线自动监测仪的冲击、比对实验、自动标定功能等方面,分析了该仪器存在的问题,并提出了相关建议.     

实验室认可中电热恒温鼓风干燥箱的期间核查

本文以DHG-9140A电热恒温鼓风干燥箱为说明对象,按照《检测和校准实验室能力的通用要求》的相关规定,介绍了实验室认可中电热恒温鼓风干燥箱的期间核查操作规程及结果,为实验室认可中期间核查的开展提供了一定的依据。     

Effect of start of main injection timing on performance,emission, and combustion characteristics of a VGT CI engine fueled with neem biodiesel

The performance of engine parameters is more influenced with fuel injection strategies namely start of main injection timing (SoMI). An experimental analysis was performed to find the optimum SoMI timing based on performance, emission, and combustion characteristics. Base fuel of diesel and neem biodiesel was used as test fuels. The neem biodiesel was prepared by esterification and transesterification process. It is found from literature that neem biodiesel blend NB20 with diesel gives optimum performance and emission characteristics; therefore, NB20 blend was used for experiments. A variable geometry turbocharger (VGT) compression ignition (CI) engine was used to conduct the experiments. Engine performance parameters were estimated and compared with a base fuel of diesel and with NB20 blends. In this experimentation, fuel injection pressure (FIP) of 800 bar and engine speed of 1700 rpm were considered. SoMI timing was varied from 2° to 10° bTDC with an increment of 2° bTDC timing. Cylinder pressure (CP) and heat release rate (HRR) were estimated and found that are higher for diesel fuel compared to NB20 blend at different SoMI timings. The addition of neem biodiesel NB20 blend to diesel fuel decreases the exhaust emissions except NOx emissions. The BSFC was considerably reduced and BTE was improved almost equivalent to the diesel fuel for NB20. From the results, it is concluded that 10° bTDC SoMI timing provides 13% improvement in BTE, 21% decrement in BSFC, and 7.5% reduction in CO₂ emissions.