自然吸气发动机多温度点重复起动特性分析及优化

为分析和优化某1.5 L自然吸气发动机多温度点的重复起动特性,利用搭载该发动机的车辆,基于电子控制单元(electronic control unit,ECU)基础数据进行20~80℃多温度点重复起动测试,通过测试结果统计并分析重复起动特征数据,最后根据分析结果对重复起动标定进行优化.结果表明:ECU基础数据在40~60℃范围重复起动最大转速上冲值低、起动时间长、转速下跌次数多;将20~80℃首次起动的点火角提前3°曲轴转角(crank angle,CA),并将40~60℃首次起动的喷油量增加5%,重复起动的喷油修正由减少25%改为减少15%后,整个温度范围的重复起动质量有一定程度提升,40~60℃范围重复起动特性差的情况得以改善.

用“一线总线”实现多点高速测温的方案

介绍一线总线工作原理及双CPU构成的对一线总线温度传感器多点高速测温的设计方法

Distributed Optical Fiber Sensor for Multi-point Temperature Measurement

The distributed optical fiber sensing technology is overviewed,which is based on Raman scattering light theory.Basic operation principle,structure,system characteristics and signal processing are discussed.This structure and method of the signal processing possess of certain spatial resolution,hence will ensure the practicability of system.

Fire Detection Method Based on Identical Fiber Bragg Grating

Wavelength division multiplex has obvious advantages when it is used in fiber Bragg grating(FBG) sensing for simultaneous measurement of various quantities, but the number of sensors is usually restricted by the bandwidth of SLED and demodulator. The identical fiber Bragg grating is introduced for fire alarm system and the method of collecting signal of identical FBG sensors is described. The experiment result shows that with identical FBG sensing. The number of the sensors coupled in one fiber increases greatly and the precision can be ensured to meet the requirement for fire alarm system.

Theoretical and experimental studies of heat transfer with moving phase-change interface in freezing and thawing of porous potting soil

Soil in a cold region is subject to frequent freezing and thawing cycles.Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture.It is important to understand the detailed heat transfer behaviors of the freezing and thawing processes to prevent freeze damage,and to devise proper mitigation measures for effective pot planting in cold regions.A theoretical model was developed to analyze the transient moving phase-change interface heat transfer in the freezing and thawing of porous potting soil.The theoretical derivation is based on the assumption that the soil freezes completely at a single temperature.Microscopic poromechanic effects on heat transfer behavior were ignored.The spatial domain of the problem was simplified to a 1D spherical coordinate system with variation in the radial direction.Green's function was applied to solve for the time-dependent body temperature.Experiments were conducted for validation of the theoretical model.Reasonable agreement between the theoretical predictions and experimental measurements was obtained.The theoretical model developed can be easily used to determine the sensitivity of various parameters in the freezing/thawing processes,e.g.,thermal properties of soil,ambient temperature,and planting pot size.

SMS Fiber Structure for Temperature Measurement Using an OTDR

A singlemode-multimode-singlemode （SMS） fiber structure for temperature measurement using an optical time domain reflectometer （OTDR）-based interrogation system is proposed. A temperature measurement range of 40 ℃-195 ℃ with a resolution of 0.12 ℃ and a linearity of 0.992 could be achieved for the multimode fiber （MMF） graded index with a length of 60mm. It was also demonstrated that two-point temperature measurement with two SMS fiber structures as temperature sensors could be made. The proposed temperature measurement system offered a high resolution and also benefited from a simple configuration with a capability of multi-point temperature measurement.