基于ARM9无线视频传输系统的设计

视频传输系统是以三星公司S3C2440芯片为核心处理器,采用VNT6656WiFi模块为无线通信载体,通过USB摄像头采集视频信息.为了手机终端上能够显示视频,在Linux操作系统下移植了网页服务器Apache、视频服务器MJPG-streamer.经过测试,该视频传输系统结构简单,数据传输可靠,具有广泛的应用前景.     

Research on the Control Strategy of Variable Nozzle Turbocharger for Natural Gas Engine

A variable nozzle turbocharger (VNT) was applied to a 2.2-liter L4 natural gas engine,and a VNT control system was designed to operate it.Based on VNT matching test results,a VNT control strategy was studied,in which VNT adjustment is carried out through pre-calibrated VNT handling rod position,combined with a closed-loop target boost pressure feedback using proportional-integral-derivative(PID) algorithm.Experimental results showed that the VNT control system presented in this thesis can lead to optimized ...     

可变喷嘴涡轮增压器喷嘴环叶片位置对柴油机性能的影响

针对普通废气涡轮增压器低速响应和高速功率不能同时兼顾的特点,对可变喷嘴涡轮增压器(VNT)进行了试验研究。通过试验分析了喷嘴环叶片位置对柴油机性能的影响,并得到了VNT的优化脉谱。同时进行了VNT的瞬态响应研究。研究结果表明:VNT通过改变涡轮喷嘴环面积可与柴油机各工况实现最佳匹配,燃油消耗率在全工况范围内明显改善,在高速低负荷时燃油消耗率降低最多,达到了10%;通过增加低速的进气量,VNT对柴油机低速高负荷工况性能有明显改善,扭矩约增加15N·m,油耗率降低2%,烟度从原机4.5 BSU降低到2.5 BSU;通过与原机外特性的对比,在中高速的NO_x和烟度排放与原机相差不大,在低速区NO_x增加约100×10~(-6),烟度降低2 BSU,在整个转速范围内油耗率降低2%～3%。     

Numerical Analysis of Nozzle Clearance's Effect on Turbine Performance

Variable nozzle turbine (VNT) has become a popular variable geometry turbine (VGT) technology for the diesel engine application. Nozzle clearance, which can’t be avoided on the hub and shroud side of the VNT turbine due to the pivoting stators, can lead to turbine performance deterioration. However, its mechanism is still not clear. In this paper, numerical investigation, which is validated by experiment, is carried out to study the mechanism of the nozzle clearance’s effect on the turbine performance. Firstly, performance of the mixed flow turbine with fixed nozzle clearances tested on flow bench. Performance of the tested turbine with the same nozzle clearance is numerically simulated. The numerical result agrees well with the test data, which proves correct of the numerical method. Then the turbine performance with different nozzle clearances is numerically analyzed. The research showed that with nozzle clearance, flow loss in the nozzle increases at first and it reaches the maximum value when the clearance ratio is 5%. Flow at the exit of the nozzle becomes less uniform with nozzle clearance. The negative incidence angle of the rotor also increases with nozzle clearance and leads to more incidence angle loss in the rotor. The low energy fluid formed in the nozzle due to the nozzle clearance migrates from hub to shroud side in the rotor, which is another main reason for the rotor’s performance degradation. The present research exposed the mechanism of the dramatically decrease of the turbine performance with nozzle clearance: (a) The loss associated with the nozzle leakage increases with the nozzle clearance; (b) The flow loss grows up quickly in the rotor due to the incidence angle loss and migration of the low energy fluid from hub to shroud side.     

可变喷嘴涡轮增压器电控系统控制策略的研究

针对可变喷嘴涡轮增压系统，基于大量的实验数据综合考虑发动机的各种运行工况，分析研究常见的几种VNT控制策略的优缺点，最终确定PID复合式控制算法是最可行，是一种最容易达到预期控制目标的控制策略。     

JK80VNT增压器的开发研究

可变喷嘴涡轮调节技术是改善增压柴油机低速性能、降低柴油机排放的有效措施。本文对JK80VNT增压器进行了设计计算，将所设计的转叶式可变喷嘴涡轮增压器进行了涡轮性能试验，试验结果表明它能够有效地调节涡轮特性。并进行了可变喷嘴涡轮增压器与CA6106柴油机的匹配试验，将其结果与带放气阀增压器的试验结果进行了比较，结果表明CA6106柴油机高速油耗和整个外特性烟度都得到明显的改善。     

带有可变喷嘴涡轮增压系统的天然气发动机试验研究

在CA4G22E发动机的基础上开发出了一台多点顺序喷射的天然气发动机。该发动机采用了增压中冷技术及可变喷嘴涡轮增压技术。试验结果表明，采用增压中冷技术争可变喷嘴涡轮技术可以提高发动机的进气量，优化发动机在全工况范围内与增压器的匹配，大幅度提高发动机的动力性与经济性。     

天然气发动机可变喷嘴涡轮增压器匹配研究

针对488天然气发动机匹配了可变喷嘴涡轮增压器(VNT),设计了电子控制系统,并通过发动机试验研究了VNT匹配规律。天然气发动机VNT调节规律不仅与节气门开度(负荷)有关,也与发动机的转速有关。匹配试验结果表明:采用VNT增压技术后天然气发动机的功率和转矩显著提高,最大功率从58 kW提高到73 kW,最大转矩从156 N.m提高到212 N.m,且最大转矩点转速降低,大幅度改善了天然气发动机的动力性与经济性。     

供油系统调整对VNT柴油机低速性能影响

基于PW泵的常规供油系统增压补偿器的存在使得可变喷嘴增压器（VNT）对柴油机性能改善不明显。研究了供油系统参数调整对VNT增压柴油机低速全负荷性能的影响。结果表明：使增压补偿器压力室与大气相通以屏蔽增压补偿器并优化VNT开度后，由于供油量减小，低速全负荷排气烟度比装配GT35增压器的基础柴油机下降56．3％～73．5％，但动力性改善不明显；屏蔽增压补偿器、调整油泵供油特性并优化VNT开度后低速全负荷工况烟度下降53．8％～68．1％，同时1000r／min全负荷转矩增加8．2％。可见，基于电控供油系统的柔性供油特性可以更充分地发挥VNT系统潜能。     

VNT可变涡轮增压器与柴油机的匹配研究

根据一款WG增压柴油机原机的基本结构参数和试验数据,匹配一款VNT废气涡轮增压器,建立VNT增压柴油机的GT-Power一维计算模型,并对柴油机外特性工况和ESC工况进行仿真计算研究。分别以动力性和经济性参数为分析指标,对外特性工况和ESC工况的VNT开度进行优化选择。研究表明,开度优化选择后的VNT柴油机与柴油机原机相比,外特性转矩均有较大幅度提高,最大转矩工况的运行范围拓宽,且VNT增压器的转速在整个转速范围内提高,联合运行曲线的高效率范围扩展;ESC工况加权比油耗值下降幅度约为3.8%,且空燃比增大,VNT柴油机经济性获得提升。可以得出结论,VNT可变涡轮增压器与柴油机匹配良好。