运用微穿孔消声理论,以某乘用车排气系统前消声器为优化对象,通过试验测试分析不同微穿孔结构参数对微穿孔消声器传递损失的影响.测试结果表明,针对该车前消声器结构,穿孔挡板厚度t为 0.6 mm,微穿孔直径d为 0.5 mm,穿孔率P为 1%,平均空气层厚度D为 66mm时,与原始玻璃纤维方案前消声器相比,声学尾管全油门加速工况下噪声测试数据相近,车内外怠速噪声优化 1～2 dB(A),排气背压差异在 1 kPa以内,均满足性能目标要求,微穿孔结构对玻璃纤维具有可替代性.

针对某1.5 L自然吸气发动机,为了能在项目开发前期有效预防并优化其排气系统怠速噪声,通过试验记录怠速工况下发动机转速、缸压、空燃比、排气系统温度和尾管噪声等数据,基于此建立GT-POWER怠速开关空调工况发动机声源模型,再将GT-POWER计算怠速尾管噪声与试验所测尾管噪声比较,优化消音器结构并预测怠速噪声水平.结果表明,GT-POWER仿真计算怠速尾管噪声整体声压级及前3个峰值与试验测试结果较吻合,整体声压级最大相差2.29 dB(A),误差3.96％,且试验结果[59.8 dB(A)]满足怠速尾管噪声不超过60 dB(A)的要求;前3个峰值最大相差2.48 dB(A),误差5.23％,峰值对应的2、4、6阶频率(29、58、87 Hz)能完好对应;所建GT-POWER怠速噪声模型可推广应用于后续该发动机及其新车型排气系统声学开发.

依据NVH源、传递路径到响应点的研究准则,从系统集成的角度对某车辆滑行工况下的车内轰鸣声加以研究.结果表明滑行工况下的车内轰鸣声主要由排气尾管2阶噪声与车辆空腔模态耦合所致,且滑行工况下自动变速箱降档策略使发动机转速频繁经过问题转速点从而加剧问题发生的频次.采用矩形管道声学传播理论可以快速近似计算出车辆的前几阶声腔模态频率,有利于问题原因快速排查;在排气系统设计上采用赫姆霍兹共振腔结构来降低源头的激励解决车内轰鸣声抱怨也是一项经济有效的措施.

本文通过计算流体力学方法,运用Fluent软件对汽车排气系统消音器冷凝水吹出性能方面进行校核计算,与试验实测结果比较,并找出影响消音器排水性能的原因;结果表明:对排气系统消音器通过Fluent多相流计算可以准确直观的模拟出冷凝水吹出的动态流动过程,模拟结果与试验结果吻合性良好.

奥钢联林茨公司为了生产厚355 mm、宽1 600 mm的特厚板坯,升级改造了第3炼钢厂的5号连铸机.该弧形连铸机最初设计生产的板坯最大厚度为285 mm,弧形半径为10 m,配置了直结晶器,对带液芯的铸坯进行弯曲和矫直.在这种类型的连铸机上生产厚度为355 mm铸坯的主要问题是板坯的几何形状.由于弯曲时铸坯角部变形,铸坯可能出现小的皮下热裂纹.为了模拟在浇注过程中结晶器液面到弧形段开始位置的连铸板坯变形,使用ABAQUS软件开发了有限元3D模型.该热力学模型结合材料的粘弹性定律计算浇注过程凝固坯壳的张应力和压应力.据观测,模拟计算出的浇注过程凝固坯壳的张应力和压应力的分布与小热裂纹的外形大致相符.还将抽样测量的板坯几何形状与有限元计算结果进行了比较.采用热机建模计算结果,通过优化结晶器锥度和强化出结晶器后铸坯窄面的冷却,改进了板坯的几何形状.

为了优化连铸过程中结晶器内的钢液流态,世界各地的钢厂在改进浸入式水口吐出孔设计方面取得了一定的进展.该技术对于连铸工序实现高效生产高品质钢显得更为重要.一般说来,要实现连铸机高效生产,必须增大浸入式水口的内径和吐出孔尺寸,以增加通钢量,从而提高生产效率.但是,浸入式水口吐出孔尺寸增大后,钢液出口形成的非均匀流导致结晶器内钢水波动及保护渣卷渣夹杂,使钢质降低,且可能导致漏钢.叙述了塔塔钢铁英国公司带钢生产部门的塔尔博特港厂3号连铸机水口设计的技术进步.通过改进水口吐出孔设计,优化浸入式水口吐出孔钢液流态,进而降低结晶器内的钢液波动,减少卷渣夹杂.此外,还对塔尔博特港厂采用改进式水口后的结晶器内钢液流态和钢质进行了调查和评估.叙述了该厂3号铸机改善结晶器钢液流态所做的工作.

The mechanism and elimination methodology of standing waves of exhaust systems were studied. The acoustic model for analyzing the noise of exhaust tailpipe was established with GT-power software. The acoustic characteristics of the exhaust tailpipe noise of different orders were obtained. It was found that the wave peak of a common frequency was caused by the standing wave of the long tailpipe of the system. Therefore, two schemes were proposed for solving the problem. One was to change the tailpipe length so that the natural frequencies of the tailpipe can avoid from the common frequency of the excitation source, the effect of the peak of the standing wave can be weakened, and the noise at the wave peak can be reduced. The other is to design a resonator to suppress this common frequency so that the noise of this frequency can be eliminated. Results of simulation show that both schemes have obvious effects for improvement of the acoustic performance of the exhaust system.

The corrosion problem of automotive exhaust system and its component have been studied in this paper,included the relationship between corrosion depth and pH value,Cl-,SO42-concentration of condensate.The application of the new local 409 stainless steel on automotive exhaust system has also been introduced.The results show that the new material has the advantage of good corrosion resistance performance and low cost.