The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and c...The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and circumferential correlation were obtained in the spacing range from 1.25 to 6.0. The spatial correlation of pressures of two pressure taps on two different cylinders at the same azimuth was investigated as well. Owing to different flow patterns in various arrangements and spacing, these correlation curves of pressure show different distributions. The lift fluctuation can be estimated qualitatively from the circumferential coefficient curve with the knowledge of the rms pressure distribution. Some critical spacing for each arrangement were found that the flow regimes and the corresponding pressure correlation take a sudden change. Flow interference between cylinders in each arrangement was also discussed with various flow regimes.展开更多
通过研究一台四缸直喷增压柴油机整机噪声和近声场噪声频谱,分析发动机的噪声特性及噪声主要来源。在不改变柴油机主要零部件结构的前提下,采取改变供油提前角、发动机功率、增压器类型、油嘴开启压力、油泵参数等措施,对比分析各措施...通过研究一台四缸直喷增压柴油机整机噪声和近声场噪声频谱,分析发动机的噪声特性及噪声主要来源。在不改变柴油机主要零部件结构的前提下,采取改变供油提前角、发动机功率、增压器类型、油嘴开启压力、油泵参数等措施,对比分析各措施对发动机噪声的影响效果,确定综合降噪措施。试验结果表明:各措施都取得了一定降噪效果,在最佳方案下柴油机整机噪声声功率级降低了1.32 d B(A)。展开更多
文摘The fluctuating pressures on the surface of three circular cylinders in equispaced arrangement were measured simultaneously in the medium subcritical regime (Re=3×104). The distributions of their rms values and circumferential correlation were obtained in the spacing range from 1.25 to 6.0. The spatial correlation of pressures of two pressure taps on two different cylinders at the same azimuth was investigated as well. Owing to different flow patterns in various arrangements and spacing, these correlation curves of pressure show different distributions. The lift fluctuation can be estimated qualitatively from the circumferential coefficient curve with the knowledge of the rms pressure distribution. Some critical spacing for each arrangement were found that the flow regimes and the corresponding pressure correlation take a sudden change. Flow interference between cylinders in each arrangement was also discussed with various flow regimes.
文摘通过研究一台四缸直喷增压柴油机整机噪声和近声场噪声频谱,分析发动机的噪声特性及噪声主要来源。在不改变柴油机主要零部件结构的前提下,采取改变供油提前角、发动机功率、增压器类型、油嘴开启压力、油泵参数等措施,对比分析各措施对发动机噪声的影响效果,确定综合降噪措施。试验结果表明:各措施都取得了一定降噪效果,在最佳方案下柴油机整机噪声声功率级降低了1.32 d B(A)。
