The use of exhaust gas turbochargers in modern engine concepts is essential to achieve high efficiencies, low fuel consumption, and low emissions. However, the high rotational speed, a wide range of compression ratios, and dynamic acceleration and deceleration processes cause both tonal and broadband sound radiation. Due to packaging constraints, the intake cycle is often characterized by deflections and cross-section jumps. That leads to a strong secondary flow at the inflow of the compressor. Therefore, in this study, we intensively investigated the influence of disturbed inflow conditions on the sound radiation of the exhaust gas turbocharger. As a result, we found that the flow caused by a 105${}^{\circ }$-bend in front of the compressor leads to an increase in broadband flow noise up to 5.5dB${}_{\text{A}}$. The decisive factor here is the amount of pre-whirl at the outer radius of the pipe. A high velocity gradient additionally shifts the surge line towards lower flow coefficients and mass flows, respectively. That indirectly reduces the sound radiation due to the greater distance of the operating points to the surge line. However, pre-whirl can counteract this effect. The surge line shifts to larger mass flows due to the decrease of the relative flow angle. In contrast, low turbulence levels and homogeneous compressor inflow lead to reduced flow separation and thus lower broadband sound radiation. The reduction of the secondary flow in the intake of the compressor, e.g. due to pre-guidance devices, therefore represents a promising way of reducing the noise emission of the exhaust gas turbocharger in a passenger car.

在现代发动机概念中使用废气涡轮增压器对于实现高效率，低油耗和低排放至关重要。但是，高旋转速度，宽范围的压缩比以及动态加速和减速过程会导致音调和宽带声音辐射。由于包装的限制，进气周期通常以变形和横截面跳跃为特征。这导致在压缩机的流入处产生强烈的二次流。因此，在这项研究中，我们深入研究了扰流条件对废气涡轮增压器声辐射的影响。结果，我们发现由105引起的流量${}^{\circ }$-压缩机前的弯曲会导致宽带流噪声增加到5.5dB${}_{\text{一个}}$。此处的决定性因素是在管道外半径处的预涡旋量。较高的速度梯度还会使喘振线分别向较低的流量系数和质量流量移动。由于工作点到喘振线的距离更大，因此间接减少了声音辐射。但是，预旋转可以抵消这种影响。由于相对流角的减小，喘振线转向较大的质量流。相反，低湍流度和均匀的压缩机流入量导致流动分离减少，从而降低了宽带声辐射。因此，例如由于预引导装置而导致的压缩机进气中的二次流的减少代表了一种减少乘用车中的排气涡轮增压器的噪声排放的有前途的方式。