基于极限工况的压气机气动噪声排放特性与机理研究

Experimental and Mechanism Study of Aerodynamic Noise Emission Characteristics from a Turbocharger Compressor of Diesel Engines Based on Extreme Operating Conditions

摘要:

发动机配备涡轮增压器是缓解能源短缺和减少气体排放的有效途径，但其压气机气动噪声排放成为了亟需解决的重要问题。在柴油机涡轮增压器研究中，压气机极限工况下（近喘振和堵塞工况）的气动噪声排放规律及其与内部流动特征之间的关系仍不清晰。为研究压气机在极限工况下的气动噪声排放特性与机理，本文采用试验和数值模拟方法对某涡轮增压器压气机的气动噪声开展分析。试验结果表明：在近喘振和堵塞工况下，压气机气动噪声总声压级随着转速的升高而增大，在低转速下，气动噪声总声压级受压气机工作流量影响较明显；在压气机气动噪声中，叶片通过频率（BPF）噪声占据主导地位，随着转速升高，叶片通过频率噪声对气动噪声总声压级贡献度增大，其占比最高达75.35%。模拟结果表明：在近喘振和堵塞工况下，压气机内部流动存在明显失速现象，其中在近堵塞工况下，压气机旋转域和扩压器域以多重单音噪声为主，叶轮与扩压器间的动静干涉对轴频及其谐频噪声均有较高贡献度；在近喘振工况下，压气机进口和出口以低频噪声为主，叶轮叶片与进气来流存在的干涉作用对诱导产生的低频噪声影响较为明显。

关键词:压气机;气动噪声;极限工况;非定常脉动压力;动静干涉

Abstract:

Diesel engines equipped with turbochargers is an effective way to alleviate energy shortage and reduce gas emissions， but their compressor aerodynamic noise emissions have become an important issue that needs to be addressed urgently. In the studies of diesel engine turbocharger compressors noise emissions， the pattern of compressor aerodynamic noise emissions in the near-surge condition， near-choke condition and its relationship with the internal flow characteristics are still unclear. Therefore， in order to study the aerodynamic noise emission characteristics and mechanism of a diesel engine turbocharger compressor in the near-surge and near-choke conditions， the experimental and numerical simulation methods were used to analyze the aerodynamic noise of a turbocharger compressor in this study. The analysis of experiment results showed that total sound pressure level （SPL） of the aerodynamic noise for the compressor increased with an increase in the speed under the near-surge and near-choke conditions. At low speed， the total SPL of aerodynamic noise was influenced by the mass flow rate of the compressor more obviously. In the compressor aerodynamic noise， the blade passing frequency （BPF） noise was dominated. With the increase of speed， the contribution of BPF noise to the total SPL of aerodynamic noise was greater， and its proportion was up to 75.35%. The analysis of simulation results showed that in the near-surge and near-choke conditions， there were obvious stall phenomena in the internal flow of the compressor. Among them， in the near-choke condition， the rotor and the diffuser regions of the compressor were dominated by multiple monophonic noise， and the dynamic-static interference between the impeller and the diffuser had a high contribution to both the axial frequency and its harmonic frequency noises. In the near-surge condition， the compressor inlet and outlet regions were dominated by low-frequency noises， and the interference between the impeller blades and the incoming air flow had a more obvious contribution to the induced low-frequency noises.

Key words:compressor;aerodynamic noise;extreme operating conditions;unsteady fluctuation pressure;dynamic-static interferences