Numerical study on the flow noise and performance of trans-critical carbon dioxide ejector
Numerical study on the flow noise and performance of trans-critical carbon dioxide ejector
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DOI：
10.1016/j.ijrefrig.2023.12.013
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发表时间：
2023-12-18
影响因子：
3.9
通讯作者：
Deng，Jianqiang
中科院分区：
文献类型：
--
作者：
Xia，Qi;He，Yang;Deng，Jianqiang
对跨临界二氧化碳喷射器的流动噪声和性能进行了数值模拟，总结了两者之间的相关性。该关系式是通过流噪声监测判断喷射器工作状态的基础。本文采用均相模型（HEM）对引射器内流场进行了数值模拟。在流场的基础上，利用宽带噪声模拟（BNS）得到了流场噪声的分布。仿真结果表明，发动机的主要噪声源位于预混段和扩压器段。预混段的噪声源是由于一、二次流速度差过大造成的。扩压器内的噪声源主要是气流分离引起的回流和涡流。变背压下的流动噪声特性是：随着背压的增加，预混噪声基本不变，扩压器噪声减小。对比不同背压下的流动噪声和性能参数变化趋势，发现随着扩压器噪声的降低，压比和引射器效率都有所提高。引射比与扩压器噪声的相关性在于：在临界背压之前，引射比随噪声的减小而保持恒定。在此之后，噪声和卷吸比同时降低。特别是，当引射比开始下降时的背压范围与扩压器噪声快速下降时的范围是一致的。因此，扩压器内流动噪声的显著下降可以作为引射器进入亚临界工况的重要判断依据。
The flow noise and the performance of trans-critical carbon dioxide ejector were simulated to summarize the correlation between them. This correlation is the basis of judging working condition of ejector by monitoring the flow noise. In this article the homogeneous model (HEM) was employed to simulate the inner flow in the ejector. Based on the flow field, the flow noise distribution was derived using broadband noise simulation (BNS). The simulation results showed that major noise sources locate in the premix and diffuser section. The noise source in the premix section is caused by the great velocity difference between primary and secondary flow. The noise sources in diffuser are the back flow and vortexes caused by flow separation. The characteristics of flow noise under variable back pressure are as following: the premix noise remains unchanged while the diffuser noise decreases with the increase of back pressure. Comparing the trend of flow noise and the performance parameters under variable back pressure, it was found that with the decrease of diffuser noise, the pressure ratio and the efficiency of ejector were increased. The correlation between the entrainment ratio and diffuser noise lies in: before the critical back pressure, the entrainment ratio remains constant with the decrease of noise. After that, the noise and entrainment ratio decrease simultaneously. Especially, the back pressure range when the entrainment ratio starts to decline is consistent with the range when the diffuser noise rapidly drops. Therefore, the significant decline of flow noise in diffuser can be viewed as an important judgment basis of ejector entering the subcritical working condition.