【作者】 王伟；

【导师】 王银燕；

【作者基本信息】 哈尔滨工程大学 ， 动力机械及工程， 2009， 硕士

【摘要】 增压技术不仅是强化内燃机的最有效手段,而且对降低内燃机的污染、噪声和提高经济性也有积极的影响。但随着柴油机强化程度的提高,要求涡轮增压器的压比进一步提高,提高压比的主要方法之一是提高压气机的性能。而现有的柴油机涡轮增压器,一般都采用离心式压气机。因此充分理解离心压气机内部三维流场的物理现象是设计高效率的压气机的前提。根据某型涡轮增压器的离心压气机叶型和通流几何的原始测量数据,用三维建模软件UG建立实体模型；利用流体分析软件NUMECA模拟了离心压气机内部的流场,对其不同转速和流量下的变工况性能进行了数值模拟；得到了离心压气机的特性曲线和各通流部件中的流场结构,分析了叶轮和扩压器内部的流动,着重讨论了造成严重损失及使流场趋于复杂紊乱的原因,包括尾迹、二次流、分离流等。本文研究了相同转速下,不同的叶顶间隙对离心压气机内部流动的影响。结果表明,随着叶顶间隙的增大,主流射流流动受影响愈发严重,流动的不均匀性增加。此外,通过改变叶轮子午流道的形状,与原子午流道进行了对比计算,结果表明扩压段渐缩型子午流道的流动状况要优于扩压段平行的子午流道。最后,讨论了在其他条件不变的情况下,改变叶轮叶片数目和叶片扩压器的数目对压气机性能影响。通过分析得出,叶轮叶片数较多时流动的阻塞比较大,叶片数较少时叶片的升压能力较差。叶片扩压器数目减少后的最大优点是压气机的特性变得较为平坦,工作范围扩大。扩压器数目增多,会引起较大的流阻损失。更多还原

【Abstract】 Turbocharging is not only an effective way to strengthen the engine, but also plays an important role in reducing the emission and the noise of the engine. Also, it can improve the efficiency of the engine.But with the improvement of the diesel engine’s strengthened degree, the pressure ratio of the turbocharger is required to further improve.To improve the pressure ratio, one of the main methods is to improve the compressor performance.And the existing diesel engine turbochargers generally used centrifugal compressor. Therefore, fully understanding the internal three-dimensional flow field of the physical phenomena of the centrifugal compressor is the premise of the designed highly efficient compressor.According to the original geometric measurement data of the blade type and through-flow of a certain type of turbocharger’s centrifugal compressor, established the Solid model by using three-dimensional modeling software of Unigraphics and simulated the internal flowfield of the centrifugal compressor by NUMECA.The three-dimensional numerical study and analysis were also done respectively under Variable conditions with different rotational speeds and mass flow.got the characteristic map of centrifugal compressor and the flow field structure of the flow passage components, analyzed the internal flow of the impeller and diffuser; and focused on the reasons which caused bad aerodynamic losses and made the flowfield complicated, including wake, secondary flow, separated flow.In this paper, the impact on the internal flow of the centrifugal compressor was studied with different tip clearance at the same speed. The results showed that with the increasement of tip clearance, the mainstream and jet flows were affected more severely, the inhomogeneity of the flow was increased. In addition, this paper changed the shape of meridional flow channel, compared to the preliminary meridional flow channel by the computation; the flow of diffuser Paragraph of the meridian flow channel which type was tapered was superior to the parallel.Finally, in the other conditions remaining unchanged, while changed the nu mber of impeller blades and Vaned diffuser, the impact on the compressor’ Performance was also discussed. To the Conclusion, The flow resistance was larger than when the number of impeller blades was more. The capacity of boost was poor when the number of impeller blades was less. The biggest advantage was that the compressor characteristic had become smoother and extended the scope of operation after decreasing the number of Vaned diffuser, increasing the number of vaned diffuser would cause a greater loss of flow resistance.更多还原