A gas-entraining diffuser exhaust gas recirculation (EGR) was proposed to induce the entry of the exhaust gas into the diffuser, to completely utilize the lower static pressure at the diffuser for reducing engine fuel consumption owing to the low engine backpressure. Thus, the induced structure was designed such that a large amount of exhaust gas enters the compressor diffuser. To improve the compressor efficiency and reduce the static pressure at the induced structure inlet, the design parameters of the induced structure (induced angle, induced effective inlet area, parallel part width, and position of the induced structure inlet) were investigated using numerical methods. The results show that the peak compressor efficiency reduced by 4% compared with the compressor prototype, and up to 90% of the compressor efficiency reduction is attributed to the induced gas entering the diffuser, except for the 10% induced gas ratio scenario over the near-choking point. This is because the entropy generation of the induced structure is close to 10% of the entropy generation increase in the diffuser system due to the induced gas at a medium flow rate. Second, in most cases, the compressor efficiency and static pressure of the induced structure inlet increase or decrease simultaneously as the design parameters vary. To select the best induced structure, it is necessary to compromise between the compressor efficiency and static pressure of the induced structure inlet. In fact, the compressor efficiency changes by less than 1% by varying the design parameters of the induced structure, compared with case ID1. This demonstrates that the design parameters have little effect on the compressor efficiency. Compared with the compressor efficiency, the static pressure of the induced structure inlet is more sensitive to the design parameters, particularly the induced effective inlet area and the position of the induced structure inlet.
The current paper presents the performance results of a variable-flow turbocharger turbine, called the ‘elastically restrained guide vane (ERGV)’ turbine, which is intended to provide an improvement over the current state-of-the-art turbochargers, namely the variable geometry turbocharger (VGT). This paper is a continuation of the previous work and concentrates on the experimental testing of the ERGV turbine performance, as well as the corresponding effects on the mass flow characteristic as a result of operating the turbocharger in its ERGV mode compared with its operation as a traditional VGT. The effects of the ERGV application are demonstrated through the first experimental testing. In this preliminary attempt, the range of the mass flow rate is effectively enlarged, the new mass flow characteristic lines can pass through the two and three lines separately of the original turbine for the two spring stiffness operations. The results of the this study were encouraging with respect to the potential of ERGV to replace the traditional VGT in particular applications. Additionally, this paper compares the experimental mass flow charateristics with the computational fluid dynamics (CFD) simulations in the radial turbine at the conditions of two spring stiffness. This preliminary comparison between numerical simulation and experimental data shows encouraging results.
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