Effect of the design parameters of induced structures on the sensitivity of compressor efficiency and static pressure of induced structure inlets

Abstract

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.