Analysis of the effect of bore/stroke ratio and scavenge port angles on the scavenging process in a two-stroke boosted uniflow scavenged direct injection gasoline engine

Abstract

In this study, a two-stroke boosted uniflow scavenged direct injection gasoline (BUSDIG) engine was proposed and researched to achieve aggressive engine downsizing and downspeeding. Compared to loop or cross scavenged twostroke engines, the BUSDIG engine can achieve excellent scavenging performance and be operated with higher boost pressure as well as the absence of air and fuel short-circuiting. As a fundamental engine geometric parameter, the bore/ stroke (B/S) ratio would directly affect the scavenging process in the uniflow scavenged two-stroke engine. Three-dimensional computational fluid dynamics simulations were used to investigate the scavenging process in the BUSDIG engine with different B/S ratios. Four B/S ratios of 0.66, 0.8, 1, and 1.3 were analyzed. The results indicate that a bigger B/S ratio leads to deteriorated swirl flow motion but better delivery ratio, scavenging efficiency, and charging efficiency. In order to fulfil the potential of the BUSDIG engine with different B/S ratios, two key scavenge port angles, i.e. axis inclination angle (AIA) and swirl orientation angle (SOA), were varied from the baseline design (AIA = 90°, SOA = 20°) to study their effects on the scavenging process for each B/S ratio design. Overall, a larger AIA leads to lower swirl ratio (SR) but achieves better scavenge performance, which is crucial for a large B/S ratio design. A small SOA design leads to noticeably lower SR but superior scavenging performances for a small B/S ratio design. An intermediate SOA, e.g. 10 and 20°, is preferred to improve the scavenging for a large B/S ratio design.

Effect of piston shape design on the scavenging performance and mixture preparation in a two-stroke boosted uniflow scavenged direct injection gasoline engine

“…The centrally mounted DI injector and spark plug on the cylinder head were positioned to place the spray recirculation region around the spark plug. The key engine design parameters, including engine bore/stroke ratio, 39 scavenge port angles, 40–42 opening profiles of scavenge ports and exhaust valves 43 and intake plenum, 44 have been analysed and evaluated for optimal scavenging performance and in-cylinder flow motions. A full review of the BUSDIG engine concept can be found in a recently published article.…”

Analysis of the Boost System for a High Performance 2-Stroke Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) Engine

“…In light of the advantages of the 2-stroke operation, a novel 2-stroke Boosted Uniflow Scavenged Direct Injection Gasoline (BUSDIG) engine has been designed and extensively researched at Brunel since 2015 [7]. Key designs of the proposed BUSDIG engine, including engine bore/stroke ratio [8], scavenge ports [9][10][11], opening profiles of scavenge ports and exhaust valves [12], intake plenum [13], injection strategies [14,15] and piston shape [16] have been systematically studied to optimise the scavenging performance and charge preparation of the BUSDIG engine.…”