Browse Publications Technical Papers 2019-26-0042
2019-01-19

Numerical and Experimental Analysis of Intake Flow Structure and Swirl Optimisation Strategies in Four-Valve Off-Highway Diesel Engine 2019-26-0042

Future emission limits for off-highway application engines need advanced power train solutions to meet stringent emissions legislation, whilst meeting customer requirements and minimising engineering costs. This has driven the development of new approaches to engine design in order to reduce emissions at the source i.e. at engine out emission levels. DI diesel engines with four valves per cylinder are widely used in off highway applications because of the fundamental advantages of higher volumetric efficiency, lower pumping loss, symmetric fuel spray & distribution in combination with the symmetric air motion which can give nearly optimal mixture formation and combustion process. As a result, the fuel consumption, smoke levels and exhaust emissions can be considerably reduced. In particular, the four-valve technology, coupled with mechanical low pressure and electronic high pressure fuel delivery systems set different requirements for inlet port performance. In the present paper four valve intake port design strategies are analysed for off highway engine using mechanical fuel injection systems. Different design strategies are adapted to enhance the swirl performance of four valve intake ports comprising of directed and helical designs within the cylinder head layout and manufacturing constraints. In the first approach, different offset chamfers are added at cylinder head bottom face for directed and helical ports. The effects of offset chamfer designs and orientations using individual and combination of directed and helical ports are verified. A numerical analysis through CFD simulation using AVL-FIRE software is carried out to get detailed information about flow structure at higher and lower valve lifts. The various combinations are experimentally tested through flow measurement using steady state swirl test rig. It is observed that only directed port with offset chamfer of 80°orientation results in optimum value of swirl performance. The similar higher swirl are also achieved by a combination of 10° & 90° orientation in offset chamfering on directed & helical ports. In the second approach, influence of two designs of directed port on flow structure is analysed. The design of directed port is optimised within the layout constraints in order to reduce the loss in swirl generated by helical port. The flow interference with helical port is reduced due to new design of directed port resulting in higher swirl performance meeting mechanical fuel injection system requirements. A detailed CFD study for flow interactions and impact on swirl performance is carried out. The experimental measurements showed that the new directed port design combination enhanced the swirl performance to desired targets. Thus, different techniques to enhance the swirl performance for desired targets are analysed though CFD and experimentally validated. This provides a flexible platform for intake port performance optimisation for multivalve diesel engines with mechanical fuel injection systems. Keywords - Four valve intake port design, steady flow test, CFD numerical simulation, off-highway engines

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