Investigation of parametric exhaust port of a heavy-duty diesel engine
Examensarbete för masterexamen
Applied mechanics (MPAME), MSc
Exhaust port developed today at Scania is based on a steady state approach in both flow rig test and simulation. A new method is required to investigate the transient effects to simulate real engine like conditions for engine exhaust port. A parametric model of an exhaust port was created by using CATIA V5 and various geometries of the port were generated using the Latin hypercube sampling approach to perform a design of experiment (DOE) study. Steady-state and transient simulations, carried out using AVL Fire, are used as two different approaches to investigate the flow characteristics between different geometries. In the steady state simulation, three different valve lifts are investigated as well as two type of boundary conditions; one from steady-state flow rig test and one similar to real engine test. Another aim of the investigating the two approaches is to develop a methodology for further optimization. Additionally, the impact on exhaust port design for different cylinder positions are investigated. Design of experiment study for each cylinder position showed a unique optimal port design. The exhaust port having two symmetric channels was not performing compared to the optimal port where the channels were asymmetric. The transient simulation showed complex flow phenomena at low valve lift compare to the high valve lifts. Additionally, transient state approach was validated against the steady state simulation. In this validation, the steady state simulation, tested for different pressure boundary conditions, showed only small discrepancies in discharged coefficient at both low and high valve lifts. Moreover, the optimal geometry in transient state was not same as the optimal geometry for steady state at low valve lift. Instead, this optimal geometry from transient simulation was same as the one in steady state at high valve lifts. However, transient simulation was very computationally expensive compared to steady state. Longer simulation time and is not suitable for larger design of experiments investigations.
Transport , Hållbar utveckling , Strömningsmekanik , Transport , Sustainable Development , Fluid mechanics