CFD driven design and optimization of a natural gas engine inlet manifold using overset mesh

Sammanfattning

With a constant strive towards sustainability, especially for vehicles, Volvo Pentahas committed towards research and development of using renewable fuels to powertheir engine platforms. One example of a renewable fuel is biogas (bio-methane)which can be used in spark ignition Otto-cycle engines. This is a substitution toone of the most widely used fossil fuels today, which is petrol. For an engine towork properly with high efficiency and minimized environmental impact, the flowof air and fuel entering the engine is of paramount importance. It is crucial to ensurethat the air-fuel mixture is delivered to each cylinder with minimal pressurelosses and that the distribution of the mixture between the cylinders is equal. Onekey component affecting this is the intake manifold which is responsible for distributingair from the turbocharger to the six cylinders, and this component wasthe main focus of the analysis conducted throughout this project. After a thoroughbackground study mapping out which parameters affect intake performance,existing concepts and patents, a design-build-test cycle (DBT) was used includinggeneration of concepts and several evaluations and design-phases. A comprehensiverequirements specification was created to use during the development process.Concepts were then designed in Creo Parametric and pre-processed in ANSA. Evaluationof concepts was carried out in STARCCM+ with 3D CFD simulations, bothwith steady state conditions and with fully transient boundary conditions importedfrom 1D simulations. A new method for simulating transient valve behaviour wasdeveloped using an overset mesh approach, allowing accurate replication of the pulsatinggas dynamics within the manifold. The simulation results were used to refineand optimize the secondary duct of the inlet manifold, focusing on minimizing thepressure drop and guaranteeing an equal distribution to all cylinders. The usedCFD-evaluation method agrees well with 1D simulation results, showcasing thatthe more data-efficient overset mesh simulation process is a viable option for futuredesign work. The results also showed promising potential for increasing engine performancethrough incremental design changes that can be implemented with minimalmodifications to the existing manifold-design.