Development Of A Novel Rapid Compression Expansion Machine

A novel rapid compression and expansion machine equipment has been developed in order to solve the problems existing in current rapid expansion(expansion)machines,such as difficult to control the piston trajectory.The new method is to use cam mechanism to drive the combustion chamber piston,and to use the design of cam profiles and a large inertia flywheel to ensure that the piston trajectory is controllable and flexible,thus improving test repeatability and test efficiency.In this new design,the piston of the combustion chamber is driven by a cam,which constitutes a small part of a large flywheel.The significant inertia of the flywheel will ensure that the piston accurately follows the profile of the cam without noticeable speed loss.Additionally,a novel fastresponse roller system is designed to tangentially move the roller thus the piston is only driven once by the cam to complete a single compressionexpansion process.A multi-body dynamics model is established to verify the feasibility of the proposed scheme.Based on this,the dynamic analysis and finite element analysis are performed to analyze the stress distribution of the key components.For the combustion chamber,sensors,optical windows,intake and exhaust ports are arranged in a various way to construct a variety of test configurations in the limited space.The key features of the flow field and velocity field in the cylinder are explained by CFD simulation.The influence of the vortex on the temperature inhomogeneity is explained.In the case of higher cylinder pressure,the influence is weaker.In addition,CFD results shows that the generation of vortices is effectively suppressed by the design of the piston crevice.Repeatability test,speed sweep and compression-ratio sweep tests were performed to demonstrate that the new equipment can work well under these conditions,and a GT-Power model was created to analyze the heat transfer and blow-by encountered in the combustion chamber.