The goal of this GOALI project is to investigate the transient dynamics of rotor systems fitted with torsional vibration absorbers. An improved understanding of these systems is directly relevant to their implementation in automotive engines that employ cylinder deactivation. The range of engine speeds over which one can deactivate cylinders is limited on the low-rpm end by vibration problems. If these vibrations can be reduced, the operating envelope for cylinder deactivation can be expanded, resulting in substantial fuel savings and lower emissions. Centrifugal pendulum vibration absorbers show great promise for providing the required vibration reduction, and are being considered for use in these engines. The PIs have developed a thorough understanding of the steady-state operation of these absorbers, but their implementation in automobile engines depends on their satisfactory behavior under transient operating conditions. Thus, the primary goal of this work is to develop a fundamental understanding of the transient dynamics of rotors fitted with systems of pendulum absorbers, and the manner in which system parameters affect this behavior. The results of this effort will expand our fundamental knowledge base about the behavior of vibration absorber systems and, more generally, about the transient response of systems with symmetries. The investigation will involve analysis, experiments, and collaboration with industry. The analysis will involve modeling, perturbation methods, and concepts from invariant manifolds and symmetry theory. Experiments will be carried out for different absorber tuning and damping conditions and various types of transient conditions. The results are of fundamental interest since they involve questions of transient response, including stability issues that are often overlooked in studies of periodically forced dynamical systems. The results will also allow for the development of guidelines that can be used in the design of absorber systems for automotive engines. In order to address broader impacts, the PIs will serve for three years as instructors for the Michigan State University High School Engineering Institute. About a quarter of the enrollment for this summer outreach program comes from under-represented groups. Energy issues will be the primary focus topic of the program, and the proposed research will be described in that context. The industrial PI will influence program content by providing a general industrial perspective on advanced engine technology. In addition, the material will be incorporated in existing courses, specifically as motivation for the importance of studying problems relevant to transient vibration response. Also, in order to fully realize the benefits of this investigation, the results will be made widely available through publications and conference presentations, thereby making them accessible to all interested automotive manufacturers.
