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Presenter: Rebecca Hoffman - Powertrain Operations, Ford Motor Company
Supervisor:

Date: Fri, February 1, 2002
Time: 11:00:00 - 12:00:00
Place: EOW 430

ABSTRACT

Abstract:

Total vehicle customer satisfaction is strongly linked to the level of satisfaction a customer has with the engine. One of the key elements of customer satisfaction is the NVH of the vehicle and the engine. Piston slap is an unwanted engine noise that is the result of piston secondary motion, that is, the departure of the piston from the nominal motion prescribed by the slider crank mechanism. This secondary motion is caused by a combination of transient forces and moments acting on the piston during engine operation and the presence of clearances between the piston and the cylinder liner. This combination results in both a lateral movement of the piston within the cylinder and a rotation of the piston about the piston pin and causes the piston to impact the cylinder wall at regular intervals. These impacts may result in the objectionable engine noise known as piston slap. By predicting this secondary motion and its effect on engine noise, the power cylinder system can be modified in the engine design phase to prevent this noise long before the first prototype has been built.

A fully dynamic analytical model including a flexible piston, rod and piston pin has been developed to predict the motion of the piston in the cylinder. The resulting piston side forces were then applied to the engine block, and the radiated sound pressure level was determined. The results of this analysis were used for a robust, up-front design of the engine power conversion system.

This seminar will address the piston secondary motion analysis, the calculation of the radiated engine sound power levels due to piston impacts and the use of these results to develop a robust power cylinder system with significantly reduced piston slap noise.