Zissimos P. Mourelatos, Associate Prof.Paras Shah, Prashant Patel; Graduate Students

Simulation of Piston Secondary Dynamics, Piston-Bore Contact and Piston Slap

•Motivation• Piston slap is an NVH phenomenon which is a

strong customer dissatisfier (unusual engine noise).

• Noise is an important contributor to Quality, Reliability, and Durability (QRD).

• Piston slap is a significant contributor to the total Engine Noise, especially at cold start.

• Simulate piston secondary motion

• Determine side thrust forces due to piston - cylinder liner contact

• Reduce piston slap excitation

• Predict engine block vibration due to side thrust forces

•Objectives

Engine “Piston – Bore” InteractionNoise Generation Mechanism

Engine Piston Noise Sources

Engine “Piston – Bore” Interaction Effects

•Analysis• Piston skirt elastic deformation

• Asperity contact analysis

• Engine block vibration

• Thermal deformation

• Piston - skirt ElastroHydroDynamic (EHD) lubrication

Piston Temperature Distribution

Datum

A

B

C

D

E

Sk

irt

Pro

file

Piston Dynamic Contact Analysis

Optimization of Skirt Profile for Minimum Contact Pressure

Piston Dynamic Forces

PP1

CM

CM1

α

PO+δP

CH

x

z

X

Z

θyXG

ZG

α-θy

θ

Schematic: Crank Slider Mechanism

Piston FEA model (incl. Thermal & elastic effects)

Piston skirt - liner contact modeling

Piston secondary dynamics

Engine Block Dynamics using Frequency Response Functions

Engine Block Vibratory Response

•Engine Vibration Prediction

Contact ForceSpectrum

Block FRFx Block Response

Spectrum

=

Contact Forcetime history

fft ifftfft

BlockImpulse response

Block response time historyconv

x =

•Uncertainty in Piston Design• Sensitivity analysis of piston design parameters

on piston slap excitation under uncertainty