Modeling for Design Optimization of Piston Crown Geometry Through Structural Strength and Lubrication Performance Correlation Analysis

Abstract

Piston subsystem is subjected to very complex but dynamic forces. Such forces include combustion gas force, inertial dynamics forces, lubricating action/damping forces, contact friction forces to name a few. Further, piston ring mounted in piston in addition to these forces experiences out ward springing action inside engine mounting due to inherent elasticity. To evaluate the strength of reciprocating piston, the simultaneous effect of all these forces should be considered, while simulating through finite element method. With effect of all these forces, the currently considered piston of Gray Cast Iron, aluminum alloy and Metal-Metric-Composite (Si-C) are given four different crown shapes for optimization of material and crown geometry for better strength. The rings mounted are considered to be coated with Nickasil. The combined numerical simulation for contact and finite element simulation of structural strength and their correlation suggest many important outcomes. Von-Misses stress is maximum in case of type-B Al-alloy crown, while it is minimum in case of type-C SiC metal matrix piston.

Coated Piston Ring Pack and Cylinder Liner Elastodynamics in Correlation to Piston Subsystem Elastohydrodynamic: Through FEA Modelling

“…Figure 3a, b shows the all-possible forces acting on a piston block and dynamic ring, which include inertial forces caused due to primary/reciprocating motion, inertial force caused due to secondary motion, gas dynamics force, lubricant reaction, friction force, and ring elastic forces. The forces involved due to elastohydrodynamic action are estimated by solving Reynolds equation, energy equation, and rheological equation simultaneously as per Mishra [9] and Mishra et al [16,25,29]. It also addresses the asperity contact issue through Greenwood and Tripp model for boundary co-action [47].…”

“…Among the losses, the mechanical frictional loss is significant and accounts for more than 15% of the total input energy. Further, the majority of this loss is due to piston subsystem loss, which happens out of errant dynamics, contacting, and connecting actions [9], hence the need for technological development to reduce losses.…”

Geometry design and optimization of piston by using finite element method

“…Minimum Axial thickness of ring t2 = 𝐷 10𝑍 (4) where z = number of rings Top land thickness b1 = 1.2 tH (5) Thickness of other land b2 = 0.75 t2 (6) Maximum thickness of barrel t3 =0.03D + t1 +0.4+4.5 (7) Thickness of piston barrel at lower end, t4= 0.3 t3…”

“…Thus, a piston needs to be designed to have low stress and temperature when operating. Recent study has shown that the amount of stress and temperature are affected by the shape of piston crown [4]. Selection of suitable piston crown decreases the temperature and stress on piston so that the piston will last longer.…”

Multi-objective Optimization and Sensitivity Analysis of the Parameters Affecting Sealing Performance of the Piston Rings Face through the Validated Model for the Four-stroke Bi-fuel Engine

“…As a result, the steep profile of the top ring face reduces friction. (Mishra et al 2019) introduced an optimization model for piston crown geometry using structural strength and lubrication performance correlation analysis. It was determined that the effects of all studied forces should be taken into account during the finite element simulation method.…”