Eicher Uses Simulation to Evaluate Tractor Muffler Transmission Loss and Pressure Drop  

"Ansys Mechanical software helped in analyzing the transmission loss — and Ansys CFD the backpressure — of a tractor muffler, which has shown good correlation with test results and helped in improving its performance."

— Pawan Singh, Senior Manager – CAE / Eicher Tractors
(a unit of TAFE Motors and Tractors Limited, a wholly owned subsidiary of TAFE)

Introduction

A muffler in the exhaust system of a tractor decreases the sound output while increasing the backpressure of the flowing exhaust gases. Transmission loss (TL) refers to the reduction in acoustic noise provided by a muffler and needs to be maximized (a higher TL means a quieter tractor). The engine must work against the backpressure; the higher the backpressure, the less power delivered to the power train, so backpressure must be minimized.

Challenges

The main challenges were to maximize transmission loss and minimize backpressure in a new tractor muffler design while keeping development costs low and accelerating time to market. Engineers also had to ensure that design parameters and muffler performance predicted using Ansys simulation solutions were validated by experimental testing of the new design.

Engineering Solution

Ansys Mechanical was used to perform acoustic harmonic analysis to simulate and maximize transmission loss. Computational fluid dynamics (CFD) using Ansys Fluent was performed to simulate and minimize the backpressure of the muffler in the exhaust system. Experimental results obtained on a prototype muffler based on the optimized Ansys design closely matched the simulation results.

Benefits

• Reduced design cycle time from 20 weeks to 8 weeks (approximate values).
• Reduced cost — including design optimization, testing, manufacturing, transportation and overhead costs — by 40%.
• Decreased time to market.
• Established a new process for design, CAE and validation, which increased productivity.
• Optimum muffler design meets all design standards.