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This paper presents a numerical study of reactive-type automotive mufflers. The main objective of the paper is to study the effects of various geometrical parameters on the muffler performance. Transmission losses (TL) are used to characterize the performance of the mufflers. Commercially available solver, ANSYS [1] is used to solve the muffler TL characteristics. The paper also summarizes the development of a general-purpose program capable of modeling complex muffler cavities using ANSYS parametric design language (APDL). APDL is a scripting language that is used to automate common tasks and build the model in terms of parameters. The program takes the key geometric parameters of the muffler as input variables and creates the muffler geometry, hexahedral-structured mesh, applies suitable boundary conditions, solves and then post-processes the results. The program provides good flexibility in creating complex (perforations) geometric models.

New product development process in tractor industry has immense challenges. Market forces are driving tractor manufacturers, to explore innovative technology, to shorten the product development time. At present, most of the tractor components are evaluated in laboratory, as per customer usage pattern. Even though these lab tests are accelerated, high development time of prototype is a severe constraint. Hence, there is more emphasis on application of Computer Aided Engineering (CAE) for validating the design, in lieu of lab test i.e. ‘Bringing LAB to CAE. There are many challenges to achieve this particularly in tractor evaluation, due to scattered usage patterns, varied field conditions and unexpected customer habits. In addition, fatigue behaviour of tractor chassis, comprising of mainly castings is not only sensitive to design but also to process and assembly.

Automotive crankshafts are subjected to fluctuating torques due to periodic explosions in the cylinders. Accurate three dimensional finite element modeling is often time consuming. The present research aims to reduce the pre-processing efforts by developing parametric software. A three-dimensional parametric finite element model of crankshaft is developed using brick and wedge elements. Crankshaft main journal bearings are modeled as linear springs and dashpots. The piston and reciprocating masses are lumped at the ends of the crank pins. Viscous damper as well as shaft material damping has been modeled. Results from the three-dimensional analysis have been compared with those obtained using beam element models to assess the capabilities and limitations of such simplified models. It has been demonstrated that the simplified beam element models result in significant errors and 3-dimensional finite element analysis is essential for accurate predictions.

The air induction system of an automobile engine contributes to the noise level generated by a passenger car. The contribution is significant in the perception of vehicle noise quality. There is a great value in reducing and controlling passenger car air induction noise. Helmholtz resonators are widely used for noise reduction in vehicle induction and exhaust system. These resonators are usually mounted as side branch volumes to the main induction system, occupying larger space. The design presented here describes the use of compact inline Helmholtz resonator (Patent application no. 190/Bombay/98) for elimination of low frequency noise character in passenger car. Finite element model of the acoustic cavity of induction system along with the inline resonator is made. The transmission loss characteristics computed analytically correlates very well with the experimental transmission loss characteristics.

Measurement of sound intensity techniques has very good application in the source identification of a particular noise character. It has been applied effectively along with modal analysis and FE experimental excitation techniques to find out root cause of a particular noise character in small gasoline engine. A FEM shell model was used to make cylinder block and cylinder head model. FEM simulation was carried out which matched with experimental results. It helped to remove the noise character from engine. The other part of the paper describes the noise reduction of the crankcase cover used for the same motorcycle. It houses crankcase as well as two speed gearbox. The methodology involves very effective combination of experimental harmonic analysis, FE model with the shell element for the 3 piece crankcase cover, and experimental measurements. A particular sequence of this experimental techniques along with computer simulation techniques gives extremely good results.

Modal Analysis is a well established technique which defines the inherent dynamic properties of the structure. At the same time the experimental harmonic analysis by shaker method is also a very important tool in solving some of the engine induced vibration problems in the automotive structure. Computer simulation technique using finite element methodology has been very effective tool in simulating the problem. However the right combination of these techniques has been a tricky situation. The paper describes the methodology of using right combination of these techniques to reduce the motorcycle chassis vibration which are induced by engine and drive-line excitation in minimum time. The method involves the Finite Element Modelling with shell elements, experimental harmonic analysis with frequency sweep upto 600 Hz, validation of the FE model, animation techniques and find out correct modification to fine tune the structure to eliminate the engine induced vibrations in the frame.

Torsional and lateral bending vibrations of cylinder block have a large effect on engine noise. Cylinder block vibration not only causes noise to radiate from the cylinder block itself but it is also the major exciting force to the oil pan and timing belt cover. In order to reduce engine noise, it is important to completely understand the mechanism of cylinder block vibrations. An analysis is conducted using FEM and BEM to compute the influence of crankshaft torsional vibrations on cylinder block vibrations. A crankshaft system for a four cylinder automobile engine was used for analysis. Finite Element model of crankshaft is created using parametric modelling software developed based on ANSYS FEA software. Finite Element model of cylinder block, bearing cap, oil sump is also created using another parametric software developed based on ANSYS FEA software.

The paper describes simulation of frontal barrier impact of a car body shell structure for crashworthiness analysis using non linear explicit finite element package LS-DYNA3D. Predicted overall collapse modes of different structural component viz.apron, side rails etc. are in a good agreement with published results and also to some extent with experimental results. In this paper crash analysis of above car structure with crash guard is simulated using LS-DYNA3D and comparative analysis of crash behaviour of car structure in the presence of crashguard is shown to indicate its possible role on crash behaviour of a vehicle.

The problem of torsional vibration of the crankshaft of high speed diesel engine has become critical with increase in exciting forces due to high combustion pressures. This results in high torsional vibration amplitudes and hence high stresses. In such a case use of the damper pulley to control the torsional vibration amplitudes and stresses is one of the desired solution. In this paper torsional vibration analysis is carried out in case of six cylinder diesel engine using standard general purpose finite element package ANSYS and a method is developed to find out torsional vibration stresses leading to the selection of damper.

Three dimensional finite element analysis of mufflers has been carried out using ANSYS general purpose program. Analysis of simple expansion chamber muffler, extended tube muffler, tapered chamber muffler, offset chamber muffler and flow reversing chamber muffler has been carried out to predict the transmission loss. This three dimensional FEA technique has proved to be successful for the analysis of geometrically complicated mufflers where one dimensional theories can not be used. Parametric analysis of a simple expansion chamber muffler has been carried out to study the effect of expansion ratio, expansion chamber length, number of partitions within a chamber and unequal partitions. Analysis of acoustic cavity of a simple expansion chamber muffler has also been carried out to predict the natural frequencies and acoustic mode shapes.