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With the stringent legislative requirements for noise in automobiles, gensets etc., the concern for properly designed silencers for specific applications is increasing. Optimized design of silencer requires an integrated study of acoustical and engine performance viz. Insertion loss and backpressure. However, the insertion loss itself depends upon engine characteristics geometry indicated by the transmission loss, flow induced noise, type of silencer - reactive, absorptive, hybrid, etc. Most of the work till date covers the acoustical and engine performance in isolation rather than in an integrated fashion due to the multidisciplinary nature of the problem. The objective of this study is to develop an integrated methodology to predict the performance of the silencer at the design stage resulting in an optimized time and cost effective design. In the present study, the acoustical and engine performance of silencer was predicted using FEM/BEM and CFD techniques.

Ever increasing demands for NVH related comfort have substantially reduced the exterior and interior noise of automobiles worldwide. This involves identification of the noise sources, paths of vibro-acoustic transfer paths and their reduction measures. Many a time, NVH is looked at after the product has been designed and even prototypes have been fabricated. The major source of noise in a vehicle is the driveline. Any changes in the driveline for noise optimization affect the performance as well as exhaust emissions of the vehicle. This makes the changes for improvement of NVH limited. One of the important criteria for the marketability of the vehicle is NVH. Hence, lot of development work is going on for noise reduction. The diesel engine plays a vital role in automobiles and agricultural equipments in the Indian scenario due to economic considerations.

Modern vehicles are designed for quiet interior with lower engine and exhaust noise levels. Under such circumstances, gear whine and rattle become one of the significant contributors towards in-cab noise, besides wind and road noise. Present paper deals with dynamic analysis, simulation and validation of the transmission system model for observed gear whine inside the cabin of a passenger car during its running condition. The exercise included development of an accurate numerical model to enable prediction of noise transmission from automatic gearbox to cabin structure. Experimental Modal Testing (EMT) of automatic transmission and suspension components, Multibody simulation of automatic transmission and Finite Element Analysis (FEA) of components and subassemblies followed by component and system level response correlations were carried out. Detailed methodology adopted for the exercise is discussed in the paper.

Performance and emission tests have to be carried out on range of engines having wide applications and varied specifications. In this context situation compels to adopt critical measures and revamp the methodologies in the area of design and development / matching of cardon shafts, rubber couplings and development of test bed systems for testing of single / two cylinder engines. Considering this need, a new strategic design approach has been formulated, which have reduced cost, loss of time and serious damages. This paper outlines a modern and practical approach used along with in-house available tools for controlling various dynamic behavioral issues involved. Redesign of shafts and couplings is done based on the comprehensive mass elastic data obtained from variety of engines. Apart from conventional torsional and bending vibration theories, FE and experimental tools are used to understand the modal behavior of engine coupled systems.

The latest requirements for automotive cabin comfort require lower sound levels inside the cabin. There are many sources contributing to this noise of which fan is an important one. The blade passage noise of the cooling fan is often unpleasant and it is generally expensive to build and test different prototypes for optimum noise performance. Also, traditional unsteady computational approaches for predicting the fan noise are time and resource consuming and do not fit within the design cycle time. This paper proposes use of a steady state computational technique to predict the fan noise performance which provides for effective design study with optimum resources. The steady state data is used with the wave analogy to predict the overall sound pressure level. First, the computational results were validated with the experimental data for a base case and then parametric study was carried out to have optimum design.

For high degree of engine performance, it is imperative that all critical parts are designed and optimised through durability assessment. The conventional engine development programme based on actual engine test on test bed is time consuming and expensive, and is being replaced by use of simulation tools and accelerated component testing. The present work is a systematic fatigue strength evaluation programme for connecting rod of an up-rated Naturally Aspirated, Direct Injection, Inline Diesel Engine The established staircase method of fatigue test is slightly modified to minimise the effect of scatter in the results and to arrive at a consistent and dependable factor of safety. Also analytical tools like Finite Element Analysis (FEA) and Statistical Techniques were used; which helped to keep design and tooling iterations to a minimum and facilitated connecting rod development in the given time frame.

This paper addresses in detail the methodology developed for the design and evaluation of engine mounting system. The design phase involves selection and laying out mount locations and specifying the insulators, in order to decouple the critical modes. The 3 main criteria to be used viz. nodal point location, centre of percussion and decoupling are discussed. The evaluation phase involves measurement of vibration and noise level at different locations in the vehicle. The evaluation tools available are the transmissibility, the Campbell diagram and peak sound pressure level. This paper presents the results of a study carried out for evaluation of existing arbitrary 3 point and 4 point mount options and a systematically developed 3 point one. It also presents a methodology for the evaluation of design and development of engine mounts.

The acceptance criterion of any vehicle in terms of user comfort invariably depends on the vehicle interior noise and vibration characteristics. The levels of sound energy and structural excitation inside the vehicle compartment measures the amount of annoyance in terms of quality and comfort. For vehicle interior noise abatement and noise treatment, it is desirable to quantify the noise sources by determining the sound power contribution from each vehicle component/panel, acoustic leakages inside the vehicle, body panel vibrations, gearshift lever and steering wheel vibrations. Many a times, it is necessary to arrive at benchmarks or targets for the various sources of noise in order to refine the systems. The present paper describes a methodology for interior noise source identification and its analysis for benchmarking. Two different vehicles of the same class but of different makes were compared and evaluated for interior noise and vibration levels.