Noise and vibration characteristics of a micro car diesel engine

Abstract

In cylinder pressure developed, noise emissions and vibrations from an engine structure are important parameters that provide information about its condition monitoring. Due to several drawbacks of conventional techniques, novel methods are becoming the next hot topic of research for major automotive companies around the world. Diesel engines are widely used for a variety of industrial as well as domestic applications. Despite their advantages in terms of fuel economy (as compared to gasoline engines), these engines are often less popular due to their worst performance in terms of noise, vibration and harness (NVH) benchmarks. Hence it is important to develop a suitable scheme which is capable enough to extract information from various signals before actual breakdown takes place. In this work, data was collected from a diesel engine installed in the laboratory of Internal combustion engine at ʹUniversity of Roma Treʹ by changing speed, load, amount and duration of fuel injected. The collected data was further processed using various MATLAB based processing tools. The presented work also discusses various models based on mathematical analysis. The discussed research work has following major objectives: Objective 1-To review different sources of noise in engines. Objective 2-To study the effects of variations of different engine operational conditions on various signals acquired from transducers mounted on test engine. Objective 3- To show the applicability of various signal processing methods. Objective 4-To analyze combustion based noise using acquired data. Objective 5-To develop various numerical models of piston lateral motion and validate them using experimental data. Objective 6-On the background of presented work, provide a guideline for further research. The presented work has been organized into six chapters. Basic principles of noise, vibration and harness (NVH) have been presented in first two chapters. Chapter 1 analysis different sources of noise in an engine and briefly discusses various techniques used for separation of these sources. Chapter 2 discusses various signal processing methods adopted for diagnosis of different signals. Chapter 3 discusses various features of different sources of noise. Chapter 4 deals with combustion based noise and discusses the use of in cylinder pressure, noise emissions and engine block vibration signals for its analysis. Chapter 5 is dedicated towards noise emissions due to lateral motion of piston assembly. The dynamic equations of piston secondary motion were solved and effects of various parameters were analyzed. Chapter 6 presents a summary of various results and relates it to previous objectives presented. Further suggestions have also been made for future research work. The novelty of methods discussed in the presented work lies in analysis of various combustion noise related indices which showed a good correlation with actual in cylinder pressure developed. Further various mathematical models were used for analysis of lateral motion of skirt and effects of various design parameters were analyzed. As output signals from various transducers mounted on the engine are available at an early stage, the discussed methods in presented work may become an attractive option for effective detection and localization of various faults and hence, form an important aspect of preventive maintenance of engines.