Lasers and optical diagnostics for next generation IC engine development: Ushering new era of engine development

Abstract

Researchers are trying to improve engine efficiencies and emission characteristics in an extremely challenging environment. This demands complying with ever-increasingly tightening emission norms and fuel economy norms globally, which are the prime forces driving the automotive industry globally. Optical diagnostic techniques have emerged as a valuable tool in development of engine powertrain and emission control technologies in last one decade. This chapter deals with variety of optical diagnostic techniques such as particle image velocimetry (PIV), phase Doppler interferometry (PDI) and endoscopy, applied to internal combustion (IC) engines. Laser based measurements in real time in the engine combustion chamber have ushered a new era of research for finding answers to some of the most intriguing in-cylinder processes, which were only speculated until recently. These optical diagnostic techniques have enabled engine researchers to sharpen their modeling tools using experimental data from realistic geometry engines firing under varying loads. Fuel-air mixing and combustion are mainly affected by in-cylinder air-flow and fuel spray characteristics. Air-flow structures developed inside the engine combustion chamber significantly influence the fuel-air mixing process. For validate this phenomenon, researchers investigated in-cylinder air-flow characteristics of motored engine using time-resolved tomographic particle imaging velocimetry (TPIV). Fuel spray characteristics could be determined using PDI, which provides information about droplet size distribution and 3D-velocity distributions. To gain visual access to the combustion process in a production engine's combustion chamber at high loads, another optical diagnostic technique "engine endoscopy" can be used, which can enable spatial combustion visualization, soot distribution as well as temperature distribution.