Improvement of premixed charge compression ignition-based combustion by two-stage injection

Abstract

The objective of this study is to find strategies for extending the load range of premixed charge compression ignition-based combustion while improving thermal efficiency and reducing combustion noise and exhaust emission levels. Experiments were performed using a single-cylinder direct-injection diesel engine equipped with a common-rail injection system and a cooled EGR system. First, experiments were carried out with single-stage injection. The results indicated a notable improvement of NO x and smoke emissions by selecting lower EGR rates and later injection timings according to the increase in injection quantity. However, the problems of high pressure rise rates and levels of unburned species emissions developed. To solve these problems, two-stage injection was applied. These additional experiments started with injection and EGR conditions that were based on the results of the single-stage injection tests, and modifications were made to mitigate the increased emissions and decreased thermal efficiency. As a result, judicious selection of injection and EGR conditions for two-stage injection provided a drastic improvement in exhaust emissions with a sufficiently low pressure rise rate to be equivalent to pilot-diesel operation.

Experimental evaluation of sensitivity of low-temperature combustion to intake charge temperature and fuel properties

“…For homogeneous/premixed fuel-air mixing, researchers employed in-cylinder charge preparation techniques using early direct injection (DI) and late DI. [5][6][7][8][9] In these techniques, fuel injection parameters, namely, start of injection (SoI) timing and fuel injection pressure (FIP), are crucial for fuel-air mixing, which directly affect the start of combustion (SoC) and heat release. However, the operating range of LTC was limited due to higher rate of pressure rise (RoPR).…”

Application of canola oil operation in a diesel engine with common rail system

“…Because of the flexibility of the common rail injection, it was possible to introduce new kinds of combustion processes, such as Premixed Charge Compression Ignition-based combustion (PCCI [1,2] in diesel engines. Recently, modified PCCI process with dual-fuels was reported by different engine researchers [3,4].…”

Effect of Timing and Pattern of Fuel Injection on Performance and Emissions of a Diesel Engine in the Low-Temperature Combustion Mode – An Experimental Investigation

“…Modern diesel engines use multiple fuel injections (Kook, 2004), in order to overcome this problem, through the use of electronically controlled common rail fuel injection systems. These systems allow variations in fuel injection timing, fuel quantity, fuel injection pressure and also allow multiple injections in one engine cycle (Zhao, 2007;Horibe, 2009 andTorregrosa, 2013). Injecting a small quantity of fuel very early during the compression stroke increases the ignition delay (Drallmeler et al, 2018) and the possibility of formation of a very lean homogeneous mixture leading towards homogeneous charge compression ignition (HCCI) combustion which helps reduce NOx and smoke emissions simultaneously (Itoli, 2006).…”