EGR Flow Control Strategy for a Smaller Capacity Diesel Engine Using a Phase Shifting Chamber

Exhaust gas recirculation (EGR) is an effective strategy to control NOx emissions in diesel engines. EGR reduces NOx through lowering the oxygen concentration in the combustion chamber, as well as through heat absorption. The stringent emission norms have forced diesel engines to further improve thermal efficiency and reduce nitrogen oxides (NOx). Throttle control is adopted in diesel intake system to control the EGR & fresh charge flow and to meet the emissions norms. In three or lesser cylinder. diesel engines, predominantly single and two-cylinder diesel engines, there is a higher possibility of the exhaust gas reaching the intake throttle and Particulate matter getting deposited on the throttle body. This can significantly affect the idling stability and intake restriction in prolonged usage. In idling condition, the clogged throttle body stagnates the fresh charge from entering the cylinder.

The work aims at the study of flow pattern for EGR reaching the throttle body. A numerical study is conducted on a two-cylinder smaller displacement diesel engine. In a two-cylinder engine with an EGR circuit the intake valve of cylinder opens at an interval of 360°crank angle, unlike the four-cylinder engines where there is always an intake valve open. This problem provided a platform to study the possibilities to control EGR entry to the intake manifold. The objective of the activity is to propose a solution to the throttle body clogging without any additional moving parts or control mechanism i.e. with no momentous cost addition and no maintenance for the customer. The activity was carried out in two stages, in the first stage the real word problem was recreated in the numerical environment. An expansion chamber which can act as a phase shifting is added to the EGR circuit and results of the same comparing with the reference engine is discussed. In the second stage, design modifications were made to overcome the problem. Different EGR layouts were made to reduce the flow towards the throttle body.