Impulse Charging for Diesel Engines: Improved Performance Characteristic and Inside-Engine Measures to Meet Future Emission Legislation

The main targets concerning development activities for diesel engines are defined by future exhaust gas legislations (EURO IV, V). Due to the conflict between particulate and NOx emissions, both components of the exhaust gas are limited: The combination of direct injection of diesel into the combustion bowl and limited adoption of air swirl causes locally fuel-rich regions which lead to soot and burn at high peak temperatures in stoichometric regions. Simultaneously, the transient drive-off torque and the maximum power output are limited due to the time which is necessary for the mixture formation process.

By means of intensified flow energy and a demand-oriented regulation of the air mass flow using an impulse charging device for diesel engines, locally fuel rich regions inside the combustion bowl can be minimized which finally influences the NOx-Soot Trade-Off by inside-engine measures and improves low-end torque and power characteristics.

Current high-pressure injection systems mainly influence the combustion process by fuel-energy guided measures (shift of timing and pressure level). The air-energy guided influencing of mixture formation by means of a required utilization of timing and swirl energy is not possible concerning current diesel engines. The energy level of the intake air is adjustable by the application of impulse charging. A significant potential is observable to influence mixture formation and combustion process.

This potential is characterized by

• A speed and load independent adjustment of the swirl energy which improves mixture formation and local air-fuel ratios concerning future exhaust gas legislations and a homogenization of the cylinder charge
• A variable adjustment of the cylinder charge (global air-fuel ratio) and therefore a possibility for a regulation of the self ignition of a more homogeneous cylinder charge
• A lower swirl number defined by the intake ports and therefore a better flow coefficient which can be used for a better torque characteristic and power output
• An improvement of the speed and power range by means of a higher cylinder charge and a better mixture formation at full load
• An improvement of the transient drive-off torque by increasing the cylinder filling and an improving of the mixture formation at low speeds