A big step in the evolution of the low-emission diesel was Exhaust Gas Recirculation. Some of the exhaust gas is recycled back through the engine under certain circumstances.
The purpose of the EGR is not to ‘re-burn the exhaust’
EGR dilutes the amount of oxygen in the intake charge. This reduces the temperature of combustion and lowers formation of NOx. But how much is too much?
NOx: At Odds with Fuel Economy In general, the more efficient the combustion, the higher the NOx output. The lower the NOx output, the lower the efficiency Efficiency, % more more less less EFFICIENCY vs. NOx NOx Reduction, %
Major improvements in NOx came with ultra high pressure fuel injection.
Higher fuel injection pressure gives finer atomization for better combustion, reducing the soot
Shaped fuel injection delivery allows pressure rise to be controlled for best possible release of power.
Proven Delphi Dual Solenoid fuel injector used since EPA’02 now delivers 35,000 psi for EPA’07 & ‘10
How Have We Been Able to Reduce NOx and Still Maintain Fuel Economy? Dual Solenoid Fuel Injector
More Exhaust Gas Recirculation?? 35% - 50+% 20% - 35% 10% - 20% EGR Flow Massive EGR Heavy EGR Light EGR Industry Definition
Keeping Everything in Balance is a Challenge… Peak Cylinder Pressure NOx to Soot Ratio Displacement Fuel Injection Pressure Air/Fuel ratio Regeneration Power Density “ Not to Exceed” Emission Window Boost Pressure
The after-treatment system utilizes an injection of a solution of urea.
Urea is a compound of nitrogen that turns to ammonia (NH 3 ) when heated. When a urea solution is injected into the exhaust stream and passed over a catalyst, the urea reacts with the NOx to form just nitrogen and water vapor – both clean components of ‘air’.
Ammonia + NOx react to make N 2 + H 2 0 – nitrogen and water vapor – nothing left over.
On Board Diagnostics (OBD) Engine EGR Fuel Fuel Mixing zone DPF Diesel Exhaust Fluid Reservoir Sensors: 3 Temperature sensors 1 Differential Pressure sensor 2 NOx-sensors OBD DEF Mixing zone SCR Exhaust Outlet
Volvo for EPA’10 Due to the lower fuel costs, and to higher reliability, SCR will clearly provide the customer’s lowest cost of operation. Cost of Operation 6. Volvo has the benefit of implementing a proven technology – 150,000 on road already, 2x+ by 2010 Durability / Reliability 5. Volvo adds a tank, with coolant line heater and pump Complexity 4. Power density with SCR is higher, not lower Power 3. D13 with SCR several hundred pounds less than 15L Weight 2.