Post by ap40rocktruck on Jan 14, 2013 17:37:25 GMT -8
In addition to the emissions explanation, DEF = Diesel Exhaust Fluid.
In the SCR (Selective Catalytic Reduction) system, the 1st part is on the engine. The exhaust manifold has 2 (on current Mack & Volvo) additional ports with EGR (Exhaust Gas Recirculator) valves which allow hot exhaust gas to be cooled by a engine mounted heat ex-changer (EGR Cooler) where the cooled exhaust is recirculated back in to the intake air flow between the charge air cooler & cylinder head.
Step 2 is the after treatment (after the exhaust has passed the back 1/2 of the turbo) first the EG (Exhaust Gas) travels past the 7th injector. This injector sprays a fine mist of diesel fuel into the EG stream where it is ignited as it passes thru the DPF. This is done to capture much of the soot (particulates) in the EG & was used to meet the 07 emissions regulations (Tier 3). SCR was added to comply with the 2010 regs.
Step 3 is the SCR, where after the EG has burned & passed the DPF, in another box a fine most of DEF is sprayed into the hot EG, reducing the temp slightly & reducing the NOx to meet the 2010 or Tier 4 emissions. When the spray hits the EG the moisture evaporates instantly & the crystallized NOx collects in the bottom if the unit.
On average for a highway truck, with SCR the usage of DEF to fuel is roughly 18 gallons of DEF to 200-250 gallons of fuel.
2 interesting points about DEF, if Diesel fuel is put into the DEF tank, the truck will burn to the ground in less than 2 minutes after starting the engine. If DEF is put into the fuel tanks, the truck will run for about 5 minutes then stop running. The fix = replace the ENTIRE fuel system, as in tanks, lines, primary & secondary filters, injector lines & injectors. DEF eats all things metal. I saw a video from Volvo on the first, and oversaw the replacement of the entire fuel system of the second.
Ap40
In the SCR (Selective Catalytic Reduction) system, the 1st part is on the engine. The exhaust manifold has 2 (on current Mack & Volvo) additional ports with EGR (Exhaust Gas Recirculator) valves which allow hot exhaust gas to be cooled by a engine mounted heat ex-changer (EGR Cooler) where the cooled exhaust is recirculated back in to the intake air flow between the charge air cooler & cylinder head.
Step 2 is the after treatment (after the exhaust has passed the back 1/2 of the turbo) first the EG (Exhaust Gas) travels past the 7th injector. This injector sprays a fine mist of diesel fuel into the EG stream where it is ignited as it passes thru the DPF. This is done to capture much of the soot (particulates) in the EG & was used to meet the 07 emissions regulations (Tier 3). SCR was added to comply with the 2010 regs.
Step 3 is the SCR, where after the EG has burned & passed the DPF, in another box a fine most of DEF is sprayed into the hot EG, reducing the temp slightly & reducing the NOx to meet the 2010 or Tier 4 emissions. When the spray hits the EG the moisture evaporates instantly & the crystallized NOx collects in the bottom if the unit.
On average for a highway truck, with SCR the usage of DEF to fuel is roughly 18 gallons of DEF to 200-250 gallons of fuel.
2 interesting points about DEF, if Diesel fuel is put into the DEF tank, the truck will burn to the ground in less than 2 minutes after starting the engine. If DEF is put into the fuel tanks, the truck will run for about 5 minutes then stop running. The fix = replace the ENTIRE fuel system, as in tanks, lines, primary & secondary filters, injector lines & injectors. DEF eats all things metal. I saw a video from Volvo on the first, and oversaw the replacement of the entire fuel system of the second.
Ap40