use more fuel-efficient operating modes b e c a u s e i t d i d n o t h a v e t o d e a l w i t h N 2 O emissions within the engine. The other main technology that will b e e m p l o y e d t o r e a c h I T 4 s t a n d a rd s i s RPF. In many cases, the RPF replaces the muffler, trapping and holding particulates remaining in the exhaust system. Trapped p a r t i c l e s a re e v e n t u a l l y o x i d i z e d w i t h i n t h e R P F i n a p ro c e s s c a l l e d r e g e n e r a t i o n . “ I n t h i s c a s e , t h e N 2 O e m i s s i o n s a re c o n -trolled within the engine without wor-r ying about particulates,” explains Hoy. “ W h a t i t d o e s w i t h t h e P M i s t o re p l a c e t h e m u ff l e r w i t h a p a r t i c u l a t e f i l t e r t r a p . That all sounds nice, but eventually the PM builds up, and periodically, the ma-chine may have to inject diesel fuel into the exhaust system to raise the exhaust gas temperatures up to bur n off the par-ticulate that has been trapped.” “When the filter starts building up soot (PM), the back-pressure in the system starts to go up, and if exhaust gas temperatures aren’t high enough, or not in the right range, this soot won’t convert to ash on its own, so something has to be done to bring it up, so diesel fuel is injected,” explains Hoy. “You might see a change in fuel consumption as these things burn.” P M i s c o n v e r t e d t o a s h d u r i n g re g e n -eration, and remains inside the filter. The amount of ash accumulated during a period of use will eventually mean the RPF w i l l n e e d re p l a c i n g a f t e r a b o u t 3 , 5 0 0 o r 4,000 hours. EnginE systEms In the agricultural market that Hoy stud-i e s , J o h n D e e re i s c o m b i n i n g a d i e s e l o x i -d a t i o n c a t a l y s t ( D O C ) w i t h R P F ( D e e re calls it a diesel particulate filter, DPF). The company’s IT4 information says that under normal operating conditions, the D O C re a c t s w i t h e x h a u s t g a s e s t o re d u c e carbon monoxide, hydrocarbons, and some PM. The downstream RPF forces exhaust gases to flow through porous channel walls, trapping and holding the remaining PM. Trapped particles are even-tually oxidized within the RPF through a self-cleaning process called passive regen-e r a t i o n , u s i n g e x h a u s t h e a t c re a t e d u n d e r normal operating conditions. When the e x h a u s t t e m p e r a t u re i s i n c a p a b l e o f o x i -dizing the PM, the RPF filter reverts to ac-t i v e re g e n e r a t i o n w i t h t h e i n j e c t i o n o f d i e -sel fuel to help bur n off the PM. H o y o b s e r v e d a J o h n D e e re I T 4 e n g i n e at a John Deere test facility. He saw that e n g i n e t o rq u e w a s w i t h i n 3 / 1 0 % b e t w e e n s o o t l o a d a n d f u l l y c l e a n e d a f t e r re g e n -e r a t i o n w i t h t h e R P F s y s t e m . T h e O rg a n i -sation for Economic Co-operation and D e v e l o p m e n t re q u i re s t e s t m e a s u re m e n t tolerances to be within 0.5–1%, so the D e e re re s u l t i s w i t h i n t h e m e a s u re m e n t re q u i re m e n t s . “ I d o h a v e t h e c o n c l u s i o n t h a t D e e re h a s a v e r y w e l l d e s i g n e d s y s t e m h e re . T h e re i s n o g u a r a n t e e t h a t s i m i l a r s y s t e m s f ro m o t h e r m a n u f a c t u r e r s w i l l b e w e l l d e s i g n e d , s o w e a re g o i n g t o a s k t h a t that this type of performance information be recorded and supplied to us,” says Hoy. D e e re t o l d C a n a d i a n B i o m a s s t h a t i t w i l l be using the same base technology for all o ff -ro a d m a r k e t s , i n c l u d i n g c u t -t o -l e n g t h , bundler, and full-tree systems being mar-keted in Canada. For the time being, the Nebraska Trac-tor Test Lab will not be conducting these www.brunetteindustries.com RepaiRs and complete chippeR Re-builds all makes all models Call today to find out more. U.S.A. Canada 604-522-3977 [email protected] 770-345-1400 Vancouver • Prince George • Toronto • Atlanta Canadian BIOMASS 27
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