metering pump diesel or additive injection, 3 l/h @ 5 bar
diagram of regeneration
hino truck , selective catalytic reduction (scr) next dpf regeneration process late fuel injection control exhaust temperature burn off soot.
regeneration process of removing accumulated soot filter. done either passively (from engine s exhaust heat in normal operation or adding catalyst filter) or actively introducing high heat exhaust system. on-board active filter management can use variety of strategies:
all on-board active systems use fuel, whether through burning heat dpf, or providing power dpf s electrical system, although use of fuel borne catalyst reduces energy required significantly. typically computer monitors 1 or more sensors measure pressure and/or temperature, , based on pre-programmed set points computer makes decisions on when activate regeneration cycle. additional fuel can supplied metering pump. running cycle while keeping pressure in exhaust system low result in high fuel consumption. not running regeneration cycle enough increases risk of engine damage and/or uncontrolled regeneration (thermal runaway) , possible dpf failure.
diesel particulate matter burns when temperatures above 600 degrees celsius attained. temperature can reduced somewhere in range of 350 450 degrees celsius use of fuel borne catalyst. actual temperature of soot burn-out depend on chemistry employed. start of combustion causes further increase in temperature. in cases, in absence of fuel borne catalyst, combustion of particulate matter can raise temperatures above structural integrity threshold of filter material, can cause catastrophic failure of substrate. various strategies have been developed limit possibility. note unlike spark-ignited engine, typically has less 0.5% oxygen in exhaust gas stream before emission control device(s), diesel engines have high ratio of oxygen available. while amount of available oxygen makes fast regeneration of filter possible, contributes runaway regeneration problems.
some applications use off-board regeneration. off-board regeneration requires operator intervention (i.e. machine either plugged wall/floor mounted regeneration station, or filter removed machine , placed in regeneration station). off-board regeneration not suitable on-road vehicles, except in situations vehicles parked in central depot when not in use. off-board regeneration used in industrial , mining applications. coal mines (with attendant explosion risk coal damp) use off-board regeneration if non-disposable filters installed, regeneration stations sited in area non-permissible machinery allowed.
many forklifts may use off-board regeneration - typically mining machinery , other machinery spend operational lives in 1 location, makes having stationary regeneration station practical. in situations filter physically removed machine regeneration there advantage of being able inspect filter core on daily basis (dpf cores non-road applications typically sized usable 1 shift - regeneration daily occurrence).
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