31 Table 3.2.2 Detail specification of the DOC catalyst
Diameter 118.4 mm with 115 mm exposed in rig
Length Single = 91 mm, Volume approximately 1 litre
Double = 182 mm, Volume approximately 2 litre Cell Density
400 cpsi Cell Pitch
1.27 mm Substrate
NGK HoneyCeram Wall Thickness
0.11 mm [4.3 thouUK,4.3 mil USA] Open frontal area non-washcoated
83.4 Bulk density of substrate
0.29 gcc 290 kgm
3
Washcoat thickness 0.085 mm
Washcoated channel dimension 1.076 mm
Washcoat loading assuming washcoat density = 1350 kgm
3
158.7 kgm
3
3.2.3 SCR Catalysts Assembly
The SCR catalyst assembly has been designed to accommodate four SCR configurations in this investigation. An assembly consisting of a single brick measuring 115 mm in diameter and of length
92.5 mm was available. Two double bricks of diameter 115 mm and length 185 mm were also available. A blank SCR with the same dimension as the single and double bricks configurations was
also used. This SCR assembly is shown in appendix 3.2b. The single SCR can, two double SCR cans and the blank SCR can allowed single, double, triple and quadruple SCR configurations to be tested. The
detailed specification of the SCR catalyst is shown in table 3.2.3.
32 Table 3.2.3 Detail specification of the SCR catalyst
Diameter 118.4 mm with 115 mm exposed in rig
Length Single = 91 mm, Volume approximately 1 litre
Double = 182 mm, Volume approximately 2 litres Triple = 273 mm, Volume approximately 3 litres
Quadruple = 364 mm, Volume approximately 4 litres Cell Density
400 cpsi Cell Pitch
1.27 mm Substrate
NGK HoneyCeram Wall Thickness
0.11 mm [4.3 thouUK,4.3 mil USA] Open frontal area non-washcoated
83.4 Bulk density of substrate
0.29 gcc 290 kgm
3
Washcoat thickness 0.089 mm
Washcoated channel dimension 1.072 mm
Washcoat loading assuming washcoat density = 1350 kgm
3
166.6 kgm
3
3.2.4 Urea Spray Mixing Chamber.
The Urea spray mixing chamber consists of a combination of a short 50 mm pipe and a 200 mm diameter by 200 mm long plenum, attached to a bell shaped converging nozzle as shown in figure
3.2.4. The urea spray mixing chamber was designed to allow uniform mixing of urea droplets in the presence of hot exhaust flow from the engine.
Figure 3.2.4 The Urea spray mixing chamber.
33 The mixing chamber has a urea spray boss fitted on top and a tiny drainage plug at the bottom. In
the event of running the test with urea spray, the chamber would house the spray injector unit while with the NH
3
gas test the boss was plugged to prevent gas leakage.
3.2.5 Instrumentation module assembly.
