Particulate trap for purifying diesel engine exhaust

The combination of a diesel engine having an exhaust line, and a particulate trap for filtering particulates from exhaust gas of the diesel engine, said particulate trap including a case having an inlet and an outlet mounted to said exhaust line of the diesel engine such that said particulate trap is disposed in-line with said exhaust line, and a filter comprising at least one filter element mounted in said case, each said filter element being a porous member of a heat-resistant metal framework having the form of a three-dimensional mesh, said porous member being tubular so as to have an outer surface and an inner surface, the pores of said porous member defining passageways extending between and open to said inner and said outer surfaces, said porous member extending longitudinally in a direction in which exhaust gas flowing through said exhaust line passes from said inlet to said outlet of the case, the surface roughness of the metal of said metal framework being at least 0.2 .mu.m as expressed in terms of Rmax, the pores of said porous member having an average diameter of 0.1-1 mm, the average number of said pores as counted in the direction of thickness of said porous member being at least 10, the amount of space occupied by said metal framework to the entire volume of space occupied by said porous member being 10-40%, and said porous member having a gas inflow filtration area of 400 cm.sup.2 or more per liter of the displacement of said diesel engine.