Acoustical inspection method for inspecting the ceramic coating of catalytic converter monolith substrates

Patent · Tue Mar 31 00:00:00 EST 1987

OSTI ID:6588606

Varterasian, J H; Blaser, D A

An acoustic inspection method is described for determining in a catalytic converter monolith substrate whether a ceramic coating was applied in a predetermined amount to the surface of exhaust gas passages extending therethrough and whether the ceramic coating is blocking any of the passages. The method comprises: (a) mounting a catalytic converter monolith substrate with ceramic coated exhaust gas passages extending therethrough in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator, (b) driving the speaker to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency and thereby produce oscillatory sound waves through the coated passages at the same frequency, (c) comparing the phase angles of the sound waves at the entrance and exit ends of the coated substrate passages and with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity of coating on the passages and no blockage, and (d) detecting whether or not the passages of the substrate being inspected have the prescribed quantity and any blockage on the basis that the occurrence of a prescribed difference in the phase angles infers a deviation in the total flow area of the passages and thereby a deviation from the desired coating as to amount and lack of blockage.

• Assignee: General Motors Corp., Detroit, MI
• Patent Number(s): US 4653327
• OSTI ID: 6588606
• Resource Relation: Patent File Date: Filed date 14 May 1986
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
CATALYTIC CONVERTERS
COATINGS
INTERNAL COMBUSTION ENGINES
ACOUSTIC MEASUREMENTS
ACOUSTIC TESTING
CAVITY RESONATORS
CERAMICS
EXHAUST GASES
INCIDENCE ANGLE
INSPECTION
SOUND WAVES
SUBSTRATES
ELECTRONIC EQUIPMENT
ENGINES
EQUIPMENT
FLUIDS
GASEOUS WASTES
GASES
HEAT ENGINES
MATERIALS TESTING
NONDESTRUCTIVE TESTING
POLLUTION CONTROL EQUIPMENT
RESONATORS
TESTING
WASTES
330700* - Advanced Propulsion Systems- Emission Control
330100 - Internal Combustion Engines