Sampling and dilution method

US3965749A · kind A · utility

Assignee

• The United States of America as represented by the Secretary of the Army · US

Inventors

• Stephen C. Hadden · Cambridge, US
• Leonard R. Hulls · Marblehead, US

Key dates

• Filing date: Mar 19, 1975
• Grant date: Jun 29, 1976
• Expiry date: Mar 19, 1995

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N1/2252
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A conduit arrangement for measuring unburned combustibles in the exhaust eam issuing from an engine. A restriction is provided in the exhaust duct to form a superatmospheric pressure zone upstream from the restriction and a subatmospheric pressure zone downstream from the restriction. A minor fraction of the exhaust gas is bypassed around the restriction through a conduit system communicating with the two above-mentioned zones. A sampling chamber containing a combustibles sensor is located in the conduit system. An auxiliary conduit communicates the interior of the sampling chamber with the ambient atmosphere so that cooling air is drawn into the chamber to dilute the sampled gas. The dilution air lowers the temperature of the gas-air mixture, thereby cooling the sensor against heat degradation by the otherwise undiluted gas. The dilution air also contributes oxygen to the gas stream, thereby enhancing catalytic oxidation processes on which certain sensors depend for response to combustibles (CO and CH).