System for extracting samples from a stream

Abstract

A system for extracting samples from a stream in a conduit utilizing a probe, placed in the stream and having a channel for passing samples from the conduit stream. First and second pressure taps measure the pressure inside and outside the probe. A feedback signal, based on a pressure differential relative to the probe, is generated and controls a valve regulating sample velocity flow through the probe channel, that bears a fixed proportion to the velocity of flow in the conduit. The constant of proportionality between flow velocities in the conduit and the probe may be 1.0, resulting in an isokinetic sampling condition.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 09 / 819,092, filed Apr. 6, 2000, and entitled “System for Extracting Samples from a Stream,” which is a divisional of U.S. patent application Ser. No. 09 / 150,632, filed Sep. 9, 1998, now U.S. Pat. No. 6,062,092, issued May 16, 2000, the entire contents of each of which is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] The present invention relates to a system for extracting samples from a stream flowing in a conduit, which is portable and operates on either an isokinetic or a constant volume sampling basis. [0003] Constant volume sampling (CVS) has been recognized as the most accurate way of measuring pollutant emissions under conditions of varying flow rate, for example, exhaust emissions of a vehicle driven at varying speeds. In a CVS system, the exhaust stream containing the pollutants is diluted with clean air such that the combined flow rate ...

AI Technical Summary

Benefits of technology

[0021] A further object of the present invention is to provide a system for sampling emissions from an exhaust conduit of an internal combustion engine which may be used to measure such emissions as a fraction of the total exhaust flow without changing the exhaust back pressure or otherwise affecting the operation of the internal combustion engine.

[0023] A further object of the present invention is to provide a system for sampling components in a conduit stream which is portable and does not require extensive adaption to engines of various sizes.

[0024] Another object of the present invention is to provide a system for sampling emissions from an exhaust conduit of an internal combustion engine which is accurate and does not require the independent measurement of the exhaust mass flow rate from the exhaust conduit of the internal combustion engine.

[0025] Another object of the present invention is to provide a system for sampling emissions from an exhaust conduit of an internal combustion engine which is capable of determining measurements of particulate matter in the exhaust conduit and provides necessary cooling without additional equipment required in the prior art.

Problems solved by technology

However, such CVS sampling systems in existence are relatively large and expensive.

As a practicality, these systems do not accurately measure exhaust streams from large engines, such as those used in locomotives and heavy trucks.

In addition, such systems are not portable.

However, such systems are generally not CVS systems.

Unfortunately, these portable pollutant concentration systems are inaccurate, since the measuring or estimating of exhaust flow rates varies from vehicle to vehicle.

In addition, present pollutant concentration measurement systems are unable to determine particulate emissions accurately.

Changing the pressure in the exhaust system affects the generation of pollutant emissions.

Inaccurate measurements ensue, especially in turbocharged engines.

In addition, the system is unwieldy for mounting to a vehicle.

If such condition is not achieved, the inertia of particles in the exhaust stream may result in a sample being enriched or depleted in particles, relative to the concentration of particles in the exhaust stream.

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