METHOD AND APPARATUS FOR MASS EMISSION SAMPLING OF MOTOR VEHICLE EXHAUST GASES

• US 3,603,155 A
• Filed: 02/02/1970
• Issued: 09/07/1971
• Est. Priority Date: 02/02/1970
• Status: Expired due to Term

• Current Assignee: Charles William Morris, John Raymond Ulyate
• Original Assignee: Charles William Morris, John Raymond Ulyate
• Inventors: Morris, Charles William, Ulyate, John Raymond
• Primary Examiner(s): Swisher, S. Clement
• Application Number:
  US05/007,734
• Time in Patent Office: 582 Days
• Field of Search: 73/421.5,23
• US Class Current: 73/863.01
• CPC Class Codes: G01M 15/102 by monitoring exhaust gases
• CPC Class Codes: G01N 1/2247 Sampling from a flowing stream of gas
• CPC Class Codes: G01N 33/0011 Sample conditioning in general G01N1/28
• CPC Class Codes: Y10S 55/30 Exhaust treatment

Abstract

An air blower draws a mixture of exhaust gases emitted from an internal combustion engine and ambient air through a through-flow duct having a valve means therein at a minimum volumetric flow rate for the mixture in excess of the maximum volumetric flow rate the engine is capable of emitting while a proportional sample of said total mixture is withdrawn into a sample container at a uniform volumetric rate during a test period, the sample thereafter being analyzed to determine the concentration of pollutants of gas constituents therein and compared with the concentration of such pollutants or gas constituents in the ambient air which is sampled concurrently at the same flow rate from an area adjacent that where the ambient air is drawn into the through-flow conduit, total mass or weight of such pollutants or constituents being calculable from the concentration thereof in said sample and the known total mass or weight of air and gas mixture drawn through the duct. Temperature sensing and transducer means produce a first or error signal which is a function of the temperature of gases flowing through said duct, volumetric flow rate sensing means and associated transducer means produce a second signal which is a function of volumetric gas flow through the duct and electrical circuit means are provided in association therewith to cause said second signal to modify said first signal to produce a control signal which causes operation of a servomotor to adjust the valve means until an actual required volumetric flow rate through the duct is attained for any given temperature thereof to maintain a constant mass or weight flow, said actual volumetric flow rate for said gases increasing with increasing gas temperatures above a standard initial flow rate for a standard temperature condition. Circuitry is provided for a system for maintaining constant the rate of mass flow of a gas through a conduit despite temperature changes. The system generates an error signal linear with the absolute temperature of the gas, generates a second signal which is linear with differential pressure across a fixed orifice in the conduit, and thus with velocity of flow therein, modifies the error signal by the second signal to produce a command signal of appropriate polarity to adjust the velocity of gas flow in an inverse feedback manner by controlling a throttling valve in the conduit.

Claims

2. The apparatus of claim 1 wherein:

said valve control means includes a servomotor means associated with said valve means;

said temperature-sensing means includes a temperature transducer means for producing a first output signal which is a function of the temperature of gases flowing through said duct at any instant;

said volumetric flow rate sensing means includes a restriction in said duct for creating a gas pressure differential thereacross indicative of volumetric flow rate therethrough; and

electrical means for modifying said first output signal in response to the magnitude of said pressure differential, said electrical means including a pressure differential transducer means adapted to sense the differential in gas pressure across said restriction and for producing a control output signal to said servomotor means which is a function of both said temperature of gas in said duct sensed by said temperature sensing means and the volumetric flow rate of gAses through said duct sensed by said flow rate sensing means, said control signal operating said servomotor means to control the positioning of said valve means.

3. The apparatus of claim 1 wherein:

said through-flow duct is connected by a flexible conduit to the exhaust pipe of a vehicle engine exhaust system and said conduit is open to ambient air as well as to said engine exhaust; and

said gas drive means operates to draw a minimum volumetric flow rate of a mixture of ambient air and exhaust gases which is greater than the maximum exhaust gas volumetric flow rate attainable by said vehicle engine.

4. The apparatus of claim 1 wherein said volumetric flow rate sensing means comprises:

a metering orifice in said duct for creating a pressure drop across an opening of known diameter; and

a differential pressure-sensing means and gas conduit means for connecting said pressure-sensing means to said duct upstream and downstream of said orifice to sense the pressure differential across said orifice at any given instant.

5. The apparatus of claim 4 wherein said volumetric flow rate sensing means also comprises:

differential pressure transducer means for converting said differential pressure value into an electrical output signal which is a function of said differential pressure magnitude.

6. The apparatus of claim 1 wherein said temperature sensing means comprises:

a sensor disposed in the path of exhaust gases passed through said duct and electrical means for amplifying and sending the output signal of said sensor to said valve control means.

7. An apparatus for collecting a sample of exhaust gases from an internal combustion engine comprising:

a gas through-flow conduit and means for drawing all of said engine exhaust gases through said conduit;

valve means in said conduit and valve control means associated with said valve means for controlling the volumetric flow rate of exhaust gas through said conduit in response to changes in temperature of said exhaust gases; and

means for withdrawing a sample of said exhaust gases from said conduit during a test run of said engine.

8. An apparatus as in claim 7 wherein:

said means for drawing all of said engine exhaust gases through said conduit includes a conduit intake portion positioned about the exhaust outlet of said engine in intake communication with said engine exhaust gases and the ambient air.

9. An apparatus as in claim 8 wherein:

said means for drawing all of said engine exhaust gases through said conduit also includes an air blower means associated with said conduit for constantly drawing an air and exhaust gas mixture through said conduit at a greater volumetric flow rate than the maximum volumetric flow rate of exhaust gases attainable by said engine.

10. An apparatus as in claim 7 wherein said valve control means comprises:

temperature sensing means associated with said conduit for sensing the temperature of gases flowing through said conduit and including temperature transducer means for producing an electrical output signal which is a function of the temperature sensed.

11. An apparatus as in claim 10 including:

means for sensing the volumetric flow rate of gases flowing through said conduit;

electrical means associated with said last-named means for modifying said temperature transducer output signal in response to the volumetric flow rate of gases flowing through said conduit to produce a control signal; and

means for operating said valve means in response to said control signal whereby said valve means is operated as a function of both the temperature and volumetric flow rate of gases flowing through said conduit.

12. An apparatus as in claim 11 wherein:

said means for sensing the volumetric flow rate of gases flowing through said conduit includes a metering orifice in said conduit and means for measuring the differential pressure across said orifice; and

said electrical means includes pressure transducer means for producing an output signal which is a function of the magnitude of said differential pressure.

13. An apparatus as in claim 8 wherein said means for withdrawing a sample of said exhaust gases includes:

a sampling tube having an inlet located in the path of flow of said gases in said conduit;

pump means for drawing a constant flow of gases from said conduit during said test run to obtain a sample thereof; and

container means for receiving said sample, said container being connected by a gas line to said sampling tube.

14. An apparatus as in claim 13 including:

a selector valve in said gas line;

a second gas line to be connected to a gas analyzer; and

means for operating said valve to selectively connect said container with said sampling tube or with said second gas line to said analyzer.

15. An apparatus as in claim 7 including an ambient air-sampling means comprising:

an inlet tube having an air inlet positioned in the general area of said internal combustion engine to receive air ambient to said engine;

an air pump means associated with said inlet tube for drawing said ambient air at a constant flow rate into said tube; and

an air sample container connected to said inlet tube to receive said air sample.

16. An apparatus as in claim 15 wherein:

said pump means for drawing said gas sample and said air pump means comprise a dual head pump for pumping both said gas sample and said ambient air sample at the identical volumetric flow rate.

17. A method of obtaining a proportional sample of total exhaust gas emission of an internal combustion engine during operation of said engine to measure the total mass of a given constituent in said emissions comprising the steps of:

drawing all of said engine exhaust gases through a flow-through duct at a given initial volumetric flow rate;

maintaining a constant mass flow of said gas through said duct by varying actual volumetric flow rate in response to change in temperature of said gas during a test period;

withdrawing a proportional sample of said gas from said duct at a generally constant volumetric flow rate during said test period; and

determining the concentration of a given constituent in said sample and computing the total mass of said constituent emitted by said engine during said test period from the product of said concentration and total mass of air passed through said duct.

18. The method of claim 17 including the step of:

introducing additional gas comprising ambient air in sufficient amounts during said step of drawing all of said engine exhaust gases through said flow-through duct at a minimum volumetric flow rate for said gases which is in excess of the maximum volumetric flow rate of exhaust gases said engine is capable of emitting during a test period.

19. The method of claim 17 including the steps of:

sensing the volumetric flow rate of gases drawn through said duct during said test, and varying the actual volumetric flow rate of said gases drawn through said duct in response to changes in both the temperature and flow rate.

20. The method of claim 19 including the steps of:

producing a first command electrical signal which is a function of the temperature of gases drawn through said duct;

modifying said first command signal by introducing thereinto an electrical signal produced as a function of the volumetric flow rate of gases drawn through said duct to produce a modified control signal; and

controlling the volumetric flow rate of gases through said duct as a function of said control signal.

21. The method of claim 17 including the steps of:

adjusting the position of a valve in said duct to vary the actual volumetric flow rate of gases drawn through said duct in response to changes in both the temperature and volumetric flow rate of gases drawn through said duct.

22. The method of claim 21 including the steps of:

producing a first command electrical signal whiCh is a function of the temperature of air and exhaust gases drawn through said duct;

modifying said first command signal by an electrical signal produced as a function of the volumetric flow rate of air and exhaust gases drawn through said duct to produce a modified control signal; and

adjusting the position of said valve by said control signal.