PORTABLE VEHICLE EXHAUST FLOW SENSOR

• US 20090211351A1
• Filed: 05/08/2009
• Published: 08/27/2009
• Est. Priority Date: 05/24/2004
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Butler, James, Colvin, Alex, Korniski, Thomas
• Granted Patent: US 7,805,986 B2
• Time in Patent Office: Days
• US Class Current: 73/114.760
• CPC Class Codes: F01N 2390/02 using electric components only
• CPC Class Codes: G01F 1/36 the pressure or differential pressure being created by the use of flow constriction
• CPC Class Codes: G01F 1/88 with differential-pressure measurement to determine the volume flow
• CPC Class Codes: G01F 7/005 by measuring pressure or differential pressure, created by the use of flow constriction

Abstract

A portable exhaust gas flow sensor includes a tube for coupling to an exhaust pipe of a vehicle and having a thin screen or similar flow restricting element to induce a pressure drop based on the exhaust gas flow with an upstream port and a downstream port relative to the flow restricting element connected to a differential pressure transducer. A thermocouple extends through a temperature port to measure exhaust gas temperature flowing through the tube. A processor in communication with the thermocouple and the differential pressure transducer determines the exhaust gas flow based on the differential pressure and the temperature. The flow restricting element includes sufficient spaces to resist formation of condensation and minimize added back pressure while providing an accurately measurable pressure drop for flows ranging from idle to full throttle.

Claims

1. A method for real-time determination of exhaust gas flow through an exhaust pipe of a vehicle, the method comprising:

measuring a pressure difference upstream and downstream of a thin screen;

measuring exhaust gas temperature; and

determining the exhaust gas flow based on the pressure difference and the temperature.

2. The method of claim 1 wherein measuring comprises measuring a pressure difference upstream and downstream of a stranded mesh screen.

3. The method of claim 1 wherein the thin screen extends substantially across a cross-sectional area of the exhaust pipe.

4. The method of claim 1 wherein measuring comprises measuring downstream of a condensation trap.

5. The method of claim 4 wherein the condensation trap comprises a conical screen having an apex positioned upstream.

6. The method of claim 5 wherein the condensation trap comprises a conical screen having about 100 strands per inch.

7. The method of claim 1 wherein the screen mesh is selected to generate a measurable pressure difference while minimizing back pressure and formation of condensation on the screen.

8. The method of claim 1 wherein measuring comprises measuring with a first differential pressure transducer having a first detection range and a second differential pressure transducer having a second detection range.

9. A portable system for determining exhaust gas flow of a vehicle, the system comprising:

a tube adapted for placement on an exhaust pipe of the vehicle, the tube including a thin flow restricting element extending substantially entirely across a cross-sectional area of the tube, a first port disposed upstream of the thin flow restricting element for measuring a first pressure, and a second port disposed downstream of the thin flow restricting element for measuring a second pressure; and

a device in communication with the tube for determining the exhaust gas flow based on a difference between the first and second pressures.

10. The system of claim 9 wherein the tube further comprises a third port for measuring temperature of exhaust gas flowing through the tube, the third port disposed downstream of the first and second ports.

11. The system of claim 9 wherein the device determines the exhaust gas flow based on a difference between the first and second pressures and the temperature of the exhaust gas.

12. The system of claim 9 wherein the flow restricting element comprises a stranded mesh screen.

13. The system of claim 12 wherein the stranded mesh screen is made of stainless steel.

14. The system of claim 12 wherein openings in the stranded mesh screen comprise between 60% and 65% of the cross-sectional area of the stranded mesh screen. a microprocessor to determine the exhaust gas flow.

15. The system of claim 9 wherein the flow restricting element includes sufficient spaces to limit any increase in back pressure to less than six percent.

16. The system of claim 9 wherein the device comprises:

a first differential pressure transducer generating a first signal based on the difference between the first and second pressures corresponding to a first range of exhaust flows; and

a second differential pressure transducer generating a second signal based on the difference between the first and second pressures corresponding to a second range of exhaust flows.

17. The system of claim 9 further comprising:

a condensation trap positioned upstream relative to the flow restricting element.

18. The system of claim 17 wherein the condensation trap comprises:

a conical screen having an apex pointing upstream; and

a baffle disposed downstream of the conical stream.

19. The system of claim 9 wherein the tube further comprises a port for extracting samples of exhaust gas passing through the tube.

20. A portable exhaust gas flow sensor for real-time measurement of exhaust gas flow from a vehicle, the sensor comprising:

a tube for connecting to an exhaust pipe of the vehicle, the tube including an interior thin, stranded mesh screen to generate a pressure drop as exhaust gas flows across the screen, an upstream port for measuring pressure upstream of the screen, a downstream port for measuring pressure downstream of the screen, and a thermocouple port for measuring exhaust gas temperature;

a differential pressure transducer in communication with the upstream and downstream ports for generating a signal based on a pressure difference between the upstream and downstream ports;

a thermocouple in communication with the thermocouple port for generating a signal based on temperature of exhaust gas flowing through the straight tube; and

a processor for receiving the signals from the differential pressure transducer and the thermocouple and determining exhaust gas flow based on the received signals.