Exhaust-gas analyzer

• US 5,218,857 A
• Filed: 05/14/1991
• Issued: 06/15/1993
• Est. Priority Date: 05/14/1990
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Horn, Horst, Decker, Hans-Josef
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): ROSKOS, JOSEPH
• Application Number:
  US07/699,746
• Time in Patent Office: 763 Days
• Field of Search: 73/23.31
• US Class Current: 73/23.31
• CPC Class Codes: G01M 15/102 by monitoring exhaust gases

Abstract

An exhaust-gas analyzer, particularly for emissions testing of motor-vehicle engines has a sampling tube into which a mixture of exhaust gas and ambient air is fed through gas lines. A gas feed pump is disposed downstream of the sampling tube with a flowmeter inserted in the air line feeding electrical signals to a computing unit. The unit computes instantaneous standard total flow rate, allowing for gas pressure and temperature.

Claims

1. An exhaust-gas analyzer such as for emissions testing of motor-vehicle engines comprises:

a sampling tube into which a mixture of exhaust gas and ambient air is fed through gas lines;

a gas feed pump disposed downstream of said sampling tube;

a flowmeter disposed in an air line upstream of said gas feed pump and producing electrical signals; and

a computing unit, which computes the instantaneous standard total flow rate using said electrical signals, while allowing for gas pressure and gas temperature.

2. The analyzer of claim 1, wherein said computing unit comprises a correction program for the precedence of flow-rate measurement over sampling.

3. The analyzer of claim 2, wherein said gas feed pump comprises a pump with constant suction capacity, and further comprises a nozzle upstream of said pump and designed as a "critical" nozzle.

4. The analyzer of claim 3, wherein said gas feed pump comprises a displacement pump.

5. The analyzer of claim 2, wherein an sample is taken from a steady-flow zone, in which the pressure and the temperature of gas are measured.

6. The analyzer of claim 2, wherein said flowmeter for the air comprises a mass flowmeter.

7. The analyzer of claim 2, wherein in said computing unit is connected to a test-stand master computer, said computing unit feeding input data for computation of the test results to said test-stand master computer.

8. The analyzer of claim 1, wherein said gas feed pump comprises a pump with constant suction capacity, and further comprises a nozzle upstream of said pump and designed as a "critical" nozzle.

9. The analyzer of claim 8 wherein said gas feed pump comprises a displacement pump.

10. The analyzer of claim 8, wherein an sample is taken from a steady-flow zone, in which the pressure and the temperature of gas are measured.

11. The analyzer of claim 1, wherein a sample is taken from a steady-flow zone, in which the pressure and the temperature of gas are measured.

12. The analyzer of claim 1, wherein said flowmeter for the air comprises a mass flowmeter.

13. The analyzer of claim 12 wherein said mass flow meter comprises a vortex flowmeter.

14. The analyzer of claim 12, wherein in said computing unit is connected to a test-stand master computer, said computing unit feeding input data for computation of the test results to said test-stand master computer.

15. The analyzer of claim 12, wherein said mass flowmeter comprises a flowmeter based on the principle of vortex tails, for measuring the air added to the exhaust gases.

16. The analyzer of claim 15, wherein said computing unit determines the instantaneous standard exhaust-gas flow rate, allowing for the precedence of the mass flow measurement from the values of the mass flowmeter, in conjunction with the pressure and temperature of the gas mixture at a constant total flow rate.

17. The analyzer of claim 1, wherein in said computing unit is connected to a test-stand master computer, said computing unit feeding input data for computation of the test results to said test-stand master computer.

18. An exhaust-gas analyzer comprising:

an air intake line having an inlet and an outlet;

an exhaust gas intake line having an inlet and an outlet;

a flowmeter, said flowmeter being disposed between said inlet and said outlet of said air intake line;

a stabilizing section, said stabilizing section having a first end and a second end, said first end of said stabilizing section being connected to said outlet of said air intake line and to said outlet of said exhaust gas intake line;

a gas feed pump, said gas feed pump being connected to said second end of said stabilizing section;

means for withdrawing a sample, said means for withdrawing a sample being disposed between said first end and said second end of said stabilizing section;

a computer; and

a gas temperature and pressure sensor, said gas temperature and pressure sensor being disposed in said stabilizing section and providing signals to said computer.

19. The exhaust gas analyzer of claim 18 wherein said stabilizing section includes two flanges and wherein said means for withdrawing a sample comprises a pipe disposed between said two flanges.

20. The exhaust gas analyzer of claim 19 further comprising a venturi nozzle disposed in said stabilizing section between said means for measuring and said second end of said stabilizing section.

21. The exhaust gas analyzer of claim 18 further comprising a venturi nozzle disposed in said stabilizing section between said means for measuring and said second end of said stabilizing section.

22. The exhaust gas analyzer of claim 21 wherein said stabilizing section has a maximum mass rate of flow and said gas feed pump has a rated section capacity greater than said maximum mass rate of flow.

23. The exhaust gas analyzer of claim 22 wherein said gas feed pump comprises a displacement pump.

24. The exhaust gas analyzer of claim 21 wherein said flow meter comprises a mass flowmeter.

25. The exhaust gas analyzer of claim 21 wherein said flow meter comprises a vortex flowmeter.

26. The exhaust gas analyzer of claim 18 wherein said stabilizing section has a maximum mass rate of flow and said gas feed pump has a rated section capacity greater than said maximum mass rate of flow.

27. The exhaust gas analyzer of claim 26 wherein said gas feed pump comprises a displacement pump.

28. The exhaust gas analyzer of claim 27 wherein said flow meter comprises a mass flowmeter.

29. The exhaust gas analyzer of claim 27 wherein said flow meter comprises a vortex flowmeter.

30. The exhaust gas analyzer of claim 26 wherein said flow meter comprises a mass flowmeter.

31. The exhaust gas analyzer of claim 26 wherein said flow meter comprises a vortex flowmeter.

32. The exhaust gas analyzer of claim 18 wherein said flow meter comprises a mass flowmeter.

33. The exhaust gas analyzer of claim 18 wherein said flow meter comprises a vortex flowmeter.