Thermocouple with out-of-line aspiration holes

- Amespace, Inc.

The response time of a thermocouple is improved by offsetting the outlet aspiration opening or openings in the thermocouple protective housing from the gas flow axis and the inlet opening. The outlet aspiration opening is located substantially at the gas separation point which is a point of minimum gas pressure. The degree of offset is thus chosen to maximize the pressure differential, .DELTA.P, between the inlet and the outlet openings. This increases the gas flow rate through the housing and past the thermocouple junction thereby substantially improving the thermocouple response time.

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Claims

1. A thermocouple assembly for measuring the temperature of a fluid stream comprising:

(a) a casing,
(b) at least one pair of dissimilar wires disposed in said casing and forming a thermocouple junction,
(c) insulation dispersed in said casing and separating said dissimilar wires from said casing and from each other,
(d) a protective housing spaced apart from and surrounding at least a portion of said casing containing a thermocouple junction,
(e) means to allow a part of the heated stream to flow through said protective housing and past said casing in the area of the thermocouple junction, including:
(1) an inlet opening in said housing positioned essentially along the flow axis of the stream,.Iadd.said inlet opening in axial alignment with said thermocouple junction, and.Iaddend.
(2) at least one outlet opening in said housing downstream from the inlet opening to establish a flow path through said housing,.Iadd.and.Iaddend.
(f) means for increasing the flow rate of the fluid through said housing by locating the outlet opening at a minimum fluid pressure point, thereby maximizing the pressure difference between inlet and outlet openings to provide rapid response of the thermocouple to changes in fluid stream temperature.

2. The thermocouple assembly according to claim 1 wherein said outlet opening is radially offset from the axis of said inlet opening.

3. The thermocouple according to claim 2 wherein an outlet opening in the housing is located either 75.degree. or 285.degree. from the downstream side of the fluid stream flow axis.

4. The thermocouple according to claim 2 wherein an outlet opening in the housing is located within a band extending either from 45.degree.-85.degree. or 275.degree.-315.degree. from the downstream side of the fluid stream flow axis.

5. The thermocouple according to claim 2 wherein offset outlet openings are located on both sides of said axis.

6. The thermocouple according to claim 5 wherein the offset outlet openings are respectively located 75.degree. and 285.degree. from the downstream side of the fluid stream flow axis.

7. The thermocouple according to claim 5 wherein the offset openings are respectively located within bands extending from 45.degree.-85.degree. and from 275.degree.-315.degree. from the downstream side of the fluid stream flow axis.

8. The thermocouple according to claim 5 wherein the outlet openings are axially offset from the plane of the inlet opening.

9. The thermocouple according to claim 8 wherein the outlet openings are respectively located above and below the plane of the inlet openings.

10. The thermocouple according to claim 6 wherein the outlet openings are axially offset from the plane of the inlet opening.

11. The thermocouple according to claim 6 wherein the outlet openings are respectively located above and below the plane of the inlet opening.

12. The thermocouple according to claim 7 wherein the outlet openings are axially offset from the plane of the inlet opening.

13. The thermocouple according to claim 7 wherein the outlet openings are respectively located above and below the plane of the inlet opening.

14. A thermocouple assembly for measuring the temperature of a gaseous stream including at least one thermocouple junction positioned in a casing surrounded by a protective housing spaced from said casing,

(a) means to expose the thermocouple junction in said housing to a gaseous stream including an inlet opening and at least one outlet opening in said housing,.Iadd.the inlet opening and thermocouple junction being axially aligned,.Iaddend.
(b) said outlet opening being.Iadd.radially.Iaddend.offset from the inlet opening, the degree of off-set being chosen to locate the outlet opening in a minimal pressure area on the outside of the housing to maximize the pressure difference across said openings and the gas flow rate through said housing.
Referenced Cited
U.S. Patent Documents
3075387 January 1963 Rademacher
3159032 December 1964 Rademacher et al.
3284246 November 1966 Macatician
3451862 June 1969 Burgess, Jr. et al.
3459598 August 1969 Cole et al.
4131756 December 26, 1978 Smith
4132114 January 2, 1979 Shah et al.
4162929 July 31, 1979 Finney
4244222 January 13, 1981 Hoyer et al.
4485263 November 27, 1984 Itoyama et al.
Foreign Patent Documents
1084989 September 1967 GBX
Other references
  • Distribution of Local Pressure and Skin Friction Around a Circular Cylinder in Cross-Flow Up to Re=5.times.10.sup.6 by E. Achenbach, Journal of Fluid Mechanics, pp. 625-639, Apr. 1969.
Patent History
Patent number: RE35674
Type: Grant
Filed: Dec 22, 1994
Date of Patent: Dec 2, 1997
Assignee: Amespace, Inc. (Wilmington, DE)
Inventor: Robert A. Pustell (Andover, MA)
Primary Examiner: Charles T. Jordan
Assistant Examiner: Chrisman D. Carroll
Law Firm: Ratner & Prestia
Application Number: 8/361,574