High temperature optical probe

• US 5,277,496 A
• Filed: 07/17/1992
• Issued: 01/11/1994
• Est. Priority Date: 10/17/1990
• Status: Expired due to Fees

• Current Assignee: Ametek Incorporated
• Original Assignee: Ametek Incorporated
• Inventors: Mayer, Christopher R., Reznikov, Leon
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): GUTIERREZ, DIEGO F
• Application Number:
  US07/916,791
• Time in Patent Office: 543 Days
• Field of Search: 374/208, 374/130, 374/131, 374/139, 374/140, 374/144, 374/148, 356/43, 250/340, 250/338.1
• US Class Current: 374/130
• CPC Class Codes: G01J 5/0014 for sensing the radiation from gases, flames
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0821 Optical fibres
• CPC Class Codes: G01J 5/0868 Means for illuminating a slit or a surface efficiently, e.g. entrance slit of a pyrometer or entrance face of a fiber
• CPC Class Codes: G01J 5/0887 Integrating cavities mimicking black bodies, wherein the heat propagation between the black body and the measuring element does not occur within a solid; Use of bodies placed inside the fluid stream for measurement of the temperature of gases; Use of the reemission from a surface, e.g. reflective surface; Emissivity enhancement by multiple reflections

Abstract

A high temperature optical probe for an optical gas temperature sensor includes a support, a generally conical hollow tip, and a joint physically interconnecting the support and the tip. The tip includes as an electromagnetic radiation emitter a sapphire-free ceramic selected from the group consisting of silicon carbide and silicon nitride.

Claims

1. A high temperature optical probe for an optical gas temperature sensor for sensing the temperature of a high-temperature, high-velocity gas stream, comprising:

(A) a support means for mounting said probe for interaction with the high-temperature, high-velocity gas stream;

(B) a generally conical hollow tip for insertion into the gas stream formed of a ceramic selected from the group consisting of silicon carbide and silicon nitride to emit electromagnetic radiation at the high temperatures to be sensed;

(C) a joint physically interconnecting said support means and said tip, said joint being formed and of a material to accommodate the thermal stresses caused by differences in thermal coefficients of expansion between said tip, said joint and said support means and the mechanical stresses caused by the interaction of said probe and the gas stream during high velocity movement of the gas stream past said tip, thereby to enable said probe to withstand said stresses; and

(D) means supported in said probe to focus and transmit electromagnetic radiation emitted from said tip to effect a measurement of the temperature of the gas stream.

2. The probe of claim 1 wherein said ceramic is dark colored.

3. The probe of claim 1 wherein said ceramic has a flexural strength in excess of 50,000 psi at 2,500°

F. on a four point bending test.

4. The probe of claim 3 wherein said ceramic has a high oxidation resistance of less than 1% weight loss for a 5,000 hour life at 2,500°

F., a high thermal shock resistance of at least 500°

F./sec, and a low thermal response time constant not exceeding 1 sec.

5. The probe of claim 1 wherein said ceramic emits infrared energy.

6. The probe of claim 1 wherein said support means is formed of metal.

7. The probe of claim 6 wherein said joint is formed of a material having a coefficient of thermal expansion that matches the coefficient of thermal expansion of said ceramic.

8. The probe of claim 7 wherein said joint is formed of a material selected from the group consisting of molybdenum and an alloy of iron/nickel/cobalt/manganese.

9. The probe of claim 6 wherein said metal is an alloy of nickel and iron.

10. The probe of claim 6 wherein said joint is connected to said support means by a threaded engagement and to said tip by a high temperature braze.

11. The probe of claim 10 wherein said high temperature braze is an alloy of silver and copper.

12. The probe of claim 1 wherein said tip is sapphire-free.

13. The probe of claim 1 wherein said ceramic is a sintered ceramic.

14. The probe of claim 1 wherein said support means in a cantilever fashion mounts said probe in the exhaust gas stream.

15. A high temperature optical probe for an optical gas temperature sensor for sensing the temperature of high-temperature, high-velocity gas stream, comprising:

(A) a support means for positioning said probe in the high-temperature, high-velocity gas stream;

(B) a hollow, generally conical tip formed of a sapphire-free ceramic having a high flexural strength, a high oxidation resistance, a high thermal shock resistance, and a low thermal response time constant selected from the group consisting of silicon carbide and silicon nitride, which ceramic emits infrared energy related to the temperature of the exhaust gases proximate said tip;

(C) a joint physically interconnecting said support and said tip and formed and of a material capable of withstanding the mechanical stresses caused by the interaction of said probe and the gas stream during high velocity movement of the gas stream past said tip and having a thermal coefficient of expansion to accommodate the mismatch in thermal expansion between said tip, said joint and said support means, said material being selected from the group consisting of molybdenum and an alloy of iron/nickel/cobalt/manganese, said joint being connected to said tip by a high temperature braze;

(D) a lens positioned within said probe to focus said infrared energy emitted from said tip; and

(E) an optical fiber positioned proximate said lens to transmit said focused infrared energy to a detector for providing a measurement of the temperature of the gases in the gas stream.

16. The probe of claim 15 wherein said support means in a cantilever fashion mounts said probe in the exhaust gas stream.

17. In combination, an engine and an optical gas temperature probe for an optical gas temperature sensor for measuring the temperature of the high-temperature, high-velocity engine exhaust gas stream, said optical gas temperature probe comprising:

(A) a probe including a support means mounting said probe in the high-temperature, high-velocity exhaust gas stream of said engine, a sapphire-free ceramic generally conical hollow tip for sensing the temperature of the exhaust gas stream, said tip being formed of a material which emits infrared radiation in response to exposure to the exhaust gas stream, and a joint physically interconnecting said support means and said tip, said joint being formed and of a material to accommodate the mechanical stresses caused by the interaction of said probe and the exhaust gas stream during high velocity movement of the exhaust gas stream past said tip and to compensate for the thermal stresses produced by the differences in the materials forming said support means, said joint and said tip;

(B) an infrared detector; and

(C) means supported in said probe for transmitting the infrared radiation from said probe to said infrared detector which produces, in response thereto, an output indicative of the temperature of the exhaust gas stream.

18. The combination of claim 17 wherein said ceramic is selected from the group consisting of silicon carbide and silicon nitride;

said ceramic being characterized by a dark color, a flexural strength in excess of 50,000 psi at 2,500°

F. on a four point bending test, a high oxidation resistance of less than 1% weight loss for a 5,000 hour life at 2,500°

F., a high thermal shock resistance of at least 500°

F. sec, and a low thermal response time constant not exceeding 1 sec.

19. The combination of claim 17 wherein said support means in a cantilever fashion mounts said probe in the exhaust gas stream.

20. A method of sensing the temperature of high-temperature, high-velocity gases in an exhaust gas stream using an optical gas temperature sensor, comprising the steps of:

(A) providing a high temperature optical probe for the optical gas temperature sensor, the probe including;

(i) a support means for mounting the probe for interaction with the high-temperature, high-velocity exhaust gas stream;

(ii) a generally conical hollow tip for insertion into the exhaust gas stream, the tip being formed of a ceramic selected from the group consisting of silicon carbide and silicon nitride to emit electromagnetic radiation at the high temperatures to be sensed;

(iii) a joint physically interconnecting the support means and the tip, the joint being formed and of a material to accommodate the thermal stresses caused by differences in thermal coefficients of expansion between the tip, the joint and the support means and the mechanical stresses caused by the interaction of the probe and the exhaust gas stream during high velocity movement of the exhaust gas stream past the tip, thereby to enable said probe to withstand both the thermal and mechanical stresses; and

(iv) means supported n the probe to focus and transmit electromagnetic radiation emitted from the tip to the sensor to effect a measurement of the temperature of the exhaust gas stream;

(B) directing the exhaust gas stream past the tip of the probe to sense the temperature of the exhaust gases.

21. The method of claim 20 wherein the support means in a cantilever fashion mounts the probe in the exhaust gas stream.

22. A method for sensing the temperature of high-temperature, high velocity exhaust gases in an engine exhaust gas stream, using an optical gas temperature sensor, comprising the steps of:

(A) providing a high temperature optical probe for the optical gas temperature sensor, the probe including;

(i) a support means for positioning the probe in the high-temperature, high-velocity engine exhaust gas stream;

(ii) a hollow, generally conical tip formed of a sapphire-free ceramic having a high flexural strength, a high oxidation resistance, a high thermal shock resistance, and a low thermal response time constant selected from the group consisting of silicon carbide and silicon nitride, which ceramic emits infrared energy related to the temperature of the exhaust gases proximate said tip;

(iii) a joint physically interconnecting the support means and the tip and formed and of a material capable of withstanding the mechanical stresses caused by the interaction of the probe and the exhaust gas stream during high velocity movement of the exhaust gas stream past the tip and having a thermal coefficient of expansion to accommodate the mismatch in thermal expansion between the tip, the joint and the support means, the material being selected from the group consisting of molybednum and an alloy of iron/nickel/cobalt/manganese, the joint being connected to the tip by a high temperature braze;

(iv) a lens positioned proximate the joint to focus the infrared energy emitted from the tip; and

(v) an optical fiber positioned proximate the lens to transmit the focused infrared energy to a detector for providing a measurement of the temperature of the gases in the exhaust gas stream; and

(B) directing the exhaust gas stream past the tip of the probe to sense the temperature of the exhaust gases.

23. The method of claim 22 wherein the support means in a cantilever fashion mounts the probe in the exhaust gas stream.