Gas sensor housing for use in high temperature gas environments

An apparatus and method for packaging and operating a gas sensor for use in high temperature gas environments. A gas sensor can be configured, which includes a sensor element and a housing in which the sensor element is located. A parallel gas path can be configured form said housing, wherein said parallel gas path is based on the natural differential pressure with respect to the velocity of said gas. The parallel gas path is preferably vertical to provide a sufficient friction to soot particles compared to the gas, such that when a partial quantity of said gas reaches said sensor element, said soot particles are avoided by said sensor element.

TECHNICAL FIELD

Embodiments are generally related to gas sensors. Embodiments are also related to sensor housing systems and methods. Embodiments are additionally related to gas sensor housings for use in high temperature gas environments.

BACKGROUND OF THE INVENTION

Many different types of gas sensor housings or units have been implemented in environments containing corrosive gases. In this type of situation, the gas sensor housing can be operatively connected to a central station to form a gas sensing signaling system or device. In the context of automotive exhaust gas applications, in order to reduce the automotive emission levels it is of prime importance to measure the constituents of exhaust gas (e.g., NOx, So2, CO, CO2, etc). In industrial applications, the ability to monitor and detect gas is also of primary importance.

In order to protect industrial plants or installations, pipe conduit channels, chemical storage areas and so forth, against fires and also to prevent humans from being exposed to toxic gases, it is desirable to detect at an incipient stage, dangerous concentrations of combustible or noxious gases. In response to such detection, it is then possible to initiate suitable counter measures, for instance shutting down operating installations, which are improperly functioning, closing off leaking pipe conduits, starting ventilators or other exhaust apparatus, opening emergency exits and otherwise signaling the occupants or personnel of the need to leave the area. In this manner fires, explosions, toxic effects and other damage may be prevented. Thus, In order to detect undesired and dangerous concentrations of oxidizable or combustible gases, gas sensing signaling or alarm systems composed of gas sensing units can be implemented, which are connected with a central station.

A typical gas sensing unit contains a gas sensor which, when exposed to the action of reducible gases, alters its electrical resistance. In terms of physical construction, electrochemical gas sensors usually include some type of external housing, which acts as a reservoir for an electrolyte. A wick may be utilized to keep the electrolyte in contact with the electrodes. External electrical terminals are also often provided, which make electrical contact with the electrodes. Many commercially available gas sensors are of the amperometric type having two or more electrodes in which a catalytically active metal is fixed to a porous substrate.

In one prior art gas sensor design, a planar sensing element can be immobilized in gas-tight fashion, by way of a sealing element, and implemented in a pass-through component of an exhaust-gas-side lower ceramic shaped element. The exhaust-gas-side ceramic shaped element can possess, on the end surface and facing away from the exhaust gas, a recess that surrounds the pass-through and into which a glass seal is introduced. A further ceramic shaped element is then joined via a metal solder join to the housing on the glass seal. The glass seal encloses the sensing element inside the recess, and constitutes a gas-tight join between ceramic shaped element and sensing element at this point. One of the problems with this type of gas sensor configurations is that the effect of high temperatures causes errors in the functionality of the sensor system.

Another type of gas sensor configuration includes the use of a sensor element that is fixed in a tubular, metallic housing in a gas-tight manner. At its lower part, the tubular housing contains a lip facing radially outward and which forms a sealing flange. Such a gas sensor can be mounted in an opening of an exhaust system, with the lip sitting on a sealing seat formed in the opening. A banjo bolt can be led over the housing and screwed into a thread arranged in the opening, thereby joining the lip to the exhaust system in a gas-tight manner. Problematic in this design is, however, that the pressing or upsetting of the relatively thin-walled material of the housing can produce micro-cracks at the lip, which can cause the housing to leak.

O2(oxygen), NOx(nitrogen oxide), NH3(ammonia), SOx(sulphur oxide), CO (carbon monoxide) and CO2(carbon dioxide) sensors are used in automotive exhaust gas pipes in most gasoline and diesel engines to control pollution and improve combustion performance. Exhaust gas contains soot particles and unburned carbon, which can damage the sensors and erode the sensor element. The sensing element of such sensors can be exposed to a very high temperature of the exhaust gas (excess of 500 C). The sensing element utilized in such sensors may also be directly exposed to high flow velocity of the exhaust gas . . . Prior art sensors, however, do not achieve such parameters.

Prior art sensors are subject over a period of time to errors that can increase due to drift, etc. Additionally, at the temperatures described above, such sensors degrade rapidly. Based on the foregoing, it can be appreciated that designing gas sensors to function at these temperatures is a precise and costly endeavor. Hence to overcome the effect of soot and high temperature, an innovative packaging concept is proposed as described in greater detail herein.

BRIEF SUMMARY

It is, therefore, one aspect of the present invention to provide for an improved sensor system and methods.

It is another aspect of the present invention to provide for an improved sensor housing method.

It is a further aspect of the present invention to provide for a better gas sensor housing for use in high temperature gas environments.

The aforementioned aspects and other objectives and advantages can now be achieved as described herein. An apparatus and method for packaging and operating a gas sensor for use in high temperature gas environments are disclosed. A gas sensor can be configured, which include a sensor element and a housing in which the sensor element is located. A parallel gas path can be configured form the housing, wherein the parallel gas path is based on the natural differential pressure with respect to the velocity of the gas. The parallel gas path is preferably vertical to provide a sufficient friction to soot particles compared to the gas, such that when a partial quantity of the gas reaches the sensor element, the soot particles are avoided by the sensor element.

A plurality of fins can be configured from the housing, wherein during an operation of the gas sensor, the temperature of the gas is reduced by providing cooling of the gas through the plurality of fins, thereby improving a performance and a life of the gas sensor, thereby permitting the sensor element to function as a lower temperature sensor element for high temperature applications.

The sensor element can be housed in the parallel gas path, which is located sufficiently away from a main exhaust gas stream. To achieve the parallel flow path, the natural draft differential pressure due to the velocity of gas can be established with a suitable packaging design. This path is preferably vertical in order provide sufficient friction to the dense particles (e.g., soot) compared to gas. Hence, when a partial quantity of gas reaches the sensor element, soot particles can be avoided. Also, during this long travel path, the temperature of the gas can be reduced due to the fins located on the sensor housing which are exposed to air flow. The gas sensor can be designed such that the temperature of the gas under steady state will be approximately 300° C. to 400° C., when main stream exhaust gas temperature is around 900° C. Such features assist in providing a stable, low cost, reliable gas sensor for high-temperature exhaust gas environments.

The gas sensor system disclosed herein can thus be utilized to measure the concentration level of the constituents of an exhaust gas and feed the levels back as feedback to a central station.

DETAILED DESCRIPTION

Referring now to the drawings and in particular toFIG. 1, a perspective view of a gas sensor100for use in high temperature gas environments is illustrated, in accordance with a preferred embodiment. The sensor100includes a by-pass tube102formed from, for expel, SS (Stainless Steel) material. A hex nut104can also be provided and formed from an SS material. The gas sensor100includes a finned housing106, which can also be formed from an SS material. Gas sensor100also includes a sensor element108formed from a ceramic material. A ceramic tube110and/or potting in ceramic with a specific AR (activity ratio) can also form a part of gas sensor100. A sensor holder112formed from an SS material can also be provided as a part of gas sensor100. Additionally, a cable guide114formed from Teflon can also form part of gas sensor100. The gas sensor100also includes a dowel116, which can be formed from an SS material. Additionally the dowell pin116can be used to orient the by-pass tube102in the direction of flow path, ensuring the flow inlet faces the flow path. A four core cable can also be provided to form an electrical connection with the sensing element108.

FIG. 2illustrates a side view of the gas sensor100for use in high temperature gas environments, in accordance with a preferred embodiment. Note that as indicated inFIG. 2, a double crimping with an “O ” ring202is shown in the side view of the gas sensor100. Note that inFIGS. 1-5, identical or similar parts or elements are indicated by identical reference numerals. The sensor100includes a by-pass tube102formed from an MS (mild steel) material. A hex nut104can also be provided and formed from an SS material. The gas sensor100includes a finned housing106, which can also be formed from an MS material. Gas sensor100also includes a sensor element108formed from a ceramic material. A ceramic tube110and/or potting in ceramic with a specific AR (activity ratio) can also form a part of gas sensor100. A sensor holder112formed from an SS material that includes a double crimping with an “O” ring202can also be provided as a part of gas sensor100. Additionally, a cable guide114formed from Teflon can also form part of gas sensor100. The gas sensor100also includes a dowel116, which can be formed from an SS material. Four core cables may also be provided to implement an electrical connection with the sensing element108. Additionally, the dowell Pin116can be utilized to orient the by-pass tube102in the direction of the flow path, thereby ensuring that the flow inlet faces the flow path.

FIG. 3illustrates a top view C-C of the gas sensor100depicted inFIGS. 1-2for use in high temperature gas environments, which can be implemented in accordance with a preferred embodiment. The gas sensor100includes a finned housing106, which can also be formed from an SS material. Gas sensor100also includes a sensor element108formed from a ceramic material. A ceramic tube110and/or potting in ceramic with a specific AR (activity ratio) can also form a part of gas sensor100. A sensor holder112formed from an SS material can also be provided as a part of gas sensor100. Additionally, a cable guide114formed from Teflon can also form part of gas sensor100. The gas sensor100also includes a dowel116, which can be formed from an SS material. Four core cables may also be provided to form an electrical connection with the sensing element108. Additionally the dowell Pin116can be used to orient the by-pass tube102in the direction of the flow path, thereby ensuring that the flow inlet faces the flow path.

FIG. 4illustrates a side sectional B-B view of the gas sensor100depicted inFIGS. 1,2and3for use in high temperature gas environments, in accordance with a preferred embodiment. A weld is shown in the sectional view B-B of gas sensor100depicted inFIG. 4. The gas sensor100includes a finned housing106, which can also be formed from an SS material. Gas sensor100also includes a sensor element108formed from a ceramic material. A ceramic tube110and/or potting in ceramic with a specific AR (activity ratio) can also form a part of gas sensor100. A sensor holder112formed from an SS material can also be provided as a part of gas sensor100. Additionally, a cable guide114formed from Teflon can also form part of gas sensor100. The gas sensor100also includes a dowel116, which can be formed from an MS material. Four core cables can also be provided to form an electrical connection with the sensing element108. Additionally the dowell pin116can be used to orient the by-pass tube102in the direction of the flow path, thereby ensuring that the flow inlet faces the flow path. The gas in-let402, gas out-let404and the exhaust pipe406is shown in the gas sensor100as the path of gas flow.

FIG. 5illustrates a high-level flow chart of operations depicting logical operational steps of a method500of configuring and operating the gas sensor100for use in high temperature gas environments, in accordance with a preferred embodiment. As depicted at block502, the process begins. Next, as indicated at block504, a sensor element108can be housed in a parallel gas path106, which is sufficiently located away from the main exhaust gas stream. Thereafter, as described at block506, for achieving the parallel flow path, the natural draft differential pressure due to the velocity of gas can be established. Next, as indicated at block508, a sufficient friction can be provided to dense particles (e.g., soot) as compared to gas in the vertical path.

Thereafter, as depicted at block510when the partial quantity of gas reaches the sensor element108the soot particle can be avoided. Next, as described at block512, temperature of the gas can be reduced due to fins106on the sensor housing which is exposed to flow air during the long run. Next as depicted at block514, the gas sensor housing106can be designed such that the temperature of the gas under steady state can be approximately 300° C. to 400° C., when a main stream exhaust gas temperature is approximately 900° C. Finally, as indicated at block516, the stable, low cost, reliable gas sensor100for exhaust gas environments can be finally configured and ready to use.