Chemistry: analytical and immunological testing – Including use of radioactive properties
Reexamination Certificate
1999-11-01
2001-09-25
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Including use of radioactive properties
C073S023310, C073S023370, C436S056000
Reexamination Certificate
active
06294389
ABSTRACT:
TECHNICAL FIELD
This invention generally relates to methods for determining engine oil consumption in internal combustion engines. More particularly, this invention relates to an apparatus and method that employ a furnace for complete combustion of a tracer compound to promote the measurement of oil consumption using laser spectroscopy of a tracer isotopic specie produced by combustion of the tracer compound.
BACKGROUND OF THE INVENTION
For evaluating the performance of an internal combustion engine and the corresponding engine design development, it is desirable to provide dynamic measurements of engine oil consumption during operation of the internal combustion engine. Early methods for determining oil consumption included the use of a dipstick, drain-weigh techniques, sulfur methods and radiometric techniques. However, each of these methods have serious shortcomings, and all fail to provide real-time analysis of oil consumption. Radiometric methods originally employed in the art provided a very precise method for measuring oil consumption through the addition of a radioactive bromine tracer 1,2-dibromooctadecane to the engine oil. With this method, the resultant combustion product from the internal combustion engine is trapped within a sodium hydroxide solution and counted by scintillation counting. Though extremely accurate, this method is undesirable because of the significant radioactive health and safety considerations and regulatory requirements necessary for its use. Another shortcoming is that radiometric methods are essentially batch processes which do not readily lend themselves to individual measurements, and require the preparation of a fresh radioactive bromine tracer for each batch operation because of the short half life of the tracer.
As a solution to the above, U.S. Pat. Nos. 4,990,780 and 5,445,964 to Lee et al., assigned to the assignee of this invention and incorporated herein by reference, provide a method for determining oil and fuel consumption that is relatively simple and precise, enables real-time measurements. Each of these patents teaches the use of nonradioactive tracer compounds, such as bromine in the form of organic bromo-compounds, which are added in small amounts to the engine oil. When combusted in the presence of hydrocarbon compounds in oil and fuel, the bromine constituent of the particular compound is converted into hydrogen bromide (HBr). A sample of the exhaust gases generated by the internal combustion engine and containing HBr is then analyzed within a sample cell, where the gas sample is maintained at a pressure at which a distinction between an absorption line of the tracer specie and the absorption lines of a related isotopic species can be discerned. Monochromatic radiation is then transmitted through the gas sample at the frequency of an absorption line for the tracer specie. Tunable diode laser spectroscopy is preferably used with collimating and collecting optics that are preferably reflective, off-axis parabolic or focusing mirrors. The sample cell is a long-path multi-pass all-reflection absorption cell or a waveguide sample cell to achieve the high sensitivity required for analysis of the extremely minute gas component.
In use, the engine exhaust measurement systems taught by Lee et al. have performed extremely well. However, under some engine operating conditions, the tracer compound has been found to incompletely combust, with the result that HBr is not completely formed and the spectrometer is unable to detect the entire specie in the engine exhaust. Also under some operating conditions, partially burnt products of combustion from the engine exhaust have been found to adhere to the mirrors of the sample cell and render them unusable after a short period of time.
Therefore, it would be desirable if improvements in the teachings of Lee et al. could be achieved by which the exhaust gas of an engine was fully combusted to ensure that gaseous HBr is present and detectable, without undesirably altering the gas sample or the performance of the engine exhaust measurement system.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method by which tracer compounds and combustion products in the exhaust gas of an internal combustion engine are more completely combusted, so that oil consumption of the engine can be precisely and concurrently measured on a real-time basis using tunable diode laser spectroscopy. The apparatus includes what is effectively a furnace capable of more completely burning nonradioactive stable oganobromo compounds and combustion products within the exhaust gas of the engine, without being reactive with the tracer compounds or the resulting tracer gas or isotopic specie.
The apparatus and method of this invention provide an improvement over the teachings of U.S. Pat. Nos. 4,990,780 and 5,445,964 to Lee et al., in which nonradioactive organobromo compounds are added to the engine oil in small amounts in order to yield hydrogen bromide (HBr) as a tracer isotopic specie upon combustion. Exhaust gas passes from the engine into the furnace, where uncombusted tracer, fuel and oil are completely burned as a result of contacting heated internal surfaces that define internal passages within the furnace. According to the invention, the internal surfaces are formed of commercially-pure titanium, such that the exhaust gas is substantially limited to contact with commercially-pure titanium while within the furnace. Also according to the invention, turbulent flow is induced in the exhaust gas within the internal passages of the furnace, and the gas within the passages is heated to a temperature sufficient to combust the compound and yield the desired tracer isotopic specie. Thereafter, a sample of the exhaust gas containing the HBr continuously flows through a sample cell, and is maintained at a pressure within the sample cell where distinction between an absorption line of the tracer specie and the absorption lines of a related isotopic species is discernible. Monochromatic radiation is then transmitted through the gaseous sample at the frequency of an absorption line for the tracer specie. Because of the high spectral power density and spectral resolution of the preferred tunable diode lasers, tunable diode laser spectroscopy is preferably used to measure the trace amount of the resultant HBr in the exhaust gases.
According to the above, the inclusion of the furnace in an exhaust measurement system employing tunable diode laser spectroscopy has been shown to completely combust organobromo compounds within the exhaust gas of an internal combustion engine, as well as any residual fuel or oil combustion products of the engine. The surfaces of the furnace that contact the exhaust gas are required to be formed of material with a high concentration of titanium in order to avoid detrimental chemical reactions with the tracer compounds. Consequently, the furnace is free of any catalysts of the type conventionally used to promote the complete combustion of engine exhaust products. The passages within the furnace preferably include suitable features for increasing the gas contact surface area and turbulent flow of the gas through the furnace in order to render the furnace more efficient.
Other objects and advantages of this invention will be better appreciated from a detailed description thereof which follows.
REFERENCES:
patent: Re. 36171 (1999-03-01), Balling et al.
patent: 4990780 (1991-02-01), Lee et al.
patent: 5129257 (1992-07-01), Carduner et al.
patent: 5211820 (1993-05-01), Poor et al.
patent: 5445964 (1995-08-01), Lee et al.
patent: 5928981 (1999-07-01), Leyrer et al.
patent: 5937641 (1999-08-01), Graham et al.
patent: 5953908 (1999-09-01), Appleby
Gushman Richard William
Vitale, Jr. Joseph Anthony
General Motors Corporation
Plant Lawrence B.
Sines Brian
Warden Jill
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