Abstract:
A gas separator system for providing contaminant-free engine crankcase gas to a gas analyzer. The system has an inlet member for receiving the crankcase gas from the engine and an oil separator for separating at least a portion of the contaminants from the crankcase gas. A pump is arranged to draw the crankcase gas through the inlet member and move the separated crankcase gas to the gas analyzer.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of United States Provisional Patent Application Serial Number 60/296,313, filed Jun. 6, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates generally to an apparatus for measuring the level of gaseous pollutants in the crankcase of an internal combustion engine. More particularly, the apparatus continuously separates particulates and lubricating oil from crankcase gas to facilitate measuring gaseous pollutants of interest.  
         DESCRIPTION OF THE RELATED ART  
         [0003]    Designers of internal combustion engines strive to reduce levels of pollutants generated in the engine. One carrier of pollutants is blow-by gas in the crankcase. This gas is typically recirculated by a Positive Crankcase Ventilation (PCV) system into the intake manifold of the engine where the gas flows into the combustion chamber to be burned. In order to optimize the design of the PCV system, it is desirable to measure, in real time, the level of pollutants in the blow-by gas. Once the level of pollutants is known it is possible to make changes to the engine control system, engine components and the PCV system to reduce pollutant levels.  
           [0004]    One method of indirectly measuring pollutant levels is to perform a spectral analysis of oil used in the engine. With this method, the engine is operated under a prescribed operating condition for a specified period. At the end of the period, a sample of the engine oil is subjected to a spectral analysis that exposes the level of contaminants in the oil. The pollutant level in the blow-by gas is then inferred from the results of the spectral analysis and knowledge of the prescribed operating condition to which the engine was subjected. While the spectral analysis test is used by engine designers, it has two shortcomings. The first shortcoming is the time needed to produce measurements of pollutant levels. A typical specified period can be 10,000 miles of operation in an automobile. With such a long test period, engine designers are limited to running a few tests before an engine design must be ready for production. Second, the spectral analysis test only provides indirect information on the aggregate level of pollutant levels in the blow-by gas. The test does not provide pollutant levels as a function of time. This leaves the engine designer guessing what mode of engine operation produces the worst pollutant level.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    Accordingly, one aspect of this invention is to provide a system for facilitating measurement of pollutant levels in the crankcase gas of a running engine.  
           [0006]    In accordance with this aspect, the present invention provides a gas separator system for providing contaminant-free engine crankcase gas to a gas analyzer. The system has an inlet member for receiving the crankcase gas from the engine and an oil separator for separating at least a portion of the contaminants from the crankcase gas. A pump is arranged to draw the crankcase gas through the inlet member and move the separated crankcase gas to the gas analyzer.  
           [0007]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a pneumatic diagram of the apparatus;  
         [0009]    [0009]FIG. 2A is side view of the oil separator and standpipe assembly with a cross section of the oil separator housing;  
         [0010]    [0010]FIG. 2B is a front view of the oil separator and standpipe assembly; and  
         [0011]    [0011]FIG. 3 is an example of crankcase gas data. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]    [0012]FIG. 1 shows a pneumatic diagram of an engine crankcase gas sampling system  1 . The system is generally constructed as a test fixture for use in an engine dynamometer cell, but may also be constructed as a piece of portable test equipment or incorporated into a vehicle. A vacuum pump  2  provides vacuum at intake  3  for drawing a continuous stream of blow-by gas through a probe  4  in the crankcase of the engine  6 . The direction of the continuous stream is indicated by arrows drawn on the lines interconnecting components of the system  1 . In an exemplar embodiment, the pump  2  is a four-head diaphragm type to provide a sufficient vacuum level with a minimum magnitude of pressure pulsations in the system  1 . At the point the probe  4  is connected to the engine  6 , the blow-by gas is contaminated with particulate matter, light (&lt;C 4 ) and heavy (&gt;=C 5 ) hydrocarbons, and engine oil in liquid and vapor phases. The contaminated blow-by gas is drawn by the vacuum through the probe  4  and into the standpipe  8  and oil separator  10 . The standpipe  8  and oil separator  10  together separate a substantial portion of the liquid and vaporous oil from the blow-by gas. The gas velocity in the standpipe  8  is low enough to allow the separated oil to drip down the inside wall of the standpipe  8  and reenter the engine  6  via the probe  4 .  
         [0013]    At the output of the oil separator  10 , the blow-by gas and oil vapor flow out through a nipple  12  and on to an optional coalescer  14 . While not required, the coalescer  14  operates to separate additional liquid oil from the stream flowing out of the oil separator  10 . Depending on the level of liquid oil entering the system through the probe  4 , using the coalescer  14  to further lower the level of liquid oil may assist in extending the service interval of a downstream coalescing filter  16 . If the coalescer  14  is not used, a simple fluid conduit may be interconnected between the nipple  12  and the input of the coalescing filter  16 .  
         [0014]    The coalescing filter  16  removes any remaining liquid and most, if not all, of the particulates from the contaminated blow-by gas. Any remaining oil vapor can be removed at a later stage by a condenser  18  (if used) and a hydrocarbon (HC) trap filter  20 . Upon leaving the coalescing filter  16 , the sampled blow-by gas is clean of particulate matter, liquid oil and a substantial amount of vaporous oil. The clean blowby gas is then vacuumed into the pump  2  and expelled therefrom at an outlet pressure into the optional condenser  18 . The flow rate and pressure of gas at the outlet of the pump  2  should be matched to the input requirement of a chosen gas analyzer  22 . This match may be performed with regulator arrangement  19  at the inlet to the gas analyzer  22 . Also at the outlet of the pump  2  is a pressure relief valve  24 . The pressure relief valve  24  prevents excessive pressure from accumulating between the output of the pump  2  and the input to the gas analyzer  22  in the event the condenser  18 , HC trap filter  20  or related plumbing become plugged. The relief pressure of the pressure relief valve  24  should be set greater than the outlet pressure of the pump  2 . In an exemplar embodiment, a relief pressure of 25 PSIG is used with an outlet pressure of 15 PSIG.  
         [0015]    The condenser  18  is desirable if, after passing through the coalescing filter  16  and pump  2 , the clean blow-by gas still contains a level of vaporous oil that may prematurely clog or destroy the HC filter  20 . If the condenser  18  is used, a condenser temperature in the range of approximately thirty-two to forty degrees Fahrenheit should be sufficient to remove remaining traces of oil vapor from the blow-by gas. In an embodiment where the condenser  18  is omitted, it may be replaced with a simple fluid conduit interconnecting the output of the pump  2  to the input of the HC trap filter  20 .  
         [0016]    The blow-by gas enters HC trap filter  20  prior to being pumped into the gas analyzer  22 . The HC trap filter  20  removes the heavy hydrocarbons from the blow-by gas. Upon exiting the apparatus at the outlet of the HC trap filter  20 , the blow-by gas has been filtered of contaminants and is in a condition for the gas analyzer  22  to accept and measure. Typical types of gas analyzers  22  used to analyze the blow-by gas include C 0   2  and NO x  analyzers.  
         [0017]    Continuing to refer to FIG. 1, components are shown to facilitate purging the separated contaminants from the system  1  after a test is performed. To purge the system  1 , an external compressed air source is attached at the purge air connector  26 . In an exemplar embodiment, the compressed air source is regulated to about 40 PSIG. Purging commences by opening of solenoids SV- 1 , SV- 2 , SV- 3  (if the coalescing sump is used), SV- 4 , and SV- 5  (if the condenser is used.) With the solenoids opened, the regulated shop air flows through SV- 1  into a first tee  28  and through SV- 2  into a second tee  30 . Purge air from the first tee  28  flows in a reverse direction through the coalescing filter  16  and, if used, the coalescing sump  14 . Oil and residual blow-by gas are pushed by the purge air out of the coalescing filter  16  and through solenoid SV- 4  to an exhaust system  32 . A portion of purge air from the first tee  28  continues to flow in a reverse direction to the coalescing sump  14 , where the sump  14  is purged through open solenoid valve SV- 3 . Purge air also flows through the oil separator  10  and standpipe  8 , thereby returning oil trapped in those components to the engine  6 .  
         [0018]    Purge air from the second tee  30  flows in a reverse direction through the HC trap filter  20  and the condenser  18 , if it is used. Purge air coming through the condenser  18  passes through the open solenoid valve SV- 5  and into the exhaust system  32 . Some purge air also moves forward toward the attached gas analyzer  22 .  
         [0019]    The exhaust system  32  collects the purge air from solenoid valves SV- 4  and SV- 5  (which is included only when the condenser is used) and passes the collected air through a separator  34 . The separator  34  collects contaminants into a bowl that must be periodically emptied. Clean air is exhausted into the atmosphere after being processed by the separator  34 .  
         [0020]    An important consideration in using the apparatus is the rate at which the pump  2  draws vacuum to pull crankcase gas through the probe  4 . It is undesirable to have the apparatus draw gas at a rate high enough to have a material effect on the PCV flow rate in the engine  6 . A suggested guideline is to limit the system  1  to drawing gas at a rate less than 10% of the rate blow-by gas is produced by the engine  6 . To achieve this limited flow rate, a flow control valve  48  may be inserted in the inlet stream of the pump  2 . In an exemplar embodiment, the flow control valve  48  is set to a flow rate of eight standard cubic feet per hour (SCFH).  
         [0021]    Turning now to FIG. 2A, the standpipe  8  is shown together with a cross-section of the oil separator  10 . The cross section is taken along section line  2 A- 2 A of FIG. 2B. The standpipe  8  has the oil separator  10  at an outlet end and may have a probe connector  36  attached at a probe end. Stainless steel has been found a suitable material for the standpipe  8 .  
         [0022]    As shown in FIG. 2B, the outlet end of the standpipe  8  is closed, and a hole  38  is formed in the wall of the standpipe  8  at a location such that the hole  38  is contained within the oil separator housing  40 . The hole  38  should be formed as close to the edge of the oil separator housing  40  as possible so that oil flows from the separator  10  into the hole  38  and then down the standpipe  8  to the engine  6 . The oil separator housing  40  is loosely filled with a fibrous material  42  such as woven copper mesh.  
         [0023]    In operation, the standpipe  8  and oil separator  10  assembly is placed in a generally vertical position with probe connector  36  at the bottom. Gas drawn from the crankcase probe  4  enters the standpipe  8  and travels upward towards the oil separator  10 . Oil in the crankcase gas accumulates on the interior wall of the standpipe  8  and drips back down to the engine  6 . At the top of the standpipe  8 , the gas may still contain engine oil vapor and some oil in liquid phase. The gas enters the hollow interior of the separator housing  40  via the hole  38  in the wall of the standpipe. The gas then flows through the fibrous material  42  and out through the nipple  12 . Oil vapor condenses onto the fibrous material  42  while the gas flows through it. The condensed oil wicks out of the fibrous material  42  and is drawn by gravity to the lowest portion of the separator housing  40  where it drips though the hole  38  and back into the engine  6 .  
         [0024]    A trade-off should be considered when choosing the dimensions of the standpipe  8  and separator housing  40 . A longer standpipe  8  and more voluminous separator housing  40  will be more effective at removing liquid and vaporous oil than shorter and smaller ones, respectively. However, the larger parts will undesirably increase the propagation delay of crankcase gas through them.  
         [0025]    Turning now to FIG. 3, a graph is shown with an example of C 0   2  pollutant data taken from blow-by gas. The blow-by gas was analyzed using a C 0   2  gas analyzer  22 . The vertical axis  44  of the graph represents crankcase C 0   2  concentration in percent and the horizontal axis  46  represents time in minutes. In this graph, the engine  6  was running at 1200 RPM from the first through the sixth minute, at 1600 RPM from the seventh through the twelfth minute, 2000 RPM from the thirteenth minute to the nineteenth minute and at 3600 RPM from the twentieth through the twenty-sixth minute of the test. Load on the engine  6  was varied at each minute interval and the gas flow rate was allowed to stabilize through the system  1 . At the end of each minute, the gas analyzer  22  produced a data point. The test was repeated several times as is indicated by the legend of FIG. 3.  
         [0026]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.