Abstract:
The disclosure is directed to a method to determine oil consumption in an internal combustion engine that does not require extended operation of the engine in the files and is adaptable to be useful at production facilities for testing of sample engines from the line without installation of the engine into a vehicle and operating the vehicle in order to determine oil consumption of the engine during operating conditions.

Description:
TECHNICAL FIELD 
   The present disclosure relates to a method to determine oil consumption in an internal combustion engine, and preferably in a compression ignition engine, such as a medium- or heavy-duty diesel engine. It has been a long felt need to assess the oil consumption in heavy duty diesel engines before the are sent to the filed in order to assess any possible warranty issues that may occur, or to assess operation of the engine over the life of the engine in a simulated environment. To this end, the engine has a coolant system in fluid communication with the engine, an oil system, with a re-circulating pump, and a piston with an expandable ring fitted to move reciprocally within at least one bore in the engine. 
   It has further been a need to provide for a method to determine oil consumption in a heavy duty diesel engine that does not require extended operation of the engine in the files and is adaptable to be useful at production facilities for testing of sample engines from the assembly line without installation of the engine into a vehicle and operating the vehicle in order to determine oil consumption of the engine during operating conditions. 
   These any other aspects of the disclosure will become apparent upon a reading of the following specification, reviewing the drawings and reading the claims. 
   BRIEF SUMMARY OF THE INVENTION 
   In one embodiment, the present disclosure is related to a method to determine engine oil consumption in an internal combustion engine having a fuel system, a cooling system, at least one piston reciprocally moveable within a piston bore, an oil reservoir in fluid communication with said bore and at least one expandable oil ring circumferentially disposed on said piston, and an exhaust system having an inlet in fluid communication with an engine exhaust manifold, and an outlet to exhaust from said engine. The steps include, 
   fueling the engine during operation for a predetermined period of time to bring the engine oil and coolant temperature to a whole boundary predetermined temperature for a predetermined period of time; 
   ceasing fueling once engine has reached whole boundary condition; 
   motoring the engine on a dynamometer to turn crankshaft at a predetermined range of rpm; 
   measuring hydrocarbon levels at said exhaust outlet for a predetermined period of time determine engine oil consumption. 
   In another embodiment, the present disclosure may include determining that engine whole boundary conditions are reached when the coolant temperature and oil temperature are at a predetermined level. In a more specific application, the whole boundary may be reached when the oil and/or coolant temperature has reached about 80° C. The whole boundary conditions may also be determined by detecting ambient temperature; Δ pressure of CAC, and exhaust gas pressure at predetermined levels for a predetermined period of time. 
   When the engine, in this example a MBE 900 available from Daimler Truck North America, LLC, has reached whole boundary conditions, the fueling is ceased and the engine is motored with a dynamometer to range of from about 1800 rpm to about 2500 rpm, and preferably, at predetermined points in said range such as, for example, about 1800 rpm, 2200 rpm, and 2500 rpm to mimic transient as well as on-highway operating conditions. After about 5-6 minutes of motoring on the dynamometer, the hydrocarbon level is measured in the exhaust gas flow at the exhaust outlet for about 5-6 minutes. It is assumed after the engine has reached whole boundary conditions, any hydrocarbons present when the engine is being motored is the result of oil slipping past the oil rings on the pistons. The detected hydrocarbon level can be quantified and determined as a logarithmic trend over time and may be expressed according to the Equation (1):
 
 HC _ppm( t )=5.028 ln( t )−13.096
         Wherein;       

   HC is hydrocarbon 
   ppm is parts per million 
   t is time in seconds 
   lnt is logarithm over time 
   The mass flow rate of hydrocarbons in the exhaust gas at a given time during motoring may, by use of Equation (1) be used to calculate mass flow rate of hydrocarbons in the exhaust gas at a given time, according to Equation (2): 
   
     
       
         
           
             HC_MFR 
             ⁢ 
             
               ( 
               t 
               ) 
             
           
           = 
           
             
               
                 
                   
                     
                       
                         ( 
                         MW_HC 
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         
                           EXH_MFR 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           kg 
                           ⁢ 
                           
                             / 
                           
                           ⁢ 
                           sec 
                         
                         ) 
                       
                     
                   
                 
                 
                   
                     
                       
                         ( 
                         
                           3600 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           sec 
                           ⁢ 
                           
                             / 
                           
                           ⁢ 
                           hr 
                         
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         
                           1000 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           g 
                           ⁢ 
                           
                             / 
                           
                           ⁢ 
                           kg 
                         
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         3 
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     10 
                     6 
                   
                   ) 
                 
                 ⁢ 
                 
                   ( 
                   MW_EXH 
                   ) 
                 
               
             
             ⁢ 
             HC_ppm 
             ⁢ 
             
               ( 
               t 
               ) 
             
           
         
       
     
       
       
         
           Wherein; 
           MW_HC=MW_C+((HC_ratio)(MW_H)) 
           EXH_MFR is the exhaust mass flow rate in kg/sec and 
           MW_EXH is the molecular weight of the exhaust gas.
 
Generally, in a dynamometer testing cell, the analytical equipment may be calibrated by propane, or some other combustible gas. Preferably, propane is used as a calibrator and, in such a case, Equation (2) is multiplied by HC_MFR(t)=(4.21258)ln(t)−10.9706 g/hr when propane is used as a calibrator.
 
         
       
     
  
   Using the above equation, the accuracy can be verified by inputting time values in sec and comparing them to the data. 
   The mass flow rate of HC at a given time is not a reliable tool to measure the oil consumption during motoring over a period of time, as oil consumption is seen to be time dependent. However, HC_MFR(t) can be integrated with respect to time to gain an oil mass that was consumed over the integration interval. 
   The integration interval was chosen to be 24 hr. or 86400 sec. in order to make a comparison with the Drain and Weigh data. It was reported that using the drain and weight data in a 24 hr. period 778.1 g of oil were consumed. 
   The following definite integral was used. 
                 HC_M   =       ⁢       1   3600     ⁢       ∫   0   86400     ⁢     HC_MFR   ⁢     (   t   )     ⁢     ⅆ   t                       =       ⁢       1   3600     ⁢       ∫   0   86400     ⁢       (         (   4.21258   )     ⁢     ln   ⁡     (   t   )         -   10.9706     )     ⁢     ⅆ   t                             HC_M   =       1   3600     [                 4.21258   ⁢   t   ⁢           ⁢     ln   ⁡     (   t   )         -               t   -     10.9706   ⁢   t             ⁢     ❘   0   86400       =     784.8   ⁢           ⁢   g               
Note that it is necessary to divide by 3600 as the logarithmic model was obtained using a seconds as a time stamp.
 
The result is close to the data from a Drain and Weigh especially if a g/hr. rate is calculated, and verifies the accuracy of the mathematical model used.
 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of an engine in a test cell; 
       FIG. 2  is a schematic representation of a flow chart detailing the step in method for determine oil consumption according to the present disclosure. 
       FIG. 3  is a graph showing the HC emissions during maturing of a heavy-duty diesel engine. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Turning now to the drawings wherein like numbers refer to like structures, and particularly to  FIG. 1 , there is disclosed, schematically, an engine  10  in a test cell  12  having an exhaust gas manifold  14  with an inlet  16  and an outlet  17 . The outlet  17  is in close, fluid communication with the testing apparatus  18 , which include an exhaust gas conduit to keep the exhaust gas outlet in fluid communication with a computer  20 , and a dynamometer  21  controlled by the computer and cooperatively engageable with the crank shaft of the engine, to motor the engine at any engine speed, measured in rpm, desired. The engine has a coolant system  23 , in fluid communication with the engine through conduit  27 . A temperature sensor  29  is in electronic communication  31  with the computer 
   Internally, and not shown, but easily understood by those skilled in the art, the engine has at least on cylinder bore with a piston reciprocally movable therein, Circumferentially positioned on the piston is at least one expandable piston ring. The piston is attached to the crank by a connecting rod as is customary in internal engine design, and is moveable within the bore when the crankshaft is rotated. 
   Turning to  FIG. 2 , there is disclosed a schematic representation of one method  24  to determine the oil consumption of an internal combustion engine. Specifically, step  26  is fueling the engine to operate it for a predetermined period of time and to predetermined operating conditions such that the engine reaches whole boundary condition. To that end, the engine fluids may be measured for temperature to determine whether they have reached a predetermined level. For example, the oil and/or coolant temperature may be measured until is abut 80° C. for a predetermined period of time, which may be about 5-6 minutes of engine fueling operation. In another embodiment, or in addition to the preceding, whole boundary conditions are determined using ambient temperature; Δ pressure of CAC, and exhaust gas pressure are at predetermined levels for a predetermined period of time. 
   Once it is determined that the engine has reached a whole boundary condition, step  28  is ceasing fueling and begin motoring the engine on a dynamometer for a predetermined period of time at a predetermine range of engine speeds. Generally, the dynamometer turns the engine crank at some range of speeds, or at various steady speeds for predetermined periods of time in order to mimic driving conditions that may be expected to occur during service life of the engine in a vehicle. In some applications, it may be desirable to motor the engine with a dynamometer at a range of about 1800 rpm to about 2500 rpm. In other situations, it may be preferable to run the engine for a predetermined period of time at various engine speeds, for example, 1800 rpm, 2200 rpm and 2500 rpm. 
   As the engine is being motored, the exhaust gas outlet is monitored at step  30  for hydrocarbon content. Normally, after the engine has no fuel added to it, on would expect that no or minimal hydrocarbons could be detected at the exhaust outlet. It is assumed that any hydrocarbons that are detected at the exhaust outlet during engine motoring is the result of oil “blowing by” the rings on the pistons during reciprocation within the bore. The hydrocarbons are detected and quantified in a computer at step  32  to determine the oil consumption that may be expected by the engine during normal engine operation. 
   Generally, the engine oil consumption may be expressed as a mathematical relation and may be linear, logarithmic or any other mathematical means to express the loss of mass. When considered as a logarithmic trend over time it may be expressed according to the Equation (1):
 
 HC _ppm( t )=5.028 ln( t )−13.096
         Wherein;
           HC is hydrocarbon   ppm is parts per million   t is time in seconds   ln t is logarithm over time.
 
Equation (1) may be used to calculate mass flow rate of hydrocarbons in the exhaust gas at a given time, according to Equation (2):
   
               

   
     
       
         
           
             HC_MFR 
             ⁢ 
             
               ( 
               t 
               ) 
             
           
           = 
           
             
               
                 
                   
                     
                       
                         ( 
                         MW_HC 
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         
                           EXH_MFR 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           kg 
                           ⁢ 
                           
                             / 
                           
                           ⁢ 
                           sec 
                         
                         ) 
                       
                     
                   
                 
                 
                   
                     
                       
                         ( 
                         
                           3600 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           sec 
                           ⁢ 
                           
                             / 
                           
                           ⁢ 
                           hr 
                         
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         
                           1000 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           g 
                           ⁢ 
                           
                             / 
                           
                           ⁢ 
                           kg 
                         
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         3 
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   
                     10 
                     6 
                   
                   ) 
                 
                 ⁢ 
                 
                   ( 
                   MW_EXH 
                   ) 
                 
               
             
             ⁢ 
             HC_ppm 
             ⁢ 
             
               ( 
               t 
               ) 
             
           
         
       
     
       
       
         
           Wherein; 
           MW_HC=MW_C+((HC_ratio)(MW_H)) 
           EXH_MFR is the exhaust mass flow rate in kg/sec and 
           MW_EXH is the molecular weight of the exhaust gas.
 
Generally such dynamometer testing apparatus&#39; are calibrated prior to testing of an engine to determine operating conditions, It has been determined that if the calibrator is propane, Equation (2) is multiplied by 3.
 
To demonstrate one such determination of engine oil consumption, and not to limit the description given, if it assumed HC_ratio=1.8, and assuming an HC ratio similar to that of diesel fuel,
 
           MW_C=12.011 
           MW_H=1.00794 
           MW_HC=13.8 
           MW_EXH=29 (average molecular wait of non-humid atmosphere), and substituting the above constant rate equation 2, yields
 
 HC   —   MFR ( t )=(0.837708) HC _ppm( t )g/hr  (2)
 
And substituting the above constants into Equation 1 yields
 
 HC   —   MFR ( t )=(4.21258)ln( t )−10.9706 g/hr  (3)
 
         
       
     
  
   Using the above equation, the accuracy can be verified by inputting time values in sec and comparing them to the data. 
   The mass flow rate of HC at a given time is not a reliable tool to measure the oil consumption during motoring over a period of time, as oil consumption is seen to be time dependent. However, HC_MFR(t) can be integrated with respect to time to gain an oil mass that was consumed over the integration interval. 
   The integration interval was chosen to be 24 hr. or 86400 sec. in order to make a comparison with the Drain and Weigh data. It was reported using the Drain and Weight data, that in a 24 hr. period 778.1 g of oil were consumed. 
   The following definite integral was used. 
                 HC_M   =       ⁢       1   3600     ⁢       ∫   0   86400     ⁢     HC_MFR   ⁢     (   t   )     ⁢     ⅆ   t                       =       ⁢       1   3600     ⁢       ∫   0   86400     ⁢       (         (   4.21258   )     ⁢     ln   ⁡     (   t   )         -   10.9706     )     ⁢     ⅆ   t                                     ⁢     HC_M   =       1   3600     [                 4.21258   ⁢   t   ⁢           ⁢     ln   ⁡     (   t   )         -               t   -     10.9706   ⁢   t             ⁢     ❘   0   86400       =     784.8   ⁢           ⁢   g                 
Note that it is necessary to divide by 3600 as the logarithmic model was obtained using a seconds as a time stamp.
 
The result is very close to the data from the Drain and Weigh especially if a g/hr. rate is calculated.
 
     FIG. 3  is a graph showing the HC Emissions during motoring of a heavy duty diesel engine. The data can be seen to have a logarithmic trend and shows 8 hours of 1 Hz HC emissions data during motoring conditions. The x axis is time in seconds, and the y axis is Hydrocarbons in parts per million. It can be seen that when the engine reaches whole boundary conditions and the dynamometer is motoring the engine, the level of hydrocarbons measured 34 is relatively level at about 40 ppm over the time measured, with an anatomy of data at  36 , which is one data point out of sync with the other data points that form the line  34  and is dismissible as such. Thus, it can be seen that by motoring the engine, using the calculations as set forth about, the oil consumption may be determined for the engine prior to placing it in service. 
   The words used in the specification are words of description, and not words of limitation. Many variations and modifications are possible without departing form the scope and spirit of the invention as set forth in the appended claims.