Exhaust Sampling System And Method For Water Vapor Management

Abstract

Disclosed is an exhaust sampling system including a plurality of exhaust sampling system zones. The zones are, at least, a sampling conduit, a fill circuit, and a read circuit. A controller is programmed to predict a minimum dilution ratio to avoid condensation in one of the exhaust sampling system zones. The controller is further programmed to run a test procedure in which a sample of exhaust is diluted with a make-up gas at a selected minimum dilution ratio that is greater than or equal to the predicted minimum dilution ratio. Further disclosed are methods of predicting whether condensation occurs during a test procedure.

What is claimed is: 
     
         1 . A method of predicting whether condensation occurs during a test procedure comprising:
 providing an exhaust sampling system including at least one sample bag;   diluting exhaust from an engine with a make-up gas;   filling the at least one sample bag with a sample of the diluted exhaust; and   determining, during a test procedure, whether condensation occurs in the at least one sample bag based on an integral of water concentration in the at least one sample bag.   
     
     
         2 . The method of  claim 1 , wherein the integral of the water concentration in the at least one sample bag is continually calculated, by a controller, during the test procedure. 
     
     
         3 . The method of  claim 1 , further comprising continuously calculating the integral of the water concentration in the at least one sample bag during the test procedure. 
     
     
         4 . The method of  claim 1 , further comprising monitoring the water concentration as a function of time during the test procedure. 
     
     
         5 . The method of  claim 4 , further comprising determining the integral of the water concentration in the at least one sample bag from a first time at the start of the test procedure to a second time during the test procedure. 
     
     
         6 . The method of  claim 5 , further comprising determining whether there is condensation in the at least one sample bag at the second time based on the integral of the water concentration in the at least one sample bag from the first time to the second time. 
     
     
         7 . The method of  claim 1 , further comprising calculating the integral of the water concentration in the at least one sample bag at set intervals during the test procedure. 
     
     
         8 . The method of  claim 1 , further comprising determining whether condensation is present in the at least one sample bag based on a comparison of the integral of water concentration in the at least one sample bag and a model. 
     
     
         9 . The method of  claim 1 , further comprising determining that condensation in the at least one sample bag is possible when the integral of water concentration in the at least one sample bag is greater than an average water concentration expected during the test procedure. 
     
     
         10 . The method of  claim 1 , further comprising diluting exhaust from the engine with the make-up gas in at least one of a sampling conduit and a mixer disposed downstream from the sampling conduit and upstream from the at least one sample bag. 
     
     
         11 . A method comprising:
 filling at least one sample bag with a sample of exhaust from an engine during a test procedure;   monitoring a water concentration in the at least one sample bag over a period of the test procedure; and   determining a likelihood that condensation is present in the at least one sample bag based on the water concentration in the at least one sample bag over the period.   
     
     
         12 . The method of  claim 11 , wherein the period is at least one second. 
     
     
         13 . The method of  claim 11 , wherein the period is from a first time at a start of the test procedure to a second time during the test procedure. 
     
     
         14 . The method of  claim 11 , further comprising:
 determining an integral of the water concentration in the at least one sample bag over the period; and   determining the likelihood that condensation is present in the at least one sample bag based on the integral of the water concentration in the at least one sample bag over the period.   
     
     
         15 . The method of  claim 11 , further comprising:
 diluting exhaust from the engine with a make-up gas; and   filling the at least one sample bag with a sample of the diluted exhaust during the test procedure.   
     
     
         16 . An exhaust sampling system, comprising:
 at least one sample bag;   a sampling conduit configured to receive exhaust gas from an engine;   a fill circuit configured to direct a sample of exhaust gas from the sampling conduit to the at least one sample bag during a test procedure; and   a controller that:
 monitors a water concentration in the at least one sample bag over a period of the test procedure; and 
 determines a likelihood that condensation is present in the at least one sample bag based on the water concentration in the at least one sample bag over the period. 
   
     
     
         17 . The exhaust sampling system of  claim 16 , wherein the period is at least one second. 
     
     
         18 . The exhaust sampling system of  claim 16 , wherein the period is from a first time at a start of the test procedure to a second time during the test procedure. 
     
     
         19 . The exhaust sampling system of  claim 16 , wherein the controller:
 determines an integral of the water concentration in the at least one sample bag over the period; and   determines the likelihood that condensation is present in the at least one sample bag based on the integral of the water concentration in the at least one sample bag over the period.   
     
     
         20 . The exhaust sampling system of  claim 16 , further comprising at least one of:
 a pump disposed at an outlet of the sampling conduit; and   a mini-diluter in fluid communication with the fill circuit at a location downstream from the sampling conduit and upstream from the at least one sample bag, wherein the controller:
 controls at least one of the pump and the mini-diluter to dilute exhaust from the engine with a make-up gas; and 
 controls the fill circuit to fill the at least one sample bag with a sample of the diluted exhaust during the test procedure.