Exhaust sampling system and method for water vapor management
View Patent ↗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.
1. An exhaust sampling system comprising:
a plurality of exhaust sampling system zones, the exhaust sampling system zones including a sampling conduit, a fill circuit, a read circuit, and at least one sampling bag; and
a controller programmed to:
predict minimum dilution ratios to avoid condensation in each of the exhaust sampling system zones; and
run a test procedure in which a sample of exhaust is diluted with make-up gas at a selected minimum dilution ratio that is greater than or equal to a maximum of the predicted minimum dilution ratios.
2. The system as recited in claim 1 , wherein the selected minimum dilution ratio is equal to the maximum of the predicted minimum dilution ratios.
3. The system as recited in claim 1 , wherein the selected minimum dilution ratio is within a range between 1:1 and 10:1.
4. A method of diluting an exhaust sample comprising:
predicting, with a controller, minimum dilution ratios to avoid condensation in each of a fill circuit, a read circuit, a sampling conduit, and at least one sample bag; and
diluting exhaust with a make-up gas, during a test procedure, at a ratio greater than or equal to a maximum of the predicted minimum dilution ratios.
5. The method as recited in claim 4 , wherein the minimum dilution ratio to avoid condensation in the fill circuit DR fill-min is predicted in accordance with:
DR
fill
-
min
≥
W
ex
-
max
W
fill
-
sat
-
W
m
where W ex-max is a maximum expected water concentration in the exhaust during the test procedure, W fill-sat is an expected saturated water concentration to be associated with the fill circuit during the test procedure, and W m is an expected water concentration in the make-up gas during the test procedure.
6. The method as recited in claim 4 , wherein the minimum dilution ratio to avoid condensation in the read circuit DR read-min is predicted in accordance with:
DR
read
-
min
≥
W
ex
-
ave
-
W
m
W
read
-
sat
-
W
m
where W ex-ave is an average expected water concentration in the exhaust during the test procedure, W read-sat is an expected saturated water concentration to be associated with the read circuit during the test procedure, and W m is an expected water concentration in the make-up gas during the test procedure.
7. The method as recited in claim 4 , wherein the minimum dilution ratio to avoid condensation in the at least one sample bag DR bag-min is predicted in accordance with:
DR
bag
-
min
≥
W
ex
-
ave
-
W
m
W
bag
-
sat
-
W
m
where W ex-ave is a maximum expected water concentration in the exhaust during the test procedure, W bag-sat is an expected saturated water concentration to be associated with the at least one sample bag during the test procedure, and W m is an expected water concentration in the make-up gas during the test procedure.
8. The method as recited in claim 4 , wherein the minimum dilution ratio to avoid condensation in the sampling conduit DR samp-cond-min is predicted in accordance with:
DR
samp
-
cond
-
min
≥
W
ex
-
max
-
W
m
W
samp
-
cond
-
sat
-
W
m
where W ex-max is a maximum expected water concentration in the exhaust during the test procedure, W samp-cond-sat is an expected saturated water concentration to be associated with the sampling conduit during the test procedure, and W m is an expected water concentration in the make-up gas during the test procedure.
9. The method as recited in claim 4 , wherein the exhaust is diluted with the make-up gas at a minimum dilution ratio DR CVS-MIN that is determined based on the minimum dilution ratio to avoid condensation in the fill circuit DR fill-min , the minimum dilution ratio to avoid condensation in the read circuit DR read-min , the minimum dilution ratio to avoid condensation in the at least one sample bag DR bag-min , and the minimum dilution ratio to avoid condensation in the sampling conduit DR samp-cond-min as follows:
DR CVS-MIN ≦max(DR fill-min ,DR read-min ,DR bag-min ,DR samp-cond-min ).
10. The method as recited in claim 9 , wherein DR CVS-MIN is within a range between 1:1 and 10:1.
11. The method as recited in claim 4 , wherein the exhaust is diluted with the make-up gas in the sampling conduit.
12. The method as recited in claim 4 , wherein the exhaust is diluted with the make-up gas at a point downstream of the sampling conduit with a mini-diluter.
13. The method as recited in claim 4 , further including predicting, with the controller, a minimum dilution ratio to avoid condensation in the sampling conduit.
14. The method as recited in claim 13 , wherein the exhaust is diluted with the make-up gas at a maximum of the minimum dilution ratios predicted to avoid condensation in the sampling conduit, the fill circuit, the read circuit, and the at least one sample bag.