1. Evaporative Emissions due to EVAP System Malfunctions
Sam R. Reddy, Ph.D.,P.E.
Evaporative Emissions Consulting, Inc.
On behalf of Stoneridge, Inc.
November 6th, 2012
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

2. Evaporative Emission Control System
Purge Vapor (air+HC) to Engine
Normally Closed Purge Control Solenoid
Gasoline
Activated Carbon Canister
Diurnal vapors expelled from the fuel tank consists of HC + Air
Evap canister traps HCs; Air escapes into the atmosphere
During engine operation, the canister is purged/cleaned/regenerated and the vapors are consumed in engine combustion
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

3. Malfunctioning Purge System
No canister purge
Electrical problems
Stuck closed purge valve
Plugged/blocked/broken purge line
Gasoline
No active purging of Evap canister
Passive purging of canister results in 65% diurnal vapor back purge into the fuel tank *
35% of diurnal vapor escapes into the atmosphere *
* EPA Report EPA420-R , “Feasibility of Evaporative Emission Control,” September
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

4. Passive Purging of EVAP canister
(No canister purge due to Purge Malfunction)
35% vapor loss
35oC
Gasoline
65% vapor adsorbed
20oC
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

5. Passive Purging of EVAP canister (Cont’d)
(No canister purge due to Purge Malfunction)
Air
35oC
Gasoline
65% vapor passively purged
During tank cool down
20oC
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

6. Large Leaks in EVAP System
Leaks in the EVAP system
> 1 mm dia leaks
Loose or missing fuel cap
Plugged/blocked/broken vapor line
Gasoline
100% of diurnal vapor escapes into atmosphere
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

7. Diurnal Vapor Generation in Two Representative Cities*
Average Vehicle fuel tank: 50 L (57.5 L total volume); 40% fuel level ** *
For comparison, Euro5 EVAP diurnal vapor generation from 50 L tank is 20.5 grams/day **
S. R. Reddy, “Prediction of Fuel Vapor Generation from a Vehicle Fuel Tank as a Function of Fuel RVP and Temperature,” SAE Paper
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

8. Vehicle Diurnal Vapor Generation in two Representative Cities
(50 L fuel tank; 40% fuel level)
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

9. Vehicle Diurnal Vapor Generation in two Representative Cities
(50 L fuel tank; 40% fuel level)
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

10. Malfunctioning Purge System
(35% diurnal vapor escapes into the atmosphere)
No canister purge
Electrical problems
Stuck closed purge valve
Plugged/blocked/broken purge line
Gasoline
Average summer diurnal vapor generation 11.1 g/summer day
Avg vapor loss into the atmosphere 0.35*11.1 = 3.9 g/summer day
Avg vapor loss into the atmosphere 0.35*7.2 = 2.5 g/avg day
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

11. Large Leaks in EVAP System
(100% diurnal vapor escapes into the atmosphere)
Leaks in the EVAP system
> 1 mm dia leaks
Loose or missing fuel cap
Plugged/blocked/broken vapor line
Gasoline
Average diurnal vapor generation 11.1 g/summer day
Avg vapor loss into the atmosphere 11.1 g/summer day
Avg vapor loss into the atmosphere 7.2 g/avg day
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

12. All EVAP System Malfunctions
(Assume 50% purge malfunctions; 50% large leaks)
Gasoline
Avg malfunction vapor loss into the atmosphere ( )/2 = 7.5 g/summer day
Avg malfunction vapor loss into the atmosphere ( )/2 = 4.9 g/avg day
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

13. Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.
Estimation of Evaporative Emission Inventory due to EVAP Malfunctions - Summer
250,000,000 vehicles in Europe; 60% petrol vehicles
150,000,000 petrol vehicles
1% EVAP malfunctions
(7.5 g/day)*(1,500,000) = 11,250,000 g/day or 11,250 kg/day
10% EVAP malfunctions
(7.5 g/day)*(15,000,000) = 112,500,000 g/day or 112,500 kg/day
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

14. Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.
Estimation of Evaporative Emission Inventory due to EVAP Malfunctions – All Year
250,000,000 vehicles in Europe; 60% petrol vehicles
150,000,000 petrol vehicles
1% EVAP malfunctions
(4.9 g/day)*(365 days/yr)*(150,000,000/100)
2.7 kt/yr or 3,832,500 liters of petrol/yr
10% EVAP malfunctions
(4.9 g/day)*(365 days/yr)*(150,000,000/10)
27 kt/yr or 38,325,000 liters of petrol/yr
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

15. Estimated Evaporative Emission Inventory due to EVAP Malfunctions
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

16. Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.
Solution
A simple low cost OBD leak detection system including canister vent solenoid valve can capture EVAP malfunctions and prevent HC emissions into the atmosphere:
13.5 kt HC emissions per year or 19 million liter petrol loss
(Conservative estimate because running loss emissions are not included)
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.

17. What about Running Loss ?
Running loss vapors are consumed in engine combustion; however,
Purge malfunctions causes running loss emissions through the canister
EVAP system leaks can cause running loss vapor emissions into the atmosphere
Estimation of running loss as % increase in diurnal:
Two trips per day: AM and PM
Ignore the effect of AM trip because it is partially accounted in diurnal vapor generation
PM trip will increase the tank fuel temperature by about 3⁰C
Re-calculate tank vapor generations by incrementing the peak tank temperature by 3⁰C
Tank vapor generation will increase by 40%
EVAP Emissions inventory and fuel loss estimation will increase by up to 30% (assuming running loss occurrence 5 days per week)
Sam R. Reddy, PhD PE Evaporative Emissions Consulting, Inc.