27-Jun-03030702 B&S ARB Workshop Comments Evaporative Emissions Control Technology – An Engine Manufacturer’s Perspective Two Threshold Design Issues:

27-Jun-03 030702 B&S ARB Workshop Comments

Evaporative Emissions Control Technology – An Engine

Manufacturer’s Perspective

• Two Threshold Design Issues:

– Pressurized Fuel Systems?

– Metal or Treated Plastic Tank?

• Implementation Issues:

– Lead-time for new fuel systems

– Equipment integration issues


Sealed Tank Systems

Fuel Cap 1999 Mazda 626


Sealed Tank System Characteristics

• Tank Pressure Control Valve

• Pressurized fuel tank

• Tank Pressure-Vacuum Relief Mechanism

• Fuel lines and connectors


Tank Pressure Control Valves

• Require dual vent and fuel shut-off valves– Isolate of carburetor from high pressures– Sequential valve actuation – start and hot restart

performance?

• Automatic valve actuation mechanism – Engine brake bail only on WBM– Blade-brake clutch solution?– Other application solution?

• Spatial relations or packaging limitations


WBM Fuel System Spatial Relationships

Brake

Brake

BrakeFuel Tank

Fuel Tank

Fuel Tank

Carburetor

Carburetor

Carburetor

Briggs & Stratton

Briggs & Stratton

Tecumseh


Tank Pressurization Concerns

• Fatigue failure consequences• Crack sprays – increased risk

for uncontrolled liquid fuel release if cracks occur

• Pressurized tanks will be less forgiving under impact conditions

• Tank deformation

5.0 psig spray


Tank Deformation Under PressureQuantum Mod Fuel Tank 498956

Deformation Due to Internal Pressure

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Pressure [psig]

Dis

pla

ce

me

nt

[in

]

Point A

Point B

Point C

Point D

Point E

Point F

Point G


Residual Tank Deformation5 Minutes After Pressure Relief

Quantum Mod Fuel Tank 498956Residual Deformation After Relief of Internal Pressure

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Pressure [psig]

Dis

pla

ce

me

nt

[in

] Point A

Point B

Point C

Point D

Point E

Point F

Point G


Tank Deformation at 3.0 psig


Tank Deformation at 5.0 psig


Automotive Fuel TankPressure-Vacuum Relief Cap


Automotive Fuel Cap (New)Air Flow vs. Gage Pressure

-300

-100

100

300

500

700

-1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50

Pressure (psi)

Flo

w (

sc

cm

)

Stant 11806 CAP034

Stant 11806 CAP035

Stant 11817 CAP036

Stant 11819 CAP037

Pressure –Vacuum Relief Performance


Duckbill - High Pressure Flare Valve Fuel Cap Cracking Pressure Histogram

0

2

4

6

8

10

12

2.2 2.6 3.2 3.6 4 4.6 5.2 5.6 6

Cracking Pressure (psi)

Fre

qu

ency

Note - On some of the caps, the pressure to leak off during the first testing was excessive ( 7-9 psi ), but after retesting the values became more consistent. For these trials, the retest numbers where used in the graph. All caps tested where virgin Walbro -Robin caps with no fuel exposure.

Duckbill - High Pressure Flare Valve

Mean = 3.866 psi Standard Deviation = 0.81 psi Coefficient of Variance = 20.9%

Pressure Relief – 30 Part Population


Pressure Relief – After SoakDuckbill - High Pressure Flare Valve Fuel Cap

Cracking Pressure (Before and After 5 Hour Gasoline Soak)

0

1

2

3

4

5

A B C D E F G

Part ID

Cra

ckin

g P

ress

ure

New Caps

After 5 Hour Soak

Note - 5 psi was the maximum pressure introduced to the caps. After 5 psi was reached, the caps where considered to have no leakoff.

Duckbill - High Pressure Flare Valve


Pressure Relief – Umbrella Valves

Data available Monday, 6/30.

Will show cracking pressure in10 piece population before and after Cert fuel soak.

Umbrella Valve Cracking PressureBefore and After Fuel Soak

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

#01 #02 #03 #04 #05 #06 #07 #08 #09 #10

Valve

PS

I

Before Soak

After Soak

65 hour soak in Cal Ph2 Cert Fuel

+/- 3 Sigma Design Criteria


Pressure-Vacuum Relief Valves Summary

• Commercially available fuel system pressure-vacuum relief valves:– Not binary (leak before relief)– Relief pressures are inconsistent– Fuel exposure affects valve performance


Fuel Hose and Connection Reliability Summary

• Pressurized fuel systems will introduce stresses to fuel system connections– Reduced reliability– Fuel spray possible at failure– Gross-emitters– Operator Risk– Maintenance and Repair Risk


J2260 Tubing and Connectors


Packaging Constraints - Fuel LineWBM Engine – Line Routing and Interferences


Automotive Fuel Cap Warnings

Subaru Forrester

Dodge Neon

Pontiac Montana

Ford Ranger


Automotive Fuel Fill Neck


Small Off-Road Engine Fuel Fill Neck B&S 6.5 Hp Vertical Shaft


Small Off Road Engine Fuel Fill Neck B&S 8 hp Horizontal Shaft


Small Off-Road Engine Fuel Fill NeckM9/10


Vapor Release Management

• Challenges are more acute than those encountered in other industries– Short fill necks– Tight packaging– Thermal management of exhaust and catalyst– Angle of operation – Refueling


Evaporative Controls TestingIndustry Capabilities

27-Jun-03030702 B&S ARB Workshop Comments Evaporative Emissions Control Technology – An Engine Manufacturer’s Perspective Two Threshold Design Issues:

Documents

pressure slide

pressure relief slide

psig slide

soak slide

valve performance slide

psig spray slide

repair risk slide

relief relief pressures