Download - Ngv Fuel Pressure Regulator
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The Natural Gas VehicleFuel Pressure Regulator
By: Jeff Gotthelf, Engineering Manager
ITT Industries / Conoflow
October 28, 2004
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The Functions of a NGV Fuel Pressure Regulator
Reduces CNG pressure from fuel cylinder(s). Inlet from 250 to 3600 psig Factory setting ranges from 30 to 175 psig
Manages gas pressure to engine fuel system. Must respond quickly to changing gas flow Must have very predictable output pressure throughout range of flow, temperature and tank pressure.
Manages varying gas compositions. Discussion of Joule-Thomson effect Requires heat to prevent icing inside regulator Resists damage from compressor oils
Enable options for pressure sensor, HP and LP gas fittings, relief valve connection, etc.
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How Does an NGV Pressure Regulator Work?CONTROL SPRING LOAD
BONNET PRESSURE
PLUG SPRING
DIAPHRAGM
REGULATEDOUTPUT PRESSURE
INLET PRESSURE
GAS FLOW
VALVE SEAT
VALVE
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How Does an NGV Pressure Regulator Work?
ITT Conoflow CNG Fuel Pressure Regulator
CONTROL SPRING
DIAPHRAGM
PLUG SPRINGVALVE
INLET
OUTLET
VALVE SEAT
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Pressure Regulator Flow Performance
REPRESENTATIVE ITT CONOFLOW HPNGV REGULATORGAS FLOW PERFORMANCE CURVES
90
95
100
105
110
115
120
125
0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68Gas Flow Rate
(SCMH)
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250 Psig Inlet500 Psig Inlet1000 Psig Inlet2000 Psig Inlet3000 Psig Inlet
PRESSURE CHANGE DUE TO CHANGING SUPPLY (10 PSI)
OVERALL PRESSUREWINDOW (16 PSI)
Is your regulators performance predictable?
IDLE WOT
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Upstream Restriction
Does your regulator get sufficient gas to operate correctly?
NGV FUEL PRESSURE REGULATOR DISCHARGE250 PSIG FUELCYLINDER PRESSUREWITH / WITHOUT SOLENOID VALVE
70
75
80
85
90
95
100
105
110
0 10 20 30 40 50 60 70 80 90 100 110 120
GAS FLOW (LB/HR)
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WITH COMMERCIALLYAVAILABLE DIRECT ACTING SOLENOID
VALVE RESTRICTION
WITHOUT SOLENOID VALVE
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Response to Changing Flow Requirements
Sudden flow changes (acceleration, deceleration) How fast does regulator need to respond? How quickly does the pressure need to recover? How quickly does regulator need to stabilize?
Do you know what the transient response is for your regulator?
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System Cleanliness / Filtration
Upstream filtration required to protect regulator and remainder of fuel system.
Downstream filtration can be used to protect fuel system from excessive compressor oil, moisture or other contaminants.
Metal particulates can damage regulator valve seat and create internal leakage
Is your system protected from debris?
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Gas Quality Effect on Fuel System
MOISTURE As CNG expands it gets very cold due to Joule-Thomson effect. Moisture in CNG can form ice and hydrate deposits if the equipment is not designed to handle it.
Standards SAE J1616 and ISO 15403 address permissible moisture in CNG for safe use, but not best performance.
COMPRESSOR OIL As gas expands and cools, oil dissolved in gas can drop out and load up system. Excessive compressor oils can cause problems to the fuel system.
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Joule Thomson Effect when CNG Expands
ITT Conoflow HPNGV RegulatorTemperature / Pressure data
50 SCMH Flow, 3000 PSIG Inlet(Pipeline Quality Natural Gas)
-80
-60
-40
-20
0
20
40
60
80
100
120
140
8:25:52 8:27:19 8:28:45 8:30:12 8:31:38 8:33:04 8:34:31 8:35:57
Time (hour:minute:second)
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Outlet Pressure (Psig)
Flow Rate (SCMH)
CNG Inlet Temp (Deg C)
CNG Outlet Temp (Deg C)
Coolant Inlet Temp(Deg C)
Will your regulator still perform correctly when it gets cold?
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Symptoms of Freeze Up
Power or smoothness degrades as vehicle is driven. Vehicle drive ability suffers. Seems to happen more often during warm weather. Problem seems to build up, then fix itself the next time the vehicle is operated.
Problem is intermittent and difficult to diagnose. Service shows downstream pressure faults when problem is present, then fault goes away next time vehicle is started.
May be related to different fueling locations.
Does your fuel system show these symptoms?
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Managing Joule-Thomson Gas Temperature
Engine coolant circulation around critical elements
Coolant circulation control to force convection over large surface areas
Flow bypass to prevent cold gas from freezing against diaphragm
Can your regulator manage chilled gas flow?
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Gas Quality Compressor Oil Carryover
Will your regulator and fuel system function with this much oil?
Example of oil deposits in regulator
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Environmental / Installation Considerations Temperature Excessive heat can cause leaks.
- Keep regulator away from exhaust system
Shock / Vibration can reduce product life. - Mount regulator to vehicle chassis, not engine - Mounting brackets must be rigid.
Is your regulator located and mounted properly?
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NGV Fuel Pressure Regulator Configurations
Regulator can be configured several ways to meet system needs. Basic model Optional items, such as sensor ports, bias ports, sub-assemblies
Base High-Pressure Natural Gas Vehicle regulator
Regulator customized as an assembly with filter, sensor, and fittings
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Conclusion
A robust regulator is an essential component of a safe and reliable NGV fuel system.
It is important to know if the regulator is able to effectively manage NGV fuel system issues such as temperature, vibration, flow changes, supply pressure changes, as well as imperfect gas composition.
Thank You!
For further information, contact me at [email protected]