1340 / 1904
FUEL SYSTEM
1
1. INTRODUCTION:
Compressed Natural Gas (CNG) is widely used as
an alternative fuel in cars for lower emissions and
fuel economy.
In CNG fuel supply system, the CNG is stored in
two high pressure cylinders that is mounted under
driver & co driver seat of the vehicle. The storage
pressure of CNG in cylinder is up to 260 bar.
An electrical cylinder valve is mounted on each of
the cylinder for the delivery of CNG to pressure
regulator.
A filler valve is used for filling CNG in cylinder.
During filling one has to remove filler cap from the
filler valve.
A Low Pressure fuel filter is used in the fuel circuit
located in between Pressure regulator & CNG gas
rail. This unit filters oil & dust from low pressure
CNG & cylinder corrosion to protect the CNG
injectors.
A Pressure gauge is mounted inside the front
bonnet on high pressure line which displays
pressure in the CNG cylinder. High pressure CNG is
carried from the cylinder to the pressure regulator
by SS tube along the under body of the vehicle.
Pressure regulator is a unit that reduces pressure
from CNG tank storage pressure (up to 260 bar) to
4 bar (at gas rail) pressure.
High Pressure (HP) Sensor is fitted on inlet side of
pressure regulator. It monitors the pressure in high
pressure line. In case of any drop in pressure in HP
line is observed, it immediately alerts the GAS ECU
about the leakage and the Gas ECU will not allow
the change over to “GAS” mode. The HP sensor
also sends pressure signal to CNG ECU to show
CNG level inside the cylinder on instrument cluster.
Pressure regulator outlet is connected to LP filter
then to gas rail through a low pressure line. Both the
ends of low pressure line are having spring band
clamp type arrangement.
The Gas rail is fitted with a Pressure & Temperature
sensor and has one inlet and two-outlet
connections.
Two gas injectors are mounted on the inlet manifold
and connected to gas rail through rubber hoses to
gas rail. Through gas injectors, the CNG is injected
inside inlet manifold.
The entire system of vehicle is controlled by a ECU
that is mounted in engine compartment near wiper
motor.
The capacity of CNG tank is 16 liters (of water
capacity) 2 nos and petrol is 15 liters.
The layout of “fuel supply system” and pipe lines
fitment” are shown in this chapter.
The CNG fuel supply system mainly consists of the
following components.
CNG Cylinder
Cylinder valve
Filler valve / Receptacle
Low pressure filter
Pressure regulator
Pressure gauge
High pressure sensor