Note: Descriptions are shown in the official language in which they were submitted.
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Vehicle Fuel Tank Arrangement
The invention relates to a vehicle fuel tank arrangement.
Motor vehicles have a petrol tank of sufficient capacity
to provide a source of fuel for an acceptable mileage
range. Saloon passenger cars, for example are normally
produced by the manufacturer with a fuel tank having
typically 30 to 80 litres of capacity to provide an
acceptable range before refuelling is necessary.
Where vehicles have been designed or modified to run on
compressed natural gas the size of the gas tank has to be
larger than the equivalent size petrol tank to provide
the same range. The size, for example, could be 3.8
times that of the petrol tank, assuming the stored
compressed gas is at a pressure of 200 bar.
If a gas tank equivalent in size to the petrol tank is
utilised then this would provide only a range of about
26% of the petrol equivalent tank.
Because of the cylindrical construction of the gas tank
which is of a substantial size, it is typical that this
is housed in the boot/trunk of the car, so reducing the
carrying capacity of the car.
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The present invention is concerned with providing an
adequate storage capacity whilst keeping dimensions low.
According to the invention there is provided a
combination vehicle fuel tank arrangement including a
first tank portion for receiving and storing a first
combustible liquid fuel and a second pressurised tank
portion for receiving and storing a second combustible
gaseous fuel under pressure.
Preferably the first portion is configured to at least
partially surround the second portion to allow the second
portion to be protected from impact by the first portion.
According to a further aspect of the invention there is
provided a fuel tank for a combination fuel vehicle
including a first tank portion for a first combustible
liquid and having a region defining a location for
receiving and retaining a second tank portion capable of
storing a second combustible gas fuel under pressure, the
first tank portion at least partially surrounding the
second tank portion when located to act as a support and
as a buffer against impact damage.
Preferably the first tank region includes a location
which is at least partially concave to accommodate a
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cylindrical second tank portion.
Further according to the invention there is provided a
method of providing fuel storage for a dual fuel vehicle
comprising the steps of providing a first fuel tank
portion for receiving and storing a first combustible
liquid fuel and providing a second pressurised tank
portion for receiving and storing a second combustible
gaseous fuel under pressure.
The invention will now be described by way of example
with reference to the accompanying drawings in which:
Figure 1 shows a standard known petrol tank mounted
between the rear wheels of a car;
Figure 2 shows a standard known petrol tank mounted
between the front and rear wheels of a car, but towards
the rear of the car;
Figure 3 shows one embodiment of the combined tank of the
invention;
Figure 4 shows a second embodiment; and
Figure 5 shows a third embodiment.
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The petrol (gasoline) tank 3 of Figure 1 is mounted
beneath the vehicle by means of several mountings 5 in
known manner, two of which are shown. The tank is
positioned between the rear wheels 1 but behind the axle
line. The boot or trunk houses the spare wheel 2. A
petrol filling point 4 is provided to replenish the tank.
The tank capacity is shown as 40 litres.
In a second version, for a larger vehicle, a 60 litre
petrol tank is shown in Figure 2 which is mounted by
mounts 5 so as to extend from a region in front of the
rear wheels 1 towards the front of the car in a position
beneath the car floor over which the rear seats 2 are
mounted.
It is seen that the shape of the tank is not uniform but
is contoured to fit in the available space.
Petrol tanks, fitted by the vehicle manufacturer, are
moulded to shape usually in a plastic material and can be
made in almost any profile to fit the available space
under the vehicle. They store the petrol in liquid form
but will accommodate any liquid vapour pressure
associated with the fuel storage.
In order to deal with the requirements of a dual fuel
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vehicle, the existing tank is replaced by a combination
tank 20, as shown in figure 3 and the new tank includes
a petrol tank portion 3 which partially surrounds a gas
tank 6. The overall dimensions of the original petrol-
tank are thus not substantially altered and this allows
the hybrid tank 20 to fit within the space which would
have been occupied by the 40 litre tank of Figure 1.
The petrol region of the hybrid tank 20 includes a
concave well or recess 26 for receiving the cylindrical
gas tank 6. The resilient nature of the moulded tank 3
allows the wall portions 22 and 23 to grip the inserted
gas tank 3 (in a jawlike action). The tank 3 serves as
a buffer to any impacts in use. The interior portion 25
of the petrol tank, beneath the gas tank, still allows
passage of petrol arriving within the smaller region 27
to reach the larger region 28 from the filling point 4.
The petrol in use will be removed under pump action (not
shown) from a suitable exit point in the tank, as in
earlier systems.
In this example, the hybrid tank now has a petrol tank
capacity of 28 litres and a gas tank capacity of 12
litres, allowing the vehicle to operate on dual fuels
without the need to sacrifice large areas of vehicle
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space, typically within the vehicle storage area.
Hence the petrol capacity will be substantially retained
and the volume displaced by the gas tank will only cause
a small reduction in the combined fuel range. This will
provide the optimum fuel density, for the 'gas + petrol'
operation, within the permissible space. The small
cylindrical gas tank is of sufficiently robust
construction to store the pressurised gas in a quantity
useful for small averyday journeys.
Although the liquid fuel is described as petrol, it could
be diesel or other liquid hydrocarbon fuel.
The gas tank 6 could be recharged regularly, e.g.
overnight, to provide an adequate supply for 30-35 miles
round trips with the 17 litre tank providing a petrol
equivalent of 4.5 litres, for a saloon car.
The gas tank 6 may be made from steel either in
heavyweight section or alternatively of lightweight
section for reduced cost and mass. The latter is
assisted by relying on the underlying protection afforded
by the petrol tank 3. Drawn steel, externally reinforced
along the cylindrical section by over wrapping with
fibreglass material, can also be utilised. These steel
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tanks require protection from water entering the tank and
causing corrosion. Aluminium tanks are an alternative if
fully wrapped with carbon fibre. Non metallic tanks
could be employed using a non permeable polyethylene
liner fully wrapped with carbon fibre. An important
consideration with non metallic reinforced tanks is that
they will expand and contract with changing internal gas
pressure and are more vulnerable to impact damage if
knocked. The configuration of the tanks assists in
protecting the gas tank from impact damage.
Although more costly, non metallic tanks are more
lightweight and less vulnerable to corrosion. The small
capacity of tank 6 helps to keep costs down.
The tank mountings 5 and petrol filling point 4 are
retained enabling the combined tank to be supplied to the
vehicle manufacturer without requiring any changes to the
manufacture of the vehicle underbody. By surrounding the
gas tank with the petrol tank, the gas tank is protected
from impact damage as the gas tank 3 sits within the well
or recess 26 within the petrol tank and also is located
beneath the vehicle body which provides topmost
protection. This particularly important where a non
metallic composite gas tank is used.
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In the Figure 4 arrangement, the hybrid tank 20 replaces
that of Figure 2 and is mounted as before in front of the
axle line of the rear wheels 1 under the body floor
beneath the rear seats 2.
The 60 litre petrol tank is replaced by a 50 litre petrol
tank and the gas tank 6 is now provided with a capacity
of 17 litres. The original mounting points 5 are
employed making fixing and accommodation straightforward
and the overall a::ternal dimensions of the hybrid tank
are not significantly different to the petrol only tank.
The gas filling point 7 on the exterior of the vehicle
body is shown connected to the gas tank 6 via a cartridge
type dryer 8 which contains a desiccant material to
remove any moisture from the high pressure gas when using
a steel tank. It is intended that the dryer cartridge
can be replaced at normal vehicle service intervals.
In a further embodiment shown in Figure 5, the hybrid
tank is such that the cylindrical gas tank 6 is elongate
in the vertical rather than horizontal plane, but once
again the petrol tank partially surrounds the gas tank to'
retain the gas tank and provide protection to the
embedded gas tank. Although of shorter length, the
increased width of the tank still overall gives a
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capacity of 17 litres for the gas, the petrol tank being
of 40 litres.
It would also be possible to provide a configuration
where the petrol tank also cushions the gas tank from
above by providing a circular aperture in the petrol tank
to allow the cylindrical gas tank to be inserted through
the opening. The gas tank would be retained with the
assistance of the resilient nature of the petrol tank
wall abutting the gas tank wall.
The gas tank described in the embodiments could be
designed to be withdrawn from the hybrid tank to allow
periodic integrity checks to be made.
Whichever arrangement is used, the design of the tank is
such that as the volume of the petrol surrounding the gas
tank falls, there is adequate passageway for the petrol
to reach the fuel offtake pipe at the bottom of the tank.
Such a hybrid tank provides dual fuels in sufficient
quantities to provide capacity for typical daily trips as
shown in the following chart.
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Typical Tank Capacities
and Refill Frequencies
Vehicle Size Small Medium
'Petrol Only' Tank Litres 40 60
Capacity
Petrol Capacity in Litres 28.6 42.9
Combined Tank
Gas Capacity in CombinedLitres of Petrol 3 4.5
Tank* Equivalent
Total Capacity in Litres of Petrol 31.6 47.4
Combined Tank Equivalent ~
Reduction in Petrol Litres 11.4 17.1
Capacity
's 28.5 28.5
Reduction in Combined 21 21
Fuel Capacity
Typical Vehicle Mileagekm/annum 16,000 20,000
Fuel Consumption km/litre 12.5 11
'Petrol Only' ForecourtRefills/annum 40 38
Refills*
Typical Mileage on Gas**km/annum 9,750 12,870
Combined Tank ForecourtRefills/annum 22 19
Refills**
Reduction in Forecourt % 45 50
Refills**
* When filled with natural
gas at 200bar pressure
** Assuming petrol tank
is refilled when fuel
level is down to
20o capacity
*** Assuming vehicle
is used 5 days per
week and gas tank is
emptied once per day
Overnight gas refuelling provides a easy mechanism to
maintain gas capacity.
Typically, between 2 to 4kg of gas (3 to 6 litres petrol
equivalent) will be supplied overnight depending upon the
vehicle size and gas tank capacity. The above table
indicates the reduction in fuel capacity for a combined
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tank verses a petrol tank of similar external volume.
Some of this capacity could be retained in vehicles where
there is space to enlarge the combined fuel volume.
If a 60 litre, 'petrol only' tank is replaced by a
combined tank having the same external shape and volume
but containing 3kg of gas (4.5 litres petrol equivalent),
the reduction in fuel storage (equivalent petrol) will be
about 12.5 litres (210). The reduction in actual petrol
storage will be 28.5. G~hilst more forecourt refuelling
stops would be required on long daily journeys, when used
predominantly for short daily journey, forecourt
refuelling would be significantly reduced by overnight
home refuelling with gas. For the examples given, daily
journeys of less than 35 miles could be achieved without
the use of petrol.
