Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FUEL SUPPLY AND CONTROL S~'STEM FOR COMPRESSION IGNITION ENGINES
sack~round:
This invention relates to compression ignition engines
or what are commonly known as diesel en~ines,which are conven-
tionally designed to operate by thecompression ignition ~
an appropriate diesel oil fuel; and to the design orconversion
of such engines so as to be operable with an alternative
~uel either in full substitution of the diesel oil fuel oth-
erwise employed~or at least in the substitution of a major
part of such diesel oil fuel~during normal operating condit-
ions of the engine.
These proposals have been made for the employment
of gases and liquid alcohol fuels as alternatives for spark
ignition internal combustion engines and compression ignition
or 'diesel' engines; and whilst considerable success has
been achieved ~ith the employment of gaseous and liquid alco-
hol fuels as alternative fuels for spaxk ignition engines,
and success to a lesser degree has been achieved with the
gas conversion of diesel engines, proposals for operating
diesel engines on a liquid alcohol fuel have not achieved
the same degree of success. The ability to convert diesel
engines to successEully and efficiently operate on an alcohol
Euel such as a methanol is affected by the fact that such
alcohol fuels do not spontaneously ignite in the combustion
chamber of a t~pical diesel engine. This problem may be
overcome by modification of a diesel engine to provide for
spark ignition of fuel in a supplementary small combustion
chamber connected to a main combustion chamber of a diesel
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2a203~7
engine; but problems have arisen in development of this system
and the system does involve substantial modifications to
the basic engine and associated component design, and the
adoption o~ such a system as a whole is not considered at
present to be a viable commercial proposition.
Prior Art
An alternative recently developed system Eor diesel en-
gines has involved the proposal to employ a pilot fuel such as
an ether having a wider inflammability ran~e and lower ignitior.
temperature than the principal alternative alcohol fuel, and
this system forms the basis of the present invention.
Re~erence is made to United States Patent Ser.~o 4,422,42
(Norton - assignor to A.E.C.I.Limited)which relates to a device
for converting an alcohol to an ether when fitted to a com-
pression ignition engine,.the device comprising a heat exch-
anger having an inlet to receive the alcohol and an outletin communication with thè inlet end o~ a catalytic conversion
chamber which contains a catalyst for conversion o~ an alcohol
to an ether. The conversion chamber has an outlet pipe to
lead the ether to a cylinder of a compression ignition engine.
~lcohol is fed ~rom a storage tank along lines and direct
to the cylinder and also along a line to a heat exchanger.
Surnmar~ o~ Invention
Whilst the theoretical aspects disclosed in the speci-
fication o~ this European patent application are basically
sound, it is considered that the speci~ication and device
disclosed does not go ~ar enough in providing a practical
solution to e~fective and e~icient operation of a diesel
engine on alcohol fuel, and it is an object of the present
invention to provide further developments which are believed
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to render the operation of a diesel engine on a alcohol fuel
such as methanol a practical and commercially viable proposi-t-
ion. Other and more particular objects and advantages of
the present invention will become apparent ~rom the ensuing
5 description.
According to this invention therefore, there is provid-
ed a ~uel supply system for an internal combustion engine
of the compression ignition kind and having liquid fuel
injection means for injecting fuel into each combustion
chamber of the engine, said system comprising a supply source
of liquid alcohol fuel as the principal fuel, a main fuel
supply line from said supply source coupled to the fuel
injection means for supply of the principal fuel to the
engine, a source of supply of an ether pilot fuel having
a wider flammability range and higher cetane number than
the principal fuel, and delivery means for delivering pres-
cribed quantities of said pilot fuel to the engine via a
condensation extraction means which removes at least part of
any readily condensible content of the pilot fuel prior to
delivery to the engine and mixing with inlet air in the com-
bustion chamber of the engine, said pilot fuel reacting with
air in the combustion chamber to ignite under compression to
raise the temperature oE the fuel mixture therein and enable
initiation and acceleration oE ignition under compression of
said principal fuel on injection.
Preferably, the system provides that the engine is
adapted or designed to operate on up to 100% alcohol fuel,
and whilst a separate source of the pilot fuel can be provi-
ded it is prefera~le that the pilot fuel be manufactured
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by a conversion of a proportion of the principal alcohol
fuel. Thus, the system may additionally include a secondary
fuel supply line from the main or a further supply source
of the principal alcohol fuel coupled to the pilot fuel
delivery means for directing a proportion of said principal
fuel to a reactor conversion device for at least partial
conversion to an ether pilot fuel.
In another aspect of the invention there is provided
a method of operating a single or multi-cylinder internal
combustion engine of the compression ignition kind and having
liquid fuel injection means for injecting fuel into the or
each combustion chamber of the engine, comprising the steps of:
a. providing a supply source of a liquid alcohol fuel
as the principal fuel for the engine and feeding said
principal fuel via a main supply line to said fuel in-
jection means for injection into the engine.
b. bye-passing a quantity of the liquid alcohol fuel
to a reactor conversion device for the production o
an ether pilot ~uel having a wider flammability range
and higher cetane number than the principal ~uel
c. subjecting the ether pilot Euel to a condensation
process for the removal o:E at least a part o~ any
readil~ condensible content Erom the ether pilot fuel,
ancl delivering prescribed quantities o~ said at least
partly separated ether fuel to the engine combustion
chamber(s) for ignition under pressure on the com-
pression stroke of the engine and prior to injection
of the liquid alcohol principal fuel, to enable initiat-
ion and acceleration of combustion of said principal
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fuel during at least initial starting and/or low load
operating phases of the engine.
In a further aspect there is provided a method operating
a single or multi.-cylinder internal combustion engine of the
compression ignition kind and having a liquid fuel injection
means for injecting fuel into the or each combustion chamber,
comprising the steps of:
a. providing a supply source of a liquid alcohol
fuel as the principal fuel for the engine and feeding
said principal fuel via a main supply line to said
fuel injection means for injection into the engine
b. bye-passing a quantity of the liquid alcohol fuel
to vapourising and reactor conversion means for the
production of alcohol fuel vapourand ether pilot fuel,
said ether pilot fuel having a wider flammability range
and higher cetane number than the principal fuel
c. subjecting the ether pilot fuel and alcohol fuel
vapour to a condensation process for the removal of at
least a part of any readily condensible content from the
ekher pilot fuel and alcohol fuel vapour,and delivering
prescribed quantities of the ethe~ pilot fuel and alcohol
fuel vapour to the engine combustion chamber~s)for
igni.tion under pressure on the compression stroke of the
engine and prior to injection of the liquid alcohol,
principal fuel, to enable initiation and acceleration o~
combustion of said principal fuel during at least initial
starting and/or low load operating phases'of the engine
and to provide additional energy to the engine in addition
to the said principal fuel under other load operating
phases.
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Drawings
Some preferred aspects of the invention will now be
described by way o~ example and with reference to the accom-
panying drawings, in which:
FIGURE 1 is a schematic diagragm illustrating one first
fuel supply system in accordance with the invention
FIGURE 2 is a similar s~ematic diagrammatic view ill~
ustrating a modification of the invention,
FIGURE 3 is a further similarsche.matic diagrammatic
view illustrating a further modification or variation of
the invention, and
FIGURE 4 is a further schematic diagrammatic view
illustrating a modification of the pilot fuel supply means.
Description of Invention
Referring firstly to figure 1 of the drawings, the
invention is particularly applicable to a typical compression
engine or diesel engine 1 of the single or multi-cylinder
kind with a reciprocating piston for each cylinder; with
an injector pump 2 driven directly or indireatly by the
engine 1 for the delivery of prescribed quantities o~ operat-
ing fuel to the respective combustion chamber(s) defined
by the cylinder(s) and piston(s). In a kypical diesel engine,
the normally provided injector pump 2 is directly connected
via a variable speed fuel delivery pump 3 to the diesel
fuel oll supply tank and is readily capable of handling
the fuel flow requirement, whereas with the employment of
an alcohol such as methanol ~of lower calorific value and
lower cetane number than diesel fuel) as the principal fuel,
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a considerably greater injection pump capacity must be pro-
vided to cope with such requirement. Having regard to
the nature of an alcohol such as methanol, it is also pre~er-
ably desirable to provide supplementary lubrication for
the injector pump (lubrication in the normal course o~ events
being provided by the diesel fuel); and thus lubricating
oil may be injected into the system by means of a suitable
metering pump 5 (electrically or engine driven)pumping pres-
cribed quantities of oil from an oil supply source or tank
6 to the input side o~ the methanol delivery pump 3 for
mixing with the methanol delivered to the injector pump
2 from the supply tank 4.
As previously indicated, whilst a separate source
of pilot ether fuel can be provided for supply to the engine
1, pre~erably the main source o~ the methanol or other prin-
cipal alcohol fuel is provided with a secondary or by-pass
fuel line 7 which passes a ~uantity of the methanol to a
controllable pilot fuel pump 8 (which can be electrically
driven or driven directly or indirectly mechanically by
the engine 1 e.g. by any direct or indirect couplin~ means)
such that the rate of operation of the pilot fuel pump 8,
and thus the ~uantity of fuel pumped thereby,is controlled
and made to vary with the rate o~ delivery of the injected
fuel and/or with the engine speed. The outlet line 9 from
the pilot fuel pump 8 is directed to a reactor or converter
device 10 in the form of a heated or heat exchanger device
having a catalytic conversion chamber containing a catalyst
for conversion of methanol fed thereto by way of the outlet
line 9 ~o an ether fuel having a greater or wider in~lamm~
ability range than the incomin~ methanol ~uel. Preferably,
the methanol fuel ls converted to a dimethylether (DME) which
may be readily mixed with the inle-t air ~or the engine l to
ignite under compression and initiate combustion o~ the
methanol injected in the diesel engine l.
Methanol can be readily converted to DME at moderate temper-
atures over a suitable dehydration catalyst, and the convers-
ion device disclosed in the aforementioned United States
Patent Ser.No. 4,422,412 or any other suitable reactor,
conversion device or ether generator,can be employed. It is pre-
ferable that the heat exchanger catalytic converter 10need not
require excessively high temperatures to operate, as one
pre~erred means o~ providing the heat for the heat exchanger
is by way o~ utilisation of the exhaust outlet system or
line 11 for the engine, the reactor or ether generator (heat
exchanger catalytic converter) 10 being arranged to be direc-
tly coupled to the exhaust line 11; and a study has found
that an inexpensive alumina catalyst can achieve good con-
version rates of methanol to DME at temperatures as low
a 250C to~OOC. Heat and mass transfer calculations indicatethat only a small part o~ the heat energy available in the
diesel engines exhaust system 11 is re~uired to power a
continuous DME reactor.
The reactor or ether generator 10can alternatively be
separate from the exhaustand beelectrically heated, but the
: existing exhaust system 11 ofthe engine1provides a convenient
source of otherwise wasted heat and obviates the continuing
electric power draw-off of a reactor or generator converter
heated and operated solely by electricity.
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It will be appreciated of course tha-t there will be
no available exhaust heat for operation of the reactor or con
verter ~Owhencoupled to the exhaust system11when the engine1is
started from cold; and there are optional cold starting
systems involving,for example:
(a) Maintaining a supply of diesel fuel ~or the engine1and
using such supply for start up in the usual manner passing,
the diesel oil fuel to the engine1 by way of the injector pump2;
followed by a switching over to methanol operationand operation
10 of the reactor converter 10 for supplementary supply of ether
or DME pilot fuel to the engine1 when the exhaustsystem 11 has
reached the desired temperature for effective operation of
the reactor converter'10.
(b) A separate supply of pre-formed ether or DME can be
' 15 provided for initial mixing with the engine inlet air, followed
by a switching over to the methanol supply line 7 to the pilot
fuel pump 8 and reactor ~,converter 10 again once the exhaust
system 11 has reached the desired temperature sufficient to
operate the reactor converter 10.
(c) The reactor converter,10 canbe provided with a supplementary
electrical heating element for initial warm-up and operation
for conversion of the methanol to ether or DME, with the exhaust
system~11t~king over the heating and conversion operation again
on reaching the desired temperature. This system is however
not favoured (except perhaps in the case of a stationary engine
and the ability to employ mains electric power), as in~the case
of a motor vehicle there would be an undesirable electric power
draw-of~ ~rom the battery prior to starting; and also a time
delay in starting of the engine 1.
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(d) Alterna-tively and as illustrated in -figures 1 to 3,
a methanol burner device 12 can be employed, fed by a
suitable methanol by-pass line 13 from the main feed line
4a from the methanol supply source and by way of a cold
start solenoid valve 14. The burner 12 being coupled to
or associated with the exhaust system 11 at or adjacent
the reactor converter 10 so as to provide initial high
temperatures to the exhaust 11, and thus reactor converter
10, for operation as required in providing the e-ther or
DME in operation of the engine 1. The burner device 12
may burn other fuels.
In the process of supply of the bye-passed quantity of
methanol or liquid alcohol fuel to the reactor converter device
10, and the conversion of some of that bye-passed fuel to the
ether or DME pilot fuel, the heat exchanger will create water and
methanol vapour (or other liquid alcohol fuel vapour) con-
taining the ether or DME pilot fuel; and figure 1 illustrates a
direct line 15 for passage of vapourized methanol and diethyl or
dimethyl ether ~rom the reactor converter 10 to the inlet air
system or manifold of the engine 1. ~Iowever,for moree~ective and
eficient operation it i5 preferred that at least a part of any
condensate or readily condensible content of the vapour is re-
moved from the pilot fuel prior to passing into the engine 1, to
enable rapi~ reaction during compression with the air in the
respective combustion chamber, and raising the temperature of the
injected methanol sufficiently to ignite under compression.
Accordingly, and with reference now to figure 2 of the drawings,
in one arrangement a liquid separator unit 16 is interposed in
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the output line 15 from the reactor converter 10 to separate
out at least a part o~ the suspended liquid and readily con-
densible content from the DME vapour supplied to the engine 1.
The separator 16 can be of various kinds and may simply provide
for membrane filtration, or alternatively provide for ~ractional
distillation, dessication or centrifugal separation. The liquid
and condensate separated out thereby can be discharged by way
of a by-pass line 17 into the engine exhaust system 11 at the
outlet or downstream side of the reactor converter 10, and thus
provide an added advantage in assisting cooling of the exhaust
system 11 at the outlet side without affecting the heat required
for operation of the heat exchanger forming part of the reactor
converter 10. Alternatively, the extracted water and condensate
(which may contain some methanol or alcohol fuel content) can be
directed to a separate storage tank for possible further treat-
ment;
In operation of the~reactor converter 10, not all of the
methanol directed thereto by way of the pilot fuel pump 8 will
at all times be converted to the preferred dimethyl ether pilot
fuel or a readily combustible (under compression) DME, methanol
and water, vapour mix; and as a preferred alternative to the
separator 16 arrangement mentioned with reference to figure 2 of
the drawings, as shown in Eigure 3 o~ the drawings a condenser 18
is employed in place of the water separator 16 and arranged to
be operab.le so as to provide direct or partly direct DME gas or
vapour mix to the engine 1 by way o:E a first line 19, and any
excess unconverted liquid methanol and extracted condensate can
be directed via a eecond line 20 to the injector pump 2 for mixiny
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with the principal methanol alcohol fuel to be injected thereby
to the engine cylinder combustion chamber(s).
Nonnally, the employment of an alternative fuel supply system
and apparatus for operation of diesel engines on a liquid alcohol fuel
such as methanol will in many instances involve the requirement to make
some modification to or adjustment of the fuel injector pump, or
to provide an alternative specially designed injector pump, so
as to be capable of accommodating the larger volume (when com-
pared with the volume of diesel oil fuel providing the same power
output - methanol having in the region of about half the calorific
value of diesel oil fuel) of methanol or other liquid alcohol fuel
to be employed as the pr:Lncipal fuel. llhe degree of charge will
of course be dependent upon the nature and required operations of
the engine conc erned, and minimal change to the fuel injection
pump may be in order where optimum performance of the engine is
of no real concern. For example, in a stationary engine set-up
with the engine arranged to normally operate at a substantially
constant speed or within a substantially constant or limited
speed range, a simple increase in the standard injector pump 2
maximum rack opening position is likely to be sufficient compen-
sation for the reduced calorific value of mathanol when compared
; with diesel oil; but for higher speeds a more complete retuning
of the injection system may be required.
However, in most cases optimum engine performance is
desirable (sometimes even essential), and another object of the
present invention is to enable the Euel supply system and apparatus
described and illustrated to be adapted and employed in a manner
enabling optimum, or near optimum, performance of an engine under
all (or at least a wide range of) operational phases without the
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requirement for costly fuel injection pump modiEication or
construction. The following involve further preferred appli-
cations of the invention.
As previously mentioned the excess or liquid ~lethanol
and/or condensate extracted by the condenser 18 can be introduced
to the liquid methanol principal fuel line for direct injection
therewith to the engine 1. The latter method of disposing of
and usefully using the methanol or alcohol vapour has been found
to be advantageous to engine efficient. As a development of this
aspect it has been found that, if, instead of passing all of the
methanol or alcohol fuel vapour (after condensation) to the engine
1 by way of the liquid fuel injectors 2, a controlled proportion
of the methanol or alcohol fuel vapour be directed with the
appropriate proportion of dlmethyl ether into the inlet air for
the engine 1, it can be more advantageously employed to supplement
the energy input of the principal liquid fuel. In this case the
dimethyl ether vapour combined with the methanol or alcohol vapour
initiate and accelerate the combustion of the principal liquid
fuel through their prior ignition and combustion in addition to
supplementing the energy input.
Whilst it is envisaged that the ether pilot fuel and
desired additional fuel vapour can be separately produced and
delivered to khe inlet air line for the engine, as the ether pilot
fuel is derived by conversion from the vapourised ~uel it is more
convenient and economical to utilise the same reactor converter
device 10 (which will operate at between 250 to 400 degrees centi-
grade - usually at about 300 degrees centigrade) and control
the proportion of ether pilo-t fuel formed relative to the re-
maining vapour; so that ether pilot fuel and methanol (or other
alcohol) vapour mix can be delivered as one by way of the ether/D~E
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pilot fuel line 15) for mixiny and combusti~n with the inlet air
in assisting rapid and efficient combustion of the injected liquid
methanol or alcohol princlpal fuel, and reducing the actual
quantity o~ principal fuel required to be injected for optimum
engine performance. This method and reduction in quantity of
principal fuel to be injected enables efficient engine operation
without the need for expensive change or modification of existing
diesel fuel injection pumps, or the provision of a custom designed
methanol or alcohol liquid fuel injection pump.
A convenient method of removing water from the pilot ether
or DME fuel produced by the reactor converter device 10 without
removing or causing unnecessary condensation of the methanol or
. alcohol vapour, is by employment of the condenser 18 as described
with reference to figure 3 of the drawings, and controlling the
condenser temperature and pressure within appropriate prescribed
limits - as methanol (or other alcahol) and water have different
condensation characteristics, the desired water separation from
the ether/DME pilot fuel and the provision of controlled quantities
of methanol or alcohol vapour is readily achievable by appropriate
temperature/pressure control. Other methods of achieving the same
separation of water from the ether/DME pilot fuel and methanol/
alcohol vapour can be employed eg as described wi.th re~erence to
figure 2 of the drawings, the separator 16 can employ absorbtion
filtration techni.ques.
The optimum proportion of methanol/alcohol fuel vapour
relative to the ether/DME pilot fuel in the pilot stream~ or line
; 15, and as delivered to the inlet air side of the engine 1,
can be simply controlled by setting the mass of catalyst in the
reactor converter device 10, as required together with adjustment
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to condensation conditions in condenser 18 - as the mass of the
reactor catalyst is reduced for any given flow rate of incoming
liquid methanol/alcohol fuel delivered by way of the bye-pass
line 7 and delivery pump 8, so the proportion of un-reacted
methanol/alcohol to ether/DME pilot fuel in the outlet stream
or line 15,19 is increased. In a typical arrangement, an input
of one kilogram of methanol to the reactor converter device 10
operating at about 300 degrees centigrade will produce a pilot
fuel vapour in the approximate proportions 0.3 kilogram Methanol,
0.2 kilogram water and 0.5 kilogram DME - this vapour can be
cooled by the condenser 18 to about 20-60 degrees centigrade
for extraction of the readily condensible water and methanol
content of the vapour.
The methods of operation of a compression ignition
engine in accordance with the present invention, and employment
of the system and apparatus described, are particularly
; applicable for smooth and efficient operation under such as low
load and/or speed phases (and/or during warm up stages), as
well as for generally obtaining optimum performance from the
engine; but it will be appreciated that with a hot engine and
high speed operations, the principal liquid methanol or other
alcohol fuel may be readily combustible and at least reasonably
efficiently employed without the need ~or initiated and
accelerated combustion by prior introduction of the ether/DME
pilot fuel, by itsel or in combination with the unconverted
methanol/alcohol vapour. Smooth and efficient operation of a
compression ignition engine throughout all stages or phases of
operation is, however, not readily attainable utilising only
liquid methanol or other alcohol fuel as the principal fuel; and
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the present invention overcomes this problem and additionally
avoids the need for special high capacity fuel injection pump
provision or changes.
In providing a self contained system providing for
'cold starting' of an engine, it is preferred to employ the
previously referred to system or method (b) of providing a
separate supply of preformed ether or DME pilot fuel for initial
mixing with the inlet air prior to switching over to the system
providing for production of the pilot fuel from the bye-passed
methanol or other alcohol fuel for ongoing operation. Another
development of the invention comprises the addition to the
previously disclosed apparatus of a pilot fuel storage vessel
and a pressure control valve in the pilot fuel delivery lines
15 and 19 from the reactor converter 10 to the water separator
16 or condenser 18; to enab'le collection and storage of a
quantity of the ether/DME pilot fuel produced during operation
of the engine and alternative fuel conversion system, for'use
in subsequent starting or re-starting operations (particularly
when no exhaust heat is available for the reactor converter 10).
The accompanying drawing in figure 4 diagrammatically
illustrates one form of this further pilot fuel supply develop-
ment. The pilot fuel bye-pass pump 8 delivers liquid rnethanol
or other alcohol fuel to the reactor converter 10, which is
heated as before by any suitable means (eg by a burner 12 or
by exhaust heat) to the desir~d temperatur,e range of between 250
and 400 degrees centigrade for the production of methanol/
alcohol fuel vapour, and at least partial conversion to ether or
DME, ~or delivery on to a cooler or condenser 18; which is set
to operate at the desired pressure and/or temperature required
to allow condensation and separation out of at least part of the
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condensible portion of the ~uel vapour (within which the
ether~DME pilot fuel is embodied). The extracted condensate
may be variable according to requirements and operating corldit-
ions and/or the kind of en~ine involved, and could involve
a small part or a major part o~ the condensate content of the
vapour passed to the condenser 18.
The separated or partly separated vapour fuel is then
passed by way of delivery line 19 to a substantially sealed
pressure vessel 24 through upper inlet and outlet connections
25, 26, and on through a pressure control valve 27 to the
engine for mixin~ with the inlet air for combustion during
operation as previously described. The pressure control valve
isset above the vapour pressure of the cooled ether or DME
pilot fuel and methanol (or other alcohol) and at a level allow-
ing pilot fuel and vapour delivery to the engine as required.
The vessel 24 is thus pressurised so that ether/DME pilot fuel
and vapour delivered thereto from the cooler/condenser 18 will
condense to liquid 28 within the vessel 24, and at least some
can be stored for subsequent use in starting or re-starting
the engine after stopping. The ether/DM~ pilot fuel can be
hled off through the outlet connection 26 as required by the
engine by lowering the set-point of the pressure control valve
27 to below the vapour pressure of the stored liquid pilot fuel
28, and allowing such liquid pilot Euel 28 (retained in the
liquid state under pressure) to flash off back to a vapour.
Mixing of the pilot fuel in the inlet air system of the
engine 1 can be simply by way of a spud type gas mixer coupled
to the engines inlet duct.
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For further efficiency in operation, over wide ranges
of engine speeds and loads, it may be desirable to provide for
regulation and boosting of the engine combustion chamber
temperatures to specific ranges above those normally maintained
for operation of the engine l using diesel fuel as the principal
fuel, to further assist and stabilise the ignition and combust-
ion of the methanol with a minimum supplement of the ether pilot
fuel. This will be particularly applicable follo~ing initial
starting up and when operating under light load conditions
and/or low engine speeds, when the temperatures within the
combustion chamber(s) may not reach the desired range necessary
to enable effective or efficieint burning of the methanol fuel.
Accordingly, boosting of gas temperatures inside the combustion
chamber(s) can be effectively obtained by providing an inlet
air throttling valve 21 in the inlet air line or duct 22 to
regulate the volume of air (and thus its cooling effect) fed
to the engine; and/or an exhaust gas throttle valve can be
provided in the engine gas exhaust sytem (provided in addition
or as an alternative to the inlet air throttling valve 21) to
enable raising and regulation of exhaust gas temperatures
suffficiently high to maintain operation of the pilot fuel
generator or converter lO. The inlet throttling valve 21 is
preferably arranged to be automatically regulated eg by electric
servo, bimetal control or other temperature sensitive means
controllable directly or indirectly by way of a temperature sensor
device ~3 coupled to the enyines exhaust system 11 in cl~ose
proximity to the engines exhaust valves and manifold assembly.
~ny similar or other suitable means can be provided for control
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of an exhaust throttle valve when fitted.
Further modifications for most effective operation under
a wide range of engine speeds and loads, as may be required
in particular in vehicle operation, can include the installation
of further cylinder head and oil temperature control devices,
and a methanol or other alcohol ~uel recirculation system to
prevent vapour lock in the injection pump 2. In more
sophisticated engine systems electronics can be employed for
the close control of principal alcohol fuel and/or pilot fuel,
whereby such supply is subject to control according to engine
loading and/or speed; but generally speaking the provision of
the basic equipment comprising the controlled pilot fuel pump
8 for determining substantially precise pilot fuel requirements
fed to the reactor converter 10 and engine 1, the catalyst
or ether generator 10 and the provision of a condensate separator
16 or condenser 18 and means controlling the supply of drier
or dry DME and fuel vapour to the engine 1 in prescribed
quantities with the inlet air, will.enable employment of the
normally provided engine and associated components without major
modifications and with sufficient efficiency to enable employment
of up to 100% methanol as the main operation fuel and without
the need to provide a separate main supply for diesel fuel. The
provision for inlet air and/or exhaust gas throttling involves
no major change to existing inlet and exhaust systems and is thus
a desirably incorporated feature facilitating effective operation
under light loads by maintaining gas exhaust temperature~s above
250 degrees centigrade.
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In the basic forms of the invention and under cold start
and initial warm up conditions, up to 60% (in ener~y value)
pilot ether fuel may be necessary for operation of the engine;
but during normal optimum operating conditions, and with the
preferred aspects of the invention the proportion (in energy
value) of the pilot fuel required may be as low as 1%.
It will thus be seen that the present invention can
be readily appli.ed to existing vehicles or machinery (station-
ary or moving) employing compression ignition engines normally
designed to operate on diesel fuel, with standard "kit-set"
componentry; and/or new vehicles and machinery employing com-
pression engines for operation on methanol as described can be
provided at relatively little.additional costs, and with ~iable
monetary savings and gains in operating costs with the generally
lower costs of methanol and other alcohol fuels - without loss in
efficiency in operation and with the further added advantages of
methanol or other alcohol fuel employment involving clean burning
. with less air polution, and also longer engine life under most
operating additions, when compared with conventional diesel
oil use.
The aforegoing description has been primarily directed
to the employment of methanol as the principal liquid alcohol
fuel, and it will be appreciated that any of the components
o~ the described system referred to as involving or using
methanol will be similarly arranged (with or without modification
as may be appropriate) to involve or use any other similar and
suitable alcohol fuel alternatively employed as the principal
alcohol fuel.
.
~2~3~7
-21-
Some preferred aspects of the invention have been
described by way of example and with reference to the
accompanying drawings, but other variations of and modifications
to the invention can take place without departing from the
scope of the appended claims.
; 15
~.
~ 20
