[0001] This invention relates to a method of deriving mechanical work from combustion gas
in an internal combustion engine by means of a new thermodynamic working cycle and
to reciprocating internal combustion engines for carrying out the method.
[0002] It is well known that as the expansion ratio of an internal combustion engine is
increased, more energy is extracted from the combustion gases and the thermodynamic
efficiency increases. It is further understood that increasing compression increases
both power and fuel economy due to further thermodynamic improvements. The objectives
for an efficient engine are to provide high compression, begin combustion at maximum
compression and then expand the gases as far as possible against a piston.
[0003] Conventional engines have the same compression and expansion ratios, the former being
limited by the octane rating of the fuel. Furthermore, since in these engines the
exploded gases can only be expanded to their initial volume, there is usually a pressure
of 70-100 osi against the piston at the time the exhaust valve opens with the resultant
loss of energy.
[0004] Many attempts have been made to extend the expansion process in internal combustion
engines to increase their thermodynamic efficiency. An early design was described
in the Brayton Cycle engine of 1872 (U.S. Patent No. 125,166). This engine expanded
the combustion gases to their initial pressure but lacked the means of transferring
and igniting the charge while maintaining maximum compression. The Atkinson cycle
engine was devised to extend the expansion process, but this engine was limited by
its mechanical complexity to a one- cylinder configuration.
[0005] A notable attempt was more recently revealed in the Wishart engine, disclosed in
U.S. Patent No. 3,408,811, in which a large piston compressed the charge into a smaller
cylinder which further compressed the charge and then transferred it into another
small "firing" cylinder where the charge was ignited and expanded to the full volume
of the smaller cylinder. It then passed the burned gases through ports uncovered by
the piston into a larger cylinder where it was expanded further. This required four
cylinders with pistons which made two working strokes for each power stroke, hence
it is an eight-stroke cycle engine with all of the mechanical and fluid friction inherent
in such a working cycle. The mechanical complexity of this engine makes it costly
to manufacture.
[0006] In another attempt (Vivian, U.S. Patent No. 4,174,683), the induction valve in the
working cylinder of the engine is kept open during part of the compression stroke
and thereafter closing the valve and compressing only a fraction of a full charge
which is then ignited and expanded against the piston to the full volume of the cylinder.
This process is very complex requiring means for both changing the point of axis of
the crankshaft and for altering the intake valve timing according to load demands.
Furthermore, no means of increasing compression or charge turbulence is provided.
This concept continues to operate with the friction inherent in the four-stroke cycle
engine. In addition, the operation of this engine at full load is the same as for
a conventional engine so that it offers improved characteristics at part load only.
[0007] Others have attempted to extract more shaft work from combustion gases using similar
systems of conducting the burned gases into other cylinders after firing for additional
expansion, also with similar results. Some have tried burning charges in one-half
the cylinders of a multi-cylinder engine and then ductinj the exhaust from the firing
cylinders into the remaining half of the cylinders for the extraction of additional
shaft work. To date none of these attempts have been successful and emissions were
generally increased over conventional engines.
[0008] Rotary engines have also been patented which strive to gain the same advantages.
One such is the new Wankel engine, U.S Patent No. 3,688,749 issued in 1972, in which
a charge is compressed in one chamber of the rotor of a four-lobed rotor engine where
the charge is ignited and expanded first in the initial chamber and then through a
duct into the next down-stream chamber. Some of the problems with this concept are
that the second expansion chamber is already half filled with recompressed exhausted
gases from the previous firing and there are extensive throttling losses in transferring
the charges.
[0009] The present invention provides a reciprocating internal combustion engine comprising
a compressor chamber for compressing an air charge, power chambers in which combustion
gas is ignited and expanded, a piston operable in each chamber and connected to a
crankshaft by connecting link means for rotating the crankshaft in response to reciprocation
of each piston, a transfer manifold communicating said compressor chamber with said
power chambers through which manifold the compressed charge is transferred to enter
the power chambers, an admission valve controlling admission of air to said compressor
chamber for compression therein, an outlet valve controlling admission of the compressed
charge from the compressor chamber to the transfer manifold, an intake valve controlling
admission of the compressed charge from the transfer manifold to said power chambers,
and an exhaust valve controlling discharge of the exhaust gases from said power chambers,
said valves being timed to operate such that the air charge is maintained within the
transfer manifold and introduced into the power chamber without any appreciable drop
in charge pressure so that ignition can commence at substantially maximum compression,
means being provided for causing fuel to be mixed with the air charge to produce a
combustible gas, means being provided for ignition of the combustible gas, and wherein
said compressor chamber and the combustion chambers of said power chambers are sized
with respect to the displaced volume of said power chamber such that the exploded
combustion gas can be expanded substantially beyond its initial volume.
[0010] The chief advantages of the present concept over existing internal combustion engines
are: the compression ratio for spark ignited engines can be increased without the
attendant problem of combustion detonation, the expansion ratio for both spark ignited
and compression ignited engines is greatly increased, and a much greater charge turbulence
is produced in the combustion chamber of both.
[0011] The higher compression, the more extensive expansion process and the increased charge
turbulence will greatly increase the thermal efficiency of an internal combustion
engine according to this invention at all loads, whilst at the same time providing
a cleaner exhaust. These features are enhanced by extra power strokes produced per
revolution of the engine crankshaft (50% more in the 4- and 8-cylinder arrangements
and 33% greater in the 3- and 6-cylinder configuration, as described in detail herein)
which operating at higher compression, will assure approximately the same power-to-weight
ratio as that of a conventional engine of the same power rating even though charge
weight is reduced. Experimental data indicate that a change in compression ratio does
not appreciably change the mechanical efficiency or the volumetric efficiency of the
engine. Therefore, any increase in thermal efficiency resulting from an increase in
compression ratio will be revealed by a corresponding increase in torque or mean effective
pressure (mep) ; this power increase being an added bonus to the actual efficiency
increase.
[0012] The extra power strokes per revolution of crankshaft translates into a nominal 2-2/3
stroke cycle engine in the tor 8-cylinder design and produces a nominal 3-stroke cycle
engine in the 3- or 6- cylinder design for reduced friction and greater mechanical
efficiency.
[0013] Embodiments of internal combustion engines according to the invention will now be
described, by way of example, with reference to the accompanying drawings, in which:-
Figure 1 is a perspective view of the cylinder block of a four-cylinder internal combustion
engine according to the invention;
Figure 2 is a part sectional view through the compressor cylinder of the engine shown
in Figure 1;
Figure 3 is a part sectional view through one power cylinder of the engine at the
intake valve;
Figure 4 is a part sectional view through one power cylinder of the engine at the
exhaust valve;
Figure 5 is a diagram showing suggested valve timing for the engine shown;
Figure 6 is a transverse sectional view through an alternate embodiment for a power
cylinder showing a sliding valve;
Figure 7 is a schematic plan view of a similar four cylinder engine modified to allow
quick compression build-up;
Figure 8 is a schematic transverse sectional view of the cylinder block of a modified
four cylinder engine;
Figure 9 is a schematic transverse section of a 6-cylinder engine having two compressor
cylinders and four power cylinders;
Figure 10 is a schematic transverse section of a 6-cylinder engine having six power
cylinders supplied with a compressed air charge by a separated compressor;
Figure 11 is a schematic transverse sectional view through a 6-cylinder engine adapted
for use with an economizer device comprising an air retarder brake;
Figure 12 is a part sectional view through one power cylinder of the engine at the
intake valve in which a projection is affixed to the crown of the piston;
Figure 13 is an expanded view of the projection on the piston and combustion chamber
of Figure 12; and
Figure 14 is a diagram showing suggested valve timing for an engine with a power cylinder
as shown in Figure 12.
[0014] Referring to the drawings, Figure 1 shows a four cylinder reciprocating internal
combustion engine for gasoline, diesel, gas or hybrid dual-fuel operation and having
four cylinders 2-5 in which pistons 6-9 respectively are arranged to reciprocate.
Pistons 6
-9 are connected to a common crankshaft 10 in conventional manner by means of connecting
rods 11-14, respectively. Engine 1 is adapted to operate in a 2-stroke cycle so as
to produce three power strokes per revolution of the crankshaft 10. To this end one
cylinder 5, functions as a compressor, so that during operation of the engine, compressor
cylinder 5 takes in an air charge at atmospheric pressure, or alternatively an air
charge which previously has been subjected to suoercharging to a higher pressure,
via an admission control valve 'a', through an intake conduit 15. During operation
of the engine 1, the air charge is compressed within the compressor cylinder 5 by
its associated piston 9, and the compressed charge is forced through outlet valve
'b' into a high-pressure transfer manifold 16. Manifold 16 is constructed and arranged
to distribute the com- pressued charge by means of branch conduits 17, 18 and 19 and
intake valves 'i' to the three remaining (expander) cylinders 2, 3 and 4 respectively
which produce the power of the engine.
[0015] The volume of the combustion chamber of each expander cylinder 2, 3 and 4 is preferably
sized to be no larger than one third that of a conventional engine having a similar
compression ratio. This is because the total volume of the combustion chambers should
not exceed the volume of charge compressed by the compressor piston and therefore
no expansion of the gases will occur before combustion takes place.
[0016] Engine 1 has a camshaft 20 which is arranged to be driven at the same speed as the
crankshaft in order to supply one working stroke per revolution for both power and
compressor pistons, as described hereinafter.
[0017] The operation of the engine is as follows:
The intake valve 'i' of each power cylinder is timed to allow the charge to begin
entering at approximately 40 before top dead center (BTDC) (see Fig. 5) and the exhaust
valve is timed to close at approximately the same crank angle. A compressed air charge
in transfer manifold 16 enters the combustion chamber of the cylinder which is to
be fired without any appreciable pressure drop occurring and at a high velocity during
which fuel may be injected simultaneously. The fuel may be injected after intake valve
closure on spark ignited engines. At about 100 BTDC (see Figure 5) the intake vale is closed and the fuel is ignited either by spark
plug or by means of auto ignition. Hence, the charge is ignited at maximum compression
and the gases expanded against the working cylinder beyond their initial volume.
[0018] At the time the intake valve opens, at about 40° BTDC, the piston has completed about
90.5% of its exhaust stroke leaving only 9.5% of its displacement volume, plus the
diminutive combustion chamber volume unoccupied. The air charge will have a velocity
similar to that of the rising piston and virtually no expansion of the charge will
take place before the piston reaches top dead center (TDC). The advancing piston prevents
admission of a charge volume greater than the volume of the combustion chamber (whose
pressure equilibrates with the manifold- reservoir pressure) at the time of the closing
of the intake valve 'i', at about 10
0 BTDC. Combustion will begin before top dead center (BTDC) for the utmost in efficiency.
As stated, in this particular arrangement if the compression ratio is 16:1 the expansion
ratio will be 48:1. Therefore, the gases are expanded to three times their initial
volume. Alternatively, one stage of compression, could be done in the compressor cylinder
5 and the slightly larger volume of charge could be received in the expander cylinders
2, 3 and 4 and a second stage of compression could then be accomplished in the expander
cylinders, the compression ratio being established by the volume of the three combustion
chamber in relation to the total displaced volume of the single compressor cylinder.
[0019] The exhaust gases are discharged via an exhaust manifold 21 and the scavenging would
be extremely efficient. In a conventional 4.2 liter 8 cylinder automobile engine each
piston displaces about 89.4% of its total cylinder volume in the exhaust stroke (displaced
volume/total volume). Similar scavenging efficiencies can be realized in the engine
according to this invention. For example, if the intake valve 'i' opened at 40
o BTDC and the exhaust valve closed at 40
0 BTDC the stroke of the piston would be 90.54% complete. Therefore, 90.54% of the
displacement volume of 522.3 cc (same 4.2 liter engine) is 472.9 cc. This amount divided
by the total volume of the cylinder of the engine of this invention is 87.8% of volume
displaced (and scavenged).
[0020] Referring now to Figure 12, there is shown a similar engine arrangement to that illustrated
in Figure 3 in which like parts are designated like reference numerals with the addition
of suffix 'b' and in which a projection 150, Figure 12, affixed to the crown of expander
cylinder piston 6b, closes the opening of the combustion chamber 151 at somewhere
near 40 degrees before top dead center (BTDC) as piston 61) rises in its exhaust stroke.
This arrangement facilitates exhaust scavenging by allowing the exhaust valve to remain
open past TDC and by virtually displacing all of the burned gases while preventing
the charge, which is passing the intake valve into the combustion chamber, from entering
the cylinder proper. The projection 150 may be fitted with a compression ring 152
residing inside the opening of the combustion chamber as shown in Figure 13.
[0021] Figure 14 is a diagram for suggested valve timing and can be used with the arrangement
shown in Figure 12 for improved scavenging for all of the designs of this invention.
The suggested operation is in this manner. In the expander cylinder (Fig. 12) the
exhaust valve opens near bottom dead center (BDC) and as the piston 6b rises, it expresses
the burned gases through the exhaust valve 'e' (not shown) about 40 degrees before
top dead center (BTDC), the intake valve opens, at approximately the same time the
projection 150 on top of the piston occludes the outlet of the combustion chamber
151 effectively sealing it. At this time (40 degrees BTDC) the piston has completed
90% of its scavenging, therefore, it only has 10% of further travel. If the piston
stroke is four inches, then the amount of stroke remaining would be 4/10 inch. Therefore,
the projection on the piston would need to be only 4/lOths inch high to seal the combustion
opening as the intake valve opens at 40 degrees BTDC. As illustrated in Figure 14,
the exhaust valve remains open as much as 30 degrees past TDC.
[0022] The diagram in Figure 14 illustrates valve timing in which at 40 degrees BTDC the
projection 150 on piston 6b closes combustion chamber port 151 and at the same time
fresh charge begins to enter intake valve 'i'. The piston continues to rise until
there is practically zero clearance with the face of the engine head, expelling virtually
all of the exhausted gases. During the 40 degrees of crank rotation the intake valve
is opened, pressure equilibrium is established between the combustion chamber 151
and the manifold 16b. At 5-10 degrees before top dead center, the intake valve closes
and fuel is injected and ignited at maximum compression for greatest efficiency. Shortly
after top dead center (TDC) the exhaust valve 'e' closes. The pressure of the burning
gases is expanded against first the piston valve crown 150 and then into the cylinder
and against the entire piston crown after the crank angle is 40degrees past top dead
center. The charge is expanded against the piston for the full length of the expansion
stroke.
[0023] The compression ratio is established by the total volume of all of the combustion
chambers which are supplied by a single compression cylinder, divided into the displaced
volume of the single compressor cylinder. For a 2 liter four cylinder engine, this
would be 500 cc divided by 31.25 for a compression ratio of 16:1. The combustion chamber
volume of this engine would be only 10.4 cc per cylinder or the 31.25 cc for the three
firing cylinders.
[0024] Although the intake manifold 16 must withstand high pressures this will not add to
the weight of the engine because the volume of air charge flowing through it should
not be more than 1/16th to 1/8th of the volume passing through the manifold of a conventional
engine as the charge is already partially, or preferably, completely compressed. This
small volume of charge allows the manifold to have a small inside diameter. The manifold
16 should be small enough for the heavier charge to have sufficient velocity to charge
the expander cylinders 2, 3 and 4 but nevertheless should nave enough volume so that
there would be no appreciable pressure drop when an expander cylinder is charged.
When the intake valves 'i' to the power cylinders open the pressures in the combustion
chamber and in themanifold equilibrate.
[0025] With the small volume of air charge introduced into the combustion chambers the intake
valves 'i' of the engine 1 can be smaller and lighter (requiring lighter springs)
and indeed may be shrouded with no loss of volumetric efficiency. Other means besides
shrouding for providing a tangential charge direction can also be used.
[0026] Although the intake valve will be open for a short time only (such as 30 or 40
0), this will be about the 1/8th of the time (or crank angle) that a conventional Otto
cycle engine intake valve is normally open. Yet, the volume of charge passing the
intake valve, assuming a 16:1 compression ratio, is only 1/48th (one-third of the
normal charge already compressed) of the volume passing the intake valve of the Otto
cycle engine. In the three or six cylinder engine the volume entering the combustion
chamber will be only 1/32 that passing the intake valve of a conventional engine.
[0027] Fuel may be injected directly into each of the expander cylinders 2, 3 and 4 or into
the individual inlet ports. The quantity of fuel may be proportionate to the engine
operating conditions by varying the effective stroke of a fuel pump- by varying the
opening time of a fuel injection nozzle fed from a constant pressure main or by varying
the rate of flow through the injection nozzle.
[0028] Alternatively, a carburetor may be placed in front on the compressor cylinder 5 and
used for maintaining the ratio of fuel to air in the region of the stoichiometric
ratio.
[0029] In the gas or spark ignited version or mode the engine may be throttled near the
atmospheric intake conduit 15 by means of a butterfly valve (not shown) in order to
prevent the engine wasting work by having to compress more air than needed to maintain
the stoichiometric fuel to air ratio. A means is described later for reducing or eliminating
required throttling in the spark ignited version or mode.
[0030] So far as compression ignition operation is concerned the speed could alternatively
be controlled by the fuel rate alone. Thus automatic fuel air ratio control would
not be required and throttle valves could be eliminated.
[0031] Figure 2 shows one means of utilizing automatic one-way valves in the compression
cylinder 5. While reed type valves 30 (admission), 31 (outlet) are illustrated on
the compressor cylinder 5, other valve types, such as sliding valves or sleeve valves
could be used.
[0032] Figures 3 and 12 of the drawings illustrate one means of operating the intake valves
'i' of the power cylinders of the engine with reference to cylinder 2. The speed of
the camshaft 20 is arranged to be the same as that of the crankshaft 10 and is driven
from the crankshaft by a gear 22 on the crankshaft and sprocket drive 23 shown in
Figure 1. Large cam 24 or 246 operates push-rod 25 or 25b and rockerarm 26 or 26b
to activate intake valve 'i' which opens at about 40° BTDC and closes at about 10°
BTDC.
[0033] Figure 4 shows how cam 27 operatespush-rod 28 and rockerarm 29 to activate exhaust
valve 'e' which opens at approximately bottom dead center (BTDC) and closes at 40°-35°
BTDC in the first design. In the alternate design, the exhaust valve may be held open
past top dead center for better scavenging if desired as illustrated in Figures 12
and 14.
[0034] To facilitate starting the engine, quick compression build-up could be achieved if
necessary, by momentarily blocking the intake to the expander cylinders (Fig. 7) The
intake valves of the expander cylinders 2, 3 and 4 could be deactivated (there are
several methods of doing this in the art, some of which are described later). For
example, one way blocking valves 32, 33 and 34 (Fig. 7) could be placed in each branch
of the transfer manifold 16 and closed. Alternatively, sliding valves could be placed
between the transfer manifold and the inlet ports of the cylinders and closed. Moreover,
one way valves 35, 36 and 37 can be placed between each expander piston and the associated
intake valves to allow each expander piston to pull in atmospheric air unrestricted
while the engine manifold was being charged. Furthermore, a bypass line 38 with a
one way valve 39 and a blocking valve 40 could be placed in the exhaust manifold 21
in order to direct the pumped air into the manifold 16 for quicker build-up of compression.
[0035] A second means to facilitate fast starting would be to open a valve leading from
a compressed air reservoir to the cylinders. This would supply compressed air for
instant firing of the cylinders or could be used to rotate the engine for starting,
as described later. The air reservoir could be supplied by an air-compressor retarder
brake described with reference to Figure 11 or by any other method.
[0036] In order to produce fast burning efficient combustion, velocities of the compressed
air in each manifold branch conduit 17, 18 and 19 should be high and charge velocities
in the combustion chamber up to sonic velocities may be achieved. Tremendous swirl
can be produced in the combustion chamber by controlling the angle of the inlet port
with respect to the cylinder radius or by the use of a shrouded intake valve.
[0037] The resulting turbulence helps promote combustion by intermixing burned and unburned
gases at the flame front as it progresses across the combustion chamber. This feature
alone should make NO
x and HC emissions negligible and virtually eliminate CO emissions. The extra burning
time of the extended expansion process should then further reduce HC emissions to
only a trace.
[0038] Referring now to Figure 8 of the drawings, there is shown a similar 4-cylinder engine
42, in which like parts are designated like reference numerals with the addition of
suffix 'a', and in which additional mid-cylinder exhaust ports 43, 44 and 45 are provided
in the walls of the expander cylinders 2a, 3a and Aa respectively, in order to improve
the scavenging efficiency. Such ports 43-45 would be uncovered by their associated
pistons 6a-8a respectively at the lowest point of the piston stroke. As the exhaust
ports 43-45 are uncovered, the pressure in the cylinders could expel much of the exhausted
gases to the atmosphere.
[0039] Alternatively, a step-up gear set 46 can be placed on the crankshaft 10a and geared
to drive a scavenging type blower 47 in order to inject fresh air into the ports 43-45
as they are uncovered by their associated pistons 6a-8a, respectively. In this arrangement,
the associated exhaust valves of each power cylinder 2a-4a would be opened at approximately
the same time as the ports 43-45 were uncovered.
[0040] In this invention, the exhaust valves are open from before BDC until about 40-45
BTDC and the piston itself displaces (scavenges) 90% of the burnt gases through the
exhaust valves. Therefore, if the blower system 46-47 is added, only a small amount
of fresh air need be supplied in order to drive some of the burnt gases through the
exhaust valve and to dilute the remainder of the gases which are then scavenged by
the stroke of the associated piston.
[0041] These arrangements would provide for cooler exhaust valves and allow the exhaust
valves to be closed earlier. In this way, the intake valves could be opened earlier
and it is envisaged that the expander cylinder could be used for additional compression
of the charge if desired. For example, the compression could take place partly in
the compressor cylinder 5a, whereafter this slightly larger charge could be further
compressed by the expander cylinders 2a-4a.
[0042] In a further arrangement of either of the four-cylinder engines the single compressor
cylinder could be double acting (not shown) although the basic operation of the engine
would remain the same. In this arrangement, the compressor cylinder would compress
an air charge to a volume sufficient to supply the three power cylinders with one-half
to two-thirds of the normal volume of charge depending on the expansion ratio required.
[0043] It is also envisaged that a 5-cylinder engine in which one of the cylinders comprised
a double acting compressor cylinder would supply four expander (power) cylinders whose
combustion chambers are half the volume of a conventional engine. This arrangement
will produce four power strokes per revolution with the expansion ratio being twice
the compression ratio.
[0044] Furthermore, in an 8-cylinder reciprocating engine any of the 4-cylinder constructions
described above could be doubled or alternatively three compressor cylinders could
compress the air charge for five power cylinders. The former would produce six power
strokes per revolution and the latter would produce five. In the latter case the combustion
chambers could be from 50% to 60% of normal volume according to the expansion ratio
desired.
[0045] In any of the engine constructions described herein the engines may be fueled by
means of gasoline, gas or diesel or indeed the engine can be constructed for hybrid
operation as a multi-fuel engine. In any event the smaller charge exploded would permit
a lighter construction for the compression ignition engine arrangement and will also
provide quieter operation for compression ignition (CI) engines.
[0046] Referring now to Figure 9 of the drawings, there is shown a schematic transverse
sectional view through a six cylinder internal combustion engine having two compressor
cylinders 68 and 69 and four expander (power) cylinders 70, 71, 72 and 73 and associated
pistons 103, 104, 105, 106, 107 and 108 all connected to a common crankshaft 74 by
means of connecting rods 75-80 respectively.
[0047] The operation of an engine constructed according to this arrangement is similar to
that previously described in that air at atmospheric pressure or supercharged to a
higher pressure is supplied to the compressor cylinders 68 and 69 via an inlet conduit
81 through admission control valve 113 and 114 and the air is compressed by way of
outlet valves 84 and 85 into a high pressure transfer manifold 82 which supplies the
compressed charge to the expander cylinders 70 to 73 through intake valves 109-112.
Therefore, each of the compressor cylinders 68 and 69 supplies two expander cylinders.
[0048] The combustion chambers of the expander cylinders are preferably dimensioned to be
no more than one-half the volume of that of a conventional engine at a similar compression
ratio and therefore the expansion ratio of the engine is at least double that of a
conventional engine. For example, at a compression ratio of 16:1 the combustion chamber
would be about one-quarter the volume (one-half the normal charge compressed to the
higher ratio) of an ordinary engine and the expansion ratio would be 32:1.
[0049] Each cylinder is a two-stroke cylinder and is scavenged by displacing the burnt gases
during the exhaust stroke of the piston. Hence, virtually no air is used in scavenging.
The working piston rises displacing the exhaust gases via an exhaust manifold 83,
the associated intake valves (109-112) open so that the charge begins to flow at about
40 BTDC and the associated exhaust valves (115-118) close at about 40°BTDC. The enhanced
scavenging system illustrated in Figures 12 and 14, and described more fully in the
description of the engine of Figure 1, would allow the exhaust valves to remain open
past top dead center without allowing the mixing of incoming charge and exhaust gases.
The intake valve can have a shroud on one side which directs air charge flow into
a very turbulent swirl as previously described. Fuel is injected at the time the intake
is in progress or as soon as the intake valve is closed at about 10 BTDC. When the
intake valve closes the charge is ignited by spark plug or by means of auto ignition.
The volume of the entering air charge in the preferred embodiment, is no greater than
1/32nd of that passing through the intake valve of a conventional engine and therefore
a good volumetric efficiency is achieved. This gives each of the expander cylinders
70 and 73 one power stroke per revolution so that a total of four power strokes per
revolution is produced by the six cylinder engine which, of course, is equal to the
number of power strokes of a conventional four-stroke eight-cylinder engine.
[0050] The valves of the power cylinders could be operated as shown in Figures 1, 3 and
6 or in the system illustrated in Figures 12 and 14. The compressor cylinders could
be arranged as shown in Figure 2. Preferably the manifold 82 would be insulated for
compression ignition operation.
[0051] The air charge could be completely compressed by the compressor cylinders 68 and
69 or, it is also envisaged that the compression could take place partly in the compressor
cylinders 68 and 69 and then this charge could be further com- pressed by the expander
cylinders 70 to 73.
[0052] Athree cylinder engine arranged to operate in a similar manner to the six cylinder
engine just described is also envisaged. In this event only one compressor cylinder
would be provided which would supply a compressed air charge to two expander cylinders
thus producing two power strokes per revolution to equal the smoothness of a four-cylinder
four-stroke cycle engine. This arrangement would be the same as shown in Figure 1
with one power cylinder removed and the volume of the combustion chambers would ideally
be no greater than one-half that of a conventional engine at a similar compression
ratio. Either of the two schemes of Figures 4 and 5 or Figures 12 and 14 may be used
for scavenging.
[0053] Reduced throttling can be achieved in any spark ignited engine of this invention
which has a plurality of compressor cylinders in the following manner. At any time
the atmospheric air intake manifold pressure dropped appreciably below ambient pressure,
for example near half throttle, the outlet from one or more of the compressor cylinders
could be closed by a shutoff valve. Work done in compressing this captive charge is
recovered as the charge expands on the back stroke of the piston with zero net induction
pumping done by that cylinder.
[0054] Throttling may be eliminated completely in spark ignited engines as illustrated in
Fig. 1 by providing late fuel injection into the combustion chamber and allowing combustion
to begin in the injected spray. The violet swirling motions of the gases will insure
that very lean mixtures will burn completely.
[0055] Pumping work create3 by throttling would be greatly reduced thereby and intake manifold
81 pressure will remain more nearly constant at all output loads, particularly over
the range including idel and one-third of maximum power output where most engine loading
occurs during typical automotive operation. This method could be used with any multiple
of the four cylinder or three cylinder arrangement.
[0056] Referring now to Figure 10 of the drawings there is shown a six-cylinder reciprocating
internal combustion engine in which all the cylinders 86-91 and associated pistons
119-124 operate on a two-stroke cycle and all cylinders are used for producing power
to a common crankshaft 98 via connecting rods 92-97 respectively.
[0057] This engine is characterized by a more extensive expansion of the burned gases and
a greater charge turbulence with combustion beginning at maximum compression. In the
case of gasoline operation the engine can operate at a higher compression ratio than
is usual.
[0058] In this two stroke design the cylinders are scavenged by positive displacement with
virtually no loss of air charge or fuel in the scavenging process. The greater expansion
ratio, higher compression ratio and increased charge turbulence produces a more fuel-efficient
engine while providing greater power to weight ratio than that of the Otto cycle engine.
[0059] The engine is constructed much the same as a four-stroke cycle internal combustion
engine but with a number of significant differences. The combustion chamber of each
cylinder is preferably made no greater than one-half to one-third the usual size for
the compression ratio desired and according to the ' expansion ratio decided upon.
The cam shaft (not shown) is geared to turn at the same``speed as the crankshaft in
order to open and close the inlet (125-130) and exhaust (131-136) valves once during
each revolution of the crankshaft. Compression takes place in one or more stages before
the air charge is admitted to the combustion chambers of the cylinders and the intake
manifold becomes a high pressure manifold reservoir. Fuel injectors are used to inject
fuel directly into the combustion chambers except for natural gas or propane operation
which can be mixed in an EMPCO type carbueretor. An efficient high compression air
compressor 99 is placed between the air intake 15 and the working cylinders.
[0060] It is also envisaged that any external source of compressed air can replace the compressor
99 and therefore the engine can operate on waste compressed air for further fuel economy.
[0061] The pressure ratio can be increased at will until the pressure ratio (nominal compression
ratio) is equal to or surpasses the expansion ratio for greater power as the load
demands. This could be accomplished simply by increasing the speed of the compressor.
[0062] One of the most important elements needed for success in this design is to provide
a compressor which will produce both the pressures and the quantity of air charge
needed for efficient operation and any suitable compressor is within the scope of
this invention. It is envisioned that three stages of radial compression would be
economical and ideal .for compression ignited engines.
[0063] The operation and,function of the six-cylinder engine depicted in Figure 10 of the
drawings is as follows: the compressor 99 aspirates air and compresses it into the
manifold-reservoir 100. A check valve at 101 may be used if compressor pressure pulsations
are great. The manifold reservoir 100 contains such a volume that there is no appreciable
drop in over-all pressure as the cylinders 86-91 are charged sequentially. As the
engine is cranked the working piston ascends to about 40
0 BTDC (see valve timing schemes shown in Figures 5 and 14) which displaces the gases
when its travel is almost to the end of its associated cylinder. This expels 90% of
the burnt gases through the exhaust valve (into the exhaust manifold 137) which opens
as the piston begins its exhaust stroke. The piston is then at about 40o BTDC. The
intake valve then opens and an increment of the compressed air charge enters through
a valve (can be shrouded) as the piston continues its stroke which is 90% complete.
Fuel can be injected at the same time (or as soon as the intake valve is closed.)
The high pressure air, the persistency of flow and the small volume of the charge
(about 1/32nd to 1/48th of the volume which normally passes an intake of a conventional
engine) assures a high volumetric efficiency. The intake valve then closes at about
10
0 BTDC and the mixture is ignited. In this manner combustion begins at maximum compression
but the air charge has at least two to three times the expansion of an equivalent
Otto cycle engine. It will be appreciated that if the combustion chamber is made half
the normal volume the expansion ratio will be twice the compression ratio and a one-third
normal volume combustion chamber will triple the expansion ratio. If the compression
ratio is 16:1, the expansion ratio can be either 32:1 or 48:1, respectively. Enhanced
scavenging may be achieved if desired by use of the scavenging system shown in Figures
12 and 14. In this scheme the mouth of the combustion chamber is blocked at about
40° BTDC and the exhaust valve is held open past top dead center, and the intake valve
is opened at the time the combustion is blocked. This scheme is better described in
the description of the engine of Figure 1.
[0064] Although less air charge is used, a correspondingly smaller increment of fuel is
used. The farther the gases expand against a piston the more work is done on the piston
and the more complete is the combustion and the cooler is the exhaust gases. In a
convention diesel engine approximately 100% excess air is aspirated at full load but
the lack of turbulence and time hinders complete mixing oE the oxygen and fuel. In
the present engine design the tangential entrance of the high velocity air as previously
referred to permits complete mixing of the fuel air charge which together with the
more extensive expansion gives more complete combustion and, of course, the density
of the air can be increased at any level deemed efficient.
[0065] Alternatively, as in other designs one stage of compression say 8:1 could be done
in the compressor 99 and the charge received and further compressed in the expander
cylinders.
[0066] It is further envisaged that a reciprocating internal combustion engine according
to any of the designs of this invention may have only one compressor cylinder for
use in charging a single expander (power) cylinder i.e. a two- cylinder engine. In
this case, the expander cylinder would be of greater volume than the compressor cylinder.
[0067] Higher than normal compression ratios can be utilized in the gasoline engines of
this invention for the following reasons. The charge being compressed outside the
hot firing cylinder will be cooler to begin with (it also will require less power
to compress this cooler charge) which causes a corresponding decrease in temperature
of the end-gas at peak pressure. Extreme charge turbulence causes mixing of the burned
and unburned gases at the flame front greatly increasing the flame speed and allows
the flame front to reach any end-gas before the pressure waive arrives. The much smaller
combustion chamber (1/4 to 1/6 normal size) presents a much shorter flame path from
the spark plug to the end gas, further assuring arrival of the flame front ahead of
the pressure wave. Furthermore, the greater expansion of the gases produces a cooler
exhaust valve which is in the region of the end-gas which again reduces the chance
of detonation. This also reduces the perk pressure temperature. The nominal time between
start of compression and peak pressure is much less since compression is done outside
the firing cylinder which fact gives less residence time for pre-knock conditions
to occur. The air charge will have such rapid swirl that burning of the fuel can take
place as injection proceeds leaving no fuel in the end-gas. In addition the entire
charge could be after-cooled for large supercharge boost when utmost power is required
as for example during an aborted landing by an aircraft.
[0068] Preignition will not be a problem in the engine of these designs becausa the residence
time of the fuel is less than that required for preignition to occur.
[0069] The power of compression ignition engines operating in this working cycle can be
greatly increased by supercharging, The inlet pressure can be boosted from a slight
boost up until the theoretical compression ratio equals the expansion rati). Some
locomotives operate with a supercharge boost of three atmospheres which, with a compression
ratio of 12:1, produces a theoretical compression ratio of 48:1. Some intercooling
or aftercooling would likely be required with very high pressure boosts in order to
lessen NO
x emissions in CI engines.
[0070] The power of spark ignition engines can be greatly increased by similarly boosting
the inlet air pressure.
[0071] Although the characteristics of this working cycle provides for very high compression
without detonation, some aftercooling would be required as the compression ratio figures
approached those of the expansion ratio.
[0072] This working cycle may under certain conditions, such as when used in a compression
ignition engine at very light loads, result in the combustion gases expanding to pressures
less than atmospheric. At such conditions the nominal compression ratio can be increased
until it is equal to the expansion ratio by increasing supercharge boost or by closing
off one or more of the expander cylinders. The latter can be done by deactivating
their intake and exhaust valves along with their respective fuel injector(s).
[0073] In the system suggested for a four-cylinder engine in which the expansion ratio is
three times the compression ratio, one expander cylinder could be closed to increase
the compression ratio to one-half the expansion ratio. If, under very light loads
the pressure at the exhaust valve was still negative, a second expander cylinder could
be closed to produce a compression ratio equal to the expansion ratio. With an eight-cylinder
engine, one cylinder could be closed at a time for finer control of the compression
ratio.
[0074] With the system suggested for the six-cylinder engine, the expansion ratio is double
the compression ratio. Under very light loads in the compression ignition engine,
one expander cylinder could be closed to increase the compression ratio to two-thirds
the expansion ratio. Two could be closed to produce equal compression and expansion
ratios. Aftercooling would not likely be required because now the lightly loaded engine
would be using much less fuel and grams NO emissions per mile should not exceed limits.
[0075] There are several systems described in the art for deactivating the poppet valves
of a cylinder. The 1899 Daimler auto engine provided such a means by removing an extra
member from between the cam follower and the valve lifter push rod. This allowed the
valve spring to hold the valve closed until such time as the spring loaded intermediate
member was released.
[0076] An electronic system of valve control is manufactured by Eaton Corporation and has
been used in several automotive engines. This latter system allows the releasing of
the rocker arm pivot support in order to deactivate the valve. This system provides
electronic controls which can sense exhaust manifold pressure and cut out the necessary
number of expander cylinders at such a time the exhaust manifold pressure drops to
or below ambient pressure.
[0077] When the valves of a cylinder are closed the energy of compression is returned to
the shaft during expansion of the same gas. Even if some of the gas contained in the
closed cylinder leaks out, there will be an equilibrium established in which the pressure
of the contained gas and the ambient atmospheric pressure will interact in such a
manner that there will be no net loss of energy. No "flow work" will be done during
the time the cylinder(s) are closed.
[0078] Alternatively in any engine in which the gases could expand to a pressure less than
atmospheric further economy could be achieved in the following manner. A pressure
sensor, 102 in Figure 9, could be placed in the exhaust manifold and monitored. The
fuel rate could then be adjusted so that there would always be a slight positive pressure
in the exhaust manifold. This sytem would work well in a constant load, constant speed
engine in particular.
[0079] Referring now to Figure 11 of the drawings, additional fuel savings can be achieved
in the engines described hereinbefore by use of an economizer constructed as an air
compressor retarder brake. This six-cylinder engine is similar to the engine shown
in Figure 9 in which like parts are designated by like reference numerals with the
addition of the suffix 'a'. The air retarder brake illustrated has a compressor 138
operatively connected to the drive shaft of vehicle or geared to the engine and stores
energy produced during braking or downhill travel which is utilized to supply compressed
air to the engine power cylinders via the transfer manifold of 82a. Such an economizer
would be coupled with an air reservoir 139 and during the time in which the economizer
reservoir air pressure was sufficiently high for use in the power cylinders of the
engine, the engine compressor could be clutchably disengaged so that no compression
work would be required of the compressor. A relief valve 140 prevents excess build
up of pressure in the air reservoir. One way valve 14
1- allows air from the reservoir to be transferred to the manifold when the pressure
in the reservoir 139 is higher than in the transfer manifold 82a. In the case of engine
constructions having compression cylinders each compression cylinder of the engine
could also be deactivated during this reserve air operation time by shutting off the
admission valve so that no net work would be done by the compressor(s) until the manifold-
reservoir pressure dropped below operating levels. Several systems of deactivating
cylinder valves are described in the art and have been mentioned previously.
[0080] Operating the engine on this reserve air supply would improve the net mean effective
pressure (NMEP) of the engine for greater power and efficiency per unit of fuel used.
[0081] This feature would produce additional savings in energy especially in heavy traffic
or in hilly country. For example, an engine producing 100 horsepower uses 12.7 pounds
of air per minute. Therefore, if all energy of braking were stored in the compressed
air in the economizer reservoir, a ten, twenty or even thirty minute supply of compressed
air can be accumulated and stored during stops and down hill travel. When the reservoir
pressure drops below the desired level for efficient operation, a solenoid will reactivate
the compression cylinder valves and they (with the supercharger, when needed) will
begin to compress the air charge needed by the engine.
[0082] This economizer or alternatively any other suitable type of air pump may also be
used to prevent excessive manifold pressure fluctuation in any of the designs of this
invention, if it is found desirable.
[0083] Using this air reservoir, the engine needs no compression build-up for starting and
as soon as the shaft is rotated far enough to open one intake valve the compressed
air and fuel would enter and be ignited for "instant" starting. Furthermore, the compressed
air could be used to rotate the engine for starting by opening simple valves at the
top of the cylinder as is common in large diesel engines, thus eliminating the need
for a starter motor.
[0084] An additional means, to those already suggested, of facilitating cranking of the
engine is to hold the intake valve 'i' or the bypass valves 35, 36 and 37 open during
the full downstroke of the associated piston thereafter closing the intake valves,
holding the exhaust valves closed and then beginning the upstroke of the piston, adding
the fuel (if not premixed) and igniting it near the completion of the upstroke, the
next downstroke becoming the power stroke.
1. A method of deriving mechanical work from combustion gas in an internal combustion
engine having a power chamber in which the combustion gas is ignited and expanded,
a compressor chamber in which an air charge is compressed and a piston operable in
each chamber, comprising the steps of compressing an air charge in the compressor
chamber transferring the compressed air charge to the power chamber such that there
is no appreciable pressure drop during transfer, causing a predetermined quantity
of fuel to be mixed with the air charge to produce a combustible mixture, causing
the mixture to be ignited at substantially maximum pressure within the power chamber
and expanding the combustion gasagainst the piston substantially beyond its initial
volume.
2. A method according to claim 1 in which the air charge is compressed partially within
said compressor chamber and further compressed to said maximum pressure in said power
chamber immediately prior to ignition of said mixture.
3. A method according to claim 1 in which the fuel is mixed with the air charge to
produce a combustible gas prior to admission into the compressor chamber.
4. A method according to claim 1 in which the fuel is mixed with the air charge to
produce a combustible gas after leaving the compressor chamber but prior to admission
into the power chamber.
5. A method according to claim 1 in which the fuel is mixed with the air charge to
produce a combustible mixture within the power chamber.
6. A method according to clam 1 in which the power chamber is provided by a cylinder
in which a piston is reciprocable, and wherein said combustible mixture is ignited
during piston travel near top dead center of the cylinder.
7. A reciprocating internal combustion engine comprising a compressor chamber for
compressing an air charge, a power chamber in which the combustion gas is ignited
and expanded, a piston operable in each chamber and connected to a common crankshaft
by connecting link means for rotating the crankshaft in response to reciprocation
of each piston, a transfer duct communicating the compressor chamber with the power
chamber through which duct the compressed charge is transferred to enter the power
chamber, an intake valve controlling admission of air to said compressor chamber for
compression, a transfer valve controlling admission of the compressed charge to said
transfer duct, an intake valve controlling admission of the compressed air charge
from the transfer duct to said power chamber, and an exhaust valve controlling discharge
of the exhaust gases from the power chamber, said valves being timed to operate such
that the air charge is maintained within the transfer duct and introduced into the
power chamber without any appreciable drop in charge pressure so that ignition can
commence at substantially maximum compression, means being provided for causing fuel
to be mixed with the air charge to produce the combustible gas, and wherein said compressor
chamber and the combustion chamber of said power chamber are sized with respect to
the displaced volume of said power chamber such that the exploded combustion gas can
be expanded substantially beyond its initial volume.
8. An engine according to claim 7 in which the power chamber and the compressor chamber
are provided by the two separate cylinders with a piston reciprocable in each cylinder
and wherein the volume of said compressor cylinder is less than that of said power
cylinder.
9. An engine according to claim 8 in which a plurality of power cylinders and at least
one compressor cylinder are provided, said transfer duct comprising a common manifold
for supplying a compressed air charge from each compressor cylinder to said power
cylinders, and wherein each power cylinder is timed to be charged and fired on alternate
strokes of its piston and scavenged primarily by positive displacement by the piston.
10. An engine according to claim 9 in which ports are provided intermediate the ends
of each power cylinder to aid scavenging, said ports being uncovered by the piston
at the completion of the power stroke towards its bottom dead center position.
11. An engine according to claim 9 in which the ports intermediate the ends of the
power cylinders are provided with means for receiving compressed air to aid in the
scavenging process.
12. An engine according to claim 9 in which each power cylinder is timed to fire before
or at top dead center position of its piston.
13. An engine according to claim 9 in which each power cylinder is timed to fire after
top dead center position of its piston.
14. An engine according to claim 9 in which valve means are provided for temporarily
preventing admission of said charge to power cylinder after said charge has been admitted
to the combustion chamber by the intake valve.
15. An engine according to claim 9 in which each compressor cylinder has a double-acting
piston the arrangement being such that an air charge is compressed during each stroke
of the double acting piston and admitted to said common manifold.
16. An engine according to claim 9 in which fuel metering means is provided for causing
fuel to be mixed with said air charge to produce a combustible gas prior to admission
in each compressor cylinder.
17. An engine according to claim 9 in which fuel metering means is provided for causing
fuel to be mixed with said air charge to produce a combustible gas after leaving each
compressor cylinder but prior to admission into each power cylinder.
18. An engine according to claim 9 in which fuel metering is provided for causing
fuel to be mixed with said air charge to produce-a combustible gas after admission
to the combustion chamber
19. An engine according to claim 9 in which valve means are provided for temporarily
preventing admission of said air charge through the intake valves of each power cylinder
in order to provide compression build up in said common manifold during engine starting.
20. A-method of deriving mechanical work from combustion gas in an internal combustion
engine having at least one two stroke power chamber in which the combustion gases
are ignited and expanded, and a piston operable in each chamber, and a compressor
in which an air charge is compressed, comprising the steps of compressing an air charge
in a compressor, transferring the compressed air charge to each power chamber such
that there is no appreciable pressure drop during transfer, causing a predetermined
quantity of fuel to be mixed with the air charge to produce a combustible mixture,
causing the mixture to be ignited at substantially maximum pressure within each power
chamber and expanding the combustion gas against the piston.