U.S. patent application number 12/366048 was filed with the patent office on 2009-10-15 for split-cycle aircraft engine.
This patent application is currently assigned to THE SCUDERI GROUP, LLC. Invention is credited to Clifford D. Heaton.
Application Number | 20090255491 12/366048 |
Document ID | / |
Family ID | 39184262 |
Filed Date | 2009-10-15 |
United States Patent
Application |
20090255491 |
Kind Code |
A1 |
Heaton; Clifford D. |
October 15, 2009 |
SPLIT-CYCLE AIRCRAFT ENGINE
Abstract
A split-cycle aircraft engine includes a crankshaft rotatable
about a crankshaft axis. A power piston is slidably received within
a power cylinder and is operatively connected to the crankshaft
such that the power piston reciprocates through an expansion stroke
and an exhaust stroke during a single rotation of the crankshaft. A
compression piston is slidably received within a compression
cylinder and is operatively connected to the crankshaft such that
the compression piston reciprocates through an intake stroke and a
compression stroke during a single rotation of the crankshaft. A
gas crossover passage operatively interconnects the compression
cylinder and the power cylinder. An air reservoir is operatively
connected to the gas crossover passage by a reservoir passage. The
air reservoir is selectively operable to receive and deliver
compressed air. The engine is mounted to an aircraft and the air
reservoir is disposed within the aircraft.
Inventors: |
Heaton; Clifford D.; (Ware,
MA) |
Correspondence
Address: |
FILDES & OUTLAND, P.C.
20916 MACK AVENUE, SUITE 2
GROSSE POINTE WOODS
MI
48236
US
|
Assignee: |
THE SCUDERI GROUP, LLC
West Springfield
MA
|
Family ID: |
39184262 |
Appl. No.: |
12/366048 |
Filed: |
February 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11518828 |
Sep 11, 2006 |
7513224 |
|
|
12366048 |
|
|
|
|
Current U.S.
Class: |
123/54.2 ;
123/71R |
Current CPC
Class: |
Y02T 50/40 20130101;
F02B 59/00 20130101; Y02T 50/44 20130101; F02B 69/00 20130101; B64D
2027/026 20130101; Y02T 50/64 20130101; F01B 17/025 20130101; B64D
27/24 20130101; Y02T 50/60 20130101 |
Class at
Publication: |
123/54.2 ;
123/71.R |
International
Class: |
F02B 75/22 20060101
F02B075/22; F02B 25/00 20060101 F02B025/00 |
Claims
1. A split-cycle radial engine comprising: a crankshaft rotatable
about a crankshaft axis; a power bank including a plurality of
power cylinders radially disposed around the crankshaft; a power
piston slidably received within each power cylinder and operatively
connected to the crankshaft such that each power piston
reciprocates through an expansion stroke and an exhaust stroke
during a single rotation of the crankshaft; a compression bank
axially adjacent the power bank, the compression bank including a
plurality of compression cylinders radially disposed around the
crankshaft and equal in quantity to the number of power cylinders;
a compression piston slidably received within each compression
cylinder and operatively connected to the crankshaft such that each
compression piston reciprocates through an intake stroke and a
compression stroke during a single rotation of the crankshaft; each
compression cylinder being paired with an associated power
cylinder; each compression and power cylinder pair including a gas
crossover passage interconnecting the compression cylinder and the
power cylinder of the pair, the gas crossover passage including an
inlet valve and an outlet valve defining a pressure chamber
therebetween; and valves controlling gas flow into the compression
cylinders and out of the power cylinders.
2. The split-cycle radial engine of claim 1, wherein the
compression cylinders of the compression bank are angled relative
to the power cylinders of the power bank.
3. The split-cycle radial engine of claim 1, wherein a longitudinal
axis of each compression cylinder is offset from a rotational axis
of the crankshaft.
4. The split-cycle radial engine of claim 1, wherein a longitudinal
axis of each power cylinder is offset from a rotational axis of the
crankshaft.
5. The split-cycle radial engine of claim 1, wherein the
compression pistons have a shorter stroke than the power
pistons.
6. The split-cycle radial engine of claim 1, wherein the
compression cylinders have a larger diameter than the power
cylinders.
7. The split-cycle radial engine of claim 1, wherein the power
cylinders are arranged to fire in sequential order as the
crankshaft rotates.
8. The split-cycle radial engine of claim 1, wherein fuel is
ignited in each power cylinder within a range of 5 to 40 degrees
crank angle after the power piston associated with the power
cylinder has reached its top dead center position.
9. The split-cycle radial engine of claim 1, including an air
reservoir operatively connected to the pressure chambers by a
reservoir passage at locations between the inlet valve and the
outlet valve of each pressure chamber, the air reservoir being
selectively operable to receive and deliver compressed air.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a division of U.S. application Ser. No.
11/518,828 filed Sep. 11, 2006.
TECHNICAL FIELD
[0002] This invention relates to split-cycle engines, and more
particularly to split-cycle aircraft engines.
BACKGROUND OF THE INVENTION
[0003] The term split-cycle engine as used in the present
application may not have yet received a fixed meaning commonly
known to those skilled in the engine art. Accordingly, for purposes
of clarity, the following definition is offered for the term
split-cycle engine as may be applied to engines disclosed in the
prior art and as referred to in the present application.
[0004] A split-cycle engine as referred to herein comprises:
[0005] a crankshaft rotatable about a crankshaft axis;
[0006] a power piston slidably received within a power cylinder and
operatively connected to the crankshaft such that the power piston
reciprocates through a power (or expansion) stroke and an exhaust
stroke during a single rotation of the crankshaft;
[0007] a compression piston slidably received within a compression
cylinder and operatively connected to the crankshaft such that the
compression piston reciprocates through an intake stroke and a
compression stroke during a single rotation of the crankshaft;
and
[0008] a gas passage interconnecting the power and compression
cylinders, the gas passage including an inlet valve and an outlet
(or crossover) valve defining a pressure chamber therebetween.
[0009] U.S. Pat. Nos. 6,543,225, 6,609,371, and 6,952,923, all
assigned to the assignee of the present invention, disclose
examples of split-cycle internal combustion engines as herein
defined. These patents contain an extensive list of United States
and foreign patents and publications cited as background in the
allowance of these patents. The term "split-cycle" has been used
for these engines because they literally split the four strokes of
a conventional pressure/volume Otto cycle (i.e., intake,
compression, power and exhaust) over two dedicated cylinders: one
cylinder dedicated to the high pressure compression stroke, and the
other cylinder dedicated to the high pressure power stroke.
[0010] It is known in the art relating to aircraft engines to use
radial engines for aeronautical applications. For example, radial
engines were commonly used in World War II aircraft and in early
model commercial airplanes. Radial engines are still presently used
in some propeller-driven aircraft.
[0011] Radial engines differ from other common internal combustion
engines such as inline and V-type engines in the arrangement of the
engine cylinders. In a radial engine, the cylinders and
corresponding pistons are arranged radially around the engine
crankshaft in a circular pattern.
[0012] Radial engines are advantageous for airplane applications
because they can produce a large amount of power, they have a
relatively low maximum engine speed (rpm), avoiding the need for
reduction gearing to drive propellers, and they are suitable for
air cooling, eliminating the need for a water cooling system.
[0013] Although radial engines have been reliable aircraft engines
and less expensive than other types of aircraft engines, use of
radial engines in airplanes has substantially decreased.
Conventional radial engines tend to be noisy and to consume more
oil than other engine designs. Also, conventional radial engines
have mechanical issues such as oil draining into the lower
cylinders during non-use of the engine. This oil must be removed
from the cylinders by turning the engine over by hand prior to
starting the engine, which is an inconvenience to the pilot or the
ground crew.
[0014] It is also known in the art of aircraft engines to use
horizontally opposed engines, also known as "boxer" engines, to
drive the aircraft's propellers. Boxer-type engines differ from
other internal combustion engines in that the engine cylinders are
arranged in a horizontally opposed relationship.
[0015] Horizontally opposed engines have the advantages of being
more compact and having a lower center of gravity than other engine
configurations. Horizontally opposed engines, like radial engines,
potentially may be air-cooled, eliminating the need for a separate
engine cooling system and thereby decreasing the overall weight of
the engine. Therefore, horizontally opposed engines are suitable
for aircraft applications. Horizontally opposed engines are also
well balanced because each piston's momentum is counterbalanced by
the corresponding movement of the piston opposing it. This reduces
or may even eliminate the need for a balance shaft or
counterweights on the crankshaft, further reducing the overall
weight of the engine.
[0016] Horizontally opposed engines, however, are often noisier
than other engine configurations such as V-type engines and inline
engines. Also, horizontally opposed engines can be more difficult
to fit into an engine compartment because horizontally opposed
engines tend to be wider than other engine configurations.
[0017] It is further known in aeronautics that there are many uses
in an aircraft for compressed air. However, conventional aircraft
lack a convenient and efficient source of compressed air, thereby
rendering these potential uses of compressed air infeasible.
SUMMARY OF THE INVENTION
[0018] The present invention provides various split-cycle engine
arrangements for propeller-driven aircraft that are capable of
storing compressed air and delivering the compressed air back to
the engine or to other components of the aircraft.
[0019] In one embodiment of the present invention, a split-cycle
air hybrid aircraft engine includes a crankshaft rotatable about a
crankshaft axis. A power piston is slidably received within a power
cylinder and operatively connected to the crankshaft such that the
power piston reciprocates through an expansion stroke and an
exhaust stroke during a single rotation of the crankshaft. A
compression piston is slidably received within a compression
cylinder and operatively connected to the crankshaft such that the
compression piston reciprocates through an intake stroke and a
compression stroke during a single rotation of the crankshaft. A
gas crossover passage operatively interconnects the compression
cylinder and the power cylinder. The gas crossover passage includes
an inlet valve and an outlet valve defining a pressure chamber
therebetween. An air reservoir is operatively connected to the
pressure chamber by a reservoir passage at a location between the
inlet valve and the outlet valve of the pressure chamber. The air
reservoir is selectively operable to receive compressed air from
the compression cylinders and to deliver compressed air to the
power cylinders for use in transmitting power to the crankshaft
during engine operation. The air reservoir may also deliver
compressed air to other components of the aircraft. Valves
selectively control gas flow into and out of the compression and
power cylinders and the air reservoir. The engine is mounted to the
aircraft and the air reservoir is disposed within the aircraft.
Optionally, the air reservoir may be located in a wing of the
aircraft, in an aft fuselage of the aircraft, or both. Alternative
locations for the air reservoir are also within the scope of the
invention.
[0020] In another embodiment of the present invention, a
split-cycle horizontally opposed (i.e., "boxer") engine that may be
used for aircraft applications is provided. A split-cycle
horizontally opposed engine allows for the power cylinders to fire
once per revolution of the crankshaft rather then every other
revolution and allows the compression cylinders to compress charge
air during every revolution of the crankshaft. The split-cycle
horizontally opposed engine also allows for the compression
cylinders to operate with a larger diameter in comparison to the
power cylinders to increase the volume of air inhaled into the
engine, allowing for supercharging of the engine without the use of
an external supercharger.
[0021] More particularly, a split-cycle horizontally opposed
("boxer") engine in accordance with the invention includes a
crankshaft rotatable about a crankshaft axis. The split-cycle boxer
engine further includes a pair of horizontally opposed power
cylinders on either side of the crankshaft. A power piston is
slidably received within each power cylinder and is operatively
connected to the crankshaft such that each power piston
reciprocates through an expansion stroke and an exhaust stroke
during a single rotation of the crankshaft. The split-cycle boxer
engine also includes a pair of horizontally opposed compression
cylinders on either side of the crankshaft. A compression piston is
slidably received within each compression cylinder and is
operatively connected to the crankshaft such that each compression
piston reciprocates through an intake stroke and a compression
stroke during a single rotation of the crankshaft. A gas crossover
passage interconnects each compression cylinder with an associated,
axially adjacent power cylinder. The gas crossover passage includes
an inlet valve and an outlet valve defining a pressure chamber
therebetween. Valves control gas flow into the compression
cylinders and out of the power cylinders. An air reservoir may be
operatively connected to the pressure chambers by a reservoir
passage at locations between the inlet valve and the outlet valve
of each pressure chamber. The air reservoir is selectively operable
to receive and deliver compressed air.
[0022] In yet another embodiment of the present invention, a
split-cycle radial engine that may be used for aircraft
applications is provided. A split-cycle radial engine allows for
sequential firing of the cylinders, which increases the torque of
the engine. A split-cycle radial engine also allows for offsetting
of the engine cylinders relative to the crankshaft, further
increasing the torque of the engine and reducing piston-skirt
friction. Moreover, a split-cycle radial engine is capable of
inhaling larger volumes of charge intake air, which improves the
performance of the engine at high altitudes where the air is
thinner.
[0023] More particularly, a split-cycle radial engine in accordance
with the invention includes a crankshaft rotatable about a
crankshaft axis. The split-cycle radial engine further includes a
power bank including a plurality of power cylinders radially
disposed around the crankshaft. A power piston is slidably received
within each power cylinder and operatively connected to the
crankshaft such that each power piston reciprocates through an
expansion stroke and an exhaust stroke during a single rotation of
the crankshaft. A compression bank is axially adjacent the power
bank. The compression bank includes a plurality of compression
cylinders radially disposed around the crankshaft and equal in
quantity to the number of power cylinders. A compression piston is
slidably received within each compression cylinder and operatively
connected to the crankshaft such that each compression piston
reciprocates through an intake stroke and a compression stroke
during a single rotation of the crankshaft. Each compression
cylinder is paired with an associated power cylinder. Each
compression and power cylinder pair includes a gas crossover
passage interconnecting the compression cylinder and the power
cylinder of the pair. The gas crossover passage includes an inlet
valve and an outlet valve defining a pressure chamber therebetween.
Valves are also provided to control gas flow into the compression
cylinders and out of the power cylinders. An air reservoir may be
operatively connected to the pressure chambers by a reservoir
passage at locations between the inlet valve and the outlet valve
of each pressure chamber. The air reservoir is selectively operable
to receive and deliver compressed air.
[0024] These and other features and advantages of the invention
will be more fully understood from the following detailed
description of the invention taken together with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In the drawings:
[0026] FIG. 1 is a side schematic view of an aircraft including a
split-cycle air hybrid engine and compressed air tanks in
accordance with the invention;
[0027] FIG. 2 is a plan schematic view of the aircraft of FIG.
1;
[0028] FIG. 3 is a cross-sectional view of the aircraft taken along
the line 3-3 in FIG. 2;
[0029] FIG. 4 is a schematic view of a split-cycle horizontally
opposed ("boxer") engine in accordance with the invention having an
air storage tank illustrating pistons of the engine around top dead
center;
[0030] FIG. 5 is a cross-sectional view of the split-cycle
horizontally opposed engine taken along the line 5-5 in FIG. 4;
[0031] FIG. 6 is a cross-sectional view of the split-cycle
horizontally opposed engine taken along the line 6-6 in FIG. 4;
[0032] FIG. 7 is another schematic view of the split-cycle
horizontally opposed engine of FIG. 4 illustrating the pistons
around bottom dead center;
[0033] FIG. 8 is a cross-sectional view of the split-cycle
horizontally opposed engine taken along the line 8-8 in FIG. 7;
[0034] FIG. 9 is a cross-sectional view of the split-cycle
horizontally opposed engine taken along the line 9-9 in FIG. 7;
[0035] FIG. 10 is a schematic view of a split-cycle radial engine
in accordance with the invention having an air storage tank;
[0036] FIG. 11 is a schematic view of a compression bank of the
split-cycle radial engine of FIG. 10; and
[0037] FIG. 12 is a schematic view of a power bank of the
split-cycle radial engine of FIG. 10.
DETAILED DESCRIPTION OF THE INVENTION
[0038] Referring now to the drawings in detail, numeral 10
generally indicates a propeller-driven aircraft. As illustrated in
FIGS. 1 through 3, the aircraft 10 has a pair of wings 12, a wing
spar 14 in the wings 12, a cockpit 16, a tail 18, and an aft
fuselage 20. The aircraft 10 may have one wing spar 14 spanning
both wings 12, or a separate wing spar may be located in each wing
12. A split-cycle engine 22 in accordance with the invention is
mounted in the aircraft 10 forward of the cockpit 16 to drive the
propeller 24. Air storage tanks 26 may be located in the wing spar
14, the aft fuselage 20, or both. The air storage tank(s) may also
be located in any other suitable location within the aircraft 10,
for example, in a suitable location within the wings 12 other than
the wing spar 14.
[0039] Turning first to FIGS. 4 through 9, in one embodiment of the
invention, the split-cycle engine 22 may be a horizontally opposed
("boxer") type split-cycle engine. The split-cycle boxer engine 22
includes a crankshaft 28 rotatable about a crankshaft axis 30. The
split-cycle boxer engine 22 further includes a pair of horizontally
opposed power cylinders 34 on either side of the crankshaft 28. A
power piston 36 is slidably received within each power cylinder 34
and is operatively connected to the crankshaft 28 such that each
power piston 36 reciprocates through an expansion stroke and an
exhaust stroke during a single rotation of the crankshaft 28. The
split-cycle boxer engine 22 also includes a pair of horizontally
opposed compression cylinders 40 on either side of the crankshaft
28. A compression piston 42 is slidably received within each
compression cylinder 40 and is operatively connected to the
crankshaft 28 such that each compression piston 42 reciprocates
through an intake stroke and a compression stroke during a single
rotation of the crankshaft 28. A gas crossover passage 44
interconnects each compression cylinder 40 with an associated,
axially adjacent power cylinder 34. The gas crossover passage 44
includes an inlet valve 46 and an outlet valve 48 defining a
pressure chamber 50 therebetween. The air pressure in the pressure
chamber 50 is maintained at an elevated minimum pressure through
the engine cycles. Valves 52 control gas flow into the compression
cylinders 40 and out of the power cylinders 34. The valves 44, 46,
52 may be check valves, poppet valves, or any other suitable valve.
The valves 44, 46, 52 may be cam actuated, electronically actuated,
pneumatically actuated, or hydraulically actuated. The air
reservoir 26 may be operatively connected to the pressure chambers
50 by a reservoir passage 54 at locations between the inlet valve
46 and the outlet valve 48 of each pressure chamber 50. The air
reservoir 26 is selectively operable to receive and deliver
compressed air.
[0040] The split-cycle boxer engine 22 shown in FIGS. 4 through 9
includes one pair of power cylinders 34 and one pair of compression
cylinders 40 for a total of four cylinders. If additional
horsepower is desired, another pair of power cylinders and
compression cylinders may be added for a total of eight cylinders.
It should be understood, however, that the engine 22 may have any
number of cylinders, so long as there are an even number of power
cylinders, an even number of compression cylinders, and an equal
number of power and compression cylinders (since each power
cylinder must be paired with a compression cylinder).
[0041] The power cylinders 34 may be disposed in front of the
compression cylinders 40 to allow for improved air-cooling of the
hotter power cylinders 34 during engine operation. A longitudinal
axis 56 of each compression cylinder 40 and each power cylinder 34
may be offset from the rotational axis 30 of the crankshaft 28. The
offset of the cylinder axes 56 from the crankshaft axis 30 allows
for greater mechanical advantage and increased torque. On each side
of the engine 22 one of a pair of horizontally opposed cylinders is
raised above the rotational axis 30 of the crankshaft 28 and the
other is lowered below the rotational axis 30 of the crankshaft 28.
Further, because the compression cylinders 40 are separate from the
power cylinders 34, the compression cylinders 40 may be designed to
have a larger diameter than the power cylinders 34. This results in
the compression cylinders 40 having a larger volume than the power
cylinders 34, allowing the engine to be supercharged without the
use of an external supercharger. This also can improve engine
efficiency at higher altitudes by allowing the engine to intake
larger volumes of thin air compared to conventional engines. The
power pistons 36 may also be designed with a longer throw on the
crankshaft 28 compared to the compression pistons 42 for a longer
stroke to over-expand the gas in the power cylinders 34 and to
provide increased efficiency, i.e., the Miller Effect.
[0042] The compression pistons 42 lag slightly behind the power
pistons 36 (in degrees of crank angle rotation). This is in
contrast to conventional horizontally opposed engines in which
neighboring pairs of pistons travel 180 crank angle degrees apart.
During operation of the engine 22, as the compression pistons 42
reach top dead center (TDC), the power pistons 36 have already
reached TDC and have begun the power stroke. Fuel is ignited in
each power cylinder 34 within a range of 5 to 40 degrees crank
angle after the power piston 36 associated with the power cylinder
34 has reached its top dead center position (degrees ATDC).
Preferably, fuel is ignited in each power cylinder 34 within a
range of 10 to 30 degrees ATDC.
[0043] FIGS. 4 through 6 illustrate the compression pistons 42 at
approximately the TDC position and the power pistons 36 moving away
from TDC towards bottom dead center (BDC). The rotational direction
of the crankshaft 28 (FIG. 5) and the relative motions of the power
pistons 36 (FIG. 6) are indicated by the arrows associated in the
drawings with their corresponding components. FIGS. 7 through 9
illustrate the compression pistons 42 at approximately the BDC
position and the power pistons 36 moving away from BDC towards TDC.
The rotational direction of the crankshaft 28 (FIGS. 8 and 9) and
the relative motions of the power pistons 36 and compression
pistons 42 (FIGS. 7 and 9) are indicated by the arrows associated
in the drawings with their corresponding components.
[0044] The power pistons 36 may be operatively connected to the
crankshaft 28 by separate crank pins/journals 43 that are 180
degrees apart relative to the crankshaft axis 30. The paired power
pistons 36 therefore reach top dead center simultaneously.
Likewise, the compression pistons 42 may be operatively connected
to the crankshaft 28 by separate crank pins/journals 42 that are
also 180 degrees apart relative to the crankshaft axis 30. The
paired compression pistons 42 therefore also reach top dead center
simultaneously.
[0045] A spark plug (not shown) may extend into the each of the
power cylinders 34 for igniting air-fuel charges at precise times
by an ignition control, also not shown. It should be understood
that the engine 22 may be made as a diesel engine and be operated
without a spark plug if desired. Moreover, the engine 22 may be
designed to operate on any fuel suitable for reciprocating piston
engines in general, such as hydrogen, natural gas or
bio-diesel.
[0046] With the use of the air reservoirs 26, the split-cycle
engine 22 can function as an air hybrid. The compression cylinders
40 may then be selectively controllable to place the compression
pistons 42 in a compression mode or an idle mode. The power
cylinders 34 similarly may be selectively controllable to place the
power pistons 36 in a power mode or an idle mode. Further, the
engine 22 may be operable in at least three modes, including an
internal combustion engine (ICE) mode, an air compressor (AC) mode
and a pre-compressed air power (PAP) mode. In the ICE mode, the
compression pistons 42 and power pistons 36 are in their respective
compression and power modes, in that the compression pistons 42
draw in and compress inlet air for use in the power cylinders 34,
and compressed air is admitted to the power cylinders 34 with fuel,
at the beginning of an expansion stroke, which is ignited, burned
and expanded on the same expansion stroke of the power pistons 36,
transmitting power to the crankshaft 28, and the combustion
products are discharged on the exhaust stroke. In the AC mode, the
compression pistons 42 are in the compression mode and they draw in
and compress air that is stored in the air reservoir 26 for later
use in the power cylinder or other aircraft components as described
in more detail below. In the PAP mode, the power cylinders 34 are
in the power mode and receive compressed air from the air reservoir
26 which is expanded on the expansion stroke of the power pistons
36, transmitting power to the crankshaft 28, and the expanded air
is discharged on the exhaust stroke.
[0047] Optionally, in the PAP mode, fuel may be mixed with the
compressed air at the beginning of an expansion stroke and the
mixture may be ignited, burned and expanded on the same expansion
stroke of the power pistons 36, transmitting power to the
crankshaft 28, and the combustion products may be discharged on the
exhaust stroke. Alternatively, in the PAP mode, the compressed air
admitted to the power cylinders 34 may be expanded without adding
fuel or initiating combustion.
[0048] Excess compressed air, i.e., air that is not used for
combustion in the power cylinders 34, is transferred from the
pressure chambers 50 to the air storage tank(s) 26 via the
reservoir passage 54. The stored compressed air may be used for a
variety of applications. Such applications may include but are not
limited to: a) starting the engine in lieu of an electric starter;
b) cabin pressurization; c) inflation of inflatable door seals in
pressurized aircraft; d) wheel braking, by either actuating the
brake shoes and/or through the active resistance of pressurized air
against spinning wheels; e) rotating the propellers for taxiing
short distances without fuel being injected into the engine (see
PAP mode above); f) driving the wheels of the aircraft to taxi the
aircraft without starting the engine and without having the
propeller turning (allowing for safer taxiing); g) spinning up the
aircraft's wheels before landing so the tires are not subjected to
as much frictional wear when they touch the ground during a
landing; h) providing a breaking force on the aircraft's wheels for
quick stopping in addition to the aircraft's conventional brakes;
i) operating the engine with compressed air when the compression
cylinders are in an idle mode (see PAP mode above); j) operating
flight instruments that utilize gyros; k) providing fuel pressure
in the event of a fuel pump failure; l) actuating flight controls
and landing gear, for example an air pressure regulating valve
could be used to provide finely tuned trim pressure on the control
surfaces and could also operate leading edge slats; m) expelling
ice from the aircraft's wings; n) inflating airbags for crash
protection; o) opening a whole aircraft recovery parachute of a
whole aircraft parachute recovery system in lieu of a rocket motor;
p) operating emergency evacuation chutes; q) deploying pesticides,
fire retardants, flares, munitions, and other items from special
use aircraft; r) ejecting water from the aircraft floats and hulls
of amphibious aircraft; and s) venting air from small holes in the
top of the wings to mimic the effects of vortex generators at slow
speeds.
[0049] Optionally, the engine 22 may also be operable in at least a
fourth mode, herein designated a high power (HP) mode. In the HP
mode, the compression cylinders 40 are selectively controllable to
operate, in effect, as additional power cylinders having expansion
strokes and exhaust strokes instead of intake strokes and
compression strokes.
[0050] During the HP mode, no ambient air is inhaled into the
compression cylinders 40 through intake valves 52. Rather, both the
compression cylinders 40 and power cylinders 34 receive compressed
air from the air reservoir 26, which is expanded on the compression
and power cylinder's respective expansion strokes and discharged on
their respective exhaust strokes.
[0051] In a preferred embodiment of the HP mode, the power piston
36 transmits power to the crankshaft 28 through the process of
combustion, while the compression piston 42 transmits power to the
crankshaft 28 through the process of expanding air from the air
reservoir 26 without combustion. That is, in the power cylinder 34,
fuel is mixed with the compressed air at the beginning of an
expansion stroke and the mixture is ignited, burned and expanded on
the same expansion stroke of the power cylinder 34. Meanwhile, in
the compression cylinder 40, compressed air admitted to the
compression cylinder 40 is expanded on the expansion stroke of the
compression cylinder 40 without adding fuel or initiating
combustion.
[0052] Operating the engine 22 in HP mode literally doubles the
number of power strokes available to the aircraft for as long as
the air reservoir 26 remains charged with enough air pressure to
maintain the HP mode. This mode is useful for increasing power to
the aircraft during critical short-term operations, such as gaining
altitude to fly over a mountain or quickly accelerating to high
speeds for short take-offs. Moreover, the air reservoir can be over
pressurized by an external compressor on the ground to enable the
engine 22 to operate in HP mode for longer periods of time during
take-offs.
[0053] Turning now to FIGS. 10 through 12, in an alternative
embodiment of the invention, the split-cycle engine 122 may be a
radial-type split-cycle engine. The split-cycle radial engine 122
includes a crankshaft 128 rotatable about a crankshaft axis 130.
The engine 122 has a power bank 132 including a plurality of power
cylinders 134 radially disposed around the crankshaft 128. A power
piston 136 is slidably received within each power cylinder 134 and
is operatively connected to the crankshaft 128 such that each power
piston 136 reciprocates through an expansion stroke and an exhaust
stroke during a single rotation of the crankshaft 128. A
compression bank 138 is axially adjacent the power bank 132. The
compression bank 138 includes a plurality of compression cylinders
140 radially disposed around the crankshaft 128 and equal in
quantity to the number of power cylinders 134. A compression piston
142 is slidably received within each compression cylinder 140 and
operatively connected to the crankshaft 128 such that each
compression piston 142 reciprocates through an intake stroke and a
compression stroke during a single rotation of the crankshaft 128.
Each compression cylinder 140 is paired with an associated power
cylinder 134. Each compression 140 and power cylinder 134 pair
includes a gas crossover passage 144 interconnecting the
compression cylinder 140 and the power cylinder 134 of the pair.
The gas crossover passage 144 includes an inlet valve 146 and an
outlet valve 148 defining a pressure chamber 150 therebetween.
Valves 152 are also provided to control gas flow into the
compression cylinders 140 and out of the power cylinders 134. The
valves 144, 146, 152 may be check valves, poppet valves, or any
other suitable valve. The valves 144, 146, 152 may be cam actuated,
electronically actuated, pneumatically actuated, or hydraulically
actuated. An air reservoir 126 may be operatively connected to the
pressure chambers 150 by a reservoir passage 154 at locations
between the inlet valve 146 and the outlet valve 148 of each
pressure chamber 150. The air reservoir 126 is selectively operable
to receive and deliver compressed air.
[0054] The power bank 132 may be disposed in front of the
compression bank 138 to allow for improved air-cooling of the
hotter power bank 132 during engine operation. The compression
cylinders 140 of the compression bank 138 may be rotated relative
to the power cylinders 134 of the power bank 132. In other words,
the compression cylinders 140 may not be directly in line with the
power cylinders 134 but instead may be rotated a few degrees
generally relative to the crankshaft 128 to enhance the flow of air
over the compression cylinders 140. Further, a longitudinal axis
156 of each compression cylinder 140 may be offset from the
rotational axis 130 of the crankshaft 128. Similarly, a
longitudinal axis 156 of each power cylinder 134 also may be offset
from the rotational axis 130 of the crankshaft 128. The compression
cylinders 140 may have a larger diameter than the power cylinders
134 to allow for a larger volume of intake air. The compression
pistons 142 may also have a shorter stroke than the power pistons
136.
[0055] One of the power pistons 136 may be operatively connected to
the crankshaft 128 by a first fixed master rod 158 and the
remainder of the power pistons 136 may be operatively connected to
the first master rod 158 by articulating rods 160. The first master
rod 158 has a hub 161 at one end (and hence is fixed to the hub
161). The articulating rods 160 are pivotally connected to the hub
by knuckle pins or other suitable means. Similarly, one of the
compression pistons 142 may be operatively connected to the
crankshaft 128 by a second fixed master rod 162 and the remainder
of the compression pistons 142 may be operatively connected to the
second master rod 162 by articulating rods 164. The second master
rod has a hub 166 at one end (and hence is fixed to the hub 166).
The articulating rods 164 are pivotally connected to the hub 166 by
knuckle pins or other suitable pivotal connection means. It should
be understood, however, that the power and compression pistons may
be operatively connected to the crankshaft by other mechanical
arrangements.
[0056] The split-cycle radial engine 122 may include between three
and nine power cylinders and an equivalent number of compression
cylinders. In the embodiment shown in the drawings, the engine 122
has five power cylinders 134 and five compression cylinders 140. It
should be understood, however, that the split-cycle radial engine
122 is not limited to any particular number of power and
compression cylinders, so long as there are an equal number of
power and compression cylinders and there are at least three power
cylinders and three compression cylinders.
[0057] If additional power is desired, the split-cycle radial
engine 122 may also optionally include a second power bank having a
plurality of power cylinders radially disposed around the
crankshaft and a second compression bank axially adjacent the
second power bank including a plurality of compression cylinders
radially disposed around the crankshaft and equal in quantity to
the number of power cylinders. The second power bank may be axially
adjacent the first compression bank in such a way that the four
banks are aligned in a row. A power piston is slidably received
within each power cylinder of the second power bank and is
operatively connected to the crankshaft such that each power piston
reciprocates through an expansion stroke and an exhaust stroke
during a single rotation of the crankshaft. Likewise, a compression
piston is slidably received within each compression cylinder and
operatively connected to the crankshaft such that each compression
piston reciprocates through an intake stroke and a compression
stroke during a single rotation of the crankshaft. Each compression
cylinder of the second compression bank is paired with an
associated power cylinder of the second power bank. Each
compression and power cylinder pair of the second compression bank
and second power bank includes a gas crossover passage
interconnecting the compression cylinder and the power cylinder of
the pair. The gas crossover passage includes an inlet valve and an
outlet valve defining a pressure chamber therebetween. Valves also
control gas flow into the compression cylinders of the second
compression bank and out of the power cylinders of the second power
bank. It should be understood that the split-cycle radial engine
122 may have any number of banks, so long as there is an equal
number of power and compression banks.
[0058] The compression pistons 142 lag slightly behind the power
pistons 136 (in degrees of crank angle rotation). During operation
of the engine, as the compression pistons 142 reach top dead center
(TDC), the power pistons 136 have already reached TDC and have
begun the power stroke. Fuel is ignited in each power cylinder 134
within a range of 5 to 40 degrees crank angle after the power
piston 136 associated with the power cylinder 134 has reached its
top dead center position (degrees ATDC). Preferably, fuel is
ignited in each power cylinder 134 within a range of 10 to 30
degrees ATDC. The power cylinders 134 may be arranged to fire in
sequential order as the crankshaft rotates. Further, each power
cylinder 134 fires once per revolution of the crankshaft 128. This
is in contrast to conventional four-stroke radial engines, wherein
as the crankshaft rotates, every other cylinder fires such that for
every two rotations of the crankshaft, every cylinder fires one
time. The rotational direction of the crankshaft 128 is indicated
by an arrow in FIGS. 10-12 that is associated with the
crankshaft.
[0059] Spark plugs 168 may be provided having electrodes extending
into the each of the power cylinders 134 for igniting air-fuel
charges at precise times by an ignition control, not shown. It
should be understood that the engine 122 may be made as a diesel
engine and be operated without a spark plug if desired.
[0060] Although the invention has been described by reference to
specific embodiments, it should be understood that numerous changes
may be made within the spirit and scope of the inventive concepts
described. Accordingly, it is intended that the invention not be
limited to the described embodiments, but that it have the full
scope defined by the language of the following claims.
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