U.S. patent number RE35,172 [Application Number 08/375,381] was granted by the patent office on 1996-03-12 for pulsed piston-compressor jet engine.
Invention is credited to Barre A. M. Clark.
United States Patent |
RE35,172 |
Clark |
March 12, 1996 |
Pulsed piston-compressor jet engine
Abstract
An air-breathing pulsed jet engine for aircraft propulsion which
employs a piston compressor rather than much more expensive axial
or centrifugal compressors and turbines employed by conventional
turbojet engines. The engine is similar to the common two-cycle
gasoline engine, except its cylinder head comprises a jet nozzle
with an internal pressure-activated nozzle-blocking valve. A spring
keeps this valve closed during the engine's compression stroke when
the piston, connected to a crankshaft and flywheels by a connecting
rod, is forced by the moment-of-inertia of the flywheels toward the
cylinder head. When ignition and combustion of the compressed air
and fuel occurs slightly before the piston reaches the top of its
stroke, the much greater pressures within the engine's combustion
chamber force the valve to pivot open. This allows a jet of
combustion gases to be released through the jet nozzle into the
atmosphere. The reactive forces of the gas jet work against the
piston to produce linear thrust (due to the moment-of-inertia of
the flywheels) and to store up energy in the flywheels to motivate
the piston through the next compression stroke. The jet pulse
continues until the pressure inside the combustion chamber drops to
a predetermined level, when the spring is able to close the valve.
Since the pressure inside the combustion chamber of a gasoline
engine are on the order of those inside many rocket motors, the
thrusts imparted to the engine during each jet pulse is
substantial.
Inventors: |
Clark; Barre A. M. (Mammoth
Lakes, CA) |
Family
ID: |
21968907 |
Appl.
No.: |
08/375,381 |
Filed: |
January 17, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
051026 |
Apr 21, 1993 |
05361581 |
Nov 8, 1994 |
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Current U.S.
Class: |
60/247 |
Current CPC
Class: |
F02K
5/023 (20130101); F02K 7/06 (20130101); Y02T
50/671 (20130101); F02B 1/04 (20130101); F02B
2075/025 (20130101); Y02T 50/60 (20130101) |
Current International
Class: |
F02K
7/06 (20060101); F02K 5/00 (20060101); F02K
5/02 (20060101); F02K 7/00 (20060101); F02B
1/04 (20060101); F02B 75/02 (20060101); F02B
1/00 (20060101); F02K 005/02 () |
Field of
Search: |
;60/247,269,729,271 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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390256 |
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Jul 1908 |
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FR |
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1027474 |
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May 1953 |
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FR |
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Primary Examiner: Thorpe; Timothy S.
Attorney, Agent or Firm: Heisler; Bradley P.
Claims
I claim:
1. A pulsed piston-compressor jet engine comprised
a. an engine cylinder having two ends .[.and attached at one of
said two ends to a cylinder head.].,
b. a piston fitted inside said cylinder in a manner allowing said
piston to reciprocate .[.towards and away from said cylinder
head.]. .Iadd.between said two ends, .Iaddend.
c. said cylinder .[.head.]. including a jet nozzle operatively
coupled thereto, said jet nozzle having an inner surface and
including a nozzle outlet opening .[.directly.]. into the
atmosphere, said cylinder .[.head.]. also including a
pressure-actuated nozzle valve having an opened position and a
closed position, and which, when in said closed position, closes
said jet nozzle between said piston and said nozzle outlet in a
substantially sealing manner for a compression of a supply of
air,
d. a combustion chamber including a space between said piston and
said nozzle valve's closed position,
e. said pressure-actuated nozzle valve having a valve face defining
.[.one.]. .Iadd.a .Iaddend.surface of said nozzle valve, said valve
face comprising part of said inner surface of said jet nozzle when
said nozzle valve is in said opened position, leaving said jet
nozzle .[.substantially unobstructed.]. .Iadd.without a
substantially detrimental obstruction, .Iaddend.a portion of said
valve face facing part of said combustion chamber and .Iadd.at
least partially .Iaddend.blocking .[.in part.]. said jet nozzle
when said nozzle valve is in said closed position, said nozzle
valve having a closing means providing closing forces to move said
nozzle valve to said closed position whenever pressures from a
combustion within said combustion chamber drop below a
.[.predetermined value.]. .Iadd.certain amount, .Iaddend..[.said
closing means also holding said nozzle valve in said closed
position with a holding force adequate to keep said nozzle valve in
said closed position during said compression of said supply of
air,.]. said combustion in said combustion chamber generating
pressures against said portion of said valve face facing part of
said combustion chamber to produce opening forces on said nozzle
valve, .[.said opening forces overcoming said holding force and
said closing forces, allowing.]. .Iadd.causing .Iaddend.said nozzle
valve to retract to said opened position, whereby a gas jet is
released substantially unhindered through said jet nozzle into the
atmosphere due to a direct action of said combustion on said nozzle
valve,
f. means to provide said supply of air into said combustion
chamber,
g. means to provide a supply of fuel into said combustion
chamber,
h. means to move said piston toward said .[.cylinder head.].
.Iadd.jet nozzle, .Iaddend.causing said compression of said supply
of air within said combustion chamber when said nozzle valve is
closed,
i. means to cause ignition of said supply of air and said supply of
fuel within said combustion chamber after said compression of said
supply of air, said ignition means causing said combustion which,
in turn, causes said nozzle valve to open and said piston to move
away from said .[.cylinder head.]. .Iadd.jet nozzle, and
.Iaddend.
j. .[.means to keep said nozzle valve closed during operation of
engine when desired, and k..]. means to impart reactive force of
said gas jet to said pulsed piston-compressor jet engine, whereby a
useful thrust is obtained.
Description
BACKGROUND-FIELD OF INVENTION
This invention relates to air-breathing jet-propulsion engines
which use a compressor to compress incoming air or air/fuel vapors
before a combustion whose gases are expelled from a jet nozzle to
produce reactive thrust for aeropropulsion.
BACKGROUND-DESCRIPTION OF PRIOR ART
Practical jet engines up to this time have been turbojet engines
which utilize either centrifugal or axial compressors. These
engines compress atmospheric air before a combustion, and then
turbines are turned by the released combustion gases to drive the
compressor. The idea of using a piston-type compressor to supply
high-pressure air or fuel/air vapors for jet propulsion has been
thought of since at least 1912.
In 1901 Pinkert patented (U.S. Pat. No. 672,287) an engine for
propelling watercraft. It exploded solid charges in a cylinder
whose underwater outlet was pointed aft of the vessel. A smaller
cylinder was set at the enclosed end of the main cylinder and
contained a piston. This piston's sole purpose was to drive a
crankshaft after an explosion to operate a mechanism for injecting
successive explosive charges into the larger cylinder. The
principle of the invention was that the exploding gases would work
against the water partly intruding into the main cylinder to propel
the vessel forward.
In 1912 Lewis patented (U.S. Pat. No. 1,035,454) an internal
combustion power apparatus for powering watercraft, aircraft, or
turbines. This two-cycle engine utilized two pistons fixed on a
single cylindrical shaft which reciprocated in two adjacent
cylinders. One of these cylinders served as a combustion chamber
and the other as an intake and holding chamber for air/fuel vapors.
The shaft extended through the combustion chamber and through a
circular opening leading to a conical jet nozzle and continued
through the circular throat of the nozzle into the nozzle itself.
Expanded-diameter lengths of the shaft acted as valves, plugging
and unplugging passages for fuel vapors and exhaust gases,
including the throat of the jet nozzle. This resulted in a pulse of
combustion gases being expelled from the jet nozzle each cycle of
the reciprocating pistons. In 1952 Swartz patented (U.S. Pat. No.
2,587,073) a compound reciprocating-pulse jet aircraft power plant
which utilized combustion gases ignited in a cylinder between a
piston and unique cylinder head. This cylinder head consisted of
two symmetric and interlocking clamshell-shaped valves which kept
the end of the cylinder closed as the piston compressed air/fuel
vapors. Upon ignition of the compressed vapors the valves would
open, .[.allow.]. .Iadd.allowing .Iaddend.combustion gases to be
released into a "combustion chamber." At the same time the
backsides of the valves would close off ports which supplyed fresh
air to this combustion chamber. Fuel would then be added to the mix
of other gases in the combustion chamber, an ignition would occur,
and the resulting gases would exit through the chamber's only
remaining opening to the atmosphere, a jet nozzle. Jet pulses were
to occur for every other cycle of the reciprocating piston.
In 1964 Reilly patented (U.S. Pat. No. 3,163,001) a reciprocating
piston pulse jet engine. This engine employed a reciprocating
piston in a cylinder and a cylinder head which had an aperture
opening into a jet nozzle. The piston had a protruding plug in the
center of its face. The piston was allowed to make contact with the
cylinder head at one end of its stroke when the plug then sealed
off the aperture to the nozzle. An annular volume between the
piston face and the cylinder head was created at this time because
of the presence of an annular indentation formed on the piston
face. Compressed air/fuel vapors injected into this volume from a
delay chamber were then ignited. The resulting high-pressure
combustion gases then pushed the piston down the cylinder. This
opened the nozzle aperture and the gases escaped out the jet nozzle
to produce thrust.
Each of the foregoing inventions have limitations which probably
prevented them from becoming useful and practical engines for
aircraft propulsion. For effective jet propulsion it is essential
that high-pressure gases be transformed into a stream of
high-speed, and therefore high-momentum, gases. An equivalent
momentum is then imparted to the engine in the opposite direction,
according to Newton's third law of motion. To transform pressure
into velocity a combustion chamber must open to the atmosphere via
a constricted opening. Where combustion chamber pressures are much
greater than twice that of the atmosphere the standardly-used De
Laval nozzle is employed. In a De Laval nozzle the combustion
chamber converges towards a constricted opening called a throat.
This throat then opens to the atmosphere via a diverging-volume
outlet. Gases emerging from such a nozzle are at supersonic
speeds.
Pinkert's engine was not designed for aircraft propulsion and thus
does not have a combustion chamber that converges towards its
outlet. Its use of solid fuel would probably result in high fuel
costs and a bulky feed mechanism. Lewis' design has several
characteristics which would limit its performance. First, there is
a relatively narrow cylindrical passageway in the nipple leading to
the nozzle throat due to the presence of the rod. This would
produce a resistance to the combustion gases flowing toward the
throat, resisting their acceleration while causing a detrimental
pressure decrease. Also, because the output of the nipple opens to
an air space between the nipple and suction tube the pressure of
the gases there would be detrimentally decreased further. In
addition, because the flow of gases into and out of a throat should
be smooth for non-turbulent flow the thrust would be diminished
further by the way the stem broadens in the nozzle and by its
abrupt flat end, both of which would cause turbulence. And finally,
it appears from Lewis' drawings that the compression ratio of the
engine is only about two-to-one, compared to the optimum of about
eight-to-one for standard gasoline piston engines.
The cylinder and piston in Swartz's engine seem to have two
purposes. The first is to open the clamshell-shaped valves to close
off the incoming-air port of the combustion chamber, in a way
similar to that of the inlet shutter valves of the pulse jet of the
German V-1 flying bomb. The second purpose is to provide combusters
gases to the combustion chamber- The valves, therefore, are only
designed for allowing and blocking the sage of gases out of the
cylinder as well as blocking the fresh-air ports. These valves can
not act as jet nozzles producing a high speed gas jet because of
their interproducing teeth and sharp internal corners, both of
which would create turbulence, and therefore low speed gas flow.
Also, the wide angle made by the diverging inner surfaces when the
valves are open is much greater than that of an effective diverging
section of a jet .[.noble.]. .Iadd.nozzle .Iaddend.which is between
approximately 20 and 50 degrees. Since these valves pass exhaust
molecules into the combustion chamber, it seems like the ensuing
combustion would be hindered rather than helped, as claimed. Also,
there is no compression in the combustion chamber besides that
caused by ram air. And since the combustion chamber is not shaped
to turn velocity into pressure, like a ram jet's internal chamber,
the compression from ramming would be small. Therefore the
resulting combustion pressure and resulting thrust would be
relatively small. In addition Swartz's engine is a four-cycle
design, which produces half as many pulses, and therefore half the
average thrust, of an otherwisely similar two-cycle engine.
Reilly's engine is very complicated, having a high parts count
which includes four valves. This would have a detrimental effect on
the engine's reliability and cost. The design would produce
relatively low thrust because the compression ratio is apparentely
only about two-to-one to three-to-one. This is apparent from the
relative sizes of the cylinder and delay chamber as shown m the
drawings. Also, the release of vapors from the delay chamber to the
firing chamber will reduce pressures in both to an equal and Dower
pressure. In addition, a large proportion of the vapors will remain
in the delay chamber for each cycle. And finally, since ignition in
Reilly's engine can only occur when the piston meets the cylinder
head there can be no spark advance as speed increases to compensate
for the finite flame speed of the combustion., which is typically
50-100 feet/sec.
OBJECTS AND ADVANTAGES
There are numerous objects and advantages of my engine relative to
the engines just discussed and conventional turbojet engines.
Compared to the turbojet engine, with its hundreds of
precision-formed, high-strength blades and vanes my engine is
vastly simpler and will be much cheaper to manufacture. Although my
engine probably could not be competitive in high-thrust
applications, such as powering high performance military aircraft
or large aircraft in general, in the smaller classes it could
probably replace turbojets in certain applications. And because
turbojet engines cannot be practically built and produce useful
thrust below a certain size, and my design is similar to engines
that power model aircraft, new applications for jet engines may
become realizable. One such application could be the strap-on jet
belt, which has only been realized using 20-second-duration rocket
engines. FIGS. 16 to 20 show some potential applications of my
engine, and are explained .[.on pages 7 and 8.]. .Iadd.below
.Iaddend..
Compared to the somewhat similar patented engines just discussed my
engine has numerous advantages that should make it powerful and
simple enough to be practical. My engine has a single piston and
single valve, and a single space between the piston and cylinder
head that serves as the compression chamber, combustion chamber and
part of the jet nozzle. Since my engine has a relatively high
compression ratio and therefore high combustion pressures (about
1000 pounds per square inch, or psi) it employs a De Laval nozzle
which has smooth and gently curving surfaces to produce supersonic
gas velocities comparable to those of many rocket engines, with a
corresponding thrust. Most of my engine employs the very mature
technologies related to the ubiquitous two-cycle gasoline engine,
which has been mass-produced for many decades. My engine uses a
simple locking pin to keep the nozzle valve closed when desired to
allow warming-up, idling, or checkout before flight. It can use a
conventional variable-timing ignition system and a conventional
carburetor. The variable ignition timing along with an adjustment
to change valve-opening pressure allow for optimum performance over
a wide range of power settings as well as tuning for changes in
fuel type, ambient temperatures-altitude, and other variables.
Further objects and advantages of my engine will become apparent in
the drawings and following description.
DRAWING FIGURES
FIG. 1 is a right-side sectional elevation of the crankcase and
cylinder head of my engine with non-sectional views of the
installed parts.
FIG. 2 is a top section of the crankcase and cylinder head with
non-sectional views of the installed parts.
FIG. 3 is a rear elevation view looking into the jet nozzle when
nozzle valve is open.
FIG. 4 is a transparent perspective view illustrating the various
features of the nozzle valve and throat region.
FIG. 5 is a perspective view of the nozzle valve.
FIG. 6 is an additional transparent perspective view of the nozzle
valve and jet nozzle showing valve closing and locking
mechanisms.
FIG. 7 illustrates an alternative design with a triangular-flap
nozzle valve and a throat region with triangular sections.
FIG. 8 illustrates an alternative design with a disk-shaped flap
nozzle valve and a conical throat region.
FIG. 9 illustrates an alternative design with a sliding-septum
nozzle valve and a conical throat region.
FIGS. 10-13 illustrate successive events occurring during one
engine cycle.
FIG. 10 illustrates the moment during the downstroke of the piston
when the induction port is uncovered and air/fuel vapors are
injected into the combustion chamber (valve closed).
FIG. 11 illustrates compression of the air/fuel vapors during the
piston's upstroke.
FIG. 12 shows the moment of ignition when combustion starts, the
valve opens, a gas jet develops, and a new air/fuel vapor charge is
inducted into the .[.cylinder and.]. crankcase.
FIG. 13 illustrates when the piston is at top-dead-center and the
jet pulse and thrust are at their approximate peaks.
FIG. 14 illustrates the continuation of the jet pulse as the piston
is on its downstroke, compressing the air/fuel vapor charge for the
next cycle.
FIG. 15 shows the piston uncovering the low-pressure exhaust port,
which causes the valve to close and the jet pulse to cease.
FIG. 16 shows my engine powering a four-to-six place passenger
plane.
FIG. 17 shows my engine powering a military drone.
FIG. 18 shows my engine powering a vertical takeoff/landing (VTOL)
aircraft.
FIG. 19 shows my engine powering a personal "jet belt."
FIG. 20 shows my engine powering a radio-controlled model
aircraft.
______________________________________ Reference Numerals in
Drawings ______________________________________ 21 piston 22
cylinder 23 connecting rod 24 crankpin 25 crankshaft 26 flywheel 27
crankcase 28 injection port 29 low-pressure exhaust port 30
cylinder head 31 cylinder head bolts 32 head gasket 33 spark plug
34 combustion chamber 35 not used 36 nozzle converging volume 37
throat 38 nozzle diverging volume 39 nozzle valve 40 valve locking
hole 41 valve spring 42 adjustment bolt 43 high-voltage lead 44
induction port 45 valve locking pin 46 valve axis 47 spring socket
48 starter/electrical ignition system 49 roller bearings 50
direction of rotation 51 air/fuel vapors 52 combustion 53 not used
54 gas jet 55 thrust 56 low-pressure exhaust 57 high-pressure force
58 not used 59 piston pin 60 crankshaft bearing holes 61 crankshaft
main journals 62 valve face 63 not used 64 not used 65 piston face
66 jet nozzle 67 nozzle outlet 68 not used 69 not used 70 valve
band 71 side band 72 valve flank 73 nozzle flank
______________________________________ -
DESCRIPTION-FIGS. 1 to 9
Overall
FIG. 1 gives a fight-side-elevation sectional view of my engine's
crankcase 27 and cylinder head 30 with non-sectional views of the
installed parts. The engine comprises the gas-tight east aluminum
crankcase 27, which includes a cylinder 22 bolted to a east and
machined steel cylinder head 30 which comprises a jet nozzle 66. A
machined aluminum or steel piston 21 tightly fits within cylinder
22 and secures one pivoting end of a forged steel connecting rod 23
by a steel cylindrical piston pin 59. The other end of connecting
rod 23 is pivotally connected to a forged steel crankshaft 25 by a
steel crankpin 24. See also FIG. 2. Parallel disk-shaped flywheels
26 are rigidly and concentrically attached by their hubs to the
axis of crankshaft main journals 61. Roller beatings 49 within
cylindrical crankshaft bearing holes 60 bear crankshaft main
journals 61. The compression ratio is about eight-to-one.
Cylinder head 30 is attached to crankcase 27 with cylinder head
bolts 31, with a head gasket 32 sandwiched between the attachment
surfaces of the two pans. Cylinder head 30 comprises a
converging/diverging (De Laval)jet nozzle 66 whose internal
surfaces are smooth and gently curving. The most constricted
internal cross-section of jet nozzle 66 is an area of predetermined
dimensions called a throat 37. The internal converging portion of
jet nozzle 66, a nozzle converging volume 36 of predetermined
dimensions, is partly defined by that part of the inner surface of
jet nozzle 66 closest to piston 21. This surface and a piston face
65, along with the part of cylinder 22 between the two, also partly
define a volume called a combustion chamber 34. Electrodes of a
spark plug 33 screwed into cylinder head 30 project into combustion
chamber
A duct leads from an opening to the volume inside crankcase 27 to
an air/fuel injection port 28 which is an opening to volume inside
cylinder 22. A low-pressure exhaust port 29 opens to the volume
inside cylinder 22 at a point closer to cylinder head 30 than
injection port 28 and opens to the atmosphere via another duct. An
air/fuel induction port 44 opens to cylinder 22 at a point farther
from cylinder head 30 than injection port 28 and is connected to a
carburetor (not shown) by a duct. Each of these ports is closed by
the side of piston 21 at different stages during each cycle.
Cylinder head 30 also comprises a pressure-actuated nozzle valve 39
which opens and closes the internal volume of jet nozzle 66 near
throat 37. When nozzle valve 39 is open combustion chamber 34 is
exposed to a nozzle diverging volume 38 of predetermined dimensions
which opens directly to the atmosphere at a nozzle outlet 67. See
FIG. 3, which is a view looking into jet nozzle 66 when nozzle
valve 39 is open.
Nozzle Valve and Throat Region
Refer to FIGS. 1, 3, 4, 5, and 6. Nozzle valve 39 and the inner
surfaces of jet nozzle 66 near throat 37 are formed such that when
nozzle valve 39 is closed it will substantially seal off jet nozzle
in a volume near and including throat 37.
When nozzle valve 39 is in its open position the internal volume of
jet nozzle 66 near throat 37 is unobstructed and has four sides.
One side is formed by part of a valve face 62 which is flush with
the internal surface of jet nozzle 66. In this open position valve
face 62 extends from one side of the surface defining nozzle
converging volume 36, through throat 37, and out into one side of
the surface defining nozzle diverging volume 38. While in this open
position the rest of nozzle valve 39 is held in a recess along the
inner surface of jet nozzle 66. Nozzle valve 39 is moved to closed
position (see FIG. 1) by pivoting out of the recess about a valve
axis 46 set in that part of jet nozzle 66 near crankcase 27. This
is accomplished by a compression-type valve spring 41 which is
adjusted by an adjustment bolt 42. Valve spring 41 acts upon the
backside of nozzle valve 39 at a spring socket 47 which is at a
predetermined lever-ann distance from valve axis 46 to cause a
closing torque. This torque causes a narrow valve band 70 across
valve face 62 to meet and press against a similar narrow side band
71 across another, opposite internal side of jet nozzle 66. These
two bands are of equal length and are contingent when they meet.
Thus they create a substantial seal on one side of inner surface of
jet nozzle 66 when nozzle valve 39 is in closed position.
Nozzle valve 39 also has two flat and parallel sides, called valve
flanks 72, which are perpendicular to valve axis 46. When nozzle
valve 39 is in closed position valve flanks 72 face two fiat
internal surfaces, called nozzle flanks 73, which form the
remaining two internal sides of jet nozzle 66. Nozzle flanks 73 are
parallel and very close to corresponding valve flanks 72, whereby
creating substantial seals of jet nozzle 66 along sides of nozzle
valve 39. Nozzle valve 39 may be locked in the closed position by
inserting a valve locking pin 45 (see FIG. 6) into a valve locking
hole 40 on one side of nozzle valve 39.
FIGS. 7, 8, and 9 show other possible valve and throat designs.
FIG. 7 shows a triangular throat which is closed by a
triangule-shaped valve which pivots on an axis which makes up one
side of the throat. FIG. 8 shows a circular throat which is closed
by a circular valve which pivots on an axis which must be tangent
to the throat. FIG. 9 shows a circular throat which is closed off
by a laterally-moving septum whose end is semi-circularly shaded.
In each of these designs the valve also emanates from the inner
nozzle surface. The valves in FIGS. 7 and 8 can be made flush with
the inner surface of the nozzle when in the open position. The
valve in FIG. 9 will leave recesses about the throat when in its
open position, causing undesirable turbulence in the gas flow. None
of the seals created by these designs would be as tight over the
operating temperature range as my nozzle valve 39 and throat region
designs. Also, the valve opening and closing mechanisms of these
designs would be much more complicated than the pressure-activated
pivoting action which opens and closes my nozzle valve 39.
Accessories
To start my engine and provide correctly-timed high-voltage pulses
for ignition a starter/electrical ignition system 48 is attached to
the side of the engine (as shown in FIGS. 2 and 3) and is connected
to one of crankshaft main journals 61. This assembly can comprise
an electric motor (not shown), or a hand-operated mechanism (not
shown) for starting smaller engines. For ignition, the system 48
can comprise a high-voltage generating device, such as a magneto
(not shown), to provide voltage pulses to a high-voltage lead 43
that runs to spark plug 33. Electrical ignition system 48
automatically advances the timing of the pulses as revolution speed
increases to compensate for the finite flame speed of the
combustion.
Operations-FIGS. 10-15
General
My engine is an embodiment of Newton's third law of motion: to
every action force there is an equal and opposite reaction force.
It utilizes forces from a chemical reaction (combustion of air/fuel
vapors 51) acting on the resulting molecules of the combustion to
propel them away from the engine at high speeds. These forces
produce an equal reaction force on surfaces in combustion chamber
34 and diverging portion of jet nozzle 66 to propel them and
whatever is attached to them in the opposite direction as the
exhaust molecules. Because my engine uses atmospheric air for its
oxident it falls in the same class as turbojet engines, however,
its combustion pressures, which can exceed 1000 psi,* and its jet
velocities, which can be greater then 6000 mph, are more similar to
those of rocket engines. Turbojet engines have combustion pressures
around 400 psi and maximum jet velocities of about 1400 mph. Since
thrust is proportional to the square of the jet velocity (i.e.,
Thrust .about..[.k.].Vel.sup.2, .[.where k is a constant).]. the
potential power of my engine is substantial. The engine is a
two-stroke, or "two-cycle", type.
While a turbojet engine uses an axial or centrifugal compressor, my
engine employs a piston compressor. And while turbojet engines
extract energy from the combustion gases before their ejection by
passing them through turbines which in turn run the compressor, my
engine extracts energy from the combustion gases during their
ejection also. They accelerate the angular velocity of flywheels 26
by motivating piston 21 down cylinder 22, thereby providing
rotational kinetic energy to motivate same piston 21 through a
successive compression stroke. However, a turbojet engine produces
a continuous jet, while my engine produces a pulsating jet.
From the foregoing description of my engine, and by the following
descriptions of sequential moments and events during one complete
cycle of my engine (illustrated in FIGS. 10-15), its operation is
easily understood.
Air/Fuel Vapor Injection
The engine is started by starter/electrical ignition system 48
which starts reciprocation of piston 21 within cylinder 22. In FIG.
10 piston 21 is shown at the bottom of its stroke. At this position
it uncovers injection port 28, allowing slightly compressed
air/fuel vapors 51 to be injected into combustion chamber 34.
Nozzle valve 39 is closed due to the force exerted on it by valve
spring 41. Air/fuel vapors 51 expel the remaining
low-pressure-exhaust 56 out low-pressure exhaust port 29. The
energy stored in flywheel 26 rotating in direction of crankshaft
rotation 50 moves piston 21 to the position shown in FIG. 11.
Compression
In FIG. 11 piston 21 has moved to a point where it blocks
low-pressure exhaust port 29 and has started compressing air/fuel
vapors 51. The force of valve spring 41 will keep nozzle valve 39
closed throughout the following compression. As stated before, the
rotational kinetic energy in flywheels 26 will motivate the piston
throughout the compression.
Ignition/Start of Jet Pulse
At a further stage of compression, before piston 21 reaches the top
of its stroke, starter/electrical ignition system 48 provides a
high voltage pulse to spark plug 33. The resulting spark initiates
a combustion 52. See FIG. 12. Combustion 52 proceeds as a flame
spreading away from spark plug 33 at a speed between 50 to 100 feet
per second. This flame has a temperature of approximately
3500.degree. F. and produces a pressure in combustion chamber 34
which can exceed 1000 psi.* This high pressure against valve face
62 produces an opening torque about valve axis 46 which overcomes
the closing torque produced by valve spring 41, and nozzle valve 39
opens. The high-pressure combustion gases then move toward opened
throat 37, reaching supersonic speeds in nozzle converging volume
36. As the gases near throat 37 they slow to approximately sonic
speed. As the gases emerge into nozzle diverging volume 38 they
expand and accelerate again, reaching speeds at nozzle outlet 67
which can exceed 6000 mph. If jet nozzle 66 is designed correctly
the pressure of gas jet 54 at nozzle outlet 67 will not be much
greater than the ambient pressure.
The thrust 55 on the engine is from the forces acting on piston 21
and imparted to crankshaft 25 and crankcase 27 by connecting rod
23. The high pressure against piston face 65 causes a force vector
along longitudinal axis of connecting rod 23 that acts on crankpin
24. Because combustion 52 and gas jet 54 start slightly before
piston 21 is near the top of its stroke and continue until piston
21 is slightly past the top of its stroke (the area of throat
determines duration of gas jet 54) the forces acting on crankcase
27 are acting in a direction approximately along the longitudinal
axis of the engine. And because of the moment-of-inertia of
flywheels 26, forces acting along connecting rod 23 when piston 21
is not at the top of its stroke still contribute to the engine's
linear acceleration, as well as the angular acceleration of
flywheels 26. The moment-of-inertia of flywheels 26 is
predetermined so that just enough force on connecting rod 23 is
transformed into angular acceleration of flywheels 26 required to
compensate for the angular deceleration experienced during the
compression stroke. This allows for steady state operation while
transforming most of force along connecting rod 23 into thrust 55
on engine, Flywheels 26 are also designed to be as light as
possible while having the required moment-of-inertia (e.g. by
having most of their mass in outer rims).
Also shown in FIG. 12 is the start of the induction of air/fuel
vapors 51 coming from the carburator into crankcase 27 via
induction port 44. These vapors are drawn into crankcase 27 by the
slight vacuum created when piston 21 is in shown position.
Gas Jet Peak
In FIG. 13 piston 21 is shown at the top of its stroke, when
combustion 52 is complete. Ignition occurs before this moment
because of the finite flame speed of combustion. Shown in the
figure are lines of high-pressure force 57 acting on the surfaces
of combustion chamber. At this moment gas jet $4 is approximately
at its peak. Because of this and the fact that connecting rod 23 is
lined-up directly with the axis of crankshaft 25 this is also
approximately the moment of greatest thrust.
Continuation of Gas Jet/Crankcase Compression Starts
In FIG. 14 piston 21 is accelerating down cylinder 22, causing
angular acceleration of flywheels 26. Since induction port 44 is
blocked compression of the next charge of air/fuel vapors 51
.Iadd.in the crankcase .Iaddend.begins. Gas jet 54 and thrust 55
are decreasing as the pressure in combustion chamber 34
decreases.
Low-Pressure Exhaust Port Uncovered/End of Gas Jet
In FIG. 15 piston 21 has uncovered low-pressure exhaust port 29
which lowers pressure in combustion chamber 34 to a level that
allows valve spring 41 to close nozzle valve 39. At this time gas
jet 54 and thrust 55 cease. Compression of air/fuel vapors 51
continues until the next event, the uncovering of injection port
28, described earlier. Thus, each major event during the operation
of this "two-cycle" engine have been discussed. Given an engine
with a cylinder diameter and piston stroke approximately the same
as that of a typical automobile engine, maximum revolution speeds
of about 4000 RPM's can be expected. This translates into 66.7 jet
pulses per second. With this high pulse rate and the mass of the
engine and its host platform, a fairly level average thrust can be
expected.
Nozzle Valve Locking
My engine may be operated with nozzle valve 39 locked in the closed
position by inserting valve locking pin 45 into valve locking hole
40 before starting the engine. The engine may then be warmed up or
idled, operating identically to a typical two-cycle internal
combustion engine. When thrust is desired the engine is run up to a
certain speed and valve locking pin 45 is pulled out of valve
locking hole 40.
Summary, Ramifications, and Scope My engine should provide a
simple, low-cost, reliable, and powerful means of jet propulsion.
It will allow jet propulsion in applications where the cost of
turbojet engines make their use prohibitive, or reduce the cost of
certain aircraft currently powered by turbojet engines. Also,
because my engine can be made smaller than the smallest effective
turbojet engine and still produce proportional amounts of thrust it
can be used in applications not yet realizable. See FIGS.
16-20.
While my description contains many specifics, these should not be
construed as limitations on the scope of the invention, but rather
as an exemplification of one preferred embodiment thereof. Many
other variations are possible, including those shown in FIGS. 7, 8,
and 9. Also, instead of a rectangular-shaped nozzle diverging
volume 38 and nozzle outlet 67, my throat-region design can
transition to a nozzle diverging volume 38 that has elliptical or
circular cross sections with an elliptical or circular nozzle
outlet 67. Many combustion chamber shapes are possible while still
having a volume that converges towards throat 37. The throat can
vary from the narrow rectangular shape shown to a broader rectangle
or even a square. The bore and stroke of piston 21 may vary to give
greater compression to allow use of lower-volatility fuels (such as
diesel fuel) and compression ignition. Piston face 65 may have a
gas-directing formation to reduce wastage of air/fuel vapors 51
which escape through low-pressure exhaust port 29. Newer
technologies, such as powder metallurgy and machine ceramics, may
be used to lower costs of certain parts or reduce cooling
requirements for certain parts (such as nozzle valve 39). The
drawings leave out any methods for cooling. Cooling of cylinder 22
and cylinder head 30 might be accomplished with air-cooling,
utilizing many closely spaced metallic cooling fins. Or liquid
cooling may be used, with one of crankshaft main journals 61
driving a coolant pump circulating liquid coolant around cylinder
22, cylinder head 30, and possibly into nozzle valve 39. The
drawings also leave out a method of lubrication. This might be
accomplished by mixing oil with the fuel, as is done with most
ordinary two-cycle engines. Or a standard pumped lubrication system
might be used. Instead of using a carburator, fuel-injection could
be employed. And instead of the crankcase-compression method to
remove exhaust and supply air or air/fuel vapors 51 to combustion
chamber 34 separate blowers and compressors might be used. Several
engines could share a common crankshaft to provide greater power
and smoother operation (if the jet pulses from each were
alternated).
Because of the very high temperatures experienced by jet nozzle 66
and nozzle valve 39 they should both be made of the same material
so they have the same temperature-coefficient-of-expansion. This
will result in nozzle valve 39 providing a constant seal over the
experienced temperature range.
Accordingly, the scope of the invention should be determined not by
the embodiments illustrated, but by the appended claims and their
legal equivalents.
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