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.

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, cylinder andkin the crankcase 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.

Claims

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 between said two ends,

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 a 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 without a substantially detrimental obstruction, a portion of said valve face facing part of said combustion chamber and at least partially 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 certain amount, 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 causing 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 jet nozzle, 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 jet nozzle, and

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.