US 3486331 A
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E. W. BROWN Dec. 30, 1969 JET ENGINES Filed Dec. 11, 1967 nited States Patent 3,486,331 JET ENGINES Earl Waldo Brown, 29200 SW. 187th Ave., Rte. 2, Homestead, F la. 33030 Filed Dec. 11, 1967, Ser. No. 689,583 Int. Cl. F02k 7/04, 7/06 US. Cl. 60-39.77 3 Claims ABSTRACT OF THE DISCLGSURE This invention relates to an improvement in pulsejet engines which may be defined as a controlled-cycle pulsejet engine.
The improved engine differs in several respects from the fixed-cycle engine. Firstly, the controlled-cycle engine has a resonance bafile plate which provides one end of an efficient combustion chamber, while also permitting the exploding gases to flow through to the tail pipe. Secondly, cycling is independently controlled by the fuel injector system. Thirdly, the tail pipe may be considerably shortened and does not control the rate of cycling.
The use of these basic changes in the conventional pulsejet engine has made it possible to develop an engine of several improved characteristics including the followmg:
(1) Easy starting in the course of which neither high air pressure nor high fuel pressure is required.
(2) Speed of firing cycle is at the will of the operator.
(3) Shorter overall length permits convenient clustering of several units and increased flexibility in use.
(4) The fuel injection system is simplified and more easily controlled.
(5) Produces a practical source of power for turbojet and turboprop engines by overcoming the vibration patterns inherent to pulsejet engines when used in multiple units.
The controlled-cycle pulsejet engine of this invention is so designed that it is independent of the length of the tail pipe in determining the rapidity of the firing cycle. The combustion chamber is designed so that its proportion of length to diameter, direction of fuel injection, location of spark plug and location and design of the resonant bafiie plate will permit ignition of the air-fuel mixture at controlled intervals. This holds true at both starting and operating speeds. The resonant bafile plate forms a rebounding surface and partial restriction in the compression chamber so that, when the air-fuel mixture ignites, there is a more rapid build-up of pressure and initial explosive force while yet permitting the continuing explosion to force the flaming gases down the tail pipe. The fuel, gasoline, is injected from a pump which functions at the will of the operator and can vary from widely spaced intervals to a very high rate. In practice it has been proved that a group of four separate engines mounted in a larger tube to drive a turbine at the rear has operated satisfactorily, and in this combination the fuel pump can be altered to provide injection and resultant firing to the four engines in any desired sequence or in any combination of engines at the same time, or at variosu speeds.
In the following, there is provided an outline of the fundamental differences between the conventional fixedcycle pulsejet engine in contrast with the controlledcycle pulsejet engine of this invention. The fixed-cycle pulsejet engine basically consists of four major components, from front to back, in a variable-tapered tube. These are:
(2) Grill assembly (air valves, air injectors, fuel injectors).
(3) Combustion chamber with spark plug.
(4) Tail pipe.
This equipment receives its thrust from a series of explosions forcing burning gases from the tail pipe. The rapidity of the explosions (pulses) is determined by two factors, velocity of sound and length of the tail pipe:
Frequency: velocity of sound 4Xlength of tail pipe The tail pipe acts as a resonance chamber in which the flashback of the explosion fires the next air-fuel mixture. Changing length of the tail pipe changes the frequency of firing. Fuel is injected during each cycle by adjusting the feed pressure so that it will flow into the combustion chamber during the low-pressure interval between explosions, and stop its flow during the explosion.
In contrast to the conventional fixed-cycle engine, the controlled-cycle pulsejet engine of this invention has for its essentials a basic engine consisting of four major components, from front to back, in a step-tapered tube, as follows:
(1) Air and fuel intake assembly (air intake cone, airvalve plate having free-floating butterfly valves, and combined air and fuel feed).
(2) Combustion chamber with spark plug.
(3) Resonance baffle.
(4) Tail pipe.
Note.a moderate-capacity fan is used to supply air to front of single or multiple engines.
The controlled-cycle pulsejet engine of this invention receives its thrust in substantially the same manner as that just previously described in connection with the fixedcycle pulsejet engine. The rapidity of explosions i determined by a single factor, namely, the timing of fuel in jections. Fuel is injected through the air inlet valve plate at intervals controlled by a pump, not illustrated, operated independently from the resonant pitch. A constant firing spark plug fires each charge as the fuel is injected.
The operation of the conventional fixed-cycle engine is discussed briefly as follows. To start, without use of a catapult, air under pressure (-200 p.s.i.) enters the combustion chamber, fuel under pressure enters through the fuel injectors, and the spark plug ignites the air-fuel mixture. The burning gases cause a build-up of pressure which becomes explosive because of the partial enclosure formed by the compression chamber. The burning gases rushing down the tail pipe create a partial vacuum and draws in a fresh supply of air and fuel. The flash-back of each explosion ignites the succeeding charge and results in continuous firing.
In contrast to this description as to the operation of a conventional fixed-cycle engine, the operation of the controlled-cycle pulsejet engine of this invention is as follows. To start, a fan provides air under moderate pressure into front of engine. Fuel is injected through open air valves into combustion chamber, and spark plug ignites the air-fuel mixture. The explosion closes the air Valves, passes through the resonance baffle and out of the tail pipe. Cycling is controlled by timing the injection of fuel.
Having in mind the foregoing discussion of theory and principles and contrasts, reference is made to the accompany drawing in which:
FIGURE 1 shows a horizontal plan sectional view through a combustion chamber which has proved satisfactory for the operation of a controlled-cycle pulsejet feature hereinbefore outlined;
FIGURE 2 is a view of the air intake plate and valves from the combustion chamber side of that plate;
FIGURE 3 is a sectional view of the resonance baflle taken on the line 33 of FIG. 1 looking in the direction of the arrows; and
FIGURE 4 is a view of a modification of the air intake throat showing the walls of the throat flaring outwardly from the air intake plate.
Referring in detail to the figures of the drawing, 1 identifies the combustion chamber which is cylindrical and extends from the air intake plate 2 to the tail pipe. The plate 2 is provided with openings 3 therethrough and through which openings air is led into the combustion chamber 1. On that side of the plate 2 opposite from the combustion chamber there is an entrance throat 4 which is smaller at the entrance side than at the air plate side. In other words, the throat flares to a slightly reduced size on the entrance side than at the side next to the air plate. A flange 4 from the throat member 4 and a flange 1 from the adjacent end of the chamber 1 are bolted to the air intake plate 2, and are secured to the plate 2 by means of bolts 1a which pass through holes 1 in the plate 2. Between the flange 1 and the plate 2 there is a gasket I In FIGURES l and 2, the air inlet plate shows that free floating buttefly valves 5 are mounted on the plate 2 and are pivoted for flapping movement at hinge points 6. The outer ends of the valve flaps 5 are adapted to impinge against fixed abutments 7 to limit the opening movement of the valves 5.
Air and fuel is discharged from a nozzle 8 which is pointed toward one of the air openings in the plate 2 and said nozzle receives fuel from a pipe line 9 and air through a pipe line 10 and the mixture of air and fuel is discharged from the nozzle 8 toward the combustion chamber.
Referring now to the combustion features of the engine, it will be noted that the spark plug 11 is located in the upper wall of the combustion chamber 1. The resonance bafile which is an important feature of this improved engine design is indicated at 12 as extending diametrically across the bore of the combustion chamber 1 between the area of the spark plug 11 on the one side and the outlet end of the combustion chamber on the other side. The baffle 12 as shown in FIGURES 1 and 3 is provided with a series of openings 13 therethrough for the passage of gases of combustion and which openings 13 are located adjacent the peripheral edge of the baffle 12. To provide a simple method of installation of the baffle 12, it is formed as the bottom of a cylindrical cup 4 14 which may be introduced into the inlet end of the combustion chamber 1 before the spark plug 11 and the air intake plate 2 are mounted on the combustion chamber. The tail pipe 15 is stepped down in size from the bore of the combustion chamber 1 by means of .1 stepped section 16 which provides a shoulder against which the cup-like element 14 is seated. This provides a simple method for introducing and securing the baflie 12 diametrically across the bore of combustion chamber 1.
In FIGURE 4, there is illustrated a modification of the form of the air intake throat 17 which is characterized by the fact that the walls of the element flare outwardly so as to provide a reduced size opening adjacent the air intake plate 2.
1. A controlled-cycle pulsejet engine comprising:
(a) an elongated combustion chamber;
(b) an air and fuel intake means at one end of said chamber, said means including an air intake cone. an air inlet valve plate means between said cone and said chamber, pressure responsive valve means on said plate opening into said chamber, and a fuel injection means adjacent to said plate;
(c) a spark plug in said chamber;
(d) a gas outlet means at the opposite end of said combustion chamber; and
(e) a resonant baflle plate means extending diametrically across said chamber, said baifle means being positioned closer to said gas outlet means than to said valve plate means and having openings therethrough only adjacent the walls of said combustion chamber. the upstream surface of said baflle means forming a rebounding surface across a major portion of said combustion chamber and a major restriction of said combustion chamber.
2. A pulsejet engine as set forth in claim 1, said openings comprising a series of apertures spaced around the periphery of said baflie means.
3. A pulsejet engine as set forth in claim 1, the position of said baffie means being approximately two-thirds of the distance from said valve plate means to said gas outlet means.
References Cited UNITED STATES PATENTS 2,674,091 4/1954 Malik 6()247 2,821,838 2/1958 Zwicky 248 2,979,901 4/1961 Curtis 60-3937 3,101,768 8/1963 Curtis 60-39.77 3,258,919 7/1966 Klein 60-39.??
MARK M. NEWMAN, Primary Examiner.
D. HART, Assistant Examiner.
US. Cl. X.R. 60-247