US1969753A - Method of operating constant volume explosion chambers - Google Patents

Description

PS- 1934- H. HOLZWARTH 1,969,753

METHOD OF OPERATING CONSTANT VOLUME EXPLOSION CHAMBERS Filed June 25, 1931 2 Sheets-Sheet l ,4 rroRNEl METHOD OF OPERATING CONSTANT VOLUME EXPLOSION CHAMBERS H. HOLZWAR-TH 1,969,753

Filed June 25, 1931 2 Sheets-Sheet 2 Patented Aug. 14, 1934 ES PATENT; OFFICE METHOD OF OPERATING CONSTANT VOLUME EHLOSION CHADIBERS Hans Holzwarth, Dusseldorf, Germany, assig'nor to Holzwarth Gas Turbine 00., San Francisco Calif., a corporation of Delaware Application June 25, 1931, Serial No. 546,730 In Germany June 30, 1930 7Claims.

The present invention relates to the operation of explosion chambers of the constant volume type into which explosive charges of fuel and air are periodically charged and periodically ignited,

6 the explosion gases being discharged intermittently in puffs after each explosion for use outside the chamber, for example, in an explosion gas turbine.

' It is an object of the present invention to provide an improved method of charging and discharging an explosion chamber of this type, whereby the capacity of the explosion chamber as compared with that of known chambers of the same general class is greatly increased. It has already been proposed by me (see my United States application, Ser. No. 297,799), to dispense with the use of separate charges of scavenging air by employing the combustion-supporting air itself to effect discharge of the residual combustion gases. The present invention contemplates an increase in the economy of operation of an explosion chamber of the kind indicated by charging the fuel simultaneously with the combustion supporting air into the combustion chamber while at the same time preignition of the charge is eliminated by causing certain conditions of flow. In the manner of operation referred to, the air destined to support the next explosion in an explosion chamber is charged in such a manner,

exhaust member of the chamber being open, drives beforeit the residual gases of the previous explosion without penetrating, or being penetrated by, such gases to any appreciable extent. To accomplish this result, the combustion air must enter the chamber when the residual gases have been expanded to somewhat below the pressure of this air and such pressure must be sufliciently greater than that of the exhaust .pressure beyond the chamber to effect the displacement of such gases within the necessarily short interval of time apportioned to this phase of the working cycle; but the difference in pressure of the residual gases and the incoming .air must not be so high that it expands and diffuses so rapidly through the chamber that whirls and eddies are createdwhich prevent such air from assuming the form of a continuous piston-like mass.

In the new method according to the invention, the charging of the fuel is accomplished in the following manner. Shortly after the opening of the air inlet member, the fuel inlet member is opened and caused to discharge fuel into the chamber, preferably along a path similar to that that it assumes the form of a piston and, the,

traversed by the air. By such timing of the fuel and air inlet members, I provide a body of pure air between the receding body of hot residual gases and the incoming fuel (which mixes with the air simultaneously charged therewith), so that 60 the fuel is protected against pre-ignition by such gases, while at the same time uniform distribution of the fuel in the chamber is promoted by the fact that the fuel is admitted during almost the vwhole of the air charging period and while the nozzle valveis open, permitting rapid flow and thorough penetration and diffusion of the fuel through the chamber. I

I .havefound that in the practice of my invention, best results are secured by the use of an elongated cylindrical explosion chamber having fuel and air inlets located at one end of the chamber and a conical section between the air inlet member and the cylindricalwalls of the ch'amber. Explosion chambers of this cpnstruction have 76 the peculiarity that the spreading of introduced air over the width of the chamber is promoted by the diffusor action of such conical section, so that when the conditions of pressure referred to above are observed, the air assumes the form of a pis- 80 ton in its movement through the. chamber.

, Through the avoidance of whirling accomplished in this manner there is formed a comparatively planar dividing 'wall between the entering air and the residual gases in the explosion chamber, the 86 timing of the opening and closing of the members controlling the residual gas outlet and the fresh air inlet being so controlled that the dividing wall can be stopped at any desired point of the explosion chamber by closing the exhaust valve at 90 the proper instant.

My invention is based upon the experience that the combustion of a mixture is more complete the more homogeneously the mixture fills the explosion space, and accomplishes such homogeneous filling of the chamber in the manner outlined above. The teaching of the prior art has been to the effect that the closure element, 1. e. the exhaust or nozzle valve, of the explosion chamber should be closed comparatively early, and in any, case before opening of the fuel inlet valve. because it was considered otherwise possible, due to the irregular distribution of the air entering the explosion chamber with respect to-the residual gases of the previous explosion in the methods of control heretofore employed, for the fuel particles to become ignited upon contact with such residual gases and thus produce an ineffective, premature explosion if the closure element was still open. The closing of the closure element before opening the fuel inlet member did indeed avoid this danger with more or less certainty, but it did not promote the filling of the explosion chamber with a homogeneous mixture, because the necessary pressure drop for effecting penetration by the fuel of the body of air in advance of the closure element was lacking.

According to the present invention, the closing Q of the closure or exhaust member in the types of explosion chambers indicated above takes place while the air and fuel inlet valves are open, only after such member has been actually or approximately reached by the dividing wall between the residual combustion gases of the previous explosion and the piston-like body of charging air which displaces the same. It has already been suggested to open again the exhaust member of the explosionchamber after the fuel inlet valve has been opened, but the carrying out of this mode of operation required the arrangement of special control devices at the exhaust member, so that this procedure found no practical use. It has also been already proposed to hold the exhaust or nozzle valve open also at the beginning of the fuel admission; but this proposal was expressly characterized as disadvantageous, because there was no possibility, due to the irregular penetration of the charging air by the residual explosion gases, of avoiding dangerous pre-ignition. It

was also not possible to close the exhaust member of the explosion chamber after it had actu- '.tween the air inlet member and the cylindrical walls of the chamber, these difficulties are eliminated, because it becomes possible to prevent the meeting of fuel or fuel-air particles with the residual combustion gases. If the air inlet valve is first opened, and only thereafter is the fuel inlet valve opened, so that the hot residual combustion gases are directly contacted and displaced by pure air only, the fuel valve being opened a definite time interval after the air valve, there arises a zone of pure air betweenthe residual gases and the mixture of fuel and air, such pure air, because of its piston-like formation, precluding any possibility of a meeting between the hot residual gases and the fuel-air mixture. As the inflowing charging air drives the fuel-air mixture toward the residual gases even when the exhaust member of the explosion chamber has already been closed, the air inlet member is advantageously closed before the fuel air mixture has reached the residual gases. In this'case the source of ignition is located within the reach of the homogeneous mixture which completely fills the chamber so that rapid and certainignition of the mixture and its complete combustion are assured by this procedure. The admission of fuel can thereby be made to continue after the closing of the air inlet member and can be'stopped when the ignition of the mixture in the chamber begins. In this way there are assured, in addition to certain ignition, the complete combustion of the charge and the maximum charging of the explosion chamber.

On the accompanying drawings are schemati-l tion of which is cylindrical.

cally represented the various steps of my new process in a constant volume explosion chamber. In said drawings,

Fig. 1 shows the conditions in the explosion chamber when the air and fuel inlet valves and the exhaust valve are open, the dividing zone between the residual gases and the intermediate protecting cushion of pure air being in advance of the igniting means;

Fig; 2 shows the closing of the exhaust valve when the said dividing zone has almost reached the same;

Fig. 3 indicates the closingof the air valve as the fuel-air mixture penetrates or diffuses into the intermediate cushion of pure air, the fuel valve still being open, as indicated by the arrow;

Fig. 4 illustrates the progress of the explosion following ignition, all the valves being closed;

and

Fig. 5 is a view illustrating a suitable form of controlling mechanism for the explosion chamber.

In all of the figures, the. numeral 1 indicates an elongated explosion chamber the main por- At one end of the chamber are located the fuel inlet member 2 and the air inlet member 3. The fuel inlet member 2 may be of any suitable construction, and in the form illustrated is constructed as a nozzle having one or more discharge openings, and may be provided in known manner with a check valve to prevent the flow of combustion gases into the fuel conduit 2d. As the specific construction of the fuel charging. member forms no part of the present invention, the same has not been illustrated in detail. The air inlet member 3 is connected with the cylindrical portion of the explosion chamber by means of a conical intermediate member 4. A closure or exhaust memher 5 is arranged opposit to the fuel and air inlet members 2, 3, the sai exhaust member closing the conical neck 7 of the explosion chamber in advance of the nozzle 6; for this reason the closure member will be referred to as a nozzle valve in the subsequent description of my invention. An igniting element 8 in the form of a spark plug is arranged in the neck portion 7 of the chamber.

According to the present invention, the method of operating an explosion chamber of the type illustrated for. obtaining certain ignition, complete combustion, and maximum filling or charge without increasing the duration of the working cycle, is conducted as follows: The nozzle valve still being open following th discharge of the products of combustion, the air valve. 3 is opened and shortly thereafter the fuel valve 2. The charging air (shown as dotted stippling) passing through the conical connecting section .4 takes the form of a piston and 'at the instant represented in Fig. 1 has nearly completely displaced the residual combustion gases (shown as curved line stippling) of the previous explosion through the open nozzle'valve 5. Be-

charging air which was formed by the opening-of the air valve in advance of the fuel valve. The

dividing zone or-wall between the residual gases and the piston-like body of air is indicated at advance of the fuel through the chamber.

Fig. 2 shows'the conditions .in the combustion 99. The dash iines in the figures indicate the chamber at the instant in which the dividing zone or wall 9-'-9 between the residual gases and the pure charging air has almost reached the nozzle valve. At this instant the nozzle valve is closed. A small amount of gases is trapped,

so as, among other reasons, to provide security against the loss of the costly charging In this position of thedividing zone 99, nearly the whole of the chamber is filled with a homogeneous mixture of fuel and air, so that further opening of the nozzle valve would be without purpose and would only be accompanied by the danger of loss of charging air from the chamber. Only the zone of pure air and also the small amount of trapped gases, if any, are at this instant free of fuel. According to the invention, therefore, the admission of fuel and also the admission of air is continued until the condition indicated in Fig. 3 is reached.

Fig. 3 shows the condition in the chamber when the fuel-airmixture begins to diffuse toward and penetrate the residual gases, so that at this instant the danger of pre-ignition appears. In order to avoid this danger, the air inlet valve is closed and the. movement of the fuel-air mixture thereby greatly reduced, the igniting element being already within the reach of the homogeneous mixture of fuel and air filling the chamber without the direct contact between the residual gases and the mixture having occurred. The fuel valve is nevertheless still open so that the chamber can be filled with a mixture of highest combustibility; at the same time the charging of the chamber with the maximum quantity of fuel and air mixture is made possible.

Fig. 4 shows the conclusion of the fuel admission and the advance of the explosion flame following the ignition of the mixture in the chamber, as indicated by the concentric arcs. The combustion thus still possesses the character of an explosion, the latter not being disturbed by the continuance of the fuel feed.

Fig. 5 shows an arrangement to control the working parts of the explosion chamber and give them the proper timing. 10 represents the fuel pump, which supplies the fuel to the fuel inlet member 2. The air inlet member 3 and the exhaust member 5 are operated by pistons 11.

which'are actuated by means of oil supplied from the revolving controller 14. The exhaust or nozzle valve 5 is provided with a piston similar to the piston 11 associated with the air valve 3, at suitably timed instants determined by the construction of the revolving controller 14, pressure oil is charged by the conduit 51': against the piston of the valve 5- to eifect'opening thereof. It will be understood that the, piston on the 'valve 5 is so arranged that the pressure fluid fed by conduit 5a acts against the lower surface thereof so as to effect opening of the valve, as distinguishedfrom-the construction of valve 3 wherein the pressure fluid acts against the upper,

or rather outer. surface of the piston 11. The

' revolving controller 14 is filled with a liquid, such as oil, under pressure which it receivesthrough a conduit 14a-from a pump (not shown), an air chamber 14b being provided to equalize the pressure of the liquid. As the revolver 14 is rotated by the gearing 15 .driven'by a motor 16. the conduits 5a and 11 of each explosion chamber are are brought into temporary communication at the proper instants with the interior of the controller through grooves 14c in the circumference of said controller which communicate with the interior thereof through ports 14d. For a more complete description of the operation of the controller, reference is bad to my United States Patents Nos. 877,194 and 1,763,154.

The words elongated cylindrical explosion chamber of the above specification are intended to include all kinds of explosion chambers which, due to their shape, provide the possibility for the incoming air to assume the form of a piston andto. drive before it the residual gases of the previous explosion without penetrating, or being penetrated by, such gases to any appreciable extent. Instead of a straight cylindrical form, there may, for instance be employed a slightly conical or spherical form of combustion chamber or any other-suitable form of elongated chamber.

- The most efficient working of the new method will be secured when the pressure of the combustion supporting air is sufllcient to produce the highest velocityof the discharging residual gases so as to shorten the phase of scavenging and charging the combustion chamber. This velocity is known as the critical velocity and a definite minimum ratio of air pressure to exhaust pressure is required to attain this velocity.

-I claim:

1. The improvement in the art of operating an elongate, substantially cylindrical, constant volume explosion chamber having a conical inlet section and a controllable air inlet and fuel inlet at the charging end and a controllable outlet A at the opposite discharge end thereof, comprising exploding an explosive mixture of fuel and air confined within said chamber, opening such outlet to effect discharge of the high temperature,

high pressure explosion gasesbefore they have before the air has penetrated far into the chamber, the air inlet and the outlet remaining open,

so that a relatively narrow body of pure air intervenes between the retreating residual gases and the incoming fuel and air mixture and fuel enters the chamber as the residual gases are being expelled by the advancing body of pure air, closing the outlet when the dividing zone between the residual gases and the body of pure air has approximately reached the same, closing the air and fuel inlets, and igniting the air and fuel mixand having an elongate, substantially cylindrical body portion and a conical inlet section; air

and fuel inlet membersat the inlet end and an exhaust member at the outlet end of said chamber opposite such inlet end; an igniting element:

and controlling mechanism operative upon said members and constructed to open first the exhaust member following an exp o ion in the chamber, then the air inlet member, and shortly thereaftemwhen the-air haspenetrated only partially into the chamber, the fuel inlet member,. while maintaining the air inletzmember and the 150 exhaust, member open, so that the air assumes the form of a piston aided by the configuration of the said'inlet section of the chamber and drives the residual gases before it, a relatively narrow body of pure air intervening between the retreating residual gases and the incoming fuel, said mechanism operative to close said exhaust member when the latter has been approximately reached by the dividing zone between the residual gases and said body of pure air, and subsequently to close the air and fuel inlet members.

6. A- pistonless, constant volume explosion chamber suitable for use in explosion turbines and having an elongate, substantially cylindrical body portion and a conical inlet section; air and fuel inlet members at the inlet end and an exhaust member atthe outlet end of said chamber opposite such inlet end; and controlling mechanism operative upon said members and constructed to open first the exhaust member following an explosion in the chamber, then the air inlet member and shortly thereafter, when the air has penetrated only partially into the chamber, the fuel inlet member, while maintaining the air inlet member and the exhaust member open so that the air assumes the form of a piston aided by the configuration of the said inlet section of the chamber and drives the residual gases before it, a relatively narrow body of pure air intervening between the retreating residual gases and the incoming fuel, said mechanism operative to close said exhaust member when the latter has been approximately reached by the dividing zone between the residual gases and said body of pure air, and to close the air inlet member in advance of the fuel inlet member.

'7. A combustion chamber as set forth in claim 5 wherein the outlet section of the chamber is of reduced size, the igniting element being located in the said reduced outlet section.

HANS HOLZWARTH.

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