Pulsed jet combustion generator for premixed charge engines

A method and device for generating pulsed jets which will form plumes comprising eddie structures, which will entrain a fuel/air mixture from the head space of an internal combustion engine, and mixing this fuel/air mixture with a pre-ignited fuel/air mixture of the plumes thereby causing combustion of the reactants to occur within the interior of the eddie structures.

FIELD OF THE INVENTION 
This invention relates to a method and apparatus for generating pulsed jets 
containing hot combustion products, that is gases of a sufficiently high 
temperature and appreciable concentration of active radicals to initiate 
ignition and sustain subsequent combustion of a relatively lean air/fuel 
mixture. When injected into a premixed charge medium in an internal 
combustion engine cylinder, such jets will form plumes which will entrain 
and ignite the premixed charge medium in the interior of the eddies of 
which such plumes consist. 
The U.S. government has rights in this invention pursuant to Contract 
DE-AC03-76SF00098 between the U.S. Department of Energy and the University 
of California for the operation of Lawrence Berkeley Laboratory. 
BACKGROUND OF THE INVENTION 
This invention is related to copending patent application entitled "Method 
and System for Controlled Combustion Engines" by A. K. Oppenheim, which 
describes a general approach of achieving control over the combustion 
process in the cylinder of internal combustion engines, i.e., by 
generating a plurality of plumes where the reactants meet in the interior 
of the eddie structures of which these plumes consist, and are caused to 
react therein by some reaction initiating reagent. High temperature 
products of combustion, containing active radicals, are used in the case 
of premixed charge engines. Compression-heated air is used in the case of 
non-premixed charge engines where it is entrained into the eddies of 
pulsed jet plumes made out of relatively low temperature air carrying 
finely atomized fuel drops. 
The present invention relates to a pulsed jet combustion generator, which 
is a device capable of furnishing the required plumes for internal 
combustion engines operating with premixed charge or Otto cycle type 
engines. 
THE PRIOR ART 
There are numerous modifications of spark plugs with chambers for igniting 
fuel-air mixtures disclosed in the literature, however, none are suitable 
for executing combustion in internal combustion engines as proposed in the 
above cited copending application by A. K. Oppenheim. Perhaps a 
fundamental reason is that the fluid dynamic concepts involved in the 
proposed method for controlling combustion were not understood or not 
accepted. 
In particular, U.S. Pat. No. 4,006,725 to Baczek, discloses a spark plug 
exhibiting an interior chamber, which surrounds the electrodes forming a 
spark gap, and which receives a rich fuel air mixture from a rich fuel 
source. Upon ignition, the combustion products exit into the cylinder head 
space through parts in the spark plug walls. The principal disadvantage is 
that the way the reactants are introduced in the prechamber does not 
provide for their proper distribution to generate a jet of sufficient 
impulse, upon ignition in the prechamber to satisfy the requirements for 
formation of the plumes capable on entraining a sufficient amount of 
compressed charge contained in engine cylinder. Also the device is 
evidently meant for use in conjunction with carburetor engines, rather 
than the state-of-the-art computer governed, direct injection engines. 
Furthermore, the device is bulky, due to the lateral fuel feed 
arrangement, and does hence not lend itself to installation of multiple 
generators per cylinder, as required to execute combustion in accordance 
with the above-cited application. 
U.S. Pat. Nos. 4,361,122; 4,416,228; 4,465,031; and 4,509,476, all assigned 
to Robert Bosch GMBH, disclose various modifications of a sparkplug with a 
preignition chamber, within which a fuel-air mixture is ignited by an 
electrical spark. Again the combustion products exit through a plurality 
of ports. However, a significant feature of the device is that the 
fuel-air mixture within the preignition chamber is obtained from the 
cylinder interior through the exit ports during the compression stroke. 
Therefore the device is not suitable for controlling and executing 
combustion as intended in out above cited application. 
The thermo-chemical features of this invention are based on the same 
principles as those used by Semenov et al. and Goosak in U.S. Pat. Nos. 
3,802,827; 3,230,933; 3,092,088 and 3,283,751. This was referred to as the 
LAG Process or Avalanche Activated Combustion and it was associated with 
jet injection of rich combustion products. However, their application to 
internal combustion engines was for three-valve engines (the third valve 
employed to admit the combustible mixture into the cavity of the jet 
generator), ruling out the use of a multiplicity of sequentially activated 
jet generators forming one of the salient features of the present device. 
In summary, the major shortcoming of similar devices of the prior art is 
that they are not capable of furnishing the required plumes capable of 
entraining a sufficient amount of the compressed charge so that ignition 
and subsequent combustion occurs in the interior of the eddies of which 
the plumes consist, but essentially ignite the main charge by establishing 
too readily the conventional flame fronts which traverse the charge at 
their own normal burning speeds. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, a primary object of the invention is to provide a device, 
capable of generating jets of high temperature gases including active 
radicals, which when injected into the head space of a cylinder containing 
a compressed medium of premixed reactants, forms a plume which entrains 
the reactants and cause them to burn within the eddies of which the plume 
consists. 
Another object of the invention is to provide a plurality of pulsed jet 
combustion generators to form plumes which, upon expansion due to the 
exothermicity of combustion will eventually occupy the whole head space. 
Yet another object of the invention is to provide a pulsed jet combustion 
generator whose physical size and shape is such that it will permit it to 
be installed into cylinder heads in groups of 2-8 using conventional spark 
plug ports. 
Still another object of the invention is to provide a pulsed jet combustion 
generator which is compatible with state-of-the-art computerized and fuel 
injected premixed charge internal combustion engines. 
A further object of the invention is to provide a pulsed jet combustion 
generator and associated system for independently varying the amounts of 
both fuel and air introduced into the prechamber, as well as the timing of 
their ignition, in response to and under the control of a microprocessor. 
The above objects are achieved as follows: 
In general, the present pulsed jet combustion PJC generator comprises 
structural means for providing a prechamber activity, means for 
introducing reactants in the appropriate quantities into the prechamber, 
means for igniting the reactants at a predetermined controlled time 
interval to generate a rapid rise in temperature and pressure within the 
prechamber, and one or more exit sharp edged orifices which will permit 
the reactant mixtures to be expelled at a minimum of interference with the 
non-equilibrium chemical composition of the mixture, in a desired 
direction within the head space of the cylinder. A critical aspect of the 
invention is to achieve the fluid dynamic conditions under which such 
plumes are formed. The parameters which control appropriate plume 
formation to cover a given fraction of cylinder volume with a given charge 
are: the volume of the chamber of the device, the quantity and chemical 
composition of reactants introduced into the chamber which govern the 
pressure rise achieved as a result of their ignition, and the 
cross-sectional area of the exit orifices. These parameters are chosen 
such that their combination will issue a jet which will form a plume of 
the desired volume and shape in the head space of the cylinder. 
The volume of the prechamber may be the parameter chosen first, dictated by 
considerations of a convenient size of the device in relation to the 
engine or, more particularly, the cylinder head space. It is generally 
desired to emplace about 2-6 PJC generators in the head of an individual 
cylinder; hence, it is convenient to use a sparkplug-size device with a 
chamber volume of about 0.1 to 0.5 in.sup.3, while the cross-section of 
the orifices may be of an order of 0.01 in.sup.2. The totality of the 
prechamber volumes is between 3% and 10% of the head space volume in the 
cylinder with the piston at top dead center, and preferably about 5%. The 
parameters which are most conveniently adjusted are those that determine 
the amount of the reactants introduced into the chamber, i.e., (1) choice 
of the reactant and (2) reactant supply pressure and the time period of 
reactant introduction into the chamber. 
It is also very important to introduce the fuel into the prechamber in the 
form of a fine spray, or preferably vapor, in order to obtain a readily 
ignitable intimately well combined mixture of fuel and air.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a preferred PJC generator with its pre-chamber presented in 
cross section. The main body 11 of the generator together with tip 13 
defines the combustion chamber 12 in the interior thereof. The tip 13 is 
threaded into the bottom part of the generator body 11 and may be 
interchangeable with other tips of different configurations. The body is 
exteriorly threaded to permit emplacing the generator into a matching 
threaded access hole 14 through wall 15 in cylinder head 16. The tip 13 
defines sharp edged orifices 17 directed into desired portions of the 
cylinder head space 18. Although only one orifice is shown, the tip 
section may have multiple orifices say anywhere between 1 and 5 as 
appropriate, filling an assigned region of the head space for proper 
control of the process of combustion. Generally the number of orifices is 
determined by the desired geometrical configuration of the plume. The 
depth of penetration is controlled by the cross-section area of the 
orifice. The orifices are generally sharp edged to minimize collisions of 
the non-equilibrium, active chemical species contained within the effluent 
stream of the combustion products, with the wall to prevent their 
recombination into stable inactive molecules. To ascertain proper large 
scale vortex structure of the plume, maximizing the entrainment of the 
external premixed charge into its interior, the opening of the orifices 
should be large enough (1 mm-3 mm in diameter) to assure subsonic efflux. 
Reactants are introduced into chamber 12 by means of tube 19, which is 
connected to a source of reactant supply (not shown), through high 
pressure fitting 20. Typically, the reactants comprise a fuel liquid, or 
vapor phase such as gasoline or methanol, optionally premixed with air 
delivered from a separate supply system or extracted from the main fuel 
supply for the engine. The reactants are ejected from tube 19, closed at 
the bottom end 21, through an adequate number of spray perforations 22 
around its periphery to enter the cavity 12 and mix with a portion of the 
main charge that has been forced in via orifices 17 in the course of the 
compression process due to piston motion towards the engine head. The 
preferred number and location of the perforations are dictated by the 
requirement for uniform distribution of the injected material in the 
medium filling initially the prechamber. 
The hollow electrode may be used to introduce: fuel in liquid or gaseous 
form, a fuel-air mixture, or one of these plus some chemical additive that 
are either premixed in the supply reservoir or introduced in the supply 
line. 
The extent to which working substance of the main charge enters the 
prechamber depends on the pressure differential between the prechamber and 
the head space during the compression stroke. As a consequence of the fact 
that oxygen is contained in the main charge, its amount forced into the 
prechamber may be sufficient for combustion. In this case air does not 
have to be supplied to the prechamber through the fuel tube. The reactant 
supply then provides only fuel. If, however, the amount of oxygen is 
insufficient, an adequate quantity of air is provided as necessary 
together with fuel to form the desired jets. 
It should be observed that the PJC generator can provide service as an 
ignitor when it is operated without injecting fuel or a fuel/air mixture 
into its cavity. Its action then would be similar to that of a Bosch plug 
mentioned here earlier, relying entirely upon the portion of the charge 
pushed in from the head space through the ejector orifice, or orifices, as 
a consequence of compression by the piston. The charge may have to be for 
this purpose richer than in the normal operation of the engine. Such 
operating conditions are, in fact, existing at the start of the engine, 
the normal operation being thereupon gradually established, under 
microprocessor control, as the engine is warmed up and the fuel supply to 
the cavity of the generator reaches proper conditions while the charge is 
being diluted for optimum performance. It may also be important to keep 
the engine in running condition in the event of a failure of the PJC fuel 
supply system. 
The fuel-air mixture contained in the prechamber is ignited by an electric 
discharge as in a conventional spark plug 28, through an electrode gap in 
chamber 12. Fuel tube 19 is electrically conductive to provide service as 
an electrode, and is for this purpose connected to a conventional supply 
of electrical power, such as a conventional ignition system (not shown) 
through terminal connector 23. 
The reactant supply line is connected to the tubular electrode 19 by 
fitting 20. Check valve 24 assures that the reactants are admitted to the 
cavity when its internal pressure is relatively low, their amount being 
then controlled by the pressure in the supply line upstream of the check 
valve 24, but it blocks back flow when pressure in the cavity gets to be 
high. Check valve 24 may be passively mechanical, i.e. having its opening 
and closing action controlled by the relative magnitude of the pressure 
exerted by the fuel supply system and the variable pressure generated by 
the action of the piston on the one hand, and that of a mechanical spring 
on the other. Check valve 24 may also be an electro-mechanical valve, such 
as a solenoid activated valve. This valve opens and closes in response to 
electrical signals issued by a microprocessor in response to signals 
received from engine condition sensing instrumentation. Check valve 24 may 
also be a combination of the two, i.e. electronically controlled in one 
direction (supply) and mechanically in the other to prevent back flow. A 
nonconductive section 25, such as an electric wedgelock fitting, 
electrically insulates the generator assembly from the upstream fuel 
supply system. If the fuel supply lines are made of nonconductive 
materials, the section 25 is of course obviated. Insulator 26 similarly 
surrounds the fuel tube 19 and keeps it electrically insulated from the 
engine head 16. 
An electric spark discharge 28 is caused to occur between the tip 21 of the 
fuel tube and electrodes 27 provided on the interior surface of the tip, 
which is in electrical conductive contact with the engine body. 
The mixture in the chamber 12, is thus ignited and will generate a 
sufficiently high internal pressure to cause jets 29 to issue at an 
appropriate velocity through exit orifices 17, creating the required 
turbulent plumes in the compressed fuel/air mixture contained within the 
head space 18. 
FIG. 2 shows in cross section an exemplary tip part 33. It will be readily 
appreciated that tip parts of different configurations and different 
numbers and locations of orifices may be made and interchangeably threaded 
into the PJC generator body 11. The tip shown comprises a generally hollow 
cylindrical body 34 with an exterially threaded section 35 which fits into 
interior threads of the jet generator body 11. The combustion chamber 
volume is thus defined by the tip and the bottom of the insulator 26 in 
the generator plug. The tip shown exhibits one main central nozzle 38, 
made by lapping the conical apex of section 40. If desired, additional 
orifices may be made around the conical end section 40 at preferred 
locations. Electrodes 27 are in the form of pins pressed into the tip body 
to provide appropriately sized gaps between them and the end of the fuel 
tube. 
FIGS. 3a-3e show the present PJC generator in operation. FIG. 3a depicts 
the engine cylinder near the end of the power stroke with the head space 
18 and prechamber volume 12 filled with combustion products while piston 9 
travels downward. In FIG. 3b the combustion products have largely escaped 
while the cylinder is scavenged with fresh charge. FIG. 3c illustrates the 
beginning of the compression stroke, while the cylinder is filled with 
fresh charge 7. In FIG. 3d the charge 7 has been compressed by the upward 
travel of piston 9, and driven into the prechamber volume, while reactants 
are injected into the prechamber from the fuel supply tube. FIG. 3e shows 
the jet plume before combustion takes place. FIG. 3f shows the plume at 
its terminal stage, when combustion in its interior approached its end 
state. 
It will be appreciated by those skilled in the art, that numerous changes 
and modifications may be made without departing from the spirit and scope 
of the present invention, whose scope should therefore be limited only by 
the following claims.