US2662515A

US2662515A - Detonation suppression piston for internal-combustion engines

Info

Publication number: US2662515A
Application number: US273276A
Authority: US
Inventors: Jr Albert G Bodine
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-02-25
Filing date: 1952-02-25
Publication date: 1953-12-15
Anticipated expiration: 1970-12-15

Description

Dec. 15, 1953 A. G. BODINE, JR DEITONATION SUPPRESSION PISTON FOR INTERNAL-COMBUSTION ENGINES Filed Feb. 25, 1952 INVENTOR. 41 B527 6. Baa/Mafia Patented Dec. 15, i953 UNITED Silt-5S FPFEQE DETONATEQN SUPPRE ZNTERNAL-CQMBU This invention relates generally to internal combustion engines and to means for suppressing irregular burning and detonation of fuel-air mixture therein. The invention is based on my discovery that detonation in combustion engines involves acoustic phenomena and can be alleviated by means of certain acoustic apparatus used in combination with the combustion chamber.

The present application is directed to improve ments in the field covered by Patent No. 2,573,536, issued October 30, 1951, and entitled Engine Detonation Control by Acoustic Methods and Apparatus. The present application is a continuation-in-part of my application Serial No. 252,318, filed October 24, 1951, for Engine Detonation Control by Acoustic Methods and Apparatus, which latter application is a division of my parent application which resulted in said Patent No. 2,573,536. For a full discussion of the acoustic aspect of detonation in combustion, and my basic solution for controlling detonation in combustion, reference should be had to my said issued patent.

Only briefly stated herein, the present invention is based on the fact that detonation in an engine combustion chamber produces sound waves, a large part of which rise to high amplitude at resonant frequencies of the chamber, and on my discovery that the sound waves produce many of the various well-known and harmful manifestations of detonation. According to my basic invention, I inhibit or attenuate these harmful effects by interfering with or attenuating the high amplitude, detonationdnduced sound waves, and this is done by use in conne tion with the combustion chamber of acoustic tenuation means made responsive to (operative at) the frequencies or Wave lengths at which detonation-induced sound waves build up to high amplitudes. One type of acoustic attenuation means broadly disclosed in my patent involved an attenuative configuration given to the upper end portion of the piston.

The general object of the present invention is the provision of an improved detonation controlling sound wave attenuator of the class involving the piston structure.

A further object is the provision of a novel piston type of detonation attenuator which has good frequency response characteristics to the frequency range at which offensive detonation is encountered.

A still further object is the provision of a piston type of detonation attenuator of improved structual simplicity.

SSION PISTON FOR STIUN ENGKNES A present illustrative embodiment of the invention is shown in the accompanying drawing, in which:

Figure 1 is an elevational view of a piston equipped with detonation attenuator characteristics in accordance with the invention, the piston being shown in an engine cylinder; and

Figure 2 is a plan view of the piston shown in Figure l.

The attenuator of the present invention is of a type, first disclosed in my said issued Patent No. 2,573,536, employing an exponential type horn, which is designed to receive the offensive detonation-inspired sound waves without reflection back and to conduct such waves to a sound wave attenuative means at its throat Such a horn must be properly designed to respond properly for the wave frequencies to be subdued, and information on this subject is found in my said issued patent. According to the present inven tion, such a horn and attenuative means is provided by a unique configuration or the upper end portion of the piston.

Referring now to the drawings, numeral 8 designates an engine combustion chamber into which opens engine cylinder 9, and numeral Hi designates generally a piston in said cylinder having one ring groove it above the wrist pin, and two ring grooves l i below the wrist pin, these grooves receiving conventional piston rings, as indicated. The upper end portion 12 of the piston, above upward ring groove H, is convergent in an upper direction, and is configured to provide a horn type space it between it and the cylinder wall it. The upper end portion l2 of the piston converges substantially on an exponential function curve i l, in such manner that the crosssectional area of the annular space it? between the piston and the cylinder wall converges downwardly from the top of the piston in the manner of an exponential type horn. It might here be mentioned that while an exponential horn shape is here principally referred to, some deviation from a true exponential curve is, in practice, permissible without loss of the substantial benefits of the invention. An equivalent but slightly modified shape which is advantageous in practice is a catenoidal horn. Other equivalent shapes are also feasible, including hyperbolic, and in general, the broad requirement is that the horn be of the usual flared type used for coupling pur poses in acoustic practice.

The horn passage 15 is reduced to relatively small transverse dimension toward the lower end, and below the point at which the transverse (iimension has been reduced to a millimeter or thereabouts, the passage develops sound wave attenuative characteristics for detonation wave frequencies because of frictional scrubbing of the high velocity oscillating gas particles in the r& stricted passage. It is thus proper to say that the lower region of the horn passage, between the piston and the cylinder wall, functions as a sound wave attenuator, which is frequency responsive to, i. e., operative at, the detonation wave frequencies, while the upper portion of the passage functions as a coupling means for conducting the detonation sound waves downwardly around the upper end portion of the piston to the attenuator without substantial reflection back.

In operation, a detonation pressure wave initiated within the combustion chamber of the engine, above the piston, enters into the large upper end of the horn passage l5, and travels down said passage to the narrow throat portion thereof with ever increasing energy-density, and without reflection. This wave encounters and transverses the fine-dimension lower portion of the where conditions are favorable for dissipation of the wave, explained above. Also, the acoustic pressure wave, with its energydensity greatly increased in the lower regions of the horn-lilze passage, acquires a very steep wave front, and a conversion to this steep wave front is accompanied by creation of high frequency wave components which are conducive to still greater wave attenuation. The result is a substantial dissipation of the energy of the wave conducted down the horn passage, and therefore substantial energy loss by the sound wave in the combustion chamber above. Such energy drain reduces the tendency of the acoustic wave in the combustion chamber to build up to the substantial amplitudes of detonation.

If a true exponential curve is employed for the horn passage :5, the lower portion of such, which constitutes the wave attenuator, may continue its reduction in transverse dimension to the lower end of the piston portion i2. Alternatively, a catenoidal horn passage may be used, the characteristics of which are that the walls of the passage become parallel at the throat. Using such a curve, the convergence may continue until a transverse dimension of about a millimeter, or less, is reached, and may then continue downwardly at such dimension.

Thus, the downwardly converging horn passage between the upper end portion 12 of the piston and the cylinder wall picks up the detonation wave from the combustion chamber and directs it downwardly to its lower end region, where it has definite attenuative or energy-dissipative characteristics.

As is well known, a true exponential horn doubles its cross-sectional area for equal increments of length. Of course, so far as the general exponential law goes, the equal increments of length are not fixed at any specific value. What is known as the expansion ratio of the horn depends upon the value at which these equal increments of length are taken in the design of the horn. The ability of the exponential horn to respond to, or accept without reflection waves of any given frequency range, is intimately related to this expansion ratio, and it accordingly becomes desirable to design an exponential curve with proper account taken for the frequency or wave length of the detonation waves which are to be attenuated. Directions for such design are set forth in my aforesaid issued Pat- 4 ent No. 2,573,536, to which reference is here made.

The piston type attenuator as described is capable of a substantial degree of attenuation for a detonation-induced sound wave in the combustion chamber. It is of course necessary in any given case to see that the physical dimensions of the horn type passage and its attenuator are proper for the frequency and wave length of the particular detonation-induced sound wave that is to be subdued. In any given engine, it is first necessary to determine the frequency of the detonation wave which is to be subdued. With this information, and with the directions given here and in my aforementioned Patent No. 2,573,536, those versed in the science of acoustics can readily design the necessary configuration for a proper frequency responsive horn passage and attenuator.

It will be understood that the drawings and description are illustrative only, and that various changes in design, structure and arrangement may be made without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. For use with an internal combustion engine having a combustion chamber and cylinder opening into chamber, a piston adapted for reciprocation in said cylinder, the upper end portion of said piston having an outer side sur face spaced from the opposed surface of the cylinder, so as to furnish a downwardly extending sound wave passage, and an acoustic attenuation means for the detonation wave frequencies at the lower region of said surface.

2. The subject matter of claim 1, wherein said surface of said piston has a substantially exponential shaped profile in a plane talacn through the longitudinal axis of the piston.

3. The subject matter of claim 1, wherein said surface of said piston a profile forming, with the opposed surface of the engine cy a downwardly converging sound wave whose cross-sectional area tape s in the manner of a flared acoustic horn.

i. The subject matter of claim 1, wherein a d surface of said piston has a profile forming, with the opposed surface of the engine cylinder, 21 downwardly converging sound wave passage whose cross-sectional area tapers substantially in the manner of an exponential horn.

5. The subject matter of c 1, wherein said surface of said piston has a profile forming, with the opposed surface of the engine cylinder, 2. downwardly converging sound wave passage whose cross-sectional area tapers in the man-- nor of a flared acoustic horn, the lower region of said piston surface approaching closely to the surface of the engine cylinder, so as to provide said attenuator means in the form of a narrow, downwardly extending sound wave passage region.

6. The subject matter of claim 1, wherein said surface of said piston has a profile forming, with the opposed surface of the engine cylinder, a downwardly converging sound wave whose cross-sectional area tapers in the manner of a flared acoustic horn, the lower end portion of said downwardly convergin passage merging with a narrow, downwardly extending clearance space between the piston and cylinder side wall to form said acoustic attenuation means.

7. The subject matter of claim 6 wherein said surface of said piston is an uninterrupted surface of revolution about the longitudinal axis of the piston.

8. The subject matter of claim 1, wherein said surface of said piston has a profile forming, with the opposed surface of the engine cylinder, an annular, downwardly converging sound wave passage whose cross-sectional area tapers substantially in the manner of an exponential horn, the lower region of said piston surface approaching closely to the surface of the engine cylinder, so as to provide said attenuation. means in the form of a narrow, downwardly extending sound wave passage region.

9. For use with an internal combustion engine having a combustion chamber and a cylinder opening into said chamber, a piston adapted for reciprocation in said cylinder, the upper end portion of said piston having an outer side surface spaced from the opposed surface of the cylinder, said surface of said piston having a shaped profile to form between it and. the opposed surface of the cylinder a downwardly extending sound Wave passage whose cross sectional area converges downwardly in the manner of a flared acoustic horn, the lower portion of said outer side surface of said piston closely approaching the opposed surface of the cylinder so as to provide an attenuator for detonation wave frequencies.

ALBERT G. BODINE, JR.

References Cited in the file of this patent FOREIGN PATENTS Number