Internal combustion piston engine using air chamber in piston driven in resonance with combustion wave frequency

A piston having a working end portion for use in an internal combustion engine having an axial bore closed at one end for receiving the piston in close fitting, axially reciprocating relationship to define a variable volume working chamber for carrying out combustion of a fuel with air between said working end portion of the piston and the closed end of the bore, the piston comprising a lower guide portion axially spaced from the working end portion and having a major diameter D;

• a peripheral seal ring receiving groove in the guide portion;
• said working end portion having a reduced diametrical cross-sectional area as compared with said guide portion;
• and an intermediate reduced peripheral portion of said piston between said guide portion and said working end portion;
• one-half of the difference between the major diameter D and the diametrical dimension of the area of reduced cross-section of the working end portion of the piston constituting a gap having a nominal width g, a peripheral length, a transverse cross sectional area S, an axial length L, and a gap volume V.sub.g equal to S.times.L;
• a volume V.sub.B including said volume V.sub.g and the remaining volume located between said intermediate reduced peripheral portion and an imaginary cylindrical surface overlying said reduced peripheral portion, said cylinderical surface having substantially a diameter D concentric with the piston, said volume V.sub.B being related to D, g, S, and L according to the following formula:
• ##EQU11## where (using metric units throughout):
• C is the speed of sound in cm./sec. in V.sub.B at approximately the autoignition temperature of a compressed charge in a working chamber associated with the piston;
• k is a Helmholtz correction factor between 0.6 and 0.85 determined on the basis of the geometry of the gap axial end limits;
• F.sub.B is a frequency having the value:
• F.sub.B =(K/D)Hz
• where K is a constant having a value between 43,000 and 51,000;
• L is dimensionally long enough such that flame propagation is prevented between the working and air chambers through the gap, but is at least equal to the minimum dimension of the gap;
• the maximum linear dimensions defining volumes V.sub.B and V.sub.g are less the 1/4 wavelength of F.sub.B at the temperature of the air chamber during combustion/expansion;
• and
• S is calculated by assuming a uniform nominal gap width g according to the formula:
• g=0.01072D+0.1143
• within the tolerance range of +0.050 cm or -0.025 cm;
• and
• wherein the relationship between L, V.sub.B, g and S satisfies the formula:
• ##EQU12##

A variable compression ratio internal combustion engine comprising:

• (a) a movable piston in a variable volume working chamber in which intake, compression, fuel combustion, expansion and exhaust events occur as the result of piston movement within the chamber, the piston having a working face defining a movable wall of the working chamber;
• (b) an air chamber in the piston adjacent its working face;
• (c) said air chamber communicating with the working chamber through a gap having a cross sectional area;
• and
• (d) said gap cross sectional area being dimensioned so that flow of gas into the air chamber from the working chamber is choked during at least part of the compression event during operation of the engine above approximately 65 percent of the maximum operating speed of the engine.

A process for carrying out radical enhanced combustion reaction of hydrocarbon fuel in air in a variable volume working chamber of an air breathing internal combustion piston engine wherein intake, compression, combustion/expansion and exhaust events comprise the operating cycle of the engine, comprising:

• (a) supplying a fuel and air charge to the working chamber for each operating cycle;
• (b) axially stratifying each charge in the working chamber so that substantially only air is adjacent the piston before each compression event;
• (c) transferring a portion of the air of the charge with a minor quantity of fuel (i.e., an insufficient quantity of fuel to form a mixture capable of sustained combustion) to a Helmholtz resonating air chamber located in the piston closely adjacent to and in heat exchange relationship with its working face during the compression event, the resonating chamber communicating with the working chamber through a restricted gap orifice located around a circumferential length of the working end of the piston;
• (d) initiating combustion reaction of the fuel in the working chamber and carrying out the combustion event at air to fuel ratios limits of approximately 16:1 at best power to approximately 20:1 at best economy;
• (e) initiating combustion in the working chamber at a charge temperature in the range of from just below the radical enhanced autoignition temperature of the fuel to just above said temperature by controlling the charge temperature within this range by varying the air to fuel ratio of the incoming charge;
• (f) carrying out the combustion with the volume of the air chamber corresponding to:
• ##EQU13## where (using metric units throughout):
• V.sub.B is the volume of the resonating air chamber;
• S is the cross sectional area of the gap orifice;
• C is the speed of sound in cm./sec. in the resonating air chamber at approximately the autoignition temperature of the compressed charge in the working chamber;
• L is the axial length of the gap;
• k is a Helmholtz correction factor numerically between 0.6 and 0.85;
• g is the lateral width of the gap, assumed to be uniform over its circumferential length, the gap width being expressed by the formula:
• g=0.01072B+0.1143
• within the tolerance range of +0.050 cm. and -0.25 cm.;
• said gap having a maximum actual width not exceeding that width that will produce choked flow between the air and working chambers at least during a fraction of the compression stroke of each compression event;
• F.sub.B is a frequency expressed by the formula:
• F.sub.B =(K/B)Hz
• where K is a non-dimensional value between 43,000 and 51,000;
• and the relationship of L, V.sub.B, g and S satisfies the formula:
• ##EQU14## (g) transferring heated air from the air chamber to the working chamber throughout the combustion/expansion event by exciting the air chamber at its Helmholtz resonant frequency by combustion shock wave interaction to cause the air to be pumped from the air chamber into the working chamber;
• (h) transferring high temperature radicals resulting from combustion to the air chamber during the exhaust event;
• (i) seeding the next incoming axially stratified charge with high temperature radicals from the air chamber during the next air intake event;
• (j) compressing the radical seeded, axially stratified charge by the piston while transferring a portion of the air with radicals and minor fuel to the air chamber in accordance with step (c) and heating the same in the air chamber by heat transfer with the working end portion of the piston that is at high temperature from the previous combustion/expansion event up to the initiation of the succeeding combustion event;
• (k) carrying out the next succeeding combustion/expansion event with pumping of air and said radicals supplied from the previous combustion event along with new pre-combustion radicals from the air chamber into the working chamber according to step (g) throughout the next succeeding combustion/expansion event;
• and
• (l) cyclically repeating the above steps to produce useful work output of the engine.

A process for carrying out radical enhanced combustion reaction of hydrocarbon fuel in air in a variable volume working chamber of an air breathing internal combustion piston engine wherein intake, compression, combustion/expansion and exhaust events comprise the operating cycle of the engine, comprising:

• (a) supplying a fuel and air charge to the working chamber for each operating cycle;
• (b) axially stratifying each charge in the working chamber so that substantially only air is adjacent the piston before each compression event;
• (c) transferring a portion of the air of the charge with a minor quantity of fuel (i.e., an insufficient quantity of fuel to form a mixture capable of sustained combustion) to a Helmholtz resonating air chamber located in the piston closely adjacent to and in heat exchange relationship with its working face during the compression event, the resonating chamber communicating with the working chamber through a restricted gap orifice located around a circumferential length of the working end of the piston, the working end of the piston above the air chamber constituting a piston cap;
• (d) initiating combustion in the working chamber by autoignition of the charge at a temperature within the radical enhanced autoignition temperature zone at a compression ratio of between 5 and 9 to 1, the piston cap having a thermal coefficient that yields a cap operating temperature that produces best power for the operating cycle with the fuel used to form the charge;
• (e) carrying out the combustion with the volume of the air chamber corresponding to:
• ##EQU15## where (using metric units throughout):
• V.sub.B is the volume of the resonating air chamber;
• S is the cross sectional area of the gap orifice;
• C is the speed of sound in cm./sec. in the resonating air chamber at approximately the autoignition temperature of the compressed charge in the working chamber;
• L is the axial length of the gap;
• k is a Helmholtz correction factor numerically between 0.6 and 0.85;
• g is the lateral width of the gap, assumed to be uniform over its circumferential length, the gap width being expressed by the formula:
• g=0.01072B+0.1143
• within the tolerance range of +0.050 cm. and -0.25 cm.;
• said gap having a maximum actual width not exceeding that width that will produce choked flow between the air and working chambers at least during a fraction of the compression stroke of each compression event;
• F.sub.B is a frequency expressed by the formula:
• F.sub.B =(K/B) Hz
• where K is a non-dimensional value between 43,000 and 51,000;
• and the relationship of L, V.sub.B, g and S satisfies the formula:
• ##EQU16## (f) transferring heated air from the air chamber to the working chamber throughout the combustion/expansion event by exciting the air chamber at its Helmholtz resonant frequency by combustion shock wave interaction to cause the air to be pumped from the air chamber into the working chamber;
• (g) transferring high temperature radicals resulting from combustion to the air chamber during the exhaust event;
• (h) seeding the next incoming axially stratified charge with high temperature radicals from the air chamber during the next air intake event;
• (i) compressing the radical seeded, axially stratified charge by the piston while transferring a portion of the air with radicals and minor fuel to the air chamber in accordance with step (c) and heating the same in the air chamber by heat transfer with the working end portion of the piston that is at high temperature from the previous combustion/expansion event up to the initiation of the succeeding combustion event;
• (j) carrying out the next succeeding combustion/expansion event with pumping of air and said radicals supplied from the previous combustion event along with new pre-combustion radicals from the air chamber into the working chamber according to step (e) throughout the next succeeding combustion/expansion event;
• and
• (k) cyclically repeating the above steps to produce useful work output of the engine.