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Mark Bierle of Earthstar Aircraft in Santa Margarita, CA, makers of the Gull-line of aircraft, has for years been working on an engine that uses a Scotch-yoke to maintain the piston at TDC for a longer dwell period with claims of better efficiency.
Sounds like the Russell Bourke engine that was developed in Penngrove California during the early 50s................
BOURKE ENGINE 101
Around 1862, a Frenchman Beau de Rochas, considered the possibility of constructing an internal combustion engine to extract energy from burning fuel. He identified four functions that would be necessary:
-intake
-compression
-power
-exhaust
He also said that a good internal combustion engine should have the following attributes:
-The greatest possible cylinder volume with the least possible cooling surface
-The greatest possible rapidity of expansion of the burning fuel
-The greatest possible amount of expansion of the fuel
-The greatest possible pressure at the commencement of expansion
-A minimum of moving parts
To understand how the Bourke Engine satisfies the four functions and good attributes identified by Beau de Rochas, it is necessary to follow the piston-rod assembly and crankshaft movement through one (1) crankshaft revolution:
As the crankshaft throw bearing rolls across the face of the rod in the rod/yoke plate assembly, the piston is stopped at or near the top of its stroke for approximately 45 degrees of crankshaft travel, holding the burning gases until they are consumed, no further flame and the maximum pressure is developed. At this stage the Bourke Engine is utilizing the following:
? The air-fuel mixture is being detonated ? 5,000 feet per second flame front.
? Exploding a hydrocarbon fuel make it burn differently, more powerfully.
? As the combustion chamber area remains fairly constant for 45 degrees
of crankshaft travel, this increases the pressure and temperature. Increased pressure raises the temperature {one (1) pound of pressure increase equals 2 degrees F. temperature increase}.
? Temperature affects chemical reaction time. If you increase the temperature by 10 degrees C., the speed of reaction is doubled. Because of the rapid temperature increase in the combustion chamber, the chemical reaction of the hydrocarbon fuel and excess air occurs in nanoseconds.
? Because there is an excess of air in the air-fuel mixture, there is sufficient oxygen available to combine the hydrogen and oxygen in an explosive reaction when the temperature reaches 1,800 degrees F.
? Before the power stroke starts, there is no flame left, only heat and pressure. Pressures are greater than 1,000 pounds per square inch (PSI) and temperatures are over 2,000 degrees F.
The following attributes that Beau de Rochas identified in 1862 have been accomplished:
? Least possible cooling surface ? the above reaction occurs when the piston is at or near top dead center (TDC), minimizing cooling surface area.
? The greatest possible pressure at the commencement of expansion.
At the same time the above process is taking place in the combustion chamber, the intake ports are opened by the piston skirt and the area between the piston and crankcase facing is filled with air-fuel mixture. The following function that Beau de Rocha identified in 1862 has been accomplished:
? Intake (under the piston)..
As soon as the crankshaft rotates to a point of mechanical advantage (approximately 22 ? degrees after (TDC), the pressure in the combustion chamber shoots (like a projectile) the piston/rod/yoke plate assembly towards bottom dead center (BDC). The crankshaft is not connected to the piston/rod/yoke plate assembly but simply floats in the box formed by that assembly. The piston/rod/yoke assembly transmits its kinetic energy to the crankshaft for approximately 135 degrees of crankshaft travel. No kinetic energy is transmitted from the crankshaft to the piston/rod/yoke plate assembly. As the piston/rod/yoke plate assembly moves inward, the piston skirt closes the intake ports and the air-fuel mixture is compressed against the crankcase facing. In the combustion chamber, because of the rapid expansion of the hot (not flaming) gases, they act like a refrigeration cycle and exhaust temperatures are around 200 degrees F. The following function and attributes that Beau de Rochas identified in 1862 has been accomplished:
? Power.
? Greatest possible cylinder volume.
? The greatest possible rapidity of expansion of the burning fuel.
? The greatest possible amount of expansion of the fuel.
As the piston approaches BDC, the compressed air-fuel mixture is transferred from the underside of the piston via the window in the piston skirt and the transfer cavity to the turbulating fins on the piston. The turbulating fins on the piston put the fresh air-fuel mixture into cyclonic motion in the top of the cylinder so it does not escape through the open exhaust ports. The incoming charge forces the exhaust gases out through the open
exhaust ports. The following functions that Beau de Rochas identified in 1862 have been accomplished:
? Intake (from under the piston to the combustion chamber area).
? Exhaust.
As the piston moves away from BDC, a partial vacuum is formed under the piston to draw in a new air-fuel mixture (when the intake ports open) for the next cycle. The air-fuel mixture that was transferred to the cylinder is compressed, ignited and detonation occurs. The following functions that Beau de Rochas identified in 1862 have been accomplished:
? Compression.
? Intake (under the piston).
The same cycle of events just described are occurring in the opposed cylinder, but in staggered sequence.
The last attribute that Beau de Rochas specified for a good internal combustion engine was that it should have a minimum of moving parts. The Bourke Engine has two (2) moving parts, the piston/rod/yoke plate assembly and the crankshaft. The Bourke Engine is nothing more than an apparatus to squeeze the maximum power from each pound of hydrocarbon fuel. A summary of advantages for the Bourke Engine are:
? Russell Bourke stated the exhaust components are carbon dioxide (CO2) and water vapor (H20).
? Exhaust gas temperature is around 200 degrees F.
? Russell Bourke stated the engine will run on any low grade of fuel such as diesel, jet fuel/kerosene, home heating oil, etc.
? This engine has only two (2) moving parts.
? Russell Bourke stated the engine uses about .25 pounds of fuel per horsepower hour.
? Russell Bourke stated the time between overhaul (TBO) will exceed 2,000 hours.
? Russell Bourke stated the horsepower of the Bourke Engine (under load) is a straight line based on how fast you want to run the engine (30 cubic inch engine ? 50 HP at 6,500 R.P.M., 76 HP at 10,000 R.P.M., 118 HP at 15,000 R.P.M.).
? Based on the stated horsepower from Russell Bourke, the power to weight ratio can be 2.5 HP per pound of engine weight, or greater.
? Russell Bourke stated the engine is like an electric motor, it uses fuel based on the load, not the R.P.M.
? Russell Bourke stated the only speed limitation on the Bourke Engine is critical piston speed and/or the inability for the engine to breathe any faster.
? The Bourke Engine has no dead strokes and produces two (2) power strokes per revolution.
