By rotating for half a turn, about the wrist pin, the piston of the conventional engine, the Pulling Rod Engine ( PRE ) results. That simple . . .
As shown in the table below, the constant volume portion of the combustion in PRE engine can be increased a lot compared to the Conventional engine. The Diesel and natural gas are not the only engines that lack time. All engines do lack time at high revs, whatever high revs means for each one of them.
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Above is the famous Bourke engine (of Russell Bourke).
The Scotch Yoke mechanism provides a harmonic, or pure sinusoidal, piston motion.
The scotch yoke was (and still is) the weak point of this design. The longer dwell of the piston near TDC is the strong point for the Bourke engine: the fuel or mixture finds better conditions into the combustion chamber, during combustion. Bourke engine can operate with high compression, lean mixture and self ignition (based on the active radicals from the previous cycle). A technology lately re-invented, HCCI .
Compared to the Bourke engine, the OPRE engine provides even longer dwell near TDC. Roughly speaking: if Bourke's engine increases, compared to conventional, the dwell of the piston near TDC by x%, the OPRE engine increases, also compared to conventional, the dwell of the piston near TDC by 2*x% (i.e. twice as much as Bourke engine does). See the relevant plot (the green curve or Harmonic stands for Bourke's piston motion profile).
The OPRE engine uses the conventional crank-rod-piston mechanism. The 30 to 40% of additional time near TDC makes the OPRE engine capable to operate efficiently as compression ignition (Diesel) in some 30 to 40% higher revs than conventional Diesel engines (Fuel's ViewPoint animation, bottom of this page). This way the naturally aspirated OPRE Diesel competes the power concentration of the naturally aspirated spark ignition engine.
Fuel's Viewpoint This animation shows the piston motion near TDC of PRE revving at 6000 rpm versus Conventional revving at 4500 rpm, for equal piston stroke and equal (1.65) con-rod to stroke ratio.
Without seeing the kinematic mechanism, how can you reply to: " WHICH is the Conventional and WHICH is the PRE ? "
Suppose you are a fuel droplet injected either into the cylinder of the conventional or into the cylinder of the PRE. What you 'see' is the 'walls' of the combustion chamber, i.e. the cylinder head (if any), the piston top and the cylinder wall. What you 'touch' is air of some temperature, pressure, turbulence and swirl. As you have no way to 'see' (or 'feel') the crankshaft or the kinematic mechanism, you cannot say (for sure) that you were injected and burned into the PRE revving at 6000 rpm or into the Conventional revving at 4500 rpm. (Just like an observer into an elevator: he cannot say whether the elevator is stopped or the elevator moves with constant velocity, he cannot also say whether the elevator is in earth's gravity or it is just accelerating with g).
If PRE's volumetric efficiency at 6000 rpm equals to that of Conventional at 4500 rpm (a matter of tuning), PRE at 6000 rpm and Conventional at 4500 rpm will provide the same torque. In case of Compression Ignition cycle (Diesel) this means a more than 30% increase of power output.
Click here for the Fuel's Viewpoint animation
