My advisor gave a different problem..... " If you had a rotating shaft with 15 hp input and you have a set of gears in the middle of the shaft taking 3 hp off, how many hp is left at the end of the first shaft. Obviously the answer is 12 hp, but students today are not taught in such a why to make this obvious. And to make the problem more interesting, you needed to understand this before you could solve the wear on the teeth of a gears.
On a more complex side of things, here is the distilled notes for improving our supermileage car engine for next year.... some of this has particular importance towards the idea of using a rotating pipe for the valves. Basically, I have had the luxury to bury my face in an engine design and fundamentals book for the last 2 days
Also remember that this engine has a very low design life, runs on 100 octane fuel, and will run for less than 30 seconds at a stretch. Efficiency is everything. And hopefully it won't spin the rear tire with ~ 50 lbs on it.
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• Put the fuel injector close to the intake – Less likely for the fuel to end up on the sidewalls of the intake
• Possible Miller Cycle with rotary pipe – choose valve timing to eliminate some of the pumping losses
• Longer Stroke than bore - better thermodynamics, better at low RPM’s, keeps mean piston speed up. (piston face area is r^2, sleeve area is just r)
• If turbo is used, place as close to the exhaust as possible for maximum energy recovery
• High Compression Ratio - faster burn, less left over exhaust air, higher theoretical thermodynamic efficiency
• Dual Spark Plugs – less burn time higher pressure and temps
• Intake diameter needs to be relatively small for carbureted engines
• Use EFI, else carburetor needs to be run near WOT
• Keep intake warm for better fuel vaporization
• Smooth intake for high velocity power (not for us), Rough intake for low speed running, which helps cause more turbulence (causes better mixing on a levels). Pg 194
• Mechanical losses go way up at higher engine speeds, therefore, the best efficiency is somewhere is the middle of the rpm band, if not slightly less. Also, most engines have their best efficiency at ~75% of their max torque at the near middle rpm. Definitely don’t go high in the rpm band or low in the torque level.
• We should close the intake valve slightly earlier than stock since we are running the engine slower (pg 195)
• No EGR valve
• Combustion chamber shape is very important to tumble, swirl, and squish
• To get more swirl, you can have the air come in at a tangent to the cylinder, which could easily be achieved by offsetting the rotary pipe. Pg 252
• Dish the piston – as the swirling air is compressed, the radius is lowered from the outside wall to the diameter of the dish, causing the air to rapidly increase the rate of swirling due to the conservation of angular momentum. A dish like the GX35 should work well for this. Pg. 254
• Lean mixture slower flame more pressure later in the stroke. This may or may not be better
• Tumble – the cylinder heads on the Cummings engine in the hallway have a deep almost squarish dish, this causes tumble
• Pg 315-318 Theory on Exhaust Timing
• Pg 321 Exhaust temperatures
• Pg 373 Engine temperatures, commonly found
• Stoichiometric AFR is 15.1:1 Energy Values are in the back of the book
• 2 Pressure rings instead of 3 due to the low RPM of our engine. Maybe even 1 pressure ring, since removing one ring could increase the engine efficiency by 1% (~7% of the mechanical losses). The oil ring provides almost no pressure resistance.
• Possible oil additive to keep oil on surfaces less start up friction
