Burner said:
So how much of this {C12 H26} is broken down? Should the fuel be heated before it hits the rails or is this occurring at the tip? ......stupid here, Ionic or covalent bond trying to be broken here?
I'll jump in. If I'm wrong, I'm sure someone will correct me.
Fuel temp around 75F and charge air temp around 120F yields the best power. Injection pressures above 25K PSI provide better atomization of fuel. Better atomization of fuel leads to quicker evaporation of the liquid fuel. The faster it evaporates, the sooner it burns. If it burns sooner, less injection timing is needed.
Now, once the cylinder gasses start to burn, pressure and temperature rise rapidly. This condition leads to molecular separation and recombination. (The Fischer-Tropf process used to synthesize fuel exploits this condition.) Some of the recombination results in NOx and CO when temperature/pressure conditions are just right. Much of the recombination results in the generation of H2O and CO2 and a lot of heat.
Now if you don't care about 'pollutant' emissions, then you would want to time fuel injection to relatively maximize cylinder pressure from just after TDC and keep it near that maximum until the crank is down to around 90 deg. after TDC. If you care about emissions, you'll want to control injection so that maximum cylinder pressure is less than that needed to produce NOx. Common rail technology will shine here, since fuel flow can be controlled electronically.
Since diesel fuel is injected for a period of time after TDC, you also need to ensure that injection pressure is high enough to achieve good atomization even when cylinder pressure is up around 8000-10,000 PSI. Again, common rail technology will shine here, since it can create much higher injection pressures than ordinary mechanical systems can produce.
Current injection technology uses one injector nozzle per cylinder. The spray pattern from the nozzle is a best compromise between spraying when the piston is at TDC, and when the piston is lower. Two nozzles per cylinder might be better. Use one when the piston is near TDC and the spray needs to be nearly horizontal, and the other when the piston is lower and the spray can be more vertical. Perhaps some clever engineer will design a coaxial injector, where the outer solenoid opens near TDC to spray horizontally, and the inner solenoid opens when the cylinder is lower to spray more vertically. Or perhaps design an injector such that when opened slightly, fuel is directed to the smaller, horizontal holes; when opened moderately, fuel is directed to both horizontal and vertical holes, and when fully open, fuel is directed to the larger, vertical holes.
Of course, alternate fuels won't hurt either. Use GTL fuel (synthesized from natural gas). It contains no sulphur. It has much greater molecular uniformity, excellent lubricity and cetane rating of 70 or better. It might even work better at high RPM (greater than 6000). And I don't see why 87 octane pump gasoline or ethanol or methanol couldn't be used in a common rail compression ignition engine (while using lubricity enhancers, of course); if the charge air is hot enough to ignite diesel fuel, it should be hot enough to ignite alcohol or gasoline.
In summary, heat the fuel to the optimal temperature. Cool the charge air to the optimal temperature. Precisely control fuel injection so as to achieve and maintain optimal (or maximal, as desired) cylinder pressure. Redesign electronic injectors to employ more than one spray pattern. Use alternate fuels that evaporate and burn better.
Once you have a fuel control system that will produce the best and cleanest power, then move on to optimizing the mechanical system to minimize charge air and exhaust flow inefficiencies.
Of course, none of this will happen until computer geeks turn into dieselheads. It is a rare gearhead indeed who can program a controller.
