12-10-2016, 03:11 PM
1458812120-mel7133 (1).ppt (Size: 2.24 MB / Downloads: 19)
Clues for Improvement- reduce heat loss
Heat losses caused by high engine turbulence level
Need high turbulence to
Wrinkle flame (premixed charge, gasoline)
Disperse fuel droplets (nonpremixed charge, Diesel)
"Inverse-engineer" engine for low-turbulenc
Gasoline - electrically-induced flame wrinkling?
Diesel - electrostatic dispersion of fuel in chamber?
Premixed-charge IC engines frequently operated at lower than maximum torque output (throttled conditions)
Throttling adjusts torque output of engines by reducing intake density through decrease in pressure ( P = rRT)
Throttling losses substantial at part load
Clues for Improvement : Reduce NOx
Homogeneous ignition engine - controlled knocking
Burn much leaner mixtures - higher efficiency, lower Nox
Need to abandon traditional combustion control strategy
Ideas - improved lean-limit operation
Recent experiments & modelling suggest lean-limit rough operation is a chaotic process
Feedback via exhaust gas residual
Could optimize spark timing on a cycle-to-cycle basis
Need to infer state of gas & predict burn time for next cycle - need in-cylinder sensors
Conclusions
IC engines are the non-ideal form of vehicle propulsion, except for all the other forms
Despite over 100 years of evolution, IC engines are far from optimized
Any new idea must consider many factors, e.g.
Where significant gains can & cannot be made
Cost
Resistance of suppliers & consumers to change
Easiest near-term change: natural-gas vehicles for fleet & commuters
Longer-term solutions mostly require improved (cheaper)
Sensors (especially in-cylinder temperature, pressure)
Actuators (especially intake valves)
TRACTIVE FORCE REQUIREMENTS
Vehicles require thrust forces, generated at the tires, to initiate and maintain motion.
These forces are usually referred to as tractive forces or the tractive force requirement.
If the required tractive force (F) is broken into various components.