F - Mech Eng,Light,Heat,Weapons – 02 – B
Patent
F - Mech Eng,Light,Heat,Weapons
02
B
F02B 23/04 (2006.01) F02B 55/14 (2006.01)
Patent
CA 2620602
For over a century, when three liters are burned in a passenger car with a typical SI (Spark-Ignition gasoline Otto), or CI (Compression-Ignition Diesel) piston engine, the 1st liter is wasted in heat, the 2nd liter is lost in throttling at the intake manifold and/or gas kinetic energy at the tail pipe - a loss that turbochargers and today's engine design attempts to suit the Atkinson thermodynamic cycle try to reduce with some power penalty - Only the 3rd liter is used to propel the vehicle. This explains why despite on-going technological efforts, the thermal efficiency of most piston engines stagnates at around 33%. The last two decade's rising gas prices and emission standards have invited the automobile industry to investigate vigorously the more promising HCCI mode. Controlling such a fast combustion in conventional piston engines throughout a useful load-speed range has proven difficult so far where two crankshaft revolutions are required for each power stroke, and where the shallow sinusoidal compression ratio (CR) variation inherent to the piston- crank kinematics near the top dead center (TDC) tends to cause either misfiring when engine is cold or runs too lean (CR value insufficient for detonation near TDC) or severe knocking, excessive vehicle noise-vibration- harshness (NVH) and structurally intolerable pressure rise rate during transients, when engine gets hot or runs under high load and low revolutions per minute (RPM) (premature detonation problem). Multi-cylinder units are faced also with cylinder detonation imbalance sensitive to unavoidable slight temperature variations of the charge when transiting through the intake manifold, and with high out-of-plane load reactions that the crankshaft bearings must withstand when one cylinder fires after the other. As a result, most HCCI concepts shown in the works are some sort of complex sensor-computer-actuator piston engines operating the HCCI mode at part load and reverting to the one-century-old-thermally-inefficient but more gentle SI mode up to full load and on cold start. The proposed concept aims to control HCCI operation thus to significantly reduce engine emissions and heat energy losses by means of a simple two-stage compressor-turbine: The 1st stage, provided by a radial vane pump with vanes positively guided by inner and outer cams, increases gradually the CR of an homogeneous air-fuel mixture while keeping it safely below the detonation point for all engine operating conditions, while the 2nd stage, by means of local profile alterations of the vane inner and outer cams, or by means of pistons placed and mechanically timed to the vane pump rotor, or by a combination of both, causes an additional and abrupt increase of the CR, which detonates the charge in the vicinity of the 1 st stage TDC. The freshly detonated mixture is then expanded quickly enough to significantly reduce the opportunity for heat exchange with the colder ambient environment to take place throughout the power stroke of the engine until the exhaust phase. The present concept provides a useful torque range at a relatively lower rpm by taking advantage of the vane pump principle where as many power strokes as there is vanes in the rotor occur per shaft revolution (for example: a five-vane motor provides ten more power strokes per shaft revolution than a one-cylinder engine). It also provides a simple and reliable mechanical timing between the two stages of the compressor-turbine allowing homogeneous charge detonation to be accurately controlled throughout the engine load-speed map. Unlike the piston-crankshaft, this concept may be easily designed with a pre-ignition CR value lower than the post-ignition CR value to benefit from the Atkinson cycle without any power penalty.
Na
Routier Laurence
Routier Thierry
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