CA2620602A1 - Homogeneous charge compression ignition (hcci) rotary engine vane-piston rotary engine - Google Patents

Abstract

For over a century, when three liters of gas are burned in a passenger car with a gasoline Spark-Ignition (SI), or Diesel Compression-Ignition (CI) piston engine, the 1st liter is wasted in heat, the 2nd liter is lost in throttling at intake manifold and/or gas kinetic energy at tail pipe (a loss that turbochargers and today's Atkinson thermodynamic cycle engine design with slightly increased expansion ratio (ER) tend to reduce), only the 3rd liter is used to propel the vehicle. This explains why, despite on-going technological efforts and billions of R&D dollars spent, thermal efficiency of most SI and CI piston- crankshaft engines stagnates at around 33%. The last three decade's rising gas prices and air emission standards have invited the automobile industry to study the more promising HCCI combustion mode. Controlling such a fast combustion in conventional piston-crankshaft engines throughout a useful load- speed range has proven difficult so far, as combustion chambers are sized for deflagration on SI, or flame diffusion on CI or Diesel, but not for detonation. In four-stroke engines two crankshaft revolutions are required for each power stroke, and the shallow sinusoidal compression ratio (CR) variation inherent to the piston-crank kinematics near 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 higher load at lower revolutions per minute (RPM) (premature detonation problem). As a result, most HCCI concepts in the works are based on sophisticated sensor-computer-actuator piston-crankshaft engines that run on HCCI mode at part load or idle, and revert to the century-old thermally and environmentally less efficient, but structurally gentler, SI or CI mode at full load, or on cold start. This invention aims to control HCCI under all operating conditions, thus to minimize engine air emissions and heat losses by means of a vane-piston engine: A radial vane pump with vanes positively guided by inner and outer cams, compresses gradually air, or a homogeneous air-fuel mixture while keeping it safely below self-ignition. Radial pistons placed in the rotor and mechanically timed to vanes motion, provide a more abrupt CR increase, which detonate the charge near an optimum rotor shaft angle. Resulting gases are then quickly expanded to minimize chamber wall heat losses throughout engine power stroke. This concept provides a useful torque range at a relatively lower RPM by taking advantage of the vane motor principle, where as many power strokes as rotor vanes occur per shaft revolution. Because there are so many, the combustion chambers can be sized much smaller than in a piston-crankshaft engine for a similar shaft power, which is a must for full-load HCCI. A simple and reliable mechanical timing between vane and piston motions is provided for accurate charge detonation control throughout engine load-speed map. Unlike a piston-crankshaft, this vane-piston engine may be designed with very unequal CR and ER values: An ER value much greater than CR followed by a cooled post-ignition recompression phase maximizes shaft power output by means of an unpublished thermodynamic cycle whose efficiency may surpass Atkinson cycle's to benefit power generators, surface vehicles or subsonic aircraft applications. A CR greater than ER provides a high-pressure and high-frequency (over a hundred Hertz) pulse-generator at exhaust ports to control pulse detonation engines (PDE) for high-speed aerospace propulsion.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1 An Homogeneous Charge Compression Ignition (HCCI) engine composed of a radially cam-controlled vane rotor inside a partially circular stator housing with a relative eccentricity as a 1st stage compressor-expander mechanically timed with a 2d stage compressor-expander in the vicinity of the 1st stage TDC (top dead center), and where the stator inner and outer cams are shaped to facilitate gas transfer between the exhaust and intake phases.

2 An engine as defined in claim 1 where the 2nd stage consists of pistons installed in a radial orientation on the rotor between each vane slot and where their radial motion is controlled mechanically by means of followers and cams installed in one or both stator flanges, and where these cams have a ramp profile optimized for the detonation (climbing ramp) followed by adiabatic expansion (descending ramp) events, and for a more efficient gas transfer between the exhaust and intake phases.

3 An engine as defined in claim 1 where the vane rotor is pistonless, and the 2nd stage is provided by means of one or more local geometric radial alterations of the vane inner and outer cams in the vicinity of the 1st stage TDC (top dead center).

4 An engine as defined in claims 1, 2 or 3 where the internal housing of the stator or the vanes inner cams have a shape other than partially circular with an eccentricity relative to the rotor in order to further optimize the 1st stage compression ratio and torque cyclic variation.

An engine as defined in claims 1, 2, 3 or 4 where the internal housing of the stator and the vanes inner cams have a geometric dissymmetry to introduce a reduced volume for the 1st stage compression phase and an increased volume for the 1st stage expansion phase to suit an Atkinson rather than an Otto thermodynamic cycle.

6 An engine as defined in claims 1, 2, 4 or 5 where the cams installed in one or both stator flanges controlling mechanically the 2nd stage pistons radial motion have a profile with positive and negative ramps timed with the angular position of two consecutive vanes in such a manner that the resisting force applied to the climbing cam follower balances instantaneously the propulsive force applied to the descending cam follower of the preceding chamber piston.

7 An engine as defined in claims 1, 2, 3, 4, 5 or 6 where two diametrically opposed and phased combustion chambers instead of one are provided in the stator.