GB2376719A

GB2376719A - Engine with two wave barrel cam having dwell periods between rise and return and return and rise profiles

Info

Publication number: GB2376719A
Application number: GB0110371A
Authority: GB
Inventors: Martin Leonard Stanley Flint
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-04-27
Filing date: 2001-04-27
Publication date: 2002-12-24
Also published as: GB0110371D0

Abstract

The invention relates to a Two Wave Barrel Cam profile of a Two Cycle Double Acting Barrel Cam Engine of the Hermann type. Whereby, the normal rise-return-rise-return barrel cam arrangement is modified to a rise-dwell-return-dwell-rise-dwell-return cam profile (See Fig. 4). Pistons connected to the cam follower, can dwell for a longer period of time at top dead centre (TDC) and bottom dead centre (BDC). This arrangement provides an increased duration of constant volume combustion, than a rod and crank mechanism at TDC for either Two or Four cycle engine types. This arrangement also increases the period of time at BDC, thereby increasing the inlet port area opening period. Conveniently, this longer dwell duration at BDC, achieves more inlet port area than is required. This can be corrected for adequate inlet air flow into the cylinder by reducing the height of the port. This advantage allows a later exhaust port opening and closing, providing a greater expansion stroke and improved thermal efficiency.

Description

A TWO WAVE BARREL CAM WITH DWELL PERIODS BETWEEN RISE AND RETURN AND RETURN AND RISE PROFILES.

The invention relates to a Two Wave Barrel Cam profile of the Hermann engine type, Whereby, the normal rise-returnrise-return barrel cam arrangement is modified to a risedwell-return-dwell-rise-dwell-return cam profile.

To provide an understanding of how the above mentioned invention can be used in a Two Cycle Double Acting Barrel Cam Engine of the Hermann type using a Uniflow Sleeve Valve arrangement, is shown in Figure 1. In addition to this invention, the engine design shown in Fig. 1 incorporates many other ideas and mechanisms already tried and tested on more conventional engine types, but not, it is believed, in a Two Cycle Double Acting Barrel Cam Engine of the Hermann type using a Uniflow Sleeve Valve arrangement.

In the barrel cam engine concept used in this patent application, the cam profile is modified from a risereturn-rise-return (See Fig. 2 and 3) to employ a risedwell-return-dwell-rise-dwell-return-dwell arrangement, (See Fig. 4), whereby the pistons connected to the cam follower, can dwell for a longer period of time at top dead centre (TDC) and bottom dead centre (BDC). This arrangement provides a longer duration of constant volume combustion than a conventional rod and crank mechanism at TDC for either Two or Four cycle engine types. In addition this arrangement also increases the period of time at BDC for the pistons connected to the cam follower thereby increasing the inlet port area opening period.

Conveniently, this longer dwell duration at BDC can achieve more inlet port area than is required for inlet air flow into the cylinder. This can be corrected for adequate inlet air flow for clean combustion by reducing the height of the port. This in turn enables a later exhaust port opening and closing at a later stage in the expansion stroke thus improving thermal efficiency.

The barrel cam's rise and return contour employs a Polynomial 56789 profile. This improves the dynamic characteristics of the cam mechanism to allow higher output shaft speeds for a given cam follower inertia, than can be expected by conventional cam contours such as Cycloidal and Modified Trapezoidal. The Polynomial 56789 contour specifies velocity, acceleration and jerk values of 0 at start and end of both rise and return cam profiles. Dwell at both TDC and

BDC are also at zero cam follower/piston movement. Referring to Fig. 4 the dwell duration for the purposes of this description is set at 100 for both TDC and BDC. Both the two rise and two return cam profiles each occur over an 80 period. Therefore for one complete revolution of the output shaft of the barrel cam, starting at BDC of 80 rise, 10 dwell at TDC, 800 return to BDC, 100 dwell at BDC, 800 rise to TDC, 10 dwell at TDC, 800 return to BDC and finally 100 at BDC. This provides the barrel cam engine with two power strokes per revolution (3600) of the barrel cam's output shaft.

The dwell of 100 selected is a starting point, the actual dwell at TDC and BDC to provide the best combustion regime at constant volume, will have to be determined by a research engine programme. This may, in the final analysis, be either more or less than 100. Therefore for the purposes of this description a limit of plus 5 and minus 10 on the nominal 100 dwell period is specified.

The dwell at BDC, will by necessity, require to be the same period as TDC for a barrel engine's double acting motion. It follows, for a given inlet port height, more inlet port area will be available than is required for good combustion ragime. Reducing the inlet port height to provide the optimum port area, will provide the opportunity to increase the expansion stroke of the engine, thus improving the engines thermal efficiency. The reduced height inlet port area requirements will depend on either natural aspiration, supercharge or turbo charging mode.

Fig. 1 Two Cycle Double Acting Barrel Cam Engine- Longitudinal Section Fig. 2 Two Wave Barrel Cam of the Hermann engine type with a Rise-Return-Rise Return profile.

Fig. 3 Shows the graph of a Two Wave Hermann engines Barrel Cam's Rise-Return-Rise-Return profile.

Fig. 4 Shows the inventions graph of a Two Wave Barrel Cam's Rise-Dwell-Return-Dwell-Rise-Dwell-Return- Dwell using a Polynomial 56789 profile.

Claims

CLAIMS 1 Improvements in a Barrel Cam Engine whereby the two wave

barrel cam is modified from a "rise-return-rise-return" to a "rise-dwell-return-dwell-rise-dwell-return-dwell" profile of the polynomial 56789 type and conforming to Figs. 4 in an engine conforming to Fig. l. The added dwell features enable the engine pistons to dwell at TDC for a period that provides constant volume combustion. The equal dwell periods at BDC provides either a larger inlet port opening area or lesser but adequate port area for inlet air with a lower inlet port height. This lower inlet port height enables a longer expansion cycle for a given stroke and improves the brake thermal efficiency (BTE) of the engine.
2 Improvement in the Brake Thermal Efficiency (BTE) and Brake Mean Effective Pressure (BMEP), whilst achieving higher and smoother torque characteristics, lower exhaust temperatures and lower levels of emissions of both naturally aspirated (NA) and pressure charged and intercooled engines of either the Two or Four Cycle type, that use either Diesel, Dimethyl Ether (DME), Syntrolium (gas to liquid), Gasoline, HC Gas or Hydrogen fuel. Each and all having a plurality of the inventions set forth in the preceding Claim 1.