enginehistory.org

[szielinski]

If you guys will accept the lack of a diagram* and lack of an explanation of the variable timing aspects of this paper engine** and the fact that this design is better suited to a nacelle than a fuselage; I will add the following:-


General type: - 9-cylinder, 2-cycle, barrel-type internal combustion engine.
Bore/Stroke: - 150mm/165mm 27L (~1650 c.i.)
Primary drive: - Rotating shaft geared to ducted fan.
Valvetrain: - Sleeve valves with variable asymmetric timing.
Induction: - Direct stratified injection with inlet air boost from axial supercharger.
Ignition: - Dual sparking plugs in cylinder head with electronic control.
Cooling: - Transcalent fluid to fan-cooled exterior, augmented with piston oil jets.
Lubrication: - Dry-sump with oil pre-heaters for starting
Low-RPM: Exhaust port opens/closes 90˚/120˚ FTDC*, air ports open/close 118˚/112˚ FTDC
High-RPM: Exhaust port opens/closes 84˚/118˚ FTDC, air ports open/close 112˚/110˚ FTDC
Firing Order: 1,6,2,7,3,8,4,9,5,1,6,2,7,3,8,4,9,5.
* From Top Dead Centre

Construction and Operational description: -

This mechanism is based on a Hermann-type face cam, where nine cylinders are arranged nonagonal, axial and parallel to the output shaft. Each piston has two roller bearings inside on separate but parallel axes (instead of one end of a connecting rod). The axes of said bearings rotate radially about a normal to the output shaft. The bearings engage with both sides of a sinusoidal cam ring that is splined to the output shaft from the interior side. There are four lobes on the ring cam (two complete sine waves); hence this two-cycle engine supplies 18 power strokes per revolution.

Pistons oscillate within a rotating, reciprocating sleeve that exposes or covers the appropriate ports in the respective cylinder. Said sleeves are of the self-sealing type with no junk head used. Each sleeve has a ring gear attached to the crank end of said sleeve. The width of the ring driving gear is the total vertical travel of the sleeve plus width of the ring gear. The primary drive for the sleeves being a ring gear driven by a fixed-cage planetary gear drive, made up of gears spaced at even intervals that engage with a gear fixed to the output shaft. The final ratio is such that the sleeves rotate at one half of crank speed. Due to the sleeve turning at half crank speed, all gear teeth on drive gear engage with all teeth on sleeve and slide at various points along the drive gear length. Hence assembly phase is not critical (NB: - although the sleeve rotates at ½ crank speed, it still reciprocates vertically at the same frequency as the crank lobes in this 2-cycle engine).

Like most other two-cycle engines, the cylinder head is devoid of valves or ports. The only protuberances are the injector and sparking plugs. These are contained within a semi-recessed portion of the cylinder head (to facilitate charge stratification). As the sleeve actually seals the combustion chamber, the head is essentially no more than a cap on the cylinder and no complex top joint, liner or gasket is required.

Main engine crankcase sits at centre of ducted fan assembly. Main fan rotates faster then crankshaft via gearbox. An axial compressor stage supplies air to cylinders. Intake air is routed through main fan, through air filter, through axial compressor thence to inlet manifold. As no conventional throttle is used, an electronically controlled electromagnetic coupling to the axial compressor controls airflow. This mechanism works in conjunction with the variable valve timing and fuel injectors to facilitate power control.

The cooling air for the transcalent finning is routed first through a fan positioned just aft of the main fan, then through the annular oil cooler. This air then travels in the space between the axial compressor and the crankcase, through the spaces between inlet air ports, through the finning of the cylinder head and exits at the rear of the engine.

Exhaust is directed to rear of engine to variable discharge nozzle.

There are three airstreams exiting from the rear of the airframe in close proximity. Listed in order of magnitude they are:-
a) The main thrust from the ducted fan driven by the output shaft
b) The exhaust efflux via the variable diameter duct
c) The engine cooling air from the transcalent finning (plus oil radiator efflux)

General comments on operation: -

A ducted fan allows tip speed to be greater than an external propeller, and enables a more compact and elegant installation. Since ducted fans also tend to operate at higher speeds than propellers, this two-cycle engine can then operate at higher speeds also, where this two-cycle engine is more economical.

Stratified charge operation permits a 2-cycle engine to run much smoother under part-load, as a sufficiently rich mixture is present near the spark plug to ensure ignition, whilst allowing complete scavenging of exhaust gases. Also the air to fuel ratio can be leaned out to almost half that of conventional four-stroke engines (25:1 w/w for one type compared to 12-14:1 for petrol). Variable port timing facilitates smooth running under all power conditions.

Due to considerable friction that can occur between sleeves and block when inoperative, an oil pre-heater and pump is used that ensures warm oil is supplied to the sleeve surface before and during the application of starting torque. Once operating, however, piston, sleeve and ring wear is considerably reduced as no component ceases to have relative motion with adjacent components; hence no breakdown in hydrodynamic lubrication occurs.

Operating temperature is reached swiftly as no cooling occurs until sufficient heat convents through the internal wicks. Once operating temperature is reached, the phase of the cooling liquid changes from liquid (next to the cylinder) and travels through internal screens and orifices where it changes to gas. Once evaporated, the gas condenses on internal fins and travels back to the cylinder wall. This system has no moving parts and can dissipate large amounts of heat if sufficient cooling air is provided. Transcalent cooling systems are also lightweight as the internal cavity is mostly empty space. Also, such systems can be independently sealed, meaning that in effect, there can be a separate cooling system for each cylinder.

* just not finished enough to do an electronic version
**it just MIGHT be a patentable idea, I would like to keep it out of the public domain until I finish the inlet port shapes.
_________________
“Make everything as simple as possible - but not simpler” – Einstein.

[gryan]

It may be possible to build a suitable piston engine by using components from established designs. Take a look at this:

http://www.bigbikeriders.com/48cyl.htm


Regards


Gerald

[szielinski]

Yes, had seen that one,
Imagine doing some 'dyno-riding' with it!
(at least it'd have the weight to stay on the rollers)
_________________
“Make everything as simple as possible - but not simpler” – Einstein.