WO2023056511A1

WO2023056511A1 - Environmentally compatible two stroke engine

Info

Publication number: WO2023056511A1
Application number: PCT/AU2022/051187
Authority: WO
Inventors: Mark Gendala
Original assignee: Mark Gendala
Priority date: 2021-10-06
Filing date: 2022-10-05
Publication date: 2023-04-13

Abstract

A two-stroke internal combustion engine, comprising a cylinder, a piston reciprocating within the cylinder, a crankcase that is correspondingly pressurised and de-pressurised beneath said piston, a throttle-controlled carburettor for creating combustible air- fuel mixture, a passageway for conducting air-fuel mixture into periodically de-pressurised crankcase, scavenging passageways conducting the air-fuel mixture from the crankcase and into the cylinder once the piston has opened said cylinder's exhaust and scavenging ports, a conduit delivering pressurised-air from the means of its pressurisation and into the cylinder via its own passageway and its own port, a pressurised-air passageway with a port residing between at least two ports through which air-fuel mixture emerges from its passageways for the purpose of jointly scavenging the cylinder's exhaust once the piston has opened their respective ports.

Description

INTRODUCTION

A quote from the report on two-stroke cycle laboratory measurements conducted by Martin Ekenberg of the Division of Combustion Engines, Lundt Institute of Heat and Power Engineering, Sweden -

“2.2.3 Scavenging principles

After the “blow-down” phase, the time period during which the pressure in the cylinder decreases rapidly due to the opening of the exhaust port, the absolute pressure in the cylinder is about 1 bar (atmospheric pressure). As the scavenging goes on, the pressure in the cylinder stays at about 1 bar, and some of the exhaust gases are replaced with fresh mixture”

THE INVENTION

This invention supplements a two stroke engine's conventional charge - usually fuel and air, with the additional charge of pressurised air.

The aforementioned process begins once the absolute pressure within the engine's cylinder has dropped to “atmospheric” or “about 1 bar”, as described in the Lundt Institute report quoted above.

PLEASE NOTE: The additional charge of air performing this invention may flow into the engine's cylinder from either the upward or the downward direction.

Drawing 1

UPWARD AIR-FLOW EMBODIMENT

Fig. 1, Drawing 1 shows a conventional two-stroke piston with full length skirt often associated with “cup-handle” transfer passages of say, go-kart engines, etc...

Fig. 2, Drawing 1 illustrates said piston in its BDC position - with circle (3) depicting its prior TDC position and cutout (2) representing the exhaust port.

Key feature of Fig. 2 is the additional charge of air (A) which enters through transfer port (1) beneath mixture (M), then travels upwards above the exhaust port (2) - while at the same time the inflow of mixture (M) is performing its conventional role of crankcase-pressurised loop-scavenging.

Although port (1) is very common in two-stroke engines, its usual role is conducting a charge of crankcase-pressurised fuel / air mixture - not the air itself.

PRESSURISING THE ADDITIONAL CHARGE OF AIR (A)

Given that additional charge of air (A) shown on Fig. 2 will need to enter the cylinder under sufficient pressure, it is likely that such relatively low pressure may readily be created by mechanical means already being powered by the engine itself.

Hence, in case of an aircraft engine such pressurisation may be obtained from rotation of the propeller, or - in case of a chainsaw, it may be obtained from rotation of the chainsaw's cooling fan, etc..

USING AIRCRAFT PROPELLER (#1)

Drawing 2 illustrates the rotation of propeller (4) intermittently forcing air (A') into a pair of air-scoops (5) - resulting in pressurisation of the captured air.

Next - after exiting said air-scoops (5), pressurised air will flow through conduits (6) into air-box (7) then through conduits (8) towards the engine's flanges (9).

Ultimately - after travelling through said flanges (9), pressurised air (A) will enter the engine's cylinder during the scavenging phase as depicted on Drawing 1.

USING AIRCRAFT PROPELLER (#2)

In the first instance, Drawing 3 shows how all of the air-pressurisation components - already illustrated on Drawing 2 - fit within the layout of a conventional two-stroke “boxer” aircraft engine.

Here, air-scoops (5) are shown mounted atop the engine's opposing cylinder heads with its air-filter and carburetor assembly (10) positioned centrally on the top of crankcase (11). To complete this depiction two-stroke boxer configuration, a pair of exhaust pipes (12) are shown placed at the engine's exhaust side.

Lastly, Drawing 3 includes a “doted arrow” (13) - symbolising the removal of water which the propeller of aircraft flying through rain would inevitably have blown into air-scoops (5) and intermixed with the additional charge of pressurised air (A) at the centre to this invention.

USING AIRCRAFT PROPELLER (#3)

THE REMOVAL OF WATER

Fig. 1, Drawing 4 illustrates a rear-view cross-section of air-box (7) mounted on the crankcase (11) - with pressurised air (A) flowing into said air-box from conduits (6)

Water droplets (W) - which would accompany pressurised air (A) during rain, are shown sliding down the bottom of air-box (7), to be promptly expelled from said box as “doted arrow” (13) by the water-sensing, electric water pump (14)

THE REMOVAL OF DUST

Fig. 1 of Drawing 4 further depicts the charge of pressurised air (A) flowing upwards through a dust-removing air filter (15) and into opening (16)

Having travelled via opening (16), air (A) enters into the adjacent section of airbox (7) connected to conduits (8). Said conduits (8) then direct its flow past engine's flanges (9) as illustrated earlier on Drawing (2) View X of Drawing 3 - depicted in plan view on Fig. 2 Drawing 4, concerns the exact direction in which air (A) - impelled backwards by propeller (4), travels relative to the aircraft's own longitudinal axis.

It is well known that such air (A) never moves parallel to the aircraft's axis - but travels beside it in a corkscrew manner.

In this context, an asymmetrically curved air-scoop (6) may prove the most efficient way obtaining air-pressure from such cork-screw motion.

Drawing 5

USING AIRCRAFT PROPELLER (#4)

Fig 1 of Drawing 5 illustrates three volumetric symbols A, M and E representing the volumes of “air” (A), “air / fuel mixture' (M) and “exhaust” (E)

For added clarity, the motion of such volumes A, M and E will also be indicated by corresponding arrows A, M and E.

SCAVENGING PHASE AND THE INFLOW

OF PRESSURISED AIR (A)

Fig 2 Drawing 5 depicts the engine's scavenging phase at BDC, which - with exhaust (E) excluded - had first been shown in isometric projection on Fig. 2 of Drawing 1.

Once port (2) opens, its gasses (E) may have blown out with velocity of some 200 m/sec. After the piston has descended to its BDC position - as depicted on Fig.2 of Drawing 5, that velocity may drop to only 50 m/sec.

By that stage, the upward streams of mixture (Ml) - which could have entered the cylinder at some 150 me/sec, might still travel at some 100 m/sec.

THE INFLOW OF PRESSURISED AIR

In addition, Fig. 2, Dr. 5 shows pressurised air (A) emerging from its transfer port (1) then travelling diagonally inbetween the two streams of mixture (M) towards the top of engine's cylinder above its exhaust port.

More specifically, given that streams of mixture (M) directly above transfer port (1) are at BDC moving upwards at the highest velocity existing within the cylinder, it follows the absolute pressure in front of said transfer port (1) must consequently be the lowest pressure within said cylinder.

THE BENEFITS

1. ESCAPE OF MIXTURE ELIMINATED

Fig.3, Drawing 5 depicts an upwardly bowing piston closing the exaust port (2) and thus ending the engine’s csavenging phase.

Here, volume (19) of air (A) is shown lost inside exhaust port (2) in place of the conventions!, envuronmentally harmful escape of mixture (M) 2. CHARGE STRATIFICATION

Fig. 3, Drawing 5 also illustrates a volume of turbulent air (20) remaining underneath a volume of mixture (21) at the end of engine’s scavenging phase - thus allowing an efficiently combustible “stratified charge” to form itself within the cylinder.

Here, the efficiency of combustion may further be enhanced by a conventional “squish” occurring when top of the piston reaches the matching botom area (22) of the cylinder head.

3. IMPROVED VOLUMETRIC EFFICIENCY

It is envisaged that once the velocity of upwardly travelling pressurised air (A) - see inflow (A), Fig. 2, Drawing 5 - had been converted into absolute pressure at the end of scavenging phase shown on Fig. 3, Drawing 5, the final absolute pressure within the cylinder shall exceed 1 bar.

This would be due to the fact that this invention's inflow of pressurised air (A) travels diagonally upwards through the cylinder's centrality above the exhaust port and a large part of said air will be inertially retained before reaching said port.

DOWNWARD AIR-INFLOW EMBODIMENT

Whilst Drawings 1- 5 had shown supplementing of the engine's conventional charge with an inflow of pressurised air (a) moving diagonally upwards, this invention may also be performed by an inflow of pressurised air (A) moving downwards.

Fig. 1, Drawing 6 depicts an otherwise conventional piston featuring cavity (23) and deflector (24) - which have the primary function of deflecting this invention's Inflow of pressurised air (A) upwards into the cylinder's central volume.

In addition, cavity (23) and deflector (24) shall largely constitute the cylinder's combustion chamber.

USING AIRCRAFT PROPELLER (#5)

Whilst Drawing 2 had shown aircraft's “tractor propeller” generating this invention's flow of pressurised air (A), Drawing 7 illustrates a “pusher propeller” being used for the same purpose.

Drawing 7 shows the propeller (25) intermitently forcing air (A’) into air-scoop (26), with said air (A) then travelling through conduit (27) into air-box (28)

The function of air-box (28) is identical to air-box (7) shown on Drawing 2 - namely, it is to remove rain-water (13) and dust from the inflow of pressurised air (A).

After exiting air-box (28), pressurised air (A) flows via pair of conduits (29) and flanges (30) into the respective cylinders of an inline two-cylinder engine - with each cylinder featuring its own carburettor / air cleaner unit PLEASE NOTE: For brevity, the description of Drawing 7 doesn't refer to mechanical links between the rearward-facing boom (F) and the aircraft's engine, or presence of a gearbox, etc... etc...

SCAVENGING PHASE AND THE INFLOW

OF PRESSURISED AIR (A)

Drawing 8 illustrates this invention being performed in a manner that is very similar to that already described in context of Drawings 1 to 5.

However, the conduit of pressurised air (A) at transfer port (1) - that was earlier pointing largely upwards, is in the presently described embodiment pointing largely downwards and sideways.

Fig 2, Drawing 8 illustrates the engine's scavenging phase at BDC. Here, the inflow of pressurised air (A) enters piston's cavity (23) sideways - to be deflected upwards into the cylinder's central volume by said piston's deflecter (24).

Fig 3. Drawing 8 shows an upwardly moving piston closing the engines's exhaust port and thus ending said engine's scavenging phase.

As described earlier in context of Drawing 5, Fig. 3, Drawing 8 likewise shows a volume of air (A) being lost into said exhaust port in place of the conventional and environmentally harmful escape of mixture (M).

Likewise, volume of air (A) is depicted as remaining underneath a volume of mixture (M), eventually allowing an efficiently combustible “stratified charge” to form itself within the cylinder - with the “squish” region (32) further enhancing the efficiency of that combustion at TDC.

USING ENGINE'S COOLING FAN (#1)

Whereas the embodiments illustrated on Drawings 1 - 8 had obtained their inflows of pressurised air (A) from the rotation of aircraft's propeller, the currently described embodiment obtains said inflow (A) from rotation of the engine's cooling fan.

Drawing 9 depicts such an engine featuring a largely conventional cooling fan (33) that rotates within housing (34) to perform two distinct, separate functions -

- COOLING THE ENGINE -

The uppermost part (35) of housing (34) upwardly delivers conventional cooling air (A') into the usually plastic enclosure (36) surrounding cylinder (37).

Having extracted heat from the cylinder's cooling fins (38), heated air generally exits from said enclosure (36) through the that openings surround muffler (39) - GENERATION OF PRESSURISED AIR (A) -

At the opposite side, the botom of housing (34) is turned into a pressure-generating volute (40) - with the engine’s cooling fan (33) now acting as impeller of a centrifugal compressor.

After passing through volute (40), pressurised air (A) is redirected by bend (41) into conduit (42) - ultimately heading for the cylinder's transfer port (1) at the center of this invention.

It is envisaged the embodiment depicted on Drawing 9 will be particularly suited for air-cooled two-stoke engines typically used to power hand-held equipment such as brush cuters, chainsaws, leaf blowers, cut-off saws, etc...

PLEASE NOTE: Although Drawing 9 presently depicts carburetor manifold (43) plus carburetor (44) positioned at the botom of engine's crankcase - hence requiring a reed valve to operate - an alternative arrangement will be described shortly.

Drawing 10

USING ENGINE'S COOLING FAN (#2)

Drawing 10 illustrates the key features of this invention viewed from the carburetor manifold's (43) end of the engine.

On its conventional section, cooling air (A’) - propelled upwards by top part of the cooling fan (33), is shown travelling towards the cylider's cooling fins.

On the invention section, air (A) is shown having entered the cylinder's transfer port (1) after first becoming pressurised within volute (40) - then redirected by bend (41) into conduit (42)

Lastly, a reed-valve operated intake manifold (43) is depicted without the engine's carburetor.

Drawing 11

USING ENGINE'S COOLING FAN (#3)

Fig. 2 and Fig. 3 of Drawing 11 illustrate the engine’s scavenging phase performed in exactly the same manner as that described earlier in relation to the aircraft engine shown on Drawing 5.

Once again, Fig 3. shows an upwardly moving piston closing the engines's exhaust port and thus ending said engine’s scavenging phase.

As described earlier in context of Drawing 5, Fig 3, Drawing 11 likewise shows a volume of air (A) being lost into said exhaust port in place of the conventional and environmentally harmful escape of mixture (M).

Given that conventional cooling fans are not designed for pressurising air (A) to the extent this invention requires, the diameter of this invention's cooling fan may need to be made comparatively larger. Drawing 12

- ELIMINATING THE REED-VALVE -

Drawing 12 schematically depicts the present invention substituting the reed-valve - mentioned earlier in context of manifold (43), with a pair of novel, piston-controlled induction ports incorporated into the engine’s cylinder.

Fig. 1, Drawing 12 shows the engine’s scavenging phase at BDC - which is the same as that described earlier in context of Fig. 2, Drawing 1 and its equivalents. Of particular significance here are the novel inlets (44) and (46) enabling mixture (M) to enter into the crankcase at TDC, as illustrated on Fig. 2, Drawing 12.

Drawing 13

PERSONAL TRANSPORTATION ENGINES

Drawing 13 shows a complete engine schematically depicted earlier on Drawing 12 - but now intended to perform key aspects of this invention in the field of lower-cost Third World transportation such as motorcycles, scooters, rickshaws, etc...

Given the cylinders of such engines are usually cooled by the forward motion of their fins through the air, a fan (49) - without which air (A) cannot be pressurised, will need to be added to the proposed engine.

- ENGINE IN OPERATION -

As the engine moves forward, external air (A') trapped within the scoop (47) passes through air filter (48). Next - after entering centrifugal fan (49) through inlet (53), said air is pressurised within volute (50) as (A), then redirected into the transfer port (1).

The benefits of ensuing charge stratification, etc... had already been described in context of Fig. 3, Drawing 5 and Fig. 3, Drawing 11.

Lastly, Drawing 13 depictsthe side view of carburetor (52), inlet manifold (44), and one of the two mixture inlets (46) symmetrically placed relative to said manifold (44), plus the engine's exhaust piping (51).

AIR-TURBOCHARGED MARINE ENGINES

This invention may further be performed by embodiments in which the all-important pressurisation of air (A) is being obtained through the use of a turbocharger.

For example, a 3-cylinder in-line outboard motor may use crankcase induction of mixture (M) in a manner shown on Drawing 12.

At the same time, the turbocharger would pressurise air (A) inside an adjacent enclosure totally independent of the crankcase induction of mixture (M)

Ultimately, the addition of such turbo-pressurised air (A) would eliminate the loss of mixture (M) through the exhaust ports, ensure stratification of the cylinders' charge prior to ignition and increase the engine's all-important volumetric efficiency.

Claims

ABSTRACT A two-stroke internal combustion engine has conventional exhaust port, crankcasebased loop-scavenging of the exhaust, plus a conduit for collecting supplementary air pressurised outside of the engine's crankcase and directing that supplementary air into a port residing inbetween said engine's conventional loop-scavenging ports and opposite of its exhaust port. Thus, given that scavenging of exhaust from the engine's cylinder will be performed by two inflows - the inflow of crankcase-pressurised air-fuel mixture plus the inflow of externally pressurised supplementary air, coordination of two such inflows shall stratify and pressurise each fresh charge while preventing the air-fuel mixture part of those fresh charges from escaping through the exhaust port. CLAIMS (9) The claims defining this invention are as follows -

Claim 1.

A two-stroke internal combustion engine, comprising a cylinder, a piston reciprocating within the cylinder, a crankcase that is correspondingly pressurised and de-pressurised beneath said piston, a throtle-controlled carburetor for creating combustible air-fuel mixture, a passageway for conducting air-fuel mixture into periodically de-pressurised crankcase, scavenging passageways conducting the air-fuel mixture from the crankcase and into the cylinder once the piston has opened said cylinder's exhaust and scavenging ports, a conduit delivering pressurised-air from the means of its pressurisation and into the cylinder via its own passageway and its own port. a pressurised-air passageway with a port residing between at least two ports through which air-fuel mixture emerges from its passageways for the purpose of jointly scavenging the cylinder's exhaust once the piston has opened their respective ports.

Claim 2.

A two-stroke internal combustion engine as described in Claim 1 in which the exhaust gas is expunged from the cylinder by inflows of loop-scavenging airfuel mixture that at first point away from the exhaust port, then cojoin on their way upwards and across the cylinder head, then complete their conventional loop-scavenging pathway by moving downwards towards the exhaust port.

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Claim 3.

A two-stroke internal combustion engine as described in Claim 2 in which the exhaust gas is furthermore expunged from the cylinder's centrality by inflow of pressurised air emerging from a port that is positioned inbetween the loop- scavanging air-fuel mixture ports, said inflow of pressurised air then heading diagonally through the cylinder's centrality and above its exhaust port.

Claim 4.

A two-stroke internal combustion engine as described in Claims 2, 3 in which the inflow of pressurised air travelling diagonally past the cylinder's centrality straight towards a region above its exhaust port reaches that region ahead of the inflow of air-fuel scavenging mixture proceeding along conventional loopscavenging pathway described in Claim 2.

Claim 5.

A two-stroke internal combustion engine as described in Claims 2, 3, 4, where as a consequence of the inflow of supplementary pressurised air reaching the exhast port region ahead of the inflow scavenging air-fuel mixture, it shall be the air - instead of the air-fuel mixture, that escapes through the exhaust port.

Claim 6.

A two-stroke internal combustion engine as described in Claims 2, 3, 4, 5, in which the inflow of supplementary pressurised air and the combined inflows of scavenging air-fuel mixture are so positioned adjacent to one another as to produce a suitably turbulent interaction between the two and consequently, a suitable degree of charge stratification.

Claim 7.

A two-stroke internal combustion engine as described in Claims 2, 3, 4, 5, 6, where - in cases of air-cooled engines utilising centrifugal air compressor, the inflow of supplementary pressurised air comes from compressor’s specially inbuilt volute and conduit for collecting said inflow and directing it to its port within the cylinder.

Claim 8.

A two-stroke internal combustion engine as described in Claims 2, 3, 4, 5, 6, where - in case of the aircraft engine rotating its propeller, impulses created by propeller passing by a scoop are turned into the inflows of supplementary pressurised air which - in case of aircraft flying through rain, would first need to have its water separated and expelled before joining the scavenging phase.

Claim 9.

A two-stroke internal combustion engine as described in Claims 2, 3, 4, 5, 6, manufactured as a water-cooled outboard, light automotive or garden-related powerplant, in which the supplementary inflow of pressurised air is generated by a turbocharher or supercharger and in which each cylinder is charged with its twin inflows of scavenging air-fuel mixture from a sequentially pressurised region of crankcase underneath.

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