WO2006080044A2

WO2006080044A2 - Gas jet fluid barrier for two cycle engines

Info

Publication number: WO2006080044A2
Application number: PCT/IT2006/000050
Authority: WO
Inventors: Renzo Dellarosa
Original assignee: Centro Ricerche Tecnologiche Srl
Priority date: 2005-01-27
Filing date: 2006-01-27
Publication date: 2006-08-03
Also published as: EP1848881A2; WO2006080044A3; ITRN20050003A1

Abstract

A system capable of avoiding or limiting the leakage of the fresh gases of a two-cycle internal-combustion engine during the exhaust/transfer stroke consists of a (pressurized) fluid barrier provided by various devices and positioned downstream of the exhaust port in the cylinder exhaust channel. In the embodiment disclosed the fluid barrier is formed by a gas jet from a pneumatic circuit provided with pressure accumulator that takes exhaust gases from the exhaust pipe of the engine and lets them crosswise in the exhaust channel of the engine' s cylinder downstream of the exhaust port through a nozzle .

Description

Gas jet fluid barrier for two cycle engines

The present invention relates to two-cycle engines and more particularly a device able to prevent the fresh charge from being exhausted from the cylinder upon filling the same apart from the number of revolutions of the engine .

As known, the two-cycle internal-combustion engine only requires an expansion stroke and a compression stroke at each operation cycle; the timing diagram is controlled by the piston through strictly symmetric ports/valves .

Operation techniques and relevant problems are known to those skilled in the art and can be summarized synthetically by that upon opening the exhaust port and/or valve, with the piston being directed to the lower dead centre, and before closing the exhaust port/valve, with the piston being directed to the top dead centre, a portion of the fresh gases is driven and intaken outside the cylinder to flow to the exhaust system and to disperse to atmosphere, thus forming a negative "short circuit" . Only a portion of the fresh gases is "trapped" in the cylinder upon closing the exhaust port and/or valve and is used for the combustion, with the result that the dispersion of fresh gases from the exhaust pipe causes , as known, the increase in the consumption and air pollution as well, this occurring because the transfer and exhaust ports and/or valves are opened and closed at the same time only by the piston . The problem that has made itself felt by technicians for years has been faced by most different, known means regarding the exhaust port and/or valve, the exhaust pipe, and the exhaust pipe from cylinder such as : resonance chambers, expansion silencers , shutter gate valves with translation or oscillation motion, rotating, shaped drum valve, etc . which failed to solve the problem satisfactorily as all other special mechanical, electronic, or pneumatic devices did, including the direct inj ection . The resonance chamber and the expansion silencers have their known, expected limitations in the poor operation flexibility and the high overall dimension . The optimum range of use is reduced to a restricted range of revolutions of the engine; the range is as more restricted as higher is the performance desired by the engine with resulting high fuel consumption and air pollution.

The shutter valves applied to the exhaust have an unsatisfying seal because of the excessive machining tolerance due to the heat deformation as well as the drawback of forming excessive carbon residues, which is the main cause of cut-off and irregular operation . They shut partially the cylinder' s exhaust port and/or valve over a restricted range of revolutions of the engine so that they do not solve the problems of fuel consumption and air pollution accordingly.

The direct inj ection in two-cycle engines is extremely complex and difficult . The most important problem to be solved is the unsatisfying reliability of the atomization (spraying) of fuel at any number of revolutions of the engine both in term of dosing amounts and repeatability and timing . In addition, it requires an auxiliary, complex, expensive system that takes power from the engine away.

This problem is unsolved today and its importance is so high as to cast doubt on the future utilization of the two-cycle engine as the fuel consumption of the latter is extremely high and the air pollution can no longer be tolerated according to the European standards .

There are some ranges in which the two-cycle engine is almost irreplaceable because of its functional capacity, solidity, construction simplicity, limited production cost, and weight/power ratio; snowmobiles and above all motocross , endurance motorcycles, scooters , and motorbike .

The solution of the relevant problems , i . e . the reduction in the hydrocarbon emission and consumption, would lead to a wide relaunching of the motorcycle division .

The invention which is the obj ect of the present patent application overcomes the problems mentioned above by an extremely simple device without wasting engine' s power .

A main obj ect of the invention is to provide a device which allows more fresh gases to be trapped in the cylinder of the engine . A further obj ect is to prevent fresh gases from being exhausted from the exhaust pipe .

These and other obj ects which will be evident to those skilled in the art are accomplished by a fluid barrier which is formed, according to the disclosed embodiment, by the pressurized exhaust gas according to the appended claims .

The device of the invention, i . e . the "fluid obstruction barrier", controls the closure of the fresh gas exhaust port and/or valve without the help of the piston at the replacement of the gases . The barrier should have a lower pressure than the exhaust gases which then can pass therethrough, and a higher pressure than the fresh gases which cannot pass beyond it .

The technical role of the fluid barrier is to control the gases to pass through the exhaust port and/or valve in the exhaust/transfer stroke as follows :

- in the first exhaust stroke controlled by the piston directed to the lower dead centre in the time period from the opening of the exhaust port and/or valve to the beginning of the opening of transfer port and/or valve, a spontaneous emptying of the cylinder occurs at a high power and pressure of the exhaust gases ;

- in such time period the fluid barrier (with lower pressure) is easily overcome and/or perforated as it does not obstruct the passage of the exhaust gases (with greater pressure) to the outlet to the atmosphere; as the energy of the exhaust output gases is exhausted, pressure variations with fluctuations from a maximum to a minimum (pressure and depression) are produced upstream; as the pressure is low enough (lower than the pressure of the barrier) a "wall" effect becomes automatically active and obstructs and closes pneumatically the exhaust port and/or valve without the help of the piston and apart from the position of the piston, then at the most suitable time as the transfer of fresh gases occurs (replacement of gases ) ; - the pressure of the fluid barrier is greater than that of the cylinder (containing fresh gases ) , thus protecting the filling of the cylinder until the closure of the exhaust port and/or valve provided by the piston directed to the top dead centre .

To sum up, because of the positive pressure difference provided in the exhaust pipe of the cylinder (exhaust side) the fluid barrier controls automatically the closure of the exhaust port and/or valve without the help of the piston, thus preventing the fresh gases from passing therethrough and providing an "asymmetric" stroke of the exhaust/transfer timing diagram with respect to the position of the piston at "any number of revolutions of the engine" ; thus, the effects are :

• greater filling of fresh gases into the cylinder of the engine;

• lower leakage of the same to the exhaust system.

For a better understanding of the invention the following tables of drawings showing a preferred embodiment of the invention only by way of a not limiting example are annexed. In the drawings :

Fig . 1 shows schematically a two-cycle internal- combustion engine provided with exhaust system 6, cylinder 1, exhaust manifold 5 , piston 5 , pneumatic circuit 7 , 8 , 9 , 11 (where pipes are designated by 7 and 11, a pressure accumulator by 8 , and a check valve by 9 ) , nozzle 10 , transfer 3, exhaust port and/or valve 4 , fluid barrier 13, exhaust gases 14 , 14b, and fresh gases 15; Figs . 2 and 2a show the exhaust stroke of cylinder 1 with the opening of the exhaust port and/or valve 4 and path β of exhaust gases 4 that perforate fluid barrier 13 ;

Figs . 3 and 3a show the filling of cylinder 1 with opening of transfers 3 by piston 3 directed to the lower dead centre and with fluid barrier 13 preventing fresh gases 15 from being exhausted from the exhausting system 5-6;

Figs . 4 and 4a show the end of the transfer stroke with the following closure of the exhaust port and/or valve 3 and valve 4 , with piston 2 being directed to the top dead centre where fluid barrier 13 continues to prevent fresh gases 15 trapped in cylinder 1 from being exhausted through manifold 5 to the exhausting system 6 ;

Figs . 5 and 5a show a cylinder 1 provided with a nozzle 10 at exhaust manifold 5 able to form fluid barrier 13 downstream of the exhaust port and/or valve 4 ;

Fig . 6 shows pneumatic circuit 1 , 8 , 9, 11 connected by its ends to exhaust system 6 and nozzle 10 at the exhaust manifold 5 of cylinder 1. Arrows 14 show the path of the exhaust gas under pressure; arrows 14b shows the portion of gases which forms fluid barrier 13 ; Fig . 7 shows pressure accumulator 8 ^' with check valves 9 and fittings (pipes ) 11-7 ;

Fig . 8 shows one of the many embodiments to supply the pneumatic circuit : gas intake from the outside of the exhaust system;

Figs . 9 , 9a and 9b show some configurations of positioning nozzle 10 in manifold 5 of cylinder 1 able to form fluid barrier 13 by a longitudinal j et ( Fig . 9 ) , and by opposed j ets ( Fig . 9b) , upstream of the exhaust port and/or valve ( Fig . 9a) .

With reference to the above-mentioned figures , the operation of device 13 in a two-cycle internal- combustion engine ( see fig . 3 ) relates to the recovery of a portion 14b of exhaust gases 14 under pressure by an intake at the end of a pipe 11 which is a portion of a suitable pneumatic circuit, which exhaust gases 14b are taken from exhaust pipe 6 and inlet into a pressure accumulator 8 (tank) of the same pneumatic circuit . Such accumulator 8 is provided with a check valve 9 and is connected on the other side by pipes 7 to exhaust pipe 5 of cylinder 1 of the engine, wherein such portion 14b of exhaust gases is driven through a suitably positioned nozzle 10 to an essentially transversal direction with respect to the path of exhaust gases 14. Exhaust gases 14b form a gas j et 13 providing a fluid obstruction barrier 13 or "pneumatic plug" downstream of the exhaust port and/or valve 4. At the beginning of the exhaust stroke (exhaust/transfer) ( fig . 2 ) , exhaust gases 14 at the output of cylinder 1 pass through and cross over the obstruction fluid barrier 13 easily and flow quickly to the exhaust system 6 and the atmosphere and empty cylinder 1 of the engine . On the contrary, in the following transfer stroke 3 ( replacement of gases) fluid barrier 13 having a greater pressure than fresh gases 15 entering into cylinder 1 forms a pneumatic plug or fluid barrier 13 which prevents the gas from being exhausted and cuts off the transfer of fresh gases 15 to the exhaust system 5-6 caused by the upstream intake (depression) of exhaust gases 14 at the output to the atmosphere . The foregoing is carried out because of the pressure difference among : - hot exhaust gases which are driven by a high pressure, as piston 2 directed to lower dead centre opens exhaust port and/or valve 4 , and quickly flow to exhaust system 6 and cause a depression upstream of pipe 5 at the exhaust port 4 and cylinder 1; during. that time period the transfer of fresh gases 15 occurs ( filling of cylinder) ;

- fresh gases 15 flowing into cylinder 1 tend to take up ( fill) the room of exhaust gases 14 ; a portion of that gases is intaken by depression to exhaust system 6-5 through exhaust port and/or valve 4 ;

- fluid barrier 13 formed by gas j et 14b as the latter is subj ected to overpressure after exhausting the exhaust gases 14. Fluid barrier 13 cuts off the depression and obstructs pneumatically exhaust port and/or valve 4 by the greater pressure of fresh gases 15 in cylinder 1 and by distributing the pressures in exhaust pipe 5 and cylinder 1 upon filling stroke . It is self-evident that the embodiment disclosed is not the sole solution to form fluid barrier 13. This barrier can actually be formed by any known technology and applied to already existing engines . Such barrier can also be formed by directing an air j et taken from the outside and pressurized by a compressor or even a mere fan to exhaust pipe 5 downstream of exhaust port 4. The barrier disclosed above reduces remarkably the leakage of fresh gases 15 (hydrocarbons ) from exhaust pipe 6 of the engine with the result of using all fuel supplied and then with a lower fuel consumption. A further direct consequence due to the lower emission of hydrocarbons is a proportional reduction in the air pollution .

The reduction in the air pollution as well as the lower cost overcome the great obstacle of using a two- cycle engine today and then allows the relaunching of such industrial division with negligible cost because of the very simple mechanical measures .

Claims

1. A device for limiting and/or avoiding the leakage of the fresh charge from the cylinder of a two-cycle internal-combustion engine during the exhaust/transfer stroke apart from the position of the piston, characterized in that there is provided means for forming at least a fluid barrier ( 13 ) located at the exhaust port of exhaust manifold ( 5 ) of cylinder ( 1 ) , said fluid barrier acting with an intermediate pressure between fresh gases ( 15 ) and exhaust gases (14 ) upon transfer .

2. The device according to the preceding claim, characterized in that said means consists of a pneumatic circuit ( 11 , 8 , 7 ) which takes a portion of exhaust gases ( 14 ) from exhaust pipe ( 6) of the engine and lets them through nozzle ( 10 ) in exhaust manifold ( 5 ) of cylinder ( 1) to a direction which is generally transversal to the latter .

3. The device according to the preceding claims , characterized in that said pneumatic circuit is provided with a pressure accumulator (8 ) provided with a check valve ( 9) having the function of making the pressure that forms fluid barrier ( 13 ) constant .

4. The device according to the preceding claim, characterized in that pressure accumulator ( 8 ) has also the function of holding a portion of unburned oil exhausted together with exhaust gases ( 14 ) and preventing the leakage thereof, thus improving the efficiency and the life time of the catalyser in the silencer .

5. The device according to claim 1, characterized in that said means consists of a pneumatic circuit that feeds pressurized air to the inside of exhaust pipe ( 5 ) by a compressor or any other fan means .

6. The device according to claim 1, characterized in that said means consists of a pneumatic circuit that feeds pressurized air through one or more nozzle ( 10 ) to the inside of exhaust pipe (5) by a fan .

7. The device according to claims 2 , 5 and 6, characterized in that nozzle or channel (10 ) is positioned obliquely with respect to the axis of the exhaust pipe .

8. The device according to claims 2 , 5 and 6, characterized in that nozzle or channel (10 ) is positioned longitudinally with respect to the axis of the exhaust pipe .

9. The device according to claims 2 , 5 and 6, characterized in that nozzle or channel ( 10 ) can be positioned anywhere in the port and/or valve ( 4 ) of exhaust pipe ( 5 ) of cylinder ( 1) .

10. The device according to claim 2 , characterized in that pressure intake ( 11) of the pneumatic circuit can be positioned anywhere in the exhaust pipe .

11. The device according to claim 2 , characterized in that pressure intake ( 11 ) of the pneumatic circuit is connected to the exhaust pipe from the outside .

12. The device according to claims 2 , 5 and 6, characterized in that nozzle or channel (10) can be positioned anywhere in exhaust system ( 6, 5 ) .

13. The device according to claims 2 , 5 and 6, characterized in that nozzle or channel ( 10 ) can be positioned upstream of the exhaust port and/or valve .

14. The device according to claims 2 , 5 and 6, characterized in that nozzle or channel (10 ) is multiple .

15. The device according to the preceding claim, characterized in that multiple nozzles or channels ( 10 ) are opposed to one another .

16. The device according to claims 2 , 5 and β, characterized in that nozzle or channel ( 10 ) is fed intermittently.

17. The device according to claim 1 , characterized in that fluid barrier ( 13 ) can be provided intermittently.

18. The device according to claim 1, characterized in that fluid barrier (13) is formed downstream of the exhaust port and/or valve .

19. The device according to claim 1 , characterized in that fluid barrier (13) is formed upstream of the exhaust port and/or valve .

20. The device according to claim 1, characterized in that fluid barrier ( 13 ) is formed by any gas type .

21. The device according to claim 1 , characterized in that fluid barriers ( 13 ) are more than one .

22. The device according to claim 2 , characterized in that nozzle or channel (10 ) of the exhaust pipe is made by casting, extrusion, or mechanical machining.

23. The device according to claim 2, characterized in that pneumatic feeding circuit (11) , ( 8 ) , ( ?) consists of a simple connecting pipe .