SUPERCHARGING INTERNAL COMBUSTION ENGINES

Abstract: A method and apparatus of supercharging an internal combustion engine (10) in which a pulsed jet of gas is injected at high velocity into a mixing chamber (18a-d) where momentum exchange between the jet and or air/fuel mixture in the mixing chamber (18a-d) will accelerate the air or air/fuel mixture towards an outlet (20) from the mixing chamber (18a-d) which is connected to an inlet port of a cylinder (10a-d) of the engine (10) and induce further air or air/fuel mixture into the mixing chamber (18a-d), to provide a pulsed induction charge at increased pressure, the pulsed induction charge being timed to arrive at the cylinder (10a-d) towards the end of the induction stroke thereof.

Description: The present invention relates to the supercharging of internal combustion engines. The power of an internal combustion engine may be increased by increasing the volume of the air/fuel mixture that is delievered to the cylinders. This process of supercharging is achieved by increasing the pressure of the air or air/fuel mixture that is delivered to the cylinders, above atmospheric pressure. In the past supercharging of internal combustion engines has been achieved by one of two methods, that is by the use of a mechanically driven positive displacement pump or supercharger, or by an exhaust driven pump or turbocharger. In both cases, all the air supplied to the engine passes through the supercharging pump. Mechanically driven superchargers work well at low engine speeds, but their size and power requirements have made these units unpopular and they have been superceded in recent years by turbochargers. Turbochargers, being driven by the exhaust gasses of the engine, impose a relatively low power loss and are relatively compact. The main drawbacks of turbochargers are their poor throttle response, their need to work at relatively high engine speeds for good performance, and problems with increase in temperature of the induced air due to conduction from the exhaust gasses. Furthermore, the known superchargers or turbochargers provide a continuous supply of pressurised air which is delivered to the engine when the inlet ports are closed as well as on the induction strokes. Moreover, pressurised air will be supplied to the engine throughout the induction stroke. However, it is more efficient to supercharge only towards the end of the induction stroke, when the amount of air drawn into the cylinder under normal aspiration is reducing. Patent Specification Nos. DE-A-3115772, DE-A-3137454, FR-A-595,814 and JP-A-6155360 disclose systems of supercharging internal combustion engines, using pulsed jets of gas to induce pulsed induction charges. DE-A-3115772 discloses a system in which a pulsed jet of air is injected into a mixing chamber to induce a pulsed induction charge which is delivered to the inlet port of a cylinder, during the latter part of the inlet stroke. This system requires an engine driven compressor and means for pulsing the compressed air produced thereby. FR-A-595,814 discloses the use of exhaust gases to induce the induction charge, but this induction charge is delivered to the cylinder at the beginning of the induction stroke. The present invention provides a method and apparatus by which one cylinder is supercharged by means of a jet of exhaust gases from another cylinder, a pulsed induction charge being delivered to the cylinder towards the end of the induction stroke. According to one aspect of the present invention a method of supercharging an internal combustion engine comprises; injecting a high velocity pulsed jet of gas into a mixing chamber containing air or an air/fuel mixture, so that momentum exchanged between the jet of gas and air or air/fuel mixture will accelerate the air or air/fuel mixture towards an outlet which is connected to an inlet port of a cylinder of the engine and further air or air/fuel mixture at atmospheric pressure will be entrained into the mixing chamber through an inlet thereto, to provide a pulsed induction charge of air or air/fuel mixture at increased pressure, said pulsed induction charge being delivered to the cylinder so that an induction charge pulse is timed to arrive at the cylinder towards the end of the induction stroke, characterised in that exhaust gases are tapped off each of the cylinders towards the end of its expansion stroke to provide high velocity pulsed jets of gas, the high velocity pulsed jet of gas produced by one cylinder being injected into a mixing chamber connected to an inlet port of another cylinder to produce a pulsed induction charge of air or air/fuel mixture which is delivered to said other cylinder towards the end of its induction stroke. According to a preferred embodiment of the invention the induction charge pulse is delivered to the cylinder after the piston has completed of the order of 90% of its induction stroke. The pulsed gas jet injected into the mixing chamber is preferably at supersonic velocity and may have a mass flow of approximately ten per cent of the cylinder capacity. In such circumstances, boost pressures of, for example the order of twenty-five per cent may be achieved. According to a further aspect of the present invention an apparatus for supercharging an internal combustion engine comprises a mixing chamber having an inlet open to a source of air or an air/fuel mixture at atmospheric pressure and an outlet adapted to be connected to an inlet port of a cylinder of an internal combustion engine, a nozzle opening into said mixing chamber and means of supplying a pulse of gas at high pressure to said nozzle to inject a high velocity jet of gas into the mixing chamber, so that said jet of gas will accelerate the air or air/fuel mixture in the mixing chamber towards the outlet and entrain more air or air/fuel mixture into the mixing chamber through the inlet to form an induction charge pulse, means being provided to time delivery of said pulse to a cylinder of the engine, towards the end of an induction stroke, characterised in that the nozzle is connected to a port in one cylinder, the port being controlled to deliver a pulsed jet of exhaust gases to the nozzle towards the end of the expansion stroke of said one cylinder, the nozzle opening into a mixing chamber connected to another cylinder so that the jet of exhaust gases passing through said nozzle will produce a pulsed induction charge timed to be delivered to said other cylinder towards the end of its induction stroke. Preferably, separate pulsed jets of gas will be produced for each cylinder of the combustion engine and these will be fed via nozzles to separate mixing chambers, each serving one of the cylinders. However, the pulsed jets of gas may be delivered to a common mixing chamber which will deliver a pulsed induction charge, via a tuned induction manifold common to all the cylinders. Various embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of a supercharging system formed in accordance with the present invention; Figure 2 is an enlarged view of the mixing chamber/jet assembly used in the system illustrated in Figure 1; Figure 3 shows an alternative form of mixing chamber/jet assembly used in a modified version of the system illustrated in Figure 1; and Figure 4 shows a schematic layout of a cylinder with piston controlled port used in the system illustrated in Figure 1. As illustrated in Figure 1 an internal combustion engine has four cylinders 10a-10d, each cylinder 10a-10d having a mixing chamber 18a-18d connected to the inlet port thereof. A nozzle 17a-17d as described in greater detail below with reference to Figure 2, opens into each of the mixing chambers 18a-18d. The nozzles 17a-17d associated with each of the cylinders 10a-10d are connected to a port 25 opening in to another cylinder 10a-10d. As illustrated in greater detail in Figure 4, the port 25 is provided in the wall of the cylinder 10a, in a position where it will be covered and uncovered by the piston 27, at a point towards the end of its stroke. Uncovering the port 25 towards the end of the expansion stroke of the piston 27 will enable a pulse of exhaust gases at high pressure to pass through the port 25 to the nozzle 17a-17d connected thereto. As illustrated in greater detail in Figure 2, the nozzles 17a-17d have a narrow throat portion 21 and a divergent nozzle portion 22. The dimensions of the nozzles 17a-17d are such that the pulse of exhaust gases that are delivered thereto, are accelerated to sonic velocity in the throat portion 21 and to supersonic velocity upon expansion into the divergent nozzle portion 22. Upon exiting from the nozzle 17a-17d into mixing chambers 18a-18d, the supersonic jet of air accelerates the air in mixing chamber 18a-18d towards an outlet 20 and entrains further air into the mixing chamber 18a-18d from atmosphere through an inlet 19, to create an induction charge pulse which is delivered to the inlet of cylinder 10a-10d. With a four cylinder engine, cylinders 10a and 10d are normally 180° out of phase with cylinders 10b and 10c, so that when cylinder 10a is on the expansion stroke, cylinder 10d will be on the induction stroke, cylinder 10b is on its exhaust stroke and cylinder 10c is on its compression stroke. The mixing chamber 18a which is connected via nozzle 17a and port 25d to cylinder 10d, is consequently arranged to deliver induction charge pulses to the inlet port of cylinder 10a, so that the induction charge pulses are delivered towards the end of the induction stroke of cylinder 10a. Similarly, the port 25 of cylinder 10a will be connected to the inlet port of cylinder 10d; port 25 of cylinder 10b will be connected to the inlet port of cylinder 10c and port 25 of cylinder 10c will be connected to the inlet port of cylinder 10b. With these arrangements, the position of the port 25 must be set to take account of delays in delivering the induction charge pulse to the inlet port of the associated cylinder, so that the appropriate timing of the pulse is achieved. The above system may be used with fuel injection systems, in which case air drawn into the mixing chamber 18a-18d to form the induction charge, is delivered directly to the cylinder 10a-10d associated with that mixing chamber 18a-18d, and the appropriate amount of fuel is injected. Alternatively, the system described above may be modified so that an air/fuel mixture is supplied via inlet 19 to mixing chamber 18a-18d. As described above, the air/fuel mixture will then be pressurised to form a pulsed induction charge and may then be fed directly to the cylinders by conventional valve means. With engines of this type the inlet valve will typically open at about 30° before top dead centre and close at about 55° after bottom dead centre. The induction charge pulse will typically be delivered to the cylinder 10a-10d after it has completed 90% of its induction stroke, so that air or air/fuel mixture at a pressure in excess of atmospheric pressure will be forced into the cylinder 10a-10d until the inlet valve closes at 55° after bottom dead centre. As illustrated in Figure 3, all four nozzles 17a-17d may be grouped together and open into a common mixing chamber 18, which may be connected to the inlet ports of all four cylinders 10a-10d, by common inlet manifolds. As pulsed jets of exhaust gas are fed to the nozzles 17a-17d, each pulse will produce an induction charge pulse as described above. A series of induction charge pulses will thus be fed to the induction manifold, these pulses being timed to arrive at one cylinder 10a-10d of the engine, at the appropriate point in its induction stroke.

Claims: 1. A method of supercharging an internal combustion engine including injecting a high velocity pulsed jet of gas into a mixing chamber (18a-d; 18) containing air or an air/fuel mixture, so that the momentum exchange between the jet of gas and air or air/fuel mixture will accelerate the air or air/fuel mixture towards an outlet (20) which is connected to an inlet port of a cylinder (10a-d) of the engine (10) and further air or air/fuel mixture at atmospheric pressure will be entrained into the mixing chamber (18a-d; 18) through an inlet (19) thereto, to provide a pulsed induction charge of air or air/fuel mixture at increased pressure, said pulsed induction charge being delivered to the cylinder (10a-d) so that an induction charge pulse is timed to arrive at the cylinder (10a-d) towards the end of the induction stroke, characterised in that exhaust gases are tapped off each of the cylinders (10a-d) towards the end of its expansion stroke to provide high velocity pulsed jets of gas, the high velocity pulsed jet of gas produced by one cylinder (10a-d) being injected into a mixing chamber (18a-d; 18) connected to an inlet port of another cylinder (10a-d) to produce a pulsed induction charge of air or air/fuel mixture which is delivered to said other cylinder (10a-d) towards the end of its induction stroke. 2. A method according to Claim 1 characterised in that the induction pulse is delivered to the cylinder (10a-d) after the piston (27) has completed of the order of 90% of its induction stroke. 3. A method according to Claim 1 or 2 characterised in that the pulsed gas jet is injected into the mixing chamber (18a-d; 18) at supersonic velocity. 4. A method according to any one of Claims 1 to 3 characterised in that the mass flow rate of the jet of gas is of the order of ten per cent of the charge requirement of the cylinder (10a-d). 5. A method according to any one of Claims 1 to 4 characterised in that the jet of gas is provided by forcing a high pressure pulse of gas through a nozzle (17a-d). 6. An apparatus for supercharging an internal combustion engine including; a mixing chamber (18a-d; 18) having an inlet (19) open to a source of air or an air/fuel mixture at atmospheric pressure and an outlet (20) adapted to be connected to an inlet port of a cylinder (10a-d) of an internal combustion engine (10), a nozzle (17a-d) opening into said mixing chamber (18a-d; 18) and means (25) for supplying a pulse of gas at high pressure to said nozzle (17a-d) to inject a high velocity jet of gas into the mixing chamber (18a-d; 18), so that said jet of gas will accelerate the air or air/fuel mixture in the mixing chamber (18a-d; 18) towards the outlet (20) and entrain more air or air/fuel mixture into the mixing chamber (18a-d; 18) through the inlet (19) to form an induction charge pulse, means being provided to time delivery of said pulse to a cylinder (10a-d) of the engine (10), towards the end of an induction stroke, characterised in that the nozzle (17a-d) is connected to a port (25) in one cylinder (10a-d), the port (25) being controlled to deliver a pulsed jet of exhaust gases to the nozzle (17a-d) towards the end of the expansion stroke of said one cylinder (10a-d), the nozzle (17a-d) opening into a mixing chamber (18a-d); 18) connected to another cylinder (10a-d) so that the jet of exhaust gases passing through said nozzle (17a-d) will produce a pulsed induction charge timed to be delivered to said other cylinder (10a-d) towards the end of its induction stroke. 7. An apparatus according to Claim 6 characterised in that the nozzle (17a-d) is connected to a piston (27) controlled port (25) in a cylinder (10a-d) of the engine (10), said port (25) being uncovered towards the end of an expansion stroke of the piston (27), so as to deliver a pulse of high pressure gas to the nozzle (17a-d). 8. An apparatus according to any one of Claims 6 or 7 characterised in that individual nozzle (17a-d)/mixing chamber (18a-d) assemblies are provided for each cylinder (10a-d) of a multi-cylinder engine (10). 9. An apparatus according to Claim 8 characterised in that several cylinders (10a-d) are each connected to an individual nozzle (17a-d), each nozzle (17a-d) serving one other of the cylinders (10a-d), the linked cylinders (10a and 10d, 10d and 10a, 10b and 10c, 10c and 10b) being arranged so that the pulse of high pressure combustion gases delivered from one cylinder (10a-d) is timed to provide a supercharging boost to the linked cylinder (10a-d), which coincides with the end of delivery of the charge to that cylinder (10a-d). 10. An apparatus according to Claim 6 or 7 characterised in that several nozzles (17a-d) open into a common mixing chamber (18) which serves a plurality of cylinders (10a-d) of a multi-cylinder engine (10).

Inventors: PARSONS, BRYAN NIGEL VICTOR
Applicants: JAGUAR CARS LIMITED
Application year: 1988
Main classification: F02B29
IPC codes: F02B29