WO2011073718A2

WO2011073718A2 - Internal combustion engine arrangement with rankine circuit and hybrid cylinder, especially for an automotive vehicle

Info

Publication number: WO2011073718A2
Application number: PCT/IB2009/008009
Authority: WO
Inventors: Benoît LOMBARD; Nicolas Espinosa
Original assignee: Renault Trucks
Priority date: 2009-12-18
Filing date: 2009-12-18
Publication date: 2011-06-23
Also published as: EP2513433A2; WO2011073718A3; BR112012014911A2

Abstract

An internal combustion engine arrangement comprising: an engine having at least one internal combustion cylinder where a piston is connected to an engine crankshaft (2), an intake line (5), a fuel injection system, an exhaust gas line (6), a closed Rankine circuit (14) having an expander, characterized in that the engine further comprises at least one hybrid cylinder (40) which is connected to the said intake line, to the said fuel injection system and to the said exhaust gas system and is further connected to the closed Rankine circuit (14) to act as the expander of the Rankine circuit.

Description

Internal combustion engine arrangement with Rankine circuit and hybrid cylinder, especially for an automotive vehicle Field of the invention

The invention concerns an internal combustion engine arrangement which has an improved efficiency and makes a better use of heat energy. Technological background

In today's economy, the demand for energy is expanding and, at the same time, energy (fossil energy such a fuel or non fossil energy such as biofuel) is becoming rarer and consequently more expensive.

Automotive vehicles, especially industrial vehicles, rely on internal combustion engines using fuel as a source of energy. It is therefore important that internal combustion engines are as efficient as possible.

An internal combustion engine converts the energy of the fuel into an output which is divided between mechanical work and heat energy.

In diesel internal combustion engines which have an efficiency that is higher than any other internal combustion engine, it is commonly admitted that only 30% to 40% of the fuel energy is released in mechanical work, while the rest is wasted in heat energy.

It therefore appears that there is room for improvement in the way heat energy can be recovered in an internal combustion engine arrangement.

Summary

In this technical context, an object of the present invention is to provide an improved internal combustion engine that recovers and utilizes at least a fraction of the heat generated in engine operation.

Another object of the invention is to provide an improved internal combustion engine arrangement making a better use of wasted heat while retaining a conventional engine architecture.

The present invention concerns an internal combustion engine arrangement comprising: - an engine having at least one internal combustion cylinder where a piston is connected to an engine crankshaft,

- an intake line,

- a fuel injection system,

- an exhaust gas line,

- a closed Rankine circuit having an expander,

characterized in that the engine further comprises at least one hybrid cylinder which is connected to the said intake line, to the said fuel injection system and to the said exhaust gas system and is further connected to the closed Rankine circuit to act as the expander of the Rankine circuit.

Thus, the engine incorporates a Rankine circuit that uses a hybrid cylinder as an expander and that retrieves heat energy from exhaust gas normally wasted. The internal engine according to the invention is based on a conventional internal combustion engine with the addition of a closed Rankine circuit that uses one of the engine cylinders as an expander. The hybrid cylinder can operate in a conventional internal combustion fashion or can operate as an expander when predetermined conditions are met such as, for example, medium load operation or exhaust gas having reached a preset temperature.

Preferably, the closed Rankine circuit is capable of injecting into said hybrid cylinder a Rankine fluid in a vapor state, heated by exhaust gas generated by fuel combustion in the at least one cylinder, where said Rankine fluid expands for producing a mechanical work which is retrieved on the engine crankshaft.

In an embodiment of the invention, the closed Rankine circuit comprises a pump for pressurizing and flowing the Rankine fluid in liquid phase, an evaporator connected to the said exhaust gas line for receiving heated exhaust gas and transferring heat energy from the exhaust gas to the Rankine gas prior to expansion in the hybrid cylinder and a condenser for condensing the Rankine fluid into liquid phase after expansion in the hybrid cylinder. In the evaporator the Rankine fluid is preheated, vaporized and superheated using the heat energy of the exhaust gas.

It is envisioned that the Rankine circuit can comprise a regenerator where residual heat from the Rankine fluid after expansion is transferred to the Rankine fluid prior to entering the evaporator. This improves the overall efficiency of the engine as residual heat energy in the Rankine fluid after expansion is recovered.

To control the operation of the hybrid cylinder, the latter comprises:

- at least one air intake valve, connected to the intake line, for controlling air introduced into the said hybrid cylinder by moving between a closed position and an open position; and

- at least one exhaust valve, connected to the exhaust gas line, for controlling the flow of exhaust by moving between a closed position and an open position ; and

- at least one Rankine fluid intake valve connected to the Rankine circuit, for controlling entry of the Rankine fluid into the hybrid cylinder before expansion by moving between a closed position and an open position; and

- at least one Rankine fluid exit valve, connected to the Rankine circuit, for controlling exit of the Rankine fluid from the hybrid cylinder after expansion by moving between a closed position and an open position.

Preferably, the Rankine fluid intake and exit valves are actuated independently from the air intake and exhaust valves. In a further refined embodiment, each valve of the hybrid cylinder is actuated independently by a dedicated actuator.

This makes it possible to alternatively use the hybrid cylinder either in an internal combustion mode where fuel is burnt in the cylinder or in a Rankine mode where the Rankine fluid expands in the hybrid cylinder.

In a preferred layout of the invention, the condenser can be located adjacent to an engine cooling fluid radiator so as to benefit from the aeraulics environment of the engine cooling fluid radiator.

Preferably, the Rankine fluid can be water based as it is usually available in a vehicle as cooling fluid, but organic fluids can be also considered.

For practical reasons, the hybrid cylinder can be located at the end of the engine.

Brief description of the drawings

The following detailed description of an embodiment of the invention is better understood when read in conjunction with the appended drawing, being understood, however, that the invention is not limited to the disclosed embodiment. In the drawings: Fig.1 is schematic view of a preferred embodiment of the present invention.

Description of the drawing

It can be appreciated that Fig 1 is a schematic representation of an internal combustion engine arrangement and that some technical features have been omitted for the sake of clarity of the following description.

The internal combustion engine 1 includes an engine block 3 having a plurality of cylinders 4. In the illustrated embodiment of the invention, the engine includes six cylinders by way of example. Each cylinder has a piston which is connected to a crankshaft 2.

Intake air is carried through an intake line 5 feeding the engine cylinders.

The engine 1 is provided with a suitable fuel injection system which is not illustrated. The fuel injection system can be of the direct injection type, where fuel is injected directly into the cylinders 4 through a dedicated fuel injector, or of the indirect type, where fuel may be injected in the intake line.

The engine 1 includes an exhaust line 6 which collects hot exhaust gas generated in the cylinders during the combustion process and carries the exhaust gas towards the atmosphere.

The internal combustion engine 2 can commonly include at least one turbocharger that incorporates a turbine 7 positioned on an exhaust line 6, and a compressor 8, linked to the turbine 7, located on the air intake line 5. An EGR (Exhaust Gas Recirculation) system, which may comprise an EGR cooler 9, can be arranged between the exhaust line 6 and the intake line 5. The air intake line 5 may also be equipped with a charge air cooler 91 located downstream of the compressor 8.

As can be seen on the drawing, each cylinder 4 can be provided with four valves, for example two intake valves 10 and two exhaust valves 1 1.

The engine is equipped with a cooling system that includes a radiator 12 wherein a cooling fluid flows. The cooling system can further include a fan 13 that is adjacent to the radiator.

The engine is also fitted with a Rankine circuit 14 wherein a Rankine fluid circulates. On the drawing, the Rankine circuit 14 is illustrated in double lines. The Rankine fluid is preferably water or a water based fluid due to its thermodynamic properties. In some cases, the Rankine fluid can also be used in the engine cooling circuit as the cooling fluid for the engine. Nevertheless, other fluids which are know to be efficient in a Rankine cycle may be contemplated, such as organic fluids.

The exhaust line 6 is connected to an evaporator 15 where exhaust gas at a high temperature flows. The evaporator 15 is part of the Rankine circuit 14. The evaporator is preferably constructed as a dedicated heat exchanger optimized to favour the heat transfer from the exhaust gases to the Rankine fluid. The evaporator is here a separate component which can be installed remotely from the engine block.

The Rankine circuit 14 shown on the Figure is a closed circuit and it includes, following the flow direction of the fluid in the circuit:

- a pump 17;

- optionally, the cold side of a regenerator 18;

- an evaporator 15;

- an expander,

- optionally, the hot side of the regenerator 18; and

- a condenser 20, the output of which is connected to the pump 17. These elements are connected on to the other by suitable pipes.

The pump 17 can be driven directly or indirectly by the engine crankshaft, or by a dedicated electromotor.

In a preferred embodiment of the invention, at least one of the engine cylinders is connected to the Rankine circuit 14. This hybrid cylinder 40 is contained in the engine block 3 and is connected to the intake line 4 and exhaust line 6 in a conventional fashion but is also connected to the Rankine circuit 14. In the following example, it will be explained how such hybrid cylinder can be used as the expander of the Rankine circuit.

The hybrid cylinder 40 includes at least two intake valves and two exit valves. The other cylinders are commonly provided with two intake valves and two exhaust valves but it can be envisaged to provide these cylinders with one intake valve and one exhaust valve.

Preferably, the hybrid cylinder 40 is one of the extreme cylinders of the six engine cylinders, for practical reasons, as it may be more convenient to connect one of these two cylinders to the Rankine circuit 14. In a preferred embodiment, the engine 1 is of the so-called cam- less type or, more generally, is of a type equipped with a valve actuation system that allows and independent control of every valve.

In a cam-less type engine, the engine does not include camshafts to operate the intake valves 10 or the exhaust valves 1 1 . Instead, the engine 1 uses actuators (not shown) to operate the exhaust and intake valves. The actuators can be of the electromagnetic or hydraulic or pneumatic type. In an embodiment, an actuator is used to open and to close a valve and in another embodiment, an actuator opens a valve while the valve is closed by a spring. Thus, the lift and the timing can be adjusted valve by valve as the control of the valves does not rely on the geometry of the lobe of the camshaft.

Preferably, all cylinders have a so-called cam-less type valve actuation mechanism. But, it could be provided that only the hybrid cylinder(s) has such type mechanism achieving an independent control of its valves, while the other cylinders have a conventional cam type actuation mechanism.

The hybrid cylinder 40 is provided with an air intake valve 10 controlled by its own actuator to command the amount of air that is fed into the cylinder for combustion with fuel which is suitably injected into the cylinder, it is to be noted that, if the engine is of the indirect injection type, then the air intake valve controls in fact the intake of an air/fuel mixture.

The hybrid cylinder also comprises a Rankine fluid intake valve 100 controlled by its own actuator to command the amount of Rankine fluid that is fed into the hybrid cylinder.

The hybrid cylinder 40 is provided with an exhaust valve 1 1 controlled by its own actuator to command the flow of exhaust gas produced by the combustion.

The hybrid cylinder also comprises a Rankine fluid exit valve 1 10 controlled by its own actuator to command the flow of Rankine fluid exiting from the cylinder.

The evaporator 15 is connected by suitable pipes to the hybrid cylinder 40.

A pipe connects the Rankine fluid exit valve 1 10 to the regenerator 18 where heat can be exchanged.

A further pipe connects the regenerator 8 to a condenser 20 which can be located adjacent or in front the radiator 20, or at any other suitable location on the vehicle. The condenser 20 is connected to the pump 17 by a pipe, in this embodiment, the condenser is air cooled, but it could also be cooled by the engine coolant or by other cooling systems.

As it will now be apparent, the engine according the invention can operate under two operational modes i.e. (i) a pure internal combustion mode using the entire engine capacity and (ii) a mixed mode combining internal combustion engine and Rankine closed cycle.

The engine 1 can operate as a conventional six cylinder engine in a pure internal combustion mode. Under this operational mode, ail six cylinders are fed with air and fuel and work is solely produced by internal combustion of fuel in all the engine cylinders.

In this operational mode, both Rankine intake valve 100 and Rankine fluid exit valve 1 10 are maintained in a closed position.

The engine can however operate under a hybrid mode wherein five cylinders 4 operate under a conventional internal combustion engine mode and the hybrid cylinder 40 operates in a Rankine mode.

Under the action of the pump 17, the Rankine fluid is pressurized and flows into the evaporator 15. Before the evaporator, the Rankine fluid is essentially in liquid form. In the evaporator 15, there is a transfer of heat energy from the exhaust gases generated by the operation of the cylinders 4 to the Rankine fluid.

Rankine fluid is superheated and is transformed essentially into vapour in the evaporator 15 and is then fed as vapour into the hybrid cylinder 40 which is used as an expander.

The valves 10 and 1 1 of the hybrid cylinder 40 which are respectively connected to the engine intake line 4 and exhaust line 6 are in a closed position. In effect, the hybrid cylinder 40 is operationally made independent from the other cylinders. This is made possible by the fact that the engine is a camless engine, thus the valves of the hybrid cylinder can be independently actuated.

The piston of the hybrid cylinder 40 remains, however, connected to the engine crankshaft and travels between two positions i.e. top dead centre and bottom dead centre.

The operation of the hybrid cylinder 40 is as follows:

The Rankine fluid inlet valve 100 is opened to allow the superheated vapour to enter the hybrid cylinder 40. The Rankine fluid inlet valve 100 is closed, the superheated vapour expands in the hybrid cylinder 40 thus causing the piston to move downwards. The energy from the Rankine fluid, which was previously retrieved from the exhaust gas in the evaporator, is thus used to produce work on the engine crankshaft.

The Rankine fluid exits the hybrid cylinder 40 through exit valve 1 10 and enters the condenser 20 where the Rankine fluid condenses into an at least partial liquid phase. After the condenser, the fluid returns to pump 17. It must be noted that a fluid reservoir can be connected to the Rankine circuit for eventually compensating certain fluid losses. In the embodiment shown, the reservoir 21 is connected to the pipe which links the output of the condenser 20 to the pump 17

In another embodiment of the invention, the Rankine fluid can be mixed into the engine radiator with the engine coolant stored therein.

The Rankine fluid is then fed into the evaporator 5 by the pump 17 where it will retrieve heat energy from the exhaust gas.

Optionally the engine can incorporate the regenerator 18. The regenerator 18 is used to retrieve some of the heat energy that remains in the Rankine fluid after expansion in the hybrid cylinder 40.

Thus, the regenerator 18 is a heat exchanger where the two sides of the exchanger are connected on two points of the Rankine circuit 14. The Rankine fluid flowing from the hybrid cylinder 40 enters a first side of the regenerator 18 and the Rankine fluid flowing from the pump 17 enters a second side of the regenerator 18 before flowing in the evaporator 15.

In the regenerator 18, the remaining heat energy of the Rankine fluid after expansion is exchanged to the Rankine fluid before it enters the evaporator 15.

It is understood that the engine is to operate as a fully internal combustion mode when the engine is required to produce a full output. The hybrid fuel internal combustion and Rankine mode is intended to be in use in medium load conditions, or more generally when full power of the engine is not required and when there is available cooling power on the condenser side.

When the hybrid cylinder is used as an expander of the Rankine vaporized liquid, this operation can be done at every crankshaft revolution (two stroke-like mode) if sufficient amount of Rankine vaporized fluid and pressure enables it and thus maximising the use of this hybrid cylinder and the energy recovered on the crankshaft 100.

On the other hand, if the Rankine cycle requests so for optimum energy recovery, this expansion might occur once every several revolutions (4 stroke-like, or six-stroke like...

Thanks to the fact that the hybrid cylinder Rankine fluid valves 100, 1 10 are controlled independently from the air intake and exhaust valves 10, 1 1 gives the possibility to adapt the expansion ratio of the cylinder depending on whether in operated as a regular combustion cylinder or as a Rankine expander cylinder. Therefore, the real expansion ratio applied to the Rankine fluid can be lower than the geometrical expansion ratio of the hybrid cylinder by programming a late opening of valve 1 0 once the piston is in intermediate position between top dead center and bottom dead center in the expansion stroke.

Also, it could be provided that the hybrid cylinder 40 may have a compression ratio different from the other cylinders 4.

Thus, the invention offers a new engine that has an overall better efficiency compared to conventional engines.

The invention is not limited to the illustrative embodiments described above and shown in the drawings, but can be varied within the scope of the following claims.

Claims

1. An internal combustion engine arrangement comprising: - an engine having at least one internal combustion cylinder where a piston is connected to an engine crankshaft (2),

- an intake line (5),

- a fuel injection system,

- an exhaust gas line (6), and

- a closed Rankine circuit (14) having an expander,

characterized in that the engine further comprises at least one hybrid cylinder (40) which is connected to the said intake line, to the said fuel injection system and to the said exhaust gas system and is further connected to the closed Rankine circuit (14) to act as the expander of the Rankine circuit.

2. The internal combustion engine arrangement according to claim 1 , characterized in that the closed Rankine circuit (14) is capable of injecting into said hybrid cylinder (40) a Rankine fluid in a vapor state heated by exhaust gas generated by fuel combustion in the at least one cylinder, where said Rankine fluid expands for producing a mechanical work which is retrieved on the engine crankshaft.

3. The internal combustion engine arrangement according to claim 1 or 2, characterized in that the closed Rankine circuit (14) comprises a pump for pressurizing and flowing the Rankine fluid in liquid phase, an evaporator connected to the said exhaust gas line (6) for receiving heated exhaust gas and transferring heat energy from the exhaust gas to the "Rankine fluid prior to expansion in the hybrid cylinder (40) and a condenser for condensing the Rankine fluid into liquid phase after expansion in the hybrid cylinder (40).

4. The internal combustion engine arrangement according to claim 3, characterized in that the Rankine circuit (14) comprises a regenerator (18) where residual heat from the Rankine fluid after expansion is transferred to the Rankine fluid prior to entering the evaporator (15).

5. The internal combustion engine arrangement according to one of claims 1 to 4, characterized in that the hybrid cylinder (40) comprises:

- at least one air intake valve, connected to the intake line (5), for controlling air introduced into the said hybrid cylinder (40) by moving between a closed position and an open position;

- at least one exhaust valve, connected to the exhaust gas line, for controlling the flow of exhaust by moving between a closed position and an open position ;

- at least one Rankine fluid intake valve (100), connected to the Rankine circuit (14), for controlling entry of the Rankine fluid into the hybrid cylinder (40) before expansion by moving between a closed position and an open position; and

- at least one Rankine fluid exit valve (1 10), connected to the Rankine circuit (14), for controlling exit of the Rankine fluid from the hybrid cylinder (40) after expansion by moving between a closed position and an open position.

6. The internal combustion engine arrangement according to claims 5, characterized in that the Rankine fluid intake (100) and exit (1 10) valves are actuated independently from the air intake and exhaust valves (10, 1 1 ).

7. The internal combustion engine arrangement according to one of claims 5 or 6, characterized in that each valve of the hybrid cylinder (40) is actuated independently by a dedicated actuator.

8. The internal combustion engine arrangement according to claim 3, characterized in that the condenser (20) is located adjacent to an engine cooling fluid radiator (12).

9. The internal combustion engine arrangement according to one of claims 1 to 8, characterized in that the Rankine fluid is water based.

10. The internal combustion engine arrangement according to one of claims 1 to 9, characterized in that the hybrid cylinder (40) is located at one end of the engine.

1 1. The internal combustion engine arrangement according to one of claims 1 to 10, characterized in that the expansion of the Rankine vapor in the hybrid cylinder 40 can be done every engine crankshaft revolution (two- stroke operation) or once every several engine crankshaft revolutions.

12. The internal combustion engine arrangement according to one of claims 1 to 1 1 , characterized in that the real expansion ratio applied to the Rankine evaporated fluid in the hybrid cylinder (40) can be lower than the geometrical expansion ratio of the hybrid cylinder by a late opening of the Rankine fluid exit valve (1 10) once the piston is in an intermediate position between top dead center and bottom dead center.

13. The internal combustion engine arrangement according to one of claims 1 to 2, characterized in that the hybrid cylinder (40) can have a compression ratio different from the other cylinders (4).