FR2960915A1 - FUEL SUPPLIED INTERNAL COMBUSTION ENGINE HAVING A LOW PRESSURE EXHAUST GAS RECIRCULATION CIRCUIT AND A SUPPLEMENTARY HYDROGEN PRODUCTION SYSTEM. - Google Patents

Abstract

Internal combustion engine (1) fueled with a turbocharger (2), a partial recirculation circuit (5) of the low pressure exhaust gas, and a hydrogen production system (11). ) having a fuel reformer (17). The reformer (17) is fed by an intake pipe (13) stitched on an air intake pipe (6) of the internal combustion engine (1) downstream of the compressor (2b) of the turbocompressor (2), the reformer comprising an outlet pipe (18) stitched in the air intake duct (6) of the internal combustion engine (1).

Description

B10-1126EN AXC / MSA / EHE PJ-09-0326

Société par Actions Simplifiée known as: RENAULT s.a.s. Fuel-powered internal combustion engine equipped with a low-pressure exhaust gas recirculation circuit and an additional hydrogen production system. Invention of: Adeline DARMON François FRESNET Frederic RAVET Adrien VALENZUELA Internal combustion engine fueled with a low-pressure exhaust gas recirculation circuit and an additional hydrogen production system.

The present invention relates to the field of internal combustion engines and more particularly, the field of internal combustion engines comprising a fuel reformer. In the context of the diversification of energy resources and the tightening of environmental regulations, car manufacturers are working on the development of engines equipped with reformers for assistance with combustion. An embedded reformer has the function of producing a gas rich in hydrogen. The reformer is a system that transforms a hydrocarbon into a mixture consisting essentially of hydrogen and carbon monoxide. This mixture is called reformate. The addition of hydrogen to the fuel used by the vehicle improves the quality of combustion. The combustion of hydrogen is fast and does not produce CO2. The use of an onboard reformer is particularly interesting because the use of hydrogen to assist the combustion can then be done without impacting the current distribution network, that is to say without having to implement a hydrogen distribution at the pump.

The addition of hydrogen in the reaction mixture significantly improves combustion yields by increasing the rate of combustion. Thus, the addition of hydrogen will be all the more relevant for slow-burning fuels such as methane, but also under unfavorable thermodynamic conditions as at startup. The addition of hydrogen is also of interest when the time available for burning the reaction mixture is short, for example when the rotational speed of the engine is high. Finally, the addition of hydrogen makes it possible to compensate for the effects of slowing the combustion by diluting the reagents (partial recirculation of exhaust gases known as EGR). Improving the combustion efficiency limits the fuel consumption of the vehicle and therefore the CO2 emissions. The reforming can be obtained by various catalytic processes, in particular by partial oxidation of the fuel by oxygen, vapor reforming of the fuel by steam, or by a combination of the two processes (autothermal reforming). The steam reforming requires a supply of water vapor, which implies the presence of a water tank. In addition, the steam reforming reaction is endothermic, that is to say that it consumes energy. It is therefore necessary to heat the catalyst continuously (by means of a burner for example) in order to maintain its temperature. Such arrangements involve increased space due to the presence of a water reservoir, as well as a significant energy consumption for steam generation. Embedded solution vaporeforming is therefore a complex process to control, bulky and requiring energy consumption that is not very compatible with the requirements for CO2 emissions.

US Patent Application 2007/0204813, US Pat. No. 6,318,306 and US Pat. No. 4,066,043 describe embedded reforming systems using steam reforming as a reforming process. US patent application US 2008/0230018 discloses a catalytic partial oxidation reforming system. However, reforming is applied to the physicochemical modification of the fuel used. The reforming system comprises a reformer capable of increasing the molar mass of the fuel in the gaseous phase, and a reformer capable of increasing the octane number of the fuel in the liquid phase. The system described is therefore not intended for the generation of a gas rich in hydrogen. US Pat. No. 4,175,523 discloses a partial oxidation reforming system coupled to an internal combustion engine using gasoline as a fuel. The reforming system is located downstream of the internal combustion engine, in order to use the heat of the exhaust gases to maintain the reforming reaction. However, the described system has the disadvantage of requiring substantial modifications of the exhaust gas lines and increasing the size of the internal combustion engine. There is a need for embedded hydrogen production of simple incorporation into an internal combustion engine and not requiring external energy input.

The object of the invention is to produce a hydrogen-rich reformate gas on board a vehicle without additional energy expenditure. An object of the invention is a hydrogen production system requiring little modification of the vehicle to be integrated with existing internal combustion engines. Another object of the invention is a process for producing hydrogen for supplying existing internal combustion engines. According to a first aspect, a fuel-powered internal combustion engine equipped with a turbocharger, a low-pressure partial exhaust gas recirculation circuit, and an additional hydrogen production system comprising a reformer. The reformer is fed by an intake pipe stitched onto an air intake pipe downstream of a turbocharger compressor, and is coupled at the outlet to an outlet pipe stitched into the air intake duct. downstream of the intake pipe. A hydrogen production system according to the invention thus has the advantage of a smaller footprint for easier integration into a vehicle. Indeed, neither a water tank nor a carburettor is required. The size is even smaller as the hydrogen production system shares the air intake lines with the internal combustion engine.

Another advantage is not to require additional energy input. Indeed, the energy required to start and maintain the reforming reaction is taken directly into the temperature of the exhaust gas and their compression.

The hydrogen production system according to the invention is also advantageous in that the same architecture can be adapted to engines of different technologies and using different fuels, liquid or gaseous. The reformer may be provided with a liquid or gaseous fuel injector. The reformer may successively comprise a mixing chamber, a combustion chamber and a catalyst chamber. The reformer combustion chamber may furthermore comprise a spark plug.

The engine may include an electronic control unit connected to a controlled exhaust gas redirection valve located at the inlet of the low-pressure partial exhaust gas recirculation circuit, to a control valve for redirection of the exhaust gas. air intake at the intake line, the fuel injector in the reformer, and the spark plug of the reformer. The engine may further include a reformate tank connected in parallel with the outlet pipe. The electronic control unit can also be connected to isolation valves of the reformate tank. In another aspect, a method of supplying fuel to an internal combustion engine equipped with a turbocharger, a partial recirculation circuit of low pressure exhaust gas, and a production system is defined. additional hydrogen having a reformer. According to a general characteristic of this aspect, the reforming is done catalytically from the admission into the reformer of a mixture of air and partially recycled exhaust gas.

The method may include a pre-reforming step of heating the reformer by burning a mixture of fuel and exhaust-gas-free air partially recycled to a catalyst temperature.

For the heating of the reformer during the preliminary step, the fuel and partially exhausted exhaust-free air can be mixed in order to obtain a reforming richness less than or equal to 1. During reforming, can maintain the reformer at the catalyst temperature by acting on the flow of partially recycled exhaust gas through the reformer. The heat released during the reforming chemical reaction helps maintain the catalyst temperature. During reforming, the fuel and air can be mixed in order to obtain a reforming richness greater than 1. Other aims, characteristics and advantages will become apparent on reading the following description given solely as an example. non-limiting and with reference to the accompanying drawings in which: - Figure 1 illustrates the main elements of an internal combustion engine with partial recirculation of low-pressure exhaust gas comprising a hydrogen production system according to a first embodiment of achievement; - Figure 2 illustrates the main elements of an internal combustion engine with partial recirculation of low pressure exhaust gas comprising a hydrogen production system according to a second embodiment; and FIG. 3 illustrates the main elements of a reformer used in a hydrogen production system.

FIG. 1 illustrates an internal combustion engine equipped with a hydrogen production system according to the invention. The internal combustion engine 1 comprises an intake manifold and an exhaust manifold. The exhaust manifold is connected at the output to the turbine 2a of a turbocharger 2 through an exhaust pipe 3. The exhaust pipe 3 extends at the outlet of the turbocharger to a controlled bypass valve 4a recirculation. The controlled recirculation bypass valve 4a is a two-way outlet valve, one channel of which is connected by a pipe to either the silencer or the catalytic device, or to the open air, depending on the vehicle design. The other path is connected to a partial exhaust gas recirculation duct 5 which is stitched on the fresh air intake duct 6, upstream of the compressor 2b of the turbocharger 2. The inlet duct 6 Fresh air continues past the compressor 2b to the intake manifold of the internal combustion engine. Such an internal combustion engine is supplied with fuel stored in a tank 7 connected to a regulation means 8 of the fuel pressure admitted by a fuel line 9 extending beyond the injection pump 8 to a rail injection 10 distributing the fuel between the various injectors of the cylinders. The regulation means 8 of the fuel pressure admitted may be a fuel pump in the case of a liquid fuel or a pressure reducer in the case of a gaseous fuel.

According to the invention, there is provided on the air intake duct 6 a hydrogen production system 11 and an air cooler 12 admitted. The intake air cooler 12 is connected in series to the air intake pipe 6 directly at the inlet of the internal combustion engine while the hydrogen production system 11 is connected in shunt to the intake pipe 6 of air between the compressor 2b and the air cooler 12 admitted. A controlled bypass valve 4b of the hydrogen production system is located immediately downstream of the connection of the intake pipe 13 to the air intake pipe 6.

The hydrogen production system 11 comprises as input an intake pipe 13 connected to the air intake duct 6. The hydrogen production system further comprises a means 14 for regulating the fuel pressure admitted connected by a fuel intake line 15 to the fuel tank 7. The fuel intake pipe extends beyond the fuel line. control means 14 of the fuel pressure admitted to a fuel injector 16. The intake pipe 13 and the fuel injector 16 are connected to the inlet of a reformer 17. The reformer 17 will be more amply described in the description of FIG. 3. The outlet of the reformer 17 is connected to the outlet duct 18 of the hydrogen production system, stitched on the duct 6 for admission of the air between the air cooler 12 admitted and the connection of the intake pipe 13 on the duct 6 of the air intake. An electronic control unit 19 of the hydrogen production system is connected to the bypass control valve 4b of the hydrogen production system via a connection 20 and to the fuel injector 16 via the connection 21, and to the valve Controlled bypass 4a through a connection 33. According to an alternative embodiment illustrated in Figure 2, a reservoir 23 of reformate gas can be connected in parallel to the outlet line 18 of the hydrogen production system. Valves 31 and 32 make it possible to isolate or put in communication the tank 23 of reformate gas with the outlet pipe 18 and / or with the reformer 17. These valves are connected by a connection 24 to the electronic control unit 19 of the hydrogen production system. Such a reservoir can make it possible to smooth the production of reformate, in particular in phases of driving requiring all the power of the engine or in order to avoid turning off the reformer when the addition of hydrogen is not necessary. In operation, a portion of the exhaust gas is recirculated through the bypass controlled valve 4a. The controlled bypass valve 4b makes it possible to take all or part of the incoming air flow comprising fresh air admitted and a part of recirculated exhaust gas. The temperature of this incoming air flow is substantially higher than the temperature of the outside air due to the presence of exhaust gas in the mixture, which gas has a high temperature when it leaves the internal combustion engine 1 The flow of incoming air is admitted into the reformer 17 after receiving a fuel injection via the fuel injector 16. The reformer 17 comprises a catalytic reaction medium which requires a supply of energy to be able to start the reforming reaction. This energy is provided through the higher or lower temperature of the intake air and the recirculated exhaust gas. Thus, it is not necessary to have additional energy input means, for example a heating system. FIG. 3 shows an exemplary embodiment of the reformer 17 comprising a mixing chamber 25, a combustion chamber 26 whose ignition is controlled by a spark plug 26a, the gas mixture thus obtained then passing to through a catalyst chamber 27 to obtain a reformate gas rich in hydrogen. At the outlet of the reformer 17, a reform gas rich in hydrogen is obtained. This reformate gas is then mixed with the air admitted into the engine 1 upstream of the gas cooler 12. The purpose of the gas cooler 12 is to reduce the temperature of the gases admitted to the internal combustion engine 1, the gas of reformate can have a high temperature, as well as the intake air comprising a high proportion of recirculated exhaust gas.

Provision can be made for the presence of a reformate gas tank making it possible to store the reformate gas for a delayed use, depending on the running conditions of the vehicle. The reformer is fueled with either liquid or gaseous fuel. Examples of fuels are gasoline, diesel and natural gas for vehicles. Any hydrocarbon fuel can be considered. To obtain fuel reforming, it is necessary that the fuel / oxidant mixture has a richness greater than 1. If the richness of the mixture is less than 1, the entire mixture is converted into CO2 and H2O, which are not suitable for combustion. of the motor. It should be noted that the richness of the mixture is also called reforming richness and is related to the stoichiometry of the mixture. Typically, when methane is employed, the optimum blend richness is equal to 4, while when diesel is employed, the optimum blend richness is 2.9. More precisely, it is possible to calculate the mixture richness in the reformer also called reforming richness Rref by applying the following formula: Rref - `efl +, 'x (Qfreuefl + Qmot) x PCO word Qair x (Vbipasse_2 + y) with Qref e1 = The flow rate of fuel injected into the reformer Qfuel word = The flow rate of fuel injected into the engine Qair = The fresh air flow rate predicted for the engine PCO = The comburivorous power of the fuel considered. By comburivore power of a fuel is meant the ratio between the amount of air and the corresponding fuel mass for complete combustion. This ratio is also called mass stoichiometric relationship. In other words, the reformer is fueled to obtain a fuel / fuel mixture richness greater than 1, the exact value of which is specific to each fuel. The reformer then produces a hydrogen-rich reformate gas. The bypass-controlled valve 4b makes it possible to divert to the reformer 17 a part of the intake air comprising recirculated exhaust gases. The proportion of air admitted deflected is noted Vbipasse_2. Knowing the capabilities of the fuel injector 14 and the requirements of richness of mixture, it is possible to determine and adjust the amount of air admitted. The flow of the reformer is defined by the following equation: Qreformer = (Qmotor + Qgas exhaust * Vbipasse 1) * Vbipasse 2 with Qreformer = The flow of the reformer Qmotor = The flow of fresh air admitted into the engine Qgaz_exhaust = The flow of gases Exhaust The bypass controlled valve 4a allows a portion of the exhaust gas to be diverted to the compressor 2b. The proportion of deflected exhaust gas is denoted Vbassasse 1. The values Vbipasse 1 and Vbipasse_2 may be defined depending on the open rate of the corresponding controlled valve. However, it may be interesting to measure the temperature of the gases and the pressure drop between pressure measurements upstream and downstream of each valve controlled. Such measurements not only make it possible to determine the effective values of Vbipasse 1 and Vbipasse 2 but also to enslave the opening of the valves to the respect of a setpoint value. In general, the flow rate of the bypass output of a three-way valve can be defined by the following equation: Q = k.JDP VT 20 with Q = the flow rate in the bypass outlet OP = the pressure drop between the upstream and downstream measurements of the valve, T = the temperature upstream of the valve k = a constant. As can be seen, the difference between the upstream pressure and the downstream pressure of the valve (also called pressure drop) is related to a volume in the formalism of the perfect gas equation. The flow rate Q therefore results from the variation of pressure drop, the gases not passing through the valve being directed towards the bypass outlet. Those skilled in the art will understand that a formality different from that of the perfect gases can be applied by modifying the value of the constant k. Whatever the formalism employed, the physical phenomenon remains that a flow is generated in the bypass outlet because of the pressure difference upstream and downstream of the valve. The gas flow rate in the reformer must be regulated in order to obtain the desired mixture richness. However, the regulation must also take into account the operating cycle of the internal combustion engine. Indeed, a pressure drop in the engine air supply circuit too large induce a significant motor overconsumption. It is possible to compensate for such a pressure drop in the engine air supply circuit by modifying the degree of closure of the controlled partial exhaust gas recirculation valve 4a. If more exhaust is redirected to the input, the load in the engine air supply system increases. It is thus possible to compensate for the pressure drop associated with the reformer's air supply.

The electronic control unit 19 is connected directly or via other means of control to the various organs involved in the operation of the reformer. The electronic control unit 19 is able to control in particular the flow of fuel injection into the reformer, the degree of opening of the controlled valve 4a and the controlled valve 4b. The electronic control unit 19 may be included in or be under the control of the electronic control means of the powertrain. The operation of the hydrogen production system will now be exposed. The reformer must be warmed up to reform the fuel. The reformer, and more particularly the catalyst contained in the reformer, must reach a temperature of between 600 ° C. and 800 ° C. The catalysis temperature is however dependent on the composition of the oxidant. The greater the amount of neutral species with respect to combustion, the higher the temperature to be reached. For this, a fuel combustion is carried out within the reformer. The fuel is fed into the reformer taking care to maintain the mixture richness at a level of less than or equal to 1. As has been seen previously, a mixture richness of less than or equal to 1 makes it possible to obtain combustion. complete. The advantage of complete combustion is more energy release than incomplete combustion, so a faster temperature rise for less fuel consumed. In addition, the controlled valve 4a is controlled so that no exhaust gas is recirculated. Indeed, the presence of exhaust gas is unfavorable to combustion. The combustion phase is brief.

When the reformer is primed, that is to say that its temperature is at a level allowing the reforming reaction, the controlled valve 4a controlling the partial recirculation of the exhaust gas is actuated so that a part of said gas exhaust is redirected to compressor 2b. The controlled valve 4b is also controlled to change the amount of air admitted. By air admitted is meant air taken downstream of the compressor 2b. In the case where a part of the exhaust gas is redirected to the compressor 2b, the air taken includes an exhaust gas fraction.

In all cases, the amount of air taken to feed the reformer and the fuel flow fed to the reformer are dependent on the amount of hydrogen to be supplied and the mixture richness constraints. For example, if the fuel considered is natural gas for vehicles (NGV), the hydrogen requirement for the highest engine load point is estimated at 300mg / s for a volume fraction of 20% in the combustion chamber. The corresponding CNG and air flow rates are respectively 1.3 g / s and 6.5 g / s.

Claims (12)

REVENDICATIONS1. Internal combustion engine (1) fueled with a turbocharger (2), a partial recirculation circuit (5) of the low pressure exhaust gas, and a hydrogen production system (11). ) comprising a reformer (17) of fuel, characterized in that the reformer (17) is supplied by an intake pipe (13) stitched on an air intake pipe (6) downstream of the compressor ( 2b) of the turbocharger (2), the reformer having an outlet pipe (18) stitched in the air intake duct (6) of the internal combustion engine (1). 2. Motor according to claim 1, wherein the reformer (17) is provided with an injector (16) of liquid or gaseous fuel. 3. Motor according to any one of claims 1 or 2, wherein the reformer (17) comprises successively a mixing chamber (25), a combustion chamber (26) and a catalyst chamber (27). 4. Engine according to claim 3, wherein the combustion chamber (26) of the reformer (17) comprises a spark plug (26a). 5. Motor according to any one of claims 1 to 4, comprising an electronic control unit (19) connected to a controlled valve (4a) of redirection of the exhaust gas located at the inlet of the partial recirculation circuit. (5) low-pressure exhaust gas, a controlled intake air redirection valve (4b) located at the intake pipe (13), the fuel injector (16) in the reformer (17) and the spark plug (26a) of the reformer (17). An engine according to any one of the preceding claims, comprising a reformate tank (23) connected in parallel with the outlet pipe (18). 7. Motor according to claim 6, wherein the electronic control unit (19) is also connected to isolation valves (31, 32) of the reformate tank (23). A method of supplying fuel to an internal combustion engine (1) provided with a turbocharger (2), a partial recirculation circuit (5) of the low pressure exhaust gas, and a additional hydrogen production system (11) comprising a fuel reformer (17), characterized in that the reforming is catalytically performed from the inlet into the reformer of a mixture of air and gas Exhaust partially recycled. 9. The method of claim 8, comprising a step, prior to reforming, heating the reformer (17) by the combustion of a mixture of fuel and air free of partially recycled exhaust gas to a temperature of catalysis. 10. The method of claim 9, wherein the fuel and partially exhausted exhaust-gas-free air are mixed in order to obtain a reforming richness of less than or equal to 1. 11. Production process according to any one of claims 8 to 10, wherein during reforming, the reformer is maintained at the catalyst temperature by acting on the flow of partially recycled exhaust gas through the reformer. 12. Production process according to claim 11, wherein the fuel is mixed with air to obtain a reforming richness greater than 1.