DE102008032105A1 - Four-cylinder internal combustion engine i.e. suction engine, operating method for motor vehicle, involves supplying fuels to engine if engine is provided in operating conditions, where one condition lies above brake mean effective pressure - Google Patents

Abstract

The method involves supplying fuel to a suction engine if the engine is provided in an operating condition, where the fuel contains 100 percentage hydrogen. Another fuel e.g. hydrocarbon fuel such as gasoline, is supplied to the engine if the engine is provided in another operating condition, where the former operating condition lies below a threshold-brake mean effective pressure (BMEP) and the latter operating condition lies above the threshold-BMEP, which lies between 6 and 8 bar. A turbocharger is connected with the engine to allow pressure charge. An independent claim is also included for a method for changing an operating mode to another operating mode in an internal combustion engine.

Description

Field of the invention

It a method for operating an internal combustion engine is disclosed, both hydrogen fuel and another fuel supplied become.

background

by virtue of from concerns regarding Greenhouse gases derived from carbonaceous fuels such as gasoline, Diesel and alcohol fuels are issued, there is a pronounced interest, motor vehicles supplied with hydrogen, which generates water when burned. Hydrogen-powered internal combustion engines suffer as compared to gasoline or diesel engines with a low power output, since hydrogen is a gaseous one Fuel is that takes up much of the volume in cylinders, in particular compared to dense fuels such as gasoline or diesel fuel. Farther is the hydrogen combustion due to increasing combustion roughness and, if this is an important issue, rapidly increasing NOx emission to operate at an equivalence ratio of limited to about 0.5 or less. An equivalence ratio of 1 is a stoichiometric Relationship, which means that the proportion of fuel to air is such that could completely burn all the oxygen and fuel. An equivalence ratio of 0.5 is a lean ratio, where the supplied Air volume twice as large as to the complete Consuming the fuel is required amount. Such a limit the equivalence ratio leads to about half the fuel flow, the amount of air in the combustion chamber could be consumed and thus about half the torque compared by the engine with a stoichiometric Share is generated.

The equivalence ratio is as the fuel / air ratio (by mass) of the mixture divided by the fuel / air ratio for a stoichiometric Mixture defined. A stoichiometric Mixture has an equivalence ratio of 1.0 on; lean mixtures are below 1.0; and fat mixtures are above 1.0.

Brief description of the invention

The Inventors of the present invention have recognized that by operating with two fuels, for example hydrogen and gasoline, the Engine at low torque values with hydrogen and at higher torque values could be operated with gasoline. Hydrogen readily burns at very lean equivalence ratios and is at very low torques with at most minimal throttling good for stable burning. Gasoline is due to his high energy density and ability for working at stoichiometry well suited for providing high torque. The inventors of the present Invention propose a biofuel engine, in which between the Operated with hydrogen and another fuel changed becomes.

Of the Fuel for high torque may be a hydrocarbon, for example Natural gas, propane, gasoline or alcohols such as methanol or ethanol. Furthermore you can also combinations of gaseous Fuel or combinations of liquid fuels used E85, a mixture of 85% ethanol with 15% Petrol. Fuels for high torque contains carbon that reacts when burned, to form carbon dioxide, a greenhouse gas. Because hydrogen is just water produced as a combustion product, it does not form a greenhouse gas. Consequently is it desirable if possible to work with hydrogen and the carbonaceous fuels as needed to provide the desired torque.

One normalized engine torque, usually by a person skilled in the art used is BMEP, mean braking power (short of English. Brake Mean Effective Pressure), which in four-stroke engines is 2 · P / (V · N), where P is the braking power, V is the displaced volume and N rpm. of the engine.

Disclosed is a method of operating an internal combustion engine in which a hydrogen fuel is supplied to the engine when the engine is at a first operating condition. Hydrocarbon fuel is supplied to the engine when the engine is in a second operating condition. The first operating condition is below a threshold BMEP and the second operating condition is above the threshold BMEP. If the engine is a naturally aspirated engine, the threshold BMEP is between 3.5 and 5 bar. When the engine is pressure charged by a turbocharger or supercharger, the threshold BMEP is between 6 and 8 bar. In another embodiment, in addition to a BMEP threshold, the first operating condition also includes an engine speed that is below a threshold piston speed. The second operating condition is above the threshold BMEP or above the threshold piston speed. The threshold piston speed is between 12 and 16 m / s. Since the piston moves both up and down when the engine is making one revolution, the piston speed is calculated as 2 · S · N where S is stroke and NU / min. of the engine. The piston speed is not during the entire revolution constant; the piston speed calculated here is a mean piston speed.

Of the Hydrocarbon fuel can be gasoline or a mixture of gasoline be with an alcohol fuel. Alternatively, the hydrocarbon fuel a gaseous one Be fuel, such as natural gas or propane.

Further a method for operating an internal combustion engine is disclosed, supplied at the hydrogen when a temperature of one connected to the engine exhaust Three-way catalyst is below a threshold temperature, and a liquid Fuel is supplied to the engine only when a temperature of the three-way catalyst above the Threshold temperature is. The liquid fuel can be gasoline, Alcohol or a combination thereof. The threshold temperature is a light-off temperature of the three-way catalyst. In one embodiment the temperature is not just above the Light-off temperature of the catalyst, but the engine generates more as a threshold BMEP, when the liquid fuel is supplied.

It is a method for making a change from a first disclosed to a second mode, wherein the air supply is lowered The feed of a first fuel is lowered and the feed a second fuel is introduced at the beginning of the change. The first fuel is essentially 100% hydrogen and the second fuel consists primarily of, for example, hydrocarbons, Gasoline or gasoline and alcohol mixtures. Alternatively, the second one Fuel a gaseous Hydrocarbon. While of change, the amount of hydrogen is constantly lowered, so that at the end the change of the engine hydrogen is no longer supplied. At the same time the amount of the second fuel during the change coordinated raised with the decrease in hydrogen. The change is initiated when a requirement for torque equals the equivalence ratio of Hydrogen fuel exceeds a limit that is about 0.5. The air intake is closed by closing the Throttle valve of the engine realized, whereby the air intake decrease while the change is in the range of 30-60%. In one embodiment the change continues to be in response to a limit being exceeded initiated the piston speed. The engine piston speed is calculated as 2 · S · N, where S is the stroke and N is the RPM. of the engine. The piston speed is during the rotation is not constant; the piston speed calculated here is the mean piston speed.

Further is a method for switching between two modes in one Internal combustion engine disclosed, wherein the air supply is substantially increased, the supply of hydrogen is initiated and the supply of a second fuel is lowered, all at about initiation the change takes place. The change will be in response to a demand for a torque decrease initiated under a threshold BMEP, wherein this BMEP is 3.5 to 5 bar for a naturally aspirated engine and at a pressure-charged motor is between 6 and 8 bar. During the In turn, the air supply increases in the range of 30-60%. The Supply of hydrogen to the engine when initiating change leaves the equivalence ratio only in terms of of the hydrogen fuel are at least 0.1.

Brief description of the drawings

The Advantages described herein are obtained by reading an example an embodiment, at the invention is used to advantage and herein as in-depth Description is better, with reference to the drawings understandable. Hereby show:

1 a schematic of an engine with two fuel supplies;

2a -B engine operating maps of BMEP and piston speed showing operating zones for two fuels;

3 an engine operating map of BMEP and catalyst temperature showing operating zones for two fuels; and

4 and 5 Timeline for change from hydrogen to gasoline.

Detailed description

In 1 is an example of a four-cylinder internal combustion engine 10 shown. The engine 10 is through an intake manifold 12 Air is supplied and it passes through an exhaust manifold 14 consumed gases. An intake passage upstream of the intake manifold 12 contains a throttle 32 , which when actuated, the amount of airflow to the engine 10 controls. sensors 34 and 36 in the intake manifold 12 are installed, measure air temperature or mass air flow (MAF). A sensor 31 in the intake manifold 14 downstream of the throttle 32 is disposed, is a manifold vacuum sensor (MAP). A partially closed throttle 32 causes compared to the pressure on the upstream side of the throttle 32 a decrease in pressure in the intake manifold 12 , If in the intake manifold 12 there is a pressure decrease, exhaust gases are caused by a channel 19 to the exhaust gas recirculation (EGR) to flow, the exhaust manifold 14 with the intake manifold 12 combines. In the EGR channel 19 is located AGR valve 18 , which is operated to control EGR flows. Hydrogen fuel becomes the engine 10 through fuel injectors 30 directly in cylinders 16 inject, and port injectors 26 putting a liquid fuel into the intake manifold 12 inject, fed. This arrangement is shown by way of example and is not intended to be limiting. Other embodiments include having port injectors 26 supplying hydrogen fuel and direct injection valves 30 that supply liquid fuel. Alternatively, both fuels are supplied by direct fuel injection valves. In yet another embodiment, both fuels are supplied through port injection valves. The fuel other than hydrogen, in another embodiment, is a gaseous hydrocarbon fuel such as methane. Every cylinder 16 of the motor 10 contains a spark plug 28 , The crankshaft (not shown) of the engine 10 is with a gear 20 connected. The proximal to the gear 20 arranged sensor 22 detects rotation of the motor 10 , Other methods of detecting crankshaft position may alternatively be employed.

In one embodiment, the engine is powered by a compressor 58 in the engine inlet pressure charged. By raising the density of the engine 10 supplied air can be fed more fuel at the same equivalence ratio. This develops the engine 10 more efficient. The compressor 58 may be a loader that is typically powered by the engine. Alternatively, the compressor 58 by means of a shaft with a turbine 56 connected, which is arranged in the engine outlet. The turbine 56 is like in 1 shown a turbine of variable geometry; but in an alternative embodiment it may be a non-variable device. In another embodiment, the engine is a naturally aspirated engine, wherein in the embodiment, the elements 56 and 58 is waived. Downstream of the turbine 56 is a three-way catalyst 66 , The three-way catalyst 66 Alternatively, it may allow faster puffing upstream of the turbine 56 be arranged. Alternatively, the catalyst 66 a lean NOx filter or lean NOx catalyst capable of reducing NOx at a lean equivalence ratio.

Two fuel tanks 60 and 64 deliver the two fuels. In the in 1 shown embodiment contains tank 60 liquid fuel and tank 64 contains hydrogen. However, as described above, the inventors of the present invention contemplate various possible combinations of fuels, including the appropriate fuel storage tank. The fuel tank is pressurized by a pump 62 liquid fuel with pressure. The fuel tank 64 is under high pressure. Typically, no pressurization is required, but a pressure regulator may be used.

Out It is known in the art to switch between engine modes perform. at For example, gasoline engines with stratified charge switch between lean, layered to premixed stoichiometric operation is known Problem is, since the equivalence ratio abruptly from lean to bold, the fuel remains constant. In the present invention changes the equivalence ratio for changes of fuels also abrupt, as the best combination of Hydrogen operating characteristics at an equivalence ratio below 0.5 is reached; whereas desirable Fuel and emissions operating characteristics with other fuels (Hydrocarbons, alcohols, etc.) at an equivalence ratio of 1.0 can be achieved. Fuel changes can be achieved in a single cycle whereas air lags, causing problems during the Change be evoked. The present invention distinguishes itself from previously known changes in stratified charge engines, since in the present invention, the fuel and the equivalence ratio change.

Out the prior art it is known to operate biofuel engines, where changes are made between two fuels, for example between gasoline and propane or between gasoline and ethanol. The Most known fuels (gaseous hydrocarbons, liquid hydrocarbons and alcohols) but have an equivalence ratio with a narrow range of flammability (about 0.65 lean limit and 1.7 fat limit) compared to hydrogen fuel (approx 0.10 lean limit and 3 bold limit). Because most fuel at very meager equivalence ratios can not burn stably, their stable lean operation takes place in an area where high NOx is generated. Thus, most fuels except Hydrogen at stoichiometry, d. H. an equivalence ratio of 1, operated. Since very lean hydrogen mixtures burn stably, the amount of NOx produced is small, which is such a lean operation without big ones Concerns regarding Allow emission. Even if hydrogen is in a wide range of equivalence ratios is burned in an internal combustion engine in the equivalence ratio range from 0.15 to 0.5, as when operating at a richer equivalence ratio than 0.5 gives rough combustion and autoignition of hydrogen, Conditions to avoid. Thus, in a biofuel engine, in which one of the two fuels is hydrogen, in making a change from hydrogen to gasoline a change from an equivalence ratio of about 0.5 or leaner to 1.0.

In summary The present invention differs from previously known changes between stratified lean operation and stoichiometric operation, such as explained above was, since a change of both the equivalence ratio as also the fuel type takes place. The present invention distinguishes itself from the previously known biofuel metabolism, because if one of Fuels Hydrogen is the switch between combustion modes According to the invention to a Increase in both fuel type and equivalence ratio leads; whereas in the prior art, neither of the two fuels Hydrogen is not the equivalence ratio changes significantly, when the fuel type changes.

Gaseous fuels, which are supplied by an electronic fuel injection valve, can in switched on, switched off, or in between be switched, with the only transient problem of stock Fuel in the intake manifold is when the fuel injection valve in the intake passage located. liquid Fuels that are transported directly to the combustion chamber (direct injected), can be affected in a single cycle. Liquid fuels used in the Inlet channel transported be (channel injected), but due to fuel films, which are on channel surfaces form some difficulties. Ie. when activating Injectors wets part of the sprayed fuel manifold walls and does not penetrate directly into the combustion chamber. When disabling liquid channel injectors become the fuel films on the walls, which remain on the intake duct walls, removed and are introduced into the combustion chamber; it requires several Intake procedures, to empty this fuel supply. The abrupt change of the introduced into a cylinder air amount is a problem there a manifold several motor cycles for filling or emptying needed. Thus, the change from one fuel to another requires at least several engine cycles. In one embodiment, switching is done between fuels over ten Cycles realized.

In an embodiment Both fuels will be during supplied to the change period, while the supplied Air is adjusted to the new operating condition. The expert is known to use hydrogen as a supplement to hydrogen Gasoline (or other hydrocarbon fuel) burning at a much leaner equivalence ratio, as possible with gasoline alone would.

In 2a is shown that fuel 2 is used when the threshold BMEP is exceeded. This threshold is associated with an equivalence ratio of hydrogen greater than a set point, e.g. B. 0.5. Ie. to produce more than the threshold BMEP, the equivalence ratio of hydrogen would exceed 0.5. In 2 B an additional constraint on hydrogen operation is made because when the piston speed exceeds a certain threshold, the engine becomes fuel 2 replaced.

When it is cold, the engine starts with hydrogen fuel that does not entail cold start evaporation and mixing problems such as liquid fuel. In 3 becomes fuel 2 used only when both the catalyst has reached its light-off temperature and the threshold BMEP has been exceeded.

In 4 An embodiment of a change from hydrogen to gasoline in a timeline is shown. Hydrogen is used before the change; after the change gas is used; and during the change, a combination of the two fuels is used. In the upper curve a, a torque increases. In the lower curve e, the equivalent ratio Φ before the change is smaller than 0.5. As explained above, a change from hydrogen to gasoline is desirable as the hydrogen equivalence ratio approaches 0.5; thus the change is initiated. In curve c, the intended amount of hydrogen increases before the change to provide the increased torque of curve a. Before the change, the air supply rate dm _a / dt of curve b remains constant, with the additional torque being provided by raising hydrogen. When initiating change, the throttle is partially closed and the amount of air is lowered. The air supply increases so that the air supplied until the end of the change is the air required to provide .phi. = 1.0, which is the target equivalent ratio for all fuels except hydrogen. One of the reasons that there is a change period is that the air supply can not be changed in one engine cycle. Even if the throttle is opened quickly, it will instead require several engine cycles until the manifold fills and the engine delivers the desired amount of air. Since the air is above the set point shortly after the start of the change, the hydrogen supply continues. It is known to those skilled in the art that by supplementing a conventional fuel with hydrogen, the conventional fuel can burn stably at an equivalence ratio where it would not be able to do so without the presence of hydrogen. Thus, hydrogen continues to be supplied through the changeover period until the equivalence ratio reaches the desired 1.0, at which time the hydrogen supply is stopped. Although not shown in the figure, the hydrogen supply could alternatively be adjusted when the equivalence ratio reaches a ratio that the conventional fuel, e.g. B. Gasoline, stable burn, for example, over 0.8. The fuel supply is initiated at the beginning of the change. However, as explained above, since the air can not be reduced as quickly as desired, the hydrogen is further supplied to the change period to ensure combustion. During the changeover period, the gasoline is raised and the hydrogen is lowered, while the air is lowered, so that until the end of the change period, the gasoline operation without hydrogen support takes over.

In 5 An alternative embodiment is shown in which the initial part of the change is similar to that in FIG 4 shown resembles. At one point during the change, however, the equivalence ratio is boosted to 1.0 and held at 1.0 for the remainder of the transition. This is done to avoid the high NOx range of 0.85-0.90 phi. During this changeover period of the equivalence ratio 1.0, however, the hydrogen supply is continuously lowered and the gasoline supply is increased. At the end of the change, the hydrogen supply ends.

at the above explanation a change from hydrogen to gasoline is described. The reference on gasoline but is exemplary and is not intended to be limiting. Further, at Φ = 0.5 changes take place also by way of example. The actual Change can be at slightly lower or higher equivalence ratios than exactly 0.5.

A change from a higher torque to a lower torque at which a gasoline operation (or other fuel operation) is put into hydrogen operation can be performed in reverse order to that in FIG 4 and 5 shown done. When the fuel, other than hydrogen, is a liquid fuel and is channel injected, the fuel supply in the intake manifold is utilized to provide the desired fuel into the combustion chamber.

While several Methods for Running the Invention closer The person skilled in the art to which this invention pertains directed, alternative interpretations and embodiments for practicing recognize the invention. The embodiments described above are intended to illustrate the invention within the scope of protection the following claims can be modified.

Claims (40)

Method for operating an internal combustion engine, which includes: Respectively a first fuel to the engine, when the engine at a first operating condition is located, with the first fuel in the Essentially 100% hydrogen; and Supplying a second fuel to the engine when the engine is at a second operating condition, wherein the second fuel is a hydrocarbon fuel, wherein the first operating condition is below a threshold MBEP and the second operating condition is above the threshold BMEP. Method according to claim 1, characterized in that that the engine is a naturally aspirated engine and that the threshold BMEP is between 3.5 and 5 bar. Method according to claim 1, characterized in that that the engine is pressure charged and the threshold BMEP between 6 and 8 bar is located. Method according to claim 1, characterized in that that the first operating condition under the threshold BMEP and a Swell piston speed and the second operating condition is above the threshold BMEP or a threshold piston speed is Method according to claim 4, characterized in that that the threshold piston speed between 12 and 16 m / s. Method according to claim 1, characterized in that that the second fuel is gasoline. Method according to claim 1, characterized in that that the second fuel is a mixture of gasoline and alcohol. Method according to claim 1, characterized in that that the second fuel is natural gas. Method for operating an internal combustion engine, which includes: Respectively from hydrogen to the engine when a temperature of one with the engine exhaust connected three-way catalyst below a threshold temperature lies; and Respectively a liquid Fuel to the engine, only if a temperature of the three-way catalyst over the Threshold temperature is. Method according to claim 9, characterized that the liquid Fuel is gasoline. Method according to claim 9, characterized that the liquid Fuel contains alcohol. Method according to claim 9, characterized that the threshold temperature is a light-off temperature of the three-way catalyst is. Method according to claim 9, characterized that the liquid Fuel supplied to the engine when a temperature of the three-way catalyst over the Threshold temperature is higher and the engine is more than a threshold BMEP generated. Method according to claim 13, characterized in that that the engine is a naturally aspirated engine and the threshold BMEP between 3.5 to 5 bar is located. Method according to claim 13, characterized in that that the engine is pressure charged and the threshold BMEP between 6 and 8 bar is located. Method according to claim 15, characterized in that that a turbocharger is connected to the engine to pressure charge provided. Method according to claim 15, characterized in that a charger is connected to the engine to provide pressure charging. Internal combustion engine with a first and second fuel supply system, which includes: one with the first and second fuel supply system electronically connected electronic control unit, wherein the electronic control unit order that a first fuel is supplied when a first engine operating condition occurs and orders that a second fuel be supplied, when a second engine operating condition occurs, the first one Fuel is hydrogen and the second fuel is a liquid fuel is the first operating condition has a BMEP under a threshold BMEP and the second operating condition has a BMEP above the threshold BMEP. Motor according to claim 18, characterized that the first operating condition also with respect to the piston speed limited is, so that the first operating condition is arranged when the Piston speed below a threshold piston speed and BMEP is below the threshold BMEP, otherwise the second Operating condition is arranged. Motor according to claim 19, characterized that the threshold speed in the range of 12 and 16 m / s lies. Method for changing from a first to a second mode in an internal combustion engine, comprising: essential Lowering an air supply, wherein lowering when initiating a change begins; Lowering a first amount of fuel supplied to the engine when initiating change; and Initiate a feed of a second fuel to the engine when initiating change Method according to claim 21, characterized that the first fuel is essentially 100% hydrogen and the second fuel consists primarily of hydrocarbons. The method of claim 21, further comprising: continuous Lowering a supplied Amount of the first fuel during the change, wherein at the end of the change of the first fuel not longer supplied to the engine becomes; and Increasing an amount of second fuel supplied while of the change coordinated with the lowering of the first fuel. Method according to claim 21, characterized that the second fuel is a liquid fuel. Method according to claim 21, characterized that the first fuel is hydrogen and the change is a reaction is initiated on a demand for an increase in torque when the equivalence ratio of Hydrogen and of air in about 0.5. Method according to claim 21, characterized that the air intake intake by closing one in an engine intake arranged throttle valve is realized. Method according to claim 21, characterized that the air supply during of change by 30-60% is lowered. Method according to claim 21, characterized that the change in response to a limit exceeding Engine piston speed is initiated. Method according to claim 1, characterized in that that the change in response to a limit crossing BMEP claim is initiated. Method for switching between two modes in an internal combustion engine, which comprises: substantial lifting an air supply, wherein the increase when initiating the change begins; Initiating the supply of a first fuel, hydrogen, to the engine when initiating the change; and Lowering a supply amount a second fuel to the engine when initiating change. Method according to claim 30, characterized that the change in response to a demand for a torque reduction under a threshold BMEP. Method according to claim 31, characterized in that that the engine is a naturally aspirated engine and that the threshold BMEP is between 3.5 to 5 bar is located. Method according to claim 31, characterized in that that the engine is pressure charged and the threshold BMEP between 6 and 8 bar is located. Method according to claim 30, characterized that the air supply during of change by 30-60% is raised. Method according to claim 30, characterized that the supply of hydrogen to the engine when initiating change the equivalence ratio with respect to only of the hydrogen fuel can be at least 0.1. Method according to claim 30, characterized that the second fuel is a liquid. Method for changing from a first to a second mode in an internal combustion engine, comprising: Command a throttle valve towards a closed position upon initiation the change; Lowering an amount of hydrogen supplied to the engine at the initiation of the change; and Initiate a supply of liquid Fuel to the engine when initiating the change. Method according to claim 37, characterized in that that change based on a call for increased BMEP what is the hydrogen equivalent ratio one Exceed limit leaves. Method according to claim 37, characterized in that that while the change the hydrogen supply only with respect to the hydrogen fuel an equivalence ratio of at least 0.1. Method according to claim 37, characterized in that that change based on a falling of an engine piston speed is introduced under a threshold piston speed.