DE102007028513A1 - Internal combustion engine and method for operating an internal combustion engine - Google Patents

Abstract

The present invention relates to an internal combustion engine for a gaseous fuel, comprising a combustion chamber (2), an inlet connection (3), an outlet connection (4), a gas injection valve (5, 6), an air supply line (7) which is located at the inlet connection (3). opens, a gas storage (8) to store the gaseous fuel under a pressure above an ambient pressure, and a pressure control module (9) which is arranged in a connecting line between the gas reservoir (8) and the Gaseinblasventil (5, 6) to to regulate a pressure level of the gaseous fuel, wherein the pressure control module (9) and / or a line region of a fuel gas supply line (17a, 17b) from the pressure control module (9) to Gaseinblasventil (5, 6) adjacent to the air supply line (7) is arranged to heat exchange between the gaseous fuel and the combustion air supplied in the air supply line (7). Furthermore, the invention relates to a method for operating an internal combustion engine.

Description

State of the art

The The present invention relates to an internal combustion engine and a Method for operating an internal combustion engine.

Internal combustion engines are known from the prior art in different configurations. Recently, more and more internal combustion engines are proposed, which are operated with alternative fuels. For example, there are internal combustion engines, which are operated in bivalent operation natural gas / gasoline or in monovalent operation only with natural gas. Also, other gaseous fuels are conceivable. The gaseous fuels are usually stored in separate pressure accumulators with a pressure of over 200 × 10 ⁵ Pa. Since this accumulator pressure is too high for normal operation, a pressure control module is provided, which supplies the fuel gas in a reduced pressure to the gas injection valves. Normally, for example, natural gas is controlled by the pressure control module to a low pressure of less than 10 × 10 ⁵ Pa.

Advantages of the invention

The inventive internal combustion engine with the features of claim 1, in contrast, the Advantage on that they compared with known internal combustion engines a higher efficiency has and very inexpensive can be provided. The internal combustion engine according to the invention uses while the big one Cooling off, which during the relaxation process of the stored under high pressure gaseous Fuel in the pressure control module to a low pressure occurs. This temperature reduction is targeted to increase a cylinder filling the Internal combustion engine used. Thus, according to the invention, the cooling of the targeted use of relaxing gas to one in an air supply line supplied combustion air cool. According to the invention thus occurs a heat exchange between the supplied Combustion air and the relaxed, cool fuel gas. hereby the density of the combustion air can be increased, whereby in particular an improved filling increase the internal combustion engine is achieved. Especially with gaseous fuels in the prior art at least a part of the in a cylinder sucked air mass through the volume of gaseous injected fuel repressed. This can be up to 15% or more. This results in particular significant loss of moment. By means of the relaxed fuel gas according to the invention, however cooled Intake air, the internal combustion engine according to the invention closer to the knock limit operate. To ensure adequate heat transfer, is the pressure control module and / or a supply area of a supply line from the pressure control module to the injection valve adjacent to the air supply line arranged. For the purposes of the invention, the term "adjacent" is a distance between the air supply line and the pressure control module or a line region the fuel gas supply to understand the pressure control module, which between 0 cm to 10 cm, preferably 0 cm to 5 cm, particularly preferred 0 cm to 1 cm. Particularly preferred is a direct contact between the air supply line and the pressure control module or the fuel gas supply line.

The under claims show preferred developments of the invention.

Especially Preferably, the pressure control module is arranged immediately adjacent to the inlet port. This can ensure that a cooling of the supplied Combustion air takes place immediately before entering the cylinder, so that a particularly high degree of filling can be achieved. Especially if the fuel gas is also short injected directly in front of the cylinder or on an inlet valve will ensure that the fuel gas is not too large volume the combustion air displaced. Further, a reheat the combustion air can be prevented.

Especially Preferably, the internal combustion engine comprises a turbocharger and the Pressure control module is adjacent to the air supply line to a line section disposed between the turbocharger and the inlet port. hereby Is it possible, the density of compressed air in front of an inlet into a combustion chamber to increase the internal combustion engine. This is especially of Advantage that at a full load request to the internal combustion engine a greater increase in temperature through the turbocharger compressed intake air occurs, but at the same time also a greater demand after combustion gas occurs, so that by relaxing the larger fuel gas provided a greater cooling capacity can be. Thus, without an additional control device in dependence from the load requirements of the internal combustion engine cooling the supplied Combustion air take place.

If, in addition to the turbocharger, a charge air cooler is preferably also provided, the pressure control module is preferably arranged adjacent to a line section between the turbocharger and the charge air cooler or to a line section between the charge air cooler and the inlet port. In particular, the intercooler, regarding its cooling capacity and its geometric dimensions, smaller di be dimensioned, as part of the cooling is taken over by the relaxing fuel gas. Depending on the design of the internal combustion engine may optionally be completely dispensed with a charge air cooler in an internal combustion engine with turbocharger.

Preferably the internal combustion engine further comprises a valve adjusting device, at an opening time and / or a closing time of a Adjust intake valve and / or an exhaust valve, wherein the valve adjusting with increasing load of the internal combustion engine a degree of rinsing of the valve increases. The Ventilverstelleinrichtung can in particular a valve opening overlap on the Adjust inlet and outlet valves to achieve the higher flushing level. Thereby becomes the degree of filling optimized in the cylinders on the one hand and on the other hand is a Temperature in the cylinders by the improved rinsing of the burned residual gas lowered. This allows the internal combustion engine with a firing angle closer to one Knock limit be operated.

Farther can through the higher Air filling in the Cylinder a higher one Air mass flow and thus achieved an increased exhaust gas mass flow what will be beneficial when using a turbocharger Response of the turbocharger effects. This leads according to the invention also lower fuel consumption and lower emissions.

Further Preferably, the internal combustion engine comprises a throttle valve and the pressure regulating module is present at a line section of the air supply line or arranged after the throttle.

Preferably the internal combustion engine comprises a separate heat exchanger, which between the pressure control module and / or a line region of the fuel gas supply line and the air supply line is arranged. By using the heat exchanger can improve heat transfer be ensured.

Especially Preferably, a liquid coolant is provided in a fluid circuit of the heat exchanger. As a result, a particularly good heat transfer can be ensured.

According to one Another preferred embodiment of the present invention arranged in the fluid circuit, a pump. This can be a forced circulation a coolant be ensured. The pump can be an electrical or mechanical Be pump. This allows optimal heat exchange between the relaxed Fuel gas and the sucked air mass done. Especially preferred the fluid circuit is designed such that an adaptation via the pump to the current operating conditions of the internal combustion engine is possible, so that in each operating range of the internal combustion engine optimal Cooling the sucked air mass to a defined temperature can.

Preferably is in the fluid circuit of the heat exchanger arranged an electric heater. This allows the coolant to temperatures above the ambient temperature are heated to freeze the pressure control module to prevent with safety.

The inventive method for operating an internal combustion engine with the features of the claim 12 has the advantage that an efficiency of the internal combustion engine when operating with a gaseous Fuel is improved. The gaseous fuel is here in a store under a pressure which is higher than the ambient pressure is stored. A pressure altitude of gaseous Fuel is in a supply line to a Einblasventil means regulated a pressure control module, wherein during the pressure reduction of the Fuel gas, the temperature of the fuel gas due to the relaxation sinks. The relaxed in the pressure control module fuel gas is doing for heat exchange used with a combustion air supplied in an air supply line. Here, on the one hand, a cooling the combustion air and, accordingly, a heating of the Fuel gas can be achieved, however, the inventive method can also be used during a cold start. If, for example, temperatures below freezing, gas-powered internal combustion engines often Starting problems. Since by the relaxation process of the fuel gas in the pressure control module additionally still a temperature reduction of the fuel gas can occur by up to 30 ° C, can thus by passing of the fuel gas at the supplied Combustion air, about Ambient temperature has reached a temperature increase of the fuel gas become. This is especially when charged combustion air achieved, as this one higher Temperature than the ambient temperature.

Preferably is the relaxed fuel gas for a heat exchange with the combustion air immediately adjacent to an inlet port, d. h., Immediately adjacent to an inlet valve, passed. hereby can be a very big one Increased efficiency can be achieved.

The inventive method is particularly preferably used in combination with a supercharged internal combustion engine, since then a temperature difference between the relaxed Fuel gas and the supplied combustion air is very high.

Further the relaxed fuel gas is preferred immediately after the pressure control module for one heat exchange with the combustion air passed by this.

It be noted that for a particularly good heat transfer between the expanded fuel gas and the supplied combustion air preferably larger areas provided could be.

The inventive device and the method according to the invention are particularly preferably used in vehicles powered by natural gas. in this connection can be used in both purely natural gas powered vehicles be provided as well with vehicles, which with natural gas and another fuel, for. As gasoline, alcohol, ethanol, etc., operate. It can however, other compressed gaseous fuels are also used become.

drawing

following become preferred embodiments the invention with reference to the accompanying drawings in Detail described. In the drawing is:

1 a schematic, partially sectioned view of an internal combustion engine according to a first embodiment of the present invention,

2 a schematic, partially sectioned view of an internal combustion engine according to a second embodiment of the present invention,

3 a schematic, partially sectioned view of an internal combustion engine according to a third embodiment of the present invention, and

4 a schematic, partially sectioned view of an internal combustion engine according to a fourth embodiment of the present invention.

Preferred embodiments the invention

The following is with reference to 1 an internal combustion engine 1 according to a first embodiment of the invention described in detail. 1 schematically shows an internal combustion engine 1 , which is designed for a gas operation, in particular a natural gas operation. The internal combustion engine 1 includes a combustion chamber 2 in a cylinder in which, in a known manner, a piston 13 is arranged. At the combustion chamber 2 is at least one inlet port 3 and an outlet port 4 arranged. The inlet connection 3 is by means of an inlet valve 11 can be opened or closed and the outlet connection 4 is by means of an exhaust valve 12 can be opened or closed. Further, in a known manner, a spark plug 10 at the combustion chamber 2 arranged. As indicated by the arrow A, ambient air as combustion air becomes an air supply passage 7 fed. A throttle 16 is in the air supply line 7 arranged. The air supply line 7 flows at the inlet connection 3 at the combustion chamber 2 , Just before the end of the air supply line 7 at the inlet connection 3 is the fuel gas by means of a first Gaseinblasventils 5 and a second injection valve 6 in the air supply line 7 blown. The blowing direction corresponds essentially to the flow direction of the air in the air supply line 7 ,

The fuel gas is in a gas storage 8th stored under high pressure over 200 × 10 ⁵ Pa. Since this pressure is too high for the operation of the internal combustion engine, this is via a line 17 from the gas storage 8th discharged gas in a pressure control module 9 relaxed to a lower pressure. The fuel gas is preferably expanded to a low pressure of below 10 × 10 ⁵ Pa. From the pressure control module 9 off goes a first fuel gas line 17a to the gas injection valve 5 and a second fuel gas passage 17b to the gas injection valve 6 , However, this relaxation process of the fuel gas to the low pressure causes a very large cooling of the fuel gas, resulting in a high temperature drop in the pressure control module 9 leads. How out 1 is apparent, is the pressure control module 9 immediately adjacent to the air supply line 7 arranged and contacted the air supply line. Due to the high temperature differences between the air supply line 7 and the pressure control module 9 There is a heat transfer between these two components and the media contained therein. During operation of the internal combustion engine can thus for the air supply line 7 supplied combustion air to be cooled. As a result, the density of the combustion air can be increased. Further, in an operation of the internal combustion engine with gaseous fuel, the degree of filling can be increased. This leads to an improved combustion and to a higher efficiency, since a cooling of the intake combustion air a greater filling increase in the combustion chamber 2 causes. This also has positive effects on the emission values.

How out 1 is apparent, is the pressure control module 9 immediately adjacent to the inlet connection 3 at the air supply line 7 arranged. This prevents the once cooled down te combustion air on its way to the combustion chamber 2 not overheated again.

at a use of natural gas as fuel gas can with the much cooler intake air and the house higher Opposite octane of natural gas the conventional one Otto fuels, the internal combustion engine additionally operated closer to the knock limit become. this leads to to a further improvement in the efficiency of the internal combustion engine. This is also for example Internal combustion engines, which have a predetermined power with one as possible to provide small space. This can be a space be reduced.

Furthermore, advantages in the operation of the internal combustion engine 1 are obtained when the inventively exploited temperature reduction in the relaxation of the fuel gas to reduce the temperature of the combustion air with a targeted adjustment of the intake valve 11 and the exhaust valve 12 combined. The adjustment of the intake and exhaust valves is thereby set such that a valve overlap, ie, a simultaneous opening of the intake valve 11 and the exhaust valve 12 is available. As a result, a higher degree of flushing can be achieved and a degree of filling in the cylinders can be optimized. Also, the temperature in the cylinders is lowered by the improved flushing out of the burned hot residual gas, so that the internal combustion engine can be operated even closer to the knock limit with the ignition angle.

How farther 1 is apparent, is an exhaust gas return line 14 provided, which combustion gases from an exhaust pipe 18 back into the air supply line 17 returns. In the exhaust gas return line 14 is a valve 15 provided, which regulates the amount of the supplied exhaust gas to the intake air. The exhaust gas return leads to a junction area 19 in the air supply line. The outflow of the exhaust gas is indicated by the arrow B.

Thus, according to the invention the temperature decrease occurring during the relaxation of the fuel gas for cooling the combustion air used, which ultimately leads to a higher efficiency the internal combustion engine leads. It should be noted that all other components and functions of the internal combustion engine thereby adopted unchanged can be.

It should also be noted that the arrangement according to the invention also has advantages in a cold start of the internal combustion engine. Before starting the internal combustion engine usually have the intake air and in the gas storage 8th stored fuel gas the same temperature. If after the start of the engine fuel gas in the pressure control module 9 is relaxed, the temperature of the fuel gas drops well below the temperature of the intake air. Here, a temperature difference of the fuel gas before and after the relaxation can be up to 30 ° C. However, since the expanded fuel gas is immediately adjacent to the warmer intake air in the air supply line 7 is passed, there is a heat transfer from the intake air to the fuel gas, so that the temperature difference remains moderate. In particular, if the intake air is warmer than the ambient temperature, for example by compression, this positive effect increases during cold start. This reduces in particular opening problems of valves with elastomeric sealing elements.

The following is with reference to 2 an internal combustion engine 1 according to a second embodiment of the invention described in detail. Identical or functionally identical parts are denoted by the same reference numerals as in the first embodiment.

The second embodiment corresponds essentially to the first embodiment, wherein, in contrast to the second embodiment, the pressure control module 9 between a throttle 16 and a junction area 19 the exhaust gas return line 14 is arranged. This arrangement has particular design advantages, as often immediately adjacent to the cylinder little to no space for the arrangement of the pressure control module 9 is available. Otherwise, this embodiment corresponds to the previous embodiment, so that reference can be made to the description given there.

3 shows an internal combustion engine 1 according to a third embodiment of the present invention. Identical or functionally identical parts are designated by the same reference numerals as in the preceding embodiments.

In contrast to the preceding embodiments, the third embodiment has a turbocharger 20 on. The turbocharger 20 compresses the intake air, being driven by means of an exhaust gas turbine. Due to the compression of the intake air increases its temperature, so that in the air supply line 7 also an intercooler 21 is provided. The pressure control module 9 is similar to the first embodiment as close as possible to the cylinder of the internal combustion engine 1 arranged. As the pressure control module 9 During operation of the internal combustion engine additionally cools the compressed intake air, in particular the intercooler 21 be designed smaller. Depending on the design of the internal combustion engine may possibly completely on the intercooler 21 be waived. Otherwise, this embodiment corresponds to the previous embodiments, so that reference can be made to the description given there.

4 shows an internal combustion engine 1 according to a fourth embodiment of the present invention. Identical or functionally identical parts are designated by the same reference numerals as in the preceding embodiments.

The fourth embodiment substantially corresponds to the third embodiment and also includes a turbocharger 20 , wherein the pressure control module 9 of the fourth embodiment on the air supply line 7 between the intercooler 21 and the throttle 16 is arranged. As a result, in particular a space requirement near the cylinder of the internal combustion engine is reduced. Otherwise, this embodiment corresponds to the previous embodiments, so that reference can be made to the description given there.

Claims (16)

Internal combustion engine for a gaseous fuel, comprising a combustion chamber ( 2 ), an inlet port ( 3 ), an outlet port ( 4 ), a gas injection valve ( 5 . 6 ), an air supply line ( 7 ), which at the inlet connection ( 3 ), a gas storage ( 8th ) to store the gaseous fuel at a pressure above ambient pressure, and a pressure control module ( 9 ), which in a connecting line between the gas storage ( 8th ) and the gas injection valve ( 5 . 6 ) is arranged to control a head of pressure of the gaseous fuel, wherein the pressure control module ( 9 ) and / or a line region of a fuel gas supply line ( 17a . 17b ) from the pressure control module ( 9 ) to the gas injection valve ( 5 . 6 ) adjacent to the air supply line ( 7 ) is arranged to heat exchange between the gaseous fuel and in the air supply line ( 7 ) to allow supplied combustion air. Internal combustion engine according to claim 1, characterized in that the pressure control module ( 9 ) immediately adjacent to the inlet port ( 3 ) is arranged. Internal combustion engine according to claim 1 or 2, further comprising a turbocharger ( 20 ), whereby the pressure control module ( 9 ) adjacent to the air supply line ( 7 ) at a line section between the turbocharger ( 20 ) and the inlet port ( 3 ) is arranged. Internal combustion engine according to claim 3, further comprising an intercooler ( 21 ), whereby the pressure control module ( 9 ) at a line section between the turbocharger ( 20 ) and the intercooler ( 21 ) or a line section between the intercooler ( 21 ) and the inlet port ( 3 ) of the air supply line ( 7 ) is arranged. Internal combustion engine according to one of the preceding Claims, further comprising a valve adjusting device to an opening time and / or a closing time an intake valve and / or an exhaust valve to adjust. Internal combustion engine according to claim 5, characterized in that the valve adjusting device with a rising load of the internal combustion engine, a flushing degree of the combustion chamber ( 2 ) by a longer simultaneous opening of the inlet valve ( 11 ) and the exhaust valve ( 12 ). Internal combustion engine according to one of the preceding claims, further comprising a throttle flap ( 16 ), whereby the pressure control module ( 9 ) at a line section of the air supply line ( 7 ) before or after the throttle valve ( 16 ) is arranged. Internal combustion engine according to one of the preceding claims, further comprising a heat exchanger, which between the pressure control module ( 9 ) and / or a line region of the fuel gas supply line ( 17a . 17b ) and the air supply line ( 7 ), wherein the heat exchanger has a separate fluid circuit. Internal combustion engine according to claim 8, characterized that in the fluid circuit of the heat exchanger a liquid coolant is used. Internal combustion engine according to claim 8 or 9, characterized in that a pump is arranged in the fluid circuit of the heat exchanger is which dependent operating conditions of the internal combustion engine is operable. Internal combustion engine according to one of claims 8 to 10, characterized in that in the fluid circuit of the heat exchanger Further, an electric heater is arranged. Method for operating an internal combustion engine, which is operated with a gaseous fuel, wherein the gaseous fuel in a gas reservoir ( 8th ) is stored under a pressure above ambient pressure, wherein a pressure level of the gaseous fuel by means of a pressure control module ( 9 ), and wherein the pressure control module ( 9 ) and / or a fuel gas supply line ( 17a . 17b ) adjacent to an air supply line ( 7 ), and wherein in the pressure control module ( 9 ) expanded gaseous fuel for heat exchange with the in the air supply line ( 7 ) too guided combustion air is used. A method according to claim 12, characterized in that in the pressure control module ( 9 ) relaxed gaseous fuel immediately adjacent to an inlet port ( 3 ) at the combustion chamber ( 2 ) on the air supply line ( 7 ) is passed for heat exchange. Method according to claim 12 or 13, characterized that the relaxed gaseous Fuel for cooling is used by compressed combustion air. Method according to one of claims 12 to 14, characterized in that the expanded gaseous fuel immediately after the pressure control module ( 9 ) for heat exchange with the combustion air at the air supply line ( 7 ) is passed. Method according to one of claims 12 to 15, characterized in that in the pressure control module ( 9 ) is relaxed at a cold start of the internal combustion engine by passing on the combustion air heated gaseous fuel.