DE102015015343A1 - Method and control device for operating an engine - Google Patents

Abstract

A method for operating a designed as a gas engine or a dual-fuel engine engine comprising a plurality of cylinders (2), wherein for the combustion of a gas / air mixture of a gaseous fuel and air, the gas / air mixture using a Zündfluids in the cylinders (2) is ignited, and depending on the exhaust emission regulations to be followed, the gas engine or the dual-fuel engine either in a first mode with a diffusion combustion of the gas / air mixture or in a second mode with a homogeneous combustion of the gas / air Is operated.

Description

The invention relates to a method for operating a motor and a control device for carrying out the method.

In practice, so-called dual-fuel engines are known in which, on the one hand in a liquid fuel operating mode, a liquid fuel such as diesel and on the other hand in a gaseous fuel operating mode, a gaseous fuel such as natural gas can be burned. Furthermore, gas engines are known which burn a gaseous fuel as the main energy carrier. The gaseous fuel is hereinafter referred to simply as "gas". In the gaseous fuel operating mode of a dual-fuel engine and in gas engines, a gas / air mixture is usually introduced into the cylinders of the engine and ignited by the supply of ignition energy into the cylinder. The ignition energy can be introduced into the cylinder, for example, but not exclusively, in the form of electrical energy or in the form of an ignition fluid. The ignition fluid can be ignition oil or diesel fuel. Next gas combustion methods are known which operate on the diffusive combustion principle. In this combustion process, no gas-air mixture, but as in diesel engines pure air is introduced into the cylinder. The fuel gas is then injected into a small, already ignited amount of ignition fluid under high pressure, flares up as a result and burns diffusively. Since diffusive combustion processes do not knock (uncontrolled reaction in the tail gas range), the number of methane plays no role in relation to the representable engine power.

For the operation of a dual-fuel engine and a gas engine increasingly stringent exhaust emission regulations are to be observed. This is especially true for dual-fuel engines and gas engines, which are used as propulsion units on ships. For example, it is known that stricter emission standards are applied near the coast than on the open seas. Such areas, which have stricter emissions regulations in shipping, are also known as Emission Control Areas (ECAs). Regions outside the Emission Control Areas are also referred to as Non-Emission Control Areas (NECAs). In order to be able to comply with the stringent emissions regulations, in particular in the so-called emission control areas, increasingly expensive exhaust aftertreatment facilities are required on ships.

There is therefore a need for a method for operating an engine as well as at a control device for carrying out the method, by means of which it is possible to comply with existing emission regulations without expensive and complex exhaust aftertreatment.

On this basis, the invention is based on the object to provide a novel method and a control device for operating a motor.

This object is achieved by a method according to claim 1. According to the invention, the internal combustion engine is designed as a reciprocating engine and operated either in a first mode with a diffusion combustion of the gas or in a second mode with a premixed combustion of a gas / air mixture depending on the exhaust emission regulations. The invention proposes for the first time, depending on exhaust emission regulations to be followed, an internal combustion engine which is operated as a main energy carrier with gas (storage in the tank liquid or gaseous), either in the first operating mode with a diffusion combustion of the gas or alternatively in the second operating mode with a premixed combustion operate a gas / air mixture.

Then, when strict emission regulations are to be met, the engine is operated in the second mode with the premixed lean combustion of the gas / air mixture, in particular to reduce nitrogen oxide emissions.

Then, if less stringent exhaust emission limits are to be met, Especially in so-called non-emission control areas, the engine is operated in the first mode with the diffusion combustion of the gas to operate here the engine with maximum efficiency without limitation by knocking.

In the first mode of operation of the engine in the diffusion combustion of the gas in each cylinder in each working cycle of the same first ignited the ignition fluid, which at the hot cylinder charge (air, residual gas and possibly. EGR) and then introduced into this inflamed Zündfluidmenge the gaseous fuel. Preferably, in the first mode in the diffusion combustion of the gas, the ignition fluid before an ignition top dead center (ignition TDC) of the respective cylinder and then the gaseous fuel partially before the ignition TDC of the respective cylinder and partially after the ignition TDC of the respective Cylinder introduced into the same. This first mode of diffusion combustion of the gas allows the combustion of the gas similar to the diesel principle with high efficiency without knocking tendency, even if the gas quality fluctuates. However, this results in relatively high exhaust emissions, in particular high nitrogen oxide emissions, so that this operating mode is used when less stringent exhaust emission limit values apply, in particular in so-called non-emission control areas.

In the second mode of operation of the engine in the premixed combustion of the gas / air mixture in each cylinder in a cycle of the same first the gaseous fuel and then the ignition fluid is introduced into the respective cylinder. Preferably, in the second mode of homogeneous combustion of the gas / air mixture, the ignition fluid before an upper ignition dead center (ignition TDC) of the respective cylinder and previously, preferably introduced in the intake stroke, the gaseous fuel in the respective cylinder. This mode of operation with premixed lean combustion of the gas / air mixture allows compliance with more stringent emissions regulations, so that it is preferably used in so-called emission control areas. In particular, in the homogeneous combustion of the gas / air mixture, the emission of nitrogen oxides compared to the diffusion combustion can be greatly reduced.

According to an advantageous development of the invention, in the second operating mode in the premixed combustion of the gas / air mixture, the gas is introduced into the respective cylinder in two stages each before the ignition fluid, namely in a first stage preferably in the intake stroke of the respective cylinder to charge air and homogenize gas optimally and in a second stage preferably in the compression stroke of the respective cylinder for local enrichment in the area around the ignition, whereby a rapid ignition is granted, but also a low tendency to knock in Endgasbereich (lean area). Preferably, the second stage of the introduction of the gas / air mixture is between 5 ° CA before the ignition oil introduction and 80 ° CA before the ignition oil introduction. Preferably, the introduced in the second phase gas / air mixture amount between 3% and 20% of the introduced in the first phase gas / air mixture amount. This development of the second operating mode for the premixed combustion of the gas / air mixture is particularly advantageous for maintaining strict exhaust emission regulations or for influencing the knocking behavior. By introducing the gas / air mixture in two stages, each before the ignition fluid, the combustion efficiency of the gas / air mixture can be increased and the tendency to knock reduced in this mode. In this operating strategy, this is a partially homogeneous operation.

The control device for carrying out the method is defined in claim 12.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 a block diagram of an engine which operates according to the described method;

2 : a first diagram to illustrate the method according to the invention for operating the engine;

3 a second diagram for further illustrating the method according to the invention for operating the engine; and

4 a third diagram for further clarification of the method according to the invention for operating the engine.

In 1 are assemblies of the engine shown, where 1 a cylinder 2 of such a motor shows. The cylinder 2 has a cylinder head 3 , In the cylinder 2 a piston moves 4 coming from a connecting rod 5 is guided, up and down. In the cylinder head 3 is a fuel injector 6 attached, by the liquid fuel, in particular diesel fuel, via a fuel line 7 from a pressure generating unit 8th out directly into a combustion chamber 9 of the cylinder 2 can be injected. The pressure is generated preferably mechanically driven by the engine. The fuel injector 6 , the fuel line 7 as well as the pressure generating unit 8th are elements of a fuel supply, the supply of liquid fuel into the combustion chamber 9 of the cylinder 2 serves. For combustion is in the respective cylinder 2 the dual-fuel engine continues charge air 10 via an inlet valve 17 einbringbar, wherein in the combustion of the fuel resulting exhaust gas 15 via an exhaust valve 18 from the cylinder 2 can be dissipated.

Next includes the combustion chamber 9 of the cylinder 2 a high pressure gas injector which injects the gas directly into the combustion chamber via a gas supply line 21 is supplied with gas.

To ignite the gas-air mixture in the (partially) homogeneous gas operation of the cylinder 2 the engine serves ignition fluid.

The ignition fluid injector 13 of in 1 shown cylinder 2 is part of an ignition fluid injection system of the engine, wherein the ignition fluid injection system for each cylinder 2 of the engine, a cylinder-individual Zündfluid injector 13 includes. The ignition fluid injectors 13 are preferably via a Zündfluidleitung 14 starting from a common Zündfluid memory 22 the Zündfluid injection system can be supplied with ignition fluid, wherein the ignition fluid storage 22 an ignition fluid feed pump 16 is assigned to the Zündfluid memory 22 supplied with ignition fluid. In the ignition fluid delivery pump 16 it is preferably a mechanically operated high-pressure pump. The ignition fluid delivery pump 16 is a suction throttle 19 assigned.

In principle, with this engine concept it is also conceivable that in addition a further diesel injector is arranged in the combustion chamber (eg also for heavy oil) with the aid of which the engine can be operated as a pure diesel engine.

As already stated above, shows 1 a cylinder 2 a designed as a dual-fuel engine engine. This may be operated in a liquid fuel operating mode and in a gaseous fuel operating mode, the invention relating to the gaseous fuel operating mode of such a dual-fuel engine.

However, the invention is not limited to use with dual-fuel engines. Rather, the invention can also be applied to a gas engine in which only a gas / air mixture of a gaseous fuel and air is ignited and burned using an ignition fluid in the cylinders of the engine. Accordingly, the invention can be used both in dual-fuel engines in the gaseous fuel operating mode and in gas engines.

The invention proposes to operate a dual-fuel engine in the gaseous fuel operating mode and a gas engine such that, depending on exhaust emission regulations to be followed, the engine either in a first mode with a diffusion combustion of the gas / air mixture or in a second mode with a homogeneous combustion of the gas / air mixture is operated. Then, if relatively strict exhaust emission regulations are to be observed, in particular in so-called emission control areas, the engine is operated in the second operating mode with the homogeneous combustion of the gas / air mixture. On the other hand, if relatively low exhaust emissions regulations apply, the engine is operated in the first mode with the diffusion combustion of the gas / air mixture. This makes it possible, without the need for expensive and expensive exhaust aftertreatment, to operate a dual-fuel engine in Garzoffletriebbetriebsmodus and a gas engine in compliance with the valid exhaust emission regulations with high efficiency.

Details of the two modes of combustion of the gas / air mixture, which are selected in accordance with exhaust emission regulations for the operation of the gas engine or the dual-fuel engine in the gaseous fuel operation mode, will be described below with reference to FIG 2 to 4 described, in 2 to 4 for a respective working cycle of a cylinder of the engine to be operated according to the invention, the introduction of the gas / air mixture and the ignition fluid into the respective cylinder is shown.

2 shows details of the first mode of operation of the internal combustion engine in the gaseous fuel operating mode in the diffusion combustion of the gas. In the first mode of operation, ignition fluid is first injected into each cylinder in each stroke thereof 23 and then introducing gaseous fuel into the respective cylinder.

It shows 2 in that in the first operating mode in the diffusion combustion of the gas, the ignition fluid is before an upper ignition dead center (also referred to as ignition TDC or ZOT) of the respective cylinder 2 completely in the cylinder 2 is introduced, wherein subsequent to the introduction of the ignition fluid, the gas before the ZOT and partially after the ZOT of the respective cylinder 2 is introduced into it and ignites on the already burning ignition fluid, whereby the gas burns diffusively. Hereby, a diesel-like combustion of the gas can be ensured at high efficiency without knocking tendency of the engine to be operated, but with relatively high pollutant emissions form, so that this first mode is then used, especially if so-called non-emission control areas to comply with less stringent exhaust emission limits are.

The second operating mode for the gas engine or the dual-fuel engine in the gaseous fuel operating mode with premixed combustion of the gas / air mixture is in 3 and 4 shown, according to 3 and 4 in the second mode, the ignition fluid 26 before an upper ignition dead center (ignition TDC or ZOT) of the respective cylinder is introduced into the same, whereas the gas 25 before the ignition fluid 26 in the respective cylinder 2 is introduced, namely after an upper charge exchange dead center (also called charge exchange OT or LWOT) of the respective cylinder 2 ,

In the variant of 3 In this case, the gas is in the second operating mode 25 in a single step into the cylinder 2 introduced, in part before a bottom dead center (also called UT) of the respective cylinder 2 after the LWOT and before the introduction of the ignition fluid 26 lies, and partly after this UT of the respective cylinder 2 , Before this UT will be the gas 25 in the second mode in the suction stroke of the respective cylinder 2 introduced, after this UT is a compression stroke.

Particularly preferred in the second mode is the premixed combustion of the gas 25 the gas 25 in two stages 25a . 25b each before the ignition fluid 26 introduced into the respective cylinder.

Two-stage introduction of the gas 25 takes place according to 4 such that in the first stage 25a the gas is introduced before the UT of the cylinder lying between the LWOT and the ZOT of the respective cylinder, whereas in the second stage 25b the gas after this UT and before the ignition fluid 26 in the respective cylinder 2 is introduced. The second phase 25b the introduction of the gas is completely between the UT, which is between the LWOT and the ZOT, and the introduction of the ignition fluid, ie in the compression stroke. The first stage 25a the introduction of the gas before the first stage 25b is completed, lies in 4 completely between the LWOT and the UT, which is between the LWOT and the ZOT, ie in the suction stroke. If necessary, it is possible that the second stage 25a extends beyond this UT. Then, if in the second mode in the premixed combustion of the gas / air mixture according to 4 the gas 25 in the two stages 25a . 25a is introduced into the respective cylinder, the premixed combustion of the gas / air mixture can be carried out with optimized efficiency, reduced tendency to knock and low exhaust emissions, so that this mode for compliance with strict emissions regulations in so-called emission control areas is particularly preferred.

The second stage 25b the introduction of the gas 25 lies after the first stage 25a and between 5 ° crankshaft angle (KW) and 80 ° CA before the introduction of the ignition fluid 26 , Preferably, this second stage 25b the introduction of the gas 25 between 5 ° CA and 60 ° CA before ignition fluid injection. The second phase 25b introduced gas mass is between 3% and 20%, preferably between 3% and 15%, in the first phase 25a introduced gas mass.

The switching between the first operating mode and the second operating mode preferably takes place automatically, depending on position data of a ship on which the respective engine is operated, wherein it is automatically decided on the basis of the position data which are preferably provided by a GPS system the ship is located in a non-emission control area or an emission control area, in which case the operating mode of the engine is automatically selected as a function of this, namely in non-emission control areas the first operating mode and in emission control Areas the second mode. In contrast, however, it is also possible to manually allow the switching or the change between the two operating modes.

In the second operating mode for premixed combustion of the gas / air mixture is preferably a lean gas / air mixture with excess air or a lambda value greater than 1 use.

With the invention it is possible to operate an engine in the gaseous fuel operating mode with optimum efficiency and a low tendency to knock in compliance with valid exhaust emission regulations, without the need for expensive and expensive exhaust aftertreatment or exhaust aftertreatment. The invention is preferably used in engines that are operated on ships.

The invention further relates to a control device for automated implementation of the method. The control device has means for carrying out the method. These include hardware-side means such as data interfaces for data exchange with the modules involved in the implementation of the method, a memory for data storage and a processor for data processing, as well as software means such as program blocks.

Claims (12)

Method for operating a motor designed as a gas engine or as a dual-fuel engine, comprising a plurality of cylinders ( 2 ), wherein for combustion of a gas / air mixture of a gaseous fuel and air, the gas / air mixture using an ignition fluid in the cylinders ( 2 ) is ignited, characterized in that depending on the exhaust emission regulations to be followed, the gas engine or the dual-fuel engine either in a first mode with a diffusion combustion of the gas / air mixture or in a second mode with a homogeneous combustion of the gas / air mixture is operated. A method according to claim 1, characterized in that in the first mode, which is activated at relatively low exhaust emission regulations (for diffusion combustion of the gas / air mixture in the area of each cylinder 2 ) in a working stroke of the same first the ignition fluid and then the gaseous fuel and the air of the gas / air mixture in the respective cylinder ( 2 ) is activated, in the second mode, which is activated under relatively strict exhaust emission regulations, for the homogeneous combustion of the gas / air mixture in the region of each cylinder ( 2 ) in a working stroke of the same first the gaseous fuel and the air of the gas / air mixture and then the ignition fluid in the respective cylinder ( 2 ) is introduced. A method according to claim 1 or 2, characterized in that in the first operating mode for diffusion combustion of the gas / air mixture, the ignition fluid before an upper ignition dead center of the respective cylinder ( 2 ) and then the gaseous fuel and the air of the gas / air mixture partially before the ignition TDC of the respective cylinder ( 2 ) and partly after the ignition TDC of the respective cylinder ( 2 ) is introduced into the same. Method according to one of claims 1 to 3, characterized in that in the second mode for the homogeneous combustion of the gas / air mixture, the ignition fluid before an upper ignition dead center of the respective cylinder ( 2 ) and before the gaseous fuel and the air of the gas / air mixture after an upper charge exchange dead center of the respective cylinder ( 2 ) is introduced into the same. A method according to claim 4, characterized in that in the second mode with the homogeneous combustion of the gas / air mixture, the gas / air mixture is introduced in two stages each before the ignition fluid in the respective cylinder, namely in a first stage at least partially before a bottom dead center of the respective cylinder ( 2 ) and in a second stage completely after the UT of the respective cylinder ( 2 ). A method according to claim 5, characterized in that the second stage of the introduction of the gas / air mixture is between 5 ° CA before Zündfluideinbringung and 80 ° CA before Zündfluideinbringung. A method according to claim 6, characterized in that the second stage of the introduction of the gas / air mixture is between 5 ° CA before Zündfluideinbringung and 60 ° CA before Zündfluideinbringung. Method according to one of claims 4 to 7, characterized in that the introduced in the second phase gas / air mixture amount is between 3% and 20% of the introduced in the first phase gas / air mixture amount. A method according to claim 8, characterized in that the introduced in the second phase gas / air mixture amount is between 3% and 15% of the introduced in the first phase gas / air mixture amount. Method according to one of claims 1 to 9, characterized in that between the first mode for diffusion combustion of the gas / air mixture and the second mode for homogeneous combustion of the gas / air mixture is automatically switched. A method according to claim 10, characterized in that, when the engine is a marine engine, is automatically switched depending on a position signal of the ship between the first mode and the second mode. Control device of an engine, characterized by means for carrying out the method according to one of claims 1 to 11.

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