ANALYSIS

FIELD OF THE DISCLOSURE

The present disclosure relates to the control of internal combustion engines, and more particularly to the control of reciprocating internal combustion piston engines capable of using gaseous fuel as main fuel. The present disclosure further concerns a control method for such engines based on fuel properties, and a respective engine system with fuel properties analysis BACKGROUND OF THE DISCLOSURE

Internal combustion engines capable of using gaseous fuel as main fuel may often be operated on different types of gaseous fuel, e.g. gases of various compositions. This is due to the fact, that the composition of natural gas varies depending on the deposit from which the gas is recovered from.

Typically, it is the provider of the gaseous fuel that also provides information on the composition of said gas, and the operator of the engine calculates fuel properties based on the given information concerning composition. The calculated fuel properties are then used to adjust engine control parameters so that the engine is better optimized for the fuel composition, and to avoid certain problems, such as knocking.

However, calculating fuel properties for a given composition always results in an estimate, which may vary to some extent from the actual properties of the gaseous fuel. Moreover, filling a gaseous fuel reservoir with various types of gaseous fuel results in a mixture of gaseous fuels, which in turn requires more complex calculations for evaluating the properties of the mixture. BRIEF DESCRIPTION OF THE DISCLOSURE

An object of the present disclosure is to provide a control method for an internal combustion engine and an engine system having an internal combustion engine, such as reciprocating internal combustion piston engine, so as to facilitate adaption between different fuel properties of gaseous fuels having different compositions.

The objects of the disclosure are achieved by a control method and an engine system which are characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

The disclosure is based on the idea of providing an analysing unit having a rapid compression machine in connection with an internal combustion engine capable of using gaseous fuel as main fuel, and using information provided by the analysing unit to control the engine.

An advantage provided by the disclosure is that information regarding fuel properties of the gaseous fuel actually delivered to the internal combustion engine is readily available for use in controlling said engine.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which:

Figure 1 is a schematic illustration of an engine system according to an embodiment of the disclosure;

Figure 2 is a schematic illustration of an engine system according to another embodiment of the disclosure, in which fuel and air are delivered via separate lines;

Figure 3 is a schematic illustration of an engine system according to yet another embodiment of the disclosure, in which fuel and air are delivered via separate lines and analysing unit environment conditions are adjusted based on engine environment conditions; and

Figure 4 is a schematic illustration of an engine system according to further embodiment of the disclosure, in which fuel and air are delivered via separate lines, such that air is provided to the analysing unit in a state corresponding to that of air being introduced to a cylinder of an engine.

It should be noted that, for the purpose of clarity, the appended drawings illustrate embodiments of the disclosure in a schematic and simplified manner, and should not thus be interpreted in a restricting manner.

DETAILED DESCRIPTION OF THE DISCLOSURE

According to a first aspect of the present disclosure, a control method for an internal combustion engine 1 is provided, said control method being based on fuel properties and said engine being capable of using gaseous fuel as main fuel.

In the method, an analysing unit 2 for analysing fuel properties of gaseous fuel is provided. Particularly, the analysing unit 2 comprises a rapid compression machine 2a arranged in fluid communication with a fuel delivery line 4; 4a of the internal combustion engine 1 , so as to receive at least gaseous fuel to be analysed. The fuel delivery line 4a may be configured as a gaseous fuel feed line, i.e. delivering only gaseous fuel, in which case air has to be provided separately both for the analysing unit 2 and the internal combustion engine 1 . Alternatively, the fuel delivery line 4 may be configured as an intake line, i.e. delivering a combination of gaseous fuel and air to be combusted together in both the analysing unit 2 and the internal combustion engine 1 .

The gaseous fuel to be analysed is compressed within a compression chamber 2b of the analysing unit so as to induce said fuel to auto-ignite and combust with air. Moreover, pressure data indicative of fuel properties is obtained from this combustion.

Information indicative of the fuel properties is transmitted to the control device 3, and engine control parameters are controlled at least based on the information indicative of fuel properties. The information indicative of fuel properties could be, for example, pressure data obtained from a pressure sensor 2c, or information derived at least from the pressure data by the analysing unit 2. Examples of such engine control parameters include, but are not limited to, ignition timing, pilot fuel injection timing, pilot fuel injection quantity, fuel/air -ratio, manifold air pressure, valve timing, maximum engine load, and engine speed.

According to an embodiment of the first aspect, fuel auto ignition delay properties are determined from the obtained pressure data, and correspondingly, engine control parameters are controlled based at least on the determined fuel auto ignition delay properties. It should be noted, that the fuel auto ignition delay properties may be determined by the analysing unit 2 and transmitted to the control device 3, or alternatively, the fuel auto ignition delay properties may be determined by the control device 3 based on the information transmitted from the analysing unit 2.

According to another embodiment of the first aspect, engine environment condition information is obtained. In the context of this disclosure, the term engine environment condition(s) is used to describe the conditions in which the engine is operated and which affect the operation of the engine. Most suitably, means for obtaining engine environment condition information 1 a are provided as conventional sensors typically present in common internal combustion engine systems capable of using gaseous fuel as main fuel. Moreover, respective analysing unit environment conditions are adjusted so as to correspond, or at least more closely to correspond with the obtained engine environment condition information. It should be noted, that although the analysing unit environment conditions may be adjusted to match the engine environment conditions, the analysing unit environment may alternatively be adjusted to correspond to the engine environment condition information according to a pre-determined set of rules, such as a chart, table or map. This has an advantage in that less approximation is needed. One option is to select and adjust he engine environment condition towards a pre-determined environment, which is closest to the engine environment condition information.

Preferably, but not necessarily, said engine environment condition information is indicative of at least one of engine intake air temperature, engine intake air pressure and engine intake air humidity. Correspondingly adjusting analysing unit environment conditions comprises preferably, but not necessarily, adjusting at least one of analysing unit intake air temperature, analysing unit intake air pressure and analysing unit intake air humidity, respectively. For example, intake air temperature can be adjusted with heat exchanger.

According to a further embodiment of the first aspect, the analysing unit 2 is provided with air for combusting with gaseous fuel to be analysed, such that the is provided from an air intake line 4b of the internal combustion engine 1 in a state corresponding to that of air being introduced to a cylinder of said engine. For example, air may be provided to the analysing unit 2 from an air intake line 4b of the internal combustion engine 1 downstream of any air processing equipment, such as a charging device, charge cooler, or both (not illustrated). In such an arrangement, the properties of the air provided to the analysing unit

2 are effectively the same as those of the air provided for the internal combustion engine 1 . Correspondingly, environment conditions similar to those of the internal combustion engine 1 are achieved for the analysing unit 2 with minimal or none analysing unit environment conditions adjustments.

According to still another embodiment of the first aspect, compressing the gaseous fuel to be analysed within the compression chamber 2b of analysing unit 2 is actuated by mechanical power or fluid power derived from the engine or peripherals thereof. Alternatively, the compression chamber 2b may be actuated by electrical power derived from a generator attached to the internal combustion engine, or from the grid.

According to a second aspect of the disclosure, an engine system with fuel properties analysis is provided.

The engine system comprises an internal combustion engine 1 capable of using gaseous fuel as main fuel, a fuel delivery line 4; 4a for providing gaseous fuel to the engine, and a control device 3 for controlling engine control parameters of the engine.

The engine system is further equipped with an analysing unit 2 for analysing fuel properties of gaseous fuel. Particularly, the analysing unit 2 comprises a rapid compression machine 2a in fluid communication with the fuel delivery line 4; 4a for receiving at least gaseous fuel to be analysed. The rapid compression machine 2a has a compression chamber 2b arranged to compress, for example with a piston (not shown), said fuel so as to induce said fuel to auto-ignite and combust with air.

The fuel delivery line 4a may be configured as a gaseous fuel feed line, i.e. delivering only gaseous fuel, in which case air has to be provided separately both for the analysing unit 2 and the internal combustion engine 1 . Alternatively, the fuel delivery line 4 may be configured as an intake line, i.e. delivering a combination of gaseous fuel and air to be combusted together in both the analysing unit 2 and the internal combustion engine 1 .

The analysing unit 2 is also equipped with a pressure sensor 2c for obtaining pressure data of a combustion within the compression chamber of the rapid compression machine, said pressure data being indicative of fuel properties. Furthermore, the analysing unit 2 is arranged to transmit information indicative of fuel properties to the control device 3. The information indicative of fuel properties could be, for example, pressure data obtained from the pressure sensors 2c, or information derived at least from the pressure data by the analysing unit 2.

Moreover, the control device 3 is being further arranged to control engine control parameters at least based on said information indicative of fuel properties. Examples of such engine control parameters include, but are not limited to, ignition timing, pilot fuel injection timing, pilot fuel injection quantity, fuel/air -ratio, manifold air pressure, valve timing, maximum engine load, and engine speed.

According to an embodiment of the second aspect, the control device is further arranged to control engine control parameters based on at least fuel auto ignition delay properties determined from pressure data obtained from the pressure sensor 2c. It should be noted, that the fuel auto ignition delay properties may be determined by the analysing unit 2 and transmitted to the control device 3, or alternatively, the fuel auto ignition delay properties may be determined by the control device 3 based on the information transmitted from the analysing unit 2.

According to another embodiment of the second aspect, the engine system comprises means for obtaining engine environment condition information 1 a. Most suitably, means for obtaining engine environment condition information 1 a are provided as conventional sensors typically present in common internal combustion engine systems capable of using gaseous fuel as main fuel. Correspondingly, the analysing unit comprises means for adjusting analysing unit environment conditions 2d. Moreover, the means for adjusting analysing unit environment conditions 2d are arranged to adjust analysing unit environment conditions corresponding to engine environment condition information. Preferably, but not necessarily, said means for obtaining engine environment condition 1 a information are arranged to obtain engine environment condition information indicative of at least one of engine intake air temperature, engine intake air pressure and engine intake air humidity. Correspondingly said means for adjusting analysing unit environment conditions 2d are preferably, but not necessarily, arranged to adjust at least one of analysing unit intake air temperature, analysing unit intake air pressure and analysing unit intake air humidity, respectively.

According to a further embodiment of the second aspect, the rapid compression machine 2a is arranged in fluid communication with an air intake line 4b of the internal combustion engine 1 so as to provide air, in a state corresponding to that of air being introduced to a cylinder of said engine, for combustion with the gaseous fuel to be analysed. For example, air may be provided to the analysing unit 2 from an air intake line 4b of the internal combustion engine 1 downstream of any air processing equipment, such as a charging device, charge cooler, or both (not illustrated). In such an arrangement, the properties of the air provided to the analysing unit 2 are effectively the same as those of the air provided for the internal combustion engine 1 . Correspondingly, environment conditions similar to those of the internal combustion engine are achieved for the analysing unit with minimal or none analysing unit environment conditions adjustments.

According to still another embodiment of the second aspect, the analysing unit 2 is arranged in power transmission with the engine for actuating the analysing unit 2, i.e. in order to compress fuel in the compression chamber 2b. Most suitably such power transmission is arranged for mechanical power or fluid power derived from the engine, or peripherals thereof. Alternatively, the compression chamber 2b may be actuated by electrical power derived from a generator attached to the internal combustion engine, or from the grid or with air from separate pressurized air vessel/container.

Fig. 1 illustrates schematically an engine system according to an embodiment of the disclosure. An internal combustion engine 1 capable of using gaseous fuel as main fuel is coupled in fluid communication with a fuel delivery line 4 for providing at least gaseous fuel. The engine control parameters of the internal combustion engine 1 are controlled by the control device 3, the communication interface between the engine 1 and the control device 3 being represented as dashed line therebetween. The analysing unit 2 having a rapid compression machine 2a with a compression chamber 2b is also coupled in fluid communication with the fuel delivery line 4 for providing at least gaseous fuel to the compression chamber 2b of the rapid compression machine 2a. As the gaseous fuel to be analysed from the fuel delivery line 4 compressed with air in the compression chamber 2b, it auto-ignites and combusts. The pressure sensor 2c obtains compression data from this combustion and this data is transmitted to the control device 3 via the communication interface represented as a dashed line therebetween. Moreover, as the pressure data is indicative of the fuel properties of the gaseous fuel analysed, this pressure data is utilized by the control device 3 to control the engine control parameters of the engine 1 so as to adapt to the fuel properties of the gaseous fuel.

As discusses earlier, the fuel delivery line 4 may deliver only gaseous fuel, or a combination of gaseous fuel and air to be combusted together in both the analysing unit 2 and the internal combustion engine 1 .

Fig. 2 illustrates schematically an engine system according an alternative embodiment of the disclosure, differing from that of Fig. 1 by having the fuel delivery line 4a configured to deliver only gaseous fuel, while a separate air intake line 4b is delivering air for combustion for both the analysing unit 2 and the internal combustion engine 1 . It should be noted, that particularly the air received from the air intake line 4b by the internal combustion engine 1 may be further treated by, e.g. a charger and/ or a charge cooler.

Fig. 3 illustrates an engine system according to a further embodiment of the disclosure. The arrangement of Fig. 3 differs from that of Fig. 2 by having means for obtaining engine environment condition information 1 a. Suitably, such means comprise one or more conventional sensors of the internal combustion engine 1 coupled to the control device 3, as illustrated by the dashed line extending therebetween. Moreover, the analysing unit 2 comprises means for adjusting analysing unit environment conditions 2d, also coupled to the control device 3, as illustrated by a dashed line therebetween. Such an arrangement enables that the air provided form the air intake line 4b to the rapid compression machine 2a, via the means for adjusting analysing unit environment conditions 2d, may be adjusted so as to correspond to the air that is delivered to a cylinder of the internal combustion engine, even if air from the air intake line 4b is processed by the internal combustion engine prior to being delivered to the cylinder for combustion.

Fig. 4 illustrates an engine system according to yet another embodiment of the disclosure. Particularly, the arrangement of Fig. 4 differs from that of Fig. 2 in that the rapid compression machine is arranged in fluid communication with an air intake line 4b of the internal combustion engine 1 at a point downstream of any possible processing by the internal combustion engine (such as a charger and/or charge cooler). This arrangement provides the analysing unit 2 with air, for combustion with the gaseous fuel to be analysed, in a state corresponding to that of air being introduced to a cylinder of said engine.