WO2025257002A1

WO2025257002A1 - A mixing system for controlling the mixing of a first gas stream with a second gas stream

Info

Publication number: WO2025257002A1
Application number: PCT/EP2025/065591
Authority: WO
Inventors: Marco GIANCOTTI; Eugenio QUARTIERI; Leonardo CHESI; Tiziano ROMA; Giovanni Tonno
Original assignee: Nuovo Pignone Technologie SRL
Current assignee: Nuovo Pignone Technologie SRL
Priority date: 2024-06-10
Filing date: 2025-06-05
Publication date: 2025-12-18
Anticipated expiration: 2026-12-10

Abstract

The present disclosure relates to a mixing system (M2, M6) for controlling the mixing of a first gas stream with a second gas stream, said mixing system (M2, M6) comprising: a mixing line (23) for supplying a mixed stream of fuel for an engine at a predefined concentration range, said mixing line (23) being configured to mix said first gas stream with said second gas stream so as to obtain the mixed stream of fuel; a first feed line (11) being coupled to said mixing line (23) for supplying said first gas stream to said mixing line (23), said first gas stream comprising a first type of fuel gas; a second feed line (12) coupled to said mixing line (23) for supplying said second gas stream to said mixing line (23), said second gas stream comprising a second type of fuel gas that is different from the first type of fuel gas, the second type of fuel gas being selected from group of fuel gases which when mixed with the first type of fuel gas to form the mixed stream of fuel at the predefined concentration range of the second type of fuel gas, the heat content and/or energy content of the resulting mixed stream of fuel has a singularity across said predefined concentration range; and a damping system including: a flow control system (33) at said first feed line being configured to adjust the flow rate of the first gas stream so as to reach a reference composition value of said mixed stream, and a pressure control system (34) at said second feed line being configured to adjust the pressure of the second gas stream, so as to maintain the pressure at a reference pressure value.

Description

A mixing system for controlling the mixing of a first gas stream with a second gas stream

Description

TECHNICAL FIELD

[0001] The present disclosure concerns a mixing system for controlling the mixing of a first gas stream with a second gas stream.

[0002] The subject matter disclosed herein also refers to an engine comprising the mixing system for controlling the mixing of a first gas stream with a second gas stream.

[0003] The subject matter disclosed herein also refers to a method for controlling the mixing of a first gas stream with a second gas stream.

[0004] The subject matter disclosed herein also refers to a controller comprising a processor to execute the above method.

[0005] The subject matter disclosed herein also refers to a computer program product comprising one or more instructions that when executed by the processor, causes the processor to perform the above method.

BACKGROUND ART

[0006] Commonly used gas turbines provide systems for automated blending of hydrogen gas with traditional fuels, such as natural gas. Automatic systems for blending a hydrogen gas with natural gas aims at controlling real-time active flow of natural gas and real time active flow of hydrogen gas to produce a consistent stream of precision-blended flow. The control is performed by utilizing active real time feedback data and active real time feed-forward data and pre-set data to blend hydrogen gas with natural gas to produce a consistent stream of usable fuel.

[0007] Known systems for automatic blending of hydrogen and natural gas include systems configured to automatically adjust the hydrogen blend for variable flow and pressures present in an existing distribution system, varying hydrogen, and consequently natural gas flow rates to maintain a repeatable percentage of hydrogen without manual operation. Those systems include a plurality of pipe segments, a programmable controller, and a plurality of valves to automatically control flow of natural gas and active flow of hydrogen gas in the pipe segments. The rationale of controlling the flow into the pipes by means of valve controlled by a programmable controller is to blend the hydrogen gas with the natural gas at the consistent blend of natural gas to hydrogen gas to produce the consistent stream of usable fuel.

[0008] However, known systems for automatic blending are not configured to reach to a consistent stream of usable fuel for percentages of hydrogen gas to natural gas higher than 5-25% in volume, mainly because above these percentages there is a risk of impact on the existing infrastructures. Such a constraint prevents the usage of fuels with high content of hydrogen gas.

[0009] Other gas blending systems provide a tracer gas with a carrier gas for use in leak detection operations during blending of gas. The tracer gas and the carrier gas, such as helium and nitrogen, are blended using flow restrictive orifices in the flow lines for each gas. Such blending systems use a process controller for automatic adjustment of a control valve in the tracer gas flow line in response to variations in pressure, temperature, and flow in the flow lines, and orifice means that serve to choke the flow in said flow lines and prevent the turbine meters from being overrun and burned out.

[0010] The implementation of orifices for tracer and carrier gas is useful during initial pressurization when the system pressure is low and would result in a low back pressure and a high volumetric flow rate. In fact, said choking serves to allow a high mass flow rate to pertain without such a high volumetric flow rate. The use of the process controller in conjunction with such flow restricting orifices enhances the ability of the system to provide accurate blending of the components. Nevertheless, the orifices for tracer and carrier gas are alternative solutions that do not match the need to follow the dynamics of the stream of natural gas and hydrogen to continuously check and contrast the instability due to the perturbation of the system coming from dramatic amount of the content of hydrogen gas into the blending system.

[0011] It appears evident the need to overcome the above limitations to the existing systems for blending of hydrogen gas with traditional fuels in order to increase the potential of such systems and to blend fuels with increased amount of content of hydrogen.

[0012] Documents US 2023/357657, US 2014/043932 and US 2004/121201 are representative of the available art.

SUMMARY

[0013] Certain aspects commensurate in scope with the originally claimed disclosure are summarized below. These aspects are not intended to limit the scope of the claimed disclosure, but rather these aspects are intended only to provide a brief summary of possible forms of the disclosure. Indeed, the full disclosure may encompass a variety of forms that may be similar to or different from the aspects set forth below.

[0014] In one aspect, the subject matter disclosed herein is directed to a mixing system for controlling the mixing of a first gas stream with a second gas stream, said mixing system comprising: a mixing line for supplying a mixed stream of fuel for an engine at a predefined concentration range, said mixing line being configured to mix said first gas stream with said second gas stream so as to obtain the mixed stream of fuel; a first feed line being coupled to said mixing line for supplying said first gas stream to said mixing line, said first gas stream comprising a first type of fuel gas; a second feed line coupled to said mixing line for supplying said second gas stream to said mixing line, said second gas stream comprising a second type of fuel gas that is different from the first type of fuel gas, the second type of fuel gas being selected from group of fuel gases which when mixed with the first type of fuel gas to form the mixed stream of fuel at the predefined concentration range of the second type of fuel gas, the heat content and/or energy content of the resulting mixed stream of fuel has a singularity across said predefined concentration range; and a damping system including: a flow control system at said first feed line being configured to adjust the flow rate of the first gas stream so as to reach a reference composition value of said mixed stream, and a pressure control system at said second feed line being configured to adjust the pressure of the second gas stream, so as to maintain the pressure at a reference pressure value.

[0015] In one aspect, the subject matter disclosed herein is directed to an engine comprising: a combustion chamber; and a mixing system as provided above to supply the mixed stream of fuel to said combustion chamber. [0016] In a further aspect, the subject matter disclosed herein is directed to a computer- implemented method for controlling the mixing system as defined above, said method comprising: obtaining a flow rate of the mixed stream of fuel; obtaining a flow rate of the first gas stream; obtaining a reference composition value indicative of a percentage of the second type of fuel gas in said mixed stream of fuel; determining a gas flow adjustment to be applied to said flow control system to adjust the flow rate of the second gas stream so as to reach the reference composition value at said mixed stream, wherein said gas flow adjustment is determined based on said reference composition value, said flow rate of the mixed stream and said flow rate of the first gas stream; applying said gas flow adjustment to said flow control system to adjust the flow rate of the first gas stream; obtaining said pressure value; determining a pressure adjustment to be applied to said pressure control system to adjust the pressure of the second gas stream so as to maintain the pressure of the second gas stream at said reference pressure value; and applying said pressure adjustment to said pressure control system.

[0017] In a further aspect, the subject matter disclosed herein is directed to a controller comprising a processor for carrying out the above method.

[0018] In further aspect, the subject matter disclosed herein is directed to a computer program product comprising instructions which, when the program is executed by a processor, cause the processor to carry out the above method.

[0019] In further aspect, the subject matter disclosed herein is directed to a computer- readable medium having stored thereon the above computer program product.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a schematic view of a gas fuelling system for blending and distribution of a mixed stream of fuel to an engine, according to the prior art;

Fig. 2 is schematic view a mixing system, according to the prior art; Fig. 3 is a schematic view the mixing system Ml for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a first illustrative non-claimed arrangement;

Fig. 4 is a flowchart of a method for controlling the mixing system according to a first illustrative non-claimed arrangement;

Fig. 5 is a flowchart of a method for controlling the gas composition of the mixing system, according to a first illustrative non-claimed arrangement;

Fig. 6 shows a schematic view the mixing system for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a first embodiment of the present invention;

Fig. 7 is a flowchart of a method for controlling the flow rate of the first gas stream of the mixing system, according to a first embodiment of the present invention;

Fig. 8 is a flowchart of a method for controlling the pressure of the second gas stream the mixing system, according to a first embodiment of the present invention;

Fig. 9 is a schematic view the mixing system for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a second illustrative non-claimed arrangement;

Fig. 10 is a schematic view the mixing system for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a third illustrative nonclaimed arrangement;

Fig. 11 is a schematic view the mixing system for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a fourth illustrative non-claimed arrangement;

Fig. 12 is a schematic view the mixing system for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a second embodiment of the present invention; Fig. 13 is a schematic of the control logic unit of the mixing system provided in any one of Figs. 9-12;

Fig. 14 is a flowchart of a method for operating the control logic unit shown in Fig. 13;

Fig. 15 is graph of the flow rate at the first feed line of the mixing system in Fig. 2;

Fig. 16 is graph of the pressure at the mixing line of the mixing system in Fig. 2.

Fig. 17 is a graph of the Lower Heat Value (LHV) and the Modified Wobbe Index (MWI) of the mixed fuel across the 0-100 vol.-% hydrogen within a mixed stream of fuel comprising hydrogen and methane;

Fig. 18 is a graph of the ratio of the pressure loss of the mixed fuel stream at constant hydrocarbon (HC) level within the mixed stream of fuel. The ratio of the pressure loss is shown in the 0-100 vol.-% hydrogen within the mixed stream of fuel.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] The present disclosure concerns a mixing system for controlling the mixing of a first fuel gas stream with a second fuel gas stream.

[0022] Reference is now made to Fig. 1, which shows a schematic of a gas fuelling system for blending and distribution of a mixed stream of fuel to an engine, such as a gas turbine (GT). The gas fuelling system comprises a mixing system or “mixing skid”. The gas fuelling system further comprises a hydrogen (H2) storage, and is fed with a methane (CH4) source that is located separately from the mixing system. The mixing system is connected to the gas turbine side to provide the mixed stream of fuel to the combustion chamber of the engine. The layout shown in Fig. 1 is divided into different areas, namely the H2 Storage side and the Gas Turbine side, delineated by dashed lines for clarity.

[0023] In the H2 Storage side, the hydrogen is stored at a predefined pressure and is delivered to the mixing system. The methane source, supplies the natural gas at lower predefined pressure. Accordingly, the mixing system receives hydrogen and methane gas from their respective sources at a constant pressure.

[0024] The mixing system enables the controlled blending of hydrogen and methane. Fig. 2 shows a schematic view the mixing system, according to the prior art. The mixing system comprises a mixing line 23 for supplying a mixed stream of fuel to an engine. The mixing system further comprises a first feed line 11 that is coupled to the mixing line 23 for supplying the first gas stream to the mixing line 23 and a second feed line 12 also coupled to the mixing line 23 for supplying the second gas stream to the mixing line 23. The mixing system performs real time-controlled blend of the hydrogen and methane stream. The blended fuel mixture is then directed towards the GT side.

[0025] The mixing system is conventionally equipped with a flow control system configured to adjust the flow rate of the second gas stream. This regulation is carried out by a controller 28 which obtains a flow rate of the mixed stream of fuel, obtains a flow rate of the second gas stream and determines a gas flow adjustment to be applied at the valve to adjust the flow rate of the second gas stream so as to reach a reference composition value at the mixed stream.

[0026] A gas fuelling system of an engine capable to digest NG/H2 blends in the range 0-100 vol.-% hydrogen can become unstable in certain conditions, for example, when moving from lower to 80 vol.-% hydrogen content in the mixed stream of fuel. This may have the consequence of tripping the engine.

[0027] Reference is now made to Fig. 3, which shows a schematic view of the mixing system Ml for controlling the mixing of a first fuel gas stream with a second fuel gas stream. The mixing system Ml allows to perform a real time-controlled blend of a first gas stream with a second gas stream.

[0028] The mixing system Ml comprises a mixing line 23 for supplying a mixed stream of fuel at a predefined concentration range. The mixing line 23 is configured to mix/blend the first gas stream with the second gas stream so as to obtain the mixed stream of fuel. The mixed stream of fuel can be supplied to a combustion chamber of an engine for efficient and effective operation of the engine. [0029] The mixing system Ml further comprises a first feed line 11 that is coupled to the mixing line 23 for supplying the first gas stream to the mixing line 23 and a second feed line 12 coupled to the mixing line 23 for supplying the second gas stream to the mixing line 23. The first feed line 11 and the second feed line 12 can be coupled to the mixing line 23 by means of a piping's fitting, such as for example a tee, designed for interconnecting sections of feed lines (pipes) 11, 12 to direct the fluid into the mixing line 23, whereby the mixing occurs.

[0030] The first gas stream comprises a first type of fuel gas. For example, the first gas stream can be a natural gas stream, comprising at least one of the following natural gases, such as methane (CF ), ethane (C2H6), propane (CsHs), butane (C4H10), and pentane (C5H12).

[0031] The second gas stream comprises a second type of fuel gas that is different from the first type of fuel gas. For example, the second gas stream may comprise at least one of hydrogen (Ft) and ammonia (NFL).

[0032] In one example, the second gas stream may comprise hydrogen, which has a high energy content compared to other fuel and is a more environmentally friendly option because during combustion the hydrogen produces water vapor and releases no carbon dioxide.

[0033] In another example, the second type of fuel may be a gas mixture, for example a mixture that comprises hydrogen and ammonia in a predefined ratio, such as a mixture that leverages the reactive properties of hydrogen.

[0034] In general, the second type of fuel gas is selected from group of fuel gases which when mixed with the first type of fuel gas to form the mixed stream of fuel at the predefined concentration range of the second type of fuel gas, the heat content and/or energy content of the resulting mixed stream of fuel has a singularity across the predefined concentration range.

[0035] The singularity can be, for example, a local peak (i.e. a local maximum) or a local trough (i.e. a local minimum) within the predefined concentration range. The singularity may be a sudden change of the heat content and/or energy content function within the predefined concentration range, such as a change in the steepness or slope of the function. The sudden change can be found using a first derivative of a function which represents the rate of change of the heat content and/or energy content function at any given point. Differentiating the function at various points provides insights into local maxima, minima, and points of inflection, helping to analyse the heat content and/or energy content function’s behaviour.

[0036] The inventors have observed an unexpected issue associated with the presence of a singularity within the predefined concentration range. In fact, the presence of a singularity within the predefined concentration range results into fluctuations, such as a pulsation disturbance, associated with at least one parameter (pressure and/or flow rate) of the mixed stream. Fluctuations of the pressure and/or flow rate of the mixed stream may lead to unacceptable levels of combustion dynamics at the engine resulting in hardware distress, reduced component life of the engine and a consequent risk of failure of the engine.

[0037] Figs. 15 and 16 shows the result of a test carried on using a conventional mixing skid, such as the mixing system shown in Fig. 2. In this case the mixing line supplies the mixed stream of fuel for an engine at a predefined concentration range by mixing the first gas stream comprising methane with a second gas stream comprising hydrogen so as to obtain the mixed stream of fuel of CH4/H2.

[0038] The test was done stepping-up the hydrogen content from 78 vol.-% to 80+ vol.-% hydrogen. After the initial perturbation, the pressure of the mixed stream started to diverge showing instability in both the model and the real mixing system.

[0039] Fig. 15 shows the flow rate at the first feed line. The flow rate exhibits a train of pulsation at this concentration ranges, mainly due to the flowing back of hydrogen, supplied at higher pressure with respect to the methane stream, into the first feed line.

[0040] Fig. 16 shows the pressure of mixed stream of fuel at the mixing line. The pressure exhibits a train of pulsation at this concentration ranges leading to unacceptable levels of combustion dynamics at the engine. Also, in this case the model of the system matches the real mixing system data thus replicating the phenomenon at these concentration ranges.

[0041] The selection criteria for the second type of fuel gas can otherwise be expressed using a parameter called Modified Wobbe Index (MWI), which is used as a standard for setting a fuel gas composition and represents a measure of the interchangeability of gaseous fuels for a given system design. For example, if an engine requires a certain heat flow as input to run, all the blended/mixed fuel streams having the same MWI are capable to make the engine running and delivering the same power as output. Thus, the MWI facilitates the comparative assessment of heat content and/or energy content of the resulting mixed stream using different fuel gases across differing temperatures as it defines the heat/energy content of a fuel stream. The MWI can be calculated using the following equation:

MWI=LHV / sqrt(SG x T[gas])

[0042] where T[gas] is the absolute temperature of the fuel gas in degrees Rankine, SG is the specific gravity of fuel gas relative to air, T represents gas fuel temperature in degrees absolute and LHV is the fuel Lower Heating Value.

[0043] Accordingly, the second type of fuel gas can be selected from group of fuel gases which when mixed with the first type of fuel gas to form the mixed stream of fuel at the predefined concentration range of the second type of fuel gas, the MWI of the resulting mixed stream of fuel shows a singularity across the predefined concentration range.

[0044] Again, the singularity can be, for example, a local peak (i.e. a local maximum) or a local trough (i.e. a local minimum) within the predefined concentration range. The singularity may be a sudden change of the MWI function within the predefined concentration range, such as a change in the steepness or slope of the MWI function, which can be identified using the derivative first of the MWI function.

[0045] Accordingly, the selection of the second type of fuel gas may comprise obtaining an MWI function, analysing the MWI function to determine a singularity within the predefined concentration range and in response to determining a singularity, selecting the fuel gas as the second type of fuel.

[0046] In one example, the first type of fuel gas may comprise methane and the second type of fuel gas can be selected as comprising hydrogen. For example, the mixing system may be configured for supplying a mixed stream of fuel at the predefined concentration range of 80-99 vol.-% hydrogen. At this concentration range the energy content of the mixed stream of fuel comprising hydrogen and methane shows a local peak which result into fluctuation of the pressure or flow rate of the mixed stream and thus unacceptable levels of combustion dynamics at the engine.

[0047] In fact, it has been experienced that when fuelling an engine, such as a gas turbine with such mixtures/compositions at a constant heating content, since either the MWI or the energy content has a singularity within the above range, without a proper design of the mixing system both flow and pressure may become unstable and pulsation/fluctuation may start to appear on the piping, leading to machinery trip.

[0048] It is evident however that the present invention should not be considered limited to the specific composition of the mixed stream of fluid mentioned in the example above as well as the predefined concentration range provided in the example. In fact, the indicated concentration range is specific for a mixed stream of fuel comprising hydrogen and methane, other fuels’ blends will present a singularity within the same or different concentration range.

[0049] Reference is made to Fig. 17 which shows a graph of the Lower Heat Value and the MWI of the mixed fuel across the 0-100 vol.-% hydrogen within the mixed stream of fuel. In the graph, the MWI shows a singularity within the concentration range of 80-99 vol.-% hydrogen.

[0050] In this case the singularity is a local minimum (local trough) which corresponds to a local maximum (local peak) within the energy content of the mixed fuel stream, due to its inverse relationship with the MWI. The energy content can be defined as E=yd^/2 whereby p represents the density of the fluid, typically measured in kilograms per cubic meter (kg/m³) and V denotes the velocity of the fluid, typically measured in meters per second (m/s).

[0051] Fig. 18 shows a graph of the ratio of the pressure loss of the mixed fuel stream at constant hydrocarbon (HC) level. As will be appreciated, increasing vol.-% hydrogen in the mixing solution results in an increase of head losses and a corresponding increase of the total pressure of the fluid stream, up to reaching respective maximums in correspondence to the local maximum of the energy content of the mixed fuel stream. [0052] Reducing head losses and thus the total pressure in order to overcome the respective increase of head losses as well as the increase of total pressure, leaves room for an instantaneous increase of the natural gas fluid flow. However, in conventional system such as the one shown in Fig. 2, the hydrogen flow control reacts by adding more hydrogen to correct the blend entering into a loop, with fluctuations of natural gas flow and pressure of the mixed fuel stream, making conventional solution unstable at this concentration range.

[0053] In general, this physical phenomenon is strongly related to the energy content fluctuations of the mixed fuel stream over 80 vol.-% hydrogen content, which are present at all pressure and loads. Same phenomenon can also happen when decreasing the vol.-% of hydrogen in the mixing solution from 100 vol.-% of hydrogen, with or without passing through the singularity, in which case the presence of the phenomenon is likely related to the presence of a huge slope of the MWI vs the low hydrogen blends side.

[0054] To reduce pulsation/fluctuations associated with the mixed stream during mixing of the first gas stream with the second gas stream, the mixing system Ml further comprises a damping system comprising a pressure drop system 13 at the first feed line 11 as shown in Fig. 3.

[0055] The pressure drop system 13 is configured to adjust a first parameter of the first gas stream, wherein the first parameter is a pressure, so as to maintain a differential pressure value across the pressure drop system 13 at a reference pressure drop value. This adjustment reduces pulsation/fluctuations associated with the mixed stream during mixing of the first gas stream with the second gas stream.

[0056] The pressure drop system 13 introduces a head loss on the first gas stream which in turn provides a flow damping effect on the mixing line 23. Accordingly, the pressure drop system 13 solves the issue of fluid dynamic instability at predefined concentration range of the second type of fuel gas when mixing the first gas stream comprising a first type of fuel gas with a second gas stream comprising the second type of fuel gas, such as for example at a concentration range of 80-99 vol.-% hydrogen in a mixed stream of fluid comprising hydrogen and methane. This adjustment avoids flow and/or pressure fluctuation at the mixing line 23 and thus reduces the fluid dynamic instability when fuelling an engine, such as a gas turbine, allowing the end user to manage all type of fuel blends that exhibit fluid dynamic instability.

[0057] The pressure drop system 13 may comprises one or more of a variable orifice valve or a pressure control valve. For example, the pressure drop system 13 may comprise a pressure differential control valve (PDCV) which controls the flow of a fluid by maintaining a pressure differential across the valve at the reference pressure drop value.

[0058] The reference pressure drop value may be a predefined pressure value, such as for example a value of 1 bar or more generally a value above or equal 0.2 bar. However, it is evident that the predefined pressure value may be different than these values/ranges and therefore the invention should not be limited to the specific values/ranges provided herein.

[0059] In another variant, the pressure drop value may be a value obtained by gradually adjusting the pressure drop system 13 until a reference pressure drop value that reduces pulsation/fluctuation associated with the mixed stream during mixing of the first gas stream with the second gas stream is achieved.

[0060] The pressure drop system 13 may comprise a first controller 17 configured to obtain the differential pressure value from the at least one pressure meter 15 of the mixing system Ml. The pressure meter 15 is configured to measure a differential pressure value of the first parameter of the first gas stream across the pressure drop system 13 and control the pressure drop system 13 to maintain the differential pressure value at the reference pressure drop value.

[0061] For example, the first controller 17 may be configured to control the pressure drop system 13 so as to gradually adjust the first parameter of the first gas stream until an optimal differential pressure value that reduces pulsation of the mixed gas stream is achieved. The optimal differential pressure value will be the reference pressure drop value. In this example, the pulsation of the mixed gas stream may be monitored using a flow meter 27 or pressure meter at the mixing line 23.

[0062] Fig. 4 provides a flowchart of a method 100 for controlling the mixing system Ml. The method 100 comprises step 101 in which the pressure drop system 13 obtains the differential pressure value. At step 102 the pressure drop system 13 adjusts the pressure of the first gas stream to maintain the differential pressure value across the pressure drop system 13 at a reference pressure drop value, thus reducing pulsation associated with the mixed stream during mixing of the first gas stream with the second gas stream.

[0063] The method 100 may be implemented at a computer, for example at step 101, the first controller 17 obtains the differential pressure value from the at least one pressure meter 15. At step 102 the first controller 17 controls the pressure drop system 13 to maintain the differential pressure value at the reference pressure drop value.

[0064] The first controller 17 may comprise a processor for carrying out the method 100. The processor may be a processor suitable for the execution of a computer program product including, by way of example, both general and special purpose microprocessor(s), and/or any one or more processors of any kind of digital computer. Generally, the processor will receive instructions and data from a read only memory (ROM), or a random-access memory (RAM), or an external memory or any combination thereof and executes the instruction to carry out the method described with reference to Fig. 4. The instructions may be part of a program product which can be stored on a computer-readable medium, such as a memory or storage internal or external to the first controller 17, such as a remote server.

[0065] With continuous reference to Fig. 3, the mixing system Ml further comprises a flow control system 14 at the second feed line 12. The flow control system 14 is configured to adjust a second parameter of the second gas stream, wherein the second parameter is a flow rate.

[0066] The mixing system Ml may also comprise a second controller 18 for carrying out the method 200 of controlling the mixing system Ml as shown in Fig. 5. The second controller 18 may be the same or a different controller with respect to the first controller 17 in Fig. 3. However, since the controllers operate on independent variables the control loops may be decoupled.

[0067] The second controller 18 may be configured to obtain at step 201 a flow rate of the mixed stream of fuel, obtain at step 202 a flow rate of the second gas stream, obtain at step 203 a reference composition value indicative of a percentage of the second type of fuel gas in the mixed stream of fuel, and determine at step 204 a gas flow adjustment to be applied to the flow control system 14 to adjust the flow rate of the second gas stream so as to reach the reference composition value at the mixed stream. The gas flow adjustment can be determined based on the reference composition value (the blending percentage), the flow rate of the mixed stream and the flow rate of the second gas stream. At step 205 the second controller applies the gas flow adjustment to the flow control system 14 to adjust the flow rate of the second gas stream.

[0068] The flow rate of the mixed fuel stream and the flow rate of the second gas stream can be measured using respective flow sensors, such as a first flow sensor 25 at the mixing line 23 and a second flow sensor 26 at the second feed line 12.

[0069] For example, the flow control system 14 may be regulated to rise the calculated flow of hydrogen. The regulation may be based on a formula that considers molecular weight of hydrogen, methane and mixed stream of fuel to give as output the expected value to be read by the flow meter 26 on the second feed line 12. Same considerations can be made with respect to other combination of fuels.

[0070] Alternatively, the gas flow adjustment to be applied to the flow control system 14 may be determined manually by an operator.

[0071] With continuous reference to Fig. 3, the mixing system Ml may also comprise a check valve 27 configured to avoid the back flow of the second gas stream into the first feed line 11 when the second gas stream, such as the hydrogen, is provided at higher pressure with respect to the first gas stream. The check valve 27 enhances the overall safety and security of the mixing system 1. However, it will be evident that for different gas compositions the check valve may be applied to the second feed line, for example, when the second gas stream is provided at a lower pressure with respect to the first gas stream.

[0072] Although not shown in Fig. 3, the flow control system 14 may comprises a first flow control device 14-1 disposed within the second feed line 12 and one or more second flow control devices 14-2, each of which is disposed within a respective parallel line of the mixing system Ml that interconnects with the first input and the first output of the first flow control device 14-1. The parallel configuration allows to extend the flow range of the second gas stream applicable at the second feed line 12.

[0073] The parallel configuration may be useful for example in the case in which design condition exceeds the physical properties of the flow control device (e.g. a valve). In other cases, the pressure value of the second gas stream and expected flow rate may be used as design constrains for an engineer to proper dimension the flow control device to withstand the applied flow conditions.

[0074] Similarly, although not shown in Fig. 3, the pressure drop system 13 may comprise a first damping device 13-1 disposed within the first feed line 11 and one or more second damping devices 13-2, each of which is disposed within a respective parallel line of the mixing system Ml that interconnects with the first input and the first output of the first damping device 13-1. Also, in this case, the parallel configuration allows to extend the flow range of the first gas stream applicable at the first feed line 11.

[0075] Nonetheless, in the case of a parallel configuration, split range control may be used to manage the plurality of flow control devices.

[0076] Further, although not shown in Fig. 3, the mixing system Ml may comprise one or more further feed lines coupled to the mixing line 23 for supplying one or more additional gas stream to the mixing line 23, each one of the additional gas streams comprising another type of fuel gas.

[0077] With continuous reference to Fig. 3, Fig. 6 shows a schematic view the mixing system M2 for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a first embodiment of the present invention. The same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig. 3 and described above, and which will not be described again.

[0078] The embodiment shown in Fig. 6 differs from the arrangement of Fig. 3 in that it comprises a different arrangement for removing pulsation/fluctuations associated with the mixed stream during mixing of the first gas stream with the second gas stream.

[0079] The embodiment shown in Fig. 6 differs from the arrangement of Fig. 3 in that it provides a flow control system 33 at the first feed line 11 being configured to adjust the flow rate of the first gas stream so as to reach a reference composition value of the mixed stream.

[0080] The mixing system M2 may further comprise a first controller 37 configured to control the flow control system 33. The first controller 37 may be configured to carry out the method 300 provided in Fig. 7.

[0081] At step 301 of the method 300 the first controller 37 obtains a flow rate of the mixed stream of fuel. For example, the first controller 37 may obtain the flow rate from at least one flow meter 45 configured for measuring a flow rate of the mixed stream of fuel at the mixing line 23.

[0082] At step 302 the first controller 37 obtains a flow rate of the first gas stream. For example, first controller 37 may obtain the flow rate from at least one first flow meter 35 configured to measure a flow rate of the first gas stream. The flow meter 35 may be located upstream the flow control system 33 or downstream the flow control system 33, as for example shown in the Fig. 6.

[0083] At step 303 the first controller 37 obtains a reference composition value indicative of a percentage of the second type of fuel gas in the mixed stream of fuel. Finally, at step 304 the first controller 37 determines a gas flow adjustment to be applied to the flow control system 33 to adjust the flow rate of the second gas stream so as to reach the reference composition value at the mixed stream. At this point, the gas flow adjustment may be determined, for example, based on the reference composition value, the flow rate of the mixed stream and the flow rate of the first gas stream.

[0084] Once the gas flow adjustment is determined, the first controller 37 proceeds to step 305 in which the gas flow adjustment is applied to the flow control system 33 to adjust the flow rate of the first gas stream.

[0085] The embodiment shown in Fig. 6 further differs from the arrangement of Fig. 3 in that it comprises a pressure control system 34 at the second feed line being configured to adjust the pressure of the second gas stream so as to maintain the pressure at a reference pressure value.

[0086] The mixing system M2 may further comprise a pressure meter 36 for measuring a pressure value of the second gas stream at the second feed line 12 and a second controller 38 configured to control the pressure control system 34.

[0087] The second controller 38 may be configured to carry out the method 400 provided in Fig. 8. At step 401 the second controller 38 obtains the pressure value. At step 402 the second controller 38 determines a pressure adjustment to be applied to the pressure control system 34 to adjust the pressure of the second gas stream so as to maintain the pressure of the second gas stream at the reference pressure value. Finally, at step 403 the second controller 38 applies the pressure adjustment to the pressure control system 34.

[0088] The method 300 and the method 400 herein described may be computer implemented methods. For example, the first controller 37 and/or the second controller 38 may comprise a processor for carrying out the respective methods 300, 400. The processor may be a processor suitable for the execution of a computer program product including, by way of example, both general and special purpose microprocessor(s), and/or any one or more processors of any kind of digital computer. Generally, the processor will receive instructions and data from a read only memory (ROM), or a random-access memory (RAM), or an external memory or any combination thereof and execute the instruction to carry out the methods 300, 400. The instructions may be part of a program product which can be stored on a computer-readable medium, such as a memory or storage internal or external to the controllers 37, 38, such as a remote server. Although shown as separate units in Fig. 6, the first controller 37 and the second controller 38 can be the same unit or different units.

[0089] The flow control system 33 on the first feed line and the pressure control system 34 on the second feed line provide a flow damping effect on the mixing line 23. The flow control system 33 and pressure control system 34 solve the issue of fluid dynamic instability at predefined concentration range of the second type of fuel gas when mixing the first gas stream comprising a first type of fuel gas with a second gas stream comprising the second type of fuel gas. This avoids pressure and consequently mass flow oscillation/fluctuation at the mixing line 23 thus reducing fluid dynamic instability when fuelling an engine and allowing the end user to manage all type of fuel blends that exhibit fluid dynamic instability. Accordingly, in Fig. 6 the damping system includes one or more of the gas control systems 33, 34. [0090] As will be appreciated in Fig. 6 the second feed line 12 does not comprise a flow control system. Accordingly, the mixing system M2, M6 provides a flow damping effect without the flow control system at the second feed line 12. Similarly, the first feed line 11 does not comprise a pressure control system, therefore the mixing system M2, M6 provides a flow damping effect without the pressure control system at the second feed line 12. In other words, the flow control system 33 is located only on the first feed line, where it adjusts the flow rate of the first gas stream to achieve the reference composition, and the pressure control system 34 is located only on the second feed line to maintain the pressure of the second gas stream at the reference pressure value.

[0091] Although not shown in Fig. 6, the mixing system M2 may further comprise a further pressure control system at the mixing line 23 being configured to adjust the pressure of the mixing line 23, so as to maintain the pressure of the mixed stream at a reference pressure value associated with the mixed stream.

[0092] In Fig. 6, the flow control system 33 may comprise a first flow control device 33-1 disposed within the first feed line 11 and one or more second flow control devices 33-2, each of which is disposed within a respective parallel line of the mixing system M2 that interconnects with the first input and the first output of the first flow control device 33-1. The parallel configuration allows to extend the flow range of the first gas stream applicable at the first feed line 11.

[0093] Similarly, although not shown in Fig. 6, the pressure control system 34 may comprise a first pressure control device disposed within the second feed line 12 and one or more second pressure control devices, each of which is disposed within a respective parallel line of the mixing system M2 that interconnects with the first input and the first output of the first pressure control device.

[0094] With continuous reference to Fig. 3, Fig. 9 shows a schematic view the mixing system M3 for controlling the mixing of a first fuel gas stream with a second fuel gas stream. The same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig. 3 and described above, and which will not be described again.

[0095] The arrangement shown in Fig. 9 differs from the arrangement of Fig. 3 in that it shows a first parallel configuration at the first feed line 11 so as to extend the flow range of the first gas stream. Specifically, the pressure drop system 13 comprises a first damping device 13-1 disposed within the first feed line 11 and a second damping devices 13-2 disposed within a respective parallel line of the mixing system M3 that interconnects with the first input and the first output of the first damping device 13-1.

[0096] The arrangement shown in Fig. 9 further differs from the arrangement of Fig. 3 in that in that it shows a second parallel configuration at the second feed line 12. Specifically, the flow control system 14 comprises a first flow control device 14-1 disposed within the second feed line 12 and a second flow control device 14-2 disposed within a respective parallel line of the mixing system M3 that interconnects with the first input and the first output of the first flow control device 14-1.

[0097] It is evident however that the present invention should not be considered limited to the use of parallel configurations as provided in Fig. 9, in fact the mixing system M3 may not comprise a parallel configuration. For example, Fig. 10 which shows a schematic view the mixing system M4 for controlling the mixing of a first fuel gas stream with a second fuel gas stream does not provide a parallel configuration. Moreover, in other variants, the mixing system M3 may comprise a different parallel configuration with a different number of additional flow control devices 14-2 and/or damping devices 13-1, each of which is disposed within a respective parallel line of the mixing system M3.

[0098] The arrangement shown in Fig. 9 differs from the arrangement of Fig. 3 in that the mixing system M3 comprises a control logic unit 51 being configured to perform the method 500 described with reference to Fig. 14. As such the control logic unit 51 acts as a disturbance frequency tuner so as to cancel or reduce the pulsation disturbance at the mixing line 23. Although shown as separate units in the figures, the control logic unit 51, the first controller 17 and the second controller 18 can be the same unit or different units.

[0099] In particular, according to the method 500 the control logic unit 51 is configured to perform step 501 in which it obtains at least one cancellation signal for controlling at least one gas control system of the pressure drop system 13 and the flow control system 14. The cancellation signal allows to counter a pulsation disturbance associated with at least one monitored parameter, such as flow rate or pressure pulsation, of the mixed stream.

[0100] At step 502 the control logic unit 51 provides the at least one cancellation signal to the at least one controller to control the respective gas control system based on the at least one cancellation signal so as to cancel or reduce the pulsation disturbance at the mixing line 23.

[0101] For example, in Fig. 9 the control logic unit 51 provides the at least one cancellation signal to the second controller 18 which determines gas flow adjustment to be applied to the flow control system 14 to adjust the flow rate of the second gas stream based on at least the cancellation signal received from the control logic unit 51.

[0102] It is evident however that in other configurations, the control logic unit 51 may provide the signal to a first controller 17 so as to determine a gas pressure adjustment to be applied by pressure drop system 13 to adjust the pressure of the first gas stream based on the at least one cancellation signal, as shown for example in Fig. 10. In this case, pressure drop system 13 may be configured to combine the pressure adjustment performed to maintain the differential pressure value across the pressure drop system 13 at a reference pressure drop value with the pressure adjustment based on the cancellation signal.

[0103] By providing a mixing system M3 which combines the pressure adjustment performed to maintain the differential pressure value across the pressure drop system 13 at a reference pressure drop value with the pressure adjustment based on the cancellation signal, it is possible to ensure increased reliability of the system in controlling the blend of a first gas stream with a second gas stream. This advantage can be observed during a transient due to a sudden change of blend, such as in response to a blend change request for the mixed stream.

[0104] The at least one cancellation signal may be a phase-inverted signal relative to the pulsation disturbance which may have a period equal to that of the pulsation disturbance. For example, the at least one cancellation signal may exhibit a phase shift of 180 degrees relative to the pulsation disturbance and may be configured to maintain a period substantially equal to that of the pulsation disturbance, thereby enabling temporal alignment with the pulsation disturbance. In this manner, when the cancellation signal and the pulsation disturbance are superimposed, noise reduction is achieved through destructive interference. However, it is evident that the cancellation signal may not correspond exactly to the inverted pulsation disturbance, but rather, may exhibit approximate similarity thereto, which are sufficient to perform reduction of the pulsation disturbance at the mixing line 23.

[0105] With continuous reference to Fig. 3, Fig. 9 and Fig. 10; Fig. 11 shows a schematic view the mixing system M5 for controlling the mixing of a first fuel gas stream with a second fuel gas stream. The same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig. 3, Fig. 9 and Fig. 10 and described above, and which will not be described again.

[0106] The arrangement shown in Fig. 11 differs from the arrangement of Fig. 10 in that it shows different configuration for controlling the respective gas control system.

[0107] For example, in a first configuration, the control logic unit 51 provides the at least one cancellation signal to the first controller 17 which determines the gas pressure adjustment to be applied by pressure drop system 13 to adjust the pressure of the first gas stream based on the at least one cancellation signal.

[0108] In a second configuration, the control logic unit 51 provides the at least one cancellation signal to the second controller 18 which determines a gas flow adjustment to be applied to the flow control system 14 to adjust the flow rate of the second gas stream based on at least the cancellation signal received from the control logic unit 51. In this case the cancellation signal is indicative of the flow adjustment to be applied.

[0109] In a third configuration, the control logic unit 51 provides the at least one cancellation signal to the third controller 19 which determines the mixed stream pressure adjustment to be applied to control the operation of the at least one pressure valve 49 at the mixing line 23 based on the at least one cancellation signal.

[0110] It is evident however that although the different configuration for controlling the respective gas control system are described herein separately, one of more of these configurations can be combined together, such as for example in the mixing system M5 of Fig. 11.

[OHl] In general, the control logic unit 51 provides the at least one cancellation signal to at least one control unit so as to control the respective gas control system based on the at least one cancellation signal thus cancelling or reducing the pulsation disturbance at the mixing line 23. Moreover, although shown as separate control units in the figures, the control logic unit 51, the first controller 17, the second controller 18 and the third controller 19 can be the same unit or different control units.

[0112] With continuous reference to Fig. 6, Fig. 12 shows a schematic view the mixing system M6 for controlling the mixing of a first fuel gas stream with a second fuel gas stream, according to a second embodiment of the present invention. The same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig. 6 and described above, and which will not be described again.

[0113] The embodiment shown in Fig. 12 differs from the embodiment of Fig. 6 in that the mixing system M6 comprises a control logic unit 51 being configured to perform the method 500 described with reference to Fig. 14. As such the control logic unit 51 acts as a disturbance frequency tuner so as to cancel or reduce the pulsation disturbance at the mixing line 23. Although shown as separate units in the figures, the control logic unit 51, the first controller 37 and the second controller 38 can be the same unit or different units.

[0114] In particular, according to the method 500 the control logic unit 51 is configured to perform step 501 in which it obtains at least one cancellation signal for controlling at least one gas control system of the pressure control system 34 and the flow control system 33 to counter a pulsation disturbance associated with at least one monitored parameter of the mixed stream.

[0115] Moreover, at step 502, the control logic unit 51 is configured to provide the at least one cancellation signal to at least one controller to control the respective gas control system based on the at least one cancellation signal so as to cancel or reduce the pulsation disturbance at the mixing line 23.

[0116] For example, in Fig. 12 the control logic unit 51 provides the at least one cancellation signal to the second controller 38 which determines gas pressure adjustment to be applied to the pressure control system 34 to adjust the pressure of the second gas stream based on at least the cancellation signal received from the control logic unit 51. [0117] It is evident however that in other configurations, the control logic unit 51 may provide the signal to the first controller 37 so as to determine a gas flow adjustment to be applied by the flow control system 33 to adjust the flow rate of the first gas stream based on the at least one cancellation signal, for example, by combining the flow adjustment to reach a reference composition value of the mixed stream with the flow adjustment based on the cancellation signal.

[0118] By providing a mixing system M6 which combines the flow adjustment to reach a reference composition value of the mixed stream with the flow adjustment based on the cancellation signal, it is possible to ensure increased reliability of the system in controlling the blend of a first gas stream with a second gas stream.

[0119] Reference is now made to Fig. 13 which provides a schematic of the control logic unit 51. As provided in Fig. 13 there are shown three different configurations for the control logic unit 51 to obtain the at least one cancellation signal that counter a pulsation disturbance at the mixing line 23.

[0120] In a first configuration, the control logic unit 51 operates using a static offline design. Specifically, in this configuration the control logic unit 51 is configured to acquire at least one characteristic of the pulsation disturbance from a data storage, and determine the cancellation signal based on the at least one characteristic between the frequency or the period of the pulsation disturbance.

[0121] In a second configuration, the operator may intervene manually through an input interface of the mixing system configured to receive user input, such as the frequency and/or the period of the at least one control signal. Accordingly, the control logic unit 51 generates a control signal in response to the user input.

[0122] Finally, in the third configuration, the control logic unit 51 operates automatically. Specifically, the control logic unit 51 is configured to determine the frequency/period of the pulsation disturbance associated with the monitored parameter; and calculate the at least one cancellation signal based on the determined frequency/period of the pulsation disturbance.

[0123] The parameters may be monitored using one or more meters of the mixing system for measuring the monitored parameter of the mixed stream and/or the flow rate of the first gas stream. For example, the mixing system may comprise at least one of a pressure meter 47, a flow meter 45, and a flow meter 53 as shown in Fig. 9-13.

[0124] Once the cancellation signal has been obtained/determined, the control logic unit 51 provides the at least one cancellation signal to at least one controller to control the respective gas control system based on the at least one cancellation signal. At this point the cancellation signal can be combined with the controlling signal from the pressure/flow regulation loop as shown in Fig. 9-12 or may be provided alone to the respective control valve so as to cancel or reduce the pulsation disturbance at the mixing line 23 by operating the respective control valve.

[0125] In other words, the control logic unit 51 introduces a control feedback to the at least one controller in order to provide a flow damping effect on the mixing line 23, thus reducing fluid dynamic instability at a predefined concentration range of the second type of fuel gas when mixing the first gas stream comprising a first type of fuel gas with a second gas stream comprising the second type of fuel gas.

[0126] A first advantage of the present disclosure is to solve the issue of fluid dynamic instability at predefined concentration range of the second type of fuel gas when mixing the first gas stream comprising a first type of fuel gas with a second gas stream comprising the second type of fuel gas, such as for example at a concentration range of 80-99 vol.-% hydrogen in a mixed stream of fluid comprising hydrogen and methane.

[0127] The invention solves this issue by implementing at least one gas control system configured to adjust at least one gas stream parameter of the first gas stream and/or the second gas stream to reduce pulsation/fluctuation associated with the mixed stream during mixing of the first gas stream with the second gas stream.

[0128] A second advantage is that the present solution is capable to avoid flow and/or pressure fluctuation and thus fluid dynamic instability when fuelling an engine, such as a gas turbine, allowing the end user to manage all type of fuel blends that exhibit fluid dynamic instability both in terms of power/load.

[0129] A third advantage is that the present solution ensures full reliability of the fuelling system and provides a reliable, performant and versatile engine that can operate across various concentration ranges of fuel blends, without limiting opportunities to lower CO2 emissions.

[0130] A fourth advantage is that the with the present solution it is possible to reduce the number of potential trips. Accordingly, the engine implementing the present solution is more robust, and requires less maintenance (e.g., for Pressure Safety Valve (PSV) reset, vibrations induced fatigue failures, etc...) which in turn extends both machinery and the mixing systems life.

[0131] While aspects of the invention have been described in terms of various specific embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without departing form the spirit and scope of the claims. In addition, unless specified otherwise herein, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments.

[0132] The subject matter described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structural means disclosed in this specification and structural equivalents thereof, or in combinations of them. The subject matter described herein can be implemented as one or more computer program products, such as one or more computer programs tangibly embodied in an information carrier (e.g., in a machine-readable storage device), or embodied in a propagated signal, for execution by, or to control the operation of, data processing apparatus (e.g., a programmable processor, a computer, or multiple computers). A computer program (also known as a program, software, software application, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file. A program can be stored in a portion of a file that holds other programs or data, in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, subprograms, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network. [0133] The processes and logic flows described in this specification, including the method steps of the subject matter described herein, can be performed by one or more programmable processors executing one or more computer programs to perform functions of the subject matter described herein by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus of the subject matter described herein can be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0134] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processor of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random-access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magnetooptical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, (e.g., EPROM, EEPROM, and flash memory devices); magnetic disks, (e.g., internal hard disks or removable disks); magnetooptical disks; and optical disks (e.g., CD and DVD disks). The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0135] To provide for interaction with a user, the subject matter described herein can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, (e.g., a mouse or a trackball), by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well. For example, feedback provided to the user can be any form of sensory feedback, (e.g., visual feedback, auditory feedback, or tactile feedback), and input from the user can be received in any form, including acoustic, speech, or tactile input. [0136] The techniques described herein can be implemented using one or more modules. As used herein, the term “module” refers to computing software, firmware, hardware, and/or various combinations thereof. At a minimum, however, modules are not to be interpreted as software that is not implemented on hardware, firmware, or recorded on a non-transitory processor readable recordable storage medium (i.e., modules are not software per se). Indeed “module” is to be interpreted to always include at least some physical, non-transitory hardware such as a part of a processor or computer. Two different modules can share the same physical hardware (e.g., two different modules can use the same processor and network interface). The modules described herein can be combined, integrated, separated, and/or duplicated to support various applications. Also, a function described herein as being performed at a particular module can be performed at one or more other modules and/or by one or more other devices instead of or in addition to the function performed at the particular module. Further, the modules can be implemented across multiple devices and/or other components local or remote to one another. Additionally, the modules can be moved from one device and added to another device, and/or can be included in both devices.

[0137] The subj ect matter described herein can be implemented in a computing system that includes a backend component (e.g., a data server), a middleware component (e.g., an application server), or a frontend component (e.g., a client computer having a graphical user interface or a web browser through which a user can interact with an implementation of the subject matter described herein), or any combination of such backend, middleware, and frontend components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (“LAN”) and a wide area network (“WAN”), e.g., the Internet.

[0138] Reference has been made in detail to the embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. Reference throughout the specification to "one embodiment" or "an embodiment" or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in one embodiment" or "in an embodiment" or "in some embodiments" in various places throughout the specification is not necessarily referring to the same embodiment s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0139] When elements of various embodiments are introduced, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Claims

1. Mixing system (M2, M6) for mixing a first gas stream with a second gas stream, said mixing system (M2, M6) comprising: a mixing line (23) for supplying a mixed stream of fuel for an engine at a predefined concentration range, said mixing line (23) being configured to mix said first gas stream with said second gas stream so as to obtain the mixed stream of fuel; a first feed line (11) being coupled to said mixing line (23) for supplying said first gas stream to said mixing line (23), said first gas stream comprising a first type of fuel gas; a second feed line (12) coupled to said mixing line (23) for supplying said second gas stream to said mixing line (23), said second gas stream comprising a second type of fuel gas that is different from the first type of fuel gas, the second type of fuel gas being selected from group of fuel gases which when mixed with the first type of fuel gas to form the mixed stream of fuel at the predefined concentration range of the second type of fuel gas, the heat content and/or energy content of the resulting mixed stream of fuel has a singularity across said predefined concentration range; and a damping system including: a flow control system (33) at said first feed line being configured to adjust the flow rate of the first gas stream so as to reach a reference composition value of said mixed stream, and a pressure control system (34) at said second feed line being configured to adjust the pressure of the second gas stream, so as to maintain the pressure at a reference pressure value.

2. The mixing system (M2, M6) of the preceding claim, further comprising a first controller (37) configured to control said flow control system (33), wherein said first controller (37) is configured to: obtain (301) a flow rate of the mixed stream of fuel; obtain (302) a flow rate of the first gas stream; obtain (303) a reference composition value indicative of a percentage of the second type of fuel gas in said mixed stream of fuel; determine (304) a gas flow adjustment to be applied to said flow control system (33) to adjust the flow rate of the first gas stream so as to reach the reference composition value at said mixed stream, wherein said gas flow adjustment is determined based on said reference composition value, said flow rate of the mixed stream and said flow rate of the first gas stream; and apply (305) said gas flow adjustment to said flow control system (33) to adjust the flow rate of the first gas stream.

3. The mixing system (M2, M6) of claim 1 or 2, wherein said flow control system (33) comprises a first flow control device (33-1) disposed within said first feed line (11) and one or more second flow control devices (33-2), each of which is disposed within a respective parallel line of the mixing system (M2, M6) that interconnects with the first input and the first output of said first flow control device (33-1).

4. The mixing system (M2, M6) of any one of the preceding claims, comprising at least one first flow meter (35) for measuring a flow rate of the first gas stream.

5. The mixing system (M2, M6) of any one of the preceding claims, comprising at least one second flow meter (45) for measuring a flow rate of the mixed stream of fuel at said mixing line (23).

6. The mixing system (M2, M6) of any one of the preceding claims, comprising a pressure meter (36) for measuring a pressure value of the second gas stream at said second feed line (12) and a second controller (38) configured to control said pressure control system (34), said second controller (38) being configured to: obtain (401) said pressure value; determine (402) a pressure adjustment to be applied to said pressure control system (34) to adjust the pressure of the second gas stream so as to maintain the pressure of the second gas stream at said reference pressure value; and apply (403) said pressure adjustment to said pressure control system (34).

7. The mixing system (M2, M6) of any one of the preceding claims, wherein said pressure control system (34) comprises a first pressure control device disposed within said first feed line (11) and one or more second pressure control devices, each of which is disposed within a respective parallel line of the mixing system (M2, M6) that interconnects with the first input and the first output of said first pressure control device.

8. The mixing system (M6) of any one of the preceding claims, wherein said mixing system (M2, M6) comprises a further pressure control system at said mixing line (23) being configured to adjust the pressure of the mixing line (23), so as to maintain the pressure at a reference pressure value of the mixed stream.

9. The mixing system (M6) of any one of the preceding claims, further comprising: a control logic unit (51) being configured to: obtain (501) at least one cancellation signal for controlling at least one gas control system of said pressure control system (34) and said flow control system (33) to counter a pulsation disturbance associated with at least one monitored parameter of the mixed stream; and provide (502) said at least one cancellation signal to at least one controller to control the respective gas control system based on said at least one cancellation signal, so as to cancel or reduce said pulsation disturbance at said mixing line (23).

10. The mixing system (M6) of claim 9, wherein said at least one cancellation signal is phase-inverted signal relative to the pulsation disturbance and has a period equal to that of the pulsation disturbance.

11. The mixing system (M6) of claim 9 or 10, wherein the monitored parameter is a flow or a pressure.

12. The mixing system (M6) of any one of claims 9-11, wherein said control logic unit (51) is configured to acquire at least one characteristic of the pulsation disturbance from a data storage, and determine the cancellation signal based on said at least one characteristic of the pulsation disturbance, preferably wherein said at least one characteristic comprises a frequency or a period of the pulsation disturbance.

13. The mixing system (M6) of any one of claims 9-11, further comprising an input interface configured to receive user input, wherein the control logic unit (51) is configured to generate a control signal in response to the user input, the user input comprising the frequency and/or the period of said at least one control signal.

14. The mixing system (M6) of any one of claims 9-11, further comprising one or more meters for measuring said monitored parameter of the mixed stream; wherein said control logic unit (51) is configured to: determine the pulsation disturbance associated with said monitored parameter; and calculate said at least one cancellation signal based on the determined pulsation disturbance.

15. The mixing system (M6) of the preceding claim, wherein said one or more meters comprise at least one of a pressure meter (47) and a flow meter (45).

16. The mixing system (M6) of the preceding claim, further comprising at least one pressure valve at said mixing line (23) being configured to adjust a pressure of said mixed stream of fuel, said control logic unit (51) being configured to control the operation of said at least one pressure valve based on said at least one control signal.

17. The mixing system (M2, M6) of any one of the preceding claims, wherein the first gas stream is a natural gas stream.

18. The mixing system (M2, M6) of the preceding claim, wherein the natural gas stream comprises methane.

19. The mixing system (M2, M6) of any one of the preceding claims, wherein the second gas stream comprises at least one of hydrogen and ammonia.

20. The mixing system (M2, M6) of claim 19, wherein said first type of fuel gas comprises methane, said second type of fuel gas comprises hydrogen, and wherein said predefined concentration range comprises a concentration range of 80-99 vol.-% hydrogen in said mixed stream of fuel.

21. The mixing system (M2, M6) of any one of the preceding claims, wherein said singularity comprises a local peak or a local trough within the predefined concentration range.

22. An engine comprising: a combustion chamber; and a mixing system (M2, M6) of any one of claims 1-21 to supply the mixed stream of fuel to said combustion chamber.

23. A method (100) for controlling the mixing system (M2, M6) as defined in any one of claims 1-21, said method comprising: obtaining (301) a flow rate of the mixed stream of fuel; obtaining (302) a flow rate of the first gas stream; obtaining (303) a reference composition value indicative of a percentage of the second type of fuel gas in said mixed stream of fuel; determining (304) a gas flow adjustment to be applied to said flow control system (33) to adjust the flow rate of the first gas stream so as to reach the reference composition value at said mixed stream, wherein said gas flow adjustment is determined based on said reference composition value, said flow rate of the mixed stream and said flow rate of the first gas stream; applying (305) said gas flow adjustment to said flow control system (33) to adjust the flow rate of the first gas stream; obtaining (401) said pressure value; determining (402) a pressure adjustment to be applied to said pressure control system (34) to adjust the pressure of the second gas stream so as to maintain the pressure of the second gas stream at said reference pressure value; and applying (403) said pressure adjustment to said pressure control system (34).

24. A controller comprising a processor for carrying out a computer-implemented method (100) for controlling the mixing system (M2, M6) as defined in any one of claims 1-21, said method comprising: obtaining (301) a flow rate of the mixed stream of fuel from at least one flow meter (45) configured for measuring the flow rate of the mixed stream of fuel at the mixing line (23); obtaining (302) a flow rate of the first gas stream at least one first flow meter (35) configured to measure the flow rate of the first gas stream; obtaining (303) a reference composition value indicative of a percentage of the second type of fuel gas in said mixed stream of fuel; determining (304) a gas flow adjustment to be applied to said flow control system (33) to adjust the flow rate of the first gas stream so as to reach the reference composition value at said mixed stream, wherein said gas flow adjustment is determined based on said reference composition value, said flow rate of the mixed stream and said flow rate of the first gas stream; applying (305) said gas flow adjustment to said flow control system (33) to adjust the flow rate of the first gas stream; obtaining (401) said pressure value from at least one pressure meter (47); determining (402) a pressure adjustment to be applied to said pressure control system (34) to adjust the pressure of the second gas stream so as to maintain the pressure of the second gas stream at said reference pressure value; and applying (403) said pressure adjustment to said pressure control system (34).

25. A computer program product comprising instructions which, when the program is executed by a processor, cause the processor to carry out the method claim 23.

26. A computer-readable medium having stored thereon the computer program product of claim 25.