Multi-gas online mixing system with wide flow range and control method of multi-gas online mixing system
By designing a multi-gas online mixing system, the problems of uneven mixing and equipment instability over a wide flow range were solved, achieving high-precision, low-cost, and safe gas mixing to meet the needs of different flow conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-14
AI Technical Summary
Existing gas mixing systems suffer from problems such as low mixing accuracy, high equipment cost, high safety risks, severe fluctuations in mixing ratios, and unstable operation of downstream equipment over a wide flow range. In particular, they are prone to blockage and detonation when there are large differences in flow rates.
A multi-gas online mixing system with a wide flow range was designed, including a first gas path channel, a second gas path channel and a third gas path channel. It is equipped with a primary and secondary pressure reducing unit, a flow regulation module and a static mixer. Through the dynamic switching of the main pipeline and branch pipelines and the mixing interface, combined with feedforward-feedback control, the system achieves precise mixing and stable delivery of gases.
It achieves high-precision gas mixing over a wide flow range, reduces equipment costs and safety risks, improves system stability and mixing uniformity, adapts to flow changes under different operating conditions, and avoids uneven mixing and equipment operation fluctuations.
Smart Images
Figure CN121846936A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fluid control and testing technology, specifically to a multi-gas online mixing system with a wide flow range and its control method. Background Technology
[0002] In the fields of energy and power engineering and fluid testing, there is often a need for precisely proportioned multi-component gas mixtures to simulate various complex combustion or reaction environments. Key applications include: Internal combustion engine research and development, such as bench testing of natural gas with hydrogen, and bench testing of gas internal combustion engines simulating various gaseous fuels such as biomass gas, industrial exhaust gas, pyrolysis gas, desorbed gas, associated petroleum gas, biogas, and high and low concentration methane, as well as simulation performance calibration of exhaust gas recirculation (EGR) systems.
[0003] Fuel cell testing requires the addition of trace amounts of impurity gases (such as CO and CO2) to high-purity hydrogen to test the catalyst poisoning characteristics.
[0004] Industrial combustion and chemical engineering, such as research on hydrogen-blended combustion in gas turbines, or the proportioning of chemical synthesis gas.
[0005] There are two main technical approaches to existing gas mixing systems: Mixing in a gas distribution cabinet or storage tank: Although the mixing accuracy is acceptable, the equipment cost is extremely high, and high-pressure gas storage poses a significant safety risk of fuel accumulation in the tank, and it occupies a large amount of laboratory space. In addition, for gases with large density differences (such as hydrogen and nitrogen), gravitational stratification easily occurs in a stationary storage tank, resulting in uneven output components.
[0006] Conventional online mixing: Direct mixing using a three-way pipe. This method is low-cost, but has serious drawbacks under "wide flow range" conditions. When the gas flow rates differ significantly between the lines (e.g., one line is a high-flow main line, and the other is a trace addition), the high-flow gas will create back pressure, "squeezing out" or even blocking the injection of the low-flow gas. Furthermore, intake pulsations in downstream equipment (such as internal combustion engines) will be directly transmitted to the mixing point, causing drastic fluctuations in the instantaneous mixing ratio. These fluctuations can then lead to operational fluctuations in downstream equipment (such as internal combustion engines), and even abnormal phenomena such as knocking, backfire, and popping. Especially for systems with a fixed main line, when the main line gas flow rate is extremely low (e.g., at idle speed) but a certain mixing ratio needs to be maintained, the main line flow velocity is insufficient to carry the branch line gas, causing the main line gas to be unable to flow due to obstruction from the branch line gas. Summary of the Invention
[0007] To address the shortcomings of existing technologies, this invention provides a multi-gas online blending system with a wide flow range and its control method, solving the problems mentioned in the background section.
[0008] This invention provides the following technical solution: a multi-gas online blending system with a wide flow range, comprising: First air passage, second air passage and third air passage; The data acquisition module is used to acquire demand signals from downstream equipment or target flow values for the first, second, and third gas passages. The controller, electrically connected to the data acquisition module, is used for overall system control. The first gas passage, the second gas passage, and the third gas passage are each provided with a primary pressure reduction unit and a secondary pressure reduction unit in sequence along the gas flow direction; The first gas passage, the second gas passage, and the third gas passage are all provided with flow regulation modules between the first-level pressure reducing unit and the second-level pressure reducing unit, and after the second-level pressure reducing unit. The flow regulation module includes at least two parallel branches for different flow ranges, and each branch of the flow regulation module is provided with a flow control valve. Multiple cascaded gas mixing interfaces are used to connect the first gas path channel, the second gas path channel, and the third gas path channel; The system also includes a manifold output pipeline, on which a first static mixer, a terminal flow regulating module, a second static mixer, and a zero-pressure valve are sequentially installed. The outlet of the zero-pressure valve is used to connect to downstream equipment. The gas mixing interface includes an intermediate pressure mixing interface disposed between the primary pressure reducing unit and the secondary pressure reducing unit, and a low-pressure mixing interface disposed after the secondary pressure reducing unit. It is also equipped with a switching valve group consisting of several flow control valves. The controller is electrically connected to the flow regulation module and the switching valve group. The controller is configured to: define the gas path with the largest flow value as the main pipeline according to the target flow value, control the switching valve group to make the main pipeline directly connected to the confluence output pipeline, and treat the gas from other gas paths as branches, selectively injecting the gas from the branches into the main pipeline through the intermediate pressure mixing interface or the low pressure mixing interface according to the pressure state of the gas in the branches.
[0009] Preferably, the flow regulation module includes three parallel branches: a high flow metering branch, a low flow metering branch, and a low flow resistance direct-through branch; the inlet end of the first gas path channel is provided with a first gas path gas booster device; the inlet ends of the second gas path channel and the third gas path channel are used to connect to a high-pressure gas source.
[0010] Preferably, the terminal flow regulation module is located between the first static mixer and the second static mixer, and includes a high flow metering branch, a medium flow metering branch, and a low flow metering branch connected in parallel; the zero-pressure valve is equipped with a sensing diaphragm to sense the negative pressure change at the air inlet of the downstream equipment and control the valve opening.
[0011] Preferably, the gas mixing interface includes a first type of mixing structure, a second type of mixing structure, and a third type of mixing structure, which are configured differently according to the installation location and pressure gradient. The first type of mixing structure is a long-slit guide sleeve structure, which has a first long and narrow outlet slit parallel to the airflow direction of the main pipeline, corresponding to the intermediate pressure mixing interface; The second type of mixing structure is a Venturi structure, which forms a constriction throat at the main pipeline, corresponding to the low-pressure mixing interface, and is used to draw in branch gas using negative pressure. The third type of mixing structure is a short-slit guide sleeve structure, which has a second-length narrow outlet slit parallel to the airflow direction of the main pipeline, and the second length is less than the first length.
[0012] Preferably, both the first static mixer and the second static mixer have three mixing components connected in series inside, namely: a first semi-circular SV mixing component, a corrugated board SK mixing component, and a second semi-circular SV mixing component.
[0013] A method for online gas mixing control in a multi-gas online mixing system with a wide flow range includes the following steps: The target gas components and target flow rates of each component required for the current operating conditions of downstream equipment are obtained through the data acquisition module. Main pipeline determination steps: Compare the target flow rates of the first and second gas passages with the preset main pipeline judgment threshold; If the target flow rate of the first gas path channel is greater than the judgment threshold and is the main component, then the control switching valve group will set the first gas path channel as the main pipeline. If the target flow rate of the first gas path is less than the judgment threshold, and the target flow rate of the second gas path is the main component, then the control switching valve group will set the second gas path as the main pipeline. Branch selection and injection steps: For the first gas path channel, the second gas path channel, or the third gas path channel, the high flow metering branch, the low flow metering branch, or the low flow resistance direct-through branch in the flow regulation module can be independently controlled to open according to their respective target flow rates. Gas from non-main pipeline channels is injected into the main pipeline through a gas mixing interface, based on the matching relationship between the branch pipeline pressure and the main pipeline pressure.
[0014] Preferably, it also includes a feedforward-feedback dual control step: Receive the target load signal or demand signal sent by the downstream equipment control unit as a feedforward signal; When a sudden change in the feedforward signal is detected and the rate of change exceeds the preset value, the target flow changes of the first, second, and third air passages are predicted in advance, and the corresponding branch or main passage in the flow regulation module is switched in advance before the actual operating conditions change.
[0015] Preferably, the method further includes a safety purging step: Before system shutdown or fuel switchover, the inlets of the first and third gas passages are closed. Control the opening of the low-flow-resistance direct branch of the second gas passage, and control the second gas passage as the main pipeline to purge the manifold output pipeline and the downstream equipment air inlet with a large flow of inert gas.
[0016] Preferably, when the second gas passage is set as the main gas passage, the system is used to simulate the exhaust gas recirculation condition or low calorific value gas condition of the engine. At this time, the first gas passage is controlled to open only the small flow metering branch, and a trace amount of base fuel gas is injected into the second gas passage, which is in a high flow state.
[0017] Preferably, it also includes gaseous fuel characteristic simulation and EGR simulation calibration steps: The second gas passage is used to transport dry nitrogen or carbon dioxide to simulate the low calorific value and fuel characteristics of different fuels, as well as as exhaust gas recirculation gas; Based on the low calorific value and fuel characteristics of real gas internal combustion engine fuels, as well as the differences in thermophysical properties between EGR exhaust gas and nitrogen or carbon dioxide, the flow rate and temperature of the three gas channels are modified and controlled. Without introducing condensate, the boundary characteristics of downstream equipment under different low calorific value, different fuel characteristics, or different equivalent EGR rates were measured by adjusting the flow ratio of the three gases. The steps specifically include: Step S1: Before the test, input the lower heating value and combustion characteristic parameters of the gas delivered in each gas passage into the controller; Step S2: Under simulated low calorific value fuel conditions, control the start of the second gas path channel as the main pipeline to output inert gas to reduce the volumetric calorific value of the mixture. Step S3: The controller automatically calculates and corrects the flow rate setpoint of each gas path channel based on the low calorific value requirement of the target simulated gas using the heat balance equation, and adjusts the corresponding flow rate adjustment module. Step S4: Without interference from condensate, gradually increase the mixing ratio of inert gas and determine the misfire limit and combustion variation coefficient of downstream equipment.
[0018] The present invention has the following beneficial effects: 1. Wide-range flow regulation capability: Through the "dynamic inversion of main / auxiliary pipelines" logic, combined with the parallel high-flow metering branches, low-flow metering branches, and low-flow-resistance straight-through branches in each gas path, it can adapt to flow changes from trace additive injection to full-load main gas supply. Even in extreme conditions where the additive gas flow rate is much smaller than the mainstream gas flow rate in high EGR rate simulations, pressure backflow can be avoided through main pipeline switching and Venturi suction structure, ensuring mixing accuracy.
[0019] 2. A first static mixer and a second static mixer are set up to achieve thorough and uniform mixing of gases with different densities. Stratification is introduced during the transportation process, and the mixture is further homogenized in the second static mixer near the internal combustion engine. This results in excellent mixing uniformity. Addressing the challenge of stratification of gases with large density differences, such as hydrogen, a dedicated three-stage static mixer structure consisting of a "first semi-circular SV mixing component, a corrugated plate SK mixing component, and a second semi-circular SV mixing component" is employed. The gas first enters the first semi-circular SV mixing component, where turbulence is created for large-area mixing to resolve stratification. It then enters the dense corrugated SK mixing component, where the flow velocity is reduced and fine mixing is achieved, resulting in thorough mixing in smaller areas. Finally, it enters the second semi-circular SV mixing component, where turbulence is created again, reducing the tendency for subsequent flow stratification. The strong radial turbulence generated by the corrugated SK mixing module section can effectively break gravitational stratification, and together with the multi-stage injection strategy, it ensures the high uniformity of the mixed gas at the micro level.
[0020] 3. To address the pain points in EGR development, the second gas path channel was used as a dry "EGR simulation source," enabling EGR combustion boundary calibration without condensate interference. This effectively solved the icing and corrosion problems caused by water content in EGR exhaust gas during methanol engine development, and shortened the development cycle.
[0021] 4. High safety and reliability: By utilizing the system's built-in low flow resistance direct-through branch path, a "one-click safety purging" function based on high-flow inert gas is realized, which significantly reduces the safety hazards caused by residual flammable gases such as hydrogen. At the same time, the design of the zero-pressure valve physically isolates the intake pulsation of downstream equipment, improving the system's operational stability.
[0022] 5. Low cost and high integration: Compared with expensive gas distribution cabinet systems, it has a small footprint and costs less than half that of gas distribution cabinets due to its pipelined design. It also eliminates the risk of high-pressure container aggregation, making it more suitable for flexible deployment in laboratories and industrial sites.
[0023] 6. Select the mixing path and flow control branch according to the flow rate. That is, when a certain gas line other than the main line needs a large flow rate, take gas from the high pressure area (before the secondary pressure reducing unit) and mix it into the main line. When a small flow rate is needed, take gas from the low pressure area (after the secondary pressure reducing unit) and mix it into the main line. This avoids situations where the pressure difference between the mixing gas line and the main gas line is not suitable, resulting in insufficient mixing (too low pressure in the mixing gas line) or the main gas in the main line being squeezed out (too high pressure in the mixing gas line).
[0024] The mixing port structure is designed according to flow conditions. A Venturi-structured mixing port is used when mixing a small flow with a large flow, while a guide tube-structured mixing port is used when mixing a large flow with a large flow. The width of the guide tube outlet gap is designed based on flow and pressure. In other words, the two mixing ports (Venturi and guide tube) are configured for different applications based on their principles. The Venturi mixing port, with its high flow rate in the main pipeline, increases the flow velocity through the Venturi tube structure, creating negative pressure, which helps to draw in small flow rates of gas from the mixing pipeline. The guide tube structure ensures that the gas in the main pipeline is not blocked by the large flow rate of gas from the mixing pipeline. The gas in the main pipeline flows within the guide tube, which blocks the incoming gas from the mixing pipeline, causing it to change direction and flow along the main pipeline, rather than perpendicularly entering and blocking it.
[0025] After blending, three main pipelines with different flow rates can be selected, depending on the total flow rate. The different proportions of gases from different gas sources result in a wide range of variations in the lower calorific value of the gas sources, which in turn leads to a wide range of total fuel flow rates required for other internal combustion engines with the same power output. Therefore, by setting three main pipelines with different flow rates, flow regulating valves and flow meters with different suitable ranges can be installed. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the complete device structure of the present invention; Figure 2 This is a schematic diagram of the mixing path of the present invention under operating condition 2; Figure 3 This is a schematic diagram of the mixing path structure of the present invention under operating condition 3; Figure 4 This is a schematic diagram of the mixing path structure of the present invention under operating condition 4; Figure 5 This is a schematic diagram of the mixing path structure of the present invention under operating condition 5; Figure 6 This is a schematic diagram of the mixing path structure of the present invention under operating condition 6; Figure 7 This is a schematic diagram of the first type of blended structure of the present invention; Figure 8 This is a schematic diagram of the second type of blended structure of the present invention; Figure 9This is a schematic diagram of the third type of blended structure of the present invention; Figure 10 This is a schematic diagram of the first static mixer structure of the present invention; Figure 11 This is a three-dimensional structural diagram of the first static mixer of the present invention; Figure 12 This is a schematic diagram of the corrugated board SK hybrid assembly structure of the present invention. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Please see Figure 1 - Figure 12 A multi-gas online blending system with a wide flow range includes: The first gas passage is used to transport basic fuel gas; The second gas passage is used to transport inert gas; The third gas passage is used to deliver highly active additive gas; The data acquisition module is used to acquire demand signals from downstream equipment or target flow values for the first, second, and third gas passages. The controller, electrically connected to the data acquisition module, is used for overall system control. The first gas passage, the second gas passage, and the third gas passage are each equipped with a primary pressure reduction unit and a secondary pressure reduction unit in sequence along the gas flow direction. The first, second, and third gas passages are all equipped with flow regulation modules between the primary and secondary pressure reducing units or after the secondary pressure reducing unit. Each flow regulation module includes at least two parallel branches for different flow ranges, and each branch of the flow regulation module is equipped with a flow control valve. Multiple cascaded gas mixing interfaces are used to connect the first gas path channel, the second gas path channel, and the third gas path channel; The system also includes a manifold output pipeline, on which a first static mixer, a terminal flow regulation module, a second static mixer, and a zero-pressure valve are sequentially installed. The outlet of the zero-pressure valve is used to connect to downstream equipment. A zero-pressure valve is installed to prevent gas fluctuations in the front-end blending system caused by changes in the operating conditions of the internal combustion engine, which would lead to changes in gas composition. It also prevents gas fluctuations caused by changes in the ratio of the front-end blending system from affecting the operation of the internal combustion engine, thus playing a role in mutual isolation.
[0029] The gas mixing interface includes an intermediate pressure mixing interface disposed between the primary pressure reducing unit and the secondary pressure reducing unit, and a low-pressure mixing interface disposed after the secondary pressure reducing unit. It is also equipped with a switching valve group consisting of several flow control valves. The controller is electrically connected to the flow regulation module and the switching valve group. The controller is configured to: obtain the target flow values of the first gas passage, the second gas passage and the third gas passage; define the gas passage with the largest flow value as the main pipeline; control the switching valve group to make the main pipeline directly connected to the confluence output pipeline; and treat the gas from the other gas passages as branches, selectively injecting the gas from the branches into the main pipeline through the intermediate pressure mixing interface or the low pressure mixing interface according to the pressure state of the gas in the branches.
[0030] A cross-connecting pipeline is provided between the first gas passage, the second gas passage, and the third gas passage. The gas mixing interface is located at the intersection of the cross-connecting pipeline and the main pipeline of the first, second, and third gas passages. With the opening and closing of the switching valve group, when any gas passage among the first, second, and third gas passages is used as the main pipeline, other gas passages can be used as branch lines to merge into it. In a preferred embodiment, the flow regulation module includes three parallel branches: a high flow metering branch, a low flow metering branch, and a low flow resistance direct-through branch; the inlet end of the first gas path channel is provided with a first gas booster device for boosting the low-pressure gas source; the inlet ends of the second and third gas path channels are used to connect to a high-pressure gas source.
[0031] In a preferred embodiment, the flow regulation module includes two parallel branches: a large flow metering branch + a small flow metering branch or a large flow metering branch + a low flow resistance direct branch.
[0032] In a preferred embodiment: the flow regulation module adds a "medium flow metering branch" to form four parallel branches: large flow metering branch + medium flow metering branch + small flow metering branch + low flow resistance straight-through branch.
[0033] In a preferred embodiment: the terminal flow regulation module is located between the first static mixer and the second static mixer, and includes a high flow metering branch, a medium flow metering branch, and a low flow metering branch connected in parallel; the zero-pressure valve is equipped with a sensing diaphragm to sense the negative pressure change at the inlet of the downstream equipment and control the valve opening to isolate the intake pulsation.
[0034] In a preferred embodiment: the connection topology of the gas mixing interface adopts a cross-stage injection structure. Some gas mixing interfaces are located between the primary pressure reducing unit and the secondary pressure reducing unit of the main pipeline, and are used to introduce a large flow of branch gas under intermediate pressure conditions. Another gas mixing interface is located after the secondary pressure reducing unit of the main pipeline, and is used to introduce a small flow of branch gas under low pressure.
[0035] In a preferred embodiment: the gas mixing interface includes a first type of mixing structure, a second type of mixing structure, and a third type of mixing structure, which are configured differently according to the installation location and pressure gradient; The first type of mixing structure is a long-slit guide sleeve structure, which has a first long and narrow outlet slit parallel to the airflow direction of the main pipeline, used to introduce branch gas into the region after the first-stage decompression when the flow velocity of the main pipeline is high. The high-pressure, high-speed flow field located after the first-stage depressurization is specifically the gas mixing interface 1 and the gas mixing interface 2 of the first gas path channel.
[0036] The long-slit guide sleeve structure includes a main pipeline and an inner sleeve coaxially inserted into the main pipeline. The outer diameter of the inner sleeve is smaller than the inner diameter of the main pipeline, forming an annular channel for the main flow. The end of the inner sleeve does not open directly, but extends a distance along the flow direction, and has a first narrow slit parallel to the axis of the main pipeline on its side wall.
[0037] In high-speed flow fields, direct vertical injection generates strong shear turbulence, disrupting flow field stability. The long-slit guide sleeve forces the branch gas to be rectified within the inner sleeve before merging into the main pipeline, ensuring that its velocity vector upon exiting is completely parallel to the main pipeline airflow. This achieves a "soft landing" convergence, protecting the laminar stability of the main airflow and facilitating subsequent precise control of the secondary decompression.
[0038] The second type of mixed structure is the Venturi structure, which forms a constriction throat at the main pipeline, and is used to draw in branch gas by negative pressure in the area after the secondary decompression where the pressure of the main pipeline is low. The low-pressure flow field located after the second-stage decompression is specifically the gas mixing interface 3 and the gas mixing interface 4 of the first gas path channel.
[0039] The inner diameter of the main pipeline narrows at the inlet to form a throat, and several small holes are provided to connect with the main pipeline. The intake port of the branch gas is located at the throat.
[0040] After the secondary depressurization, the pressure of the mainstream gas is relatively low. If the branch gas pressure is insufficient at this point, backflow can easily occur. The Venturi structure utilizes Bernoulli's principle: when the mainstream flows through the throat, the flow velocity increases and the static pressure decreases, creating a local negative pressure zone. Even if the branch gas pressure is very low, it can be actively "drawn" into the main pipeline by this negative pressure. This eliminates the risk of small flow rates of gas failing to inject or backflowing under high back pressure.
[0041] The third type of mixing structure is a short-slit guide sleeve structure, which has a second-length narrow outlet slit parallel to the airflow direction of the main pipeline, and the second length is less than the first length. The short-slit guide sleeve structure is located at the gas mixing interface 2 of the second gas passage.
[0042] The principle of the third type of short-slit guide sleeve structure is similar to that of the first type of long-slit guide sleeve structure, but the length of the narrow slit at the end of the inner sleeve of the third type of short-slit guide sleeve structure is shorter than that of the first type.
[0043] For gases like hydrogen that diffuse very easily and have extremely low density, convergence can be achieved without an excessively long guide path. The shorter gap structure is compact, reducing component size while still ensuring that hydrogen smoothly enters the nitrogen flow.
[0044] The first and second static mixers each have three mixing components connected in series inside: the first semi-circular SV mixing component, the corrugated plate SK mixing component, and the second semi-circular SV mixing component. The corrugated SK mixing assembly is used to generate radial turbulence to eliminate stratification of gases of different densities; The first and second semicircular SV mixing components are used to increase the density of local mixing.
[0045] The three-section structure of the first semi-circular SV mixing component, the corrugated plate SK mixing component, and the first semi-circular SV mixing component is designed based on deep fluid dynamics mechanisms to solve the problem of gas stratification due to the large density difference between hydrogen and nitrogen. The first semi-circular SV mixing component performs initial cutting, using several sets of mutually perpendicular semi-circular baffles to rotate the fluid, initially cutting the "large blocks" of gas components into "strips" or "sheets" to increase the contact area.
[0046] The SK corrugated plate mixing assembly uses forced turbulence to destratify the gas. Hydrogen has an extremely low density (0.089 kg / m³), making it easily float above the pipe. The SK corrugated plate mixing assembly is composed of multiple layers of corrugated plates stacked together, forcing the fluid to undergo intense radial (perpendicular to the flow direction) motion. This turbulence acts like a "stirrer," breaking down gravitational stratification caused by density differences and dispersing the "strip-like" gas to achieve molecular-level homogeneous mixing.
[0047] The second semi-circular SV mixing component performs micro-homogenization and flow stabilization. After the intense turbulence of the corrugated plate SK mixing component section, the flow field becomes relatively chaotic. The last set of second semi-circular SV mixing components further refines the mixing and also acts as a rectifier, allowing the fluid to be output in a relatively stable state.
[0048] In a preferred embodiment, the thermal management and density compensation module includes high-precision temperature sensors installed at the outlets of each level of pressure reducing unit, and heat tracing devices wrapped around the valve body and critical pipelines of the pressure reducing unit.
[0049] The logic for real-time density correction involves an embedded gas state equation in the controller, which reads temperature sensor data T and pressure data P in real time. The compressibility factor Z is corrected according to PV=ZRT, thereby calculating the real-time gas density ρ. The controller then multiplies the volumetric flow rate Qv read from the flow meter by the real-time density ρ to obtain the corrected mass flow rate Qm, eliminating the influence of temperature drop caused by the Joule-Thomson effect on metering.
[0050] The logic for heat tracing and freeze protection involves setting a low-temperature threshold for the controller. When the temperature of the gas after depressurization is detected to be lower than this threshold, the relay of the heat tracing device is automatically closed to heat the pipeline; when the temperature rises back above the safety threshold, the heating is automatically disconnected to prevent water vapor from freezing or the pipeline material from becoming brittle.
[0051] In a preferred embodiment, the safety linkage monitoring module includes an intermediate pressure sensor disposed in the closed pipe section between the "first gas path primary pressure reducing unit" and the "first gas path secondary pressure reducing unit".
[0052] In a preferred embodiment, the safety linkage monitoring module includes an intermediate pressure sensor disposed in the closed pipe section between the "second gas path primary pressure reducing unit" and the "second gas path secondary pressure reducing unit".
[0053] In a preferred embodiment, the safety linkage monitoring module includes an intermediate pressure sensor installed in the closed pipe section between the "third gas path primary pressure reducing unit" and the "third gas path secondary pressure reducing unit".
[0054] The leakage detection logic is as follows: under pressure-holding conditions with the system shut down and all valves closed, the controller continuously reads the intermediate pressure value Pt. The pressure decay rate is calculated as dP / dt = (Pt1 − Pt2) / Δt.
[0055] The logic for judgment and execution is based on a preset natural leakage rate threshold ϵ in the controller. If the calculated |dP / dt|>ϵ, a minor leak is determined to exist in the system. At this time, the controller immediately triggers an audible and visual alarm and forcibly shuts off the emergency shut-off valve at the inlet of the third gas passage through hardware interlocking, preventing the system from starting until manual troubleshooting and reset.
[0056] Example 2: Expansion of Gas Media This invention is not limited to the combination of "natural gas / nitrogen / hydrogen" and can be applied to various scenarios. In specific implementations, the medium transported by each channel can be adjusted according to requirements, but the system architecture remains unchanged: Internal combustion engine test: First gas passage (natural gas / methanol), second gas passage (nitrogen / EGR simulated gas), third gas passage (hydrogen / combustion oxidizer).
[0057] Fuel cell testing: The third gas path acts as the main pipeline to deliver hydrogen, the first gas path delivers trace amounts of CO (simulating impurities), and the second gas path delivers nitrogen (for purging / protection). In this case, hydrogen becomes the main gas.
[0058] Industrial combustion: First gas path (natural gas), third gas path (hydrogen), HCNG hydrogen-blended combustion test.
[0059] (like Figure 1 As shown in the figure, its physical architecture mainly consists of three parallel gas channels, a cascaded hybrid network, and a terminal processing unit. It also includes a controller, which receives sensor signals and controls the operation of each valve.
[0060] The gas channel unit includes a first gas channel, a second gas channel, a third gas channel, and a terminal processing unit.
[0061] First gas passage: serving as the basic gas transport passage.
[0062] Connection logic: First gas inlet (low pressure) → First gas booster (roots blower preferred in this embodiment, frequency converter control is available) → First gas primary pressure reducing unit → First gas primary flow regulating module → First gas channel gas mixing interface 1 → First gas channel gas mixing interface 2 → First gas channel secondary pressure reducing unit → First gas secondary flow regulating module → First gas channel gas mixing interface 3 → First gas channel gas mixing interface 4 → First gas channel gas mixing interface 5.
[0063] The first gas path gas booster device is set up to solve the problem that the pressure of low-pressure gas sources (such as municipal pipeline natural gas) is insufficient to meet the high-pressure mixing requirements. The outlet pressure can be adjusted in real time according to the target flow rate through frequency conversion control.
[0064] First gas path primary flow regulation module: After the first gas path channel primary pressure reduction unit, the gas path is divided into three parallel branches: the first gas path channel high flow metering branch, the first gas path channel low flow metering branch, and the first gas path channel low flow resistance direct branch.
[0065] The first gas path channel high-flow metering branch is equipped with a large-diameter regulating valve and a mass flow meter, suitable for operating conditions with a rated flow of 30% to 100%.
[0066] The first air path channel small flow metering branch is equipped with a high-precision micro flow regulating valve and flow meter, which is suitable for idling or micro-addition conditions and ensures the linearity of regulation at low flow rates.
[0067] The first gas path channel is a low-resistance direct-through branch: it does not have a precision regulating valve, but only a large-diameter shut-off valve, which is used for low-resistance delivery or rapid venting under ultra-high flow conditions.
[0068] The three parallel branches of the first gas path channel—the high-flow-rate metering branch, the low-flow-rate metering branch, and the low-flow-resistance direct-through branch—converge at the outlet and connect to the first gas path channel gas mixing interface 1. They then connect to the first gas path channel secondary pressure reducing unit via the first gas path channel gas mixing interface 2. At this stage, the higher pressure after the first-stage pressure reduction is used for preliminary "high-pressure coarse mixing."
[0069] First gas path secondary flow regulation module: After the second-level pressure reduction unit of the first gas path channel, the pressure drops to the working pressure, and the gas path is divided again into the second-level high flow metering branch of the first gas path channel and the second-level low flow metering branch of the first gas path channel.
[0070] After the two branches of the first gas path channel, the secondary high-flow metering branch and the secondary low-flow metering branch, merge, they are connected in series through the first gas path channel gas mixing interface 3, the first gas path channel gas mixing interface 4, and the first gas path channel gas mixing interface 5. This stage is for "low-pressure fine mixing".
[0071] Second gas path: serves as a passage for inert / diluted gas delivery.
[0072] Connection logic: Second gas path high pressure inlet → Second gas path primary pressure reducing unit → Second gas path primary flow regulating module → Second gas path secondary pressure reducing unit → Second gas path secondary flow regulating module → Second gas path gas mixing interface 1 → Second gas path gas mixing interface 2 → Second gas path gas mixing interface 3 → Connect to auxiliary test equipment interface.
[0073] The second gas path channel primary flow regulation module also includes three parallel channels: a high-flow-rate metering branch, a low-flow-rate metering branch, and a low-flow-resistance straight-through branch. This low-flow-resistance straight-through branch plays a crucial role in the "safety purging mode," providing a large flow of inert gas to rapidly replace residual combustible gas in the pipeline.
[0074] Cross-connection: After the first-stage flow regulation module of the second gas path channel, a diversion node is designed, which is connected to the gas mixing interface 1 of the first gas path channel for high-pressure and high-flow mixing, the gas mixing interface 5 of the first gas path channel for micro-adjustment mixing, and the second-stage pressure reducing unit of the second gas path channel through pipelines respectively.
[0075] The second gas path secondary flow regulation module: After the second gas path channel secondary pressure reducing unit, the gas path is further divided into the second gas path channel secondary high flow metering branch and the second gas path channel secondary low flow metering branch. After the above two branches merge, they are connected in series through the second gas path channel gas mixing interface 1, the second gas path channel gas mixing interface 2, the second gas path channel gas mixing interface 3, and connected to the auxiliary testing equipment interface (such as the sampling port of the gas analyzer).
[0076] The third gas path channel serves as a delivery path for highly active / trace additive gases.
[0077] Connection logic: High pressure inlet of the third gas path channel → First-level pressure reducing unit of the third gas path channel → First-level flow regulating module of the third gas path channel → Second-level pressure reducing unit of the third gas path channel → Second-level flow regulating module of the third gas path.
[0078] The second gas path channel primary flow regulation module also includes three parallel channels: the third gas path channel high flow metering branch, the third gas path channel low flow metering branch, and the third gas path channel low flow resistance direct-through branch.
[0079] After the outlets of the high-flow-rate metering branch, the low-flow-rate metering branch, and the low-flow-resistance direct-through branch of the third gas path converge, a diversion node is set up, which is respectively connected to the secondary pressure reducing unit of the third gas path, the gas mixing interface 2 of the first gas path for injecting high-pressure natural gas flow, or the gas mixing interface 2 of the second gas path for injecting high-pressure nitrogen flow.
[0080] The third gas path secondary flow regulation module: After the secondary pressure reduction unit of the third gas path channel, the gas path is divided into the secondary high flow metering branch of the third gas path channel and the secondary low flow metering branch of the third gas path channel. After the above two branches merge, they are respectively connected to the gas mixing interface 3 of the second gas path channel or the gas mixing interface 4 of the first gas path channel.
[0081] The first gas path low flow resistance direct-through branch, the second gas path low flow resistance direct-through branch, and the third gas path low flow resistance direct-through branch all use direct-through valves to achieve on / off control. The low-flow-resistance direct-through branch of the second air passage can be configured as normally open or equipped with a UPS power supply to ensure that purging capability is still available in case of failure.
[0082] Terminal processing unit: In order to adapt to the wide range of flow requirements of the internal combustion engine from idle to full load after mixing, and to ensure the uniformity and pressure stability of the final gas entering the engine, this embodiment adopts a unique series structure at the end of the flow manifold. Connection logic: First static mixer → Terminal flow regulation module → Second static mixer → Zero pressure valve → Downstream equipment (such as internal combustion engine intake manifold).
[0083] First static mixer: Receives the confluence gas from the gas passage currently set as the main pipeline (first gas passage or second gas passage), and performs primary turbulent mixing using the internal semi-circular SV mixing component / corrugated SK mixing component to initially eliminate the concentration gradient of each component.
[0084] Second static mixer: Performs secondary mixing to eliminate flow field disturbances that may be introduced by valves in the terminal flow regulation module, ensuring uniform gas composition entering the engine.
[0085] Terminal flow regulation module: includes parallel high flow metering branch, medium flow metering branch and low flow metering branch after mixing, and is set between the first static mixer and the second static mixer.
[0086] The terminal flow regulation module allows the system to finely adjust the total flow rate after mixing, especially for internal combustion engines operating under varying conditions, enabling rapid response to changes in intake volume.
[0087] Zero-pressure valve: Connected to downstream equipment (such as the intake manifold of an internal combustion engine). The zero-pressure valve contains a sensing diaphragm, one side connected to atmospheric pressure or a reference pressure, and the other side connected to the engine intake manifold. When the engine draws in negative pressure, the diaphragm is forced open, causing the valve core to open. This physically isolates the upstream flow meter from intake pulsations, ensuring the stability of the mixing ratio.
[0088] When using a multi-gas online blending system with a wide flow range on a gas internal combustion engine test bench, there are five different blending paths for various flow ratios, as shown in the table below: Based on the flow ratios of the five ranges mentioned above, and according to the paths shown in the five diagrams, shut-off valves are set up and their opening and closing are controlled to achieve the required paths. At the same time, appropriate pipe diameters and equipment are selected according to the range of each flow.
[0089] Specifically, the gas path for different operating conditions is as follows: Operating Condition 1 (Base fuel dominant, low-flow blending) Natural Gas: First Gas Path (Main Pipeline): First Gas Path Inlet → First Gas Path Gas Booster → First Gas Path Primary Pressure Reduction Unit → First Gas Path Low Flow Resistance Straight-Through Branch → First Gas Path Gas Mixing Interface 1 → First Gas Path Gas Mixing Interface 2 → First Gas Path Secondary Pressure Reduction Unit → First Gas Path High Flow Metering Branch → First Gas Path Gas Mixing Interface 3 → First Gas Path Gas Mixing Interface 4 → First Gas Path Gas Mixing Interface 5 → Terminal Processing Unit.
[0090] Nitrogen: Second gas path channel (branch): Second gas path channel inlet → Second gas path channel primary pressure reducing unit → Second gas path channel low flow resistance direct branch → Second gas path channel secondary pressure reducing unit → Second gas path channel small flow metering branch → Second gas path channel gas mixing interface 1 → Second gas path channel gas mixing interface 2 → Second gas path channel gas mixing interface 3 → First gas path channel gas mixing interface 3.
[0091] Hydrogen: Third gas path channel (branch): Third gas path channel inlet → Third gas path channel primary pressure reducing unit → Third gas path channel low flow resistance direct branch → Third gas path channel secondary pressure reducing unit → Third gas path channel low flow metering branch → First gas path channel gas mixing interface 4.
[0092] Operating Condition 2 (Low Calorific Value Gas Simulation) Natural gas: First gas route (main pipeline): Path is the same as in operating condition 1.
[0093] Nitrogen: Second gas path channel (branch): Second gas path channel inlet → Second gas path channel primary pressure reduction unit → Second gas path channel high flow metering branch → First gas path channel gas mixing interface 1 (using the high pressure after primary pressure reduction for high flow coarse mixing).
[0094] Hydrogen: Third gas path channel (branch): Path is the same as in operating condition 1.
[0095] Operating Condition 3 (Full Load, High Flow Rate) Natural Gas: First Gas Line (Main Line): First Gas Line Inlet → First Gas Line Gas Pressurization Unit → First Gas Line Primary Pressure Reduction Unit → First Gas Line High Flow Metering Branch → First Gas Line Gas Mixing Interface 1 → First Gas Line Gas Mixing Interface 2 → First Gas Line Secondary Pressure Reduction Unit → First Gas Line High Flow Metering Branch → First Gas Line Gas Mixing Interface 3 → First Gas Line Gas Mixing Interface 4 → First Gas Line Gas Mixing Interface 5 → Terminal Processing Unit.
[0096] Nitrogen: Second gas path (branch): Path is the same as in operating condition 2.
[0097] Hydrogen: Third gas path channel (branch): Third gas path channel inlet → Third gas path channel primary pressure reducing unit → Third gas path channel low flow resistance direct branch → First gas path channel gas mixing interface 2.
[0098] Operating Condition 4 (High EGR Rate / Extra-Lean Combustion Simulation) Natural Gas: First Gas Path (Branch): First Gas Path Inlet → First Gas Path Gas Pressurization Unit → First Gas Path Primary Pressure Reduction Unit → First Gas Path Low Flow Resistance Straight-Through Branch → First Gas Path Gas Mixing Interface 1 → First Gas Path Gas Mixing Interface 2 → First Gas Path Secondary Pressure Reduction Unit → First Gas Path Small Flow Metering Branch → Second Gas Path Gas Mixing Interface 1.
[0099] Nitrogen: Second gas path channel (main line): Second gas path channel inlet → Second gas path channel primary pressure reducing unit → Second gas path channel low flow resistance direct branch → Second gas path channel secondary pressure reducing unit → Second gas path channel high flow metering branch → Second gas path channel gas mixing interface 1 → Second gas path channel gas mixing interface 2 → Second gas path channel gas mixing interface 3 → Terminal processing unit.
[0100] Hydrogen: Third gas path channel (branch): Third gas path channel inlet → Third gas path channel primary pressure reducing unit → Third gas path channel high flow metering branch → Second gas path channel gas mixing interface 1.
[0101] Operating Condition 5 (Idle / Slight Mixing) Natural gas: First gas route (branch): Path is the same as in operating condition 4.
[0102] Nitrogen: Second gas path (main pipeline): Path is the same as in operating condition 4.
[0103] Hydrogen: Third gas path channel (branch): Third gas path channel inlet → Third gas path channel primary pressure reducing unit → Third gas path channel low flow resistance direct branch → Third gas path channel secondary pressure reducing unit → Third gas path channel small flow metering branch → Second gas path channel gas mixing interface 3.
[0104] A method for online gas mixing control in a multi-gas online mixing system with a wide flow range includes the following steps: The target gas components and target flow rates of each component required for the current operating conditions of downstream equipment are obtained through the data acquisition module. Main pipeline determination steps: Compare the target flow rates of the first and second gas passages with the preset main pipeline judgment threshold; If the target flow rate of the first gas path channel is greater than the judgment threshold and is the main component, the control valve will set the first gas path channel as the main pipeline. If the target flow rate of the first gas path channel is less than the determination threshold and the target flow rate of the second gas path channel is the main component, the control valve sets the second gas path channel as the main pipeline; Branch selection and injection steps: For the first gas path channel, the second gas path channel or the third gas path channel, independently control the opening of the large flow rate metering branch, the small flow rate metering branch or the low flow resistance direct through branch in the flow rate adjustment module according to their respective target flow rate magnitudes; Inject the gas in the non-main pipeline channel into the main pipeline via the gas mixing interface according to the matching relationship between the branch pressure and the main pipeline pressure.
[0105] Dynamic switching logic of the main pipeline: The controller collects the target flow rate data of each channel in real time and executes the following determination logic: Flow rate comparison and decision-making: The system compares the target flow rates Q1 and Q2 of the first gas path channel and the second gas path channel with the preset main pipeline determination threshold Qth.
[0106] Situation A: Base fuel dominant Q1 > Qth: Determine that the first gas path channel is the main pipeline. The controller sends an instruction to adjust the low flow resistance direct through branch or the large flow rate metering branch of the first gas path channel to the open state, so that the gas is directly transported to the confluence output pipeline through the low flow resistance direct through branch or the large flow rate metering branch of the first gas path channel and reaches the end of the confluence pipeline. At the same time, control the first-stage flow rate adjustment module or the second-stage flow rate adjustment module of the third gas path to inject its gas into the gas mixing interface on the first gas path channel.
[0107] Situation B: EGR simulation or lean burn Q1 < Qth and Q2 > Q1: Determine that the second gas path channel is the main pipeline. The controller executes master-slave inversion and opens the low flow resistance direct through branch or the large flow rate metering branch of the second gas path channel. At this time, the first gas path channel and the third gas path channel are defined as branches, and the controller switches its internal valves to inject the gas into the gas mixing interface on the second gas path channel.
[0108] Switching dead zone control: To prevent frequent switching jitter near the critical flow rate point, the controller is provided with a hysteresis dead zone. For example, the threshold for switching from situation A to situation B is Qth_low, and the threshold for switching back from situation B to situation A is Qth_high, and Qth_high > Qth_low.
[0109] Valve action sequence: During the switching process, the controller follows the principle of "open first and then close". First, open the valve of the new main pipeline, and after the pressure is stable (for example, delay 500 ms), then close the valve of the old main pipeline to ensure that downstream equipment (such as an internal combustion engine) will not stall due to instant interruption of the flow.
[0110] In a preferred embodiment, the method further includes a feedforward-feedback dual control step. Receive the target load signal or demand signal sent by the downstream equipment control unit as a feedforward signal; When a sudden change in the feedforward signal is detected and the rate of change exceeds the preset value, the target flow changes of the first, second, and third air passages are predicted in advance, and the corresponding branch or main passage in the flow regulation module is switched in advance before the actual operating conditions change.
[0111] Logic explanation of feedforward-feedback dual control: The controller receives "target load" or "accelerator pedal position" signals from downstream devices (such as the engine ECU) via the CAN bus. When a step change in this signal is detected (predicting an impending flow surge), the system no longer waits for feedback lag from the flow meter, but directly looks up the table and pre-switch the branch of the flow regulation module or the main flow control branch 0.5 seconds in advance. This effectively eliminates pressure oscillations and mixture ratio fluctuations under transient operating conditions.
[0112] In a preferred embodiment, the method further includes a safety purging step: Before system shutdown or fuel switchover, the inlets of the first and third gas passages are closed. Control the opening of the low-flow-resistance direct branch of the second gas path channel, and control the second gas path channel as the main pipeline to purge the manifold output pipeline and the air inlet of downstream equipment with a large flow of inert gas.
[0113] When a shutdown command or emergency cut-off signal is triggered, the control closes the inlet of the first gas passage and the inlet of the third gas passage; the second gas passage is fully opened, the low flow resistance direct branch of the second gas passage and all downstream valves are opened, and the entire system is flushed with a large flow of inert gas at high speed to dilute the residual hydrogen concentration to below the lower explosive limit.
[0114] In a preferred embodiment: when the second gas passage is set as the main passage, the system is used to simulate the exhaust gas recirculation (EGR) condition or low calorific value gas condition of the engine. At this time, the first gas passage is controlled to open only the small flow metering branch, and a trace amount of base fuel gas is injected into the second gas passage, which is in a high flow state.
[0115] In a preferred embodiment, the method further includes gaseous fuel characteristic simulation and EGR simulation calibration steps. The second gas passage is used to transport dry nitrogen or carbon dioxide to simulate the low calorific value and fuel characteristics of different fuels, as well as as exhaust gas recirculation gas; Based on the low calorific value and fuel characteristics of real gas internal combustion engine fuels, as well as the differences in thermophysical properties between EGR exhaust gas and nitrogen or carbon dioxide, the flow rate and temperature of the three gas channels are modified and controlled. Without introducing condensate, the boundary characteristics of downstream equipment under different low calorific value, different fuel characteristics, or different equivalent EGR rates were measured by adjusting the flow ratio of the three gases. The steps specifically include: Step S1: Before the test, input the lower heating value and combustion characteristic parameters of the gas delivered in each gas passage into the controller; Step S2: Under simulated low calorific value fuel conditions, control the start of the second gas path channel as the main pipeline to output inert gas to reduce the volumetric calorific value of the mixture. Step S3: The controller automatically calculates and corrects the flow rate setpoint of each gas path channel based on the low calorific value requirement of the target simulated gas using the heat balance equation, and adjusts the corresponding flow rate adjustment module. Step S4: Without interference from condensate, gradually increase the mixing ratio of inert gas and determine the misfire limit and combustion variation coefficient of downstream equipment.
[0116] Specifically, the anhydrous EGR calibration method based on a multi-gas online blending system with a wide flow range includes: Step S1: Before the test, the controller records the curve data of the thermophysical parameters (specific heat capacity, density, etc.) of EGR exhaust gas (containing H2O / CO2) and dry nitrogen as a function of temperature. Step S2: Start the second gas path channel as the main pipeline and output dry nitrogen to replace the EGR exhaust gas; Step S3: Calculate the required actual exhaust gas mass flow rate based on the target EGR rate; Based on the difference in thermophysical properties in step S1, the controller automatically calculates and corrects the required nitrogen flow rate QN2 using the heat balance equation QN2×CpN2=QEGR×CpEGR. Adjust the flow regulation module of the second gas path channel to accurately output the corrected nitrogen flow rate; Step S4: Without condensate interference, gradually increase the nitrogen blending ratio, measure key indicators such as misfire limit and combustion variation coefficient (COV) of downstream equipment (such as internal combustion engine), and generate EGR control MAP.
[0117] In a preferred embodiment, the system enables physical simulation of gaseous fuels with different properties (such as low-calorific-value biomass gas and syngas).
[0118] This system utilizes a combination of three gas pathways to reconstruct the physicochemical properties of the target gas: First gas path (base fuel): provides the main calorific value (such as natural gas, methane).
[0119] The second gas path (inert dilution): uses nitrogen (N2) or carbon dioxide (CO2) as a diluent. By increasing its proportion, the volumetric calorific value (LHV) of the mixture can be reduced, simulating low-calorific-value fuels such as lean mine gas and landfill gas.
[0120] The third gas path channel (activity adjustment): utilizes hydrogen (H2) as a combustion promoter. By adjusting its ratio, the laminar flame velocity and ignition limit of the gas mixture can be changed to simulate highly reactive syngas or hydrogen-rich natural gas.
[0121] The controller integrates a "fuel characteristic calculation model." The user inputs the lower calorific value (LHVtarget) of the target fuel, and the controller calculates the required inert gas to fuel gas flow ratio using the following formula: LHVmix=Q1×LHV1+Q3×LHV3Q1+Q2+Q3 Wherein, Q1, Q2, and Q3 are the mass flow rates of the three channels, and LHV1 and LHV3 are the lower calorific values of the base fuel and hydrogen, respectively.
[0122] The specific operating steps include: Step S1 (Parameter Input): Before the test begins, input the basic parameters of the gas source for each channel into the controller via the host computer.
[0123] Step S2 (Operating Condition Establishment and Master-Slave Switching): When simulating extremely low calorific value fuels (e.g., <15 MJ / Nm³), the demand for inert gas is high. The system automatically judges and executes "dynamic inversion of main / auxiliary pipelines", switching the second gas passage (inert gas) to the main pipeline and opening its low flow resistance direct branch or high flow metering branch; The first and third gas channels are used as branch channels for gas injection; Step S3 (Dynamic Correction): The controller collects temperature and pressure signals in real time and automatically compensates for density changes caused by gas expansion.
[0124] Fail-safe mode logic description: In the event of a power outage or loss of communication, all inlet shut-off valves and pressure reducing units will automatically reset to normally closed.
[0125] All inlet shut-off valves refer to the inlet shut-off valves of the first gas passage, the second gas passage, and the third gas passage; The pressure reduction unit refers to: the first-level pressure reduction unit of the first air path, the second-level pressure reduction unit of the first air path, the first-level pressure reduction unit of the second air path, the second-level pressure reduction unit of the second air path, the first-level pressure reduction unit of the third air path, and the second-level pressure reduction unit of the third air path.
[0126] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0127] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A multi-gas online blending system with a wide flow range, characterized in that, include: First air passage, second air passage and third air passage; The data acquisition module is used to acquire demand signals from downstream equipment or target flow values for the first, second, and third gas passages. The controller, electrically connected to the data acquisition module, is used for overall system control. The first gas passage, the second gas passage, and the third gas passage are each provided with a primary pressure reduction unit and a secondary pressure reduction unit in sequence along the gas flow direction; The first gas passage, the second gas passage, and the third gas passage are all provided with flow regulation modules between the first-level pressure reducing unit and the second-level pressure reducing unit, and after the second-level pressure reducing unit. The flow regulation module includes at least two parallel branches for different flow ranges, and each branch of the flow regulation module is provided with a flow control valve. Multiple cascaded gas mixing interfaces are used to connect the first gas path channel, the second gas path channel, and the third gas path channel; The system also includes a manifold output pipeline, on which a first static mixer, a terminal flow regulating module, a second static mixer, and a zero-pressure valve are sequentially installed. The outlet of the zero-pressure valve is used to connect to downstream equipment. The gas mixing interface includes an intermediate pressure mixing interface disposed between the primary pressure reducing unit and the secondary pressure reducing unit, and a low-pressure mixing interface disposed after the secondary pressure reducing unit. It is also equipped with a switching valve group consisting of several flow control valves. The controller is electrically connected to the flow regulation module and the switching valve group. The controller is configured to: define the gas path with the largest flow value as the main pipeline according to the target flow value, control the switching valve group to make the main pipeline directly connected to the confluence output pipeline, and treat the gas from other gas paths as branches, selectively injecting the gas from the branches into the main pipeline through the intermediate pressure mixing interface or the low pressure mixing interface according to the pressure state of the gas in the branches.
2. The multi-gas online blending system with a wide flow range according to claim 1, characterized in that, The flow regulation module includes three parallel branches: a high flow metering branch, a low flow metering branch, and a low flow resistance direct-through branch; the inlet end of the first gas path channel is provided with a first gas booster device; the inlet ends of the second and third gas path channels are used to connect to a high-pressure gas source.
3. The multi-gas online blending system with a wide flow range according to claim 1, characterized in that, The terminal flow regulation module is located between the first static mixer and the second static mixer, and includes a high flow metering branch, a medium flow metering branch, and a low flow metering branch connected in parallel; the zero-pressure valve is equipped with a sensing diaphragm to sense the negative pressure change at the air inlet of the downstream equipment and control the valve opening.
4. The multi-gas online blending system with a wide flow range according to claim 1, characterized in that, The gas mixing interface includes a first type of mixing structure, a second type of mixing structure, and a third type of mixing structure, which are configured differently according to the installation location and pressure gradient. The first type of mixing structure is a long-slit guide sleeve structure, which has a first long and narrow outlet slit parallel to the airflow direction of the main pipeline, corresponding to the intermediate pressure mixing interface; The second type of mixing structure is a Venturi structure, which forms a constriction throat at the main pipeline, corresponding to the low-pressure mixing interface, and is used to draw in branch gas using negative pressure. The third type of mixing structure is a short-slit guide sleeve structure, which has a second-length narrow outlet slit parallel to the airflow direction of the main pipeline, and the second length is less than the first length.
5. A multi-gas online blending system with a wide flow range according to claim 1, characterized in that, Both the first static mixer and the second static mixer have three mixing components connected in series inside: the first semi-circular SV mixing component, the corrugated board SK mixing component, and the second semi-circular SV mixing component.
6. A gas online mixing control method for a multi-gas online mixing system with a wide flow range based on any one of claims 1-5, characterized in that, Includes the following steps: The target gas components and target flow rates of each component required for the current operating conditions of downstream equipment are obtained through the data acquisition module. Main pipeline determination steps: Compare the target flow rates of the first and second gas passages with the preset main pipeline judgment threshold; If the target flow rate of the first gas path channel is greater than the judgment threshold and is the main component, then the control switching valve group will set the first gas path channel as the main pipeline. If the target flow rate of the first gas path is less than the judgment threshold, and the target flow rate of the second gas path is the main component, then the control switching valve group will set the second gas path as the main pipeline. Branch selection and injection steps: For the first gas path channel, the second gas path channel, or the third gas path channel, the high flow metering branch, the low flow metering branch, or the low flow resistance direct-through branch in the flow regulation module can be independently controlled to open according to their respective target flow rates. Gas from non-main pipeline channels is injected into the main pipeline through a gas mixing interface, based on the matching relationship between the branch pipeline pressure and the main pipeline pressure.
7. A method for controlling online mixing of multiple gases over a wide flow range according to claim 6, characterized in that, It also includes a feedforward-feedback dual control step: Receive the target load signal or demand signal sent by the downstream equipment control unit as a feedforward signal; When a sudden change in the feedforward signal is detected and the rate of change exceeds the preset value, the target flow changes of the first, second, and third air passages are predicted in advance, and the corresponding branch or main passage in the flow regulation module is switched in advance before the actual operating conditions change.
8. A method for controlling online mixing of multiple gases over a wide flow range according to claim 6, characterized in that, The method also includes a safety purging procedure: Before system shutdown or fuel switchover, the inlets of the first and third gas passages are closed. Control the opening of the low-flow-resistance direct branch of the second gas passage, and control the second gas passage as the main pipeline to purge the manifold output pipeline and the downstream equipment air inlet with a large flow of inert gas.
9. A method for controlling online mixing of multiple gases over a wide flow range according to claim 6, characterized in that, When the second gas passage is set as the main gas passage, the system is used to simulate the exhaust gas recirculation condition or low calorific value gas condition of the engine. At this time, the first gas passage is controlled to open only the small flow metering branch, and a trace amount of base fuel gas is injected into the second gas passage, which is in a high flow state.
10. A method for controlling online mixing of multiple gases over a wide flow range according to claim 6, characterized in that, It also includes gaseous fuel characteristic simulation and EGR simulation calibration steps: The second gas passage is used to transport dry nitrogen or carbon dioxide to simulate the low calorific value and fuel characteristics of different fuels, as well as as exhaust gas recirculation gas; Based on the low calorific value and fuel characteristics of real gas internal combustion engine fuels, as well as the differences in thermophysical properties between EGR exhaust gas and nitrogen or carbon dioxide, the flow rate and temperature of the three gas channels are modified and controlled. Without introducing condensate, the boundary characteristics of downstream equipment under different low calorific value, different fuel characteristics, or different equivalent EGR rates were measured by adjusting the flow ratio of the three gases. The steps specifically include: Step S1: Before the test, input the lower heating value and combustion characteristic parameters of the gas delivered in each gas passage into the controller; Step S2: Under simulated low calorific value fuel conditions, control the start of the second gas path channel as the main pipeline to output inert gas to reduce the volumetric calorific value of the mixture. Step S3: The controller automatically calculates and corrects the flow rate setpoint of each gas path channel based on the low calorific value requirement of the target simulated gas using the heat balance equation, and adjusts the corresponding flow rate adjustment module. Step S4: Without interference from condensate, gradually increase the mixing ratio of inert gas and determine the misfire limit and combustion variation coefficient of downstream equipment.