Patent Description:
There are known various kinds of systems wherein a main compressor (or a pump) delivers fluid to a splitter that supplies the fluid to a plurality of outlets, wherein the flow of fluid at each outlet is controlled by a dedicated outlet valve. For example, such systems are used in climate control (wherein the fluid is air, and the outlets are air supply units to various rooms in a building).

In a basic scenario, the main compressor may operate at its maximum efficiency to deliver fluid with its full power, wherein the dedicated outlet valves control the rate of fluid delivery to each outlet. This scenario is ineffective, because if the amount of fluid discharged at all the outlets is lower than the compression efficiency, pressure is built inside the system which causes load to system components and decreases its lifetime.

Alternatively, it is known to optimize the workload to the system by continuously adjusting the efficiency of the compressor so as to deliver, by the compressor, the fluid in the amount corresponding to the cumulative outlet demand from all outlets. However, this approach has the drawback that a feedback loop that adjusts the efficiency has some delay, therefore it is possible that such optimized system will not react quickly enough if a demand for the fluid increases quickly.

For example a US patent document <CIT> discloses a fluid distribution system comprising connected conduits such as pipes within a building wherein fluid flows through the conduits. The conduits may be configured to: (i) include multiple lines that connect at intersections (some of the intersections will be identified as nodes); and (ii) incorporate node units associated with line pressure loss simulation assemblies ("LLSAs"). Activities of a node unit incorporating a LLSA can result in alterations in fluid pressure, such as by a loop control process to reposition balancing valves or other valves of one or more LLSAs, and/or by alteration of the speed of the system pump. These activities adjust fluid pressure to cause the system to produce a balanced and high efficiency energy transfer (e.g., heating or cooling), and do not involve or require any identification or use of any specific, fixed or absolute pressure value. They function based on an operation locus (for a node unit) and/or an operation locus range (for node unit groupings) to adjust the fluid pressure.

For example a US patent application <CIT> discloses a self-organizing multi-stream flow delivery process wherein enabling actuation and control are introduced. The method and apparatus of building a general-purpose self-organizing multi-stream flow delivery process are presented. The flow delivery process comprises a number of flow streams, each of which is regulated by a flow valve. A pressure valve is added onto the main flow line to "choke" the pressure to allow the flow control valves to work in their relatively linear ranges so that they can regulate the flows adequately.

For example a Japanese patent application<CIT> discloses a method and a device for controlling fluid pressure, wherein the fluid is supplied with high efficiency by selecting the proper pressure in accordance with the switching states of valves provided to plural branch pipes of a main pipe and controlling the number of revolutions of a pump motor based on the deviation between said proper pressure and the pressure generated actually.

For example an international patent application <CIT> relates to pumping and water distribution systems for pools/spas, and methods for control thereof. A system includes a pump including a variable speed motor, a controller configured to control the speed of the motor, a plurality of pool/spa components, a plumbing subsystem placing the components in fluidic communication with the pump, and a plurality of control valves switchable between an open position and a closed position. Each of the control valves is associated with one of the components, positioned in the plumbing subsystem between the associated component and the pump to control the flow of fluid to the associated component, and is configured to provide a specific flow rate of fluid to the associated component based on a set system pressure when in the open position. The controller adjusts the speed of the motor to adjust the fluid pressure within the plumbing subsystem to match the set system pressure value.

Therefore, there is a need to provide an alternative method for flow control in a system of valves connected to a splitter which will be devoid of at least some of the disadvantages discussed above.

The object of the invention is a system according to the appended claims.

The main system controller can be configured to initially set the main pressure setpoint at a middle of the range of values and perform a re-adjustment of the main pressure setpoint when that largest opening angle of the valves moves beyond the range of values.

The flow controllers and/or the main flow controller can be proportional-integral-derivative controllers.

The system according to the invention operates such as to maintain the opening angle of the widest open valve at a value or range indicated by the valve opening setpoint. Consequently, the pressurizer operates at an optimal efficiency - its operating efficiency is decreased when the demand for fluid is low and increased when the demand is high. The pressure within the separator is kept at relatively low level. Since the widest open valve is never fully open (i.e. the valve opening setpoint is lower than <NUM>%, preferably between <NUM>% and <NUM>%), there is some pressure heat to quickly compensate for the small increasing demand. Moreover, if the demand for fluid at one of the outlets suddenly increases, the internal fluid pressure at the separator can quickly compensate the increasing demand (while the power of the pressurizer will be increased subsequently), so the system is rapidly responsive to variations in demand for fluid at the outlets.

The invention is applicable to various kinds of systems with valves, such as systems for climate control (wherein the fluid is air and the outlets are air supply units to various rooms in a building), for fuel burning, for drying, for chemical processing, for air circulation, for conveying.

Further aspects and features of the present invention are described in following description of the drawings.

Aspects and features of the present invention will become apparent by describing, in detail, exemplary embodiment of the present invention with reference to the attached drawing, wherein:.

Reference will now be made to an embodiment of the system. Aspects and features of the embodiment will be described with reference to the accompanying drawing. The present invention, however, may be embodied in various different forms and should not be construed as being limited only to the illustrated embodiment. Rather, these embodiment is provided as an example so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present invention to those skilled in the art. It shall be understood that not all of the features shown in the embodiment are essential and the scope of the protection is defined not by means of literally shown embodiment, but by the features provided in the claims.

The system as shown in <FIG> comprises a main pressurizer <NUM> (i.e. a compressor if the fluid is a gas or a pump if the fluid is a liquid) that is configured to compress an input flux FIN of fluid to a pressurized flux FP to be delivered to a splitter <NUM> that distributes the pressurized flux FP to a plurality of valves <NUM>, <NUM>, <NUM>. The efficiency of the pressurizer <NUM> is controlled by controlling the power of the motor <NUM> that drives the pressurizer <NUM>. The motor power is controlled by a main flow controller <NUM>, preferably a PID (proportional-integral-derivative) controller, that adjusts the operation of the motor <NUM> such that the pressure of the pressurized flux FP measured by a main pressure sensor <NUM> is substantially equal to a main pressure setpoint S output from a main system controller <NUM>. The use of the PID controller has the advantages that it is commonly used and well known, therefore it can be easily adapted to the system.

Each valve <NUM>, <NUM>, <NUM> is controlled by its dedicated flow controller <NUM>, <NUM>, <NUM>, preferably a PID controller. The flow controllers <NUM>, <NUM>, <NUM> adjust the opening angle of the valve such that the flow measured by the dedicated outlet flow sensors <NUM>, <NUM>, <NUM> is equal to an outlet setpoint S1, S2, S3 adjusted by the user. For example, the outlet setpoint S1, S2, S3 may be adjusted by a manual controller (e.g. a mechanic knob or electronic adjuster) or an automated controller (e.g. outlet from an automated climate control system). The control signals C1, C2, C3 that set the opening angle of individual valves <NUM>, <NUM>, <NUM> are input to the corresponding valves <NUM>, <NUM>, <NUM> and to the main system controller <NUM>.

The main system controller <NUM> is configured to set the main pressure setpoint S such as to set the valve <NUM>, <NUM>, <NUM> that operates at the largest opening angle (wherein the opening angle is determined based on the control signals C1, C2, C3) to opening angle defined by a valve opening setpoint FS. The valve opening setpoint FS can be a predefined constant set for the particular system or can be input to the main system controller <NUM> as a control variable set by a manual or automated controller. For example, the valve opening setpoint FS can define a value of <NUM>%.

Alternatively, the valve opening setpoint FS can define a range of values, for example between <NUM>% and <NUM>%. In that case, the main system controller <NUM> may be configured to initially set the main pressure setpoint S such that the largest opening angle of the valves is in the middle of the range (e.g. <NUM>% when the range is from <NUM>% to <NUM>%) and perform a re-adjustment of the main pressure setpoint S when that largest opening angle moves beyond the range (e.g. if it falls below <NUM>% or rises above <NUM>%). This reduces the amount of control operations and keeps a more stable point of operation of the motor <NUM>.

The main system controller <NUM> may set the main pressure setpoint S using various methods. For example, it may comprise one or more tables that include values of main pressure setpoint S to be set depending on the control signals C1, C2, C3. Alternatively, it may operate according to some function based on the control signals C1, C2, C3. Alternatively, it may operate in a feedback loop such as to increase the main pressure setpoint S if one of the control signal C1, C2, C3 indicates a valve opening value higher than the valve opening setpoint FS (or its value is above the upper limit of a range) and to decrease the main pressure setpoint S if one of the control signal C1, C2, C3 indicates a valve opening value lower than the valve opening setpoint FS (or its value is below the lower limit of a range).

The pressurizer <NUM> is selected such that it can deliver pressurized fluid FP at a rate such that outlet setpoints S1, S2, S3 can be set to <NUM>% so that the fluid can flow to the outlets at <NUM>% of desired flowrate from each outlet. The valve opening setpoint range FSR is defined to a range of <NUM>% to <NUM>%, i.e. the middle of the range is <NUM>%.

Let's assume that a user of the system adjusts the outlet setpoint S1 to <NUM>% of maximum possible flow, the outlet setpoint S2 to <NUM>% and the outlet setpoint S3 to <NUM>%. In that case the cumulative demand from all outlets is (<NUM>%+<NUM>%+<NUM>%)/<NUM> = <NUM>% of the possible maximum demand. If the first valve <NUM> is to be opened at <NUM>%, the pump motor <NUM> would have to be set to a <NUM>% efficiency. However, since the FS is set to <NUM>%, the pump motor <NUM> efficiency shall be increased by <NUM>-<NUM>/<NUM> = <NUM>%, i.e. from <NUM>% to <NUM>%. Then, if the pump motor <NUM> efficiency is set to <NUM>%, the opening angle of the first valve <NUM> will be set to <NUM>%, the opening angle of the second valve <NUM> will be set to <NUM>*<NUM>/<NUM> = <NUM>% and the opening angle of the third valve <NUM> will be set to <NUM>*<NUM>/<NUM>=<NUM>%.

<FIG> shows a TVS R410 EATON compressor efficiency map. Let's assume an exemplary operating point with an air flow equal to <NUM>/h and with an air pressure at the inlet equal to <NUM> bar.

A first curve (<NUM>) (magenta color) on the map is a pressure-flow curve of an exemplary air-fed system.

A second curve (<NUM>) (red color) fixed at <NUM> bars presents an example of the compressor operation without implementing the presented invention (flow regulation) then the compressor is controlled to maintain "constant pressure". At the considered operating point, the compressor works with the power of ~ <NUM>. 8kW to generate the desired flow and pressure difference.

A third curve (<NUM>) (yellow color) presents the compressor operation with the control proposed by the present invention. For small flows, the energy gain is significant. A fourth curve (<NUM>) (green color) presents an operation of a perfectly matched compressor and is added as a reference goal of the system operation.

As the presented algorithm aims to reduce the pressure loss (the control valves are opened at <NUM>-<NUM>%), the invention causes that the operating point lies at a much lower operating pressure than the one presented by the red curve.

The compressor in the example is a positive displacement machine. In such machines the flow is not that significantly dependent on the degree of compression but is strongly related to the rotational speed. After implementing the present solution it is possible to decrease the rotational speed from about <NUM> RPM to <NUM> RPM. However for the machines operating on a dynamic principle (for example such as a fan) the difference in rotational speed will be more significant.

Operation without maximum pressure limitation (at constant speed) for low flows will cause the compressor to operate with a very high compression ratio.

While the invention presented herein has been depicted, described, and has been defined with reference to particular preferred embodiments, such references and examples of implementation in the foregoing specification do not imply any limitation on the invention. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope of the technical concept. The presented preferred embodiments are exemplary only, and are not exhaustive of the scope of the technical concept presented herein.

Claim 1:
A fluid distribution system comprising a system of valves (<NUM>, <NUM>, <NUM>) connected to a splitter (<NUM>) wherein a pressurized fluid (FP) is supplied to the splitter (<NUM>) by a pressurizer (<NUM>) driven by a motor (<NUM>), and a flow control system for controlling flow in the system of valves (<NUM>, <NUM>, <NUM>), the fluid distribution system further comprising:
- a plurality of flow sensors (<NUM>, <NUM>, <NUM>), each flow sensor (<NUM>, <NUM>, <NUM>) being respectively connected individually at an output of a separate one of the valves (<NUM>, <NUM>, <NUM>) to measure output flow from that particular valve (<NUM>, <NUM>, <NUM>);
- a plurality of flow controllers (<NUM>, <NUM>, <NUM>), each flow controller being respectively connected individually to a separate one of the valves (<NUM>, <NUM>, <NUM>) configured to output a control signal (C1, C2, C3) to control an opening angle of that particular valve (<NUM>, <NUM>, <NUM>) in response to an output from a flow sensor (<NUM>, <NUM>, <NUM>) connected at the output of that particular valve (<NUM>, <NUM>, <NUM>) and an outlet setpoint (S1, S2, S3) provided for that particular valve (<NUM>, <NUM>, <NUM>);
characterized in that it further comprises:
- a main pressure sensor (<NUM>) configured to measure pressure of fluid (FP) output from the pressurizer (<NUM>);
- a main flow controller (<NUM>) configured to adjust operation of the motor (<NUM>) driving the pressurizer (<NUM>) such that the pressure of the pressurized flux (FP) measured by the main pressure sensor (<NUM>) is equal to a main pressure setpoint (S);
- a main system controller (<NUM>) configured to set the main pressure setpoint (S) based on the control signals (C1, C2, C3) such as to set the valve (<NUM>, <NUM>, <NUM>) that operates at the largest opening angle to an opening angle defined by a valve opening setpoint (FS) that is a value lower than <NUM>% of the valve maximum possible flow.