Fluid handling – Processes – Involving pressure control
Reexamination Certificate
2003-02-04
2004-07-06
Krishnamurthy, Ramesh (Department: 3753)
Fluid handling
Processes
Involving pressure control
C137S102000, C137S487500, C137S613000, C251S030010
Reexamination Certificate
active
06758233
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to gas pressure regulators and more particularly to regulators for regulating pressure in large volume, highly dynamic flows of gas.
BACKGROUND
One of the technical challenges facing the natural gas vehicle (NGV) industry, and other pressurised gas using devices, is the need for an accurate, reliable pressure regulator to supply gas to the system. Currently, mechanical (analogue) regulators are being used that have inherent errors due to dynamic droop, hysteresis, and supply-pressure effects. These are single-stage or two-stage designs that use either a diaphragm or a piston coupled to a valve to control pressure. Durability has been a problem with a number of regulators. Some regulators have been prone to failures of the valve-seat, diaphragm, and o-rings. Others have been reported to jam or stick in the open position, or resonate (squawking, honking).
To address these concerns an electronic regulator has been developed that is controlled by a proportional-integral-derivative (PID) controller. This regulator is described in U.S. Pat. No. 6,003,543, filed Jun. 11, 1997, the disclosure of which is incorporated herein by reference. The regulator includes a high-speed solenoid valve, a pressure sensor, and an electronic control unit. This regulator can significantly improve the accuracy of the injector supply pressure by reducing droop (steady-state error), hysteresis, and the error due to changes in storage tank pressure. However, this system at present can only meet the fuel flow requirements of smaller engines.
U.S. Pat. No. 3,455,323 to Haupt, provides a gas regulator using electronic pressure control. The regulator includes a housing having an inlet, an outlet and a regulator valve for controlling flow through the housing from the inlet to the outlet. A pressure responsive member supported in a control chamber within the housing controls displacement of the regulator valve. The control of pressure in the control chamber however requires multiple valves each having a solenoid to control the bleeding and feeding of the control pressure in the control chamber therethrough. The arrangement of valves and solenoids is complex to assemble upon manufacture and requires awkward manipulation in use. Furthermore, the valves are arranged to be vented to the atmosphere when bleeding gas from the control chamber which is undesirable when the gas to be regulated involves fuels and the like which are typically not friendly to the environment.
British Patent Application 2 121 563 provides a pressure regulating apparatus for gaseous and liquid flow media. The apparatus includes a housing having an inlet, an outlet and a regulator valve controlled by a pressure responsive member mounted in a control chamber similarly to the above noted U.S. patent to Haupt. Control of the pressure in the control chamber however requires a complex arrangement of ports and valves for selectively feeding or bleeding the control chamber on both sides of the pressure responsive member. Furthermore, bleeding of the control chamber on both sides of the pressure responsive member requires venting externally of the housing. This is undesirable as noted above when regulating pressure of fuels and the like which should not be vented to the atmosphere.
The present invention is concerned with certain improvements to gas regulators for large volume, highly dynamic flows of gas which address some of the deficiencies of the above noted prior art.
SUMMARY
According to one aspect of the present invention there is provided a gas pressure regulator for regulating the pressure of a gas flowing from a source of the gas under pressure to a device for using the gas, the regulator comprising:
a regulator housing having a gas inlet for receiving the gas and a gas outlet for the delivery of the gas from the housing;
a pressure reducing valve in the housing for controlling the flow of gas from the inlet to the outlet;
a pressure reducing valve controller comprising:
a control chamber;
a feed valve having an inlet for receiving gas from said source of gas under pressure and a control pressure outlet coupled to the control chamber, the feed valve having an open state in which the valve is fully open and a closed state in which the valve is fully closed;
a bleed valve having an inlet coupled to the control chamber and an outlet coupled to the gas outlet of the regulator housing, the bleed valve having open state in which the valve is fully open and a closed state in which the valve is fully closed;
a high speed solenoid valve actuator for operating the feed and bleed valves;
a pressure responsive member in the control chamber and coupled to the pressure reducing valve for movement therewith, the pressure responsive member being movable in response to variations in a control pressure in the control chamber;
a pressure monitor for monitoring an actual gas pressure at the gas outlet of the regulator housing;
a controller coupled to the pressure monitor and to the solenoid valve actuator for controlling operation of the feed and bleed valves between their respective closed and open states to produce a desired gas pressure at the gas outlet of the regulator housing.
The regulator of the present invention provides an effective means of regulating pressure of large volume, highly dynamic flows of gas using a pressure reducing valve which is simple in design and use. The arrangement of the bleed valve is particularly useful for ensuring that gaseous fuels being regulated are not vented to the atmosphere, but rather are vented to the outlet of the regulator where the fuel can be subsequently consumed with the pressure regulated gaseous fuel exiting the regulator.
This regulator is of the piston or diaphragm type, with the pressure responsive member, e.g. piston or diaphragm, moving in response to a pressure difference across the member, and controlling the pressure reducing valve. In this case, the control pressure is supplied by the gas being regulated, under the control of feed and bleed valves. This allows the rapid regulation of the supply pressure with a limited energy input. The back pressure is the outlet pressure.
To adjust the regulator in response to a reduced gas or fuel demand, the control chamber pressure must be reduced using the bleed valve. Because the control gas may be gaseous fuel, it is not acceptable to bleed this gas into the atmosphere, so that the gas used for control is bled from the control chamber into the gas outlet of the regulator housing to be used as fuel.
The use of a high speed solenoid actuator for the feed and bleed valves allows the same kind of dynamic control of the control pressure that can be achieved with the pressure control system disclosed in prior U.S. Pat. No. 6,003,543, referred to above, but for much larger flow rates.
The solenoid valve actuator may be a single solenoid coil opening and closing the feed and bleed valves in opposition. Pulse width modulation and/or frequency modulation may be used to vary the ratio of open and closed times and thus the pressure in the control chamber. Alternatively, two coils may be used for the two valves. This allows independent control of the valves to compensate for inertial effects, for example pressure spikes or time lags in flow changes, in response to rapid changes in flow demand.
The desired gas pressure at the gas outlet is preferably a set point pressure. The controller thus preferably comprises a mechanism for controllably varying the set point pressure.
The controller preferably includes a signal generating mechanism for delivering a pulsed electrical signal for operating the feed and bleed valves and a signal varying mechanism for controllably varying the pulse width of the electrical signal.
The high speed solenoid valve actuator preferably includes a pressure reducing valve closing mechanism for closing the pressure reducing valve in response to deactivation of the high speed solenoid valve actuator. This arrangement provides a positive shut-off for ensuring no gaseous fuel is released from the regu
Hill Sheldon
Sulatisky Michael
Battison Adrian D.
Dupuis Ryan W.
Krishnamurthy Ramesh
Saskatchewan Research Council
Williams Michael R.
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