Pumps – Expansible chamber type – Having separate noncyclic valve
Reexamination Certificate
1998-06-10
2001-05-08
Freay, Charles G (Department: 3746)
Pumps
Expansible chamber type
Having separate noncyclic valve
C417S228000, C417S283000, C417S303000, C417S505000
Reexamination Certificate
active
06227823
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention utilizes a balanced, dual crank reciprocator of the type disclosed in our U.S. Pat. No. 5,674,053, issued Oct. 7, 1997, entitled, “High Pressure Compressor with Controlled Cooling During the Compression Phase,” and U.S. Pat. No. 5,716,197, issued Feb. 10, 1998 entitled, “High Pressure Compressor with Internal Inter-Stage Cooled Compression having Multiple Inlets.”
The present invention defines a gas compressor and dispensing station with a new and improved cyclic control system for high and ultra high pressure compressors. The compressor in this system is capable of achieving in one stage, ultra high pressure ratios of over 40/1. The invented system eliminates the need for multi-stage compressors, compressor assemblies, particularly for natural gas compressors, requiring delivery pressures of 3600-4000 psi, for NGV (natural gas vehicle) supply stations and natural gas line transportation systems.
This invention relates to a gas compressor with a new cyclic control system that is provided with a control module and sensors for controlling a group of electronically activated, electro-hydraulic valves for regulating pressurized gas flow through the compressor. The electro-hydraulic valves are selectively operated during the reciprocal cycle of the compressor in an electronic-loop of cycle control format for routing gas at two discrete pressures through separate circuits in the compressor.
In this specification, the system described in our provisional application is refined with the construction of the electro-hydraulic valves controlling flow of high pressure gases from the compressor to the respective high pressure gas receiving tanks being detailed.
The single-stage compressor of this invention is designed to be inexpensively fabricated and operated for alternate fuel vehicles. Natural gas is a relatively clean, burning fuel, and, comprised largely of methane, has advantages over other hydrocarbon fuels in minimizing production of the greenhouse gas, carbon dioxide. Although natural gas is relatively abundant, it has not been widely used as an alternate fuel for vehicles because of the lack of a distribution system. Many cities have an existing infrastructure of gas distribution lines for heating and cooking. However, these are relatively low pressure lines, 30-40 p.s.i. at the street. At this pressure, the gas volume for powering a vehicle is too large to provide the driving range deemed acceptable.
Pressurized gas vessels have been designed to contain natural gas at the high pressure necessary for the fuel capacity for the driving range desired in a reasonably sized bottle. One fueling alternative is to replace prefilled gas bottles at a refueling station. It is not economical, however to prefill bottles and deliver such prefilled bottles to fueling stations for exchange with customer bottles.
While bottles may be pre-filled on the site of the fueling station, this requires an on-site compressor, and, if a fueling station has an on-site compressor it may as well fill a customer's fuel bottle already in the customer's vehicle. For the fuel to be competitively priced compared with gasoline, the on-site compression system must be efficient and productive, requiring minimal storage of compressed gas.
The high pressure gas compressor of this invention utilizes a positive displacement compressor with an expansion gas scavenging of the residual gases in the compressor. By strategic timing of the gas flow in the compression and expansion cycle, gas can be compressed in a single stage with a resultant temperature well within the thermal limits of the structural components of the compressor.
The gas compression system of this invention is targeted toward the natural gas industry both for high pressure transportation of gas in gas lines, and for destination stations where natural gas is dispensed to customer bottles for use as a vehicle fuel. It is to be understood, however, that the gas compression system can be utilized for gasses other than fuel gas where a cost-effective, high-pressure compression is required.
SUMMARY OF THE INVENTION
The ultra high pressure gas compressor in the compressed gas dispensing station of this invention is characterized by a control system controlling two high-pressure, electro-hydraulic valves. One valve is a delivery valve for regulating a 3600 psi branch, and the second valve is a delivery and recirculation valve for regulating a 400 psi branch. The compressor is also provided with an automatic or electro-hydraulic intake valve for regulating gas intake into the compressor.
The compressor cycle starts with the intake and mixture of an initial remaining charge of precooled, expanded cryogenic gas injected at the end of the previous cycle, followed by the compression stroke achieving 4000 psi. Pressure is monitored by an electronic pressure transducer, which is informing an electronic control module (ECM), that controls the activation of the delivery recirculation valve (DRV). This valve (DVR) is provided with two channels, one conducting the high pressure relative hot gases through a check valve, into a 4000 psi cooled receiver tank, and the second channel conducting a recirculated cooled gas from the cooled receiver tank back into the compression chamber.
The recirculation process is started by the activation of the 3600 psi delivery valve, which produces a pressure drop in the compression chamber, which causes the opening of the recirculation check valve, controlling the exit of 4000 psi gas from the cooled receiver tank. In that moment, the scavenging process of purging the hot gases toward the 3500 psi branch, and replacing the displaced gas with cooled high pressure 4000 psi gases is accomplished.
The 40-1 expansion of the cooled and high pressure 4000 psi gas, that remains in the compression chamber, produces a very low temperature cryogenic gas, which is mixed with the new intake charge, producing a low temperature mixture, also cryogenic, at the start of the compression cycle. The compression stroke will produce at the end, a relatively low temperature, high pressure delivery gas for the single stage compression.
The result will be an equivalent of an isothermic compression cycle. The high pressure compressor of this invention is particularly adapted for use in a gaseous fuel dispensing station. The embodiments described in this specification are designed for natural gas, which is typically a mixture of hydrocarbon gases, primarily methane.
REFERENCES:
patent: 4576015 (1986-03-01), Crawford
patent: 5097857 (1992-03-01), Mayhew
patent: 5674053 (1997-10-01), Paul et al.
patent: 5716197 (1998-02-01), Paul et al.
patent: 5769610 (1998-06-01), Paul et al.
Paul Ana
Paul Marius A.
Freay Charles G
Peterson Richard Esty
Tyler Cheryl J.
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