CYLINDER MANAGEMENT SYSTEM
BACKGROUND OF THE INVENTION
Natural gas powered vehicles store fuel in high-pressure cylinders at nominal pressures ranging from 3000-3600 psig. As the cylinders store an enormous amount of energy, they are potentially explosive. To minimize the chance of explosions, legal requirements stipulate that cylinders be taken out of service long before they should pose any burst risk. For example, regulations might require a cylinder to be designed for 20,000 fill-empty cycles (e.g. fatigue cycles), and that it be taken out of service at
14,000 cycles, when it might really only see 7,300 fill-empty cycles (e.g. one cycle per day for 20 years is equivalent to 7,300 cycles). Thus, cylinders are over designed.
Most cylinder valves are restrictive to flow during filling, which can extend filling times. Further, most valves direct the filling flow along the centerline of the cylinder, which is a non-ideal approach to filling. Maximum filling has been found to occur with radial gas inlets, with the "jets" directed against the cylinder wall. As the cylinder is filled the gas gets hot, "artificially" raising the pressure and preventing a complete fill. That is, once the gas cools back down to the ambient temperature, the pressure drops accordingly. Thus, a typical fill only uses 85-90% of the cylinder's capacity.
Since the pressure in the cylinder decreases as the fuel is consumed, a regulator is needed to provide a nearly constant pressure to the fuel injection system.
Depending on the fuel injection system used, such pressures may vary from 30-150 psig. Such regulators tend to be large and tend to provide relatively poor pressure control.
As commercial natural gas contains water, the pressure regulators must be heated to control the potential formation of hydrates (which can block the flow of fuel). This heating requirement detracts from the vehicle's heater and defroster performance, and thus should ideally be minimized. Most natural gas regulators have no thermal regulation system and are poor at exchanging heat between the engine's coolant and the fuel.
Most systems place the regulator in or near the engine compartment. This increases the length of expensive high-pressure stainless steel line and fittings that
must be used. This standard system is more prone to leak and has greater opportunity for dangerous situations to arise during accidents or as the result of mechanical damage.
SUMMARY OF THE INVENTION
This invention provides a system to manage cylinders of high-pressure fluid including master and slave cylinders, each equipped with a valve. The master valve (mounted on the master cylinder) include pressure and temperature sensors, a high- pressure solenoid (though any appropriate fuel withdrawal or portal mechanism would also suffice) and a pressure regulator. The sensors communicate the cylinder conditions to the filling station during refueling, so that a maximum fill could be achieved. The sensors also allow integral electronics to accumulate fatigue information and to permanently take the cylinder out of service once the safety limit point was reached. The regulator is contained outside but near the neck of the cylinder and would acquire some amount of heat from the massive cylinder (typically 150" lbs.).
Each slave cylinder has a slave valve. Both the slave valves and the master valve have high-pressure solenoids, PRD's (pressure relief devices), and bleed valves. In both cases, fill gas would pass through the solenoid, which acts as a back check valve. The solenoids direct the fill gas radially against the walls for maximum filling. If electrically energized, the solenoid allows the gas in the cylinder to flow to the common inlet/outlet line.
This system would provide the following benefits:
• Faster filling due to benefits of radial inlet geometry • Faster filling by communicating pressure and temperature to filling station
• Reduced heat extraction from engine coolant due to:
- heat taken from cylinder neck
- more efficient heat exchanger design
- use of a thermostat; • Potential to reduce cylinder design weight (since cylinder come out of service at a known safety limit point);
• Potential to reduce frequency of cylinder inspections or extend inspection interval;
• Reduced cost by fewer high pressure joints, and less high pressure tubing; and
• Enhanced crashworthiness due to regulator, solenoid, and pressure sensors being inside the cylinder neck.
BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will be described by way of example and with reference to the drawings in which:
FIG. 1 is a front view of the present invention as incorporated into fluid cylinders;
FIG. 2 is a schematic diagram of the controller module;
FIG. 3 is a side view of one embodiment of the invention; FIG. 4 is a front view of one embodiment of the invention;
FIG. 5 is a horizontal cross-sectional view of one embodiment of the invention;
FIG. 6 is a vertical cross-sectional view of one embodiment of the invention;
FIG. 7 is another horizontal cross-sectional view of one embodiment of the invention showing the pressure relief device and the bleed mechanism; and FIG. 8 is another vertical cross-sectional view of one embodiment of the invention showing the heating circuitry through the valve.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention provides a system to manage high-pressure cylinders. A gas- powered vehicle would preferably have one master and any number of slave cylinders, each equipped with a valve. The master valve (mounted on the master cylinder) would preferably include pressure and temperature sensors, a high- pressure solenoid (though any appropriate fuel withdrawal or portal mechanism would also suffice) and a pressure regulator. The sensors communicate the cylinder conditions to the filling station during refueling, so that a maximum fill could be achieved. The sensors would also allow integral electronics to accumulate fatigue information and to permanently take the cylinder out of service once the safety limit point was reached. The "out of service" state would be achieved by permanently disabling the internal high-pressure solenoid (e.g. solenoid not externally accessible). The regulator would preferably receive gas from all the cylinders and reduce the output to the desired low pressure (e.g. in the 30-150 psig range). Thus, only a low- pressure line would be routed from the master cylinder to the engine compartment.
The regulator would preferably be contained outside but near the neck of the cylinder and would acquire some amount of heat from the massive cylinder (typically 150" lbs.). Thus, the amount of heat required from engine coolant would be reduced. The regulator could include a means to control fuel temperature, further reducing the heat extracted from the engine's coolant.
Each slave cylinder would preferably have a slave valve. Both the slave valves and the master valve would preferably have high-pressure solenoids, PRD's (pressure relief devices), and bleed valves. Preferably in both cases, fill gas would pass through the solenoid, which acts as a back check valve. The solenoids would preferably direct the fill gas radially against the walls for maximum filling. If electrically energized, the solenoid allows the gas in the cylinder to flow to the common inlet/outlet line.
Optionally, the master valve could be equipped with a V* turn master shut-off valve (required by some jurisdictions and some vehicle manufacturers). Each slave valve would normally have its own pressure sensor and fatigue cycle counter system.
In the preferred embodiment, each valve would have a multi-turn manual valve for isolating each cylinder from the common inlet/outlet line.
Figure 1 depicts one preferred embodiment of the system. The system shown has one master cylinder 20 and two slave cylinders 21. However, any number of slave cylinders could be used. The cylinders, as shown, are equipped with a master valve 40, and slave valves 30 and 31 (which are identical). The high pressure filling receptacle 10 is preferably connected by high pressure tubing 11 to slave valve 30. During filling, some of the gas would pass into the first cylinder through valve 30. The remainder would pass on to valve 31 by high pressure tube 12. During filling, some of the gas would pass on to valve 40 through high pressure tube 13. Valves 30, 31, and 40 preferably all have internal high pressure solenoids. During filling the solenoids preferably act as check valves, blowing open to allow filling to occur. All solenoids would preferably have approximately radial holes, directing the filling "jets" against the cylinder wall. After filing, the solenoids would close, keeping the gas inside the individual cylinders. If the solenoids were energized, the gas from each cylinder would be allowed to exit the cylinder and enter the high-pressure common rail formed by lines 12 and 13.
The high-pressure rail is connected inside valve 40 to the system's pressure regulator. If desired, an optional valve, such as a % turn valve, could be included in
valve 40, serving to block the flow of fuel from the common rail to the pressure regulator. The output of the pressure regulator would pass via outlet fitting 146 and low-pressure line 60 to the engine's fueling system. The electrical connections 70 from each of the 3 valves would preferably be connected to the vehicle's electrical system. Each of the valves would preferably have a thermally activated pressure relief device (PRD) 143, to protect the cylinder from rupture in case of a fire. The outputs from PRD's 143 are connected to a common vent line 50 via lines 51 and 52 and suitable tee's. The output of the vent rail 50 could be plumbed away to a preferred discharge point. Each cylinder valve (30, 31 , and 40) would also have a multi-turn manual valve 142. Valve 142 serve to isolate the gas in each cylinder from the high-pressure rail. A shown, the valves 142 have a small external hex for the operator. Alternatively, a knob or tee handle could be provided to turn valves 142.
A key feature of a preferred system is an electrical control module 152 (seen in Figures 3 and 5) which is contained within the cylinder to preventing tampering. Module 152 continuously monitors the pressure inside the cylinder. In normal use, the pressure might swing from about 4500 psig during filling to about 300 psig just before the next refueling. Module 152 computes and attributes a fatigue value for each pressure swing as a function of a number of variables including the maximum and minimum pressure values, and calculates a lifetime cumulative fatigue level. When the cumulative fatigue level has reached the maximum allowable level (the fatigue threshold), the cylinder is taken out of service. One way of effecting the removal of the cylinder from service is the following: when the limit is reached, the module destroys a fusible link, which permanently prevents the high-pressure solenoid from opening. The cylinder may then be drained of fuel via a bleed valve, so that it can be safely removed from the vehicle.
Figure 2 is a schematic diagram depicting the configuration of module 152. Module 152 would typically be a printed circuit or a hybrid thick film circuit. It could be mounted within the valve body 140, or attached to the high-pressure solenoid (which is contained within the cylinder) by an electrical receiving component located on the solenoid. Module 152 would receive the power input at points 200 and 202 (typically 12Vdc and ground respectively). The unregulated input voltage at 200 would be routed to an appropriate voltage regulator 207, which could be either a linear or chopper type of regulator. The input and output of the regulator would preferably be capacitively filtered (208, 209) to eliminate high frequency spikes and to smooth out short term power interruptions. The regulated voltage (typically 5Vdc) would be
preferably applied to cylinder pressure sensor 210, cylinder temperature sensor 212, and microcontroller 217 (also known as a controller)
Pressure sensor 210 would typically be an absolute pressure sensor, to eliminate the need for an atmospheric reference connection. Sensor 212 would preferably be in a chip form an attached top the circuit board, or it could be a separately packaged unit, which is interfaced with the board. The output of sensor 210 would be connected to the analog input section 218 of microcontroller 217. Section 218 would preferably include an analog to digital converter, so that the analog signals could be processed digitally. Cylinder temperature sensor 212 would typically be a thermistor, and would be biased by a series resistor 211. The output of the voltage divider formed by 211 and 212 would be fed to analog section 218. A voltage divider formed by resistors 213 and 214 would also be fed to the analog section 218, so that microcontroller's program could correct for any errors in the reference voltage from regulator 207. In order to ensure accurate performance, an external crystal 222 would preferably trigger the microcontroller's clock section 220. The microcontroller's internal start-up and sequencing section 223 would preferably be stabilized by external components 223a. Calibration values and the fatigue accumulator values would be stored in the non-volatile random access memory (RAM) 224 section of micrcontroller 217. When energized, so long as the maximum fatigue level had not been reached, preferably microcontroller 217 would energize the coil 205 of high-pressure solenoid 151. The solenoid's relatively high current would be handled by power driver 206, which would be turned on by the digital output section 221 of microcontroller 217. A low resistance fusible link 215 is in series with a high resistance resistor 216. The output of the 215-216 voltage divider would be connected to the analog section 218 of the microcontroller, normally delivering a high voltage (e.g. a logical 1). Once the cumulative fatigue limit was reached, the microcontroller would preferably destroy the fusible link, opening the 215-216 voltage divider and permanently assuring a zero voltage (logical 0). The fusible link would be destroyed by the digital output section 221 turning on a high current driver 225, which would short the 215-216 node to ground, blowing the fusible link. From that point on the microcontroller would not allow high-pressure solenoid 151 to open.
The microcontroller could also optionally calculate the amount of energy in the cylinder from sensors 210 and 212. The result could be provided as an electrical output, for purposes of driving a fuel gauge. In those cases, the calculated value would be preferably converted to a frequency, which would drive one channel of the
digital output section 221. That frequency would be delivered to a frequency to dc converter 226, which would deliver an appropriate DC voltage to point 203, the fuel gauge (e.g. 0-5 Vdc = 0 - 100% fuel level).
In a further variation, the microcontroller could communicate with the outside world. Such communications could include self-diagnostics information and the current fatigue accumulator level. In such a case, input data (queries) could be received on lines 201 , which would be buffered by appropriate circuitry 227 and delivered to the digital input section 219 of microcontroller 217. For example, the communications port could use a RS232 protocol. Data out could be provided by output lines from digital output section 221 driving an appropriate buffer 228, causing the desired information to appear at lines 204. Such communications could have separate input and output lines, or could be bi-directional on common lines.
Figure 3 is a side view of valve 40 depicting several of the salient parts. Body
140 is preferably threaded into the neck of master cylinder 20 via threads 150. The pressure relief valve 143 and low-pressure outlet fitting 146 can be seen, as can the hex operator of manual valve 142. A pressure relief valve 144 is preferably provided to protect the low pressure output section from dangerous overpressures. Port 147 provides an atmospheric reference for the regulator's mechanism. The regulator, which is preferably internal to the valve body 140, but situated outside of the receptacle, is presumed to have an external adjuster 149, which is contained within the neck of the cylinder and is thus tamperproof. The high-pressure solenoid assembly 151 is also preferably contained within the neck of the cylinder. The electronic control module 152 is preferably attached, as shown, to the rear of the high-pressure solenoid 151. The electrical leads 154 preferably pierce the body 140 via a number of wire pass through schemes 153.
Figure 4 is a frontal view of valve 40 depicting the location of additional salient parts in another preferred embodiment. An external pressure sensor 148 would be used in cases where the microcontroller was not used to calculate and retransmit fuel level. The high-pressure inlet fitting 141 can also be seen in figure 4. Cover 145 provides a means to load the regulator section into the valve body during manufacturing.
Figure 5 is a horizontal sectional view of valve 40, through section 1-1 as shown on Figure 3. High-pressure gas, from the other cylinders or from a refueling station, enters the valve through a suitable fitting 141 that is preferably threaded into body
140. The gas flows from 141 into the interior of filter 155 that may be of sintered metal or wire cloth construction, amongst other possibilities. Filtering is required during withdrawal to remove very small particles which might be contained in the fuel and which would be large enough to block the regulator open. For example, at 4,500 psig the regulator's opening may be only 0.0008" (20 microns) in order to supply enough fuel to produce over 200 horsepower. Thus, a 20 micron particle, if caught between the regulating seal and seat, could cause 200 BHP worth of fuel to be continuously delivered. Filtering during refueling is not physically or economically practical. Refueling rates may be 20-50 times the withdrawal rates. Thus, in order to provide a satisfactorily small restriction during refueling, the filter would have to be inordinately large and expensive. If a normal size filter were used, and subjected to the refueling flow, an unacceptably high restriction would occur across the filter. That restriction could cause the filter to be destroyed, or greatly lengthen the refueling time, or both.
From the filter the gas enters connecting passage 161. If the manual valve
142 is open (as shown), its seal 163 is moved away from the raised 162 formed in body 140 seat, permitting the gas to flow into passage 164. Passage 164 communicates with passage 165 in solenoid adapter 166, which is preferably threaded into body 140. The opposite end of solenoid adapter 166 is preferably threaded into and supports the solenoid assembly 151. Solenoid 151 is shown in the open condition. In most but not all cases, solenoid 151 would be a pilot operated type as shown; however, for example, a direct acting solenoid could also be used. A pilot operated solenoid would typically have a coil 205, a magnetic pole piece 151a, a magnetic pilot piston 151b, a return spring 151c, a non magnetic primary piston
151d, and a non magnetic core tube 151 e which both pistons slides in. A flux return path 151j would typically be used to increase magnetic efficiency. Flux return path 151j could be in the form of a u-shaped yoke (as shown), a deep drawn cylindrical coil cover with a bottom magnetic flux washer, or a cylindrical coil cover with both top and bottom magnetic flux washers. Pilot piston 151b would preferably have a suitable elastomeric pilot seal 151f for sealing the pilot orifice 151g in primary piston 151d. A typical size for the pilot orifice would be about 0.020". An appropriate sealing land 151h on piston 151d preferably provides a seal against suitable elastomeric primary seal 151L In the normal state (i.e. pressures in cylinders equalized and valves 30, 31, 40 de-energized) return spring 151c would move both pistons towards their respective seals, stopping the flow of gas. During refueling, the higher pressure
in passage 164 would force the solenoid open, allowing gas to move past the front face of primary piston 151d and exit the solenoid through radial drillings 167.
During fuel withdrawal (engine running), the solenoid would be electrically energized and would open, allowing fuel from the cylinder to pass from radial drilling 167, past primary piston 151d and into passage 165. Gas would continue to flow from 165 into passage 164, and if manual valve 142 is open, on into passage 162. If manual valve 142 were closed, the gas could not pass further and the cylinder would be isolated from the regulator. From passage 162 the gas would enter the center of filter 155 and join gas entering valve 140 from the other cylinders via fitting 141. The combined gases would turn an angle, for example about 90°, and pass through filter 155 being filtered. After passing through the filter, the gas would be in the annular area 160 between the filter and the companion bore in body 140. The filtered gas would exit space 160 via passage 168, which is plugged via, for example, conventional ball plug 169. The continuing routing of the gas from passage 168 to the regulator section is shown in Figure 6 and discussed below.
Figure 5 also depicts the integration of a suitable thermally-triggered pressure relief device 143. Pressure relief device 143 is installed in a suitable port 179 which may use either a dryseal pipe thread or straight thread and o-ring to effect a gas tight seal, amongst other alternatives. Gas from inside the cylinder is always in communication with one end of pressure relief device 143 (e.g. the inlet), through passage 181 which connects with inlet chamber 180. Shown directly opposed of pressure relief device 143 is the bottom portion of plug 185, which seals the bleed port. As the bleed port is vertically offset from the centerline of pressure relief device 143, this section mostly misses the bleed mechanisms and plug. They are shown in Figure 7.
Figure 6 is a generally vertical cross-sectional view, through section 2-2 as shown in Figure 4. Filtered gas in passage 168 turns an angle, for example about 90° and enters radial passage 170, which delivers the gas to a compensation mechanism's inlet chamber 170a. A seal, preferably a conventional ball plug 169, seals passage 170. High pressure filtered gas in chamber 170a enters compensation piston 171. Gas pressure tends to move piston 171 to the right, which is resisted by compensation springs 172. Under no flow conditions, as shown, the seal 175 in sensor piston 173 rests against the end of piston 171 to prevent flow. Gas at the regulated pressure passes from chamber 170b into the center bore 176 of piston
173, then through radial drillings 177 into outlet annulus 178 which is connected to outlet port 156. A suitable outlet fitting 146 is threaded into port 156. Atmospheric reference port 147 (Figure 3) intersects chamber 170c (intersection not shown), so that sensor piston 173 responds to the outlet pressure. The outlet pressure tends to move piston 173 to the left, which is resisted by sensor springs 174. The two pistons and their spring sets cooperate to provide a nearly constant outlet pressure, regardless of flow and input pressure.
Figure 7 is a horizontal cross-sectional view, through section 3-3 as shown in Figure 3. This section is located vertically above the section shown in Figure 5 and shows the entire bleed mechanism. As this section is above the centerline of the inlet fitting 141 and manual valve 142, it will be appreciated that only the top portions of those parts show in this view. The longitudinal passage 181 communicates with inlet chamber 180. Chamber 180 communicates with transverse passage 183, which has a first wider diameter and a second narrower diameter. A suitable check valve cartridge 182 is installed in the wider section of passage 183. As shown, a conventional metal-seat hydraulic check valve is used. However, other types could be substituted. The check valve is installed "backwards" so that the normal gas pressure serves to seat the valve and prevent gas from passing on into the bleed port 184. As check valve 183 may have a very slight leak, bleed port 184 is plugged with a suitable plug 185. A shown, plug 185 is preferably an SAE o-ring sealed port plug. However other plug types could be used. When it is necessary to drain the cylinder, plug 185 is removed and a drain tool installed in its place. The drain tool includes a narrow pin, which pushes the check valve's ball open allowing flow to occur.
Figure 8 is a vertical cross-sectional view, through section 4-4 as shown in Figure 4. This figure depicts one possible arrangement for heating the body in order to enhance regulator performance. Specifically, this figure depicts a way for routing warm engine coolant through a series of passages in order to warm body 140. Two access holes 186 and 187, which are part of the coolant circuit, are identified on Figure 4. Figure 8 is a cross section through the left hole 186. As shown in Figure 8, access hole 186 connects to longitudinal passage 190 and is plugged by, for example, a conventional ball plug 169. A coolant inlet port 188 is located on the bottom face of body 140 and would be suitable threaded construction to accept an appropriate fitting. Coolant inlet port 189 is connected to passage 190 by a short drilling 189. Passage 190 is also intersected at its end by a second drilling 191, which
is also plugged by, for example, a conventional ball plug 169. A transverse drilling 192 intersects 191 and continues to the opposite side body 140, where it intersects a mirror, though not restricted to such, image of the 188-189-190-191 circuit. The mirror image circuit (not shown) is anchored at access point 187 (Figure 4) in the same fashion as the 188-189-190-191 circuit is anchored at access point 186. Thus, coolant would enter at the bottom left side of body at 188. The coolant would flow upwards through 188 and 189, turn an angle, such as 90° and flow rearwards through 190, turn a further angle, in this case 90°, and flow downwards through 191, turn an angle, such as 90°, and flow transversely through 192 to the opposite of body 140. On the opposite side the coolant would flow through a mirror image of 188-189- 190-191 circuit and would exit through a suitable port, similar to 188, on the right bottom side of body.
It will be appreciated that the above description relates to the preferred embodiments by way of example only. Many variations on the apparatus for delivering the invention will be obvious to those knowledgeable in the field, and such obvious variations are within the scope of the invention as described and claimed, whether or not expressly described.
All patents, patent applications, and publications referred to in this paper are incorporated by reference in their entirety.