TWO STAGES GAS PRESSURE REGULATOR WITH CYLINDRICAL BODY

Technical field

[0001] The invention is directed to the field of gas pressure regulators, notably for industrial gases and more particularly for fuel gases compressed at more than 200 bar, like compressed natural gas (CNG).

Background art

[0002] Prior art patent document published EP 0 420 599 A2 discloses a flow control system for used in a compressible fluid (like CNG) fuelled internal combustion engine. The system comprises a gas pressure regulator with a body on which an electromagnetic shut-off valve and a mechanical pressure reducer are mounted. The body can also comprise a U-shaped channel for circulating a heating fluid like the coolant of the engine. The construction and location of the heating channel is however not detailed. Also, the body shows a complicated design with many ports, in particular on its underside.

[0003] Prior art patent document published US 210/0180960 A1 discloses a temperature controlled pressure regulator comprising U-shaped tubular passageways located in a heating chamber fed with a heating fluid. The heat exchange between the heating auxiliary fluid and the gas flowing in the U-shaped tubing is quite high but the use of this tubing increases the manufacturing cost of the regulator and also increases its vulnerability with regard to the integrity of the tubing. In addition, the pressure regulator is a single-stage regulator without dynamic adjustment of the pressure.

[0004] Prior art patent document published DE 39 14 278 A1 discloses a pressure regulator for compressed air installations. The regulator comprises a body with a square-shaped section. A selection valve and a pressure reducer are mounted on opposed end sides of the body. The square-shaped section of the body is important because a connecting plate is to be mounted in a gas tight fashion to the body, the connecting plate connecting to the gas source and to the device(s) to be operated by the regulated gas flow. Consequently the production cost of the body remain high, essentially due to the fact that the bores that receive the selection valve and the pressure reducer have to be made by means of a milling machine equipped with specific milling tools specially designed to form these bores.

Summary of invention

Technical Problem

[0005] The invention has for technical problem to overcome at least one drawback of the above cited prior art. More particularly, the invention has for technical problem to provide a multi-stage gas pressure reducer exhibiting lower manufacturing costs.

Technical solution

[0006] The invention is directed to a gas pressure regulator comprising: a body with a longitudinal axis, a first end face and a second end face, said first and second end faces being opposed along said axis; a first stage valve or regulator mounted on the first end face of the body; a second stage valve or regulator mounted on the second end face of the body; wherein the body comprises a gas inlet, a gas outlet and a gas passage interconnecting said inlet and outlet via the first and second stage valve(s) or regulator(s); wherein the body is generally cylindrical around the longitudinal axis.

[0007] The external surface of the body is generally cylindrical. It can show one or more flattened areas of minor extent compared to the rest which is cylindrical.

[0008] According to a preferred embodiment, at least one of the first and second end faces comprises a bore concentric with the longitudinal axis, said bore(s) housing the corresponding valve or regulator and preferably being made by turning.

[0009] According to a preferred embodiment, the body comprises a heating fluid inlet, a heating fluid outlet and a heating cavity fluidly connected to said inlet and outlet, said cavity being configured for heating the gas flowing in said body. [0010] According to a preferred embodiment, the heating cavity is annular and concentric with the longitudinal axis.

[001 1] According to a preferred embodiment, the heating cavity is formed by a circular groove on one of the first and second end faces, and by a ring placed in, and closing, said groove. The ring can be held by an elastic ring snapped in a corresponding groove. It can also be held by the one of the first stage valve or regulator and second stage valve or regulator that is mounted on the end face where the ring is provided.

[0012] According to a preferred embodiment, the heating cavity is formed on the second end face of the body, the first stage valve or regulator being a pressure reducer configured for reducing the gas pressure by at least 100 bar, more preferably 150 bar.

[0013] According to a preferred embodiment, the heating fluid inlet and outlet are on the one of first and second end faces of the body that is opposed to the heating cavity, the bore comprising two drill holes extending longitudinally from said inlet and outlet to said cavity. The heating fluid inlet and outlet, and the corresponding drill holes, are preferably diametrically opposed.

[0014] According to a preferred embodiment, the second stage valve or regulator is an electromagnetic proportional valve.

[0015] According to a preferred embodiment, the gas passage in the second stage valve or regulator, or between said valve or regulator and the first stage valve or regulator, comprises an annular portion with a mean diameter that decreases in a downstream flow direction.

[0016] According to a preferred embodiment, the annular portion of the gas passage is formed between an inner sleeve and an outer sleeve, the inner sleeve being inside the outer sleeve, and said sleeves being housed in the bore of the second end face, against the bottom of said bore.

[0017] According to a preferred embodiment, the outer and inner sleeves are configured such that the annular portion of the gas passage opens out radially into a buffering chamber inside the inner sleeve.

[0018] According to a preferred embodiment, the outer sleeve comprises at an end opposed to the bottom of the bore a seat of the second stage valve or regulator. [0019] According to a preferred embodiment, the gas passage comprises several longitudinal holes opening out through the bottom of the bore of the second end face, at the periphery of said bottom.

[0020] According to a preferred embodiment, the several longitudinal holes open out through a bottom of a bore in the first end face of the body in order to be fluidly connected with a regulating chamber of the first stage regulator.

[0021] According to a preferred embodiment, the inlet is on the cylindrical outer surface of the body, the gas passage comprising a portion extending radially from the inlet to the longitudinal axis.

Advantages of the invention

[0022] The invention is particularly interesting in that it provides a cost effective construction of a dual stage gas pressure regulator. Indeed, the use of the two opposed end sides of a cylindrical body for housing the two stages is particularly interesting on a manufacturing point of view. The body can be easily machined, essentially by turning with a lathe, from a section of a cylindrical rod. The bores on both end faces and the heating cavity can be easily machined by rotating the workpiece on the lathe. The longitudinal drill holes can also be easily machined. Also, the heat transfer is quite efficient, essentially due to the annular passage for the gas between the two stages and the heating chamber that circumvent said passage. The metallic material of the body transfers the heat in an efficient manner to the gas.

Brief description of the drawings

[0023] Figure 1 is a perspective view of a gas pressure regulator according to an embodiment of the invention.

[0024] Figure 2 is a cross-sectional view along a longitudinal plane of the gas pressure regulator of figure 1.

[0025] Figure 3 is an enlarged cross-sectional view of the gas pressure regulator of figure 1 , along a longitudinal plane passing through the inlet port, i.e. a longitudinal plane different from the one of figure 2.

[0026] Figure 4 is cross-sectional IV-IV of the gas pressure regulator of figure 3. Description of an embodiment [0027] Figure 1 illustrate in perspective a gas pressure regulator 2 according to an embodiment of the invention.

[0028] The regulator 2 is a two stages regulator for compressed natural gas at 200-250 bar. The invention will be described in relation with that regulator being however understood that the invention does not necessarily need to be implemented for compressed natural gas.

[0029] The regulator 2 comprises a body 4 that is made of metal like aluminium, stainless steel or brass. The body 4 comprises a gas inlet 6, a gas outlet 8 and a gas passage (inside the body, not visible in figure 1 ) interconnecting said inlet and outlet. The regulator 2 can also comprise a fluid connector 10 to the exhaust of a pressure relief valve (inside the body, not visible) at the outlet. It can also comprises a pressure sensor or detector 12, with an electronic connector, at the inlet. The regulator 2 can also comprise two connectors 14 for a heating circuit.

[0030] In thermodynamics, the Joule-Thomson effect (also known as the Joule- Kelvin effect, Kelvin-Joule effect, or Joule-Thomson expansion) describes the temperature change of a real gas or liquid (as differentiated from an ideal gas) when it is forced through a valve or porous plug while kept insulated so that no heat is exchanged with the environment. Consequently some gases like CNG (contrary to hydrogen or helium) will cool sufficiently to cause freezing when expanding from high pressures. A solution to this problem is to heat the gas in the regulator by means of a heating circuit.

[0031] One of the fluid connectors 10 is an inlet and the other is an outlet for a heating fluid like the cooling liquid of the combustion engine of a vehicle that is equipped with CNG storage tank(s). The heating chamber inside the regulator 2 will be described more in details in relation with figures 2 and 3.

[0032] As is visible in figure 1 , the regulator is a two stages regulator with a first mechanical stage 16 (pressure reducer) and a second electromechanical stage 18 (proportional valve) that is fluidly downstream of the first stage [0033] Figure 2 is a cross-sectional view of the regulator of figure 1 along a plane that passes along the longitudinal axis L of the regulator. As is apparent, the body 4 comprises a first end face 4.1 and a second end face 4.2 opposed to the first one. The first stage pressure reducer 16 is mounted on the first end face 4.1. The connectors 14 for the inlet and outlet of the heating circuit are also mounted on the first end face 4.1. The second stage regulator 18 is mounted on the second end face 4.2.

[0034] The gas passage 20 in the body is in direct fluid connection with the inlet 6 (figure 1 ). The pressure reducer 16 comprises essentially a piston 22 housed in a cylindrical cavity formed by a cap 24 mounted on the body 4. The piston 22 comprises a main portion 22.1 and a tubular portion 22.2. The tubular portion 22.2 comprises a regulating edge 26 that cooperates with a seat 28 carried by the cap 24. The main portion 22.1 of the piston 22 comprises channels 22.3 fluidly interconnecting the area of the regulating edge 26 and the seat 28 and the regulating chamber 28 on the opposite side of the piston 22. A spring 32 urges the piston 22 and the regulating edge 26 away from the seat 28 so as to open the flow passage. The gas flows then through the channels 22.3 to the regulating chamber 30. In case of pressure increase in the regulating chamber 30, the resulting force exerted on the piston moves said piston against the resilient force of the spring 32, thereby reducing the flow section between the regulating edge 26 and the seat 28, and thereby reducing the pressure downstream of said flow section. The above principle of regulation and reduction of pressure is well known as such from the skilled person and does not need to be further detailed.

[0035] The gas in the regulating chamber 30 flows then through the passage sections 20.2 towards the second stage regulator 18 via a passage section 20.3 that is annular and generally conical.

[0036] The body 4 comprises a heating cavity 34 that is formed by a circular groove formed on the second end face 4.2 of said body. A ring 36 with sealing means like gaskets is placed in the groove and held by a retaining elastic ring 38 snapped in a corresponding slot formed in the outer surface of the groove 34. The ring 38 can even comprise a circular slot on its face in vis-a-vis with the bottonn of the groove 34. The groove 34 and the ring 36 are designed to leave a residual closed cross-section forming the cavity. This latter is in fluid connection with the inlet and outlet 14 via the drill holes 40 extending from the first end face 4.1 to the bottom of the groove 34. The inlet and outlet 14, as well as the corresponding drill holes 40, are preferably diametrically opposed. The heating fluid can therefore flow in the cavity 34 along two half-circle shaped channels and thereby transfer heat to the body 4.

[0037] Figure 3 is an enlarged cross-sectional view of the gas pressure regulator of figures 1 and 2, the section being however according to a different longitudinal plane as in figure 2.

[0038] As is apparent in figure 3, the annular section 20.3 of the gas passage 20 can be formed between an inner sleeve 42 and an outer sleeve 44. The inner sleeve 42 is housed in the outer sleeve 44. The inner sleeve 42 is generally conically-shaped with a base (with a larger diameter) resting on the bottom of a bore formed in the body 4 on the second end face 4.2. The inner surface of the outer sleeve 44 is distant from the outer surface of the inner sleeve 42 in order to form the annular gas passage 20.3. The ring- shaped end of the inner sleeve with a reduced diameter engages with the outer sleeve 44 so as to close the passage 20.3. Apertures 42.1 are provided at the ring-shaped end so as to guide the gas towards the buffer chamber 46 inside the inner sleeve 42.

[0039] The outer sleeve 44 comprises at its end opposed to the bottom of the bore in the body 4 a central aperture for allowing the gas to flow out of the buffer chamber 46 towards an exit chamber 48. This latter is in direct fluid connection with the outlet 8 (figure 1 ). The outer sleeve 44 forms a seat 44.1 of the second stage regulator 18. This latter comprises a plunger 50 housed in a body part 52 and that can be actuated by an electromagnetic coil mounted on said body part 52. The plunger 50 can carry a gasket that can contact the seat 44.1 in a gas tight fashion. The plunger 50 can also carry a mandrel with a tapering end able to enter the aperture inside the seat 44.1. The position of the mandrel in the aperture determines the flow section. The second-stage regulator 18 is a proportional electromagnetic valve that allows depending on the level of energisation of the coil to increase or decrease the outlet pressure. The pressure drop in this second-stage regulator 18 is advantageously much lower than in the first stage regulator 16.

[0040] The construction of the above described section 20.3 of the gas passage is particularly interesting in that it forms a passage with an increased contact surface with metallic parts, for instance the inner and outer sleeves 42 and 44, which are in direct contact with the metallic body 4 in which the heating cavity 34 is formed. The heat provided by the heating fluid is therefore optimally transferred to the gas. In addition, the provision of a buffer chamber 46 allows the gas to stabilize its pressure and temperature before subject to the second stage regulation.

[0041] Figure 4 is the cross-section IV-IV of figure 3. The section 20.2 of the passage 20 interconnecting the two stages are well visible. It is formed by a series of drill hole around a circle centred on the longitudinal axis L of the body and the regulator. We can also observe the section 20.4 of the passage interconnecting the inlet 6 with the first stage regulator, as well as the section 20.5 interconnecting the inlet 6 with the pressure sensor 12.

[0042] During assembly of the gas pressure regulator 2, both first and second stage regulators 16 and 18 can be easily mounted on the body 4 by mere insertion of their constituting parts followed by a securing action of the cap 24 and the body part 52, e.g. by a threaded engagement with the body 4. In addition, the bores formed on each of the first and second end faces 4.1 and 4.2 can be easily formed by turning since these bores are concentric with the longitudinal axis of the cylindrical body 4. The latter can be held in the chuck jaws of a lathe and the bore can be easily machined by means a simple cutting tool. The same applies for the cavity 34. The sections 20.2 (figures 2 and 4) of the passage interconnecting both stages can also be easily made by drilling parallel to the longitudinal axis of the body. The same applies to the drill holes 40 (figures 2 and 4) interconnecting the heating fluid inlet and outlet with the cavity 34 (figure 2).