Porous barriers to reduce peak explosion pressure inside a flame-proof enclosure of a synchronous reluctance motor

Abstract

A synchronous reluctance motor (SynRM), includes an open rotor with a drive end that is fluidly connected to a non-drive end using one or more open passages. The one or more open passages include a plurality of porous barriers. An ignition source ignites a reactant fluid within a first volume of the open rotor to cause a flame to propagate from the first volume to a second volume. The first volume is a drive end volume within the drive end, a non-drive end volume within the non-drive end, an air gaps volume within a motor enclosure of the SynRM or an open passages volume within the one or more open passages. The plurality of porous barriers reduces a flow rate of the flame as the flame propagates from the first volume to the second volume based on the flame interacting with the plurality of porous barriers.

Description

POROUS BARRIERS TO REDUCE PEAK EXPLOSION PRESSURE INSIDE A FLAME-PROOF ENCLOSURE OF A SYNCHRONOUS RELUCTANCE MOTORFIELD

[0001] The present disclosure relates to electrical machines. In particular, the present disclosure relates to synchronous reluctance motors (SynRM) with open rotors that operate in an explosive atmosphere.BACKGROUND

[0002] When combustible gas is ignited inside of a motor enclosure, the flame propagates in outward direction from the point of ignition at a subsonic velocity, giving rise to deflagration. The burnt gases that are downstream of the flame front expand rapidly, further accelerating the flame and sending pressure waves that compresses the unbumt mixture ahead of the flame front. Certain conditions such as fuel type, stoichiometry and geometry of enclosure can provide favorable condition for the flame to transition to detonation. In detonations cases, the burnt gases attain sonic velocity and push the deflagration flame to attain sonic velocity as well. This transition from deflagration to detonation causes detonation / shock wave that leads to a drastic rise in pressure downstream of the detonation wave.SUMMARY

[0003] A first aspect of the present disclosure provides a synchronous reluctance motor (SynRM), comprising: an open rotor comprising: a drive end; a non-drive end; and one or more open passages that fluidly connect the drive end to the non-drive end, wherein the one or more open passages comprise a plurality of porous barriers, wherein a reactant fluid is distributed within the SynRM, an ignition source ignites the reactant fluid within a first volume of the open rotor to cause a flame to propagate from the first volume to a second volume, wherein the first volume is a drive end volume within the drive end, a non-drive end volume within the non- drive end, an air gaps volume within a motor enclosure of the SynRM or an open passages volume within the one or more open passages, and wherein the plurality of porous barriers reduces flow rate (e.g., speed) of the flame as the flame propagates from the first volume to the second volume based on the flame interacting with the plurality of porous barriers.

[0004] According to an implementation of the first aspect, the plurality of porous barriers are positioned within the one or more channels to create a plurality of compartments within the one or more channels, and wherein the plurality of porous barriers reduce the flow rate of theflame by compartmentalizing an unbumt portion of the reactant fluid accumulated in the second volume end of the SynRM such that the unbumt portion of the reactant fluid cannot be reached by the flame.

[0005] According to an implementation of the first aspect, the first volume is the drive end volume and the second volume is the non-drive end volume, and wherein the flame propagates from the drive end volume to the non-drive end volume through the one or more open passages.

[0006] According to an implementation of the first aspect, the first volume is the non-drive end volume and the second volume is the drive end volume, and wherein the flame propagates from the non-drive end volume to the drive end volume through the one or more open passages.

[0007] According to an implementation of the first aspect, the first volume is the open passages volume and the second volume is the drive end volume, and wherein the flame propagates from the open passages volume to the drive end volume and a third volume within the non-drive end volume through the one or more open passages.

[0008] According to an implementation of the first aspect, the first volume is the air gaps volume and the second volume is the drive end volume, wherein the flame propagates from the air gaps volume to the drive end volume and a third volume within the non-drive end volume through the one or more open passages.

[0009] According to an implementation of the first aspect, each porous barrier of the plurality of porous barriers is composed of a porous medium, and wherein the porous medium has a high surface area that absorbs heat from a burnt portion of the reactant fluid to cool the flame.

[0010] According to an implementation of the first aspect, the plurality of porous barriers reduce a second flowrate of the burnt portion of the reactant fluid based on the burnt portion of the reactant fluid interacting with the plurality of porous barriers.

[0011] According to an implementation of the first aspect, the porous medium is composed of at least one of a composite, metal wool, meal foam, sintered metal mesh, metal mesh, and a multi-layered wire mesh.

[0012] According to an implementation of the first aspect, the SynRM further comprises a second porous medium, wherein the second porous medium is coupled to the porous medium to create each porous barrier of the plurality of porous barriers.

[0013] According to an implementation of the first aspect, the SynRM further comprises a second porous medium, wherein the second porous medium is placed a predetermined distance away from the porous medium to create each porous barrier of the plurality of porous barriers.

[0014] According to an implementation of the first aspect, the porous medium comprises a meshed structure of uniform pore sizes.

[0015] According to an implementation of the first aspect, the porous medium comprises a meshed structure of non-uniform pore sizes.

[0016] According to an implementation of the first aspect, the porous medium comprises open pores with interconnected passageways.

[0017] According to an implementation of the first aspect, a subset of porous barriers of the plurality of porous barriers comprise a flame retardant lining.

[0018] A second aspect of the present disclosure provides a method, comprising: igniting, using an ignition source, a reactant fluid within a first volume of an open rotor of a synchronous reluctance motor (SynRM), wherein a reactant fluid is distributed within the SynRM, wherein the open rotor comprises a drive end, a non-drive end, and one or more open passages that fluidly connect the drive end to the non-drive end, and wherein the one or more open passages comprise a plurality of porous barriers; and based on igniting the reactant fluid, causing a flame to propagate from the first volume to a second volume, wherein the first volume is a drive end volume within the drive end, a non-drive end volume within the non-drive end, an air gaps volume within a motor enclosure of the SynRM, or an open passages volume within the one or more open passages, and wherein the plurality of porous barriers reduces a flow rate of the flame as the flame propagates from the first volume to the second volume based on the flame interacting with the plurality of porous barriers.

[0019] According to an implementation of the second aspect, the plurality of porous barriers are positioned within the one or more channels to create a plurality of compartments within the one or more channels, and wherein the plurality of porous barriers reduce the flow rate of the flame by compartmentalizing an unbumt portion of the reactant fluid accumulated in the second volume end of the SynRM such that the unbumt portion of the reactant fluid cannot be reached by the flame.

[0020] According to an implementation of the second aspect, the first volume is the drive end volume and the second volume is the non-drive end volume, and wherein the flame propagates from the drive end volume to the non-drive end volume through the one or more open passages.

[0021] According to an implementation of the second aspect, the first volume is the non- drive end volume and the second volume is the drive end volume, and wherein the flame propagates from the non-drive end volume to the drive end volume through the one or more open passages.

[0022] A third aspect of the present disclosure provides one or more open passages that fluidly connect a first volume of the open rotor to a second volume of the open rotor, wherein the one or more open passages comprise a plurality of porous barriers, wherein a reactant fluid is distributed within the open rotor; and an ignition source ignites the reactant fluid within a first volume of the open rotor to cause a flame to propagate from the first volume to a second volume, wherein the first volume is a drive end volume within the drive end, a non-drive end volume within the non-drive end, an air gaps volume, or an open passages volume within the one or more open passages, and wherein the plurality of porous barriers reduces a flow rate of the flame as the flame propagates from the first volume to the second volume based on the flame interacting with the plurality of porous barriers.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and / or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:

[0024] FIGS. 1A-1B illustrate simplified diagrams of an electrical motor having an induction rotor and a SynRM with an open rotor, according to one or more examples of the present disclosure;

[0025] FIGS. 2A-2D illustrate graphs depicting pressure evolution in electrical machines with induction rotors and SynRMs with open rotors when flammable fluids are burnt in the respective enclosures of the electric machines, according to one or more examples of the present disclosure;

[0026] FIGS. 3A-3B illustrate simplified diagrams depicting deflagration and detonation, according to one or more examples of the present disclosure;

[0027] FIG. 4 illustrates a simplified diagram of a SynRM with an open rotor having porous barriers, according to one or more examples of the present disclosure; and

[0028] FIGS. 5A-5B illustrate graphs that show a reduction in overpressure in a rectangular duct using a stainless steel multilayer wire mesh when a flammable gas is ignited in the rectangular duct, according to one or more examples of the present disclosure.DETAILED DESCRIPTION

[0029] Examples of the present application will now be described more fully hereinafter with reference to the accompanying FIGs., in which some, but not all, examples of the application are shown. Indeed, the application may be exemplified in different forms and should not be construed as limited to the examples set forth herein; rather, these examples are provided so that the application will satisfy applicable legal requirements. Where possible, any terms expressed in the singular form herein are meant to also include the plural form and vice versa, unless explicitly stated otherwise. Also, as used herein, the term “a” and / or “an” shall mean “one or more” even though the phrase “one or more” is also used herein. Furthermore, when it is said herein that something is “based on” something else, it may be based on one or more other things as well. In other words, unless expressly indicated otherwise, as used herein “based on” means “based at least in part on” or “based at least partially on”.

[0030] When combustible gas is ignited inside of a motor enclosure, the flame propagates in outward direction from the point of ignition at a subsonic velocity, giving rise to deflagration. In some embodiments, the transition from deflagration to detonation may happen any part of the (e.g., a main motor enclosure) of the electrical machine based on a number of factors such as fuel type, stoichiometry, volume of enclosure and transition.

[0031] For example, the open rotors in an electrical machine (e.g., SynRM) may provide favorable conditions for a deflagration flame to transition to detonation. When a reactant fluid (e.g., a type II-C explosive gas such as acetylene) is ignited at a first volume (e.g., drive end volume) of a motor enclosure of a SynRM with an open rotor, a deflagration flame propagates in an outward direction from the first volume to a second volume (e.g., non-drive end volume) of the motor enclosure at a subsonic velocity. The burnt reactant fluid that is downstream of the flame front expand rapidly, further accelerating the flame and sending pressure waves that compresses the unbumt mixture ahead of the flame. Due to a fast burning rate of the type II-C gases, the burnt gases are likely to attain sonic velocity and push the deflagration flame to attain sonic velocity as well. In some embodiments, certain operating conditions such as stoichiometry of air-fuel mixture, geometry of enclosure, fuel type can also provide favorable condition for the deflagration flame to transition to detonation.

[0032] This leads to a transition from deflagration to detonation. This causes a drastic rise in pressure downstream of the detonation wave. The detonation and the drastic rise in pressure may lead to an explosion in the motor enclosure of the SynRM.

[0033] Embodiments of the present disclosure discuss reducing peak explosion pressure in SynRMs with open rotors by properly compartmentalizing the open rotor of motor enclosure of the SynRM with porous flame quenching barriers. With the porous flame quenching barriers installed, the peak explosion pressure inside of the motor enclosures of SynRMs will be lowered. Hence lighter construction SynRM enclosure will be sufficient to pass a certification test for International Electrotechnical Commission (IEC) standard 60079-1, saving materials and manufacturing cost.

[0034] FIGS. 1A-1B illustrate simplified diagrams of an electrical motor having an induction rotor and a SynRM with an open rotor, according to one or more examples of the present disclosure. In some embodiments, the motors depicted in FIG. 1A and IB are identical except for the use of the SynRM and the induction rotor.

[0035] FIG. 1A illustrates a sectional view 100 of an electrical machine 102 (e.g., a 200 frame size Ex d motor) with a solid induction rotor 104. In some embodiments, 200 frame size may be the vertical height of the motor measured from center (e.g., center of the end-shield) to the bottom. The solid induction rotor 104 connects a drive end volume 108 of the motor 102 to a non-drive end volume 110 of the motor 102. Air gaps 106 are present around the solid induction rotor 104. As will be described with respect to FIGS. 2A-2D in more detail, the peak explosion pressure within an enclosure of a motor 102 with a solid induction rotor 104, when a reactant fluid (e.g., a type II-C flammable fluid such as acetylene) are ignited within the enclosure, is significantly lower than a peak explosion pressure within an enclosure of a SynRM with an open rotor, under similar conditions.

[0036] FIG. IB illustrates a sectional view 150 of a SynRM 152 (e.g., 200 frame size Ex d motor) with an open rotor. Air gaps 158 are present around the open rotor. The open rotor includes passages 160 that connect a drive end volume 154 of the motor 152 to a non-drive end volume 156 of the motor 152 of the motor 152. When a reactant fluid (e.g., a type II-C flammable fluid such as acetylene) is ignited in a motor enclosure of the motor 152, the open passages 160 in the motor 152 provide favorable conditions for a deflagration flame to transition to detonation.

[0037] FIGS. 2A-2D illustrate graphs depicting pressure evolution in electrical machines with induction rotors and SynRMs with open rotors when flammable fluids are burnt in the respective enclosures of the electric machines, according to one or more examples of the present disclosure.

[0038] The graphs 2A-2D are prepared based on four different experiments conducted. In each experiment, the ignition source was placed at the drive end of the induction and SynRmmotors to ignite flammable fluids within the motors enclosures of the respective motors. Pressures were measured at the drive end and the non-drive end of the respective motors.

[0039] In a first experiment, the flammable fluid ethylene gas, was filled within the motor enclosure of an induction motor. The ethylene gas was ignited at the drive end of the induction motor. The pressure that was measured at the drive end of the induction motor, after the ethylene gas is ignited, is depicted by curve 208 of FIG. 2A. The pressure that was measured at the non-drive end of the induction motor, after the ethylene gas is ignited, is depicted by curve 212 of FIG. 2B.

[0040] In a second experiment, the flammable fluid ethylene gas, was filled within the motor enclosure of a SynRM. The ethylene gas was ignited at the drive end of the SynRM. The pressure that was measured at the drive end of the SynRM, after the ethylene gas is ignited, is depicted by curve 206 of FIG. 2A. The pressure that was measured at the non-drive end of the SynRM, after the ethylene gas is ignited, is depicted by curve 210 of FIG. 2B.

[0041] Graph 202 of FIG. 2A plots the pressure measured at a drive end of motor enclosures of electric machines having induction rotors and open rotors (e.g., SynRMs) when a flammable fluid (e.g., ethylene gas) is burnt in the motor enclosures of the respective motors. The y-axis of the graph 202 of FIG. 2A plots the pressure (in Bar) at the drive end of a motor enclosure and the x-axis of the graph 202 of FIG. 2A plots time (in milliseconds). Curve 206 represents the pressure measured at the drive end of a SynRM, and curve 208 representes the pressure measured at a drive end of an electrical machine having an induction rotor.

[0042] Graph 204 of FIG. 2B plots the pressure measured at a non-drive end of motor enclosures of electric machines having induction rotors and open rotors (e.g., SynRMs) when a flammable fluid (e.g., ethylene gas) is burnt in the motor enclosures of the respective motors. The y-axis of the graph 204 of FIG. 2B plots the pressure (in Bar) at the non-drive end of a motor enclosure and the x-axis of the graph 204 of FIG. 2B plots time (in milliseconds). Curve 210 represents the pressure measured at the non-drive end of a SynRM, and curve 212 representes the pressure measured at a non-drive end of an electrical machine having an induction rotor.

[0043] In some emboiments, it can be inferred from FIGS. 2A and 2B that in induction motor with a solid rotor, pressure piling is observed. For example, the peak pressure measured in a secondary compartment (e.g., NDE) of induction motor (curve 212 of figure 2B) is higher and the rate of increase of pressure is also faster than in primary compartment (DE - where ignition starts) (as shown in curve 208 of figure 2A). However, in SynRMs, pressure piling effect is avoided due to an open rotor. Peak pressure measured in both compartments (DE andNDE) as shown by curve 206 of figure 2A and curve 210 of figure 2B is similar and pressure increases and decreases in both compartments simultaneously.

[0044] Due to narrow air-gap connecting drive end (DE) and non-drive end (NDE) volumes of an induction motor, a pressure piling effect is observed in the induction motor when flammable fluids are ignited within the motor enclosure. In some embodiments, peak pressure at the non-drive end is higher than the peak pressure at the drive end, where ignition starts. This effect is not observed in SynRMs where DE and NDE volume are connected with multiple open passages in the rotor. The pressure evolution at the DE and the NDE in the SynRM is similar when the flammable fluid is ignited at the drive end. Hence when ethylene gas was ignited in the two motor enclosures, use of SynRM with open rotor resulted in reduction of overall peak pressure by avoiding pressure piling effect.

[0045] Therefore, in some embodiments, the peak explosion pressure resulting from DE ignition of ethylene gas inside SynRM enclosure is lower than the peak explosion pressure resulting from ignition of ethylene at a DE of an induction motor. From the experiments, we can ascertain a benefit of using an SynRM instead of an induction motor in case of IIB flammable gases.

[0046] In a third experiment, the flammable fluid acetylene gas, was filled within the motor enclosure of an induction motor. The acetylene gas was ignited at the drive end of the induction motor. The pressure that was measured at the drive end of the induction motor, after the ethylene gas is ignited, is depicted by curve 220 of FIG. 2C. The pressure that was measured at the non-drive end of the induction motor, after the ethylene gas is ignited, is depicted by curve 224 of FIG. 2D.

[0047] In a fourth experiment, the flammable fluid acetylene gas, was filled within the motor enclosure of a SynRM. The acetylene gas was ignited at the drive end of the SynRM. The pressure that was measured at the drive end of the SynRM, after the ethylene gas is ignited, is depicted by curve 218 of FIG. 2C. The pressure that was measured at the non-drive end of the SynRM, after the acetylene gas is ignited, is depicted by curve 222 of FIG. 2D.

[0048] Graph 214 of FIG. 2C plots the pressure measured at a drive end of motor enclosures of electric machines having induction rotors and open rotors (e.g., SynRMs) when a reactant fluid (e.g., a type II-C flammable fluid such as acetylene) is burnt in the motor enclosures of the respective motors. The y-axis of the graph 214 of FIG. 2C plots the pressure (in Bar) at the drive end of a motor enclosure and the x-axis of the graph 214 of FIG. 2C plots time (in milliseconds). Curve 218 represents the pressure measured at the drive end of aSynRM, and curve 220 representes the pressure measured at a drive end of an electrical machine having an induction rotor.

[0049] Graph 216 of FIG. 2D plots the pressure measured at a non-drive end of motor enclosures of electric machines having induction rotors and open rotors (e.g., SynRMs) when a reactant fluid (e.g., a type II-C flammable fluid such as acetylene) is burnt in the motor enclosures of the respective motors. The y-axis of the graph 216 of FIG. 2D plots the pressure (in Bar) at the non-drive end of a motor enclosure and the x-axis of the graph 216 of FIG. 2D plots time (in milliseconds). Curve 222 represents the pressure measured at the non-drive end of a SynRM, and curve 224 representes the pressure measured at a non-drive end of an electrical machine having an induction rotor. A maximum pressure (peak explosion pressure) plotted on curve 222 is much higher than a maximum pressure plotted on curve 224. Thus, the peak explosion pressure measured at a non-drive end of a SynRM with an open rotor is much greater than the peak explosion pressure measured at a drive end of an electric machine with an induction rotor when acetylene gas is burnt in the respective motor enclosures. From the graph 216, it is also inferred that the rate of increase of pressure at the non-drive end of a SynRM with an open rotor is drastic and greater than the rate of increase of pressure at the non- drive end of an electrical machine with an induction rotor.

[0050] From results of acetylene ignition in induction motor (curve 220 of FIG. 2C and curve 224 of figure 2D) a pressure piling effect is observed. Due to narrow air-gap connecting DE and NDE volumes of induction motor, peak pressure at the non-drive end (as shown in curve 224) is significantly higher than peak pressure at the drive end, where ignition starts (as shown in curve 220). Also rate of increase of pressure in secondary compartment (NDE) shown by curve 224 is faster than in drive end shown by curve 220. For SynRM case (Curves 218 and 222), pressure increase is almost instantaneous indicating detonation and overall peak pressure is significantly higher than in induction motor.

[0051] FIGS. 3A-3B illustrate simplified diagrams depicting deflagration and detonation in a motor, according to one or more examples of the present disclosure. FIG. 3A depicts a simplified diagram 300 depicting a deflagration flame in a motor enclosure 302. The deflagration flame starts with igniting a flammable fluid (e.g., ethylene) that is present within a motor enclosure 302. At time t=0, the flammable fluid is ignited within the motor enclosure 302 using a spark ignition at point 308. In some embodiments, the point of ignition of the flammable fluid within the motor enclosure may be close to a drive end volume of the motor enclosure. The spark ignition introduced at point 308 of the motor enclosure 302, converts to a flame that travels outward from the point of ignition 308 through the motor enclosure 302 ata subsonic velocity. A front of the flame 304 bums the fluid that is present in the motor enclosure 302. The burnt portion of the fluid 312 in the motor enclosure 302 expands and accelerates the front of the flame 304 to travel fast through the motor enclosure 302. The acceleration of the front of the flame 304 sends pressure waves 306 through the remainder of the motor enclosure 302 that compresses the unbumt fluid present ahead 310 of the front of the flame 304. As long as the speed (e.g., flow rate) of the front of the flame remains subsonic, the acceleration of the front of the flame 304 in the motor enclosure 302 leads to a constant pressure or a gradual decrease in pressure downstream of the front of the flame 304 and an increase in temperature downstream of the front of the flame 304.

[0052] When deflagration is initiated using a reactant fluid (e.g., a type II-C flammable fluid such as acetylene), the fluid is burnt at a faster burning rate and the burnt fluids expand at a rapid pace. This may lead to the front of the flame attaining sonic velocity, leading to a transition from deflagration (as described in FIG. 3A) to detonation (as described in FIG. 3B). In detonation, the rapid expansion of burnt gases at sonic velocity forms shock / detonation waves that preceded the combustion zone.

[0053] FIG. 3B depicts a simplified diagram 350 depicting a detonation in a motor enclosure 314. A flammable fluid (e.g., a type II-C flammable fluid such as acetylene) is present within a motor enclosure 314. At time t=0, the flammable fluid is ignited within the motor enclosure 314 using a spark ignition at point 308. In some embodiments, the point of ignition of the flammable fluid within the motor enclosure may be close to a drive end volume of the motor enclosure. The spark ignition introduced at point 308 of the motor enclosure 302, converts to a flame that travels outward from the point of ignition 308 through the motor enclosure 302 a subsonic velocity. The burnt portion of the fluid 322 in the motor enclosure 314 expands rapidly and accelerates the front of the flame 304 to attain the speed of sound through the motor enclosure 314. This causes formation of shock wave 318 creating high pressure and temperature in a region 316 behind the shock wave 318. As shock wave passes through the reactant fluid it instantaneously increases temperature and pressure of the downstream reactant gas, the downstream reactant gas ignites and causes further pressure and temperature increase leading to detonation.

[0054] The transition from deflagration to detonation in motor enclosures, that is seen when a reactant fluid (e.g., a type II-C gas such as acetylene gas) is ignited within a motor enclosure as observed in our experiments discussed above may be avoided by using porous barriers within the motor enclosures.

[0055] FIG. 4 illustrates a simplified diagram of a SynRM with an open rotor having porous barriers, according to one or more examples of the present disclosure . FIG. 4 depicts a sectional view 400 of a SynRM 152 (e.g., 200 frame size Ex d motor) with an open rotor, as shown in FIG. IB. A plurality of porous barriers 402 are distributed within the open passages 160 (e.g., tunnels and / or channels), the drive end volume 154 and the non-drive end volume 156 of the motor enclosure of the motor 152. The plurality of porous barriers 402 act as deflagration / detonation arrestors by reducing the peak explosion pressure and extinguishing the deflagration flame as it travels through the motor enclosure of the motor 152. In cases where the deflagration flame transitions to a detonation, the porous barriers also act as shock attenuating structures that absorb the shock wave energy of a detonation.

[0056] As described with respect to FIG. 3 A above, a deflagration flame may be introduced within the motor enclosure of the motor 152 by way of a spark ignition within the motor enclosure during operation of the motor 152. Additionally and / or alternatively, a deflagration flame may be introduced within the motor enclosure of the motor 152 by way of a hot spot within the motor enclosure of the motor 152 during the operation of the motor. In some embodiments, the spark ignition or hot spot may occur at any location within the motor enclosure of the motor 152. For example, the spark ignition or hot spot may occur at the drive end volume 154, at the non-drive end volume 156, within the open passages 160 or within air gaps of the enclosure of the motor 152. From the point of ignition or hot spot, the flame may propagate throughout the enclosure of the motor 152. For example, the flame may propagate from the drive end volume 154 to the non-drive end volume 156. In some cases, the flame may propagate from the non-drive end volume 156 to the drive end volume 154. In some examples, the flame may propagate from the air gaps of the enclosure of the motor 152 to the drive end 154 and the non-drive volume 156. In some cases, the flame may propagate from the open passages 160 to the drive end 154 and the non-drive volume 156.

[0057] As the deflagration flame travels through the motor enclosure of the motor 152, the deflagration flame bums a flammable mixture (e.g., a fluid and gaseous mixture of a reactant flammable type II-C fluid) present in the motor enclosure of the motor 152. As also described above with respect to FIG. 3A, during the process of deflagration, the burnt portion of the mixture expands rapidly and increases the speed of the deflagration flame that generates pressure waves that compress the unbumt flammable mixture.

[0058] The plurality of porous barriers 402 are used to compartmentalize the motor enclosure of the motor 152. In some embodiments, the plurality of porous barriers 402 separate the motor enclosure of the motor 152 from the open passages 160 of the open rotor of the motor152. In some other embodiments, plurality of porous barriers 402 may be used to divide the open passages 160 of the open rotor of the motor 152 into various compartments. By dividing the motor enclosure and / or the open passages 160 of the motor 152 into various compartments using the plurality of porous barriers 402, the plurality of porous barriers 402 are able to bleed off the compressed flammable mixture present in the motor enclosure of the motor 152 away from the deflagration flame, so that the deflagration flame is unable to reach the compressed flammable unbumt mixture. As the deflagration flame does not reach the compressed flammable unbumt mixture, the amount of burnt mixture does not increase rapidly, the burnt mixture do not expand rapidly and push the deflagration flame to achieve a speed high enough to transition from deflagration to detonation to transmit shock waves through the motor enclosure.

[0059] Additionally and / or alternatively, the plurality of porous barriers 402 also help in reducing the velocity (e.g., speed and / or flow rate) of the burnt mixture as it passes through the plurality of porous barriers 402. As the burnt mixture does not expand rapidly, the burnt mixture is not able to increase the speed of the flame from a subsonic to a supersonic level, reducing the possibility of the deflagration flame transitioning to a detonation.

[0060] Additionally and / or alternatively, the plurality of porous barriers 402 also act as flame quenching barriers to extinguish the flame as the deflagration flame travels through the plurality of porous barriers 402 distributed within the enclosure of the motor 152. For example, a high surface area of the porous medium used in the porous barriers of the plurality of porous barriers 402, allows for absorption of heat from the burnt mixture hence cooling down, and eventually extinguishing the deflagration flame.

[0061] In cases where the deflagration flame transitions to a detonation, the porous barriers also act as shock attenuating structures that absorb the shock wave energy of a detonation.

[0062] By bleeding off the unbumt mixture away from the deflagration flame and extinguishing the deflagration flame using the plurality of porous barriers 402, the peak explosion pressure and the risk of the deflagration flame transitioning to a detonation is significantly reduced.

[0063] In some embodiments, the design of the porous barriers is based on a plurality of factors such as the type of flammable mixture that is used, related stoichiometry, and geometry of the motor enclosure such as volume and shape.

[0064] In some embodiments, a variety of porous material such as a composite, metal wool (e.g., steel), meal foam, sintered metal mesh (e.g., sintered bronze plate), metal mesh (e.g., stainless steel metal mesh), or a multi-layered wire mesh may be used to form the plurality ofporous barriers 402. Additionally and / or alternatively, a flame retardant lining or sheet may be used in addition to the porous material to further assist in flame quenching.

[0065] In some embodiments, the porous barriers of the plurality of porous barriers 402 may comprise of a single porous layer. In some other embodiments, the porous barriers of the plurality of porous barriers 402 may comprise multiple porous layers attached together. In some other embodiments, the porous barriers of the plurality of porous barriers 402 may comprise multiple porous layers separated by a distance.

[0066] In some embodiments, the porous barriers of the plurality of porous barriers 402 may be used to fill the cavity of end plates of the open rotor of the motor 152. In some other embodiments, the porous barriers 402 may be used to fill a drive end volume 154 and / or a nondrive end volume 156 of the motor 152 with the open rotor.

[0067] In some embodiments, the porous barriers of the plurality of porous barriers 402 may have a meshed structure of uniform pore sizes. In some embodiments, the pore sizes of the porous barriers of the plurality of porous barriers 402 may vary along a direction from a drive end of the motor 152 to a non-drive end of the motor 152. In some other embodiments, the pore sizes may vary along a radial direction of the open rotor of the motor 152.

[0068] In some other embodiments, the porous barriers of the plurality of porous barriers 402 may have high and open porosity to allow air through the porous barriers. In some embodiments, the pores of the porous barriers of the plurality of porous barriers 402 may include open pores with interconnected passageways that helps to slow down and extinguish the deflagration flame.

[0069] Experiments conducted on a plurality of possible porous materials that may be used in the porous barriers of the plurality of porous barriers 402 show that by using the plurality of porous (and flame quenching) barriers 402 to prevent the deflagration flame from reaching compressed the flammable mixture, peak explosion pressure can be significantly reduced. Table 1, shown below, provides a summary of the properties of a list of materials that may be used as porous barriers of the plurality of porous barriers 402 that are capable of arresting the deflagration flame and / or detonation in an open rotor of a motor 152.TABLE 1: List of porous barriers to be used in a motor enclosure of a motor with an open rotor (e.g., SynRM) to reduce peak explosion pressure

[0070] The data associated with Table 1 is retrieved from the following references, which are incorporated by reference herein in their entirety:

[0071] Boyd, M. G., Marshall, T. P., Martin, F. J., & Noesen, S. J. (1981, January). Explosion pressures in enclosures compartmented by porous barriers. In Symp.(Int.) Combust., (Proc.); (United States) (No. CONF-800809-). GE.

[0072] Jianhua, Sun, et al. “The comparative experimental study of the porous materials suppressing the gas explosion.” Procedia Engineering 26 (2011): 954-960.

[0073] Nie, B.S., He, X.Q., Zhang, R.M., Chen, W.X., Zhang, J.F., 2011. The roles of foam ceramics in suppression of gas explosion overpressure and quenching of flame propagation. J. Hazard. Mater 192, 741e747.

[0074] Li, Y., Zhao, Q., Liu, L., Chen, X., Huang, C., & Yuan, B. (2022). Investigation on the flame and explosion suppression of hydrogen / air mixtures by porous copper foams in the pipe with large aspect ratio. Journal of Loss Prevention in the Process Industries, 76. 104744.

[0075] FIGS. 5A-5B illustrate graphs that show a reduction in overpressure (e.g., peak explosion pressure) in a rectangular duct using a stainless steel multilayer wire mesh when a flammable mixture is ignited in the rectangular duct, according to one or more examples of the present disclosure.

[0076] Graphs 502 and 552 of FIG. 5A and FIG. 5B plot a pressure measured within a rectangular duct (measured in Mega Pascal (MPa)) on the y-axis and time (measured in milliseconds) on the x-axis when a flammable mixture is ignited within the rectangular duct. Curve 504 in graphs 502 and 552 of FIGS. 5A and 5B plots the overpressure measured in the rectangular duct without a stainless steel multilayer wire mesh when a flammable mixture is ignited in the rectangular duct. Curves 506 of graph 502 of FIG. 5A and curves 554 of graph 552 of FIG. 5B plot the overpressure measured in the same rectangular duct while using astainless steel multilayer wire mesh when a flammable mixture is ignited in the rectangular duct.

[0077] The data associated with graphs 502 and 552 is retrieved from the following reference, which is incorporated by reference herein in their entirety:

[0078] Jin, K., Duan, Q., Chen, J., Liew, K. M., Gong, L., & Sun, J. (2017). Experimental study on the influence of multi-layer wire mesh on dynamics of premixed hydrogen-air flame propagation in a closed duct. International Journal of Hydrogen Energy, 42(21), 14809- 14820.

[0079] Curves 506 of FIG. 5 A depict the pressure measured in the rectangular duct when a stainless steel multilayer mesh of different mesh and layers is used. For example, the curves 506 of graph 502 of FIG. 5A depict overpressure measured in the rectangular duct when a stainless steel wire mesh of 40 mesh, 60 mesh, 80 mesh, and a 100 mesh of varying number of layers is used in the rectangular duct. Similarly, the curves 554 of graph 552 of FIG. 5B depict overpressure measured in the rectangular duct when a stainless steel wire mesh of 60 mesh, 80 mesh, and a 100 mesh of varying number of layers is used in the rectangular duct.

[0080] The peak pressure measured by curves 506 in graph 502 and the peak pressure measured by curves 554 of graph 552 are drastically smaller than the peak pressure of curve 504, which indicates the measurements of overpressure when no stainless steel multilayer wire mesh is used in the rectangular duct when a flammable mixture is ignited in the rectangular duct. Therefore, it is inferred that using a multilayer stainless steel wire mesh is capable of significantly reducing overpressure in a rectangular duct, and by extension in a motor enclosure of a motor 152 with an open rotor when a flammable mixture is ignited in the motor enclosure.

[0081] While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above.

[0082] The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context orthe foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and / or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

Claims

CLAIMSWhat is claimed is:

1. A synchronous reluctance motor (SynRM), comprising: an open rotor comprising: a drive end; a non-drive end; one or more open passages that fluidly connect the drive end to the non-drive end, wherein the one or more open passages comprise a plurality of porous barriers, wherein a reactant fluid is distributed within the SynRM; and an ignition source ignites the reactant fluid within a first volume of the open rotor to cause a flame to propagate from the first volume to a second volume, wherein the first volume is a drive end volume within the drive end, a non-drive end volume within the non-drive end, an air gaps volume within a motor enclosure of the SynRM or an open passages volume within the one or more open passages, and wherein the plurality of porous barriers reduces a flow rate of the flame as the flame propagates from the first volume to the second volume based on the flame interacting with the plurality of porous barriers.

2. The SynRM of claim 1, wherein the plurality of porous barriers are positioned within the one or more channels to create a plurality of compartments within the one or more channels, and wherein the plurality of porous barriers reduce the flow rate of the flame by compartmentalizing an unbumt portion of the reactant fluid accumulated in the second volume end of the SynRM such that the unbumt portion of the reactant fluid cannot be reached by the flame.

3. The SynRM of claim 1, wherein the first volume is the drive end volume and the second volume is the non-drive end volume, and wherein the flame propagates from the drive end volume to the non-drive end volume through the one or more open passages.

4. The SynRM of claim 1, wherein the first volume is the non-drive end volume and the second volume is the drive end volume, and wherein the flame propagates from the non-drive end volume to the drive end volume through the one or more open passages.

5. The SynRM of claim 1, wherein the first volume is the open passages volume and the second volume is the drive end volume, and wherein the flame propagates from theopen passages volume to the drive end volume and a third volume within the non-drive end volume through the one or more open passages.

6. The SynRM of claim 1, wherein the first volume is the air gaps volume and the second volume is the drive end volume, wherein the flame propagates from the air gaps volume to the drive end volume and a third volume within the non-drive end volume through the one or more open passages.

7. The SynRM of claim 1, wherein each porous barrier of the plurality of porous barriers is composed of a porous medium, and wherein the porous medium has a high surface area that absorbs heat from a burnt portion of the reactant fluid to cool the flame.

8. The SynRM of claim 7, wherein the plurality of porous barriers reduce a second flowrate of the burnt portion of the reactant fluid based on the burnt portion of the reactant fluid interacting with the plurality of porous barriers.

9. The SynRM of claim 7, wherein the porous medium is composed of at least one of a composite, metal wool, meal foam, sintered metal mesh, metal mesh, and a multi-layered wire mesh.

10. The SynRM of claim 7, further comprising a second porous medium, wherein the second porous medium is coupled to the porous medium to create each porous barrier of the plurality of porous barriers.

11. The SynRM of claim 7, further comprising a second porous medium, wherein the second porous medium is placed a predetermined distance away from the porous medium to create each porous barrier of the plurality of porous barriers.

12. The SynRM of claim 7, wherein the porous medium comprises a meshed structure of uniform pore sizes.

13. The SynRM of claim 7, wherein the porous medium comprises a meshed structure of non-uniform pore sizes.

14. The SynRM of claim 7, wherein the porous medium comprises open pores with interconnected passageways.

15. The SynRM of claim 1, wherein a subset of porous barriers of the plurality of porous barriers comprise a flame retardant lining.

16. A method, comprising: igniting, using an ignition source, a reactant fluid within a first volume of an open rotor of a synchronous reluctance motor (SynRM), wherein a reactant fluid is distributed within the SynRM, wherein the open rotor comprises a drive end, a non-drive end, and one or more open passages that fluidly connect the drive end to the non-drive end, and wherein the one or more open passages comprise a plurality of porous barriers; and based on igniting the reactant fluid, causing a flame to propagate from the first volume to a second volume, wherein the first volume is a drive end volume within the drive end, a non- drive end volume within the non-drive end, an air gaps volume within a motor enclosure of the SynRM, or an open passages volume within the one or more open passages, and wherein the plurality of porous barriers reduces a flow rate of the flame as the flame propagates from the first volume to the second volume based on the flame interacting with the plurality of porous barriers.

17. The method of claim 16, wherein the plurality of porous barriers are positioned within the one or more channels to create a plurality of compartments within the one or more channels, and wherein the plurality of porous barriers reduce the flow rate of the flame by compartmentalizing an unbumt portion of the reactant fluid accumulated in the second volume end of the SynRM such that the unbumt portion of the reactant fluid cannot be reached by the flame.

18. The method of claim 16, wherein the first volume is the drive end volume and the second volume is the non-drive end volume, and wherein the flame propagates from the drive end volume to the non-drive end volume through the one or more open passages.

19. The method of claim 16, wherein the first volume is the non-drive end volume and the second volume is the drive end volume, and wherein the flame propagates from the non-drive end volume to the drive end volume through the one or more open passages.20 An open rotor comprising: one or more open passages that fluidly connect a first volume of the open rotor to a second volume of the open rotor, wherein the one or more open passages comprisea plurality of porous barriers, wherein a reactant fluid is distributed within the open rotor; and an ignition source ignites the reactant fluid within a first volume of the open rotor to cause a flame to propagate from the first volume to a second volume, wherein the first volume is a drive end volume within the drive end, a non-drive end volume within the non-drive end, an air gaps volume, or an open passages volume within the one or more open passages, and wherein the plurality of porous barriers reduces a flow rate of the flame as the flame propagates from the first volume to the second volume based on the flame interacting with the plurality of porous barriers.

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