FORM-2
THE PATENT ACT,1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
(As Amended)
COMPLETE SPECIFICATION (See section 10;rule 13)
"AN APPARATUS WHICH REDUCES HEAT LOSS AND IMPROVES AIR CIRCULATION AROUND BURNER CAP FOR INCREAING THERMAL EFFICIENCY OF LPG DOMESTIC COOKING STOVE"
AN APPARATUS WHICH REDUCES HEAT LOSS AND IMPROVES AIR
CIRCULATION AROUND BURNER CAP FOR INCREAING THERMAL
EFFICIENCY OF LPG DOMESTIC COOKING STOVE
FIELD OF THE INVENTION
The present invention is related to the field of LPG gaseous fuel combustion, in particular to the class of low-pressure LPG cooking stoves that utilize natural draft for the venting of the combustion products/flue gas. This is related to the phenomenon of pre-mixed combustion. Furthermore, this is related to thermal efficiency improvement for use in LPG based domestic cooking stoves. This invention particularly relates to a vessel support assembly that effectively minimize heat losses from the burner top area, and thereby improves thermal efficiency of the LPG stove.
BACKGROUND OF THE INVENTION
Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
A major percentage of population continues to depend on LPG for their cooking needs. The market for LPG fuel usage is mainly dominated by cooking stove system that typically uses liquefied petroleum gas (LPG) as a fuel source. In particular, cooking stoves have redefined the cooking style and conventional kitchen setup in most of the developing nations including India and urbanized groups across the world.
Currently there are natural draft burners that use the energy of the gas injecting jet to pre-mix the gas with a portion of air required for combustion. This pre-mixed air is called “primary air” and normally accounts for at least 50% of air required for combustion. This mixture is ignited at the burner top where additional air, called “secondary air”, is mixed into the flame, thus providing the remainder of the air required for combustion.
In an LPG burner, there are various design parameters such as primary air entrainment, port area and size of ports, design of drip tray and fuel jet, loading height (gap between burner top and vessel), and pan support design, which play an important role in its thermal efficiency.
Optimization of the above-mentioned design parameters with the help of extensive experimentation as well as with numerical modelling helps to design the LPG cooking stove components, resulting in increased thermal efficiency.
Various arrangements of such gas burners are known in the prior art. US Patent 20080213715 relates to controlled, low emissions, combustion and pressurized hydrocarbon gas burners with heat exchanger. This burner is not related to the design of natural draft.
Indian patent IN 215495 discloses a multi-purpose stove useful for cooking, baking, space heating, and drying. The multipurpose stove disclosed here is capable of conducting many heating processes, such as cooking, baking, space heating (room heating) and drying of various materials at a time or separately as per requirement. One of the main uses of this multipurpose stove is pollution free space heating along with cooking with minimal fuel consumption. However, this patent is associated with burning solid fuels efficiently.
US Patent 6,093,018 discloses an improved gas burner that comprises: a burner head and a receiving chamber where primary air and fuel gas are mixed. The burner head contains circumferentially positioned lateral apertures for issuing and uniformly distributing the mixture around the burner head to form a flame. A gas burner provides controlled feeding and admixing of the secondary air directly to the base of the flame that enables the combustion process characterized by high-elevated temperature. Indian patent 916/CHE/2015 discloses a LPG stove with minimum radiation heat loss by integrating a characterized circular ring in the LPG stove to transfer maximum possible heat to the cooking food, thereby reducing the escape of heat to the surroundings.
Indian patent 113/CHE/2015 discloses a swirling-flow burner assembly that includes a burner tube and an oxidizer supply tube concentric with and spaced from the burner tube, defining an annular fuel gas conduit between the tubes. The burner thermal efficiency is higher by 10-30% than that of conventional burners. Indian patent 1269/KOL/2013 discloses an improved,
efficient, cost effective, environmentally compatible and modified LPG stove suitable for all sizes of vessels with reduced heat wastage and enhanced efficiency compared to conventional LPG stoves.
Indian patent 3205/CHE/2010 discloses a device which reduces the consumption of LPG and also reduces the duration of cooking. The device comprises multiple vessels having an inner vessel and an outer vessel creating an annular space between them, wherein the outer vessel rests in the lip of the inner vessel. The outer vessel is provided with a hole at the centre of bottom face for entry of flue gas. WO 2011/121609 discloses an apparatus for combustion of gaseous fuel from organic wastes that include biogas burner for domestic cooking purpose having improved thermal efficiency.
The domestic cooking stove typically includes a metal burner body that defines a burner chamber with an inlet that receives a mixture of gas and primary air, and includes burner ports where the mixture exits and burns in the presence of secondary air.
In view of the above, most of the conventional domestic LPG stoves that are well known in the art have typically relied on an open combustion flame, which loses a large amount of energy through the flue gas, leading to relatively low thermal efficiency.
Referring to other embodiments, generally the gas burners are completely sealed circumferentially by the use of the drip tray. The drip tray serves the main purpose of collecting spillage of solid and liquid food. However, this may in turn reduce the supply of secondary air. Therefore, the disclosed arrangement in the above embodiments does not ensure the effective utilization of thermal inertia supplied from the combustion.
Therefore, there is a long felt but unresolved need in the state of art to effectively minimize the heat losses from the LPG stove and thereby improving thermal efficiency of the LPG stove.
SUMMARY OF THE INVENTION
It is intended that all such features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. The following summary is provided to facilitate an understanding of some of the innovative features
unique to the disclosed embodiment and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
A vessel support assembly disclosed here addresses the above-mentioned need to effectively minimize the heat losses from the LPG stove, and thereby improving thermal efficiency of the LPG stove. As used herein, the “vessel support assembly” refers to a pan support that is used to support a vessel such as a pan that is placed over on an LPG stove. The vessel support assembly comprises a circumferential metallic element, a set of metallic resting plates, and a set of metallic protrusions. The circumferential metallic element encloses an area around a burner top flame exit and bottom area of a vessel. The metallic resting plates are integrated with the circumferential metallic element, wherein the metallic resting plates are positioned at equidistant intervals. Each metallic resting plate is attached to an inner portion of the circumferential metallic element and a portion of each metallic resting plate extends above the top portion of the circumferential metallic element. The metallic protrusions are positioned equidistant with each other and integrated at a bottom section of the circumferential metallic element, wherein a distance is defined between each metallic resting plate and each metallic protrusion.
In an embodiment, the metallic resting plates are positioned at the equidistant intervals with a controlled height for optimal distance between the burner top flame to the bottom area of a vessel. In an embodiment, the circumferential metallic element provides waste heat recovery from combustion flue gas to increase flue gas residence time that results in reduced heat loss leading to an increase in thermal efficiency. In an embodiment, the metallic protrusions are welded at the bottom section of the circumferential metallic element. In an embodiment, three metallic resting plates are integrated with the circumferential metallic element. In an embodiment, two metallic protrusions are positioned equidistant with each other and integrated at the bottom section of the circumferential metallic element.
The object of the present invention is to provide an apparatus or the vessel support assembly for increasing the heat flux to the vessel and reducing the heat losses to the surrounding. In other words, the vessel support assembly or a pan support disclosed here increases the thermal efficiency of the LPG domestic cooking stove, wherein a circumferential metallic element (or circular ring) encloses the burner, which effectively decreases the amount of energy loss and,
thus, reduces LPG consumption in the cooking stove. In an embodiment, the burner thermal efficiency is, for example, higher by 3 ± 0.5% than that of conventional burners. In a preferred embodiment, the vessel support assembly (arrangement for resting the vessel) incorporates the circumferential metallic element with a defined length, height, diameter, and thickness. Preferably, the vessel support assembly has 3 metallic resting plates for resting the complete apparatus on the cook stove body metallic top frame.
The present invention discloses as vessel support assembly to be used in LPG domestic cook stoves suitable for sizes of vessels with diameter, for example, ranging from 180 mm up to 300 mm. A flow passage mixing tube is provided below the body frame for the gas and air mixture to enter into the inlet port of the burner top from a LPG cylinder. A knob is placed on a predetermined position in the body frame to control gas flow rate from the LPG cylinder. A ring integrated vessel support assembly is fixed on the top of the hole of the body frame to reduce the heat losses, and to transfer the maximum possible heat to the vessel. The invention is characterized with the ring that is circular in shape with predetermined ring diameter, ring height and protrusion positioning.
BRIEF DESCRIPTION OF DRAWINGS
The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
FIG. 1 is the assembled isometric view of the complete setup of existing design of a vessel support assembly (or a pan support) in a domestic LPG stove, as one of its subsystems.
FIG. 2 is the exploded view of the complete setup of existing design of vessel support assembly in a domestic LPG stove, as one of its subsystems.
FIG. 3 is an isometric view of an embodiment of the vessel support assembly, in an example embodiment.
FIG. 4A is a top view of the embodiment of the vessel support assembly, in an example embodiment.
FIG. 4B is a front view of the embodiment of the vessel support assembly, in an example embodiment.
DESCRIPTION OF THE INVENTION
The aim of the present invention is to provide an apparatus for combustion of gaseous fuel for domestic cooking purpose having improved thermal efficiency. The above aim has been achieved through minimization of heat losses.
The foregoing advantages as well as the particular construction of the improved cooking stove will become more noticeable and understandable from the following detail description thereof when read in conjunction with the accompanying drawings.
With respect to the design of vessel support assembly 300 in the present disclosure as shown in FIGS. 3-4B, the correct positioning of the object to be heated (e.g. a pot of food to be cooked) above the flame is therefore important. If the object is too close to the flame, the flame is quenched and the combustion is incomplete and the efficiency of the stove is reduced. If the object is too far away from the flame, heat is lost to the atmosphere and the stove is again less efficient. The best position for the base of the object being heated is just above the tip of the visible flame, just outside the outer mantle, above the hottest part of the flame. The flame height, though, depends on a variety of factors.
FIG. 1 is the assembled isometric view of the complete setup of existing design of a vessel support assembly 102 (or a pan support) in a domestic LPG stove 100. The preferred embodiment of LPG flow rate, for example, ranges from 30 lt/hr to 100 lt/hr and is intended for use in the domestic LPG stove 100. As shown in Fig. 1, the existing design of the vessel support assembly 102 includes 4 numbers of resting plates 104 for the vessel support. As observed from the adjacent portions of vessel support assembly 102 in FIG. 1, there is sufficient space available around the vessel support assembly 102 that amounts to substantial heat losses.
FIG. 2 is the exploded view of the complete setup of existing design of vessel support assembly 102 in a domestic LPG stove 100. As shown in the FIG. 2, nozzle holder 202 is machined and fitted to the primary tube 204. The gaseous fuel present at line pressure is accelerated into the nozzles 206, and is expelled as jets into the mixing tube 208. At the throat 210 of the mixing tube 208, the air from the atmosphere, or the primary air, is inducted into the mixing tube 208 due to the negative pressure in the throat 210 and propagates further. The amount of air that is aspirated depends on the opening area of the throat 210, nozzle gas flow rate, or gas exit velocity. The gas being injected from the nozzle 206 accelerates the inducted primary air and mixing of gas and air takes place. Due to the design of the nozzle 206, the gas expands along the width as per the spray pattern. The gas and air mixture fills the throat 210 with a relatively high velocity mixture, at a slight negative pressure relative to the atmospheric pressure.
This high velocity mixture is then decelerated in mixing tube 208, having a cylindrical pipe 212 attached to the cup 214 resulting in the increase in the static pressure. The straight tube of the mixing tube 208 discharges into the diffuser cap which comprises a cap with the profile for the air-gas mixture flow. The gas at the discharge of the diffuser cup is at a slightly positive pressure and then the air-gas mixture flows into the burner top 216. The burner top 216 is, for example, a solid end cap having multiple holes on the periphery. The holes are of pre¬determined diameter and placed at defined pitch. Combustion occurs on the outside of the burner top 216.
Since, the LPG stove 100 is used for cooking purposes at home, hence the dip tray 218 is provided to collect the spilled substance. The legs 220 are provided at 4 corners of the burner body 222 to provide the support to the burner body 222 and for providing space for cleaning. Two knobs 224 are provided on the burner body 222 whose position can be adjusted from ‘Sim to Full’ to enable the user to control the gas flow rate as per the cooking requirement. Based on the arrangement details provided above, the drawback for the heat loss was observed. Therefore, the vessel support assembly 300 that is disclosed in FIGS. 3-4B is beneficial in reducing the heat losses.
FIG. 3 is an isometric view of an embodiment of the vessel support assembly 300, in an example embodiment. The vessel support assembly 300 comprises a circumferential metallic element 302, a set of metallic protrusions 304, and a set of metallic resting plates 306. The
circumferential metallic element 302 encloses an area around a burner top flame exit and bottom area of a vessel. The metallic resting plates 306 are integrated with the circumferential metallic element 302, wherein the metallic resting plates 306 are positioned at equidistant intervals. In an embodiment, each metallic resting plate 306 is attached to an inner portion 302a of the circumferential metallic element 302 and a portion of each metallic resting plate 306 extends above the top portion 302b of the circumferential metallic element 302, as shown in FIG. 3. In an example embodiment, three metallic resting plates 306 are integrated with the circumferential metallic element 302. The 2 metallic protrusions 304 are positioned equidistant with each other and integrated at a bottom section 302c of the circumferential metallic element 302, wherein a distance 308 is defined between each metallic resting plate 306 and each metallic protrusion 304. In an embodiment, the metallic resting plates 306 are positioned at the equidistant intervals with a controlled height for optimal distance between the burner top flame to the bottom area of a vessel. Furthermore, in an example embodiment, two metallic protrusions 304 are positioned equidistant with each other and integrated at the bottom section 302c of the circumferential metallic element 302.
The vessel support assembly 300 increases the thermal efficiency of the LPG domestic cooking stove 100, wherein a circumferential metallic element 302 encloses the burner, which effectively decreases the heat loss, and hence reduces LPG consumption in the cooking stove 100. The metallic resting plates 306 are required for the firm placement of the vessel. In an embodiment, the burner thermal efficiency is higher by 3±0.5% than that of conventional burners. In the preferred embodiment, there are 2 metallic protrusions 304 welded at the bottom section 302c of the circumferential metallic element 302 as shown in FIG. 3. The metallic protrusions 304 are provided for fixing with the burner body 222, as shown in FIG. 3. In an embodiment, the circumferential metallic element 302 provides waste heat recovery from combustion flue gas to increase flue gas residence time that results in reduced heat loss leading to an increase in thermal efficiency. The benefits of this vessel support assembly 300 includes, (1) increased heat flux to the vessel; (2) reduced heat losses; (3) increased residence time of the flue gases; and (4) reduced time and LPG usage.
Furthermore, in the embodiment, vessel support assembly 300 is enclosed circumferentially by circumferential metallic element 302 so that most of the heat from the burner is directed towards the vessel. The apparatus or the vessel support assembly 300 is designed in such a way
that the exhaust flue gas, which is at high temperature is allowed to be contained within the surroundings of the burner top 216 (as shown in FIG. 2) leading to increased residence time. This phenomenon is termed as introduction of semi-confined flame in the existing design of LPG stove 100. This design recovers waste heat. Furthermore, this embodiment of the vessel support assembly 300 has 3 numbers of metallic resting plates 306 as compared to the existing design that includes 4 resting plates 104 (as shown in FIG. 1) that are provided for vessel support for the similar weight. Hence, the heat absorption is also lowered in the preferred embodiment of the vessel support assembly 300.
FIGS. 4A and 4B show a top view and a front view of the embodiment of the vessel support assembly 300, in an example embodiment. The dimensions of the vessel support assembly 300 is, for example, constructed to create a gap of about 20±5 mm between the burner top 216 and the flat bottom vessel base. The diameter of vessel support assembly 300 is, for example, 210±20 mm for burner of LPG flow rate 71 to 75 LPH and corresponding vessel number 5 (BIS standard IS 4246: 2002) and 190±20 mm for burner of LPG flow rate 61 to 65 LPH and corresponding vessel number 4 (BIS standard IS 4246: 2002). The height of each metallic resting plate 306 should be 10±3 mm for the proper spacing between the vessel bottom and the burner top 216. The spacing of the metallic protrusions 304 should be equal for proper fitment of the vessel support assembly 300 on the burner body 222. All the other dimensions are less critical. Material used for making the vessel support assembly 300 is MS and to get finished product, powder coating is performed. The vessel support assembly 300 is suitable for a vessel size ranging with external diameter from, for example, 180 mm to 295 mm. This embodiment of the vessel support assembly 300 is capable of exhibiting the improved thermal efficiency under varying conditions of gas flow rate and vessel size.
The dimensions of the vessel support assembly 300, for example, is constructed to create a gap of about 20±5 mm between the burner top 216 and the flat bottom vessel base. The diameter of vessel support assembly 300 is: 210 ±20 mm, thickness 2 ± 0.5 mm, 3 holders or metallic resting plates 306 with length of 60 ± 15 mm, for LPG flow rate 71 to 75 LPH and corresponding vessel number 5 (BIS standard IS 4246: 2002) and 190 ±20 mm for LPG flow rate 61 to 65 LPH and corresponding vessel number 4 (BIS standard IS 4246: 2002). An optimum distance between vessel bottom and burner top 216 enables better heat transfer and reduces the heat losses. In other words, an optimum distance is maintained between the bottom
surface of the vessel and the burner top 216 using the vessel support assembly 300, which results in optimum flame impingement at the bottom surface of the vessel and further results in better heat transfer.
The experiments were conducted in association with the vessel support assembly 300 for thermal efficiency measurement as per IS:4246, wherein all the stipulated conditions were controlled. Upon conducting multiple set of experiments by only replacing the preferred embodiment, the thermal efficiency improvement was observed in the range of 3 ± 0.5 %. The increase in thermal efficiency is attributed to the reduced time and reduced LPG consumption for the end user.
The geometry can easily be modified to suit packaging requirements in any cooking stove application. The preferred embodiment utilizes the metallic protrusions 304 attached to the bottom of the circumferential metallic element 302 so as to fit firmly to the burner body top frame. Hence, upon providing minor changes in the radial spacing of the metallic protrusions 304, it is possible to utilize vessel support assembly 300 in any LPG domestic cook stove appliance.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore, contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.
We claim
1. A vessel support assembly comprising:
a circumferential metallic element that encloses an area around a burner top flame exit and bottom area of a vessel;
a set of metallic resting plates integrated with the circumferential metallic element, wherein the metallic resting plates are positioned at equidistant intervals; and
a set of metallic protrusions that are positioned equidistant with each other and integrated at a bottom section of the circumferential metallic element, wherein a distance is defined between each metallic resting plate and each metallic protrusion.
2. The vessel support assembly as claimed in claim 1, wherein the metallic resting plates are positioned at the equidistant intervals with a controlled height for optimal distance between the burner top flame to the bottom area of a vessel.
3. The vessel support assembly as claimed in claim 1, wherein each metallic resting plate is attached to an inner portion of the circumferential metallic element and a portion of each metallic resting plate extends above a top portion of the circumferential metallic element.
4. The vessel support assembly as claimed in claim 1, wherein the circumferential metallic element provides waste heat recovery from combustion flue gas to increase flue gas residence time that results in reduced heat loss leading to an increase in thermal efficiency.
5. The vessel support assembly as claimed in claim 1, wherein the set of metallic protrusions are welded at the bottom section of the circumferential metallic element.
6. The vessel support assembly as claimed in claim 1, wherein three metallic resting plates are integrated with the circumferential metallic element.
7. The vessel support assembly as claimed in claim 1, wherein two metallic protrusions are positioned equidistant with each other and integrated at the bottom section of the circumferential metallic element.