Title of Invention

A LIQUEFIED PETROLEUM GAS (LPG)-AIR MIXING DEVICE FOR STATIONARY ENGINES

Abstract

A Liquefied Petroleum Gas (LPG) - air mixing device for stationary engines comprising: (i) a substantially cylindrical enclosure with additional chamber having an inlet for entry of gas into the enclosure; (ii) a nozzle having a convergent portion and a divergent portion enveloped by said enclosure and adapted for guiding air from one end of the nozzle to the other end of the nozzle; (iii) said nozzle having a throat part between the convergent and divergent portions wherein a plurality of holes are disposed in the throat part for passage of gas from the inlet into the nozzle for mixing with air to form a combustible air-gas mixture.

Full Text

FORM -2 THE PATENTS ACT, 1970 COMPLETE SPECIFICATION SECTION 10 TITLE : A LIQUEFIED PETROLEUM GAS (LPG) - AIR MIXING DEVICE FOR STATIONARY ENGINES. APPLICANT (S): THE AUTOMOTIVE RESEARCH ASSOCIATION OF INDIA (A RESEARCH ORGANISATION JOINTLY SET UP BY THE AUTOMOTIVE INDUSTRY & MINISTRY OF INDUSTRY GOVERNMENT OF INDIA) S. NO. 102, VETAL HILL OFF PAUD ROAD, KOTHRUD, PUNE - 411 038, MAHARASHTRA, INDIA AND SHRI SHAKTI LPG LTD., ADJACENT TO AIRPORT BEGUMPET, HYDERABAD - 500 016, ANDHRA PARADESH, INDIA. The following Specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed :- GRANTED ORIGINAL 354-BOM-1999 04-11-2003 TITLE : A LIQUEFIED PETROLEUM GAS (LPG) -AIR MIXING DEVICE FOR STATIONARY ENGINES FIELD OF INVENTION: The present invention relates to the field of gas-air mixing device for engines. Particularly, the present invention relates to a gas-air mixing device for bi-fuel stationary engines those especially coupled to a portable generator. BACKGROUND ART: Stationary application engines are popularly known to be powered by gasoline, kerosene, diesel etc. because of their cost- effectiveness. Kerosene fired engines which are generally designed based on the physio-chemical characteristics of kerosene normally possess restricted design such as low compression ratio which results in associated higher level of exhaust emissions. In an attempt to reduce the exhaust emissions from the engine, use of Liquefied Petroleum Gas as an alternate fuel is one of the best options. Such engines which normally run on kerosene are fitted with 'Add-On' systems which supply Liquefied Petroleum Gas (LPG) as alternate source of fuel to the engine. In such Add-On systems, it is pertinent to supply gas-air mixture in appropriate proportion in response to the load and speed of the engine. Conventionally, venturi devices like carburetor are used for mixing fuels such as kerosene or gasoline with air in appropriate proportion for supply to engine. However, use of such conventional venturi devices for mixing fuels have not been found suitable for mixing LPG with air for supply to engine. There has been a need for designing optimized gas-air mixing devices for use with LPG Add-On system and achieve stoichiometric air fuel ratio, better combustion and thereby result in reduced exhaust emission. Our inventors by determined research & intuitive knowledge, have developed gas-air mixed with chamber which is provided surrounding the venturi and connected through appropriate number of holes with predetermined size, suitability for use with LPG fuel, stoichiometric air-fuel ratio, better combustion and reduced exhaust emission are obtained. Due to additional chamber, the gas flow rate is lower than the prior art mixer, which causes stoichiometric air-fuel ratio rather than rich mixture hence better fuel economy & lower emission for stationery applicants on engines, OBJECTS OF THE INVENTION: An object of the present invention is to provide a gas-air mixing device wherein the device is capable of mixing homogeneously air and gas at different loads and at different speeds of engine. Another object of the present invention is to provide a device wherein at different load and speed conditions of the engine, optimum quantity of gas is mixed with air to maintain desired air-fuel ratio and thereby deliver required power along with low fuel consumption and exhaust emissions. A more detailed explanation of the invention is provided in the following description and appended claims taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: To complement the description that is being given and in order to promote a better understanding of the characteristics of the invention in accordance with a practical embodiment of the same and as an integral part of the said description a set of drawings accompany it in which, in an illustrative and non-restrictive way, the following are represented :- Fig.1: is schematic representation of the components of the fuel supply system according to the present invention. Fig. 2: is the sectional and side view of the gas air mixer according to the present invention. Fig.3A: shows the comparative graph of carbon monoxide emission against load of the engine for kerosene and LPG fuels. Fig.3B: shows the comparative graph of hydro carbon emission against engine load for kerosene and LPG fuels. DETAILED DESCRIPTION OF THE INVENTION: The present invention discloses a gas-air mixing device especially suitable for stationary applications. Preferably for a 4-stroke spark-ignition coupled to a engine generator FIG.1: In the embodiment shown to illustrate how the gas-air mixer is connected to the engine, an LPG cylinder (1) with a needle valve (20) is connected to the inlet of a primary regulator (3) using a high pressure tube (2). According to the present invention, the needle valve (20) draws out vapour from the LPG cylinder for supply to the primary regulator (3). The outlet of the primary regulator (3) is connected to the inlet of an LPG solenoid valve (4). The outlet of LPG solenoid valve (4) is connected to a mechanically operated second stage regulator (5) which is connected to the inlet of a power screw (7) through a low pressure line (6). The outlet of the power screw (7) is connected to the inlet of a gas-air mixer (8). The gas-air mixer (8) supplies air-fuel mixture through a carburetor (10) to an engine (11) coupled to a generator. One end of the gas-air mixer (8) is connected to the air filter (9) The structure and functions of the second stage metering regulator (5) used in this invention has been described in detail and claimed in applicant's co-pending patent application No.654/Mum/1998. FIG.2: The gas-air mixer (8) according to the present invention comprises a substantially cylindrical enclosure (19) having an inlet (13) for gas. A convergent -divergent nozzle hereinafter referred to as a venturi, having a throat in-between the convergent section and the divergent section, is enveloped within the enclosure (19). A plurality of through-holes (14) are provided in the throat. The number and size of the through holes (14) are kept optimum based on the design of the engine and requirement of gas-air mixing ratio. The area ratio of the venturi portion is kept optimum to generate required depression dispersion at the throat and minimize the pumping losses during operation.. The size and number of holes in the throat decide the required gas-air mixing ratio for supply to the engine. The pumping action of the engine causes air to flow from the air filter (9) towards the engine (11) through the gas air mixture (8). During this stage, air pressure drops below the atmospheric pressure at the throat of the venturi. LPG is metered through the second stage regulator (5) in response to the pressure drop at the venture for supply to the gas inlet (13) of the gas air mixture (8). The gas entering through the inlet (13 ) passes through the additional chamber (20) and the holes (14) in the throat and gets mixed with air axially entering into the venturi through the convergent section. Due to this additional chamber (20), the gas flow rate is lower than the prior art mixer, which causes stoichiometric air-flue ratio rather than rich mixture hence better fuel economy & lower emission for stationary application engines. Figs 3A and 3B represent comparative graphs of carbon monoxide and hydro carbon emission against load of the engine for kerosene and LPG fuels. The variation in load and corresponding engine speed and fuel consumption are given in the following table. Thus, while there have been shown and described and pointed out fundamental novel features of the present invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described may be made by those skilled in the art without departing from the spirit of the present invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the We Claim: 1. A Liquefied Petroleum Gas (LPG) - air mixing device for stationary engines comprising: (i) a substantially cylindrical enclosure with additional chamber having an inlet for entry of gas into the enclosure; (ii) a nozzle having a convergent portion and a divergent portion enveloped by said enclosure and adapted for guiding air from one end of the nozzle to the other end of the nozzle; (iii) said nozzle having a throat part between the convergent and divergent portions wherein a plurality of holes are disposed in the throat part for passage of gas from the inlet into the nozzle for mixing with air to form a combustible air-gas mixture. 2. The device according to claim 1 the the area ratio of the venturi portion is kept optimum to generate required dispersion at the throat and minimize the pumping losses during operation. . 3. The device according to claim 1 or 2 wherein the size and number of holes in the throat decide the required gas-air mixing ratio for supply to the engine. Dated this 10th day of May, 1999, FOR THE AUTOMOTIVE RESEARCH ASSOCIATION OF INDIA and SHRI SHAKTI LPG LTD. By their Agent (R. LAKSHMINARAYANAN) KRISHNA & SAURASTRI

Documents:

354-bom-1999-cancelled pages(4-11-2003).pdf

354-bom-1999-claims(granted)-(4-11-2003).doc

354-bom-1999-claims(granted)-(4-11-2003).pdf

354-bom-1999-correspondence(16-12-2003).pdf

354-bom-1999-correspondence(ipo)-(24-2-2004).pdf

354-bom-1999-drawing(4-11-2003).pdf

354-bom-1999-form 1(11-5-1999).pdf

354-bom-1999-form 13(4-11-2003).pdf

354-bom-1999-form 2(granted)-(4-11-2003).doc

354-bom-1999-form 2(granted)-(4-11-2003).pdf

354-bom-1999-form 3(29-9-2003).pdf

354-bom-1999-form 4(10-11-2003).pdf

354-bom-1999-form 4(10-5-1999).pdf

354-bom-1999-power of authority(29-9-2003).pdf

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