Red marquis: /* Tank */

2009-08-22T20:43:38Z

Tank

← Older revision		Revision as of 20:43, 22 August 2009
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	===Tank===		===Tank===

	:''{{~~See~~\|Gas tank\|Gas cylinder\|Storage tank\|Pressure vessel}}		:''{{main\|Gas tank\|Gas cylinder\|Storage tank\|Pressure vessel}}

	Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications. In passenger car applications, the tank is typically either a cylindrical tank mounted in the boot of the vehicle or a toroidal tank or set of permanently interconnected cylinders placed in the spare wheel well. In commercial vehicle applications, the tanks are generally cylindrical tanks mounted either in the cargo space or on the chassis underneath the body.		Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications. In passenger car applications, the tank is typically either a cylindrical tank mounted in the boot of the vehicle or a toroidal tank or set of permanently interconnected cylinders placed in the spare wheel well. In commercial vehicle applications, the tanks are generally cylindrical tanks mounted either in the cargo space or on the chassis underneath the body.

Red marquis: /* Tank */

2009-08-22T20:43:19Z

Tank

← Older revision		Revision as of 20:43, 22 August 2009
Line 77:		Line 77:
	===Tank===		===Tank===

	:''{{See\|Gas tank}}		:''{{See\|Gas tank\|Gas cylinder\|Storage tank\|Pressure vessel}}

	Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications. In passenger car applications, the tank is typically either a cylindrical tank mounted in the boot of the vehicle or a toroidal tank or set of permanently interconnected cylinders placed in the spare wheel well. In commercial vehicle applications, the tanks are generally cylindrical tanks mounted either in the cargo space or on the chassis underneath the body.		Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications. In passenger car applications, the tank is typically either a cylindrical tank mounted in the boot of the vehicle or a toroidal tank or set of permanently interconnected cylinders placed in the spare wheel well. In commercial vehicle applications, the tanks are generally cylindrical tanks mounted either in the cargo space or on the chassis underneath the body.

Red marquis at 20:35, 22 August 2009

2009-08-22T20:35:49Z

New page

'''Autogas''' is the common name for liquefied petroleum gas (LPG) when it is used as a [[fuel]] in [[internal combustion engine]]s in [[vehicles]]. The same equipment is also used for similar engines in stationary applications such as generators.

Autogas is widely used as a "green" fuel as it decreases [[Automobile emissions control|exhaust emissions]]. In particular, it reduces CO<sub>2</sub> emissions by around 20% compared to [[gasoline|petrol]]. It has an [[octane rating]] (MON/RON) that is between 90 and 110 and an energy content (higher heating value—HHV) that is between 25.5 megajoules per litre (for pure propane) and 28.7 megajoules per litre (for pure butane) depending upon the actual fuel composition.

== Terminology variations ==
In countries where petrol is called ''petrol'' rather than ''gasoline'', it is common for autogas to be simply referred to as ''gas''. This can be confusing for people from countries where petrol is called ''gasoline'', as they often use the abbreviation ''gas'' to refer to petrol.

In the United States, autogas is more commonly known under the name of its primary constituent, ''propane''. The term ''autogas'' is used in the United States to refer to automobile petrol, when used in piston-powered small aircraft. Aircraft owners using this fuel in place of the more common aviation fuel or ''avgas'', require a Supplemental Type Certificate issued by the United States Federal Aviation Agency.

In the UK "LPG" and "autogas" are used interchangeably.

In Asian countries, particularly those with historical American influences such as the Philippines, the term ''autogas'' is not commonly recognized as a generic term and the use of the term "LPG" or "autoLPG" is more widely used by consumers, especially by taxi drivers many of whom use converted vehicles.<ref>[http://newsinfo.inquirer.net/breakingnews/metro/view/20081217-178514/AutoLPG-prices-down-by-P1L AutoLPG prices down by P1/L ]</ref> The converted vehicles are commonly called ''LGP vehicles'' or ''LPG cars''.

==Vehicle manufacturers==

[[Toyota Motor Corporation|Toyota]] made a number of LPG-only engines in their 1970s ''[[Toyota M engine|M]]'', ''[[Toyota R engine|R]]'', and ''[[Toyota Y engine|Y]]'' engine families.

Currently, a number of [[automobile]] manufacturers—[[Citroën]], [[Fiat]], [[Ford Motor Company|Ford]], [[Hyundai Motor Company|Hyundai]], [[General Motors]] (including [[Daewoo]], [[Holden]], [[Opel]]/[[Vauxhall Motors|Vauxhall]], [[Saab automobile|Saab]]), [[Maruti Suzuki]], [[Peugeot]], [[Renault]] (including [[Dacia]]), [[Toyota]], [[Volvo|Volvo]], and more recently Volkswagen —have OEM ''bi-fuel'' (dual fuel) models that will run equally well on both LPG and petrol.

Petrol engined cars which have not been fitted with LPG/autogas systems by the manufacturers can usually accept third party systems to enable them to use both LPG or petrol.

Vialle manufacture OEM LPG powered scooters and LPG powered mopeds that run equally well on LPG. Ford Australia have offered an LPG-only variant of their Falcon model since 2000.

==Countries==
Autogas enjoys great popularity in numerous countries and territories including Australia, Bulgaria, Croatia, European Union, Hong Kong, India, the Philippines, Republic of Macedonia, South Korea, Serbia and Turkey. It is also available at larger petrol stations in several countries. The Republic of Armenia may, however, be the world leader in autogas use. The Armenian transport ministry estimates as much as 20 to 30% of vehicles use autogas compared with traditional gasoline, once again due to the fact that it offers a very cheap alternative to both diesel and petrol, being less than half the price of petrol and some 40% cheaper than diesel. The recent rises in oil-derived fuels has sharply raised the difference.

=== Australia ===
LPG is popular in Australia, because it is less than half the price of petrol in urban areas (approx $A0.57-0.73 per litre, as opposed to $A1.60 per litre for unleaded fuel and $A1.85 per litre for diesel, as of June 2008), and it is locally produced. The three major local manufacturers ([[Ford Motor Company|Ford]], [[Holden]] and [[Toyota Motor Corporation|Toyota]]) offer factory fitted autogas in some models of their locally made large cars. All factory autogas vehicles are ''dual fuel'' vehicles, with the exception of the ''E-Gas'' [[Ford Falcon|Ford Falcon]] model, which runs on autogas only.

Autogas is especially popular with taxis, except in remote areas where transportation costs make autogas prices uncompetitive.

Whilst autogas is currently excise-free, excise is to be imposed on all vehicle fuels that are not currently subject to excise, being added incrementally from 2011 to 2015. The excise on autogas will start at 2.5 cents per litre in 2011 and reach 12.5 cents per litre by 2015. By comparison, the excise on petrol will remain at its existing 38 cents per litre. The additional excise on autogas is being offset somewhat by a subsidy that was implemented in 2006 for private motorists, paying either AU$2000 to convert their existing vehicle to autogas, or AU$1000 for purchasing a new vehicle that was manufactured to operate on autogas.<ref>{{cite web|url=http://www.lpgautogas.com.au|title=LPG Autogas Australia|accessdate=2007-02-09}}</ref> The subsidy does not apply to business vehicles or vehicles with a Gross Vehicle Mass of over 3500 kilograms. In addition to the subsidy provided by the Australian federal government, the Western Australian government also provides a AU$1000 subsidy under the long-running LPG subsidy scheme.

==System types==
The different autogas systems generally use the same type of filler, tanks, lines and fittings but use different components in the engine bay. Some injection systems use special tanks with circulation pumps and return lines similar to petrol [[fuel injection]] systems.

There are three basic types of autogas system. The oldest of these is the conventional ''converter-and-mixer'' system, which has existed since the 1940s and is still widely used today. The other two types are known as ''injection'' systems, but there are significant differences between the two.

A converter-mixer system uses a converter to change liquid fuel from the tank into vapour, then feeds that vapour to the mixer where it is mixed with the intake air.

Vapour phase injection systems use a converter in much the same way as with a mixer, but have a series of electrical shutoff solenoids and nozzles (collectively referred to as injectors) that are controlled by a computer. The computer works in much the same way as a petrol fuel injection computer. This allows much more accurate metering of fuel to the engine than is possible with mixers, improving economy and/or power while reducing emissions.

Liquid phase injection systems do not use a converter, but instead deliver the liquid fuel into a ''fuel rail'' in much the same manner as a petrol injection system. These systems are still very much in their infancy. Because the fuel vapourises in the intake, the air around it is cooled significantly. This increases the density of the intake air and can potentially lead to substantial increases in engine power output, to the extent that such systems are usually ''de-tuned'' to avoid damaging other parts of the engine. Liquid phase injection has the potential to achieve much better economy and power plus lower emission levels than are possible using mixers or vapour phase injectors.

==System components==

===Filler===
The fuel is transferred into a vehicle tank as liquid by connecting the [[Gas pump|bowser]] at the [[filling station]] to the ''filler'' fitting on the vehicle.

The type of filler used varies from country to country and in some cases different types are used within the same country.<ref>[http://www.boostlpg.co.uk/driver_industry/going_abroad.htm Untitled Document]</ref>

The three types are:
* ACME thread. This type has a threaded fitting onto which the bowser nozzle is screwed before the trigger is pulled to establish a seal before fuel transfer. This type is used in Australia, USA, Germany, Austria, Belgium, Republic of Ireland.
* 'Dutch' Bayonet. This type establishes a gas proof seal by a push and twist action. This type is used in the United Kingdom, Netherlands and Switzerland.
* 'Italian' Dish. This type is used in Italy, France, Scandinavia and Portugal.

Adaptors that allow a vehicle fitted with a particular system to refuel at a station equipped with another system are available.

The fill valve contains a check valve so that the liquid in the line between the filler and the tank(s) does not escape when the bowser nozzle is disconnected.

In installations where more than one tank is fitted, T-fittings may be used to connect the tanks to one filler so that the tanks are filled simultaneously. In some applications, more than one filler may be fitted, such as on opposite sides of the vehicle. These may be connected to separate tanks, or may be connected to the same tanks using T-fittings in the same manner as for connecting multiple tanks to one filler.

===Hoses, pipes and fittings===

The hose between the filler and tank(s) is called the ''fill hose'' or ''fill line''. The hose or pipe between the tank(s) and the converter is called the ''service line''. These both carry liquid under pressure.

The flexible hose between the converter and mixer is called the ''vapour hose'' or ''vapour line''. This line carries vapour at low pressure and has a much larger diameter to suit.

Where the tank valves are located inside an enclosed space such as the boot of a sedan, a plastic ''containment'' hose is used to provide a gas-tight seal between the gas components and the inside of the vehicle.

Liquid hoses for LPG are specifically designed and rated for the pressures that exist in LPG systems, and are made from materials designed to be compatible with the fuel. Some hoses are made with crimped fittings, while others are made using ''re-usable'' fittings that are pressed or screwed onto the end of the hose.

Rigid sections of liquid line are usually made using copper tubing, although in some applications, steel pipes are used instead. The ends of the pipes are always double-flared and fitted with flare nuts to secure them to the fittings.

Liquid line fittings are mostly made from brass. The fittings typically adapt from a thread in a component, such as a BSP or NPT threaded hole on a tank, to an SAE flare fitting to suit the ends of pipes or hoses.

===Tank===

:''{{See|Gas tank}}
Vehicles are often fitted with only one tank, but multiple tanks are used in a some applications. In passenger car applications, the tank is typically either a cylindrical tank mounted in the boot of the vehicle or a toroidal tank or set of permanently interconnected cylinders placed in the spare wheel well. In commercial vehicle applications, the tanks are generally cylindrical tanks mounted either in the cargo space or on the chassis underneath the body.

The tanks have fittings for filling, liquid outlet, emergency relief of excess pressure, fuel level gauge and sometimes a vapour outlet. These may be separate valves mounted into a series of 3 to 5 holes in a plate welded into the tank shell, or may be assembled onto a ''multi-valve'' unit which is bolted into one large hole on a boss welded into the tank shell.

Modern fill valves are usually fitted with an ''automatic fill limiter'' (AFL) to prevent overfilling. The AFL has a float arm which restricts the flow significantly but does not shut it off entirely. This is intended to cause the pressure in the line to rise enough to tell the bowser to stop pumping but not cause dangerously high pressures. Before AFLs were introduced, it was common for the filler (with integral check valve) to be screwed directly into the tank, as the operator had to open an ''ullage'' valve at the tank while filling, allowing vapour out of the top of the tank and stopping filling when liquid started coming out of the ullage valve to indicate that the tank was full. Modern tanks are not fitted with ullage valves.

The liquid outlet is usually used to supply fuel to the engine, and is usually referred to as the ''service valve''. Modern service valves incorporate an electric shutoff solenoid. In applications using very small engines such as small generators, vapour may be withdrawn from the top of the tank instead of liquid from the bottom of the tank.

The emergency pressure relief valve in the tank is called a hydrostatic pressure relief valve. It is designed to open if the pressure in the tank is dangerously high, thus releasing some vapour to the atmosphere to reduce the pressure in the tank. The release of a small quantity of vapour reduces the pressure in the tank, which causes some of the liquid in the tank to vapourise to re-establish equilibrium between liquid and vapour. The ''latent heat of vapourisation'' causes the tank to cool, which reduces pressure even further.

The gauge sender is usually a magnetically coupled arrangement, with a float arm inside the tank rotating a magnet, which rotates an external gauge. The external gauge is usually readable directly, and most also incorporate an electronic sender to operate a fuel gauge on the dashboard.

===Valves===
There are a number of types of valve used in autogas systems. The most common ones are ''shutoff'' or ''filterlock'' valves, which are used to stop flow in the service line. These may be operated by vacuum or electricity. On dual-fuel systems with a petrol carburettor, a similar shutoff valve is usually fitted in the petrol line between the pump and carburettor.

Check valves are fitted in the filler and on the fill input to the fuel tank to prevent fuel flowing back the wrong way.

Service valves are fitted to the outlet from the tank to the service line. These have a tap to turn the fuel on and off. The tap is usually only closed when the tank is being worked on. In some countries, an electrical shutoff valve is built into the service valve.

Where multiple tanks are fitted, a combination of check valves and a hydrostatic relief valve are usually installed to prevent fuel from flowing from one tank to another. In Australia, there is a common assembly designed for this purpose. It is a combined twin check valve and hydrostatic relief valve assembly built in the form of a T-fitting, such that the lines from the tanks come into the sides of the valve and the outlet to the converter comes out the end. Because there is only one common brand of these valves, they are known colloquially as a ''Sherwood valve''.

===Converter===
The converter (also known as vaporiser) is a device designed to change the fuel from a pressurised liquid to a vapour at around atmospheric pressure for delivery to the mixer or vapour phase injectors. Because of the refrigerant characteristic of the fuel, heat must be put into the fuel by the converter. This is usually achieved by having engine coolant circulated through a heat exchanger that transfers heat from that coolant to the LPG.

There are two distinctly different basic types of converter for use with mixer type systems. The ''European'' style of converter is a more complex device that incorporates an idle circuit and is designed to be used with a simple fixed venturi mixer. The ''American'' style of converter is a simpler design which is intended to be used with a variable venturi mixer that incorporates an idle circuit.

Engines with a low power output such as; scooters, quad bikes and generators can use a simpler type of converter (also known as governor or regulator). These converters are fed with fuel in vapour form.
Evaporation takes place in the tank where refrigeration occurs as the liquid fuel boils. The tanks large surface area exposed to the ambient air temperature combined with the low power output (fuel requirement) of the engine make this type of system viable. The refrigeration of the fuel tank is proportional to fuel demand hence this setup is only used on smaller engines.
This type of converter can either fed with vapour at tank pressure (called a 2 stage regulator) or be fed via a tank mounted regulator at a fixed reduced pressure (called a single stage regulator).

===Mixer===
The mixer is the device that mixes the fuel into the air flowing to the engine. The mixer incorporates a venturi designed to draw the fuel into the airflow due to the movement of the air.

Mixer type systems have existed since the 1940s and some designs have changed little over that time. Mixers are now being increasingly superseded by injectors.

===Vapour phase injectors===
Most vapour phase injection systems mount the solenoids in a manifold block or ''injector rail'', then run hoses to the nozzles, which are screwed into holes drilled and tapped into the runners of the intake manifold. There is usually one nozzle for each cylinder. Some vapour injection systems resemble petrol injection, having separate injectors that fit into the manifold or head in the same manner as petrol injectors, and are fed fuel through a ''fuel rail''.

===Liquid phase injectors===
Liquid phase injectors are mounted onto the engine in a manner similar to petrol injectors, being mounted directly at the inlet manifold and fed liquid fuel from a fuel rail.

===Electrical and electronic controls===
The are four distinct electrical systems that may be used in autogas systems - [[fuel gauge]] sender, fuel shutoff, closed loop feedback mixture control and injection control.

In some installations, the fuel gauge sender fitted to the autogas tank is matched to the original fuel gauge in the vehicle. In others, an additional gauge is added to display the level of fuel in the autogas tank separately from the existing petrol gauge.

In most modern installations, an electronic device called a ''tachometric relay'' or ''safety switch'' is used to operate electrical shutoff solenoids. These work by sensing that the engine is running by detecting ignition pulses. Some systems use an engine oil pressure sensor instead. In all installations, there is a filterlock (consisting of a filter assembly and a vacuum or electric solenoid operated shutoff valve) located at the input to the converter. In ''European'' converters, there is also a solenoid in the converter to shut off the idle circuit. These valves are usually both connected to the output of the tachometric relay or oil pressure switch. Where solenoids are fitted to the outputs of fuel tanks, these are also connected to the output of the tachometric relay or oil pressure switch. In installations with multiple tanks, a switch or ''changeover'' relay may be fitted to allow the driver to select which tank to use fuel from. On dual-fuel systems, the switch used to change between fuels is used to turn off the tachometric relay.

Closed loop feedback systems use an electronic controller that operates in much the same way as in a petrol [[fuel injection]] systems, using an oxygen sensor to effectively measure the air/fuel mixture by measuring the oxygen content of the exhaust and control valve on the converter or in the vapour line to adjust the mixture. Mixer type systems that do not have a closed loop feedback fitted are sometimes referred to as ''open loop'' systems.

Injection systems use a computerised control system which is very similar to that used in petrol injection systems. In virtually all systems, the injection control system integrates the tachometric relay and closed loop feedback functions.

==Converter-and-mixer system operation==
The designs of converters and mixers are matched to each other by matching sizes and shapes of components within the two.

In European style systems, the size and shape of the venturi is designed to match the converter. In American style systems, the air valve and metering pins in the mixer are sized to match the diaphragm sizes and spring stiffnesses in the converter. In both cases, the components are matched by the manufacturers and only basic adjustments are needed during installation and tuning.

An autogas [[carburetor|carburettor]] may simply consist of a throttlebody and a mixer, sometimes fitted together using an adapter.

Cold start enrichment is achieved by the fact that the engine coolant is cold when the engine is cold. This causes denser vapour to be delivered to the mixer. As the engine warms up, the coolant temperature rises until the engine is at operating temperature and the mixture has leaned off to the normal running mixture. Depending on the system, the throttle may need to be held open further when the engine is cold in the same manner as with a petrol carburetor. On others, the normal mixture is intended to be somewhat lean and no cold-start throttle increase is needed. Because of the way enrichment is achieved, no additional ''choke'' butterfly is required for cold starting with LPG.

The temperature of the engine is critical to the tuning of an autogas system. The engine thermostat effectively controls the temperature of the converter, thus directly affecting the mixture. A faulty thermostat, or a thermostat of the wrong temperature range for the design of the system may not operate correctly.

The power output capacity of a system is limited by the ability of the converter to deliver a stable flow of vapour. A coolant temperature lower than intended will reduce the maximum power output possible, as will an air bubble trapped in the cooling circuit or complete loss of coolant. All converters have a limit, beyond which mixtures become unstable. Unstable mixtures typically contain tiny droplets of liquid fuel that were not heated enough in the converter and will vapourise in the mixer or intake to form an excessively rich mixture. When this occurs, the mixture will become so rich that the engine will flood and stall. Because the outside of the converter will be at or below 0°C when this happens, water vapour from the air will freeze onto the outside of the converter, forming an icy white layer. Some converters are very suceptible to cracking when this happens.

==LPG injection for diesel vehicles==
The performance, economy and emission profile of diesel engines can be improved by injecting a small quantity of LPG into the inlet manifold. It is claimed that the LPG increases the burning efficiency of the diesel fuel from typically 75-85%, to 95-98%.<ref name=dga_tech>[http://www.dieselgasaustralia.com.au/default.aspx?ID=Technical Diesel Gas Australia]</ref>

The systems typically operate by metering a small quantity of LPG, at a pressure slightly above atmospheric, into the intake manifold, where it enters the combustion chamber and is ignited with the diesel. LPG flow is regulated to ensure smooth operation, and will typically only deliver LPG under power.

It is claimed that such a system can result in a 10% to 20% increase in power and torque,<ref>[http://www.ilovesponge.com/spongecars/diesel/dieseltechnical.htm SpongeCars - UK LPG Vehicles - Diesel LPG]</ref><ref name=dga_tech /> and a reduction in overall fuel costs. Any actual savings are dependent on the relative cost of diesel versus LPG. In Australia, where diesel costs substantially more than LPG, savings of 10 to 20% are claimed. <ref name=dga_econ>[http://www.dieselgasaustralia.com.au/default.aspx?ID=Economy Diesel Gas Australia]</ref>

The above systems add small quantities of LPG with the primary aim of improving economy, but much larger quantities of LPG can be injected in order to increase power. Even at full output a diesel engine runs about 50% lean of [[Air-fuel_ratio|stoichiometric]] to avoid black smoke production, so there is a substantial amount of oxygen in the intake charge which is not consumed in the combustion process. This oxygen is therefore available for the combustion of a substantial addition of LPG resulting in a large increase in power output.

== See also ==
*[[Hybrid vehicle]]
*[[Fuel injection]]
*[[Gas engine]]

==External links==
*[http://www.aegpl.com/ European LPG Association]
*[http://www.worldlpgas.com/gain/publications.php?id=01 Global Autogas Updates] — Quarterly publication (free download)
*[http://www.worldlpgas.com World LP Gas Association]. For a cleaner, healthier and more prosperous world.
*[http://www.worldlpgas.com/gain Global Autogas Industry Network (GAIN)].
*[http://www.drivelpg.co.uk Drive LPG - UKLPG's Autogas website]
*[http://www.lpgaustralia.com.au/ ALPGA] — Australian LP Gas Association
*[http://www.eere.energy.gov/afdc/altfuel/propane.html DOE Alternative Fuels Data Center - Propane]
*[http://rgl.faa.gov/REGULATORY_AND_GUIDANCE_LIBRARY/RGADVISORYCIRCULAR.NSF/0/ed533ebb7ceb125d862569b200751ed2/$FILE/ATT84JFC]



[[Category:Engine fuel system technology]]
[[Category:Fuel gas]]
[[Category:LPG vehicles|*]]

Autogas - Revision history

Red marquis: /* Tank */

Red marquis: /* Tank */

Red marquis at 20:35, 22 August 2009