Bi-fuel vehicle

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The Brazilian Fiat Siena Tetrafuel 1.4 is the first bi-fuel car that runs with natural gas (CNG) alternating automatically with any of the typical fuel blends used in flexible-fuel vehicles, pure gasoline, or gasohol E25, or just ethanol (E100). Shown below are the CNG storage tanks in the trunk. SAO 09 2008 Fiat Siena TetraFuel 2 views v1.jpg
The Brazilian Fiat Siena Tetrafuel 1.4 is the first bi-fuel car that runs with natural gas (CNG) alternating automatically with any of the typical fuel blends used in flexible-fuel vehicles, pure gasoline, or gasohol E25, or just ethanol (E100). Shown below are the CNG storage tanks in the trunk.

Bi-fuel vehicles are vehicles with multifuel engines capable of running on two fuels. The two fuels are stored in separate tanks and the engine is able to run on one fuel at a time. On internal combustion engines, a bi-fuel engine typically burns gasoline and a volatile alternate fuel such as natural gas (CNG), LPG, or hydrogen. [1] Bi-fuel vehicles have the capability to switch back and forth from the gasoline to the other fuel, manually or automatically. [2] [3] [4] [5] A related concept is the duel-fuel vehicle which must burn both fuels in combination. Diesel engines converted to use gaseous fuels fall into this class due to the different ignition system.

Contents

The most common technology and alternate fuel available in the market for bi-fuel gasoline cars is Autogas (LPG), followed by natural gas (CNG), [6] and it is used mainly in Europe. Poland, the Netherlands and the Baltic states have many cars running with LPG. Italy currently has the largest number of CNG vehicles, followed by Sweden. They are also used in South America, where these vehicles are mainly used as taxicabs in main cities of Brazil and Argentina. Normally, standard gasoline vehicles are retrofitted in specialized shops, which involve installing the gas cylinder in the trunk and the LPG or CNG injection system and electronics. The conversion is possible because the gases can use the spark-ignition of a gasoline engine. [7]

Diesel conversions

A Diesel engine is a compression ignition engine and does not have a spark plug. To operate a diesel engine with an alternate combustible fuel source such as natural gas, a Dual-Fuel system used with natural gas as the main fuel while diesel fuel is used for the ignition of the gas/air mixture inside the cylinder. In other words, a portion of diesel is injected at the end of the compression stroke, thereby maintaining the original diesel operation principle. (Running gas-only is possible, but requires more extensive modification.) [8] [9]

Dual-fuel operation in this case means the engine uses two fuels (gas and diesel) at the same time, as opposed to Bi-Fuel which would mean the engine could have the option of using either fuel separately.

There usually two type of conversions – low speed (below 1000 RPM) and high speed (between 1200 and 1800 RPM).

Low and middle speed conversion

Gas is injected into the cylinder inlet manifold by individual gas electromagnetic valves installed as close to the intake valves as possible. The valves are separately timed and controlled by injection control unit. This system interrupts the gas supply to the cylinder during the long overlap of the intake and exhaust valves (just typical for slow-speed and medium-speed engines – within the valve overlap cylinder scavenging is performed). This avoids substantial gas losses and prevents dangerous gas flow to the exhaust manifold.

High-speed conversion

Gas is mixed with air by a common mixer installed before turbocharger(s). Gas flow is controlled by a throttle valve, which is electronically operated by the special control system according to the required engine output and speed. In order to avoid knocking of the engine, knocking detector/controller is installed, thus enabling engine operation at the most efficient gas/diesel ratio. [10]

Conversion features and benefits

Benefits relating to conversion to bi-fuel vehicles include savings on operation costs, little to no engine modification of the existing vehicle and non-derated output power. Other benefits also include emissions reduction (due to different C/H atom ratio) and fuel flexibility.

Gas types used

It is common to use CNG (Compressed Natural Gas) or LNG (Liquid Natural Gas) for bi-fuel operations. Both are also mostly used for generator sets conversions, because the engine does not lose the output power.

In recent years biogas is being used. The biogas composition and calorific value must be known in order to evaluate if the particular biogas type is suitable. Calorific value may be an issue as biogas is derived from different sources and there is low calorific value in many cases. You can imagine you have to inject sufficient volume of gas into the cylinder to substitute diesel oil (or, better to say, substitute energy delivered by diesel oil). If the calorific value (energy) of the biogas was very low, there is a need to inject really big volume of biogas into the cylinder, which might be technically impossible. Additionally, the composition of the biogas has to lean towards ignitable gases and be filtered as much as possible of non-combustible compounds such as carbon dioxide.

Associated gas is the last type of gas which is commonly used for bi-fuel conversions of generator sets. Associated gas is a natural gas found in association with oil, either dissolved in the oil or as a cap of free gas above the oil. It means it has almost the same quality as CNG or LNG. [11]

Diesel/gas ratio

It depends on the technical state of the engine, especially of the injection system. The typical Diesel/Gas ratio is 40/60% for the high-speed engines. If the operating output of the engine is constant and between 70–80% of nominal output, than it is possible to reach up to 30/70% ratio. [12] If the operating output is lower (for example 50% of the nominal output) or if there are variations, the rate is about 45/55% (more of diesel is used). For Low Speed conversions it is possible to reach the Diesel/gas ratio up to 10/90%. Generally, it is not possible to guarantee an exact diesel/gas ratio without a test being done after the conversion.

Vehicles

Aftermarket 'bi-fuel' and even 'tri-fuel' conversions are also available.

Factory bi-fuel passenger cars

Factory bi-fuel pickups

See also

Related Research Articles

<span class="mw-page-title-main">Compression ratio</span> Ratio of the volume of a combustion chamber from its largest capacity to its smallest capacity

The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values.

<span class="mw-page-title-main">Diesel engine</span> Type of internal combustion engine

The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.

<span class="mw-page-title-main">Reciprocating engine</span> Engine utilising one or more reciprocating pistons

A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.

A stratified charge engine describes a certain type of internal combustion engine, usually spark ignition (SI) engine that can be used in trucks, automobiles, portable and stationary equipment. The term "stratified charge" refers to the working fluids and fuel vapors entering the cylinder. Usually the fuel is injected into the cylinder or enters as a fuel rich vapor where a spark or other means are used to initiate ignition where the fuel rich zone interacts with the air to promote complete combustion. A stratified charge can allow for slightly higher compression ratios without "knock," and leaner air/fuel ratio than in conventional internal combustion engines.

<span class="mw-page-title-main">Four-stroke engine</span> Internal combustion engine type

A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:

  1. Intake: Also known as induction or suction. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing a partial vacuum in the cylinder through its downward motion.
  2. Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.
  3. Combustion: Also known as power or ignition. This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. the compressed air-fuel mixture is ignited by a spark plug or by heat generated by high compression, forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.
  4. Exhaust: Also known as outlet. During the exhaust stroke, the piston, once again, returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust port.
<span class="mw-page-title-main">Liquefied petroleum gas</span> Fuel for heating, cooking and vehicles

Liquefied petroleum gas is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane, and n-butane.

Compressed natural gas (CNG) is a fuel gas mainly composed of methane (CH4), compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 20–25 megapascals (2,900–3,600 psi), usually in cylindrical or spherical shapes.

<span class="mw-page-title-main">Natural gas vehicle</span> Vehicle powered by natural gas

A Natural Gas Vehicle (NGV) is an alternative fuel vehicle that uses compressed natural gas (CNG) or liquefied natural gas (LNG). Natural gas vehicles should not be confused with autogas vehicles powered by liquefied petroleum gas (LPG), mainly propane, a fuel with a fundamentally different composition.

Lean-burn refers to the burning of fuel with an excess of air in an internal combustion engine. In lean-burn engines the air–fuel ratio may be as lean as 65:1. The air / fuel ratio needed to stoichiometrically combust gasoline, by contrast, is 14.64:1. The excess of air in a lean-burn engine emits far less hydrocarbons. High air–fuel ratios can also be used to reduce losses caused by other engine power management systems such as throttling losses.

Homogeneous Charge Compression Ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer are compressed to the point of auto-ignition. As in other forms of combustion, this exothermic reaction produces heat that can be transformed into work in a heat engine.

<span class="mw-page-title-main">Autogas</span> Liquefied petroleum gas when it is used as a fuel in internal combustion engines

Autogas or LPG is liquefied petroleum gas (LPG) used as a fuel in internal combustion engines in vehicles as well as in stationary applications such as generators. It is a mixture of propane and butane.

<span class="mw-page-title-main">Gas engine</span> Internal combustion engine powered by gaseous fuel

A gas engine is an internal combustion engine that runs on a fuel gas, such as coal gas, producer gas, biogas, landfill gas, natural gas or hydrogen. In the United Kingdom and British English-speaking countries, the term is unambiguous. In the United States, due to the widespread use of "gas" as an abbreviation for gasoline (petrol), such an engine is sometimes called by a clarifying term, such as gaseous-fueled engine or natural gas engine.

<span class="mw-page-title-main">Fuel gas-powered scooter</span>

A fuel gas-powered scooter is a scooter powered by fuel gas. Fuel gases include such fuels such as liquefied petroleum gas (LPG), compressed natural gas (CNG), biogas and hydrogen (HICE). Hydrogen use in two-wheelers has only recently being started to be looked into, mainly by developing countries, to decrease local pollution at an affordable cost.

<span class="mw-page-title-main">Bivalent (engine)</span>

A bivalent engine is an engine that can use two different types of fuel. Examples are petroleum/CNG and petroleum/LPG engines, which are widely available in the European passenger vehicle aftermarket.

The following items are commonly used automotive acronyms and abbreviations:

<span class="mw-page-title-main">Alternative fuel vehicle</span> Type of vehicle

An alternative fuel vehicle is a motor vehicle that runs on alternative fuel rather than traditional petroleum fuels. The term also refers to any technology powering an engine that does not solely involve petroleum. Because of a combination of factors, such as environmental and health concerns including climate change and air pollution, high oil-prices and the potential for peak oil, development of cleaner alternative fuels and advanced power systems for vehicles has become a high priority for many governments and vehicle manufacturers around the world.

<span class="mw-page-title-main">IKCO EF engines</span> Reciprocating internal combustion engine

IKCO EF Engines are a family of four-cylinder engines by the Iranian car manufacturer Iran Khodro (IKCO). The first engines of this family were designed jointly by Iran Khodro Powertrain Company (IPCO) and F.E.V GmbH of Germany. The later models were designed by IPCO alone. IPCO is the powertrain design and production company of IKCO.

Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.

Skyactiv is a brand name for a series of automobile technologies developed by Mazda that increase fuel efficiency and engine output. The initial announcement of the Skyactiv technologies included new engines, transmissions, body, and chassis, which appeared in Mazda products from 2011 onwards.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.

References

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  8. "Technology – Diesel to Dual Fuel".
  9. DFPS Brochure
  10. Archived at Ghostarchive and the Wayback Machine : "Caterpillar Diesel Generator Bi-Fuel on 70% Methane". YouTube .
  11. "'Frack the Future': Halliburton Leads Effort to Clean up Drilling Fields". HuffPost . 27 May 2013.
  12. "HHP Insight".
  13. "Fiat website" . Retrieved 2008-04-22.[ permanent dead link ]
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