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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 runs 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 switch between gasoline and the other fuel, manually or automatically. [2] [3] [4] [5] A related concept is the dual-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.
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 install 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]
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).
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.
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]
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.
The preferred method for diesel generators to be converted to dual fuel would be to use piped natural gas due to the volume of gas required based on the operating cycle of the engine. [11] It is less common to use CNG (Compressed Natural Gas) or LNG (Liquid Natural Gas) for bi-fuel operations, due to logistics of fuel delivery frequency and amount of fuel required to maintain operations. Natural Gas is preferred for generator sets conversions, because the engine does not lose the output power. [12]
In recent years biogas is being used. [13] 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. [14]
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. [15] 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.
Aftermarket 'bi-fuel' and even 'tri-fuel' conversions are also available.
The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine.
The diesel engine, named after the German engineer 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.
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.
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:
Liquefied petroleum gas, also referred to as liquid petroleum gas, is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, n-butane and isobutane. It can sometimes contain some propylene, butylene, and isobutene.
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; 200–250 atm), usually in cylindrical or spherical shapes.
The GM High Feature engine is a family of modern DOHC V6 engines produced by General Motors. The series was introduced in 2004 with the Cadillac CTS and the Holden Commodore (VZ).
A natural gas vehicle (NGV) utilizes compressed natural gas (CNG) or liquefied natural gas (LNG) as an alternative fuel source. Distinguished from autogas vehicles fueled by liquefied petroleum gas (LPG), NGVs rely on methane combustion, resulting in cleaner emissions due to the removal of contaminants from the natural gas source.
Indirect injection in an internal combustion engine is fuel injection where fuel is not directly injected into the combustion chamber.
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.
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.
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.
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.
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:
Engine efficiency of thermal engines is the relationship between the total energy contained in the fuel, and the amount of energy used to perform useful work. There are two classifications of thermal engines-
An alternative fuel vehicle is a motor vehicle that runs on alternative fuel rather than traditional petroleum-based fossil fuels such as gasoline, petrodiesel or liquefied petroleum gas (autogas). The term typically refers to internal combustion engine vehicles or fuel cell vehicles that utilize synthetic renewable fuels such as biofuels, hydrogen fuel or so-called "Electrofuel". The term can also be used to describe an electric vehicle, which should be more appropriately called an "alternative energy vehicle" or "new energy vehicle" as its propulsion actually rely on electricity rather than motor fuel.
IKCO EF Engines, also known as National Engines, are a family of four-cylinder engines produced by the Iranian car manufacturer Iran Khodro (IKCO). The first engines in this family, the EF7 series, 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.
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. This process transforms chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.
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