LPGAutogas Designates liquid gas intended for use in vehicle internal combustion engines (LPG, Liquefied Petroleum Gas). It is not to be confused with compressed natural gas (CNG, Compressed Natural Gas) or liquefied natural gas (LNG, Liquefied Natural Gas) as a fuel.
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Table of Contents
1 Liquid gas as a fuel 2 Vehicle conversion 3 Technology of liquid gas vehicles 3.1 Venturi technology 3.2 Partially sequential systems 3.3 Fully sequential systems 3.4 LPI systems 3.5 Refueling technology
5.1 Billing problems when refueling
LPG as fuel
Liquid gas (butane/propane) is used as fuel for gasoline engines. It was already very common in Italy in the 1970s and remains so today. The entire bus fleet of the Vienna Public Transport Company also runs on LPG.
It burns more environmentally friendly than gasoline. Pollutant emissions of nitrogen oxides are about 20% of gasoline combustion, CO2 emissions decrease by 15%, and unburned hydrocarbons by 50%. In addition, LPG exhaust gases can be converted into vehicle catalytic converters at lower temperatures due to their better chemical utilizability. LPG-powered forklifts are the only vehicles – apart from natural gas forklifts – that may be operated with an internal combustion engine in enclosed spaces. Diesel trucks, on the other hand, emit soot. High levels of nitrogen oxides.
In direct comparison with gasoline, depending on the gas system (see below), there is a volumetric (liters vs. Kg) additional consumption of 5 to 20 % for LPG, because LPG has a lower density. For comparison: premium gasoline with 95 octane has a density of ca. 0.76 g/cm³, liquid gas (around 108 octane) between 0.51 and 0.56 g/cm³ depending on the mixing ratio. At first glance, this results in an additional consumption of 40%, but this is offset by the higher calorific value of LPG (46.1 MJ/kg (12.8 kWh/kg) vs. 43.6 MJ/kg (12.1 kWh/kg)) is theoretically reduced to 33 %. By consuming starting gasoline (and neglecting it in the consumption calculation), the theoretical additional consumption of 33 % is reduced to practically 5 to 25 % depending on the average distance traveled. The higher the proportion of short trips, the lower the typical "additional consumption" From.
At first, LPG was used in cabs (z. B. All cabs in Istanbul), later also in the private car sector, in the 1980s very common in Austria due to low prices. Due to the higher taxation for private vehicles, however, it became uninteresting again in Austria. However, the Wiener Linien have converted all buses to LPG since LPG remained tax-free for public vehicles.
Today, LPG is established as a fuel in most of the European neighboring countries (like B, F, GB, I, NL, PL…). In Germany, the number of cars and gas stations is growing rapidly. The reason is the low tax. Under the Energy Tax Act, liquefied petroleum gas (LPG/autogas) is taxed as a fuel at 16.6 cents/kg – 1.29 cents/kWh (= ca. 9 cents/l) until the end of 2018.
In Germany, a liter of LPG currently costs between 52 and 76 cents at the filling station (as of 15. November 2007) – although there is a clear north-south divide here. LPG filling stations exist z. Currently. 3284 (14. December 2007). By August 2008, the number of filling stations in Germany is expected to reach 4000.
In Switzerland, liquefied petroleum gas is to be tax-privileged as of 2008 and thus increase by approx. 0.30 francs (0.40 francs gasoline equivalent) cheaper. At the moment it costs between 1.20 and 1.69 francs/liter (as of 7. November 2007).
Conversion of passenger cars to liquid petroleum gas (LPG) is relatively straightforward. Almost any vehicle with a gasoline engine can be converted for about 1500 to 3500 euros, depending on the number of cylinders, power and the emission standard to be achieved. The unladen weight of an LPG system is about 40 kg.
There are various installation options for the tank:
– In the spare wheel well (34 to 85 liters), the spare wheel is then replaced with a breakdown spray.
– In the trunk (60 to 200 liters), usually in cylinder form.
– Underfloor tanks are also possible.
The range in gas mode is 350 to 1000 km, depending on tank size and consumption. During the conversion, the gasoline tank is retained so that the vehicle can be operated with either gasoline or LPG (bivalent drive). Switching between gasoline and LPG operation can be done automatically or manually while driving. If the Switchover point automatically selected, this should be done by a water temperature sensor. This ensures that the switch is only made when the engine is at operating temperature and the liquid gas can burn optimally. With the installation of the gas tank is thus also a substantial range increase connected, if also still accordingly gasoline is carried along.
Some retrofitters additionally recommend the installation of additive admixtures in the intake tract to reduce wear on the valves and valve seats with the changed fuel type and combustion conditions, since the combustion temperatures are considerably higher than those of gasoline for the same fuel-air mixture. In some vehicles, the valve seats are much less resistant to temperature than in other vehicles, so that engine damage can occur under certain circumstances during gas operation. Higher combustion temperatures and the resulting engine damage can be avoided from the outset if an installed gas system is correspondingly "richer" in the upper load range is set.
Technology of liquefied gas vehicles
Vehicles running on LPG are either started on gasoline and then, depending on the system installed, switched to gas operation either by switch or automatically to avoid any warm-up problems, or they run directly on LPG. A distinction is made between Venturi systems, sequential systems and LPI systems.
The first two types of system have in common that the pressurized liquid gas in the tank is fed to the engine in gaseous form via a vaporizer and pressure regulator. Since the gas cools down strongly during evaporation, the evaporator is heated with cooling water. For this reason, most LPG systems are only used from approx. 30 °C cooling water temperature to gas in order to prevent the gas system from icing up at low outside temperatures.
LPI systems have also been offered since 2004. These systems use a fuel pump to deliver liquid gas under pressure in a ring line, from where it is injected in liquid form into the intake tract through metering valves. Due to the heat absorbed for evaporation, there is a cooling effect of the intake air, which can be 5 to 15 Kelvin depending on the load. This results in a slight increase in power (see turbo engine/intercooler) or a lower loss of power in relation to evaporator systems, since gasoline, d. H. The original fuel, also liquid is injected and this already the mentioned cooling effect occurs. Therefore, one cannot speak of a general increase in performance -related to gasoline-.
LPG combustion takes place with lower pollutant emissions and increased running smoothness. The latter is due to the high knock resistance of 105 to 115 octane.
In the event of a fire, most tanks are tested up to an overpressure of 30-35 bar (downpressure ca. 60-90 bar). Depending on the type of tank (1-hole/4-hole), either a separate pressure relief valve or a pressure relief valve integrated into the multivalve is installed. This opens at a pressure of approx. 25-28 bar, which ensures that the gas is released in a controlled manner in the event of a fire and that the tank cannot burst. The Venturi technique is the oldest. Cheapest solution. Here, a vacuum-controlled metering valve is mounted in the intake manifold and gas is metered in a vacuum-controlled manner. Due to the narrowing of the intake cross section, a slight loss of power and extra consumption can be expected. In addition, this technology can lead to recombustion in the intake tract. This phenomenon, known as backfire, can occur when a fault in the ignition system ignites the gas that is constantly present in the intake tract in this technique. Pressure relief valves installed in the intake manifold and/or air filter box, which open in the event of an explosion and allow the pressure to escape, can prevent damage from backfire. The Venturi technology is suitable up to exhaust emission standard Euro 2 (or. Z. T. Also suitable for D3) without loss of a tax class.
Partial sequential systems
Partially sequential systems use a more precise electronically controlled metering valve that directs the gas into the intake ports of the cylinders by means of a star-shaped gas distributor. A cross-section narrowing in the intake tract. So that a loss of power does not take place. These systems often have their own programmable map generator for gas operation. Therefore also older automobiles. Equip passenger cars up to Euro 3 emission standard with this system.
Fully sequential systems
Fully sequential systems (currently state of the art) have their own metering valve per cylinder. These modern systems often no longer have their own autonomous map computer, but convert the injection map for gasoline stored in the on-board computer to equivalent gas quantities. Therefore, the conversion and programming is easier, but requires sequential or group sequential fuel injection. Modern vehicles already have this technology since the mid-1990s. The introduction of the emission standards Euro 3 and Euro 4 with EOBD (Euro-On-Board-Diagnosis) made the sequential gasoline injection mandatory. The exhaust gas standard Euro 4 is reached without problems and/or. Undercut (at least that's what the rebuilders claim). In any case, a gas confirmation about the currently valid (resp. The vehicle corresponding) emission standard to require, otherwise an acceptance (TÜV) in Germany not (or. Only very difficult, thus expensive) is to be obtained. Likewise, a certificate of correct installation and leak test according to VDTÜV 750, etc. To demand. (This is also necessary for the aforementioned systems and is often not present in systems installed abroad.)
LPI is the abbreviation for Liquid Propane Injection, which means liquid gas injection. Sequential gas injection in liquid form is probably the latest (so called) 5. Generation of autogas systems represent. Although this technology was introduced in the early 1990s, the technical implementation is still problematic. These systems are usually more expensive compared to vaporization systems and the LPG pumps/tanks are relatively noisy and vulnerable. The manufacturers advertise combustion chamber cooling, as the LPG is injected into the engine in liquid form. Even if under circumstances clearly before the inlet valves of the combustion chambers the autogas is injected into the intake manifold and the LPG should already evaporate in the intake manifold, the charge air flow of the engine is cooled nevertheless and thus the delivery degree is increased, whereby it should not be a substantial difference whether the evaporation of the LPG takes place in the suction pipe or in the combustion chamber. This does not apply to systems with vaporizers. Here the cooling effect of the evaporating LPG seeps into the cooling water. Cannot be used to increase the level of supply.
The ICOM system uses LPG injectors that are similar in their characteristics to gasoline injectors. (The characteristics are not always perfectly the same, with the result that some converted vehicles run either too rich or too lean in certain load ranges in gas operation, and the slow adaptation of the engine control unit is thereby misadjusted, so that problems result in turn in the gasoline starting behavior.) This means that the injection times of the gasoline control unit can be used, the gas control unit only works as a switch between gasoline and gas injector. This will eliminate the need to adjust the gas control unit, but the gas injectors will have to be calibrated when the system is installed.
Three different connection systems have been introduced worldwide for refueling an autogas vehicle. Depending on the country, a corresponding adapter is required for the use of the gas pump. This is the ACME connection ("Europe adapter"), screw connection), the Dish connection ("Italy adapter", Dish Coupling) and the bayonet connection ( NL adapter). Planned is a single European connection called Euronozzle.
Overview of the currently used connection systems:
Gas stations in Europe
In Germany there were already more than 3100  autogas filling stations in November 2007. The tendency is strongly increasing; z.Zt. (November 2007), a further 360 service stations are in the planning stage. By July 2008, 4000 autogas refueling stations are forecasted. (Graphs on the development of the number of LPG and natural gas filling stations in Germany.)
In Austria there are currently 6 public refueling stations and 1 is planned.. An explanatory statement to a parliamentary question from January 2006 shows why liquefied petroleum gas is not promoted as a fuel in Austria.
In the Switzerland it is possible to refuel at 13 stations. Another 7 are planned. Due to a tax reduction of LPG to 1. January 2008 by approx. 0.40 francs, one can assume a further expansion of the filling stations.
In very many European countries (Netherlands, Belgium, Italy, Poland, Czech Republic, France etc.) and Turkey, there is a nationwide network of service stations.
Service stations worldwide
You can fill up with LPG in many countries. The largest consumption of LPG has South Korea (22%), followed by Japan (9%), Turkey (8%), Mexico (8%), Australia (7%). Autogas is also widespread in Russia, Armenia, China, the USA and Canada.
Prices and costs
The prices for LPG in Germany are between €0.52 and €0.76 per liter (on average €0.67 per liter), and between €0.30 and €0.64 per liter abroad.
When comparing prices with gasoline, however, it must be taken into account that the consumption per liter of LPG increases by 15% on average, since LPG has a much lower density than gasoline, and thus a lower calorific value per liter. Therefore, when comparing the fuel costs between gasoline/super. LPG can be roughly assumed to account for 60 to 70% of fuel costs. Gasoline engines can reach or even undercut the fuel costs of a corresponding diesel engine when running on LPG. Car gas stations for company fleets can be purchased from about 5.000 € established. With about 40 to 45 cent per l are supplied.000 € set up and supplied with about 40 to 45 cents per l. A calibrated fuel dispenser including data transmission for cash register systems costs about 15.000 to 20.000 €.
Billing problems with refueling
A defined Mass of gas costs z. B. In the 11 kg (net) propane gas bottle 11 to 18 €. Parameters such as pressure. Temperature not specified. At an autogas filling station the Volume (liters) measured. However, the density and thus the mass of the gas depends on the temperature. At a higher temperature, less gas mass is filled in. Here it is not regulated by law at which standard pressure and standard temperature the indicated number of liters applies.
Comparison of liquefied petroleum gas (LPG) and natural gas (CNG) for motor vehicles
– Chemical – LPG is propane/butane, the octane number, depending on the butane content, is between 105 – 115.
– CNG consists mainly of methane (about 84 – 99 vol.-%), the octane number is 120 – 140.
– Physical – LPG is stored in liquid form at about 5 – 10 bar pressure (approx. 400 g of gaseous fuel per liter of gross tank volume).
– CNG is stored in gaseous form at about 200 bar (ca. 160 g of expanded fuel per liter of compressed gas tank volume) and reduced to 7 bar by a high-pressure regulator.
– Engine performance: each gas (LPG and CNG) displaces air from the cylinder, thus less oxygen is available for combustion. In the part-load range relevant for everyday use, engine performance can be increased by a more homogeneous. Better cylinder filling even slightly increase. In turbocharged engines such as turbos or supercharged vehicles, the loss of power can be compensated by a higher boost pressure and thus a higher oxygen charge. The high octane rating of well over 100 of the LPG. CNG favors this measure. With classic naturally aspirated engines, a loss of power must be expected with both fuels, depending on the fuel used. – LPG: One molecule of propane consumes five molecules of oxygen during combustion, while one molecule of butane consumes six and a half molecules. Depending on the gas composition, up to 4% of the cylinder charge consists of LPG. Old venturi systems or. Whose nozzle (permissible only up to Euro 2) can cause up to 10% power loss due to additional throttling losses in the intake tract. With newer sequential vaporizer systems, a power loss of up to 3.8 % can theoretically be expected, but this is not noticeable in practice. A liquid-injection system cools the air in the intake tract, which improves cylinder filling (analogous to the intercooler). Therefore, often no loss of power is measurable or even a slight gain in power can be observed.
– CNG: One molecule of natural gas consumes two oxygen molecules during combustion, so significantly more natural gas (typically 12%) must be metered into the cylinder, and even more atmospheric oxygen is displaced as a result. This oxygen is therefore not available for combustion. A loss of power of just these 12 to 15 % must be expected. The loss of power can be reduced, especially in the case of low-powered vehicles. High full-load enrichment clearly noticeable.
– Carbon dioxide emissions – The LPG CO2 emissions are 1980 g per liter.
– LPG reduces CO2 emissions by about 15% compared to gasoline combustion.
– CNG reduces CO2 emissions by about 25% compared to gasoline combustion. In engines optimized for CNG combustion, a greater reduction in CO2 is possible by increasing compression and thus efficiency. In reserve operation under gasoline, however, higher consumption occurs (more than when a Super-Plus optimized vehicle has to run under normal gasoline).
– Tank technology – LPG can be retrofitted in wheeled tanks without loss of trunk space. Cylinder tanks are available in volumes of up to more than 200 l; wheel trough tanks are offered in volumes of up to more than 100 l, depending on trough size. The net tank volume is 80 % of the gross volume. This is necessary for safety reasons (expansion in hot vehicle). The test pressure of these tank systems (TÜV) is 40 bar with normal operating pressures of 8 to 12 bar.
– CNG is carried in cylinder tanks located in the trunk or, as is now common in production vehicles, underfloor or in tanks located on the roof (commercial vehicles). CNG tanks have a test pressure of over 300 bar, and the burst pressure is 600 bar.
– Distribution – CNG: Currently being promoted aggressively in Germany due to its better carbon footprint, although the number of filling stations is still lower compared to LPG (per 1. January 2007 42.759 vehicles in Germany (source: Federal Motor Transport Authority), Switzerland, Austria, Italy, Argentina) CNG filling stations currently number 750 in Germany (as of April 2007 ).
– Distribution – LPG, like gasoline and diesel fuels, is usually transported by road to the filling station, thus burdening road traffic. However, the service station operator is not necessarily tied to a regional gas supplier. CNG, on the other hand, consists of natural gas. Finds its way to the consumer via pipelines. Filling stations receive the natural gas from the network of local gas supply companies; compression to the tank pressure of more than 220 bar takes place on site. Rural CNG filling stations without a connection to a natural gas network are difficult or impossible to find. Expensive to supply. Here bio natural gas filling stations represent a reasonable alternative.
– Practical consequences – LPG is effectively slightly more expensive as a fuel than CNG (December 2005 ), but conversions are much cheaper and achievable ranges generally higher due to lower pressure and higher penetration worldwide. If a gasoline engine is retrofitted for gas operation, LPG is often an option for reasons of cost and space.
– CNG is effectively somewhat cheaper as a fuel than LPG (December 2005 ), but requires thicker-walled and thus heavier tanks due to the higher pressure, and often allows only shorter ranges, from 240 to 300 km depending on fuel consumption. If a vehicle is equipped with underfloor tanks ex works, ranges of over 400 km can be achieved with a single tank of CNG. Often, new purchases and retrofits are subsidized by the local gas utility company. Liquefied petroleum gas storage tank systems are systems requiring monitoring under the Industrial Safety Ordinance. Must therefore be inspected by an approved monitoring body at regular intervals (gas system inspection) before being put into operation. The provisions of the Ordinance on Industrial Safety and Health with regard to explosion protection must also be observed.
Special measures are required when working below ground level (basement u. Ä. Liquid gas is heavier than air. Can gather as a "lake. Floor openings (manhole covers, hatches, basement exits) must also be included in the safety consideration.
The transport of liquid gas is regulated by the ADR regulations.
Already since 1998 it has been established within most of the garage ordinances (GaVo) of the individual federal states that it is basically allowed to drive with LPG cars in underground garages. Restrictions apply only in Berlin, Bremen and Saarland. However, sometimes the garage owners still prohibit the entry by signs. In this case, the garage owner's house right must be respected.