Car fuel

30-01-2015, 11:39Print
The mileage gives the amount from fuel which burns an internal combustion engine within a certain time or is used while putting back a certain distance by a vehicle.

With high-way vehicles the average consumption on a distance of 100 kilometres is pulled up in Europe normally as a comparative size. With other surface vehicles as well as airplanes and vessels and with drives information is spread in litre per hour (l/h) or kilogramme per hour (kg / H). For internal combustion engines themselves the specific mileage in gramme per kilowatt hour (g / kWh) is an important characteristic.

The energy supplied in chemically engaged form (heat value of the Strength or fuel) is converted in the internal combustion engine into mechanical work. Nevertheless, the thermal efficiency reflects only the efficiency of the energy conversion without effecting quantitative statements about supplied chemical energy and done mechanical work. The energy not taken as mechanical work of the fuel gets lost mostly extensively as a thermal energy; hence, other specific base factors dependent on the use serve, for example, for the judgement of the mileage of vehicles, like put back distance, time, personal kilometre or tonne kilometre.

Consumption data with vehicles
Cover to the produced transport work
Except the drive the construction of the vehicle (weight, drag coefficient (Cw), frontal area) and the logistics plays for the consumption also a role. Means of transportation can be better compared if the consumption is covered to the transport work. Examples:

Mileage per personal kilometre (per person or seat and kilometre)
Mileage per cargo tonnes (or cubic metres) and kilometres
Besides, the extent of utilisation of the means of transportation, with airplanes also plays the air route a big role. Thus the Lufthansa group used in 2010 with 82% of extent of utilisation on an average 4.2 l per 100 person's kilometres, on flights less than 800 km these were on an average 7.5 l 100 person's kilometres. Certain modern large airplanes got by on completely occupied long-distance flights in 2003 with a fuel consumption of 2.7 l per 100 person's kilometres. Similar is valid also for other public means of transportation like the railway, though on average energy-efficient is as some other motorised means of transportation, but on branch lines because of the low extent of utilisation and in the high-speed traffic because of the air resistance of the high-speed trains has a higher energy consumption and final energy consumption per personal kilometre. Also with the motorised individual traffic which occurs in Germany quite predominantly through passenger car the extent of utilisation plays an important role. Thus were cancelled from a good 924 billion personal kilometres which were produced in 2008 in Germany, the extent of utilisation only about 30% amounted to only about 30 percent on passenger, with on an average just 1.5 people in the car. As a countermove 44 billion l of fuel were used with which 4.8 l arise 100 person's kilometres.

Comparison after means of transportation
Road: approx. 2 l per 100 person's kilometres (the German railways 52 grammes CO2 per personal kilometre; 0.20 kWh per personal kilometre)
Passenger car: approx. 3-5 l per 100 person's kilometres (per vehicle 6-10 l of petrol per 100 km; 185 grammes CO2 / km; 0.60 kWh per personal kilometre)
Airplane: approx. 3-8 l per 100 person's kilometres (Lufthansa: Flights less than 800 km 7.5 l, long-distance flights 2.7 l; from 0.60 to 2.0 kWh per personal kilometre; state: 2012)
Specific consumption
With internal combustion engines the spent fuel amount is usually given working unity, so the specific mileage in g / kWh or kg / kWh. The information in g / kWh occurs primarily for the Bestpunkt, the company point with the highest fuel efficiency. The actual specific consumption as a function of rev and power output is shown in a consumption identity field whose graphic representation reminds of a shell. Hence, the consumption identity field is also called mussel diagramme.

With rocket engines the specific fuel consumption is given as a specific impulse.

Cover to the heat value
Though with power stations the amount of the fuel spent per time or fuel is logistically interesting, nevertheless, efficiency is given by the converted energy amount per heat value of the fuel. Modern gas steam-estate car power stations can convert up to 60% of the heat value into electric energy, with coal-fired power stations and diesel generators this value lies with about 40%.

Calculation of the CO2 issue on the basis of the mileage

By the discussion about the greenhouse effect the carbon dioxide portion (CO2) is valued in the exhaust gases. A fuel ideal in this sense is hydrogen. He is moved completely to water. Pure carbon (coal) forms the other extreme, he burns completely to carbon dioxide (CO2). Current fuels exist predominantly of hydrocarbons and lie in between (hydrogen it is won primarily of hydrocarbons and then also carbon dioxide becomes free; see main article hydrogen). The carbon portion of fuels is steady and a carbon atom with two oxygen atoms forms a CO2 molecule. Other connections hardly form. Hence, the amount of the generated CO2 can be calculated by the consumption immediately, while accordingly of the Molaren measures too in each case 12 g of carbon 32 g of oxygen are added.

With the combustion develops from

1 kg of carbon 3.67 kg CO2
Hydrogen no CO2, only water
Beside water and small quantities of other combustion products develops with the combustion from

1 l of petrol about 2.32 kg CO2
1 l of liquefied petroleum gas from about 1.8 to 2.0 kg CO2
1.16 l of liquefied petroleum gas from about 2.1 to 2.3 kg CO2 (corresponds possibly to the energy in 1 l of petrol, because the energy density of petrol is higher)
With the combustion of 1 litre of diesel there develop therefore about 14% more CO2 than with the combustion of 1 litre of petrol, i.e. if an internal combustion engine has an additional consumption of about 14% compared with a diesel engine, the engines are equivalent concerning the CO2 output. Hence, petrol and diesel vehicles cannot be simply compared about the mileage measured in litres. The cause are differences in the specific weight (density of diesel about 12% higher) as well as comparatively between carbon and hydrogen atoms in the molecules of both fuels.

From the European Commission for passenger car suggested appoximate value of 130 g CO2 per km corresponds to a consumption of 5.0 l / 100 km of diesel or 5.6 l / 100 km of petrol. The EU-issue law coming into force in 2012 prescribes a naval issue of 120 g CO2 / km.

Conversion with automobiles of consumption data given in [l / 100 km] in [g / km CO2]: Arithmetic example of a petrol car with 5.6 l / 100 km of consumption:

5.6 l / 100 km * 2.32 kg CO2 / l = 12,992 kg CO2/100 km = 129.92 g CO2 / km

Besides, it concerns over 100 kilometres of gemittelte values. Distances raise uphill the issues drastically, while mountain departures cause no kilometre-related issues with engine overrun cut-off.

Conversion between l / 100 km and mpg

The blue graph shows the US liquid gallons; the red graph points Imperial gallons (UK).
In the Anglo-American dimension system the mileage is given with vehicles in miles by gallon. The abbreviation is: mpg or MPG. The unity mpg calls the put back distance in miles (1.6093 km) for which a gallon fuel is used. In some African countries, in Italy, Japan and South America as well as partially in the Netherlands the unity kilometre per litre is common.

The Anglo-American volume unity gallon is not fixed uniformly. In the USA it corresponds to 3,785 litres, in Great Britain, however, to 4,546 litres. Hence, it is distinguished between the mpg (US) and mpg (UK).

For automobiles the mileage is given in Europe usually in litre per 100 km of journey distance for the genormten driving cycle according to 70 / 220 / EEC. He shows above all a comparability of vehicles with uniform measurement; a statement about the actual consumption of a vehicle type in the day-to-day traction mode is second-rate. Hence, he is only restrictedly expressively with regard to the judgement of the economic efficiency and the height of the CO2 output of cars. The value is determined, while the vehicle an agreed driving cycle is finished and the fuel amount spent on this occasion is measured. Critics criticise that to the inquiry of the data experienced drivers would be used who achieve an as low as possible consumption within the default.

To create uniform edge terms, the inquiry of the mileage occurs since the 1st of January, 1996 in general on a role test bench.

The genormten driving cycles show average treads. They make the vehicles together comparable, however, do not agree with the tread of utilisation of every customer, in particular not with the tread of customers who go a little with foresight (frequent acceleration and braking) which put back a high portion of its journey distance in the short distance traffic and town traffic and/or drive the speeds very high on highways.

Widespread driving cycles are:

In the European Union the mileage for automobiles based on the NEFZ (New European driving cycle) by the directive 80 / in 1268 / EEC becomes an appendix I, zul. changed by 93 / 116 / the EC ascertained. Besides, a synthetic driving cycle becomes with clearly separated acceleration, used Konstantfahr and brake phases on a test state. Moreover, with vehicles with hand transmission the driven gear ratios are prescribed.
the US-American FTP75 is a cycle which shows the picture of a journey carried out in the public traffic.
In Japan it is used so-called 10-15 fashions. It is a synthetic cycle, has, however, an other course (like the NEFZ).
The consumption arising by the different cycles differs partly considerably and, hence, is not comparable directly with each other. Technical measures of the car manufacturers to the lowering of the mileage concern more efficient engines, reduction of the air resistance and the road resistance of the tyres as well as alternative drive concepts. Because newer vehicle generations are mostly wide and higher, the enlargement of the frontal area stands in the way of an improvement of the air resistance by the c_\mathrm W value. Besides above all the behaviour of utilisation can lower („power-saving driving manner“) the energy consumption strongly.

The consumption referring on the engine power is sometimes given to propagate the putative efficiency of a highly competitive engine. In addition, e.g., the mileage ascertained in the NEFZ is divided by the rated horsepower. Nevertheless, this marketing statement (see also Greenwashing) cannot be pulled up for an objective comparison, because with maximum performance consumption appears which far lies beyond the values ascertained in the driving cycles and no direct connection exists between the rated horsepower of an engine and the consumption in a genormten cycle.

Truck and strength coaches
Because truck and penalty can be shown only badly about the NEFZ applying for passenger car, the other basic conditions which are written down in German Institute for Standardization 70030 (part 2) are valid for them.

Also these vehicles to German Institute for Standardization 70010 (to which also truck and penalty belong) are in the measuring journey with production lubricants and company parametres (tyre pressure to manufacture...). The vehicle weight corresponds to the middle weight (means from at most allowed and empty weight).

Strict demands are also made to the surroundings terms. Thus dry and calm weather of a certain temperature and a certain atmospheric pressure must rule.

The test speed corresponds to 75% of the vehicle maximum speed.

To compensate uncertainties, the fuel spent about a test distance is to be banked about 10%.

Manufacturer's data to the mileage

Since the publication duty leads to the comparability and also influences the purchase decisions, the car manufacturers try to publish very good values. In addition all measures which influence the result positively are taken. In this train it is accused of the manufacturers also of using conflicting measures over and over again unrealistic or even to the norm default. In addition count, for example:

Application especially poor in road resistance, with high atmospheric pressure befüllte special tyres (mostly especially small and narrowly; the atmospheric pressure must still lie within the manufacturer's data and the tyres must be for sale in the market freely and be admitted for the vehicle type)
Use of the special lubricants which decrease the energy loss by friction (also within the oil types admitted by the manufacturers)
Switch off from energy consumers
Correction of the track (can raise the wear and/or make worse the safety)
as low as possible weight by withdrawal not of necessary accessories (spare, board tools among other things)
Measurement in entry-level version without optional equipment
the optimised mode if the vehicle control devices recognise that a test on a role test bench occurs
Uncouple to the dynamo by the control device, so that no mileage results for the loading of the battery
Reduction of the vehicle weight by special equipment
Door slits and radiator grille are stuck together to reach a better aerodynamics
Choice of a prominent vehicle from the production.

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