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Absolute cylinder pressure is used to calculate the dynamic compression ratio, using the following formula: = where is a polytropic value for the ratio of specific heats for the combustion gases at the temperatures present (this compensates for the temperature rise caused by compression, as well as heat lost to the cylinder)
Compressed natural gas vehicles require a greater amount of space for fuel storage than conventional petrol-powered vehicles. Since it is a compressed gas, rather than a liquid like petrol, CNG takes up more space for each GGE (petrol gallon equivalent). However, the cylinders used to store the CNG take up space in the trunk of a car or bed of ...
With a compressed natural gas (CNG) engine, the mixing of the fuel and the air is more effective since gases typically mix well in a short period of time. Still, at typical CNG compression pressures, the fuel itself is less energy dense than gasoline or diesel thus the result is a lower energy dense air-fuel mixture.
One GGE of natural gas is 126.67 cubic feet (3.587 m 3) at standard conditions. This volume of natural gas has the same energy content as one US gallon of gasoline (based on lower heating values: 900 BTU/cu ft (9.3 kWh/m 3) of natural gas and 114,000 BTU/US gal (8.8 kWh/L) for gasoline). [22]
The gas is compressed adiabatically with little temperature change (approaching a reversible isothermal system) and heat loss (approaching an isentropic system). This advantage is in addition to the low cost of constructing the gas storage system, using the underground walls to assist in containing the pressure.
The model assumptions are: the uncompressed volume of the cylinder is one litre (1 L = 1000 cm 3 = 0.001 m 3); the gas within is the air consisting of molecular nitrogen and oxygen only (thus a diatomic gas with 5 degrees of freedom, and so γ = 7 / 5 ); the compression ratio of the engine is 10:1 (that is, the 1 L volume of uncompressed ...
The 2016 Chevrolet Malibu Hybrid car features an Exhaust gas Heat Recovery (EGHR) system to accelerate coolant heat up time. This gives faster heat up of the engine coolant which in turn heats up the engine faster. Less fuel is used giving reduced emissions. This will also quicken cabin heating warm up for passenger comfort and window defrosting.
Compressed air cars are emission free. They also do not require a connection to the electric grid. A wind turbine or other renewable energy source can directly drive an air compressor or hydraulic pump. Compressed air cars do not rely on petrol stations or an electric grid. While centralized infrastructure might not be needed, it is an option.