Abstract
It is predicted that the number of 900 million, world automobiles in-use today, will increase to 1.6 billion in 2030. Now the mitigation of the global warming by reducing CO2 emission is urgent issue, due to the global environmental concerns. And, the target imposed on automobiles to reduce CO2 emission is very severe because the number of automobiles in-use is now increasing quite rapidly. Therefore, this paper shows the prospects of reducing fuel consumption in the future based on specific predicted effects of a hypothetical mass-produced compact four-passenger gasoline-hybrid car. These predicted effects are as follows.
i) By improving internal combustion engine efficiency and adopting hybrid technology, the time average of power train system efficiency is expected to reach to 45%.
ii) By following the mass reduction cycle with respect to the body, chassis and power train, a higher vehicle mass reduction rate of over 30% can be achieved.
iii) By continuing to reduce both aerodynamic drag and rolling resistance, a driving resistance (road load) reduction rate of 20% can be achieved, even excluding the effect of mass reduction.
These effects are capable of reducing mode fuel consumption by nearly half even of a car powered by hybrid system, which is said to reduce it already by more than 30% for a conventional car. Such technologies to improve the automobile basic efficiency are regarded as core issues for automotive development for the time being.
On the other hand, larger amounts of fuel are consumed in actual driving conditions compared with mode driving. The following measures are capable of reducing actual fuel consumption.
iv) Thermal managements, such as warm up of engine and drive train and HVAC, have a major effect on actual fuel consumption.
Improving these items and also lowering electrical loads can reduce by 70% the increase in fuel consumption particularly in winter. In addition to reducing mode fuel consumption, it has become particularly important to reduce fuel consumption in actual driving conditions as a measure to help resolve global environmental concerns.
At some stage, the CO2 emissions of certain featured compact car will be reduced to approximately 50 g/km. In this event, the purpose of measures such as mass reduction, energy management and electrification will not simply be to help increase automobile efficiency. In fact, these measures will also play a role in accelerating the switch to non-petroleum-based fuels and the electrification of power trains. In this case, automobiles will be close to achieving the ultimate aim of reducing CO2 emissions to virtually zero.
Keywords: hybrid power train system efficiency, mass reduction, tire rolling resistance, thermal management, actual fuel consumption