|
A steam car is a light car (automobile) powered by a steam engine. Steam locomotives, or steam engines capable of propelling themselves along either road or rails, were developed around one hundred years earlier than the internal combustion engine, although their weight restricted them to agricultural and heavy haulage work on roads. The light steam car was developed simultaneously with cars powered by internal combustion engines, as both engineering and road building matured. As the steam car could use the vast experience of steam engines already developed with steam locomotives, it initially had the advantage. In 1900 the steam car was broadly superior and even held absolute land speed records. By 1920 the internal combustion engine had progressed to a degree of refinement that made the steam car obsolete. Not many steam cars have been built since the 1920s, although the technology is practical, and projects intermittently occur to create a contemporary steam car with contemporary levels of convenience, performance and efficiency. The greatest technical challenges to the steam car have focused on its boiler. This represents much of the total mass of the vehicle, making the car heavy (an internal combustion-engined car requires no boiler), and requires careful attention from the driver, although even the cars of 1900 had considerable automation to manage this. The single largest restriction is the need to supply feedwater to the boiler. This must either be carried and frequently replenished, or the car must also be fitted with a condenser, a further weight and inconvenience. The steam car does have advantages over internal combustion-powered cars, although most of these are now less important than in the early 20th century. The engine (excluding the boiler) is smaller and lighter than an internal combustion engine. It is also better suited to the speed and torque characteristics of the axle, thus avoiding the need for the heavy and complex transmission required for an internal combustion engine. The car is also quieter, even without a silencer. == Technology == A steam engine is an external combustion engine (ECE: the fuel is combusted away from the engine), as opposed to an internal combustion engine (ICE: the fuel is combusted within the engine). While gasoline-powered ICE cars have an operational thermal efficiency of 15% to 30%, early automotive steam units were capable of only about half this efficiency. A significant benefit of the ECE is that the fuel burner can be configured for very low emissions of carbon monoxide, nitrogen oxides and unburned carbon in the exhaust, thus avoiding pollution. Steam-powered and electric cars outsold gasoline-powered ones in many US states prior to the invention of the electric starter, since internal combustion cars relied on a hand crank to start the engine, which was difficult and occasionally dangerous to use, as improper cranking could cause a backfire capable of breaking the arm of the operator. Electric cars were popular to some extent, but had a short range, and could not be charged on the road if the batteries ran low. Early steam cars, once working pressure was attained, could be instantly driven off with high acceleration; but they typically take several minutes to start from cold, plus time to get the burner to operating temperature. To overcome this, development has been directed toward flash boilers, which heat a much smaller quantity of water to get the vehicle started, and, in the case of Doble cars, spark ignition diesel burners. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「steam car」の詳細全文を読む スポンサード リンク
|