ZERO-EMISSION NITROGEN PROPULSION SYESTEM

ABSTRACT

A car powered by liquid nitrogen may be seen cruising the streets. Cylinder injection of a heat transfer fluid followed by liquefied gas has raised efficiency to a point where fuel costs are comparable with petrol, but, more importantly, without the pollution. As well as solving a problem, which has long plagued all Rankine cycle engines, it leads to pollution-free vehicles without the associated cost and weight penalties incurred by batteries.

An automotive propulsion concept is presented which utilizes liquid nitrogen as the working fluid for an open Rankine cycle. Ambient heat exchangers are used to power an engine that is configured to maximize heat transfer during the expansion stroke. If sufficient heat input during the expansion process can be realized then this cryogenic propulsive system would provide greater automotive ranges and lower operating costs than those of electric vehicles currently, being considered for practical use.

Nitrogen gas formed in the heat exchanger expands to about 700 times the volume of its liquid form. This highly pressurized gas is then fed to the expander, where the force of the nitrogen gas is converted into mechanical power by pushing on the engine's pistons. The only exhaust is nitrogen, and since nitrogen is a major part of the atmosphere, the car gives off zero pollution.
An engine propelled by liquid nitrogen is a remarkable step in the development of environment friendly concept cars, which can surely be the next generation technology to be used for mass production.

This paper describes the fundamental concepts of cryogenic automotive propulsion. This includes the thermodynamic theory, which gives the basis of how nitrogen can be used to power engines.

The individual system components and their constructional features so as to maximize the utility of the system and design a system, which can give the desired efficiency. Case study of a vehicle developed by the University of Washington. The performance characteristics, based on the actual driving conditions and it’s significance over other ZEV’s and the advantages of using this system for powering a car. Also it gives the drawbacks, which were incurred while designing the system and few remedies to overcome them. Lastly the conclusions derived and the future scope of the system to actually have its application.
With gas prices soaring, as they have over the past two years, it might not be long before many motorists turn to vehicles powered by alternative fuels. Although air-powered vehicles are still behind their gasoline counterparts when it comes to power and performance, they cost less to operate and are arguably more environmentally friendly, which makes them attractive as the future of highway transportation. To have a close encounter with this revolutionary system, it is must to carefully read the preceding pages.

INTRODUCTION

The development of road-worthy zero emission vehicles (ZEVs) have been stimulated by the approach, various countries has taken to improve its urban air quality to meet Federal standards. In 1990 the state government of California passed legislation requiring that, starting in 1998, at least 2% of all new vehicles sold within its jurisdiction to be zero emission vehicles (ZEVs), with the minimum fraction of new vehicle sales to increase to l0% by the year 2003. Several other states have adopted the California regulations and full compliance would result in over 500,000 new ZEVs being sold every year in just the U.S.A. The environmental impact of the energy storage technology chosen to power such a large fleet of vehicles must be carefully evaluated.

Under present regulations, a ZEV is one that does not produce any tailpipe pollutants, regardless of the emissions produced in the manufacture of the vehicle or in generating the electricity to recharge its energy storage system. Some of the available technologies for storing energy that meet these qualifications are electrochemical batteries, fuel cells, and flywheels.1 Improvements in each of these energy storage systems continue to be made; however, only the electrochemical battery has reached a high enough state of development to be considered useful and practical in a large EV fleet. Among the different battery concepts being developed, the lead-acid battery still appears to offer the best compromise of performance, utility, and economy for transportation applications.

A significant fraction of the lead produced each year is used in lead-acid batteries for automobiles and a typical EV requires 20-30 conventional batteries to have a useful range. The growing public awareness of the health hazards arising from elevated concentrations of lead in the environment has resulted in a steady decrease in the amounts of lead used in industry and personal products over the years.

The potential of cryogenic energy storage for automotive propulsion has been under investigation at the University of Washington as an alternative to electrochemical batteries for zero-emission vehicles (ZEV). It is anticipated that the use of an inert cryogen, such as liquid nitrogen (LN2), as an energy storage medium would not pose any environmental burden, and in particular would avoid the issues of heavy metals pollution associated with lead-acid batteries. Another potential advantage over electro-chemical batteries is that the installation of a cryogen distribution system could be realized by straight-forward modifications to the existing petroleum retail stations. Several means of utilizing the thermal energy potential of cryogens have been examined and their performance capabilities are presented.

This paper describes the fundamental concepts of cryogenic automotive propulsion. This includes the thermodynamic theory, the individual system components. Finally, conclusions and recommendations for future research are presented.

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