With the development of society, cars have changed from luxury goods to transportation tools, and now the global car ownership has reached 800 million. Correspondingly, even the most optimistic estimates, global oil storage can only last for four or fifty years; natural accidents caused by environmental damage occur frequently.

This has made mankind have to face two major problems, the depletion of oil resources and the seriousness of environmental pollution. Therefore, people's eyes are focused on "green cars", energy conservation and environmental protection has become the basic requirements of modern car design. In 1991, French Formula 1 racing engineer Guy Ngre obtained a patent for a compressed air engine and in 1998 produced the world's first "zero pollution" car that was technically and cost-effective.

1 The working principle of a compressed aerodynamic vehicle uses high-pressure air as a power source, and air acts as a medium to convert the compressive energy stored in the compressed air into the kinetic energy of the vehicle through the power device while the vehicle is running. Vehicles powered by liquid air or liquid nitrogen endothermic expansion are also in this category. The principle of aerodynamic vehicles is basically the same as that of traditional vehicles. The main difference is that the power sources of the vehicles are different. The structure of the engines is reciprocating pistons and air motors. However, at present, only the reciprocating pistons can be seen at home and abroad. The overall structural form of this engine can be borrowed from a conventional reciprocating piston engine.

The working principle diagram of the compressed air power system can be seen. The high pressure compressed air stored in the gas tank is reduced to the working pressure by the pressure regulator. Through the division, the special allowance of the government of the State Laboratories is obtained. The director of the Key Laboratory of Automotive Engineering of Jiangsu Province, the first batch of Jiangsu A cross-century academic leader in colleges and universities in the province. The main research direction is comprehensive energy saving and purification technology for automobiles. Received 7 provincial-level scientific and technological progress awards. After the heat exchanger heats up, it is controlled by the gas distribution system to enter the work machine for energy conversion, and the pressure energy is converted into mechanical energy. By changing the value of the gas pressure entering the aerodynamic engine, the dynamic characteristics of the engine can be controlled.

2 Feasibility Analysis of Compressed Aerodynamic Vehicle 2.1 Energy Analysis of Compressed Aerodynamic Vehicle The driving range of compressed air powered vehicle is mainly determined by the energy stored in the high pressure gas tank. Due to the limited space of the automobile, a suitable gas storage pressure must be selected. It is assumed that the gas storage pressure of the high pressure gas tank is pl, and the pressure value at the end of the expansion is the atmospheric pressure p, which gives an expansion process from high pressure to low pressure. In the figure, curve 1 is an isothermal expansion process, and curve 2 is an adiabatic expansion process.

When the compressed air-powered engine works according to the ideal isothermal expansion process and expands to the ambient pressure, the system is closed-system thermodynamic energy is a single-valued function of temperature during the expansion process, so U=0. thermodynamic state parameters in the isothermal process; v, v - specific volume before and after expansion; Rg - gas constant.

Adiabatic expansion When the compressed air-powered engine performs work in the adiabatic expansion 1 process and expands to ambient pressure: Equation (2) shows that the functional force of the compressed aerodynamic engine is affected by the initial temperature of expansion. Compressed aerodynamic engine in summer (expansion initial temperature is 300K ambient temperature) and winter (expansion initial temperature is ambient temperature 273K) respectively, adiabatic and isothermal expansion to atmospheric pressure, the available energy can be compared, it can be seen that the air motor summer do The functional power is about 10% higher than that in winter, and the functional force of the isothermal expansion process is much higher than the adiabatic expansion. Therefore, the engine works better in areas with high ambient temperature. It can be used with an auxiliary heating system or in combination with an internal combustion engine. The heat of the exhaust gas is used to heat the working medium, the initial temperature of the expanding gas is raised, and the working cycle is as close as possible. Isothermal process to improve its performance.

As the initial pressure of expansion increases, the specific energy of the compressed air tends to increase, but the magnitude of the increase gradually decreases. Considering energy utilization, current gas tank material limitations and high-pressure air storage safety, compressed air is now typically stored at a pressure of 30 MPa.

2.2 Analysis of driving range The compressed air is isothermally expanded to the ambient pressure, and the energy of the aerodynamic engine is ignored when the energy loss such as throttling and air leakage is neglected: assuming that the mini-car driven by the aerodynamic engine runs on a horizontal road at a constant speed, The car parameters are as follows: car windward area: A=1.95m2, wind resistance coefficient: Cd=0.3, rolling friction coefficient: f=0.018, mechanical transmission efficiency: n=.9. From the car power balance equation: with the increase of the speed of the car The mileage has dropped rapidly. When the car is driving at 100 kn/h, the mileage is reduced by nearly half compared to when driving at 50 kn/h. When the car is running at a high speed, the shorter mileage will quickly consume compressed air. It can be seen that the car is suitable for running at a lower speed. When the car is running at 50 kn/h, it can drive nearly 200 kn. In today's complex urban traffic environment, the speed of the car is usually less than 50 kn / h, and 200 kn. The mileage can also meet the requirements of urban driving, so the rut is fully capable of being used as a city vehicle.

The main power consumed by the car when driving at a constant level is the rolling resistance power Pf=Gfoa/3600 and the air resistance power Pw=CDAu, 3/76410. It can be seen that the driving range of the car is closely related to the quality and drag coefficient of the car. It shows the relationship between the uniform driving range of the compressed aerodynamic vehicle with Cd = 0.3 and the total mass of the vehicle during isothermal expansion.

It can be seen that with the increase of the total mass of the car, the mileage is reduced by a large margin. When the total mass is 2000kg, the driving range of the compressed aerodynamic vehicle is only about half of that of 1000kg, so reducing the mass is to increase the mileage. An important means, which is especially important for compressed aerodynamic vehicles that have a shorter range. The air resistance coefficient also has a certain impact on the mileage, but it is very difficult to greatly reduce the air resistance coefficient, and its increase in mileage is limited.

23Environmental Protection and Energy Consumption The exhaust gas from aerodynamic vehicles is clean air close to atmospheric pressure. It is completely pollution-free, and the compressed air it consumes can be obtained by using compressed air, which is a renewable energy source. It can be obtained by a variety of cleaning methods. Nowadays, the world's power resources are very rich, while the oil reserves are reduced. It is estimated that it can only be used for several decades, and the burning of a large amount of non-renewable energy in vehicles causes an energy crisis and generates a lot of pollution. The use of aerodynamic vehicles not only matches the adjustment of the world's energy structure but also reduces environmental pollution.

24 Economics In theory, the process of isothermal compression of air consumes the least energy, and the adiabatic compression process consumes the most energy. In order to save energy, the process of compressing air should be as close as possible to the isothermal process, which can be achieved by multi-stage compression with intercooling. For multi-stage compression processes, the compressor consumes the lowest energy when the boost ratios are equal. The total power consumption of the compressor can be calculated by the power consumption calculated by single-stage compression and multiplied by the corresponding number of stages to obtain P8. The energy consumption of the compressed gas in different working states of the compressor is as follows: p2—the inlet and exhaust of the air compressor Gas pressure; Rg - gas constant, initial temperature of compressed gas; k - adiabatic coefficient; z - number of stages of multistage compression. In the above compressed air-powered vehicle, 300L compressed air with a pressure of 30MPa can make the aerodynamic vehicle travel at 190km at a speed of 50km/h. The energy consumed by using six-stage compression to make so much compressed air is 5.6446X10. 2.5 Structural arrangement and vehicle quality The principle of a compressed air-powered car is basically the same as that of a conventional car. It transmits power through a mechanical drive train. The main difference is that the compressed air motor replaces the traditional internal combustion engine, and the compressed air motor is installed in the traditional car engine. position. Compared with the conventional engine, the compressed air-powered engine has no combustion process during operation, has low requirements on engine materials, and has a simple structure, small size, and light weight. The biggest problem with compressed air-powered car layouts is the location of 300L of compressed air, which can be used to position the fuel tank, which can be used to embed multiple elongated gas tanks under the floor and chassis of the car body and chassis. Between the chassis or the chassis, due to the small size of the compressed air-powered engine, it is also possible to utilize the space vacated by the engine. This allows for a larger compartment and trunk space for passengers.

The total mass of 300L pressure 30MPa compressed air is 104.5kg, while the weight of the same class automobile fuel tank is usually 40kg40kg. Because the compressed air motor is simple in structure and less equipment than the internal combustion engine, the size is small and the quality is much reduced. Based on the quality of the gas storage tank and other factors, the total mass of the compressed air-powered vehicle is basically close to that of the same-class internal combustion engine.

2.6 Safety of high-pressure gas storage The high-pressure gas is stored in an ultra-high-pressure carbon fiber storage tank, which is a composite gas tank, which adopts a thin-walled aluminum alloy liner, and the outer wall is wound with a high-strength carbon fiber structure, and has a light weight. It is resistant to high pressure, safe and durable. When the pressure is more than 50MPa, it will not explode even when the high-pressure gas is broken. It will only cause leakage of similar tires. It is very suitable for use as a vehicle compressed air storage tank, and its shortcoming is that the current cost is still high.

3 Conclusions Compressed aerodynamic vehicles as a new type of “zero pollution” car is theoretically feasible. Its short mileage, high speed gas consumption and zero pollution make it more suitable for urban vehicles and scenic tourism. Use the car.

The increase in energy efficiency is an important indicator of the performance improvement of compressed air-powered vehicles. Therefore, the potential of compressed air should be fully utilized, so that the pressure at the end of expansion is as close as possible to atmospheric pressure. The auxiliary heating system is used or combined with the internal combustion engine to utilize the heat of the exhaust gas. Heating the working medium, increasing the initial temperature of the expanding gas, and keeping the working cycle as close as possible to the isothermal: process, thereby improving its performance.

Operating at a lower speed, reducing the total mass of the car, and reducing the air resistance coefficient Cd value play an important role in increasing the mileage of the compressed air-powered vehicle.

According to the analysis of factors such as the driving range of aerodynamic vehicles, environmental protection, energy consumption, economy, safety and structural arrangement, it shows that aerodynamic vehicles are technically feasible.

As a new type of energy-saving and environmentally-friendly car that meets the needs of the current society, compressed air-powered vehicles have the advantages that other cars do not have. Its emergence will inject new vitality into the development of automotive technology. It is believed that compressed air-powered vehicles will be in the near future. Will be applied and promoted.

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