1 Compressed aerodynamic car 1.1 The principle of compressed air powered cars Air-Powered Vehicles (APV) are often called pneumatic cars. It uses high-pressure compressed air as the power source, and air as the medium. When the car is running, the pressure energy stored in the compressed air is converted into other forms of mechanical energy (automobile kinetic energy).
Other gas-powered vehicles powered by endothermic expansion such as liquid air and liquid nitrogen should also belong to the category of pneumatic vehicles. The principle of pneumatic vehicles is different from that of traditional vehicles. The biggest difference between the source of the vehicle and the overall structure of the engine can be borrowed. The existing structural mode of the traditional automobile is mainly in the form of a reciprocating piston type or a rotary piston type. The appearance and structure of the hybrid electric vehicle engine of the compressed air power and internal combustion engine power produced by the French MDI company.
The burning chamber and its corresponding device are removed, that is, an engine that is purely compressed air.
Air Syringe X Expansion 迤 Active 迤 Intake Compression Piston The structure of the compressed aerodynamic engine can also be of various configurations such as reciprocating piston type, rotary piston type and air motor type. Currently, only the reciprocating piston type structure has been reported.
The power distribution modes of compressed air-powered engines are series, parallel, and series and parallel hybrids. Taking the reciprocating piston structure as an example, the power distribution shown is a series mode, and the aerodynamic force between the cylinder and the cylinder is serially connected, and the residual pressure of the previous cylinder is the initial power of the next cylinder. The lower-level working cylinder of this mode has a larger structural size, but the power utilization is higher and the heat exchange is more sufficient. The parallel way of power distribution is that the aerodynamic force between the cylinder and the cylinder is the same as the initial power of the different cylinders connected in parallel. The parallel-sized cylinders have the same structural dimensions and a stable output, but the residual pressure is slightly higher.
The components are an intake compression cylinder, an expansion cylinder and a spherical constant volume combustion chamber. It switches fuel combustion power and compressed air power through an electronic control unit. If the ball type is made to stabilize the sn storage pressure, the mechanical efficiency is improved, the exhaust loss and the pressure loss are reduced, and energy recovery and energy utilization are fully utilized.
Urban taxis based on compressed air-powered engines are being promoted in Johannesburg, Mexico City, South Africa.
After the decompression of the high-pressure compressed air of the automobile technology and the medium storage cylinder, the heat is absorbed by the heat exchanger into the action cylinder to push the load. Reasonable design of the pressure switching of the series and parallel channels, as well as the phase relationship of the angles of the cylinders on the crankshaft; the smooth power output of the engine can be obtained. The dynamic characteristics of the engine can be varied by adjusting the gas pressure and flow into the cylinder.
1.2 Energy Analysis The performance requirements for compressed air-powered vehicles are the same as those of conventional vehicles. The key issue in the future of compressed air-powered vehicles is the overall vehicle efficiency problem. To this end, energy analysis is required for compressed air powered vehicles.
The compressed air-powered vehicle adopts flow or pressure regulation directly, and the mechanical loss of the drive train will be greatly reduced. Although there is no pumping loss of the conventional automobile engine, the pressure loss in the residual gas of the compressed air-powered automobile engine (residual gas) Loss) will have a major impact on the efficiency of the entire compressed air powered vehicle. The use of pressure grading control and series power distribution will reduce the energy in the residual gas and the recovery of the vehicle braking energy will solve the problem of the overall efficiency of the compressed air power vehicle.
It can generally be assumed that during the power control of a compressed air-powered vehicle, the heat is absorbed sufficiently when the gas is decompressed, and the process is considered to be an isothermal process. This allows calculation of the energy released during the entire process.
Assume that the pressure of the high pressure gas is 30 MPa and the volume of the gas storage is 300 L. When the compressed air is fully isothermally expanded from 30 MPa to 0.1 MPa, all the expansion work can be done: (1), formula (2) and corresponding parameters can be calculated. The total expansion work between the initial and final states is: assuming that the mass of the gas storage tank is 100 kg, the mass ratio energy of the corresponding compressed air at normal temperature can be about 75 Wh/kg. To obtain a larger mileage, It is assumed that the tank capacity and storage are assumed to drive a certain car with a compressed air-powered engine, and the air resistance coefficient is 0.25, the windward area is 1.7:2, the vehicle equipment quality is 700kg, the load mass is 250kg, and the rolling friction coefficient is 0.015. According to the average speed of 60km / h, the required traction force is about 216N. The ratio of the effective expansion work done by the compressed air to the total expansion work of the compressed air storage is the efficiency of the compressed air. And assume that all compressed air isothermal expansion work, the mechanical transmission efficiency of the car is 0.85, when the car needs to travel 150km, the above calculation can be used to achieve compressed air use efficiency of 68 to improve compressed air use efficiency, increase tank capacity and increase inflation Pressure is the primary means of increasing the mileage of a car's air intake. Of course, increasing the tank capacity is limited by the effective space of the car. Increasing the inflation pressure is limited by the tank process, and there is an optimal matching parameter between the tank capacity, the inflation pressure and the mileage of the vehicle. The variables with the highest efficiency of compressed air need to be studied in depth. With the optimization of engine structure, energy recovery, and loss reduction control, the use efficiency of compressed air will continue to increase.
The mass of compressed aerodynamics is higher than that of a larger part of the fuel cell, and is at a medium level. However, as long as the performance of the gas tank material allows, this indicator will be greatly improved.
1.3 Characteristics of Compressed Aerodynamic Vehicles Compressed aerodynamic vehicles are fuel-free and emit non-polluting, non-thermal radiation air is a true "green" concept car. Its energy transmission is fast, storage is easy, the medium source is convenient and clean, and the required power is easy to obtain; the cost of inflatable equipment and social infrastructure is not easy to build.
Compared with the traditional automobile, the engine has no fuel burning process when working, so the engine has low material requirements, simple structure, small size, light weight, low cost, and is easy to design and manufacture. The vehicle is low in maintenance and production costs, and can be developed and developed using existing pneumatic technology, automotive design and manufacturing technology.
City centers, key tourist areas, nature reserves, which require particularly strict environmental pollution, and small and medium-sized tools, transportation vehicles, military submarines, etc., which have high noise requirements or indoor use, have great market potential and wide range. Application prospects.
2 Domestic and foreign research work summarized the patent of aerodynamic engine, and joined MDI company. In 1998, the first compressed air-powered vehicle prototype was launched. MDI's current research work abroad is mainly focused on the research team led by French engineer Gury N-gre, who has obtained more than 20 related patents. A compressed air powered taxi called "TOP" designed for them.
According to reports, this type of car can drive more than 150km with a compressed air of 300 430MPa pressure. The maximum speed is up to American RogerLee and a similar patent; the International Automobile Research Center of the Netherlands and some European countries such as Austria are also active. Conduct relevant research.
In 1997, the University of Washington developed a liquid nitrogen-powered pneumatic prototype car. The basic working principle is the same as that of a compressed air-powered car, except that the power is derived from the expansion of the gas after the liquid nitrogen is heated and evaporated. Liquid nitrogen does not need to be stored in a high pressure tank, and the safety is good. However, the preparation and storage of liquid nitrogen requires a very low temperature, and the cost of nitrogen production is not low. During the use, there is a problem that the amount of nitrogen gas is large and the amount of heat exchange of liquid nitrogen vaporization is also large.
Recently, some people have proposed the idea of ​​a liquid aerodynamic vehicle, but it also has the problem of a liquid nitrogen gas powered vehicle.
At present, there is no research report on compressed air powered vehicles in China.
The pneumatic vehicle research group of Zhejiang University has carried out experimental research on single-cylinder and two-cylinder compressed air-powered engines with cam gas distribution and valve gas distribution on the pneumatic motorcycle power platform. The principle experiment of compressed air-powered engine has been carried out. A certain result.
3Comparative analysis of automobile characteristics In order to further illustrate the characteristics of pneumatic vehicles powered by compressed air, the popular fuel cell electric vehicles are generally considered as a comprehensive comparison object. Table 1 lists the comparison of the commonly used characteristics of these two types of vehicles.
Compressed aerodynamic vehicles are highly practical and competitive in terms of manufacturing, use, safety, etc., especially with good environmental characteristics and low manufacturing costs. The “energy density†and “energy conversion rate†items in the table indicate that the shortage of compressed air-powered vehicles is also the two most important indicators limiting the wide application of compressed aerodynamic vehicles. However, the "energy density" can be improved by the performance of the gas storage tank, which can be improved by rationally designing the pneumatic circuit and performing energy recovery.
Table 1 Comparison of characteristics of compressed air-powered vehicles and hydrogen fuel cells Electric vehicles Ammonia fuel cells Electric vehicles Compressed aerodynamics Vehicle energy conversion methods Chemical energy! Power! Mechanical energy! Compressed energy! Mechanical energy emissions, pressure control, gas conversion rate, higher engine operating temperature, local temperature, ambient temperature, energy consumption, ammonia production, ammonia storage, high-pressure air control, simple, simple manufacturing cost, low maintenance cost, low cost of use High cost of ammonia and ammonia storage, convenient inflation, low cost, small heat radiation, no starting characteristics, good longevity, long life, longer inflation time, higher energy density, greater energy storage, better energy storage, better 4, compressed air Power cars are viable with outstanding environmental characteristics in line with the spirit of the car "green design".
There are still many tasks to be done in the practical application of compressed air-powered vehicles, mainly in the following aspects: the efficiency of compressed air-powered vehicles and the control of pneumatic systems.
Principle study and structural optimization design of compressed air powered automobile engine.
C. Research on the form of engine aerodynamic power distribution.
Compressed air volumetric pressure reduction control technology.
Research on pneumatic vehicle energy recovery system.
Exploration of other pneumatic vehicle engine structural forms.
Design and selection of high pressure compressed air storage devices.
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