Except for subways that need to run in long tunnels, most of the existing rail cars run in the wild or even in areas without electricity. The body is longer and the roof is straighter than the general wheeled car, the track curvature and slope are small, the rolling friction resistance is small, and the Most rail cars have been developed to the stage of electric cars, so they are most suitable for the development of solar electric rail cars. From the perspective of power supply mode, the existing electric rail cars are powered by batteries, which are equivalent to wheeled pure electric cars. Most of the short-distance transportation in factory freight yards and lines belong to this category; Freight and suburban trams are mostly in this category, but the recent development of suburban trams is transitioning to a contactless network. Another is that the monorail sky train emerging in China still uses rubber wheels and concrete rails for transmission, and the steel wheels only play a guiding role on the rail side, which is not much different from the operation of wheeled cars.
1. battery powered rail car
(1) Examples of flat-panel electric rail cars and their comparison with wheeled cars. China has a variety of lightweight rail flatbed electric cars that are widely used in railways, ports, warehousing, heavy steel mills, metal products, casting, metallurgy, shipbuilding, machinery manufacturing, etc. . Features are: ① battery powered, optional maintenance or maintenance-free battery (no need to add distilled water, just charging), green, no pollution, no noise, zero emissions. ②Using the battery as the power source, the brake is sensitive and the use safety is high. ③It can be started and stopped by electronic control, forward and backward, and stepless speed regulation. ④It can be remotely controlled within 100m. ⑤Easy to install and use, suitable for long-distance straight or curved running. Small electric flatbed cars can also be made into wheeled cars. Now, three kinds of rail flatbed cars are selected for comparison, and the advantages of rail cars in terms of power can be seen. The specific power and body plane of the wheeled car increase with the increase of the car weight. Compared with the 0.8t wheeled car and the 5t rail car , the load increases by 5 times, the power increases by 1.78 times, the total weight increases by 12.3 times, and the body plane increases. 2.96 times. Compared with the 20t car, the load is increased by 24 times, the power is increased by 2.75 times, the total weight is increased by 34 times, and the body plane is increased by 3.4 times. It can be seen that rail cars have obvious advantages over wheeled cars.
(2) Parameter analysis of the electric flatbed. The technical parameters of the products of early manufacturers are shown in Figure 1. This series of electric flatbed trucks all have a standard gauge of 1435mm. Except that the rails change in steps, the other parameters increase regularly and in a certain proportion with the increase of the load. When the load is low, the motor power, table size and self-weight increase slowly, and when the load is large, all parameters change quickly.
(3) Technical parameters of new products. The parameters of the new rail car are shown in Figure 2(a) and (b). The comparison with the power parameters of the old product is shown in the attached table in Figure 2. The variation laws and values are relatively close in the large load capacity range. The difference is that the old 5t car only uses a 1.5kW/24V motor, and its battery capacity Increases with load weight but not by much. It can be seen from the picture that the technical parameters of the old product have a lighter self-weight and a smaller body plane, indicating that some designs to reduce the weight of the car are adopted, or a battery with high specific power is used.
(4) The structure and technical parameters of a typical electric flatbed truck. The technical parameters of a typical electric flatbed are shown in Figure 3. The underframe and bogie are similar to general rail trucks, but use a low-voltage DC motor as power, use a battery as a power source, and use a control system to control the operation of the car. As can be seen from the technical parameters in the figure, except for the 5t and 10t two narrow-body narrow-gauge cars, the rest are wide-body standard gauge cars. The operating speed is 20km/h or 25km/h, the load range and input power range are very wide, and the motors are 48V DC motors within 100t cars. Larger trucks are driven by high-voltage dual motors. The self-weight of the car increases with the increase of the load, and its growth rate is lower than that of the load growth rate and the motor power growth rate.
(5) Further analysis of the structure and technical parameters of the electric flatbed. It can be seen from Figure 4(a) that within the 100t load range, the parameters and changing laws of the first two flatbed trucks are relatively close. Comparing the parameters of the early car/recent car/this car, the power ratio of the 10t car is 2.2/3.2/3.2; the self-weight ratio is 3.9/2.3/3.3; the speed ratio is 25/25/25; the power ratio of the 20t car is 3/ 3/4; self-weight ratio is 5/2.8/4.3; speed ratio is 25/25/25; power ratio of 30t car is 4.5/4.5/3.5; self-weight ratio is 6.4/4.1/5.0; speed ratio is 25/25/ 25; the power ratio of the 50-ton car is 6.3/3.3/5.5; the self-weight ratio is 8.1/5.3/7.1; the speed ratio is 20/25/25; the power ratio of the 100-ton car is 10/10/7.5; the self-weight ratio is 12.5/ 15/14. The characteristics of this series of cars are that various parameters increase in a certain proportion according to the increase in load. All parameters of cars above 100t have been greatly improved except for speed.
2. Development of catenary-powered electric cars
The development of urban trams is the earliest. In 1899, the German Siemens Company constructed the earliest trams in China. In 1904, Hong Kong opened trams, and since then, Tianjin, Shanghai, Dalian and many cities in Northeast China have opened tram lines. Later, with the exception of very few cities that were still in operation, most of them were out of service or abandoned, and were basically replaced by fuel cars. Due to the increasing depletion of oil and gas resources and exhaust emissions, urban trams in various countries have rapidly emerged and developed rapidly in recent years. Railway electric trains are also powered by catenary networks. They have experienced the development of steam locomotives, diesel locomotives and electric locomotive traction. The EMU trains that are driven by centralized large power to smaller power dispersed combined traction appear later. The common feature of electric traction is that it is driven by the mains Access to a special substation to supply power to the motor of the car in the form of a catenary
Now the new type of trams have great changes in shape, structure and power, but the operation mode is that the steel wheel is in contact with the rail, which is obviously different from the car; at the same time, it is powered by the catenary and the electric flat track powered by the battery. Cars are different.
Comparison with the aforementioned dynamic parameters of wheeled electric cars and battery electric rail cars. The comparison of several types of cars is shown in Figure 5. It can be seen from the figure that: ①The ratio of 0.5t truck and 11-seat sightseeing car has the same power, the same load, and similar car surface, but the self-weight of the passenger-carrying sightseeing car 2 times, the speed is 1/5 lower. Due to the increase of the body structure and the passenger structure of the passenger car, the dead weight increases and the total weight increases, so the car speed decreases. ②The ratio of 5t electric flatbed truck to 0.5t electric truck has the same speed, 4 times higher load, and 1/2 lower power. This is because the rolling friction coefficient of rail-type cars is lower than that of wheeled cars , and the resistance of the car is small, so the drive The power requirement is small and the energy saving is significant. ③The 11-seat sightseeing car and the tram, all of which are passenger models, have the same speed, 4.5 times higher power, 4 times higher load, 5.5 times higher dead weight, and the increase in total weight is much higher than the increase in power. The energy-saving effect of the car is obvious. ④Comparing the power parameters of the battery electric rail car and the catenary electric car, which are also rail cars, the load is very similar, the self-weight is 1/2 lower, the speed is 1/5 higher, and the power demand is only 1/8, because the former is directly connected to the battery. The nearest DC power supply, and the catenary power supply, in addition to the conversion efficiency of the traction substation, the line loss of the catenary, the contact resistance loss of the contact conductive block and the resistance loss to the motor, greatly reduce the use efficiency of electric energy, and significantly increase the power demand of the driving model. Therefore, it is an important development direction to gradually replace the catenary power supply with battery power supply. There are already cases in which large-capacity lithium batteries or supercapacitor batteries are used to replace the catenary in trams. For example, the combination with on-board solar energy will achieve longer cruising mileage and better results.
3. Dynamic analysis of fast and high-speed railway trains
The main technical features of several rail transit rolling stock are shown in Figure 6. It can be seen from the table that the capacity, train quality, running speed and required power of rail transit locomotives are much greater than those of automobiles, so it is more difficult to promote the application of solar energy than automobiles. It is still difficult to use the silicon solar cells and the best lithium-ion batteries currently in common use in high-speed rail transit rolling stock, and even more difficult for high-speed trains. Unless the output power per unit area of the solar cell and the storage capacity of the battery are greatly improved, the body mass is greatly reduced, the running resistance is greatly reduced, and the running speed cannot be too high. However, the advantages of rail transit locomotives compared with automobiles are small curves, small slopes, and low ground running frictional resistance. If it is a magnetic levitation car, the ground running frictional resistance is close to zero. In addition, increasing the roof and body solar energy as auxiliary energy or hybrid cars to reduce the power supply demand of the catenary is still an important way for high-speed trains to save energy and reduce emissions.
4. Special new type rail trains
(1) Sky rail train. Air rail trains have the characteristics of less land occupation, faster construction and less investment. They have emerged rapidly in recent years. There are two types of suspension type and straddle type. The wheel-rail system is that the rubber wheels run in contact with the reinforced concrete rails, and the steel wheels only play a guiding and stabilizing role on the rail side. The combination of these two frictions increases the running resistance, so the energy consumption is large. However, the speed of sky rail trains is generally not too fast, the body is long, and it runs at high altitudes with plenty of sunshine, which is the most suitable for the development of solar power.
(2) Vacuum pipeline maglev train. The maglev train uses magnetic force to float the body from the track and is driven by a linear motor. There is no wheel-rail friction, so the energy requirement is small, but the speed of the train will not exceed that of the high-speed train due to the influence of air resistance. Under low vacuum conditions, the speed can reach more than 1000km/h. It is easy to arrange solar panels on the top of the vacuum pipe, which can not only be used for vacuuming and car dealerships, but also the surplus electricity can be sold to enterprises and residents along the line.
5. Lightweight body structure and development of solar electric cars
According to the analysis of the car operation law, the power requirement of driving the car is proportional to the total weight of the car (self-weight + load) and speed, proportional to the mass and acceleration during operation, and proportional to the windward surface area of the car body and the cube of the speed . The influence of the latter two is small at low speed, and the influence of the latter two is particularly large at high speed. If it is running on a straight lane, the weight of the car and the rolling friction coefficient between the car body and the bearing surface are mainly considered. Therefore, reducing the driving resistance and vigorously developing the lightweight of rail cars and car bodies to reduce power requirements are two important directions for land cars . To further reduce the driving resistance is to develop maglev trains, and to develop vacuum tube maglev trains at ultra-high speeds. Another important way is to develop solar electric cars, which can not only solve the increasingly depleted fossil energy crisis, but also solve the pollution of harmful gases and fine dust Pm².5 and the increasingly serious smog problem. From the previous analysis, it can be seen that there is only one step away from electric cars to solar electric cars, especially the newly developed air rail cars and vacuum tube maglev trains have unique advantages in developing solar electric cars.
6. Dynamic Analysis and Calculation of Rail Car
(1) Analysis from the basic equation. The power calculation of the rail car is the same as that of the wheeled car, and the balance equation is still used. Therefore, reducing car weight, reducing car speed on demand, streamlining the car body and avoiding frequent starts and stops are important ways to reduce the energy consumption of all cars.
(2) Energy saving from reducing rolling frictional resistance. It can be seen from the balance equation that the main resistance of the car at low speed comes from the ground friction. The rolling friction coefficients of several friction pairs are shown in Table 4.4. The rolling friction coefficient of the general rail car system is the smallest, so the power demand is the smallest, which is about 1/2 smaller than the rolling friction coefficient of high-quality road surfaces and pneumatic tires, that is, only this one can save energy by 1/2. If the car is driving on non-high-quality roads, it will consume more energy, and if using solid tires, the energy consumption will be doubled again. However, the main friction system of the current air rail car is the tire to the concrete rail beam, which is the same as the rolling friction coefficient of the car, but also increases the friction between the steel wheel and the concrete rail beam. The rolling friction coefficient of the road surface and the solid tire running on the high-quality road surface is similar. At the same time, the rail beam road surface cannot be as high-quality as the general road, and the energy consumption is higher than that of the wheeled car. Therefore, the development of the rail air-rail train and the maglev train should be new. development direction.
(3) Improve energy efficiency and energy saving analysis. It can be seen from the energy balance equation that the energy demand for car operation is inversely proportional to the efficiency. For example, the use of electric cars instead of fuel cars can greatly improve the energy utilization efficiency. At the same time, due to the simplification of the mechanical transmission system, the mechanical transmission efficiency is improved. In the past, trolleybuses and current rail cars are powered by catenary. In addition to the conversion efficiency of the traction substation, the line loss of the catenary, the contact resistance loss of the contact conductive block and the resistance loss to the motor greatly reduce the use efficiency of electric energy. The power requirements of the models have increased significantly. The battery-driven rail car is directly powered by the nearest DC, so it is an important development direction to gradually replace the catenary power supply with the battery power supply. At present, large-capacity lithium batteries or supercapacitor batteries are regularly charged at charging stations in trams to replace catenary. If combined with on-board solar energy to develop solar-powered wheeled cars and rail cars, and use their own energy to continuously charge the batteries, not only can longer cruising mileage be obtained and the battery can be used reasonably to prolong its service life, it can also achieve better energy saving and reduction row effect.
(4) The running resistance of the rail car on the flat track.
Rail car resistance: Take an electric car with a speed of 40km/h and a car weight of 1t as an example, R=598.74N. The wheeled car is 2093N. The resistance of the former is less than 1/3 of the latter, which can reduce the power demand by more than 2/3, and the power can be reduced from 3.7kW to 1.23kW.
(5) Other resistances when the rail car is running. ①Ramp resistance: The number of car resistance N/t is represented by the percentage per thousand of the ramp. ②Starting resistance: 6~8Nt for sliding bearings and 3~5N/t for rolling bearings. ③Acceleration resistance: 31aW for electric locomotives, electric locomotives and EMUs (a is acceleration); 30aW for diesel locomotives, passenger trucks and general trains. ④The curve resistance is Rc=600W/r (r is the radius of the curve and W is the weight of the car).
(6) Characteristics of DC electric rail cars and traction-speed characteristics of various power cars. Figure 9(a) is an example of the characteristics of a DC series motor electric rail car, the abscissa is the current of the traction motor, the ordinate is the relationship between efficiency, speed and traction after considering the transmission efficiency, the solid thick line is the normal working curve, The intersection is the rated speed and traction value, which is also the most efficient, at about 70% of peak. Figure 9(b) shows the traction-speed characteristics of various power cars. It can be seen from the figure that the traction force changes greatly at high speed and low speed, which can be used as a reference for selecting motor types. The starting traction of electric cars B, C, and D is large, which is conducive to ramp start and heavy-duty traction, but the traction decreases rapidly at high speed, which is not conducive to speed improvement. This characteristic is most obvious in DC series motor B. In the DC series motor D, weak magnetic field control is often used to improve its traction force at high speed; AC commutator motor C is used for high traction force at high speed; speed and control. The relationship between traction force and speed can be calculated as:
F=3.6nEIηη’/ν,N
where v——speed (km/h);
E——motor terminal voltage, V;
I——motor current, A;
n——the number of motors;
η——DC motor efficiency, AC motor multiplied by power factor;
η’——transmission efficiency.
Required motor power (power) = total driving resistance x speed.
