The matching of the air compressor displacement and the volume of the air reservoir of the articulated city bus Fan Yiming (Jiangsu Agricultural Machinery Research Institute, Nanjing 029, Jiangsu) determined that the air compressor output rate and the air reservoir volume mismatch did not match the inflation time. The problem of slower delivery. 1 Introduction China is a country with a large population and a dense population. In order to alleviate the pressure of urban public transportation and solve the problem of public transportation difficulties, Nanjing Bus Vehicle Factory has developed the NJ666F articulated city bus. In the process of putting into operation, the characteristics of its large passenger capacity are particularly prominent, which alleviates the contradiction of fewer passengers during peak passenger hours, and the economic and social benefits are obvious. However, the driver reported that the car was inflated for a longer period of time and slower to get out of the car. To solve this problem, we conducted analysis and checking. GB7258 97 "Safety Technical Conditions for Motor Vehicle Operation" requires that the vehicle with the air brake system, the engine at medium speed, 4 min (8 min for urban articulated buses and trolley buses), the indicated air pressure should be from zero To the starting air pressure (until the starting air pressure, according to 392 kPa). The capacity of the air reservoir should be such that, after the vehicle is not fully inflated, the air pressure is not lower than the starting air pressure after 5 consecutive full braking. Since the city bus is often in a low-speed operation state and the station distance is short, the starting and braking are frequent, the number of passenger door opening is large, the amount of gas used is large, and the speed of the vehicle is required to be fast. Therefore, it is necessary to ensure the number of continuous braking and the large amount of gas used, and to ensure that the inflation time is short and the speed of the vehicle is fast. It is particularly important to select the appropriate volume of the air reservoir and the displacement of the air compressor. 2 Checking the volume of the air reservoir The NJ666F city bus uses the CA6102 engine, and the air pump output rate is 78 l/min. The dual-line brake system has 4 air reservoirs. The volume of the wet cylinder is 20 l, and the volume of the front, middle and rear axle air reservoirs is 30 l. The total volume of the air reservoir is l. (1) What is the sum of the maximum volume of the brake chamber pressure chamber? The V NJ666F articulated city bus adopts Shanghai Pujiang four types of passenger car chassis, and the front and rear axle brake chambers are all piston type. The parameters are as follows: front brake chamber: stroke L = 16 mm (measured) piston diameter D front front brake chamber volume: front and rear brake chamber: stroke L = 18 mm (measured) piston diameter D rear brake gas Chamber volume: After the brake chamber total volume is: (2) the total volume of the brake pipe? V NJ666F city bus brake pipe total length of about 30 m, brake pipe diameter (3) after a complete braking, the pressure drop of the air reservoir Δp set the air expansion process is isothermal process, then: in the formula: for the air reservoir The maximum air pressure, generally p is the standard atmospheric pressure for the volume of the air reservoir, V result: Δp generally requires a full brake, the pressure drop of the air reservoir Δp 2. When the air compressor is not working, the air pressure of the air reservoir is from 2, continuous full braking The number of times can reach 15 journals of Jiangsu Radio and Television University. Obviously, the choice of the volume of the air reservoir meets the requirements, but the volume is slightly larger. 3 Air compressor air outlet rate check The air compressor air outlet rate is determined according to the sum of the air consumption rate of all the pneumatic devices of the car. (1) The weight of the compressed air consumed by the brake W The volume of compressed air consumed per brake, the weight of the compressed air consumed per brake is: where: p is the brake line The pressure is generally taken as p = 0.6N/mm. The weight of compressed air consumed per unit time is: W is the number of brakes per unit time, and W(2) is obtained for urban bus passengers. Pump air consumption rate W door pump volume: door type: door pump cylinder diameter D door pump piston stroke L door pump air consumption rate: W door type: n is the number of door pumps, where n = 3 . Through calculation, the total outflow rate of the W(3) vehicle is W: where W is the allowable air leakage per unit time. For the convenience of calculation, set W =0 (no air leakage), then: W (4) air compressor air output rate V considers that there are some gas equipment, such as: pneumatic horn, pneumatic rain, etc., but also consider Unpredictable loss of compressed air and the possibility of air compressor stop working, the air outlet rate of the air compressor should be: take the air weight of 12.7N / m: V and the air compressor used has a displacement of 78 l /min, obviously the air compressor output rate is insufficient. 4 Improvement measures Through the above calculations, the NJ666F articulated city bus has a slightly larger volume in terms of the volume of the air reservoir, but in terms of the selection of the air compressor, the displacement of the air compressor is obviously insufficient, and the result will inevitably lead to too long inflation time. , affecting timely delivery, or low-voltage out of the car, bringing significant hidden dangers to safe driving. To solve this problem, we can start from two aspects. First, increase the air compressor outlet rate, choose a large displacement air compressor, but it should not be too large, otherwise it will consume engine power, reduce the vehicle's power, excess air volume, and also cause waste. Second, under the premise of ensuring the total number of brakes, the volume of the air reservoir is appropriately reduced. According to the specific conditions of the bus, if you replace the large displacement air compressor, it will increase the cost. If there is no air compressor with proper displacement, it will bring problems to the engine manufacturers, taking into account the power and accessories of the bus. Versatility, we can reduce the volume of the air reservoir and keep the inspection of the pipeline tightness and reduce the loss of compressed air to solve this problem while keeping the original air compressor displacement unchanged. Change the volume of the wet cylinder from the original 20 l to 15 l, and change the volume of the front, middle and rear air reservoir from the original 30 l to 20 l. After calculation and actual measurement, the relevant data meets the requirements of the standard, and there is no use. The phenomenon that the amount of compressed air is insufficient is found to have a remarkable effect. The relevant data before and after improvement are shown in Table 1 below. From 0 to the inflation time at medium speed, the pressure is reduced from 0.7 to the number of complete brakes. Before the improvement, the improvement is made. 5 Conclusion By checking the example, in terms of the volume of the air reservoir and the air outlet rate of the air pump, the number of complete braking must be guaranteed first. This is the guarantee of driving safety. For vehicles that operate at low speed for a long period of time and use a large amount of gas at the same time, it is necessary to appropriately increase the volume of the air reservoir to prevent the problem of a sharp drop in the air pressure in the air reservoir due to the large amount of gas used. The displacement of the air pump should meet the volume requirement of all gas-using components, so that the vehicle has a shorter starting inflation time, avoiding low-voltage exit and eliminating safety hazards.
Luffing tower cranes are a type of Tower Crane commonly used in construction projects. Unlike traditional tower cranes, luffing tower cranes have a jib that can be raised or lowered to adjust the height and reach of the crane. This allows them to work in tight spaces or in areas with height restrictions.
Luffing Crane,Luffing Jib Crane,Inner Climbing Tower Crane,Luffing Jib Tower Crane,Tower Crane 10t SHEN YANG BAOQUAN BUSINESS CO., LTD , https://www.sytopkittowercrane.com
Luffing tower cranes are especially useful in urban environments where space is limited. The ability to adjust the jib angle allows the crane to work around obstacles such as buildings or other structures. They are often seen on high-rise construction sites, where their versatility and compact design make them ideal for lifting and moving heavy loads.
The luffing mechanism of these cranes allows for precise control over the load, making them suitable for projects that require delicate or precise movements. They are also known for their quick and efficient operation, with the ability to lift heavy loads to great heights in a relatively short amount of time.
Overall, luffing tower cranes are a valuable asset in the construction industry, providing flexibility, efficiency, and safety in various construction projects.
Matching of air compressor displacement of articulated city bus and air reservoir volume