4The effect of the reforming fan is chemically reduced to reduce the gap between the impeller inlet and the inlet. The wind turbine has been tested and tested. The test shows that the air volume and pressure of the fan are increased. The efficiency is increased from 60.7 to 72.76. Fan performance is listed in Table 1.
The air volume before and after the modification of the gap δ filled with AB glue (m wind pressure (N/m fan electric power (kW) efficiency () one year running time (h) annual electricity saving (kW?h) 5 conclusion fan impeller inlet The gap between the air inlet and the air inlet not only affects the air volume and wind pressure of the fan, but also affects the efficiency of the fan. According to the standard of the fan, the gap δ is generally taken as (0.005~0.010) D. If advanced technology can be used, the gap can be used. Up to 3 inches or less. However, when the fan is installed, the impeller and the casing are transported separately to the site, and the adjustment of the gap is always affected by human factors. In addition, after the fan is used for a period of time, the bearing and the shaft are worn together, causing a series of movements. It is difficult to avoid increasing the gap.
By using a chemical method, that is, evenly coating a layer of JZ-AB glue in the gap, the gap can be effectively reduced. We have extended this method to other high-pressure centrifugal fans, and have achieved significant economic benefits.
Practice has proved that this is a simple and easy way to reform the fan energy, which can significantly reduce the leakage loss inside the fan and improve the efficiency of the fan.
Hengyang City, Central South Institute of Technology, Department of Civil Engineering, Department of Heating and Air-Conditioning, Oil-free Air Compressor, Piston Parts Improvement, Shandong Weifang Shengjian Group, Yukang Yanghu Lin Guangyao 1 Introduction LW-10/8 type oil-free air compressor is widely used at present. The utility model relates to an oil-free compressor, which is an L-shaped two-row two-stage two-cylinder double-acting water-cooled oil-free lubricating piston structure. Since it was put into operation in the 1980s, it has been found that the wearing parts of the machine have a short life, especially the average life of the two-stage filled PTFE piston ring and the supporting ring is less than 1000h, far lower than JB/T53054-92. With the requirements of the product quality classification of reciprocating piston air compressors (qualified products 2000h first-class products 4000h superior products 6000h) and user requirements, it will cause great trouble to normal production. In order to improve its reliability, extend the life of consumable parts, and accumulate experience in the design and manufacture of filled PTFE piston rings and support rings, we have redesigned the structural dimensions of the two-stage piston rings, support rings and piston bodies. And completed the improvement in December 1995. After the improvement, the compressor has been running so far and the effect is good.
2 design calculation and structural improvement 2.1 piston ring design calculation piston ring and piston ring groove structure size shown in Figure 1.
2.1.1 Number of piston rings Z determines the number of piston rings mainly considering the gas pressure difference, and secondly considers its structure, material and usage. Generally, the value is as follows: ΔP in the formula—the maximum pressure difference between the two ends of the piston, MPa and check according to the following formula: P—the pressure acting on the piston ring, MPa V—the average speed of the piston , m / s 2.1.2 cut type of the original piston ring is a 45 ° oblique cut (Figure 2a), as the amount of wear increases, the amount of leakage is increasing, so that the amount of exhaust is reduced. Now adopt the interface form (Fig. 2b), so that they can overlap each other during operation, the gas can not directly pass through the slit and need to be bucked twice, thus greatly reducing the leakage. At the same time, the lap length is increased so that the wear amount can reach the maximum allowable value and can still be overlapped. In order to increase the strength of the joint and prevent its deformation and breakage, the axial height of the piston ring is made larger.
2.1.3 Radial thickness t The radial thickness of the piston ring should be comprehensively considered according to the material, elastic force, temperature, structure and other factors. Generally take: D - cylinder inner diameter, mm 2.1.4 axial height h piston ring axial The height has little effect on the sealing performance, but increasing the axial height is beneficial to increase the strength of the ring, reduce the cold flow of the ring, increase the elastic force of the ring, and easily overcome the friction between the end face and the groove of the piston ring, and consider To the piston ring adopts the interface form, which should take a larger value, generally take h = t.
2.1.5 Opening gap S The smaller the opening gap of the piston ring, the better the sealing performance, but too small will cause the friction ring to be worn or even damaged due to the thermal expansion of the piston ring, and the swelling phenomenon will occur in severe cases. If the gap is too large, the amount of leakage is large. Generally take: D - "piston ring outer diameter, mm a -- the coefficient of linear expansion of the piston ring material, 1 / ° C -- the temperature of the piston ring when working, ° C -- the piston when the size S is checked Ring temperature, °C2.1.6 slot width gap δ piston ring groove width gap is too large, the piston ring and piston ring groove will cause impact, deformation or damage, and increase noise if the gap is too small, the piston ring will cause It expands in the ring groove due to thermal expansion, and cannot move in the radial direction, losing the sealing effect. Generally determined by the following formula: 2.2 Design of the support ring The function of the support ring is to bear the weight of the piston component, improve the coaxiality of the linear motion of the piston, prevent the piston from directly contacting the cylinder, and reduce the cylinder wear. The dimensions of the support ring and the ring groove are shown in Figure 3.
2.2.1 Axial Height The axial height of the H-bearing ring depends on the allowable specific pressure on the piston bearing surface.
Where G—the sum of the mass of the piston and the half of the mass of the piston rod, kg b—the projection width of the bearing surface (Fig. 4), mm [k]—the allowable specific pressure of the bearing surface, k ≤0.003～2.2.2 Radial thickness B The radial thickness of the support ring depends on the amount of radial wear allowed, and is also related to its structure, temperature, rigidity, material and so on. The recommended values ​​for the radial thickness of the support ring are shown in Table 1.
2.2.3 Axial clearance y The calculation of the axial clearance of the support ring is based on the same clearance δ as the piston ring groove and is calculated by equation (5).
Cylinder diameter (mm) open type integral type 2.2.4 radial clearance ζ too small radial clearance will cause thermal expansion when the support ring is working, which will aggravate wear and increase power consumption. In severe cases, it will swell in the cylinder. If it is too large, the guiding effect will be too large. difference.
In the formula α'--the coefficient of linear expansion of the piston material, 1/°Cd--the diameter of the bottom surface of the support ring groove on the piston. When considering the value of mm, the material and the piston body, the support ring, the cylinder machining size, and the piston component should also be considered. Assembly situation, etc.
2.3 Improvement of piston components For the short life of the LW-10/8 oil-free air compressor secondary piston components, we have redesigned and calculated the piston ring support ring according to the above design calculation method, and made corresponding improvements. . The relevant parameters of the piston ring and the support ring before and after improvement are shown in Table 2. The structure of the secondary piston parts before and after the improvement is shown in Figure 5.
Before the improvement of the component parameters, the calculated value is the calculated value. The actual value of the piston ring support ring piston ring, support ring and other parts, without changing the cylinder, cylinder block, cylinder head and piston rod and other components, thus, the implementation workload is small The cycle is short and the cost is low.
3Improved effect LW-10/8 oil-free air compressor has been put into operation after the above improvement, and the life of the two-stage piston ring and the support ring has been continuously operated for more than 8000h, reaching JB/T53054-92 "General Reciprocating Piston Air Compressor Products" The quality grade specified in the “Quality Classification†greatly reduces the operating cost, prolongs the maintenance cycle, reduces the maintenance amount, and provides great convenience for normal production. Practice has proved that this is an easy and effective method.
He is mainly engaged in the design and research of compressors. He has won many ministerial and bureau-level scientific and technological progress awards. In 1997, he was awarded the title of Excellent Science and Technology Worker of the Province. Mailing address: 261011 Shandong Weifang Shengjian Group Research Institute, Health West Road, Weifang City, Shandong Province.
More power.
(2) When the automatic pumping system is operated and operated, the flow rate of the ejector must be strictly controlled. 1. If the flow rate of the ejector is too small, the automatic pumping effect will not be achieved. On the contrary, if the ejector flow rate is too large, This will cause the liquid pressure at the nozzle outlet to be lower than the saturated water vapor partial pressure in its corresponding state, resulting in cavitation, reduced pumping performance, and even no pumping at all.
(3) In the assembly, the nozzle distance Z must be strictly guaranteed. The nozzle distance between too large and too small can not play the role of pumping, so it is best to accurately determine the nozzle distance Z by experiment.
(4) When manufacturing and processing, the coaxiality of the d and D axes should be strictly guaranteed.
Huang Kunrong 401 Department of Mechanical Engineering, Central South Institute of Technology, Hengyang City, Hunan Province
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