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Application and Practice of Ternary Impeller Technology in Gas Blowers / Chen Songze, Zhao Chunjing / Coking Plant of Hebei Handan Iron & Steel Co., Ltd. Abstract: This paper mainly discusses the application and practice of the \"fully controllable vortex\" ternary impeller design and manufacturing technology in gas blowers, and explores the feasibility of energy savings, consumption reduction, and upgrading of blower systems under current technical conditions. Keywords: centrifugal blower ； Ternary impeller ； renovation ； Energy Saving Chinese Library Classification Number: TH442 Document Code: B Article Number: 1006-8155(2007)06-0062-02 The Application and Practice of 3-D Impeller Technique on Gas Blowers Abstract: This paper mainly discusses the application and practice of the 3-D impeller design and manufacturing technique based on the “all controlled vortex” concept in gas blowers, and highlights the feasibility of energy-saving measures and upgrading renovations for blower units under the current technical conditions. Keywords: centrifugal blower; 3-D impeller; renovation; energy saving 0 Introduction At present, the technology related to three-dimensional impellers is developing rapidly both domestically and internationally. The design methods for such impellers can be divided into two categories: the forward-design approach and the reverse-design approach. In the former approach, the geometric shape and dimensions of the impeller are determined first, after which an analysis of the flow field within the impeller is carried out. Based on the results of this analysis, it is determined whether the impeller design is satisfactory; the shape and dimensions of the impeller are then modified until the desired result is achieved. It is easy to see that such a design method requires designers to have extensive experience in making judgments and making modifications to designs, and it also results in a long design cycle ； In the latter approach, a desired flow field is specified first, after which the geometry and dimensions of the impeller that can produce such a flow field are determined. This method makes use of the positive theorem for three-dimensional flow; by inputting the distribution of velocity differences between the pressure and suction surfaces on two or three streamlines within the impeller, and through a series of assumptions, it is possible to determine the impeller’s geometry and dimensions based on the known flow field. However, since this approach fails to resolve the conflict between controlling the entire flow field within the impeller and ensuring smooth blade fabrication, it can only control the flow conditions along two streamlines – those at the tip and root of the blades. When the blades are wide or when the impeller’s radial curvature radius (axial dimension) is small, the flow field varies significantly across the blade height, which results in a decrease in the impeller’s efficiency or even leads to inconsistencies in the computational design. 1 The “fully controllable vortex” three-dimensional impeller design method addresses the conflict between controlling the entire flow field within the impeller and achieving smooth blade surfaces. In this design approach, the inverse formula for three-dimensional flow is utilized; by inputting the distribution of “vortices” (velocity circulation RCu) for all fluid particles within the impeller, the shape of the three-dimensional blades can be determined directly, thereby enabling control over the velocity distribution of all fluid particles inside the impeller. **It reduces the calculation time for impeller design and ensures convergence of the design calculations under conditions of wide blades or small axial dimensions. The efficient and energy-saving \"fully controllable vortex\" three-dimensional flow centrifugal blower design and manufacturing technology invented by Professor Wang Shangjin from Xi’an Jiaotong University features a rotor design in which arbitrary surface design methods are employed for the meridional surface, rotational surface, and blade profile of the impeller. This approach differs from the foreign-derived technology, whose three-dimensional impellers with \"linear elements\" can only control the flow conditions of fluid particles at the tip and root of the blades; whereas this technology enables control over the flow conditions of all fluid particles within the impeller. As a result, its efficiency is higher by more than 2% compared to conventional three-dimensional impellers, and it offers an 8%–12% improvement in efficiency over two-dimensional designed impellers, with the overall efficiency reaching 84%–86%. “The manufacturing of the \"fully controllable vortex\" three-dimensional impeller involves an integral milling process, in which the blank is machined directly on the disk using a CNC machining center to shape the blades, ensuring that their shape matches the aerodynamic design precisely. This not only enhances the efficiency of the blower but also guarantees the strength of the impeller due to the integration of the blades and the disk. “In the fully controllable vortex two-body welded ternary impeller, both the disk and the cover are made of high-strength alloy steel; they are welded together to form the impeller assembly. After welding, overall heat treatment is carried out for process hardening. This not only ensures a fine grain structure throughout the impeller but also eliminates residual stresses after welding, thereby **improving the safety and reliability of the impeller’s operation. The stator diffuser blades use numerically controlled milling to produce airfoil-shaped blades with fixed yet adjustable installation angles, providing a means for adjustment when it is necessary to change the matching characteristics between the unit and the coke oven as well as the pipeline network. 2 Application and practice of the \"fully controllable vortex\" three-dimensional impeller technology: With the expansion of China’s coking industry and the construction of more new coking ovens, for factories and mines that already have a considerable scale, the recovery capacity of the blowers in the existing gas recovery systems becomes insufficient once additional coking oven systems are added. In the past, there were two main approaches to solving such problems: one was to expand the fan room by adding new fans or replacing the existing ones; the other was to use a dual-fan operation mode in order to improve the capacity for recovering gas. The former is extremely costly, while the latter is not only difficult to operate and has high operating costs, but it also reduces the number of backup fans, posing a serious threat to the normal operation of coking production; therefore, both of these methods have their own drawbacks. It is entirely feasible to upgrade old fans using the \"fully controllable vortex\" three-dimensional impeller technology. Energy-saving compressor rotors designed and manufactured using the \"fully controllable vortex\" three-dimensional impeller technology have been widely used in the fan manufacturing industry. There are many successful cases of applying this technology to upgrade blowers, which have yielded good economic benefits; some examples are listed below. Our factory currently has two D900-0.976/1.333 type gas blowers. Due to the requirements of the production process, it is necessary to increase the capacity of these gas blowers, from the current 45,000 m3/h to 61,000 m3/h. After contacting Xi’an Jiaotong University’s Cailab in July 2005, without altering the motor, gearbox, fan casing, etc., only the rotor of the fan and its stator guide vanes were modified. The fan rotor was designed and manufactured using the “fully controllable vortex” three-dimensional impeller technology; as a result, the fan’s capacity was increased to D1250-0.976/1.333. The total pressure head remained unchanged. The motor originally used was 1000 kW, but this factor was not taken into account during the modification. After testing, the fan met the requirements specified in the design; the maximum gas flow rate was 63,000 m3/h, the total pressure head was 30 kPa, and the maximum current drawn by the motor was 97 A. The fan operated stably. The total cost of modifying the two gas fans was 980,000 yuan, which saved 2.6 million yuan in terms of the overall cost of modification, resulting in considerable economic benefits. The renovation of the D900-2.8/0.97-YDTZ40/55 type blower in the ironmaking plant of Nanchang Iron and Steel Company involved modifying only the rotor and stator vanes of the blower, without altering its casing. As a result, it was successfully transformed into a D1160-3.0/0.97 model; its operational parameters were superior to those of the original blower, and the utilization efficiency of the blast furnace increased by 0.875 t/m3•d, resulting in good economic benefits. The renovation of the D750-2-1 type gas blower at the coking plant of Nanjing Iron and Steel Company involved modifying only the rotor and stator vanes of the blower, without changing components such as the motor (630kW), the gearbox, or the blower casing. As a result, it was successfully transformed into a D1000-1.25/0.95 type gas blower. The operational parameters met the design requirements, and the performance was stable and reliable. This renovation saved 2.4 million yuan in costs, while also reducing annual operating electricity expenses by 1.135 million yuan (domestic dual-stage blowers typically require 900kW of power; here, 270kW of power is saved, with an electricity cost of 0.48 yuan/kW·h). The economic benefits are therefore very significant. At present, the gas centrifugal compressors with adjustable stator vanes developed by Xi’an Jiaotong University’s Cail using the \"fully controllable vortex\" three-dimensional impeller technology exhibit excellent performance. Their efficiency is about 12% higher than that of current compressors with two-dimensional impellers, and about 3% higher than that of conventional three-dimensional impeller compressors. Moreover, the motors used in these compressors are generally of smaller size; for example, the 4 D900 fans at Jinan Iron and Steel Company are equipped with 630kW motors, the D1470 fans at Chongqing Iron and Steel Co.’s coking plant use 1000kW motors, while the D3000 fans at Tangsteel Group are powered by 1600kW motors. 3 Conclusions (1) The design and manufacturing technology of the \"fully controllable vortex\" three-dimensional flow centrifugal blower currently offers the most significant energy-saving effects among centrifugal blowers ； (2) Utilizing the \"fully controllable vortex\" three-dimensional impeller technology to upgrade blowers is currently the most feasible approach under China’s existing technical conditions; it yields excellent unit performance and the lowest renovation costs ； (3) With the expansion of China’s coking industry and the increasing number of new coke ovens being built, it is essential to reduce energy consumption in blower systems under current conditions. The widespread adoption of the \"fully controllable vortex\" three-dimensional impeller technology is a requirement of the times, and it provides strong technical support for enterprises in their efforts to save energy and reduce consumption. References: Song Yingchen, Shu Shize, Bai Qiaozhi. Reforming gas blowers using the three-dimensional flow theory. Fuel & Chemical Engineering, 1999(1): 31-32. Yang Renjin, Xu Kechun. Practical experience in reforming the Nangang D1160-3.0/0.97 three-dimensional flow blower. Jiangxi Metallurgy, 2000(3): 27-30.