fan blade design calculations

| December 10, 2020

The associated flow fields of all three profiles indicate that the original flow separation at the shroud was improved in the two new profiles. After the final 3D modification, the fitness and efficiency are further improved from those obtained for the 2D blade design by GA. Typical Applications: High pressure industrial. Axial flow fan • The calculation assumes a free vortex velocity profile downstream of the fan. 6. The critical flow separation affecting performance happens at the shroud near the blade leading edge. In the real-world, it is very common to find oversized fans operating under conditions of poor performance, resulting in excessive and unnecessary consumption of electrical energy. When the volute was coupled with the impeller, the impeller efficiency for the NEW impeller dropped from the impeller-design prediction of 95.5% to 89%. The fitness plot in Figure 13 is an inverse measurement of the defined objective function shown in (7). Typical for ducted fans where outlet energy can be recovered. In other words, the NEW impeller generates less total head with the same width as the B#1 impeller; however, with increased width, the NEW impeller is able to produce the same total head as the B#1 impeller. Axial flow fan • Velocity triangles for rotor -only fan. The blade may be of simply a plate with camber angles or an aerofoil shape. For the impeller-flow calculation, all boundary conditions used for the CFD design calculations were maintained except for eliminating the periodic boundary condition and controlling the exit back pressure through the interface information exchange. B. Design and Analysis of an Axial Fan used in Kiln Shell Cooling 43. The progressive damage analysis of the composite fan blade shows that ply damage is initiated at a speed of 4870 rpm while blade fracture takes place at 7640 rpm. The measured power reduction for the new impeller is 8.8% lower than the baseline. The Axial Momentum theory [10]. Geometry of a forward curved blade centrifugal fan centrifugal fan an overview sciencedirect topics impeller design of a centrifugal fan with blade optimization design of a three dimensional centrifugal fan with controlled. Suitable for low air volume at high static pressure. (9) The dovetail can have a straight or curved (skewed) geometry design. For starting the calculations with efficiency assumed to 89% as an initial guess. 2.2. The advantage of adapting the 11 blade arrangement is to reduce ShaftPWR by 2.38% for the impeller with the 0.0476 shroud as compared with the 12-bladed impeller with the same shroud curvature. Note the condition of the inlet and outlet flow • Velocity triangles • IGVs can lead to excessive inlet losses but does give a well conditioned outlet flow. Propeller efficiencies of approx. Similarly, the measured power reductions for the three impellers at the design condition are 5.7%, 7.8%, and 14.0% lower than the required power shown in (3), respectively. Your email address will not be published. The width for the NEW impeller was chosen to be 0.1213 D. In order to evaluate the fan performance, it is necessary to include the volute with each impeller. The aerodynamic design principles for a modern wind turbine blade are detailed, including blade plan shape/quantity, aerofoil selection and optimal attack angles. greater for any given air flow. Test data for all three fans was collected from the 1/5-scale fan test rig as shown in Figure 20. The width of the impeller is almost linearly related to the impeller total head generated. Fan Power Consumption. Purchase plans for turbine blades after your design is complete. calculations has a number of approximately 200,000 nodes, which was found to be a good compromise between the results accuracy and the computation speed. With blading design in process, efficiency is calculated and checked for convergence. Higher speed than forward curved. Fig. We are pleased to be able to present the Ninth Edition of Fan Engineering, which is recognised worldwide as THE definitive handbook on fan design and fan applications, and reflects our lengthy experience with fan design.. Table 2 shows the performance data obtained from the impeller/volute coupling calculations for all fans. (ii) The shroud gap between the bellmouth and the shroud carries less than 1% of the inflow back from the volute to the impeller for the current fans. A blade leading-edge extension and sweep into the shroud turning area prevents the air from separating from the shroud surface and improves the impeller’s efficiency. Numerous researches were done to improve the operating or the controlling system as well as the efficiency of the ceiling fan motor. Several groups have reported their findings on the performance of impeller-volute systems. CFD predictions shown in Figure 21 for the FS and MS fans clearly demonstrate the Re effect, which is larger for the B#1 and B#2 impellers than the NEW impeller. The matching volute design plays an important role in determining fan efficiency, which is improved by 1.2% for the new fan over the baseline fan. The blade is divided into many small elements and various parameters are determined separately for each element. The large curvature of the shroud as it approaches the blade may be partially responsible for the flow separation seen at the shroud due to the difficulty of the boundary layer to remain attached as the flow negotiates the turn near the shroud. design, radial fans are well suited for high temperatures and medium blade tip speeds. Suitable for high air volumes at low static pressure. The deformation was performed on a 2D airfoil shape and maintained along the spanwise direction. Axial fans have less rotating mass and are more compact than centrifugal fans of compa-rable capacity. Another aspect of fan blade design is the dovetail/single tooth attachment. • Design of shrouded fan blades with a high length-to-chord aspect ratio or of large-chord fan blades with honeycomb core. A repeated stage calculation is made to calculate the above parameters along compressor stages. 3 Current fan blade design flow chart We needed a few months to design a new blade on average, because one loop of those work had few weeks. (i) Volute feedback to the impeller reduces impeller efficiency by five to six percentage points from the original range of 93–95%. (iv)Blade trailing-edge shape control (or blade steering) effectively modifies the impeller exit flow and reduces power (from 0.945 to 0.896 PWRref or a 31.3 kW reduction) while maintaining efficiency. Read more. A refined CFD assessment of the impeller/volute coupling and the gap between the stationary duct and the rotating shroud revealed a reduction in efficiency due to the volute and the gap. B. It represents the blade trailing-edge span with the shroud terminating at the blade trailing edge. Figure 4 shows the assembly of the bellmouth and impeller for one half of the fan. "ˆ ˘ ˜ ! Comparing the design requirement with the measured data, it is obvious from Figure 21 that both impellers B#1 and B#2 generate more-than-required pressure at the volute lift-side discharge. A total drop of five to six percentage points in the impeller efficiency with the volute feedback is considered. In Figure 12, the impeller total head generated and efficiency associated with each blade design during the 6 generation calculations are plotted in black diamond symbols versus the shaft power. Although the gap flow alleviates the shroud flow separation, it affects the blade trailing-edge flow, particularly at the volute tongue locations. The conclusions drawn from the comparisons are as follows. Table 1 compares the predicted power, the impeller (total) head, and the efficiency between the two impellers. They also suffer from a pronounced stall characteristic at high resistance. However, the impeller efficiency remains nearly constant while the width changes. P i = dp q (1). PROP_DESIGN can be used for all altitudes covered by the U.S. Standard Atmosphere of 1976. However, the impeller efficiency remains nearly constant while the width changes. J. J. Phelan, S. H. Russel, and W. C. Zeluff, “A study of the influence of reynolds number on the performance of centrifugal fans,” ASME Paper No. Fan Brake Horsepower: Flowrate (CFM): Static Pressure at Discharge (in. The performance data shown in Figure 9(b) suggests that the shroud labelled with 0.0476 provides the largest gain in efficiency. Fan efficiency is further reduced to the 74–78% range by including the volute losses. 3 shows the current design process. A schematic of the design optimization framework is shown in Figure 10. Furthermore the deformation was propagated to the grid points of the CFD grid associated with the newly deformed blade shape within SCULPTOR. Lower cost than airfoil and backward inclined. In our case, since we are primarily interested in performance of the lift fan system, we have catalogued the performance degradation with the addition of a hard-constrained volute. Whats people lookup in this blog: Centrifugal Fan Design; Centrifugal Fan Design Calculations Calculations were also performed to investigate the effect of using the wall-function procedure. More noise. you are good man. 1 in. The design requirements called for improving the efficiency of lift fan while meeting the set design criteria for the output fluid power delivered by the impeller. Fig. Although a drop of 2.14% in total head for the latter impeller occurred, the efficiency was maintained. Copyright © 2011 Yu-Tai Lee et al. The standard high Reynolds number formulation of the - equations forms the basis for the turbulence modelling in CRUNCH. T. J. Barth, “A 3D upwind euler solver for unstructured meshes,” Paper No. Industrial Fan Software. The highest efficiency of all of the centrifugal fans. However, the majority of the prior related investigations in the literature dealt with centrifugal impellers and single discharge volutes. Although they can sometimes be used interchange-ably with centrifugal fans, axial fans are commonly used in “clean air,” low-pressure, high-volume applications. In order to effectively manage the craft fuel consumption, a reduction in fan’s operating power is necessary. In one of my previous videos I designed and 3D printed a pc 120mm fan. Note that the current volute inlet has a sudden expansion (shown in Figure 3) from the impeller exit versus Kim’s volute which has a smooth connection between the volute and the impeller. Impeller Design of a Centrifug al Fan with Blade Optimization Y u-T ai Lee, 1 Vinee t Ahu ja, 2 Ashvin Hosangadi, 2 Michael E. Slipper, 3 Lawrence P . CFD prediction results were also made for the 11-bladed B#2 impeller, which was constructed based on the 12-bladed impeller to maintain a constant throat area, that is, at the location with the maximum blade thickness. Conversely, for a fixed impeller width, altering the blade geometry can play an important role in lowering shaft power and increasing impeller efficiency. This reduction in power agrees with the 8.7% reduction obtained from the CFD predictions. The current low-specific-speed (≈0.2) baseline lift-fan impeller (named the B#1 impeller in the present paper) shown in Figure 1 is fitted with a double-discharge volute (DDV) shown in Figure 2 to provide air for both cushion lift and thrust vectoring. Whats people lookup in this blog: Centrifugal Fan Design; Centrifugal Fan Design Calculations (v)The width of the impeller is almost linearly related to the impeller total head generated. A variety of different techniques were utilized in the redesign process: for example, the hub was modified by streamline tracing; the bellmouth/shroud was modified by altering the local curvature near the blade whereas a formal genetic algorithm- (GA-) based optimization procedure was used to redesign the blade profile. Comparing the data between Tables 2 and 3, the gap effect for the B#1 impeller inversely affects performance as compared to the other two impellers. Figure 8 shows similar flow traces for impeller B#2’s surfaces. Overview. Impeller Design of a Centrifug al Fan with Blade Optimization Y u-T ai Lee, 1 Vinee t Ahu ja, 2 Ashvin Hosangadi, 2 Michael E. Slipper, 3 Lawrence P . The shaft power was calculated using (4) while imp was obtained by integrating the torque from all the impeller blades. The new 3D blade generated high head of 1.548 ref versus 1.471 ref with a higher efficiency of 95.08% versus 93.66% at the expense of a higher shaft power of 0.968 PWRref versus 0.936 PWRref. [15] also recorded increased head and a slight efficiency increase. Although the calculated static pressures are all higher than the required lift-side discharge pressure (/ref>1), the air static pressures at the lift side for both NEW and B#2 impellers are lower than that of the B#1 impeller. CFD predictions were validated with the measurements. The speed at the blade root will be close to that of the blade tip. Nowadays, ventilation engineering cannot be effective if it does not resort to specific analytical calculation programs. The unstructured cells help to reduce the overall size of the grid thereby reducing turnaround time for the calculations. • Use of Foreign Object Damage criteria (e.g. Given the impeller diameter and the flow rate, this parameter controls the maximum achievable flow velocity. There are two other parameters related to the lift-side performance. 4.0 out of 5 stars Good Reference Handbook for Fan Engineering. Three design options (straight blades, C-type blades and forward swept blades) are examined in this paper. Later, an incidence loss was incorporated in the isentropic calculations, resulting in additional losses at off-design conditions. Unlike the other parameters mentioned above, the efficiency seems to be independent of the width change. This procedure essentially improves the blade efficiency. The ONR Program Manager was Dr. Ki-Han Kim. The design calculations are performed with presumption of flow through cascade of blade and it is the main governing factor of the design too. Fans … (iii) The test data of the lift-side pressure rise for the existing and new impellers agrees well with the CFD predictions based on the model Reynolds number. Suitable for higher static pressure, up to 14″ (3.5 KPa) . 2. (iii)The 2D blade profile optimization, based on a numerical coupling between a CFD calculation and a genetic algorithm optimization scheme, is able to achieve a composite objective with a projected shaft power and a power output. where lift, ()lift, , , and are defined as the lift flow rate, fan lift discharge static pressure, fan tip diameter, fan tip speed, and air density, respectively. 8. Practical Concepts and Calculations Jurandir Primo, PE 2012 PDH Online | PDH Center 5272 Meadow Estates Drive Fairfax, VA 22030-6658 Phone & Fax: 703-988-0088 www.PDHonline.org www.PDHcenter.com . Suitable for applications up to 10″ (2.5KPa) Static pressure. This blade shape generated a total head of 1.459 ref at 93.68% efficiency and requires a shaft power of 0.926 PWRref. From here on out, when this 3D version of the steer blade is integrated with the impeller, it is referred to as the NEW design impeller. Figure 2.1 shows static pressure vs. airflow comparison for 24" x 24" dampers. Adapted from the grid topology used for the impeller design CFD, the impeller grid ended at a fixed radius for all coupling calculations except for the NEW impeller, which ended at a slightly smaller radius. Comparisons shown in Figure 21 include the original design required pressure rise, model test data, and CFD predictions for the full-scale (FS) and model-scale (MS) fans. Lower efficiency than backward-curved fan. Do not select fan in the pressure curve to the left of peak pressure. A1 , are used to secure the blades to the hub or disk (Fig. The profiled blade theory is used for designing. References [9–12] provide additional details. It should be noted that the volute inlet width was the same as the impeller width in their study. In summary, the NEW impeller improves fan efficiency by 1.2 percentage points and reduces power by 5.8%. It is interesting to note that the B#2 impeller now requires less shaft power (0.8%) than the B#1 impeller. For the B#1 impeller, a sudden pressure rise exists near the design condition. Such algorithms are implemented in prof. Drela’s DFDC software. Air enters the fan axially and discharged perpendicular to fan axis. The dramatic reduction in the volute loss for the NEW impeller suggests that the exit flow from the new impeller matches better with the downstream volute flow than those for the existing impellers. … Also shown in Figure 16 is the performance data from the B#1 and B#2 impellers. [18], Re based on and should be between 1.0 × 106 for the backward-swept centrifugal fans and 2.0 × 106 for airfoil-bladed centrifugal fans to reach the Re independent regime. Depending on the number of blades designed for each fan, the total impeller grid was approximately 3 to 4 million cells. The blade was designed as a 2D blade to reduce the manufacturing cost. In contrast, the shroud gap flow improves both the impeller and the fan efficiencies for the B#1 impeller. Single width airfoil wheel in a cylinder, air is discharged radially, then vanes are used to deflect air parallel with the fan shaft to straighten the flow. The impeller flow field is unsteady and periodic due to the interaction between each blade and the asymmetric volute casing (Figure 2), particularly at the two tongue locations. CFD results also include predictions using off-design flow rates. The conditions at the interface serve as information exchange between the impeller and the volute and are obtained as a part of the solution. variable flow fans. Suitable for low pressure applications like domestic furnace, medium size air conditioning units up to 25 tons (87.0Kw). The blade shape was parameterized by 10 design variables of 5 control points (5 design variables on the pressure side and 5 design variables on the suction side shown in Figures 11(b) and 11(c)). Comment Report abuse. (7) Motors may be overloaded and burn out if fan is operated outside certain pressure range. The steady nonrotating volute flow is calculated from the interface to each volute exit. Y. T. Lee, L. Mulvihill, R. Coleman et al., “LCAC lift fan redesign and CFD evaluation,”, Y. T. Lee, V. Ahuja, A. Hosangadi, and M. Ebert, “Shape optimization of a multi-element foil using an evolutionary algorithm,”, S. Kim, J. high static pressure and ducted systems applications. The dovetail attachment of fan blades as shown in Fig. Obtainable from: VGB PowerTech Service GmbH Publisher of techno-scientific papers P.O. Impeller B#2 was used to investigate the grid density requirement. Hillewaert and Van den Braembussche [3] used numerical predictions of the 3D unsteady inviscid impeller flow interacting with the steady volute flow in centrifugal compressors at off-design conditions and found reasonable agreements with measurements. 1 Statement of Confidentiality The complete senior project report was submitted to the project advisor and sponsor. Similar improvement in the compressor performance by increasing the volute inlet width was reported by Kim et al. Fan performance data obtained from impeller/volute coupling CFD with the shroud gap. It should be noted that final fan selection should be made by using Hudson’s Tuf-Lite® ‚ Fan Selection Program or by contacting Hudson Products Corporation at 713-914-5700 or 1-800-634-9160. The widths for the two existing impellers shown in Figure 2 are 0.1207 D and 0.1350 D, respectively. of blade for rotor and stator, Mach number, flow and blade angles. At the design point, 57% of the fan air flows through the lift diffuser to maintain the required lift pressure. The interaction between the impeller and its associated volute can significantly alter the performance of the impeller. We utilized a mathematical function that was a combination of a target efficiency (95%) and a target power requirement as an objective function. The shroud gap flow accounts for 0.52%, 0.92%, and 0.58% of the inflow at the design condition for the three impellers. The goal was to reduce power consumption while maintaining a specified output pressure at the lift-side volute exit. Fan Speed Measured Wind Speed (m/s) Measured Wind Speed (mph) Blade RPM Tip Speed Ratio Generator RPM (6.1:1 Gearbox) Voltage Fast 4.4 9.8 750 3.9 4575 3.85 Medium 3.8 8.5 520 3.1 3172 3.1 Slow 2.9 6.5 380 3.0 2318 2.1 Fan Setting RPM Inches/min Feet/min Mile/min Mph Fast 750 450055.3 3337.9 0.632 37.93 Since flow separation occurs in each impeller while operating at high efficiency, the redesign calculations must accurately account for all aerodynamic losses in order to predict any performance difference within a few percentage points. dp = total pressure increase in the fan (Pa, N/m 2). This enables a single speed axial fan to be capable of a wide range of duties. This reduction in power agrees with the 8.7% reduction obtained from the CFD predictions. It also occurs at the blade suction side of the tip trailing edge. The MS CFD predictions agree well with the model test data for both B#1 and NEW impellers, particularly the rise and fall for the NEW impeller. Figure 16 shows the effects of the total pressure generated and the efficiency when changing the impeller width for the 11-bladed B#2 (B#2-11) impeller and the NEW impeller. The baseline volute shown in Figure 3 is connected to the impeller with a sudden expansion in the flow path area. This time-varying flow field could be approximated by a time-averaged or steady flow field with a fixed geometric relationship between the impeller and the volute. Fan Types The convergence of the solution is determined by the variation of the calculated impeller torque and the mass-averaged total and static pressure variations at the inlet and outlet planes. The optimization improves the impeller efficiency from 92.6% to 93.7%. Air leaves the impeller at a velocity less than its tip speed. 4- Radial, blades: Simple in its design… Both fans with the existing impellers and the fan system with the redesigned impeller were tested to verify improvement in performance. Mulvihill, 1 Similar exit pressures were applied for all other impeller calculations to obtain the lift flowrates shown in Tables 2 and 3. Some small modifications were made to the 2D blade through a steering process followed by the construction of a 3D blade by sweeping the 2D sections. FANS AND BLOWERS 1. In addition, this modification required a blade redesign to recover the drop in the total head. Table 3 provides the performance data at the design condition for the three impellers. The CFD underpredicts the lift pressure for the B#2 impeller which may have resulted from the deviation in geometry used for the calculations and the experiments. Volute feedback to the impeller reduces impeller efficiency by five to six percentage points from the original range of 93–95%. 4 shows the newly developed design process flow. Suitable for low pressure applications like domestic furnace, medium size air conditioning units up to 25 tons (87.0Kw). Motor can be onside air stream provides energy saving in cooling applications. Using our software, match blades to your existing generators RPM and power output. Never move a fan blade to a faster or more powerful motor. Working range is from 40% to 70% of full range flow rate. 3.) The goal of the design study is to achieve a reduction in the power coefficient shown in (3) while maintaining the lift-flow characteristics of (1) and (2). The grid + was controlled between 10 and 50 for the wall-function modelling and below 1 for the near-wall modelling. The B#2 and NEW impellers suffer about 0.5% reduction in fan efficiency due to the gap-affected impeller exit flow [17] into the volute which induces impeller blade trailing-edge flow recirculation, as shown in Figure 19. Customize the blade radius, number and TSR to find power output for your average wind speed. It also reduces fan efficiency by 0.5%. The structural evaluation of the composite fan blade indicates that the blade would buckle at a rotor speed that is 3.5 times the design speed of 2000 rpm. A method is presented for redesigning a centrifugal impeller and its inlet duct. Approval of the thesis: DESIGN OF AN AXIAL FLOW FAN FOR A VERTICAL WIND TUNNEL FOR PARATROOPERS submitted by FATİH ÇEVİK in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering Department, Middle East Technical University by, … The highest speed of the centrifugal fans. Aerofoil blades . The design modification was completed by decoupling the impeller from the volute. ∞∞∞ = ⎛⎞ =⎜⎟ ⎝⎠ 9 to 16 blades of airfoil curved away from the direction of rotation. ft.) Velocity Pressure (in. • Fan blade-off and containment analysis methods (e.g. The calculations verified that the new impeller matches better with the original volute. Notes on ducted fan design - by - R. C. Turner In general, conventional compressor stages are designed by the cascads method, while high stagger low solidity ductcd fans are designed on modified isolated aerofoil theory. up to 83%. Using the developed design strategy, the following results are identified. In structural analysis, the design or geometry tends to play a role in dissipating high stress areas in the fan blade body. The prediction results for all these later modifications are also plotted in Figures 12 and 13 as “Non-GA” points. A large diameter, low speed axial flow fan has been designed to drive the Centre for Railway Research (CRR) wind tunnel at IIT Kharagpur. CalQlata has tried to keep the operation of this calculation option as simple as possible, given that it is recommended for general purpose calculations only and not for actual purchase specifications (see Fan Calculator – Technical Helpbelow). net . This simplification is referred to as the frozen impeller approach. The resulting flow path modifications not only met the pressure requirement, but also reduced the fan power by 8.8% over the baseline. system design. The GA uses the traditional selection, crossover, and mutation operators, whose implementation details are provided in [14]. International Journal of Rotating Machinery, Distance parameter used in defining the optimization objective function shown in  (, Fan tip speed (141.77 m/s@design condition), K. A. Kaupert and T. Staubli, “The unsteady pressure field in a high specific speed centrifugal pump impeller—part I: influence of the volute,”, K. Hillewaert and R. A. Customize the blade radius, number and TSR to find power output for your average wind speed. Experiential steering was used to alter the optimized two-dimensional blade profile into a three-dimensional swept blade that further enhanced the performance of the impeller. In particular, both impellers were susceptible to flow separations near the leading edge of the blade and near the shroud region where the hub transitioned into the common backplate for the impeller system. The flow field formulation was implemented within a 3D unstructured code CRUNCH. 5/8 in. The double-discharge volute casing is a structural constraint and is maintained for its shape. Is this recommendation for India? Suitable for higher static pressure, up to 12″ (3.0 KPa). We are committed to sharing findings related to COVID-19 as quickly as possible. This allows the 14-bladed baseline B#1 impeller to be redesigned as the 11-bladed NEW impeller. In the main part of the text, the developments of the axial fan design discipline are summarized; ... the momentum theory cannot be considered an effective design method as, on the contrary, the blade element theory, which is described in the next section. $ ˙ ˘ ˆ˘ ˙!˜ the calculation: • Range of hub-to-tip ratios to be used, in this case 0.1 to 0.9 • Design flow rate • Design fan total-to-static pressure • Tip radius • Fan rotational speed • Estimate of fan annulus efficiency • Estimate of aerofoil section drag to lift ratio. ): Velocity Pressure: Flowrate (CFM): Cross Sectional Flow Area (sq. The study revealed that although the existing impellers were high performing to start with, there was some margin for improvement. Calculations are provided for estimating fan power consumption and noise. No. The calculated shaft power, total head, and efficiency are 0.870 PWRref, 1.376 ref, and 93.87% for the steer blade-1; 0.896 PWRref, 1.414 ref, and 93.8% for the steer blade. 4 shows the newly developed design process flow. Less efficiency than airfoil and backward curved fans. The grid topology used for the impeller design calculation shown in Figure 5 was maintained. The objective function was set to compare impeller B#1’s performance data of 603.3 and 558.5 kWs, which has an impeller efficiency of 92.6% as described previously. A heavy-duty air cushion vehicle usually employs centrifugal lift fans to pressurize the air cushion and power the steering thruster. The selected 2D blade shape, circled in the solid black circle in Figure 12, has a near peak fitness value plotted in Figure 13 and the highest efficiency in Figure 12 among all GA designs.

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