Wind Turbine Compressor Design

Wind Turbine Compressor Design

In wind turbines, the air entering the inlet subjected to a process that subsequently expanded through the turbine. To do this, the air compressed by the compressor, one of the two basic types of compression, or radial flow, or axial. The radial flow compressor is a single-stage or two-stage unit utilizes an impeller for accelerating the air, and a diffuser to generate the required pressure increase. Unlike the axial flow compressor is a multistage unit with rotating and fixed blades, to accelerate the propagation of air until the required pressure increase. In certain cases, especially in small engines used an axial compressor to boost the inlet pressure to a radial flow. These two types, of course, have advantages and disadvantages. More specifically, the radial flow compressor is more potent than that of the axial and easier to develop and manufacture. The axial flow compressor, but absorbs much larger volume of air than the compressor same radial frontal surface, and can be designed to achieve a much higher pressure ratio. Since the airflow is an important factor in determining the amount of thrust, this means that the engine axial compressor will also give more thrust for the same face. This, plus the ability of the pressure ratio increases by adding more steps, led to the adoption of the use of axial compressors in engine design. Certainly the radial compressor because of its simplicity and durability that far exceeds any other disadvantage is preferred for application to smaller engines. The development of high-pressure indicators favored the adoption of axial compressors and is one reason for optimal efficacy results. This in turn leads to improved fuel consumption articles for a given thrust. Compressor radial flow The radial flow compressors have a single or double-sided impeller, while rarely have a single two-stage impeller. The impeller is located within a housing containing ring with fixed diffuser vanes. Where an impeller with double inlet, the flow of air to the turbine is reversed direction, and it becomes necessary to use the combustion chamber. Very basic is the operating principles of this type of compressor. The turbine is connected to the compressor and thus the impeller rotates at high speed so that air is continuously induced in the center. centrifugal forces caused in the radial outlet flow along the edge of the blades of the impeller, the air speed and thus achieve pressure increase. There is the case in the introduction of the engine there are flaps which provide an initial swirl to the flow of air entering the compressor. The air leaving this impeller, passes through the diffuser section wherein the passages form a divergent nozzle, thereby converting the greater part of the kinetic energy into compression. Practically, the compressor is designed to display about half of the increase in pressure in the impeller and the other half in the diffusion chamber. To maximize the air flow and the pressure increase in the compressor, the impeller must rotate at high speed. For this reason, the impellers are designed to operate at a rotation speed of about 487.68 m / s. To maintain the efficiency of the compressor, it is necessary to prevent excessive air leakage between the impeller and casing. This is done by keeping as low as possible gap between impeller and casing. The construction of the compressor is a relatively simple structure as the axis of the impeller rotates in a cylindrical bearing (bearing) and is common with the axis of the turbine or linked by conjugation. This coupling is usually designed in such a way as to detach easily. The rotor consists of a forged tray combination with fixed blades radially positioned on one or both sides, forming converging passages in conjunction with the compressor housing. These blades may be extended to the rear, although for ease of manufacture used blades radial form. To facilitate axial flow of the air entering the rotating impeller, the blades are curved in the direction of rotation. These curved portions may be integral with the radial vanes or placed separately for greater accuracy and ease of manufacture. As mentioned earlier, the compressor housing are fixed guide vanes, involved in the diffusion of air into the engine. This device may be an integral part of the housing or attached assembly. In both cases comprises a number of vanes which abut on the rotor. These flaps diverge to convert kinetic energy into compression energy and their inner edges are in accordance with the direction of air flow resulting from the impeller. The gap between the impeller and the diachyntira (vanes provision in shell) is an important factor, since very small gap causes major turbulence propelled air thus creating instability in the flow and vibrations on the blades. Compressor axial flow The axial flow compressor consisting of one or more rotor assemblies that carry blades. These bearings are disposed between the protective casing and are integrated with the vanes. The compressor is a multistage unit itself that the increase in pressure from each stage is very small. A step consists of a series of rotating blades and then a series of fixed vanes. So when operating various stages in series one after the other, it becomes necessary to vary the angle of the vanes to allow the compressor to operate efficiently at lower speeds. As the pressure ratio increases the incorporation of changing static vanes ensure that the airflow is directed in the next step of the movable vanes in an acceptable way. Going from low to high pressure, i.e. from the front of the compressor backwards, there is a gradual reduction of air between the rotating shaft and the stationary housing. This is necessary to preserve as far as possible constant velocity as the density increases during compression. By transforming the rotor (rotating part) or of the housing a conical form can be achieved by the contraction of the air. It may however be possible to combine both, the device being affected by manufacturing problems and other engineering design factors. A single-stage compressor comprises a rotor assembly and stators to what steps are necessary to achieve the desired pressure ratio and flow air compressor inlet. While the multi-stage consists of two or more rotor assemblies, which moves at optimal speed to achieve thereby higher pressure ratio and to allow greater flexibility in the operation. Nevertheless, a two stage compressor can be used in propelling machine, although it is best suited for application to engines formula by-pass, wherein the low pressure compressor is designed to withstand high air flow than the high pressure compressor. In this embodiment only a small percentage of air passes from the compressor to the high-low pressure compressor, while the bulk of the passes through the by-pass directly into the high pressure compressor. These two streams are mixed in the exhaust system before finally passed the advancing nozzle. In this arrangement the jet velocity coincides with the optimal requirements of aircraft and leads to higher fuel consumption with lower promotion returns. For this reason, the jet engines are now obsolete for high speed aircraft, where all the air passes through the full compression cycle. Therefore, for a by-pass rate of the turbo-fan engines evolve more. Inlet air is subjected to a compression step, before the fan shared between the core or the shunt system at a ratio of 5: 1. This results in the optimal adaptation of passenger and / or transport aircraft flying at a speed less than the speed of sound. The fan may be coupled to the front portion of a number of key compressor stages (two-shaft turbine) turbine or three axes. Then lists the basic operating principles of the axial compressor. Air is continuously induced within the compressor as the rotor is rotated at high speeds by the turbine. Then, accelerated by the rotating blades and is directed to the following sequence of static vanes. At the entrance of air into the rotor, attached to this energy which causes an increase in pressure and velocity. Then the air is decelerated by means of the following stationary blade and the kinetic energy is converted to compressive. The stationary blades serve to correct the output deflection of the air by the rotating blades and be guided (air) in the introduction of the combustion system with high speed. During compression there are multiple variations of pressure and speed of the air flow. These changes were accompanied by a progressive increase in temperature. The ratio of the total pressure of the exhaust air and inlet air through all steps is approximately of 1: 2, i.e. quite small. This small increase in pressure due to the fact that the rate of diffusion and deflection angle of the blades is limited, if the loss of the diverted air passing through the system of mobile and stationary blades can be avoided. But the ratio of pressure of each step is small, since each step increases the pressure exiting from the previous step. Thus, the first step increases the pressure of the incoming air of about 9-12 kg / cm2, in the last step can be up to 240 kg / cm2, at thirty-stage compressor. Certainly now, the design capacity of multistage axial flow compressors, with controlled air velocity, minimizing losses, and results in high efficiency, and thus lower fuel consumption. This gives another advantage over the radial flow compressors, where such conditions are difficult to achieve. At maximum speed, the greater the pressure ratio, the more difficult to achieve an efficient operation. This is because the ratio necessary input and output at high speeds, leading to a much higher input and results in a reduction of the pressure ratio. The axial velocity of the incoming air in the early stages of compression is related to the speed of the blades which changes the impingement air onto the blades causing the flow to separate and be cleaved into the compressor. When the pressure ratio required is large, this problem can be solved by introducing static variable fins in front of the compressor. This can correct the effects of air into the rotating blades. Another solution is the incorporation of the intermediate drain step, wherein the air ratio at the inlet of the compressor is shifted to an intermediate stage and added to the flow by-pass. In this method, correct the axial velocity of the preceding stage, but that energy is lost and thus the preferred embodiment of the variable vanes. The fan of the high rate of by-pass of a turbo-fan is an example of axial compressor, which is optimized to meet the specific requirements of the cycle. The mass of air passing through the fan is typically one-sixth that required at the center (core), while the remaining five-sixths bypassed via coaxial or single nozzle and mixed with the stream at its output. To optimize the pressure of the bypass flow cycle should be increased by approximately 1.5-fold relative to the inlet pressure. This is accomplished in a fan using a very high rotational speed (457,2 m / s) and air flow such that the by-pass portion of the blades operating at supersonic inlet velocity to 1,5 Mach. The capacity of such a compressor achieves the requirements of the cycle for high flow per unit area, high performance and high pressure rate in a series of rotating blades without inlet guide vanes, for motor diameter to acceptable levels. Thereby maintaining the weight and mechanical complexity to a satisfactory framework. Fitting The axis of the rotor is supported by a cylindrical and a spherical bearing and connected to the turbine shaft in a manner which allows any small change in the alignment. The assembly of the cylindrical housing can be done using two semicircles bolted together, but also by several cylindrical shells bolted together. For its assembly is required to use one of two methods. Fins In designing a compressor, the rotational speed is such that requires a tray for supporting the centrifugal blades. A number of discs are mounted on a shaft which can be coupled and secured together by mechanical fastening, but generally the disks are assembled and welded together near their periphery, thus forming an integral drum. Typical rotor blade locking methods to drive down either axially or circumferentially. Generally the aim is to design a stable means of giving the smallest possible load to support the disk thus minimizing weight. The blades on the disc is positioned either slidably or screw. In the first case, i.e. where it is slidably mounted is constructed such that they pass through parallel rods with grooves one after the other and clamped between the rods. In the case where screw-type, positioned next to one another and because of the different construction of the blades, are bolted at their base on the hinge. While most projects have separate compressor blades construction and maintenance requirements for the smaller engines is something very difficult what the practical solidity. However, this can be overcome by producing blades integral with the disc, called "blisk". Rotor Blades The rotor blades are part of the airfoil and usually are designed to provide a pressure gradient along the air path, to thereby ensure that air maintains a reasonably uniform axial velocity. When the air flow higher peak pressure is equilibrated with the centrifugal force of the rotor. To obtain these conditions, it is necessary to '' distorted '' blades from base to tip to give the correct angle of incidence at each point. The air on its way through a compressor, creates two stagnant boundary layers of air in the inner and outer walls. To compensate for the slow air flow in the boundary layer, locally increased due to the introduction of the curved blades both at the blade tip and at the base. The ends of the blades seem to have been bent from every angle, and thus arises the term «end-bend» (end bending). Vanes The vanes are also in the arrangement of the airfoil and secured inside the compressor housing or inside retaining rings, which are secured to the shell. The fins are often assembled in sections on the front steps and can their inner ends are wound to minimize the effects of vibration by changing the flow in the larger fins. Also it is necessary to lock the blades of the stator in such a manner as not to rotate around the shell. Operating conditions