Kinetic Energy Recovery from the Chimney Flue Gases Using Ducted Turbine System

An innovative idea of extracting kinetic energy from man-made wind resources using ducted turbine system for on-site power generation is introduced in this paper. A horizontal axis ducted turbine is attached to the top of the chimney to harness the kinetic energy of flue gases for producing electricity. The turbine system is positioned beyond the chimney outlet, to avoid any negative impact on the chimney performance. The convergentdivergent duct causes increase in the flue gas velocity and hence enhances the performance of the turbine. It also acts as a safety cover to the energy recovery system. The results from the CFD based simulation analysis indicate that sig- nificant power 34 kW can be harnessed from the chimney exhaust. The effect of airfoils NACA4412 and NACA4416 and the diffuser angle on the power extraction by the energy recovery system using a 6-bladed ducted turbine has been studied with the CFD simulation. It is observed that the average flue gas velocity in the duct section at the throat is approximately twice that of the inlet velocity, whereas maximum velocity achieved is 2.6 times the inlet velocity. The simulated results show that about power may be extracted from the chimney flue gases of 660 MW power plant. The system can be retrofitted to existing chimneys of thermal power plants, refineries and other industries.

Numerical investigation of the power generation of a ducted composite material marine current turbine

In the hostile and highly corrosive marine environment,advanced composite materials can be used in marine current turbines due to their high strength-to-weight ratios and excellent resistance to corrosion.A composite material marine current turbine(CMMCT),which has significant advantages over traditional designs,has been developed and investigated numerically.A substantial improvement in turbine performance is achieved by placement of a duct to concentrate the energy.Computational fluid dynamics(CFD) results show that the extracted power of a ducted CMMCT can be three to four times the power extracted by a bare turbine of the same turbine area.The results provide an insight into the hydrodynamic design and operation of a CMMCT used to shorten the design period and improve technical performance.

Design performance evaluation and vortex structure investigation of different S-shaped intermediate turbine ducts

The demand of further increasing bypass ratio of aeroengine will lead to low pressure turbines with higher diameter. Therefore, it is necessary to design a duct to guide the hot gas flow which is expelled from the upstream high pressure (HP) turbine stage to the downstream low pressure (LP) turbine stage. Named by its position, this kind of duct is always called intermediate turbine ducts (ITDs). Due to the pursuit of higher thrust ratio of the aeroengine, this kind of ITDs has to beas short as possible which leads to aggressive (high diffusion) S-shaped ITDs' geometry. In this paper, two different schemes of high diffusion separation-free S-shaped ITDs were studied with the aid of three-dimensional CFD programs. Although these two ITDs have the same area ratios (AR), because of the different duct length, they have totally different area as well as area change rates. With the detailed calculation results, comparisons were made to investigate the underneath physical mechanisms. Additionally, a direct estimation of the ITDs' loss is given at the end of this paper and some ITDs' novel design idea is proposed to initiate some further discussions.

Influence of Reynolds Number on the Unsteady Aerodynamics of Integrated Aggressive Intermediate Turbine Duct

The ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine due to advantages of high efficiency and low Specific Fuel Consumption(SFC). One of the characteristics of ultra-high bypass ratio turbofan is the intermediate turbine duct which guides the flow leaving high pressure turbine(HPT) to low pressure turbine(LPT) at a larger diameter, and this kind of design will lead to aggressive intermediate turbine duct(AITD) design concept. Thus, it is important to design the AITD without any severe loss. From the unsteady flow's point of view, in actual operating conditions, the incoming wake generated by HPT is unsteady which will take influence on boundary layer's transition within the ITD and LPT. In this paper, the three-dimensional unsteady aerodynamics of an AITD taken from a real engine is studied. The results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX(RANS simulation with transitional model), are critically evaluated against experimental data. After validation of the numerical model, the physical mechanisms inside the flow channel are analyzed, with an aim to quantify the sensitivities of different Reynolds number effect on both the ITD and LPT nozzle. Some general physical mechanisms can be recognized in the unsteady environment. It is recognized that wake characteristics plays a crucial role on the loss within both the ITD and LPT nozzle section, determining both time-averaged and time-resolved characteristics of the flow field. Meanwhile, particular attention needs to be paid to the unsteady effect on the boundary layer of LPT nozzle's suction side surface.

Effects of Nozzle-Strut Integrated Design Concepton on the Subsonic Turbine Stage Flowfield

In order to shorten aero-engine axial length,substituting the traditional long chord thick strut design accompanied with the traditional low pressure(LP) stage nozzle,LP turbine is integrated with intermediate turbine duct(ITD).In the current paper,five vanes of the first stage LP turbine nozzle is replaced with loaded struts for supporting the engine shaft,and providing oil pipes circumferentially which fulfilled the areo-engine structure requirement.However,their bulky geometric size represents a more effective obstacle to flow from high pressure(HP) turbine rotor.These five struts give obvious influence for not only the LP turbine nozzle but also the flowfield within the ITD,and hence cause higher loss.Numerical investigation has been undertaken to observe the influence of the Nozzle-Strut integrated design concept on the flowfield within the ITD and the nearby nozzle blades.According to the computational results,three main conclusions are finally obtained.Firstly,a noticeable low speed area is formed near the strut's leading edge,which is no doubt caused by the potential flow effects.Secondly,more severe radial migration of boundary layer flow adjacent to the strut's pressure side have been found near the nozzle's trailing edge.Such boundary layer migration is obvious,especially close to the shroud domain.Meanwhile,radial pressure gradient aggravates this phenomenon.Thirdly,velocity distribution along the strut's pressure side on nozzle's suction surface differs,which means loading variation of the nozzle.And it will no doubt cause nonuniform flowfield faced by the downstream rotor blade.

Effects of Rising Angle on Upstream Blades and Intermediate Turbine Duct

With the improvement of requirement,design and manufacture technology,aero-engines for the future are characterized by further reduction in fuel consumption,cost,but increment in propulsion efficiency,which leads to ultra-high bypass ratio.The intermediate turbine duct(ITD),which connects the high pressure turbine(HPT) with the low pressure turbine(LPT),has a critical impact on the overall performances of such future engines.Therefore,it becomes more and more urgent to master the design technique of aggressive,even super-aggressive ITDs.Over the last years,a lot of research works about the flow mechanism in the diffuser ducts were carried out.Many achievements were reported,but further investigation should be performed.With the aid of numerical method,this paper focuses on the change of performance and flow field of ITD,as well as nearby turbines,brought by rising angle(RA).Eight ITDs with the same area ratio and length,but different RAs ranges from 8 degrees to 45 degrees,are compared.According to the investigation,flow field,especially outlet Ma of swirl blade is influenced by RA under potential effect,which is advisable for designers to modify HPT rotor blades after changing ITD.In addition to that,low velocity area moves towards upstream until the first bend as RA increases,while pressure loss distribution at S2 stream surface shows that hub boundary layer is more sensitive to RA,and casing layer keeps almost constant.On the other hand,the overall total pressure loss could keep nearly equivalent among different RA cases,which implies the importance of optimization.

Numerical Investigation of the Effects of ITD Length on Low Pressure Nozzle

The advantage of high efficiency, low SFC(Specific Fuel Consumption), ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine. The intermediate turbine duct(ITD), which connects high pressure turbine(HPT) with low pressure turbine(LPT), has a critical impact on the overall performance of turbine by guiding flow coming from HPT to LPT without too much loss. Therefore, it becomes more and more urgent to master the technique of designing aggressive, even super-aggressive ITD. Much more concerns have been concentrated on the duct. However, in order to further improve turbine, LPT nozzle is arranged into ITD to shorten low pressure axle. With such design concept, it is obvious that LPT nozzle flow field is easily influenced by upstream duct structure, but receives much less interests on the contrary. In this paper, numerical method is used to investigate the effects of length of ITD with upstream swirl blades on LPT nozzle. Nine models with the same swirl and nozzle blades, while the length of ITD is the only parameter to be changed, will be discussed. Finally, several conclusions and advices for designers are summarized. After changing axial length of ducts, inlet and outlet flow field of nozzle differs, correspondingly. On the other hand, the shearing stress on nozzle blade(suction and pressure) surface presents individual feature under various inlet flow. In addition to that, "Clocking-like effect" is described in this paper, which will contribute much to the pressure loss and should be paid enough attention.