Showing papers on "Ram air turbine published in 2021"

Second Order Sliding Mode Control of Oscillating Water Column Wave Energy Converters for Power Improvement

Abstract: Ocean wave energy is a renewable energy which remains too costly for large-scale electricity generation. The oscillating water column (OWC) wave energy converter (WEC) is a promising device-type with a rectifying air turbine and generator which convert alternating airflow induced by the water motion into kinetic energy then into electric energy. Applying control at each stage of energy conversion could increase the electric energy output of the device. As researchers overcome the modeling challenges of OWC, such as the nonlinearities due to air compressibility and power take-off (PTO) dynamics, we can integrate specific control algorithms to test their ability to improve the efficiency of the OWC. Herein, we present a state-space model of an array of OWC WECs restricted to heave motion with nonlinear PTO dynamics. We apply second-order sliding mode control (SMC) which commands a smooth torque signal to a direct-drive generator to maintain a reference turbine angular velocity. Because the algorithm can yield high turbine torques, we investigate a simple feed-forward relation for the control of a valve to limit the turbine airflow and discard mechanical power. We find that implementing the SMC algorithm and valve control can improve electric energy conversion most effectively in less energetic sea states.

Experimental investigation on performance improvement by mid-plane guide-vanes in a biplane-rotor Wells turbine for wave energy conversion

Abstract: The Wells turbine is the most frequently used or proposed self-rectifying air turbine for oscillating-water-column wave-energy converter application, largely because of its conceptual and mechanical simplicity. Biplane Wells turbines allow a higher total blade solidity to be attained than monoplane turbines do, but this results in larger aerodynamic losses associated with the swirl kinetic energy loss at turbine exit. This may be overcome by the presence of a row of guide vanes between the two rotor planes, a solution that had been proposed and investigated theoretically or by numerical modelling. Results of turbine overall performance and flow details are reported from laboratory tests of a biplane Wells turbine without guide vanes and with specially designed guide vanes. The presence of the guide vanes was found to increase the peak efficiency by seven percentual points, while reducing (for fixed rotational speed) the damping provided by the turbine. Measured losses in the guide vane row were much smaller than in the rotors. Experimental results are compared with previously published numerical results. A stochastic theoretical transform was applied to obtain averaged results for the turbine performance subject to the irregular bidirectional air flow induced by real sea waves.

Combined Casing Groove and Blade Tip Treatment for Wave Energy Harvesting Turbine

Abstract: The Wells turbine is a self-rectifying air turbine, used in oscillating water column (OWC) to harvest wave energy. It produces unidirectional torque as the flow oscillates inside the OWC chamber. It has inherent disadvantage of narrow operating range due to stall at high airflow rate. Whereas, a wider operating range is essential to improve the turbine power output. A casing groove modifies the tip leakage flow pattern and improves the operating range. In addition, a radiused tip can alter the tip leakage flow and delay the stall. To enhance the performance further, this paper investigates the combined effect of tip groove and radiused tip (CG&RT) design modification. The flow was simulated by solving steady, incompressible Reynolds averaged Navier–Stokes equations in Ansys CFX 15.0. As expected, the CG&RT blade enhanced the relative operating range and the turbine power output by 44.4% and 23.8%, respectively.

Experimental Investigation of a Bidirectional Impulse Turbine for Oscillating Flows at Various Resistive Loads

Abstract: A bidirectional impulse turbine is a self-rectifying air turbine used in an oscillating water column wave energy converters. Most of the study on bidirectional impulse turbines involves steady-state performance analysis; however, the performance under oscillating airflow conditions is necessary to understand its behavior. The objective of this study is to experimentally analyze an optimized and numerically investigated bidirectional impulse turbine with fixed guide vane subjected to oscillating airflow conditions. A bidirectional airflow test facility developed at Indian Institute of Technology Madras, Chennai, India is employed to determine the aerodynamic characterization of the turbine and the dynamics involved in each of the coupling stages. The test rig consists of a piston chamber assembly, which provides different airflow rates by varying the stroke length (SL) and cycle time. Emphasis is made on the pressure and flow rate coefficients of the turbine, turbine-generator coupling, and power developed for different input conditions. The operating range of the turbine is mapped for four different frequencies and three SLs. Different electrical loading and the power output were analyzed for accelerations and decelerations of inflow and outflow. The preliminary dynamic characterization of the turbine with respect to nondimentionalized pressure coefficient and flow coefficient was determined for inflow and outflow. The power output is found to be in strong correlation with the flow rate and angular rotation of the rotor. The turbine analyzed in the experimental test rig will be proceeded with real sea testing on the Indian coast by the National Institute of Ocean Technology, Chennai, India.

CFD Simulation Study on the Performance of a Modified Ram Air Turbine (RAT) for Power Generation in Aircrafts

Abstract: The present paper aims to study the possibility of dispensing an auxiliary power unit (APU) in an aircraft powered by fossil fuels to reduce air pollution. It particularly seeks to evaluate the amount of power generated by the ram air turbine (RAT) using the novel counter-rotating technique while characterizing its optimum axial distance. The ram air turbine (RAT), which is already equipped in aircrafts, was enhanced to generate the amount of energy produced by the APU. The approach was implemented by a CRRAT system. Six airfoil profiles were tested based on 2D models and the best airfoil was chosen for implantation on the RAT and CRRAT systems. The performance of the conventional single-rotor RAT and CRRAT were analyzed using FLUENT software based on 3D models. The adopted numerical scheme was the Navier–Stokes equation with k–ω SST turbulence modeling. The dynamic mesh and user-defined function (UDF) were used to revolve the rotor turbine via wind. The results indicated that the FX63-137 airfoil profile showed a higher performance in terms of the lift-to-drag ratio compared to the other airfoils. The optimum axial distance between the two rotors was 0.087 m of the rotor diameter and the efficiency of the new CRRAT increased to almost 45% compared to the single-rotor RAT.

Observation of flow structure past a full-stage axial air turbine at the nominal and off-design states

Abstract: The air flow inside single-stage test turbine is studied experimentally by Particle Image Velocimetry (PIV). Here we report the measurements results at axial-tangential plane just behind the rotor wheel at middle blade radius. We studied one nominal state and two off-design states. We discuss the applicability of resolution of our PIV system to this flow – we can distinguish the largest vortical structures in the shear layers between blade wake and jet, but the bottom part of the cascade is invisible for us at this moment. Spatial distributions of statistical moments of vorticity show a non-classical behavior at the cross-points of stator and rotor jets. We use our previously published algorithm for calculating spatial energy spectrum and display the turbulent kinetic energy colored by different length-scales of the fluctuations.

3D printed radial impulse cantilever micro-turboexpander for preliminary air testing

Abstract: This work introduces a modular experimental micro turboexpander system designed to perform air turbine tests of a radial impulse cantilever turbine. The system has high modularity and is intended primarily to test flow-path components which are manufactured by 3D printing and rapid prototyping. System design from the fluid dynamic viewpoint is based on a previously described tool proven and validated during the design of micro turboexpanders in range of mainly dozens of kW. In order to achieve maximal simplicity, the system uses a converted aeromodelling motor as a permanent magnet generator and housing for bearings. Overall parameters are obtained from electrical performance and known generator’s characteristics. The mechanical design then takes into account request of simplicity, modularity and properties of materials in additive manufacturing, especially plastics. First experimental tests show a comparison between different manufacturing technologies and resulting flow components surface roughness and the impact of pressure ratio on the isentropic efficiency.

Air turbine starter with spark mitigation screen

Abstract: An air turbine starter for starting an engine, comprising a housing defining an inlet, an outlet, and a flow path extending between the inlet and the outlet for communicating a flow of gas there through. A turbine member is journaled within the housing and disposed within the flow path for rotatably extracting mechanical power from the flow of gas. A gear train is drivingly coupled with the turbine member, a drive shaft is operably coupled with the gear train, and an output shaft is selectively operably coupled to rotate with the engine. A screen is located within the interior between the at least one turbine member and the set of outlets and adapted to mitigate ejection of ignited particles from within the housing.

Effective Power Transmission by Means of Air Compressor, Air Turbine System and Solar Concentrators

Abstract: Usually Electrical Power is generated in large scale using Air Compressors and Gas Turbine Systems. This type of Power plants is usually used as Peak load Power Plants. These Power Plants can assist in various power generation process along with base load power plants like Thermal Power Plants, Combined cycle power plants etc. Here in this Research paper, a new method of Power generation is being discussed. It utilizes an Air Compressor-Air Turbine System for Electrical Power generation by means of effective power transmission. This method is simple and less costly. It requires less space and less skilled laborer. It can be used in Stand by and Emergency power generation systems. An ANN model is carried out which gives satisfactory working conditions. The cost analysis is being carried out by considering small capacity and micro power production conditions. The efficiency attained during this method of power generation is around 55%. By incorporating large macro energy systems, we can produce more power output and also generate more electrical power. By considering all these factors it can be considered as a very good working model.

Cogeneration turbines for power and desalination of sea water

Abstract: By using the gas turbine and closed cycle gas/(air or nitrogen) turbine in cascade way we can get the required heat for the heat exchanger chamber (for adding heat) in the closed cycle gas turbine, by using the heat diverted with exhaust gases from the open cycle gas turbine. Also we can get the heat from nuclear plant instead the open cycle gas turbine if it is available. When we get the very hot air to the heat exchanger chamber (for cooling the air) after leave the turbine in the closed cycle gas/air turbine, we use the sea water in multi heat exchanger to cool the air and use the heat make desalination of the sea water, so at the end we can produce fresh water and electricity by the open and closed gas turbine same time.

Emergency air turbine system comprising turbine rotation locking device

Abstract: FIELD: turbines or turbomachines.SUBSTANCE: invention relates to an emergency aircraft air turbine. Emergency air turbine system for aircraft comprises structure made with possibility of attachment on external surface, emergency air turbine (22), connected to structure and made with possibility of movement relative to structure between retracted and extended positions. Emergency air turbine (22) includes post (23), turbine (25) and locking device. Locking device is configured to lock rotation of housing (30) of turbine (25) about axis (26) of rotation, when emergency air turbine (22) moves between retracted position and extended position, wherein axis (35) of blade leg forms acute and non-zero angle (α) locking with orthogonal projection (24') of longitudinal axis (24) of post (23) on plane (P), which extends substantially perpendicular to turbine (25) axis (26) and in which blade axis (35) is located, wherein angle (α) locking ranges from 10 to 45°.EFFECT: reduced weight and dimensions.4 cl, 5 dwg

Design of a Drag and Lift Type Blade for Power Generation via Air Turbine

Abstract: Compressed air is a vital medium for transferring energy in industrial processes. Compressors are efficient and reliable in meeting need and demand, especially in the industry while at the same time helping to reduce carbon footprint. However, there are several constraints using an air turbine as an operational element in generating electricity from compressed air. One of the key factors involved is the design of a blade that capable to increase the performance of the turbine and electricity generation from compressed air. Thus, this paper objectives are to develop a proposed design of a drag and lift type blade design and to evaluate the power generate that able to be harnessed from the force of the air. Additionally, the power coefficient that is harnessed from the generator using these new designs of blade also evaluated. In the experiment, the model is set up using the proposed concept of Savonius and Darrieus typed in order to generate electricity for small power equipment. Results show that these blade designs able to generate of 21-v for Savonius whereas 24-v for Darrieus from 0.3 MPa input source. Based on the result of an experiment, this study reveals that both type of blade design able to generate electricity constantly however, the performance of Darrieus vertical axis blade design is better compared to Savonius vertical axis blade design.

Wave Height Prediction for Maximum Power Extraction Scheme of Air-Turbine of an OWC based Wave Energy Plant

Abstract: Ocean wave energy has not yet gained popularity as a renewable energy source, because of highly varying nature of available wave power. Despite the seasonal/daily variations in the input hydraulic power available, extracting the maximum power from the installation requires controlling the reflected electrical load on the generator dynamically guessing the wave height on short-time basis. Such an effort of maximizing the air- turbine’s efficiency is not complete without a wave height prediction algorithm setting reference to the turbine speed. Considering wave data pertaining to the site of Indian Wave energy plant, prediction of Significant wave height on hourly basis is carried out using a Neural Network employing Levenberg Marquardt (LM) algorithm for back propagation/ supervised learning. Normal back-propagation based (Least Mean Square) algorithm is compared with LM method, and the latter one is found to yield better results. Based on predicted significant wave height, prediction of the actual height of the immediately following wave is obtained by employing Non-linear Auto-Regressive Neural Network (NARNN) using previous actual wave heights as input and this model is compared with NAR neural network with exogenous input (NARXNN). The results obtained for typical significant wave heights are provided. Improvement achieved in the efficiency of the impulse turbine of OWC based Wave Energy Plant is verified by employing the concept of prediction of wave height.