Our recent progress on studying wave interaction with a lift-type rotor is discussed in this paper. The particular focus is on characterization of the rotor’s unidirectional responsiveness in waves. The rotor consists of six hydrofoil blades in two sets. One blade set has three blades laid out as a vertical-axis wind turbine of the Darrieus type. The other blade set has three blades configured like a Wells turbine. In combination, the formed rotor can be driven by flows in any direction to perform unidirectional rotation about its vertically mounted shaft. This unidirectional responsiveness of the rotor also holds in waves, making the rotor a valuable device for wave energy conversion. For parametric study of the rotor, hydrofoil blades using different cross sectional profiles and chord lengths have been employed to configure the rotor. The rotor was then tested in a wave flume under various wave conditions in a freewheeling mode. Experimental results were analyzed and discussed. The yielded research findings will greatly enhance the fundamental understanding on the rotor performance in waves, and effectively guide the prototype rotor development for practical applications.

Prior to choosing a site for a wind farm, its wind resources must be known. On-site measurement of wind speed, using an anemometer or any other appropriate measuring device or the use of historical meteorological data for the site (if they exist) enhance the knowledge of the site’s wind resources. Typically, the use of 50-year historical data is recommended by Wind Energy Engineering Standards. For the offshore site in study, only the 24-year historical data from the National Oceanic and Atmospheric Administration (NOAA) data base is available. Wind speed determined from NOAA’s error bars is used to plot Rayleigh probability distribution curves for each month of the year, based on the operational limit of the 5MW NREL reference wind turbine. The site’s average wind speed and gust are determined based on average wind energy capture. A Gumbel probability distribution curve is plotted based on the operational range of the wind turbine in study, using NOAA’s error bars for the 24year historical hourly wind gust for the site. This study uses the estimated mean wind speed and mean gust, to implement BEMT simulations to investigate the aerodynamic forces caused by the wind or gust on the blades of the HAWT rotor. The wind power captured and the power coefficient are estimated for each scenario. Empirical formulae are developed for the estimation of the rotor blade airfoil’s chord length in terms of blade element radius and the axial induction factor for each scenario, in terms of blade element radius.

An experimental investigation has been performed to study the film cooling performance of a smooth expansion exit at the leading edge of a gas turbine vane. A two-dimensional cascade has been employed to measure the cooling performance of the proposed expansion using the transient Thermochromatic Liquid Crystal technique. One row of cylindrical holes, located on the stagnation line, is investigated with two expansion levels, 2d and 4d, in addition to the standard hole. The air is injected at 90° and 60° inclination angle relative to the vane surface at four blowing ratios ranging from 1 to 2 at a 0.9 density ratio. The Mach number and the Reynolds number based on the cascade exit velocity and the axial chord are 0.23 and 1.4E5, respectively. The detailed local heat transfer coefficient over both the pressure side and the suction side are presented in addition to the lateral-averaged normalized heat transfer coefficient. The proposed expansion provides a lower heat transfer coefficient compared with the standard cylindrical hole over the investigated blowing ratios. Combining the heat transfer coefficient with the corresponding cooling effectiveness, previously presented, the smooth expansion shows a significant reduction in the heat load with more uniform distribution of the coolant over the leading edge region. The strong confrontation between the coolant jet and the mainstream, in case of 90° injection, yields a strong dispersion of the coolant with higher heat transfer coefficient and high thermal load over the vane surface.

A small personal use wind turbine (PWT) is studied and tested for power, exergy and energy evaluation under different operating conditions. The wind turbine incorporates non-twisted blades of 1.5 m span and 0.27 m chord, using NACA 63418 airfoil. Using the earlier test results at pitch angles of 22°, 34° and 38° between the wind speeds of 4 m/s to 7 m/s, torque produced by each blade is determined. It is desired to calculate the torque as it is difficult to measure it for a small wind turbine. Using the governing equations and available computational fluid dynamics software, the total torque on each blade is determined. The resultant torque yielded the mechanical power output of the PWT. Using the available power, energy and exergy in the air flow, corresponding efficiencies are determined. To determine the changes in energy and exergy with respect to the wind speed, wind-chill factor expression is utilized. Results are collected for a wide range of wind speeds and pitch angles. Power, energy, exergy and their corresponding efficiency is evaluated to determine the optimal use pitch angle and ambient conditions. The pitch angles of 22° and 38o yielded high efficiencies although 22° produced the higher rotational speed as compared to 38°. The result suggests better performance for continuous wind speed conditions at low pitch angles — with respect to the rotating plane. For non-continuous wind conditions, higher pitch angles appeared beneficial.

A small horizontal axis wind turbine rotor was designed and tested with aerodynamically efficient, economical and easy to manufacture blades. Basic blade aerodynamic analysis was conducted using commercially available software. The blade span was constrained such that the complete wind turbine can be rooftop mountable with the envisioned wind turbine height of around 8 m. The blade was designed without any taper or twist to comply with the low cost and ease of manufacturing requirements. The aerodynamic analysis suggested laminar flow airfoils to be the most efficient airfoils for such use. Using NACA 63-418 airfoil, a rectangular blade geometry was selected with chord length of 0.27[m] and span of 1.52[m]. Glass reinforced plastic was used as the blade material for low cost and favorable strength to weight ratio with a skin thickness of 1[mm]. Because of the resultant velocity changes with respect to the blade span, while the blade is rotating, an optimal installed angle of attack was to be determined. The installed angle of attack was required to produce the highest possible rotation under usual wind speeds while start at relatively low speed. Tests were conducted at multiple wind speeds with blades mounted on free rotating shaft. The turbine was tested for three different installed angles and rotational speeds were recorded. The result showed increase in rotational speed with the increase in blade angle away from the free-stream velocity direction while the start-up speeds were found to be within close range of each other. At the optimal angle was found to be 22° from the plane of rotation. The results seem very promising for a low cost small wind turbine with no twist and taper in the blade. The tests established that non-twisted wind turbine blades, when used for rooftop small wind turbines, can generate useable electrical power for domestic consumption. It also established that, for small wind turbines, non-twisted, non-tapered blades provide an economical yet productive alternative to the existing complex wind turbine blades.

The reduction in cost of energy from wind turbines requires many technical contributions from all areas of Wind Energy Conversion Systems. The concept of a telescopic blade has been analyzed to improve rotor blade performance. The effect of a step change is significant for any extension. The current simulation model in WT Perf with a Prandtl tip and hub loss model over-predicts the rotor performance. The correlations developed herein for telescopic blades with step change in the blade chord are in good agreement with the experimental data. The maximum loss for a rotor blade with a step change occurs when the extension is equal to the root blade chord.

Axial microfan is widely used as cooling equipment for electronic devices such as PCs. Currently, the PC size becomes smaller and smaller while their operating speed becomes faster and faster, which calls for better cooling performance of axial microfan. As an important and effective design approach, the similitude design has been widely used in the design of large and medium fans, but not yet in the design of axial microfan. The traditional similitude design approach may work well in self-similitude area for Reynolds number, such as the flow inside the large and medium fans, where simple geometric similitude can promise the aerodynamic similitude. But the flow inside the microfan locates in non self-similitude area for Reynolds number, where the traditional similitude design for large and medium fans may be out of work on microfans, which results in poor performance of the microfan designed by the traditional similitude approach. In this paper, the aerodynamic similitude conditions for axial microfan are presented according to the similitude principle for aerodynamics. Compared to large and medium fans in self-similitude area, a new criterion called ‘Chord Reynolds Number Criterion’ suitable to the flow in non self-similitude area is proposed and is numerically validated with discussions on its applicability and limitation. Results indicate that ‘Chord Reynolds Number Criterion’ can well realize the aerodynamic similitude for the axial microfan but it requires that the revolution speed of the impeller should be in direct proportion to the squared minification of the model impeller, so the reduced scale of model impeller shall not be too large, otherwise new non similitude factors may occur again due to too high revolution speed.

A higher efficiency gain is necessary for steam turbine plants to reduce their fuel consumption rate and lessen their environmental disruption factor. Power plant manufacturers have continued to make an effort to raise steam turbine internal efficiency by developing new technologies. High pressure (HP) steam turbines should have increased efficiency owing to relatively shorter blade height compared with other turbine sections (intermediate and low pressure turbines). In order to increase efficiency, it is important to improve the steam path determined by design parameters such as degree of reaction, number of stages and rotor diameter and to develop a high performance blade applied to it. The advanced computational fluid dynamics (CFD) technique is a useful design tool, and has come to be applied generally to evaluate energy loss. A new rotating blade has been developed for small and mid-class steam turbines with a shorter blade height. The robust design method, based on the statistical theory for design of experiments, is used for the blade root profile design. It is combined with the inverse method and 2-D turbulent blade-to-blade flow analysis to evaluate the aerodynamic performance. The blade configuration is expressed by four control factors, which are turning angle, leading edge radius, pitch-chord ratio and maximum blade loading location. Linear cascade experiments are also carried out due to verify the blade performance under the optimized conditions obtained by the robust design. Consequently, the blade section has a blunt-nose, flat incidence characteristics and low energy loss, compared with the conventional one and the optimized conditions given by the robust design are aerodynamically reasonable. Finally, air turbine model tests and 3-D Reynolds-averaged Navier-Stokes analyses are performed to investigate the detailed flow pattern and stage performance of the new optimized reaction blade. An experimental investigation is still important to evaluate the performance in the real turbine stage structure, while the numerical analysis method is used based on the implicit TVD scheme with the modified k-ε turbulence model. It is found that the new optimized reaction blade has greatly improved stage efficiency of about 1.5% at the design point including the effect of leakage flow (3% improvement in stage efficiency excluding leakage flow) and realized an increase of pitch-chord ratio by about 35%. Consequently, the new optimized reaction blade is considered effective to raise the internal efficiency of the high-pressure steam turbine with improved steam path.