A theoretical model is developed for the effect of the operating parameters and the geometric parameters on the Kaplan turbine performance under design and off-design conditions. In the theoretical model, the incidence loss at the runner inlet that exists under off-design conditions for both positive and negative incidence angles is taken into account. The runner internal loss and the draft tube loss, which exist even under design conditions, are also taken into consideration through the use of simple and reasonable empirical expressions. The experimental works were carried out to validate the theoretical results. An optimization technique is adopted to obtain the operating parameters that achieve the best possible efficiency of a Kaplan turbine. A chart is deduced for detecting the suitable values of the operating parameters that achieve efficiency higher than 88% for different geometric parameters of the axial flow turbine, constant runner inlet blade angle. Comparisons of the obtained results with the present experimental and available published works show an acceptable agreement

Experimental study of natural convection heat transfer inside smooth and rough surfaces of horizontal equilateral triangular channels with a uniformly heated surface are performed. The effect of smooth and rough surface of average roughness, ra = 0.02μm, on the heat transfer characteristics are studied. The local and average heat transfer coefficients and Nusselt number are obtained for smooth and rough channel at different Rayleigh numbers from 6.45 × 105 to 4.45 × 106. The findings show that the values of temperature difference between the inside surface and ambient air increase with increase of axial distance from both ends of the channel until a maximum value at the middle of the channel. The results show a higher values of local (Nux) for rough channel along the axial distance compared with the smooth channel. The average Num of rough channel is higher than Num of smooth channel by about 7%. The results obtained are correlated using dimensionless groups for both rough and smooth surfaces of the equilateral horizontal triangular channels

This study presents two different Fault Ride Through (FRT) techniques to keep and restore stability of Fixed Speed Wind Generation system (FSWGs) installed in standalone Micro-Grid (MG). The first technique is an electrical FRT and is implemented by inserting a series resistance with the terminals of FSWGs during fault to maintain reasonable value of terminal voltage and consequently help stability restoration. The second controller is a mechanical FRT controller and is performed by change the gear ratio of wind generation systems to spill part of extracted mechanical power and consequently improving stability issue. Obtained results proved that each controller able to maintain the stability of FSWGs under the most severe disturbance conditions (400 ms three phase fault at FSWGs terminals). The first controller is faster than the second controller in restoring FSWGs stability. Superior results and performances are obtained when the two FRT techniques are employed simultaneously. Without employing any one of the two FRT techniques, FSWGs is not able to maintain or restore its stability after fault clearing. Consequently, MG will lose one of its micro-sources and cannot keep its stability during the standalone mode, unless load shedding strategy is activated. The two proposed controllers are simple, effective, and economical attractive.

In this paper a mathematical model for swash plate compressor is presented. Using this model, the description of the swash plate motion and the average power input to the compressor was derived as a function of the compressor geometry and angular speed under different operating conditions. The performance of an automotive air conditioning system provided with a swash compressor type is experimentally studied. The theoretical and experimental studies of the swash plate compressor indicate that the average power acting on the swash compressor mainly depends upon the swash plate inclination angle, rotational speed and system pressure. It is concluded that, small value of the swash plate inclined angle is necessary for decreasing the power lost due to friction between the slipper and the swash plate and decreasing the shaft power required for the swash compressor. Also, in the design case when a long stroke and minimum shaft power for the swash plate compressor are required, the present analysis is very important for selecting the suitable inclined angle and the stroke length of the swash compressor. The experimental results show that low rotational speed, high cooling capacity and low shaft power per unit refrigerant mass flow rates are required for high values of coefficient of performance and volumetric efficiency. The coefficient of performance relative to that obtained for the corresponding Carnot cycle is parabolically decreased by increasing the shaft power per unit refrigerant mass flow rates. The shaft power values obtained from the theoretical results agree with those obtained from a simulated program prepared by the manufacture company of the swash compressor [8] under different operating conditions.

Cavitation erosion resistance of steels is important in many applications. The investigation of such resistance, under different conditions, should be very useful. Cavitation erosion tests were carried out on carbon steel AISI-1045 using an ultrasonic induced cavitation facility. Cavitation erosion pits and their effect on the localized corrosion were investigated in detail in three different corrosive media: distilled water, tap water, and 3% NaCl water. The results of the investigation using SEM indicated the formation of three types of pits on cavitating specimen surfaces: corrosion pits, erosion pits, and erosion-corrosion pits. The corrosion pits have different shapes, however, the lamellar structure is the dominant structure, and has a large size of about 100 μm. The erosion pits that were formed by the cavitation microjet impacts have sizes of a few micrometers. The erosion-corrosion pits were similar to the corrosion pits, except the erosion pits formed on the corrosion pit surface due to dissolution. The eroded surface removal was the largest in the case of saline water.

The aim of the present study is the simulation of the particulate flow in spiral separators. The study is based on Eulerian approach and turbulence modeling. The results focus on particulate-flow characteristics such as the velocity, the distribution, and concentration of particulates on the spiral trough. The predicted results are compared with the experimental findings from LD9 coal spiral. The comparison shows good agreement and indicates that the most accurate turbulence model is RNG K–ε.