Ahmed Helal

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I’m a professor of aerospace and mechanical power engineering.Worked as professor in Egypt , USA, UK, Belgium, Libya, Austria, Japan, China, Syria, UAE, and Russia.I’m author of 15 books on aircraft and rocket propulsion, Bird Strike, Foreign Object Debris and Damage in Aviation, and history and evolution of aircraft,I worked in research projects with Westinghouse, Rolls Royce, European Renewable Energy.

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Papers by Ahmed Helal

Antibacterial and Antifungal Activities of the Essential Oils of Two Saltcedar Species from Tunisia

Journal of the American Oil Chemists' Society, 2008

Natural products such as essential oils have been studied since ancient times to understand their... more Natural products such as essential oils have been studied since ancient times to understand their biological properties. Essential oils are noted for their antimicrobial activity. Thus, the focus of this study was to evaluate the antimicrobial effect of five essential oils (EOs) from selected medicinal plants found in the South Pacific, on selected human pathogenic bacteria and fungi affecting agricultural industries. The disc diffusion method was carried out and the diameter of inhibition zones (mm) (DZI) using 0.25, 0.5, 5, 25, 50 and 100% (v/v) of essential oil concentrations were reported. The activity of Cananga odorata essential oils against Thermus thermophiles and Pseudomonas aeruginosa were among the selected bacteria that only showed the susceptibility at the lowest concentration (0.25% v/v). The diameter inhibition zones were 1.60 mm and 4.20 mm, respectively. The inhibitory effect of Ocimum tenuiflorum L essential oils at the highest concentration (100%) showed DZI ranging above 14 mm for all the selected bacteria and above 25 mm for the all selected fungi. The inhibitory effect of selected bacteria and fungi increased with stronger concentrations of essential oils. Hence, the essential oils from medicinal plants found in the South Pacific hold great potential for the antibacterial and antifungal properties.

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Erosion of an Axial Transonic Fan due to Dust Ingestion

American Journal of Aerospace Engineering, 2015

This paper deals with the prediction of the particle dynamic and erosion characteristics due to d... more This paper deals with the prediction of the particle dynamic and erosion characteristics due to dust ingestion in an axial flow fan, installed in a high bypass-ratio turbofan engine that operates in a dusty environment. Dynamic behavior comprises the particle trajectory and its impact velocity and location. While the erosion characteristics are resembled by the impact frequency, erosion rate, erosion parameter and the penetration rate. The study was carried out in two flight regimes, namely, takeoff, where the sand particles are prevailing, and cruise, where the fly ashes are dominated. In both cases, the effect of the particle size on its trajectory, impact location, and the erosion characteristics was studied. To simulate the problem in a more realistic manner, a Rosin Rambler particle diameter distribution was assumed at takeoff and cruise conditions. At takeoff, this distribution varies from 50 to 300 µm with a mean diameter of 150 µm sand particles. While at cruise, this distribution varies from 5 to 30 µm with a mean diameter of 15 µm fly ash particles. The computational domain employed was a periodic sector through both the fan and its intake bounding an angle of (360/38) where the number of fan blades is (38). The intake is a stationary domain while the fan is a rotating one and the FLUENT solver is used to solve this problem. Firstly, the flow field was solved in the computational domain using the Navier-Stokes finite-volume supported by the Spalart-Allmaras turbulence model. The governing equations, representing the particle motion through the moving stream of a compressible flow are introduced herein to calculate the particle trajectory. The solution of these equations is carried out based on the Lagrangian approach. Next, empirical equations representing the particle impact characteristics with the walls are introduced to calculate the rebound velocity, the erosion rate, erosion parameter, impact frequency and penetration rate. Moreover, a method to smoothen the irregularity in the calculated scattered data was discussed as well. During takeoff flight regime, the pressure side of fan blade experienced higher particle impact and erosion damage. The highest erosion rate was found at the corner formed by blade tip and trailing edge of pressure side. During cruise conditions, less erosion rates resulted. Maximum erosion rates are found at the leading edge of the pressure side.

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Computer Predictions of Erosion Damage in Gas Turbines

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1987

In this article an iterative procedure is presented for estimating erosion in axial gas turbine b... more In this article an iterative procedure is presented for estimating erosion in axial gas turbine blades. The procedure is applied to a two stage turbine and the erosion is estimated for a 12,000 hour engine running time. The effect of the erosion on engine performance is estimated through changes in pressure coefficient distribution around a blade section.

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Performance Analysis of Cold Sections of High BYPASS Ratio Turbofan Aeroengine

Journal of Robotics and Mechanical Engineering Research, Oct 31, 2017

The turbofan engine had many developments in the past 60 years and becomes the common power plant... more The turbofan engine had many developments in the past 60 years and becomes the common power plant employed in both civil airliners and military aircrafts. It combines the advantages of both of turboprop engines (high propulsive efficiency and thrust) and turbojet engines (high flight speed and altitude). To cope with the needs of high thrust forces that propel wide body airliner and increase of their payload and range as well as enlarging maneuver capabilities of military aircrafts, successive developments of turbofan engines are needed. These developments in turbofan design have endeavors of larger thrust force, low noise and emission as well as better fuel economy. These goals were achieved by increasing of the bypass ratio (BR), fan pressure ratio (FPR), overall pressure ratio (OPR), turbine inlet temperature (TIT) as well as using new materials, production and cooling techniques for both turbines and combustion chamber such modifications led to improvements in thermal, propulsive and overall efficiencies, decreases in thrust specific fuel consumption (TSFC) and increase the specific thrust. This paper presents a parametric study and design point selection of the cold sections of high bypass ratio turbofan engine (close to GEnx-1B-70). Cold sections include the intake, the fan, and the compressor. This engine is one of the products of GE Aviation Company. Performance analysis is performed using MATLAB program code for both taking-off and cruise conditions.

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Effect of Different Parameters on the Drag Coefficient for Commercial Vehicles

International Conference on Aerospace Sciences and Aviation Technology, 2001

Large commercial vehicles (e.g. truck-trailer combination), due to their function, are bluff bodi... more Large commercial vehicles (e.g. truck-trailer combination), due to their function, are bluff bodies by nature. The truck-trailer combination usually gives a drag coefficient that is less than that for a trailer alone. The interference between the commercial vehicles and other small vehicles is of primary importance especially when moving in driving tunnels that are characterized by their limited space. 1/19-scale models for commercial vehicles are employed in the experimental work performed here. Three-dimensional pressure measurements are recorded for analyzing the aerodynamic behavior and calculating the drag coefficient. Add-on devices (deflectors) are used. Measurements are supported by both numerical calculations and flow visualization. Results show that add-on devices play a very important role in improving the aerodynamic characteristics of commercial vehicles.

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Aero-Engines Intake: A Review and Case Study

Journal of Robotics and Mechanical Engineering Research, 2016

This paper presents an aerodynamic review for intakes of aero-engines. Classification of differen... more This paper presents an aerodynamic review for intakes of aero-engines. Classification of different types is introduced for both subsonic and supersonic aircrafts. Important parameters influencing intake performance like pressure recovery and spillage drag are discussed. In addition, crucial performance issues such as the angle of attack, ground vortex, swirl flow, noise propagation and icing are presented. These are critical issues which are carefully considered by airframe rather than engine manufacturers. Intake icing may be extremely dangerous and leads to drastic decrease in air mass flow and consequently aircraft propulsion. Calculation of intake performance is explained. The effect of intake performance on the whole engine performance is highlighted. Numerical analyses for present and previous researches are explained and critical parameters are identified. Finally, a case study resembling the intake of a high bypass ratio turbofan engine (in close similarity to that of GE CF-6 Turbofan Engine) is numerically analysed using the commercial code "ESI-CFD 2010" is thoroughly described and analysed. This paper is the first of a series of research work that will cover several R & D activities in HBPR and future EBPR turbofan intakes.

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Aerodynamics of intakes of high bypass ratio (hbpr) turbofan engines

Int Robot Automat J, 2020

The regulation characteristic and the transfer function of the electromagnetoelastic actuator are... more The regulation characteristic and the transfer function of the electromagnetoelastic actuator are investigated for nano robotics system. The electromagnetoelastic actuator is used in nanotechnology, scanning microscopy, adaptive optics, laser systems, focusing and image stabilization systems, vibration damping, nano and micro manipulator to penetrate the cell and to work with the genes. The mechanical and control characteristics of the electromagnetoelastic actuator are obtained to calculate the nano mechatronics robotics system. The piezo actuator is used in nano and micro dosing devices, nano manipulators in nano and micro surgery.

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Dynamics of Vertical Axis Wind Turbines (Darrieus Type)

International Journal of Rotating Machinery, 1995

A computing package that combines finite element methods for evaluating the resonance frequencies... more A computing package that combines finite element methods for evaluating the resonance frequencies and modes of turbine subcomponents (blade, tower and shaft) together with the aerodynamic calculations for forces and moments taking into consideration the dynamic stall as well as the dynamic response is developed. This method was applied to a realistic VAWT; namely; the PIONEER I built in the Netherlands by Fokker company. A reasonable agreement between the calculated and field results was predicted.

format_quoteAt 30 rpm, maximum power of 10 kW is obtained at 7 m/s; at 50 rpm, power reaches 53 kW at 12 m/s, highlighting dynamic stall effects.format_quote

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Performance Analysis of Hypersonic Vehicle

Optimizing the propulsion system for a hypersonic aircraft is examined. A combined cycle engine i... more Optimizing the propulsion system for a hypersonic aircraft is examined. A combined cycle engine is selected; where the thrust is to be delivered by a turbine based combined cycle engine (TBCC).The engine cycle is analyzed and optimized to give the required thrust over the entire Mach envelope with minimum fuel consumption. The variation of cycle parameters versus the Mach number is the output of that study. It is to be used further in selecting the design point of each cycle.

Bird Strike in Aviation

Aircraft Propulsion and Gas Turbine Engines

A Review of Basic Laws for a Compressible Flow

Fundamentals of Aircraft and Rocket Propulsion

Centrifugal and Axial Compressors