amin imani

In this paper, in order to investigate the performance of a geared turbofan engine and its control system, the thermodynamic modeling of the engine along with the modeling of the corresponding hydromechanical controller is conducted. Engine test data is used for validation of engine performance simulation. The maximum difference between engine modeling outputs and engine data in take-off conditions is 3.2% and with engine test data in different rotor speeds is 7.6%. In order to model the controller, a comprehensive structure is extracted for the controller by using the engine data and the governing logic. The simulation results of the engine performance along with the control system according to the throttle commands from the maximum degree to the minimum, indicate the accurate performance of the controller model in fulfilment of thrust and limit protection. In addition to analyzing the performance of the engine in different operating conditions, the results of this research can also be used to examine the strengths and weaknesses of the existing control system. Since the capabilities of hydromechanical control systems for managing engine fuel, bleed system and peripheral systems are limited, therefore, simulating the existing controller structure in connection with the engine model is important to develop the hydromechanical type controller to an autonomous electronic type containing condition monitoring, health management and fault-tolerant control.

Nowadays, micro-turbojet engines are widely used in various fields, from recreational devices to drones and missiles in the military industry. Given their remarkable performance, numerous companies have entered this area and produced a variety of products. This widespread use and diverse range of products have led to an increased importance of review studies in this subject. In this research, an extensive study has been conducted on micro-turbojet engines with a thrust force below 1000 Newtons. These engines have a diameter less than 300 mm, compressor pressure ratio less than 5 and fuel consumption lower than 2500 gr/min. Statistical analysis of the engines within this thrust range has yielded valuable information regarding the structural and performance specifications of this category of engines, which is presented in the form of tables and graphs. In this study, the main components of these engines, including the compressor, combustion chamber, turbine, and auxiliary systems, as well as their interconnections, are described. Although the overall structure of these engines is similar to large-scale aircraft engines, there are significant differences in design philosophy, types of main components, and details. At the end of the paper, specifications of over one hundred micro-turbojet engines available worldwide including thrust range, dimensions, engine rotor speed, air flow rate, fuel consumption, and turbine temperature are presented.

Despite the wide use of micro-turbine engines in various aerospace fields, these engines consume a relatively high amount of fuel to provide desired thrust. The fuel consumption is a key parameter in the efficiency, endurance and range of an unmanned air vehicle. An effective approach to reduce the fuel consumption of these engines while maintaining the thrust value is to convert them into micro-turbofan engines. In this research, a mixed flow micro-turbofan engine structure derived from a micro-turbojet engine is employed. In order to analyze the performance of this structure, a thermodynamic modeling using matrix iteration method and Newton-Raphson solver is performed for a micro-turbofan engine. The findings of engine modeling are validated against a gas turbine performance simulation software. Afterwards, the required fan module is designed for the converted engine. The operation of the micro-turbofan engine in the steady-state and transient regime is investigated. Comparing the performance of the new engine with the experimental data of baseline engine indicates that despite no change in thrust value, the specific fuel consumption is reduced by 20%.

The growing consumer demand for produces without chemical residues has focusedefforts on the assessment of innovative natural antimicrobials. Tomato is one of most important vegetable in the world in terms of its economic value. The present study determined the effects of Aloe Vera gel (50 and 100%) and Chitosan (0.5 and 1%) for improve quality properties and shelf life of tomato during storage with 4±1 degrees Celsius temperature and 85 to 90 percent humidity. Sampling and evaluation of traits were performed on 1, 7, 14 and 21 days. Results showed that the highest weight loss and total soluble solids were obtained in control on day 14. The highest titratable acidity, pH, vitamin C and total chlorophyll were observed in control on day 1 and the highest carotenoid content was obtained in Aloe Vera gel 50+ Chitosan 0.5 on day 14. The lowest weight loss and carotenoid content were observed in control on day 1. The lowest vitamin C and total chlorophyll were obtained in control on day 21. The lowest titratable acidity, total soluble solids and pH were reported on Chitosan 1, Aloe Vera gel 50 and Aloe Vera gel 100 on day 14, respectively. Therefore, according to the results of the present study, the use of edible coatings of Aloe Vera gel and Chitosan can be recommended to improve the quality and shelf life of tomatoes.

An efficient approach to control the engine of a commercial aircraft is the Min-Max multi-loop structure. In this paper, a Min-Max controller with a switching structure containing output feedback regulators and a saturation function on the fuel flow rate is designed for a turbofan engine. In addition to desirable performance, the stability analysis is an important issue in the process of controller design for aero-engines. Because of the switching behavior of the Min-Max approach, the stability of each single loop by itself does not ensure the stability of the whole system. Therefore, a procedure is provided to analyze the stability of the closed loop system. For this purpose, the Min and Max operators and the saturation function are replaced by their nonlinear equivalents and the structure of the control system is converted to the canonical configuration of the Lure’s system. Then, the conditions for asymptotic stability are extracted and using the presented approach, an asymptotic stability proof is achieved for the closed loop system. In a simulation study with the nonlinear model of a turbofan engine, the performance of the designed Min-Max controller in the thrust attainment and limitation management is compared with the Min-Max/SMC technique.