The aim of the present paper is focused on nucleation onset and development morphologies of acicular ferrite and to evaluate microstructure and mechanical properties during isothermal austenite transformation in titanium free micro-alloyed steel. Isothermal treatment was carried out in the temperature range 350 to 450 C. These treatments were interrupted at different times between 2 and 1800 s in order to analyze the evolution of the microstructure. Yield stress was determined by compression testing on samples with final Microstructure. The metallographic evaluation was done by using optical and scanning electron microscopy (SEM) enabled determination of the nucleation onset at all treatments and subsequent on the development of acicular ferrite of isothermally treated titanium free micro-alloyed steel. The results show that during continuous cooling, dominantly acicular ferrite microstructure is formed. Main characteristics of acicular ferrite are intragranular nucleation and strongly disorganized microstructure with a larger ability to deflect cracks. Acicular ferrite is, therefore, widely recognized to be a desirable microstructure due to good mechanical properties.

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ABSTRACT

Swirl stabilised combustion is one of the most widely used techniques for flame stabilisation in gas turbine combustors. Lean premixed combustion systems allow the reduction of NOx coupled with fair flame stability. The swirl mechanism produces an aerodynamic region known as central recirculation zone (CRZ) providing a low velocity region where the flame speed matches the flow velocity, thus anchoring the flame whilst serving to recycle heat and active chemical species to the root of the f

ormer. Another beneficial feature of the CRZ is the enhancement of the mixing in and around this region. However, the mixing and stabilisation processes inside of this zone have shown to be extremely complex. The level of swirl, burner outlet configuration and combustor expansion are very important variables that define the features of the CRZ.

Therefore, in this paper swirling flame dynamics are investigated using computational fluid dynamics (CFD) with commercial software (ANSYS). A new generic swirl burner operated under lean-premixed conditions was modelled. A variety of nozzles were analysed using several gaseous blends at a constant power output. The investigation was based on recognising the size and strength of the central recirculation zones. The dimensions and turbulence of the Central Recirculation Zone were measured and correlated to previous experiments. The results show how the strength and size of the recirculation zone are highly influenced by the blend and infer that it is governed by both the shear layer surrounding the Central Recirculation Zones (CRZ) and the gas composition

. The aim of the present paper is focused on post weld heat treatment qualification by

describes the results of an investigation to understand the micro structural changes that taken place in type 304L stainless steel weld deposits as function of temperature / time by showing any presence of re-crystallization and / or strain induced grain boundary migration and the dissolution of any carbide formed at grain boundaries in welding monitored by metallographic examination.

Abstract Rapid Prototyping of embedded hardware/software systems is important, because it shortens the path from specification to the final product. Prototypes play a major role in decision making, concept and design validation, feature and limit exploration, as well as design verification in every phase of the product development cycle, including product planning, requirement engineering, and product development. Rapid prototyping of embedded systems can emulate different kind of processes, through the mathematical modelling that represent their dynamic characteristics. This make easier to emulate different control strategies, which can interact with the real signals of the embedded process, making a better approach of the real response than a simple simulation. This paper presents the results of the emulation of the dynamic behaviour in the study case to work, in order to validate control strategies like PID and Fuzzy, using the concepts of rapid prototyping and hardware-in-the-loop (HIL). To achieve this objective, two embedded systems were employed, the first one to emulate the dynamics of the process, and the second one to implement the control strategy. Both systems were interconnected using the Controller Area Network protocol (CAN). The principal contribution of this work is the methodological development in the application of the control strategies through HIL 

Abstract The characteristics of non-minimum phase and static unstable of a tail controlled tactical missile are presented firstly. Then, in order to eliminate the static error, a cascade PI compensator was introduced to the classic two loop autopilot. Due to the slow tracking for command acceleration, the longitudinal three-loop autopilot design is driven based on LTI model of missile plant to stabilize the non-minimum phase static unstably missile airframe. The focus is to explain the performance and the control effect at different values of velocity and stability derivative (𝑀𝜶) of two algorithms on missile plant. The analysis is executed by establishing a standard algorithm in virtue of MATLAB/Simulink for autopilot design. The simulation results indicated that three-loop topology gives better tracking than two-loop with a cascade PI compensator at different value of stability derivative 𝑀𝜶. On the other hand, two-loop has a better response and less control effort at different velocities. fin angle and fin angle rate are less than the three loop for static unstable and stable missile. 

A B S T R A C T

Swirl stabilised combustion is one of the most successful technologies for flame stabilisation in gas turbine combustors. Lean premixed combustion systems allow the reduction of NOx coupled with fair flame stability. The swirl mechanism produces an aerodynamic region known as central recirculation zone (CRZ) providing a low velocity

region where the flame speed matches the flow velocity, thus anchoring the flame whilst serving to recycle heat and active chemical species to the root of the former. Another beneficial feature of the CRZ is the enhancement of the mixing in and around this region. However, the mixing and stabilisation processes inside of this zone have shown to be extremely complex. The level of swirl, burner outlet configuration and combustor expansion are very important variables that define the features of the CRZ. The complex fluid dynamics and lean conditions pose a problem for stabilization of the flame. The

problem is even more acute when alternative fuels are used for flexible operation.

Therefore, in this paper swirling flame dynamics are investigated using computational fluid dynamics (CFD) with commercial software (ANSYS). A new generic swirl burner operated under lean-premixed conditions was modelled. A variety of nozzles were analysed using isothermal case to recognize the the behavers of swirl.

The investigation was based on recognising the size and strength of the central recirculation zones. The dimensions and turbulence of the Central Recirculation Zone were measured and correlated to previous experiments. The results show how the strength and size of the recirculation zone are highly influenced by both the shear layer surrounding the Central

Recirculation Zones (CRZ) and outlet configurations.

Combustion systems are the least amenable of all gas turbine components to analyze. Among the literature overview made, it was realized that even though significant steps have been made in improving the combustor design procedure via the use of computational fluid dynamics, much of the design process still relies upon empirically derived rules. These rules include the calculation procedure of the required airflow rate by each zone of the combustion chamber to attain a suitable gas temperature, high values of combustion efficiency, low concentrations of pollutant species together with the determination of liner geometry that matches the chamber required performance goals with the constraints imposed by the engine dimensions [1,2,3, and 4]. The main target of this research work is to identify the proper procedure to distribute a predetermined airflow rate in annular type combustor and to generalize an effective calculation method that formulate and solve the problems in as much simplified and accurate manner as possible. The combustor dimensions and airflow rates in each zone is found in reference [5] and shown in Figure 1. It is designed with central vaporizing unit to deliver 516.3 KW of power with a geometrical constraint of 142 mm & 140 mm overall length and casing diameter, respectively, while the airflow rate is 0.8 kg/sec and the fuel flow rate is 0.012 kg/sec [5, 6].

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