Preliminary Design Level Research Articles

Comparative scoping study report for the extraction of microalgae oils from two subspecies of Chlorella vulgaris

Abstract The production of microalgae as a fatty acid oil resource for use in biofuels production is a widespread research topic at the lab scale. Microalgae contain a higher lipid content on a dry-weight basis compared to oilseeds such as soybeans. Additionally, the growth and cultivation cycle of microalgae is 15 days, in comparison to soybeans, for which the cycle occurs once or twice annually. However, to date, it has been uneconomical to produce microalgae oils in a world-scale facility due to limitations in cultivating microalgae at commercial scales. Recent developments suggest that the use of heterotrophic microalgae may be economically feasible for large-scale oil production. To assess this feasibility, a comparative scoping study was performed analysing the feasibility of an industrial-scale process plant for the growth and extraction of oil from microalgae. Processes were developed at the preliminary design level using heterotrophic subspecies and autotrophic subspecies of Chlorella vulgaris. AACE Class 4 cost estimates and economic analyses were performed. This study concludes that processes based on heterotrophic microalgae are more likely to reach economic feasibility than processes using autotrophic microalgae. However, a few barriers still remain to achieving free-market economic viability.

Scaling laws and similarity models for the preliminary design of multirotor drones

Multirotor drones modelling and parameter estimation have gained great interest because of their vast application for civil, industrial, military and agricultural purposes. At the preliminary design level the challenge is to develop lightweight models which remain representative of the physical laws and the system interdependencies. Based on the dimensional analysis, this paper presents a variety of modelling approaches for the estimation of the functional parameters and characteristics of the key components of the system. Through this work a solid framework is presented for helping bridge the gaps between optimizing idealized models and selecting existing components from a database. Special interest is given to the models in terms of reliability and error. The results are compared for various existing drone platforms with different requirements and their differences discussed.

A Framework to Evaluate the Benefit of Seismic Upgrading

Earthquakes are among the most catastrophic natural disasters. Existing buildings constructed in earthquake prone locations prior to 1970s generally do not meet the criteria of modern seismic design codes. Structural seismic upgrading is a very effective strategy to mitigate the earthquake risk for existing structures. However, in many cases, seismic upgrade design is criticized as overly conservative resulting in expensive structural interventions. The present study proposes a framework that combines key elements of the performance-based seismic design with the actuarial “frequency-severity” method to perform a cost-benefit analysis of structural seismic upgrading. A curve that quantifies the avoided losses and casualties for different levels of partial seismic upgrade at the site of interest is introduced. This curve provides a tool that enables engineers to optimize rapidly, at a preliminary design level, the seismic upgrading strategy using a cost-benefit analysis. The proposed framework is applied to existing residential buildings located in two different seismic hazard environments, namely Zurich (Switzerland) and L'Aquila (Italy), to identify the optimal seismic upgrading level.

Chemical Reactor Modeling of Oxy–Fuel Combustion Chamber for Semiclosed Combined Cycle

This paper compares standard gas turbine combustion chambers and CO2-diluted oxy–fuel combustion chambers for a semiclosed combined cycle at a preliminary design level. To this end, simple chemical reactor networks, based on the well-stirred reactor plus plug flow reactor scheme, are analyzed using the Cantera package and the GRI 3.0 chemical kinetics mechanism. The focus is put on the CO consumption process and the final CO concentration. The behavior of this model suggests the use of the adiabatic equilibrium temperature to characterize the composition at any station inside the chamber and the incipient lean blow-out equilibrium temperature to fix the well-stirred reactor volume. This model is applied to a feasible design point of a power production cycle (combustion exit temperature 1600 K, combustion pressure 30 bar). The fuel is a natural gas with an 87% by volume CH4 content, the ASU stream is a 95% O2 gas, and the recirculated gas is an 82% CO2 gas. The residence times required for CO burnout are approximately 30% greater than those for air combustion for the same conditions, although the required lengths are much closer. The residence times and lengths would be reduced if the combustion exit temperature or the combustion pressure of the cycle was increased.

Multicontrol Surface Optimization for Blended Wing–Body Under Handling Quality Constraints

Control architecture sizing is a main challenge of blended-wing–body design. This aircraft configuration typically features redundant elevons located at the trailing edge of the wing, acting simultaneously on pitch and roll axes. Consequently, a proper sizing requires one to consider coupled longitudinal and lateral criteria. Moreover, significant hinge moments due to large control surface areas, combined with high deflection rates in order to safely control the longitudinal instability, may result in excessive power consumption and actuator mass penalty. Therefore, it is highly desirable at the preliminary design level to minimize control surface areas, while ensuring adequate closed-loop handling qualities, with limited deflections and deflection rates. The problem of integrated design of control surface sizes and flight control laws for an unstable blended-wing–body aircraft is addressed here. The latest tools for nonsmooth optimization of structured controllers are used to optimize in a single step the gains for both longitudinal and lateral control laws, as well as a control allocation module, while minimizing the control surface span. The following constraints are ensured: maximal deflection angles and rates for 1) pilot longitudinal pull up, 2) pilot bank angle order, and 3) longitudinal turbulence. Using this coupled approach, significant gains in terms of the outer elevon’s span as compared to the initial layout are demonstrated, whereas closed-loop handling quality constraints are guaranteed.

Two-Level Design Optimization for Compression Stiffened Panel

In this paper, a two-level design optimization approach is presented for compression stiffened panel sizing. First, the stiffened panel design procedure is described by means of a structural index concept. This method is based on the analytical formulations for structures and is used for the preliminary design level. In this procedure, the final results have a general form without being restricted by the geometrical parameters. The final results can be used for sizing different types of compression stiffened panels. Using the results obtained in the first level, the surrogate-based optimization is employed for design optimization in the second level. The analysis tool in the second level is the finite element method. Using Sequential Quadratic Programming algorithm, a novel technique is developed to find the global optimum of the surrogate model. The proposed two-level design approach is employed for design optimization of a flanged stiffened panel. In this panel design problem, which has six design variables, an initial training set with 57 points is created. Using 173 infill points, the optimum solution is obtained. In comparison with the conventional optimization methods, the surrogate modeling reduces the required nonlinear buckling analyses significantly. An estimate of the required number of analyses in the conventional methods is 57,201. The results of both levels are compared with each other. The final results of the optimization process are the optimum design non-dimensional ratios for plate elements of the flanged stiffened panel.

RAPID GEOMETRY DEFINITION FOR MULTIDISCIPLINARY DESIGN AND ANALYSIS OF AN AIRCRAFT

Conceptual and preliminary design level of aircraft design is searching for an easy, flexible and efficient way of computational geometry definition. Accelerating the process of geometry definition is the basic step for acceleration of all computations. It also enables optimization, where changes of numerical model are made automatically according to the optimization algorithms. The geometry definition has to be robust, free from errors and stay feasible.

Aerodynamics of Centrifugal Turbine Cascades

The centrifugal turbine architecture is a promising solution for small-to-medium organic Rankine cycle (ORC) power systems. The inherent compactness of the multistage arrangement makes this configuration very attractive for dealing with the high volumetric flow ratios typical of ORC turbines. In absence of experimental evidence, a thorough assessment of the technology can be uniquely based on sufficiently accurate computational fluid dynamic (CFD) simulations. In the present work, the aerodynamic performance of a fixed and a rotating cascade of centrifugal turbine are investigated by applying a three-dimensional CFD model. Precisely, the study is focused on the sixth stage of the transonic centrifugal turbine proposed in Pini et al. (2013, “Preliminary Design of a Centrifugal Turbine for ORC Applications,” ASME J. Eng. Gas Turbines Power, 135(4), p. 042312). After recalling the blade design methodology, the blade-to-blade and secondary flow patterns are carefully studied for both stator and rotor. Results show that the centrifugal configuration exhibits distinctive features if compared to axial turbine layouts. The diverging shape of the bladed channel and the centrifugal force alter significantly the pressure distribution on the profile. Moreover, the Coriolis force induces a slip effect that should be properly included in the preliminary design phase. Provided that the flaring angle is limited, the almost uniform spanwise blade loading greatly augments the three-dimensional performance of the cascades compared to axial rows. In the rotor, the low inlet endwall vorticity and the Coriolis force further weaken the secondary flows, resulting in even lower secondary losses with respect to those predicted by loss models developed for axial turbines. Ultimately, the efficiency of the stage is found to be two points higher than that estimated at preliminary design level, demonstrating the high potential of the centrifugal turbine for ORC applications.

Modelling of shear characteristics at the concrete–rock mass interface

An analysis of shear characteristics on the concrete–rock mass interface is presented, in order to simulate the effect of load at the contact of concrete structure of the dam and the rock foundation. The analysis is based on the real mechanism of shear, which is different from the so-called the “saw tooth” model that simulate the walls of joints in the rock mass. As a result, the analytic form of shear deformation and shear strength as a function of normal and shear loads, as well as the mechanical characteristics of the rock mass, is established. In this way, mathematical models are derived that can be used for structural analysis of Concrete Dams for the Preliminary Design level. The models are developed on the basis of a large number of shear tests carried out on the concrete blocks at the concrete dam sites, during the period from the seventies to the present day.

Preliminary design of the ITER ECH Upper Launcher

The design of the ITER electron cyclotron launchers recently reached the preliminary design level - the last major milestone before design finalization. The ITER ECH system contains 24 installed gyrotrons providing a maximum ECH injected power of 20MW through transmission lines towards the tokamak. There are two EC launcher types both using a front steering mirror; one equatorial launcher (EL) for plasma heating and four upper launchers (UL) for plasma mode stabilization (neoclassical tearing modes and the sawtooth instability). A wide steering angle range of the ULs allows focusing of the beam on magnetic islands which are expected on the rational magnetic flux surfaces q=1 (sawtooth instability), q=3/2 and q=2 (NTMs).In this paper the preliminary design of the ITER ECH UL is presented, including the optical system and the structural components. Highlights of the design include the torus CVD-diamond windows, the frictionless, front steering mechanism and the plasma facing blanket shield module (BSM). Numerical simulations as well as prototype tests are used to verify the design

Multilevel/Multiobjective Design of Composite Structures

A multilevel multiobjective platform for structural sizing reproducing the sequence of actions taken during design and structural sizing in industry is presented in this paper. This platform is integrated at two design levels labeled as Preliminary Design Level and Detailed Design Level. The set of design variables can be divided into a group of variables describing the main conceptual layout that affect the dimensions and architecture of the model and a second group of variables influencing the material and mechanical behavior. This kind of approach can be effective if it is possible to separate the constraints that are strongly dependent on the design variables of different design levels.

Development of preliminary design program for combustor of regenerative cooled liquid rocket engine

An integrated program was established to design a combustor for a liquid rocket engine and to analyze regenerative cooling results on a preliminary design level. Properties of burnt gas from a kerosene-LOx mixture in the combustor and rocket performance were calculated from CEA which is the code for the calculation of chemical equilibrium. The heat transfer of regenerative cooling was analyzed by using SUPERTRAPP code for coolant properties and by one-dimensional correlations of the heat transfer coefficient from the combustor liner to the coolant. Profiles of the combustors of F-1 and RS-27A engines were designed from similar input data and the present results were compared to actual data for validation. Finally, the combustors of 30 tonf class, 75 tonf class and 150 tonf class were designed from the required thrust, combustion chamber, exit pressure and mixture ratio of propellants. The wall temperature, heat flux and pressure drop were calculated for heat transfer analysis of regenerative cooling using the profiles.

Design Optimization of a Space Launch Vehicle Using a Genetic Algorithm

This paper describes an effort to optimize the design of an entire space launch vehicle to lowEarth (circular) orbit, consisting of multiple stages using a genetic algorithm with the goal of minimizing vehicle weight and ultimately vehicle cost. The entire launch vehicle system is analyzed using various multistage configurations to reach low Earth orbit. Specifically, threeand four-stage solid propellant vehicles have been analyzed. The vehicle performance modeling requires that analysis from four separate disciplines be integrated into the design optimization process. The disciplines of propulsion characteristics, aerodynamics,mass properties, andflight dynamics have been integrated to produce a high-fidelity systemmodel of the entire vehicle. In addition, the systemmodel has been validated using the existing launch vehicle data. The cost model is mass based and uses extensive historical data to produce a cost estimating relationship for a solid propellant vehicle. For the design optimization, the goal is for the genetic algorithm tominimize the differences between thedesired andactual orbital parameters. This ensures that thepayload achieves the desired orbit. One final goal is to minimize the overall vehicle mass, thus minimizing the system cost per launch. This paper will represent the first effort of its kind to minimize the solid propellant launch vehicle cost at the preliminary design level using a genetic algorithm.

Spatial Layout Planning in Sub-Surface Rail Station Design for Effective Fire Evacuation

Spatial layout planning is an important part of the underground railway station design process, taking into account its need-driven nature and the resulting infrastructure that is sized on demand. The predicted passenger flow rates are the underlining factor and are divided into ‘levels of service’ for space planning considerations. This paper reports on the development of a knowledge-based computer design environment capable of generating multiple spatial layout solutions, thus providing for more effective fire evacuation analysis when compared with the traditional design process. The developed programme, titled SGEvac in this research, utilizes shape grammar theory to provide for automatic generation of solutions at the reference (preliminary) design level, based on visual rules of shape recognition and replacement, their connectivity and spatial relationships. Although it has been developed to meet London Underground Station Planning Standards and Guidelines (SPSG) and related codes of practice, it has both the scope and potential for redevelopment to any other country's design legislation. Novel shape grammar and functional logic design rules that incorporate station planning design knowledge and guidance are developed and specified, along with the theoretical research. Validation of the results thus far is discussed, with a ‘train on fire in a station’ evacuation scenario analysed.

Practical Hydrodynamic Design of Bulbous Bows for Ships

Although in modern times, bulbous bows have become an integral part of commercial ships, the hydrodynamic design of bulbous bows is still difficult because of costly tank tests and patent-driven knowledge banks. The design of a bulbous bow is needed even at the preliminary design level to predict speed and power. In this work, a design method is presented that combines and extends two famous theories i.e., Kracht (1978a) and Yim (1980) for a particular set of requirements within a narrow range of parameters. The method uses a reanalysis of an approximate linear theory with sheltering effect for resistance estimation, and re-correlation with statistical analysis via a non-linear multivariate regression analysis from existing literature and tank test results available in the public domain. The optimization of design parameters has been done for the design speed. The effect of change in the speed has been discussed and suitably incorporated in the design process. In the present work, the effect of production constraints on the design of bulb parameters has also been briefly examined. The results of this study are presented in the form of design parameters related to main hull parameters for a set of input data in a narrow range. The first six parameters have been derived by re-correlation with statistical analysis and the seventh parameter by reanalysis of an approximate linear theory with sheltering effect for resistance estimation. Finally, a design example, which includes tank test results, of an additive bulbous bow for a container ship has been presented.

A method for predicting low-speed aerodynamic characteristics of transport aircraft

A preliminary design level methodology for predicting the global aerodynamic characteristics of transport aircraft in low-speed/high-lift configurations has been developed, based on recent advances in computational aerodynamics analysis methods. The new method involves two economical, user oriented, computer programs. One, an advanced lifting-surface theory for the potential flow analysis of swept-wing/body combinations with multi-element high-lift devices, provides the basic theoretical structure. The second program combines potential flow analysis results with available data from previous airplane models to predict the performance of new designs. The overall procedure is highly automated and produces generally satisfactory results for preliminary design purposes. Example results based on recent transport aircraft wind tunnel data are shown.

Multiple-Tactical Aircraft Combat Performance Evaluation System

The multiple-tactical aircraft combat performance evaluation system (MULTAC) is designed to analyze the outcome of a close-in M-on-N air battle involving up to 20 aircraft and their associated weapons. Construction of MULTAC including target selection, guidance and control laws, weapon system modeling, and other aspects involved in the computation of up to 20 simultaneous reacting aircraft flight paths are discussed. Encounter outcome is rated by the average survival probability of each aircraft force. Either a cokill probability model or a Monte-Carlo model may be employed in this evaluation. Typical results emphasizing the difference between oneon-one and M-on-N encounters are presented. These results illustrate the tradeoff between advanced technology and number of aircraft in aerial combat encounters. Construction of the MULTAC system provides fighter designers with a tool for evaluating the impact of advanced technology items on aerial combat performance at the preliminary design level. System Outline T HE multiple-tactical aircraft combat performance evaluation system (MULTAC) is illustrated in schematic fashion in Fig. 1. The trajectories of up to 20 aircraft engaged in an aerial combat encounter are simultaneously integrated using the fourth-order Runge-Kutta algorithm. These trajectories are integrated under time-varying angle of attack, bank angle, and throttle history control. Appropriate control histories are developed by a combat tactics logic which combines the target selection, control law specification, single-shot kill probability Pk computation, and firing opportunity selection functions. Encounter outcome may be determined by a sudden death model in which aircraft are removed from the encounter on the basis of single-shot Pk and the application of a random chance mechanism. Using this approach an encounter must be repetitively simulated using Monte-Carlo methods to determine the average result. Such an approach provides an estimate of both the mean result and the associated scatter about the mean. An alternate approach, the cokill probability model, * develops an approximation to the mean result on the basis of a single-encounter simulation. Generally the computation of mini-max solutions to an aerial combat engagement must be limited to far more simplified dynamic models of aerial combat than the one considered here. For example, the constant-speed planar games of Ref. 2 yield to mini-max solution by application of Isaacs' differential game theory.3 However, computation of differential game solutions for many aircraft using realistic three-dimensional dynamics is computational ly infeasible by current methodology and equipment. An alternative approach is to fix the control laws of one side in the encounter and then to determine the response of the second force in response to the tactics of the first force. This approach has a certain intuitive appeal for it closely parallels the evolution of optimal tactics in aerial warfare where historically one side will find a combat tactic which leads to a temporary advantage. The second side will then develop a response by trial-and-err or methods which effectively nullifies the advantage of the first side. In this sense