Evolutionary Algorithm as a Tool for Advanced Designing of Diesel Engines

none4Abstract: An evolutionary algorithm has been developed for the design of a diesel engine combustion chamber in order to fulfill present day and future regulations about pollutant emissions and greenhouse gases. The competitive goals to be achieved in engine optimization are the reduction of emission levels (soot, NOx and HC) and the improvement of specific fuel consumption. They have been taken into account by using a multi-objective approach implemented in an optimization tool called HiPerGEO, which is characterized by a very small population and a mechanism of reinizialization, combined with an external memory to store non-dominated solutions. The method was applied to the design of the combustion chamber profile and numerical simulations were performed with a modified version of the KIVA3V code to evaluate the fitness values of the solutions. The chamber profile was defined according to five geometrical parameters used as inputs to the optimization method. The output of the simulations in terms of emissions and IMEP were used to define four different objective functions. The search for the optimum was performed by applying the Pareto optimality criterion so that it is not bounded to arbitrary weights assigned to each objective. At the end of the simulation, the user can choose from the final Pareto set the best compromise solution for different applications. The method allows the optimization with respect to different engine operating conditions, i.e. load and speed values. In the present investigation, four operating modes were considered and weights were assigned to them according to their importance in the reduction of emissions and fuel consumption. The use of a 3D simulation code to simulate the behavior of the engine with respect to four operating modes is a very time expensive approach. To reduce the required computational time, which is prohibitive on a sequential machine, grid technologies were implemented in a grid portal named DESGrid.D. LAFORGIA; DONATEO T; ALOISIO G; MOCAVERO SLaforgia, Domenico; Donateo, Teresa; Aloisio, Giovanni; Mocavero, S

Publications of the Jet Propulsion Laboratory, July 1961 through June 1962

Jpl bibliography on space science, 1961-196

Energy efficient transport technology: Program summary and bibliography

The Energy Efficient Transport (EET) Program began in 1976 as an element of the NASA Aircraft Energy Efficiency (ACEE) Program. The EET Program and the results of various applications of advanced aerodynamics and active controls technology (ACT) as applicable to future subsonic transport aircraft are discussed. Advanced aerodynamics research areas included high aspect ratio supercritical wings, winglets, advanced high lift devices, natural laminar flow airfoils, hybrid laminar flow control, nacelle aerodynamic and inertial loads, propulsion/airframe integration (e.g., long duct nacelles) and wing and empennage surface coatings. In depth analytical/trade studies, numerous wind tunnel tests, and several flight tests were conducted. Improved computational methodology was also developed. The active control functions considered were maneuver load control, gust load alleviation, flutter mode control, angle of attack limiting, and pitch augmented stability. Current and advanced active control laws were synthesized and alternative control system architectures were developed and analyzed. Integrated application and fly by wire implementation of the active control functions were design requirements in one major subprogram. Additional EET research included interdisciplinary technology applications, integrated energy management, handling qualities investigations, reliability calculations, and economic evaluations related to fuel savings and cost of ownership of the selected improvements

Aeronautical Engineering. A continuing bibliography with indexes, supplement 156

This bibliography lists 288 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1982

Measurement and evaluation of near-field spray kinematics for nozzles with asymmetrical inlet geometries

In diesel engines, fuel injection parameters have a commanding effect on mixing andcombustion quality. This research aims to enhance the fundamental knowledge of fuelsprays and their primary break-up. In addition, this research provides statistical data tovalidate simulation models and improve the prediction accuracy in mixing and combustion.This thesis report is based on evaluating the behavior and velocity profiles of near-fieldsprays generated by different inlet geometries under a range of injection pressures. Thestudied nozzles include single-hole nozzles with on-axis and off-axis orifices and a two-holenozzle with angled orifices. We applied time-gated ballistic imaging to capture high-resolutionspray images at the near-field. These high-resolution images provide a clearliquid/gas interface, which enables tracking of the spray structures. Furthermore, thedisplacement of the spray interface in two consecutive images over a specific time frameyields spray kinematics in two dimensions.The results show how velocity measurements can describe spray development and evolution.Asymmetrical inlet geometries significantly affect near-field spray profile and targetingbecause the distribution of velocity magnitude on the two sides of the spray is notsymmetric. In addition to inlet geometry, internal flow characteristics play a significantrole in spray behavior. The outlook for this project mainly consists of the validationand development of simulation models. The obtained results provide an opportunityto correlate the near-field spray to the internal nozzle flow and study the effect ofasymmetrical inlets on the internal flow

Nonlinear Aspects of Combustion Instability in Liquid Propellant Rocket Motors. Second Yearly Progress Report for the Period 1 June 1961 to 31 May 1962

Combustion instability in liquid-propellant rocket engine

Experimental and Numerical Analysis of Ethanol Fueled HCCI Engine

Presently, the research on the homogeneous charge compression ignition (HCCI) engines has gained importance in the field of automotive power applications due to its superior efficiency and low emissions compared to the conventional internal combustion (IC) engines. In principle, the HCCI uses premixed lean homogeneous charge that auto-ignites volumetrically throughout the cylinder. The homogeneous mixture preparation is the main key to achieve high fuel economy and low exhaust emissions from the HCCI engines. In the recent past, different techniques to prepare homogeneous mixture have been explored. The major problem associated with the HCCI is to control the auto-ignition over wide range of engine operating conditions. The control strategies for the HCCI engines were also explored. This dissertation investigates the utilization of ethanol, a potential major contributor to the fuel economy of the future. Port fuel injection (PFI) strategy was used to prepare the homogeneous mixture external to the engine cylinder in a constant speed, single cylinder, four stroke air cooled engine which was operated on HCCI mode. Seven modules of work have been proposed and carried out in this research work to establish the results of using ethanol as a potential fuel in the HCCI engine. Ethanol has a low Cetane number and thus it cannot be auto-ignited easily. Therefore, intake air preheating was used to achieve auto-ignition temperatures. In the first module of work, the ethanol fueled HCCI engine was thermodynamically analysed to determine the operating domain. The minimum intake air temperature requirement to achieve auto-ignition and stable HCCI combustion was found to be 130 °C. Whereas, the knock limit of the engine limited the maximum intake air temperature of 170 °C. Therefore, the intake air temperature range was fixed between 130-170 °C for the ethanol fueled HCCI operation. In the second module of work, experiments were conducted with the variation of intake air temperature from 130-170 °C at a regular interval of 10 °C. It was found that, the increase in the intake air temperature advanced the combustion phase and decreased the exhaust gas temperature. At 170 °C, the maximum combustion efficiency and thermal efficiency were found to be 98.2% and 43% respectively. The NO emission and smoke emissionswere found to be below 11 ppm and 0.1% respectively throughout this study. From these results of high efficiency and low emissions from the HCCI engine, the following were determined using TOPSIS method. They are (i) choosing the best operating condition, and (ii) which input parameter has the greater influence on the HCCI output. In the third module of work, TOPSIS - a multi-criteria decision making technique was used to evaluate the optimum operating conditions. The optimal HCCI operating condition was found at 70% load and 170 °C charge temperature. The analysis of variance (ANOVA) test results revealed that, the charge temperature would be the most significant parameter followed by the engine load. The percentage contribution of charge temperature and load were63.04% and 27.89% respectively. In the fourth module of work, the GRNN algorithm was used to predict the output parameters of the HCCI engine. The network was trained, validated, and tested with the experimental data sets. Initially, the network was trained with the 60% of the experimental data sets. Further, the validation and testing of the network was done with each 20% data sets. The validation results predicted that, the output parameters those lie within 2% error. The results also showed that, the GRNN models would be advantageous for network simplicity and require less sparse data. The developed new tool efficiently predicted the relation between the input and output parameters. In the fifth module of work, the EGR was used to control the HCCI combustion. An optimum of 5% EGR was found to be optimum, further increase in the EGR caused increase in the hydrocarbon (HC) emissions. The maximum brake thermal efficiency of 45% was found for 170 °C charge temperature at 80% engine load. The NO emission and smoke emission were found to be below 10 ppm and 0.61% respectively. In the sixth module of work, a hybrid GRNN-PSO model was developed to optimize the ethanol-fueled HCCI engine based on the output performance and emission parameters. The GRNN network interpretive of the probability estimate such that it can predict the performance and emission parameters of HCCI engine within the range of input parameters. Since GRNN cannot optimize the solution, and hence swarm based adaptive mechanism was hybridized. A new fitness function was developed by considering the six engine output parameters. For the developed fitness function, constrained optimization criteria were implemented in four cases. The optimum HCCI engine operating conditions for the general criteria were found to be 170 °C charge temperature, 72% engine load, and 4% EGR. This model consumed about 60-75 ms for the HCCI engine optimization. In the last module of work, an external fuel vaporizer was used to prepare the ethanol fuel vapour and admitted into the HCCI engine. The maximum brake thermal efficiency of 46% was found for 170 °C charge temperature at 80% engine load. The NO emission and smoke emission were found to be below 5 ppm and 0.45% respectively. Overall, it is concluded that, the HCCI combustion of sole ethanol fuel is possible with the charge heating only. The high load limit of HCCI can be extended with ethanol fuel. High thermal efficiency and low emissions were possible with ethanol fueled HCCI to meet the current demand