Domenico Laforgia

Optimization of the Combustion Chamber of Direct Injection Diesel Engines

The optimization procedure adopted in the present investigation is based on Genetic Algorithms (GA) and allows different fitness functions to be simultaneously maximized. The parameters to be optimized are related to the geometric features of the combustion chamber, which ranges of variation are very wide. For all the investigated configurations, bowl volume and squish-to-bowl volume ratio were kept constant so that the compression ratio was the same for all investigated chambers. This condition assures that changes in the emissions were caused by geometric variations only. The spray injection angle was also considered as a variable parameter. The optimization was simultaneously performed for different engine operating conditions, i.e. load and speed, and the corresponding fitness values were weighted according to their occurrence in the European Driving Test. The evaluation phase of the genetic algorithm was performed by simulating the behavior of each chamber with a modified version of the KIVA3V code. The parameters for the sprays and the combustion models were adjusted according to the experimental data of a commercial chamber geometry taken as baseline case. Three fitness functions were defined according to engine emission levels (soot, NOx and HC) and a penalty function was used to account for engine performance. The goal of the optimization process was to select a chamber giving the best compromise of the selected fitness functions. Furthermore, chambers optimizing each single fitness function were also analyzed. The influence of the geometric characteristics on emissions has also been investigated in the paper.

Effects of Pilot Injection Parameters on Combustion for Common Rail Diesel Engines

The aim of the present work is to evaluate the influence of the pilot injection on combustion of a TDI Diesel engine for different engine torque and speed conditions. For this investigation, pilot injection timing and duration were varied on a wide range of values, and their effects on combustion pressure, rate of heat release, pilot and main combustion delay, combustion process and exhaust emissions in terms of NO x and smoke were analyzed. An in-line, four-cylinder, turbocharged FIAT 1930 cm 3 TDI Diesel engine, equipped with Common Rail injection system, was tested. A piezoelectric sensor was located in the combustion chamber in order to acquire combustion pressure; from these signals, gross heat release rate was,derived in order to analyze the combustion behavior. Pollutant emission levels have been measured by means of a gas analyzer, while for smoke an opacimeter was used. It was found that both timing and duration of pilot injection strongly influence its autoignition tendency; in particular, pilot injection autoignition mainly occurs with low values of timing and high durations. Moreover, pilot injection timing effect is more evident on pilot ignition delay than pilot duration, whereas the effect of both variables on the main ignition delay depends on the engine operating conditions. The effect of pilot injection parameters is evident on engine emission behavior too; in particular, NO x emissions levels are mainly influenced by the pilot duration, whereas pilot timing effect is more evident at lower engine load and speed. Smoke emission seems to be influenced by both variables, but their effect is stronger especially at medium and high load.

EFFECTS ON COMBUSTION AND EMISSIONS OF EARLY AND PILOT FUEL INJECTIONS IN DIESEL ENGINES

Abstract Different injection strategies applied to a common rail direct injection diesel engine were tested for different engine torque and speed conditions. The injection strategies differ for the use of early and pilot injections; during the tests the injection parameters were varied, in terms of duration and timing of early, pilot, and main injections. The combustion behaviour and the engine performances, in terms of brake specific fuel consumption, were analysed. In addition, data on nitrogen oxides (NOx), total unburned hydrocarbons, and particulate emissions were collected. The injection strategy based on both early and pilot injections has been compared with the techniques using either pilot or early injections. Results show that, particularly at lower values of engine torque and speed, the small fuel quantity injected during early injection, coupled with the pilot injection, leads to comparable levels or even to a sensible reduction in fuel consumption compared with the only-pilot or only-early injection cases. Furthermore, a reduction in NOx and particulate is generally observed, while the level of unburned hydrocarbons usually increases. Experimental tests have shown that, using the early injection, a very lean premixed charge is obtained, both globally and locally, inside the combustion chamber, thus avoiding diesel problems (in particular, high NOx and soot production), mainly caused by the locally rich mixture. On the other hand, by using the pilot injection the ignition delay of the main injection is reduced, contributing to the NOx reduction.

Numerical simulation of flow-field and dioxins chemistry for incineration plants and experimental investigation

The development of incineration units (kiln and afterburner) for hazardous wastes in terms of design and fluid-dynamic optimization has been carried out together with definition of a new design methodology. An extensive theoretical and experimental analysis has been carried out on a hazardous waste incineration pilot plant to test the methodologies and to optimize the entire system in terms of reduction of the polluting emissions and higher combustion eAciency. In particular, the combustion chamber and the afterburner have been thoroughly studied. A computer code for multiple chemical reactions occurring in an afterburner chamber of an incineration system was developed, based on the equations presented herein, to evaluate the decomposition rate of dioxins for diAerent chamber geometries. The results of these analysis are presented herein. # 2000 Elsevier Science Ltd. All rights reserved.

An innovative methodology to improve the design and the performance of direct injection diesel engines

Abstract The present investigation aims at defining a new methodology to analyse the effect of combustion chamber shape and injection strategy on diesel engine emissions and to find an optimized configuration to reduce NOx, soot and HC without significantly decreasing engine performance. This was achieved by using a multistep optimization process based on genetic algorithms. The first step was related to the optimization of combustion chamber shape for a fixed injection strategy. The optimization was firstly performed with respect to a single-pulse injection strategy and a six-hole injector design. Then the process was repeated for an innovative injection strategy characterized by the injection of a relevant quantity of fuel far from top dead centre (large early injection) and a seven-hole injector. The combustion chamber shape was defined according to five geometric parameters, whose ranges of variation were very wide. For all the investigated configurations, the bowl volume and squish-bowl volume ratio were kept constant so that the compression ratio was the same for all the investigated chambers. The spray injection angle was also considered as a variable parameter. The optimization was simultaneously performed for different engine operating conditions, i.e. load and speed values, weighted according to their occurrence in the European Driving Test. From the results of this step, an optimized chamber configuration was selected and, at the same time, the effect of each geometric characteristic on NOx and soot emissions was underlined. In the second step, the combustion chamber shape was kept constant and the optimization process was aimed at identifying an optimized injection strategy for a fixed engine operating mode. Injection pressure, pilot and main advances and pilot energizing time were considered as input for the second step of the optimization process. The numerical tools used in the investigation include a modified version of the KIVA-3V code and a multiobjective genetic algorithm. The code capability to simulate engine performance was assessed by comparing numerical results with experimental data available for the baseline engine configuration. Three fitness functions were defined according to engine emission levels (soot, NOx and HC) and a penalty function was used to account for engine performance and fuel consumption.

Energy conservation in alcohol distillery with the application of pinch technology

Abstract The energy audit of an operating distillery producing ethyl alcohol from low quality wine and wine dregs is presented. Three different processes were analyzed: the production of raw (unrefined) alcohol using stripping columns working at pressure lower than atmospheric, the same production using columns at higher pressure and the production of neutral (refined) alcohol. The operational and design data of these three processes were used to compute mass and energy balances. The liquid streams in a distillery are multicomponent nonideal solutions. The data reported in the literature for ethyl and methyl alcohol–water mixtures were utilized, together with purposely developed correlations for density, specific heat and vapor–liquid equilibrium and simplified exergy formulas. The methodologies used to study the alcohol production are based on the pinch technology approach: the detailed energy balances of the three industrial processes are presented. The main step was to present the heat sources and sinks of the production processes in the grand composite curve, laying out all the thermodynamic opportunities of any heat recovery. Thermodynamic analysis methods were used to minimize the heating energy needed by the production processes when using heat pump systems. The use of heat pump systems, mainly based on mechanical vapor re-compression, has proven to be effective in energy saving and profitable in other applications, as the concentration of gelatine, distillation of organic vapors, pulp drying and beer production. Different heat pump systems were investigated and compared with respect to fuel utilization and capital expenditures: electrical engine driven compressors, gas engine driven compressors, steam turbine driven compressors, gas absorption chillers, steam absorption chillers and thermo-vapor re-compression. It showed that the cogeneration of mechanical energy and heat to drive vapor compression (the so-called thermodynamic heating method of Frutschi et al.) is superior to other types of systems. Then, for mechanical vapor compression systems, two different applications to different production processes were analyzed: (a) a system using commercially available refrigerants and (b) a heat pump cycle using water from the bottom of the distillation columns or steam condensate as working fluid. The thermodynamic analysis, based on performance coefficients and fuel utilization, as well as the economic profitability in terms of costs, benefits and payback period, were discussed in detail.

Optimization of High Pressure Common Rail Electro-injector Using Genetic Algorithms

The aim of the present investigation is the implementation of an innovative procedure to optimise the design of a high pressure common rail electroinjector. The optimization method is based on the use of genetic programming, a search procedure developed by John Holland at the University of Michigan. A genetic algorithm (GA) creates a random population which evolves combining the genetic code of the most capable individual of the previous generation. For the present investigation an algorithm which includes the operators of crossover, mutation and elitist reproduction has been developed. This genetic algorithm allows the optimization of both single and multicriteria problems. For the determination of the multi-objective fitness function, the concept of Pareto optimality has been implemented. The performance of the multiobjective genetic algorithm was examined by using appropriate mathematical functions and was compared with the single objective one. The proposed genetic algorithm was used to define the geometrical and dynamic characteristics of high pressure injectors that optimize the injection profile and the time response of the system. As evaluation function for the GA a 1D simulation code of injection systems, already developed and extensively tested by the authors, has been used. The 1D model is based on the concentrated volume method and includes the effect of friction on the dynamics of the movable parts. The conservation equations were integrated by using the characteristic method. The electromagnetic force on the anchor of the injector has been simulated with an empirical function obtained by fitting experimental data. For the optimization the geometrical and dynamical data of a commercial five holes VCO injector were used as baseline case and the best combination of different groups of parameter has been found. The optimized combinations of the investigated parameters were compared with the original values of the commercial injector. Finally a feasibility analysis of the optimized parameters was performed.

Modelling and Simulation of a Hydraulic Breaker

Abstract This paper deals with the simulation of the working behaviour of a hydraulic breaker. A detailed parameterised model was realized in order to simulate physical phenomena occurring during the functioning of the machine. An appreciable agreement between experimental and theoretical pressure and frequency encouraged about the quality of the model. The dynamic behaviour of the moving masses was presented and thoroughly discussed. As a special remark, it is to be highlighted that the theoretical results suggested by the model came out not to vary if the real waveform concerning input flow rate is replaced with its average.

Experimental and Numerical Investigations of Cavitating Flows

Cavitating flows have been investigated using both numerical and experimental methods. Three different cavitation models, based on mechanical or thermal equilibrium hypotesis, have been implemented in a general-purpose CFD code. As an external flows example, the behavior of a NACA 0015 hydrofoil was investigated. The cavitating flow field over the hydrofoil was predicted, and the results compared with experimental data, reported in literature. The general characteristics of the cavitating flow were well predicted. Especially, the cavity length was calculated with reasonable accuracy. Further, the cavitation models were applied to flows through an orifice, and the computed results were compared with the experimental observations, obtained with a CCD camera. The cavitation originates at the inlet of the flow constriction area. It grows intensively and transforms into a dense cloud. Shedding is observed in this stage. As flow rate was increased, it was observed that the cloud travels downstream of the hole oscillating about the exit position and it is connected to the hole inlet through a sheet having a complex turbulent structures.

An Integrated Tool to Monitor Renewable Energy Flows and Optimize the Recharge of a Fleet of Plug-In Electric Vehicles in the Campus of the University of Salento: Preliminary Results

A tool has been developed to integrate electric vehicles into a general systems for the energy management and optimization of energy from renewable sources in the Campus of the University of Salento. The tool is designed to monitor the status of plug-in vehicles and recharging station and manage the recharging on the basis of the prediction of power from the photovoltaic roofs and usage of electricity in three buildings used by the Department of engineering. The tool will allow the surplus of electricity from photovoltaic to be used for the recharge of the plug-in vehicles. In the present investigation, the benefits in terms of CO2 and costs of the scheduled recharge with respect to free recharge are evaluated on the basis of the preliminary data acquired in the first stage of the experimental campaign.