Bi-fuel SI Engine Model for Analysis and Optimization

YesThe natural gas as an alternative fuel has economical and environmental benefits. Bi-fuel engines powered by gasoline and compressed natural gas (CNG) are an intermediate and alternative step to dedicated CNG engines. The conversion to bi-fuel CNG engine could be a short-term solution to air pollution problem in many developing countries. In this paper a mathematical model of a bi-fuel four-stroke spark ignition (SI) engine is presented for comparative studies and analysis. It is based on the two-zone combustion model, and it has the ability to simulate turbulent combustion. The model is capable of predicting the cylinder temperature and pressure, heat transfer, brake work , brake thermal and volumetric efficiency, brake torque, brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). The effect of engine speed, equivalence ratio and performance parameters using gasoline and CNG fuels are analysed. The model has been validated by experimental data using the results obtained from a bi-fuel engine. The results show the capability of the model in terms of engine performance optimization and minimization of the emissions. The engine used in this study is a typical example of a modified bi-fuel engine conversion, which could benefit the researchers in the field

Numerical modelling of an H-type Darrieus wind turbine performance under turbulent wind

This paper presents the force interaction between fluid flow and a rotating H-type Darrieus vertical axis wind turbine. The main goal of this study is to determine the wind rotor’s performance characteristics under turbulent wind: torque M = f (n), normal force FN = f (n), output power P = f (n) and the aerodynamic characteristics CM = f (λ), CN = f (λ), CP = f (λ). The flow passing through the turbine has a complex structure due to the rotation of the rotor. The constantly changing angular position of the turbine’s blades is leading to a variation in the blades angle of attack. This angle can vary from positive to negative values in just a single turbine revolution. The constant fluctuations of the angle of attack are the main factor which leads to the unsteady nature of the flow passing through the turbine. At low tip-speed ratios, the phenomena deep dynamic stall occurs which leads to intensive eddy generation. When the turbine is operating at higher tip-speed ratio the flow is mainly attached to the blades and the effect of the dynamic stall over the turbine performance is from weak to none. The Darrius turbine performance characteristics are obtained through a numerical investigation carried out for several tip-speed ratios. The used CFD technique is based upon the URANS approach for solving the Navier-Stokes equations in combination with the turbulence model k – ω SST. Also, a numerical sensitive study concerning some of the simulation parameters is carried out

Ojačanje spojeva između LVL elemenata polimerima ojačanim staklenim vlaknima i analiza metodom konačnih elemenata

The goal of this study was to investigate the effect of glass fiber reinforced polymer (GFRP) on joints made of laminated veneer lumber (LVL), through experimental data and evaluation by ANSYS finite element (FE) software. In order to fabricate LVL, veneer from poplar (Populus deltoides Bartr. ex Marsh) with 2.5 mm thickness and PVA adhesive were used. T-shape joints out of LVL were made and two wooden dowels were incorporated as well. Then GFRP was applied to reinforce the joints. GFRP in three grammages (100, 200 and 300 g/ m2) was adhered to joints with epoxy resin. Joints reinforcement was performed by a two-layer reinforcing agent. For comparing the effectiveness, half of the specimens were reinforced on sides and the other half on edges. Specimens were tested in static bending. The results have shown that GFRP had a significant effect on the strength of joints. Reinforced joints on both sides were stronger than those reinforced on edge. Joints reinforced with 300 g/m2 GFRP were improved by 35 % and 43 %, respectively, compared to 100 and 200 g/m2 grammage. Failure modes of specimens are dependent on GFRP grammage. The results of FE have shown that the highest concentration of stress and elastic strain was generated in the tension and compression zones of joints.Cilj rada bio je na temelju eksperimentalnih podataka i analize konačnih elemenata (FE) te uz pomoć softvera ANSYS istražiti utjecaj polimera ojačanog staklenim vlaknima (GFRP) na spojeve od lamelirane drvne građe (LVL). Za izradu LVL-a upotrijebljen je furnir drva topole (Populus deltoides Bartr. ex Marsh) debljine 2,5 mm i PVA ljepilo. Izrađeni su T-spojevi od LVL-a i ugrađena su dva drvena moždanika. Zatim je za ojačanje spojeva primijenjen GFRP u tri gramature (100, 200 i 300 g/m2) tako da je epoksidnom smolom zalijepljen na spojeve. Ojačanje spojeva izvedeno je dvoslojnim armaturnim sredstvom. Radi usporedbe učinkovitosti, polovica uzoraka ojačana je sa strane, a druga polovica na rubovima. Uzorci su ispitani na statičko savijanje. Rezultati su pokazali da GFRP ima značajan utjecaj na čvrstoću spojeva. Spojevi ojačani s obje strane bili su jači od onih ojačanih na rubu. Spojevi ojačani GFRP-om od 300 g/m2 poboljšani su za 35 % odnosno za 43 % u usporedbi s GFRP-om gramature100 i 200 g/m2. Načini loma uzoraka ovisili su o gramaturi GFRP-a. Rezultati analize konačnih elemenata pokazali su da se najveća koncentracija naprezanja i elastične deformacije pojavljuje u vlačnoj i tlačnoj zoni spojeva

Heat exchanger dynamic analysis

The modeling and dynamic analysis of shell and tube heat exchangers will be considered in this contribution. Procedures which incorporate the heat transfer and the fluid flow system properties, for these processes, will be developed. An incremental, energy balance yielding the system, partial differential equations presents the governing process. The multivariable, multi-dimensional, Laplace transformed, distributed parameter formulation of heat exchanger representations, are provided. A frequency domain description of the system model is derived enabling the recovery of Laplace function rationality for both parallel and counter flow heat exchanger models. Suitable feedback control techniques are identified, as a prelude to closed loop design studies. The dynamics, for tubular heat exchangers are computed, for purposes of comparison with alternative response and regulation approaches. A typical application study is outlined

Some New Concepts of Shape Memory Effect of Polymers

In this study some new concepts regarding certain aspects related to shape memory polymers are presented. A blend of polylactic acid (PLA) (80%) and polybutylene succinate (PBS) (20%) was prepared first by extrusion, then by injection molding to obtain the samples. Tensile, stress-relaxation and recovery tests were performed on these samples at 70 °C. The results indicated that the blend can only regain 24% of its initial shape. It was shown that, this partial shape memory effect could be improved by successive cycles of shape memory tests. After a fourth cycle, the blend is able to regain 82% of its shape. These original results indicated that a polymer without (or with partial) shape memory effect may be transformed into a shape memory polymer without any chemical modification. In this work, we have also shown the relationship between shape memory and property memory effect. Mono and multi-frequency DMA (dynamic mechanical analyzer) tests on virgin and 100% recovered samples of polyurethane (PU) revealed that the polymer at the end of the shape memory tests regains 100% of its initial form without regaining some of its physical properties like glass transition temperature, tensile modulus, heat expansion coefficient and free volume fraction. Shape memory (with and without stress-relaxation) tests were performed on the samples in order to show the role of residual stresses during recovery tests. On the basis of the results we have tried to show the origin of the driving force responsible for shape memory effect

Holistic simulation for integrated vehicle design

A holistic vehicle simulation capability is necessary for front-loading component, subsystem, and controller design, for the early detection of component and subsystem design flaws, as well as for the model-based calibration of powertrain control modules. The current document explores the concept of holistic vehicle simulation by means of reviewing the current trends automotive system design and available solutions in terms of model interfaces and neutral modelling environments. The review is followed by the presentation of a Simulink-based Multi- disciplinary Modelling Environment (MME) developed by the authors to accommodate simulation work across the vehicle development cycle

Internal combustion engine model for combined heat and power (CHP) systems design

A model based, energy focused, quasi-stationary waste heat driven, internal combustion engine (ICE) centred design methodology for cogeneration (heat and electricity) systems is presented. The developed parametric model could be used for system sizing, performance evaluation, and optimization. This paper presents a systematic approach to model the behaviour of the CHP system using heat recovery prediction methods. The modular, physics based modelling environment shows the power flow between the system components, with a special emphasis on the ICE subsystems, parameter identification, and model validation

Clonk: an onomatopoeic response in torsional impact of automotive drivelines

Vehicular driveline is a lightly damped non-linear dynamic system that is prone to noise and vibration response when subjected to excitation. There are many sources of excitation such as torsional impact caused by the take-up of backlash in the powertrain system. Such sources of excitation exist in transmission backlash, in driveline splines and in pinion-ring gear contact in the differential. Abrupt application or release of the throttle in slow moving traffic or rapid engagement of the clutch can be followed by an onomatopoeic response of the driveshafts, referred to in the industry as clonk. This is a disagreeable, audible and tactile response in some vehicles and can also coincide with every cycle of low-frequency longitudinal vehicle response, commonly referred to as shuffle or shunt. This paper describes the phenomenon of clonk and investigates its occurrence both by an experimental technique and by detailed modal analysis of driveshaft pieces. It is shown that finite element predictions agree well with the experimental findings and that the high-frequency structural modes can lead to discernible radiated noise. The preliminary findings reported here point to a need for a more detailed elasto-acoustic analysis

A hybrid model for a drilling process for hydrocarbon well-boring operations

In hydrocarbon well-drilling operations, self-excited, stick-slip vibration is considered as a source of drilling equipment failures, which also causes a reduction in the drilling penetration. This leads to delays and increase in the operational and equipment costs. A new approach using distributed-lumped (hybrid) modelling is considered as the first step in understanding the stick-slip phenomena in order to determine a solution to this problem. In this paper, a hybrid modelling scheme is the advocated modelling method proposed in contrast to the conventional lumped modelling. Three case studies are used to show that hybrid modelling is an accurate technique in the representation of stick-slip oscillations, particularly when the length of the drill string is high. The results show that the modelling technique adopted in this work can more accurately present the phenomena associated with stick-slip process

Production and Characterization of Biosurfactants Using Bacteria Isolated from Acidic Hot Springs

  Background and objective: Biosurfactants are increasingly used by food industries due to their low toxicities and unique structures. In this study, biosurfactants were produced and characterized for the first time using acidic bacteria isolated from acidic hot springs in Bushehr Province, Iran. Material and methods: Screening and identification of the most efficient species for biosurfactant production were carried out on 12 bacterial species using several experiments such as hemolysis, surface tension, emulsification index and diameter of clear zone. In addition to biosurfactant production, kinetics, stability and structural and thermal analysis were carried out for the bacterial strains using thin layer chromatography, Fourier Transform Infrared, nuclear magnetic resonance and differential scanning calorimetry. Results and conclusion: The biosurfactant from the selected bacteria (0.1 g l-1) was thermally stable at 120°C for 30 min. Stability at temperatures up to 140°C was confirmed using differential scanning calorimetry. The most significant novelty included the fact that the surface property was preserved until an osmolarity of 4% w v-1. Decreased surface tension and the emulsification potential were only reported at concentrations higher the highlighted concentration. Biological assay showed that Staphylococcus aureus was susceptible to produced biosurfactants, while no susceptibility was seen in Escherichia coli. Degeneration of SW480 cell line exposed to 0.601 µg µl-1 of the biosurfactant was detected after 24 h. The structural analysis showed that the biosurfactant was similar to surfactin as a food bioemulsifier. Conflict of interest: The authors declare that they have no conflict of interest