The effects of injection timing on NOx emissions of a low heat rejection indirect diesel injection engine

Higher NO_x is one of the major problems to be overcomed in a low heat rejection (LHR) diesel engine as insulation leads to an increase in combustion temperature about 200–250 °C compared to an identical standard (STD) diesel engine. High combustion temperatures alter optimum injection timing of a LHR engine. With the proper adjustment of the injection timing, it is possible to partially offset the adverse effect of insulation on heat release rate and hence to obtain improved performance and lower NO_x. However, the injection timing and brake specific fuel consumption (BSFC) trade-off must be considered together in performance and NO_x emission point of view. In this study, optimum injection timing was found with 4 crank angle (34° CA) retarded before top dead centre (BTDC) in LHR diesel engine in comparison to that of STD diesel engine (38° CA BTDC). When the LHR engine was operated with the injection timing of the 38 crank angle, which is the optimum value of the STD engine, it was shown that NO_x emission increased about 15%. However, when the injection timing was retarded to 34° CA in the LHR case, it was observed a decrease on the NO_x emissions with about 40% and the brake specific fuel consumption (BSFC) with about 6% compared to that of the STD case. Thus, by retarding the injection timing, an additional 1.5% saving in fuel consumption was obtained.     

A Finite Volume Analysis of Thermoelectric Generators

ABSTRACT

The electric power produced by a thermoelectric generator (TEG) is strongly influenced by the applied heat sink. While a TEG is aimed at harvesting waste heat, the optimization of the efficiency of the heat sink is a key task for the design of waste heat recovery systems implementing TEG. A TEG model is proposed and implemented in an open source toolbox for field operation and manipulation (OpenFOAM) for the purpose of performing optimizations of the heat sink, using a commercially available TEG as basis. This model includes the multi-physics thermoelectric coupled effects. Conservation principles of energy and current are considered simultaneously. This includes the thermal and electric conduction, Seebeck effect, Peltier effect, Thomson effect, and Joule heating. Particular attention is given to a proper modeling of the boundary conditions. The thermoelectric model is implemented in such a way that it can readily be combined with other physical models in OpenFOAM. The model is validated by comparing the predictions to analytical results, measurements as well as the simulation data of other authors.     

Statistical phase-shifting step estimation algorithm based on the continuous wavelet transform for high-resolution interferometry metrology

We propose a statistical phase-shifting estimation algorithm for temporal phase-shifting interferometry (PSI) based on the continuous wavelet transform (CWT). The proposed algorithm explores spatial information redundancy in the intraframe interferogram dataset using the phase recovery property on the power ridge of the CWT. Despite the errors introduced by the noise of the interferogram, the statistical part of the algorithm is utilized to give a sound estimation of the phase-shifting step. It also introduces the usage of directional statistics as the statistical model, which was validated, so as to offer a better estimation compared with other statistical models. The algorithm is implemented in computer codes, and the validations of the algorithm were performed on numerical simulated signals and actual phase-shifted moiré interferograms. The major advantage of the proposed algorithm is that it imposes weaker conditions on the presumptions in the temporal PSI, which, under most circumstances, requires uniform and precalibrated phase-shifting steps. Compared with other existing deterministic estimation algorithms, the proposed algorithm estimates the phase-shifting step statistically. The proposed algorithm allows the temporal PSI to operate under dynamic loading conditions and arbitrary phase steps and also without precalibration of the phase shifter. The proposed method can serve as a benchmark method for comparing the accuracy of the different phase-step estimation methods.     

SYNTHESIS AND CHARACTERIZATION OF A METHACRYLATE POLYMER WITH SIDE CHAIN KETONE AND ITS DERIVATIVES

A new type of methacrylate monomer, 2-(4-benzoylphenoxy)-2-oxoethyl methylacrylate (BOEMA) was synthesized. The radical homopolymerization of BOEMA was performed at 65℃ in a 1,4-dioxane solution with benzoyl peroxide as an initiator. The oxime and thiosemicarbazone derivatives of poly[2-(4-benzoylphenoxy)-2-oxoethyl methylacrylate] poly(BOEMA) were prepared with hydroxylamine hydrochloride, and thiosemicarbazone hydrochloride, respectively. The monomer and its homopolymer were characterized with Fourier transform infrared and NMR techniques. The thermal stabilities of poly(BOEMA) and its derivatives were investigated with thermogravimetric analysis and differential scanning calorimetry. The ultraviolet stability of the polymers was compared. The antibacterial and antifungal effects of the monomer and the polymer and its derivatives were also investigated on various bacteria and fungi. The activation energies of the thermal degradation of the polymers were calculated with the Ozawa and Kissinger methods.     

Energy and cost analysis for greenhouse and open-field grape production

The objective of this study was to examine the energy use patterns and cost of production in greenhouse and open-field grape production. Data used in the study were obtained from the experiment conducted at the Akdeniz university research field. In the study, energy values were calculated by multiplying the amount of inputs and outputs by the related energy conversion factors. The results indicated that total input energy use in greenhouse and open-field production was found to be 24513.0 and 23640.9 MJ/ha, respectively. However, the output energy of greenhouse grapes (73396.0 MJ/ha) was lower than open-field grapes (120596 MJ/ha). The output–input ratio for greenhouse and open-field grape production was found to be 2.99 and 5.10, respectively. The economic analysis revealed that production costs for greenhouse grapes were higher than open-field grapes but greenhouse grapes were more profitable than open-field due to premium prices for greenhouse grapes.     

Rigid suspensions in viscous fluid

In a previous paper [1]I presented a continuum theory of rigid suspensions. In this work the effect of the torque (due to surrounding viscous fluid) on the rotations of fibers was ignored. Here I consider this effect.     

Electrochemical synthesis of EDOT–ECZ–EDOT copolymer on carbon fiber micro-electrodes

3,6 bis(3,4-ethylenedioxythiophenyl)-9-Ethylcarbazole (EDOT-ECZ-EDOT or EEE) films are coated electrochemically onto carbon fiber micro-electrodes. Deposition conditions on the electroactivity of the resulting polymers are studied. Structural studies of the polymers have been conducted using different techniques such as cyclic voltammetry, ATR-FTIR, scanning electron microscopy and four-point probe conductivity.     

Gain–bandwidth limitations of microwave transistor

This work enables one to obtain the potential gain (G_T) characteristics with the associated source (Z_S) and load (Z_L) termination functions, depending upon the input mismatching (V_i), noise (F), and the device operation parameters, which are the configuration type (CT), bias conditions (V_DS, I_DS), and operation frequency (f). All these functions can straightforwardly provide the following main properties of the device for use in the design of microwave amplifiers with optimum performance: the extremum gain functions (G_{T max}, G_{T min}) and their associated Z_S, Z_L terminations for the V_i and F couple and the CT, V_DS, I_DS, and f operation parameters of the device point by point; all the compatible performance (F, voltage–standing wave ratio V_i, G_T) triplets within the physical limits of the device, which are F ≥ F_min, V_i ≥ 1, G_{T min} ≤ G_T ≤ G_{T max}, together with their Z_S, Z_L termination functions; and the potential operation frequency bandwidth for a selected performance (F, V_i, G_T) triplet. The selected performance triplet and termination functions can be realized together with their potential operation bandwidth using the novel amplifier design techniques. Many examples are presented for the potential gain characteristics of the chosen low‐noise or ordinary types of transistor. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 483–495, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10049