Atilla Bilgin

The effects of diesel-ethanol blends on diesel engine performance

The performance of a variable compression ratio compression ignition engine operating on ethanol-diesel fuel blends has been evaluated experimentally. We aimed to determine the optimum percentage of ethanol and the compression ratio of the engine that give the best performance and efficiency at the same time. The engine was operated with ethanol-diesel fuel blends having 2, 4, and 6% ethanol on a volume basis as well as on diesel fuel alone. The experiments were performed for the compression ratios of 19, 21, and 23. Experimental results indicate that the addition of 4% ethanol to diesel fuel increases power output and efficiency of the engine while it decreases specific fuel consumption for various compression ratios. The best efficiency was attained at the compression ratio of 21 with an increment ratio over 3.5%.

Exergy analysis of SI engines

In this study, exergy (availability) analysis of a Spark Ignition (SI) engine has been performed theoretically during compression, combustion and expansion processes of the engine cycle. For this purpose, a thermodynamic-based engine cycle model is developed without considering the geometric features of fluid motion. Through the analysis, the effects of changing some design and operating parameters, such as compression ratio, fuel-air equivalence ratio and spark timing on the variation and destruction of exergy have been investigated. It was obtained that design and operation conditions have considerable effects on the variation of exergy and irreversibilities during investigated parts of the cycle.

Mathematical analysis of spark ignition engine operation via the combination of the first and second laws of thermodynamics

This study aims at the theoretical exergetic evaluation of spark ignition engine operation. For this purpose, a two-zone quasi-dimensional cycle model was installed, not considering the complex calculation of fluid motions. The cycle simulation consists of compression, combustion and expansion processes. The combustion phase is simulated as a turbulent flame propagation process. Intake and exhaust processes are also computed by a simple approximation method. The results of the model were compared with experimental data to demonstrate the validation of the model. Principles of the second law are applied to the model to perform the exergy (or availability) analysis. In the exergy analysis, the effects of various operational parameters, i.e. fuel–air equivalence ratio, engine speed and spark timing on exergetic terms have been investigated. The results of exergy analysis show that variations of operational parameters examined have considerably affected the exergy transfers, irreversibilities and efficiencies. For instance, an increase in equivalence ratio causes an increase in irreversibilities, while it decreases the first and also the second law efficiencies. The irreversibilities have minimum values for the specified engine speed and optimum spark timing, while the first and second law efficiencies reach a maximum at the same engine speed and optimum spark timing.

Numerical simulation of the cold flow in an axisymmetric non-compressing engine-like geometry

Fluid motion within the cylinder of a piston engine has a major influence on the performance of the engine. The general motion within the cylinder and the associated turbulence affect the charge stratification, combustion and heat transfer processes. In order to predict the charge stratification, one must understand and be able to predict the turbulent mixing processes (Reynolds, 1980). There are numerous alternative turbulence modelling approaches of varying degrees of complexity, but two of them, k-e turbulence models and Reynolds stress models, are commonly used in engine modelling activities. In the present study, k-e turbulence model was used to predict the flow in the cylinder of a non-compressing engine-like configuration. Wall function treatment was employed in order to bridge the wall layer to the inner region. Finite volume method incorporated with hybrid (central/upwind) spatial and implicit temporal schemes, and SIMPLE algorithm (Patankar, 1980) were used to obtain numerical solutions. Results were compared with the measurements of Morse et al. (1978) and predictions of Gosman et al. (1980). Although the degree of agreement between the predictions and the measurements varies throughout the cycle and the flow field, the overall agreement is found to be satisfactory.

Exergy and energy analysis with economic aspects of a diesel engine running on biodiesel-diesel fuel blends

In this paper, energy, exergy and economic evaluation of a single cylinder diesel engine fuelled with diesel fuel and two types of biodiesel-diesel fuel blends (i.e., B10 and B50) were conducted by evaluating experimental data. Experiments were carried out at five different engine speeds and full load conditions. Energy and exergy components of the engine were calculated and compared for each operating conditions and test fuels. Results obtained from biodiesel-diesel fuel blends were found to be better than neat diesel fuel in respect of both energy and exergy analysis. The maximum brake thermal efficiency and exergy efficiency of the test engine were found to be 40.41% and 37.83%, respectively, at 2000 rpm for B10. Also, the minimum exergy destruction occurred at 2000 rpm for all test fuels. However, from the point of specific fuel costs, B10 and B50 gave quite higher economic costs in compared to diesel fuel. Since fuel price per litre of biodiesel is quite higher than diesel fuel, higher biodiesel rates in the blend dominate increase in specific fuel costs even specific fuel consumption decrease.

Development of Two-Dimensional Models for Estimating Densities of Biodiesel-Diesel-Alcohol Ternary Blends

Recently, biodiesel has become one of the most significant clean alternative biofuels because of many advantages. However, it has also some shortcomings such as: higher density and viscosity. The high density of biodiesel can cause an increase in the fuel consumption and NOX emissions. In order to overcome this problem, the blending of biodiesel with diesel fuel or alcohols is generally recommended in the existing literature. Although many one-dimensional models are proposed by different authors for predicting fuel properties of biodiesel-diesel binary blends, two-dimensional models are still inadequate for estimating densities of biodiesel-diesel fuel-alcohol ternary blends. Therefore, in this study, (1) densities of waste cooking oil biodiesel-diesel fuel-ethanol ternary blends were measured at different temperatures (278.15 K–343.15 K) according to ISO test method, and (2) some two-dimensional models, previously suggested by the authors, were fitted to the density data of ternary blends obtained from the authors and specialized literature to determine the best correlation for prediction of density. The quadratic surface model is found to be best predictor to estimate densities of ternary blends.

Temperature Dependence of Densities of Different Biodiesel-Diesel-Alcohol Ternary Blends

In this study, waste cooking oil ethyl ester (biodiesel) was produced via basic transesterification reaction, ethyl ester-diesel-methanol ternary blends including different volume ratios of alcohol (2% and 4%) were prepared, densities of the ternary blends were measured at different temperatures (278.15 K, 283.15 K, 288.15 K, 293.15 K, 298.15 K, 303.15 K, 308.15 K, 313.15 K, 318.15 K, 323.15 K, 328.15 K, and 333.15 K) according to ISO 4787 standard, and the exponential model as a function of temperature was derived using the least squares method to predict density values. Moreover, the exponential model was compared to the well-known linear model, and the reliability of these models was investigated using the density data of rapeseed oil methyl ester-diesel-bioethanol ternary blends measured by Barabas. According to result, the exponential model, suggested by the authors, qualitatively and quantitatively better reflects the variations in densities of different biodiesel-diesel-alcohol ternary blends measured by the authors and Barabas.

Effects of Temperature and Biodiesel Fraction on Dynamic Viscosities of Commercially Available Diesel Fuels and Its Blends with the Highest Methyl Ester Yield Corn Oil Biodisel Produced by Using KOH

The objective of this chapter is to determine the effects of biodiesel fraction in blend (X) and temperature (T) on dynamic viscosities of the highest methyl ester content corn oil biodiesel and its blends with commercially available diesel fuel. For this objective, first, the highest methyl ester content corn oil biodiesel was produced by using potassium hydroxide (KOH) as catalyst and methanol (CH3OH) as alcohol, and the biodiesel was blended with commercially available diesel fuel at the volume ratios of 5, 10, 15, and 20%. Then, dynamic viscosities of pure biodiesel and diesel fuel, their blends were measured at different temperatures of 10, 20, 30, and 40 °C by following DIN 53015 test methods. From the obtained experimental data, one- and two-dimensional models as a function of X or T were derived using the least square regression for estimating dynamic viscosity values of pure fuels or fuel blends. Also, these models were compared to previously published models and measurements to show their validities. According to regression analysis results, among the proposed one-dimensional models, rational ones such as μ = μ(X) = (aX + 1)/(b + cX) with minimum correlation coefficient (R) value of 0.9942 and maximum error value of 4.5976%, μ = μ(X) = (a ∙ X + 1)/(b + c ∙ X) and power ones such as μ = μ(T) = aTb + c with minimum R value of 0.9914 and maximum error value of 3.9733% better represent the dynamic viscosity–biodiesel fraction and dynamic viscosity–temperature relationship, respectively, and these models give higher accuracies for predicting viscosity values. Also, two-dimensional combination surface model including exponential and linear terms such as μ = μ(T, X) = a ∙ ebT + c ∙ edX + eX with the higher R value of 0.9952 and lower maximum error value of 3.2319% was recommended for demonstrating the variations in dynamic viscosity values with respect to biodiesel fraction and temperature simultaneously. Furthermore, the quality of the corn oil biodiesel and its blends were evaluated by determining the other important fuel properties, such as kinematic viscosity, flash point temperature, and higher heating value.

Regression Models for Predicting Some Important Fuel Properties of Corn and Hazelnut Oil Biodiesel–Diesel Fuel Blends

Abstract This chapter deals with the derivation of one-dimensional models to estimate some important fuel features of different biodiesel–diesel fuel (DF) blends. For the derivation of the models, biodiesels were synthesized through a transesterification reaction using hazelnut and corn oils, and the produced biodiesels were mixed with DF at 5%, 10%, 15%, 20%, 50%, and 75% on a volume basis. The kinematic viscosity, higher heating value, and flash point of the prepared Corn oil biodiesel–DF and Hazelnut oil biodiesel–DF blends were determined according to the related international standards. One-dimensional models were derived through the least squares regression method to estimate these fuel features. For all models that were tried, calculated regression constants and correlation coefficients are given as tables.

Exergetic Analysis of Using the Gaseous Fuels in Spark Ignition Engines

This paper aims to investigate the use of alternative gaseous fuels in spark ignition engines via an exergy analysis. A quasi-dimensional two-zone thermodynamic cycle model is used for this purpose. The intake and exhaust processes are computed by a simple approximation method, and the processes (that is, compression, combustion, and expansion) are simulated in detail. The turbulent flame propagation process is used for the combustion simulation. The second law of thermodynamics is applied to the cycle model to perform the exergy analysis. The exergy transfers associated with heat, work, and exhaust; the irreversibilities, thermomechanical exergy, fuel chemical exergy, and total exergy have been computed in the exergy analysis. A distribution of the fuel exergy, the energy-based (the first law) efficiency, and the exergetic (the second law) efficiency were also calculated during the exergy analysis. Thus, the effects of using natural gas and liquefied petroleum gas on the exergetic terms and the efficienc...