Mustafa Canakci

BIODIESEL PRODUCTION FROM OILS AND FATS WITH HIGH FREE FATTY ACIDS

Biodiesel is an alternative fuel for diesel engines consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Most of the biodiesel that is currently made uses soybean oil, methanol, and an alkaline catalyst. The high value of soybean oil as a food product makes production of a cost–effective fuel very challenging. However, there are large amounts of low–cost oils and fats such as restaurant waste and animal fats that could be converted to biodiesel. The problem with processing these low cost oils and fats is that they often contain large amounts of free fatty acids (FFA) that cannot be converted to biodiesel using an alkaline catalyst. In this study, a technique is described to reduce the free fatty acids content of these feedstocks using an acid–catalyzed pretreatment to esterify the free fatty acids before transesterifying the triglycerides with an alkaline catalyst to complete the reaction. Initial process development was performed with synthetic mixtures containing 20% and 40% free fatty acids, prepared using palmitic acid. Process parameters such as the molar ratio of alcohol, type of alcohol, acid catalyst amount, reaction time, and free fatty acids level were investigated to determine the best strategy for converting the free fatty acids to usable esters. The work showed that the acid level of the high free fatty acids feedstocks could be reduced to less than 1% with a 2–step pretreatment reaction. The reaction mixture was allowed to settle between steps so that the water–containing alcohol phase could be removed. The 2–step pretreatment reaction was demonstrated with actual feedstocks, including yellow grease with 12% free fatty acids and brown grease with 33% free fatty acids. After reducing the acid levels of these feedstocks to less than 1%, the transesterification reaction was completed with an alkaline catalyst to produce fuel–grade biodiesel.

COMPARISON OF ENGINE PERFORMANCE AND EMISSIONS FOR PETROLEUM DIESEL FUEL, YELLOW GREASE BIODIESEL, AND SOYBEAN OIL BIODIESEL

Biodiesel is a non-toxic, biodegradable and renewable alternative fuel that can be used with little or no engine modifications. Biodiesel is currently expensive but would be more cost effective if it could be produced from low-cost oils (restaurant waste, frying oils, animal fats). These low-cost feedstocks are more challenging to process because they contain high levels of free fatty acids. A process for converting these feedstocks to fuel-grade biodiesel has been developed and described previously. The objective of this study was to investigate the effect of the biodiesel produced from high free fatty acid feedstocks on engine performance and emissions. Two different biodiesels were prepared from animal fat-based yellow grease with 9% free fatty acids and from soybean oil. The neat fuels and their 20% blends with No. 2 diesel fuel were studied at steady-state engine operating conditions in a four-cylinder turbocharged diesel engine. Although both biodiesel fuels provided significant reductions in particulates, carbon monoxide, and unburned hydrocarbons, the oxides of nitrogen increased by 11% and 13% for the yellow grease methyl ester and soybean oil methyl ester, respectively. The conversion of the biodiesel fuels energy to work was equal to that from diesel fuel.

Energy and Exergy Analyses of a Diesel Engine Fuelled with Various Biodiesels

This study deals with comparative energy and exergy analyses of a four-cylinder turbocharged diesel engine using two different biodiesel fuels, petroleum diesel fuel, and blends of the biodiesels with petroleum diesel. Utilizing experimental data obtained from steady-state tests, balances of energy and exergy rates for the engine were determined. Then, various performance parameters of the engine were evaluated for each fuel operation. It was found that the tested biodiesels offer almost the same energetic performance as petroleum diesel fuel, while the exergetic performance parameters usually follow similar trends with the corresponding energetic ones.

Biodiesel production from vegetable oil and waste animal fats in a pilot plant

In this study, corn oil as vegetable oil, chicken fat and fleshing oil as animal fats were used to produce methyl ester in a biodiesel pilot plant. The FFA level of the corn oil was below 1% while those of animal fats were too high to produce biodiesel via base catalyst. Therefore, it was needed to perform pretreatment reaction for the animal fats. For this aim, sulfuric acid was used as catalyst and methanol was used as alcohol in the pretreatment reactions. After reducing the FFA level of the animal fats to less than 1%, the transesterification reaction was completed with alkaline catalyst. Due to low FFA content of corn oil, it was directly subjected to transesterification. Potassium hydroxide was used as catalyst and methanol was used as alcohol for transesterification reactions. The fuel properties of methyl esters produced in the biodiesel pilot plant were characterized and compared to EN 14214 and ASTM D6751 biodiesel standards. According to the results, ester yield values of animal fat methyl esters were slightly lower than that of the corn oil methyl ester (COME). The production cost of COME was higher than those of animal fat methyl esters due to being high cost biodiesel feedstock. The fuel properties of produced methyl esters were close to each other. Especially, the sulfur content and cold flow properties of the COME were lower than those of animal fat methyl esters. The measured fuel properties of all produced methyl esters met ASTM D6751 (S500) biodiesel fuel standards.

Comparison of performance and combustion parameters in a heavy-duty diesel engine fueled with iso-butanol/diesel fuel blends

This study discusses the suitability of iso-butanol/diesel fuel blends as an alternative fuel and determines their effects on the performance and combustion characteristics of a heavy-duty diesel engine. For this purpose, various iso-butanol/diesel fuel blends containing 5%, 10% and 15% iso-butanol were prepared in volume basis and tested in a turbo-charged, six-cylinder direct injection diesel engine at the speed of 1400 rpm and three different loads (150, 300 and 450 Nm). The results indicate that when the test engine was fueled with the iso-butanol/diesel fuel blends, the brake thermal efficiency decreased, while the brake specific fuel consumption increased with proportion to using conventional diesel fuel. When iso-butanol/diesel fuel blends were used, the heat release rate, the peak cylinder gas pressure slightly increased compared to the neat diesel fuel use. Although the iso-butanol/diesel fuel blends have poor performance values at partial engine loads, their fuel properties affected the combustion and injection characteristics. They caused reductions in CO, NOx emissions and smoke opacity. However, unburned HC emission slightly increased.

Numerical Evaluation by Models of Load and Spark Timing Effects on the In-Cylinder Heat Transfer of a SI Engine

The aim of this study is to examine numerically the effects of spark timing and load parameters on the in-cylinder heat transfer of a SI engine by using experimental engine test data. For the investigation, a four-stroke, air-cooled, single-cylinder SI engine was tested at different spark timings and loads at a single engine speed of 2000 rpm. Woschni, Hohenberg, and Han models were employed to estimate the in-cylinder heat transfer coefficient in the case of different test conditions because of being favorable models on the SI engine operations. The evaluations show that the in-cylinder heat transfer characteristics of the air-cooled SI engine strongly depend on the load while they slightly depend on the spark timing.

An Experimental and Modeling Study to Investigate Effects of Two-Stage Direct Injection Variations on HCCI Combustion

In this study, homogenous charge compression ignition (HCCI) combustion with two-stage direct injection (TSDI) strategies was modeled with stochastic reactor model (SRM) and validated by using the experimental results of the TSDI gasoline HCCI engine. For the experimental study, a diesel engine was converted to an electronically controlled HCCI gasoline engine. The effects of injection timings and injection ratios on the HCCI combustion characteristics were studied at high equivalence ratio and constant engine speed. The injection timings (first and second) and fuel quantity for each injection were adjusted to get desired mixture formation in the cylinder. During the experiments, the maximum cylinder gas pressure, pressure rise rate and start of combustion were directly controlled by using the second fuel injection timing and injection ratio. Using optimal second fuel injection timing and injection ratio caused a reduction on NOx and HC emissions. The model results of the HCCI combustion were in good agreement with the experimental results. Both of the experimental and modeling results showed that the second fuel injection timing had a strong effect on the HCCI combustion when compared to the first injection timing.

Energy and Exergy Analysis of an R134A Automotive Heat Pump System for Various Heat Sources in Comparison with Baseline Heating System

Performance of an automotive heat pump (AHP) system using R134a and driven by a diesel engine has been evaluated in this study. For this purpose, an experimental AHP system capable of providing a conditioned air stream by utilizing the heat absorbed from the ambient air, engine coolant and exhaust gas was developed. The experimental system was equipped with instruments for measuring engine torque and speed, refrigerant and coolant mass flow rates, refrigerant and air temperatures as well as refrigerant pressures. The system was tested by varying the engine speed, engine load and air temperatures at the inlets of the indoor and outdoor coils. Using experimental data, an energy analysis of the system was performed, and its performance parameters for each heat source were evaluated for transient and steady-state operations. Then, the performance of the AHP system for each source was compared with that of the system using other heat sources and with that of the baseline heating system. The investigated performance parameters include air temperature at the outlet of the indoor coil, heating capacity, coefficient of performance and exergy destruction rates in the components of the AHP system. The total exergy destruction rate in the AHP with engine coolant is higher than those in the AHP with ambient air and with exhaust gas mainly because of the greater refrigerant mass flow rate and heating capacity.

The effects of ethanol-gasoline blends on combustion and performance in a DI-HCCI engine

In this study, the effects of two stage direct injection (TSDI) strategy were investigated on the combustion and performance of an engine fueled with ethanol-gasoline blends. A diesel engine was converted to an electronically controlled HCCI engine. For each injection the injection timings and fuel quantity were adjusted to get desired mixture formation in the cylinder. The first injections were selected to be during the intake stroke and second injections were at the end of the compression stroke by using different injection ratios. Three different fuels (gasoline, E10 and E20) were used at the same energy input and constant engine speed conditions. The results showed that the maximum pressure rise rate (MPRR) increased with earlier start of first injection (SOI2) timing by using ethanol-gasoline blends. It was found that start of second injection (SOI2) timing has strong effects on the HCCI combustion and performance parameters when compared to the SOI1 timing although injection ratio (IR) and fuel blends were changed. The maximum cylinder gas pressure (Pmax), indicate mean effective pressure (imep) and thermal efficiency can be directly controlled by using the SOI2 timing at high and low equivalence ratio conditions. It was observed that the operating ranges of the ethanol-gasoline fuel blends were extended, as the MPRRs of these blends were decreased with the use of optimum injection parameters at high equivalence ratio.